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Sample records for graphite andesite volcano

  1. Magma heating by decompression-driven crystallization beneath andesite volcanoes.

    Science.gov (United States)

    Blundy, Jon; Cashman, Kathy; Humphreys, Madeleine

    2006-09-07

    Explosive volcanic eruptions are driven by exsolution of H2O-rich vapour from silicic magma. Eruption dynamics involve a complex interplay between nucleation and growth of vapour bubbles and crystallization, generating highly nonlinear variation in the physical properties of magma as it ascends beneath a volcano. This makes explosive volcanism difficult to model and, ultimately, to predict. A key unknown is the temperature variation in magma rising through the sub-volcanic system, as it loses gas and crystallizes en route. Thermodynamic modelling of magma that degasses, but does not crystallize, indicates that both cooling and heating are possible. Hitherto it has not been possible to evaluate such alternatives because of the difficulty of tracking temperature variations in moving magma several kilometres below the surface. Here we extend recent work on glassy melt inclusions trapped in plagioclase crystals to develop a method for tracking pressure-temperature-crystallinity paths in magma beneath two active andesite volcanoes. We use dissolved H2O in melt inclusions to constrain the pressure of H2O at the time an inclusion became sealed, incompatible trace element concentrations to calculate the corresponding magma crystallinity and plagioclase-melt geothermometry to determine the temperature. These data are allied to ilmenite-magnetite geothermometry to show that the temperature of ascending magma increases by up to 100 degrees C, owing to the release of latent heat of crystallization. This heating can account for several common textural features of andesitic magmas, which might otherwise be erroneously attributed to pre-eruptive magma mixing.

  2. The anatomy of an andesite volcano: A time-stratigraphic study of andesite petrogenesis and crustal evolution at Ruapehu volcano, New Zealand

    DEFF Research Database (Denmark)

    Price, R.C.; Gamble, J.A.; Smith, I.E.M.

    2012-01-01

    Ruapehu, New Zealand’s largest active andesite volcano is located at the southern tip of the Taupo Volcanic Zone (TVZ), the main locus of subduction-related volcanism in the North Island. Geophysical data indicate that crustal thickness transitions from ... Ruapehu. The volcano is built on a basement of Mesozoic metagreywacke and geophysical evidence together with xenoliths contained in lavas indicates that this is underlain by oceanic, meta-igneous lower crust. The present-day Ruapehu edifice has been constructed by a series of eruptive events that produced...... and andesite. Dacite also occurs but only one basalt flow has been identified. There have been progressive changes in the minor and trace element chemistry and isotopic composition of Ruapehu eruptives over time. In comparison with rocks from younger formations, Te Herenga eruptives have lower K2O abundances...

  3. A dearth of intermediate melts at subduction zone volcanoes and the petrogenesis of arc andesites.

    Science.gov (United States)

    Reubi, Olivier; Blundy, Jon

    2009-10-29

    Andesites represent a large proportion of the magmas erupted at continental arc volcanoes and are regarded as a major component in the formation of continental crust. Andesite petrogenesis is therefore fundamental in terms of both volcanic hazard and differentiation of the Earth. Andesites typically contain a significant proportion of crystals showing disequilibrium petrographic characteristics indicative of mixing or mingling between silicic and mafic magmas, which fuels a long-standing debate regarding the significance of these processes in andesite petrogenesis and ultimately questions the abundance of true liquids with andesitic composition. Central to this debate is the distinction between liquids (or melts) and magmas, mixtures of liquids with crystals, which may or may not be co-genetic. With this distinction comes the realization that bulk-rock chemical analyses of petrologically complex andesites can lead to a blurred picture of the fundamental processes behind arc magmatism. Here we present an alternative view of andesite petrogenesis, based on a review of quenched glassy melt inclusions trapped in phenocrysts, whole-rock chemistry, and high-pressure and high-temperature experiments. We argue that true liquids of intermediate composition (59 to 66 wt% SiO(2)) are far less common in the sub-volcanic reservoirs of arc volcanoes than is suggested by the abundance of erupted magma within this compositional range. Effective mingling within upper crustal magmatic reservoirs obscures a compositional bimodality of melts ascending from the lower crust, and masks the fundamental role of silicic melts (>/=66 wt% SiO(2)) beneath intermediate arc volcanoes. This alternative view resolves several puzzling aspects of arc volcanism and provides important clues to the integration of plutonic and volcanic records.

  4. Persistent growth of a young andesite lava cone: Bagana volcano, Papua New Guinea

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    Wadge, G.; McCormick Kilbride, B. T.; Edmonds, M.; Johnson, R. W.

    2018-05-01

    Bagana, an andesite lava cone on Bougainville Island, Papua New Guinea, is thought to be a very young central volcano. We have tested this idea by estimating the volumes of lava extruded over different time intervals (1-, 2-, 3-, 9-, 15-, 70-years) using digital elevation models (DEMs), mainly created from satellite data. Our results show that the long-term extrusion rate at Bagana, measured over years to decades, has remained at about 1.0 m3 s-1. We present models of the total edifice volume, and show that, if our measured extrusion rates are representative, the volcano could have been built in only 300 years. It could also possibly have been built at a slower rate during a longer, earlier period of growth. Six kilometres NNW of Bagana, an andesite-dacite volcano, Billy Mitchell, had a large, caldera-forming plinian eruption 437 years ago. We consider the possibility that, as a result of this eruption, the magma supply was diverted from Billy Mitchell to Bagana. It seems that Bagana is a rare example of a very youthful, polygenetic, andesite volcano. The characteristics of such a volcano, based on the example of Bagana, are: a preponderance of lava products over pyroclastic products, a high rate of lava extrusion maintained for decades, a very high rate of SO2 emission, evidence of magma batch fractionation and location in a trans-tensional setting at the end of an arc segment above a very steeply dipping and rapidly converging subduction zone.

  5. The genetic relationship between andesites and dacites at Tungurahua volcano, Ecuador

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    Nauret, F.; Samaniego, P.; Ancellin, M.-A.; Tournigand, P.-Y.; Le Pennec, J.-L.; Vlastelic, I.; Gannoun, A.; Hidalgo, S.; Schiano, P.

    2018-01-01

    Volcanic eruptions of intermediary and silica-rich magmas (andesites, dacites and rhyolites) in convergent arc settings generate voluminous and explosive eruptions that can strongly affect human activity and have significant environmental impacts. It is therefore crucial to understand how these magmas are generated in order to anticipate their potential impact. At convergent margins, primitive magmas (primitive basalts and/or andesites) are derived from the mantle wedge and they are progressively modified by physical and chemical processes operating between the melting zone and the surface to produce silica-rich magmas. In order to elucidate the relationship between andesites and dacites, we focus on Tungurahua volcano, located in the Ecuadorian Andes. We collected a set of samples comprising such lithologies that were erupted during the last 3000 year BP. This relatively short period of time allows us to assume that the geodynamic parameters remain constant. Petrology and major-trace element compositions of these lavas have already been examined, and so we performed a complementary Pb-Sr isotope study in order to determine the nature and origin of the components involved in andesite and dacite genesis. Sr isotopes range from 0.70417 to 0.70431, and Pb isotope compositions range from 18.889 to 19.154 for 206Pb/204Pb, from 15.658 to 15.696 for 207Pb/204Pb, and from 38.752 to 38.918 for 208Pb/204Pb. Dacites display a remarkably homogeneous Pb isotopic composition, with higher 206Pb/204Pb values for a given 207-208Pb/204Pb compared to andesites. Andesites show notable 207Pb/206Pb variations for a given SiO2 content, whereas dacites have lower and homogenous 207Pb/206Pb values. Andesite and dacite altogether plot in a roughly triangular distribution, with dacitic magmas systematically plotting at the high SiO2 and 87Sr/86Sr and low 207Pb/206Pb fields. Based on our new dataset, we show that at least 3 different components are required to explain the Tungurahua

  6. The glaciovolcanic evolution of an andesitic edifice, South Crater, Tongariro volcano, New Zealand

    Science.gov (United States)

    Cole, R. P.; White, J. D. L.; Conway, C. E.; Leonard, G. S.; Townsend, D. B.; Pure, L. R.

    2018-02-01

    Unusual deposits, mapped and logged in detail, around the summit area of Tongariro volcano, Tongariro Volcanic Centre, New Zealand indicate that the construction and evolution of a substantial portion of this andesitic stratovolcano was beneath a significant ice cap or summit glacier. As the edifice was built under and through the overlying ice, the style of volcanism evolved in a complex history of growth. Initially, a ≥ 100 m thick, widespread hyaloclastite deposit was emplaced within a subglacial, eruption-formed meltwater lake. This was followed by several phases of effusive and explosive eruptions, producing lava flows and primary volcaniclastic deposits emplaced along channels carved into the ice by heated meltwater. The clastic deposits contain quenched bombs and structural features that indicate waterlain transport and emplacement, and soft sediment deformation. Such accumulation of water on a steep-sided edifice without evidence for a subaerial crater lake, along with lava flow features indicating confinement, suggest that a substantial summit glacier was responsible for the production and retention of water, and the architecture of these deposits. Recent studies at nearby Ruapehu volcano have provided good evidence for glaciovolcanic interactions during the last glacial period. However, until now, little was known of the physical lava-ice interactions in the Centre during the last interglacial period and the earlier part of the last glacial period (110-64 ka). These new data support a reinterpretation for the volcanic evolution of the older Tongariro edifice and the emplacement mechanisms of primary volcaniclastic deposits. They also help to constrain local ice thicknesses and extents at the times of eruption. In addition, this study contributes to a sparse global catalogue of glaciovolcanic deposits of andesitic composition, particularly of primary volcaniclastics preserved at mid-latitude stratovolcanoes. The variety of deposit types indicates a

  7. Long-term changes in explosive and effusive behaviour at andesitic arc volcanoes: Chronostratigraphy of the Centre Hills Volcano, Montserrat

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    Coussens, Maya; Cassidy, Michael; Watt, Sebastian F. L.; Jutzeler, Martin; Talling, Peter J.; Barfod, Dan; Gernon, Thomas M.; Taylor, Rex; Hatter, Stuart J.; Palmer, Martin R.; Montserrat Volcano Observatory

    2017-03-01

    Volcanism on Montserrat (Lesser Antilles arc) has migrated southwards since the formation of the Silver Hills 2.5 Ma, and has formed three successively active volcanic centres. The Centre Hills volcano was the focus of volcanism from 1-0.4 Ma, before activity commenced at the currently active Soufrière Hills volcano. The history of activity at these two volcanoes provides an opportunity to investigate the pattern of volcano behaviour on an andesitic arc island over the lifetime of individual volcanoes. Here, we describe the pyroclastic stratigraphy of subaerial exposures around central Montserrat; identifying 11 thick (> 1 m) pumiceous units derived from sustained explosive eruptions of Centre Hills from 0.8-0.4 Ma. Over 10 other, less well- exposed pumiceous units have also been identified. The pumice-rich units are interbedded with andesite lava breccias derived from effusive, dome-forming eruptions of Centre Hills. The stratigraphy indicates that large (up to magnitude 5) explosive eruptions occurred throughout the history of Centre Hills, alongside effusive activity. This behaviour at Centre Hills contrasts with Soufrière Hills, where deposits from sustained explosive eruptions are much less common and restricted to early stages of activity at the volcano, from 175-130 ka. Subsequent eruptions at Soufriere Hills have been dominated by andesitic effusive eruptions. The bulk composition, petrography and mineral chemistry of volcanic rocks from Centre Hills and Soufrière Hills are similar throughout the history of both volcanoes, except for occasional, transient departures to different magma compositions, which mark shifts in vent location or dominant eruption style. For example, the final recorded eruption of Centre Hills, before the initiation of activity at Soufrière Hills, was more silicic than any other identified eruption on Montserrat; and the basaltic South Soufrière Hills episode marked the transition to the current stage of predominantly effusive

  8. Erratum: Correction to: Emplacement controls for the basaltic-andesitic radial dikes of Summer Coon volcano and implications for flank vents at stratovolcanoes

    Science.gov (United States)

    Harp, A. G.; Valentine, G. A.

    2018-06-01

    In the article "Emplacement controls for the basaltic-andesitic radial dikes of Summer Coon volcano and implications for flank vents at stratovolcanoes", the vertical axis for Fig. 8 a was incorrectly labeled (i.e., the value for dikes per km2).

  9. Emplacement controls for the basaltic-andesitic radial dikes of Summer Coon volcano and implications for flank vents at stratovolcanoes

    Science.gov (United States)

    Harp, A. G.; Valentine, G. A.

    2018-02-01

    Mafic flank eruptions are common events that pose a serious hazard to the communities and infrastructure often encroaching on the slopes of stratovolcanoes. Flank vent locations are dictated by the propagation path of their feeder dikes. The dikes are commonly thought to propagate either laterally from the central conduit or vertically from a deeper source. However, these interpretations are often based on indirect measurements, such as surface deformation and seismicity at active systems, and several studies at eroded volcanoes indicate the propagation paths may be more complex. We investigated the Oligocene age Summer Coon volcano (Colorado, USA), where erosion has exposed over 700 basaltic-andesitic radial dikes, to constrain the propagation directions, geometries, and spatial distributions of mafic dikes within a stratovolcano. The mean fabric angle of aligned plagioclase crystals was measured in oriented samples from the margins of 77 dikes. Of the 41 dikes with statistically significant flow fabrics, 85% had fabric angles that were inclined—plunging both inward and outward relative to the center of the volcano. After comparing fabric angles to those reported in other studies, we infer that, while most of the dikes with outward-plunging fabrics descended toward the flanks from a source within the edifice and near its axis, dikes with inward-plunging fabrics ascended through the edifice and toward the flanks from a deeper source. A possible control for the inclination of ascending dikes was the ratio between magma overpressure and the normal stress in the host rock. While higher ratios led to high-angle propagation, lower ratios resulted in inclined emplacement. Dikes crop out in higher frequencies within a zone surrounding the volcano axis at 2500 m radial distance from the center and may be the result of ascending dikes, emplaced at similar propagation angles, intersecting the current level of exposure at common distances from the volcano axis. The process

  10. Decompression Induced Crystallization of Basaltic Andesite Magma: Constraints on the Eruption of Arenal Volcano, Costa Rica.

    Science.gov (United States)

    Szramek, L. A.; Gardner, J. E.; Larsen, J. F.

    2004-12-01

    Arenal Volcano is a small stratovolcano located 90 km NW of San Jose, Costa Rica. In 1968 current activity began with a Plinian phase, and has continued to erupt lava flows and pyroclastic flows intermittently since. Samples from the Plinian, pyroclastic flow, strombolian, and effusive phases have been studied texturally. Little variation in crystallinity occurs amongst the different phases. Number density of crystals, both 2D and 3D are 50-70 mm-2 and 30,000-50,000 mm-3 in the Plinian sample, compared to the lesser values in other eruptive types. Characteristic crystal size also increases as explosivity decreases. Two samples, both lava flows collected while warm, overlap with the Plinian sample. This suggests that the variations seen may be a result of cooling history. Plagioclase differs between the Plinian sample, in which they are only tabular in shape, and the other eruptive types, which contain both tabular and equant crystals. To link decompression paths of the Arenal magma to possible pre-eruptive conditions, we have carried out hydrothermal experiments. The experiments were preformed in TZM pressure vessels buffered at a fugacity of Ni-NiO and water saturation. Phase equilibria results in conjunction with mineral compositions and temperature estimates by previous workers from active lava flows and two-pyroxene geothermometry, constrain the likely pre-eruptive conditions for the Arenal magma to 950-1040° C with a water pressure of 50-80 MPa. Samples that started from conditions that bracket our estimated pre-eruptive conditions were decompressed in steps of 5-30 MPa and held for various times at each step until 20 MPa was reached, approximating average decompression rates of 0.25, 0.025, 0.0013 MPa/s. Comparison of textures found in the natural samples to the experimentally produced textures suggest that the Plinian eruption likely was fed by magma ascending at 0.05-1 m/s, whereas the less explosive phases were fed by magma ascending at 0.05 m/s or less.

  11. Petrogenesis of andesites and dacites of White Island volcano, Bay of Plenty, New Zealand, in the light of new geochemical and isotopic data

    International Nuclear Information System (INIS)

    Graham, I.J.; Cole, J.W.

    1991-01-01

    White Island volcano comprises three main lava types: (1) silicic andesite, forming Western Cone and a tholoid at Troup Head, (2) dacite forming the Central Cone, and (3) mafic-silicic andesite erupted in March 1977 from the currently active crater. All lavas are calc-alkalic and medium-K orogenic types. The older andesites of Western Cone and Troup Head were probably formed from chemically dissimilar parental magmas by processes of assimilation and fractional crystallisation (AFC). Andesite blocks and bombs ejected during phreatomagmatic activity in March 1977 are geochemically primitive having high Mg-numbers, high Cr and Ni contents, and containing forsteritic olivine. They cannot be derived from magmatic compositions similar to known basaltic lavas of Taupo Volcanic Zone, and it is possible that the blocks are hybrid magmas resulting from mixing of a high Mg basalt parent and Central Cone dacite. The bombs appear to be fractionated derivatives. Central Cone dacites may also be AFC derivatives of a common parent to the 1977 lavas, in which substantial chemical diffusion has occurred. Their earlier eruption might represent unloading of a zoned magma chamber. (author). 49 refs., 8 figs., 3 tabs

  12. Chemical compositions and Sr, Nd isotope ratios of gabbroic xenoliths in calc-alkali andesites of Naeba and Torikabuto volcanoes, North Fossa Magna, central Japan

    International Nuclear Information System (INIS)

    Shimazu, Mitsuo; Kawano, Yoshinobu; Kaji, Kiyoshi; Igarashi, Satoshi.

    1991-01-01

    Gabbroic, doleritic and basaltic xenoliths found in calc-alkali andesites of Naeba and Torikabuto volcanoes are geochemically divided into three groups. Gabbro A of the group 1 from Naeba is rich in MgO and Ni, poor in alkalis, and shows depleted REE pattern resembling those of Ichinomegata (Sp. No.2232) and Hakone (HKG1, HKG2) volcanoes. On the basis the REE pattern and high Al IV contents in clinopyroxenes, gabbro A is interpreted to have been cumulate from a primary magma generated by partial melting of upper mantle. From REE pattern, gabbros of the group 2 from Ichinomegata (Sp. No.2218) may have derived from low alkali tholeiite magma which have been formed by removal of material such as the group 1 gabbro at shallow depth. Doleritic and basaltic xenoliths of the group 3 from Naeba, gabbroic xenoliths from Torikabuto and Umikawa are poorer in MgO and richer in alkalis than those of the group 1 and show enriched pattern in REE resembling that of high alkali tholeiite and contain clinopyroxenes having low Al IV . Therefore, these rocks are considered to be differentiates of high alkali tholeiite magma at shallow depth. On εNd- 87 Sr/ 86 Sr diagram, isotope data of gabbro A of the group 1 plot near those of andesites from Asama and Myoko volcanoes of the North Fossa Magna. It is interpreted that these rocks have derived from the same mantle source as the Asama and Myoko volcanoes which are richer in incompatible elements than those of MORB. (author)

  13. The 2006-2009 activity of the Ubinas volcano (Peru): Petrology of the 2006 eruptive products and insights into genesis of andesite magmas, magma recharge and plumbing system

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    Rivera, Marco; Thouret, Jean-Claude; Samaniego, Pablo; Le Pennec, Jean-Luc

    2014-01-01

    Following a fumarolic episode that started six months earlier, the most recent eruptive activity of the Ubinas volcano (south Peru) began on 27 March 2006, intensified between April and October 2006 and slowly declined until December 2009. The chronology of the explosive episode and the extent and composition of the erupted material are documented with an emphasis on ballistic ejecta. A petrological study of the juvenile products allows us to infer the magmatic processes related to the 2006-2009 eruptions of the andesitic Ubinas volcano. The juvenile magma erupted during the 2006 activity shows a homogeneous bulk-rock andesitic composition (56.7-57.6 wt.% SiO2), which belongs to a medium- to high-K calc-alkaline series. The mineral assemblage of the ballistic blocks and tephra consists of plagioclase > two-pyroxenes > Fe-Ti oxide and rare olivine and amphibole set in a groundmass of the same minerals with a dacitic composition (66-67 wt.% SiO2). Thermo-barometric data, based on two-pyroxene and amphibole stability, records a magma temperature of 998 ± 14 °C and a pressure of 476 ± 36 MPa. Widespread mineralogical and textural features point to a disequilibrium process in the erupted andesite magma. These features include inversely zoned "sieve textures" in plagioclase, inversely zoned clinopyroxene, and olivine crystals with reaction and thin overgrowth rims. They indicate that the pre-eruptive magmatic processes were dominated by recharge of a hotter mafic magma into a shallow reservoir, where magma mingling occurred and triggered the eruption. Prior to 2006, a probable recharge of a mafic magma produced strong convection and partial homogenization in the reservoir, as well as a pressure increase and higher magma ascent rate after four years of fumarolic activity. Mafic magmas do not prevail in the Ubinas pre-historical lavas and tephras. However, mafic andesites have been erupted during historical times (e.g. AD 1667 and 2006-2009 vulcanian eruptions). Hence

  14. An Overview of the Dynamics of the Volcanic Paroxysmal Explosive Activity, and Related Seismicity, at Andesitic and Dacitic Volcanoes (1960–2010

    Directory of Open Access Journals (Sweden)

    Vyacheslav M. Zobin

    2018-05-01

    Full Text Available Understanding volcanic paroxysmal explosive activity requires the knowledge of many associated processes. An overview of the dynamics of paroxysmal explosive eruptions (PEEs at andesitic and dacitic volcanoes occurring between 1960 and 2010 is presented here. This overview is based mainly on a description of the pre-eruptive and eruptive events, as well as on the related seismic measurements. The selected eruptions are grouped according to their Volcanic Explosivity Index (VEI. A first group includes three eruptions of VEI 5-6 (Mount St. Helens, 1980; El Chichón, 1982; Pinatubo, 1991 and a second group includes three eruptions of VEI 3 (Usu volcano, 1977; Soufriere Hills Volcano (SHV, 1996, and Volcán de Colima, 2005. The PEEs of the first group have similarity in their developments that allows to propose a 5-stage scheme of their dynamics process. Between these stages are: long (more than 120 years period of quiescence (stage 1, preliminary volcano-tectonic (VT earthquake swarm (stage 2, period of phreatic explosions (stage 3 and then, PEE appearance (stage 4. It was shown also that the PEEs of this group during their Plinian stage “triggered” the earthquake sequences beneath the volcanic structures with the maximum magnitude of earthquakes proportional to the volume of ejecta of PEEs (stage 5. Three discussed PEEs of the second group with lower VEI developed in more individual styles, not keeping within any general scheme. Among these, one PEE (SHV may be considered as partly following in development to the PEEs of the first group, having stages 1, 3, and 4. The PEEs of Usu volcano and of Volcán de Colima had no preliminary long-term stages of quiescence. The PEE at Usu volcano came just at the end of the preceding short swarm of VT earthquakes. At Volcán de Colima, no preceding swarm of VT occurred. This absence of any regularity in development of lower VEI eruptions may refer, among other reasons, to different conditions of opening

  15. Investigation of Mineral Alteration in Andesite and Dacite from Three Different Volcano Hydrothermal Systems on Dominica, Lesser Antilles

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    Smith, C. I. V.; Frey, H. M.; Joseph, E. P.; Manon, M. R. F.

    2017-12-01

    The thermal discharges of Dominica are classified as steam-heated acidic-sulphate waters, produced by the mixing of shallow ground waters heated by sulphur bearing gases coming from magmatic sources. This study investigates the mineral alteration associated with three hydrothermal areas in Dominica that exhibit different temperature, pH, water composition and surface water abundance. Hydrothermal features (fumaroles, pools, springs) from Sulphur Springs ranged in temperature from 41 - 97 °C and pH from 1-3 in a predominantly gaseous environment, whereas the Valley of Desolation (69-98 °C and pH 1- 4) and the Cold Soufriere (18-32 °C and pH 1-4) have significant inputs of surface water. At each location, the host andesite-dacite rock was enveloped by a thin rind (up 2 cm) of precipitates, but the degree of alteration and rind thickness/composition varied with location. Cobbles from Sulphur Springs (SS) are grayish white in color with a thin outer rind (3-13 mm), and seemingly unaltered cores. Valley of Desolation (VoD) samples have a variety of patterns of alteration, with some clasts a uniform white-orange color, whereas others have variable thicknesses of an altered rind (1-20 mm), with relatively unaltered cores. Multiple hydrothermal minerals precipitated in the outer rinds display distinctive colors, suggestive of sulphides (dark gray), sulphates (orange and yellow), and iron oxides(?) (pink and purple). Cold Soufriere (CS) samples appear to be the most altered, often crumbling at touch. Others had rinds (2-10 mm) and pinkish gray cores that suggest more alteration compared to VoD and SS samples. Preliminary mineral identification of rind compositions was determined by XRD. Scans indicate the presence of silica polymorphs cristobalite and tridymite, as well as pyrite and sulphur. Elemental maps created using a SEM to identify any gradation caused by the elemental leaching and/or precipitation show that the boundaries between the weathering rind and the host

  16. The Dynamics of an Ongoing Andesitic Eruption: What We Have Learned From Surface Deformation at Soufriere Hills Volcano, Montserrat, BWI

    Science.gov (United States)

    Mattioli, G.; Herd, R.; Aponte, M.; Dixon, T.; Jansma, P.; Smith, A.

    2002-05-01

    The Soufriere Hills volcano (SHV) CGPS network consists of 6 dual-frequency code-phase receivers, with Dorn-Margolin choke-ring antennae, which share a common RF telemetry network. All GPS data were processed using GIPSY-OASISII to obtain free-network point positions using final orbit, clock, and earth orientation parameters from JPL. Positions were recast into ITRF97 and these positions were used to calculate component velocities. Final site velocities for each site are reported relative a fixed Caribbean reference frame (DeMets et al., 2000). By examination of the individual time series of both the campaign and continuous sites, we have been able to divide the ground deformation observations in several distinct phases, correlated with the type of eruptive behavior manifested at the surface. While the CGPS data is limited in space, and has some important and substantial gaps because of equipment failures (some of which could not be fixed due to hazardous eruptive activity), we find that the entire GPS data set can be usefully discussed in terms of three distinct periods: (1) late 1995 to the end of 1997; (2) early 1998 to late 1999; and (3) early 2000 to the present. The primary criterion used for this distinction is the vertical velocity field. During the first period (1995-1997), all stations show strong subsidence as a function of radial distance from the SH dome (Mattioli et al., 1998). Although there is a data gap between late fall 1997 and the re-establishment of the CGPS network in early 1998, all sites show inflation at about half the rate observed for the previous period of subsidence. Thus periods of significant surface outflow (1995-1997) are strongly correlated with surface subsidence, while periods of no apparent surface magma flux are strongly correlated with ground surface inflation. Although the exact timing is somewhat equivocal, subsidence resumed at all CGPS sites just prior to the emergence of the Millennium Dome in late November to Early

  17. Experimental determination of dissolved CO2 content in nominally anhydrous andesitic melts at graphite/diamond saturation - Remobilization of deeply subducted reduced carbon via partial melts of MORB-like eclogite

    Science.gov (United States)

    Eguchi, J.; Dasgupta, R.

    2015-12-01

    Experimental phase relations of carbonated lithologies [1] and geochemistry of deep diamonds [2] suggest that deep recycling of carbon has likely been efficient for a significant portion of Earth's history. Both carbonates and organic carbon subduct into the mantle, but with gradual decrease of fO2 with depth [3] most carbon in deep mantle rocks including eclogite could be diamond/graphite [4]. Previous studies investigated the transfer of CO2 from subducted eclogite to the ambient mantle by partial melting in the presence of carbonates, i.e., by generation of carbonate-rich melts [5]. However, the transfer of carbon from subducted eclogite to the mantle can also happen, perhaps more commonly, by extraction of silicate partial melt in the presence of reduced carbon; yet, CO2 solubility in eclogite-derived andesitic melt at graphite/diamond saturation remains unconstrained. CO2content of eclogite melts is also critical as geochemistry of many ocean island basalts suggest the presence of C and eclogite in their source regions [6]. In the present study we determine CO2 concentration in a model andesitic melt [7] at graphite/diamond saturation at conditions relevant for partial melting of eclogite in the convecting upper mantle. Piston cylinder and multi anvil experiments were conducted at 1-6 GPa and 1375-1550 °C using Pt/Gr double capsules. Oxygen fugacity was monitored with Pt-Fe sensors in the starting mix. Completed experiments at 1-3 GPa show that CO2 concentration increases with increasing P, T, and fO2 up to ~0.3 wt%. Results were used to develop empirical and thermodynamic models to predict CO2 concentration in partial melts of graphite saturated eclogite. This allowed us to quantify the extent to which CO2 can mobilize from eclogitic heterogeneities at graphite/diamond saturated conditions. With estimates of eclogite contribution to erupted basaltic lavas, the models developed here allow us to put constraints on the flux of CO2 to mantle source regions

  18. Morphological analysis of Nevado de Toluca volcano (Mexico): new insights into the structure and evolution of an andesitic to dacitic stratovolcano

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    Norini, Gianluca; Groppelli, Gianluca; Capra, Lucia; De Beni, Emanuela

    2004-09-01

    We present a morphological analysis of Nevado de Toluca volcano located 80 km WSW of Mexico City based on digital elevation model study, where slope and aspect maps have been generated and analysed. Aerial photograph and satellite image observations improve the morphological analysis. The synoptic view which is offered by this analysis allowed for recognition and localization of the main volcanic and tectonic features of the area. On the basis of digital elevation model value distribution and surface textures, five morphological domains were defined. The most interesting domain, south of the crater, reflects the occurrence of an ancient complex volcano distinct from the adjacent areas. Interaction between the volcanic and volcano-tectonic evolution and the basement produced the other domains. Single volcanic edifices, like lava domes and scoria cones, and eruptive fractures were recognized. Finally, flank collapse scarps opened to the east and to the north were identified and four relevant morphostructural lineaments and their possible role in the Nevado de Toluca geological and structural evolution are discussed.

  19. Graphite

    Science.gov (United States)

    Robinson, Gilpin R.; Hammarstrom, Jane M.; Olson, Donald W.; Schulz, Klaus J.; DeYoung,, John H.; Seal, Robert R.; Bradley, Dwight C.

    2017-12-19

    Graphite is a form of pure carbon that normally occurs as black crystal flakes and masses. It has important properties, such as chemical inertness, thermal stability, high electrical conductivity, and lubricity (slipperiness) that make it suitable for many industrial applications, including electronics, lubricants, metallurgy, and steelmaking. For some of these uses, no suitable substitutes are available. Steelmaking and refractory applications in metallurgy use the largest amount of produced graphite; however, emerging technology uses in large-scale fuel cell, battery, and lightweight high-strength composite applications could substantially increase world demand for graphite.Graphite ores are classified as “amorphous” (microcrystalline), and “crystalline” (“flake” or “lump or chip”) based on the ore’s crystallinity, grain-size, and morphology. All graphite deposits mined today formed from metamorphism of carbonaceous sedimentary rocks, and the ore type is determined by the geologic setting. Thermally metamorphosed coal is the usual source of amorphous graphite. Disseminated crystalline flake graphite is mined from carbonaceous metamorphic rocks, and lump or chip graphite is mined from veins in high-grade metamorphic regions. Because graphite is chemically inert and nontoxic, the main environmental concerns associated with graphite mining are inhalation of fine-grained dusts, including silicate and sulfide mineral particles, and hydrocarbon vapors produced during the mining and processing of ore. Synthetic graphite is manufactured from hydrocarbon sources using high-temperature heat treatment, and it is more expensive to produce than natural graphite.Production of natural graphite is dominated by China, India, and Brazil, which export graphite worldwide. China provides approximately 67 percent of worldwide output of natural graphite, and, as the dominant exporter, has the ability to set world prices. China has significant graphite reserves, and

  20. An Integrative Approach for Defining Plinian and Sub-Plinian Eruptive Scenarios at Andesitic Volcanoes: Event-Lithostratigraphy, Eruptive Parameters and Pyroclast Textural Variations of the Largest Late-Holocene Eruptions of Mt. Taranaki, New Zealand.

    Science.gov (United States)

    Torres-Orozco, R.; Cronin, S. J.; Damaschke, M.; Kosik, S.; Pardo, N.

    2016-12-01

    Three eruptive scenarios were determined based on the event-lithostratigraphic reconstruction of the largest late-Holocene eruptions of the andesitic Mt. Taranaki, New Zealand: a) sustained dome-effusion followed by sudden stepwise collapse and unroofing of gas-rich magma; b) repeated plug and burst events generated by transient open-/closed-vent conditions; and c) open-vent conditions of more mafic magmas erupting from a satellite vent. Pyroclastic density currents (PDCs) are the most frequent outcome in every scenario. They can be produced in any/every eruption phase by formation and either repetitive-partial or total gravity-driven collapse of lava domes in the summit crater (block-and-ash flows), frequently followed by sudden magma decompression and violent, highly unsteady to quasi-steady lateral expansion (blast-like PDCs); by collapse or single-pulse fall-back of unsteady eruption columns (pyroclastic flow- and surge-type currents); or during highly unsteady and explosive hydromagmatic phases (wet surges). Fall deposits are produced during the climatic phase of each eruptive scenario by the emplacement of (i) high, sustained and steady, (ii) sustained and height-oscillating, (iii) quasi-steady and pulsating, or (iv) unsteady and totally collapsing eruption columns. Volumes, column heights and mass- and volume-eruption rates indicate that these scenarios correspond to VEI 4-5 plinian and sub-plinian multi-phase and style-shifting episodes, similar or larger than the most recent 1655 AD activity, and comparable to plinian eruptions of e.g. Apoyeque, Colima, Merapi and Tarawera volcanoes. Whole-rock chemistry, textural reconstructions and density-porosity determinations suggest that the different eruptive scenarios are mainly driven by variations in the density structure of magma in the upper conduit. Assuming a simple single conduit model, the style transitions can be explained by differing proportions of alternating gas-poor/degassed and gas-rich magma.

  1. Volcanoes

    Science.gov (United States)

    ... rock, steam, poisonous gases, and ash reach the Earth's surface when a volcano erupts. An eruption can also cause earthquakes, mudflows and flash floods, rock falls and landslides, acid rain, fires, and even tsunamis. Volcanic gas ...

  2. Strontium isotope data for recent andesites in Ecuador and North Chile

    International Nuclear Information System (INIS)

    Francis, P.W.; Thorpe, R.S.; Moorbath, S.

    1977-01-01

    New Sr isotope data are presented for andesite lavas from active volcanoes in Ecuador and North Chile. Twenty-three samples from five Ecuadorian volcanoes have 87 Sr/ 86 Sr ratios most of which are essentially within analytical error, and average 0.7044. In contrast, 16 samples from the San Pedro-San Pablo volcano complex in North Chile have 87 Sr/ 86 Sr ratios between 0.7058 and 0.7072. These samples show no correlation between 87 Sr/ 86 Sr and 87 Rb/ 86 Sr, nor between 87 Sr/ 86 Sr and other elements or ratios. The major difference in setting between the two volcanic provinces lies in the thickness of the continental crust; 40-50 km beneath Ecuador, 70 km beneath North Chile. Andesites from both areas are derived primarily from the mantle, but those from North Chile show evidence of a significant Sr isotopic contribution from the continental crust. (Auth.)

  3. Andesite Petrogenesis in Nevado de Toluca Stratovolcano, Central Mexico

    Science.gov (United States)

    Gomez-Tuena, A.; Capra, L.; Cai, Y.; Goldstein, S. L.

    2007-05-01

    A popular model for andesite petrogenesis in continental arcs involves a hydrous parental basalt that fractionates and probably assimilates continental crust during ascent. Nevertheless, andesites erupted from polygenetic volcanoes in the Trans-Mexican Volcanic Belt are not entirely consistent with this scenario because: (1) they display a shift to higher SiO2 contents at similar Mg# than true basalts, (2) they trend to lower HREE and HFSE contents with increasing SiO2, and (3) they often show correlated isotopic compositions with proxies for slab inputs but not with fractionation indexes. Young andesites from Toluca stratovolcano (1-0.042 Ma) also display modest adakite-like features (Sr/YToluca rock-suite revealed that some other andesites (2.6-1 Ma) also exhibit very strong negative Ce (Ce/Ce~0.25) anomalies, fractionated HREE patterns (Gd/Yb~4.2), as well as low Zr/Sm (~12.6), and Sr/Y (~12) ratios. These features are not easily explained by low or even high pressure differentiation from a common primitive magma, unless enormous quantities of fractionating accessory minerals are taken into account. And yet these geochemical signals are almost identical to those observed in the pelagic sedimentary horizon of the subducted Cocos plate sampled at DSDP site 487, and thus provide strong evidence for slab-derived sediment contributions to the petrogenesis of Toluca andesites. Since sediment transfer to the Toluca source must have occurred in the form of a silicate melt, the new evidence brings further support to the slab melting hypothesis in the Mexican subduction zone. Interestingly, Ce/Pb ratios of the Toluca rocks display a linear positive correlation with Pb isotopes, that departs from the pelagic sediment values, and extends to the enriched Pb isotopic compositions of intraplate-type volcanic rocks from the Chichinautzin volcanic field. Thus the Toluca rocks likely represent discrete slab-derived melts coming from different portions of the subducted slab that

  4. K-Ar age and chemical composition of basalt, andesite distributed in Shimabara peninsula

    Energy Technology Data Exchange (ETDEWEB)

    Nakata, Setsuya; Kamata, Hirotake

    1987-10-01

    Regarding the volcanic rocks genarated by eruption of volcanos in Shimabara Penisula, historical process of change of chemical compositions were studied. For determining the chemical compositions of basalt, andesite, X-ray fluorescence analysis was applied. By this result, distribution map of potassium and other microelements contained in the basalt and andesite was completed. It was considered that magma of similar composition were continuously kept supplied to north-western Kyushu including Shimabara Penisula since later Mesozoic era, that island arc type magma was generated at least 1.4 million years ago by the action of ocean plate, and that andesites were produced by mixing magma of hot spot type with that of island arc type. (3 figs, 2 tabs, 31 refs)

  5. K-Ar ages of the Hiruzen volcano group and the Daisen volcano

    International Nuclear Information System (INIS)

    Tsukui, Masashi; Nishido, Hirotsugu; Nagao, Keisuke.

    1985-01-01

    Seventeen volcanic rocks of the Hiruzen volcano group and the Daisen volcano, in southwest Japan, were dated by the K-Ar method to clarify the age of volcanic activity in this region and the evolution of these composite volcanoes. The eruption ages of the Hiruzen volcano group were revealed to be about 0.9 Ma to 0.5 Ma, those of the Daisen volcano to be about 1 Ma to very recent. These results are consistent with geological and paleomagnetic data of previous workers. Effusion of lavas in the area was especially vigorous at 0.5+-0.1 Ma. It was generally considered that the Hiruzen volcano group had erupted during latest Pliocene to early Quaternary and it is older than the Daisen volcano, mainly from their topographic features. However, their overlapping eruption ages and petrographical similarities of the lavas of the Hiruzen volcano group and the Daisen volcano suggest that they may be included in the Daisen volcano in a broad sense. The aphyric andesite, whose eruption age had been correlated to Wakurayama andesite (6.34+-0.19 Ma) in Matsue city and thought to be the basement of the Daisen volcano, was dated to be 0.46+-0.04 Ma. It indicates that petrographically similar aphyric andesite erupted sporadically at different time and space in the San'in district. (author)

  6. Eruption cycles in a basaltic andesite system: insights from numerical modeling

    Science.gov (United States)

    Smekens, J. F.; Clarke, A. B.; De'Michieli Vitturi, M.

    2015-12-01

    Persistently active explosive volcanoes are characterized by short explosive bursts, which often occur at periodic intervals numerous times per day, spanning years to decades. Many of these systems present relatively evolved compositions (andesite to rhyolite), and their cyclic activity has been the subject of extensive work (e.g., Soufriere Hills Volcano, Montserrat). However, the same periodic behavior can also be observed at open systems of more mafic compositions, such as Semeru in Indonesia or Karymsky in Kamchatka for example. In this work, we use DOMEFLOW, a 1D transient numerical model of magma ascent, to identify the conditions that lead to and control periodic eruptions in basaltic andesite systems, where the viscosity of the liquid phase can be drastically lower. Periodic behavior occurs for a very narrow range of conditions, for which the mass balance between magma flux and open-system gas escape repeatedly generates a viscous plug, pressurizes the magma beneath the plug, and then explosively disrupts it. The characteristic timescale and magnitude of the eruptive cycles are controlled by the overall viscosity of the magmatic mixture, with higher viscosities leading to longer cycles and lower flow rates at the top of the conduit. Cyclic eruptions in basaltic andesite systems are observed for higher crystal contents, smaller conduit radii, and over a wider range of chamber pressures than the andesitic system, all of which are the direct consequence of a decrease in viscosity of the melt phase, and in turn in the intensity of the viscous forces generated by the system. Results suggest that periodicity can exist in more mafic systems with relatively lower chamber pressures than andesite and rhyolite systems, and may explain why more mafic magmas sometimes remain active for decades.

  7. Petrogenesis of Mount Rainier andesite: magma flux and geologic controls on the contrasting differentiation styles at stratovolcanoes of the southern Washington Cascades

    Science.gov (United States)

    Sisson, Thomas W.; Salters, V.J.M.; Larson, P.B.

    2013-01-01

    Quaternary Mount Rainier (Washington, USA) of the Cascades magmatic arc consists of porphyritic calc-alkaline andesites and subordinate dacites, with common evidence for mingling and mixing with less evolved magmas encompassing andesites, basaltic andesites, and rarely, basalts. Basaltic andesites and amphibole andesites (spessartites) that erupted from vents at the north foot of the volcano represent some of Mount Rainier's immediate parents and overlap in composition with regional basalts and basaltic andesites. Geochemical (major and trace elements) and isotopic (Sr, Nd, Pb, O) compositions of Mount Rainier andesites and dacites are consistent with modest assimilation (typically ≤20 wt%) of evolved sediment or sediment partial melt. Sandstones and shales of the Eocene Puget Group, derived from the continental interior, are exposed in regional anticlines flanking the volcano, and probably underlie it in the middle to lower crust, accounting for their assimilation. Mesozoic and Cenozoic igneous basement rocks are unsuitable as assimilants due to their high 143Nd/144Nd, diverse206Pb/204Pb, and generally high δ18O.

  8. Fusion of arkosic sand by intrusive andesite

    Science.gov (United States)

    Bailey, Roy A.

    1954-01-01

    An andesite dike in the Valles Mountains of northern New Mexico has intruded and partly fused arkosic sediments for a distance of 50 feet from its contacts. The dike is semi-circular in form, has a maximum width of about 100 feet, and is about 500 feet long. Small associated arcuate dikes are arranged in spiral fashion around the main dike, suggesting that they were intruded along shear fractures similar to those described by Burbank (1941). The fused rocks surrounding the andesite dike are of three general types: 1) partly fused arkosic sand, 2) fused clay, and 3) hybrid rocks. The fused arkosic sand consists of relict detrital grains of quartz, orthoclose, and plagioclase, imbedded in colorless glass containing microlites of tridymite, cordierite, and magnetite. The relict quartz grains are corroded and embayed by glass; the orthoclase is sanidinized and partly fused; and the plagioclase is inverted to the high temperature form and is partly fused. The fused clay, which was originally a mixture of montmorillonite and hydromica, consists primarily of cordierite but also contains needle-like crystals of sillimanite (?) or mullite (?). The hybrid rocks originated in part by intermixing of fused arkosic sediments and andesitic liquid and in part by diffusion of mafic constituents through the fused sediments. They are rich in cordierite and magnetite and also contain hypersthene, augite, and plagioclase. The composition of pigeonite in the andesite indicates that the temperature of the andesite at the time of intrusion probably did not exceed 1200?C. Samples of arkosic sand were fused in the presence of water in a Morey bomb at 1050?C. Stability relations of certain minerals in the fused sand suggest that fusion may have taken place at a lower temperature, however, and the fluxing action of volatiles from the andesite are thought to have made this possible.

  9. Brazing graphite to graphite

    International Nuclear Information System (INIS)

    Peterson, G.R.

    1976-01-01

    Graphite is joined to graphite by employing both fine molybdenum powder as the brazing material and an annealing step that together produce a virtually metal-free joint exhibiting properties similar to those found in the parent graphite. Molybdenum powder is placed between the faying surfaces of two graphite parts and melted to form molybdenum carbide. The joint area is thereafter subjected to an annealing operation which diffuses the carbide away from the joint and into the graphite parts. Graphite dissolved by the dispersed molybdenum carbide precipitates into the joint area, replacing the molybdenum carbide to provide a joint of graphite

  10. Carbonate assimilation at Merapi volcano, Java Indonesia

    DEFF Research Database (Denmark)

    Chadwick, J.P; Troll, V.R; Ginibre,, C.

    2007-01-01

    Recent basaltic andesite lavas from Merapi volcano contain abundant, complexly zoned, plagioclase phenocrysts, analysed here for their petrographic textures, major element composition and Sr isotope composition. Anorthite (An) content in individual crystals can vary by as much as 55 mol% (An40^95...

  11. Special graphites; Graphites speciaux

    Energy Technology Data Exchange (ETDEWEB)

    Leveque, P [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

    1964-07-01

    A large fraction of the work undertaken jointly by the Commissariat a l'Energie Atomique (CEA) and the Pechiney Company has been the improvement of the properties of nuclear pile graphite and the opening up of new fields of graphite application. New processes for the manufacture of carbons and special graphites have been developed: forged graphite, pyro-carbons, high density graphite agglomeration of graphite powders by cracking of natural gas, impervious graphites. The physical properties of these products and their reaction with various oxidising gases are described. The first irradiation results are also given. (authors) [French] Ameliorer les proprietes du graphite nucleaire pour empilements et ouvrir de nouveaux domaines d'application au graphite constituent une part importante de l'effort entrepris en commun par le Commissariat a l'Energie Atomique (CEA) et la compagnie PECHINEY. Des procedes nouveaux de fabrication de carbones et graphites speciaux ont ete mis au point: graphite forge, pyrocarbone, graphite de haute densite, agglomeration de poudres de graphite par craquage de gaz naturel, graphites impermeables. Les proprietes physiques de ces produits ainsi que leur reaction avec differents gaz oxydants sont decrites. Les premiers resultats d'irradiation sont aussi donnes. (auteurs)

  12. Fracture and compaction of andesite in a volcanic edifice.

    Science.gov (United States)

    Heap, M J; Farquharson, J I; Baud, P; Lavallée, Y; Reuschlé, T

    The failure mode of lava-dilatant or compactant-depends on the physical attributes of the lava, primarily the porosity and pore size, and the conditions under which it deforms. The failure mode for edifice host rock has attendant implications for the structural stability of the edifice and the efficiency of the sidewall outgassing of the volcanic conduit. In this contribution, we present a systematic experimental study on the failure mode of edifice-forming andesitic rocks (porosity from 7 to 25 %) from Volcán de Colima, Mexico. The experiments show that, at shallow depths (1 km), while low-porosity (explosive potential of a volcano may therefore be subject to increase over time if the progressive compaction and permeability reduction in the lower edifice cannot be offset by the formation of permeable fracture pathways in the upper edifice. The mode of failure of the edifice host rock is therefore likely to be an important factor controlling lateral outgassing and thus eruption style (effusive versus explosive) at stratovolcanoes.

  13. Eruptive viscosity and volcano morphology

    International Nuclear Information System (INIS)

    Posin, S.B.; Greeley, R.

    1988-01-01

    Terrestrial central volcanoes formed predominantly from lava flows were classified as shields, stratovolcanoes, and domes. Shield volcanoes tend to be large in areal extent, have convex slopes, and are characterized by their resemblance to inverted hellenic war shields. Stratovolcanoes have concave slopes, whereas domes are smaller and have gentle convex slopes near the vent that increase near the perimeter. In addition to these differences in morphology, several other variations were observed. The most important is composition: shield volcanoes tend to be basaltic, stratovolcanoes tend to be andesitic, and domes tend to be dacitic. However, important exceptions include Fuji, Pico, Mayon, Izalco, and Fuego which have stratovolcano morphologies but are composed of basaltic lavas. Similarly, Ribkwo is a Kenyan shield volcano composed of trachyte and Suswa and Kilombe are shields composed of phonolite. These exceptions indicate that eruptive conditions, rather than composition, may be the primary factors that determine volcano morphology. The objective of this study is to determine the relationships, if any, between eruptive conditions (viscosity, erupted volume, and effusion rate) and effusive volcano morphology. Moreover, it is the goal of this study to incorporate these relationships into a model to predict the eruptive conditions of extraterrestrial (Martian) volcanoes based on their morphology

  14. Volcano-hydrothermal energy research at white Island, New Zealand

    International Nuclear Information System (INIS)

    Allis, R.G.

    1994-01-01

    This paper presents the White Island (New Zealand) volcano-hydrothermal research project by the N.Z. DSIR and the Geological Survey of Japan, which is investigating the coupling between magmatic and geothermal systems. The first phase of this investigation is a geophysical survey of the crater floor of the andesite volcano, White Island during 1991/1992, to be followed by drilling from the crater floor into the hydrothermal system. (TEC). 4 figs., 8 refs

  15. Geochemical signatures of tephras from Quaternary Antarctic Peninsula volcanoes

    OpenAIRE

    Kraus,Stefan; Kurbatov,Andrei; Yates,Martin

    2013-01-01

    In the northern Antarctic Peninsula area, at least 12 Late Plelstocene-Holocene volcanic centers could be potential sources of tephra layers in the region. We present unique geochemical fingerprints for ten of these volcanoes using major, trace, rare earth element, and isotope data from 95 samples of tephra and other eruption products. The volcanoes have predominantly basaltic and basaltic andesitic compositions. The Nb/Y ratio proves useful to distinguish between volcanic centers located on ...

  16. Special graphites

    International Nuclear Information System (INIS)

    Leveque, P.

    1964-01-01

    A large fraction of the work undertaken jointly by the Commissariat a l'Energie Atomique (CEA) and the Pechiney Company has been the improvement of the properties of nuclear pile graphite and the opening up of new fields of graphite application. New processes for the manufacture of carbons and special graphites have been developed: forged graphite, pyro-carbons, high density graphite agglomeration of graphite powders by cracking of natural gas, impervious graphites. The physical properties of these products and their reaction with various oxidising gases are described. The first irradiation results are also given. (authors) [fr

  17. Paleoproterozoic andesitic volcanism in the southern Amazonian craton (northern Brazil); lithofacies analysis and geodynamic setting

    Science.gov (United States)

    Roverato, Matteo; Juliani, Caetano; Capra, Lucia; Dias Fernandes, Carlos Marcelo

    2016-04-01

    Precambrian volcanism played an important role in geological evolution and formation of new crust. Most of the literature on Precambrian volcanic rocks describes settings belonging to subaqueous volcanic systems. This is likely because subaerial volcanic rocks in Proterozoic and Archean volcano-sedimentary succession are poorly preserved due to erosive/weathering processes. The late Paleoproterozoic Sobreiro Formation (SF) here described, seems to be one of the rare exceptions to the rule and deserves particular attention. SF represents the subaerial expression of an andesitic magmatism that, linked with the upper felsic Santa Rosa F., composes the Uatumã Group. Uatumã Group is an extensive magmatic event located in the Xingú region, southwestern of Pará state, Amazonian Craton (northern Brazil). The Sobreiro volcanism is thought to be related to an ocean-continent convergent margin. It is characterized by ~1880 Ma well-preserved calc-alkaline basaltic/andesitic to andesitic lava flows, pyroclastic rocks and associated reworked successions. The superb preservation of its rock-textures allowed us to describe in detail a large variety of volcaniclastic deposits. We divided them into primary and secondary, depending if they result from a direct volcanic activity (pyroclastic) or reworked processes. Our study reinforces the importance of ancient volcanic arcs and rocks contribution to the terrestrial volcaniclastic sedimentation and evolution of plate tectonics. The volcanic activity that produced pyroclastic rocks influenced the amount of detritus shed into sedimentary basins and played a major role in the control of sedimentary dispersal patterns. This study aims to provide, for the first time, an analysis of the physical volcanic processes for the subaerial SF, based in field observation, lithofacies analysis, thin section petrography and less geochemical data. The modern volcanological approach here used can serve as a model about the evolution of Precambrian

  18. Petrographic and Geochemical Investigation of Andesitic Arc Volcanism: Mount Kerinci, Sunda Arc, Indonesia

    Science.gov (United States)

    Tully, M.; Saunders, K.; Troll, V. R.; Jolis, E.; Muir, D. D.; Deegan, F. M.; Budd, D. A.; Astbury, R.; Bromiley, G. D.

    2014-12-01

    Present knowledge of the chain of dominantly andesitic volcanoes, which span the Sumatran portion of the Sunda Arc is extremely limited. Previous studies have focused on Toba and Krakatau, although over 13 further volcanic edifices are known. Several recent explosive eruptions in Sumatra such as that of Mt. Sinabung, 2014, have highlighted the potential hazard that these volcanoes pose to the local and regional communities. Mount Kerinci, is one of the most active of the volcanoes in this region, yet little is known about the petrogenesis of the magma by which it is fed. Kerinci is located approximately mid-way between Toba in the North and Krakatau in the south. Along arc variations are observed in the major, minor and trace elements of whole rock analyses. However, bulk rock approaches produce an average chemical composition for a sample, potentially masking important chemical signatures. In-situ micro-analytical analysis of individual components of samples such as melt inclusions, crystals and groundmass provides chemical signatures of individual components allowing the evolution of volcanic centres to be deciphered in considerably more detail. Examination of whole rock chemistry indicates its location may be key to unravelling the petrogenesis of the arc as significant chemical changes occur between Kerinci and Kaba, 250 km to the south. Kerinci samples are dominantly porphyritic with large crystals of plagioclase, pyroxene and Fe-Ti oxides, rare olivine crystals are observed. Plagioclase and pyroxene crystals are chemically zoned and host melt inclusions. Multiple plagioclase populations are observed. A combination of in-situ micro-analysis techniques will be used to characterise the chemical composition of melt inclusions and crystals. These data can be used along with extant geothermobarometric models to help determine the magma source, storage conditions and composition of the evolving melt. Integration of the findings from this study with existing data for

  19. Measurements of the Activity of dissolved H2O in an Andesite Melt

    Science.gov (United States)

    Moore, G. M.; Touran, J. P.; Pu, X.; Kelley, K. A.; Cottrell, E.; Ghiorso, M. S.

    2016-12-01

    The large effect of dissolved H2O on the physical and chemical nature of silicate melts, and its role in driving volcanism, is well known and underscores the importance of this volatile component. A complete understanding of the chemical behavior of dissolved H2O in silicate melts requires the quantification of its thermodynamic activity as a function of pressure, temperature, and melt composition, particularly at low H2O contents (i.e. at under-saturated conditions). Knowledge of the activity of H2O in silicate melts at H2O-undersaturated conditions will improve our understanding of hydrous phase equilibria, as well as our models of physical melt properties. Measurement of the activity of any silicate melt component, much less that of a volatile component such as H2O, is a difficult experimental task however. By using a modified double capsule design (Matjuschkin et al, 2015) to control oxygen fugacity in piston cylinder experiments, along with high precision X-ray absorption techniques (XANES) to measure iron oxidation state in silicate glasses (Cottrell et al, 2009), we are able to constrain the H2O activity in silicate melts at under-saturated conditions. Preliminary results on an andesite melt with low H2O content (3 wt%) have been shown (Moore et al, 2016) to match predicted H2O activity values calculated using the H2O equation of state of Duan and Zhang (1996) and the H2O solubility model of Ghiorso and Gualda (2015). More recent results on the same andesite melt containing approximately 5 wt% H2O however show a large negative deviation from the predicted values. Reversal experiments involving an oxidized starting material are ongoing, as well as further characterization of the samples to detect the presence of possible contaminants that would induce reduction of the melt beyond that related to the H2O activity (e.g. graphite contamination).

  20. Genesis of Cenozoic intraplate high Mg# andesites in Northeast China

    Science.gov (United States)

    Liu, J. Q.; Chen, L. H.; Zhong, Y.; Wang, X. J.

    2017-12-01

    High-Mg# andesites (HMAs) are usually generated in the converged plate boundary and have genetic relationships with slab subduction. However, it still remained controversial about the origin of those HMAs erupted in the intra-plate setting. Here we present major, trace element, and Sr-Nd-Pb-Hf isotopic compositions for the Cenozoic intra-plate HMAs from Northeast China to constrain their origin and formation process. Cenozoic Xunke volcanic rocks are located in the northern Lesser Khingan Range, covering an area of about 3, 000 km2. These volcanic rocks are mainly basaltic andesite and basaltic trachyandesite, with only several classified as trachyandesite and andesites. They have high SiO2 contents (54.3-57.4 wt%) and Mg# (49.6-57.8), falling into the scope of high Mg# andesites. The Xunke HMAs are enriched in large ion lithophile elements but depleted in high field strength elements, with positive Ba, K, Sr and negative Zr-Hf, and Ti anomalies. Their trace element absolute concentrations are between those of potassic basalts and Wuchagou HMAs. The Xunke HMAs have relatively enriched Sr-Nd-Hf isotopes (87Sr/86Sr = 0.705398-0.705764, ɛNd=-8.8-3.8, ɛHf=0.5-11.7), and low radiogenic Pb isotopes (206Pb/204Pb = 16.701-17.198), towards to the EM1 end-member, which indicates that they are ultimately derived from ancient, recycled crustal components. Primitive silica-rich melts were generated from higher degrees of partial melting of recycled crustal materials (relative to potassic basalts) and then interacted with the peridotite to produce the Xunke HMAs.

  1. What Are Volcano Hazards?

    Science.gov (United States)

    ... Sheet 002-97 Revised March 2008 What Are Volcano Hazards? Volcanoes give rise to numerous geologic and ... as far as 15 miles from the volcano. Volcano Landslides A landslide or debris avalanche is a ...

  2. Complex investigation of thermo-technical parameters of Ruskov andesite

    Directory of Open Access Journals (Sweden)

    František Krepelka

    2006-12-01

    Full Text Available The research of thermo-technical parameters of Ruskov andesite was made as a part of the complex research of its properties as well as of rock disintegration by the action of chemical flame on the rock surface, i.e. thermal spalling in particular. Thermal spalling is a process in which thermal stresses are induced in the surface layer of rock whose surface is thereby disintegrated into small parts, the so called spalls, by the brittle manner. The evaluation of thermo-technical properties of the studied rocks is necessary for the qualification and quantification of the thermal spalling process. The measured and evaluated parameters were the coefficient of linear thermal expansion, the coefficient of thermal conductivity, the specific heat capacity and the coefficient of thermal diffusivity. Andesite from the Ruskov locality was chosen as a basic experimental material for the investigation of thermal spalling upon preliminary experiments. The estimated thermo-technical parameters were analyzed regarding the application of thermal spalling for the disintegration of the Ruskov andesite. The outcome as that the values of determine thermo-technical parameters established an expectation for its successful application.

  3. Chemical trends in a perhumid soil catena on the Turrialba volcano (Costa Rica)

    NARCIS (Netherlands)

    Meijer, E.L.; Buurman, P.

    2003-01-01

    The variation in chemical composition of soil samples (XRFS data) from a soil catena of 14 soil profiles on the northern slope and foot slope of the andesitic Turrialba volcano (3300 m) has been analysed to test the two hypotheses, which underlie our interpretation that this catena is a weathering

  4. Magma crust interaction at Merapi volcano, Java Indonesia: insights from crystal isotope stratigraphy

    NARCIS (Netherlands)

    Chadwick, J.P.; Troll, V.R.; Ginibre, C.; Morgan, D.; Gertisser, R.; Waight, T.; Davidson, J.P.

    2007-01-01

    Recent basaltic andesite lavas from Merapi volcano contain abundant, complexly zoned, plagioclase phenocrysts, analysed here for their petrographic textures, major element composition and Sr isotope composition. Anorthite (An) content in individual crystals can vary by as much as 55 mol% (An

  5. Mutnovsky and Gorely Volcanoes, Kamchatka as Planetary Analogue Sites

    Science.gov (United States)

    Evdokimova, N.; Izbekov, P. E.; Krupskaya, V.; Muratov, A.

    2016-12-01

    Recent advances in Mars studies suggest that volcanic rocks, which dominated Martian surface in the past, have been exposed to alteration processes in a water-bearing environment during Noachian, before 3.7 Gy. Active volcanoes on Earth are natural laboratories, where volcanic processes and their associated products can be studied directly. This is particularly important for studying of alteration of juvenile volcanic products in aqueous environment because of the transient nature of some of the alteration products, as well as the environment itself. Terrestrial analogues help us to better understand processes on Mars; they are particularly useful as a test sites for preparation to future Mars missions. In this presentation we describe planetary analogue sites at Mutnovsky and Gorely Volcanoes in Kamchatka, which might be helpful for comparative studies and preparation to future Mars missions. Mutnovsky and Gorely Volcanoes are located 75 km south of Petropavlovsk-Kamchatsky, in the southern part of the Kamchatka Peninsula, Russia. The modern volcanic landscape in the area was shaped in Holocene (recent 10,000 years) through intermittent eruption of magmas ranging in composition from basalts to dacites and rhyodacites, with basaltic andesite lavas dominating in the modern relief. Two localities could be of a particular interest: (1) Mutnovsky NW thermal field featuring processes of active hydrothermal alteration of lavas of basaltic andesite and (2) dry lake at the bottom of Gorely caldera featuring products of mechanical disintegration of basaltic andesite lavas by eolian processes with short seasonal sedimentation in aqueous environment.

  6. Artificial graphites

    International Nuclear Information System (INIS)

    Maire, J.

    1984-01-01

    Artificial graphites are obtained by agglomeration of carbon powders with an organic binder, then by carbonisation at 1000 0 C and graphitization at 2800 0 C. After description of the processes and products, we show how the properties of the various materials lead to the various uses. Using graphite enables us to solve some problems, but it is not sufficient to satisfy all the need of the application. New carbonaceous material open application range. Finally, if some products are becoming obsolete, other ones are being developed in new applications [fr

  7. Chemical compositions of lavas from Myoko volcano group

    International Nuclear Information System (INIS)

    Hasenaka, Toshiaki; Yoshida, Takeyoshi; Hayatsu, Kenji.

    1995-01-01

    In the volcanic rocks produced in island arc and continental margin arc, the phenomena of magma mixing is observed considerably generally. The research on these phenomena has been carried out also in Japan, and the periodically refilled magma chamber model has been proposed. In this report, the results of the photon activation analysis for the volcanic rock samples of Myoko volcano, for which the magma chamber model that the supply of basalt magma is periodically received was proposed, and of which the age of eruption and the stratigraphy are clearly known, are shown, and the above model is examined together with the published data of fluorescent X-ray analysis and others. The history of activities and the rate of magma extrusion of Myoko volcano group are described. The modal compositions of the volcanic rock samples of Myoko and Kurohime volcanos, for which photon activation analysis was carried out, are shown and discussed. The results of the analysis of the chemical composition of 39 volcanic rock samples from Myoko, Kurohime and Iizuna volcanos are shown. The primary magma in Myoko volcano group, the crystallization differentiation depth and moisture content of magma in Myoko and Kurohime volcanos, the presumption of Felsic and Mafic end-members in R type andesite in Myoko volcano group, and the change of magma composition with lapse of time are described. (K.I.)

  8. Chemical compositions of lavas from Myoko volcano group

    Energy Technology Data Exchange (ETDEWEB)

    Hasenaka, Toshiaki; Yoshida, Takeyoshi [Tohoku Univ., Sendai (Japan). Faculty of Science; Hayatsu, Kenji

    1995-08-01

    In the volcanic rocks produced in island arc and continental margin arc, the phenomena of magma mixing is observed considerably generally. The research on these phenomena has been carried out also in Japan, and the periodically refilled magma chamber model has been proposed. In this report, the results of the photon activation analysis for the volcanic rock samples of Myoko volcano, for which the magma chamber model that the supply of basalt magma is periodically received was proposed, and of which the age of eruption and the stratigraphy are clearly known, are shown, and the above model is examined together with the published data of fluorescent X-ray analysis and others. The history of activities and the rate of magma extrusion of Myoko volcano group are described. The modal compositions of the volcanic rock samples of Myoko and Kurohime volcanos, for which photon activation analysis was carried out, are shown and discussed. The results of the analysis of the chemical composition of 39 volcanic rock samples from Myoko, Kurohime and Iizuna volcanos are shown. The primary magma in Myoko volcano group, the crystallization differentiation depth and moisture content of magma in Myoko and Kurohime volcanos, the presumption of Felsic and Mafic end-members in R type andesite in Myoko volcano group, and the change of magma composition with lapse of time are described. (K.I.)

  9. Comparative features of volcanoes on Solar system bodies

    Science.gov (United States)

    Vidmachenko, A. P.

    2018-05-01

    The bark of many cosmic bodies is in motion because of the displacement of tectonic plates on magma. Pouring molten magma through cracks in the cortex is called a volcanic eruption. There are two main types of volcanoes: basaltic, appearing where a new material of tectonic plates is formed, and andesitic, which located in the places of destruction of these plates.The third type of volcanoes is cryovolcanoes, or ice volcanoes. This type of volcano ejects matter in the form of ice volcanic melts or steam from water, ammonia, methane. After the eruption, the cryomagma at a low temperature condenses to a solid phase. Cryovolcanoes can be formed on such objects as Pluto, Ceres, Titan, Enceladus, Europe, Triton, etc. Potential sources of energy for melting ice in the production of cryovolcanoes are tidal friction and/or radioactive decay. Semi-transparent deposits of frozen materials that can create a subsurface greenhouse effect, with the possibility of accumulating the required heat with subsequent explosive eruption, are another way to start the cryovolcano action. This type of eruption is observed on Mars and Triton. The first and second types of eruptions (basaltic and andesitic) are characteristic of terrestrial planets (Mercury, Venus, Mars) and for some satellites of the planets of the Solar system.

  10. Magma-carbonate interaction processes and associated CO2 release at Merapi volcano, Indonesia: insights from experimental petrology

    NARCIS (Netherlands)

    Deegan, F.M.; Troll, V.R.; Freda, C.; Misti, V.; Chadwick, J.P.

    2010-01-01

    There is considerable evidence for continuing, late-stage interaction between the magmatic system at Merapi volcano, Indonesia, and local crustal carbonate (limestone). Calc-silicate xenoliths within Merapi basaltic-andesite eruptive rocks display textures indicative of intense interaction between

  11. A graphite foam reinforced by graphite particles

    Energy Technology Data Exchange (ETDEWEB)

    Zhu, J.J.; Wang, X.Y.; Guo, L.F.; Wang, Y.M.; Wang, Y.P.; Yu, M.F.; Lau, K.T.T. [DongHua University, Shanghai (China). College of Material Science and Engineering

    2007-11-15

    Graphite foam was obtained after carbonization and graphitization of a pitch foam formed by the pyrolysis of coal tar based mesophase pitch mixed with graphite particles in a high pressure and temperature chamber. The graphite foam possessed high mechanical strength and exceptional thermal conductivity after adding the graphite particles. Experimental results showed that the thermal conductivity of modified graphite foam reached 110W/m K, and its compressive strength increased from 3.7 MPa to 12.5 MPa with the addition of 5 wt% graphite particles. Through the microscopic observation, it was also found that fewer micro-cracks were formed in the cell wall of the modified foam as compared with pure graphite foam. The graphitization degree of modified foam reached 84.9% and the ligament of graphite foam exhibited high alignment after carbonization at 1200{sup o}C for 3 h and graphitization at 3000{sup o}C for 10 min.

  12. Studi Potensi Sumberdaya Andesit Menggunakan Metode Geolistrik Di Daerah Kokap, Kabupaten Kulonprogo, Daerah Istimewa Yogyakarta

    Directory of Open Access Journals (Sweden)

    Eko Bayu Purwasatriya

    2013-06-01

    Full Text Available The study of andesite resources was carried out in Hargowilis village, Kokap sub-district, Kulonprogo regency, Daerah Istimewa Yogyakarta province using geoelectrical data with Schlumberger configuration, as much as 14 point which is spreading on 8 hectares area. Based on regional geological map of Yogyakarta area, study area include on intrusive rock lithology’s unit compose of hipersten andesite to augite-hornblende andesite and trachiandesite. Geoelectrical method is one of geophysical method that used to observed geological condition in subsurface based on rock’s electrical properties. Andesite is one type of igneous rock which have contrast electrical properties with its surrounding rock, generally sedimentary rocks, makes it suitable for geoelectrical method to identify the presence of andesite in subsurface and also estimate its thickness to calculate the resources. Geoelectrical configuration used is 1D Schlumberger configuration where this method have advantage more accurate to calculate the thickness of rock layer especially in shallow area. The result of geoelectrical survey showing that it consist 2 layer of andesite, there are shallow layer and deep layer. This result indicate that the igneous rock in study area not only intrusion type, but also lava flow type. Resources potential of andesite both shallow and deep layer are 5,072,354 tons and resources potential of shallow andesite only is 3,162,566 tons.

  13. Ejection age of volcano rocks and trend of volcanic activity

    Energy Technology Data Exchange (ETDEWEB)

    Sakaguchi, Keiichi

    1987-10-01

    This report is II-7 of an interim report on research and development of the Sunshine Project for 1986. This report considers on the trend of volcanic activities in the South of Kyushu area. K-Ar age measurement was newly made and reported. Age values obtained were 1.09 plus minus 0.21 Ma for Nagaoyama andesite, 1.33 plus minus 0.18 Ma for Nozato andesite, and 0.3 plus minus 0.1 Ma for Imuta volcanos. Including these age values, from the age values and their distribution of the volcanic rocks in the South Kyushu district, the following three districts were selected to represent the volcanic activities since the Pliocene Epoch. As these districts are mutually overwrapped, verification at these overwrapped districts are necessary. (4 figs, 1 tab, 12 refs)

  14. Thermally exfoliated graphite oxide

    Science.gov (United States)

    Prud'Homme, Robert K. (Inventor); Aksay, Ilhan A. (Inventor); Abdala, Ahmed (Inventor)

    2011-01-01

    A modified graphite oxide material contains a thermally exfoliated graphite oxide with a surface area of from about 300 sq m/g to 2600 sq m/g, wherein the thermally exfoliated graphite oxide displays no signature of the original graphite and/or graphite oxide, as determined by X-ray diffraction.

  15. Bridged graphite oxide materials

    Science.gov (United States)

    Herrera-Alonso, Margarita (Inventor); McAllister, Michael J. (Inventor); Aksay, Ilhan A. (Inventor); Prud'homme, Robert K. (Inventor)

    2010-01-01

    Bridged graphite oxide material comprising graphite sheets bridged by at least one diamine bridging group. The bridged graphite oxide material may be incorporated in polymer composites or used in adsorption media.

  16. Process for purifying graphite

    International Nuclear Information System (INIS)

    Clausius, R.A.

    1985-01-01

    A process for purifying graphite comprising: comminuting graphite containing mineral matter to liberate at least a portion of the graphite particles from the mineral matter; mixing the comminuted graphite particles containing mineral matter with water and hydrocarbon oil to form a fluid slurry; separating a water phase containing mineral matter and a hydrocarbon oil phase containing grahite particles; and separating the graphite particles from the hydrocarbon oil to obtain graphite particles reduced in mineral matter. Depending upon the purity of the graphite desired, steps of the process can be repeated one or more times to provide a progressively purer graphite

  17. Geology of El Chichon volcano, Chiapas, Mexico

    Science.gov (United States)

    Duffield, Wendell A.; Tilling, Robert I.; Canul, Rene

    1984-03-01

    The (pre-1982) 850-m-high andesitic stratovolcano El Chichón, active during Pleistocene and Holocene time, is located in rugged, densely forested terrain in northcentral Chiapas, México. The nearest neighboring Holocene volcanoes are 275 km and 200 km to the southeast and northwest, respectively. El Chichón is built on Tertiary siltstone and sandstone, underlain by Cretaceous dolomitic limestone; a 4-km-deep bore hole near the east base of the volcano penetrated this limestone and continued 770 m into a sequence of Jurassic or Cretaceous evaporitic anhydrite and halite. The basement rocks are folded into generally northwest-trending anticlines and synclines. El Chichón is built over a small dome-like structure superposed on a syncline, and this structure may reflect cumulative deformation related to growth of a crustal magma reservoir beneath the volcano. The cone of El Chichón consists almost entirely of pyroclastic rocks. The pre-1982 cone is marked by a 1200-m-diameter (explosion?) crater on the southwest flank and a 1600-m-diameter crater apparently of similar origin at the summit, a lava dome partly fills each crater. The timing of cone and dome growth is poorly known. Field evidence indicates that the flank dome is older than the summit dome, and K-Ar ages from samples high on the cone suggest that the flank dome is older than about 276,000 years. At least three pyroclastic eruptions have occurred during the past 1250 radiocarbon years. Nearly all of the pyroclastic and dome rocks are moderately to highly porphyritic andesite, with plagioclase, hornblende and clinopyroxene the most common phenocrysts. Geologists who mapped El Chichón in 1980 and 1981 warned that the volcano posed a substantial hazard to the surrounding region. This warning was proven to be prophetic by violent eruptions that occurred in March and April of 1982. These eruptions blasted away nearly all of the summit dome, blanketed the surrounding region with tephra, and sent pyroclastic

  18. A dynamical analysis of the seismic activity of Villarrica volcano (Chile) during September-October 2000

    Energy Technology Data Exchange (ETDEWEB)

    Tarraga, Marta [Departamento de Volcanologia. Museo Nacional de Ciencias Naturales, CSIC, Madrid (Spain)], E-mail: martat@mncn.csic.es; Carniel, Roberto [Dipartimento di Georisorse e Territorio, Universita di Udine, Via Cotonificio 114, 33100 Udine (Italy)], E-mail: roberto.carniel@uniud.it; Ortiz, Ramon; Garcia, Alicia [Departamento de Volcanologia. Museo Nacional de Ciencias Naturales, CSIC, Madrid (Spain); Moreno, Hugo [Observatorio Volcanologico de los Andes del Sur (OVDAS), Servicio Nacional de Geologia y Mineria de Chile (SERNAGEOMIN), Temuco, IX Region (Chile)

    2008-09-15

    Although Villarrica volcano in Chile is one of the most active in the southern Andes, the literature studying its seismic activity is relatively scarce. An interesting problem recently tackled is the possibility for a regional tectonic event to trigger a change in the volcanic activity of this basaltic to basaltic-andesitic volcano, which is in turn reflected in the time evolution of the properly volcanic seismicity, especially in the form of a continuous volcanic tremor. In this work, we conduct a spectral, dynamical and statistical analysis of the tremor recorded during September and October 2000, in order to characterize the anomalous behaviour of the volcano following a tectonic event recorded on 20th September 2000. The observed dynamical transitions are compared with remote sensing and visual observations describing the changes in the eruptive style of the volcano.

  19. A dynamical analysis of the seismic activity of Villarrica volcano (Chile) during September-October 2000

    International Nuclear Information System (INIS)

    Tarraga, Marta; Carniel, Roberto; Ortiz, Ramon; Garcia, Alicia; Moreno, Hugo

    2008-01-01

    Although Villarrica volcano in Chile is one of the most active in the southern Andes, the literature studying its seismic activity is relatively scarce. An interesting problem recently tackled is the possibility for a regional tectonic event to trigger a change in the volcanic activity of this basaltic to basaltic-andesitic volcano, which is in turn reflected in the time evolution of the properly volcanic seismicity, especially in the form of a continuous volcanic tremor. In this work, we conduct a spectral, dynamical and statistical analysis of the tremor recorded during September and October 2000, in order to characterize the anomalous behaviour of the volcano following a tectonic event recorded on 20th September 2000. The observed dynamical transitions are compared with remote sensing and visual observations describing the changes in the eruptive style of the volcano

  20. Magmatic controls on eruption dynamics of the 1950 yr B.P. eruption of San Antonio Volcano, Tacaná Volcanic Complex, Mexico-Guatemala

    Science.gov (United States)

    Mora, Juan Carlos; Gardner, James Edward; Macías, José Luis; Meriggi, Lorenzo; Santo, Alba Patrizia

    2013-07-01

    San Antonio Volcano, in the Tacaná Volcanic Complex, erupted ~ 1950 yr. B.P., with a Pelean type eruption that produced andesitic pyroclastic surges and block-and-ash flows destroying part of the volcano summit and producing a horse-shoe shaped crater open to the SW. Between 1950 and 800 yr B.P. the eruption continued with effusive andesites followed by a dacite lava flow and a summit dome, all from a single magma batch. All products consist of phenocrysts and microphenocrysts of zoned plagioclase, amphibole, pyroxene, magnetite ± ilmenite, set in partially crystallized groundmass of glass and microlites of the same mineral phases, except for the lack of amphibole. Included in the andesitic blocks of the block-and-ash flow deposit are basaltic andesite enclaves with elongated and ellipsoidal forms and chilled margins. The enclaves have intersertal textures with brown glass between microphenocrysts of plagioclase, hornblende, pyroxene, and olivine, and minor proportions of phenocrysts of plagioclase, hornblende, and pyroxene. A compositional range obtained of blocks and enclaves resulted from mixing between andesite (866 °C ± 22) and basaltic andesite (enclaves, 932 °C ± 22), which may have triggered the explosive Pelean eruption. Vestiges of that mixing are preserved as complex compositional zones in plagioclase and clinopyroxene-rich reaction rims in amphibole in the andesite. Whole-rock chemistry, geothermometry, experimental petrology and modeling results suggest that after the mixing event the eruption tapped hybrid andesitic magma (≤ 900 °C) and ended with effusive dacitic magma (~ 825 °C), all of which were stored at ~ 200 MPa water pressure. A complex open-system evolution that involved crustal end-members best explains the generation of effusive dacite from the hybrid andesite. Amphibole in the dacite is rimmed by reaction products of plagioclase, orthopyroxene, and Fe-Ti oxides produced by decompression during ascent. Amphibole in the andesite

  1. The graphite deposit at Borrowdale (UK): A catastrophic mineralizing event associated with Ordovician magmatism

    Science.gov (United States)

    Ortega, L.; Millward, D.; Luque, F. J.; Barrenechea, J. F.; Beyssac, O.; Huizenga, J.-M.; Rodas, M.; Clarke, S. M.

    2010-04-01

    The volcanic-hosted graphite deposit at Borrowdale in Cumbria, UK, was formed through precipitation from C-O-H fluids. The δ 13C data indicate that carbon was incorporated into the mineralizing fluids by assimilation of carbonaceous metapelites of the Skiddaw Group by andesite magmas of the Borrowdale Volcanic Group. The graphite mineralization occurred as the fluids migrated upwards through normal conjugate fractures forming the main subvertical pipe-like bodies. The mineralizing fluids evolved from CO 2-CH 4-H 2O mixtures (XCO 2 = 0.6-0.8) to CH 4-H 2O mixtures. Coevally with graphite deposition, the andesite and dioritic wall rocks adjacent to the veins were intensely hydrothermally altered to a propylitic assemblage. The initial graphite precipitation was probably triggered by the earliest hydration reactions in the volcanic host rocks. During the main mineralization stage, graphite precipitated along the pipe-like bodies due to CO 2 → C + O 2. This agrees with the isotopic data which indicate that the first graphite morphologies crystallizing from the fluid (cryptocrystalline aggregates) are isotopically lighter than those crystallizing later (flakes). Late chlorite-graphite veins were formed from CH 4-enriched fluids following the reaction CH 4 + O 2 → C + 2H 2O, producing the successive precipitation of isotopically lighter graphite morphologies. Thus, as mineralization proceeded, water-generating reactions were involved in graphite precipitation, further favouring the propylitic alteration. The structural features of the pipe-like mineralized bodies as well as the isotopic homogeneity of graphite suggest that the mineralization occurred in a very short period of time.

  2. Environmental and energy assessment of the use of Andesite in cement

    Directory of Open Access Journals (Sweden)

    Hamidi Moussa

    2018-01-01

    Full Text Available The present study is a contribution to the research of new sources of supply of additions and raw materials in order to valorize local materials in the manufacture of cement. It consists in checking the environmental validity of the industrial use of andesite by evaluating the energy consumption of manufacturing andesitic cement. This evaluation was made on CEMI 52.5R type cement mortars whose basic constituent is clinker, with substitution rates of raw and calcined andesitic rock at 800 °C varying from 0-40%. and this through mechanical performance tests at several deadlines (2 days, 7 days, 28 days and 90 days. The results show that the analysis of the influence on the environment of this addition, in its raw state or calcined at 800 ° C, made it possible to say that globally the impact of andesite on the matrices seems positive to long term. The replacement of the cement by andesite systematically induces a reduction in the energy required to produce one ton of binder, due to the lower energy demand for grinding than that required for the thermal treatment of the clinker. Overall, the energy cost of andesite cement (in kWh per MPa compressive strength is lower than that of ordinary cement for low rates of clinker replacement and obtaining cements with moderate strengths.

  3. Global Volcano Locations Database

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NGDC maintains a database of over 1,500 volcano locations obtained from the Smithsonian Institution Global Volcanism Program, Volcanoes of the World publication. The...

  4. A Scientific Excursion: Volcanoes.

    Science.gov (United States)

    Olds, Henry, Jr.

    1983-01-01

    Reviews an educationally valuable and reasonably well-designed simulation of volcanic activity in an imaginary land. VOLCANOES creates an excellent context for learning information about volcanoes and for developing skills and practicing methods needed to study behavior of volcanoes. (Author/JN)

  5. Update of map the volcanic hazard in the Ceboruco volcano, Nayarit, Mexico

    Science.gov (United States)

    Suarez-Plascencia, C.; Camarena-Garcia, M. A.; Nunez-Cornu, F. J.

    2012-12-01

    The Ceboruco Volcano (21° 7.688 N, 104° 30.773 W) is located in the northwestern part of the Tepic-Zacoalco graben. Its volcanic activity can be divided in four eruptive cycles differentiated by their VEI and chemical variations as well. As a result of andesitic effusive activity, the "paleo-Ceboruco" edifice was constructed during the first cycle. The end of this cycle is defined by a plinian eruption (VEI between 3 and 4) which occurred some 1020 years ago and formed the external caldera. During the second cycle an andesitic dome built up in the interior of the caldera. The dome collapsed and formed the internal caldera. The third cycle is represented by andesitic lava flows which partially cover the northern and south-southwestern part of the edifice. The last cycle is represented by the andesitic lava flows of the nineteenth century located in the southwestern flank of the volcano. Actually, moderate fumarolic activity occurs in the upper part of the volcano showing temperatures ranging between 20° and 120°C. Some volcanic high frequency tremors have also been registered near the edifice. Shows the updating of the volcanic hazard maps published in 1998, where we identify with SPOT satellite imagery and Google Earth, change in the land use on the slope of volcano, the expansion of the agricultural frontier on the east sides of the Ceboruco volcano. The population inhabiting the area is 70,224 people in 2010, concentrated in 107 localities and growing at an annual rate of 0.37%, also the region that has shown an increased in the vulnerability for the development of economic activities, supported by highway, high road, railroad, and the construction of new highway to Puerto Vallarta, which is built in the southeast sector of the volcano and electrical infrastructure that connect the Cajon and Yesca Dams to Guadalajara city. The most important economic activity in the area is agriculture, with crops of sugar cane (Saccharum officinarum), corn, and jamaica

  6. Volcano seismology

    Science.gov (United States)

    Chouet, B.

    2003-01-01

    A fundamental goal of volcano seismology is to understand active magmatic systems, to characterize the configuration of such systems, and to determine the extent and evolution of source regions of magmatic energy. Such understanding is critical to our assessment of eruptive behavior and its hazardous impacts. With the emergence of portable broadband seismic instrumentation, availability of digital networks with wide dynamic range, and development of new powerful analysis techniques, rapid progress is being made toward a synthesis of high-quality seismic data to develop a coherent model of eruption mechanics. Examples of recent advances are: (1) high-resolution tomography to image subsurface volcanic structures at scales of a few hundred meters; (2) use of small-aperture seismic antennas to map the spatio-temporal properties of long-period (LP) seismicity; (3) moment tensor inversions of very-long-period (VLP) data to derive the source geometry and mass-transport budget of magmatic fluids; (4) spectral analyses of LP events to determine the acoustic properties of magmatic and associated hydrothermal fluids; and (5) experimental modeling of the source dynamics of volcanic tremor. These promising advances provide new insights into the mechanical properties of volcanic fluids and subvolcanic mass-transport dynamics. As new seismic methods refine our understanding of seismic sources, and geochemical methods better constrain mass balance and magma behavior, we face new challenges in elucidating the physico-chemical processes that cause volcanic unrest and its seismic and gas-discharge manifestations. Much work remains to be done toward a synthesis of seismological, geochemical, and petrological observations into an integrated model of volcanic behavior. Future important goals must include: (1) interpreting the key types of magma movement, degassing and boiling events that produce characteristic seismic phenomena; (2) characterizing multiphase fluids in subvolcanic

  7. Volcanoes: Nature's Caldrons Challenge Geochemists.

    Science.gov (United States)

    Zurer, Pamela S.

    1984-01-01

    Reviews various topics and research studies on the geology of volcanoes. Areas examined include volcanoes and weather, plate margins, origins of magma, magma evolution, United States Geological Survey (USGS) volcano hazards program, USGS volcano observatories, volcanic gases, potassium-argon dating activities, and volcano monitoring strategies.…

  8. Copahue volcano and its regional magmatic setting

    Science.gov (United States)

    Varekamp, J C; Zareski, J E; Camfield, L M; Todd, Erin

    2016-01-01

    Copahue volcano (Province of Neuquen, Argentina) has produced lavas and strombolian deposits over several 100,000s of years, building a rounded volcano with a 3 km elevation. The products are mainly basaltic andesites, with the 2000–2012 eruptive products the most mafic. The geochemistry of Copahue products is compared with those of the main Andes arc (Llaima, Callaqui, Tolhuaca), the older Caviahue volcano directly east of Copahue, and the back arc volcanics of the Loncopue graben. The Caviahue rocks resemble the main Andes arc suite, whereas the Copahue rocks are characterized by lower Fe and Ti contents and higher incompatible element concentrations. The rocks have negative Nb-Ta anomalies, modest enrichments in radiogenic Sr and Pb isotope ratios and slightly depleted Nd isotope ratios. The combined trace element and isotopic data indicate that Copahue magmas formed in a relatively dry mantle environment, with melting of a subducted sediment residue. The back arc basalts show a wide variation in isotopic composition, have similar water contents as the Copahue magmas and show evidence for a subducted sedimentary component in their source regions. The low 206Pb/204Pb of some backarc lava flows suggests the presence of a second endmember with an EM1 flavor in its source. The overall magma genesis is explained within the context of a subducted slab with sediment that gradually looses water, water-mobile elements, and then switches to sediment melt extracts deeper down in the subduction zone. With the change in element extraction mechanism with depth comes a depletion and fractionation of the subducted complex that is reflected in the isotope and trace element signatures of the products from the main arc to Copahue to the back arc basalts.

  9. A generic model for the shallow velocity structure of volcanoes

    Science.gov (United States)

    Lesage, Philippe; Heap, Michael J.; Kushnir, Alexandra

    2018-05-01

    The knowledge of the structure of volcanoes and of the physical properties of volcanic rocks is of paramount importance to the understanding of volcanic processes and the interpretation of monitoring observations. However, the determination of these structures by geophysical methods suffers limitations including a lack of resolution and poor precision. Laboratory experiments provide complementary information on the physical properties of volcanic materials and their behavior as a function of several parameters including pressure and temperature. Nevertheless combined studies and comparisons of field-based geophysical and laboratory-based physical approaches remain scant in the literature. Here, we present a meta-analysis which compares 44 seismic velocity models of the shallow structure of eleven volcanoes, laboratory velocity measurements on about one hundred rock samples from five volcanoes, and seismic well-logs from deep boreholes at two volcanoes. The comparison of these measurements confirms the strong variability of P- and S-wave velocities, which reflects the diversity of volcanic materials. The values obtained from laboratory experiments are systematically larger than those provided by seismic models. This discrepancy mainly results from scaling problems due to the difference between the sampled volumes. The averages of the seismic models are characterized by very low velocities at the surface and a strong velocity increase at shallow depth. By adjusting analytical functions to these averages, we define a generic model that can describe the variations in P- and S-wave velocities in the first 500 m of andesitic and basaltic volcanoes. This model can be used for volcanoes where no structural information is available. The model can also account for site time correction in hypocenter determination as well as for site and path effects that are commonly observed in volcanic structures.

  10. Volcanoes: observations and impact

    Science.gov (United States)

    Thurber, Clifford; Prejean, Stephanie G.

    2012-01-01

    Volcanoes are critical geologic hazards that challenge our ability to make long-term forecasts of their eruptive behaviors. They also have direct and indirect impacts on human lives and society. As is the case with many geologic phenomena, the time scales over which volcanoes evolve greatly exceed that of a human lifetime. On the other hand, the time scale over which a volcano can move from inactivity to eruption can be rather short: months, weeks, days, and even hours. Thus, scientific study and monitoring of volcanoes is essential to mitigate risk. There are thousands of volcanoes on Earth, and it is impractical to study and implement ground-based monitoring at them all. Fortunately, there are other effective means for volcano monitoring, including increasing capabilities for satellite-based technologies.

  11. Phonon scattering in graphite

    International Nuclear Information System (INIS)

    Wagner, P.

    1976-04-01

    Effects on graphite thermal conductivities due to controlled alterations of the graphite structure by impurity addition, porosity, and neutron irradiation are shown to be consistent with the phonon-scattering formulation 1/l = Σ/sub i equals 1/sup/n/ 1/l/sub i/. Observed temperature effects on these doped and irradiated graphites are also explained by this mechanism

  12. An overview of the 2009 eruption of Redoubt Volcano, Alaska

    Science.gov (United States)

    Bull, Katharine F.; Buurman, Helena

    2013-06-01

    In March 2009, Redoubt Volcano, Alaska erupted for the first time since 1990. Explosions ejected plumes that disrupted international and domestic airspace, sent lahars more than 35 km down the Drift River to the coast, and resulted in tephra fall on communities over 100 km away. Geodetic data suggest that magma began to ascend slowly from deep in the crust and reached mid- to shallow-crustal levels as early as May, 2008. Heat flux at the volcano during the precursory phase melted ~ 4% of the Drift glacier atop Redoubt's summit. Petrologic data indicate the deeply sourced magma, low-silica andesite, temporarily arrested at 9-11 km and/or at 4-6 km depth, where it encountered and mixed with segregated stored high-silica andesite bodies. The two magma compositions mixed to form intermediate-silica andesite, and all three magma types erupted during the earliest 2009 events. Only intermediate- and high-silica andesites were produced throughout the explosive and effusive phases of the eruption. The explosive phase began with a phreatic explosion followed by a seismic swarm, which signaled the start of lava effusion on March 22, shortly prior to the first magmatic explosion early on March 23, 2009 (UTC). More than 19 explosions (or “Events”) were produced over 13 days from a single vent immediately south of the 1989-90 lava domes. During that period multiple small pyroclastic density currents flowed primarily to the north and into glacial ravines, three major lahars flooded the Drift River Terminal over 35 km down-river on the coast, tephra fall deposited on all aspects of the edifice and on several communities north and east of the volcano, and at least two, and possibly three lava domes were emplaced. Lightning accompanied almost all the explosions. A shift in the eruptive character took place following Event 9 on March 27 in terms of infrasound signal onsets, the character of repeating earthquakes, and the nature of tephra ejecta. More than nine additional

  13. Visions of Volcanoes

    Directory of Open Access Journals (Sweden)

    David M. Pyle

    2017-12-01

    Full Text Available The long nineteenth century marked an important transition in the understanding of the nature of combustion and fire, and of volcanoes and the interior of the earth. It was also a period when dramatic eruptions of Vesuvius lit up the night skies of Naples, providing ample opportunities for travellers, natural philosophers, and early geologists to get up close to the glowing lavas of an active volcano. This article explores written and visual representations of volcanoes and volcanic activity during the period, with the particular perspective of writers from the non-volcanic regions of northern Europe. I explore how the language of ‘fire’ was used in both first-hand and fictionalized accounts of peoples’ interactions with volcanoes and experiences of volcanic phenomena, and see how the routine or implicit linkage of ‘fire’ with ‘combustion’ as an explanation for the deep forces at play within and beneath volcanoes slowly changed as the formal scientific study of volcanoes developed. I show how Vesuvius was used as a ‘model’ volcano in science and literature and how, later, following devastating eruptions in Indonesia and the Caribbean, volcanoes took on a new dimension as contemporary agents of death and destruction.

  14. Ring and Volcano Structures Formed by a Metal Dipyrromethene Complex

    Energy Technology Data Exchange (ETDEWEB)

    Son, Seung Bae; Hahn, Jae Ryang [Chonbuk National Univ., Jeonju (Korea, Republic of); Miao, Qing; Shin, Jiyoung; Dolphin, David [Univ. of British Columbia, Columbia (Canada)

    2014-06-15

    Dichloromethane liquid droplets containing a cobalt dipyrromethene trimer deposited on a graphite surface were found to form coffee ring, toroid ring, or volcano dot structures due to the redistribution of the solute during solvent evaporation. The shapes and size distributions of the ring structures depended on the drying temperature. The shape differences were attributed to the fact that the solvent evaporation rate controlled the self-assembly process that yielded the coffee stain and pinhole structures.

  15. The material from Lampung as coarse aggregate to substitute andesite for concrete-making

    Science.gov (United States)

    Amin, M.; Supriyatna, Y. I.; Sumardi, S.

    2018-01-01

    Andesite stone is usually used for split stone material in the concrete making. However, its availability is decreasing. Lampung province has natural resources that can be used for coarse aggregate materials to substitute andesite stone. These natural materials include limestone, feldspar stone, basalt, granite, and slags from iron processing waste. Therefore, a research on optimizing natural materials in Lampung to substitute andesite stone for concrete making is required. This research used laboratory experiment method. The research activities included making cubical object samples of 150 x 150 x 150 mm with material composition referring to a standard of K.200 and w/c 0.61. Concrete making by using varying types of aggregates (basalt, limestone, slag) and aggregate sizes (A = 5-15 mm, B = 15-25 mm, and 25-50 mm) was followed by compressive strength test. The results showed that the obtained optimal compressive strengths for basalt were 24.47 MPa for 50-150 mm aggregate sizes, 21.2 MPa for 15-25 mm aggregate sizes, and 20.7 MPa for 25-50 mm aggregate sizes. These results of basalt compressive strength values were higher than the same result for andesite (19.69 MPa for 50-150 mm aggregate sizes), slag (22.72 MPa for 50-150 mm aggregate sizes), and limestone (19.69 Mpa for 50-150 mm aggregate sizes). These results indicated that basalt, limestone, and slag aggregates were good enough to substitute andesite as materials for concrete making. Therefore, natural resources in Lampung can be optimized as construction materials in concrete making.

  16. A graphite nanoeraser

    DEFF Research Database (Denmark)

    Liu, Ze; Bøggild, Peter; Yang, Jia-rui

    2011-01-01

    We present here a method for cleaning intermediate-size (up to 50 nm) contamination from highly oriented pyrolytic graphite and graphene. Electron-beam-induced deposition of carbonaceous material on graphene and graphite surfaces inside a scanning electron microscope, which is difficult to remove...... by conventional techniques, can be removed by direct mechanical wiping using a graphite nanoeraser, thus drastically reducing the amount of contamination. We discuss potential applications of this cleaning procedure....

  17. Vulnerability mapping in kelud volcano based on village information

    Science.gov (United States)

    Hisbaron, D. R.; Wijayanti, H.; Iffani, M.; Winastuti, R.; Yudinugroho, M.

    2018-04-01

    Kelud Volcano is a basaltic andesitic stratovolcano, situated at 27 km to the east of Kediri, Indonesia. Historically, Kelud Volcano has erupted with return period of 9-75 years, had caused nearly 160,000 people living in Tulungagung, Blitar and Kediri District to be in high-risk areas. This study aims to map vulnerability towards lava flows in Kediri and Malang using detailed scale. There are four major variables, namely demography, asset, hazard, and land use variables. PGIS (Participatory Geographic Information System) is employed to collect data, while ancillary data is derived from statistics information, interpretation of high resolution satellite imagery and Unmanned Aerial Vehicles (UAVs). Data were obtained from field checks and some from high resolution satellite imagery and UAVs. The output of this research is village-based vulnerability information that becomes a valuable input for local stakeholders to improve local preparedness in areas prone to improved disaster resilience. The results indicated that the highest vulnerability to lava flood disaster in Kelud Volcano is owned by Kandangan Hamlet, Pandean Hamlet and Kacangan Hamlet, because these two hamlets are in the dominant high vulnerability position of 3 out of 4 scenarios (economic, social and equal).

  18. Oxidation Resistant Graphite Studies

    Energy Technology Data Exchange (ETDEWEB)

    W. Windes; R. Smith

    2014-07-01

    The Very High Temperature Reactor (VHTR) Graphite Research and Development Program is investigating doped nuclear graphite grades exhibiting oxidation resistance. During a oxygen ingress accident the oxidation rates of the high temperature graphite core region would be extremely high resulting in significant structural damage to the core. Reducing the oxidation rate of the graphite core material would reduce the structural effects and keep the core integrity intact during any air-ingress accident. Oxidation testing of graphite doped with oxidation resistant material is being conducted to determine the extent of oxidation rate reduction. Nuclear grade graphite doped with varying levels of Boron-Carbide (B4C) was oxidized in air at nominal 740°C at 10/90% (air/He) and 100% air. The oxidation rates of the boronated and unboronated graphite grade were compared. With increasing boron-carbide content (up to 6 vol%) the oxidation rate was observed to have a 20 fold reduction from unboronated graphite. Visual inspection and uniformity of oxidation across the surface of the specimens were conducted. Future work to determine the remaining mechanical strength as well as graphite grades with SiC doped material are discussed.

  19. Sr isotope zoning in plagioclase from andesites at Cabo De Gata, Spai

    DEFF Research Database (Denmark)

    Waight, Tod Earle; Tørnqvist, Jakob

    2018-01-01

    Plagioclase crystals in andesites from the Cabo De Gata region show generally radiogenic Sr isotope compositions and consistent core to rim increases in 87Sr/86Sr that are indicative of open system processes in the lithosphere and crustal contamination during crystallization. High-grade metamorphic...... rocks of the Alpujárride and Nevado-Filábride complexes represent the most likely crustal contaminants. The plagioclases are characterized by subtly zoned and resorbed calcic cores (An73-86). These cores also have radiogenic 87Sr/86Sr (0.7127-0.7129), although less radiogenic than plagioclase rims......, groundmass plagioclase and whole rock compositions (up to 87Sr/86Sr = 0.7135). These cores are interpreted to represent early crystallization of plagioclase from hydrous melts emplaced into the lower crust. The parental melts to these andesites must therefore have already inherited their radiogenic Sr...

  20. PENENTUAN TAHANAN JENIS BATUAN ANDESIT MENGGUNAKAN METODE GEOLISTRIK KONFIGURASI SCHLUMBERGER (STUDI KASUS DESA POLOSIRI

    Directory of Open Access Journals (Sweden)

    - Munaji

    2013-11-01

    Full Text Available Telah dilakukan penelitian untuk menentukan nilai resistivitas dan kedalaman batuan andesit di Desa Polosiri. Prinsip kerja metode geolistrik adalah mempelajari aliran listrik di dalam bumi dan cara mendeteksi di permukaan bumi. Metode tahanan jenis didasari oleh hukum Ohm, untuk mengetahui jenis lapisan batuan didasarkan pada distribusi nilai resistivitas pada tiap lapisan. Variasi harga tahanan jenis akan didapatkan jika jarak masing-masing elektroda diubah, sesuai konfigurasi alat yang dipakai (konfigurasi Schlumberger. Data hasil pengukuran di lapangan berupa beda potensial dan arus yang dapat digunakan untuk menghitung resistivitas semu. Penelitian ini dilakukan sebanyak tiga lintasan. Data hasil pengukuran diolah menggunakan software IPI2Win. Berdasarkan hasil penelitian diperoleh bahwa batuan andesit di Desa Polisiri memiliki resistivitas 212 Ωm – 300 Ωm dengan kedalaman 1.3 m - 1.86 m.

  1. Method for producing dustless graphite spheres from waste graphite fines

    Science.gov (United States)

    Pappano, Peter J [Oak Ridge, TN; Rogers, Michael R [Clinton, TN

    2012-05-08

    A method for producing graphite spheres from graphite fines by charging a quantity of spherical media into a rotatable cylindrical overcoater, charging a quantity of graphite fines into the overcoater thereby forming a first mixture of spherical media and graphite fines, rotating the overcoater at a speed such that the first mixture climbs the wall of the overcoater before rolling back down to the bottom thereby forming a second mixture of spherical media, graphite fines, and graphite spheres, removing the second mixture from the overcoater, sieving the second mixture to separate graphite spheres, charging the first mixture back into the overcoater, charging an additional quantity of graphite fines into the overcoater, adjusting processing parameters like overcoater dimensions, graphite fines charge, overcoater rotation speed, overcoater angle of rotation, and overcoater time of rotation, before repeating the steps until graphite fines are converted to graphite spheres.

  2. Graphite targets at LAMPF

    International Nuclear Information System (INIS)

    Brown, R.D.; Grisham, D.L.

    1983-01-01

    Rotating polycrystalline and stationary pyrolytic graphite target designs for the LAMPF experimental area are described. Examples of finite element calculations of temperatures and stresses are presented. Some results of a metallographic investigation of irradiated pyrolytic graphite target plates are included, together with a brief description of high temperature bearings for the rotating targets

  3. K-Ar age of bronzite-andesite from Choshi, Chiba Prefecture, Japan

    International Nuclear Information System (INIS)

    Tatsumi, Yoshiyuki; Ishizaka, Kyoichi

    1979-01-01

    The authors have forwarded the study on the activity period of Setouchi volcanic rocks and the research on Sanukitoid which characterizes it. It was already mentioned that the activity period of Setouchi volcanic rocks is only the middle period of Mid-cainozoic era, and that Setouchi volcanic rocks can be treated as one rock region. In this paper, the K-Ar age of bronzite-andesite in Choshi, Chiba Prefecture, is reported, which the authors think as the eastern end of Setouchi volcanic rock region. The outline of the geological features in the vicinity of Choshi is explained. The rock samples for the measurement were collected in May, 1978, in the reconstruction site of the fishing port. The rock samples were fresh, and the effects of degeneration, wathering and others were not observed. The K-Ar age of these bronzite-andesite was determined by Teledyne Isotopes Co. in commission. The determination of K and Ar was carried out on all rock samples twice respectively. The isotopic age of the bronzite-andesite in Choshi was 11.8 +- 0.6 m.y., and it was produced by the volcanic activity in the middle period of Mid-cainozoic era, same as the volcanic rocks of Setouchi. It is considered that the eastern end of Setouchi volcanic rock region is Choshi according to the results of chemical properties and isotopic age. (Kako, I.)

  4. Melting of hydrous upper mantle and possible generation of andesitic magma: an approach from synthetic systems

    Energy Technology Data Exchange (ETDEWEB)

    Kushiro, I

    1974-07-01

    Phase equilibria in a portion of the system forsterite--plagioclase (An/sub 50/Ab/sub 50/ by weight)--silica--H/sub 2/O have been determined at 15 kbar pressure under H/sub 2/O-saturated conditions. The composition of the liquid pertinent to the piercing point forsterite + enstatite solid solution + amphibole + liquid + vapor is similar to that of calc-alkaline andesite. The electron microprobe analysis of the glass coexisting with the above three crystalline phases is very close to that of the piercing point determined by phase assemblage observations; however, the glass near (less than 8 ..mu..m) forsterite crystals is significantly depleted in the normative forsterite component. With the addition of 10 wt. percent KAlSi/sub 3/O/sub 8/, the composition of this piercing point becomes even closer to the compositions of calc-alkaline andesites. It is also shown that the liquid coexisting with forsterite and enstatite solid solution remains silica-rich (60 to 62 wt. percent) over a wide (approximately 100/sup 0/C) temperature range. The present experimental studies support the view that liquids similar in composition to calc-alkaline andesites can be generated by direct partial melting of hydrous upper mantle at least at or near 15 kbar.

  5. Isotopic composition of strontium in three basalt-andesite centers along the Lesser Antilles arc

    Science.gov (United States)

    Hedge, C.E.; Lewis, J.F.

    1971-01-01

    Si87/Sr86 ratios have been determined for lavas and py lastic rocks from three basalt-andesite centers along the Lesser Antilles arc-Mt. Misery on the island of St. Kitts, Soufriere on the island of St. Vincent, and Carriacou, an island of The Grenadines. The average Si87/Sr86 content of these rocks is 0.7038 for Mt. Misery, 0.7041 for Soufriere, and 0.7053 for Carriacou. All the Sr87/Sr86 values from each center are the same within analytical uncertainty (??0.0002). The constancy of strontium isotopic data within each center supports the hypothesis that basalts and andesites for each specific center investigated are generated from the same source - in agreement with petrographic and major- and minor-element data. Strontium isotopic compositions and elemental concentrations, particularly of strontium and nickel, indicate that this source was mantle peridotite and that the relationship between the respective basalts and andesites is probably fractional crystallization. ?? 1971 Springer-Verlag.

  6. Electrochemical treatment of graphite

    Energy Technology Data Exchange (ETDEWEB)

    Podlovilin, V.I.; Egorov, I.M.; Zhernovoj, A.I.

    1983-01-01

    In the course of investigating various modes of electrochemical treatment (ECT) it has been found that graphite anode treatment begins under the ''glow mode''. A behaviour of some marks of graphite with the purpose of ECT technique development in different electrolytes has been tested. Electrolytes have been chosen of three types: highly alkaline (pH 13-14), neutral (pH-Z) and highly acidic (pH 1-2). For the first time parallel to mechanical electroerosion treatment, ECT of graphite and carbon graphite materials previously considered chemically neutral is proposed. ECT of carbon graphite materials has a number of advantages as compared with electroerrosion and mechanical ones with respect to the treatment rate and purity (ronghness) of the surface. A small quantity of sludge (6-8%) under ECT is in highly alkali electrolytes.

  7. Electrochemical treatment of graphite

    International Nuclear Information System (INIS)

    Podlovilin, V.I.; Egorov, I.M.; Zhernovoj, A.I.

    1983-01-01

    In the course of investigating various modes of electroche-- mical treatment (ECT) it has been found that graphite anode treatment begins under the ''glow mode''. A behaviour of some marks of graphite with the purpose of ECT technique development in different electrolytes has been tested. Electrolytes have been chosen of three types: highly alkaline (pH 13-14), neutral (pH-Z) and highly acidic (pH 1-2). For the first time parallel to mechanical electroerosion treatment ECT graphite and carbon graphite materials previously considered chemically neutral is proposed. ECT of carbon graphite materials has a number of advantages as compared with electroerrosion and mechanical ones this is treatment rate and purity (ronghness) of the surface. A sMall quantity of sludge (6-8%) under ECT is in highly alkali electrolytes

  8. Cristobalite in volcanic ash of the soufriere hills volcano, montserrat, british west indies

    Science.gov (United States)

    Baxter; Bonadonna; Dupree; Hards; Kohn; Murphy; Nichols; Nicholson; Norton; Searl; Sparks; Vickers

    1999-02-19

    Crystalline silica (mostly cristobalite) was produced by vapor-phase crystallization and devitrification in the andesite lava dome of the Soufriere Hills volcano, Montserrat. The sub-10-micrometer fraction of ash generated by pyroclastic flows formed by lava dome collapse contains 10 to 24 weight percent crystalline silica, an enrichment of 2 to 5 relative to the magma caused by selective crushing of the groundmass. The sub-10-micrometer fraction of ash generated by explosive eruptions has much lower contents (3 to 6 percent) of crystalline silica. High levels of cristobalite in respirable ash raise concerns about adverse health effects of long-term human exposure to ash from lava dome eruptions.

  9. Eruption of soufriere volcano on st. Vincent island, 1971-1972.

    Science.gov (United States)

    Aspinall, W P; Sigurdsson, H; Shepherd, J B

    1973-07-13

    The Soufrière volcano in St. Vincent erupted from October 1971 to March 1972, as 80 x 10(6) m(3) of basaltic andesite lava was quietly extruded inside the mile-wide crater. The eruption was largely subaqueous, taking place in the 180-m-deep crater lake, and resulted in the emergence of a steep-sided island. The mild character of the eruption and the absence of seismic activity stand in direct contrast to the highly explosive character of the eruption of 1902 to 1903.

  10. Manupulation of microstructure, phase evolution and mechanical properties by devitrification of andesite for use as proppant

    Science.gov (United States)

    Koseski, Ryan P.

    Small, roughly spherical ceramic particles, approximately 1mm in size are used for a number of applications including casting sands, catalysts, and cement fillers. The oil and natural gas industry utilizes such materials in tonnage quantities yearly as extraction aids. Particles intended for this application are referred to as proppants. Proppants are composed of materials that differ by density, strength and cost, and are selected on a site by site basis. Recently, competing usage and depletion of reserves of one of the most popular category of proppant materials, sintered aluminosilicates (e.g. kaolinite, bauxite) have driven the need for alternative raw materials for proppant manufacturing. Andesite, a by-product of mining operations in the south-west United States was identified as an abundant, readily available, and low cost alternative proppant material that can be fused and net-shaped into a glass which when crystallized results in microstructures which may offer substantial toughening and fracture characteristics which may serve to their advantage for use as proppants that do not decrease the permeability ("blind") the particle bed. This study addressed the devitrification behavior and its role on the mechanical properties of andesite-based glass-ceramic spheres for use as proppants. Timetemperature- transformation studies were performed to evaluate the devitrification behavior of andesite glass. Crystalline phase evolution and microstructural development were evaluated using quantitative x-ray diffraction, scanning electron microscopy, differential thermal analysis, and spectrophotometry. The andesite glass devitrification commenced with the precipitation of iron oxides (magnetite) which served as seeds for the epitaxial growth of dendritic pyroxenes. Mechanical properties, such as diametral compressive strength, fracture toughness, hardness, and fracture morphology were correlated with crystalline phase evolution. Selected heat treatments resulting in the

  11. Digital Geologic Map Database of Medicine Lake Volcano, Northern California

    Science.gov (United States)

    Ramsey, D. W.; Donnelly-Nolan, J. M.; Felger, T. J.

    2010-12-01

    map, whose area is partly covered by a late Holocene andesite flow. Silicic lava flows are mostly confined to the main edifice of the volcano, with the youngest rhyolite flows found in and near the summit caldera, including the rhyolitic Little Glass Mountain (~1,000 yr B.P.) and Glass Mountain (~950 yr B.P.) flows, which are the youngest eruptions at Medicine Lake volcano. In postglacial time, 17 eruptions have added approximately 7.5 km3 to the volcano’s total estimated volume of 600 km3, which may be the largest by volume among Cascade Range volcanoes. The volcano has erupted nine times in the past 5,200 years, a rate more frequent than has been documented at all other Cascade volcanoes except Mount St. Helens.

  12. Asymptomatic Intracorneal Graphite Deposits following Graphite Pencil Injury

    OpenAIRE

    Philip, Swetha Sara; John, Deepa; John, Sheeja Susan

    2012-01-01

    Reports of graphite pencil lead injuries to the eye are rare. Although graphite is considered to remain inert in the eye, it has been known to cause severe inflammation and damage to ocular structures. We report a case of a 12-year-old girl with intracorneal graphite foreign bodies following a graphite pencil injury.

  13. Cook Inlet and Kenai Peninsula, Alaska ESI: VOLCANOS (Volcano Points)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This data set contains the locations of volcanos in Cook Inlet and Kenai Peninsula, Alaska. Vector points in the data set represent the location of the volcanos....

  14. The 2003 phreatomagmatic eruptions of Anatahan volcano - Textural and petrologic features of deposits at an emergent island volcano

    Science.gov (United States)

    Pallister, J.S.; Trusdell, F.A.; Brownfield, I.K.; Siems, D.F.; Budahn, J.R.; Sutley, S.F.

    2005-01-01

    Stratigraphic and field data are used in conjunction with textural and chemical evidence (including data from scanning electron microscope, electron microprobe, X-ray fluorescence, X-ray diffraction, and instrumental neutron activation analysis) to establish that the 2003 eruption of Anatahan volcano was mainly phreatomagmatic, dominated by explosive interaction of homogeneous composition low-viscosity crystal-poor andesite magma with water. The hydromagmatic mode of eruption contributed to the significant height of initial eruptive columns and to the excavation and eruption of altered rock debris from the sub-volcanic hydrothermal system. Volatile contents of glass inclusions in equilibrium phenocrysts less abundances of these constituents in matrix glass times the estimated mass of juvenile magma indicate minimum emissions of 19 kt SO2 and 13 kt Cl. This petrologic estimate of SO2 emission is an order-of-magnitude less than an estimate from TOMS. Similarly, inferred magma volumes from the petrologic data are an order of magnitude greater than those modeled from deformation data. Both discrepancies indicate additional sources of volatiles, likely derived from a separate fluid phase in the magma. The paucity of near-source volcanic-tectonic earthquakes preceding the eruption, and the dominance of sustained long-period tremor are attributed to the ease of ascent of the hot low-viscosity andesite, followed by a shallow phreatomagmatic mode of eruption. Phreatomagmatic eruptions are probably more common at emergent tropical island volcanoes, where shallow fresh-water lenses occur at near-sea-level vents. These relations suggest that phreatomagmatic explosions contributed to the formation of many of the near-sea-level craters and possibly even to the small calderas at the other Mariana islands.

  15. Sr, Nd and Pb isotope and geochemical data from the Quaternary Nevado de Toluca volcano, a source of recent adakitic magmatism, and the Tenango Volcanic Field, Mexico

    Science.gov (United States)

    Martínez-Serrano, Raymundo G.; Schaaf, Peter; Solís-Pichardo, Gabriela; Hernández-Bernal, Ma. del Sol; Hernández-Treviño, Teodoro; Julio Morales-Contreras, Juan; Macías, José Luis

    2004-11-01

    Volcanic activity at Nevado de Toluca (NT) volcano began 2.6 Ma ago with the emission of andesitic lavas, but over the past 40 ka, eruptions have produced mainly lava flows and pyroclastic deposits of predominantly orthopyroxene-hornblende dacitic composition. In the nearby Tenango Volcanic Field (TVF) pyroclastic products and lava flows ranging in composition from basaltic andesite to andesite were erupted at most of 40 monogenetic volcanic centers and were coeval with the last stages of NT. All volcanic rocks in the study area are characterized by a calc-alkaline affinity that is consistent with a subduction setting. Relatively high concentrations of Sr (>460 ppm) coupled with low Y (45 km) that underlies the volcanoes of the study area, the geochemical and isotopic patterns of these rocks indicate low interaction with this crust. NT volcano was constructed at the intersection of three fault systems, and it seems that the Plio-Quaternary E-W system played an important role in the ascent and storage of magmas during the recent volcanic activity in the two regions. Chemical and textural features of orthopyroxene, amphibole and Fe-Ti oxides from NT suggest that crystallization of magmas occurred at polybaric conditions, confirming the rapid upwelling of magmas.

  16. Recent developments in graphite

    International Nuclear Information System (INIS)

    Cunningham, J.E.

    1983-01-01

    Overall, the HTGR graphite situation is in excellent shape. In both of the critical requirements, fuel blocks and support structures, adequate graphites are at hand and improved grades are sufficiently far along in truncation. In the aerospace field, GraphNOL N3M permits vehicle performance with confidence in trajectories unobtainable with any other existing material. For fusion energy applications, no other graphite can simultaneously withstand both extreme thermal shock and neutron damage. Hence, the material promises to create new markets as well as to offer a better candidate material for existing applications

  17. Graphite for fusion energy applications

    International Nuclear Information System (INIS)

    Eatherly, W.P.; Clausing, R.E.; Strehlow, R.A.; Kennedy, C.R.; Mioduszewski, P.K.

    1987-03-01

    Graphite is in widespread and beneficial use in present fusion energy devices. This report reflects the view of graphite materials scientists on using graphite in fusion devices. Graphite properties are discussed with emphasis on application to fusion reactors. This report is intended to be introductory and descriptive and is not intended to serve as a definitive information source

  18. Volcanoes: Coming Up from Under.

    Science.gov (United States)

    Science and Children, 1980

    1980-01-01

    Provides specific information about the eruption of Mt. St. Helens in March 1980. Also discusses how volcanoes are formed and how they are monitored. Words associated with volcanoes are listed and defined. (CS)

  19. Organizational changes at Earthquakes & Volcanoes

    Science.gov (United States)

    Gordon, David W.

    1992-01-01

    Primary responsibility for the preparation of Earthquakes & Volcanoes within the Geological Survey has shifted from the Office of Scientific Publications to the Office of Earthquakes, Volcanoes, and Engineering (OEVE). As a consequence of this reorganization, Henry Spall has stepepd down as Science Editor for Earthquakes & Volcanoes(E&V).

  20. Late Holocene volcanism at Medicine Lake Volcano, northern California Cascades

    Science.gov (United States)

    Donnelly-Nolan, Julie M.; Champion, Duane E.; Grove, Timothy L.

    2016-05-23

    Late Holocene volcanism at Medicine Lake volcano in the southern Cascades arc exhibited widespread and compositionally diverse magmatism ranging from basalt to rhyolite. Nine well-characterized eruptions have taken place at this very large rear-arc volcano since 5,200 years ago, an eruptive frequency greater than nearly all other Cascade volcanoes. The lavas are widely distributed, scattered over an area of ~300 km2 across the >2,000-km2 volcano. The eruptions are radiocarbon dated and the ages are also constrained by paleomagnetic data that provide strong evidence that the volcanic activity occurred in three distinct episodes at ~1 ka, ~3 ka, and ~5 ka. The ~1-ka final episode produced a variety of compositions including west- and north-flank mafic flows interspersed in time with fissure rhyolites erupted tangential to the volcano’s central caldera, including the youngest and most spectacular lava flow at the volcano, the ~950-yr-old compositionally zoned Glass Mountain flow. At ~3 ka, a north-flank basalt eruption was followed by an andesite eruption 27 km farther south that contains quenched basalt inclusions. The ~5-ka episode produced two caldera-focused dacitic eruptions. Quenched magmatic inclusions record evidence of intrusions that did not independently reach the surface. The inclusions are present in five andesitic, dacitic, and rhyolitic host lavas, and were erupted in each of the three episodes. Compositional and mineralogic evidence from mafic lavas and inclusions indicate that both tholeiitic (dry) and calcalkaline (wet) parental magmas were present. Petrologic evidence records the operation of complex, multi-stage processes including fractional crystallization, crustal assimilation, and magma mixing. Experimental evidence suggests that magmas were stored at 3 to 6 km depth prior to eruption, and that both wet and dry parental magmas were involved in generating the more silicic magmas. The broad distribution of eruptive events and the relative

  1. Hawaii's volcanoes revealed

    Science.gov (United States)

    Eakins, Barry W.; Robinson, Joel E.; Kanamatsu, Toshiya; Naka, Jiro; Smith, John R.; Takahashi, Eiichi; Clague, David A.

    2003-01-01

    Hawaiian volcanoes typically evolve in four stages as volcanism waxes and wanes: (1) early alkalic, when volcanism originates on the deep sea floor; (2) shield, when roughly 95 percent of a volcano's volume is emplaced; (3) post-shield alkalic, when small-volume eruptions build scattered cones that thinly cap the shield-stage lavas; and (4) rejuvenated, when lavas of distinct chemistry erupt following a lengthy period of erosion and volcanic quiescence. During the early alkalic and shield stages, two or more elongate rift zones may develop as flanks of the volcano separate. Mantle-derived magma rises through a vertical conduit and is temporarily stored in a shallow summit reservoir from which magma may erupt within the summit region or be injected laterally into the rift zones. The ongoing activity at Kilauea's Pu?u ?O?o cone that began in January 1983 is one such rift-zone eruption. The rift zones commonly extend deep underwater, producing submarine eruptions of bulbous pillow lava. Once a volcano has grown above sea level, subaerial eruptions produce lava flows of jagged, clinkery ?a?a or smooth, ropy pahoehoe. If the flows reach the ocean they are rapidly quenched by seawater and shatter, producing a steep blanket of unstable volcanic sediment that mantles the upper submarine slopes. Above sea level then, the volcanoes develop the classic shield profile of gentle lava-flow slopes, whereas below sea level slopes are substantially steeper. While the volcanoes grow rapidly during the shield stage, they may also collapse catastrophically, generating giant landslides and tsunami, or fail more gradually, forming slumps. Deformation and seismicity along Kilauea's south flank indicate that slumping is occurring there today. Loading of the underlying Pacific Plate by the growing volcanic edifices causes subsidence, forming deep basins at the base of the volcanoes. Once volcanism wanes and lava flows no longer reach the ocean, the volcano continues to submerge, while

  2. Carbon-14 Graphitization Chemistry

    Science.gov (United States)

    Miller, James; Collon, Philippe; Laverne, Jay

    2014-09-01

    Accelerator Mass Spectrometry (AMS) is a process that allows for the analysis of mass of certain materials. It is a powerful process because it results in the ability to separate rare isotopes with very low abundances from a large background, which was previously impossible. Another advantage of AMS is that it only requires very small amounts of material for measurements. An important application of this process is radiocarbon dating because the rare 14C isotopes can be separated from the stable 14N background that is 10 to 13 orders of magnitude larger, and only small amounts of the old and fragile organic samples are necessary for measurement. Our group focuses on this radiocarbon dating through AMS. When performing AMS, the sample needs to be loaded into a cathode at the back of an ion source in order to produce a beam from the material to be analyzed. For carbon samples, the material must first be converted into graphite in order to be loaded into the cathode. My role in the group is to convert the organic substances into graphite. In order to graphitize the samples, a sample is first combusted to form carbon dioxide gas and then purified and reduced into the graphite form. After a couple weeks of research and with the help of various Physics professors, I developed a plan and began to construct the setup necessary to perform the graphitization. Once the apparatus is fully completed, the carbon samples will be graphitized and loaded into the AMS machine for analysis.

  3. Melting temperature of graphite

    International Nuclear Information System (INIS)

    Korobenko, V.N.; Savvatimskiy, A.I.

    2001-01-01

    Full Text: Pulse of electrical current is used for fast heating (∼ 1 μs) of metal and graphite specimens placed in dielectric solid media. Specimen consists of two strips (90 μm in thick) placed together with small gap so they form a black body model. Quasy-monocrystal graphite specimens were used for uniform heating of graphite. Temperature measurements were fulfilled with fast pyrometer and with composite 2-strip black body model up to melting temperature. There were fulfilled experiments with zirconium and tungsten of the same black body construction. Additional temperature measurements of liquid zirconium and liquid tungsten are made. Specific heat capacity (c P ) of liquid zirconium and of liquid tungsten has a common feature in c P diminishing just after melting. It reveals c P diminishing after melting in both cases over the narrow temperature range up to usual values known from steady state measurements. Over the next wide temperature range heat capacity for W (up to 5000 K) and Zr (up to 4100 K) show different dependencies of heat capacity on temperature in liquid state. The experiments confirmed a high quality of 2-strip black body model used for graphite temperature measurements. Melting temperature plateau of tungsten (3690 K) was used for pyrometer calibration area for graphite temperature measurement. As a result, a preliminary value of graphite melting temperature of 4800 K was obtained. (author)

  4. In-situ observations of bubble growth in basaltic, andesitic and rhyodacitic melts

    Science.gov (United States)

    Masotta, M.; Ni, H.; Keppler, H.

    2013-12-01

    Bubble growth strongly affects the physical properties of degassing magmas and their eruption dynamics. Natural samples and products from quench experiments provide only a snapshot of the final state of volatile exsolution, leaving the processes occurring during its early stages unconstrained. In order to fill this gap, we present in-situ high-temperature observations of bubble growth in magmas of different compositions (basalt, andesite and rhyodacite) at 1100 to 1240 °C and 1 bar, obtained using a moissanite cell apparatus. The data show that nucleation occurs at very small degrees of supersaturaturation (bubbles occurring simultaneously with the nucleation of crystals. During the early stages of exsolution, melt degassing is the driving mechanism of bubble growth, with coalescence becoming increasingly important as exsolution progresses. Ostwald ripening occurs only at the end of the process and only in basaltic melt. The average bubble growth rate (GR) ranges from 3.4*10-6 to 5.2*10-7 mm/s, with basalt and andesite showing faster growth rates than rhyodacite. The bubble number density (NB) at nucleation ranges from 1.8*108 to 7.9*107 cm-3 and decreases exponentially over time. While the rhyodacite melt maintained a well-sorted bubble-size distribution (BSD) through time, the BSD's of basalt and andesite are much more inhomogeneous. Our experimental observations demonstrate that bubble growth cannot be ascribed to a single mechanism but is rather a combination of many processes, which depend on the physical properties of the melt. Depending on coalescence rate, annealing of bubbles following a single nucleation event can produce complex bubble size distributions. In natural samples, such BSD's may be misinterpreted as resulting from several separate nucleation events. Incipient crystallization upon cooling of a magma may allow bubble nucleation already at very small degrees of supersaturation and could therefore be an important trigger for volatile release and

  5. Magma evolution at Copahue volcano (Chile/Argentina border): insights from melt inclusions

    Science.gov (United States)

    Cannatelli, C.; Aracena, C.; Leisen, M.; Moncada, D.; Roulleau, E.; Vinet, N.; Petrelli, M.; Paolillo, A.; Barra, F.; Morata, D.

    2016-12-01

    Copahue volcano is an active stratovolcano in the Andean Southern Volcanic Zone (SVZ), straddling at the border between Central Chile and Argentina. The volcano's eruptive style during its history has changed from mainly effusive in the Pleistocene to explosive in the Holocene. The prehistoric eruptions can be divided into pre-glacial (PG), syn-glacial (SG) and post-glacial (PM) stages, with products ranging from basaltic andesites to andesites. In order to investigate the evolution of the magma source and volatiles through time, we have focused our study on the eruptive products from the SG to the 2014 eruption (SUM2014). Sampled rocks are glomero-porphyritic, with a paragenetic mineral sequence of feldspars, ortho- and clinopyroxene, and olivine in order of abundance. All samples present a variable number of vesicles, with SUM2014 samples containing the biggest amount. Feldspar composition varies from Na-rich (andesine) in SG to Ca-rich (labradorite) in SUM2014. Two pyroxene types are present in SG and PM samples (augite and enstatite), while SUM2014 presents augite, pigeonite and enstatite. Thermobarometric estimation, based on mineral chemistry, show a bimodal distribution for SG and SUM2014 (P=10-12 kbars and 5-8 kbars) and only one interval for PM (P=7-8 kbars). Melt Inclusions Assemblages (MIAs) are found in all mineral phases, mostly re-crystallized, with one or more bubbles and daughter oxide minerals. Compositions vary from trachy-andesitic to dacitic for SG, andesitic to trachydacitic for PM, and basaltic andesitic to trachydacitic for SUM2014. Major elements systematics show the existence of a bimodal distribution of pyroxene and feldspar hosted-MIA in SUM2014, which together with the co-presence of pigeonite (low-Ca pyroxene) and augite and the bimodal distribution of P, can be interpreted as evidence of mixing of two types of magmas, evolving at different depths. Trace elements systematics for MIA in SG, PM and SUM2014 show a negative anomaly for Nb

  6. Geologic field-trip guide to Mount Shasta Volcano, northern California

    Science.gov (United States)

    Christiansen, Robert L.; Calvert, Andrew T.; Grove, Timothy L.

    2017-08-18

    The southern part of the Cascades Arc formed in two distinct, extended periods of activity: “High Cascades” volcanoes erupted during about the past 6 million years and were built on a wider platform of Tertiary volcanoes and shallow plutons as old as about 30 Ma, generally called the “Western Cascades.” For the most part, the Shasta segment (for example, Hildreth, 2007; segment 4 of Guffanti and Weaver, 1988) of the arc forms a distinct, fairly narrow axis of short-lived small- to moderate-sized High Cascades volcanoes that erupted lavas, mainly of basaltic-andesite or low-silica-andesite compositions. Western Cascades rocks crop out only sparsely in the Shasta segment; almost all of the following descriptions are of High Cascades features except for a few unusual localities where older, Western Cascades rocks are exposed to view along the route of the field trip.The High Cascades arc axis in this segment of the arc is mainly a relatively narrow band of either monogenetic or short-lived shield volcanoes. The belt generally averages about 15 km wide and traverses the length of the Shasta segment, roughly 100 km between about the Klamath River drainage on the north, near the Oregon-California border, and the McCloud River drainage on the south (fig. 1). Superposed across this axis are two major long-lived stratovolcanoes and the large rear-arc Medicine Lake volcano. One of the stratovolcanoes, the Rainbow Mountain volcano of about 1.5–0.8 Ma, straddles the arc near the midpoint of the Shasta segment. The other, Mount Shasta itself, which ranges from about 700 ka to 0 ka, lies distinctly west of the High Cascades axis. It is notable that Mount Shasta and Medicine Lake volcanoes, although volcanologically and petrologically quite different, span about the same range of ages and bracket the High Cascades axis on the west and east, respectively.The field trip begins near the southern end of the Shasta segment, where the Lassen Volcanic Center field trip leaves

  7. Nuclear graphite ageing and turnaround

    International Nuclear Information System (INIS)

    Marsden, B.J.; Hall, G.N.; Smart, J.

    2001-01-01

    Graphite moderated reactors are being operated in many countries including, the UK, Russia, Lithuania, Ukraine and Japan. Many of these reactors will operate well into the next century. New designs of High Temperature Graphite Moderated Reactors (HTRS) are being built in China and Japan. The design life of these graphite-moderated reactors is governed by the ageing of the graphite core due to fast neutron damage, and also, in the case of carbon dioxide cooled reactors by the rate of oxidation of the graphite. Nuclear graphites are polycrystalline in nature and it is the irradiation-induced damage to the individual graphite crystals that determines the material property changes with age. The life of a graphite component in a nuclear reactor can be related to the graphite irradiation induced dimensional changes. Graphites typically shrink with age, until a point is reached where the shrinkage stops and the graphite starts to swell. This change from shrinkage to swelling is known as ''turnaround''. It is well known that pre-oxidising graphite specimens caused ''turnaround'' to be delayed, thus extending the life of the graphite, and hence the life of the reactor. However, there was no satisfactory explanation of this behaviour. This paper presents a numerical crystal based model of dimensional change in graphite, which explains the delay in ''turnaround'' in the pre-oxidised specimens irradiated in a fast neutron flux, in terms of crystal accommodation and orientation and change in compliance due to radiolytic oxidation. (author)

  8. Anatomy of a volcano

    NARCIS (Netherlands)

    Hooper, A.; Wassink, J.

    2011-01-01

    The Icelandic volcano Eyjafjallajökull caused major disruption in European airspace last year. According to his co-author, Freysteinn Sigmundsson, the reconstruction published in Nature six months later by aerospace engineering researcher, Dr Andy Hooper, opens up a new direction in volcanology. “We

  9. Spying on volcanoes

    Science.gov (United States)

    Watson, Matthew

    2017-07-01

    Active volcanoes can be incredibly dangerous, especially to those who live nearby, but how do you get close enough to observe one in action? Matthew Watson explains how artificial drones are providing volcanologists with insights that could one day save human lives

  10. Geology of kilauea volcano

    Science.gov (United States)

    Moore, R.B.; Trusdell, F.A.

    1993-01-01

    This paper summarizes studies of the structure, stratigraphy, petrology, drill holes, eruption frequency, and volcanic and seismic hazards of Kilauea volcano. All the volcano is discussed, but the focus is on its lower cast rift zone (LERZ) because active exploration for geothermal energy is concentrated in that area. Kilauea probably has several separate hydrothermal-convection systems that develop in response to the dynamic behavior of the volcano and the influx of abundant meteoric water. Important features of some of these hydrothermal-convection systems are known through studies of surface geology and drill holes. Observations of eruptions during the past two centuries, detailed geologic mapping, radiocarbon dating, and paleomagnetic secular-variation studies indicate that Kilauea has erupted frequently from its summit and two radial rift zones during Quaternary time. Petrologic studies have established that Kilauea erupts only tholeiitic basalt. Extensive ash deposits at Kilauea's summit and on its LERZ record locally violent, but temporary, disruptions of local hydrothermal-convection systems during the interaction of water or steam with magma. Recent drill holes on the LERZ provide data on the temperatures of the hydrothermal-convection systems, intensity of dike intrusion, porosity and permeability, and an increasing amount of hydrothermal alteration with depth. The prehistoric and historic record of volcanic and seismic activity indicates that magma will continue to be supplied to deep and shallow reservoirs beneath Kilauea's summit and rift zones and that the volcano will be affected by eruptions and earthquakes for many thousands of years. ?? 1993.

  11. Sources of Magmatic Volatiles Discharging from Subduction Zone Volcanoes

    Science.gov (United States)

    Fischer, T.

    2001-05-01

    Subduction zones are locations of extensive element transfer from the Earth's mantle to the atmosphere and hydrosphere. This element transfer is significant because it can, in some fashion, instigate melt production in the mantle wedge. Aqueous fluids are thought to be the major agent of element transfer during the subduction zone process. Volatile discharges from passively degassing subduction zone volcanoes should in principle, provide some information on the ultimate source of magmatic volatiles in terms of the mantle, the crust and the subducting slab. The overall flux of volatiles from degassing volcanoes should be balanced by the amount of volatiles released from the mantle wedge, the slab and the crust. Kudryavy Volcano, Kurile Islands, has been passively degassing at 900C fumarole temperatures for at least 40 years. Extensive gas sampling at this basaltic andesite cone and application of CO2/3He, N2/3He systematics in combination with C and N- isotopes indicates that 80% of the CO2 and approximately 60% of the N 2 are contributed from a sedimentary source. The mantle wedge contribution for both volatiles is, with 12% and 17% less significant. Direct volatile flux measurements from the volcano using the COSPEC technique in combination with direct gas sampling allows for the calculation of the 3He flux from the volcano. Since 3He is mainly released from the astenospheric mantle, the amount of mantle supplying the 3He flux can be determined if initial He concentrations of the mantle melts are known. The non-mantle flux of CO2 and N2 can be calculated in similar fashion. The amount of non-mantle CO2 and N2 discharging from Kudryavy is balanced by the amount of CO2 and N2 subducted below Kudryavy assuming a zone of melting constrained by the average spacing of the volcanoes along the Kurile arc. The volatile budget for Kudryavy is balanced because the volatile flux from the volcano is relatively small (75 t/day (416 Mmol/a) SO2, 360 Mmol/a of non-mantle CO2 and

  12. Elution behavior into the high pressured hot water and the organizational change of granite and andesite

    Energy Technology Data Exchange (ETDEWEB)

    Matsunaga, Isao; Miyazaki, Akira; Yamaguchi, Tsutomu; kuriyakawa, Michio

    1988-04-01

    In the development of a high temperature rock system, the interaction between the rock and hot water which occurs in a reservoir provides big effects. The decline of the strength and the increase of the permeability are caused by the elusion of the rock on the surface of the hydraulic fracture and the redeposition of the eluded material also causes to narrow or close the channel. However, studies concerning the organizational change of the rock by the hot water or the material change associated with the organizational change are small in number. In this research, Inaba granite and Honkomatsu andesite were treated in heat with an autoclave in order to investigate the organizational changes of the rocks and at the same time, the elusion behavior of the rocks into the hot water was investigated by examining chemical components which were eluded into the fluid and the components remaining on the rock surface. The decreased amount per specific surface area due to the autoclave treatment is the order of 10/sup -3/(gcm/sup -2/) for both rocks and changeable depending upon the heating temperature and the kind of rock. As a result of the analysis of the fluids in the autoclave after the heat treatment, the Si concentration of Honkomatsu andesite was higher in the same temperature and the heating time. (2 figs, 3 tabs, 6 refs)

  13. Recompressed exfoliated graphite articles

    Science.gov (United States)

    Zhamu, Aruna; Shi, Jinjun; Guo, Jiusheng; Jang, Bor Z

    2013-08-06

    This invention provides an electrically conductive, less anisotropic, recompressed exfoliated graphite article comprising a mixture of (a) expanded or exfoliated graphite flakes; and (b) particles of non-expandable graphite or carbon, wherein the non-expandable graphite or carbon particles are in the amount of between about 3% and about 70% by weight based on the total weight of the particles and the expanded graphite flakes combined; wherein the mixture is compressed to form the article having an apparent bulk density of from about 0.1 g/cm.sup.3 to about 2.0 g/cm.sup.3. The article exhibits a thickness-direction conductivity typically greater than 50 S/cm, more typically greater than 100 S/cm, and most typically greater than 200 S/cm. The article, when used in a thin foil or sheet form, can be a useful component in a sheet molding compound plate used as a fuel cell separator or flow field plate. The article may also be used as a current collector for a battery, supercapacitor, or any other electrochemical cell.

  14. Bromine intercalated graphite for lightweight composite conductors

    KAUST Repository

    Amassian, Aram; Patole, Archana

    2017-01-01

    A method of fabricating a bromine-graphite/metal composite includes intercalating bromine within layers of graphite via liquid-phase bromination to create brominated-graphite and consolidating the brominated-graphite with a metal nanopowder via a

  15. Micro-earthquake signal analysis and hypocenter determination around Lokon volcano complex

    Energy Technology Data Exchange (ETDEWEB)

    Firmansyah, Rizky, E-mail: rizkyfirmansyah@hotmail.com [Geophysical Engineering, Faculty of Mining and Petroleum Engineering, Institut Teknologi Bandung, Bandung, 40132 (Indonesia); Nugraha, Andri Dian, E-mail: nugraha@gf.itb.ac.id [Global Geophysical Group, Faculty of Mining and Petroleum Engineering, Institut Teknologi Bandung, Bandung, 40132 (Indonesia); Kristianto, E-mail: kris@vsi.esdm.go.id [Center for Volcanology and Geological Hazard Mitigation (CVGHM), Geological Agency, Bandung, 40122 (Indonesia)

    2015-04-24

    Mount Lokon is one of five active volcanoes which is located in the North Sulawesi region. Since June 26{sup th}, 2011, standby alert set by the Center for Volcanology and Geological Hazard Mitigation (CVGHM) for this mountain. The Mount Lokon volcano erupted on July 4{sup th}, 2011 and still continuously erupted until August 28{sup th}, 2011. Due to its high seismic activity, this study is focused to analysis of micro-earthquake signal and determine the micro-earthquake hypocenter location around the complex area of Lokon-Empung Volcano before eruption phase in 2011 (time periods of January, 2009 up to March, 2010). Determination of the hypocenter location was conducted with Geiger Adaptive Damping (GAD) method. We used initial model from previous study in Volcan de Colima, Mexico. The reason behind the model selection was based on the same characteristics that shared between Mount Lokon and Colima including andesitic stratovolcano and small-plinian explosions volcanian types. In this study, a picking events was limited to the volcano-tectonics of A and B types, hybrid, long-period that has a clear signal onset, and local tectonic with different maximum S – P time are not more than three seconds. As a result, we observed the micro-earthquakes occurred in the area north-west of Mount Lokon region.

  16. Micro-earthquake signal analysis and hypocenter determination around Lokon volcano complex

    International Nuclear Information System (INIS)

    Firmansyah, Rizky; Nugraha, Andri Dian; Kristianto

    2015-01-01

    Mount Lokon is one of five active volcanoes which is located in the North Sulawesi region. Since June 26 th , 2011, standby alert set by the Center for Volcanology and Geological Hazard Mitigation (CVGHM) for this mountain. The Mount Lokon volcano erupted on July 4 th , 2011 and still continuously erupted until August 28 th , 2011. Due to its high seismic activity, this study is focused to analysis of micro-earthquake signal and determine the micro-earthquake hypocenter location around the complex area of Lokon-Empung Volcano before eruption phase in 2011 (time periods of January, 2009 up to March, 2010). Determination of the hypocenter location was conducted with Geiger Adaptive Damping (GAD) method. We used initial model from previous study in Volcan de Colima, Mexico. The reason behind the model selection was based on the same characteristics that shared between Mount Lokon and Colima including andesitic stratovolcano and small-plinian explosions volcanian types. In this study, a picking events was limited to the volcano-tectonics of A and B types, hybrid, long-period that has a clear signal onset, and local tectonic with different maximum S – P time are not more than three seconds. As a result, we observed the micro-earthquakes occurred in the area north-west of Mount Lokon region

  17. Cesium diffusion in graphite

    International Nuclear Information System (INIS)

    Evans, R.B. III; Davis, W. Jr.; Sutton, A.L. Jr.

    1980-05-01

    Experiments on diffusion of 137 Cs in five types of graphite were performed. The document provides a completion of the report that was started and includes a presentation of all of the diffusion data, previously unpublished. Except for data on mass transfer of 137 Cs in the Hawker-Siddeley graphite, analyses of experimental results were initiated but not completed. The mass transfer process of cesium in HS-1-1 graphite at 600 to 1000 0 C in a helium atmosphere is essentially pure diffusion wherein values of (E/epsilon) and ΔE of the equation D/epsilon = (D/epsilon) 0 exp [-ΔE/RT] are about 4 x 10 -2 cm 2 /s and 30 kcal/mole, respectively

  18. Irradiation Creep in Graphite

    Energy Technology Data Exchange (ETDEWEB)

    Ubic, Rick; Butt, Darryl; Windes, William

    2014-03-13

    An understanding of the underlying mechanisms of irradiation creep in graphite material is required to correctly interpret experimental data, explain micromechanical modeling results, and predict whole-core behavior. This project will focus on experimental microscopic data to demonstrate the mechanism of irradiation creep. High-resolution transmission electron microscopy should be able to image both the dislocations in graphite and the irradiation-induced interstitial clusters that pin those dislocations. The team will first prepare and characterize nanoscale samples of virgin nuclear graphite in a transmission electron microscope. Additional samples will be irradiated to varying degrees at the Advanced Test Reactor (ATR) facility and similarly characterized. Researchers will record microstructures and crystal defects and suggest a mechanism for irradiation creep based on the results. In addition, the purchase of a tensile holder for a transmission electron microscope will allow, for the first time, in situ observation of creep behavior on the microstructure and crystallographic defects.

  19. Conditions of deep magma chamber beneath Fuji volcano estimated from high- P experiments

    Science.gov (United States)

    Asano, K.; Takahashi, E.; Hamada, M.; Ushioda, M.; Suzuki, T.

    2012-12-01

    Fuji volcano, the largest in volume and eruption rate in Japan, is located at the center of Honshu, where North America, Eurasia and Philippine Sea plates meets. Because of the significance of Fuji volcano both in tectonic settings and potential volcanic hazard (particularly after the M9 earthquake in 2011), precise knowledge on its magma feeding system is essentially important. Composition of magma erupted from Fuji volcano in the last 100ky is predominantly basalt (SiO2=50-52wt%, FeO/MgO=1.5-3.0). Total lack of silica-rich magma (basaltic andesite and andesite) which are always present in other nearby volcanoes (e.g., Hakone, Izu-Oshima, see Fig.1) is an important petrologic feature of Fuji volcano. Purpose of this study is to constrain the depth of magma chamber of Fuji volcano and explain its silica-nonenrichment trend. High pressure melting experiments were carried out using two IHPVs at the Magma Factory, Tokyo Institute of Technology (SMC-5000 and SMC-8600, Tomiya et al., 2010). Basalt scoria Tr-1 which represents the final ejecta of Hoei eruption in AD1707, was adopted as a starting material. At 4kbar, temperature conditions were 1050, 1100 and 1150C, and H2O contents were 1.3, 2.7 and 4.7 wt.%, respectively. At 7kbar, temperature conditions were 1075, 1100 and 1125C, and H2O contents were 1.0, 1.1, 3.6 and 6.3wt.%, respectively. The fO2 was controlled at NNO buffer. At 4kbar, crystallization sequence at 3 wt% H2O is magnetite, plagioclase, clinopyroxene and finally orthopyroxene. At 7 kbar, and ~3 wt% H2O, the three minerals (opx, cpx, pl) appears simultaneously near the liquidus. Compositional trend of melt at 4 kbar and 7 kbar are shown with arrows in Fig.1. Because of the dominant crystallization of silica-rich opx at 7 kbar, composition of melt stays in the range SiO2=50-52wt% as predicted by Fujii (2007). Absence of silica-rich rocks in Fuji volcano may be explained by the tectonic setting of the volcano. Because Fuji volcano locates on the plate

  20. Intercomparison of graphite irradiations

    Energy Technology Data Exchange (ETDEWEB)

    Hering, H; Perio, P; Seguin, M [Commissariat a l' Energie Atomique, Saclay (France).Centre d' Etudes Nucleaires

    1959-07-01

    While fast neutrons only are effective in damaging graphite, results of irradiations are more or less universally expressed in terms of thermal neutron fluxes. This paper attempts to correlate irradiations made in different reactors, i.e., in fluxes of different spectral compositions. Those attempts are based on comparison of 1) bulk length change and volume expansion, and 2) crystalline properties (e.g., lattice parameter C, magnetic susceptibility, stored energy, etc.). The methods used by various authors for determining the lattice constants of irradiated graphite are discussed. (author)

  1. Deposits, petrology and mechanism of the 2010-2013 eruption of Kizimen volcano in Kamchatka, Russia

    Science.gov (United States)

    Auer, A.; Belousov, A.; Belousova, M.

    2018-04-01

    Kizimen volcano in Kamchatka is well known as a source of highly heterogeneous poorly mingled magmas ranging from dacites to basaltic andesites. In 2010-2013, the volcano produced its first historical magmatic eruption with the deposition of 0.27 km3 of block and ash pyroclastic flows accompanied by slow extrusion of a 200-m-thick, highly viscous (1010-1011 Pa s) block lava flow with a volume of 0.3 km3. The total volume of erupted magma comprised approximately 0.4 km3 DRE. We provide description of the eruption chronology, as well as the lithology and petrology of eruptive products. The erupted material is represented by banded dacite and high-silica andesite. The dacitic magma was formed during a long dormancy after the previous magmatic eruption several hundred years ago with mineral compositions indicating average pre-eruptive temperatures of 810 °C, fO2 of 0.9-1.6 log units above the nickel-nickel oxide (NNO) buffer and shallow crustal storage conditions at 123 MPa. The silica-rich andesite represents a hybrid magma, which shows signs of recent thermal and compositional disequilibrium. We suggest that the hybrid magma started to form in 1963 when a swarm of deep earthquakes indicated an input of mafic magma from depth into the 6-11-km-deep silicic magma chamber. It took the following 46 years until the magma filling the chamber reached an eruptible state. Poor mingling of the two melts is attributed to its unusually high viscosity that could be associated with the pre-eruptive long-term leakage of volatiles from the chamber through a regional tectonic fault. Our investigations have shown that shallow magma chambers of dormant volcanoes demonstrating strong persistent fumarolic activity can contain highly viscous, degassed magma of evolved composition. Reactivation of such magma chambers by injection of basic magma takes a long time (several decades). Thus, eruption forecasts at such volcanoes should include a possibility of long time lag between a swarm of

  2. Late Pleistocene-Holocene cataclysmic eruptions at Nevado de Toluca and Jocotitlan volcanoes, central Mexico

    Science.gov (United States)

    Macias, J.L.; Garcia, P.A.; Arce, J.L.; Siebe, C.; Espindola, J.M.; Komorowski, J.C.; Scott, K.

    1997-01-01

    This field guide describes a five day trip to examine deposits of Late Pleistocene-Holocene cataclysmic eruptions at Nevado de Toluca and Jocotitlan volcanoes in central Mexico. We will discuss the stratigraphy, petrology, and sedimentological characteristics of these deposits which provide insights into the eruptive history, type of volcanic activity, and transport and emplacement mechanisms of pyroclastic materials. These parameters will allow us to discuss the kinds of hazards and the risk that they pose to populations around these volcanoes. The area to be visited is tectonically complex thus we will also discuss the location of the volcanoes with respect to the tectonic environment. The first four days of the field trip will be dedicated to Nevado de Toluca Volcano (19 degrees 09'N; 99 degrees 45'W) located at 23 km. southwest of the City of Toluca, and is the fourth highest peak in the country, reaching an elevation of 4,680 meters above sea level (m.a.s.l.). Nevado de Toluca is an andesitic-dacitic stratovolcano, composed of a central vent excavated upon the remains of older craters destroyed by former events. Bloomfield and Valastro, (1974, 1977) concluded that the last cycle of activity occurred nearly equal 11,600 yr. ago. For this reason Nevado de Toluca has been considered an extinct volcano. Our studies, however, indicate that Nevado de Toluca has had at least two episodes of cone destruction by sector collapse as well as several explosive episodes including plinian eruptions and dome-destruction events. These eruptions occurred during the Pleistocene but a very young eruption characterized by surge and ash flows occurred ca. 3,300 yr. BP. This new knowledge of the volcano's eruptive history makes the evaluation of its present state of activity and the geological hazards necessary. This is important because the area is densely populated and large cities such as Toluca and Mexico are located in its proximity.

  3. Thermal properties of andesite from Popocatepetl and Volcán de Colima, México.

    Science.gov (United States)

    Cardenas-Sanchez, Enrique; De la Cruz-Reina, Servando; Varley, Nick

    2015-04-01

    The thermal conductivity (K), specific heat (Cp) and the coefficient of heat transfer surface (H) are the basic parameters to describe the process of cooling a volcanic rock fragment released in an explosive event. The analysis of the cooling process by conduction, convection and radiation of heat in volcanic rock fragments, has been limited to basalts, and various minerals such as olivine, pyroxene, quartz, etc. (Miao & Chen, 2014; Branlund & Hofmeister, 2012; Romine et al, 2012;. Schön, 2011; Stroberg et al, 2010;. Schatz & Simmons, 1972). There are no detailed studies on the thermal properties of the andesites, abundant in continental stratovolcanoes, and particularly susceptible from lava domes with frequent destruction processes, such as Popocatepetl and Volcan de Colima. Previously, we developed an algorithm for calculation of the grain-size distribution, degree of fragmentation, the thermal energy released and its possible correlation with Volcanic Explosive Index (VEI) from the cooling curves of fragments from vulcanian and strombolian explosions. These curves were obtained from sequences of time over incandescent deposits recorded at selected pixel thermal images of vulcanian activity in the Popocatepetl and Volcan de Colima, Mexico. However, the model was limited by the lack of thermal parameters of the andesites, forcing a first approximation using basalts data. We present a simple model for the cooling process using andesites samples from Popocatépetl and Volcan de Colima. First, the samples were subjected to a rounding process to minimize surface effects. Then, heated to 800 ° C were extracted from the muffle and cooling rate is measured. The thermal conductivity and coefficient of surface heat are determined using a thermal camera and three thermocouples embedded at various depths within the sample. An inversion method was implemented to determine the thermal properties parameters , by comparing the observed data regarding cooling model for a solid

  4. In situ observations of bubble growth in basaltic, andesitic and rhyodacitic melts

    Science.gov (United States)

    Masotta, M.; Ni, H.; Keppler, H.

    2014-02-01

    Bubble growth strongly affects the physical properties of degassing magmas and their eruption dynamics. Natural samples and products from quench experiments provide only a snapshot of the final state of volatile exsolution, leaving the processes occurring during its early stages unconstrained. In order to fill this gap, we present in situ high-temperature observations of bubble growth in magmas of different compositions (basalt, andesite and rhyodacite) at 1,100 to 1,240 °C and 0.1 MPa (1 bar), obtained using a moissanite cell apparatus. The data show that nucleation occurs at very small degrees of supersaturaturation (bubbles occurring simultaneously with the nucleation of crystals. During the early stages of exsolution, melt degassing is the driving mechanism of bubble growth, with coalescence becoming increasingly important as exsolution progresses. Ostwald ripening occurs only at the end of the process and only in basaltic melt. The average bubble growth rate ( G R) ranges from 3.4 × 10-6 to 5.2 × 10-7 mm/s, with basalt and andesite showing faster growth rates than rhyodacite. The bubble number density ( N B) at nucleation ranges from 7.9 × 104 mm-3 to 1.8 × 105 mm-3 and decreases exponentially over time. While the rhyodacite melt maintained a well-sorted bubble size distribution (BSD) through time, the BSDs of basalt and andesite are much more inhomogeneous. Our experimental observations demonstrate that bubble growth cannot be ascribed to a single mechanism but is rather a combination of many processes, which depend on the physical properties of the melt. Depending on coalescence rate, annealing of bubbles following a single nucleation event can produce complex bubble size distributions. In natural samples, such BSDs may be misinterpreted as resulting from several separate nucleation events. Incipient crystallization upon cooling of a magma may allow bubble nucleation already at very small degrees of supersaturation and could therefore be an important

  5. The statitistical evaluation of the uniaxial compressive strength of the Ruskov andesite

    Directory of Open Access Journals (Sweden)

    Krepelka František

    2002-03-01

    Full Text Available The selection of a suitable model of the statistical distribution of the uniaxial compressive strength is discussed in the paper. The uniaxial compressive strength was studied on 180 specimens of the Ruskov andesite. The rate of loading was 1MPa.s-1. The experimental specimens had a prismatic form with a square base; the slightness ratio of specimens was 2:1. Three sets of specimens with a different length of the base edge were studied, namely 50, 30 and 10 mm. The result of the measurement were three sets with 60 values of the uniaxial compressive strength. The basic statistical parameters: the sample mean, the sample standard deviation, the variational interval, the minimum and maximum value, the sample obliqueness coefficient and the sharpness coefficient were evaluated for each collection. Two types of the distribution which can be joined with the real physical fundamentals of the desintegration of rocks ( the normal and the Weibull distribution were tested. The two-parametric Weibull distribution was tested. The basic characteristics of both distributions were evaluated for each set and the accordance of the model distribution with an experimental distribution was tested. The ÷2-test was used for testing. The two-parametric Weibull distribution was selected following the comparison of the test results of both model distributions as a suitable distribution model for the characterization of uniaxial compressive strength of the Ruskov andesite. The two-parametric Weibull distribution showed better results of the goodness-of-fit test. The normal distribution was suitable for two sets; one of the sets showed a negative result of the goodness-of-fit testing. At the uniaxial compressive strength of the Ruskov andesite, a scale effect was registered : the mean value of uniaxial compressive strength decreases with increasing the specimen base edge. This is another argument for using the Weibull distribution as a suitable statistical model of the

  6. Silica-enriched mantle sources of subalkaline picrite-boninite-andesite island arc magmas

    Science.gov (United States)

    Bénard, A.; Arculus, R. J.; Nebel, O.; Ionov, D. A.; McAlpine, S. R. B.

    2017-02-01

    compositions extracted from these hybrid sources are higher in normative quartz and hypersthene (i.e., they have a more silica-saturated character) in comparison with basalts derived from prior melt-depleted asthenospheric mantle beneath ridges. These primary arc melts range from silica-rich picrite to boninite and high-Mg basaltic andesite along a residual spinel harzburgite cotectic. Silica enrichment in the mantle sources of arc-related, subalkaline picrite-boninite-andesite suites coupled with the amount of water and depth of melting, are important for the formation of medium-Fe ('calc-alkaline') andesite-dacite-rhyolite suites, key lithologies forming the continental crust.

  7. Sulfur isotope fractionation between fluid and andesitic melt: An experimental study

    Science.gov (United States)

    Fiege, Adrian; Holtz, François; Shimizu, Nobumichi; Mandeville, Charles W.; Behrens, Harald; Knipping, Jaayke L.

    2014-01-01

    Glasses produced from decompression experiments conducted by Fiege et al. (2014a) were used to investigate the fractionation of sulfur isotopes between fluid and andesitic melt upon magma degassing. Starting materials were synthetic glasses with a composition close to a Krakatau dacitic andesite. The glasses contained 4.55–7.95 wt% H2O, ∼140 to 2700 ppm sulfur (S), and 0–1000 ppm chlorine (Cl). The experiments were carried out in internally heated pressure vessels (IHPV) at 1030 °C and oxygen fugacities (fO2) ranging from QFM+0.8 log units up to QFM+4.2 log units (QFM: quartz–fayalite–magnetite buffer). The decompression experiments were conducted by releasing pressure (P) continuously from ∼400 MPa to final P of 150, 100, 70 and 30 MPa. The decompression rate (r) ranged from 0.01 to 0.17 MPa/s. The samples were annealed for 0–72 h (annealing time, tA) at the final P and quenched rapidly from 1030 °C to room temperature (T).The decompression led to the formation of a S-bearing aqueous fluid phase due to the relatively large fluid–melt partitioning coefficients of S. Secondary ion mass spectrometry (SIMS) was used to determine the isotopic composition of the glasses before and after decompression. Mass balance calculations were applied to estimate the gas–melt S isotope fractionation factor αg-m.No detectable effect of r and tA on αg-m was observed. However, SIMS data revealed a remarkable increase of αg-m from ∼0.9985 ± 0.0007 at >QFM+3 to ∼1.0042 ± 0.0042 at ∼QFM+1. Noteworthy, the isotopic fractionation at reducing conditions was about an order of magnitude larger than predicted by previous works. Based on our experimental results and on previous findings for S speciation in fluid and silicate melt a new model predicting the effect of fO2 on αg-m (or Δ34Sg–m) in andesitic systems at 1030 °C is proposed. Our experimental results as well as our modeling are of high importance for the interpretation of S isotope

  8. Graphite-based photovoltaic cells

    Science.gov (United States)

    Lagally, Max; Liu, Feng

    2010-12-28

    The present invention uses lithographically patterned graphite stacks as the basic building elements of an efficient and economical photovoltaic cell. The basic design of the graphite-based photovoltaic cells includes a plurality of spatially separated graphite stacks, each comprising a plurality of vertically stacked, semiconducting graphene sheets (carbon nanoribbons) bridging electrically conductive contacts.

  9. Geology of Kilauea volcano

    Energy Technology Data Exchange (ETDEWEB)

    Moore, R.B. (Geological Survey, Denver, CO (United States). Federal Center); Trusdell, F.A. (Geological Survey, Hawaii National Park, HI (United States). Hawaiian Volcano Observatory)

    1993-08-01

    This paper summarizes studies of the structure, stratigraphy, petrology, drill holes, eruption frequency, and volcanic and seismic hazards of Kilauea volcano. All the volcano is discussed, but the focus is on its lower east rift zone (LERZ) because active exploration for geothermal energy is concentrated in that area. Kilauea probably has several separate hydrothermal-convection systems that develop in response to the dynamic behavior of the volcano and the influx of abundant meteoric water. Important features of some of these hydrothermal-convection systems are known through studies of surface geology and drill holes. Observations of eruptions during the past two centuries, detailed geologic mapping, radiocarbon dating, and paleomagnetic secular-variation studies indicate that Kilauea has erupted frequently from its summit and two radial rift zones during Quaternary time. Petrologic studies have established that Kilauea erupts only tholeiitic basalt. Extensive ash deposits at Kilauea's summit and on its LERZ record locally violent, but temporary, disruptions of local hydrothermal-convection systems during the interaction of water or steam with magma. Recent drill holes on the LERZ provide data on the temperatures of the hydrothermal-convection systems, intensity of dike intrusion, porosity and permeability, and an increasing amount of hydrothermal alteration with depth. The prehistoric and historic record of volcanic and seismic activity indicates that magma will continue to be supplied to deep and shallow reservoirs beneath Kilauea's summit and rift zones and that the volcano will be affected by eruptions and earthquakes for many thousands of years. 71 refs., 2 figs.

  10. Catalogue of Icelandic Volcanoes

    Science.gov (United States)

    Ilyinskaya, Evgenia; Larsen, Gudrún; Gudmundsson, Magnús T.; Vogfjörd, Kristin; Jonsson, Trausti; Oddsson, Björn; Reynisson, Vidir; Pagneux, Emmanuel; Barsotti, Sara; Karlsdóttir, Sigrún; Bergsveinsson, Sölvi; Oddsdóttir, Thorarna

    2017-04-01

    The Catalogue of Icelandic Volcanoes (CIV) is a newly developed open-access web resource (http://icelandicvolcanoes.is) intended to serve as an official source of information about volcanoes in Iceland for the public and decision makers. CIV contains text and graphic information on all 32 active volcanic systems in Iceland, as well as real-time data from monitoring systems in a format that enables non-specialists to understand the volcanic activity status. The CIV data portal contains scientific data on all eruptions since Eyjafjallajökull 2010 and is an unprecedented endeavour in making volcanological data open and easy to access. CIV forms a part of an integrated volcanic risk assessment project in Iceland GOSVÁ (commenced in 2012), as well as being part of the European Union funded effort FUTUREVOLC (2012-2016) on establishing an Icelandic volcano supersite. The supersite concept implies integration of space and ground based observations for improved monitoring and evaluation of volcanic hazards, and open data policy. This work is a collaboration of the Icelandic Meteorological Office, the Institute of Earth Sciences at the University of Iceland, and the Civil Protection Department of the National Commissioner of the Iceland Police, with contributions from a large number of specialists in Iceland and elsewhere.

  11. Sorption Behavior of Cu(II From Acidic SolutionUsing Weathered Basalt Andesite Products

    Directory of Open Access Journals (Sweden)

    Rajesh Singh

    2007-01-01

    Full Text Available Wastewater discharged from electroplating industry pose a serioushazard due to their heavy metal load. The objective of this work is to evaluatethe removal of Cu(II from acidic solution by sorption onto Weathered BasaltAndesite Products (WBAP. WBAP has been characterized and utilized forremoval of copper from aqueous solution over wide range of initial metal ionconcentration (25 mg/L to 500 mg/L, contact duration (0-8 h, sorbent dose(5-35 g/L, pH (1.0 to 6.0, and temperature (276 K to 333 K. The sorptionpattern of Cu ions onto WBAP followed Langmuir, Freundlich, and Dubinin-Kaganer-Radushkevich isotherms. The thermodynamic parameters (∆H0, ∆S0,and ∆G0 for Cu sorption onto WBAP were also determined.

  12. Electronic properties of graphite

    International Nuclear Information System (INIS)

    Schneider, J.

    2010-10-01

    In this thesis, low-temperature magneto-transport (T ∼ 10 mK) and the de Haas-van Alphen effect of both natural graphite and highly oriented pyrolytic graphite (HOPG) are examined. In the first part, low field magneto-transport up to B = 11 T is discussed. A Fourier analysis of the background removed signal shows that the electric transport in graphite is governed by two types of charge carriers, electrons and holes. Their phase and frequency values are in agreement with the predictions of the SWM-model. The SWM-model is confirmed by detailed band structure calculations using the magnetic field Hamiltonian of graphite. The movement of the Fermi at B > 2 T is calculated self-consistently assuming that the sum of the electron and hole concentrations is constant. The second part of the thesis deals with high field magneto-transport of natural graphite in the magnetic field range 0 ≤ B ≤ 28 T. Both spin splitting of magneto-transport features in tilted field configuration and the onset of the charge density wave (CDW) phase for different temperatures with the magnetic field applied normal to the sample plane are discussed. Concerning the Zeeman effect, the SWM calculations including the Fermi energy movement require a g-factor of g* equal to 2.5 ± 0.1 to reproduce the spin spilt features. The measurements of the charge density wave state confirm that its onset magnetic field can be described by a Bardeen-Cooper-Schrieffer (BCS)-type formula. The measurements of the de Haas-van Alphen effect are in agreement with the results of the magneto-transport measurements at low field. (author)

  13. The Massive Compound Cofre de Perote Shield Volcano: a Volcanological Oddity in the Eastern Mexican Volcanic Belt

    Science.gov (United States)

    Siebert, L.; Carrasco-Nunez, G.; Diaz-Castellon, R.; Rodriguez, J. L.

    2007-12-01

    Cofre de Perote volcano anchors the northern end of the easternmost of several volcanic chains orthogonal to the E-W trend of the Mexican Volcanic Belt (MVB). Its structure, geochemistry, and volcanic history diverge significantly from that of the large dominantly andesitic stratovolcanoes that have been the major focus of research efforts in the MVB. Andesitic-trachyandesitic to dacitic-trachydacitic effusive activity has predominated at Cofre de Perote, forming a massive low-angle compound shield volcano that dwarfs the more typical smaller shield volcanoes of the central and western MVB. The 4282-m-high volcano overlooking Xalapa, the capital city of the State of Veracruz, has a diameter of about 30 km and rises more than 3000 m above the coastal plain to the east. Repeated edifice collapse has left massive horseshoe-shaped scarps that truncate the eastern side of the edifice. Five major evolutionary stages characterize the growth of this compound volcano: 1) emplacement of a multiple-vent dome complex forming the basal structure of Cofre de Perote around 1.9-1.3 Ma; 2) construction of the basal part of the compound shield volcano from at least two main upper-edifice vents at about 400 ka; 3) effusion of the summit dome-like lavas through multiple vents at ca. 240 ka; 4) eruption of a large number of geochemically diverse, alkaline and calc-alkaline Pleistocene-to-Holocene monogenetic cones (likely related to regional volcanism) through the flanks of the Cofre de Perote edifice; 5) late-stage, large-volume edifice collapse on at least two occasions (ca. 40 ka and ca. 10 ka), producing long-runout debris avalanches that traveled to the east. An undated tephra layer from Cofre de Perote overlies deposits likely of the youngest collapse. Cofre de Perote is one of several volcanoes in the roughly N-S-trending chain that has undergone major edifice collapse. As with Citlaltepetl (Pico de Orizaba) and Las Cumbres volcanoes, Cofre de Perote was constructed at the

  14. Volcano stratigraphy interpretation of Mamuju area based on Landsat-8 imagery analysis

    International Nuclear Information System (INIS)

    Frederikus Dian Indrastomo; I Gde Sukadana; Dhatu Kamajati; Asep Saepuloh; Agus Handoyo Harsolumakso

    2015-01-01

    Mamuju and its surrounding area are constructed mainly by volcanic rocks. Volcanoclastic sedimentary rocks and limestones are laid above the volcanic rocks. Volcanic activities create some unique morphologies such as craters, lava domes, and pyroclastic flow paths as their volcanic products. These products are identified from their circular features characters on Landsat-8 imagery. Geometric and atmospheric corrections had been done, a visual interpretation on Landsat-8 imagery was conducted to identify structure, geomorphology, and geological condition of the area. Regional geological structures show trend to southeast – northwest direction which is affects the formation of Adang volcano. Geomorphology of the area are classified into 16 geomorphology units based on their genetic aspects, i.e Sumare fault block ridge, Mamuju cuesta ridge, Adang eruption crater, Labuhan Ranau eruption crater, Sumare eruption crater, Ampalas volcanic cone, Adang lava dome, Labuhan Ranau intrusion hill, Adang pyroclastic flow ridge, Sumare pyroclastic flow ridge, Adang volcanic remnant hills, Malunda volcanic remnant hills, Talaya volcanic remnant hills, Tapalang karst hills, Mamuju alluvium plains, and Karampuang reef terrace plains. Based on the Landsat-8 imagery interpretation result and field confirmation, the geology of Mamuju area is divided into volcanic rocks and sedimentary rocks. There are two groups of volcanic rocks; Talaya complex and Mamuju complex. The Talaya complex consists of Mambi, Malunda, and Kalukku volcanic rocks with andesitic composition, while Mamuju complex consist of Botteng, Ahu, Tapalang, Adang, Ampalas, Sumare, and Labuhan Ranau volcanic rocks with andesite to leucitic basalt composition. The volcano stratigraphy of Mamuju area was constructed based on its structure, geomorphology and lithology distribution analysis. Volcano stratigraphy of Mamuju area is classified into Khuluk Talaya and Khuluk Mamuju. The Khuluk Talaya consists of Gumuk Mambi, Gumuk

  15. Late Pleistocene flank collapse of Zempoala volcano (Central Mexico) and the role of fault reactivation

    Science.gov (United States)

    Arce, José Luis; Macías, Rodolfo; García Palomo, Armando; Capra, Lucia; Macías, José Luis; Layer, Paul; Rueda, Hernando

    2008-11-01

    Zempoala is an extinct Pleistocene (˜ 0.7-0.8 Ma) stratovolcano that together with La Corona volcano (˜ 0.9 Ma) forms the southern end of the Sierra de las Cruces volcanic range, Central Mexico. The volcano consists of andesitic and dacitic lava flows and domes, as well as pyroclastic and epiclastic sequences, and has had a complex history with several flank collapses. One of these collapses occurred during the late Pleistocene on the S-SE flank of the volcano and produced the Zempoala debris avalanche deposit. This collapse could have been triggered by the reactivation of two normal fault systems (E-W and NE-SW), although magmatic activity cannot be absolutely excluded. The debris avalanche traveled 60 km to the south, covers an area of 600 km 2 and has a total volume of 6 km 3, with a calculated Heim coefficient (H/L) of 0.03. Based on the textural characteristics of the deposit we recognized three zones: proximal, axial, and lateral distal zone. The proximal zone consists of debris avalanche blocks that develop a hummocky topography; the axial zone corresponds with the main debris avalanche deposit made of large clasts set in a sandy matrix, which transformed to a debris flow in the lateral distal portion. The deposit is heterolithologic in composition, with dacitic and andesitic fragments from the old edifice that decrease in volume as bulking of exotic clasts from the substratum increase. Several cities (Cuernavaca, Jojutla de Juárez, Alpuyeca) with associated industrial, agricultural, and tourism activities have been built on the deposit, which pose in evidence the possible impact in case of a new event with such characteristics, since the area is still tectonically active.

  16. 3D geophysical insights into the Ciomadu volcano

    Science.gov (United States)

    Besutiu, Lucian; Zlagnean, Luminita

    2017-04-01

    RATIONALE Located at the south easternmost end of the Neogene to Quaternary volcanic chain of East Carpathians, the Ciomadu volcano (last erupted approx 30 ka ago) seems to represent the latest volcanic manifestation within the Carpatho-Pannonian region. Based on the interpretation of some large-scale electromagnetic and seismological surveys, the hypothesis of the in depth (8 -15 km) existence of a magma reservoir raises the volcanic hazard in the region. The close neighbourhood of the Vrancea active geodynamic zone, where intermediate-depth seismicity occurs within full intra-continental environment makes the study of the Ciomadu volcano of higher interest. METHOD During the time numerous geological investigations have been conducted in the area, but except for the previously mentioned large-scale electromagnetic and seismological approaches geophysical tools have been less employed. Relatively recent, within the frame of the INSTEC project, funded through a CNCS-UEFISCDI (Romanian Science Foundation) grant, the area has been subject to an integrated gravity and geomagnetic survey accompanied by outcrops sampling and lab determinations on rock physics. Field data have been highly processed and models of their sources have been constructed through 3D inversion techniques. RESULTS Overall, the potential fields have revealed a large gravity low covering the whole volcano area associating a residual geomagnetic anomaly with local effects mainly bordering the gravity anomaly. 3D inversion of the gravity data provided an intriguing image on the mass distribution within the volcanic structure, with underground densities much bellow the figures provided by the lab determinations on rock samples collected at the surface. The geometry of the revealed gravity source clearly suggests an andesitic/dacitic intrusion acceding to the surface along a deep fault that seems to belong to the alpine overthrust system of East Carpathians. Attempts to interpret the low value densities

  17. Stratigraphy and Petrology of the Grande Soufriere Hills Volcano, Dominica, Lesser Antilles

    Science.gov (United States)

    Daly, G.; Smith, A. L.; Garcia, R.; Killingsworth, N.

    2007-12-01

    The Grande Soufriere Hills volcanic center is located on the south east coast of the island of Dominica in the Lesser Antilles. Although the volcano is deeply dissected, a distinct circular crater that opens to the east can be observed. Within the crater is a lava dome and unconsolidated pyroclastic deposits mantle the southeast flanks of the volcano. These pyroclastic deposits are almost entirely matrix-supported block and ash flows and surges suggesting that Pelean-style eruptions have dominated its most recent activity. Within this sequence is a relatively thin (30-50 cm) clast-supported deposit that has been interpreted as a possible blast deposit. Two age dates from these younger deposits suggest that much of this activity occurred between l0,000 and 12,000 years ago. On the southeastern coast at Pointe Mulâtre and extending approximately 4 km north and at a maximum 2 km west, is a megabreccia of large (up to 3 m) flow-banded andesite clasts set in a semi-lithified medium grained ash matrix. At Pointe Mulâtre this megabreccia is overlain by unconsolidated block and ash flow deposits. To the north of the megabreccia, exposures in the sea cliffs reveal a consolidated sequence of well-bedded alternating coarse and fine deposits suggesting deltaic foreset beds; which in turn appears to be overlain by a yellow- colored relatively coarse flow deposit with an irregular upper surface. The uppermost deposits in the sea cliffs are a sequence of unconsolidated block and ash flow deposits and interbedded fluviatile conglomerates equivalent to the younger flow deposits logged inland. Volcanic rocks from the Grande Soufriere Hills are all porphyritic andesites often containing hypabyssal inclusions. Dominant phenocrysts are plagioclase often with inclusion-rich cores and well developed zoning. Mafic phenocrysts include hornblende, augite and hypersthene. Geochemically these andesites range from 58- 63% SiO2 and show trends of decreasing values for Al2O3, FeO, MgO, CaO, Ti

  18. 238U-230Th-226Ra radioactive disequilibria in the products from 1707 eruption of Fuji volcano, Japan

    International Nuclear Information System (INIS)

    Kurihara, Yuichi; Takahashi, Masaomi; Sato, Jun

    2008-01-01

    Time scale of magmatic processes in the 1707 eruptive activity of Fuji volcano, Japan, was estimated by the 238 U- 230 Th- 226 Ra disequilibria observed in the 1707 volcanic products. The activity ratios of 226 Ra/ 230 Th in the products were larger than unity, being enriched in 226 Ra relative to 230 Th. The decay-corrected 226 Ra/ 230 Th activity ratio to the time of the eruption versus 238 U/ 230 Th activity ratio diagram for the 1707 volcanic products showed a positive correlation, suggesting that the 238 U/ 230 Th- 226 Ra disequilibria occurred during the magma genesis of Fuji volcano. The 230 Th- 226 Ra disequilibria in the 1707 volcanic products suggested that the time scale from the magma genesis to the eruption, including the melting of the mantle wedge, magma storage and magmatic differentiation from basalt to andesite, was less than 8000 years. (author)

  19. Ruiz Volcano: Preliminary report

    Science.gov (United States)

    Ruiz Volcano, Colombia (4.88°N, 75.32°W). All times are local (= GMT -5 hours).An explosive eruption on November 13, 1985, melted ice and snow in the summit area, generating lahars that flowed tens of kilometers down flank river valleys, killing more than 20,000 people. This is history's fourth largest single-eruption death toll, behind only Tambora in 1815 (92,000), Krakatau in 1883 (36,000), and Mount Pelée in May 1902 (28,000). The following briefly summarizes the very preliminary and inevitably conflicting information that had been received by press time.

  20. Harwell Graphite Calorimeter

    International Nuclear Information System (INIS)

    Linacre, J.K.

    1970-01-01

    The calorimeter is of the steady state temperature difference type. It contains a graphite sample supported axially in a graphite outer jacket, the assembly being contained in a thin stainless steel outer can. The temperature of the jacket and the temperature difference between sample and jacket are measured by chromel-alumel thermocouples. The instrument is calibrated by means of an electric heater of low mass positioned on the axis of the sample. The resistance of the heater is known and both current through the heater and the potential across it may be measured. The instrument is filled with nitrogen at a pressure of one half atmosphere at room temperature. The calorimeter has been designed for prolonged operation at temperatures up to 600°C, and dose rates up to 1 Wg -1 , and instruments have been in use for periods in excess of one year

  1. a Microgravity Survey to Determine the Extent of AN Andesitic Sill that Intrudes across the Rio Grande River Basin, Rio Grande Rift Valley, Sunland Park, New Mexico

    Science.gov (United States)

    Baker, L. A.; Shinagel, S.; Villalobos, J. I.; Avila, V.; Montana, C. J.; Kaip, G.

    2012-12-01

    In Sunland Park, NM, there is an andesite outcrop near the bank of the Rio Grande (called the River Andesite) which does not match the surrounding sedimentary deposition. Studies of the River Andesite by Garcia (1970) indicate the outcrop is petrologically similar to the Muleros Andesite of Mt. Cristo Rey located several km to the south. A limited GPR and magnetic survey conducted by UTEP students in 2008 suggested the River Andesite was part of a dike, although Garcia mapped smaller outcrops of andesite ~300 m west of the river that may be part of the same body. We have recently (June 2012) found large andesite boulders that may be the outcrops Garcia mapped, although it is uncertain whether these boulders are in-situ. We initially collected microgravity and magnetic data in a small region near the river outcrop in December 2011 to determine the extent of the outcrop. Our preliminary modeling of these data showed the river outcrop appeared to merge with a more extensive igneous body at depth. Ground conductivity data collected near the river outcrop in March 2012 suggested that the outcrop impacts groundwater flow and sediment deposition adjacent to the river. From May through July 2012 we have been collecting additional microgravity data on a grid with 100-200 m spacing extending ~ 500 m from both sides of the river outcrop to better determine the extent of the buried andesite body. We also plan to conduct GPR and magnetic surveys near the recently discovered andesite boulders to determine if these are truly in-situ and part of the same igneous body as the river outcrop. Our eventual goal is to determine how extensive the andesite unit is and how it may impact groundwater flow and flooding in this area of growing urbanization.

  2. Geophysical image of the hydrothermal system of Merapi volcano

    Science.gov (United States)

    Byrdina, S.; Friedel, S.; Vandemeulebrouck, J.; Budi-Santoso, A.; Suhari; Suryanto, W.; Rizal, M. H.; Winata, E.; Kusdaryanto

    2017-01-01

    We present an image of the hydrothermal system of Merapi volcano based on results from electrical resistivity tomography (ERT), self-potential, and CO2 flux mappings. The ERT models identify two distinct low-resistivity bodies interpreted as two parts of a probably interconnected hydrothermal system: at the base of the south flank and in the summit area. In the summit area, a sharp resistivity contrast at ancient crater rim Pasar-Bubar separates a conductive hydrothermal system (20-50 Ω m) from the resistive andesite lava flows and pyroclastic deposits (2000-50,000 Ω m). The existence of preferential fluid circulation along this ancient crater rim is also evidenced by self-potential data. The significative diffuse CO2 degassing (with a median value of 400 g m-2 d-1) is observed in a narrow vicinity of the active crater rim and close to the ancient rim of Pasar-Bubar. The total CO2 degassing across the accessible summital area with a surface of 1.4 ṡ 105 m2 is around 20 t d-1. Before the 2010 eruption, Toutain et al. (2009) estimated a higher value of the total diffuse degassing from the summit area (about 200-230 t d-1). This drop in the diffuse degassing from the summit area can be related to the decrease in the magmatic activity, to the change of the summit morphology, to the approximations used by Toutain et al. (2009), or, more likely, to a combination of these factors. On the south flank of Merapi, the resistivity model shows spectacular stratification. While surficial recent andesite lava flows are characterized by resistivity exceeding 100,000 Ω m, resistivity as low as 10 Ω m has been encountered at a depth of 200 m at the base of the south flank and was interpreted as a presence of the hydrothermal system. No evidence of the hydrothermal system is found on the basis of the north flank at the same depth. This asymmetry might be caused by the asymmetry of the heat supply source of Merapi whose activity is moving south or/and to the asymmetry in

  3. A standard graphite block

    Energy Technology Data Exchange (ETDEWEB)

    Ivkovic, M; Zdravkovic, Z; Sotic, O [Department of Reactor Physics and Dynamics, Boris Kidric Institute of nuclear sciences Vinca, Belgrade (Yugoslavia)

    1966-04-15

    A graphite block was calibrated for the thermal neutron flux of the Ra-Be source using indium foils as detectors. Experimental values of the thermal neutron flux along the central vertical axis of the system were corrected for the self-shielding effect and depression of flux in the detector. The experimental values obtained were compared with the values calculated on the basis of solving the conservation neutron equation by the continuous slowing-down theory. In this theoretical calculation of the flux the Ra-Be source was divided into three resonance energy regions. The measurement of the thermal neutron diffusion length in the standard graphite block is described. The measurements were performed in the thermal neutron region of the system. The experimental results were interpreted by the diffusion theory for point thermal neutron source in the finite system. The thermal neutron diffusion length was calculated to be L= 50.9 {+-}3.1 cm for the following graphite characteristics: density = 1.7 g/cm{sup 3}; boron content = 0.1 ppm; absorption cross section = 3.7 mb.

  4. A standard graphite block

    International Nuclear Information System (INIS)

    Ivkovic, M.; Zdravkovic, Z.; Sotic, O.

    1966-04-01

    A graphite block was calibrated for the thermal neutron flux of the Ra-Be source using indium foils as detectors. Experimental values of the thermal neutron flux along the central vertical axis of the system were corrected for the self-shielding effect and depression of flux in the detector. The experimental values obtained were compared with the values calculated on the basis of solving the conservation neutron equation by the continuous slowing-down theory. In this theoretical calculation of the flux the Ra-Be source was divided into three resonance energy regions. The measurement of the thermal neutron diffusion length in the standard graphite block is described. The measurements were performed in the thermal neutron region of the system. The experimental results were interpreted by the diffusion theory for point thermal neutron source in the finite system. The thermal neutron diffusion length was calculated to be L= 50.9 ±3.1 cm for the following graphite characteristics: density = 1.7 g/cm 3 ; boron content = 0.1 ppm; absorption cross section = 3.7 mb

  5. Structural disorder of graphite and implications for graphite thermometry

    Science.gov (United States)

    Kirilova, Martina; Toy, Virginia; Rooney, Jeremy S.; Giorgetti, Carolina; Gordon, Keith C.; Collettini, Cristiano; Takeshita, Toru

    2018-02-01

    Graphitization, or the progressive maturation of carbonaceous material, is considered an irreversible process. Thus, the degree of graphite crystallinity, or its structural order, has been calibrated as an indicator of the peak metamorphic temperatures experienced by the host rocks. However, discrepancies between temperatures indicated by graphite crystallinity versus other thermometers have been documented in deformed rocks. To examine the possibility of mechanical modifications of graphite structure and the potential impacts on graphite thermometry, we performed laboratory deformation experiments. We sheared highly crystalline graphite powder at normal stresses of 5 and 25 megapascal (MPa) and aseismic velocities of 1, 10 and 100 µm s-1. The degree of structural order both in the starting and resulting materials was analyzed by Raman microspectroscopy. Our results demonstrate structural disorder of graphite, manifested as changes in the Raman spectra. Microstructural observations show that brittle processes caused the documented mechanical modifications of the aggregate graphite crystallinity. We conclude that the calibrated graphite thermometer is ambiguous in active tectonic settings.

  6. Structural disorder of graphite and implications for graphite thermometry

    Directory of Open Access Journals (Sweden)

    M. Kirilova

    2018-02-01

    Full Text Available Graphitization, or the progressive maturation of carbonaceous material, is considered an irreversible process. Thus, the degree of graphite crystallinity, or its structural order, has been calibrated as an indicator of the peak metamorphic temperatures experienced by the host rocks. However, discrepancies between temperatures indicated by graphite crystallinity versus other thermometers have been documented in deformed rocks. To examine the possibility of mechanical modifications of graphite structure and the potential impacts on graphite thermometry, we performed laboratory deformation experiments. We sheared highly crystalline graphite powder at normal stresses of 5 and 25  megapascal (MPa and aseismic velocities of 1, 10 and 100 µm s−1. The degree of structural order both in the starting and resulting materials was analyzed by Raman microspectroscopy. Our results demonstrate structural disorder of graphite, manifested as changes in the Raman spectra. Microstructural observations show that brittle processes caused the documented mechanical modifications of the aggregate graphite crystallinity. We conclude that the calibrated graphite thermometer is ambiguous in active tectonic settings.

  7. May 2011 eruption of Telica Volcano, Nicaragua: Multidisciplinary observations

    Science.gov (United States)

    Witter, M. R.; Geirsson, H.; La Femina, P. C.; Roman, D. C.; Rodgers, M.; Muñoz, A.; Morales, A.; Tenorio, V.; Chavarria, D.; Feineman, M. D.; Furman, T.; Longley, A.

    2011-12-01

    Telica volcano, an andesitic stratovolcano in north-western Nicaragua, erupted in May 2011. The eruption, produced ash but no lava and required the evacuation of over 500 people; no injuries were reported. We present the first detailed report of the eruption, using information from the TElica Seismic ANd Deformation (TESAND) network, that provides real-time data, along with visual observations, ash leachate analysis, and fumarole temperature measurements. Telica is located in the Maribios mountain range. It is one of the most active volcanoes in Nicaragua and has frequent small explosions and rare large (VEI 4) eruptions, with the most recent sizable eruptions (VEI 2) occurring in 1946 and 1999. The 2011 eruption is the most explosive since 1999. The eruption consisted of a series of ash explosions, with the first observations from May 8, 2011 when local residents reported ash fall NE of the active crater. Popping sounds could be heard coming from the crater on May 10. On May 13, the activity intensified and continued with some explosions every day for about 2 weeks. The well-defined plumes originated from the northern part of the crater. Ash fall was reported 4 km north of the active crater on May 14. The largest explosion at 2:54 pm (local time) on May 21 threw rocks from the crater and generated a column 2 km in height. Fresh ash samples were collected on May 16, 18, and 21 and preliminary inspection shows that the majority of the material is fragmented rock and crystalline material, i.e. not juvenile. Ash leachates (ash:water = 1:25) contain a few ppb As, Se, and Cd; tens of ppb Co and Ni; and up to a few hundred ppb Cu and Zn. Telica typically has hundreds of small seismic events every day, even when the volcano is not erupting. The TESAND network detected an increase in the rate and magnitude of seismic activity, with a maximum magnitude of 3.3. Elevated fumarole temperatures at locations near the active vent were also observed throughout the May 2011

  8. Bromine intercalated graphite for lightweight composite conductors

    KAUST Repository

    Amassian, Aram

    2017-07-20

    A method of fabricating a bromine-graphite/metal composite includes intercalating bromine within layers of graphite via liquid-phase bromination to create brominated-graphite and consolidating the brominated-graphite with a metal nanopowder via a mechanical pressing operation to generate a bromine-graphite/metal composite material.

  9. Chemical stabilization of graphite surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Bistrika, Alexander A.; Lerner, Michael M.

    2018-04-03

    Embodiments of a device, or a component of a device, including a stabilized graphite surface, methods of stabilizing graphite surfaces, and uses for the devices or components are disclosed. The device or component includes a surface comprising graphite, and a plurality of haloaryl ions and/or haloalkyl ions bound to at least a portion of the graphite. The ions may be perhaloaryl ions and/or perhaloalkyl ions. In certain embodiments, the ions are perfluorobenzenesulfonate anions. Embodiments of the device or component including stabilized graphite surfaces may maintain a steady-state oxidation or reduction surface current density after being exposed to continuous oxidation conditions for a period of at least 1-100 hours. The device or component is prepared by exposing a graphite-containing surface to an acidic aqueous solution of the ions under oxidizing conditions. The device or component can be exposed in situ to the solution.

  10. Two types of adakites revealed by 238U-230Th disequilibrium from Daisen volcano, southwestern Japan

    International Nuclear Information System (INIS)

    Tokunaga, Saimi; Nakai, Shun'ichi; Orihashi, Yuji

    2010-01-01

    Daisen volcano is located on the Quaternary volcanic front in southwestern Japan. The volcano is composed mainly of andesite and dacite, which chemically resemble adakites, with high Al 2 O 3 and Sr/Y, steep REE patterns, and no negative Eu anomaly. ( 238 U/ 230 Th) disequilibrium (herein, a ratio in parentheses denotes the activity ratio) and trace element analyses of adakites from two volcanic domes, Karasugasen and Misen, indicate two adakite types. Adakite from Karasugasen is characterized by excess ( 230 Th) over ( 238 U), typical of most adakites, whereas adakite from Misen is characterized by excess ( 238 U) over ( 230 Th). The latter is consistent with enrichment in fluid-mobile elements relative to fluid immobile elements compared to rocks from Karasugasen. The values of ( 230 Th/ 232 Th) of adakites from Karasugasen and Misen are, respectively, around 0.75 and 0.81. These low ( 230 Th/ 232 Th) ratios result from the incorporation of subducted sedimentary material. The ratios, nevertheless, are higher than that for the estimate of lower crustal material suggesting significant incorporation of lower crust is unlikely. As adakites from Misen have ( 238 U) excess over ( 230 Th), adakite magma must have interacted with wedge mantle metasomatized by a slab-derived fluid, confirming the presence of a fluid-metasomatized mantle beneath Daisen volcano. (author)

  11. Heat exchanger using graphite foam

    Science.gov (United States)

    Campagna, Michael Joseph; Callas, James John

    2012-09-25

    A heat exchanger is disclosed. The heat exchanger may have an inlet configured to receive a first fluid and an outlet configured to discharge the first fluid. The heat exchanger may further have at least one passageway configured to conduct the first fluid from the inlet to the outlet. The at least one passageway may be composed of a graphite foam and a layer of graphite material on the exterior of the graphite foam. The layer of graphite material may form at least a partial barrier between the first fluid and a second fluid external to the at least one passageway.

  12. Soufriere Hills Volcano

    Science.gov (United States)

    2002-01-01

    In this ASTER image of Soufriere Hills Volcano on Montserrat in the Caribbean, continued eruptive activity is evident by the extensive smoke and ash plume streaming towards the west-southwest. Significant eruptive activity began in 1995, forcing the authorities to evacuate more than 7,000 of the island's original population of 11,000. The primary risk now is to the northern part of the island and to the airport. Small rockfalls and pyroclastic flows (ash, rock and hot gases) are common at this time due to continued growth of the dome at the volcano's summit.This image was acquired on October 29, 2002 by the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) on NASA's Terra satellite. With its 14 spectral bands from the visible to the thermal infrared wavelength region, and its high spatial resolution of 15 to 90 meters (about 50 to 300 feet), ASTER images Earth to map and monitor the changing surface of our planet.ASTER is one of five Earth-observing instruments launched December 18, 1999, on NASA's Terra satellite. The instrument was built by Japan's Ministry of Economy, Trade and Industry. A joint U.S./Japan science team is responsible for validation and calibration of the instrument and the data products.The broad spectral coverage and high spectral resolution of ASTER will provide scientists in numerous disciplines with critical information for surface mapping, and monitoring of dynamic conditions and temporal change. Example applications are: monitoring glacial advances and retreats; monitoring potentially active volcanoes; identifying crop stress; determining cloud morphology and physical properties; wetlands evaluation; thermal pollution monitoring; coral reef degradation; surface temperature mapping of soils and geology; and measuring surface heat balance.Dr. Anne Kahle at NASA's Jet Propulsion Laboratory, Pasadena, California, is the U.S. Science team leader; Bjorn Eng of JPL is the project manager. The Terra mission is part of NASA

  13. Purification and preparation of graphite oxide from natural graphite

    Energy Technology Data Exchange (ETDEWEB)

    Panatarani, C., E-mail: c.panatarani@phys.unpad.ac.id; Muthahhari, N.; Joni, I. Made [Instrumentation Systems and Functional Material Processing Laboratory, Department of Physics, Faculty of Mathematics and Natural Sciences, Universitas Padjadjaran, Padjadjaran University, Jl. Raya Bandung-Sumedang KM 21, Jatinangor, 45363, Jawa Barat (Indonesia); Rianto, Anton [Grafindo Nusantara Ltd., Belagio Mall Lantai 2, Unit 0 L3-19, Kawasan Mega Kuningan, Kav. B4 No.3, Jakarta Selatan (Indonesia)

    2016-03-11

    Graphite oxide has attracted much interest as a possible route for preparation of natural graphite in the large-scale production and manipulation of graphene as a material with extraordinary electronic properties. Graphite oxide was prepared by modified Hummers method from purified natural graphite sample from West Kalimantan. We demonstrated that natural graphite is well-purified by acid leaching method. The purified graphite was proceed for intercalating process by modifying Hummers method. The modification is on the reaction time and temperature of the intercalation process. The materials used in the intercalating process are H{sub 2}SO{sub 4} and KMNO{sub 4}. The purified natural graphite is analyzed by carbon content based on Loss on Ignition test. The thermo gravimetricanalysis and the Fouriertransform infrared spectroscopy are performed to investigate the oxidation results of the obtained GO which is indicated by the existence of functional groups. In addition, the X-ray diffraction and energy dispersive X-ray spectroscopy are also applied to characterize respectively for the crystal structure and elemental analysis. The results confirmed that natural graphite samples with 68% carbon content was purified into 97.68 % carbon content. While the intercalation process formed a formation of functional groups in the obtained GO. The results show that the temperature and reaction times have improved the efficiency of the oxidation process. It is concluded that these method could be considered as an important route for large-scale production of graphene.

  14. Characteristics of Hawaiian volcanoes

    Science.gov (United States)

    Poland, Michael P.; Takahashi, T. Jane; Landowski, Claire M.

    2014-01-01

    Founded in 1912 at the edge of the caldera of Kīlauea Volcano, HVO was the vision of Thomas A. Jaggar, Jr., a geologist from the Massachusetts Institute of Technology, whose studies of natural disasters around the world had convinced him that systematic, continuous observations of seismic and volcanic activity were needed to better understand—and potentially predict—earthquakes and volcanic eruptions. Jaggar summarized the aim of HVO by stating that “the work should be humanitarian” and have the goals of developing “prediction and methods of protecting life and property on the basis of sound scientific achievement.” These goals align well with those of the USGS, whose mission is to serve the Nation by providing reliable scientific information to describe and understand the Earth; minimize loss of life and property from natural disasters; manage natural resources; and enhance and protect our quality of life.

  15. Volcanoes, Third Edition

    Science.gov (United States)

    Nye, Christopher J.

    It takes confidence to title a smallish book merely “Volcanoes” because of the impliction that the myriad facets of volcanism—chemistry, physics, geology, meteorology, hazard mitigation, and more—have been identified and addressed to some nontrivial level of detail. Robert and Barbara Decker have visited these different facets seamlessly in Volcanoes, Third Edition. The seamlessness comes from a broad overarching, interdisciplinary, professional understanding of volcanism combined with an exceptionally smooth translation of scientific jargon into plain language.The result is a book which will be informative to a very broad audience, from reasonably educated nongeologists (my mother loves it) to geology undergraduates through professional volcanologists. I bet that even the most senior professional volcanologists will learn at least a few things from this book and will find at least a few provocative discussions of subjects they know.

  16. Management of UKAEA graphite liabilities

    International Nuclear Information System (INIS)

    Wise, M.

    2001-01-01

    The UK Atomic Energy Authority (UKAEA) is responsible for managing its liabilities for redundant research reactors and other active facilities concerned with the development of the UK nuclear technology programme since 1947. These liabilities include irradiated graphite from a variety of different sources including low irradiation temperature reactor graphite (the Windscale Piles 1 and 2, British Energy Pile O and Graphite Low Energy Experimental Pile at Harwell and the Material Testing Reactors at Harwell and Dounreay), advanced gas-cooled reactor graphite (from the Windscale Advanced Gas-cooled Reactor) and graphite from fast reactor systems (neutron shield graphite from the Dounreay Prototype Fast Reactor and Dounreay Fast Reactor). The decommissioning and dismantling of these facilities will give rise to over 6,000 tonnes of graphite requiring disposal. The first graphite will be retrieved from the dismantling of Windscale Pile 1 and the Windscale Advanced Gas-cooled Reactor during the next five years. UKAEA has undertaken extensive studies to consider the best practicable options for disposing of these graphite liabilities in a manner that is safe whilst minimising the associated costs and technical risks. These options include (but are not limited to), disposal as Low Level Waste, incineration, or encapsulation and disposal as Intermediate Level Waste. There are a number of technical issues associated with each of these proposed disposal options; these include Wigner energy, radionuclide inventory determination, encapsulation of graphite dust, galvanic coupling interactions enhancing the corrosion of mild steel and public acceptability. UKAEA is currently developing packaging concepts and designing packaging plants for processing these graphite wastes in consultation with other holders of graphite wastes throughout Europe. 'Letters of Comfort' have been sought from both the Low Level Waste and the Intermediate Level Waste disposal organisations to support the

  17. Graphite in Science and Nuclear Technique

    OpenAIRE

    Zhmurikov, E. I.; Bubnenkov, I. A.; Dremov, V. V.; Samarin, S. I.; Pokrovsky, A. S.; Harkov, D. V.

    2013-01-01

    The monograph is devoted to the application of graphite and graphite composites in science and technology. The structure and electrical properties, the technological aspects of production of high-strength synthetic graphites, the dynamics of the graphite destruction, traditionally used in the nuclear industry are discussed. It is focuses on the characteristics of graphitization and properties of graphite composites based on carbon isotope 13C. The book is based, generally, on the original res...

  18. Pre-eruptive conditions of the ~31 ka rhyolitic magma of Tlaloc volcano, Sierra Nevada Volcanic Range, Central Mexico

    Science.gov (United States)

    Macias, J.; Arce, J.; Rueda, H.; Gardner, J.

    2008-12-01

    Tlaloc volcano is located at the northern tip of the Sierra Nevada Volcanic Range in Central Mexico. This Pleistocene to Recent volcanic range consists from north to south of Tlaloc-Telapón-Teyotl-Iztaccíhuatl-and- Popocatépetl volcanoes. While andesitic to barely dacitic volcanism dominates the southern part of the range (i.e. Popocatépetl and Iztaccíhuatl); dacitic and rare rhyolithic volcanism (i.e. Telapón, Tlaloc) dominates the northern end. The known locus of rhyolitic magmatism took place at Tlaloc volcano with a Plinian-Subplinian eruption that occurred 31 ka ago. The eruption emplaced the so-called multilayered fallout and pumiceous pyroclastic flows (~2 km3 DRE). The deposit consists of 95% vol. of juvenile particles (pumice + crystals) and minor altered lithics 5% vol. The mineral association of the pumice fragments (74-76 % wt. SiO2) consists of quartz + plagioclase + sanidine + biotite and rare oxides set in a glassy groundmass with voids. Melt inclusions in quartz phenocrysts suggest that prior to the eruption the rhyolitic contain ~7% of H2O and Nevado de Toluca volcano (~6 km) some 50 km to the southwest.

  19. Volcanoes in Eruption - Set 1

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The word volcano is used to refer to the opening from which molten rock and gas issue from Earth's interior onto the surface, and also to the cone, hill, or mountain...

  20. Volcanoes in Eruption - Set 2

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The word volcano is used to refer to the opening from which molten rock and gas issue from Earth's interior onto the surface, and also to the cone, hill, or mountain...

  1. Volcano warning systems: Chapter 67

    Science.gov (United States)

    Gregg, Chris E.; Houghton, Bruce F.; Ewert, John W.

    2015-01-01

    Messages conveying volcano alert level such as Watches and Warnings are designed to provide people with risk information before, during, and after eruptions. Information is communicated to people from volcano observatories and emergency management agencies and from informal sources and social and environmental cues. Any individual or agency can be both a message sender and a recipient and multiple messages received from multiple sources is the norm in a volcanic crisis. Significant challenges to developing effective warning systems for volcanic hazards stem from the great diversity in unrest, eruption, and post-eruption processes and the rapidly advancing digital technologies that people use to seek real-time risk information. Challenges also involve the need to invest resources before unrest to help people develop shared mental models of important risk factors. Two populations of people are the target of volcano notifications–ground- and aviation-based populations, and volcano warning systems must address both distinctly different populations.

  2. Effect of fO2 on phase relationship in basaltic andesites during magmatic differentiation: Control of fO2 and sulphur speciation in piston cylinder experiments.

    Science.gov (United States)

    Matjuschkin, Vladimir; Tattitch, Brian; Blundy, Jonathan D.; Skora, Susanne

    2014-05-01

    Within the mantle wedge above subduction zones, oxidation reaction take place by interaction of reduced mantle rocks with more oxidized, hydrous fluids, which can cause a local drop of the solidus, resulting in partial melting (2,6,7). The resultant melts are more oxidized that their ocean floor counterparts, which has implications for their subsequent differentiation paths, the speciation of multivalent elements and the solubility and transport of chemical compounds in magmatic systems (1,4,5). We present a series of sulphur-doped high-pressure experiments conducted to investigate the effect of oxygen fugacity on phase relationships and the behaviour of sulphur in silicate melts. Natural aphyric andesite (FM37) erupted from Laguna del Maule volcano, Chile (3) was selected as a starting composition. Experiments were carried out at 5kbar, 950-1150° C and variable oxygen fugacity conditions. New experiments buffered at Co-CoO and Ni-NiO buffer conditions have been performed using a new "MTB capsule design" developed in order to accurately control fO2 by means of a double capsule containing metal-oxide buffers and a pyrex sleeve to minimise H2 diffusion. This new design constrains oxygen fugacity to within ±0.1-0.2logfO2 units of the target value. Before conducting these experiments, the assemblage was tested multiple times at 10kbar, 1000° C over 24-48 hours and demonstrated consistent, accurate fO2 control. Analyses of the preliminary experimental run products, from a related Chilean basaltic andesite starting composition, demonstrate a clear effect of fO2 on phase relationships and the proportion of melt generated during experiments. Under oxidized conditions, as temperature decreased from 1150° C to 1050° C, the amount of melt decreased from 100% to ~80%, due to the formation of orthopyroxene, anhydrite and plagioclase. In contrast, in reduced runs the system remains nearly liquid (~5% crystals) down to 950° C due to the change in sulphur speciation and

  3. Multiplets: Their behavior and utility at dacitic and andesitic volcanic centers

    Science.gov (United States)

    Thelen, W.; Malone, S.; West, M.

    2011-01-01

    Multiplets, or groups of earthquakes with similar waveforms, are commonly observed at volcanoes, particularly those exhibiting unrest. Using triggered seismic data from the 1980-1986 Mount St. Helens (MSH) eruption, we have constructed a catalog of multiplet occurrence. Our analysis reveals that the occurrence of multiplets is related, at least in part, to the viscosity of the magma. We also constructed catalogs of multiplet occurrence using continuous seismic data from the 2004 eruption at MSH and 2007 eruption at Bezymianny Volcano, Russia. Prior to explosions at MSH in 2004 and Bezymianny in 2007, the multiplet proportion of total seismicity (MPTS) declined, while the average amplitudes and standard deviations of the average amplitude increased. The life spans of multiplets (time between the first and last event) were also shorter prior to explosions than during passive lava extrusion. Dome-forming eruptions that include a partially solidified plug, like MSH (1983-1986 and 2004-2008), often possess multiplets with longer life spans and MPTS values exceeding 50%. Conceptually, the relatively unstable environment prior to explosions is characterized by large and variable stress gradients brought about by rapidly changing overpressures within the conduit. We infer that such complex stress fields affect the number of concurrent families, MPTS, average amplitude, and standard deviation of the amplitude of the multiplets. We also argue that multiplet detection may be an important new monitoring tool for determining the timing of explosions and in forecasting the type of eruption.

  4. Modification of structural graphite machining

    International Nuclear Information System (INIS)

    Lavrenev, M.M.

    1979-01-01

    Studied are machining procedures for structural graphites (GMZ, MG, MG-1, PPG) most widely used in industry, of the article mass being about 50 kg. Presented are dependences necessary for the calculation of cross sections of chip suction tappers and duster pipelines in machine shops for structural graphite machining

  5. GLACIERS OF THE KORYAK VOLCANO

    Directory of Open Access Journals (Sweden)

    T. M. Manevich

    2012-01-01

    Full Text Available The paper presents main glaciological characteristics of present-day glaciers located on the Koryaksky volcano. The results of fieldwork (2008–2009 and high-resolution satellite image analysis let us to specify and complete information on modern glacial complex of Koryaksky volcano. Now there are seven glaciers with total area 8.36 km2. Three of them advance, two are in stationary state and one degrades. Moreover, the paper describes the new crater glacier.

  6. Radon emanometry in active volcanoes

    Energy Technology Data Exchange (ETDEWEB)

    Seidel, J.L.; Monnin, M. (CNRS, IN2P3, BP45/F63170 Aubiere (France)); Cejudo, J. (Instituto Nacional de Investigaciones Nucleares, Mexico City)

    1984-01-01

    Radon emission measurements from active volcanoes has, since 1981, been continuously measured at monitoring stations in Mexico and in Costa Rica. Counting of etched alpha tracks on cellulose nitrate LR-115 detectors give varying results at the several stations. Radon emanation at Chichon, where an explosive eruption occurred in 1982, fell down. Radon detection at the active volcano in Colima shows a pattern of very low emission. At the Costa Rica stations located at Poas, Arenal and Irazu, the radon emanation shows regularity.

  7. Trace Elements and Minerals in Fumarolic Sulfur: The Case of Ebeko Volcano, Kuriles

    Directory of Open Access Journals (Sweden)

    E. P. Shevko

    2018-01-01

    Full Text Available Native sulfur deposits on fumarolic fields at Ebeko volcano (Northern Kuriles, Russia are enriched in chalcophile elements (As-Sb-Se-Te-Hg-Cu and contain rare heavy metal sulfides (Ag2S, HgS, and CuS, native metal alloys (Au2Pd, and some other low-solubility minerals (CaWO4, BaSO4. Sulfur incrustations are impregnated with numerous particles of fresh and altered andesite groundmass and phenocrysts (pyroxene, magnetite as well as secondary minerals, such as opal, alunite, and abundant octahedral pyrite crystals. The comparison of elemental abundances in sulfur and unaltered rocks (andesite demonstrated that rock-forming elements (Ca, K, Fe, Mn, and Ti and other lithophile and chalcophile elements are mainly transported by fumarolic gas as aerosol particles, whereas semimetals (As, Sb, Se, and Te, halogens (Br and I, and Hg are likely transported as volatile species, even at temperatures slightly above 100°C. The presence of rare sulfides (Ag2S, CuS, and HgS together with abundant FeS2 in low-temperature fumarolic environments can be explained by the hydrochloric leaching of rock particles followed by the precipitation of low-solubility sulfides induced by the reaction of acid solutions with H2S at ambient temperatures. The elemental composition of native sulfur can be used to qualitatively estimate elemental abundances in low-temperature fumarolic gases.

  8. Fluid inclusions study in thermal gradient wells, Nevado del Ruiz Volcano

    International Nuclear Information System (INIS)

    Uruena Suarez, Cindy L; Zuluaga, Carlos A; Molano, Juan Carlos

    2012-01-01

    A fluid inclusions study in the Nevado del Ruiz volcano hydrothermal system allowed to characterize fluids involved in the evolution of the geothermal system. Fluid inclusions hosted in quartz, plagioclase and carbonate from samples of the deepest parts of three thermal gradient wells were analyzed to understand fluid-rock interaction. Fluid inclusions hosted in carbonate veins with coloform microestructure represent hydrothermal fluids with temperatures higher than 250 Celsius degrade. This interpretation is supported by microprobe and cathodoluminescence analysis that also indicate a hydrothermal origin for the veins. Fluid inclusions hosted in quartz (mylonite) were originated by metamorphic fluids and fluid inclusions hosted in plagioclase (andesitic lavas) are considered to be originated from magmatic fluids (H 2 O + CO 2 system).

  9. Glass-Graphite Composite Materials

    International Nuclear Information System (INIS)

    Mayzan, M.Z.H.; Lloyd, J.W.; Heath, P.G.; Stennett, M.C.; Hyatt, N.C.; Hand, R.J.

    2016-01-01

    A summary is presented of investigations into the potential of producing glass-composite materials for the immobilisation of graphite or other carbonaceous materials arising from nuclear power generation. The methods are primarily based on the production of base glasses which are subsequently sintered with powdered graphite or simulant TRISO particles. Consideration is also given to the direct preparation of glass-graphite composite materials using microwave technology. Production of dense composite wasteforms with TRISO particles was more successful than with powdered graphite, as wasteforms containing larger amounts of graphite were resistant to densification and the glasses tried did not penetrate the pores under the pressureless conditions used. Based on the results obtained it is concluded that the production of dense glassgraphite composite wasteforms will require the application of pressure. (author)

  10. Flank Collapse Assessment At Kick-'em-Jenny Submarine Volcano (Lesser Antilles): A Combined Approach Using Modelling and Experiments

    Science.gov (United States)

    Dondin, F. J. Y.; Heap, M. J.; Robertson, R. E. A.; Dorville, J. F. M.; Carey, S.

    2016-12-01

    In the Lesser Antilles over 52 volcanic landslide episodes have been identified. These episodes serve as a testament to the hazard posed by volcanic landslides to a region composed of many islands that are small independent countries with vulnerable local economies. This study presents a relative slope stability analysis (RIA) to investigate the stability condition of the only active submarine volcano of the Lesser Antilles Arc: Kick-'em-Jenny Submarine Volcano (KeJ). Thus we hope to provide better constraint on the landslide source geometry to help mitigate volcanic landslide hazards at a KeJ. KeJ is located ca. 8 km north of Grenada island. KeJ lies within a collapse scar from a prehistorical flank collapse. This collapse was associated with a voluminous landslide deposit of about 4.4km3 with a 14 km runout. Numerial simulations showed that this event could generate a regional tsunami. We aim to quantify potential initial volumes of collapsed material using a RIA. The RIA evaluates the critical potential failure surface associated with factor of safety (Fs) inferior to unity and compares them to areas of deficit/surplus of mass/volume obtained from the comparison of an high resolution digital elevation model of the edifice with an ideal 3D surface. We use freeware programs VolcanoFit 2.0 and SSAP 4.7. and produce a 3D representation of the stability map. We report, for the first time, results of a Limit Equilibrium Method performed using geomechanical parameters retrieved from rock mechanics tests performed on two rock basaltic-andesite rock samples collected from within the crater of the volcano during the 1-18 November 2013 NA039 E/V Nautilus cruise. We performed triaxial and uniaxial deformation tests to obtain values of strength at the top and bottom of the edifice. We further characterized the permeability and P-wave velocity of the samples collected. The chosen internal structure for the model is composed of three bodies: (i) a body composed of basaltic-andesite

  11. Vertical Motions of Oceanic Volcanoes

    Science.gov (United States)

    Clague, D. A.; Moore, J. G.

    2006-12-01

    Oceanic volcanoes offer abundant evidence of changes in their elevations through time. Their large-scale motions begin with a period of rapid subsidence lasting hundreds of thousands of years caused by isostatic compensation of the added mass of the volcano on the ocean lithosphere. The response is within thousands of years and lasts as long as the active volcano keeps adding mass on the ocean floor. Downward flexure caused by volcanic loading creates troughs around the growing volcanoes that eventually fill with sediment. Seismic surveys show that the overall depression of the old ocean floor beneath Hawaiian volcanoes such as Mauna Loa is about 10 km. This gross subsidence means that the drowned shorelines only record a small part of the total subsidence the islands experienced. In Hawaii, this history is recorded by long-term tide-gauge data, the depth in drill holes of subaerial lava flows and soil horizons, former shorelines presently located below sea level. Offshore Hawaii, a series of at least 7 drowned reefs and terraces record subsidence of about 1325 m during the last half million years. Older sequences of drowned reefs and terraces define the early rapid phase of subsidence of Maui, Molokai, Lanai, Oahu, Kauai, and Niihau. Volcanic islands, such as Maui, tip down toward the next younger volcano as it begins rapid growth and subsidence. Such tipping results in drowned reefs on Haleakala as deep as 2400 m where they are tipped towards Hawaii. Flat-topped volcanoes on submarine rift zones also record this tipping towards the next younger volcano. This early rapid subsidence phase is followed by a period of slow subsidence lasting for millions of years caused by thermal contraction of the aging ocean lithosphere beneath the volcano. The well-known evolution along the Hawaiian chain from high to low volcanic island, to coral island, and to guyot is due to this process. This history of rapid and then slow subsidence is interrupted by a period of minor uplift

  12. Tremor Source Location at Okmok Volcano

    Science.gov (United States)

    Reyes, C. G.; McNutt, S. R.

    2007-12-01

    Initial results using an amplitude-based tremor location program have located several active tremor episodes under Cone A, a vent within Okmok volcano's 10 km caldera. Okmok is an andesite volcano occupying the north-eastern half of Umnak Island, in the Aleutian islands. Okmok is defined by a ~2000 y.b.p. caldera that contains multiple cinder cones. Cone A, the youngest of these, extruded lava in 1997 covering the caldera floor. Since April 2003, continuous seismic data have been recorded from eight vertical short-period stations (L4-C's) installed at distances from Cone A ranging from 2 km to 31 km. In 2004 four additional 3- component broadband stations were added, co-located with continuous GPS stations. InSAR and GPS measurements of post-eruption deformation show that Okmok experienced several periods of rapid inflation (Mann and Freymueller, 2002), from the center of the 10 km diameter caldera. While there are few locatable VT earthquakes, there has been nearly continuous low-level tremor with stronger amplitude bursts occurring at variable rates and durations. The character of occurrence remained relatively constant over the course of days to weeks until the signal ceased in mid 2005. Within any day, tremor behavior remains fairly consistent, with bursts closely resembling each other, suggesting a single main process or source location. The tremor is composed of irregular waves with a broad range of frequencies, though most energy resides between ~2 Hz and 6 Hz. Attempts to locate the tremor using traditional arrival time methods fail because the signal is emergent, with envelopes too ragged to correlate on time scales that hold much hope for a location. Instead, focus was shifted to the amplitude ratios at various stations. Candidates for the tremor source include the center of inflation and Cone A, 3 km to the south-west. For all dates on record, data were band pass filtered between 1 and 5 Hz, then evaluated in 20.48 second windows (N=2048, sampling rate

  13. Chiliques volcano, Chile

    Science.gov (United States)

    2002-01-01

    A January 6, 2002 ASTER nighttime thermal infrared image of Chiliques volcano in Chile shows a hot spot in the summit crater and several others along the upper flanks of the edifice, indicating new volcanic activity. Examination of an earlier nighttime thermal infrared image from May 24,2000 showed no thermal anomaly. Chiliques volcano was previously thought to be dormant. Rising to an elevation of 5778 m, Chiliques is a simple stratovolcano with a 500-m-diameter circular summit crater. This mountain is one of the most important high altitude ceremonial centers of the Incas. It is rarely visited due to its difficult accessibility. Climbing to the summit along Inca trails, numerous ruins are encountered; at the summit there are a series of constructions used for rituals. There is a beautiful lagoon in the crater that is almost always frozen.The daytime image was acquired on November 19, 2000 and was created by displaying ASTER bands 1,2 and 3 in blue, green and red. The nighttime image was acquired January 6, 2002, and is a color-coded display of a single thermal infrared band. The hottest areas are white, and colder areas are darker shades of red. Both images cover an area of 7.5 x 7.5 km, and are centered at 23.6 degrees south latitude, 67.6 degrees west longitude.Both images cover an area of 7.5 x 7.5 km, and are centered at 23.6 degrees south latitude, 67.6 degrees west longitude.These images were acquired by the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) on NASA's Terra satellite. With its 14spectral bands from the visible to the thermal infrared wavelength region, and its high spatial resolution of 15 to 90 meters (about 50 to 300 feet), ASTER will image Earth for the next 6 years to map and monitor the changing surface of our planet.ASTER is one of five Earth-observing instruments launched December 18,1999, on NASA's Terra satellite. The instrument was built by Japan's Ministry of Economy, Trade and Industry. A joint U

  14. The rise and fall of periodic 'drumbeat' seismicity at Tungurahua volcano, Ecuador

    Science.gov (United States)

    Bell, Andrew F.; Hernandez, Stephen; Gaunt, H. Elizabeth; Mothes, Patricia; Ruiz, Mario; Sierra, Daniel; Aguaiza, Santiago

    2017-10-01

    Highly periodic 'drumbeat' long period (LP) earthquakes have been described from several andesitic and dacitic volcanoes, commonly accompanying incremental ascent and effusion of viscous magma. However, the processes controlling the occurrence and characteristics of drumbeat, and LP earthquakes more generally, remain contested. Here we use new quantitative tools to describe the emergence, evolution, and degradation of drumbeat LP seismicity at the andesitic Tungurahua volcano, Ecuador, in April 2015. The signals were recorded during an episode of minor explosive activity and ash emission, without lava effusion, and are the first to be reported at Tungurahua during the ongoing 17 yrs of eruption. Following four days of high levels of continuous and 'pulsed' tremor, highly-periodic LP earthquakes first appear on 10 April. Over the next four days, inter-event times and event amplitudes evolve through a series of step-wise transitions between stable behaviors, each involving a decrease in the degree of periodicity. Families of similar waveforms persist before, during, and after drumbeat activity, but the activity levels of different families change coincidentally with transitions in event rate, amplitude, and periodicity. A complex micro-seismicity 'initiation' sequence shows pulse-like and stepwise changes in inter-event times and amplitudes in the hours preceding the onset of drumbeat activity that indicate a partial de-coupling between event size and rate. The observations increase the phenomenology of drumbeat LP earthquakes, and suggest that at Tungurahua they result from gas flux and rapid depressurization controlled by shear failure of the margins of the ascending magma column.

  15. Groundwater circulations within a tropical humid andesitic volcanic watershed using the temperature as a tracer

    Science.gov (United States)

    Selles, Adrien; Violette, Sophie; Hendrayana, Heru

    2014-05-01

    Groundwater flow within volcano-detritic environment, is of prime importance to many human needs and activities, from the supply of clean drinking water to the extraction of hydrocarbons or geothermal energy. However, the heterogeneity of the geological formations makes difficult to quantify the groundwater spatial distribution. Moreover, its temporal variation in tropical humid regions is sometimes poorly known. For instance, the surronding of the Merapi volcano, in Central Java, Indonesia, is an area of high but seasonal rainfall, and extensive crop irrigation. It has a large population and a need to increase food and potable water supplies depending upon exploiting groundwater ressources. The stress on these resources increases with the intensification of the demography, the agricultural practices and the industrial exploitations. In order to implement a sustainable management of the water resources, the description of the groundwater circulations and the quantification of the resources is needed. A mutidisciplinary approach has been performed at the watershed scale, including geology, hydrogeochemistry and long term hydrogeological monitoring. The data synthesis and constisency have been confirm with a numerical model of physical processes. Based on a geological and geomorphological study, the hydrogeological watershed on the Eastern flank of the Merapi volcano is composed by an alternation of aquitards (mainly ashes, tuffs and clay) and aquifers (sand, gravel and boulders). The deep aquifers are agenced in conduit following the burried channel of the paleo-rivers. The eastern flank of Merapi provides excellent example of a volcanic-sedimentary environment. From 20 cold springs of 3 spring zones, sampled on 2 hydrological years (2011 to 2013), the study of the transfer into the saturated zone from upstream to downstream, given the geological context and topography, allows to estimate the role of supply from high and low altitudes to the recharge processes. The

  16. Hypervelocity impacts into graphite

    Science.gov (United States)

    Latunde-Dada, S.; Cheesman, C.; Day, D.; Harrison, W.; Price, S.

    2011-03-01

    Studies have been conducted into the characterisation of the behaviour of commercial graphite (brittle) when subjected to hypervelocity impacts by a range of projectiles. The experiments were conducted with a two-stage gas gun capable of launching projectiles of differing density and strength to speeds of about 6kms-1 at right angles into target plates. The damage caused is quantified by measurements of the crater depth and diameters. From the experimental data collected, scaling laws were derived which correlate the crater dimensions to the velocity and the density of the projectile. It was found that for moderate projectile densities the crater dimensions obey the '2/3 power law' which applies to ductile materials.

  17. Hypervelocity impacts into graphite

    International Nuclear Information System (INIS)

    Latunde-Dada, S; Cheesman, C; Day, D; Harrison, W; Price, S

    2011-01-01

    Studies have been conducted into the characterisation of the behaviour of commercial graphite (brittle) when subjected to hypervelocity impacts by a range of projectiles. The experiments were conducted with a two-stage gas gun capable of launching projectiles of differing density and strength to speeds of about 6kms -1 at right angles into target plates. The damage caused is quantified by measurements of the crater depth and diameters. From the experimental data collected, scaling laws were derived which correlate the crater dimensions to the velocity and the density of the projectile. It was found that for moderate projectile densities the crater dimensions obey the '2/3 power law' which applies to ductile materials.

  18. Acoustic emission from polycrystalline graphites

    International Nuclear Information System (INIS)

    Ioka, I.; Yoda, S.; Oku, T.; Miyamoto, Y.

    1987-01-01

    Acoustic emission was monitored from polycrystalline graphites with different microstructure (pore size and pore volume) subjected to compressive loading. The graphites used in this study comprised five brands, that is, PGX, ISEM-1, IG-11, IG-15, and ISO-88. A root mean square (RMS) voltage and event counts of acoustic emission for graphites were measured during compressive loading. The acoustic emission was measured using a computed-based data acquisition and analysis system. The graphites were first deformed up to 80 % of the average fracture stress, then unloaded and reloaded again until the fracture occured. During the first loading, the change in RMS voltage for acoustic emission was detected from the initial stage. During the unloading, the RMS voltage became zero level as soon as the applied stress was released and then gradually rose to a peak and declined. The behavior indicated that the reversed plastic deformation occured in graphites. During the second loading, the RMS voltage gently increased until the applied stress exceeded the maximum stress of the first loading; there is no Kaiser effect in the graphites. A bicrystal model could give a reasonable explanation of this results. The empirical equation between the ratio of σ AE to σ f and σ f was obtained. It is considered that the detection of microfracture by the acoustic emission technique is effective in macrofracture prediction of polycrystalline graphites. (author)

  19. Radiolytic graphite oxidation revisited

    International Nuclear Information System (INIS)

    Minshall, P.C.; Sadler, I.A.; Wickham, A.J.

    1996-01-01

    The importance of radiolytic oxidation in graphite-moderated CO 2 -cooled reactors has long been recognised, especially in the Advanced Gas-Cooled Reactors where potential rates are higher because of the higher gas pressure and ratings than the earlier Magnox designs. In all such reactors, the rate of oxidation is partly inhibited by the CO produced in the reaction and, in the AGR, further reduced by the deliberate addition of CH 4 . Significant roles are also played by H 2 and H 2 O. This paper reviews briefly the mechanisms of these processes and the data on which they are based. However, operational experience has demonstrated that these basic principles are unsatisfactory in a number of respects. Gilsocarbon graphites produced by different manufacturers have demonstrated a significant difference in oxidation rate despite a similar specification and apparent equivalence in their pore size and distribution, considered to be the dominant influence on oxidation rate for a given coolant-gas composition. Separately, the inhibiting influence of CH 4 , which for many years had been considered to arise from the formation of a sacrificial deposit on the pore walls, cannot adequately be explained by the actual quantities of such deposits found in monitoring samples which frequently contain far less deposited carbon than do samples from Magnox reactors where the only source of such deposits is the CO. The paper also describes the current status of moderator weight-loss predictions for Magnox and AGR Moderators and the validation of the POGO and DIFFUSE6 codes respectively. 2 refs, 5 figs

  20. The violent Strombolian eruption of 10 ka Pelado shield volcano, Sierra Chichinautzin, Central Mexico

    Science.gov (United States)

    Lorenzo-Merino, A.; Guilbaud, M.-N.; Roberge, J.

    2018-03-01

    Pelado volcano is a typical example of an andesitic Mexican shield with a summital scoria cone. It erupted ca. 10 ka in the central part of an elevated plateau in what is today the southern part of Mexico City. The volcano forms a roughly circular, 10-km wide lava shield with two summital cones, surrounded by up to 2.7-m thick tephra deposits preserved up to a distance of 3 km beyond the shield. New cartographic, stratigraphic, granulometric, and componentry data indicate that Pelado volcano was the product of a single, continuous eruption marked by three stages. In the early stage, a > 1.5-km long fissure opened and was active with mild explosive activity. Intermediate and late stages were mostly effusive and associated with the formation of a 250-m high lava shield. Nevertheless, during these stages, the emission of lava alternated and/or coexisted with highly explosive events that deposited a widespread tephra blanket. In the intermediate stage, multiple vents were active along the fissure, but activity was centered at the main cone during the late stage. The final activity was purely effusive. The volcano emitted > 0.9 km3 dense-rock equivalent (DRE) of tephra and up to 5.6 km3 DRE of lavas. Pelado shares various features with documented "violent Strombolian" eruptions, including a high fragmentation index, large dispersal area, occurrence of plate tephra, high eruptive column, and simultaneous explosive and effusive activity. Our results suggest that the associated hazards (mostly tephra fallout and emplacement of lava) would seriously affect areas located up to 25 km from the vent for fallout and 5 km from the vent for lava, an important issue for large cities built near or on potentially active zones, such as Mexico City.

  1. Chemisputtering of interstellar graphite grains

    International Nuclear Information System (INIS)

    Draine, B.T.

    1979-01-01

    The rate of erosion of interstellar graphite grains as a result of chemical reaction with H, N, and O is estimated using the available experiment evidence. It is argued that ''chemical sputtering'' yields for interstellar graphite grains will be much less than unity, contrary to earlier estimates by Barlow and Silk. Chemical sputtering of graphite grains in evolving H II regions is found to be unimportant, except in extremely compact (n/sub H/> or approx. =10 5 cm -3 ) H II regions. Alternative explanations are considered for the apparent weakness of the lambda=2175 A extinction ''bump'' in the direction of several early type stars

  2. Obtention of nuclear grade graphite

    International Nuclear Information System (INIS)

    Ferreira, M.L.

    1984-01-01

    The impurity level of natural graphite found in some of the most important mines of the State of Minas Gerais - Brasil is determined. It is also concerned with the development and use of natural graphite in nuclear reactors. Standard methods for chemical and instrumentsal analysis such as Spectrografic Determination by Emission, Spectrografic Determination by X-Rays, Spectrografic Determination by Atomic Asorption, Photometric Determination, and also chemical and physical methods for separation of impurities as well standard method for Estimating the Thermal Neutron Absorption Cross Section of graphite were employed. Some aditionals methods of purification to the ordinary treatment such as the use of metanol and halogens are also described. (Author) [pt

  3. Characterization of Ignalina NPP RBMK Reactors Graphite

    International Nuclear Information System (INIS)

    Hacker, P.J.; Neighbour, G.B.; Levinskas, R.; Milcius, D.

    2001-01-01

    The paper concentrates on the investigations of the initial physical properties of graphite used in production of graphite bricks of Ignalina NPP. These graphite bricks are used as nuclear moderator and major core structural components. Graphite bulk density is calculated by mensuration, pore volumes are measured by investigation of helium gas penetration in graphite pore network, the Young's modulus is determined using an ultrasonic time of flight method, the coefficient of thermal expansion is determined using a Netzsch dilatometer 402C, the fractured and machined graphite surfaces are studied using SEM, impurities are investigated qualitatively by EDAX, the degree of graphitization of the material is tested using X-ray diffraction. (author)

  4. Global Volcano Mortality Risks and Distribution

    Data.gov (United States)

    National Aeronautics and Space Administration — Global Volcano Mortality Risks and Distribution is a 2.5 minute grid representing global volcano mortality risks. The data set was constructed using historical...

  5. Graphite in Science and Nuclear Technology

    OpenAIRE

    Zhmurikov, Evgenij

    2015-01-01

    This review is devoted to the application of graphite and graphite composites in the science and technology. Structure and electrical properties, technological aspects of producing of high-strength artificial graphite and dynamics of its destruction are considered. These type of graphite are traditionally used in the nuclear industry, so author concentrates on actual problems of application and testing of graphite materials in modern science and technology. Translated from chapters 1 of monog...

  6. Mesostructure of graphite composite and its lifetime

    OpenAIRE

    Zhmurikov, Evgenij

    2015-01-01

    This review is devoted to the application of graphite and graphite composites in science and technology. Structure and electrical properties, as so technological aspects of producing of high strength artificial graphite and dynamics of its destruction are considered. These type of graphite are traditionally used in the nuclear industry. Generally, the review relies, on the original results and concentrates on actual problems of application and testing of graphite materials in modern nuclear p...

  7. Global Volcano Model

    Science.gov (United States)

    Sparks, R. S. J.; Loughlin, S. C.; Cottrell, E.; Valentine, G.; Newhall, C.; Jolly, G.; Papale, P.; Takarada, S.; Crosweller, S.; Nayembil, M.; Arora, B.; Lowndes, J.; Connor, C.; Eichelberger, J.; Nadim, F.; Smolka, A.; Michel, G.; Muir-Wood, R.; Horwell, C.

    2012-04-01

    Over 600 million people live close enough to active volcanoes to be affected when they erupt. Volcanic eruptions cause loss of life, significant economic losses and severe disruption to people's lives, as highlighted by the recent eruption of Mount Merapi in Indonesia. The eruption of Eyjafjallajökull, Iceland in 2010 illustrated the potential of even small eruptions to have major impact on the modern world through disruption of complex critical infrastructure and business. The effects in the developing world on economic growth and development can be severe. There is evidence that large eruptions can cause a change in the earth's climate for several years afterwards. Aside from meteor impact and possibly an extreme solar event, very large magnitude explosive volcanic eruptions may be the only natural hazard that could cause a global catastrophe. GVM is a growing international collaboration that aims to create a sustainable, accessible information platform on volcanic hazard and risk. We are designing and developing an integrated database system of volcanic hazards, vulnerability and exposure with internationally agreed metadata standards. GVM will establish methodologies for analysis of the data (eg vulnerability indices) to inform risk assessment, develop complementary hazards models and create relevant hazards and risk assessment tools. GVM will develop the capability to anticipate future volcanism and its consequences. NERC is funding the start-up of this initiative for three years from November 2011. GVM builds directly on the VOGRIPA project started as part of the GRIP (Global Risk Identification Programme) in 2004 under the auspices of the World Bank and UN. Major international initiatives and partners such as the Smithsonian Institution - Global Volcanism Program, State University of New York at Buffalo - VHub, Earth Observatory of Singapore - WOVOdat and many others underpin GVM.

  8. Graphite surveillance in N Reactor

    International Nuclear Information System (INIS)

    Woodruff, E.M.

    1991-09-01

    Graphite dimensional changes in N Reactor during its 24 yr operating history are reviewed. Test irradiation results, block measurements, stack profiles, top of reflector motion monitors, and visual observations of distortion are described. 18 refs., 14 figs., 1 tab

  9. Graphite oxidation in HTGR atmosphere

    International Nuclear Information System (INIS)

    Growcock, F.B.; Barry, J.J.; Finfrock, C.C.; Rivera, E.; Heiser, J.H. III

    1982-01-01

    On-going and recently completed studies of the effect of thermal oxidation on the structural integrity of HTGR candidate graphites are described, and some results are presented and discussed. This work includes the study of graphite properties which may play decisive roles in the graphites' resistance to oxidation and fracture: pore size distribution, specific surface area and impurity distribution. Studies of strength loss mechanisms in addition to normal oxidation are described. Emphasis is placed on investigations of the gas permeability of HTGR graphites and the surface burnoff phenomenon observed during recent density profile measurements. The recently completed studies of catalytic pitting and the effects of prestress and stress on reactivity and ultimate strength are also discussed

  10. Graphite materials for nuclear reactors

    International Nuclear Information System (INIS)

    Oku, Tatsuo

    1991-01-01

    Graphite materials have been used in the nuclear fission reactors from the beginning of the reactor development for the speed reduction and reflection of neutron. Graphite materials are used both as a moderator and as a reflector in the core of high temperature gas-cooled reactors, and both as a radiation shielding material and as a reflector in the surrounding of the core for the fast breeder reactor. On the other hand, graphite materials are being positively used as a first wall of plasma as it is known that low Z materials are useful for holding high temperature plasma in the nuclear fusion devices. In this paper the present status of the application of graphite materials to the nuclear fission reactors and fusion devices (reactors) is presented. In addition, a part of results on the related properties to the structural design and safety evaluation and results examined on the subjects that should be done in the future are also described. (author)

  11. Postglacial eruptive history and geochemistry of Semisopochnoi volcano, western Aleutian Islands, Alaska

    Science.gov (United States)

    Coombs, Michelle L.; Larsen, Jessica F.; Neal, Christina A.

    2018-02-14

    Semisopochnoi Island, located in the Rat Islands group of the western Aleutian Islands and Aleutian volcanic arc, is a roughly circular island composed of scattered volcanic vents, the prominent caldera of Semisopochnoi volcano, and older, ancestral volcanic rocks. The oldest rocks on the island are gently radially dipping lavas that are the remnants of a shield volcano and of Ragged Top, which is an eroded stratocone southeast of the current caldera. None of these oldest rocks have been dated, but they all are likely Pleistocene in age. Anvil Peak, to the caldera’s north, has the morphology of a young stratocone and is latest Pleistocene to early Holocene in age. The oldest recognized Holocene deposits are those of the caldera-forming eruption, which produced the 7- by 6-km caldera in the center of the island, left nonwelded ignimbrite in valleys below the edifice, and left welded ignimbrite high on its flanks. The caldera-forming eruption produced rocks showing a range of intermediate whole-rock compositions throughout the eruption sequence, although a majority of clasts analyzed form a fairly tight cluster on SiO2-variation diagrams at 62.9 to 63.4 weight percent SiO2. This clustering of compositions at about 63 weight percent SiO2 includes black, dense, obsidian-like clasts, as well as tan, variably oxidized, highly inflated pumice clasts. The best estimate for the timing of the eruption is from a soil dated at 6,920±60 14C years before present underlying a thin facies of the ignimbrite deposit on the island’s north coast. Shortly after the caldera-forming eruption, two scoria cones on the northwest flank of the volcano outside the caldera, Ringworm crater and Threequarter Cone, simultaneously erupted small volumes of andesite.The oldest intracaldera lavas, on the floor of the caldera, are andesitic to dacitic, but are mostly covered by younger lavas and tephras. These intracaldera lavas include the basaltic andesites of small Windy cone, as well as the

  12. Relative chronology of Martian volcanoes

    International Nuclear Information System (INIS)

    Landheim, R.; Barlow, N.G.

    1991-01-01

    Impact cratering is one of the major geological processes that has affected the Martian surface throughout the planet's history. The frequency of craters within particular size ranges provides information about the formation ages and obliterative episodes of Martian geologic units. The Barlow chronology was extended by measuring small craters on the volcanoes and a number of standard terrain units. Inclusions of smaller craters in units previously analyzed by Barlow allowed for a more direct comparison between the size-frequency distribution data for volcanoes and established chronology. During this study, 11,486 craters were mapped and identified in the 1.5 to 8 km diameter range in selected regions of Mars. The results are summarized in this three page report and give a more precise estimate of the relative chronology of the Martian volcanoes. Also, the results of this study lend further support to the increasing evidence that volcanism has been a dominant geologic force throughout Martian history

  13. Field-trip guide to the geologic highlights of Newberry Volcano, Oregon

    Science.gov (United States)

    Jensen, Robert A.; Donnelly-Nolan, Julie M.

    2017-08-09

    Newberry Volcano and its surrounding lavas cover about 3,000 square kilometers (km2) in central Oregon. This massive, shield-shaped, composite volcano is located in the rear of the Cascades Volcanic Arc, ~60 km east of the Cascade Range crest. The volcano overlaps the northwestern corner of the Basin and Range tectonic province, known locally as the High Lava Plains, and is strongly influenced by the east-west extensional environment. Lava compositions range from basalt to rhyolite. Eruptions began about half a million years ago and built a broad composite edifice that has generated more than one caldera collapse event. At the center of the volcano is the 6- by 8-km caldera, created ~75,000 years ago when a major explosive eruption of compositionally zoned tephra led to caldera collapse, leaving the massive shield shape visible today. The volcano hosts Newberry National Volcanic Monument, which encompasses the caldera and much of the northwest rift zone where mafic eruptions occurred about 7,000 years ago. These young lava flows erupted after the volcano was mantled by the informally named Mazama ash, a blanket of volcanic ash generated by the eruption that created Crater Lake about 7,700 years ago. This field trip guide takes the visitor to a variety of easily accessible geologic sites in Newberry National Volcanic Monument, including the youngest and most spectacular lava flows. The selected sites offer an overview of the geologic story of Newberry Volcano and feature a broad range of lava compositions. Newberry’s most recent eruption took place about 1,300 years ago in the center of the caldera and produced tephra and lava of rhyolitic composition. A significant mafic eruptive event occurred about 7,000 years ago along the northwest rift zone. This event produced lavas ranging in composition from basalt to andesite, which erupted over a distance of 35 km from south of the caldera to Lava Butte where erupted lava flowed west to temporarily block the Deschutes

  14. Systematic radon survey over active volcanoes

    Energy Technology Data Exchange (ETDEWEB)

    Seidel, J.L.; Monnin, M.; Garcia Vindas, J.R. [Centre National de la Recherche Cientifique, Montpellier (France). Lab. GBE; Ricard, L.P.; Staudacher, T. [Observatoire Volcanologique Du Pitou de la Fournaise, La Plaine des Cafres (France)

    1999-08-01

    Data obtained since 1993 on Costa Rica volcanos are presented and radon anomalies recorded before the eruption of the Irazu volcano (December 8, 1994) are discussed. The Piton de la Fournaise volcano is inactive since mid 1992. The influence of the external parameters on the radon behaviour is studied and the type of perturbations induced on short-term measurements are individuate.

  15. Graphite selection for the PBMR reflector

    International Nuclear Information System (INIS)

    Marsden, B.J.; Preston, S.D.

    2000-01-01

    A high temperature, direct cycle gas turbine, graphite moderated, helium cooled, pebble-bed reactor (PBMR) is being designed and constructed in South Africa. One of the major components in the PBMR is the graphite reflector, which must be designed to last thirty-five full power years. Fast neutron irradiation changes the dimensions and material properties of reactor graphite, thus for design purposes a suitable graphite database is required. Data on the effect of irradiation on nuclear graphites has been gathered for many years, at considerable financial cost, but unfortunately these graphites are no longer available due to rationalization of the graphite industry and loss of key graphite coke supplies. However, it is possible, using un-irradiated graphite materials properties and knowledge of the particular graphite microstructure, to determine the probable irradiation behaviour. Three types of nuclear graphites are currently being considered for the PBMR reflector: an isostatically moulded, fine grained, high strength graphite and two extruded medium grained graphites of moderately high strength. Although there is some irradiation data available for these graphites, the data does not cover the temperature and dose range required for the PBMR. The available graphites have been examined to determine their microstructure and some of the key material properties are presented. (authors)

  16. Multiphase modelling of mud volcanoes

    Science.gov (United States)

    Colucci, Simone; de'Michieli Vitturi, Mattia; Clarke, Amanda B.

    2015-04-01

    Mud volcanism is a worldwide phenomenon, classically considered as the surface expression of piercement structures rooted in deep-seated over-pressured sediments in compressional tectonic settings. The release of fluids at mud volcanoes during repeated explosive episodes has been documented at numerous sites and the outflows resemble the eruption of basaltic magma. As magma, the material erupted from a mud volcano becomes more fluid and degasses while rising and decompressing. The release of those gases from mud volcanism is estimated to be a significant contributor both to fluid flux from the lithosphere to the hydrosphere, and to the atmospheric budget of some greenhouse gases, particularly methane. For these reasons, we simulated the fluid dynamics of mud volcanoes using a newly-developed compressible multiphase and multidimensional transient solver in the OpenFOAM framework, taking into account the multicomponent nature (CH4, CO2, H2O) of the fluid mixture, the gas exsolution during the ascent and the associated changes in the constitutive properties of the phases. The numerical model has been tested with conditions representative of the LUSI, a mud volcano that has been erupting since May 2006 in the densely populated Sidoarjo regency (East Java, Indonesia), forcing the evacuation of 40,000 people and destroying industry, farmland, and over 10,000 homes. The activity of LUSI mud volcano has been well documented (Vanderkluysen et al., 2014) and here we present a comparison of observed gas fluxes and mud extrusion rates with the outcomes of numerical simulations. Vanderkluysen, L.; Burton, M. R.; Clarke, A. B.; Hartnett, H. E. & Smekens, J.-F. Composition and flux of explosive gas release at LUSI mud volcano (East Java, Indonesia) Geochem. Geophys. Geosyst., Wiley-Blackwell, 2014, 15, 2932-2946

  17. Evidence for tectonic, lithologic, and thermal controls on fracture system geometries in an andesitic high-temperature geothermal field

    Science.gov (United States)

    Massiot, Cécile; Nicol, Andrew; McNamara, David D.; Townend, John

    2017-08-01

    Analysis of fracture orientation, spacing, and thickness from acoustic borehole televiewer (BHTV) logs and cores in the andesite-hosted Rotokawa geothermal reservoir (New Zealand) highlights potential controls on the geometry of the fracture system. Cluster analysis of fracture orientations indicates four fracture sets. Probability distributions of fracture spacing and thickness measured on BHTV logs are estimated for each fracture set, using maximum likelihood estimations applied to truncated size distributions to account for sampling bias. Fracture spacing is dominantly lognormal, though two subordinate fracture sets have a power law spacing. This difference in spacing distributions may reflect the influence of the andesitic sequence stratification (lognormal) and tectonic faults (power law). Fracture thicknesses of 9-30 mm observed in BHTV logs, and 1-3 mm in cores, are interpreted to follow a power law. Fractures in thin sections (˜5 μm thick) do not fit this power law distribution, which, together with their orientation, reflect a change of controls on fracture thickness from uniform (such as thermal) controls at thin section scale to anisotropic (tectonic) at core and BHTV scales of observation. However, the ˜5% volumetric percentage of fractures within the rock at all three scales suggests a self-similar behavior in 3-D. Power law thickness distributions potentially associated with power law fluid flow rates, and increased connectivity where fracture sets intersect, may cause the large permeability variations that occur at hundred meter scales in the reservoir. The described fracture geometries can be incorporated into fracture and flow models to explore the roles of fracture connectivity, stress, and mineral precipitation/dissolution on permeability in such andesite-hosted geothermal systems.

  18. Alaska volcanoes guidebook for teachers

    Science.gov (United States)

    Adleman, Jennifer N.

    2011-01-01

    Alaska’s volcanoes, like its abundant glaciers, charismatic wildlife, and wild expanses inspire and ignite scientific curiosity and generate an ever-growing source of questions for students in Alaska and throughout the world. Alaska is home to more than 140 volcanoes, which have been active over the last 2 million years. About 90 of these volcanoes have been active within the last 10,000 years and more than 50 of these have been active since about 1700. The volcanoes in Alaska make up well over three-quarters of volcanoes in the United States that have erupted in the last 200 years. In fact, Alaska’s volcanoes erupt so frequently that it is almost guaranteed that an Alaskan will experience a volcanic eruption in his or her lifetime, and it is likely they will experience more than one. It is hard to imagine a better place for students to explore active volcanism and to understand volcanic hazards, phenomena, and global impacts. Previously developed teachers’ guidebooks with an emphasis on the volcanoes in Hawaii Volcanoes National Park (Mattox, 1994) and Mount Rainier National Park in the Cascade Range (Driedger and others, 2005) provide place-based resources and activities for use in other volcanic regions in the United States. Along the lines of this tradition, this guidebook serves to provide locally relevant and useful resources and activities for the exploration of numerous and truly unique volcanic landscapes in Alaska. This guidebook provides supplemental teaching materials to be used by Alaskan students who will be inspired to become educated and prepared for inevitable future volcanic activity in Alaska. The lessons and activities in this guidebook are meant to supplement and enhance existing science content already being taught in grade levels 6–12. Correlations with Alaska State Science Standards and Grade Level Expectations adopted by the Alaska State Department of Education and Early Development (2006) for grades six through eleven are listed at

  19. Rhyolitic calderas and centers clustered within the active andesitic belt of Ecuador's Eastern Cordillera

    Energy Technology Data Exchange (ETDEWEB)

    Mothes, Patricia A; Hall, Minard L [Instituto Geofisico, Escuela Politecnica Nacional, Quito (Ecuador)], E-mail: pmothes@igepn.edu.ec

    2008-10-01

    In the Ecuadorian volcanic arc a cluster of scattered rhyolitic and dacitic centers within the mainly andesitic Eastern Cordillera includes large caldera structures (Chalupas, Chacana, Cosanga) as well as smaller edifices, built upon the Paleozoic-Mesozoic metamorphic basement. At the Chacana caldera magmatism dates from 2.7 Ma to historic times. These centers erupted enormous ash flows and thick pumice lapilli falls that covered the InterAndean Valley near Quito. The role of the 50-70 km-thick crust with a notable negative gravity anomaly appears to be related to the generation of this highly silicic magmatism occurring along the crest of the Andes in the NVZ.

  20. Crust-Mantle Interactions at Pico de Orizaba (Citlaltepetl) Volcano, Mexico.

    Science.gov (United States)

    Schaaf, P.; Carrasco, G.

    2006-12-01

    Pico de Orizaba (Citlaltepetl) volcano constitutes the easternmost and highest stratovolcano of the subduction- related Plio-Quaternary Trans-Mexican Volcanic Belt (TMVB). The volcano can be divided into three main constructional stages. Its activity started during the mid-Pleistocene. The present cone was built on the remnants of the ancestral buildings by eruption of amphibole-two pyroxene dacitic lava flows, the most recent of which was erupted in the seventeenth century. The volcano is surrounded to the SW by monogenetic Quaternary cindercones and maars. All representative units were sampled in this work for geochemical and isotopic purposes, including a small quartzitic xenolith found in the basaltic monogenetic suite. Volcanic products of the stratocone are quite heterogeneous and range from calc-alkaline basaltic andesites to dome rhyolites, also displayed by a wide range of SiO2 and MgO (72.6-53.2 and 7.0-0.3 wt. %, respectively). In comparison to other TMVB stratovolcanoes (e.g., Colima, Nevado de Toluca), Pico de Orizaba shows similar 87Sr/86Sr ratios (0.7037-0.7048) but considerably more evolved Nd-Pb isotopic ratios (eNd: -1.8 to + 1.4; 206Pb/204Pb: 18.61-18.78). Elevated LILE concentrations and depleted HFSE witness the importance of slab- derived aqueous fluids and metasomatic reactions between the subducting lithosphere and overlying mantle wedge. On the other hand, Pico de Orizaba volcano shows additionally high crustal contributions of a source with depleted Sr and enriched Nd and Pb isotopic signatures, best explained by considerable assimilation of the local Grenvillian basement in magma generation processes. In contrast to Popocatépetl volcano with a high-level magma reservoir emplacement (7-8 km) and obvious interaction with the carbonate-dominated shallow basement rocks (e.g. elevated 87Sr/86Sr ratios and CO2 in gas plumes), this effect cannot be observed at Pico de Orizaba volcano, although a regional Cretaceous limestone basement is also

  1. Laboratory volcano geodesy

    Science.gov (United States)

    Færøvik Johannessen, Rikke; Galland, Olivier; Mair, Karen

    2014-05-01

    intrusion can be excavated and photographed from several angles to compute its 3D shape with the same photogrammetry method. Then, the surface deformation pattern can be directly compared with the shape of underlying intrusion. This quantitative dataset is essential to quantitatively test and validate classical volcano geodetic models.

  2. The PROTEUS Experiment: Active Source Seismic Imaging of the Crustal Magma Plumbing Structure of the Santorini Arc Volcano

    Science.gov (United States)

    Hooft, E. E. E.; Morgan, J. V.; Nomikou, P.; Toomey, D. R.; Papazachos, C. V.; Warner, M.; Heath, B.; Christopoulou, M. E.; Lampridou, D.; Kementzetzidou, D.

    2016-12-01

    The goal of the PROTEUS seismic experiment (Plumbing Reservoirs Of The Earth Under Santorini) is to examine the entire crustal magma plumbing system beneath a continental arc volcano and determine the magma geometry and connections throughout the crust. These physical parameters control magma migration, storage, and eruption and inform the question of how physical and chemical processing of magma at arc volcanoes forms the andesitic rock compositions that dominate the lower continental crust. These physical parameters are also important to understand volcanic-tectonic interactions and geohazards. Santorini is ideal for these goals because the continental crust has been thinned by extension and so the deep magmatic system is more accessible, also it is geologically well studied. Since the volcano is a semi-submerged, it was possible to collect a unique 3D marine-land active source seismic dataset. During the PROTEUS experiment in November-December of 2015, we recorded 14,300 marine sound sources from the US R/V Langseth on 89 OBSIP short period ocean bottom seismometers and 60 German and 5 Greek land seismometers. The experiment was designed for high-density spatial sampling of the seismic wavefield to allow us to apply two state-of-the-art 3D inversion methods: travel time tomography and full waveform inversion. A preliminary travel time tomography model of the upper crustal seismic velocity structure of the volcano and surrounding region is presented in an accompanying poster. We also made marine geophysical maps of the seafloor using multi-beam bathymetry and of the gravity and magnetic fields. The new seafloor map reveals the detailed structure of the major fault system between Santorini and Amorgos, of associated landslides, and of newly discovered volcanic features. The PROTEUS project will provide new insights into the structure of the whole crustal magmatic system of a continental arc volcano and its evolution within the surrounding tectonic setting.

  3. Evolution of Rajabasa Volcano in Kalianda Area and Its Vicinity, South Lampung Regency

    Directory of Open Access Journals (Sweden)

    Sutikno Bronto

    2014-06-01

    Full Text Available DOI: 10.17014/ijog.v7i1.132Rajabasa Volcano (± 1281 m and Lampung Tuff, located in the South Lampung Regency, is the main point in order to understand the evolution of Quaternary volcanism in the area. A remote sensing analysis and field geologic work are the methods of the study. The volcanism began with the construction period of the Pre-Rajabasa composite cone which was followed by the destruction period of the cone to form the Pre-Rajabasa Caldera having ca. 25 km in diameter. The present Rajabasa Volcano, along with cones of flank eruptions and monogenesis, has appeared in the Pre-Rajabasa Caldera depression. Those volcanic activities are considered as the second construction period. During the first and the second construction periods, basaltic to andesitic lava flows, pyroclastic breccias, and tuffs were erupted. The Rajabasa eruption points moved in WNW - ESE direction, which were possibly controlled by a subsurface weak zone. The Pre-Rajabasa Caldera erupted voluminous Lampung Tuffs having rhyolite in composition, and they are considered as a combination of pyroclastic falls, flows, and surges, or pyroclastic density currents.

  4. Alteration related to hydrothermal activity of the Nevado del Ruiz volcano (NRV), Colombia

    International Nuclear Information System (INIS)

    Forero, Jhon; Zuluaga, Carlos; Mojica, Jaime

    2011-01-01

    The hydrothermal activity in the NRV generates alteration characterized by mineral associations depending one number of physic-chemical factors of the hydrothermal system. Petrography of unaltered rocks was used to establish the mineral assemblage prior to rock-fluid interaction. XRD was used in altered rocks, where it was not possible to recognize the alteration products. the observed mineral assemblages indicate advanced and intermediate argillic alterations, this and the observation of very low modal proportion of sulphates, sulphides and native sulphur in some areas could point to a low sulphidation zone. However, the proximity to the volcano and the presence of acid thermal waters and steam pose an apparent contradiction with an expected high sulphidation zone which is explained by climatic conditions, where excess water has dissolved and leached sulfides, sulphur and sulphates close to the volcano. fault zones serve as conducts for fluid transport and have acid-sulphate mineral associations produced by atmospheric oxidation at the water table in a steam-heated environment of H 2 S released by deeper, boiling fluids or by the disproportionation of magmatic SO 2 to H 2 S and H 2 SO 4 during condensation of magmatic vapor plume at intermedia depths in magmatic hydrothermal environment in andesitic volcanic terrain characteristic of high sulphidation zones.

  5. What Happened to Our Volcano?

    Science.gov (United States)

    Mangiante, Elaine Silva

    2006-01-01

    In this article, the author presents an investigative approach to "understanding Earth changes." The author states that students were familiar with earthquakes and volcanoes in other regions of the world but never considered how the land beneath their feet had experienced changes over time. Here, their geology unit helped them understand…

  6. Grand Sarcoui volcano (Chaîne des Puys, Massif Central, France), a case study for monogenetic trachytic lava domes

    Science.gov (United States)

    Miallier, D.; Pilleyre, T.; Boivin, P.; Labazuy, P.; Gailler, L.-S.; Rico, J.

    2017-10-01

    The Grand Sarcoui is a prominent trachytic volcano of the intraplate Quaternary volcanic field of Chaîne des Puys (Massif Central, France), which fulfills basic requirements for being qualified as monogenetic. Grand Sarcoui looks like a simple axisymmetric lava dome, but close observation reveals a complex and dissymmetric structure and composition. The construction of the dome, about 12.5 ka ago, combined both endogenous and exogenous growth which resulted in variable modes of emplacement and textures of the lava. One of its most interesting features is a large ( 0.29 106 m2) fan of deposits bearing hummocks and secondary hydro-eruption craters. Cross sections of these deposits demonstrate that they originated from a sector collapse accompanied by a blast-like event. The dome is covered by a thin layer of lapilli and ash, attributed to a delayed summit eruption which occurred about 10.6 ka ago, surprisingly late after its construction. So, this volcano has, at a reduced scale, features that are more usually observed in large composite volcanoes. However, some of these features differ slightly from those that have been documented to date, and they remain partly unexplained. This shows that monogenetic, well preserved, trachytic lava domes, are uncommon and poorly known, unlike rhyolitic, andesitic and dacitic domes.

  7. Flowage differentiation in an andesitic dyke of the Motru Dyke Swarm (Southern Carpathians, Romania) inferred from AMS, CSD and geochemistry

    Science.gov (United States)

    Nkono, Collin; Féménias, Olivier; Diot, Hervé; Berza, Tudor; Demaiffe, Daniel

    2006-06-01

    Two dykes of different thickness (5.5 m for TJ31 and 23 m for TJ34) from the late Pan-African calc-alkaline Motru Dyke Swarm (S. Carpathians, Romania) have been studied by electron microprobe (mineral chemistry), crystal size distribution (CSD), anisotropy of magnetic susceptibility (AMS) and whole-rock geochemistry. All the physical and chemical variations observed across the dyke's width point to concordant results and show that the variations of both modal abundance and size of the amphibole and biotite microphenocrysts inside the dykes (deduced from the classical CSD measurements) are the result of a mechanical segregation of suspended crystals during magmatic transport. Despite a pene-contemporaneous regional tectonic, the flow-induced differentiation in the thicker dyke is characterized by the concentration of pre-existing Ti-rich pargasite-tschermakite, clinopyroxene and plagioclase crystals in the core of the dyke and of the extracted differentiated liquid near the walls. This mechanical differentiation induces a chemical differentiation with a basaltic andesite composition for the core of the dyke whereas the margins are andesitic. Thus the chilled margins appear as a slightly more evolved liquid with a Newtonian behaviour when compared to the average composition of the dyke. The localization of the liquid on both sides of the dyke has certainly facilitated the ascent of the central part of the dyke that behaved as a Binghamian mush.

  8. Geological influence of andesite intrusion on diatomite. Pt. 2. Physical property changes of diatomite and self-sealing mechanism

    Energy Technology Data Exchange (ETDEWEB)

    Chigira, Masahiro; Nakata, Eiji [Central Research Inst. of Electric Power Industry, Abiko, Chiba (Japan). Abiko Research Lab.

    1996-03-01

    Diatomite alteration by andesite intrusion was studied especially on their physical property changes and the dynamic alteration processes for the diatomite of the Miocene Iwaya Formation in the Akita Prefecture, northern Japan. Diatomite is altered in different ways according to the extent of infiltration of hydrothermal solution into diatomite from dike. When the solution infiltrates into diatomite in large amount, smectite is formed in diatomite which is subsequently compacted to the most, and amorphous silica and poorly crystallized opal-CT precipitate in the compacted zone to form impermeable opaline chert. The chert zone becomes a hydraulic barrier against the infiltration of hydrothermal solution to make a closed system around the heat source, where opal-A transforms into opal-CT. When hydrothermal solution does not infiltrate into diatomite, diatomite is altered only by the heat from the andesitic dike: diatomite is compacted under higher temperatures near the dike, and consequently permeability is lowered. In both cases, diatomite is altered so as to mitigate the influence of magma intrusion. (author). 66 refs.

  9. Geological influence of andesite intrusion on diatomite. Pt. 2. Physical property changes of diatomite and self-sealing mechanism

    International Nuclear Information System (INIS)

    Chigira, Masahiro; Nakata, Eiji

    1996-01-01

    Diatomite alteration by andesite intrusion was studied especially on their physical property changes and the dynamic alteration processes for the diatomite of the Miocene Iwaya Formation in the Akita Prefecture, northern Japan. Diatomite is altered in different ways according to the extent of infiltration of hydrothermal solution into diatomite from dike. When the solution infiltrates into diatomite in large amount, smectite is formed in diatomite which is subsequently compacted to the most, and amorphous silica and poorly crystallized opal-CT precipitate in the compacted zone to form impermeable opaline chert. The chert zone becomes a hydraulic barrier against the infiltration of hydrothermal solution to make a closed system around the heat source, where opal-A transforms into opal-CT. When hydrothermal solution does not infiltrate into diatomite, diatomite is altered only by the heat from the andesitic dike: diatomite is compacted under higher temperatures near the dike, and consequently permeability is lowered. In both cases, diatomite is altered so as to mitigate the influence of magma intrusion. (author). 66 refs

  10. Sr isotope zoning in plagioclase from andesites at Cabo De Gata, Spain: Evidence for shallow and deep contamination

    Science.gov (United States)

    Waight, Tod E.; Tørnqvist, Jakob B.

    2018-05-01

    Plagioclase crystals in andesites from the Cabo De Gata region show generally radiogenic Sr isotope compositions and consistent core to rim increases in 87Sr/86Sr that are indicative of open system processes in the lithosphere and crustal contamination during crystallization. High-grade metamorphic rocks of the Alpujárride and Nevado-Filábride complexes represent the most likely crustal contaminants. The plagioclases are characterized by subtly zoned and resorbed calcic cores (An73-86). These cores also have radiogenic 87Sr/86Sr (0.7127-0.7129), although typically less radiogenic than plagioclase rims, groundmass plagioclase and whole rock compositions (up to 87Sr/86Sr = 0.7135). These cores are interpreted to represent early crystallization of plagioclase from hydrous melts emplaced into the lower crust. The parental melts to these andesites must therefore have already inherited their radiogenic Sr isotope compositions prior to entering the lower crust and before the onset of crystallization of plagioclase, which is inconsistent with previous models suggesting that the generally radiogenic nature of Sr in these volcanics reflects large amounts of crustal contamination. Instead, the isotope systematics are consistent with models invoked significant addition of a subducted sediment component to the mantle source. The high-An% plagioclase cores are characterized by resorption textures, which are consistent with dissolution during rapid decompression and/or devolatisation during magma migration from the lower crust into upper crustal magma chambers.

  11. Seismic and Gas Analyses Imply Magmatic Intrusion at Iliamna Volcano, Alaska in 2012

    Science.gov (United States)

    Prejean, S. G.; Werner, C. A.; Buurman, H.; Doukas, M. P.; Kelly, P. J.; Kern, C.; Ketner, D.; Stihler, S.; Thurber, C. H.; West, M. E.

    2012-12-01

    In early 2012, Iliamna Volcano, an ice-covered andesitic stratovolcano located in the Cook Inlet region of Alaska, had a vigorous earthquake swarm that included both brittle-failure earthquakes (Mvolume has otherwise been seismically quiet except during a possible magmatic intrusion at Iliamna in 1996, when it sustained a similar swarm (Roman et al., 2004, J. Volc. Geotherm. Res., v. 130, p. 265-284). Analysis of the relative amplitudes between the small low-frequency and located brittle failure events indicates that their sources are geographically separate, with the low-frequency events sourced closer to the fumarolically active summit region, ~4 km north of the brittle failure events. Airborne gas-emission measurements on March 17 revealed emission rates of up to 2000 and 580 tonnes per day (t/d) of CO2 and SO2, respectively, and a molar C/S ratio of 5. Visual observations from the flight revealed unusually vigorous fumarole activity near the summit. Subsequent measurements on June 20 and 22 showed continued high emissions of up to 1190 and 440 t/d of CO2 and SO2, respectively, with a C/S ratio of 4. These emission measurements are similar to those measured during the height of the 1996 unrest episode and are significantly above background measurements between 1998 and August 2011, which were typically below 100 and 60 t/d of CO2 and SO2. Taken together, gas and seismic data suggest that the earthquake swarm was driven by magmatic intrusion. Gas flux rates are consistent with those measured for degassing andesitic magmas in the shallow crust at other Cook Inlet volcanoes. Increased heat and degassing likely caused small low-frequency events in the shallow hydrothermal system near the volcano's summit, and/or may have destabilized the glacier, triggering shallow low-frequency glacial events. This unrest episode demonstrates how magmatic intrusions can cause spatially disparate earthquake swarms in hydrothermal systems and on pre-existing crustal structures.

  12. Poás volcano in Costa Rica as a hydrothermal analog for Mars

    Science.gov (United States)

    Elmaarry, M. R.; Hynek, B. M.

    2017-12-01

    Mars has experienced intensive volcanic and impact activity early in its history, coinciding with a similarly extensive hydrologic activity on a global scale. These activities constitute the main ingredients of hydrothermal activity. Data acquired from the study of Martian meteorites, remote sensing spectral observations, and robotic rovers has shown the surface of Mars to be mineralogically diverse including mineral assemblages that resemble those of analogous hydrothermal systems on Earth. In particular, evidence for extensive acid-sulfate weathering has been observed by the MERs at Gusev and Meridiani, as well as by MSL at Gale crater. Furthermore, there is growing evidence for silicic volcanism on Mars as indicated by the detection of silica-rich mudstone at Gale containing tridymite and cristobalite coupled with spectral observations indicative of felsic rocks in geographically disparate locations on Mars. For that, the Poás volcano in Costa Rica offers a geologic setting that can be analogous to similar environments on Mars. The Poás volcano is a basaltic andesite stratovolcano in central Costa Rica. Its caldera houses a highly acidic lake inside the caldera 130 m below the crater rim. The volcano has been active in recent historical times, and is currently displaying intensive activity since Apr 2017. Unaltered andesitic basalts collected from the 1953-1955 magmatic activity are mainly composed of plagioclase and minor amounts of orthopyroxene and olivine. We collected samples during our fieldwork in March 2017 (few weeks before its eruption) from fumaroles inside the caldera. The fumaroles were emitting gases at 92°C, and the acidic lake minor abundances of hematite, anatase, and amorphous silica. Most of these minerals have been observed on Mars under potentially similar settings. We plan to continue our investigation by carrying out additional analyses and compare to samples collected from earlier campaigns to gain a better understanding of how the

  13. Morphometry of terrestrial shield volcanoes

    Science.gov (United States)

    Grosse, Pablo; Kervyn, Matthieu

    2018-03-01

    Shield volcanoes are described as low-angle edifices built primarily by the accumulation of successive lava flows. This generic view of shield volcano morphology is based on a limited number of monogenetic shields from Iceland and Mexico, and a small set of large oceanic islands (Hawaii, Galápagos). Here, the morphometry of 158 monogenetic and polygenetic shield volcanoes is analyzed quantitatively from 90-meter resolution SRTM DEMs using the MORVOLC algorithm. An additional set of 24 lava-dominated 'shield-like' volcanoes, considered so far as stratovolcanoes, are documented for comparison. Results show that there is a large variation in shield size (volumes from 0.1 to > 1000 km3), profile shape (height/basal width (H/WB) ratios mostly from 0.01 to 0.1), flank slope gradients (average slopes mostly from 1° to 15°), elongation and summit truncation. Although there is no clear-cut morphometric difference between shield volcanoes and stratovolcanoes, an approximate threshold can be drawn at 12° average slope and 0.10 H/WB ratio. Principal component analysis of the obtained database enables to identify four key morphometric descriptors: size, steepness, plan shape and truncation. Hierarchical cluster analysis of these descriptors results in 12 end-member shield types, with intermediate cases defining a continuum of morphologies. The shield types can be linked in terms of growth stages and shape evolution, related to (1) magma composition and rheology, effusion rate and lava/pyroclast ratio, which will condition edifice steepness; (2) spatial distribution of vents, in turn related to the magmatic feeding system and the tectonic framework, which will control edifice plan shape; and (3) caldera formation, which will condition edifice truncation.

  14. Iridium emissions from Hawaiian volcanoes

    International Nuclear Information System (INIS)

    Finnegan, D.L.; Zoller, W.H.; Miller, T.M.

    1988-01-01

    Particle and gas samples were collected at Mauna Loa volcano during and after its eruption in March and April, 1984 and at Kilauea volcano in 1983, 1984, and 1985 during various phases of its ongoing activity. In the last two Kilauea sampling missions, samples were collected during eruptive activity. The samples were collected using a filterpack system consisting of a Teflon particle filter followed by a series of 4 base-treated Whatman filters. The samples were analyzed by INAA for over 40 elements. As previously reported in the literature, Ir was first detected on particle filters at the Mauna Loa Observatory and later from non-erupting high temperature vents at Kilauea. Since that time Ir was found in samples collected at Kilauea and Mauna Loa during fountaining activity as well as after eruptive activity. Enrichment factors for Ir in the volcanic fumes range from 10,000 to 100,000 relative to BHVO. Charcoal impregnated filters following a particle filter were collected to see if a significant amount of the Ir was in the gas phase during sample collection. Iridium was found on charcoal filters collected close to the vent, no Ir was found on the charcoal filters. This indicates that all of the Ir is in particulate form very soon after its release. Ratios of Ir to F and Cl were calculated for the samples from Mauna Loa and Kilauea collected during fountaining activity. The implications for the KT Ir anomaly are still unclear though as Ir was not found at volcanoes other than those at Hawaii. Further investigations are needed at other volcanoes to ascertain if basaltic volcanoes other than hot spots have Ir enrichments in their fumes

  15. Iridium emissions from Hawaiian volcanoes

    Science.gov (United States)

    Finnegan, D. L.; Zoller, W. H.; Miller, T. M.

    1988-01-01

    Particle and gas samples were collected at Mauna Loa volcano during and after its eruption in March and April, 1984 and at Kilauea volcano in 1983, 1984, and 1985 during various phases of its ongoing activity. In the last two Kilauea sampling missions, samples were collected during eruptive activity. The samples were collected using a filterpack system consisting of a Teflon particle filter followed by a series of 4 base-treated Whatman filters. The samples were analyzed by INAA for over 40 elements. As previously reported in the literature, Ir was first detected on particle filters at the Mauna Loa Observatory and later from non-erupting high temperature vents at Kilauea. Since that time Ir was found in samples collected at Kilauea and Mauna Loa during fountaining activity as well as after eruptive activity. Enrichment factors for Ir in the volcanic fumes range from 10,000 to 100,000 relative to BHVO. Charcoal impregnated filters following a particle filter were collected to see if a significant amount of the Ir was in the gas phase during sample collection. Iridium was found on charcoal filters collected close to the vent, no Ir was found on the charcoal filters. This indicates that all of the Ir is in particulate form very soon after its release. Ratios of Ir to F and Cl were calculated for the samples from Mauna Loa and Kilauea collected during fountaining activity. The implications for the KT Ir anomaly are still unclear though as Ir was not found at volcanoes other than those at Hawaii. Further investigations are needed at other volcanoes to ascertain if basaltic volcanoes other than hot spots have Ir enrichments in their fumes.

  16. High temperature soldering of graphite

    International Nuclear Information System (INIS)

    Anikin, L.T.; Kravetskij, G.A.; Dergunova, V.S.

    1977-01-01

    The effect is studied of the brazing temperature on the strength of the brazed joint of graphite materials. In one case, iron and nickel are used as solder, and in another, molybdenum. The contact heating of the iron and nickel with the graphite has been studied in the temperature range of 1400-2400 ged C, and molybdenum, 2200-2600 deg C. The quality of the joints has been judged by the tensile strength at temperatures of 2500-2800 deg C and by the microstructure. An investigation into the kinetics of carbon dissolution in molten iron has shown that the failure of the graphite in contact with the iron melt is due to the incorporation of iron atoms in the interbase planes. The strength of a joint formed with the participation of the vapour-gas phase is 2.5 times higher than that of a joint obtained by graphite recrystallization through the carbon-containing metal melt. The critical temperatures are determined of graphite brazing with nickel, iron, and molybdenum interlayers, which sharply increase the strength of the brazed joint as a result of the formation of a vapour-gas phase and deposition of fine-crystal carbon

  17. Experience with graphite in JET

    International Nuclear Information System (INIS)

    Pick, M.A.; Celentano, G.; Deksnis, E.; Dietz, K.J.; Shaw, R.; Sonnenberg, K.; Walravens, M.

    1987-01-01

    During the current operational period of JET more than 50% of the internal area of the machine is covered in graphite tiles. This includes the 15 m 2 of carbon tiles installed in the new toroidal limiter, the 40 poloidal belts of graphite tiles covering the U-joints and bellows as well as a two metre high ring (-- 20 m 2 ) or carbon tiles on the inner wall of the Torus. A ring of tiles in the equatorial plane (3 tiles high) consists of carbon-carbon fibre tiles. Test bed results indicated that the fine grained graphite tiles cracked at ∼ 1 kW/cm 2 for 2s of irradiation whereas the carbon-carbon fibre tiles were able to sustain a flux, limited by the irradiation facility, of 3.5 kW for 3s without any damage. The authors report on the generally positive experience they have had had with the installed graphite during the present and previous in-vessel configurations. This includes the physical integrity of the tiles under severe conditions such as high energy run-away electron beams, plasma disruptions and high heat fluxes. They report on the importance of the precise positioning of the inner wall and x-point tiles at the very high power fluxes of JET and the effect of deviations on both graphite and carbon-fibre tiles

  18. Porous (Swiss-Cheese Graphite

    Directory of Open Access Journals (Sweden)

    Joseph P. Abrahamson

    2018-05-01

    Full Text Available Porous graphite was prepared without the use of template by rapidly heating the carbonization products from mixtures of anthracene, fluorene, and pyrene with a CO2 laser. Rapid CO2 laser heating at a rate of 1.8 × 106 °C/s vaporizes out the fluorene-pyrene derived pitch while annealing the anthracene coke. The resulting structure is that of graphite with 100 nm spherical pores. The graphitizablity of the porous material is the same as pure anthracene coke. Transmission electron microscopy revealed that the interfaces between graphitic layers and the pore walls are unimpeded. Traditional furnace annealing does not result in the porous structure as the heating rates are too slow to vaporize out the pitch, thereby illustrating the advantage of fast thermal processing. The resultant porous graphite was prelithiated and used as an anode in lithium ion capacitors. The porous graphite when lithiated had a specific capacity of 200 mAh/g at 100 mA/g. The assembled lithium ion capacitor demonstrated an energy density as high as 75 Wh/kg when cycled between 2.2 V and 4.2 V.

  19. Thermal Pyrolytic Graphite Enhanced Components

    Science.gov (United States)

    Hardesty, Robert E. (Inventor)

    2015-01-01

    A thermally conductive composite material, a thermal transfer device made of the material, and a method for making the material are disclosed. Apertures or depressions are formed in aluminum or aluminum alloy. Plugs are formed of thermal pyrolytic graphite. An amount of silicon sufficient for liquid interface diffusion bonding is applied, for example by vapor deposition or use of aluminum silicon alloy foil. The plugs are inserted in the apertures or depressions. Bonding energy is applied, for example by applying pressure and heat using a hot isostatic press. The thermal pyrolytic graphite, aluminum or aluminum alloy and silicon form a eutectic alloy. As a result, the plugs are bonded into the apertures or depressions. The composite material can be machined to produce finished devices such as the thermal transfer device. Thermally conductive planes of the thermal pyrolytic graphite plugs may be aligned in parallel to present a thermal conduction path.

  20. Friction anisotropy in boronated graphite

    International Nuclear Information System (INIS)

    Kumar, N.; Radhika, R.; Kozakov, A.T.; Pandian, R.; Chakravarty, S.; Ravindran, T.R.; Dash, S.; Tyagi, A.K.

    2015-01-01

    Graphical abstract: - Highlights: • Friction anisotropy in boronated graphite is observed in macroscopic sliding condition. • Low friction coefficient is observed in basal plane and becomes high in prismatic direction. • 3D phase of boronated graphite transformed into 2D structure after friction test. • Chemical activity is high in prismatic plane forming strong bonds between the sliding interfaces. - Abstract: Anisotropic friction behavior in macroscopic scale was observed in boronated graphite. Depending upon sliding speed and normal loads, this value was found to be in the range 0.1–0.35 in the direction of basal plane and becomes high 0.2–0.8 in prismatic face. Grazing-incidence X-ray diffraction analysis shows prominent reflection of (0 0 2) plane at basal and prismatic directions of boronated graphite. However, in both the wear tracks (1 1 0) plane become prominent and this transformation is induced by frictional energy. The structural transformation in wear tracks is supported by micro-Raman analysis which revealed that 3D phase of boronated graphite converted into a disordered 2D lattice structure. Thus, the structural aspect of disorder is similar in both the wear tracks and graphite transfer layers. Therefore, the crystallographic aspect is not adequate to explain anisotropic friction behavior. Results of X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy shows weak signature of oxygen complexes and functional groups in wear track of basal plane while these species dominate in prismatic direction. Abundance of these functional groups in prismatic plane indicates availability of chemically active sites tends to forming strong bonds between the sliding interfaces which eventually increases friction coefficient

  1. Friction anisotropy in boronated graphite

    Energy Technology Data Exchange (ETDEWEB)

    Kumar, N., E-mail: niranjan@igcar.gov.in [Materials Science Group, Indira Gandhi Centre for Atomic Research, Kalpakkam (India); Radhika, R. [Crystal Growth Centre, Anna University, Chennai (India); Kozakov, A.T. [Research Institute of Physics, Southern Federal University, Rostov-on-Don (Russian Federation); Pandian, R. [Materials Science Group, Indira Gandhi Centre for Atomic Research, Kalpakkam (India); Chakravarty, S. [UGC-DAE CSR, Kalpakkam (India); Ravindran, T.R.; Dash, S.; Tyagi, A.K. [Materials Science Group, Indira Gandhi Centre for Atomic Research, Kalpakkam (India)

    2015-01-01

    Graphical abstract: - Highlights: • Friction anisotropy in boronated graphite is observed in macroscopic sliding condition. • Low friction coefficient is observed in basal plane and becomes high in prismatic direction. • 3D phase of boronated graphite transformed into 2D structure after friction test. • Chemical activity is high in prismatic plane forming strong bonds between the sliding interfaces. - Abstract: Anisotropic friction behavior in macroscopic scale was observed in boronated graphite. Depending upon sliding speed and normal loads, this value was found to be in the range 0.1–0.35 in the direction of basal plane and becomes high 0.2–0.8 in prismatic face. Grazing-incidence X-ray diffraction analysis shows prominent reflection of (0 0 2) plane at basal and prismatic directions of boronated graphite. However, in both the wear tracks (1 1 0) plane become prominent and this transformation is induced by frictional energy. The structural transformation in wear tracks is supported by micro-Raman analysis which revealed that 3D phase of boronated graphite converted into a disordered 2D lattice structure. Thus, the structural aspect of disorder is similar in both the wear tracks and graphite transfer layers. Therefore, the crystallographic aspect is not adequate to explain anisotropic friction behavior. Results of X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy shows weak signature of oxygen complexes and functional groups in wear track of basal plane while these species dominate in prismatic direction. Abundance of these functional groups in prismatic plane indicates availability of chemically active sites tends to forming strong bonds between the sliding interfaces which eventually increases friction coefficient.

  2. Rheology of the 2006 eruption at Tungurahua volcano, Ecuador

    Science.gov (United States)

    Hanson, J. B.; Lavallée, Y.; Hess, K.-U.; von Aulock, F. W.; Dingwell, D. B.

    2009-04-01

    During August 16th to 18th 2006, the eruptive crisis at Tungurahua volcano (Ecuador) culminated in VEI 2 eruption with tens of pyroclastic flows and the extrusion of a lava flow. The nearly simultaneous occurrence of a lava flow and a pyroclastic flow from a single vent deserves attention. Generally, the rheology is a chief determinant of eruption style. Specifically, magmas are ductile (effusive) at low strain rates whereas they are brittle (explosive) at high strain rates. Although this distinction has been extensively described for single-phase magmas, there remain many questions as to the rheological implications of crystals and bubbles present in magmas. Here we present preliminary characterizations of the complex rheology of the magma involved in the 2006 eruption at Tungurahua volcano. The magma present in this eruption was andesitic with an interstitial melt composition averaging ~58 wt.% SiO2. The bombs present in the pyroclastic deposit show an open porosity ranging from 15 to 35 vol.% and a crystallinity generally greater than ~30 vol.% and occasionally up to 60 vol.% in samples affected by microlite growth. Petrographic analyses revealed magma batches with different crystallization histories. In high-porosity samples containing microlites, a recrystallization rim around clinopyroxene and resorption of the plagioclase were observed. In contrast, the dense samples show pristine, euhedral crystals and a near absence of microlites. The heterogeneous petrographic structures suggest the possibilities of mingling in the conduit or of magma batches with different decompression rates. Dilatometric analyses suggest glass transition temperatures (Tg) of ~974 °C for the dense material (porosity~15 vol.%) and as high as ~1060 °C for the high-porosity bombs (porosity~35 vol.%). Successive series of heating and cooling of the glass reveal an increase of Tg by as much as 60 °C indicative of significant water left in the melt. Preliminary analyses of images obtained

  3. Raman characterization of bulk ferromagnetic nanostructured graphite

    International Nuclear Information System (INIS)

    Pardo, Helena; Divine Khan, Ngwashi; Faccio, Ricardo; Araújo-Moreira, F.M.; Fernández-Werner, Luciana

    2012-01-01

    Raman spectroscopy was used to characterize bulk ferromagnetic graphite samples prepared by controlled oxidation of commercial pristine graphite powder. The G:D band intensity ratio, the shape and position of the 2D band and the presence of a band around 2950 cm -1 showed a high degree of disorder in the modified graphite sample, with a significant presence of exposed edges of graphitic planes as well as a high degree of attached hydrogen atoms.

  4. Fabrication of Graphene by Cleaving Graphite Chemically

    Institute of Scientific and Technical Information of China (English)

    ZHAO Shu-hua; ZHAO Xiao-ting; FAN Hou-gang; YANG Li-li; ZHANG Yong-jun; YANG Jing-hai

    2011-01-01

    Graphite was chemically cleaved to graphene by Billups Reaction,and the morphologies and microstructures of graphene were characterized by SEM,Raman and AFM.The results show that the graphite was first functionalized by l-iodododecane,which led to the cleavage of the graphene layer in the graphite.The second decoration cleaved the graphite further and graphene was obtained.The heights of the graphene layer were larger than 1 nm due to the organic decoration.

  5. Method of Joining Graphite Fibers to a Substrate

    Science.gov (United States)

    Beringer, Durwood M. (Inventor); Caron, Mark E. (Inventor); Taddey, Edmund P. (Inventor); Gleason, Brian P. (Inventor)

    2014-01-01

    A method of assembling a metallic-graphite structure includes forming a wetted graphite subassembly by arranging one or more layers of graphite fiber material including a plurality of graphite fibers and applying a layer of metallization material to ends of the plurality of graphite fibers. At least one metallic substrate is secured to the wetted graphite subassembly via the layer of metallization material.

  6. Aleutian Islands Coastal Resources Inventory and Environmental Sensitivity Maps: VOLCANOS (Volcano Points)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This data set contains point locations of active volcanoes as compiled by Motyka et al., 1993. Eighty-nine volcanoes with eruptive phases in the Quaternary are...

  7. Photoemission study of K on graphite

    NARCIS (Netherlands)

    Bennich, P.; Puglia, C.; Brühwiler, P.A.; Nilsson, A.; Sandell, A.; Mårtensson, N.; Rudolf, P.

    1999-01-01

    The physical and electronic structure of the dispersed and (2×2) phases of K/graphite have been characterized by valence and core-level photoemission. Charge transfer from K to graphite is found to occur at all coverages, and includes transfer of charge to the second graphite layer. A rigid band

  8. Separation medium containing thermally exfoliated graphite oxide

    Science.gov (United States)

    Prud'homme, Robert K. (Inventor); Aksay, Ilhan A. (Inventor); Herrera-Alonso, Margarita (Inventor)

    2012-01-01

    A separation medium, such as a chromatography filling or packing, containing a modified graphite oxide material, which is a thermally exfoliated graphite oxide with a surface area of from about 300 m.sup.2/g to 2600 m.sup.2/g, wherein the thermally exfoliated graphite oxide has a surface that has been at least partially functionalized.

  9. NMR studies on graphite-methanol system

    International Nuclear Information System (INIS)

    El-Akkad, T.M.

    1977-01-01

    The nuclear magnetic relaxation times for protons of methanol on graphite have been studied. The perpendicular and the transversal magnetization as a function of temperature were measured. The results show that the presence of graphite slowed down the methanol movement compared with that in the pure alcohol, and that the methanol molecules are attached to the graphite surface via methyl groups. (author)

  10. The Solarya Volcano-Plutonic Complex (NW Turkey): Petrography, Petrogenesis and Tectonic Implications

    Science.gov (United States)

    Ünal, Alp; Kamacı, Ömer; Altunkaynak, Şafak

    2014-05-01

    The post collisional magmatic activity produced several volcano-plutonic complexes in NW Anatolia (Turkey) during the late Oligocene- Middle Miocene. One of the major volcano-plutonic complexes, the Solarya volcano-plutonic complex is remarkable for its coeval and cogenetic plutonic (Solarya pluton), hypabysal and volcanic rocks of Early Miocene (24-21 Ma) age. Solarya pluton is an epizonal pluton which discordantly intruded into metamorphic and nonmetamorphic basement rocks of Triassic age. It is a N-S trending magmatic body covering an area of 220 km2,approximatelly 20 km in length and 10 km in width. Based on the field and petrographic studies, three main rock groups distinguished in Solarya pluton; K-feldspar megacrystalline granodiorite, microgranite-granodiorite and haplogranite. Porphyritic and graphic-granophyric textures are common in these three rock groups. Pluton contains magmatic enclaves and syn-plutonic dykes of dioritic composition. Hypabyssal rocks are represented by porphyritic microdiorite and porphyritic quartz-diorite. They form porphyry plugs, sheet inrusions and dykes around the pluton. Porphyrites have microcrystalline-cryptocrystalline groundmass displaying micrographic and granophyric textures. Petrographically similar to the hypabyssal rocks, volcanic rocks are formed from andesitic and dasitic lavas and pyroclastic rocks. Plutonic, hypabyssal and volcanic rocks of Solarya volcano-plutonic complex show similar major-trace element and Sr-Nd-Pb isotopic compositions, indicating common magmatic evolution and multicomponent melt sources including mantle and crustal components. They are mainly metaluminous, medium to high-K calc alkaline rocks and display enrichment in LILE and depletion in Nb, Ta, P and Ti. They have initial 87Sr/86Sr values of 0.70701- 0.70818 and 143Nd/144Nd values of 0.51241-0.51250. These geochemical characteristics and isotopic signatures are considered to reflect the composition of the magmas derived from a

  11. Flank tectonics of Martian volcanoes

    International Nuclear Information System (INIS)

    Thomas, P.J.; Squyres, S.W.; Carr, M.H.

    1990-01-01

    On the flanks of Olympus Mons is a series of terraces, concentrically distributed around the caldera. Their morphology and location suggest that they could be thrust faults caused by compressional failure of the cone. In an attempt to understand the mechanism of faulting and the possible influences of the interior structure of Olympus Mons, the authors have constructed a numerical model for elastic stresses within a Martian volcano. In the absence of internal pressurization, the middle slopes of the cone are subjected to compressional stress, appropriate to the formation of thrust faults. These stresses for Olympus Mons are ∼250 MPa. If a vacant magma chamber is contained within the cone, the region of maximum compressional stress is extended toward the base of the cone. If the magma chamber is pressurized, extensional stresses occur at the summit and on the upper slopes of the cone. For a filled but unpressurized magma chamber, the observed positions of the faults agree well with the calculated region of high compressional stress. Three other volcanoes on Mars, Ascraeus Mons, Arsia Mons, and Pavonis Mons, possess similar terraces. Extending the analysis to other Martian volcanoes, they find that only these three and Olympus Mons have flank stresses that exceed the compressional failure strength of basalt, lending support to the view that the terraces on all four are thrust faults

  12. Radioactive equilibria and disequilibria of U-series nuclides in the products from Izu arc volcanoes, Japan

    Energy Technology Data Exchange (ETDEWEB)

    Kurihara, Y.; Sato, J. [Meiji Univ., Kawasaki, Kanagawa (Japan). Dept. of Applied Chemistry; Takahashi, M. [Central Research Institute of Electric Power Industry, Tokyo (Japan). Radiation Safety Research Center

    2011-07-01

    Activity ratios among {sup 238}U-{sup 230}Th-{sup 226}Ra in the products from Izu arc volcanoes, Japan, were observed in order to estimate the time scale of magmatic processes and the magma generation for Izu arc volcanism. Activity ratios of {sup 238}U/{sup 230}Th and {sup 226}Ra/{sup 230}Th in the basaltic and andesitic products from Izu arc volcanoes were greater than unity, being enriched in {sup 238}U and {sup 226}Ra relative to {sup 230}Th. The {sup 226}Ra/{sup 230}Th activity ratio versus {sup 238}U/{sup 230}Th activity ratio diagram for these products showed positive correlation, suggesting that the {sup 238}U-{sup 230}Th-{sup 226}Ra disequilibria occurred during the magma genesis by the additions of U- and Ra-rich fluids derived from the subducting slab by dehydration to the mantle wedge. The {sup 230}Th-{sup 226226}Ra radioactive disequilibria observed in the basaltic and andesitic products imply a short period of time (<8000 years) between the magma genesis and the eruption. The majority of rhyolitic products was considered to be almost in equilibrium of {sup 238}U={sup 230}Th={sup 226}Ra. The observation that {sup 238}U-{sup 230}Th-{sup 226}Ra for the rhyolite are in radioactive equilibrium suggested that the rhyolitic magma from Izu arc was generated in the partial melting of the earth crust heated by the basaltic magma of high temperature. (orig.)

  13. Analysis of noise pollution in an andesite quarry with the use of simulation studies and evaluation indices.

    Science.gov (United States)

    Kosała, Krzysztof; Stępień, Bartłomiej

    2016-01-01

    This paper presents the verification of two partial indices proposed for the evaluation of continuous and impulse noise pollution in quarries. These indices, together with the sound power of machines index and the noise hazard index at the workstation, are components of the global index of assessment of noise hazard in the working environment of a quarry. This paper shows the results of acoustic tests carried out in an andesite quarry. Noise generated by machines and from performed blasting works was investigated. On the basis of acoustic measurements carried out in real conditions, the sound power levels of machines and the phenomenon of explosion were determined and, based on the results, three-dimensional models of acoustic noise propagation in the quarry were developed. To assess the degree of noise pollution in the area of the quarry, the continuous and impulse noise indices were used.

  14. Superconductivity in graphite intercalation compounds

    Energy Technology Data Exchange (ETDEWEB)

    Smith, Robert P. [Cavendish Laboratory, University of Cambridge, Madingley Road, Cambridge CB3 0HE (United Kingdom); Weller, Thomas E.; Howard, Christopher A. [Department of Physics & Astronomy, University College of London, Gower Street, London WCIE 6BT (United Kingdom); Dean, Mark P.M. [Department of Condensed Matter Physics and Materials Science, Brookhaven National Laboratory, Upton, NY 11973 (United States); Rahnejat, Kaveh C. [Department of Physics & Astronomy, University College of London, Gower Street, London WCIE 6BT (United Kingdom); Saxena, Siddharth S. [Cavendish Laboratory, University of Cambridge, Madingley Road, Cambridge CB3 0HE (United Kingdom); Ellerby, Mark, E-mail: mark.ellerby@ucl.ac.uk [Department of Physics & Astronomy, University College of London, Gower Street, London WCIE 6BT (United Kingdom)

    2015-07-15

    Highlights: • Historical background of graphite intercalates. • Superconductivity in graphite intercalates and its place in the field of superconductivity. • Recent developments. • Relevant modeling of superconductivity in graphite intercalates. • Interpretations that pertain and questions that remain. - Abstract: The field of superconductivity in the class of materials known as graphite intercalation compounds has a history dating back to the 1960s (Dresselhaus and Dresselhaus, 1981; Enoki et al., 2003). This paper recontextualizes the field in light of the discovery of superconductivity in CaC{sub 6} and YbC{sub 6} in 2005. In what follows, we outline the crystal structure and electronic structure of these and related compounds. We go on to experiments addressing the superconducting energy gap, lattice dynamics, pressure dependence, and how these relate to theoretical studies. The bulk of the evidence strongly supports a BCS superconducting state. However, important questions remain regarding which electronic states and phonon modes are most important for superconductivity, and whether current theoretical techniques can fully describe the dependence of the superconducting transition temperature on pressure and chemical composition.

  15. Superconductivity in graphite intercalation compounds

    International Nuclear Information System (INIS)

    Smith, Robert P.; Weller, Thomas E.; Howard, Christopher A.; Dean, Mark P.M.; Rahnejat, Kaveh C.; Saxena, Siddharth S.; Ellerby, Mark

    2015-01-01

    Highlights: • Historical background of graphite intercalates. • Superconductivity in graphite intercalates and its place in the field of superconductivity. • Recent developments. • Relevant modeling of superconductivity in graphite intercalates. • Interpretations that pertain and questions that remain. - Abstract: The field of superconductivity in the class of materials known as graphite intercalation compounds has a history dating back to the 1960s (Dresselhaus and Dresselhaus, 1981; Enoki et al., 2003). This paper recontextualizes the field in light of the discovery of superconductivity in CaC 6 and YbC 6 in 2005. In what follows, we outline the crystal structure and electronic structure of these and related compounds. We go on to experiments addressing the superconducting energy gap, lattice dynamics, pressure dependence, and how these relate to theoretical studies. The bulk of the evidence strongly supports a BCS superconducting state. However, important questions remain regarding which electronic states and phonon modes are most important for superconductivity, and whether current theoretical techniques can fully describe the dependence of the superconducting transition temperature on pressure and chemical composition

  16. Graphite oral tattoo: case report.

    Science.gov (United States)

    Moraes, Renata Mendonça; Gouvêa Lima, Gabriela de Morais; Guilhermino, Marinaldo; Vieira, Mayana Soares; Carvalho, Yasmin Rodarte; Anbinder, Ana Lia

    2015-10-16

    Pigmented oral lesions compose a large number of pathological entities, including exogenous pigmentat oral tattoos, such as amalgam and graphite tattoos. We report a rare case of a graphite tattoo on the palate of a 62-year-old patient with a history of pencil injury, compare it with amalgam tattoos, and determine the prevalence of oral tattoos in our Oral Pathology Service. We also compare the clinical and histological findings of grafite and amalgam tattoos. Oral tattoos affect women more frequently in the region of the alveolar ridge. Graphite tattoos occur in younger patients when compared with the amalgam type. Histologically, amalgam lesions represent impregnation of the reticular fibers of vessels and nerves with silver, whereas in cases of graphite tattoos, this impregnation is not observed, but it is common to observe a granulomatous inflammatory response, less evident in cases of amalgam tattoos. Both types of lesions require no treatment, but in some cases a biopsy may be done to rule out melanocytic lesions.

  17. 'In situ' expanded graphite extinguishant

    International Nuclear Information System (INIS)

    Cao Qixin; Shou Yuemei; He Bangrong

    1987-01-01

    This report is concerning the development of the extinguishant for sodium fire and the investigation of its extinguishing property. The experiment result shows that 'in situ' expanded graphite developed by the authors is a kind of extinguishant which extinguishes sodium fire quickly and effectively and has no environment pollution during use and the amount of usage is little

  18. Anomalous Diffuse CO2 Emission Changes at San Vicente Volcano Related to Earthquakes in El Salvador, Central America

    Science.gov (United States)

    Salazar, J.; Hernandez, P.; Perez, N.; Barahona, F.; Olmos, R.; Cartagena, R.; Soriano, T.; Notsu, K.; Lopez, D.

    2001-12-01

    San Vicente or Chichontepeque (2,180 m a.s.l.) is a composite andesitic volcano located 50 Km east of San Salvador. Its paired edifice rises from the so-called Central Graben, an extensional structure parallel to the Pacific coast, and has been inactive for the last 3000 yrs. Fumaroles (98.2°C ) and hot spring waters are present along radial faults at two localities on the northern slope of the volcano (Aguas Agrias and El Infiernillo). CO2 is the most abundant component in the dry gas (>90%) and its mean isotopic composition (δ 13C(CO2)=-2.11 ‰ and 3He/4He of 6.9 Ra) suggests a magmatic origin for the CO2. These manifestations are supposed to be linked to a 1,200 m depth 250°C reservoir with a CO2 partial pressure of 14 bar extended beneath the volcano (Aiuppa et al., 1997). In February 13, 2001, a 6.6 magnitude earthquake with epicenter about 20 Km W of San Vicente damaged and destroyed many towns and villages in the north area of the volcano causing some deceases. In addition, two seismic swarms were recorded beneath the northeastern flank of the volcano in April and May 2001. Searching for any link between the actual seismic activity and changes in the diffuse CO2 degassing at San Vicente, an NDIR instrument for continuos monitoring of the diffuse CO2 degassing was set up at Aguas Agrias in March 2001. Soil CO2 efflux and several meteorological and soil physical variables were measured in an hourly basis. Very significative pre-seismic and post-seismic relationships have been found in the observed diffuse CO2 efflux temporal variations related to the May 2001 seismic swarms. A sustained 50% increase on the average diffuse CO2 efflux was observed 8 days before the May 8, 5.1 magnitude earthquake. This pre-seismic behaviour may be considered a precursor of the May 2001 seismic swarm at San Vicente volcano. However, about a three-fold increase in the diffuse CO2 efflux was also observed after the intense seismicity recorded on May 8-9. These preliminary

  19. Late Cretaceous (ca. 95 Ma) magnesian andesites in the Biluoco area, southern Qiangtang subterrane, central Tibet: Petrogenetic and tectonic implications

    Science.gov (United States)

    He, Haiyang; Li, Yalin; Wang, Chengshan; Zhou, Aorigele; Qian, Xinyu; Zhang, Jiawei; Du, Lintao; Bi, Wenjun

    2018-03-01

    The tectonic evolutionary history of the Lhasa and Qiangtang collision zones remains hotly debated because of the lack of pivotal magmatic records in the southern Qiangtang subterrane, central Tibet. We present zircon U-Pb dating, whole-rock major and trace-element geochemical analyses, and Sr-Nd isotopic data for the newly discovered Biluoco volcanic rocks from the southern Qiangtang subterrane, central Tibet. Zircon U-Pb dating reveals that the Biluoco volcanic rocks were crystallized at ca. 95 Ma. The samples are characterized by low SiO2 (50.26-54.53 wt%), high Cr (109.7-125.92 ppm) and Ni (57.4-71.58 ppm), and a high Mg# value (39-56), which plot in the magnesian andesites field on the rock classification diagram. They display highly fractionated rare earth element patterns with light rare earth element enrichment ([La/Yb]N = 21.04-25.24), high Sr/Y (63.97-78.79) and no negative Eu anomalies (Eu/Eu* = 0.98-1.04). The Biluoco volcanic rocks are depleted in Nb, Ta and Ti and enriched in Ba, Th, U and Pb. Moreover, the eight samples of Biluoco volcanic rocks display constant (87Sr/86Sr)i ratios (0.70514-0.70527), a positive εNd(t) value (2.16-2.68) and younger Nd model ages (0.56-0.62 Ga). These geochemical signatures indicate that the Biluoco volcanic rocks were most likely derived from partial melting of the mantle wedge peridotite metasomatized by melts of subducted slab and sediment in the subducted slab, invoked by asthenospheric upwelling resulting from the slab break-off of the northward subduction of the Bangong-Nujiang oceanic lithosphere. Identification of ca. 95 Ma Biluoco magnesian andesites suggests they were a delayed response of slab break-off of the northward subduction of the Bangong-Nujiang oceanic lithosphere at ca. 100 Ma.

  20. Graphite nanoreinforcements in polymer nanocomposites

    Science.gov (United States)

    Fukushima, Hiroyuki

    Nanocomposites composed of polymer matrices with clay reinforcements of less than 100 nm in size, are being considered for applications such as interior and exterior accessories for automobiles, structural components for portable electronic devices, and films for food packaging. While most nanocomposite research has focused on exfoliated clay platelets, the same nanoreinforcement concept can be applied to another layered material, graphite, to produce nanoplatelets and nanocomposites. Graphite is the stiffest material found in nature (Young's Modulus = 1060 GPa), having a modulus several times that of clay, but also with excellent electrical and thermal conductivity. The key to utilizing graphite as a platelet nanoreinforcement is in the ability to exfoliate this material. Also, if the appropriate surface treatment can be found for graphite, its exfoliation and dispersion in a polymer matrix will result in a composite with not only excellent mechanical properties but electrical properties as well, opening up many new structural applications as well as non-structural ones where electromagnetic shielding and high thermal conductivity are requirements. In this research, a new process to fabricate exfoliated nano-scale graphite platelets was established (Patent pending). The size of the resulted graphite platelets was less than 1 um in diameter and 10 nm in thickness, and the surface area of the material was around 100 m2/g. The reduction of size showed positive effect on mechanical properties of composites because of the increased edge area and more functional groups attached with it. Also various surface treatment techniques were applied to the graphite nanoplatelets to improve the surface condition. As a result, acrylamide grafting treatment was found to enhance the dispersion and adhesion of graphite flakes in epoxy matrices. The resulted composites showed better mechanical properties than those with commercially available carbon fibers, vapor grown carbon fibers

  1. Graphite suspension in carbon dioxide

    International Nuclear Information System (INIS)

    Roche, R.

    1965-01-01

    Since 1963 the Atomic Division of SNECMA has been conducting, under a contract with the CEA, an experimental work with a two-component fluid comprised of carbon dioxide and small graphite particles. The primary purpose was the determination of basic engineering information pertaining to the stability and the flowability of the suspension. The final form of the experimental loop consists mainly of the following items: a light-phase compressor, a heavy-phase pump, an electrical-resistance type heater section, a cooling heat exchanger, a hairpin loop, a transparent test section and a separator. During the course of the testing, it was observed that the fluid could be circulated quite easily in a broad range of variation of the suspension density and velocity - density from 30 to 170 kg/m 3 and velocity from 2 to 24 m/s. The system could be restarted and circulation maintained without any difficulty, even with the heavy-phase pump alone. The graphite did not have a tendency to pack or agglomerate during operation. No graphite deposition was observed on the wall of the tubing. A long period run (250 hours) has shown the evolution of the particle dimensions. Starting with graphite of surface area around 20 m 2 /g (graphite particles about 1 μ), the powder surface area reaches an asymptotic value of 300 m 2 /g (all the particles less than 0.3 μ). Moisture effect on flow stability, flow distribution between two parallel channels, pressure drop in straight tubes, recompression ratio in diffusers were also investigated. (author) [fr

  2. Characterisation of Chlorine Behavior in French Graphite

    International Nuclear Information System (INIS)

    Blondel, A.; Moncoffre, N.; Toulhoat, N.; Bererd, N.; Petit, L.; Laurent, G.; Lamouroux, C.

    2016-01-01

    Chlorine 36 is one of the main radionuclides of concern for French graphite waste disposal. In order to help the understanding of its leaching behaviour under disposal conditions, the respective impact of temperature, irradiation and gas radiolysis on chlorine release in reactor has been studied. Chlorine 36 has been simulated through chlorine 37 ion implantation in virgin nuclear graphite samples. Results show that part of chlorine is highly mobile in graphite in the range of French reactors operating temperatures in relation with graphite structural recovering. Ballistic damage generated by irradiation also promotes chlorine release whereas no clear impact of the coolant gas radiolysis was observed in the absence of graphite radiolytic corrosion. (author)

  3. On the time-scales of magmatism at island-arc volcanoes.

    Science.gov (United States)

    Turner, S P

    2002-12-15

    Precise information on time-scales and rates of change is fundamental to an understanding of natural processes and the development of quantitative physical models in the Earth sciences. U-series isotope studies are revolutionizing this field by providing time information in the range 10(2)-10(4) years, which is similar to that of many modern Earth processes. I review how the application of U-series isotopes has been used to constrain the time-scales of magma formation, ascent and storage beneath island-arc volcanoes. Different elements are distilled-off the subducting plate at different times and in different places. Contributions from subducted sediments to island-arc lava sources appear to occur some 350 kyr to 4 Myr prior to eruption. Fluid release from the subducting oceanic crust into the mantle wedge may be a multi-stage process and occurs over a period ranging from a few hundred kyr to less than one kyr prior to eruption. This implies that dehydration commences prior to the initiation of partial melting within the mantle wedge, which is consistent with recent evidence that the onset of melting is controlled by an isotherm and thus the thermal structure within the wedge. U-Pa disequilibria appear to require a component of decompression melting, possibly due to the development of gravitational instabilities. The preservation of large (226)Ra disequilibria permits only a short period of time between fluid addition and eruption. This requires rapid melt segregation, magma ascent by channelled flow and minimal residence time within the lithosphere. The evolution from basalt to basaltic andesite probably occurs rapidly during ascent or in magma reservoirs inferred from some geophysical data to lie within the lithospheric mantle. The flux across the Moho is broadly andesitic, and some magmas subsequently stall in more shallow crustal-level magma chambers, where they evolve to more differentiated compositions on time-scales of a few thousand years or less.

  4. Complex conductivity of volcanic rocks and the geophysical mapping of alteration in volcanoes

    Science.gov (United States)

    Ghorbani, A.; Revil, A.; Coperey, A.; Soueid Ahmed, A.; Roque, S.; Heap, M. J.; Grandis, H.; Viveiros, F.

    2018-05-01

    Induced polarization measurements can be used to image alteration at the scale of volcanic edifices to a depth of few kilometers. Such a goal cannot be achieved with electrical conductivity alone, because too many textural and environmental parameters influence the electrical conductivity of volcanic rocks. We investigate the spectral induced polarization measurements (complex conductivity) in the frequency band 10 mHz-45 kHz of 85 core samples from five volcanoes: Merapi and Papandayan in Indonesia (32 samples), Furnas in Portugal (5 samples), Yellowstone in the USA (26 samples), and Whakaari (White Island) in New Zealand (22 samples). This collection of samples covers not only different rock compositions (basaltic andesite, andesite, trachyte and rhyolite), but also various degrees of alteration. The specific surface area is found to be correlated to the cation exchange capacity (CEC) of the samples measured by the cobalthexamine method, both serving as rough proxies of the hydrothermal alteration experienced by these materials. The in-phase (real) conductivity of the samples is the sum of a bulk contribution associated with conduction in the pore network and a surface conductivity that increases with alteration. The quadrature conductivity and the normalized chargeability are two parameters related to the polarization of the electrical double layer coating the minerals of the volcanic rocks. Both parameters increase with the degree of alteration. The surface conductivity, the quadrature conductivity, and the normalized chargeability (defined as the difference between the in-phase conductivity at high and low frequencies) are linearly correlated to the CEC normalized by the bulk tortuosity of the pore space. The effects of temperature and pyrite-content are also investigated and can be understood in terms of a physics-based model. Finally, we performed a numerical study of the use of induced polarization to image the normalized chargeability of a volcanic edifice

  5. Volcano-tectonic control of Merapi's lava dome splitting observed from high resolution TerraSAR-X data

    KAUST Repository

    Luehr, Birger-G.

    2015-04-01

    Volcanism at active andesite-dacite volcanoes is often associated with the formation and collapse of circular shaped protrusions of extruded, highly viscous lava, the so-called domes, which are emplaced in the near summit region. Growing domes may experience stable and instable structural phases, with a gradual transition in between. Dome collapse and the break-off of instable blocks of viscous lava may lead to pyroclastic flows, one of the most lethal hazards at stratovolcanoes. At Merapi volcano, Indonesia, nearly 50 % of all eruptions are accompanied by these phenomena. After the climactic eruption in 2010 which left an amphitheater in the summit region, a new dome started growing. Three years later, the dome reached a height of approximately 100 m and diameters of 220 and 190 m with a plateau-like surface area of 40,000m2 approximately. On 18/11/2013, an explosion occurred without identified precursors, leaving a major fracture cutting the complete dome structure. Based on high resolution TerraSAR-X satellite radar imagery, we could identify this linear fracture, traceable over ~200m in the long axis, and up to 40m width. After geocoding of the radar amplitude imagery, the fractures azimuthal trend could be compared to other structural lineaments, indicative of a significant NNW-SSE structural direction that has formed on Merapi volcano in the past. This alignment is also visible in a seismic velocity tomographic imagery for the upper crust, down to 15 km depth. The Merapi dome fractured in a NW-SE direction, and is consistent with the alignment of regional tectonic structures and of anticipated directions of pyroclastic flows. The fracture may be part of a larger volcano-tectonic system and may affect the dynamics and the stability of the Merapi dome.

  6. Volcano-tectonic control of Merapi's lava dome splitting observed from high resolution TerraSAR-X data

    KAUST Repository

    Luehr, Birger-G.; Walter, Thomas R.; Subandriyo, Joko; Sri Brotopuspito, Kirbani; Vasyura-Bathke, Hannes; Suryanto, Wiwit; Aisyah, Naning; Darmawan, Herlan; Nikkhoo, Mehdi; Richter, Nicole; Jousset, Philippe; Dahm, Torsten

    2015-01-01

    Volcanism at active andesite-dacite volcanoes is often associated with the formation and collapse of circular shaped protrusions of extruded, highly viscous lava, the so-called domes, which are emplaced in the near summit region. Growing domes may experience stable and instable structural phases, with a gradual transition in between. Dome collapse and the break-off of instable blocks of viscous lava may lead to pyroclastic flows, one of the most lethal hazards at stratovolcanoes. At Merapi volcano, Indonesia, nearly 50 % of all eruptions are accompanied by these phenomena. After the climactic eruption in 2010 which left an amphitheater in the summit region, a new dome started growing. Three years later, the dome reached a height of approximately 100 m and diameters of 220 and 190 m with a plateau-like surface area of 40,000m2 approximately. On 18/11/2013, an explosion occurred without identified precursors, leaving a major fracture cutting the complete dome structure. Based on high resolution TerraSAR-X satellite radar imagery, we could identify this linear fracture, traceable over ~200m in the long axis, and up to 40m width. After geocoding of the radar amplitude imagery, the fractures azimuthal trend could be compared to other structural lineaments, indicative of a significant NNW-SSE structural direction that has formed on Merapi volcano in the past. This alignment is also visible in a seismic velocity tomographic imagery for the upper crust, down to 15 km depth. The Merapi dome fractured in a NW-SE direction, and is consistent with the alignment of regional tectonic structures and of anticipated directions of pyroclastic flows. The fracture may be part of a larger volcano-tectonic system and may affect the dynamics and the stability of the Merapi dome.

  7. The 13 ka Pelée-Type Dome Collapse at Nevado de Toluca Volcano, México.

    Science.gov (United States)

    D'Antonio, M.; Capra, L.; Sarocchi, D.; Bellotti, F.

    2007-05-01

    The Nevado de Toluca is an active volcano located in the central sector of the Trans-Mexican Volcanic Belt, 80 km southwest of Mexico City. Activity at this andesitic to dacitic stratovolcano began ca. 2.6 Ma ago. During the last 42 ka, the volcano has been characterized by different eruptive styles, including five dome collapses dated at 37, 32, 28, 26, and 13 ka and five Plinian eruptions at 42 ka, 36 ka, 21.7 ka, 12.1 ka and 10.5 ka. The 13 ka dome collapse is the youngest event of this type, and originated a 0.11 km3 block-and-ash flow deposit on the north-eastern sector of the volcano. The deposit consists of two facies: channel-like, 10 m thick, monolitologic, that is composed of up to five units, with decimetric dacitic clasts set in a sandy matrix; and a lateral facies that consists of a gray, sandy horizon, up to 4 m thick, with a 30 cm-thick surge layer at the base. The main component is a dacitic lava, with different degree of vesciculation, with mineral association of Pl-Hbl-Opx. Plagioclases show two different textures: in equilibrium, with normal zoning (core = An37-64.3, rim = An30.7-45.8) or with spongy cellular texture with inverse zoning (core = An38-43.5, rim = An45-51.2). Hornblende is normally light green, barren of oxidation. The rock matrix contains up to 53 perc. of glass with abundant microlites, indicating over-pressure on the crystallizing magma and a rapid expulsion. All these stratigraphic and petrographic features indicate that the dome was quickly extruded on the summit of the volcano, probably triggered by a magma mixing process, and its collapse was accompanied by an explosive component, being classified as a Pelée-type event.

  8. AGC-2 Graphite Preirradiation Data Package

    Energy Technology Data Exchange (ETDEWEB)

    David Swank; Joseph Lord; David Rohrbaugh; William Windes

    2012-10-01

    The NGNP Graphite R&D program is currently establishing the safe operating envelope of graphite core components for a Very High Temperature Reactor (VHTR) design. The program is generating quantitative data necessary for predicting the behavior and operating performance of the new nuclear graphite grades. To determine the in-service behavior of the graphite for pebble bed and prismatic designs, the Advanced Graphite Creep (AGC) experiment is underway. This experiment is examining the properties and behavior of nuclear grade graphite over a large spectrum of temperatures, neutron fluences and compressive loads. Each experiment consists of over 400 graphite specimens that are characterized prior to irradiation and following irradiation. Six experiments are planned with the first, AGC-1, currently being irradiated in the Advanced Test Reactor (ATR) and pre-irradiation characterization of the second, AGC-2, completed. This data package establishes the readiness of 512 specimens for assembly into the AGC-2 capsule.

  9. Progress in radioactive graphite waste management

    International Nuclear Information System (INIS)

    2010-07-01

    Radioactive graphite constitutes a major waste stream which arises during the decommissioning of certain types of nuclear installations. Worldwide, a total of around 250 000 tonnes of radioactive graphite, comprising graphite moderators and reflectors, will require management solutions in the coming years. 14 C is the radionuclide of greatest concern in nuclear graphite; it arises principally through the interaction of reactor neutrons with nitrogen, which is present in graphite as an impurity or in the reactor coolant or cover gas. 3 H is created by the reactions of neutrons with 6 Li impurities in graphite as well as in fission of the fuel. 36 Cl is generated in the neutron activation of chlorine impurities in graphite. Problems in the radioactive waste management of graphite arise mainly because of the large volumes requiring disposal, the long half-lives of the main radionuclides involved and the specific properties of graphite - such as stored Wigner energy, graphite dust explosibility and the potential for radioactive gases to be released. Various options for the management of radioactive graphite have been studied but a generally accepted approach for its conditioning and disposal does not yet exist. Different solutions may be appropriate in different cases. In most of the countries with radioactive graphite to manage, little progress has been made to date in respect of the disposal of this material. Only in France has there been specific thinking about a dedicated graphite waste-disposal facility (within ANDRA): other major producers of graphite waste (UK and the countries of the former Soviet Union) are either thinking in terms of repository disposal or have no developed plans. A conference entitled 'Solutions for Graphite Waste: a Contribution to the Accelerated Decommissioning of Graphite Moderated Nuclear Reactors' was held at the University of Manchester 21-23 March 2007 in order to stimulate progress in radioactive graphite waste management

  10. Voronoi-Tessellated Graphite Produced by Low-Temperature Catalytic Graphitization from Renewable Resources.

    Science.gov (United States)

    Zhao, Leyi; Zhao, Xiuyun; Burke, Luke T; Bennett, J Craig; Dunlap, Richard A; Obrovac, Mark N

    2017-09-11

    A highly crystalline graphite powder was prepared from the low temperature (800-1000 °C) graphitization of renewable hard carbon precursors using a magnesium catalyst. The resulting graphite particles are composed of Voronoi-tessellated regions comprising irregular sheets; each Voronoi-tessellated region having a small "seed" particle located near their centroid on the surface. This suggests nucleated outward growth of graphitic carbon, which has not been previously observed. Each seed particle consists of a spheroidal graphite shell on the inside of which hexagonal graphite platelets are perpendicularly affixed. This results in a unique high surface area graphite with a high degree of graphitization that is made with renewable feedstocks at temperatures far below that conventionally used for artificial graphites. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  11. Graphite structure and magnetic parameters of flake graphite cast iron

    Czech Academy of Sciences Publication Activity Database

    Vértesy, G.; Uchimoto, T.; Takagi, T.; Tomáš, Ivan; Kage, H.

    2017-01-01

    Roč. 442, Nov (2017), s. 397-402 ISSN 0304-8853 R&D Projects: GA ČR GB14-36566G Institutional support: RVO:68378271 Keywords : magnetic NDE * magnetic adaptive testing * cast iron * graphite structure * pearlite content Subject RIV: BM - Solid Matter Physics ; Magnetism OBOR OECD: Condensed matter physics (including formerly solid state physics, supercond.) Impact factor: 2.630, year: 2016

  12. On the absence of InSAR-detected volcano deformation spanning the 1995-1996 and 1999 eruptions of Shishaldin Volcano, Alaska

    Science.gov (United States)

    Moran, S.C.; Kwoun, O.; Masterlark, Timothy; Lu, Z.

    2006-01-01

    Shishaldin Volcano, a large, frequently active basaltic-andesite volcano located on Unimak Island in the Aleutian Arc of Alaska, had a minor eruption in 1995–1996 and a VEI 3 sub-Plinian basaltic eruption in 1999. We used 21 synthetic aperture radar images acquired by ERS-1, ERS-2, JERS-1, and RADARSAT-1 satellites to construct 12 coherent interferograms that span most of the 1993–2003 time interval. All interferograms lack coherence within ∼5 km of the summit, primarily due to persistent snow and ice cover on the edifice. Remarkably, in the 5–15 km distance range where interferograms are coherent, the InSAR images show no intrusion- or withdrawal-related deformation at Shishaldin during this entire time period. However, several InSAR images do show deformation associated with a shallow ML 5.2 earthquake located ∼14 km west of Shishaldin that occurred 6 weeks before the 1999 eruption. We use a theoretical model to predict deformation magnitudes due to a volumetric expansion source having a volume equivalent to the 1999 erupted volume, and find that deformation magnitudes for sources shallower than 10 km are within the expected detection capabilities for interferograms generated from C-band ERS 1/2 and RADARSAT-1 synthetic aperture radar images. We also find that InSAR images cannot resolve relatively shallow deformation sources (1–2 km below sea level) due to spatial gaps in the InSAR images caused by lost coherence. The lack of any deformation, particularly for the 1999 eruption, leads us to speculate that magma feeding eruptions at the summit moves rapidly (at least 80m/day) from > 10 km depth, and that the intrusion–eruption cycle at Shishaldin does not produce significant permanent deformation at the surface.

  13. Geoflicks Reviewed--Films about Hawaiian Volcanoes.

    Science.gov (United States)

    Bykerk-Kauffman, Ann

    1994-01-01

    Reviews 11 films on volcanic eruptions in the United States. Films are given a one- to five-star rating and the film's year, length, source and price are listed. Top films include "Inside Hawaiian Volcanoes" and "Kilauea: Close up of an Active Volcano." (AIM)

  14. Orographic Flow over an Active Volcano

    Science.gov (United States)

    Poulidis, Alexandros-Panagiotis; Renfrew, Ian; Matthews, Adrian

    2014-05-01

    Orographic flows over and around an isolated volcano are studied through a series of numerical model experiments. The volcano top has a heated surface, so can be thought of as "active" but not erupting. A series of simulations with different atmospheric conditions and using both idealised and realistic configurations of the Weather Research and Forecast (WRF) model have been carried out. The study is based on the Soufriere Hills volcano, located on the island of Montserrat in the Caribbean. This is a dome-building volcano, leading to a sharp increase in the surface skin temperature at the top of the volcano - up to tens of degrees higher than ambient values. The majority of the simulations use an idealised topography, in order for the results to have general applicability to similar-sized volcanoes located in the tropics. The model is initialised with idealised atmospheric soundings, representative of qualitatively different atmospheric conditions from the rainy season in the tropics. The simulations reveal significant changes to the orographic flow response, depending upon the size of the temperature anomaly and the atmospheric conditions. The flow regime and characteristic features such as gravity waves, orographic clouds and orographic rainfall patterns can all be qualitatively changed by the surface heating anomaly. Orographic rainfall over the volcano can be significantly enhanced with increased temperature anomaly. The implications for the eruptive behaviour of the volcano and resulting secondary volcanic hazards will also be discussed.

  15. Graphite moderated 252Cf source

    International Nuclear Information System (INIS)

    Sajo B, L.; Barros, H.; Greaves, E. D.; Vega C, H. R.

    2014-08-01

    The thorium molten salt reactor is an attractive and affordable nuclear power option for developing countries with insufficient infrastructure and limited technological capability. In the aim of personnel training and experience gathering at the Universidad Simon Bolivar there is in progress a project of developing a subcritical thorium liquid fuel reactor. The neutron source to run this subcritical reactor is a 252 Cf source and the reactor will use high-purity graphite as moderator. Using the MCNP5 code the neutron spectra of the 252 Cf in the center of the graphite moderator has been estimated along the channel where the liquid thorium salt will be inserted; also the ambient dose equivalent due to the source has been determined around the moderator. (Author)

  16. Fission Product Sorptivity in Graphite

    Energy Technology Data Exchange (ETDEWEB)

    Tompson, Jr., Robert V. [Univ. of Missouri, Columbia, MO (United States); Loyalka, Sudarshan [Univ. of Missouri, Columbia, MO (United States); Ghosh, Tushar [Univ. of Missouri, Columbia, MO (United States); Viswanath, Dabir [Univ. of Missouri, Columbia, MO (United States); Walton, Kyle [Univ. of Missouri, Columbia, MO (United States); Haffner, Robert [Univ. of Missouri, Columbia, MO (United States)

    2015-04-01

    Both adsorption and absorption (sorption) of fission product (FP) gases on/into graphite are issues of interest in very high temperature reactors (VHTRs). In the original proposal, we proposed to use packed beds of graphite particles to measure sorption at a variety of temperatures and to use an electrodynamic balance (EDB) to measure sorption onto single graphite particles (a few μm in diameter) at room temperature. The use of packed beds at elevated temperature is not an issue. However, the TPOC requested revision of this initial proposal to included single particle measurements at elevated temperatures up to 1100 °C. To accommodate the desire of NEUP to extend the single particle EDB measurements to elevated temperatures it was necessary to significantly revise the plan and the budget. These revisions were approved. In the EDB method, we levitate a single graphite particle (the size, surface characteristics, morphology, purity, and composition of the particle can be varied) or agglomerate in the balance and measure the sorption of species by observing the changes in mass. This process involves the use of an electron stepping technique to measure the total charge on a particle which, in conjunction with the measured suspension voltages for the particle, allows for determinations of mass and, hence, of mass changes which then correspond to measurements of sorption. Accommodating elevated temperatures with this type of system required a significant system redesign and required additional time that ultimately was not available. These constraints also meant that the grant had to focus on fewer species as a result. Overall, the extension of the original proposed single particle work to elevated temperatures added greatly to the complexity of the proposed project and added greatly to the time that would eventually be required as well. This means that the bulk of the experimental progress was made using the packed bed sorption systems. Only being able to recruit one

  17. Graphite for high-temperature reactors

    International Nuclear Information System (INIS)

    Hammer, W.; Leushacke, D.F.; Nickel, H.; Theymann, W.

    1976-01-01

    The different graphites necessary for HTRs are being developed, produced and tested within the Federal German ''Development Programme Nuclear Graphite''. Up to now, batches of the following graphite grades have been manufactured and fully characterized by the SIGRI Company to demonstrate reproducibility: pitch coke graphite AS2-500 for the hexagonal fuel elements and exchangeable reflector blocks; special pitch coke graphite ASI2-500 for reflector blocks of the pebble-bed reactor and as back-up material for the hexagonal fuel elements; graphite for core support columns. The material data obtained fulfill most of the requirements under present specifications. Production of large-size blocks for the permanent side reflector and the core support blocks is under way. The test programme covers all areas important for characterizing and judging HTR-graphites. In-pile testing comprises evaluation of the material for irradiation-induced changes of dimensions, mechanical and thermal properties - including behaviour under temperature cycling and creep behaviour - as well as irradiating fuel element segments and blocks. Testing out-of-pile includes: evaluation of corrosion rates and influence of corrosion on strength; strength measurements; including failure criteria. The test programme has been carried out extensively on the AS2-graphite, and the results obtained show that this graphite is suitable as HTGR fuel element graphite. (author)

  18. AGC-3 Graphite Preirradiation Data Analysis Report

    Energy Technology Data Exchange (ETDEWEB)

    William Windes; David Swank; David Rohrbaugh; Joseph Lord

    2013-09-01

    This report describes the specimen loading order and documents all pre-irradiation examination material property measurement data for the graphite specimens contained within the third Advanced Graphite Capsule (AGC-3) irradiation capsule. The AGC-3 capsule is third in six planned irradiation capsules comprising the Advanced Graphite Creep (AGC) test series. The AGC test series is used to irradiate graphite specimens allowing quantitative data necessary for predicting the irradiation behavior and operating performance of new nuclear graphite grades to be generated which will ascertain the in-service behavior of the graphite for pebble bed and prismatic Very High Temperature Reactor (VHTR) designs. The general design of AGC-3 test capsule is similar to the AGC-2 test capsule, material property tests were conducted on graphite specimens prior to loading into the AGC-3 irradiation assembly. However the 6 major nuclear graphite grades in AGC-2 were modified; two previous graphite grades (IG-430 and H-451) were eliminated and one was added (Mersen’s 2114 was added). Specimen testing from three graphite grades (PCEA, 2114, and NBG-17) was conducted at Idaho National Laboratory (INL) and specimen testing for two grades (IG-110 and NBG-18) were conducted at Oak Ridge National Laboratory (ORNL) from May 2011 to July 2013. This report also details the specimen loading methodology for the graphite specimens inside the AGC-3 irradiation capsule. The AGC-3 capsule design requires "matched pair" creep specimens that have similar dose levels above and below the neutron flux profile mid-plane to provide similar specimens with and without an applied load. This document utilized the neutron flux profile calculated for the AGC-3 capsule design, the capsule dimensions, and the size (length) of the selected graphite and silicon carbide samples to create a stacking order that can produce "matched pairs" of graphite samples above and below the AGC-3 capsule elevation mid-point to

  19. Pyroclast textural variation as an indicator of eruption column steadiness in andesitic Plinian eruptions at Mt. Ruapehu

    Science.gov (United States)

    Pardo, Natalia; Cronin, Shane J.; Wright, Heather M.N.; Schipper, C. Ian; Smith, Ian; Stewart, Bob

    2014-01-01

    Between 27 and 11 cal. ka BP, a transition is observed in Plinian eruptions at Mt. Ruapehu, indicating evolution from non-collapsing (steady and oscillatory) eruption columns to partially collapsing columns (both wet and dry). To determine the causes of these variations over this eruptive interval, we examined lapilli fall deposits from four eruptions representing the climactic phases of each column type. All eruptions involve andesite to basaltic andesite magmas containing plagioclase, clinopyroxene, orthopyroxene and magnetite phenocrysts. Differences occur in the dominant pumice texture, the degree of bulk chemistry and textural variability, the average microcrystallinity and the composition of groundmass glass. In order to investigate the role of ascent and degassing processes on column stability, vesicle textures were quantified by gas volume pycnometry (porosity), X-ray synchrotron and computed microtomography (μ-CT) imagery from representative clasts from each eruption. These data were linked to groundmass crystallinity and glass geochemistry. Pumice textures were classified into six types (foamy, sheared, fibrous, microvesicular, microsheared and dense) according to the vesicle content, size and shape and microlite content. Bulk porosities vary from 19 to 95 % among all textural types. Melt-referenced vesicle number density ranges between 1.8 × 102 and 8.9 × 102 mm−3, except in fibrous textures, where it spans from 0.3 × 102 to 53 × 102 mm−3. Vesicle-free magnetite number density varies within an order of magnitude from 0.4 × 102 to 4.5 × 102 mm−3 in samples with dacitic groundmass glass and between 0.0 and 2.3 × 102 mm−3 in samples with rhyolitic groundmass. The data indicate that columns that collapsed to produce pyroclastic flows contained pumice with the greatest variation in bulk composition (which overlaps with but extends to slightly more silicic compositions than other eruptive products); textures

  20. Environmentally benign graphite intercalation compound composition for exfoliated graphite, flexible graphite, and nano-scaled graphene platelets

    Science.gov (United States)

    Zhamu, Aruna; Jang, Bor Z.

    2014-06-17

    A carboxylic-intercalated graphite compound composition for the production of exfoliated graphite, flexible graphite, or nano-scaled graphene platelets. The composition comprises a layered graphite with interlayer spaces or interstices and a carboxylic acid residing in at least one of the interstices, wherein the composition is prepared by a chemical oxidation reaction which uses a combination of a carboxylic acid and hydrogen peroxide as an intercalate source. Alternatively, the composition may be prepared by an electrochemical reaction, which uses a carboxylic acid as both an electrolyte and an intercalate source. Exfoliation of the invented composition does not release undesirable chemical contaminants into air or drainage.

  1. Electrochemical Ultracapacitors Using Graphitic Nanostacks

    Science.gov (United States)

    Marotta, Christopher

    2012-01-01

    Electrochemical ultracapacitors (ECs) have been developed using graphitic nanostacks as the electrode material. The advantages of this technology will be the reduction of device size due to superior power densities and relative powers compared to traditional activated carbon electrodes. External testing showed that these materials display reduced discharge response times compared to state-of-the-art materials. Such applications are advantageous for pulsed power applications such as burst communications (satellites, cell phones), electromechanical actuators, and battery load leveling in electric vehicles. These carbon nanostructures are highly conductive and offer an ordered mesopore network. These attributes will provide more complete electrolyte wetting, and faster release of stored charge compared to activated carbon. Electrochemical capacitor (EC) electrode materials were developed using commercially available nanomaterials and modifying them to exploit their energy storage properties. These materials would be an improvement over current ECs that employ activated carbon as the electrode material. Commercially available graphite nanofibers (GNFs) are used as precursor materials for the synthesis of graphitic nanostacks (GNSs). These materials offer much greater surface area than graphite flakes. Additionally, these materials offer a superior electrical conductivity and a greater average pore size compared to activated carbon electrodes. The state of the art in EC development uses activated carbon (AC) as the electrode material. AC has a high surface area, but its small average pore size inhibits electrolyte ingress/egress. Additionally, AC has a higher resistivity, which generates parasitic heating in high-power applications. This work focuses on fabricating EC from carbon that has a very different structure by increasing the surface area of the GNF by intercalation or exfoliation of the graphitic basal planes. Additionally, various functionalities to the GNS

  2. Geology and geochemistry of Pelagatos, Cerro del Agua, and Dos Cerros monogenetic volcanoes in the Sierra Chichinautzin Volcanic Field, south of México City

    Science.gov (United States)

    Agustín-Flores, Javier; Siebe, Claus; Guilbaud, Marie-Noëlle

    2011-04-01

    This study focuses on the geology and geochemistry of three closely-spaced monogenetic volcanoes that are located in the NE sector of the Sierra Chichinautzin Volcanic Field near México City. Pelagatos (3020 m.a.s.l.) is a small scoria cone (0.0017 km 3) with lava flows (0.036 km 3) that covered an area of 4.9 km 2. Cerro del Agua scoria cone (3480 m.a.s.l., 0.028 km 3) produced several lava flows (0.24 km 3) covering an area of 17.6 km 2. Dos Cerros is a lava shield which covers an area of 80.3 km 2 and is crowned by two scoria cones: Tezpomayo (3080 m.a.s.l., 0.022 km 3) and La Ninfa (3000 m.a.s.l., 0.032 km 3). The eruptions of Cerro del Agua and Pelagatos occurred between 2500 and 14,000 yr BP. The Dos Cerros eruption took place close to 14,000 yr BP as constrained by radiocarbon dating. Rocks from these three volcanoes are olivine-hypersthene normative basaltic andesites and andesites with porphyritic, aphanitic, and glomeroporphyritic textures. Their mineral assemblages include olivine, clinopyroxene, and orthopyroxene phenocrysts (≤ 10 vol.%) embedded in a trachytic groundmass which consists mainly of plagioclase microlites and glass. Pelagatos rocks also present quartz xenocrysts. Due to their high Cr and Ni contents, and high Mg#s, Pelagatos rocks are considered to be derived from primitive magmas, hence the importance of this volcano for understanding petrogenetic processes in this region. Major and trace element abundances and petrography of products from these volcanoes indicate a certain degree of crystal fractionation during ascent to the surface. However, the magmas that formed the volcanoes evolved independently from each other and are not cogenetically related. REE, HFSE, LILE, and isotopic (Sr, Nd, and Pb) compositions point towards a heterogeneous mantle source that has been metasomatized by aqueous/melt phases from the subducted Cocos slab. There is no clear evidence of important crustal contributions in the compositions of Pelagatos and

  3. Pyrolytic graphite gauge for measuring heat flux

    Science.gov (United States)

    Bunker, Robert C. (Inventor); Ewing, Mark E. (Inventor); Shipley, John L. (Inventor)

    2002-01-01

    A gauge for measuring heat flux, especially heat flux encountered in a high temperature environment, is provided. The gauge includes at least one thermocouple and an anisotropic pyrolytic graphite body that covers at least part of, and optionally encases the thermocouple. Heat flux is incident on the anisotropic pyrolytic graphite body by arranging the gauge so that the gauge surface on which convective and radiative fluxes are incident is perpendicular to the basal planes of the pyrolytic graphite. The conductivity of the pyrolytic graphite permits energy, transferred into the pyrolytic graphite body in the form of heat flux on the incident (or facing) surface, to be quickly distributed through the entire pyrolytic graphite body, resulting in small substantially instantaneous temperature gradients. Temperature changes to the body can thereby be measured by the thermocouple, and reduced to quantify the heat flux incident to the body.

  4. Attenuation of thermal neutron through graphite

    International Nuclear Information System (INIS)

    Adib, M.; Ismaail, H.; Fathaallah, M.; Abbas, Y.; Habib, N.; Wahba, M.

    2004-01-01

    Calculation of the nuclear capture, thermal diffuse and Bragg scattering cross-sections as a function of graphite temperature and crystalline from for neutron energies from 1 me V< E<10 eV were carried out. Computer programs have been developed which allow calculation for the graphite hexagonal closed-pack structure in its polycrystalline form and pyrolytic one. I The calculated total cross-section for polycrystalline graphite were compared with the experimental values. An overall agreement is indicated between the calculated values and experimental ones. Agreement was also obtained for neutron cross-section measured for oriented pyrolytic graphite at room and liquid nitrogen temperatures. A feasibility study for use of graphite in powdered form as a cold neutron filter is details. The calculated attenuation of thermal neutrons through large mosaic pyrolytic graphite show that such crystals can be used effectively as second order filter of thermal neutron beams and that cooling improve their effectiveness

  5. Uranium Oxide Aerosol Transport in Porous Graphite

    Energy Technology Data Exchange (ETDEWEB)

    Blanchard, Jeremy; Gerlach, David C.; Scheele, Randall D.; Stewart, Mark L.; Reid, Bruce D.; Gauglitz, Phillip A.; Bagaasen, Larry M.; Brown, Charles C.; Iovin, Cristian; Delegard, Calvin H.; Zelenyuk, Alla; Buck, Edgar C.; Riley, Brian J.; Burns, Carolyn A.

    2012-01-23

    The objective of this paper is to investigate the transport of uranium oxide particles that may be present in carbon dioxide (CO2) gas coolant, into the graphite blocks of gas-cooled, graphite moderated reactors. The transport of uranium oxide in the coolant system, and subsequent deposition of this material in the graphite, of such reactors is of interest because it has the potential to influence the application of the Graphite Isotope Ratio Method (GIRM). The GIRM is a technology that has been developed to validate the declared operation of graphite moderated reactors. GIRM exploits isotopic ratio changes that occur in the impurity elements present in the graphite to infer cumulative exposure and hence the reactor’s lifetime cumulative plutonium production. Reference Gesh, et. al., for a more complete discussion on the GIRM technology.

  6. The enormous Chillos Valley Lahar: An ash-flow-generated debris flow from Cotopaxi Volcano, Ecuador

    Science.gov (United States)

    Mothes, P.A.; Hall, M.L.; Janda, R.J.

    1998-01-01

    The Chillos Valley Lahar (CVL), the largest Holocene debris flow in area and volume as yet recognized in the northern Andes, formed on Cotopaxi volcano's north and northeast slopes and descended river systems that took it 326 km north-northwest to the Pacific Ocean and 130+ km east into the Amazon basin. In the Chillos Valley, 40 km downstream from the volcano, depths of 80-160 m and valley cross sections up to 337000m2 are observed, implying peak flow discharges of 2.6-6.0 million m3/s. The overall volume of the CVL is estimated to be ???3.8 km3. The CVL was generated approximately 4500 years BP by a rhyolitic ash flow that followed a small sector collapse on the north and northeast sides of Cotopaxi, which melted part of the volcano's icecap and transformed rapidly into the debris flow. The ash flow and resulting CVL have identical components, except for foreign fragments picked up along the flow path. Juvenile materials, including vitric ash, crystals, and pumice, comprise 80-90% of the lahar's deposit, whereas rhyolitic, dacitic, and andesitic lithics make up the remainder. The sand-size fraction and the 2- to 10-mm fraction together dominate the deposit, constituting ???63 and ???15 wt.% of the matrix, respectively, whereas the silt-size fraction averages less than ???10 wt.% and the clay-size fraction less than 0.5 wt.%. Along the 326-km runout, these particle-size fractions vary little, as does the sorting coefficient (average = 2.6). There is no tendency toward grading or improved sorting. Limited bulking is recognized. The CVL was an enormous non-cohesive debris flow, notable for its ash-flow origin and immense volume and peak discharge which gave it characteristics and a behavior akin to large cohesive mudflows. Significantly, then, ash-flow-generated debris flows can also achieve large volumes and cover great areas; thus, they can conceivably affect large populated regions far from their source. Especially dangerous, therefore, are snowclad volcanoes

  7. The 2014 eruptions of Pavlof Volcano, Alaska

    Science.gov (United States)

    Waythomas, Christopher F.; Haney, Matthew M.; Wallace, Kristi; Cameron, Cheryl E.; Schneider, David J.

    2017-12-22

    Pavlof Volcano is one of the most frequently active volcanoes in the Aleutian Island arc, having erupted more than 40 times since observations were first recorded in the early 1800s . The volcano is located on the Alaska Peninsula (lat 55.4173° N, long 161.8937° W), near Izembek National Wildlife Refuge. The towns and villages closest to the volcano are Cold Bay, Nelson Lagoon, Sand Point, and King Cove, which are all within 90 kilometers (km) of the volcano (fig. 1). Pavlof is a symmetrically shaped stratocone that is 2,518 meters (m) high, and has about 2,300 m of relief. The volcano supports a cover of glacial ice and perennial snow roughly 2 to 4 cubic kilometers (km3) in volume, which is mantled by variable amounts of tephra fall, rockfall debris, and pyroclastic-flow deposits produced during historical eruptions. Typical Pavlof eruptions are characterized by moderate amounts of ash emission, lava fountaining, spatter-fed lava flows, explosions, and the accumulation of unstable mounds of spatter on the upper flanks of the volcano. The accumulation and subsequent collapse of spatter piles on the upper flanks of the volcano creates hot granular avalanches, which erode and melt snow and ice, and thereby generate watery debris-flow and hyperconcentrated-flow lahars. Seismic instruments were first installed on Pavlof Volcano in the early 1970s, and since then eruptive episodes have been better characterized and specific processes have been documented with greater certainty. The application of remote sensing techniques, including the use of infrasound data, has also aided the study of more recent eruptions. Although Pavlof Volcano is located in a remote part of Alaska, it is visible from Cold Bay, Sand Point, and Nelson Lagoon, making distal observations of eruptive activity possible, weather permitting. A busy air-travel corridor that is utilized by a numerous transcontinental and regional air carriers passes near Pavlof Volcano. The frequency of air travel

  8. Unearthing The Eruptive Personality Of El Salvador's Santa Ana (Ilamatepec) Volcano Though In-depth Stratigraphic Analysis Of Pre-1904 Deposits

    Science.gov (United States)

    Gallant, E.; Martinez-Hackert, B.

    2011-12-01

    The Santa Ana (Ilamatepec) volcano (2384 m) in densely populated El Salvador Central America presents serious volcanic hazard potential. The volcano is a prevalent part of every day life in El Salvador; the sugarcane and coffee belt of the country are to its Southern and Western flanks, recreational areas lies to its East, and second and third largest cities of El Salvador exist within its 25 km radius. Understanding the eruptive characteristics and history is imperative due to the volcano's relative size (the highest in the country) and it's explosive, composite nature. Historical records indicate at least 9 potential VEI 3 eruptions since 1521 AD. The volcano's relative inaccessibility and potential hazards do not promote a vast reservoir of research activity, as can be seen in the scarcity of published papers on topics prior to the 1904 eruption. This research represents the first steps towards creating a comprehensive stratigraphic record of the crater and characterizing its eruptive history, with an eventual goal of recreating the volcanic structure prior to its collapse. Samples of pre-1904 eruptive material were taken from the southern wall of an E-W oriented fluvial gully located within the SSW of the tertiary crater. These were analyzed using thin sections and optical microscopy, grain size distribution techniques, and scanning electron microscopy. The 15-layer sequence indicates an explosive history characterized by intense phreatomagmatic phases, plinian, sub-plinian and basaltic/andesitic composition strombolian activity. Another poster within the session will discuss an older sequence within the walls of the secondary crater. Further detailed studies will be required to gain a better understanding of the characteristics of Santa Ana Volcano.

  9. Dynamics of graphite flake on a liquid

    Science.gov (United States)

    Miura, K.; Tsuda, D.; Kaneta, Y.; Harada, R.; Ishikawa, M.; Sasaki, N.

    2006-11-01

    One-directional motion, where graphite flakes are driven by a nanotip on an octamethylcyclotetrasiloxane (OMCTS) liquid surface, is presented. A transition from quasiperiodic to chaotic motions occurs in the dynamics of a graphite flake when its velocity is increased. The dynamics of graphite flakes pulled by the nanotip on an OMCTS liquid surface can be treated as that of a nanobody on a liquid.

  10. Sealing nuclear graphite with pyrolytic carbon

    International Nuclear Information System (INIS)

    Feng, Shanglei; Xu, Li; Li, Li; Bai, Shuo; Yang, Xinmei; Zhou, Xingtai

    2013-01-01

    Pyrolytic carbon (PyC) coatings were deposited on IG-110 nuclear graphite by thermal decomposition of methane at ∼1830 °C. The PyC coatings are anisotropic and airtight enough to protect IG-110 nuclear graphite against the permeation of molten fluoride salts and the diffusion of gases. The investigations indicate that the sealing nuclear graphite with PyC coating is a promising method for its application in Molten Salt Reactor (MSR)

  11. Exploring Geology on the World-Wide Web--Volcanoes and Volcanism.

    Science.gov (United States)

    Schimmrich, Steven Henry; Gore, Pamela J. W.

    1996-01-01

    Focuses on sites on the World Wide Web that offer information about volcanoes. Web sites are classified into areas of Global Volcano Information, Volcanoes in Hawaii, Volcanoes in Alaska, Volcanoes in the Cascades, European and Icelandic Volcanoes, Extraterrestrial Volcanism, Volcanic Ash and Weather, and Volcano Resource Directories. Suggestions…

  12. Asymmetrical hydrothermal system below Merapi volcano imaged by geophysical data.

    Science.gov (United States)

    Byrdina, Svetlana; Friedel, Sven; Budi-Santoso, Agus; Suryanto, Wiwit; Suhari, Aldjarishy; Vandemeulebrouck, Jean; Rizal, Mohhamed H.; Grandis, Hendra

    2017-04-01

    A high-resolution image of the hydrothermal system of Merapi volcano is obtained using electrical resistivity tomography (ERT), self-potential, and CO2 flux mappings. The ERT inversions identify two distinct low-resistivity bodies, at the base of the south flank and in the summit area, that represent likely two parts of an interconnected hydrothermal system. In the summit area, the extension of the hydrothermal system is clearly limited by the main geological structures which are actual and ancient craters. A sharp resistivity contrast at ancient crater rim Pasar-Bubar separates a conductive hydrothermal system (20 - 50 Ωm) from the resistive andesite lava flows and pyroclastic deposits (2000 - 50 000 Ωm). High diffuse CO2 degassing (with a median value of 400g m -2 d -1) is observed in a narrow vicinity of the active crater rim and close to the Pasar-Bubar. The existence of preferential fluid circulation along this ancient crater rim is also evidenced by self-potential data. The total CO2 degassing across the accessible summit area with a surface of 1.4 · 10 5 m 2 is around 20 td -1. Before the 2010 eruption, Toutain et al. (2009) estimated a higher value of the total diffuse degassing from the summit area (about 200 - 230 td -1). This drop in the diffuse degassing can be related to the decrease in the magmatic activity, to the change of the summit morphology or to a combination of these factors. On the south flank of Merapi, the resistivity model shows spectacular stratification. While surficial recent andesite lava flows are characterized by resistivity exceeding 100 000 Ωm, resistivity as low as 10 Ωm has been encountered at a depth of 200 m at the base of the south flank and was interpreted as a presence of the hydrothermal system. We suggest that a sandwich-like structure of stratified pyroclastic deposits on the flanks of Merapi screen and separate the flow of hydrothermal fluids with the degassing occurring mostly through the fractured crater rims

  13. Geophysical Exploration on the Structure of Volcanoes: Two Case Histories

    Energy Technology Data Exchange (ETDEWEB)

    Furumoto, A. S.

    1974-01-01

    Geophysical methods of exploration were used to determine the internal structure of Koolau Volcano in Hawaii and of Rabaul Volcano in New Guinea. By use of gravity and seismic data the central vent or plug of Koolau Volcano was outlined. Magnetic data seem to indicate that the central plug is still above the Curie Point. If so, the amount of heat energy available is tremendous. As for Rabaul Volcano, it is located in a region characterized by numerous block faulting. The volcano is only a part of a large block that has subsided. Possible geothermal areas exist near the volcano but better potential areas may exist away from the volcano.

  14. Instrumentation Recommendations for Volcano Monitoring at U.S. Volcanoes Under the National Volcano Early Warning System

    Science.gov (United States)

    Moran, Seth C.; Freymueller, Jeff T.; LaHusen, Richard G.; McGee, Kenneth A.; Poland, Michael P.; Power, John A.; Schmidt, David A.; Schneider, David J.; Stephens, George; Werner, Cynthia A.; White, Randall A.

    2008-01-01

    As magma moves toward the surface, it interacts with anything in its path: hydrothermal systems, cooling magma bodies from previous eruptions, and (or) the surrounding 'country rock'. Magma also undergoes significant changes in its physical properties as pressure and temperature conditions change along its path. These interactions and changes lead to a range of geophysical and geochemical phenomena. The goal of volcano monitoring is to detect and correctly interpret such phenomena in order to provide early and accurate warnings of impending eruptions. Given the well-documented hazards posed by volcanoes to both ground-based populations (for example, Blong, 1984; Scott, 1989) and aviation (for example, Neal and others, 1997; Miller and Casadevall, 2000), volcano monitoring is critical for public safety and hazard mitigation. Only with adequate monitoring systems in place can volcano observatories provide accurate and timely forecasts and alerts of possible eruptive activity. At most U.S. volcanoes, observatories traditionally have employed a two-component approach to volcano monitoring: (1) install instrumentation sufficient to detect unrest at volcanic systems likely to erupt in the not-too-distant future; and (2) once unrest is detected, install any instrumentation needed for eruption prediction and monitoring. This reactive approach is problematic, however, for two reasons. 1. At many volcanoes, rapid installation of new ground-1. based instruments is difficult or impossible. Factors that complicate rapid response include (a) eruptions that are preceded by short (hours to days) precursory sequences of geophysical and (or) geochemical activity, as occurred at Mount Redoubt (Alaska) in 1989 (24 hours), Anatahan (Mariana Islands) in 2003 (6 hours), and Mount St. Helens (Washington) in 1980 and 2004 (7 and 8 days, respectively); (b) inclement weather conditions, which may prohibit installation of new equipment for days, weeks, or even months, particularly at

  15. Pyroclastic flows generated by gravitational instability of the 1996-97 lava dome of Soufriere Hills Volcano, Montserrat

    Science.gov (United States)

    Cole, P.D.; Calder, E.S.; Druitt, T.H.; Hoblitt, R.; Robertson, R.; Sparks, R.S.J.; Young, S.R.

    1998-01-01

    Numerous pyroclastic flows were produced during 1996-97 by collapse of the growing andesitic lava dome at Soufriere Hills Volcano, Montserrat. Measured deposit volumes from these flows range from 0.2 to 9 ?? 106 m3. Flows range from discrete, single pulse events to sustained large scale dome collapse events. Flows entered the sea on the eastern and southern coasts, depositing large fans of material at the coast. Small runout distance (Soufriere Hills Volcano, Montserrat. Measured deposit volumes from these flows range from 0.2 to 9??106 m3. Flows range from discrete, single pulse events to sustained large scale dome collapse events. Flows entered the sea on the eastern and southern coasts, depositing large fans of material at the coast. Small runout distance (<1 km) flows had average flow front velocities in the order of 3-10 m/s while flow fronts of the larger runout distance flows (up to 6.5 km) advanced in the order of 15-30 m/s. Many flows were locally highly erosive. Field relations show that development of the fine grained ash cloud surge component was enhanced during the larger sustained events. Periods of elevated dome pyroclastic flow productivity and sustained collapse events are linked to pulses of high magma extrusion rates.

  16. Estimating rates of decompression from textures of erupted ash particles produced by 1999-2006 eruptions of Tungurahua volcano, Ecuador

    Science.gov (United States)

    Wright, Heather M.N.; Cashman, Katharine V.; Mothes, Patricia A.; Hall, Minard L.; Ruiz, Andrés Gorki; Le Pennec, Jean-Luc

    2012-01-01

    Persistent low- to moderate-level eruptive activity of andesitic volcanoes is difficult to monitor because small changes in magma supply rates may cause abrupt transitions in eruptive style. As direct measurement of magma supply is not possible, robust techniques for indirect measurements must be developed. Here we demonstrate that crystal textures of ash particles from 1999 to 2006 Vulcanian and Strombolian eruptions of Tungurahua volcano, Ecuador, provide quantitative information about the dynamics of magma ascent and eruption that is difficult to obtain from other monitoring approaches. We show that the crystallinity of erupted ash particles is controlled by the magma supply rate (MSR); ash erupted during periods of high magma supply is substantially less crystalline than during periods of low magma supply. This correlation is most easily explained by efficient degassing at very low pressures (<<50 MPa) and degassing-driven crystallization controlled by the time available prior to eruption. Our data also suggest that the observed transition from intermittent Vulcanian explosions at low MSR to more continuous periods of Strombolian eruptions and lava fountains at high MSR can be explained by the rise of bubbles through (Strombolian) or trapping of bubbles beneath (Vulcanian) vent-capping, variably viscous (and crystalline) magma.

  17. Nanostructured carbon films with oriented graphitic planes

    International Nuclear Information System (INIS)

    Teo, E. H. T.; Kalish, R.; Kulik, J.; Kauffmann, Y.; Lifshitz, Y.

    2011-01-01

    Nanostructured carbon films with oriented graphitic planes can be deposited by applying energetic carbon bombardment. The present work shows the possibility of structuring graphitic planes perpendicular to the substrate in following two distinct ways: (i) applying sufficiently large carbon energies for deposition at room temperature (E>10 keV), (ii) utilizing much lower energies for deposition at elevated substrate temperatures (T>200 deg. C). High resolution transmission electron microscopy is used to probe the graphitic planes. The alignment achieved at elevated temperatures does not depend on the deposition angle. The data provides insight into the mechanisms leading to the growth of oriented graphitic planes under different conditions.

  18. Production of nuclear graphite in France

    International Nuclear Information System (INIS)

    Legendre, P.; Mondet, L.; Arragon, Ph.; Cornuault, P.; Gueron, J.; Hering, H.

    1955-01-01

    The graphite intended for the construction of the reactors is obtained by the usual process: confection of a cake from coke of oil and tar, cooked (in a electric oven) then the product of cook is graphitized, also by electric heating. The use of the air transportation and the control of conditions cooking and graphitization have permitted to increase the nuclear graphite production as well as to better control their physical and mechanical properties and to reduce to the minimum the unwanted stains. (M.B.) [fr

  19. AC induction field heating of graphite foam

    Science.gov (United States)

    Klett, James W.; Rios, Orlando; Kisner, Roger

    2017-08-22

    A magneto-energy apparatus includes an electromagnetic field source for generating a time-varying electromagnetic field. A graphite foam conductor is disposed within the electromagnetic field. The graphite foam when exposed to the time-varying electromagnetic field conducts an induced electric current, the electric current heating the graphite foam. An energy conversion device utilizes heat energy from the heated graphite foam to perform a heat energy consuming function. A device for heating a fluid and a method of converting energy are also disclosed.

  20. Nuclear graphite for high temperature reactors

    International Nuclear Information System (INIS)

    Marsden, B.J.

    2001-01-01

    The cores and reflectors in modern High Temperature Gas Cooled Reactors (HTRs) are constructed from graphite components. There are two main designs; the Pebble Bed design and the Prism design. In both of these designs the graphite not only acts as a moderator, but is also a major structural component that may provide channels for the fuel and coolant gas, channels for control and safety shut off devices and provide thermal and neutron shielding. In addition, graphite components may act as a heat sink or conduction path during reactor trips and transients. During reactor operation, many of the graphite component physical properties are significantly changed by irradiation. These changes lead to the generation of significant internal shrinkage stresses and thermal shut down stresses that could lead to component failure. In addition, if the graphite is irradiated to a very high irradiation dose, irradiation swelling can lead to a rapid reduction in modulus and strength, making the component friable.The irradiation behaviour of graphite is strongly dependent on its virgin microstructure, which is determined by the manufacturing route. Nevertheless, there are available, irradiation data on many obsolete graphites of known microstructures. There is also a well-developed physical understanding of the process of irradiation damage in graphite. This paper proposes a specification for graphite suitable for modern HTRs. (author)

  1. Structural analysis of polycrystalline (graphitized) materials

    International Nuclear Information System (INIS)

    Efremenko, M.M.; Kravchik, A.E.; Osmakov, A.S.

    1993-01-01

    Specific features of the structure of polycrystal carbon materials (CM), characterized by high enough degree of structural perfection and different genesis are analyzed. From the viewpoint of fine and supercrystallite structure analysis of the most characteristic groups of graphitized CM: artificial graphites, and natural graphites, as well, has been carried out. It is ascertained that in paracrystal CM a monolayer of hexagonally-bound carbon atoms is the basic element of the structure, and in graphitized CM - a microlayer. The importance of the evaluation of the degree of three-dimensional ordering of the microlayer is shown

  2. Principle design and data of graphite components

    International Nuclear Information System (INIS)

    Ishihara, Masahiro; Sumita, Junya; Shibata, Taiju; Iyoku, Tatsuo; Oku, Tatsuo

    2004-01-01

    The High Temperature Engineering Test Reactor (HTTR) constructed by Japan Atomic Energy Research Institute (JAERI) is a graphite-moderated and helium-gas-cooled reactor with prismatic fuel elements of hexagonal blocks. The reactor internal structures of the HTTR are mainly made up of graphite components. As well known, the graphite is a brittle material and there were no available design criteria for brittle materials. Therefore, JAERI had to develop the design criteria taking account of the brittle fracture behavior. In this paper, concept and key specification of the developed graphite design criteria is described, and also an outline of the quality control specified in the design criteria is mentioned

  3. Low temperature vapor phase digestion of graphite

    Energy Technology Data Exchange (ETDEWEB)

    Pierce, Robert A.

    2017-04-18

    A method for digestion and gasification of graphite for removal from an underlying surface is described. The method can be utilized to remove graphite remnants of a formation process from the formed metal piece in a cleaning process. The method can be particularly beneficial in cleaning castings formed with graphite molding materials. The method can utilize vaporous nitric acid (HNO.sub.3) or vaporous HNO.sub.3 with air/oxygen to digest the graphite at conditions that can avoid damage to the underlying surface.

  4. The Fracture Toughness of Nuclear Graphites Grades

    Energy Technology Data Exchange (ETDEWEB)

    Burchell, Timothy D. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Erdman, III, Donald L. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Lowden, Rick R. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Hunter, James A. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Hannel, Cara C. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)

    2017-04-01

    New measurements of graphite mode I critical stress intensity factor, KIc (commonly referred to as the fracture toughness) and the mode II critical shear stress intensity, KIIc, are reported and compared with prior data for KIc and KIIc. The new data are for graphite grades PCEA, IG-110 and 2114. Variations of KIc and acoustic emission (AE) data with graphite texture are reported and discussed. The Codes and Standards applications of fracture toughness, KIc, data are also discussed. A specified minimum value for nuclear graphite KIc is recommended.

  5. Dynamic observations of vesiculation reveal the role of silicate crystals in bubble nucleation and growth in andesitic magmas

    Energy Technology Data Exchange (ETDEWEB)

    Pleše, P.; Higgins, M. D.; Mancini, L.; Lanzafame, G.; Brun, F.; Fife, J. L.; Casselman, J.; Baker, D. R.

    2018-01-01

    Bubble nucleation and growth control the explosivity of volcanic eruptions, and the kinetics of these processes are generally determined from examinations of natural samples and quenched experimental run products. These samples, however, only provide a view of the final state, from which the initial conditions of a time-evolving magmatic system are then inferred. The interpretations that follow are inexact due to the inability of determining the exact conditions of nucleation and the potential detachment of bubbles from their nucleation sites, an uncertainty that can obscure their nucleation location – either homogeneously within the melt or heterogeneously at the interface between crystals and melts. We present results of a series of dynamic, real-time 4D X-ray tomographic microscopy experiments where we observed the development of bubbles in crystal bearing silicate magmas. Experimentally synthesized andesitic glasses with 0.25–0.5 wt% H2O and seed silicate crystals were heated at 1 atm to induce bubble nucleation and track bubble growth and movement. In contrast to previous studies on natural and experimentally produced samples, we found that bubbles readily nucleated on plagioclase and clinopyroxene crystals, that their contact angle changes during growth and that they can grow to sizes many times that of the silicate on whose surface they originated. The rapid heterogeneous nucleation of bubbles at low degrees of supersaturation in the presence of silicate crystals demonstrates that silicates can affect when vesiculation ensues, influencing subsequent permeability development and effusive vs. explosive transition in volcanic eruptions.

  6. Dynamic observations of vesiculation reveal the role of silicate crystals in bubble nucleation and growth in andesitic magmas

    Science.gov (United States)

    Pleše, P.; Higgins, M. D.; Mancini, L.; Lanzafame, G.; Brun, F.; Fife, J. L.; Casselman, J.; Baker, D. R.

    2018-01-01

    Bubble nucleation and growth control the explosivity of volcanic eruptions, and the kinetics of these processes are generally determined from examinations of natural samples and quenched experimental run products. These samples, however, only provide a view of the final state, from which the initial conditions of a time-evolving magmatic system are then inferred. The interpretations that follow are inexact due to the inability of determining the exact conditions of nucleation and the potential detachment of bubbles from their nucleation sites, an uncertainty that can obscure their nucleation location - either homogeneously within the melt or heterogeneously at the interface between crystals and melts. We present results of a series of dynamic, real-time 4D X-ray tomographic microscopy experiments where we observed the development of bubbles in crystal bearing silicate magmas. Experimentally synthesized andesitic glasses with 0.25-0.5 wt% H2O and seed silicate crystals were heated at 1 atm to induce bubble nucleation and track bubble growth and movement. In contrast to previous studies on natural and experimentally produced samples, we found that bubbles readily nucleated on plagioclase and clinopyroxene crystals, that their contact angle changes during growth and that they can grow to sizes many times that of the silicate on whose surface they originated. The rapid heterogeneous nucleation of bubbles at low degrees of supersaturation in the presence of silicate crystals demonstrates that silicates can affect when vesiculation ensues, influencing subsequent permeability development and effusive vs. explosive transition in volcanic eruptions.

  7. Two types of gabbroic xenoliths from rhyolite dominated Niijima volcano, northern part of Izu-Bonin arc: petrological and geochemical constraints

    Science.gov (United States)

    Arakawa, Yoji; Endo, Daisuke; Ikehata, Kei; Oshika, Junya; Shinmura, Taro; Mori, Yasushi

    2017-03-01

    We examined the petrography, petrology, and geochemistry of two types of gabbroic xenoliths (A- and B-type xenoliths) in olivine basalt and biotite rhyolite units among the dominantly rhyolitic rocks in Niijima volcano, northern Izu-Bonin volcanic arc, central Japan. A-type gabbroic xenoliths consisting of plagioclase, clinopyroxene, and orthopyroxene with an adcumulate texture were found in both olivine basalt and biotite rhyolite units, and B-type gabbroic xenoliths consisting of plagioclase and amphibole with an orthocumulate texture were found only in biotite rhyolite units. Geothermal- and barometricmodelling based on mineral chemistry indicated that the A-type gabbro formed at higher temperatures (899-955°C) and pressures (3.6-5.9 kbar) than the B-type gabbro (687-824°C and 0.8-3.6 kbar). These findings and whole-rock chemistry suggest different parental magmas for the two types of gabbro. The A-type gabbro was likely formed from basaltic magma, whereas the B-type gabbro was likely formed from an intermediate (andesitic) magma. The gabbroic xenoliths in erupted products at Niijima volcano indicate the presence of mafic to intermediate cumulate bodies of different origins at relatively shallower levels beneath the dominantly rhyolitic volcano.

  8. Two types of gabbroic xenoliths from rhyolite dominated Niijima volcano, northern part of Izu-Bonin arc: petrological and geochemical constraints

    Directory of Open Access Journals (Sweden)

    Arakawa Yoji

    2017-03-01

    Full Text Available We examined the petrography, petrology, and geochemistry of two types of gabbroic xenoliths (A- and B-type xenoliths in olivine basalt and biotite rhyolite units among the dominantly rhyolitic rocks in Niijima volcano, northern Izu-Bonin volcanic arc, central Japan. A-type gabbroic xenoliths consisting of plagioclase, clinopyroxene, and orthopyroxene with an adcumulate texture were found in both olivine basalt and biotite rhyolite units, and B-type gabbroic xenoliths consisting of plagioclase and amphibole with an orthocumulate texture were found only in biotite rhyolite units. Geothermal- and barometricmodelling based on mineral chemistry indicated that the A-type gabbro formed at higher temperatures (899–955°C and pressures (3.6–5.9 kbar than the B-type gabbro (687–824°C and 0.8–3.6 kbar. These findings and whole-rock chemistry suggest different parental magmas for the two types of gabbro. The A-type gabbro was likely formed from basaltic magma, whereas the B-type gabbro was likely formed from an intermediate (andesitic magma. The gabbroic xenoliths in erupted products at Niijima volcano indicate the presence of mafic to intermediate cumulate bodies of different origins at relatively shallower levels beneath the dominantly rhyolitic volcano.

  9. Electrolysis of acidic sodium chloride solution with a graphite anode. I. Graphite electrode

    NARCIS (Netherlands)

    Janssen, L.J.J.; Hoogland, J.G.

    1969-01-01

    A graphite anode evolving Cl from a chloride soln. is slowly oxidized to CO and CO2. This oxidn. causes a change in the characteristics of the electrode in aging, comprising a change of the nature of the graphite surface and an increase of the surface area. It appears that a new graphite electrode

  10. Unzipping of the volcano arc, Japan

    Science.gov (United States)

    Stern, R.J.; Smoot, N.C.; Rubin, M.

    1984-01-01

    A working hypothesis for the recent evolution of the southern Volcano Arc, Japan, is presented which calls upon a northward-progressing sundering of the arc in response to a northward-propagating back-arc basin extensional regime. This model appears to explain several localized and recent changes in the tectonic and magrnatic evolution of the Volcano Arc. Most important among these changes is the unusual composition of Iwo Jima volcanic rocks. This contrasts with normal arc tholeiites typical of the rest of the Izu-Volcano-Mariana and other primitive arcs in having alkaline tendencies, high concentrations of light REE and other incompatible elements, and relatively high silica contents. In spite of such fractionated characteristics, these lavas appear to be very early manifestations of a new volcanic and tectonic cycle in the southern Volcano Arc. These alkaline characteristics and indications of strong regional uplift are consistent with the recent development of an early stage of inter-arc basin rifting in the southern Volcano Arc. New bathymetric data are presented in support of this model which indicate: 1. (1) structural elements of the Mariana Trough extend north to the southern Volcano Arc. 2. (2) both the Mariana Trough and frontal arc shoal rapidly northwards as the Volcano Arc is approached. 3. (3) rugged bathymetry associated with the rifted Mariana Trough is replaced just south of Iwo Jima by the development of a huge dome (50-75 km diameter) centered around Iwo Jima. Such uplifted domes are the immediate precursors of rifts in other environments, and it appears that a similar situation may now exist in the southern Volcano Arc. The present distribution of unrifted Volcano Arc to the north and rifted Mariana Arc to the south is interpreted not as a stable tectonic configuration but as representing a tectonic "snapshot" of an arc in the process of being rifted to form a back-arc basin. ?? 1984.

  11. Modelling of Magma Density and Viscocity Changes and Their Influences towards the Characteristic of Kelud Volcano Eruption

    Directory of Open Access Journals (Sweden)

    Hanik Humaida

    2014-06-01

    Full Text Available DOI: 10.17014/ijog.v6i4.129The effusive eruption of Kelud Volcano in 2007 was different from the previous ones, which in general were more explosive. Among others, density and viscosity are factors that determine the type of eruption. Therefore, the study on the difference of the recent eruption style based on the density and viscosity of magma was carried out. The method used in this study was based on geochemical analysis of the rock and then a modeling was established by using the above parameter. The study on the explosive eruption was emphasized on the data of 1990 eruption, whereas the effusive eruption was based on the data of 2007 eruption. The result shows that the magma viscosity of Kelud Volcano depend on the H O concentration as one of the volatile compound in magma, and temperature which gives the exponential equation. The higher the increase of H O content the smaller the value of its viscosity as well as the higher the temperature. The H O content in silica fluid can break the polymer bond of the silica fluid, because a shorter polymer will produce a lower viscosity. The density of the silica content of Kelud Volcano ranges between andesitic and basaltic types, but andesite is more likely. The fluid density of the material of 1990 eruption is different from 2007 eruption. Compared to the 2007, the 1990 eruption material gave a lower density value in its silica fluid than that of the 2007 one. The low density value of the silica fluid of the 1990 eruption material was reflecting a more acid magma. The level of density value of silica fluid depends on its temperature. At the temperature of 1073 K the density of the 1990 Kelud magma is 2810 kg/m3 and the 2007 magma is 2818 kg/m3, whereas at a temperature of 1673 K, the density is 2672 kg/m3 and 2682 kg/m3 of the 1990 and 2007 eruptions respectively. A modeling by using an ideal gas law of Henry’s Law illustrated that the ascent of Kelud’s magma to the surface may cause changes

  12. Volcanoes

    Science.gov (United States)

    ... Extreme Heat Older Adults (Aged 65+) Infants and Children Chronic Medical Conditions Low Income Athletes Outdoor Workers Pets Hot Weather Tips Warning Signs and Symptoms FAQs Social Media How to Stay Cool Missouri Cooling Centers Extreme ...

  13. Common processes at unique volcanoes – a volcanological conundrum

    OpenAIRE

    Katharine eCashman; Juliet eBiggs

    2014-01-01

    An emerging challenge in modern volcanology is the apparent contradiction between the perception that every volcano is unique, and classification systems based on commonalities among volcano morphology and eruptive style. On the one hand, detailed studies of individual volcanoes show that a single volcano often exhibits similar patterns of behavior over multiple eruptive episodes; this observation has led to the idea that each volcano has its own distinctive pattern of behavior (or “personali...

  14. Linking space observations to volcano observatories in Latin America: Results from the CEOS DRM Volcano Pilot

    Science.gov (United States)

    Delgado, F.; Pritchard, M. E.; Biggs, J.; Arnold, D. W. D.; Poland, M. P.; Ebmeier, S. K.; Wauthier, C.; Wnuk, K.; Parker, A. L.; Amelug, F.; Sansosti, E.; Mothes, P. A.; Macedo, O.; Lara, L.; Zoffoli, S.; Aguilar, V.

    2015-12-01

    Within Latin American, about 315 volcanoes that have been active in the Holocene, but according to the United Nations Global Assessment of Risk 2015 report (GAR15) 202 of these volcanoes have no seismic, deformation or gas monitoring. Following the 2012 Santorini Report on satellite Earth Observation and Geohazards, the Committee on Earth Observation Satellites (CEOS) has developed a 3-year pilot project to demonstrate how satellite observations can be used to monitor large numbers of volcanoes cost-effectively, particularly in areas with scarce instrumentation and/or difficult access. The pilot aims to improve disaster risk management (DRM) by working directly with the volcano observatories that are governmentally responsible for volcano monitoring, and the project is possible thanks to data provided at no cost by international space agencies (ESA, CSA, ASI, DLR, JAXA, NASA, CNES). Here we highlight several examples of how satellite observations have been used by volcano observatories during the last 18 months to monitor volcanoes and respond to crises -- for example the 2013-2014 unrest episode at Cerro Negro/Chiles (Ecuador-Colombia border); the 2015 eruptions of Villarrica and Calbuco volcanoes, Chile; the 2013-present unrest and eruptions at Sabancaya and Ubinas volcanoes, Peru; the 2015 unrest at Guallatiri volcano, Chile; and the 2012-present rapid uplift at Cordon Caulle, Chile. Our primary tool is measurements of ground deformation made by Interferometric Synthetic Aperture Radar (InSAR) but thermal and outgassing data have been used in a few cases. InSAR data have helped to determine the alert level at these volcanoes, served as an independent check on ground sensors, guided the deployment of ground instruments, and aided situational awareness. We will describe several lessons learned about the type of data products and information that are most needed by the volcano observatories in different countries.

  15. Hydrogen storage in graphitic nanofibres

    OpenAIRE

    McCaldin, Simon Roger

    2007-01-01

    There is huge need to develop an alternative to hydrocarbons fuel, which does not produce CO2 or contribute to global warming - 'the hydrogen economy' is such an alternative, however the storage of hydrogen is the key technical barrier that must be overcome. The potential of graphitic nanofibres (GNFs) to be used as materials to allow the solid-state storage of hydrogen has thus been investigated. This has been conducted with a view to further developing the understanding of the mechanism(s) ...

  16. Hydrothermal systems and volcano geochemistry

    Science.gov (United States)

    Fournier, R.O.

    2007-01-01

    The upward intrusion of magma from deeper to shallower levels beneath volcanoes obviously plays an important role in their surface deformation. This chapter will examine less obvious roles that hydrothermal processes might play in volcanic deformation. Emphasis will be placed on the effect that the transition from brittle to plastic behavior of rocks is likely to have on magma degassing and hydrothermal processes, and on the likely chemical variations in brine and gas compositions that occur as a result of movement of aqueous-rich fluids from plastic into brittle rock at different depths. To a great extent, the model of hydrothermal processes in sub-volcanic systems that is presented here is inferential, based in part on information obtained from deep drilling for geothermal resources, and in part on the study of ore deposits that are thought to have formed in volcanic and shallow plutonic environments.

  17. Mixed graphite cast iron for automotive exhaust component applications

    OpenAIRE

    De-lin Li

    2017-01-01

    Both spheroidal graphite iron and compacted graphite iron are used in the automotive industry. A recently proposed mixed graphite iron exhibits a microstructure between the conventional spheroidal graphite iron and compacted graphite iron. Evaluation results clearly indicate the suitability and benefits of mixed graphite iron for exhaust component applications with respect to casting, machining, mechanical, thermophysical, oxidation, and thermal fatigue properties. A new ASTM standard speci...

  18. Nuclear graphite waste management. Proceedings of a technical committee meeting

    International Nuclear Information System (INIS)

    2001-05-01

    The purpose of the seminar was to bring together the specialists dealing with various aspects of radioactive graphite waste management to exchange and review information on the decommissioning, characterisation, processing and disposal of irradiated graphite from reactor cores and other graphite waste associated with reactor operation. The seminar covered radioactive graphite characterisation, the effect of irradiation on graphite components, Wigner energy, radioactive graphite waste treatment, conditioning, interim storage and long term disposal options. Individual papers presented at the seminar were indexed separately

  19. A submarine andesite-rhyodacite lineage of arc affinity hosting hydrothermal mineralisation, Pual Ridge, Eastern Manus back-arc basin, Papua New Guinea

    International Nuclear Information System (INIS)

    Binns, R.A.; Waters, J.C.; Parr, J.M.; Carr, G.R.; Whitford, D.J.

    2000-01-01

    Pual Ridge, host to the PACMANUS hydrothermal field, is a composite edifice formed by recent submarine eruptions, with a continuous suite of consanguineous andesite, dacite and rhyodacite (58 to 74% SiO 2 , mg 41 to 17). The lavas are vesicular, hyaline, and aphyric to sparsely porphyritic. Dacites dominate the PACMANUS hydrothermal field at the ridge crest. The Pual Ridge volcanic suite is subalkalic, with a calcic character, bordering on calcalkaline (Fig. 1). It falls just within the medium-K field, and has geochemical characteristics (K/Rb ∼500, K/Ba∼40, mild enrichment in light rare earth elements (LREE) ((La/Sm) N ∼1.7, (La/Yb) N ∼2.1) which fall into the spectrum of modern arc volcanic rock suites on New Britain to the south. By contrast, the basalts from the central Manus back-arc spreading zone are very low-K. When major and trace element data are plotted against silica contents in Harker diagrams, gently curved trends extend from andesite to rhyodacite. The trends can be interpreted in terms of low-pressure fractionation of the observed (albeit rare) phenocryst assemblage (plagioclase, ortho- and clinopyroxene, magnetite), with progressive enrichment of incompatible elements such as K, Ba, Zr and the REE. Basaltic andesites (mg 42-45) from features adjacent to Pual Ridge exhibit Ti and P contents falling below this fractionation trend, but trend towards a possible parent magma from which Pual Ridge andesites were derived by extraction of an olivine-dominated assemblage. Moderately potassic picritic basalts (mg 56) representing the potential parent magmas also occur on edifices east of Pual Ridge. Like the Pual lavas, these have low Nb (1-2 ppm) consistent with an arc affinity

  20. Analysis of Wigner energy release process in graphite stack of shut-down uranium-graphite reactor

    OpenAIRE

    Bespala, E. V.; Pavliuk, A. O.; Kotlyarevskiy, S. G.

    2015-01-01

    Data, which finding during thermal differential analysis of sampled irradiated graphite are presented. Results of computational modeling of Winger energy release process from irradiated graphite staking are demonstrated. It's shown, that spontaneous combustion of graphite possible only in adiabatic case.

  1. Mixed graphite cast iron for automotive exhaust component applications

    Directory of Open Access Journals (Sweden)

    De-lin Li

    2017-11-01

    Full Text Available Both spheroidal graphite iron and compacted graphite iron are used in the automotive industry. A recently proposed mixed graphite iron exhibits a microstructure between the conventional spheroidal graphite iron and compacted graphite iron. Evaluation results clearly indicate the suitability and benefits of mixed graphite iron for exhaust component applications with respect to casting, machining, mechanical, thermophysical, oxidation, and thermal fatigue properties. A new ASTM standard specification (A1095 has been created for compacted, mixed, and spheroidal graphite silicon-molybdenum iron castings. This paper attempts to outline the latest progress in mixed graphite iron published.

  2. Lahar hazards at Mombacho Volcano, Nicaragua

    Science.gov (United States)

    Vallance, J.W.; Schilling, S.P.; Devoli, G.

    2001-01-01

    Mombacho volcano, at 1,350 meters, is situated on the shores of Lake Nicaragua and about 12 kilometers south of Granada, a city of about 90,000 inhabitants. Many more people live a few kilometers southeast of Granada in 'las Isletas de Granada and the nearby 'Peninsula de Aseses. These areas are formed of deposits of a large debris avalanche (a fast moving avalanche of rock and debris) from Mombacho. Several smaller towns with population, in the range of 5,000 to 12,000 inhabitants are to the northwest and the southwest of Mombacho volcano. Though the volcano has apparently not been active in historical time, or about the last 500 years, it has the potential to produce landslides and debris flows (watery flows of mud, rock, and debris -- also known as lahars when they occur on a volcano) that could inundate these nearby populated areas. -- Vallance, et.al., 2001

  3. Analysis of volcano rocks by Moessbauer spectroscopy

    International Nuclear Information System (INIS)

    Sitek, J.; Dekan, J.

    2012-01-01

    In this work we have analysed the basalt rock from Mount Ba tur volcano situated on the Island of Bali in Indonesia.We compared our results with composition of basalt rocks from some other places on the Earth. (authors)

  4. Moessbauer Spectroscopy study of Quimsachata Volcano materials

    International Nuclear Information System (INIS)

    Dominguez, A.G.B.

    1988-01-01

    It has been studied volcanic lava from Quimsachata Volcano in Pem. Moessbauer Spectroscopy, X-ray diffraction, electronic and optical microscopy allowed the identification of different mineralogical phases. (A.C.AS.) [pt

  5. Lahar hazards at Agua volcano, Guatemala

    Science.gov (United States)

    Schilling, S.P.; Vallance, J.W.; Matías, O.; Howell, M.M.

    2001-01-01

    At 3760 m, Agua volcano towers more than 3500 m above the Pacific coastal plain to the south and 2000 m above the Guatemalan highlands to the north. The volcano is within 5 to 10 kilometers (km) of Antigua, Guatemala and several other large towns situated on its northern apron. These towns have a combined population of nearly 100,000. It is within about 20 km of Escuintla (population, ca. 100,000) to the south. Though the volcano has not been active in historical time, or about the last 500 years, it has the potential to produce debris flows (watery flows of mud, rock, and debris—also known as lahars when they occur on a volcano) that could inundate these nearby populated areas.

  6. Methodology of characterization of radioactive graphite

    International Nuclear Information System (INIS)

    Pina, G.; Rodriguez, M.; Lara, E.; Magro, E.; Gascon, J. L.; Leganes, J. L.

    2014-01-01

    Since the dismantling of Vandellos I, ENRESA has promoted the precise knowledge of the inventory of irradiated graphite (graphite-i) through establishing methodologies for radiological characterization of the vector of radionuclides of interest and their correlations as the primary means of characterization strategy to establish the safer management of this material in its life cycle. (Author)

  7. Significance of primary irradiation creep in graphite

    CSIR Research Space (South Africa)

    Erasmus, C

    2013-05-01

    Full Text Available Traditionally primary irradiation creep is introduced into graphite analysis by applying the appropriate amount of creep strain to the model at the initial time-step. This is valid for graphite components that are subjected to high fast neutron flux...

  8. Inhibition of oxidation in nuclear graphite

    International Nuclear Information System (INIS)

    Winston, Philip L.; Sterbentz, James W.; Windes, William E.

    2015-01-01

    Graphite is a fundamental material of high-temperature gas-cooled nuclear reactors, providing both structure and neutron moderation. Its high thermal conductivity, chemical inertness, thermal heat capacity, and high thermal structural stability under normal and off-normal conditions contribute to the inherent safety of these reactor designs. One of the primary safety issues for a high-temperature graphite reactor core is the possibility of rapid oxidation of the carbon structure during an off-normal design basis event where an oxidising atmosphere (air ingress) can be introduced to the hot core. Although the current Generation IV high-temperature reactor designs attempt to mitigate any damage caused by a postulated air ingress event, the use of graphite components that inhibit oxidation is a logical step to increase the safety of these reactors. Recent experimental studies of graphite containing between 5.5 and 7 wt% boron carbide (B 4 C) indicate that oxidation is dramatically reduced even at prolonged exposures at temperatures up to 900 deg. C. The proposed addition of B 4 C to graphite components in the nuclear core would necessarily be enriched in B-11 isotope in order to minimise B-10 neutron absorption and graphite swelling. The enriched boron can be added to the graphite during billet fabrication. Experimental oxidation rate results and potential applications for borated graphite in nuclear reactor components will be discussed. (authors)

  9. Metal/graphite - composites in fusion engineering

    International Nuclear Information System (INIS)

    Staffler, R.; Kneringer, G.; Kny, E.; Reheis, N.

    1989-01-01

    Metal/graphite composites have been well known in medical industry for many years. X-ray tubes used in modern radiography, particularly in computerized tomography are equipped with rotating targets able to absorb a maximum of heat in a given time. Modern rotating targets consist of a refractory metal/graphite composite. Today the use of graphite as a plasma facing material is one predominant concept in fusion engineering. Depending on the thermal load, the graphite components have to be directly cooled (i.e. divertor plates) or inertially cooled (i.e. firstwall tiles). In case of direct cooling a metallurgical joining such as high temperature brazing between graphite and a metallic cooling structure shows the most promising results /1/. Inertially cooled graphite tiles have to be joined to a metallic backing plate in order to get a stable attachment to the supporting structure. The main requirements on the metallic partner of a metal/graphite composite used in the first wall area are: high melting point, high thermal strength, high thermal conductivity, low vapor pressure and a thermal expansion matching that of graphite. These properties are typical for the refractory metals such as molybdenum, tungsten and their alloys. 4 refs., 13 figs., 1 tab

  10. Metal/graphite - composites in fusion engineering

    International Nuclear Information System (INIS)

    Staffler, R.; Kneringer, G.; Kny, E.; Reheis, N.

    1995-01-01

    Metal/graphite composites have been well known in medical industry for many years. X-ray tubes used in modern radiography, particulary in computerized tomography are equipped with rotating targets able to absorb a maximum of heat in a given time. Modern rotating targets consist of a refractory metal/graphite composite. Today the use of graphite as a plasma facing material is one predominant concept in fusion engineering. Depending on the thermal load, the graphite components have to be directly cooled (i.e. divertor plates) or inertially cooled (i.e. firstwall tiles). In case of direct cooling a metallurgical joining such as high temperature brazing between graphite and a metalic cooling structure shows the most promising results /1/. Inertially cooled graphite tiles have to be joined to a metallic backing plate in order to get a stable attachment to the supporting structure. The main requirements on the metallic partner of a metal/graphite composite and in the first wall area are: high melting point, high thermal strength, high thermal conductivity, low vapour pressure and a thermal expansion matching that of graphite. These properties are typical for the refractory metals such as molybdenum, tungsten and their alloys. (author)

  11. Tire containing thermally exfoliated graphite oxide

    Science.gov (United States)

    Prud'homme, Robert K. (Inventor); Aksay, Ilhan A. (Inventor)

    2011-01-01

    A tire, tire lining or inner tube, containing a polymer composite, made of at least one rubber and/or at least one elastomer and a modified graphite oxide material, which is a thermally exfoliated graphite oxide with a surface area of from about 300 sq m/g to 2600 sq m/g.

  12. Effect of graphite target power density on tribological properties of graphite-like carbon films

    Science.gov (United States)

    Dong, Dan; Jiang, Bailing; Li, Hongtao; Du, Yuzhou; Yang, Chao

    2018-05-01

    In order to improve the tribological performance, a series of graphite-like carbon (GLC) films with different graphite target power densities were prepared by magnetron sputtering. The valence bond and microstructure of films were characterized by AFM, TEM, XPS and Raman spectra. The variation of mechanical and tribological properties with graphite target power density was analyzed. The results showed that with the increase of graphite target power density, the deposition rate and the ratio of sp2 bond increased obviously. The hardness firstly increased and then decreased with the increase of graphite target power density, whilst the friction coefficient and the specific wear rate increased slightly after a decrease with the increasing graphite target power density. The friction coefficient and the specific wear rate were the lowest when the graphite target power density was 23.3 W/cm2.

  13. Hydrogen storage in graphite nanofibers

    Energy Technology Data Exchange (ETDEWEB)

    Park, C.; Tan, C.D.; Hidalgo, R.; Baker, R.T.K.; Rodriguez, N.M. [Northeastern Univ., Boston, MA (United States). Chemistry Dept.

    1998-08-01

    Graphite nanofibers (GNF) are a type of material that is produced by the decomposition of carbon containing gases over metal catalyst particles at temperatures around 600 C. These molecularly engineered structures consist of graphene sheets perfectly arranged in a parallel, perpendicular or at angle orientation with respect to the fiber axis. The most important feature of the material is that only edges are exposed. Such an arrangement imparts the material with unique properties for gas adsorption because the evenly separated layers constitute the most ordered set of nanopores that can accommodate an adsorbate in the most efficient manner. In addition, the non-rigid pore walls can also expand so as to accommodate hydrogen in a multilayer conformation. Of the many varieties of structures that can be produced the authors have discovered that when gram quantities of a selected number of GNF are exposed to hydrogen at pressures of {approximately} 2,000 psi, they are capable of adsorbing and storing up to 40 wt% of hydrogen. It is believed that a strong interaction is established between hydrogen and the delocalized p-electrons present in the graphite layers and therefore a new type of chemistry is occurring within these confined structures.

  14. Petro-geochemical constraints on the source and evolution of magmas at El Misti volcano (Peru)

    Science.gov (United States)

    Rivera, Marco; Martin, Hervé; Le Pennec, Jean-Luc; Thouret, Jean-Claude; Gourgaud, Alain; Gerbe, Marie-Christine

    2017-01-01

    El Misti volcano, a large and hazardous edifice of the Andean Central Volcanic Zone (CVZ) of southern Peru, consists of four main growth stages. Misti 1 (> 112 ka) is an old stratovolcano partly concealed by two younger stratocones (Misti 2, 112-40 ka; Misti 3, 38-11 ka), capped in turn by a recent summit cone (Misti 4, Peru. Geochemical evidence indicates that magmatic evolution is mostly controlled by Assimilation-Fractional Crystallisation (AFC) mechanisms. Modelling reveals a mass-assimilated/mass-fractionated ratio (ρ) ≤ 2.2, which suggests an assimilated crust fraction below 14 wt.% on average. Our isotopic data clearly identify the Proterozoic "Charcani gneiss" basement as the main contaminant. Both contamination and assimilation processes peaked at 30 wt.%, during the Misti 3 stage when rhyolites were generated. We ascribe the general depletion in HREE and Y and elevated La/Yb and Sr/Y ratios in El Misti samples to the enrichment of the mantle wedge source of the parental magmas by a felsic melt of adakitic composition and hydrous fluids. Our work highlights that El Misti's magmatic system has remained relatively homogeneous since at least 0.12 Ma, with a marked influence of the contaminating crust in the Late Pleistocene Misti 3 stage, which resulted in highly explosive eruptions. Andesitic-dacitic compositions are dominant in the Holocene and historical Misti 4 stage, and are expected for future volcanic events at El Misti.

  15. Methane generated from graphite--tritium interaction

    International Nuclear Information System (INIS)

    Coffin, D.O.; Walthers, C.R.

    1979-01-01

    When hydrogen isotopes are separated by cryogenic distillation, as little as 1 ppM of methane will eventually plug the still as frost accumulates on the column packings. Elemental carbon exposed to tritium generates methane spontaneously, and yet some dry transfer pumps, otherwise compatible with tritium, convey the gas with graphite rotors. This study was to determine the methane production rate for graphite in tritium. A pump manufacturer supplied graphite samples that we exposed to tritium gas at 0.8 atm. After 137 days we measured a methane synthesis rate of 6 ng/h per cm 2 of graphite exposed. At this rate methane might grow to a concentration of 0.01 ppM when pure tritium is transferred once through a typical graphite--rotor transfer pump. Such a low methane level will not cause column blockage, even if the cryogenic still is operated continuously for many years

  16. Chemical sputtering of graphite by H+ ions

    International Nuclear Information System (INIS)

    Busharov, N.P.; Gorbatov, E.A.; Gusev, V.M.; Guseva, M.I.; Martynenko, Y.V.

    1976-01-01

    In a study of the sputtering coefficient S for the sputtering of graphite by 10-keV H + ions as a function of the graphite temperature during the bombardment, it is found that at T> or =750degreeC the coefficient S is independent of the target temperature and has an anomalously high value, S=0.085 atom/ion. The high rate of sputtering of graphite by atomic hydrogen ions is shown to be due to chemical sputtering of the graphite, resulting primarily in the formation of CH 4 molecules. At T=1100degreeC, S falls off by a factor of about 3. A model for the chemical sputtering of graphite is proposed

  17. Graphite selection for the FMIT test cell

    International Nuclear Information System (INIS)

    Morgan, W.C.

    1982-06-01

    This document provides the basis for procuring a grade of graphite, at minimum cost, having minimum dimensional changes at low irradiation temperatures (nominal range 90 to 140 0 C). In light of those constraints, the author concludes that the most feasible approach is to attempt to reproduce a grade of graphite (TSGBF) which has exhibited a high degree of dimensional stability during low-temperature irradiations and on which irradiation-induced changes in other physical properties have been measured. The effects of differences in raw materials, especially coke morphology, and processing conditions, primarily graphitization temperture are briefly reviewed in terms of the practicality of producing a new grade of graphite with physical properties and irradiation-induced changes which would be very similar to those of TSGBF graphite. The production history and physical properties of TSGBF are also reviewed; no attempt is made, to project changes in dimensions or physical properties under the projected irradiation conditions

  18. AGC-2 Graphite Preirradiation Data Analysis Report

    Energy Technology Data Exchange (ETDEWEB)

    William Windes; W. David Swank; David Rohrbaugh; Joseph Lord

    2013-08-01

    This report described the specimen loading order and documents all pre-irradiation examination material property measurement data for the graphite specimens contained within the second Advanced Graphite Capsule (AGC-2) irradiation capsule. The AGC-2 capsule is the second in six planned irradiation capsules comprising the Advanced Graphite Creep (AGC) test series. The AGC test series is used to irradiate graphite specimens allowing quantitative data necessary for predicting the irradiation behavior and operating performance of new nuclear graphite grades to be generated which will ascertain the in-service behavior of the graphite for pebble bed and prismatic Very High Temperature Reactor (VHTR) designs. Similar to the AGC-1 specimen pre-irradiation examination report, material property tests were conducted on specimens from 18 nuclear graphite types but on an increased number of specimens (512) prior to loading into the AGC-2 irradiation assembly. All AGC-2 specimen testing was conducted at Idaho National Laboratory (INL) from October 2009 to August 2010. This report also details the specimen loading methodology for the graphite specimens inside the AGC-2 irradiation capsule. The AGC-2 capsule design requires “matched pair” creep specimens that have similar dose levels above and below the neutron flux profile mid-plane to provide similar specimens with and without an applied load. This document utilized the neutron flux profile calculated for the AGC-2 capsule design, the capsule dimensions, and the size (length) of the selected graphite and silicon carbide samples to create a stacking order that can produce “matched pairs” of graphite samples above and below the AGC-2 capsule elevation mid-point to provide specimens with similar neutron dose levels.

  19. Modeling Fission Product Sorption in Graphite Structures

    International Nuclear Information System (INIS)

    Szlufarska, Izabela; Morgan, Dane; Allen, Todd

    2013-01-01

    The goal of this project is to determine changes in adsorption and desorption of fission products to/from nuclear-grade graphite in response to a changing chemical environment. First, the project team will employ principle calculations and thermodynamic analysis to predict stability of fission products on graphite in the presence of structural defects commonly observed in very high-temperature reactor (VHTR) graphites. Desorption rates will be determined as a function of partial pressure of oxygen and iodine, relative humidity, and temperature. They will then carry out experimental characterization to determine the statistical distribution of structural features. This structural information will yield distributions of binding sites to be used as an input for a sorption model. Sorption isotherms calculated under this project will contribute to understanding of the physical bases of the source terms that are used in higher-level codes that model fission product transport and retention in graphite. The project will include the following tasks: Perform structural characterization of the VHTR graphite to determine crystallographic phases, defect structures and their distribution, volume fraction of coke, and amount of sp2 versus sp3 bonding. This information will be used as guidance for ab initio modeling and as input for sorptivity models; Perform ab initio calculations of binding energies to determine stability of fission products on the different sorption sites present in nuclear graphite microstructures. The project will use density functional theory (DFT) methods to calculate binding energies in vacuum and in oxidizing environments. The team will also calculate stability of iodine complexes with fission products on graphite sorption sites; Model graphite sorption isotherms to quantify concentration of fission products in graphite. The binding energies will be combined with a Langmuir isotherm statistical model to predict the sorbed concentration of fission products

  20. Crystallization and Melt Removal at Arenal Volcano, Polytopic Vector Analysis

    Science.gov (United States)

    Hidalgo, P. J.; Vogel, T. A.; Bolge, L. L.; Ehrlich, R.; Alvarado, G. E.

    2007-12-01

    Tephra sequences ET3 and ET4 from Arenal volcano in Costa Rica have recently been interpreted to be a product of crystal fractionation by Bolge and coworkers in a series of papers (2004, 2006). The two tephra units are part of a sequence of 22 tephra units that represent a 7000 year span of the Arenal volcano activity. The tephro- stratigraphy has been described extensively by Melson (1982; 1994). The ET3 and ET4 tephras were interpreted (based on major- and trace-element, isotopic analyses of whole rocks and microchemical analyses of individual phases) as clear evidence of crystal separation by gravity settling (Bolge et al., 2004, 2006). The lower ET4 tephra sequence (andesitic and crystal poor) and the upper ET3 tephra (basaltic and crystal rich) represent an inverted snapshot of the magma chamber with contrasting geochemical properties. The ET3 sequence (deeper part of the magma chamber) has nearly constant composition with only a few elements varying stratigraphically (best represented by CaO). This is consistent with gradually decreasing amounts of melt in the upper part of ET3. The lower ET4 tephra (upper part of the magma chamber) contains large chemical gradients in both incompatible and compatible elements. In the present study we use whole-rock geochemical data from the recent tephra sequences ET3 and ET4 as inputs to Polytopic Vector Analysis (PVA) (for a review of this method see Vogel and coworkers, in press). With this method we produce a three end member solution that is consistent with crystallization of Olivine, plagioclase and pyroxene from the most mafic end member (EM1) resulting in a crystal rich mush zone. As crystallization progresses the compositions of the liquids are driven towards an intermediate end member (EM3), which has an intermediate composition liquid. At EM3 composition, rapid depletion of FeO, MgO and TiO2 by crystallization of Fe-Ti oxides, rapidly drives the liquid composition towards the silicic EM1 (incompatible element

  1. Graphite Oxidation Thermodynamics/Reactions

    International Nuclear Information System (INIS)

    Propp, W.A.

    1998-01-01

    The vulnerability of graphite-matrix spent nuclear fuel to oxidation by the ambient atmosphere if the fuel canister is breached was evaluated. Thermochemical and kinetic data over the anticipated range of storage temperatures (200 to 400 C) were used to calculate the times required for a total carbon mass loss of 1 mgcm-2 from a fuel specimen. At 200 C, the time required to produce even this small loss is large, 900,000 yr. However, at 400 C the time required is only 1.9 yr. The rate of oxidation at 200 C is negligible, and the rate even at 400 C is so small as to be of no practical consequence. Therefore, oxidation of the spent nuclear fuel upon a loss of canister integrity is not anticipated to be a concern based upon the results of this study

  2. Low cost sic coated erosion resistant graphite

    International Nuclear Information System (INIS)

    Zafar, M.F.; Nicholls, J.R.

    2007-01-01

    The development of materials with unique and improved properties using low cost processes is essential to increase performance and reduce cost of the solid rocket motors. Specifically advancements are needed for boost phase nozzle. As these motors operate at very high pressure and temperatures, the nozzle must survive high thermal stresses with minimal erosion to maintain performance. Currently three material choices are being exploited; which are refractory metals, graphite and carbon-carbon composites. Of these three materials graphite is the most attractive choice because of its low cost, light weight, and easy forming. However graphite is prone to erosion, both chemical and mechanical, which may affect the ballistic conditions and mechanical properties of the nozzle. To minimize this erosion high density graphite is usually preferred; which is again very expensive. Another technique used to minimize the erosion is Pyrolytic Graphite (PG) coating inside the nozzle. However PG coating is prone to cracking and spallation along with very cumbersome deposition process. Another possible methodology to avoid this erosion is to convert the inside surface of the rocket nozzle to Silicon Carbide (SiC), which is very erosion resistant and have much better thermal stability compared to graphite and even PG. Due to its functionally gradient nature such a layer will be very adherent and resistant to spallation. The current research is focused on synthesizing, characterizing and oxidation testing of such a converted SiC layer on commercial grade graphite. (author)

  3. Geomorphology and petrography of the Angeles lava flow and the Monte de la Cruz cinder cone, Barva Volcano, Costa Rica

    International Nuclear Information System (INIS)

    Rojas, Vanessa; Barahona, Dione; Alvarado, Guillermo E

    2017-01-01

    A geomorphological and pretrographic study was carried out at the lava flow Angeles and the Monte de la Cruz cone in the foothills of the Volcan Barva in Costa Rica. The 1967 aerial photographs at scale 1: 17,000 and 1: 13,000, 1992 at scale 1: 60,000 and TERRA 1997 at scale 1: 40,000 were used for the photogeological study, supplemented with the analysis of the eastern sector of the Hoja Topografica Barva (1: 50 000) of the Instituto Geografico Nacional (IGN) and other topographic maps at different scales (1: 25 000 and 1: 10 000), in addition to the digital elevation models developed through Sistemas de Informacion Geografica (SIG). The information extracted from the wells of the Sistema Nacional de Aguas Subterraneas, Riego y Avenamiento (SENARA) for underground control was reinterpreted. In the field work thicknesses were measured and an estimation of the volumes, dimensions of the cast and other associated geoforms was made. Likewise, 9 samples of rock were selected for the elaboration of thin sections and for their respective petrographic analysis, which allowed to define the main lava flow units and their possible flows. As a result of the volcanic activity of the cone, two flow units of the Angeles wash were identified, the Lower Angels unit and the Superior Angels unit. Petrographically, Angeles Inferior was reciprocated with an andesitic vesical basaltic lava with a porphyritic to slightly glomeroporphyric hypocrystalline texture, with plagioclase, clinopyroxene, orthopyroxene, olivine and opaque phenocrysts. On the other hand, Superior Angeles has been vesicular andesitic with a hypocrystalline texture, glomeroporfiritica to serial glomeroporfiritica, with plagioclase, clinopyroxene, orthopyroxene, olivine and opaque phenocrysts. Morphologically, kipukas and levees were observed. Regionally, it was observed that the Monte de la Cruz cone, along with other smaller satellite cones, are aligned N19 O W along 8.5 km, evidencing an origin associated with a

  4. Stratigraphic reconstruction of the 13 ka BP debris avalanche deposit at Colima volcano (Mexico): effect of climatic conditions on the flow mobility

    Science.gov (United States)

    Roverato, M.; Capra, L.

    2010-12-01

    Colima volcano is an andesitic stratovolcano located in the western part of the Trans-Mexican Volcanic Belt (TMVB) and at the southern end of the N-S trending Colima graben, about 70 km from the Pacific Ocean coast. It is probably the most active Mexican volcano in historic time and one of the most active of North America. Colima volcano yielded numerous partial edifice collapses with emplacement of debris avalanche deposits (DADs) of contrasting volume, morphology, texture and origin. This work has the aim to provide the evidences of how the climatic condition during the 13 ka flank collapse of the Colima volcano affected the textural characteristic and the mobility of the debris avalanche and debris flow originated from this event that occurred just after the Last Glacial Maximum in Mexico (18.4-14.5 ka 14C BP with snow line at 3600 m a.s.l. up to 13 ka BP). The 13,000 yrs old debris avalanche deposit, here named Tonila (TDAD) presents the typical debris avalanche textural characteristics (angular to sub-angular clasts, coarse matrix, jigsaw fit) but at approximately 13 km from the source, the deposit transforms to an hybrid phase with debris avalanche fragments imbedded in a finer, homogenous and indurated matrix more similar to a debris flow deposit. The debris avalanche deposit is directly overly by debris flows, often more than 10 m thick that contains large amount of logs from pine tree, mostly accumulated toward the base and imbricated down flow. Fluvial deposits also occur throughout all successions, representing periods of stream and river reworking highly localized and re-establishment. All these evidences point to the presence of water in the mass previous to the failure. The event here described represent an anomalous event between the previously described deposit associated to volcanic complex, and evidence as climatic condition can alter and modifies the depositional sequences incrementing the hazard.

  5. Magmas with slab fluid and decompression melting signatures coexisting in the Gulf of Fonseca: Evidence from Isla El Tigre volcano (Honduras, Central America)

    Science.gov (United States)

    Mattioli, Michele; Renzulli, Alberto; Agostini, Samuele; Lucidi, Roberto

    2016-01-01

    Isla El Tigre volcano is located in the Gulf of Fonseca (Honduras) along the Central America volcanic front, where a significant change in the strike of the volcanic chain is observed. The studied samples of this poorly investigated volcano are mainly subalkaline basic to intermediate lavas (basalts and basaltic andesites) and subordinate subalkaline/alkaline transitional basalts, both having the typical mineralogical and geochemical characteristics of arc volcanic rocks. On the basis of petrographic and geochemical features, two groups of rocks have been distinguished. Lavas from the main volcanic edifice are highly porphyritic and hy-qz normative, and have lower MgO contents ( 5 wt.%), are ol-hy normative and show lower HFSE depletions relative to LILE and LREE, with lower Ba/La, Ba/Nb and Zr/Nb ratios. This suggests that mantle-derived magmas were not produced by the same process throughout the activity of the volcano. The bulk rock geochemistry and 87Sr/86Sr (0.70373-0.70382), 143Nd/144Nd (0.51298-0.51301), 206Pb/204Pb (18.55-18.58), 207Pb/204Pb (15.54-15.56) and 208Pb/204Pb (38.23-38.26) isotopic data of Isla El Tigre compared with the other volcanoes of the Gulf of Fonseca and all available literature data for Central America suggests that this stratovolcano was mainly built by mantle-derived melts driven by slab-derived fluid-flux melting, while magmas erupted through its parasitic cones have a clear signature of decompression melting with minor slab contribution. The coexistence of these two different mantle melting generation processes is likely related to the complex geodynamic setting of the Gulf of Fonseca, where the volcanic front changes direction by ca. 30° and two fundamental tectonic structures of the Chortis continental block, mainly the N-S Honduras Depression and the NE-SW Guayape Fault Zone, cross each other.

  6. Channel uranium-graphite reactor mounting

    International Nuclear Information System (INIS)

    Polushkin, K.K.; Kuznetsov, A.G.; Zheleznyakov, B.N.

    1981-01-01

    According to theoretical principles of general engineering technology the engineering experience of construction-mounting works at the NPP with channel uranium-graphite reactors is systematized. Main parameters and structural features of the 1000 MW channel uranium-graphite reactors are considered. The succession of mounting operations, premounting equipment and pipelines preparation and mounting works technique are described. The most efficient methods of fitting, welding and machining of reactor elements are recommended. Main problems of technical control service are discussed. A typical netted diagram of main equipment of channel uranium-graphite reactors mounting is given

  7. Synthesis of soluble graphite and graphene.

    Science.gov (United States)

    Kelly, K F; Billups, W E

    2013-01-15

    Because of graphene's anticipated applications in electronics and its thermal, mechanical, and optical properties, many scientists and engineers are interested in this material. Graphene is an isolated layer of the π-stacked hexagonal allotrope of carbon known as graphite. The interlayer cohesive energy of graphite, or exfoliation energy, that results from van der Waals attractions over the interlayer spacing distance of 3.34 Å (61 meV/C atom) is many times weaker than the intralayer covalent bonding. Since graphene itself does not occur naturally, scientists and engineers are still learning how to isolate and manipulate individual layers of graphene. Some researchers have relied on the physical separation of the sheets, a process that can sometimes be as simple as peeling of sheets from crystalline graphite using Scotch tape. Other researchers have taken an ensemble approach, where they exploit the chemical conversion of graphite to the individual layers. The typical intermediary state is graphite oxide, which is often produced using strong oxidants under acidic conditions. Structurally, researchers hypothesize that acidic functional groups functionalize the oxidized material at the edges and a network of epoxy groups cover the sp(2)-bonded carbon network. The exfoliated material formed under these conditions can be used to form dispersions that are usually unstable. However, more importantly, irreversible defects form in the basal plane during oxidation and remain even after reduction of graphite oxide back to graphene-like material. As part of our interest in the dissolution of carbon nanomaterials, we have explored the derivatization of graphite following the same procedures that preserve the sp(2) bonding and the associated unique physical and electronic properties in the chemical processing of single-walled carbon nanotubes. In this Account, we describe efficient routes to exfoliate graphite either into graphitic nanoparticles or into graphene without

  8. Adsorption of lead over graphite oxide.

    Science.gov (United States)

    Olanipekun, Opeyemi; Oyefusi, Adebola; Neelgund, Gururaj M; Oki, Aderemi

    2014-01-24

    The adsorption efficiency and kinetics of removal of lead in presence of graphite oxide (GO) was determined using the Atomic Absorption Spectrophotometer (AAS). The GO was prepared by the chemical oxidation of graphite and characterized using FTIR, SEM, TGA and XRD. The adsorption efficiency of GO for the solution containing 50, 100 and 150 ppm of Pb(2+) was found to be 98%, 91% and 71% respectively. The adsorption ability of GO was found to be higher than graphite. Therefore, the oxidation of activated carbon in removal of heavy metals may be a viable option to reduce pollution in portable water. Published by Elsevier B.V.

  9. Interface structure between tetraglyme and graphite

    Science.gov (United States)

    Minato, Taketoshi; Araki, Yuki; Umeda, Kenichi; Yamanaka, Toshiro; Okazaki, Ken-ichi; Onishi, Hiroshi; Abe, Takeshi; Ogumi, Zempachi

    2017-09-01

    Clarification of the details of the interface structure between liquids and solids is crucial for understanding the fundamental processes of physical functions. Herein, we investigate the structure of the interface between tetraglyme and graphite and propose a model for the interface structure based on the observation of frequency-modulation atomic force microscopy in liquids. The ordering and distorted adsorption of tetraglyme on graphite were observed. It is found that tetraglyme stably adsorbs on graphite. Density functional theory calculations supported the adsorption structure. In the liquid phase, there is a layered structure of the molecular distribution with an average distance of 0.60 nm between layers.

  10. Status of Chronic Oxidation Studies of Graphite

    Energy Technology Data Exchange (ETDEWEB)

    Contescu, Cristian I. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Mee, Robert W. [Univ. of Tennessee, Knoxville, TN (United States)

    2016-05-01

    Graphite will undergo extremely slow, but continuous oxidation by traces of moisture that will be present, albeit at very low levels, in the helium coolant of HTGR. This chronic oxidation may cause degradation of mechanical strength and thermal properties of graphite components if a porous oxidation layer penetrates deep enough in the bulk of graphite components during the lifetime of the reactor. The current research on graphite chronic oxidation is motivated by the acute need to understand the behavior of each graphite grade during prolonged exposure to high temperature chemical attack by moisture. The goal is to provide the elements needed to develop predictive models for long-time oxidation behavior of graphite components in the cooling helium of HTGR. The tasks derived from this goal are: (1) Oxidation rate measurements in order to determine and validate a comprehensive kinetic model suitable for prediction of intrinsic oxidation rates as a function of temperature and oxidant gas composition; (2) Characterization of effective diffusivity of water vapor in the graphite pore system in order to account for the in-pore transport of moisture; and (3) Development and validation of a predictive model for the penetration depth of the oxidized layer, in order to assess the risk of oxidation caused damage of particular graphite grades after prolonged exposure to the environment of helium coolant in HTGR. The most important and most time consuming of these tasks is the measurement of oxidation rates in accelerated oxidation tests (but still under kinetic control) and the development of a reliable kinetic model. This report summarizes the status of chronic oxidation studies on graphite, and then focuses on model development activities, progress of kinetic measurements, validation of results, and improvement of the kinetic models. Analysis of current and past results obtained with three grades of showed that the classical Langmuir-Hinshelwood model cannot reproduce all

  11. Diffusive exchange of trace elements between basaltic-andesite and dacitic melt: Insights into potential metal fractionation during magma mixing

    Science.gov (United States)

    Fiege, A.; Ruprecht, P.; Simon, A. C.; Holtz, F.

    2017-12-01

    Mafic magma recharge is a common process that triggers physical and chemical mixing in magmatic systems and drives their evolution, resulting in, e.g., hybridization and volcanic eruptions. Once magma-magma contact is initiated, rapid heat-flux commonly leads to the formation of a cooling-induced crystal mush on the mafic side of the interface. Here, on a local scale (µm to cm), at the magma-magma interface, melt-melt diffusive exchange is required to approach equilibrium. Significant chemical potential gradients drive a complex, multi-element mass flux between the two systems (Liang, 2010). This diffusive-equilibration often controls crystal dissolution rates within the boundary layers and, thus, the formation of interconnected melt or fluid networks. Such networks provide important pathways for the transport of volatiles and trace metals from the mafic recharge magma to the felsic host magma, where the latter may feed volcanic activities and ore deposits. While major element diffusion in silicate melts is mostly well understood, even in complex systems, the available data for many trace element metals are limited (Liang, 2010; Zhang et al., 2010). Differences in diffusivity in a dynamic, mixing environment can cause trace element fractionation, in particular during crystallization and volatile exsolution and separation. This may affect trace element signatures in phenocrysts and magmatic volatile phases that can form near a magma-magma boundary. As a result, the chemistry of volcanic gases and magmatic-hydrothermal ore deposits may be partially controlled by such mixing phenomena. We performed melt-melt diffusion-couple experiments at 150 MPa, 1100°C, FMQ, FMQ+1 and FMQ+3 (FMQ: fayalite-magnetite-quartz oxygen fugacity buffer). Hydrated, sulfur-bearing cylinders of dacite and basaltic andesite were equilibrated for up to 20 h. Major and trace element gradients were measured by using laser-ablation ICP-MS and electron microprobe analyses. The results we will

  12. Diverse lavas from closely spaced volcanoes drawing from a common parent: Emmons Lake Volcanic Center, Eastern Aleutian Arc

    Science.gov (United States)

    Mangan, M.; Miller, T.; Waythomas, C.; Trusdell, F.; Calvert, A.; Layer, P.

    2009-01-01

    Emmons Lake Volcanic Center (ELVC) on the lower Alaskan Peninsula is one of the largest and most diverse volcanic centers in the Aleutian Arc. Since the Middle Pleistocene, eruption of ~ 350 km3 of basalt through rhyolite has produced a 30 km, arc front chain of nested calderas and overlapping stratovolcanoes. ELVC has experienced as many as five major caldera-forming eruptions, the most recent, at ~ 27 ka, produced ~ 50 km3 of rhyolitic ignimbrite and ash fall. These violent silicic events were interspersed with less energetic, but prodigious, outpourings of basalt through dacite. Holocene eruptions are mostly basaltic andesite to andesite and historically recorded activity includes over 40 eruptions within the last 200 yr, all from Pavlof volcano, the most active site in the Aleutian Arc. Geochemical and geophysical observations suggest that although all ELVC eruptions derive from a common clinopyroxene + spinel + plagioclase fractionating high-aluminum basalt parent in the lower crust, magma follows one of two closely spaced, but distinct paths to the surface. Under the eastern end of the chain, magma moves rapidly and cleanly through a relatively young (~ 28 ka), hydraulically connected dike plexus. Steady supply, short magma residence times, and limited interaction with crustal rocks preserve the geochemistry of deep crustal processes. Below the western part of the chain, magma moves haltingly through a long-lived (~ 500 ka) and complex intrusive column in which many generations of basaltic to andesitic melts have mingled and fractionated. Buoyant, silicic melts periodically separate from the lower parts of the column to feed voluminous eruptions of dacite and rhyolite. Mafic lavas record a complicated passage through cumulate zones and hydrous silicic residues as manifested by disequilibrium phenocryst textures, incompatible element enrichments, and decoupling of REEs and HFSEs ratios. Such features are absent in mafic lavas from the younger part of the chain

  13. Effects of Volcanoes on the Natural Environment

    Science.gov (United States)

    Mouginis-Mark, Peter J.

    2005-01-01

    The primary focus of this project has been on the development of techniques to study the thermal and gas output of volcanoes, and to explore our options for the collection of vegetation and soil data to enable us to assess the impact of this volcanic activity on the environment. We originally selected several volcanoes that have persistent gas emissions and/or magma production. The investigation took an integrated look at the environmental effects of a volcano. Through their persistent activity, basaltic volcanoes such as Kilauea (Hawaii) and Masaya (Nicaragua) contribute significant amounts of sulfur dioxide and other gases to the lower atmosphere. Although primarily local rather than regional in its impact, the continuous nature of these eruptions means that they can have a major impact on the troposphere for years to decades. Since mid-1986, Kilauea has emitted about 2,000 tonnes of sulfur dioxide per day, while between 1995 and 2000 Masaya has emotted about 1,000 to 1,500 tonnes per day (Duffel1 et al., 2001; Delmelle et al., 2002; Sutton and Elias, 2002). These emissions have a significant effect on the local environment. The volcanic smog ("vog" ) that is produced affects the health of local residents, impacts the local ecology via acid rain deposition and the generation of acidic soils, and is a concern to local air traffic due to reduced visibility. Much of the work that was conducted under this NASA project was focused on the development of field validation techniques of volcano degassing and thermal output that could then be correlated with satellite observations. In this way, we strove to develop methods by which not only our study volcanoes, but also volcanoes in general worldwide (Wright and Flynn, 2004; Wright et al., 2004). Thus volcanoes could be routinely monitored for their effects on the environment. The selected volcanoes were: Kilauea (Hawaii; 19.425 N, 155.292 W); Masaya (Nicaragua; 11.984 N, 86.161 W); and Pods (Costa Rica; 10.2OoN, 84.233 W).

  14. Volcanic Processes and Geology of Augustine Volcano, Alaska

    Science.gov (United States)

    Waitt, Richard B.; Beget, James E.

    2009-01-01

    recently in A.D. 1883. The decapitated summit after the 1883 eruption, replaced by andesite domes of six eruptions since, shows a general process: collapse of steep summit domes, then the summit regrown by later dome eruptions. The island's stratigraphy is based on six or seven coarse-pumice tephra 'marker beds'. In upward succession they are layers G (2,100 yr B.P.), I (1,700 yr B.P.), H (1,400 yr B.P.), C (1,200-1,000 yr B.P.), M (750 yr B.P.), and B (390 yr B.P.). A coarse, hummocky debris-avalanche deposit older than about 2,100 yr B.P. - or perhaps a stack of three of them - lies along the east coast, the oldest exposed such bouldery diamicts on Augustine Island. Two large debris avalanches swept east and southeast into the sea between about 2,100 and 1,800 yr B.P. A large debris avalanche shed east and east-northeast into the sea between 1,700 and 14,00 yr B.P. Between about 1,400 and 1,100 yr B.P. debris avalanches swept into the sea on the volcano's south, southwest, and north-northwest. Pumiceous pyroclastic fans spread to the southeast and southwest, lithic pyroclastic flows and lahars (?) to the south and southeast. Pyroclastic flows, pyroclastic surges, and lahars swept down the west and south flanks between about 1,000 and 750 yr B.P. A debris avalanche swept into the sea on the west, and a small one on the south-southeast, between about 750 and 400 yr B.P. Large lithic pyroclastic flows shed to the southeast; smaller ones descended existing swales on the southwest and south. Between about 400 yr B.P. and historical time (late 1770s), three debris avalanches swept into the sea on the west-northwest, north-northwest, and north flanks. One of them (West Island) was large and fast: most of it rode to sea far beyond a former sea cliff, and its surface includes geomorphic evidence of having initiating a tsunami. Augustine's only conspicuous lava flow erupted on the north flank. During this prehistoric period numerous domes grew at th

  15. Superhydrophilic graphite surfaces and water-dispersible graphite colloids by electrochemical exfoliation

    Energy Technology Data Exchange (ETDEWEB)

    Li, Yueh-Feng [Department of Chemical and Materials Engineering, National Central University, Jhongli, 320 Taiwan (China); Chen, Shih-Ming; Lai, Wei-Hao [Materials and Chemical Research Laboratories, Industrial Technology Research Institute, Chutung, Hsinchu, 31040 Taiwan (China); Sheng, Yu-Jane [Department of Chemical Engineering, National Taiwan University, Taipei, 106 Taiwan (China); Tsao, Heng-Kwong [Department of Chemical and Materials Engineering, Department of Physics, National Central University, Jhongli, 320 Taiwan (China)

    2013-08-14

    Superhydrophilic graphite surfaces and water-dispersible graphite colloids are obtained by electrochemical exfoliation with hydrophobic graphite electrodes. Such counterintuitive characteristics are caused by partial oxidation and investigated by examining both graphite electrodes and exfoliated particles after electrolysis. The extent of surface oxidation can be explored through contact angle measurement, scanning electron microscope, electrical sheet resistance, x-ray photoelectron spectroscopy, zeta-potential analyzer, thermogravimetric analysis, UV-visible, and Raman spectroscopy. The degree of wettability of the graphite anode can be altered by the electrolytic current and time. The water contact angle declines generally with increasing the electrolytic current or time. After a sufficient time, the graphite anode becomes superhydrophilic and its hydrophobicity can be recovered by peeling with adhesive tape. This consequence reveals that the anodic graphite is oxidized by oxygen bubbles but the oxidation just occurs at the outer layers of the graphite sheet. Moreover, the characteristics of oxidation revealed by UV peak shift, peak ratio between D and G bands, and negative zeta-potential indicate the presence of graphite oxide on the outer shell of the exfoliated colloids. However, thermogravimetric analysis for the extent of decomposition of oxygen functional groups verifies that the amount of oxygen groups is significantly less than that of graphite oxide prepared via Hummer method. The structure of this partially oxidized graphite may consist of a graphite core covered with an oxidized shell. The properties of the exfoliated colloids are also influenced by pH of the electrolytic solution. As pH is increased, the extent of oxidation descends and the thickness of oxidized shell decreases. Those results reveal that the degree of oxidation of exfoliated nanoparticles can be manipulated simply by controlling pH.

  16. Performance of AC/graphite capacitors at high weight ratios of AC/graphite

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Hongyu [IM and T Ltd., Advanced Research Center, Saga University, 1341 Yoga-machi, Saga 840-0047 (Japan); Yoshio, Masaki [Advanced Research Center, Department of Applied Chemistry, Saga University, 1341 Yoga-machi, Saga 840-0047 (Japan)

    2008-03-01

    The effect of negative to positive electrode materials' weight ratio on the electrochemical performance of both activated carbon (AC)/AC and AC/graphite capacitors has been investigated, especially in the terms of capacity and cycle-ability. The limited capacity charge mode has been proposed to improve the cycle performance of AC/graphite capacitors at high weight ratios of AC/graphite. (author)

  17. Volcanoes in the Classroom--an Explosive Learning Experience.

    Science.gov (United States)

    Thompson, Susan A.; Thompson, Keith S.

    1996-01-01

    Presents a unit on volcanoes for third- and fourth-grade students. Includes demonstrations; video presentations; building a volcano model; and inviting a scientist, preferably a vulcanologist, to share his or her expertise with students. (JRH)

  18. Volcanostratigraphic Approach for Evaluation of Geothermal Potential in Galunggung Volcano

    Science.gov (United States)

    Ramadhan, Q. S.; Sianipar, J. Y.; Pratopo, A. K.

    2016-09-01

    he geothermal systems in Indonesia are primarily associated with volcanoes. There are over 100 volcanoes located on Sumatra, Java, and in the eastern part of Indonesia. Volcanostratigraphy is one of the methods that is used in the early stage for the exploration of volcanic geothermal system to identify the characteristics of the volcano. The stratigraphy of Galunggung Volcano is identified based on 1:100.000 scale topographic map of Tasikmalaya sheet, 1:50.000 scale topographic map and also geological map. The schematic flowchart for evaluation of geothermal exploration is used to interpret and evaluate geothermal potential in volcanic regions. Volcanostratigraphy study has been done on Galunggung Volcano and Talaga Bodas Volcano, West Java, Indonesia. Based on the interpretation of topographic map and analysis of the dimension, rock composition, age and stress regime, we conclude that both Galunggung Volcano and Talaga Bodas Volcano have a geothermal resource potential that deserve further investigation.

  19. Stratigraphy, distribution, and evidence for mafic triggering of the ca. 8.5 ka Driftwood Pumice eruption, Makushin Volcano, Alaska, U.S.A

    Science.gov (United States)

    Lerner, Allan H.; Crowley, Peter D.; Nicolaysen, Kirsten P.; Hazlett, Richard W.

    2018-05-01

    Makushin Volcano on Unalaska Island, Alaska, threatens the Aleutian's largest population centers (Unalaska and Dutch Harbor), yet its eruption mechanisms are poorly known. This study presents a detailed stratigraphic and geochemical investigation of Makushin's most recent highly explosive event: the ca. 8.5 ka Driftwood Pumice eruption. The Driftwood Pumice has measured thicknesses of over 2.5 m, and isopach reconstructions estimate a total deposit volume of 0.3 to 1.6 km3, indicating a VEI 4-5 eruption. Proximal deposits consist of normally-graded, tan, dacitic to andesitic pumice, capped by a thinner dark layer of lower-silica andesitic scoria mixed with abundant lithic fragments. This stratigraphy is interpreted as an initial vent-clearing eruption that strengthened into a climactic ejection of pumice and ash and concluded with vent destabilization and the eruption of somewhat more mafic, gas-poor magma. Within the pumice, geochemical trends, disequilibrium mineral populations, and mineral zonation patterns show evidence of magma mixing between a bulk silicic magma and a mafic melt. Euhedral high-Ca plagioclase (An68-91) and high-Mg olivine (Fo69-77) phenocrysts are in disequilibrium with trachydacitic glass (65-68 wt% SiO2) and more abundant sodic plagioclase (An34-55), indicating the former originally crystallized in a more mafic melt. Tephra whole rock compositions become more mafic upwards through the deposit, ranging from a basal low-silica dacite to an andesite (total range: 60.8-63.3 wt% SiO2). Collectively, these compositional variations suggest magma mixing in the Driftwood Pumice (DWP) magma reservoir, with a systematic increase in the amount of a mafic component (up to 25%) upward through the deposit. Olivine-liquid and liquid-only thermometry indicate the mafic magma intruded at temperatures 140-200 °C hotter than the silicic magma. Diffusion rates calculated for 5-7 μm thick, lower-Mg rims on the olivine phenocrysts (Fo60 rim vs Fo76 bulk) suggest

  20. Management of radioactive waste in nuclear power: handling of irradiated graphite from water-cooled graphite reactors

    International Nuclear Information System (INIS)

    Anfimov, S.S.

    2001-01-01

    In this paper an radioactive waste processing of graphite from graphite moderated nuclear reactors at its decommissioning is discussed. Methods of processing of irradiated graphite are presented. It can be concluded that advanced methods for graphite radioactive waste handling are available nowadays. Implementation of these methods will allow to enhance environmental safety of nuclear power that will benefit its progress in the future

  1. A Graphite Isotope Ratio Method: A Primer on Estimating Plutonium Production in Graphite Moderated Reactors

    International Nuclear Information System (INIS)

    Gesh, Christopher J.

    2004-01-01

    The Graphite Isotope Ratio Method (GIRM) is a technique used to estimate the total plutonium production in a graphite-moderated reactor. The cumulative plutonium production in that reactor can be accurately determined by measuring neutron irradiation induced isotopic ratio changes in certain impurity elements within the graphite moderator. The method does not require detailed knowledge of a reactor's operating history, although that knowledge can decrease the uncertainty of the production estimate. The basic premise of the Graphite Isotope Ratio Method is that the fluence in non-fuel core components is directly related to the cumulative plutonium production in the nuclear fuel

  2. Synthesis of graphene nanoplatelets from peroxosulfate graphite intercalation compounds

    OpenAIRE

    MELEZHYK A.V.; TKACHEV A.G.

    2014-01-01

    Ultrasonic exfoliation of expanded graphite compound obtained by cold expansion of graphite intercalated with peroxodisulfuric acid was shown to allow the creation of graphene nanoplatelets with thickness of about 5-10 nm. The resulting graphene material contained surface oxide groups. The expanded graphite intercalation compound was exfoliated by ultrasound much easier than thermally expanded graphite. A mechanism for the cleavage of graphite to graphene nanoplatelets is proposed. It include...

  3. Graphite reactor physics; Physique des piles a graphite

    Energy Technology Data Exchange (ETDEWEB)

    Bacher, P; Cogne, F [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires; Noc, B [Electricite de France (EDF), 75 - Paris (France)

    1964-07-01

    The study of graphite-natural uranium power reactor physics, undertaken ten years ago when the Marcoule piles were built, has continued to keep in step with the development of this type of pile. From 1960 onwards the critical facility Marius has been available for a systematic study of the properties of lattices as a function of their pitch, of fuel geometry and of the diameter of cooling channels. This study has covered a very wide field: lattice pitch varying from 19 to 38 cm. uranium rods and tubes of cross-sections from 6 to 35 cm{sup 2}, channels with diameters between 70 and 140 mm. The lattice calculation methods could thus be checked and where necessary adapted. The running of the Marcoule piles and the experiments carried out on them during the last few years have supplied valuable information on the overall evolution of the neutronic properties of the fuel as a function of irradiation. More detailed experiments have also been performed in Marius with plutonium-containing fuels (irradiated or synthetic fuels), and will be undertaken at the beginning of 1965 at high temperature in the critical facility Cesar, which is just being completed at Cadarache. Spent fuel analyses complement these results and help in their interpretation. The thermalization and spectra theories developed in France can thus be verified over the whole valid temperature range. The efficiency of control rods as a function of their dimensions, the materials of which they are made and the lattices surrounding them has been measured in Marius, and the results compared with calculation on the one hand and with the measurements carried out in EDF 1 on the other. Studies on the control proper of graphite piles were concerned essentially with the risks of spatial instability and the means of detecting and controlling them, and with flux distortions caused by the control rods. (authors) [French] Entreprise il y a dix ans a l'occasion de la construction des piles de Marcoule, l'etude de la

  4. Volcano Trial Case on GEP: Systematically processing EO data

    OpenAIRE

    Baumann, Andreas Bruno Graziano

    2017-01-01

    Volcanoes can be found all over the world; on land and below water surface. Even nowadays not all volcanoes are known. About 600 erupted in geologically recent times and about 50-70 volcanoes are currently active. Volcanoes can cause earthquakes; throw out blasts and tephras; release (toxic) gases; lava can flow relatively slow down the slopes; mass movements like debris avalanches, and landslides can cause tsunamis; and fast and hot pyroclastic surge, flows, and lahars can travel fast down ...

  5. Seismic research on graphite reactor core

    International Nuclear Information System (INIS)

    Lai Shigang; Sun Libin; Zhang Zhengming

    2013-01-01

    Background: Reactors with graphite core structure include production reactor, water-cooled graphite reactor, gas-cooled reactor, high-temperature gas-cooled reactor and so on. Multi-body graphite core structure has nonlinear response under seismic excitation, which is different from the response of general civil structure, metal connection structure or bolted structure. Purpose: In order to provide references for the designing and construction of HTR-PM. This paper reviews the history of reactor seismic research evaluation from certain countries, and summarizes the research methods and research results. Methods: By comparing the methods adopted in different gas-cooled reactor cores, inspiration for our own HTR seismic research was achieved. Results and Conclusions: In this paper, the research ideas of graphite core seismic during the process of designing, constructing and operating HTR-10 are expounded. Also the project progress of HTR-PM and the research on side reflection with the theory of similarity is introduced. (authors)

  6. Review: BNL Tokamak graphite blanket design concepts

    International Nuclear Information System (INIS)

    Fillo, J.A.; Powell, J.R.

    1976-01-01

    The BNL minimum activity graphite blanket designs are reviewed, and three are discussed in the context of an experimental power reactor (EPR) and commercial power reactor. Basically, the three designs employ a 30 cm or thicker graphite screen. Bremsstrahlung energy is deposited on the graphite surface and re-radiated away as thermal radiation. Fast neutrons are slowed down in the graphite, depositing most of their energy, which is then radiated to a secondary blanket with coolant tubes, as in types A and B, or removed by intermittent direct gas cooling (type C). In types A and B, radiation damage to the coolant tubes in the secondary blanket is reduced by one or two orders of magnitude, while in type C, the blanket is only cooled when the reactor is shut down, so that coolant cannot quench the plasma. (Auth.)

  7. Immobilization of Rocky Flats Graphite Fines Residue

    International Nuclear Information System (INIS)

    Rudisill, T.S.

    1999-01-01

    The development of the immobilization process for graphite fines has proceeded through a series of experimental programs. The experimental procedures and results from each series of experiments are discussed in this report

  8. Optical motion control of maglev graphite.

    Science.gov (United States)

    Kobayashi, Masayuki; Abe, Jiro

    2012-12-26

    Graphite has been known as a typical diamagnetic material and can be levitated in the strong magnetic field. Here we show that the magnetically levitating pyrolytic graphite can be moved in the arbitrary place by simple photoirradiation. It is notable that the optical motion control system described in this paper requires only NdFeB permanent magnets and light source. The optical movement is driven by photothermally induced changes in the magnetic susceptibility of the graphite. Moreover, we demonstrate that light energy can be converted into rotational kinetic energy by means of the photothermal property. We find that the levitating graphite disk rotates at over 200 rpm under the sunlight, making it possible to develop a new class of light energy conversion system.

  9. Study on graphite samples for nuclear usage

    International Nuclear Information System (INIS)

    Suarez, J.C.M.; Silva Roseira, M. da

    1994-01-01

    Available as short communication only. The graphite, due to its properties (mechanical strength, thermal conductivity, high-temperature stability, machinability etc.) have many industrial applications, and consequently, an important strategic value. In the nuclear area, it has been used as moderator and reflector of neutrons in the fission process of uranium. The graphite can be produced from many types of carbonaceous materials by a variety of process dominated by the manufactures. This is the reason why there are in the world market a lot of graphite types with different physical and mechanical properties. The present investigation studies some physical characteristics of the graphite samples destined to use in a nuclear reactor. (author). 8 refs, 1 fig, 1 tab

  10. Collective modes in superconducting rhombohedral graphite

    Energy Technology Data Exchange (ETDEWEB)

    Kauppila, Ville [O.V. Lounasmaa Laboratory, Aalto University (Finland); Hyart, Timo; Heikkilae, Tero [University of Jyvaeskylae (Finland)

    2015-07-01

    Recently it was realized that coupling particles with a Dirac dispersion (such as electrons in graphene) can lead to a topologically protected state with flat band dispersion. Such a state could support superconductivity with unusually high critical temperatures. Perhaps the most promising way to realize such coupling in real materials is in the surface of rhombohedrally stacked graphite. We consider collective excitations (i.e. the Higgs modes) in surface superconducting rhombohedral graphite. We find two amplitude and two phase modes corresponding to the two surfaces of the graphite where the superconductivity lives. We calculate the dispersion of these modes. We also derive the Ginzburg-Landau theory for this material. We show that in superconducting rhombohedral graphite, the collective modes, unlike in conventional BCS superconductors, give a large contribution to thermodynamic properties of the material.

  11. Large Scale Reduction of Graphite Oxide

    Data.gov (United States)

    National Aeronautics and Space Administration — This project seeks to develop an optical method to reduce graphite oxide into graphene efficiently and in larger formats than currently available. Current reduction...

  12. Analysis of picosecond pulsed laser melted graphite

    International Nuclear Information System (INIS)

    Steinbeck, J.; Braunstein, G.; Speck, J.; Dresselhaus, M.S.; Huang, C.Y.; Malvezzi, A.M.; Bloembergen, N.

    1986-01-01

    A Raman microprobe and high resolution TEM have been used to analyze the resolidified region of liquid carbon generated by picosecond pulse laser radiation. From the relative intensities of the zone center Raman-allowed mode for graphite at 1582 cm -1 and the disorder-induced mode at 1360 cm -1 , the average graphite crystallite size in the resolidified region is determined as a function of position. By comparison with Rutherford backscattering spectra and Raman spectra from nonosecond pulsed laser melting experiments, the disorder depth for picosecond pulsed laser melted graphite is determined as a function of irradiating energy density. Comparisons of TEM micrographs for nanosecond and picosecond pulsed laser melting experiments show that the structure of the laser disordered regions in graphite are similar and exhibit similar behavior with increasing laser pulse fluence

  13. Plagioclase Textures and Zoning Patterns in the Miocene Dowdy Ranch Andesite, Central California Coast Ranges: Implications for Open and Closed System Behavior in Magmatic Systems

    Science.gov (United States)

    Bavishi, D. K.; Metzger, E. P.; Miller, J. S.

    2010-12-01

    The Miocene Dowdy Range Andesite (DRA) of the Central California Coast Ranges is part of a northwestward-younging sequence of volcanic rocks that were apparently formed by northward movement of the Mendocino triple junction, formation of a slab window, and infilling by asthenospheric mantle. The highly porphyritic andesite contains plagioclase phenocrysts with a wide array of disequilibrium textures and zoning patterns, providing an opportunity to reconstruct andesite-forming processes in a tectonic environment that evolved from subduction to transform motion. The DRA encloses metasedimentary, granulitic, and gabbroic xenoliths (described elsewhere) and displays arc-like trace element chemistry. It features glomeroporphyritic, intersertal and hyalopilitic textures with plagioclase as the dominant phase both as phenocrysts and in the groundmass. Other groundmass minerals include orthopyroxene, clinopyroxene, and ilmenite. Plagioclase exhibits normal, reverse, oscillatory and patchy zoning patterns and sieve and sponge textures, with several populations of plagioclase crystals observed on the scale of a single thin section. The presence of abundant quartz xenocrysts rimmed by augite and absence of mafic enclaves suggest that incorporation of crustal material played an important role in forming the andesite. Preliminary examination of back-scattered electron images and electron microprobe analysis of zoned plagioclase shows both concordant and discordant relationships between An and FeO, suggesting that the andesite was formed by a combination of open and closed system magmatic processes. Plagioclase cores vary from An 45-65%. Clear rims surrounding spongy zones are common and show abrupt and significant (~10-50% An and 5-20% FeO) increases in both An and FeO, as expected for magma recharge by more mafic magma. Clear rim compositions are consistent from sample to sample, suggesting that the phenocrysts experienced a common history during later stages of

  14. Vapour pressure of caesium over nuclear graphite

    International Nuclear Information System (INIS)

    Faircloth, R.L.; Pummery, F.C.W.

    1976-01-01

    The vapour pressure of caesium over a fine-grained isotropic moulded gilsocarbon nuclear graphite intended for use in the manufacture of fuel tubes for the high temperature reactor has been determined as a function of temperature and concentration by means of the Knudsen effusion technique. The concentration range 0 to 10 μg caesium/g graphite was investigated and it was concluded that a Langmuir adsorption situation exists under these conditions. (author)

  15. Elastic properties of graphite and interstitial defects

    International Nuclear Information System (INIS)

    Ayasse, J.-B.

    1977-01-01

    The graphite elastic constants C 33 and C 44 , reflecting the interaction of the graphitic planes, were experimentally measured as a function of irradiation and temperature. A model of non-central strength atomic interaction was established to explain the experimental results obtained. This model is valid at zero temperature. The temperature dependence of the elastic properties was analyzed. The influence of the elastic property variations on the specific heat of the lattice at very low temperature was investigated [fr

  16. Energy evaluations, graphite corrosion in Bugey I

    International Nuclear Information System (INIS)

    Brisbois, J.; Fiche, C.

    1967-01-01

    Bugey I presents a problem of radiolytic corrosion of the graphite by the CO 2 under pressure at high temperature. This report aims to evaluate the energy transferred to the gas by a Bugey I core cell, in normal operating conditions. The water, the carbon oxides and the hydrogen formed quantities are deduced as the consumed graphite and methane. Experimental studies are realized in parallel to validate the presented results. (A.L.B.)

  17. High temperature tests for graphite materials

    OpenAIRE

    Zhmurikov, Evgenij

    2015-01-01

    This study was performed within the framework of the EURISOL for facilities SPIRAL-II (GANIL, France) and SPES (LNL, Italy), and aims to investigate the anticipated strength properties of fine-grained graphite at elevated temperatures. It appears that the major parameters that affect to the lifetime of a graphite target of this IP are the temperature and heating time. High temperature tests were conducted to simulate the heating under the influence of a beam of heavy particles by passing thro...

  18. Volcano Geodesy: Recent developments and future challenges

    Science.gov (United States)

    Fernandez, Jose F.; Pepe, Antonio; Poland, Michael; Sigmundsson, Freysteinn

    2017-01-01

    Ascent of magma through Earth's crust is normally associated with, among other effects, ground deformation and gravity changes. Geodesy is thus a valuable tool for monitoring and hazards assessment during volcanic unrest, and it provides valuable data for exploring the geometry and volume of magma plumbing systems. Recent decades have seen an explosion in the quality and quantity of volcano geodetic data. New datasets (some made possible by regional and global scientific initiatives), as well as new analysis methods and modeling practices, have resulted in important changes to our understanding of the geodetic characteristics of active volcanism and magmatic processes, from the scale of individual eruptive vents to global compilations of volcano deformation. Here, we describe some of the recent developments in volcano geodesy, both in terms of data and interpretive tools, and discuss the role of international initiatives in meeting future challenges for the field.

  19. Soil radon response around an active volcano

    International Nuclear Information System (INIS)

    Segovia, N.; Valdes, C.; Pena, P.; Mena, M.; Tamez, E.

    2001-01-01

    Soil radon behavior related to the volcanic eruptive period 1997-1999 of Popocatepetl volcano has been studied as a function of the volcanic activity. Since the volcano is located 60 km from Mexico City, the risk associated with an explosive eruptive phase is high and an intense surveillance program has been implemented. Previous studies in this particular volcano showed soil radon pulses preceding the initial phase of the eruption. The radon survey was performed with LR-115 track detectors at a shallow depth and the effect of the soil moisture during the rainy season has been observed on the detectors response. In the present state of the volcanic activity the soil radon behavior has shown more stability than in previous eruptive stages

  20. Graphite Composite Panel Polishing Fixture

    Science.gov (United States)

    Hagopian, John; Strojny, Carl; Budinoff, Jason

    2011-01-01

    The use of high-strength, lightweight composites for the fixture is the novel feature of this innovation. The main advantage is the light weight and high stiffness-to-mass ratio relative to aluminum. Meter-class optics require support during the grinding/polishing process with large tools. The use of aluminum as a polishing fixture is standard, with pitch providing a compliant layer to allow support without deformation. Unfortunately, with meter-scale optics, a meter-scale fixture weighs over 120 lb (.55 kg) and may distort the optics being fabricated by loading the mirror and/or tool used in fabrication. The use of composite structures that are lightweight yet stiff allows standard techniques to be used while providing for a decrease in fixture weight by almost 70 percent. Mounts classically used to support large mirrors during fabrication are especially heavy and difficult to handle. The mount must be especially stiff to avoid deformation during the optical fabrication process, where a very large and heavy lap often can distort the mount and optic being fabricated. If the optic is placed on top of the lapping tool, the weight of the optic and the fixture can distort the lap. Fixtures to support the mirror during fabrication are often very large plates of aluminum, often 2 in. (.5 cm) or more in thickness and weight upwards of 150 lb (68 kg). With the addition of a backing material such as pitch and the mirror itself, the assembly can often weigh over 250 lb (.113 kg) for a meter-class optic. This innovation is the use of a lightweight graphite panel with an aluminum honeycomb core for use as the polishing fixture. These materials have been used in the aerospace industry as structural members due to their light weight and high stiffness. The grinding polishing fixture consists of the graphite composite panel, fittings, and fixtures to allow interface to the polishing machine, and introduction of pitch buttons to support the optic under fabrication. In its

  1. Predicting the Timing and Location of the next Hawaiian Volcano

    Science.gov (United States)

    Russo, Joseph; Mattox, Stephen; Kildau, Nicole

    2010-01-01

    The wealth of geologic data on Hawaiian volcanoes makes them ideal for study by middle school students. In this paper the authors use existing data on the age and location of Hawaiian volcanoes to predict the location of the next Hawaiian volcano and when it will begin to grow on the floor of the Pacific Ocean. An inquiry-based lesson is also…

  2. Interdisciplinary studies of eruption at Chaiten Volcano, Chile

    Science.gov (United States)

    John S. Pallister; Jon J. Major; Thomas C. Pierson; Richard P. Hoblitt; Jacob B. Lowenstern; John C. Eichelberger; Lara. Luis; Hugo Moreno; Jorge Munoz; Jonathan M. Castro; Andres Iroume; Andrea Andreoli; Julia Jones; Fred Swanson; Charlie Crisafulli

    2010-01-01

    There was keen interest within the volcanology community when the first large eruption of high-silica rhyolite since that of Alaska's Novarupta volcano in 1912 began on 1 May 2008 at Chaiten volcano, southern Chile, a 3-kilometer-diameter caldera volcano with a prehistoric record of rhyolite eruptions. Vigorous explosions occurred through 8 May 2008, after which...

  3. How Do Volcanoes Affect Human Life? Integrated Unit.

    Science.gov (United States)

    Dayton, Rebecca; Edwards, Carrie; Sisler, Michelle

    This packet contains a unit on teaching about volcanoes. The following question is addressed: How do volcanoes affect human life? The unit covers approximately three weeks of instruction and strives to present volcanoes in an holistic form. The five subject areas of art, language arts, mathematics, science, and social studies are integrated into…

  4. Living with Volcanoes: Year Eleven Teaching Resource Unit.

    Science.gov (United States)

    Le Heron, Kiri; Andrews, Jill; Hooks, Stacey; Larnder, Michele; Le Heron, Richard

    2000-01-01

    Presents a unit on volcanoes and experiences with volcanoes that helps students develop geography skills. Focuses on four volcanoes: (1) Rangitoto Island; (2) Lake Pupuke; (3) Mount Smart; and (4) One Tree Hill. Includes an answer sheet and resources to use with the unit. (CMK)

  5. Structure and functionality of bromine doped graphite.

    Science.gov (United States)

    Hamdan, Rashid; Kemper, A F; Cao, Chao; Cheng, H P

    2013-04-28

    First-principles calculations are used to study the enhanced in-plane conductivity observed experimentally in Br-doped graphite, and to study the effect of external stress on the structure and functionality of such systems. The model used in the numerical calculations is that of stage two doped graphite. The band structure near the Fermi surface of the doped systems with different bromine concentrations is compared to that of pure graphite, and the charge transfer between carbon and bromine atoms is analyzed to understand the conductivity change along different high symmetry directions. Our calculations show that, for large interlayer separation between doped graphite layers, bromine is stable in the molecular form (Br2). However, with increased compression (decreased layer-layer separation) Br2 molecules tend to dissociate. While in both forms, bromine is an electron acceptor. The charge exchange between the graphite layers and Br atoms is higher than that with Br2 molecules. Electron transfer to the Br atoms increases the number of hole carriers in the graphite sheets, resulting in an increase of conductivity.

  6. Volcanoes muon imaging using Cherenkov telescopes

    International Nuclear Information System (INIS)

    Catalano, O.; Del Santo, M.; Mineo, T.; Cusumano, G.; Maccarone, M.C.; Pareschi, G.

    2016-01-01

    A detailed understanding of a volcano inner structure is one of the key-points for the volcanic hazards evaluation. To this aim, in the last decade, geophysical radiography techniques using cosmic muon particles have been proposed. By measuring the differential attenuation of the muon flux as a function of the amount of rock crossed along different directions, it is possible to determine the density distribution of the interior of a volcano. Up to now, a number of experiments have been based on the detection of the muon tracks crossing hodoscopes, made up of scintillators or nuclear emulsion planes. Using telescopes based on the atmospheric Cherenkov imaging technique, we propose a new approach to study the interior of volcanoes detecting of the Cherenkov light produced by relativistic cosmic-ray muons that survive after crossing the volcano. The Cherenkov light produced along the muon path is imaged as a typical annular pattern containing all the essential information to reconstruct particle direction and energy. Our new approach offers the advantage of a negligible background and an improved spatial resolution. To test the feasibility of our new method, we have carried out simulations with a toy-model based on the geometrical parameters of ASTRI SST-2M, i.e. the imaging atmospheric Cherenkov telescope currently under installation onto the Etna volcano. Comparing the results of our simulations with previous experiments based on particle detectors, we gain at least a factor of 10 in sensitivity. The result of this study shows that we resolve an empty cylinder with a radius of about 100 m located inside a volcano in less than 4 days, which implies a limit on the magma velocity of 5 m/h.

  7. Volcanoes muon imaging using Cherenkov telescopes

    Energy Technology Data Exchange (ETDEWEB)

    Catalano, O. [INAF, Istituto di Astrofisica Spaziale e Fisica cosmica di Palermo, via U. La Malfa 153, I-90146 Palermo (Italy); Del Santo, M., E-mail: melania@ifc.inaf.it [INAF, Istituto di Astrofisica Spaziale e Fisica cosmica di Palermo, via U. La Malfa 153, I-90146 Palermo (Italy); Mineo, T.; Cusumano, G.; Maccarone, M.C. [INAF, Istituto di Astrofisica Spaziale e Fisica cosmica di Palermo, via U. La Malfa 153, I-90146 Palermo (Italy); Pareschi, G. [INAF Osservatorio Astronomico di Brera, Via E. Bianchi 46, I-23807, Merate (Italy)

    2016-01-21

    A detailed understanding of a volcano inner structure is one of the key-points for the volcanic hazards evaluation. To this aim, in the last decade, geophysical radiography techniques using cosmic muon particles have been proposed. By measuring the differential attenuation of the muon flux as a function of the amount of rock crossed along different directions, it is possible to determine the density distribution of the interior of a volcano. Up to now, a number of experiments have been based on the detection of the muon tracks crossing hodoscopes, made up of scintillators or nuclear emulsion planes. Using telescopes based on the atmospheric Cherenkov imaging technique, we propose a new approach to study the interior of volcanoes detecting of the Cherenkov light produced by relativistic cosmic-ray muons that survive after crossing the volcano. The Cherenkov light produced along the muon path is imaged as a typical annular pattern containing all the essential information to reconstruct particle direction and energy. Our new approach offers the advantage of a negligible background and an improved spatial resolution. To test the feasibility of our new method, we have carried out simulations with a toy-model based on the geometrical parameters of ASTRI SST-2M, i.e. the imaging atmospheric Cherenkov telescope currently under installation onto the Etna volcano. Comparing the results of our simulations with previous experiments based on particle detectors, we gain at least a factor of 10 in sensitivity. The result of this study shows that we resolve an empty cylinder with a radius of about 100 m located inside a volcano in less than 4 days, which implies a limit on the magma velocity of 5 m/h.

  8. Tracing Magmatic Degassing Timescales at Soufrière Hills Volcano using Short-Lived Uranium Series Isotopes

    Science.gov (United States)

    Turner, S.; McGee, L. E.; Handley, H. K.; Reagan, M. K.; Turner, M. B.; Berlo, K.; Barclay, J.; Sparks, R. S. J.

    2016-12-01

    Soufrière Hills Volcano, on the Caribbean island of Montserrat, is one of the most intensively studied and constantly monitored volcanic systems in the world. Since 1995, the island has seen five phases of eruption, interspersed with periods of quiescence of varying length. The last eruptive phase ended in 2010, and the current period of quiescence is the longest since 1995. Mafic recharge is thought to contribute volatiles which may lead to system overpressure and trigger a volcanic eruption. At Soufrière Hills Volcano, enclaves of mafic material are a notable feature within the andesitic dome collapse material from all five eruptive phases and have been the focus of several recent petrogenetic studies, meaning that they are extremely well-characterised. We present a 210Pb-226Ra isotope data of enclave-andesite pairs from all five recent eruption phases of Soufrière Hills to investigate the timescale on which volatile transfer occurs prior to eruptions. 210Pb-226Ra disequilibria is a powerful tool in tracing gas movement within recently erupted (<100 years) volcanic material, as one of the intermediary daughters involved in the chain (222Rn) is released in the gas phase of magmas. Subsequent deficits or excesses of 210Pb over 226Ra provide information on whether gas transfer occurred over a short time-frame or if gas fluxing from a mafic magma was maintained for some time previous to each eruption. This vital information may elucidate whether the system is recharging and preparing for a new eruptive phase or draining its current magma supply thus diminishing the possibility of further, explosive eruptions. Preliminary results suggest that gas fluxing from mafic magma was particularly effective in the first two eruptive phases, supporting the mafic-trigger hypothesis. However, we observe a possible change in this behaviour from phase 3 onwards. We complement these time-sensitive geochemical data with comparison to high resolution monitoring data with the hope

  9. Volcano geodesy in the Cascade arc, USA

    Science.gov (United States)

    Poland, Michael; Lisowski, Michael; Dzurisin, Daniel; Kramer, Rebecca; McLay, Megan; Pauk, Benjamin

    2017-01-01

    Experience during historical time throughout the Cascade arc and the lack of deep-seated deformation prior to the two most recent eruptions of Mount St. Helens might lead one to infer that Cascade volcanoes are generally quiescent and, specifically, show no signs of geodetic change until they are about to erupt. Several decades of geodetic data, however, tell a different story. Ground- and space-based deformation studies have identified surface displacements at five of the 13 major Cascade arc volcanoes that lie in the USA (Mount Baker, Mount St. Helens, South Sister, Medicine Lake, and Lassen volcanic center). No deformation has been detected at five volcanoes (Mount Rainier, Mount Hood, Newberry Volcano, Crater Lake, and Mount Shasta), and there are not sufficient data at the remaining three (Glacier Peak, Mount Adams, and Mount Jefferson) for a rigorous assessment. In addition, gravity change has been measured at two of the three locations where surveys have been repeated (Mount St. Helens and Mount Baker show changes, while South Sister does not). Broad deformation patterns associated with heavily forested and ice-clad Cascade volcanoes are generally characterized by low displacement rates, in the range of millimeters to a few centimeters per year, and are overprinted by larger tectonic motions of several centimeters per year. Continuous GPS is therefore the best means of tracking temporal changes in deformation of Cascade volcanoes and also for characterizing tectonic signals so that they may be distinguished from volcanic sources. Better spatial resolution of volcano deformation can be obtained through the use of campaign GPS, semipermanent GPS, and interferometric synthetic aperture radar observations, which leverage the accumulation of displacements over time to improve signal to noise. Deformation source mechanisms in the Cascades are diverse and include magma accumulation and withdrawal, post-emplacement cooling of recent volcanic deposits, magmatic

  10. The origin of the Hawaiian Volcano Observatory

    International Nuclear Information System (INIS)

    Dvorak, John

    2011-01-01

    I first stepped through the doorway of the Hawaiian Volcano Observatory in 1976, and I was impressed by what I saw: A dozen people working out of a stone-and-metal building perched at the edge of a high cliff with a spectacular view of a vast volcanic plain. Their primary purpose was to monitor the island's two active volcanoes, Kilauea and Mauna Loa. I joined them, working for six weeks as a volunteer and then, years later, as a staff scientist. That gave me several chances to ask how the observatory had started.

  11. Volcano geodesy in the Cascade arc, USA

    Science.gov (United States)

    Poland, Michael P.; Lisowski, Michael; Dzurisin, Daniel; Kramer, Rebecca; McLay, Megan; Pauk, Ben

    2017-08-01

    Experience during historical time throughout the Cascade arc and the lack of deep-seated deformation prior to the two most recent eruptions of Mount St. Helens might lead one to infer that Cascade volcanoes are generally quiescent and, specifically, show no signs of geodetic change until they are about to erupt. Several decades of geodetic data, however, tell a different story. Ground- and space-based deformation studies have identified surface displacements at five of the 13 major Cascade arc volcanoes that lie in the USA (Mount Baker, Mount St. Helens, South Sister, Medicine Lake, and Lassen volcanic center). No deformation has been detected at five volcanoes (Mount Rainier, Mount Hood, Newberry Volcano, Crater Lake, and Mount Shasta), and there are not sufficient data at the remaining three (Glacier Peak, Mount Adams, and Mount Jefferson) for a rigorous assessment. In addition, gravity change has been measured at two of the three locations where surveys have been repeated (Mount St. Helens and Mount Baker show changes, while South Sister does not). Broad deformation patterns associated with heavily forested and ice-clad Cascade volcanoes are generally characterized by low displacement rates, in the range of millimeters to a few centimeters per year, and are overprinted by larger tectonic motions of several centimeters per year. Continuous GPS is therefore the best means of tracking temporal changes in deformation of Cascade volcanoes and also for characterizing tectonic signals so that they may be distinguished from volcanic sources. Better spatial resolution of volcano deformation can be obtained through the use of campaign GPS, semipermanent GPS, and interferometric synthetic aperture radar observations, which leverage the accumulation of displacements over time to improve signal to noise. Deformation source mechanisms in the Cascades are diverse and include magma accumulation and withdrawal, post-emplacement cooling of recent volcanic deposits, magmatic

  12. Volcanology and volcano sedimentology of Sahand region

    International Nuclear Information System (INIS)

    Moine Vaziri, H.; Amine Sobhani, E.

    1977-01-01

    There was no volcano in Precambrian and Mesozoic eras in Iran, but in most place of Iran during the next eras volcanic rocks with green series and Dacites were seen. By the recent survey in Sahand mountain in NW of Iran volcanography, determination of rocks and the age of layers were estimated. The deposits of Precambrian as sediment rocks are also seen in the same area. All of volcanic periods in this place were studied; their extrusive rocks, their petrography and the result of their analytical chemistry were discussed. Finally volcano sedimentology of Sahand mountain were described

  13. The origin of the Hawaiian Volcano Observatory

    Energy Technology Data Exchange (ETDEWEB)

    Dvorak, John [University of Hawaii' s Institute for Astronomy (United States)

    2011-05-15

    I first stepped through the doorway of the Hawaiian Volcano Observatory in 1976, and I was impressed by what I saw: A dozen people working out of a stone-and-metal building perched at the edge of a high cliff with a spectacular view of a vast volcanic plain. Their primary purpose was to monitor the island's two active volcanoes, Kilauea and Mauna Loa. I joined them, working for six weeks as a volunteer and then, years later, as a staff scientist. That gave me several chances to ask how the observatory had started.

  14. Recent Inflation of Kilauea Volcano

    Science.gov (United States)

    Miklius, A.; Poland, M.; Desmarais, E.; Sutton, A.; Orr, T.; Okubo, P.

    2006-12-01

    Over the last three years, geodetic monitoring networks and satellite radar interferometry have recorded substantial inflation of Kilauea's magma system, while the Pu`u `O`o eruption on the east rift zone has continued unabated. Combined with the approximate doubling of carbon dioxide emission rates at the summit during this period, these observations indicate that the magma supply rate to the volcano has increased. Since late 2003, the summit area has risen over 20 cm, and a 2.5 km-long GPS baseline across the summit area has extended almost half a meter. The center of inflation has been variable, with maximum uplift shifting from an area near the center of the caldera to the southeastern part of the caldera in 2004-2005. In 2006, the locus of inflation shifted again, to the location of the long-term magma reservoir in the southern part of the caldera - the same area that had subsided more than 1.5 meters during the last 23 years of the ongoing eruption. In addition, the southwest rift zone reversed its long-term trend of subsidence and began uplifting in early 2006. The east rift zone has shown slightly accelerated rates of extension, but with a year-long hiatus following the January 2005 south flank aseismic slip event. Inflation rates have varied greatly. Accelerated rates of extension and uplift in early 2005 and 2006 were also associated with increased seismicity. Seismicity occurred not only at inflation centers, but was also triggered on the normal faulting area northwest of the caldera and the strike-slip faulting area in the upper east rift zone. In early 2006, at about the time that we started recording uplift on the southwest rift zone, the rate of earthquakes extending from the summit into the southwest rift zone at least quadrupled. The most recent previous episode of inflation at Kilauea, in 2002, may have resulted from reduced lava- transport capacity, as it was associated with decreased outflow at the eruption site. In contrast, eruption volumes

  15. The 2012-2014 eruptive cycle of Copahue Volcano, Southern Andes. Magmatic-Hydrothermal system interaction and manifestations.

    Science.gov (United States)

    Morales, Sergio; Alarcón, Alex; Basualto, Daniel; Bengoa, Cintia; Bertín, Daniel; Cardona, Carlos; Córdova, Maria; Franco, Luis; Gil, Fernando; Hernandez, Erasmo; Lara, Luis; Lazo, Jonathan; Mardones, Cristian; Medina, Roxana; Peña, Paola; Quijada, Jonathan; San Martín, Juan; Valderrama, Oscar

    2015-04-01

    Copahue Volcano (COPV), in Southern Andes of Chile, is an andesitic-basaltic stratovolcano, which is located on the western margin of Caviahue Caldera. The COPV have a NE-trending fissure with 9 aligned vents, being El Agrio the main currently active vent, with ca. 400 m in diameter. The COPV is placed into an extensive hydrothermal system which has modulated its recent 2012-2014 eruptive activity, with small phreatic to phreatomagmatic eruptions and isolated weak strombolian episodes and formation of crater lakes inside the main crater. Since 2012, the Southern Andes Volcano Observatory (OVDAS) carried out the real-time monitoring with seismic broadband stations, GPS, infrasound sensors and webcams. In this work, we report pre, sin, and post-eruptive seismic activity of the last two main eruptions (Dec, 2012 and Oct, 2014) both with different seismic precursors and superficial activity, showing the second one a particularly appearance of seismic quiescence episodes preceding explosive activity, as an indicator of interaction between magmatic-hydrothermal systems. The first episode, in late 2012, was characterized by a low frequency (0.3-0.4 Hz and 1.0-1.5 Hz) continuous tremor which increased gradually from background noise level amplitude to values of reduced displacement (DR), close to 50 cm2 at the peak of the eruption, reaching an eruptive column of ~1.5 km height. After few months of recording low energy seismicity, a sequence of low frequency, repetitive and low energy seismic events arose, with a frequency of occurrence up to 300 events/hour. Also, the VLP earthquakes were added to the record probably associated with magma intrusion into a deep magmatic chamber during all stages of eruptive process, joined to the record of VT seismicity during the same period, which is located throughout the Caviahue Caldera area. Both kind of seismic patterns were again recorded in October 2014, being the precursor of the new eruptive cycle at this time as well as the

  16. Volcanic activity in the Acambay Graben: a < 25 Ka subplinian eruption from the Temascalcingo volcano and implications for volcanic hazard.

    Science.gov (United States)

    Pedrazzi, Dario; Aguirre Díaz, Gerardo; Sunyé Puchol, Ivan; Bartolini, Stefania; Geyer, Adelina

    2016-04-01

    The Trans-Mexican Volcanic Belt (TMVB) contains a large number of stratovolcanoes, some well-known, as Popocatepetl, Iztaccihuatl, Nevado de Toluca, or Colima and many others of more modest dimensions that are not well known but constitute the majority in the TMVB. Such volcanoes are, for example, Tequila, San Juan, Sangangüey, Cerro Culiacán, Cerro Grande, El Zamorano, La Joya, Palo Huerfano, Jocotitlán, Altamirano and Temascalcingo, among many others. The Temascalcingo volcano (TV) is an andesitic-dacitic stratovolcano located in the Trans-Mexican Volcanic Belt (TMVB) at the eastern part of the Acambay Graben (northwest portion of Estado de México). The TV is composed mainly by dacitic, porphyritic lavas, block and ash deposits and subordinate pumice fall deposits and ignimbrites (Roldán-Quintana et al., 2011). The volcanic structure includes a summit caldera that has a rectangular shape, 2.5×3.5 km, with the largest side oriented E-W, parallel to major normal faults affecting the edifice. The San Mateo Pumice eruption is one of the greatest paroxysmal episodes of this volcano with pumice deposits mainly exposed at the scarp of the Acambay-Tixmadeje fault and at the northern and northeastern flanks of TV. It overlies a paleosol dated at 25 Ka. A NE-trending dispersion was obtained from field data covering an area of at least 80 km2. These deposits overlie older lava flows and mud flows and are discontinuously covered and eroded by younger reworked deposits of Temascalcingo volcano. This event represents a highly explosive phase that generated a relatively thick and widespread pumice fallout deposit that may occur again in future eruptions. A similar eruption today would have a significantly impact in the region, overall due to the fact that there has been no systematic assessment of the volcanic hazard in any of the studies that have been conducted so far in the area. So, this is a pending and urgent subject that must be tackled without delay. Financed by

  17. Production of nuclear graphite in France; Production de graphite nucleaire en France

    Energy Technology Data Exchange (ETDEWEB)

    Legendre, P; Mondet, L [Societe Pechiney, 74 - Chedde (France); Arragon, Ph; Cornuault, P; Gueron, J; Hering, H [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

    1955-07-01

    The graphite intended for the construction of the reactors is obtained by the usual process: confection of a cake from coke of oil and tar, cooked (in a electric oven) then the product of cook is graphitized, also by electric heating. The use of the air transportation and the control of conditions cooking and graphitization have permitted to increase the nuclear graphite production as well as to better control their physical and mechanical properties and to reduce to the minimum the unwanted stains. (M.B.) [French] Le graphite destine a la construction des reacteurs est obtenu par le procede usuel: confection d'une pate a partir de coke de petrole et de brai, cuisson de cette pate (au four electrique) puis graphitation du produit cuit, egalement par chauffage electrique. L'usage du transport pneumatique et le controle des conditions cuisson et de graphitation ont permit d'augmenter la production de graphite nucleaire ainsi que de mieux controler ses proprietes physiques et mecaniques et de reduire au minimum les souillures accidentelles. (M.B.)

  18. Temperature distribution in graphite during annealing in air cooled reactors

    International Nuclear Information System (INIS)

    Oliveira Avila, C.R. de.

    1989-01-01

    A model for the evaluation temperature distributions in graphite during annealing operation in graphite. Moderated an-cooled reactors, is presented. One single channel and one dimension for air and graphite were considered. A numerical method based on finite control volumes was used for partioning the mathematical equations. The problem solution involves the use of unsteady equations of mass, momentum and energy conservation for air, and energy conservation for graphite. The source term was considered as stored energy release during annealing for describing energy conservation in the graphite. The coupling of energy conservation equations in air and graphite is performed by the heat transfer term betwen air and graphite. The results agree with experimental data. A sensitivity analysis shown that the termal conductivity of graphite and the maximum inlet channel temperature have great effect on the maximum temperature reached in graphite during the annealing. (author)

  19. Growth and degradation of Hawaiian volcanoes: Chapter 3 in Characteristics of Hawaiian volcanoes

    Science.gov (United States)

    Clague, David A.; Sherrod, David R.; Poland, Michael P.; Takahashi, T. Jane; Landowski, Claire M.

    2014-01-01

    The 19 known shield volcanoes of the main Hawaiian Islands—15 now emergent, 3 submerged, and 1 newly born and still submarine—lie at the southeast end of a long-lived hot spot chain. As the Pacific Plate of the Earth’s lithosphere moves slowly northwestward over the Hawaiian hot spot, volcanoes are successively born above it, evolve as they drift away from it, and eventually die and subside beneath the ocean surface.

  20. Graphite matrix materials for nuclear waste isolation

    International Nuclear Information System (INIS)

    Morgan, W.C.

    1981-06-01

    At low temperatures, graphites are chemically inert to all but the strongest oxidizing agents. The raw materials from which artificial graphites are produced are plentiful and inexpensive. Morover, the physical properties of artificial graphites can be varied over a very wide range by the choice of raw materials and manufacturing processes. Manufacturing processes are reviewed herein, with primary emphasis on those processes which might be used to produce a graphite matrix for the waste forms. The approach, recommended herein, involves the low-temperature compaction of a finely ground powder produced from graphitized petroleum coke. The resultant compacts should have fairly good strength, low permeability to both liquids and gases, and anisotropic physical properties. In particular, the anisotropy of the thermal expansion coefficients and the thermal conductivity should be advantageous for this application. With two possible exceptions, the graphite matrix appears to be superior to the metal alloy matrices which have been recommended in prior studies. The two possible exceptions are the requirements on strength and permeability; both requirements will be strongly influenced by the containment design, including the choice of materials and the waste form, of the multibarrier package. Various methods for increasing the strength, and for decreasing the permeability of the matrix, are reviewed and discussed in the sections in Incorporation of Other Materials and Elimination of Porosity. However, it would be premature to recommend a particular process until the overall multi-barrier design is better defined. It is recommended that increased emphasis be placed on further development of the low-temperature compacted graphite matrix concept

  1. Method of producing exfoliated graphite, flexible graphite, and nano-scaled graphene platelets

    Science.gov (United States)

    Zhamu, Aruna; Shi, Jinjun; Guo, Jiusheng; Jang, Bor Z.

    2010-11-02

    The present invention provides a method of exfoliating a layered material (e.g., graphite and graphite oxide) to produce nano-scaled platelets having a thickness smaller than 100 nm, typically smaller than 10 nm. The method comprises (a) dispersing particles of graphite, graphite oxide, or a non-graphite laminar compound in a liquid medium containing therein a surfactant or dispersing agent to obtain a stable suspension or slurry; and (b) exposing the suspension or slurry to ultrasonic waves at an energy level for a sufficient length of time to produce separated nano-scaled platelets. The nano-scaled platelets are candidate reinforcement fillers for polymer nanocomposites. Nano-scaled graphene platelets are much lower-cost alternatives to carbon nano-tubes or carbon nano-fibers.

  2. EEL Calculations and Measurements of Graphite and Graphitic-CNx Core-Losses

    International Nuclear Information System (INIS)

    Seepujak, A; Bangert, U; Harvey, A J; Blank, V D; Kulnitskiy, B A; Batov, D V

    2006-01-01

    Core EEL spectra of MWCNTs (multi-wall carbon nanotubes) grown in a nitrogen atmosphere were acquired utilising a dedicated STEM equipped with a Gatan Enfina system. Splitting of the carbon K-edge π* resonance into two peaks provided evidence of two nondegenerate carbon bonding states. In order to confirm the presence of a CN x bonding state, a full-potential linearised augmented plane-wave method was utilised to simulate core EEL spectra of graphite and graphitic-CN x compounds. The simulations confirmed splitting of the carbon K-edge π* resonance in graphitic-CN x materials, with the pristine graphite π* resonance remaining unsplit. The simulations also confirmed the increasing degree of amorphicity with higher concentrations (25%) of substitutional nitrogen in graphite

  3. Removal of 14C from Irradiated Graphite for Graphite Recycle and Waste Volume Reduction

    International Nuclear Information System (INIS)

    Dunzik-Gougar, Mary Lou; Windes, Will; Marsden, Barry

    2014-01-01

    The aim of the research presented here was to identify the chemical form of 14 C in irradiated graphite. A greater understanding of the chemical form of this longest-lived isotope in irradiated graphite will inform not only management of legacy waste, but also development of next generation gas-cooled reactors. Approximately 250,000 metric tons of irradiated graphite waste exists worldwide, with the largest single quantity originating in the Magnox and AGR reactors of UK. The waste quantity is expected to increase with decommissioning of Generation II reactors and deployment of Generation I gas-cooled, graphite moderated reactors. Of greatest concern for long-term disposal of irradiated graphite is carbon-14 14 C, with a half-life of 5730 years.

  4. Probing magma reservoirs to improve volcano forecasts

    Science.gov (United States)

    Lowenstern, Jacob B.; Sisson, Thomas W.; Hurwitz, Shaul

    2017-01-01

    When it comes to forecasting eruptions, volcano observatories rely mostly on real-time signals from earthquakes, ground deformation, and gas discharge, combined with probabilistic assessments based on past behavior [Sparks and Cashman, 2017]. There is comparatively less reliance on geophysical and petrological understanding of subsurface magma reservoirs.

  5. Biological Studies on a Live Volcano.

    Science.gov (United States)

    Zipko, Stephen J.

    1992-01-01

    Describes scientific research on an Earthwatch expedition to study Arenal, one of the world's most active volcanoes, in north central Costa Rica. The purpose of the two-week project was to monitor and understand the past and ongoing development of a small, geologically young, highly active stratovolcano in a tropical, high-rainfall environment.…

  6. Of volcanoes, saints, trash, and frogs

    DEFF Research Database (Denmark)

    Andersen, Astrid Oberborbeck

    , at the same time as political elections and economic hardship. During one year of ethnographic fieldwork volcanoes, saints, trash and frogs were among the nonhuman entities referred to in conversations and engaged with when responding to the changes that trouble the world and everyday life of Arequipans...

  7. Geophysical monitoring of the Purace volcano, Colombia

    Directory of Open Access Journals (Sweden)

    M. Arcila

    1996-06-01

    Full Text Available Located in the extreme northwestern part of the Los Coconucos volcanic chain in the Central Cordillera, the Purace is one of Colombia's most active volcanoes. Recent geological studies indicate an eruptive history of mainly explosive behavior which was marked most recently by a minor ash eruption in 1977. Techniques used to forecast the renewal of activity of volcanoes after a long period of quiescence include the monitoring of seismicity and ground deformation near the volcano. As a first approach toward the monitoring of the Purace volcano, Southwest Seismological Observatory (OSSO, located in the city of Cali, set up one seismic station in 1986. Beginning in June 1991, the seismic signals have also been transmitted to the Colombian Geological Survey (INGEOMINAS at the Volcanological and Seismological Observatory (OVS-UOP, located in the city of Popayan. Two more seismic stations were installed early in 1994 forming a minimum seismic network and a geodetic monitoring program for ground deformation studies was established and conducted by INGEOMINAS.

  8. Muons reveal the interior of volcanoes

    CERN Multimedia

    Francesco Poppi

    2010-01-01

    The MU-RAY project has the very challenging aim of providing a “muon X-ray” of the Vesuvius volcano (Italy) using a detector that records the muons hitting it after traversing the rock structures of the volcano. This technique was used for the first time in 1971 by the Nobel Prize-winner Louis Alvarez, who was searching for unknown burial chambers in the Chephren pyramid.   The location of the muon detector on the slopes of the Vesuvius volcano. Like X-ray scans of the human body, muon radiography allows researchers to obtain an image of the internal structures of the upper levels of volcanoes. Although such an image cannot help to predict ‘when’ an eruption might occur, it can, if combined with other observations, help to foresee ‘how’ it could develop and serves as a powerful tool for the study of geological structures. Muons come from the interaction of cosmic rays with the Earth's atmosphere. They are able to traverse layers of ro...

  9. Gas transport in graphitic materials

    International Nuclear Information System (INIS)

    Hoinkis, E.

    1995-02-01

    The characterization of the gas transport properties of porous solids is of interest in several fields of science and technology. Many catalysts, adsorbents, soils, graphites and carbons are porous. The gas transport through most porous solids can be well described by the dusty gas model invented by Evans, Watson and Mason. This model includes all modes of gas tranport under steady-state conditions, which are Knudsen diffusion, combined Knudsen/continuum diffusion and continuum diffusion, both for gas pairs with equal and different molecular weights. In the absence of a pressure difference gas transport in a pore system can be described by the combined Knudsen/continuum diffusion coefficient D 1 for component 1 in the pores, the Knudsen diffusion coefficient D 1K in the pores, and the continuum diffusion coefficient D 12 for a binary mixture in the pores. The resistance to stationary continuum diffusion of the pores is characterized by a geometrical factor (ε/τ) 12 = (ε/τ)D 12 , were D 12 is the continuum diffusion coefficient for a binary mixture in free space. The Wicke-Kallenbach method was often used to measure D 1 as function of pressure. D 12 and D 1K can be derived from a plot 1/D 1 νs P, and ε/τcan be calculated since D 12 is known. D 1K and the volume of dead end pores can be derived from transient measurements of the diffusional flux at low pressures. From D 1K the expression (ε/τ c ) anti l por may be calculated, which characterizes the pore system for molecular diffusion, where collisions with the pore walls are predominant. (orig.)

  10. False Color Image of Volcano Sapas Mons

    Science.gov (United States)

    1991-01-01

    This false-color image shows the volcano Sapas Mons, which is located in the broad equatorial rise called Atla Regio (8 degrees north latitude and 188 degrees east longitude). The area shown is approximately 650 kilometers (404 miles) on a side. Sapas Mons measures about 400 kilometers (248 miles) across and 1.5 kilometers (0.9 mile) high. Its flanks show numerous overlapping lava flows. The dark flows on the lower right are thought to be smoother than the brighter ones near the central part of the volcano. Many of the flows appear to have been erupted along the flanks of the volcano rather than from the summit. This type of flank eruption is common on large volcanoes on Earth, such as the Hawaiian volcanoes. The summit area has two flat-topped mesas, whose smooth tops give a relatively dark appearance in the radar image. Also seen near the summit are groups of pits, some as large as one kilometer (0.6 mile) across. These are thought to have formed when underground chambers of magma were drained through other subsurface tubes and lead to a collapse at the surface. A 20 kilometer-diameter (12-mile diameter) impact crater northeast of the volcano is partially buried by the lava flows. Little was known about Atla Regio prior to Magellan. The new data, acquired in February 1991, show the region to be composed of at least five large volcanoes such as Sapas Mons, which are commonly linked by complex systems of fractures or rift zones. If comparable to similar features on Earth, Atla Regio probably formed when large volumes of molten rock upwelled from areas within the interior of Venus known as'hot spots.' Magellan is a NASA spacecraft mission to map the surface of Venus with imaging radar. The basic scientific instrument is a synthetic aperture radar, or SAR, which can look through the thick clouds perpetually shielding the surface of Venus. Magellan is in orbit around Venus which completes one turn around its axis in 243 Earth days. That period of time, one Venus day

  11. Hazard maps of Colima volcano, Mexico

    Science.gov (United States)

    Suarez-Plascencia, C.; Nunez-Cornu, F. J.; Escudero Ayala, C. R.

    2011-12-01

    Colima volcano, also known as Volcan de Fuego (19° 30.696 N, 103° 37.026 W), is located on the border between the states of Jalisco and Colima and is the most active volcano in Mexico. Began its current eruptive process in February 1991, in February 10, 1999 the biggest explosion since 1913 occurred at the summit dome. The activity during the 2001-2005 period was the most intense, but did not exceed VEI 3. The activity resulted in the formation of domes and their destruction after explosive events. The explosions originated eruptive columns, reaching attitudes between 4,500 and 9,000 m.a.s.l., further pyroclastic flows reaching distances up to 3.5 km from the crater. During the explosive events ash emissions were generated in all directions reaching distances up to 100 km, slightly affected nearby villages as Tuxpan, Tonila, Zapotlán, Cuauhtemoc, Comala, Zapotitlan de Vadillo and Toliman. During the 2005 this volcano has had an intense effusive-explosive activity, similar to the one that took place during the period of 1890 through 1900. Intense pre-plinian eruption in January 20, 1913, generated little economic losses in the lower parts of the volcano due to low population density and low socio-economic activities at the time. Shows the updating of the volcanic hazard maps published in 2001, where we identify whit SPOT satellite imagery and Google Earth, change in the land use on the slope of volcano, the expansion of the agricultural frontier on the east and southeast sides of the Colima volcano, the population inhabiting the area is approximately 517,000 people, and growing at an annual rate of 4.77%, also the region that has shown an increased in the vulnerability for the development of economic activities, supported by the construction of highways, natural gas pipelines and electrical infrastructure that connect to the Port of Manzanillo to Guadalajara city. The update the hazard maps are: a) Exclusion areas and moderate hazard for explosive events

  12. The Effect of CO2 on Partial Reactive Crystallization of MORB-Eclogite-derived Basaltic Andesite in Peridotite and Generation of Silica-Undersaturated Basalts

    Science.gov (United States)

    Mallik, A.; Dasgupta, R.

    2012-12-01

    Recycled oceanic crust (MORB-eclogite) is considered to be the dominant heterogeneity in Earth's mantle. Because MORB-eclogite is more fusible than peridotite, siliceous partial melt derived from it must react with peridotite while the latter is still in the subsolidus state. Thus, studying such reactive process is important in understanding melting dynamics of the Earth's mantle. Reaction of MORB-eclogite-derived andesitic partial melt with peridotite can produce alkalic melts by partial reactive crystallization but these melts are not as silica-undersaturated as many natural basanites, nephelinites or melititites [1]. In this study, we constrain how dissolved CO2 in a siliceous MORB-eclogite-derived partial melt affects the reaction phase equilibria involving peridotite and can produce nephelinitic melts. Here we compare experiments on CO2-free [1] and 2.6 wt.% CO2 bearing andesitic melt+lherzolite mixtures conducted at 1375 °C and 3 GPa with added melt fraction of 8-50 wt.%. In both CO2-free and CO2-bearing experiments, melt and olivine are consumed and opx and garnet are produced, with the extent of modal change for a given melt-rock ratio being greater for the CO2-bearing experiments. While the residue evolves to a garnet websterite by adding 40% of CO2-bearing melt, the residue becomes olivine-free by adding 50% of the CO2-free melt. Opx mode increases from 12 to ~55 wt.% for 0 to 40% melt addition in CO2-bearing system and 12 to ~43 wt.% for 0 to 50% melt addition in CO2-free system. Garnet mode, for a similar range of melt-rock ratio, increases from ~10 to ~15 wt.% for CO2 bearing system and to ~11 wt.% for CO2-free system. Reacted melts from 25-33% of CO2-bearing melt-added runs contain ~39 wt.% SiO2 , ~11-13 wt.% TiO2, ~9 wt.% Al2O3, ~11 wt.% FeO*, 16 wt.% MgO, 10-11 wt.% CaO, and 3 wt.% Na2O whereas experiments with a similar melt-rock ratio in a CO2-free system yield melts with 44-45 wt.% SiO2, 6-7 wt.% TiO2, 13-14 wt.% Al2O3, 10-11 wt.% FeO*, 12-13 wt

  13. Influence of Metal-Coated Graphite Powders on Microstructure and Properties of the Bronze-Matrix/Graphite Composites

    Science.gov (United States)

    Zhao, Jian-hua; Li, Pu; Tang, Qi; Zhang, Yan-qing; He, Jian-sheng; He, Ke

    2017-02-01

    In this study, the bronze-matrix/x-graphite (x = 0, 1, 3 and 5%) composites were fabricated by powder metallurgy route by using Cu-coated graphite, Ni-coated graphite and pure graphite, respectively. The microstructure, mechanical properties and corrosive behaviors of bronze/Cu-coated-graphite (BCG), bronze/Ni-coated-graphite (BNG) and bronze/pure-graphite (BPG) were characterized and investigated. Results show that the Cu-coated and Ni-coated graphite could definitely increase the bonding quality between the bronze matrix and graphite. In general, with the increase in graphite content in bronze-matrix/graphite composites, the friction coefficients, ultimate density and wear rates of BPG, BCG and BNG composites all went down. However, the Vickers microhardness of the BNG composite would increase as the graphite content increased, which was contrary to the BPG and BCG composites. When the graphite content was 3%, the friction coefficient of BNG composite was more stable than that of BCG and BPG composites, indicating that BNG composite had a better tribological performance than the others. Under all the values of applied loads (10, 20, 40 and 60N), the BCG and BNG composites exhibited a lower wear rate than BPG composite. What is more, the existence of nickel in graphite powders could effectively improve the corrosion resistance of the BNG composite.

  14. Glassy carbon coated graphite for nuclear applications

    International Nuclear Information System (INIS)

    Delpeux S; Cacciaguerra T; Duclaux L

    2005-01-01

    Taking into account the problems caused by the treatment of nuclear wastes, the molten salts breeder reactors are expected to a great development. They use a molten fluorinated salt (mixture of LiF, BeF 2 , ThF 4 , and UF 4 ) as fuel and coolant. The reactor core, made of graphite, is used as a neutrons moderator. Despite of its compatibility with nuclear environment, it appears crucial to improve the stability and inertness of graphite against the diffusion of chemicals species leading to its corrosion. One way is to cover the graphite surface by a protective impermeable deposit made of glassy carbon obtained by the pyrolysis of phenolic resin or polyvinyl chloride precursors. The main difficulty in the synthesis of glassy carbon is to create exclusively, in the primary pyrolysis product, a micro-porosity of about twenty Angstroms which closes later at higher temperature. Therefore, the evacuation of the volatile products occurring mainly between 330 and 600 C, must progress slowly to avoid the material to crack. In this study, the optimal parameters for the synthesis of glassy carbon as well as glassy carbon deposits on nuclear-type graphite pieces are discussed. Both thermal treatment of phenolic and PVC resins have been performed. The structure and micro-texture of glassy carbon have been investigated by X-ray diffraction, scanning and transmission electron microscopies and helium pycno-metry. Glassy carbon samples (obtained at 1200 C) show densities ranging from 1.3 to 1.55 g/cm 3 and closed pores with nano-metric size (∼ 5 to 10 nm) appear clearly on the TEM micrographs. Then, a thermal treatment to 2700 C leads to the shrinkage of the entangled graphene ribbons, in good agreement with the proposed texture model for glassy carbon. Glassy carbon deposits on nuclear graphite have been developed by an impregnation method. The uniformity of the deposit depends clearly on the surface texture and the chemistry of the graphite substrate. The deposit regions where

  15. Glassy carbon coated graphite for nuclear applications

    Energy Technology Data Exchange (ETDEWEB)

    Delpeux, S.; Cacciaguerra, T.; Duclaux, L. [Orleans Univ., CRMD, CNRS, 45 (France)

    2005-07-01

    Taking into account the problems caused by the treatment of nuclear wastes, the molten salts breeder reactors are expected to a great development. They use a molten fluorinated salt (mixture of LiF, BeF{sub 2}, ThF{sub 4}, and UF{sub 4}) as fuel and coolant. The reactor core, made of graphite, is used as a neutrons moderator. Despite of its compatibility with nuclear environment, it appears crucial to improve the stability and inertness of graphite against the diffusion of chemicals species leading to its corrosion. One way is to cover the graphite surface by a protective impermeable deposit made of glassy carbon obtained by the pyrolysis of phenolic resin [1,2] or polyvinyl chloride [3] precursors. The main difficulty in the synthesis of glassy carbon is to create exclusively, in the primary pyrolysis product, a micro-porosity of about twenty Angstroms which closes later at higher temperature. Therefore, the evacuation of the volatile products occurring mainly between 330 and 600 C, must progress slowly to avoid the material to crack. In this study, the optimal parameters for the synthesis of glassy carbon as well as glassy carbon deposits on nuclear-type graphite pieces are discussed. Both thermal treatment of phenolic and PVC resins have been performed. The structure and micro-texture of glassy carbon have been investigated by X-ray diffraction, scanning and transmission electron microscopies and helium pycno-metry. Glassy carbon samples (obtained at 1200 C) show densities ranging from 1.3 to 1.55 g/cm{sup 3} and closed pores with nano-metric size ({approx} 5 to 10 nm) appear clearly on the TEM micrographs. Then, a thermal treatment to 2700 C leads to the shrinkage of the entangled graphene ribbons (Fig 1), in good agreement with the proposed texture model for glassy carbon (Fig 2) [4]. Glassy carbon deposits on nuclear graphite have been developed by an impregnation method. The uniformity of the deposit depends clearly on the surface texture and the chemistry

  16. Mauna Kea volcano's ongoing 18-year swarm

    Science.gov (United States)

    Wech, A.; Thelen, W. A.

    2017-12-01

    Mauna Kea is a large postshield-stage volcano that forms the highest peak on Hawaii Island. The 4,205-meter high volcano erupted most recently between 6,000 and 4,500 years ago and exhibits relatively low rates of seismicity, which are mostly tectonic in origin resulting from lithospheric flexure under the weight of the volcano. Here we identify deep repeating earthquakes occurring beneath the summit of Mauna Kea. These earthquakes, which are not part of the Hawaiian Volcano Observatory's regional network catalog, were initially detected through a systematic search for coherent seismicity using envelope cross-correlation, and subsequent analysis revealed the presence of a long-term, ongoing swarm. The events have energy concentrated at 2-7 Hz, and can be seen in filtered waveforms dating back to the earliest continuous data from a single station archived at IRIS from November 1999. We use a single-station (3 component) match-filter analysis to create a catalog of the repeating earthquakes for the past 18 years. Using two templates created through phase-weighted stacking of thousands of sta/lta-triggers, we find hundreds of thousands of M1.3-1.6 earthquakes repeating every 7-12 minutes throughout this entire time period, with many smaller events occurring in between. The earthquakes occur at 28-31 km depth directly beneath the summit within a conspicuous gap in seismicity surrounding the flanks of the volcano. Magnitudes and periodicity are remarkably stable long-term, but do exhibit slight variability and occasionally display higher variability on shorter time scales. Network geometry precludes obtaining a reliable focal mechanism, but we interpret the frequency content and hypocenters to infer a volcanic source distinct from the regional tectonic seismicity responding to the load of the island. In this model, the earthquakes may result from the slow, persistent degassing of a relic magma chamber at depth.

  17. Geochemical studies on island arc volcanoes

    International Nuclear Information System (INIS)

    Notsu, Kenji

    1998-01-01

    This paper summarizes advances in three topics of geochemical studies on island arc volcanoes, which I and my colleagues have been investigating. First one is strontium isotope studies of arc volcanic rocks mainly from Japanese island arcs. We have shown that the precise spatial distribution of the 87 Sr/ 86 Sr ratio reflects natures of the subduction structure and slab-mantle interaction. Based on the 87 Sr/ 86 Sr ratio of volcanic rocks in the northern Kanto district, where two plates subduct concurrently with different directions, the existence of an aseismic portion of the Philippine Sea plate ahead of the seismic one was suggested. Second one is geochemical monitoring of active arc volcanoes. 3 He/ 4 He ratio of volcanic volatiles was shown to be a good indicator to monitor the behavior of magma: ascent and drain-back of magma result in increase and decrease in the ratio, respectively. In the case of 1986 eruptions of Izu-Oshima volcano, the ratio began to increase two months after big eruptions, reaching the maximum and decreased. Such delayed response is explained in terms of travelling time of magmatic helium from the vent area to the observation site along the underground steam flow. Third one is remote observation of volcanic gas chemistry of arc volcanoes, using an infrared absorption spectroscopy. During Unzen eruptions starting in 1990, absorption features of SO 2 and HCl of volcanic gas were detected from the observation station at 1.3 km distance. This was the first ground-based remote detection of HCl in volcanic gas. In the recent work at Aso volcano, we could identify 5 species (CO, COS, CO 2 , SO 2 and HCl) simultaneously in the volcanic plume spectra. (author)

  18. Hydrogen adsorption on and solubility in graphites

    International Nuclear Information System (INIS)

    Kanashenko, S.L.; Wampler, W.R.

    1996-01-01

    The experimental data on adsorption and solubility of hydrogen isotopes in graphite over a wide range of temperatures and pressures are reviewed. Langmuir adsorption isotherms are proposed for the hydrogen-graphite interaction. The entropy and enthalpy of adsorption are estimated, allowing for effects of relaxation of dangling sp 2 bonds. Three kinds of traps are proposed: edge carbon atoms of interstitial loops with an adsorption enthalpy relative to H 2 gas of -4.4 eV/H 2 (unrelaxed, Trap 1), edge carbon atoms at grain surfaces with an adsorption enthalpy of -2.3 eV/H 2 (relaxed, Trap 2), and basal plane adsorption sites with an enthalpy of +2.43 eV/H 2 (Trap 3). The adsorption capacity of different types of graphite depends on the concentration of traps which depends on the crystalline microstructure of the material. The number of potential sites for the 'true solubility' (Trap 3) is assumed to be about one site per carbon atom in all types of graphite, but the endothermic character of this solubility leads to a negligible H inventory compared to the concentration of hydrogen in type 1 and type 2 traps for temperatures and gas pressures used in the experiments. Irradiation with neutrons or carbon atoms increases the concentration of type 1 and type 2 traps from about 20 and 200 appm respectively for unirradiated (POCO AXF-5Q) graphite to about 1500 and 5000 appm, respectively, at damage levels above 1 dpa. (orig.)

  19. Irradiation-induced amorphization process in graphite

    Energy Technology Data Exchange (ETDEWEB)

    Abe, Hiroaki [Japan Atomic Energy Research Inst., Takasaki, Gunma (Japan). Takasaki Radiation Chemistry Research Establishment

    1996-04-01

    Effects of the element process of irradiation damage on irradiation-induced amorphization processes of graphite was studied. High orientation thermal decomposed graphite was cut about 100 nm width and used as samples. The irradiation experiments are carried out under the conditions of electronic energy of 100-400 KeV, ion energy of 200-600 KeV, ionic species Xe, Ar, Ne, C and He and the irradiation temperature at from room temperature to 900 K. The critical dose ({phi}a) increases exponentially with increasing irradiation temperature. The displacement threshold energy of graphite on c-axis direction was 27 eV and {phi}a{sup e} = 0.5 dpa. dpa is the average number of displacement to atom. The critical dose of ion irradiation ({phi}a{sup i}) was 0.2 dpa at room temperature, and amorphous graphite was produced by less than half of dose of electronic irradiation. Amorphization of graphite depending upon temperature is discussed. (S.Y.)

  20. Pre-eruption deformation caused by dike intrusion beneath Kizimen volcano, Kamchatka, Russia, observed by InSAR

    Science.gov (United States)

    Ji, Lingyun; Lu, Zhong; Dzurisin, Daniel; Senyukov, Sergey

    2013-01-01

    Interferometric synthetic aperture radar (InSAR) images reveal a pre-eruption deformation signal at Kizimen volcano, Kamchatka, Russia, where an ongoing eruption began in mid-November, 2010. The previous eruption of this basaltic andesite-to-dacite stratovolcano occurred in 1927–1928. InSAR images from both ascending and descending orbital passes of Envisat and ALOS PALSAR satellites show as much as 6 cm of line-of-sight shortening from September 2008 to September 2010 in a broad area centered at Kizimen. About 20 cm of opening of a nearly vertical dike provides an adequate fit to the surface deformation pattern. The model dike is approximately 14 km long, 10 km high, centered 13 km beneath Kizimen, and strikes NE–SW. Time-series analysis of multi-temporal interferograms indicates that (1) intrusion started sometime between late 2008 and July 2009, (2) continued at a nearly constant rate, and (3) resulted in a volume expansion of 3.2 × 107 m3 by September 2010, i.e., about two months before the onset of the 2010 eruption. Earthquakes located above the tip of the dike accompanied the intrusion. Eventually, magma pressure in the dike exceeded the confining strength of the host rock, triggering the 2010 eruption. Our results provide insight into the intrusion process that preceded an explosive eruption at a Pacific Rim stratovolcano following nearly a century of quiescence, and therefore have implications for monitoring and hazards assessment at similar volcanoes elsewhere.

  1. Dislocation density and graphitization of diamond crystals

    International Nuclear Information System (INIS)

    Pantea, C.; Voronin, G.A.; Zerda, T.W.; Gubicza, J.; Ungar, T.

    2002-01-01

    Two sets of diamond specimens compressed at 2 GPa at temperatures varying between 1060 K and 1760 K were prepared; one in which graphitization was promoted by the presence of water and another in which graphitization of diamond was practically absent. X-ray diffraction peak profiles of both sets were analyzed for the microstructure by using the modified Williamson-Hall method and by fitting the Fourier coefficients of the measured profiles by theoretical functions for crystallite size and lattice strain. The procedures determined mean size and size distribution of crystallites as well as the density and the character of the dislocations. The same experimental conditions resulted in different microstructures for the two sets of samples. They were explained in terms of hydrostatic conditions present in the graphitized samples

  2. Capacitive behavior of highly-oxidized graphite

    Science.gov (United States)

    Ciszewski, Mateusz; Mianowski, Andrzej

    2014-09-01

    Capacitive behavior of a highly-oxidized graphite is presented in this paper. The graphite oxide was synthesized using an oxidizing mixture of potassium chlorate and concentrated fuming nitric acid. As-oxidized graphite was quantitatively and qualitatively analyzed with respect to the oxygen content and the species of oxygen-containing groups. Electrochemical measurements were performed in a two-electrode symmetric cell using KOH electrolyte. It was shown that prolonged oxidation causes an increase in the oxygen content while the interlayer distance remains constant. Specific capacitance increased with oxygen content in the electrode as a result of pseudo-capacitive effects, from 0.47 to 0.54 F/g for a scan rate of 20 mV/s and 0.67 to 1.15 F/g for a scan rate of 5 mV/s. Better cyclability was observed for the electrode with a higher oxygen amount.

  3. Reactivity of lithium exposed graphite surface

    International Nuclear Information System (INIS)

    Harilal, S.S.; Allain, J.P.; Hassanein, A.; Hendricks, M.R.; Nieto-Perez, M.

    2009-01-01

    Lithium as a plasma-facing component has many attractive features in fusion devices. We investigated chemical properties of the lithiated graphite surfaces during deposition using X-ray photoelectron spectroscopy and low-energy ion scattering spectroscopy. In this study we try to address some of the known issues during lithium deposition, viz., the chemical state of lithium on graphite substrate, oxide layer formation mechanisms, Li passivation effects over time, and chemical change during exposure of the sample to ambient air. X-ray photoelectron studies indicate changes in the chemical composition with various thickness of lithium on graphite during deposition. An oxide layer formation is noticed during lithium deposition even though all the experiments were performed in ultrahigh vacuum. The metal oxide is immediately transformed into carbonate when the deposited sample is exposed to air.

  4. Reduced graphite oxide in supercapacitor electrodes.

    Science.gov (United States)

    Lobato, Belén; Vretenár, Viliam; Kotrusz, Peter; Hulman, Martin; Centeno, Teresa A

    2015-05-15

    The current energy needs have put the focus on highly efficient energy storage systems such as supercapacitors. At present, much attention focuses on graphene-like materials as promising supercapacitor electrodes. Here we show that reduced graphite oxide offers a very interesting potential. Materials obtained by oxidation of natural graphite and subsequent sonication and reduction by hydrazine achieve specific capacitances as high as 170 F/g in H2SO4 and 84F/g in (C2H5)4NBF4/acetonitrile. Although the particle size of the raw graphite has no significant effect on the physico-chemical characteristics of the reduced materials, that exfoliated from smaller particles (materials may suffer from a drop in their specific surface area upon fabrication of electrodes with features of the existing commercial devices. This should be taken into account for a reliable interpretation of their performance in supercapacitors. Copyright © 2015 Elsevier Inc. All rights reserved.

  5. Graphite core design in UK reactors

    International Nuclear Information System (INIS)

    Davies, M.W.

    1996-01-01

    The cores in the first power producing Magnox reactors in the UK were designed with only a limited amount of information available regarding the anisotropic dimensional change behaviour of Pile Grade graphite. As more information was gained it was necessary to make modifications to the design, some minor, some major. As the cores being built became larger, and with the switch to the Advanced Gas-cooled Reactor (AGR) with its much higher power density, additional problems had to be overcome such as increased dimensional change and radiolytic oxidation by the carbon dioxide coolant. For the AGRs a more isotropic graphite was required, with a lower initial open pore volume and higher strength. Gilsocarbon graphite was developed and was selected for all the AGRs built in the UK. Methane bearing coolants are used to limit radiolytic oxidation. (author). 5 figs

  6. Sensing capabilities of graphite based MR elastomers

    International Nuclear Information System (INIS)

    Tian, T F; Li, W H; Deng, Y M

    2011-01-01

    This paper presents both experimental and theoretical investigations of the sensing capabilities of graphite based magnetorheological elastomers (MREs). In this study, eight MRE samples with varying graphite weight fractions were fabricated and their resistance under different magnetic fields and external loadings were measured with a multi-meter. With an increment of graphite weight fraction, the resistance of MRE sample decreases steadily. Higher magnetic fields result in a resistance increase. Based on an ideal assumption of a perfect chain structure, a mathematical model was developed to investigate the relationship between the MRE resistance with external loading. In this model, the current flowing through the chain structure consists of both a tunnel current and a conductivity current, both of which depend on external loadings. The modelling parameters have been identified and reconstructed from comparison with experimental results. The comparison indicates that both experimental results and modelling predictions agree favourably well

  7. Cluster Ion Implantation in Graphite and Diamond

    DEFF Research Database (Denmark)

    Popok, Vladimir

    2014-01-01

    Cluster ion beam technique is a versatile tool which can be used for controllable formation of nanosize objects as well as modification and processing of surfaces and shallow layers on an atomic scale. The current paper present an overview and analysis of data obtained on a few sets of graphite...... and diamond samples implanted by keV-energy size-selected cobalt and argon clusters. One of the emphases is put on pinning of metal clusters on graphite with a possibility of following selective etching of graphene layers. The other topic of concern is related to the development of scaling law for cluster...... implantation. Implantation of cobalt and argon clusters into two different allotropic forms of carbon, namely, graphite and diamond is analysed and compared in order to approach universal theory of cluster stopping in matter....

  8. Graphite based Schottky diodes formed semiconducting substrates

    Science.gov (United States)

    Schumann, Todd; Tongay, Sefaattin; Hebard, Arthur

    2010-03-01

    We demonstrate the formation of semimetal graphite/semiconductor Schottky barriers where the semiconductor is either silicon (Si), gallium arsenide (GaAs) or 4H-silicon carbide (4H-SiC). The fabrication can be as easy as allowing a dab of graphite paint to air dry on any one of the investigated semiconductors. Near room temperature, the forward-bias diode characteristics are well described by thermionic emission, and the extracted barrier heights, which are confirmed by capacitance voltage measurements, roughly follow the Schottky-Mott relation. Since the outermost layer of the graphite electrode is a single graphene sheet, we expect that graphene/semiconductor barriers will manifest similar behavior.

  9. Graphite moderated reactor for thermoelectric generation

    International Nuclear Information System (INIS)

    Akazawa, Issei; Yamada, Akira; Mizogami, Yorikata

    1998-01-01

    Fuel rods filled with cladded fuel particles distributed and filled are buried each at a predetermined distance in graphite blocks situated in a reactor core. Perforation channels for helium gas as coolants are formed to the periphery thereof passing through vertically. An alkali metal thermoelectric power generation module is disposed to the upper lid of a reactor container while being supported by a securing receptacle. Helium gas in the coolant channels in the graphite blocks in the reactor core absorbs nuclear reaction heat, to be heated to a high temperature, rises upwardly by the reduction of the specific gravity, and then flows into an upper space above the laminated graphite block layer. Then the gas collides against a ceiling and turns, and flows down in a circular gap around the circumference of the alkali metal thermoelectric generation module. In this case, it transfers heat to the alkali metal thermoelectric generation module. (I.N.)

  10. Nondestructive evaluation of nuclear-grade graphite

    Science.gov (United States)

    Kunerth, D. C.; McJunkin, T. R.

    2012-05-01

    The material of choice for the core of the high-temperature gas-cooled reactors being developed by the U.S. Department of Energy's Next Generation Nuclear Plant Program is graphite. Graphite is a composite material whose properties are highly dependent on the base material and manufacturing methods. In addition to the material variations intrinsic to the manufacturing process, graphite will also undergo changes in material properties resulting from radiation damage and possible oxidation within the reactor. Idaho National Laboratory is presently evaluating the viability of conventional nondestructive evaluation techniques to characterize the material variations inherent to manufacturing and in-service degradation. Approaches of interest include x-ray radiography, eddy currents, and ultrasonics.

  11. Electrostatic Manipulation of Graphene On Graphite

    Science.gov (United States)

    Untiedt, Carlos; Rubio-Verdu, Carmen; Saenz-Arce, Giovanni; Martinez-Asencio, Jesús; Milan, David C.; Moaied, Mohamed; Palacios, Juan J.; Caturla, Maria Jose

    2015-03-01

    Here we report the use of a Scanning Tunneling Microscope (STM) under ambient and vacuum conditions to study the controlled exfoliation of the last layer of a graphite surface when an electrostatic force is applied from a STM tip. In this work we have focused on the study of two parameters: the applied voltage needed to compensate the graphite interlayer attractive force and the one needed to break atomic bonds to produce folded structures. Additionally, we have studied the influence of edge structure in the breaking geometry. Independently of the edge orientation the graphite layer is found to tear through the zig-zag direction and the lifled layer shows a zig-zag folding direction. Molecular Dinamics simulations and DFT calculations have been performed to understand our results, showing a strong correlation with the experiments. Comunidad Valenciana through Prometeo project.

  12. THE EFFECT OF APPLIED STRESS ON THE GRAPHITIZATION OF PYROLYTIC GRAPHITE

    Energy Technology Data Exchange (ETDEWEB)

    Bragg, R H; Crooks, D D; Fenn, Jr, R W; Hammond, M L

    1963-06-15

    Metallographic and x-ray diffraction studies were made of the effect of applied stress at high temperature on the structure of pyrolytic graphite (PG). The dominant factor was whether the PG was above or below its graphitization temperature, which, in turn, was not strongly dependent on applied stress. Below the graphitization temperature, the PG showed a high proportion of disordered layers (0.9), a fairly large mean tilt angle (20 deg ) and a small crystailite size (La --150 A). Fracture occurred at low stress and strain and the materiai exhibited a high apparent Young's modulus ( approximates 4 x 10/sup 6/ psi). Above the graphitization temperature, graphitization was considerably enhanced by strain up to about 8%. The disorder parameter was decreased from a zero strain value of 0.3 to 0.l5 with strain, the mean tilt angle was decreased to 4 deg , and a fivefold increase in crystallite size occurred. When the strainenhanced graphitization was complete, the material exhibited a low apparent modulus ( approximates 0.5 x 10/sup 6/ psi) and large plastic strains (>100%) for a constant stress ( approximates 55 ksi). Graphitization was shown to be a spontaneous process that is promoted by breaking cross-links thermally, and the process is furthered by chemical attack and plastic strain. (auth)

  13. Space Radar Image of Colombian Volcano

    Science.gov (United States)

    1999-01-01

    This is a radar image of a little known volcano in northern Colombia. The image was acquired on orbit 80 of space shuttle Endeavour on April 14, 1994, by the Spaceborne Imaging Radar C/X-Band Synthetic Aperture Radar (SIR-C/X-SAR). The volcano near the center of the image is located at 5.6 degrees north latitude, 75.0 degrees west longitude, about 100 kilometers (65 miles) southeast of Medellin, Colombia. The conspicuous dark spot is a lake at the bottom of an approximately 3-kilometer-wide (1.9-mile) volcanic collapse depression or caldera. A cone-shaped peak on the bottom left (northeast rim) of the caldera appears to have been the source for a flow of material into the caldera. This is the northern-most known volcano in South America and because of its youthful appearance, should be considered dormant rather than extinct. The volcano's existence confirms a fracture zone proposed in 1985 as the northern boundary of volcanism in the Andes. The SIR-C/X-SAR image reveals another, older caldera further south in Colombia, along another proposed fracture zone. Although relatively conspicuous, these volcanoes have escaped widespread recognition because of frequent cloud cover that hinders remote sensing imaging in visible wavelengths. Four separate volcanoes in the Northern Andes nations ofColombia and Ecuador have been active during the last 10 years, killing more than 25,000 people, including scientists who were monitoring the volcanic activity. Detection and monitoring of volcanoes from space provides a safe way to investigate volcanism. The recognition of previously unknown volcanoes is important for hazard evaluations because a number of major eruptions this century have occurred at mountains that were not previously recognized as volcanoes. Spaceborne Imaging Radar-C and X-band Synthetic Aperture Radar (SIR-C/X-SAR) is part of NASA's Mission to Planet Earth. The radars illuminate Earth with microwaves allowing detailed observations at any time, regardless of

  14. Cementation of Nuclear Graphite Using Geopolymers

    International Nuclear Information System (INIS)

    Girke, N.A.; Steinmetz, H-J.; Bukaemsky, A.; Bosbach, D.; Hermann, E.; Griebel, I.

    2016-01-01

    Geopolymers are solid aluminosilicate materials usually formed by alkali hydroxide or alkali silicate activation of solid precursors such as coal fly ash, calcined clay and/or metallurgical slag. Today the primary application of geopolymer technology is in the development of alternatives to Portland-based cements. Variations in the ratio of aluminium to silicon, and alkali to silicon or addition of structure support, produce geopolymers with different physical and mechanical properties. These materials have an amorphous three-dimensional structure that gives geopolymers certain properties, such as fire and acid resistance, low leach rate, which make them an ideal substitute for ordinary Portland cement (OPC) in a wide range of applications especially in conditioning and storage of radioactive waste. Therefore investigations have been initiated on how and to which amount graphite as a hydrophobic material can be mixed with cement or concrete to form stable waste products and which concretes fulfil the necessary specifications best. As a result, geopolymers have been identified as a promising matrix for graphite containing nuclear wastes. With geopolymers, both favourable properties in the cementation process and a high long time structural stability of the products can be achieved. Investigations include: • direct mixing of graphite with geopolymers with or without sand as a mechanically stabilizing medium; • production of cement-graphite granulates as intermediate products and embedding of these granulates in geopolymer; • coating of formed graphite pieces with geopolymer.The report shows that carbon in the form of graphite can both be integrated with different grain size spectra as well as shaped in the hydraulic binder geopolymer and meets the requirements for a stable long-term immobilisation. (author)

  15. Common processes at unique volcanoes – a volcanological conundrum

    Directory of Open Access Journals (Sweden)

    Katharine eCashman

    2014-11-01

    Full Text Available An emerging challenge in modern volcanology is the apparent contradiction between the perception that every volcano is unique, and classification systems based on commonalities among volcano morphology and eruptive style. On the one hand, detailed studies of individual volcanoes show that a single volcano often exhibits similar patterns of behaviour over multiple eruptive episodes; this observation has led to the idea that each volcano has its own distinctive pattern of behaviour (or personality. In contrast, volcano classification schemes define eruption styles referenced to type volcanoes (e.g. Plinian, Strombolian, Vulcanian; this approach implicitly assumes that common processes underpin volcanic activity and can be used to predict the nature, extent and ensuing hazards of individual volcanoes. Actual volcanic eruptions, however, often include multiple styles, and type volcanoes may experience atypical eruptions (e.g., violent explosive eruptions of Kilauea, Hawaii1. The volcanological community is thus left with a fundamental conundrum that pits the uniqueness of individual volcanic systems against generalization of common processes. Addressing this challenge represents a major challenge to volcano research.

  16. Graphite crystals grown within electromagnetically levitated metallic droplets

    International Nuclear Information System (INIS)

    Amini, Shaahin; Kalaantari, Haamun; Mojgani, Sasan; Abbaschian, Reza

    2012-01-01

    Various graphite morphologies were observed to grow within the electromagnetically levitated nickel–carbon melts, including primary flakes and spheres, curved surface graphite and eutectic flakes, as well as engulfed and entrapped particles. As the supersaturated metallic solutions were cooled within the electromagnetic (EM) levitation coil, the primary graphite flakes and spheres formed and accumulated near the periphery of the droplet due to EM circulation. The primary graphite islands, moreover, nucleated and grew on the droplet surface which eventually formed a macroscopic curved graphite crystal covering the entire liquid. Upon further cooling, the liquid surrounding the primary graphite went under a coupled eutectic reaction while the liquid in the center formed a divorced eutectic due to EM mixing. This brought about the formation of graphite fine flakes and agglomerated particles close to the surface and in the center of the droplet, respectively. The graphite morphologies, growth mechanisms, defects, irregularities and growth instabilities were interpreted with detailed optical and scanning electron microscopies.

  17. Expansion and exfoliation of graphite to form graphene

    KAUST Repository

    Patole, Shashikan P.; Da Costa, Pedro M. F. J.

    2017-01-01

    Graphene production methods are described based on subjecting non- covalent graphite intercalated compounds, such as graphite bisulfate, to expansion conditions such as shocks of heat and/or microwaves followed by turbulence-assisted exfoliation

  18. A 2-D nucleation-growth model of spheroidal graphite

    International Nuclear Information System (INIS)

    Lacaze, Jacques; Bourdie, Jacques; Castro-Román, Manuel Jesus

    2017-01-01

    Analysis of recent experimental investigations, in particular by transmission electron microscopy, suggests spheroidal graphite grows by 2-D nucleation of new graphite layers at the outer surface of the nodules. These layers spread over the surface along the prismatic direction of graphite which is the energetically preferred growth direction of graphite when the apparent growth direction of the nodules is along the basal direction of graphite. 2-D nucleation-growth models first developed for precipitation of pure substances are then adapted to graphite growth from the liquid in spheroidal graphite cast irons. Lateral extension of the new graphite layers is controlled by carbon diffusion in the liquid. This allows describing quantitatively previous experimental results giving strong support to this approach.

  19. Coordinated Isotopic and TEM Studies of Presolar Graphites from Murchison

    Science.gov (United States)

    Croat, T. K.; Stadermann, F. J.; Zinner, E.; Bernatowicz, T. J.

    2004-03-01

    TEM and NanoSIMS investigations of the same presolar Murchison KFC graphites revealed high Zr, Mo, and Ru content in refractory carbides within the graphites. Along with isotopically light carbon, these suggest a low-metallicity AGB source.

  20. Thermal Properties of G-348 Graphite

    Energy Technology Data Exchange (ETDEWEB)

    McEligot, Donald M. [Idaho National Lab. (INL), Idaho Falls, ID (United States); Swank, W. David [Idaho National Lab. (INL), Idaho Falls, ID (United States); Cottle, David L. [Idaho National Lab. (INL), Idaho Falls, ID (United States); Valentin, Francisco I. [City Univ. (CUNY), NY (United States)

    2017-04-01

    Fundamental measurements have been obtained in the INL Graphite Characterization Laboratory to deduce the temperature dependence of thermal conductivity for G-348 isotropic graphite, which has been used by City College of New York in thermal experiments related to gas-cooled nuclear reactors. Measurements of thermal diffusivity, mass, volume and thermal expansion were converted to thermal conductivity in accordance with ASTM Standard Practice C781-08 (R-2014). Data are tabulated and a preliminary correlation for the thermal conductivity is presented as a function of temperature from laboratory temperature to 1000C.

  1. London forces in highly oriented pyrolytic graphite

    Directory of Open Access Journals (Sweden)

    L.V. Poperenko

    2017-07-01

    Full Text Available Surface of highly oriented pyrolytic graphite with terrace steps was studied using scanning tunneling microscopy with high spatial resolution. Spots with positive and negative charges were found in the vicinity of the steps. Values of the charges depended both on the microscope needle scan velocity and on its motion direction. The observed effect was theoretically explained with account of London forces that arise between the needle tip and the graphite surface. In this scheme, a terrace step works as a nanoscale diode for surface electric currents.

  2. Large Scale Reduction of Graphite Oxide Project

    Science.gov (United States)

    Calle, Carlos; Mackey, Paul; Falker, John; Zeitlin, Nancy

    2015-01-01

    This project seeks to develop an optical method to reduce graphite oxide into graphene efficiently and in larger formats than currently available. Current reduction methods are expensive, time-consuming or restricted to small, limited formats. Graphene has potential uses in ultracapacitors, energy storage, solar cells, flexible and light-weight circuits, touch screens, and chemical sensors. In addition, graphite oxide is a sustainable material that can be produced from any form of carbon, making this method environmentally friendly and adaptable for in-situ reduction.

  3. Chemical atomization of graphite by H+ ions

    International Nuclear Information System (INIS)

    Busharov, I.P.; Gorbatov, E.A.; Gusev, V.M.; Guseva, M.I.; Martynenko, Yu.V.

    A simple model of the mechanism of chemical atomization is given, on whose basis a decrease in chemical atomization is qualitatively predicted for high temperatures. Mass spectrometric investigations of the atomization products cited, which found CH 4 and CH 3 molecules during the irradiation of graphite and H + ions thereby confirmed the presence of chemical atomization. A relationship of S and temperature of graphite T during irradiation was obtained which showed a decrease in the coefficient of atomization of a high temperature. (U.S.)

  4. The electrochemical properties of graphite and carbon

    International Nuclear Information System (INIS)

    Yeager, E.; Gupta, S.; Molla, J.A.

    1983-01-01

    Carbon and graphite are often used as supports for electrocatalysts, but also have an electrocatalytic function in such electrode reactions as O 2 reduction in alkaline electrolytes, Cl 2 generation in brine and SOCl 2 reduction in lithium-thionyl chloride batteries. These catalytic functions involve specific chemical functional groups bound to the carbon and graphite surfaces. The factors controlling O 2 reduction with various types of carbon electrodes of both low and high surface area are reviewed. Of particular importance is the role of hydrogen peroxide. The role of the functionality of the carbon in the electrocatalysis will be discussed

  5. Radiation creep of graphite. An introduction

    Energy Technology Data Exchange (ETDEWEB)

    Blackstone, R [Commission of the European Communities, Petten (Netherlands). Joint Nuclear Research Center

    1977-03-01

    Graphite, a class of materials with many unique and unusual properties, shows a remarkably high creep ductility under irradiation. As this behaviour compensates to some extent some of the more worrying radiation effects, such as dimensional changes and their strong temperature dependence, it is a property of large technological interest. There are various ways of observing and measuring in-pile creep of graphite, varying in degree of sophistication and in cost, in accuracy and in the type of data that is generated. This paper attempts to review briefly the various experimental methods, and the knowledge generated so far. An indication is given of the areas in which further knowledge is wanted.

  6. Radiation creep of graphite. An introduction

    International Nuclear Information System (INIS)

    Blackstone, R.

    1977-01-01

    Graphite, a class of materials with many unique and unusual properties, shows a remarkably high creep ductility under irradiation. As this behavior compensates to some extent some of the more worrying radiation effects, such as dimensional changes and their strong temperature dependence, it is a property of large technological interest. There are various ways of observing and measuring in-pile creep of graphite, varying in degree of sophistication and in cost, in accuracy and in the type of data that is generated. This paper attempts to review briefly the various experimental methods, and the knowledge generated so far. An indication is given of the areas in which further knowledge is wanted

  7. Radiation creep of graphite. An introduction

    International Nuclear Information System (INIS)

    Blackstone, R.

    1977-01-01

    Graphite, a class of materials with many unique and unusual properties, shows a remarkably high creep ductility under irradiation. As this behaviour compensates to some extent some of the more worrying radiation effects, such as dimensional changes and their strong temperature dependence, it is a property of large technological interest. There are various ways of observing and measuring in-pile creep of graphite, varying in degree of sophistication and in cost, in accuracy and in the type of data that is generated. This paper attempts to review briefly the various experimental methods, and the knowledge generated so far. An indication is given of the areas in which further knowledge is wanted. (Auth.)

  8. Electrical properties of Egyptian natural graphite

    International Nuclear Information System (INIS)

    El-Shazly, O.; El-Wahidy, E.F.; Elanany, N.; Saad, N.A.

    1992-06-01

    The electrical properties of Egyptian natural graphite flakes, obtained from the graphite schists of Wadi Bent, Eastern Desert, were measured. The flakes were ground and compressed into pellets. The standard four probe dc method was used to measure the temperature dependence of the electric resistivity from room temperature down to 12 K. The transverse and longitudinal magnetoresistance were measured in the low magnetic field range at temperatures 300 K, 77 K and 12 K. The transverse magnetoresistance data was used to estimate the average mobility, assuming a simple two-band model. (author). 20 refs, 4 figs, 1 tab

  9. Direct reading spectrochemical analysis of nuclear graphite

    International Nuclear Information System (INIS)

    Roca Adell, M.; Becerro Ruiz, E.; Alvarez Gonzalez, F.

    1964-01-01

    A description is given about the application of a direct-reading spectrometer the Quantometer, to the determination of boron. calcium, iron, titanium and vanadium in nuclear grade graphite. for boron the powdered sample is mixed with 1% cupric fluoride and excited in a 10-amperes direct current arc and graphite electrodes with a crater 7 mm wide and 10 mm deep. For the other elements a smaller crater has been used and dilution with a number of matrices has been investigated; the best results are achieved by employing 25% cupric fluoride. The sensitivity limit for boron is 0,15 ppm. (Author) 21 refs

  10. Graphite target for the spiral project

    International Nuclear Information System (INIS)

    Putaux, J.C.; Ducourtieux, M.; Ferro, A.; Foury, P.; Kotfila, L.; Mueller, A.C.; Obert, J.; Pauwels, N.; Potier, J.C.; Proust, J.; Loiselet, M.

    1996-01-01

    A study of the thermal and physical properties of graphite targets for the SPIRAL project is presented. The main objective is to develop an optimized set-up both mechanically and thermally resistant, presenting good release properties (hot targets with thin slices). The results of irradiation tests concerning the mechanical and thermal resistance of the first prototype of SPIRAL target with conical geometry are presented. The micro-structural properties of the graphite target is also studied, in order to check that the release properties are not deteriorated by the irradiation. Finally, the results concerning the latest pilot target internally heated by an electrical current are shown. (author)

  11. Monte Carlo calculation of standard graphite block

    International Nuclear Information System (INIS)

    Ljubenov, V.

    2000-01-01

    This paper presents results of calculation of neutron flux space and energy distribution in the standard graphite block (SGB) obtained by the MCNP TM code. VMCCS nuclear data library, based on the ENDF / B-VI release 4 evaluation file, is used. MCNP model of the SGB considers detailed material, geometric and spectral properties of the neutron source, source carrier, graphite moderator medium, aluminium foil holders and proximate surrounding of SGB Geometric model is organised to provide the simplest homogeneous volume cells in order to obtain the maximum acceleration of neutron history tracking (author)

  12. Characteristics and Origins of Hot Springs in the Tatun Volcano Group in Northern Taiwan

    Directory of Open Access Journals (Sweden)

    Chia-Mei Liu

    2011-01-01

    Full Text Available This paper systematically surveyed distribution and field occurrences of 13 hot springs as well as geochemical investigation on the geothermal area of the Tatun Volcano Group (TVG. According to Piper diagrams, pH values, field occurrences and water-rock interactions, these hot springs can be classified into three types: (1 Type I, SO42- acidic water where the reservoir is located in the Wuchishan Formation; (2 Type II, HCO3- a near neutral spring where waters originate from the volcanic terrane (andesite; and (3 Type III, Cl- -rich acidic water where waters emanate from shallower Wuchishan Formation. In terms of isotopic ratio, δD and δ18O values, two groups of hot spring can be recognized. One is far away from the meteoric water line of the Tatun area with values ranging between -26.2‰ and -3.5‰, and from -3.2‰ to 1.6‰, respectively. However, another close to the meteoric water line of the Tatun area is between -28.4‰ and -13.6‰, and from -5.5‰ to -4.2‰, respectively. In addition, the δ34S value of thermal waters can also be distinguished into two groups, one ranging from 26.1‰ to 28.5‰, and the other between 0.8‰ and 7.8‰. Based on field occurrences and geochemical characteristics, a model has been proposed to illustrate the origin of these hot springs.

  13. Continuous monitoring of volcanoes with borehole strainmeters

    Science.gov (United States)

    Linde, Alan T.; Sacks, Selwyn

    Monitoring of volcanoes using various physical techniques has the potential to provide important information about the shape, size and location of the underlying magma bodies. Volcanoes erupt when the pressure in a magma chamber some kilometers below the surface overcomes the strength of the intervening rock, resulting in detectable deformations of the surrounding crust. Seismic activity may accompany and precede eruptions and, from the patterns of earthquake locations, inferences may be made about the location of magma and its movement. Ground deformation near volcanoes provides more direct evidence on these, but continuous monitoring of such deformation is necessary for all the important aspects of an eruption to be recorded. Sacks-Evertson borehole strainmeters have recorded strain changes associated with eruptions of Hekla, Iceland and Izu-Oshima, Japan. Those data have made possible well-constrained models of the geometry of the magma reservoirs and of the changes in their geometry during the eruption. The Hekla eruption produced clear changes in strain at the nearest instrument (15 km from the volcano) starting about 30 minutes before the surface breakout. The borehole instrument on Oshima showed an unequivocal increase in the amplitude of the solid earth tides beginning some years before the eruption. Deformational changes, detected by a borehole strainmeter and a very long baseline tiltmeter, and corresponding to the remote triggered seismicity at Long Valley, California in the several days immediately following the Landers earthquake are indicative of pressure changes in the magma body under Long Valley, raising the question of whether such transients are of more general importance in the eruption process. We extrapolate the experience with borehole strainmeters to estimate what could be learned from an installation of a small network of such instruments on Mauna Loa. Since the process of conduit formation from the magma sources in Mauna Loa and other

  14. Paleozoic and Paleoproterozoic Zircon in Igneous Xenoliths Assimilated at Redoubt Volcano, Alaska

    Science.gov (United States)

    Bacon, C. R.; Vazquez, J. A.; Wooden, J. L.

    2010-12-01

    Historically active Redoubt Volcano is a basalt-to-dacite cone constructed upon the Jurassic-early Tertiary Alaska-Aleutian Range batholith. New SHRIMP-RG U-Pb age and trace-element concentration results for zircons from gabbroic xenoliths and crystal-rich andesitic mush from a late Pleistocene pyroclastic deposit indicate that ~310 Ma and ~1865 Ma igneous rocks underlie Redoubt at depth. Two gabbros have sharply terminated prismatic zircons that yield ages of ~310 Ma. Zircons from a crystal mush sample are overwhelmingly ~1865 Ma and appear rounded due to incomplete dissolution. Binary plots of element concentrations or ratios show clustering of data for ~310-Ma grains and markedly coherent trends for ~1865-Ma grains; e.g., ~310-Ma grains have higher Eu/Eu* than most of the ~1865-Ma grains, the majority of which form a narrow band of decreasing Eu/Eu* with increasing Hf content which suggests that ~1865-Ma zircons come from igneous source rocks. It is very unlikely that detrital zircons from a metasedimentary rock would have this level of homogeneity in age and composition. One gabbro contains abundant ~1865 Ma igneous zircons, ~300-310 Ma fluid-precipitated zircons characterized by very low U and Th concentrations and Th/U ratios, and uncommon ~100 Ma zircons. We propose that (1) ~310 Ma gabbro xenoliths from Redoubt Volcano belong to the same family of plutons dated by Aleinikoff et al. (USGS Circular 1016, 1988) and Gardner et al. (Geology, 1988) located ≥500 km to the northeast in basement rocks of the Wrangellia and Alexander terranes and (2) ~1865 Ma zircons are inherited from igneous rock, potentially from a continental fragment that possibly correlates with the Fort Simpson terrane or Great Bear magmatic zone of the Wopmay Orogen of northwestern Laurentia. Possibly, elements of these Paleoproterozoic terranes intersected the Paleozoic North American continental margin where they may have formed a component of the basement to the Wrangellia

  15. STS Observations of Landau Levels at Graphite Surfaces

    OpenAIRE

    Matsui, T.; Kambara, H.; Niimi, Y.; Tagami, K.; Tsukada, M.; Fukuyama, Hiroshi

    2004-01-01

    Scanning tunneling spectroscopy measurements were made on surfaces of two different kinds of graphite samples, Kish graphite and highly oriented pyrolytic graphite (HOPG), at very low temperatures and in high magnetic fields. We observed a series of peaks in the tunnel spectra, which grow with increasing field, both at positive and negative bias voltages. These are associated with Landau quantization of the quasi two-dimensional electrons and holes in graphite in magnetic fields perpendicular...

  16. Electronic structure of incident carbon ions on a graphite surface

    International Nuclear Information System (INIS)

    Kiuchi, Masato; Takeuchi, Takae; Yamamoto, Masao.

    1997-01-01

    The electronic structure of an incident carbon ion on a graphite surface is discussed on the basis of ab initio molecular orbital calculations. A carbon cation forms a covalent bond with the graphite, and a carbon nonion is attracted to the graphite surface through van der Waals interaction. A carbon anion has no stable state on a graphite surface. The charge effects of incident ions become clear upon detailed examination of the electronic structure. (author)

  17. Darwin's triggering mechanism of volcano eruptions

    Science.gov (United States)

    Galiev, Shamil

    2010-05-01

    Charles Darwin wrote that ‘… the elevation of many hundred square miles of territory near Concepcion is part of the same phenomenon, with that splashing up, if I may so call it, of volcanic matter through the orifices in the Cordillera at the moment of the shock;…' and ‘…a power, I may remark, which acts in paroxysmal upheavals like that of Concepcion, and in great volcanic eruptions,…'. Darwin reports that ‘…several of the great chimneys in the Cordillera of central Chile commenced a fresh period of activity ….' In particular, Darwin reported on four-simultaneous large eruptions from the following volcanoes: Robinson Crusoe, Minchinmavida, Cerro Yanteles and Peteroa (we cite the Darwin's sentences following his The Voyage of the Beagle and researchspace. auckland. ac. nz/handle/2292/4474). Let us consider these eruptions taking into account the volcano shape and the conduit. Three of the volcanoes (Minchinmavida (2404 m), Cerro Yanteles (2050 m), and Peteroa (3603 m)) are stratovolcanos and are formed of symmetrical cones with steep sides. Robinson Crusoe (922 m) is a shield volcano and is formed of a cone with gently sloping sides. They are not very active. We may surmise, that their vents had a sealing plug (vent fill) in 1835. All these volcanoes are conical. These common features are important for Darwin's triggering model, which is discussed below. The vent fill material, usually, has high level of porosity and a very low tensile strength and can easily be fragmented by tension waves. The action of a severe earthquake on the volcano base may be compared with a nuclear blast explosion of the base. It is known, that after a underground nuclear explosion the vertical motion and the surface fractures in a tope of mountains were observed. The same is related to the propagation of waves in conical elements. After the explosive load of the base. the tip may break and fly off at high velocity. Analogous phenomenon may be generated as a result of a

  18. Effect of thermal annealing on property changes of neutron-irradiated non-graphitized carbon materials and nuclear graphite

    International Nuclear Information System (INIS)

    Matsuo, Hideto

    1991-06-01

    Changes in dimension of non-graphitized carbon materials and nuclear graphite, and the bulk density, electrical resistivity, Young's modulus and thermal expansivity of nuclear graphite were studied after neutron irradiation at 1128-1483 K and the successive thermal annealing up to 2573 K. Carbon materials showed larger and anisotropic dimensional shrinkage than that of nuclear graphite after the irradiation. The irradiation-induced dimensional shrinkage of carbon materials decreased during annealing at temperatures from 1773 to 2023 K, followed by a slight increase at higher temperatures. On the other hand, the irradiated nuclear graphite hardly showed the changes in length, density and thermal expansivity under the thermal annealing, but the electrical resistivity and Young's modulus showed a gradual decrease with annealing temperature. It has been clarified that there exists significant difference in the effect of thermal annealing on irradiation-induced dimensional shrinkage between graphitized nuclear graphite and non-graphitized carbon materials. (author)

  19. Fracture behavior of nuclear graphites under tensile impact loading

    International Nuclear Information System (INIS)

    Ugachi, Hirokazu; Ishiyama, Shintaro; Eto, Motokuni

    1994-01-01

    Impact tensile strength test was performed with two kinds of HTTR graphites, fine grained isotropic graphite, IG-11 and coarse grained near isotropic graphite, PGX and deformation and fracture behavior under the strain rate of over 100s -1 was measured and the following results were derived: (1) Tensile strength for IG-11 graphite does not depend on the strain rate less than 1 s -1 , but over 1 s -1 , tensile strength for IG-11 graphite increase larger than that measured under 1 s -1 . At the strain rate more than 100 s -1 , remarkable decrease of tensile strength for IG-11 graphite was found. Tensile strength of PGX graphite does not depend on the strain rate less than 1 s -1 , but beyond this value, the sharp tensile strength decrease occurs. (2) Under 100 s -1 , fracture strain for both graphites increase with increase of strain rate and over 100 s -1 , drastic increase of fracture strain for IG-11 graphite was found. (3) At the part of gage length, volume of specimen increase with increase of tensile loading level and strain rate. (4) Poisson's ratio for both graphites decrease with increase of tensile loading level and strain rate. (5) Remarkable change of stress-strain curve for both graphites under 100 s -1 was not found, but over 100 s -1 , the slope of these curve for IG-11 graphite decrease drastically. (author)

  20. Oxidation behavior of IG and NBG nuclear graphites

    Energy Technology Data Exchange (ETDEWEB)

    Choi, Woong-Ki; Kim, Byung-Joo [Jeonju Institute of Machinery and Carbon Composites Palbokdong-2ga, 817, Jeonju, Jeollabuk-do 561-844 (Korea, Republic of); Kim, Eung-Seon; Chi, Se-Hwan [Dept. of Nuclear Hydrogen Project, Korea Atomic Energy Research Institute, Daejeon 305-353 (Korea, Republic of); Park, Soo-Jin, E-mail: sjpark@inha.ac.k [Dept. of Chemistry, Inha Univ., 253, Nam-gu, Incheon 402-751 (Korea, Republic of)

    2011-01-15

    Graphical abstract: Water contact angles on nuclear graphite before and after oxidation treatments: the pictures show the contact angles obtained under deionized water on oxidation-treated and untreated nuclear graphite. The water contact angles are decreased after oxidation due to the increase in the hydrophilic. Display Omitted Research highlights: The average pore size of graphites shows an increase after the oxidation treatments. They also show that oxidation produces the surface functional groups on the graphite surfaces. The surface area of each graphite behaves in a unique manner. - Abstract: This work studies the oxidation-induced characteristics of four nuclear graphites (NBG-17, NBG-25, IG-110, and IG-430). The oxidation characteristics of the nuclear graphites were measured at 600 {sup o}C. The surface properties of the oxidation graphites were characterized by means of scanning electron microscopy, X-ray photoelectron spectroscopy, and contact angle methods. The N{sub 2}/77 K adsorption isotherm characteristics, including the specific surface area and micropore volume, were investigated by means of BET and t-plot methods. The experimental results show an increase in the average pore size of graphites; they also show that oxidation produces the surface functional groups on the graphite surfaces. The surface area of each graphite behaves in a unique manner. For example the surface area of NBG-17 increases slightly whereas the surface area of IG-110 increases significantly. This result confirms that the original surface state of each graphite is unique.

  1. Influence of irradiation on high-strength graphites

    International Nuclear Information System (INIS)

    Virgil'ev, Yu.S.; Grebennik, V.N.; Kalyagina, I.P.

    1989-01-01

    To ensure efficiency of the graphite elements of the construction of the masonry of reactors, the graphite must possess high radiation stability, strength, and heat resistance. In this connection, the physical properties of graphites based on uncalcined petroleum coke with a binder - high-temperature hard coal pitch - the amount of which reaches 40% are considered in this paper

  2. Porous graphite electrodes for rechargeable ion-transfer batteries

    Energy Technology Data Exchange (ETDEWEB)

    Novak, P; Scheifele, W; Haas, O [Paul Scherrer Inst. (PSI), Villigen (Switzerland)

    1997-06-01

    The influence of preparation pressure and pore-forming additives on the properties of graphite-based, Li{sup +}-intercalating electrodes for ion-transfer batteries have been investigated. The electrochemical performance of graphite electrodes could be improved by adjusting the porosity. Specific charge of >300 Ah/kg (with respect to the graphite mass) could be achieved. (author) 4 figs., 2 refs.

  3. Silicic magma generation at Askja volcano, Iceland

    Science.gov (United States)

    Sigmarsson, O.

    2009-04-01

    Rate of magma differentiation is an important parameter for hazard assessment at active volcanoes. However, estimates of these rates depend on proper understanding of the underlying magmatic processes and magma generation. Differences in isotope ratios of O, Th and B between silicic and in contemporaneous basaltic magmas have been used to emphasize their origin by partial melting of hydrothermally altered metabasaltic crust in the rift-zones favoured by a strong geothermal gradient. An alternative model for the origin of silicic magmas in the Iceland has been proposed based on U-series results. Young mantle-derived mafic protolith is thought to be metasomatized and partially melted to form the silicic end-member. However, this model underestimates the compositional variations of the hydrothermally-altered basaltic crust. New data on U-Th disequilibria and O-isotopes in basalts and dacites from Askja volcano reveal a strong correlation between (230Th/232Th) and delta 18O. The 1875 AD dacite has the lowest Th- and O isotope ratios (0.94 and -0.24 per mille, respectively) whereas tephra of evolved basaltic composition, erupted 2 months earlier, has significantly higher values (1.03 and 2.8 per mille, respectively). Highest values are observed in the most recent basalts (erupted in 1920 and 1961) inside the Askja caldera complex and out on the associated fissure swarm (Sveinagja basalt). This correlation also holds for older magma such as an early Holocene dacites, which eruption may have been provoked by rapid glacier thinning. Silicic magmas at Askja volcano thus bear geochemical signatures that are best explained by partial melting of extensively hydrothermally altered crust and that the silicic magma source has remained constant during the Holocene at least. Once these silicic magmas are formed they appear to erupt rapidly rather than mixing and mingling with the incoming basalt heat-source that explains lack of icelandites and the bi-modal volcanism at Askja

  4. Decision Analysis Tools for Volcano Observatories

    Science.gov (United States)

    Hincks, T. H.; Aspinall, W.; Woo, G.

    2005-12-01

    Staff at volcano observatories are predominantly engaged in scientific activities related to volcano monitoring and instrumentation, data acquisition and analysis. Accordingly, the academic education and professional training of observatory staff tend to focus on these scientific functions. From time to time, however, staff may be called upon to provide decision support to government officials responsible for civil protection. Recognizing that Earth scientists may have limited technical familiarity with formal decision analysis methods, specialist software tools that assist decision support in a crisis should be welcome. A review is given of two software tools that have been under development recently. The first is for probabilistic risk assessment of human and economic loss from volcanic eruptions, and is of practical use in short and medium-term risk-informed planning of exclusion zones, post-disaster response, etc. A multiple branch event-tree architecture for the software, together with a formalism for ascribing probabilities to branches, have been developed within the context of the European Community EXPLORIS project. The second software tool utilizes the principles of the Bayesian Belief Network (BBN) for evidence-based assessment of volcanic state and probabilistic threat evaluation. This is of practical application in short-term volcano hazard forecasting and real-time crisis management, including the difficult challenge of deciding when an eruption is over. An open-source BBN library is the software foundation for this tool, which is capable of combining synoptically different strands of observational data from diverse monitoring sources. A conceptual vision is presented of the practical deployment of these decision analysis tools in a future volcano observatory environment. Summary retrospective analyses are given of previous volcanic crises to illustrate the hazard and risk insights gained from use of these tools.

  5. Preparation of graphite derivatives by selective reduction of graphite oxide and isocyanate functionalization

    Czech Academy of Sciences Publication Activity Database

    Kumar, A. R. S. S.; Piana, Francesco; Mičušík, M.; Pionteck, J.; Banerjee, S.; Voit, B.

    2016-01-01

    Roč. 182, 1 October (2016), s. 237-245 ISSN 0254-0584 Institutional support: RVO:61389013 Keywords : graphite oxide * surface modification * conductive nanoparticles Subject RIV: CD - Macromolecular Chemistry Impact factor: 2.084, year: 2016

  6. Ion irradiation to simulate neutron irradiation in model graphites: Consequences for nuclear graphite

    Science.gov (United States)

    Galy, N.; Toulhoat, N.; Moncoffre, N.; Pipon, Y.; Bérerd, N.; Ammar, M. R.; Simon, P.; Deldicque, D.; Sainsot, P.

    2017-10-01

    Due to its excellent moderator and reflector qualities, graphite was used in CO2-cooled nuclear reactors such as UNGG (Uranium Naturel-Graphite-Gaz). Neutron irradiation of graphite resulted in the production of 14C which is a key issue radionuclide for the management of the irradiated graphite waste. In order to elucidate the impact of neutron irradiation on 14C behavior, we carried out a systematic investigation of irradiation and its synergistic effects with temperature in Highly Oriented Pyrolitic Graphite (HOPG) model graphite used to simulate the coke grains of nuclear graphite. We used 13C implantation in order to simulate 14C displaced from its original structural site through recoil. The collision of the impinging neutrons with the graphite matrix carbon atoms induces mainly ballistic damage. However, a part of the recoil carbon atom energy is also transferred to the graphite lattice through electronic excitation. The effects of the different irradiation regimes in synergy with temperature were simulated using ion irradiation by varying Sn(nuclear)/Se(electronic) stopping power. Thus, the samples were irradiated with different ions of different energies. The structure modifications were followed by High Resolution Transmission Electron Microscopy (HRTEM) and Raman microspectrometry. The results show that temperature generally counteracts the disordering effects of irradiation but the achieved reordering level strongly depends on the initial structural state of the graphite matrix. Thus, extrapolating to reactor conditions, for an initially highly disordered structure, irradiation at reactor temperatures (200 - 500 °C) should induce almost no change of the initial structure. On the contrary, when the structure is initially less disordered, there should be a "zoning" of the reordering: In "cold" high flux irradiated zones where the ballistic damage is important, the structure should be poorly reordered; In "hot" low flux irradiated zones where the ballistic

  7. Polyphase diffusion of fission products in graphite

    International Nuclear Information System (INIS)

    Dannert, V.

    1989-05-01

    The report attempts to give an introduction into the subject of fission product transport in nuclear graphite and results in an extended proposal of a transport-model. Beginning with a rough description of the graphite in question, an idea about the physical transport-phenomena in graphite is developed. Some of the basic experimental methods, especially techniques of porosimetry, determination of sorption-isotherms and of course several transport-experiments, are briefly described and their results are discussed. Some of the most frequent transport models are introduced and assessed with the criteria emphasized in this report. An extended model is proposed including the following main ideas: The transport of the fission-products is regarded as a two-phase-diffusion process through the open pores of the graphite. The two phases are: surface-diffusion and gas-diffusion. A time-dependent coupling of the two diffusion-phases by sorption-isotherms and a concentration-dependence of the surface diffusion coefficient, also related to the physical behaviour of the sorption-isotherms, are the basic properties of the proposed model. (orig./HP) [de

  8. US graphite reactor D ampersand D experience

    International Nuclear Information System (INIS)

    Garrett, S.M.K.; Williams, N.C.

    1997-02-01

    This report describes the results of the U.S. Graphite Reactor Experience Task for the Decommissioning Strategy Plan for the Leningrad Nuclear Power Plant (NPP) Unit 1 Study. The work described in this report was performed by the Pacific Northwest National Laboratory (PNNL) for the Department of Energy (DOE)

  9. Analysis of a T-10 graphite limiter

    International Nuclear Information System (INIS)

    Hildebrandt, D.; Laux, M.; Lingertat, J.; Pech, P.; Reiner, H.D.; Strusny, H.; Wolff, H.

    1981-01-01

    Parts of a T-10 graphite limiter used during ohmic heated discharges have been investigated. Erosion and deposition phenomena have been studied by morphological and elemental surface analysis methods. From the results estimates of the plasma parameters near the limiter surface have been made. (orig.)

  10. Raw materials for reflector graphite (for reactors)

    International Nuclear Information System (INIS)

    Wilhelmi, G.; Mindermann, D.

    1992-01-01

    The manufacturing concept for the core components of German high temperature reactor (HTR) types of graphite was previously entirely directed to the use of German tar coke (St coke). As the plants for producing this material no longer complied technically with the current environmental protection requirements, one had to assume that they would soon be shut down. To prevent bottlenecks in the erection of future HTR plants, alternative cokes produced by modern processes by Japanese manufacturers were checked for their suitability for the manufacture of reactor graphite. This report describes the investigations carried out on these materials from the safe delayed coking process. The project work, apart from analysis of the main data of the candidate coke considered, included the processing of the raw materials into directly and secondarily extruded graphite rods on the laboratory scale, including characterisation. As the results show, the material data achieved with the previous raw material can be reproduced with Japanese St coke. The tar coke LPC-A from the Nippon Steel Chemical Co., Ltd was decided on as the new standard coke for manufacturing reflector graphite. (orig.) With 15 tabs., 2 figs [de

  11. Formation of dislocation dipoles in irradiated graphite

    International Nuclear Information System (INIS)

    Niwase, Keisuke

    2005-01-01

    Recently, we have proposed a dislocation dipole accumulation model to explain the irradiation-induced amorphization of graphite. However, the structure of dislocation dipole in the hexagonal networks is still an open question at the atomic-level. In this paper, we propose a possible formation process of the dislocation dipole

  12. Functional interface of polymer modified graphite anode

    Energy Technology Data Exchange (ETDEWEB)

    Komaba, S.; Ozeki, T.; Okushi, K. [Department of Applied Chemistry, Tokyo University of Science, 1-3 Kagurazaka, Shinjuku, Tokyo 162-8601 (Japan)

    2009-04-01

    Graphite electrodes were modified by polyacrylic acid (PAA), polymethacrylic acid (PMA), and polyvinyl alcohol (PVA). Their electrochemical properties were examined in 1 mol dm{sup -3} LiClO{sub 4} ethylene carbonate:dimethyl carbonate (EC:DMC) and propylene carbonate (PC) solutions as an anode of lithium ion batteries. Generally, lithium ions hardly intercalate into graphite in the PC electrolyte due to a decomposition of the PC electrolyte at ca. 0.8 V vs. Li/Li{sup +}, and it results in the exfoliation of the graphene layers. However, the modified graphite electrodes with PAA, PMA, and PVA demonstrated the stable charge-discharge performance due to the reversible lithium intercalation not only in the EC:DMC but also in the PC electrolytes since the electrolyte decomposition and co-intercalation of solvent were successfully suppressed by the polymer modification. It is thought that these improvements were attributed to the interfacial function of the polymer layer on the graphite which interacted with the solvated lithium ions at the electrode interface. (author)

  13. Functional interface of polymer modified graphite anode

    Science.gov (United States)

    Komaba, S.; Ozeki, T.; Okushi, K.

    Graphite electrodes were modified by polyacrylic acid (PAA), polymethacrylic acid (PMA), and polyvinyl alcohol (PVA). Their electrochemical properties were examined in 1 mol dm -3 LiClO 4 ethylene carbonate:dimethyl carbonate (EC:DMC) and propylene carbonate (PC) solutions as an anode of lithium ion batteries. Generally, lithium ions hardly intercalate into graphite in the PC electrolyte due to a decomposition of the PC electrolyte at ca. 0.8 V vs. Li/Li +, and it results in the exfoliation of the graphene layers. However, the modified graphite electrodes with PAA, PMA, and PVA demonstrated the stable charge-discharge performance due to the reversible lithium intercalation not only in the EC:DMC but also in the PC electrolytes since the electrolyte decomposition and co-intercalation of solvent were successfully suppressed by the polymer modification. It is thought that these improvements were attributed to the interfacial function of the polymer layer on the graphite which interacted with the solvated lithium ions at the electrode interface.

  14. Removal of iron from impure graphites

    International Nuclear Information System (INIS)

    Growcock, F.B.; Heiser, J.

    1979-01-01

    Iron-impregnated and ash-rich graphites have been purified by leaching with gaseous I 2 at 900 0 C. With addition of H 2 , the rate of removal of impurity iron can be markedly increased and becomes comparable to that obtained with Cl 2 . I 2 has an advantage in that it can also volatilize Ca and perhaps Ba and Sr

  15. Structural strength of core graphite bars

    International Nuclear Information System (INIS)

    Kikuchi, K.; Futakawa, M.

    1987-01-01

    A HTR core consists of fuel, hot plenum, reflector and thermal barrier blocks. Each graphite block is supported by three thin cylindrical graphite bars called support post. Static and dynamic core loads are transmitted by the support posts to the thermal barrier blocks and a support plate. These posts are in contact with the blocks through hemispherical post seats to absorb the relative displacement caused by seismic force and the difference of thermal expansion of materials at the time of the start-up and shutdown of a reactor. The mixed fracture criterion of principal stress and modified Mohr-Coulomb's theory as well as the fracture criterion of principal stress based on elastic stress analysis was discussed in connection with the application to HTR graphite components. The buckling fracture of a support post was taken in consideration as one of the fracture modes. The effect that the length/diameter ratio of a post, small rotation and the curvature of post ends and seats exerted on the fracture strength was studied by using IG-110 graphite. Contacting stress analysis was carried out by using the structural analysis code 'COSMOS-7'. The experimental method, the analysis of buckling strength and the results are reported. The fracture of a support post is caused by the mixed mode of bending deformation, split fracture and shearing fracture. (Kako, I.)

  16. Thermoexpanded graphite modification by titanium dioxide

    International Nuclear Information System (INIS)

    Semko, L.S.; Gorbik, P.P.; Chujko, O.O.; Kruchek, Ya.Yi.; Dzyubenko, L.S.; Orans'ka, O.Yi.

    2006-01-01

    A method of the synthesis of thermoexpanded graphite (TEG) powders coated by titanium dioxide is developed. The conversion of n-buthylorthotitanate into TiO 2 on the TEG surface is investigated. The optimal parameters of the synthesis and the structure of titanium dioxide clusters on the TEG surface are determined

  17. GRAPHITIZED STEELS IN MACHINE-BUILDING

    Directory of Open Access Journals (Sweden)

    I. V. Akimov

    2010-01-01

    Full Text Available It is shown that graphitized steels in some cases due to its intermediate disposition by structure and characteristics among low-carbon steels and cast irons, can provide the necessary combination of characteristics of construction material and consequently to increase safety and durability of details of metallurgical and machinebuilding industry machines.

  18. Geothermal Exploration of Newberry Volcano, Oregon

    Energy Technology Data Exchange (ETDEWEB)

    Waibel, Albert F. [Columbia Geoscience, Pasco, WA (United States); Frone, Zachary S. [Southern Methodist Univ., Dallas, TX (United States); Blackwell, David D. [Southern Methodist Univ., Dallas, TX (United States)

    2014-12-01

    Davenport Newberry (Davenport) has completed 8 years of exploration for geothermal energy on Newberry Volcano in central Oregon. Two deep exploration test wells were drilled by Davenport on the west flank of the volcano, one intersected a hydrothermal system; the other intersected isolated fractures with no hydrothermal interconnection. Both holes have bottom-hole temperatures near or above 315°C (600°F). Subsequent to deep test drilling an expanded exploration and evaluation program was initiated. These efforts have included reprocessing existing data, executing multiple geological, geophysical, geochemical programs, deep exploration test well drilling and shallow well drilling. The efforts over the last three years have been made possible through a DOE Innovative Exploration Technology (IET) Grant 109, designed to facilitate innovative geothermal exploration techniques. The combined results of the last 8 years have led to a better understanding of the history and complexity of Newberry Volcano and improved the design and interpretation of geophysical exploration techniques with regard to blind geothermal resources in volcanic terrain.

  19. Electrical structure of Newberry Volcano, Oregon

    Science.gov (United States)

    Fitterman, D.V.; Stanley, W.D.; Bisdorf, R.J.

    1988-01-01

    From the interpretation of magnetotelluric, transient electromagnetic, and Schlumberger resistivity soundings, the electrical structure of Newberry Volcano in central Oregon is found to consist of four units. From the surface downward, the geoelectrical units are 1) very resistive, young, unaltered volcanic rock, (2) a conductive layer of older volcanic material composed of altered tuffs, 3) a thick resistive layer thought to be in part intrusive rocks, and 4) a lower-crustal conductor. This model is similar to the regional geoelectrical structure found throughout the Cascade Range. Inside the caldera, the conductive second layer corresponds to the steep temperature gradient and alteration minerals observed in the USGS Newberry 2 test-hole. Drill hole information on the south and north flanks of the volcano (test holes GEO N-1 and GEO N-3, respectively) indicates that outside the caldera the conductor is due to alteration minerals (primarily smectite) and not high-temperature pore fluids. On the flanks of Newberry the conductor is generally deeper than inside the caldera, and it deepens with distance from the summit. A notable exception to this pattern is seen just west of the caldera rim, where the conductive zone is shallower than at other flank locations. The volcano sits atop a rise in the resistive layer, interpreted to be due to intrusive rocks. -from Authors

  20. Monitoring active volcanoes: The geochemical approach

    Directory of Open Access Journals (Sweden)

    Takeshi Ohba

    2011-06-01

    Full Text Available

    The geochemical surveillance of an active volcano aims to recognize possible signals that are related to changes in volcanic activity. Indeed, as a consequence of the magma rising inside the volcanic "plumbing system" and/or the refilling with new batches of magma, the dissolved volatiles in the magma are progressively released as a function of their relative solubilities. When approaching the surface, these fluids that are discharged during magma degassing can interact with shallow aquifers and/or can be released along the main volcano-tectonic structures. Under these conditions, the following main degassing processes represent strategic sites to be monitored.

    The main purpose of this special volume is to collect papers that cover a wide range of topics in volcanic fluid geochemistry, which include geochemical characterization and geochemical monitoring of active volcanoes using different techniques and at different sites. Moreover, part of this volume has been dedicated to the new geochemistry tools.

  1. Nanoscale volcanoes: accretion of matter at ion-sculpted nanopores.

    Science.gov (United States)

    Mitsui, Toshiyuki; Stein, Derek; Kim, Young-Rok; Hoogerheide, David; Golovchenko, J A

    2006-01-27

    We demonstrate the formation of nanoscale volcano-like structures induced by ion-beam irradiation of nanoscale pores in freestanding silicon nitride membranes. Accreted matter is delivered to the volcanoes from micrometer distances along the surface. Volcano formation accompanies nanopore shrinking and depends on geometrical factors and the presence of a conducting layer on the membrane's back surface. We argue that surface electric fields play an important role in accounting for the experimental observations.

  2. Metal/graphite-composite materials for fusion device

    International Nuclear Information System (INIS)

    Kneringer, G.; Kny, E.; Fischer, W.; Reheis, N.; Staffler, R.; Samm, U.; Winter, J.

    1995-01-01

    The utilization of graphite as a structural material depends to an important extent on the availability of a joining technique suitable for the production of reliable large scale metal/graphite-composites. This study has been conducted to evaluate vacuum brazes and procedures for graphite and metals which can be used in fusion applications up to about 1500 degree C. The braze materials included: AgCuTi, CuTi, NiTi, Ti, ZrTi, Zr. Brazing temperatures ranged from 850 degree C to 1900 degree C. The influence of graphite quality on wettability and pore-penetration of the braze has been investigated. Screening tests of metal/graphite-assemblies with joint areas exceeding some square-centimeters have shown that they can only successfully be produced when graphite is brazed to a metal, such as tungsten or molybdenum with a coefficient of thermal expansion closely matching that of graphite. Therefore all experimental work on evaluation of joints has been concentrated on molybdenum/graphite brazings. The tensile strength of molybdenum/graphite-composites compares favorably with the tensile strength of bulk graphite from room temperature close to the melting temperature of the braze. In electron beam testing the threshold damage line for molybdenum/graphite-composites has been evaluated. Results show that even composites with the low melting AgCuTi-braze are expected to withstand 10 MW/m 2 power density for at least 10 3 cycles. Limiter testing in TEXTOR shows that molybdenum/graphite-segments with 3 mm graphite brazed on molybdenum-substrate withstand severe repeated TEXTOR plasma discharge conditions without serious damage. Results prove that actively cooled components on the basis of a molybdenum/graphite-composite can sustain a higher heat flux than bulk graphite alone. (author)

  3. Acceptance test for graphite components and construction status of HTTR

    International Nuclear Information System (INIS)

    Iyoku, T.; Ishihara, M.; Maruyama, S.; Shiozawa, S.; Tsuji, N.; Miki, T.

    1996-01-01

    In March, 1991, the Japan Atomic Energy Research Institute (JAERI) started to constructed the High Temperature engineering Test Reactor(HTTR) which is a 30-MW(thermal) helium gas-cooled reactor with a core composed of prismatic graphite blocks piled on the core support graphite structures. Two types of graphite materials are used in the HTTR. One is the garde IG-110, isotropic fine grain graphite, another is the grade PGX, medium-to-fine grained molded graphite. These materials were selected on the basis of the appropriate properties required by the HTTR reactor design. Industry-wide standards for an acceptance test of graphite materials used as main components of a nuclear reactor had not been established. The acceptance standard for graphite components of the HTTR, therefore, was drafted by JAERI and reviewed by specialists outside JAERI. The acceptance standard consists of the material testing, non-destructive examination such as the ultrasonic and eddy current testings, dimensional and visual inspections and assembly test. Ultrasonic and eddy current testings are applied to graphite logs to detect an internal flaw and to graphite components to detect a surface flaw, respectively. The assembly test is performed at the works, prior to their installation in the reactor pressure vessel, to examine fabricating precision of each component and alignment of piled-up structures. The graphite components of the HTTR had been tested on the basis of the acceptance standard. It was confirmed that the graphite manufacturing process was well controlled and high quality graphite components were provided to the HTTR. All graphite components except for the fuel graphite blocks are to be installed in the reactor pressure vessel of the HTTR in September 1995. The paper describes the construction status of the HTTR focusing on the graphite components. The acceptance test results are also presented in this paper. (author). Figs

  4. Quantifying microstructural dynamics and electrochemical activity of graphite and silicon-graphite lithium ion battery anodes

    Science.gov (United States)

    Pietsch, Patrick; Westhoff, Daniel; Feinauer, Julian; Eller, Jens; Marone, Federica; Stampanoni, Marco; Schmidt, Volker; Wood, Vanessa

    2016-09-01

    Despite numerous studies presenting advances in tomographic imaging and analysis of lithium ion batteries, graphite-based anodes have received little attention. Weak X-ray attenuation of graphite and, as a result, poor contrast between graphite and the other carbon-based components in an electrode pore space renders data analysis challenging. Here we demonstrate operando tomography of weakly attenuating electrodes during electrochemical (de)lithiation. We use propagation-based phase contrast tomography to facilitate the differentiation between weakly attenuating materials and apply digital volume correlation to capture the dynamics of the electrodes during operation. After validating that we can quantify the local electrochemical activity and microstructural changes throughout graphite electrodes, we apply our technique to graphite-silicon composite electrodes. We show that microstructural changes that occur during (de)lithiation of a pure graphite electrode are of the same order of magnitude as spatial inhomogeneities within it, while strain in composite electrodes is locally pronounced and introduces significant microstructural changes.

  5. Nuclear graphite wear properties and estimation of graphite dust production in HTR-10

    Energy Technology Data Exchange (ETDEWEB)

    Luo, Xiaowei, E-mail: xwluo@tsinghua.edu.cn; Wang, Xiaoxin; Shi, Li; Yu, Xiaoyu; Yu, Suyuan

    2017-04-15

    Highlights: • Graphite dust. • The wear properties of graphite. • Pebble bed. • High Temperature Gas-cooled Reactor. • Fuel element. - Abstract: The issue of the graphite dust has been a research focus for the safety of High Temperature Gas-cooled Reactors (HTGRs), especially for the pebble bed reactors. Most of the graphite dust is produced from the wear of fuel elements during cycling of fuel elements. However, due to the complexity of the motion of the fuel elements in the pebble bed, there is no systematic method developed to predict the amount the graphite dust in a pebble bed reactor. In this paper, the study of the flow of the fuel elements in the pebble bed was carried out. Both theoretical calculation and numerical analysis by Discrete Element Method (DEM) software PFC3D were conducted to obtain the normal forces and sliding distances of the fuel elements in pebble bed. The wearing theory was then integrated with PFC3D to estimate the amount of the graphite dust in a pebble bed reactor, 10 MW High Temperature gas-cooled test Reactor (HTR-10).

  6. Graphite oxidation and structural strength of graphite support column in VHTR

    International Nuclear Information System (INIS)

    Park, Byung Ha; No, Hee Cheno; Kim, Eung Soo; Oh, Chang H.

    2009-01-01

    The air-ingress event by a large pipe break is an important accident considered in design of very high-temperature gas-cooled reactors (VHTR). Core-collapse prediction is a main safety issue. Structural failure model are technically required. The objective of this study is to develop structural failure model for the supporting graphite material in the lower plenum of the GT-MHR (gas-turbine-modular high temperature reactor). Graphite support column is important for VHTR structural integrity. Graphite support columns are under the axial load. Critical strength of graphite column is related to slenderness ratio and bulk density. Through compression tests for fresh and oxidized graphite columns we show that compressive strength of IG-110 was 79.46 MPa. And, the buckling strength of IG-110 column was expressed by the empirical formula: σ 0 =σ straight-line - C L/r, σ straight-line =91.31 MPa, C=1.01. The results of uniform and non-uniform oxidation tests show that the strength degradation of oxidized graphite column is expressed in the following non-dimensional form: σ/σ 0 =exp(-kd), k=0.111. Also, from the results of the uniform oxidation test with a complicated-shape column, we found out that the above non-dimensional equation obtained from the uniform oxidation test is applicable to a uniform oxidation case with a complicated-shape column. (author)

  7. Efficient inversion of volcano deformation based on finite element models : An application to Kilauea volcano, Hawaii

    Science.gov (United States)

    Charco, María; González, Pablo J.; Galán del Sastre, Pedro

    2017-04-01

    The Kilauea volcano (Hawaii, USA) is one of the most active volcanoes world-wide and therefore one of the better monitored volcanoes around the world. Its complex system provides a unique opportunity to investigate the dynamics of magma transport and supply. Geodetic techniques, as Interferometric Synthetic Aperture Radar (InSAR) are being extensively used to monitor ground deformation at volcanic areas. The quantitative interpretation of such surface ground deformation measurements using geodetic data requires both, physical modelling to simulate the observed signals and inversion approaches to estimate the magmatic source parameters. Here, we use synthetic aperture radar data from Sentinel-1 radar interferometry satellite mission to image volcano deformation sources during the inflation along Kilauea's Southwest Rift Zone in April-May 2015. We propose a Finite Element Model (FEM) for the calculation of Green functions in a mechanically heterogeneous domain. The key aspect of the methodology lies in applying the reciprocity relationship of the Green functions between the station and the source for efficient numerical inversions. The search for the best-fitting magmatic (point) source(s) is generally conducted for an array of 3-D locations extending below a predefined volume region. However, our approach allows to reduce the total number of Green functions to the number of the observation points by using the, above mentioned, reciprocity relationship. This new methodology is able to accurately represent magmatic processes using physical models capable of simulating volcano deformation in non-uniform material properties distribution domains, which eventually will lead to better description of the status of the volcano.

  8. Geologic map of Medicine Lake volcano, northern California

    Science.gov (United States)

    Donnelly-Nolan, Julie M.

    2011-01-01

    Medicine Lake volcano forms a broad, seemingly nondescript highland, as viewed from any angle on the ground. Seen from an airplane, however, treeless lava flows are scattered across the surface of this potentially active volcanic edifice. Lavas of Medicine Lake volcano, which range in composition from basalt through rhyolite, cover more than 2,000 km2 east of the main axis of the Cascade Range in northern California. Across the Cascade Range axis to the west-southwest is Mount Shasta, its towering volcanic neighbor, whose stratocone shape contrasts with the broad shield shape of Medicine Lake volcano. Hidden in the center of Medicine Lake volcano is a 7 km by 12 km summit caldera in which nestles its namesake, Medicine Lake. The flanks of Medicine Lake volcano, which are dotted with cinder cones, slope gently upward to the caldera rim, which reaches an elevation of nearly 8,000 ft (2,440 m). The maximum extent of lavas from this half-million-year-old volcano is about 80 km north-south by 45 km east-west. In postglacial time, 17 eruptions have added approximately 7.5 km3 to its total estimated volume of 600 km3, and it is considered to be the largest by volume among volcanoes of the Cascades arc. The volcano has erupted nine times in the past 5,200 years, a rate more frequent than has been documented at all other Cascades arc volcanoes except Mount St. Helens.

  9. The critical role of volcano monitoring in risk reduction

    Directory of Open Access Journals (Sweden)

    R. I. Tilling

    2008-01-01

    Full Text Available Data from volcano-monitoring studies constitute the only scientifically valid basis for short-term forecasts of a future eruption, or of possible changes during an ongoing eruption. Thus, in any effective hazards-mitigation program, a basic strategy in reducing volcano risk is the initiation or augmentation of volcano monitoring at historically active volcanoes and also at geologically young, but presently dormant, volcanoes with potential for reactivation. Beginning with the 1980s, substantial progress in volcano-monitoring techniques and networks – ground-based as well space-based – has been achieved. Although some geochemical monitoring techniques (e.g., remote measurement of volcanic gas emissions are being increasingly applied and show considerable promise, seismic and geodetic methods to date remain the techniques of choice and are the most widely used. Availability of comprehensive volcano-monitoring data was a decisive factor in the successful scientific and governmental responses to the reawakening of Mount St. elens (Washington, USA in 1980 and, more recently, to the powerful explosive eruptions at Mount Pinatubo (Luzon, Philippines in 1991. However, even with the ever-improving state-of-the-art in volcano monitoring and predictive capability, the Mount St. Helens and Pinatubo case histories unfortunately still represent the exceptions, rather than the rule, in successfully forecasting the most likely outcome of volcano unrest.

  10. Graphite Oxidation Simulation in HTR Accident Conditions

    Energy Technology Data Exchange (ETDEWEB)

    El-Genk, Mohamed

    2012-10-19

    Massive air and water ingress, following a pipe break or leak in steam-generator tubes, is a design-basis accident for high-temperature reactors (HTRs). Analysis of these accidents in both prismatic and pebble bed HTRs requires state-of-the-art capability for predictions of: 1) oxidation kinetics, 2) air helium gas mixture stratification and diffusion into the core following the depressurization, 3) transport of multi-species gas mixture, and 4) graphite corrosion. This project will develop a multi-dimensional, comprehensive oxidation kinetics model of graphite in HTRs, with diverse capabilities for handling different flow regimes. The chemical kinetics/multi-species transport model for graphite burning and oxidation will account for temperature-related changes in the properties of graphite, oxidants (O2, H2O, CO), reaction products (CO, CO2, H2, CH4) and other gases in the mixture (He and N2). The model will treat the oxidation and corrosion of graphite in geometries representative of HTR core component at temperatures of 900°C or higher. The developed chemical reaction kinetics model will be user-friendly for coupling to full core analysis codes such as MELCOR and RELAP, as well as computational fluid dynamics (CFD) codes such as CD-adapco. The research team will solve governing equations for the multi-dimensional flow and the chemical reactions and kinetics using Simulink, an extension of the MATLAB solver, and will validate and benchmark the model's predictions using reported experimental data. Researchers will develop an interface to couple the validated model to a commercially available CFD fluid flow and thermal-hydraulic model of the reactor , and will perform a simulation of a pipe break in a prismatic core HTR, with the potential for future application to a pebble-bed type HTR.

  11. Graphite waste incineration in a fluidized bed

    International Nuclear Information System (INIS)

    Guiroy, J.J.

    1996-01-01

    French gas-cooled reactors belonging to the Atomic Energy Commission (CEA), Electricite de France (EDF), Hifrensa (Spain), etc., commissioned between the 1950s and 1970s, have generated large quantities of graphite wastes, mainly in the form of spent fuel sleeves. Furthermore, some of these reactors scheduled for dismantling in the near future (such as the G2 and G3 reactors at Marcoule) have cores consisting of graphite blocks. Consequently, a fraction of the contaminated graphite, amounting to 6000 t in France for example, must be processed in the coming years. For this processing, incineration using a circulating fluidized bed combustor has been selected as a possible solution and validated. However, the first operation to be performed involves recovering this graphite waste, and particularly, first of all, the spent fuel sleeves that were stored in silos during the years of reactor operation. Subsequent to the final shutdown of the Spanish gas-cooled reactor unit, Vandellos 1, the operating utility Hifrensa awarded contracts to a Framatome Iberica SA/ENSA consortium for removing, sorting, and prepackaging of the waste stored in three silos on the Vandellos site, essentially graphite sleeves. On the other hand, a program to validate the Framatome fluidized bed incineration process was carried out using a prototype incinerator installed at Le Creusot, France. The validation program included 22 twelve-hour tests and one 120-hour test. Particular attention was paid to the safety aspects of this project. During the performance of the validation program, a preliminary safety assessment was carried out. An impact assessment was performed with the help of the French Institute for Protection and Nuclear Safety, taking into account the preliminary spectra supplied by the CEA and EDF, and the activities of the radionuclides susceptible of being released into the atmosphere during the incineration. (author). 4 refs, 11 figs, 1 tab

  12. Graphitization in Carbon MEMS and Carbon NEMS

    Science.gov (United States)

    Sharma, Swati

    Carbon MEMS (CMEMS) and Carbon NEMS (CNEMS) are an emerging class of miniaturized devices. Due to the numerous advantages such as scalable manufacturing processes, inexpensive and readily available precursor polymer materials, tunable surface properties and biocompatibility, carbon has become a preferred material for a wide variety of future sensing applications. Single suspended carbon nanowires (CNWs) integrated on CMEMS structures fabricated by electrospinning of SU8 photoresist on photolithographially patterned SU8 followed by pyrolysis are utilized for understanding the graphitization process in micro and nano carbon materials. These monolithic CNW-CMEMS structures enable the fabrication of very high aspect ratio CNWs of predefined length. The CNWs thus fabricated display core---shell structures having a graphitic shell with a glassy carbon core. The electrical conductivity of these CNWs is increased by about 100% compared to glassy carbon as a result of enhanced graphitization. We explore various tunable fabrication and pyrolysis parameters to improve graphitization in the resulting CNWs. We also suggest gas-sensing application of the thus fabricated single suspended CNW-CMEMS devices by using the CNW as a nano-hotplate for local chemical vapor deposition. In this thesis we also report on results from an optimization study of SU8 photoresist derived carbon electrodes. These electrodes were applied to the simultaneous detection of traces of Cd(II) and Pb(II) through anodic stripping voltammetry and detection limits as low as 0.7 and 0.8 microgL-1 were achieved. To further improve upon the electrochemical behavior of the carbon electrodes we elucidate a modified pyrolysis technique featuring an ultra-fast temperature ramp for obtaining bubbled porous carbon from lithographically patterned SU8. We conclude this dissertation by suggesting the possible future works on enhancing graphitization as well as on electrochemical applications

  13. Volcano-Monitoring Instrumentation in the United States, 2008

    Science.gov (United States)

    Guffanti, Marianne; Diefenbach, Angela K.; Ewert, John W.; Ramsey, David W.; Cervelli, Peter F.; Schilling, Steven P.

    2010-01-01

    The United States is one of the most volcanically active countries in the world. According to the global volcanism database of the Smithsonian Institution, the United States (including its Commonwealth of the Northern Mariana Islands) is home to about 170 volcanoes that are in an eruptive phase, have erupted in historical time, or have not erupted recently but are young enough (eruptions within the past 10,000 years) to be capable of reawakening. From 1980 through 2008, 30 of these volcanoes erupted, several repeatedly. Volcano monitoring in the United States is carried out by the U.S. Geological Survey (USGS) Volcano Hazards Program, which operates a system of five volcano observatories-Alaska Volcano Observatory (AVO), Cascades Volcano Observatory (CVO), Hawaiian Volcano Observatory (HVO), Long Valley Observatory (LVO), and Yellowstone Volcano Observatory (YVO). The observatories issue public alerts about conditions and hazards at U.S. volcanoes in support of the USGS mandate under P.L. 93-288 (Stafford Act) to provide timely warnings of potential volcanic disasters to the affected populace and civil authorities. To make efficient use of the Nation's scientific resources, the volcano observatories operate in partnership with universities and other governmental agencies through various formal agreements. The Consortium of U.S. Volcano Observatories (CUSVO) was established in 2001 to promote scientific cooperation among the Federal, academic, and State agencies involved in observatory operations. Other groups also contribute to volcano monitoring by sponsoring long-term installation of geophysical instruments at some volcanoes for specific research projects. This report describes a database of information about permanently installed ground-based instruments used by the U.S. volcano observatories to monitor volcanic activity (unrest and eruptions). The purposes of this Volcano-Monitoring Instrumentation Database (VMID) are to (1) document the Nation's existing

  14. Data assimilation strategies for volcano geodesy

    Science.gov (United States)

    Zhan, Yan; Gregg, Patricia M.

    2017-09-01

    Ground deformation observed using near-real time geodetic methods, such as InSAR and GPS, can provide critical information about the evolution of a magma chamber prior to volcanic eruption. Rapid advancement in numerical modeling capabilities has resulted in a number of finite element models targeted at better understanding the connection between surface uplift associated with magma chamber pressurization and the potential for volcanic eruption. Robust model-data fusion techniques are necessary to take full advantage of the numerical models and the volcano monitoring observations currently available. In this study, we develop a 3D data assimilation framework using the Ensemble Kalman Filter (EnKF) approach in order to combine geodetic observations of surface deformation with geodynamic models to investigate volcanic unrest. The EnKF sequential assimilation method utilizes disparate data sets as they become available to update geodynamic models of magma reservoir evolution. While the EnKF has been widely applied in hydrologic and climate modeling, the adaptation for volcano monitoring is in its initial stages. As such, our investigation focuses on conducting a series of sensitivity tests to optimize the EnKF for volcano applications and on developing specific strategies for assimilation of geodetic data. Our numerical experiments illustrate that the EnKF is able to adapt well to the spatial limitations posed by GPS data and the temporal limitations of InSAR, and that specific strategies can be adopted to enhance EnKF performance to improve model forecasts. Specifically, our numerical experiments indicate that: (1) incorporating additional iterations of the EnKF analysis step is more efficient than increasing the number of ensemble members; (2) the accuracy of the EnKF results are not affected by initial parameter assumptions; (3) GPS observations near the center of uplift improve the quality of model forecasts; (4) occasionally shifting continuous GPS stations to

  15. Method of manufacturing a graphite coated fuel can

    International Nuclear Information System (INIS)

    Saito, Koichi; Uchida, Shunsuke.

    1984-01-01

    Purpose: To improve the close bondability and homogeneity of a graphite coating formed at the inner surface of a fuel can. Method: A coating containing graphite dispersed in a volatile organic solvent is used and a graphite coating is formed to the inner surface of a fuel can by way of a plunger method. After applying graphite coating, an inert gas is caused to flow at a certain flow rate to the inside of the fuel can horizontally rotaged so that gassification and evaporation of the volatile organic solvent contained in the graphite coating may be promoted. Since drying of the graphite coating coated to the inner surface of the fuel can thus be controlled, a graphite coating with satisfactory close bondability and homogeneity can be formed. (Kawakami, Y.)

  16. Ion irradiated graphite exposed to fusion-relevant deuterium plasma

    International Nuclear Information System (INIS)

    Deslandes, Alec; Guenette, Mathew C.; Corr, Cormac S.; Karatchevtseva, Inna; Thomsen, Lars; Ionescu, Mihail; Lumpkin, Gregory R.; Riley, Daniel P.

    2014-01-01

    Graphite samples were irradiated with 5 MeV carbon ions to simulate the damage caused by collision cascades from neutron irradiation in a fusion environment. The ion irradiated graphite samples were then exposed to a deuterium plasma in the linear plasma device, MAGPIE, for a total ion fluence of ∼1 × 10 24 ions m −2 . Raman and near edge X-ray absorption fine structure (NEXAFS) spectroscopy were used to characterize modifications to the graphitic structure. Ion irradiation was observed to decrease the graphitic content and induce disorder in the graphite. Subsequent plasma exposure decreased the graphitic content further. Structural and surface chemistry changes were observed to be greatest for the sample irradiated with the greatest fluence of MeV ions. D retention was measured using elastic recoil detection analysis and showed that ion irradiation increased the amount of retained deuterium in graphite by a factor of four

  17. GRAPHITIZATION OF METASEDIMENTARY ROCKS IN THE WESTERN KONYA

    Directory of Open Access Journals (Sweden)

    Hüseyin KURT

    2000-01-01

    Full Text Available The Paleozoic-Mesozoic metasedimentary rocks in the study area are metacarbonate, metachert, metapelite, metasandstone and metaconglomerate. Graphite layers are 1cm to 2m thick, extend laterally for tens of meters and are intercalated with metasedimentary rocks. Generally, the graphite is black in color, with a well developed cleavage which is concordant with the cleavage of the host rocks. In addition, the crystal and flake graphites formed in metasedimentary rocks are mostly aligned parallel to the cleavage planes. These metamorphic rocks are subjected to shearing and granulation providing structural control for the development of graphite. It was probably this phenomenon that first led to emphasize the relationship between graphite and metasedimentary rocks. Graphite mineralization has been controlled by bedding, microfractures and granulations. Briefly, the metamorphism has converted carbonaceous matter into graphite .

  18. Hydrophilization of graphite using plasma above/in a solution

    Science.gov (United States)

    Hoshino, Shuhei; Kawahara, Kazuma; Takeuchi, Nozomi

    2018-01-01

    A hydrophilization method for graphite is required for applications such as conductive ink. In typical chemical oxidation methods for graphite have the problems of producing many defects in graphite and a large environmental impact. In recent years, the plasma treatment has attracted attention because of the high quality of the treated samples and the low environmental impact. In this study, we proposed an above-solution plasma treatment with a high contact probability of graphite and plasma since graphite accumulates on the solution surface due to its hydrophobicity, which we compared with a so-called solution plasma treatment. Graphite was hydrophilized via reactions with OH radicals generated by the plasma. It was confirmed that hydroxyl and carboxyl groups were modified to the graphite and the dispersibility was improved. The above-solution plasma achieved more energy-efficient hydrophilization than the solution plasma and it was possible to enhance the dispersibility by increasing the plasma-solution contact area.

  19. Crystallization degree change of expanded graphite by milling and annealing

    International Nuclear Information System (INIS)

    Tang Qunwei; Wu Jihuai; Sun Hui; Fang Shijun

    2009-01-01

    Expanded graphite was ball milled with a planetary mill in air atmosphere, and subsequently thermal annealed. The samples were characterized by using X-ray diffraction spectroscopy (XRD), scanning electron microscopy (SEM) and thermal gravimetric analysis (TGA). It was found that in the milling initial stage (less than 12 h), the crystallization degree of the expanded graphite declined gradually, but after milling more than 16 h, a recrystallization of the expanded graphite toke place, and ordered nanoscale expanded graphite was formed gradually. In the annealing initial stage, the non-crystallization of the graphite occurred, but, beyond an annealing time, recrystallizations of the graphite arise. Higher annealing temperature supported the recrystallization. The milled and annealed expanded graphite still preserved the crystalline structure as raw material and hold high thermal stability.

  20. Progress in radioactive graphite waste management. Additional information

    International Nuclear Information System (INIS)

    2010-06-01

    Radioactive graphite constitutes a major waste stream which arises during the decommissioning of certain types of nuclear installations. Worldwide, a total of around 250 000 tonnes of radioactive graphite, comprising graphite moderators and reflectors, will require management solutions in the coming years. 14 C is the radionuclide of greatest concern in nuclear graphite; it arises principally through the interaction of reactor neutrons with nitrogen, which is present in graphite as an impurity or in the reactor coolant or cover gas. 3 H is created by the reactions of neutrons with 6 Li impurities in graphite as well as in fission of the fuel. 36 Cl is generated in the neutron activation of chlorine impurities in graphite. Problems in the radioactive waste management of graphite arise mainly because of the large volumes requiring disposal, the long half-lives of the main radionuclides involved and the specific properties of graphite - such as stored Wigner energy, graphite dust explosibility and the potential for radioactive gases to be released. Various options for the management of radioactive graphite have been studied but a generally accepted approach for its conditioning and disposal does not yet exist. Different solutions may be appropriate in different cases. In most of the countries with radioactive graphite to manage, little progress has been made to date in respect of the disposal of this material. Only in France has there been specific thinking about a dedicated graphite waste-disposal facility (within ANDRA): other major producers of graphite waste (UK and the countries of the former Soviet Union) are either thinking in terms of repository disposal or have no developed plans. A conference entitled 'Solutions for Graphite Waste: a Contribution to the Accelerated Decommissioning of Graphite Moderated Nuclear Reactors' was held at the University of Manchester 21-23 March 2007 in order to stimulate progress in radioactive graphite waste management

  1. Nucleation and growth characteristics of graphite spheroids in bainite during graphitization annealing of a medium carbon steel

    International Nuclear Information System (INIS)

    Gao, J.X.; Wei, B.Q.; Li, D.D.; He, K.

    2016-01-01

    The evolution of microstructure in bainite during graphitization annealing at 680 °C of Jominy-quenched bars of an Al-Si bearing medium carbon (0.4C wt%) steel has been studied and compared with that in martensite by using light, scanning and transmission electron microscopy. The results show that the graphitization process in bainite is different from that in martensite in many aspects such as the initial carbon state, the behavior of cementite, the nucleation-growth feature and kinetics of formation of graphite spheroids during graphitization annealing, and the shape, size and distribution of these graphite spheroids. The fact that the graphitization in bainite can produce more homogeneous graphite spheroids with more spherical shape and finer size in a shorter annealing time without the help of preexisting coring particles implies that bainite should be a better starting structure than martensite for making graphitic steel. - Highlights: • This article presents a microstructural characterization of formation of graphite spheroids in bainite. • Nucleation and growth characteristics of graphite spheroids formed in bainite and martensite are compared. • Bainite should be a better starting structure for making graphitic steel as results show.

  2. Erosion of pyrolytic graphite and Ti-doped graphite due to high flux irradiation

    International Nuclear Information System (INIS)

    Ohtsuka, Yusuke; Ohashi, Junpei; Ueda, Yoshio; Isobe, Michiro; Nishikawa, Masahiro

    1997-01-01

    The erosion of pyrolytic graphite and titanium doped graphite RG-Ti above 1,780 K was investigated by 5 keV Ar beam irradiation with the flux from 4x10 19 to 1x10 21 m -2 ·s -1 . The total erosion yields were significantly reduced with the flux. This reduction would be attributed to the reduction of RES (radiation enhanced sublimation) yield, which was observed in the case of isotropic graphite with the flux dependence of RES yield of φ -0.26 (φ: flux) obtained in our previous work. The yield of pyrolytic graphite was roughly 30% higher than that of isotropic graphite below the flux of 10 20 m -2 ·s -1 whereas each yield approached to very close value at the highest flux of 1x10 21 m -2 ·s -1 . This result indicated that the effect of graphite structure on the RES yield, which was apparent in the low flux region, would disappear in the high flux region probably due to the disordering of crystal structure. In the case of irradiation to RG-Ti at 1,780 K, the surface undulations evolved with a mean height of about 3 μm at 1.2x10 20 m -2 ·s -1 , while at higher flux of 8.0x10 20 m -2 ·s -1 they were unrecognizable. These phenomena can be explained by the reduction of RES of graphite parts excluding TiC grains. (author)

  3. Preliminary Volcano-Hazard Assessment for Gareloi Volcano, Gareloi Island, Alaska

    Science.gov (United States)

    Coombs, Michelle L.; McGimsey, Robert G.; Browne, Brandon L.

    2008-01-01

    Gareloi Volcano (178.794 degrees W and 51.790 degrees N) is located on Gareloi Island in the Delarof Islands group of the Aleutian Islands, about 2,000 kilometers west-southwest of Anchorage and about 150 kilometers west of Adak, the westernmost community in Alaska. This small (about 8x10 kilometer) volcano has been one of the most active in the Aleutians since its discovery by the Bering expedition in the 1740s, though because of its remote location, observations have been scant and many smaller eruptions may have gone unrecorded. Eruptions of Gareloi commonly produce ash clouds and lava flows. Scars on the flanks of the volcano and debris-avalanche deposits on the adjacent seafloor indicate that the volcano has produced large landslides in the past, possibly causing tsunamis. Such events are infrequent, occurring at most every few thousand years. The primary hazard from Gareloi is airborne clouds of ash that could affect aircraft. In this report, we summarize and describe the major volcanic hazards associated with Gareloi.

  4. Volcano art at Hawai`i Volcanoes National Park—A science perspective

    Science.gov (United States)

    Gaddis, Ben; Kauahikaua, James P.

    2018-03-26

    Long before landscape photography became common, artists sketched and painted scenes of faraway places for the masses. Throughout the 19th century, scientific expeditions to Hawaiʻi routinely employed artists to depict images for the people back home who had funded the exploration and for those with an interest in the newly discovered lands. In Hawaiʻi, artists portrayed the broad variety of people, plant and animal life, and landscapes, but a feature of singular interest was the volcanoes. Painters of early Hawaiian volcano landscapes created art that formed a cohesive body of work known as the “Volcano School” (Forbes, 1992). Jules Tavernier, Charles Furneaux, and D. Howard Hitchcock were probably the best known artists of this school, and their paintings can be found in galleries around the world. Their dramatic paintings were recognized as fine art but were also strong advertisements for tourists to visit Hawaiʻi. Many of these masterpieces are preserved in the Museum and Archive Collection of Hawaiʻi Volcanoes National Park, and in this report we have taken the opportunity to match the artwork with the approximate date and volcanological context of the scene.

  5. Evolution of deep crustal magma structures beneath Mount Baekdu volcano (MBV) intraplate volcano in northeast Asia

    Science.gov (United States)

    Rhie, J.; Kim, S.; Tkalcic, H.; Baag, S. Y.

    2017-12-01

    Heterogeneous features of magmatic structures beneath intraplate volcanoes are attributed to interactions between the ascending magma and lithospheric structures. Here, we investigate the evolution of crustal magmatic stuructures beneath Mount Baekdu volcano (MBV), which is one of the largest continental intraplate volcanoes in northeast Asia. The result of our seismic imaging shows that the deeper Moho depth ( 40 km) and relatively higher shear wave velocities (>3.8 km/s) at middle-to-lower crustal depths beneath the volcano. In addition, the pattern at the bottom of our model shows that the lithosphere beneath the MBV is shallower (interpret the observations as a compositional double layering of mafic underplating and a overlying cooled felsic structure due to fractional crystallization of asthenosphere origin magma. To achieve enhanced vertical and horizontal model coverage, we apply two approaches in this work, including (1) a grid-search based phase velocity measurement using real-coherency of ambient noise data and (2) a transdimensional Bayesian joint inversion using multiple ambient noise dispersion data.

  6. Understanding cyclic seismicity and ground deformation patterns at volcanoes: Intriguing lessons from Tungurahua volcano, Ecuador

    Science.gov (United States)

    Neuberg, Jürgen W.; Collinson, Amy S. D.; Mothes, Patricia A.; Ruiz, Mario C.; Aguaiza, Santiago

    2018-01-01

    Cyclic seismicity and ground deformation patterns are observed on many volcanoes worldwide where seismic swarms and the tilt of the volcanic flanks provide sensitive tools to assess the state of volcanic activity. Ground deformation at active volcanoes is often interpreted as pressure changes in a magmatic reservoir, and tilt is simply translated accordingly into inflation and deflation of such a reservoir. Tilt data recorded by an instrument in the summit area of Tungurahua volcano in Ecuador, however, show an intriguing and unexpected behaviour on several occasions: prior to a Vulcanian explosion when a pressurisation of the system would be expected, the tilt signal declines significantly, hence indicating depressurisation. At the same time, seismicity increases drastically. Envisaging that such a pattern could carry the potential to forecast Vulcanian explosions on Tungurahua, we use numerical modelling and reproduce the observed tilt patterns in both space and time. We demonstrate that the tilt signal can be more easily explained as caused by shear stress due to viscous flow resistance, rather than by pressurisation of the magmatic plumbing system. In general, our numerical models prove that if magma shear viscosity and ascent rate are high enough, the resulting shear stress is sufficient to generate a tilt signal as observed on Tungurahua. Furthermore, we address the interdependence of tilt and seismicity through shear stress partitioning and suggest that a joint interpretation of tilt and seismicity can shed new light on the eruption potential of silicic volcanoes.

  7. Volcano monitoring with an infrared camera: first insights from Villarrica Volcano

    Science.gov (United States)

    Rosas Sotomayor, Florencia; Amigo Ramos, Alvaro; Velasquez Vargas, Gabriela; Medina, Roxana; Thomas, Helen; Prata, Fred; Geoffroy, Carolina

    2015-04-01

    This contribution focuses on the first trials of the, almost 24/7 monitoring of Villarrica volcano with an infrared camera. Results must be compared with other SO2 remote sensing instruments such as DOAS and UV-camera, for the ''day'' measurements. Infrared remote sensing of volcanic emissions is a fast and safe method to obtain gas abundances in volcanic plumes, in particular when the access to the vent is difficult, during volcanic crisis and at night time. In recent years, a ground-based infrared camera (Nicair) has been developed by Nicarnica Aviation, which quantifies SO2 and ash on volcanic plumes, based on the infrared radiance at specific wavelengths through the application of filters. Three Nicair1 (first model) have been acquired by the Geological Survey of Chile in order to study degassing of active volcanoes. Several trials with the instruments have been performed in northern Chilean volcanoes, and have proven that the intervals of retrieved SO2 concentration and fluxes are as expected. Measurements were also performed at Villarrica volcano, and a location to install a ''fixed'' camera, at 8km from the crater, was discovered here. It is a coffee house with electrical power, wifi network, polite and committed owners and a full view of the volcano summit. The first measurements are being made and processed in order to have full day and week of SO2 emissions, analyze data transfer and storage, improve the remote control of the instrument and notebook in case of breakdown, web-cam/GoPro support, and the goal of the project: which is to implement a fixed station to monitor and study the Villarrica volcano with a Nicair1 integrating and comparing these results with other remote sensing instruments. This works also looks upon the strengthen of bonds with the community by developing teaching material and giving talks to communicate volcanic hazards and other geoscience topics to the people who live "just around the corner" from one of the most active volcanoes

  8. Imaging magma plumbing beneath Askja volcano, Iceland

    Science.gov (United States)

    Greenfield, Tim; White, Robert S.

    2015-04-01

    Volcanoes during repose periods are not commonly monitored by dense instrumentation networks and so activity during periods of unrest is difficult to put in context. We have operated a dense seismic network of 3-component, broadband instruments around Askja, a large central volcano in the Northern Volcanic Zone, Iceland, since 2006. Askja last erupted in 1961, with a relatively small basaltic lava flow. Since 1975 the central caldera has been subsiding and there has been no indication of volcanic activity. Despite this, Askja has been one of the more seismically active volcanoes in Iceland. The majority of these events are due to an extensive geothermal area within the caldera and tectonically induced earthquakes to the northeast which are not related to the magma plumbing system. More intriguing are the less numerous deeper earthquakes at 12-24km depth, situated in three distinct areas within the volcanic system. These earthquakes often show a frequency content which is lower than the shallower activity, but they still show strong P and S wave arrivals indicative of brittle failure, despite their location being well below the brittle-ductile boundary, which, in Askja is ~7km bsl. These earthquakes indicate the presence of melt moving or degassing at depth while the volcano is not inflating, as only high strain rates or increased pore fluid pressures would cause brittle fracture in what is normally an aseismic region in the ductile zone. The lower frequency content must be the result of a slower source time function as earthquakes which are both high frequency and low frequency come from the same cluster, thereby discounting a highly attenuating lower crust. To image the plumbing system beneath Askja, local and regional earthquakes have been used as sources to solve for the velocity structure beneath the volcano. Travel-time tables were created using a finite difference technique and the residuals were used to solve simultaneously for both the earthquake locations

  9. Mineralogical and geochemical study of mud volcanoes in north ...

    African Journals Online (AJOL)

    The gulf of Cadiz is one of the most interesting areas to study mud volcanoes and structures related to cold fluid seeps since their discovery in 1999. In this study, we present results from gravity cores collected from Ginsburg and Meknes mud volcanoes and from circular structure located in the gulf of Cadiz (North Atlantic ...

  10. Fuego Volcano eruption (Guatemala, 1974): evidence of a tertiary fragmentation?

    International Nuclear Information System (INIS)

    Brenes-Andre, Jose

    2014-01-01

    Values for mode and dispersion calculated from SFT were analyzed using the SFT (Sequential Fragmentation/Transport) model to Fuego Volcano eruption (Guatemala, 1974). Analysis results have showed that the ideas initially proposed for Irazu, can be applied to Fuego Volcano. Experimental evidence was found corroborating the existence of tertiary fragmentations. (author) [es

  11. 36 CFR 7.25 - Hawaii Volcanoes National Park.

    Science.gov (United States)

    2010-07-01

    ... 36 Parks, Forests, and Public Property 1 2010-07-01 2010-07-01 false Hawaii Volcanoes National Park. 7.25 Section 7.25 Parks, Forests, and Public Property NATIONAL PARK SERVICE, DEPARTMENT OF THE INTERIOR SPECIAL REGULATIONS, AREAS OF THE NATIONAL PARK SYSTEM § 7.25 Hawaii Volcanoes National Park. (a...

  12. Using Google Earth to Study the Basic Characteristics of Volcanoes

    Science.gov (United States)

    Schipper, Stacia; Mattox, Stephen

    2010-01-01

    Landforms, natural hazards, and the change in the Earth over time are common material in state and national standards. Volcanoes exemplify these standards and readily capture the interest and imagination of students. With a minimum of training, students can recognize erupted materials and types of volcanoes; in turn, students can relate these…

  13. Volcano ecology: Disturbance characteristics and assembly of biological communities

    Science.gov (United States)

    Volcanic eruptions are powerful expressions of Earth’s geophysical forces which have shaped and influenced ecological systems since the earliest days of life. The study of the interactions of volcanoes and ecosystems, termed volcano ecology, focuses on the ecological responses of organisms and biolo...

  14. Electrochemical behaviour of rhenium-graphite electrode

    International Nuclear Information System (INIS)

    Varypaev, V.N.; Krasikov, V.L.

    1980-01-01

    Electrochemical behaviour of combination electrode from graphite with electrodeposited thin coating of electrolytic rhenium is studied. Solution of 0.5 m NaCl+0.04 m AlCl 3 served as an electrolite. Polarization galvanostatic curves of hydrogen evolution upon electrodes with conditional rhenium thickness of 3.5 and 0.35 μm, 35 and 3.5 nm are obtained. Possibility of preparation of rhenium-graphite cathode with extremely low rhenium consume, electro-chemical properties of which are simu-lar to purely rhenium cathode is shown. Such electrode is characterized with stable in time low cathode potential of hydrogen evolution in chloride electrolyte and during cathode polarization it is not affected by corrosion

  15. Graphite moderated {sup 252}Cf source

    Energy Technology Data Exchange (ETDEWEB)

    Sajo B, L.; Barros, H.; Greaves, E. D. [Universidad Simon Bolivar, Nuclear Physics Laboratory, Apdo. 89000, 1080A Caracas (Venezuela, Bolivarian Republic of); Vega C, H. R., E-mail: fermineutron@yahoo.com [Universidad Autonoma de Zacatecas, Unidad Academica de Estudios Nucleares, Cipres No. 10, Fracc. La Penuela, 98068 Zacatecas (Mexico)

    2014-08-15

    The thorium molten salt reactor is an attractive and affordable nuclear power option for developing countries with insufficient infrastructure and limited technological capability. In the aim of personnel training and experience gathering at the Universidad Simon Bolivar there is in progress a project of developing a subcritical thorium liquid fuel reactor. The neutron source to run this subcritical reactor is a {sup 252}Cf source and the reactor will use high-purity graphite as moderator. Using the MCNP5 code the neutron spectra of the {sup 252}Cf in the center of the graphite moderator has been estimated along the channel where the liquid thorium salt will be inserted; also the ambient dose equivalent due to the source has been determined around the moderator. (Author)

  16. Magnetic response of certain curved graphitic geometries

    International Nuclear Information System (INIS)

    Wang, L.; Davids, P.S.; Saxena, A.; Bishop, A.R.

    1992-01-01

    The quasi-particle energy spectra associated with some members of buckyfamily (curved graphitic geometries), in particular C 50 , C 60 , C 70 and related fullerenes as well as coaxial helical microtubules of graphite, are obtained analytically within the mean-field approximation. These energy spectra are then used to calculate various response functions. Specifically, we calculate the specific heat, magnetization and magnetic susceptibility in the presence of an external magnetic field at low temperatures. For a single microtubule an extra peak superimposed on the first de Haas van Alphen (dHvA) oscillation in magnetic susceptibility is found in the 50--170 Tesla range depending on the radius which is possibly accessible in special (explosive flux compression) experiments. Finally, we point to important potential applications of these novel mesoscopic structures in nanotechnology

  17. Imaging of tritium implanted into graphite

    International Nuclear Information System (INIS)

    Malinowski, M.E.; Causey, R.A.

    1988-01-01

    The extensive use of graphite in plasma-facing surfaces of tokamaks such as the Tokamak Fusion Test Reactor, which has planned tritium discharges, makes two-dimensional tritium detection techniques important in helping to determine torus tritium inventories. We have performed experiments in which highly oriented pyrolytic graphite (HOPG) samples were first tritium implanted with fluences of ∼10 16 T/cm 2 at energies approx. 0 C resulted in no discernible motion of tritium along the basal plane, but did show that significant desorption of the implanted tritium occurred. The current results indicate that tritium in quantities of 10 12 T/cm 2 in tritiated components could be readily detected by imaging at lower magnifications

  18. Preparation of nanoporous carbons from graphite nanofibres

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Byung-Joo [Department of Green Chemistry and Environmental Biotechnology, University of Science and Technology, PO Box 107, Yuseong, Daejeon 305-600 (Korea, Republic of); Park, Soo-Jin [Department of Chemistry, Inha University, 253, Nam-gu, Incheon 402-751 (Korea, Republic of)

    2006-09-14

    In this study we manufactured highly porous graphite nanofibres (GNFs) by physical activation in order to develop promising energy storage materials. The activation was performed at activation temperatures in the range of 800-1050 deg. C. The pore structures of the porous GNFs were analysed using N{sub 2}/77 K adsorption isotherms. After the activation, the porous GNFs showed a decrease in diameter and scratches on their surfaces, resulting from surface oxidation and the opening of the graphitic layers, respectively. It was found that the specific surface area of the porous GNFs prepared at 1050 deg. C was more than 2000 m{sup 2} g{sup -1} without loss of their fibre shape or serious increase in electrical resistivity. This result indicates that porous GNFs prepared under optimal conditions can have a much higher specific surface area and are promising materials for energy storage technologies.

  19. Spectroscopical determination of impurities in nuclear graphite

    International Nuclear Information System (INIS)

    Lordello, A.R.; Tognini, R.P.

    1975-01-01

    A spectrochemical method for the direct determination of B, Cd, Si, Hg, Fe, Mg, Mn, Cr, Ni, Al, Mo, Ti, Sr, Na, Zn, and As in nuclear grade graphite is described. A 9:1 ratio of graphite to copper difluoride is used in the preparation of samples and standards. The excitation is carried out in a d-c at 10 amperes. The copper fluoride used as spectrographic buffer serves to increase the volatilization rate of the impurities and to diminish the differences in the nature of the analytical and calibration samples. The relative standard deviations for the determination of the 16 trace elements, except Sr, Fe, Cd, Al and Si, are in the range of 8 - 20% in their appropriate calibration levels. For the latter five elements they are approximately 20-40%

  20. Effect of total pressure on graphite oxidation

    International Nuclear Information System (INIS)

    Burnette, R.D.; Hoot, C.G.

    1983-04-01

    Graphite corrosion in the high-temperature gas-cooled reactor (HTGR) is calculated using two key assumptions: (1) the kinetic, catalysis, and transport characteristics of graphite determined by bench-scale tests apply to large components at reactor conditions and (2) the effects of high pressure and turbulent flow are predictable. To better understand the differences between laboratory tests and reactor conditions, a high-pressure test loop (HPTL) has been constructed and used to perform tests at reactor temperature, pressure, and flow conditions. The HPTL is intended to determine the functional dependence of oxidation rate and characteristics on total pressure and gas velocity and to compare the oxidation results with calculations using models and codes developed for the reactor