Mineral dissolution and precipitation in carbonate dominated terranes assessed using Mg isotopes

Science.gov (United States)

Tipper, E.; Calmels, D.; Gaillardet, J.; Galy, A.

2013-12-01

to be congruent, meaning that the Mg released to solutes during mineral dissolution should have the same composition as the host rock. Some of this difference is likely accounted for by atmospheric deposition or cyclic inputs, but this cannot account for all of the 1.5permil shift between rock and water. It is plausible that some of the difference is explained by trace levels of Mg-silicate dissolution (with a delta26Mg of circa 0permil), but equally carbonate precipitation and attendant Mg isotope fractionation could theoretically account for the difference between rock and water. The various plausible explications will be discussed, as well as the implications of the data for better understanding carbonate weathering.

Host Rock Classification (HRC) system for nuclear waste disposal in crystalline bedrock

International Nuclear Information System (INIS)

Hagros, A.

2006-01-01

A new rock mass classification scheme, the Host Rock Classification system (HRC-system) has been developed for evaluating the suitability of volumes of rock mass for the disposal of high-level nuclear waste in Precambrian crystalline bedrock. To support the development of the system, the requirements of host rock to be used for disposal have been studied in detail and the significance of the various rock mass properties have been examined. The HRC-system considers both the long-term safety of the repository and the constructability in the rock mass. The system is specific to the KBS-3V disposal concept and can be used only at sites that have been evaluated to be suitable at the site scale. By using the HRC-system, it is possible to identify potentially suitable volumes within the site at several different scales (repository, tunnel and canister scales). The selection of the classification parameters to be included in the HRC-system is based on an extensive study on the rock mass properties and their various influences on the long-term safety, the constructability and the layout and location of the repository. The parameters proposed for the classification at the repository scale include fracture zones, strength/stress ratio, hydraulic conductivity and the Groundwater Chemistry Index. The parameters proposed for the classification at the tunnel scale include hydraulic conductivity, Q' and fracture zones and the parameters proposed for the classification at the canister scale include hydraulic conductivity, Q', fracture zones, fracture width (aperture + filling) and fracture trace length. The parameter values will be used to determine the suitability classes for the volumes of rock to be classified. The HRC-system includes four suitability classes at the repository and tunnel scales and three suitability classes at the canister scale and the classification process is linked to several important decisions regarding the location and acceptability of many components of

Support to other nuclear waste disposal programmes considering clay as a potential host rock

International Nuclear Information System (INIS)

Volckaert, G.

2009-01-01

SCK-CEN started to study the Boom Clay as potential host rock for nuclear waste disposal in 1974. Since then, SCK-CEN has been involved in other international projects studying clay as potential host rock in order to get a broader support for disposal in clay and to acquire broader insight in clay behaviour. Besides Belgium, France and Switzerland are currently investigating clay formations as potential host rock for the disposal of radioactive waste. In the Netherlands, clay formations have always been considered as an alternative to disposal in salt. The general interest in clays is increasing: in Germany and The United Kingdom, it was decided a few years ago that besides respectively salt and crystalline rock also clays need to be evaluated. In Eastern and Central Europe, the Slovak republic and Lithuania consider both clay and granite as possible host rocks for spent fuel while in Russia recently a project was started to study the possible disposal of low and medium level waste in a clay formation in the Leningrad area. Within the EC research and development framework programs and the OECD/NEA Clay Club, collaborations were developed between countries studying clay and with a strong involvement of SCK-CEN. The collaboration with the Eastern and Central European countries is supported through the support programme of the Belgian Ministry of Economic affairs. The objectives of these co-operations are to deliver expert services to other nuclear waste disposal programs considering clay as host rock; to to acquire broader international recognition of our expertise and support for the development of nuclear waste disposal in clay; to get a broader insight in the properties and behaviour of clays

Do Hf isotopes in magmatic zircons represent those of their host rocks?

Science.gov (United States)

Wang, Di; Wang, Xiao-Lei; Cai, Yue; Goldstein, Steven L.; Yang, Tao

2018-04-01

Lu-Hf isotopic system in zircon is a powerful and widely used geochemical tracer in studying petrogenesis of magmatic rocks and crustal evolution, assuming that zircon Hf isotopes can represent initial Hf isotopes of their parental whole rock. However, this assumption may not always be valid. Disequilibrium partial melting of continental crust would preferentially melt out non-zircon minerals with high time-integrated Lu/Hf ratios and generate partial melts with Hf isotope compositions that are more radiogenic than those of its magma source. Dissolution experiments (with hotplate, bomb and sintering procedures) of zircon-bearing samples demonstrate this disequilibrium effect where partial dissolution yielded variable and more radiogenic Hf isotope compositions than fully dissolved samples. A case study from the Neoproterozoic Jiuling batholith in southern China shows that about half of the investigated samples show decoupled Hf isotopes between zircons and the bulk rocks. This decoupling could reflect complex and prolonged magmatic processes, such as crustal assimilation, magma mixing, and disequilibrium melting, which are consistent with the wide temperature spectrum from ∼630 °C to ∼900 °C by Ti-in-zircon thermometer. We suggest that magmatic zircons may only record the Hf isotopic composition of their surrounding melt during crystallization and it is uncertain whether their Hf isotopic compositions can represent the primary Hf isotopic compositions of the bulk magmas. In this regard, using zircon Hf isotopic compositions to trace crustal evolution may be biased since most of these could be originally from disequilibrium partial melts.

Organic tissues, graphite, and hydrocarbons in host rocks of the Rum Jungle Uranium Field, northern Australia

Science.gov (United States)

Foster, C.B.; Robbins, E.I.; Bone, Y.

1990-01-01

The Rum Jungle Uranium field consists of at least six early Proterozoic deposits that have been mined either for uranium and/or the associated base and precious metals. Organic matter in the host rocks of the Whites Formation and Coomalie Dolomite is now predominantly graphite, consistent with the metamorphic history of these rocks. For nine samples, the mean total organic carbon content is high (3.9 wt%) and ranged from 0.33 to 10.44 wt%. Palynological extracts from the host rocks include black, filamentous, stellate (Eoastrion-like), and spherical morphotypes, which are typical of early Proterozoic microbiota. The colour, abundance, and shapes of these morphotypes reflect the thermal history, organic richness, and probable lacustrine biofacies of the host rocks. Routine analysis of rock thin sections and of palynological residues shows that mineral grains in some of the host rocks are coated with graphitized organic matter. The grain coating is presumed to result from ultimate thermal degradation of a petroleum phase that existed prior to metamorphism. Hydrocarbons are, however, still present in fluid inclusions within carbonates of the Coomalie Dolomite and lower Whites Formation. The fluid inclusions fluoresce dull orange in blue-light excitation and their hydrocarbon content is confirmed by gas chromatography of whole-rock extracts. Preliminary analysis of the oil suggests that it is migrated, and because it has escaped graphitization through metamorphism it is probably not of early Proterozoic age. The presence of live oil is consistent with fluid inclusion data that suggest subsequent, low-temperature brine migration through the rocks. The present observations support earlier suggestions that organic matter in the host formations trapped uranium to form protore. Subsequent fluid migrations probably brought additional uranium and other metals to these formations, and the organic matter provided a reducing environment for entrapment. ?? 1990.

A preliminary study on the suitability of host rocks for deep geological disposal of high level radioactive waste in Korea

Energy Technology Data Exchange (ETDEWEB)

Kim, Chun Soo; Bae, Dae Seok; Kim, Kyung Su; Park, Byung Yun; Koh, Young Kown

2000-02-01

It is expected that the key issues are listed as the disposal concept, reference disposal system and other relevant technical development for the deep geological disposal of HLW in each country. First above all, however, the preferred host rocks should be suggested prior execution of these activities. And, it is desirable to be reviewed and proposed some host rocks representative its country. For the reviewing of host rocks in Korean peninsula, several issues were considered such as the long-term geological stability, fracture system, surface and groundwater system and geochemical characteristics in peninsula. The three rock types such as plutonic rocks, crystalline gneisses and massive volcanic rocks were suggested as the preferred host rocks for the R and D of HLW disposal based on the upper stated information. In the following stages, it is suggested that these preferred host rocks would be made an object of all relevant R and D activities for HLW disposal. And, many references for these geologic medium should be characterized and constructed various technical development for the Korean reference disposal system.

A preliminary study on the suitability of host rocks for deep geological disposal of high level radioactive waste in Korea

International Nuclear Information System (INIS)

Kim, Chun Soo; Bae, Dae Seok; Kim, Kyung Su; Park, Byung Yun; Koh, Young Kown

2000-02-01

It is expected that the key issues are listed as the disposal concept, reference disposal system and other relevant technical development for the deep geological disposal of HLW in each country. First above all, however, the preferred host rocks should be suggested prior execution of these activities. And, it is desirable to be reviewed and proposed some host rocks representative its country. For the reviewing of host rocks in Korean peninsula, several issues were considered such as the long-term geological stability, fracture system, surface and groundwater system and geochemical characteristics in peninsula. The three rock types such as plutonic rocks, crystalline gneisses and massive volcanic rocks were suggested as the preferred host rocks for the R and D of HLW disposal based on the upper stated information. In the following stages, it is suggested that these preferred host rocks would be made an object of all relevant R and D activities for HLW disposal. And, many references for these geologic medium should be characterized and constructed various technical development for the Korean reference disposal system

Evaporite dissolution relevant to the WIPP site, northern Delaware Basin, southeastern New Mexico

International Nuclear Information System (INIS)

Lambert, S.J.

1982-01-01

Evaluation of the threat of natural dissolution of host evaporites to the integrity of the Waste Isolation Pilot Plant (WIPP) in southeastern New Mexico has taken into consideration (1) the volume of missing rock salt, (2) the occurrence (or not) of characteristic dissolution brines, (3) geomorphic features, some of which are unrelated to dissolution, and (4) the time intervals over which dissolution may have been active. Even under the assumption that all missing halite was originally present and has been removed by dissolution, there is no evidence of active preferential removal of the lower Salado Formation halite by any geologically reasonable process. The geologic record contains evidence of dissolution in the Triassic and Jurassic; to constrain all removal of basinal halite to the late Cenozoic yields an unrealistically high rate of removal. Application to the lower Salado of a stratabound mechanism known to be active in Nash Draw, a near-surface feature within the Basin, allows a minimum survival time of 2,500,000 years to be predicted for the subsurface facility for storage of radioactive waste at WIPP. This calculation is based on an analysis of all known dissolution features in the Delaware Basin, and takes into account the wetter (pluvial) climate during the past 600,000 years. 2 figures, 1 table

The effect of clay on the dissolution of nuclear waste glass

Science.gov (United States)

Lemmens, K.

2001-09-01

In a nuclear waste repository, the waste glass can interact with metals, backfill materials (if present) and natural host rock. Of the various host rocks considered, clays are often reported to delay the onset of the apparent glass saturation, where the glass dissolution rate becomes very small. This effect is ascribed to the sorption of silica or other glass components on the clay. This can have two consequences: (1) the decrease of the silica concentration in solution increases the driving force for further dissolution of glass silica, and (2) the transfer of relatively insoluble glass components (mainly silica) from the glass surface to the clay makes the alteration layer less protective. In recent literature, the latter explanation has gained credibility. The impact of the environmental materials on the glass surface layers is however not well understood. Although the glass dissolution can initially be enhanced by clay, there are arguments to assume that it will decrease to very low values after a long time. Whether this will indeed be the case, depends on the fate of the released glass components in the clay. If they are sorbed on specific sites, it is likely that saturation of the clay will occur. If however the released glass components are removed by precipitation (growth of pre-existing or new secondary phases), saturation of the clay is less likely, and the process can continue until exhaustion of one of the system components. There are indications that the latter mechanism can occur for varying glass compositions in Boom Clay and FoCa clay. If sorption or precipitation prevents the formation of protective surface layers, the glass dissolution can in principle proceed at a high rate. High silica concentrations are assumed to decrease the dissolution rate (by a solution saturation effect or by the impact on the properties of the glass alteration layer). In glass corrosion tests at high clay concentrations, silica concentrations are, however, often higher

The effect of clay on the dissolution of nuclear waste glass

International Nuclear Information System (INIS)

Lemmens, K.

2001-01-01

In a nuclear waste repository, the waste glass can interact with metals, backfill materials (if present) and natural host rock. Of the various host rocks considered, clays are often reported to delay the onset of the apparent glass saturation, where the glass dissolution rate becomes very small. This effect is ascribed to the sorption of silica or other glass components on the clay. This can have two consequences: (1) the decrease of the silica concentration in solution increases the driving force for further dissolution of glass silica, and (2) the transfer of relatively insoluble glass components (mainly silica) from the glass surface to the clay makes the alteration layer less protective. In recent literature, the latter explanation has gained credibility. The impact of the environmental materials on the glass surface layers is however not well understood. Although the glass dissolution can initially be enhanced by clay, there are arguments to assume that it will decrease to very low values after a long time. Whether this will indeed be the case, depends on the fate of the released glass components in the clay. If they are sorbed on specific sites, it is likely that saturation of the clay will occur. If however the released glass components are removed by precipitation (growth of pre-existing or new secondary phases), saturation of the clay is less likely, and the process can continue until exhaustion of one of the system components. There are indications that the latter mechanism can occur for varying glass compositions in Boom Clay and FoCa clay. If sorption or precipitation prevents the formation of protective surface layers, the glass dissolution can in principle proceed at a high rate. High silica concentrations are assumed to decrease the dissolution rate (by a solution saturation effect or by the impact on the properties of the glass alteration layer). In glass corrosion tests at high clay concentrations, silica concentrations are, however, often higher

Dissolution kinetics of smectite in geological repository system of TRU waste

International Nuclear Information System (INIS)

Sato, Tsutomu

2005-02-01

Extensive use of cement for encapsulation, mine timbering, and grouting purposes is envisaged in geological repositories of TRU waste. Degradation of cement materials in the repositories can produce a high pH pore fluid initially ranging from pH 13.0 to 13.5. The high pH pore fluids can migrate and react chemically with the host rock and bentonites which were employed to enhance repository's integrity. These chemical reactions can effect the capacity of the rocks and bentonites in retarding the migration of radionuclides. Smectite, main component of bentonite, can lose some of their desirable properties at the early stages of bentonite-cement fluid interaction. This has been a key research issue in performance assessment of TRU waste disposal. In this study, firstly, the factors affected on dissolution rate of smectite and equations describing dissolution rate were reviewed. Secondly, the effect of dissolved silica on the dissolution behavior of Na-montmorillonite was investigated. Bulk sample flow-through dissolution experiments at alkaline condition (pH 13.3) with different dissolved silica concentrations at different temperatures were performed. Titration experiments were also carried out at similar conditions. Atomic Force Microscopy (AFM) ex situ observations (i.e. on samples from flow-through experiments) was also performed to obtain the dissolution rate. Current results from bulk sample surface titration experiments indicate that dissolved silica has no pronounced effect on the surface titration behavior of Na-montmorillonite at any temperature. However, the trends for the surface titration behavior represent the averaged behavior of all particle sizes (i.e. including colloids) such that within an order of magnitude change cannot be quantified appreciably. Bulk flow-through dissolution experiments coupled with ex situ AFM observations indicate that there is also no effect of dissolved silica with comparatively low concentration of the reacting solution on

Use of structural geology in exploration for and mining of sedimentary rock-hosted Au deposits

Science.gov (United States)

Peters, Stephen G.

2001-01-01

Structural geology is an important component in regional-, district- and orebody-scale exploration and development of sedimentary rock-hosted Au deposits.Identification of timing of important structural events in an ore district allows analysis and classification of fluid conduits and construction of genetic models for ore formation.The most practical uses of structural geology deal with measurement and definition of various elements that comprise orebodies, which can then be directly applied to ore-reserve estimation,ground control,grade control, safety issues,and mine planning.District- and regional-scale structural studies are directly applicable to long-term strategic planning,economic analysis,and land ownership. Orebodies in sedimentary rock-hosted Au deposits are discrete, hypogene, epigenetic masses usually hosted in a fault zone,breccia mass, or lithologic bed or unit. These attributes allow structural geology to be directly applied to the mining and exploration of sedimentary rock-hosted Au deposits. Internal constituents in orebodies reflect unique episodes relating to ore formation.The main internal constituents in orebodies are ore minerals, gangue, and alteration minerals that usually are mixed with one another in complex patterns, the relations among which may be used to interpret the processes of orebody formation and control.Controls of orebody location and shape usually are due to structural dilatant zones caused by changes in attitude, splays, lithologic contacts,and intersections of the host conduit or unit.In addition,conceptual parameters such as district fabric,predictable distances, and stacking also are used to understand the geometry of orebodies.Controls in ore districts and location and geometry of orebodies in ore districts can be predicted to various degrees by using a number of qualitative concepts such as internal and external orebody plunges,district plunge, district stacking, conduit classification, geochemical, geobarometric and

Evaluation of Five Sedimentary Rocks Other Than Salt for Geologic Repository Siting Purposes

Energy Technology Data Exchange (ETDEWEB)

Croff, A.G.; Lomenick, T.F.; Lowrie, R.S.; Stow, S.H.

2003-11-15

The US Department of Energy (DOE), in order to increase the diversity of rock types under consideration by the geologic disposal program, initiated the Sedimary ROck Program (SERP), whose immediate objectiv eis to evaluate five types of secimdnary rock - sandstone, chalk, carbonate rocks (limestone and dolostone), anhydrock, and shale - to determine the potential for siting a geologic repository. The evaluation of these five rock types, together with the ongoing salt studies, effectively results in the consideration of all types of relatively impermeable sedimentary rock for repository purposes. The results of this evaluation are expressed in terms of a ranking of the five rock types with respect to their potential to serve as a geologic repository host rock. This comparative evaluation was conducted on a non-site-specific basis, by use of generic information together with rock evaluation criteria (RECs) derived from the DOE siting guidelines for geologic repositories (CFR 1984). An information base relevant to rock evaluation using these RECs was developed in hydrology, geochemistry, rock characteristics (rock occurrences, thermal response, rock mechanics), natural resources, and rock dissolution. Evaluation against postclosure and preclosure RECs yielded a ranking of the five subject rocks with respect to their potential as repository host rocks. Shale was determined to be the most preferred of the five rock types, with sandstone a distant second, the carbonate rocks and anhydrock a more distant third, and chalk a relatively close fourth.

Evaluation of Five Sedimentary Rocks Other Than Salt for Geologic Repository Siting Purposes

International Nuclear Information System (INIS)

Croff, A.G.; Lomenick, T.F.; Lowrie, R.S.; Stow, S.H.

2003-01-01

The US Department of Energy (DOE), in order to increase the diversity of rock types under consideration by the geologic disposal program, initiated the Sedimary ROck Program (SERP), whose immediate objectiv eis to evaluate five types of secimdnary rock - sandstone, chalk, carbonate rocks (limestone and dolostone), anhydrock, and shale - to determine the potential for siting a geologic repository. The evaluation of these five rock types, together with the ongoing salt studies, effectively results in the consideration of all types of relatively impermeable sedimentary rock for repository purposes. The results of this evaluation are expressed in terms of a ranking of the five rock types with respect to their potential to serve as a geologic repository host rock. This comparative evaluation was conducted on a non-site-specific basis, by use of generic information together with rock evaluation criteria (RECs) derived from the DOE siting guidelines for geologic repositories (CFR 1984). An information base relevant to rock evaluation using these RECs was developed in hydrology, geochemistry, rock characteristics (rock occurrences, thermal response, rock mechanics), natural resources, and rock dissolution. Evaluation against postclosure and preclosure RECs yielded a ranking of the five subject rocks with respect to their potential as repository host rocks. Shale was determined to be the most preferred of the five rock types, with sandstone a distant second, the carbonate rocks and anhydrock a more distant third, and chalk a relatively close fourth.

Analysis of hydraulic gradients across the host rock at the proposed Texas Panhandle nuclear-waste repository site

International Nuclear Information System (INIS)

Bair, E.S.

1987-01-01

Analysis of the direction of ground-water flow across the host rock at the proposed high-level nuclear-waste repository site in Deaf Smith County, Texas, is complicated by vertical and lateral changes in the density of formation fluids in the various hydrogeologic units that overlie and underlie the proposed host rock. Because the concept of hydraulic head is not valid when evaluating vertical hydraulic gradients in a variably-density flow system, other methods were used to determine the direction and magnitude of vertical hydraulic gradients at the proposed site where the specific gravity of formation fluids varies between 1.00 and 1.28. The direction of ground-water flow across the proposed host rock, an 80-foot-thick salt bed in the Lower San Andres Formation, was determined by calculating vertical hydraulic gradients based on formation pressure and fluid density data, and by analysis of pressure-depth diagrams. Based on data from the vicinity of the proposed site, both methods indicate the potential for downflow across the host rock. Downflow or predominantly horizontal flow is considered a favorable prewaste emplacement condition because it prolongs the travel time to the biosphere of any naturally or accidentally released radionuclides

Microorganisms in potential host rocks for geological disposal of nuclear waste and their interactions with radionuclides

Energy Technology Data Exchange (ETDEWEB)

Cherkouk, A.; Liebe, M.; Luetke, L.; Moll, H.; Stumpf, T. [Helmholtz-Zentrum Dresden-Rossendorf e.V., Dresden (Germany). Inst. of Resource Ecology

2015-07-01

The long-term safety of nuclear waste in a deep geological repository is an important issue in our society. Microorganisms indigenous to potential host rocks are able to influence the oxidation state, speciation and therefore the mobility of radionuclides as well as gas generation or canister corrosion. Therefore, for the safety assessment of such a repository it is necessary to know which microorganisms are present in the potential host rocks (e.g. clay, salt) and if these microorganisms can influence the performance of a repository. Microbial diversity in potential host rocks for geological disposal of nuclear waste was analyzed by culture-independent molecular biological methods (e.g. 16S rRNA gene retrieval) as well as enrichment and isolation of indigenous microbes. Among other isolates, a Paenibacillus strain, as a representative of Firmicutes, was recovered in R2A media under anaerobic conditions from Opalinus clay from the Mont Terri in Switzerland. Accumulation experiments and potentiometric titrations showed a strong interaction of Paenibacillus sp. cells with U(VI) within a broad pH range (3-7). Additionally, the interactions of the halophilic archaeal strain Halobacterium noricense DSM 15987, a salt rock representative reference strain, with U(VI) at high ionic strength was investigated. After 48 h the cells were still alive at uranium concentrations up to 60 μM, which demonstrates that Halobacterium noricense can tolerate uranium concentrations up to this level. The formed uranium sorption species were examined with time-resolved laser-induced fluorescence spectroscopy (TRLFS). The results about the microbial communities present in potential host rocks for nuclear waste repositories and their interactions with radionuclides contribute to the safety assessment of a prospective nuclear waste repository.

Microorganisms in potential host rocks for geological disposal of nuclear waste and their interactions with radionuclides

International Nuclear Information System (INIS)

Cherkouk, A.; Liebe, M.; Luetke, L.; Moll, H.; Stumpf, T.

2015-01-01

The long-term safety of nuclear waste in a deep geological repository is an important issue in our society. Microorganisms indigenous to potential host rocks are able to influence the oxidation state, speciation and therefore the mobility of radionuclides as well as gas generation or canister corrosion. Therefore, for the safety assessment of such a repository it is necessary to know which microorganisms are present in the potential host rocks (e.g. clay, salt) and if these microorganisms can influence the performance of a repository. Microbial diversity in potential host rocks for geological disposal of nuclear waste was analyzed by culture-independent molecular biological methods (e.g. 16S rRNA gene retrieval) as well as enrichment and isolation of indigenous microbes. Among other isolates, a Paenibacillus strain, as a representative of Firmicutes, was recovered in R2A media under anaerobic conditions from Opalinus clay from the Mont Terri in Switzerland. Accumulation experiments and potentiometric titrations showed a strong interaction of Paenibacillus sp. cells with U(VI) within a broad pH range (3-7). Additionally, the interactions of the halophilic archaeal strain Halobacterium noricense DSM 15987, a salt rock representative reference strain, with U(VI) at high ionic strength was investigated. After 48 h the cells were still alive at uranium concentrations up to 60 μM, which demonstrates that Halobacterium noricense can tolerate uranium concentrations up to this level. The formed uranium sorption species were examined with time-resolved laser-induced fluorescence spectroscopy (TRLFS). The results about the microbial communities present in potential host rocks for nuclear waste repositories and their interactions with radionuclides contribute to the safety assessment of a prospective nuclear waste repository.

Lithophysal Rock Mass Mechanical Properties of the Repository Host Horizon

International Nuclear Information System (INIS)

D. Rigby

2004-01-01

The purpose of this calculation is to develop estimates of key mechanical properties for the lithophysal rock masses of the Topopah Spring Tuff (Tpt) within the repository host horizon, including their uncertainties and spatial variability. The mechanical properties to be characterized include an elastic parameter, Young's modulus, and a strength parameter, uniaxial compressive strength. Since lithophysal porosity is used as a surrogate property to develop the distributions of the mechanical properties, an estimate of the distribution of lithophysal porosity is also developed. The resulting characterizations of rock parameters are important for supporting the subsurface design, developing the preclosure safety analysis, and assessing the postclosure performance of the repository (e.g., drift degradation and modeling of rockfall impacts on engineered barrier system components)

Repository for high level radioactive wastes in Brazil: the importance of geochemical (Micro thermometric) studies and fluid migration in potential host rocks

International Nuclear Information System (INIS)

Rios, Francisco Javier; Fuzikawa, Kazuo; Alves, James Vieira; Neves, Jose Marques Correia

2003-01-01

A detailed fluid inclusion study of host rocks, is of fundamental importance in the selection of geologically suitable areas for high level nuclear waste repository constructions (HLRW). The LIFM-CDTN is enabled to develop studies that confirm: the presence or not, of corrosive fluid in minerals from host rocks of the repository and the possible presence of micro fractures (and fluid leakage) when these rocks are submitted to high temperatures. These fluid geochemistry studies, with permeability determinations by means of pressurized air injection must be carried out in rocks hosting nuclear waste. Micro fracture determination is of vital importance since many naturally corrosive solutions, present in the mineral rocks, could flow out through these plans affecting the walls of the repository. (author)

Clay club initiative: self-healing of fractures in clay-rich host rocks

International Nuclear Information System (INIS)

Horseman, S.T.; Cuss, R.J.; Reeves, H.J.

2004-01-01

The capacity of fractures in argillaceous rocks to self-heal (or become, with the passage of time, less conductive to groundwater) is often cited as a primary factor favouring the choice of such materials as host rocks for deep disposal. The underlying processes which contribute to self-healing can be broadly subdivided into: (a) mechanical and hydro-mechanical processes linked to the change in the stress field, movement of pore water, swelling, softening, plastic deformation and creep, and (b) geochemical processes linked to chemical alterations, transport in aqueous solution and the precipitation of minerals. Since chemical alteration can cause profound changes to the mechanical properties of argillaceous rocks, it is often difficult to draw a firm line between these two subdivisions. Based on the deliberations of the recent Cluster Conference in Luxembourg, there would appear to be some support for the use of the term 'self-sealing' for processes affecting fracture conductivity in argillaceous rock that are largely mechanical or hydro-mechanical in their origin. There are four main areas in which the self-healing capacity of the host rock becomes relevant to repository design and performance assessment: - potential for radionuclide transport within the excavation damage zone (EDZ); - design and performance of repository sealing systems; - potential impact of gas migration; - long-term performance considering erosional unloading, seismicity and fault reactivation. The presence of an EDZ is acknowledged to be a particularly important issue in performance assessment. Interconnection of fractures in the EDZ could lead to the development of a preferential flow path extending along the emplacement holes, access tunnels and shafts of a repository towards overlying aquifers and the biosphere. In the preliminary French Safety Analyses, for example, the treatment of scenarios relating to early seal failure have highlighted the hydraulic role of the damaged zone as a

Instability of an infiltration-driven dissolution-precipitation front with a nonmonotonic porosity profile

Science.gov (United States)

Kondratiuk, Paweł; Dutka, Filip; Szymczak, Piotr

2016-04-01

Infiltration of a rock by an external fluid very often drives it out of chemical equilibrium. As a result, alteration of the rock mineral composition occurs. It does not however proceed uniformly in the entire rock volume. Instead, one or more reaction fronts are formed, which are zones of increased chemical activity, separating the altered (product) rock from the yet unaltered (primary) one. The reaction fronts propagate with velocities which are usually much smaller than those of the infiltrating fluid. One of the simplest examples of such alteration is the dissolution of some of the minerals building the primary rock. For instance, calcium carbonate minerals in the rock matrix can be dissolved by infiltrating acidic fluids. In such a case the product rock has higher porosity and permeability than the primary one. Due to positive feedbacks between the reactant transport, fluid flow, and porosity generation, the reaction fronts in porosity-generating replacement systems are inherently unstable. An arbitrarily small protrusion of the front gets magnified and develops into a highly porous finger-like or funnel-like structure. This feature of dissolution fronts, dubbed the "reactive-infiltration instability" [1], is responsible for the formation of a number of geological patterns, such as solution pipes or various karst forms. It is also of practical importance, since spontaneous front breakup and development of localized highly porous flow paths (a.k.a. "wormholes") is favourable by petroleum engineers, who apply acidization to oil-bearing reservoirs in order to increase their permeability. However, more complex chemical reactions might occur during infiltration of a rock by a fluid. In principle, the products of dissolution might react with other species present either in the fluid or in the rock and reprecipitate [2]. The dissolution and precipitation fronts develop and and begin to propagate with equal velocities, forming a single dissolution-precipitation front

Finite-element modeling of magma chamber-host rock interactions prior to caldera collapse

Science.gov (United States)

Kabele, Petr; Žák, Jiří; Somr, Michael

2017-06-01

Gravity-driven failure of shallow magma chamber roofs and formation of collapse calderas are commonly accompanied by ejection of large volumes of pyroclastic material to the Earth's atmosphere and thus represent severe volcanic hazards. In this respect, numerical analysis has proven as a key tool in understanding the mechanical conditions of caldera collapse. The main objective of this paper is to find a suitable approach to finite-element simulation of roof fracturing and caldera collapse during inflation and subsequent deflation of shallow magma chambers. Such a model should capture the dominant mechanical phenomena, for example, interaction of the host rock with magma and progressive deformation of the chamber roof. To this end, a comparative study, which involves various representations of magma (inviscid fluid, nearly incompressible elastic, or plastic solid) and constitutive models of the host rock (fracture and plasticity), was carried out. In particular, the quasi-brittle fracture model of host rock reproduced well the formation of tension-induced radial and circumferential fractures during magma injection into the chamber (inflation stage), especially at shallow crustal levels. Conversely, the Mohr-Coulomb shear criterion has shown to be more appropriate for greater depths. Subsequent magma withdrawal from the chamber (deflation stage) results in further damage or even collapse of the chamber roof. While most of the previous studies of caldera collapse rely on the elastic stress analysis, the proposed approach advances modeling of the process by incorporating non-linear failure phenomena and nearly incompressible behaviour of magma. This leads to a perhaps more realistic representation of the fracture processes preceding roof collapse and caldera formation.

Reactive Transport at the Pore Scale with Applications to the Dissolution of Carbonate Rocks for CO2 Sequestration Operations

Science.gov (United States)

Boek, E.; Gray, F.; Welch, N.; Shah, S.; Crawshaw, J.

2014-12-01

In CO2 sequestration operations, CO2 injected into a brine aquifer dissolves in the liquid to create an acidic solution. This may result in dissolution of the mineral grains in the porous medium. Experimentally, it is hard to investigate this process at the pore scale. Therefore we develop a new hybrid particle simulation algorithm to study the dissolution of solid objects in a laminar flow field, as encountered in porous media flow situations. First, we calculate the flow field using a multi-relaxation-time lattice Boltzmann (LB) algorithm implemented on GPUs, which demonstrates a very efficient use of the GPU device and a considerable performance increase over CPU calculations. Second, using a stochastic particle approach, we solve the advection-diffusion equation for a single reactive species and dissolve solid voxels according to our reaction model. To validate our simulation, we first calculate the dissolution of a solid sphere as a function of time under quiescent conditions. We compare with the analytical solution for this problem [1] and find good agreement. Then we consider the dissolution of a solid sphere in a laminar flow field and observe a significant change in the sphericity with time due to the coupled dissolution - flow process. Second, we calculate the dissolution of a cylinder in channel flow in direct comparison with corresponding dissolution experiments. We discuss the evolution of the shape and dissolution rate. Finally, we calculate the dissolution of carbonate rock samples at the pore scale in direct comparison with micro-CT experiments. This work builds on our recent research on calculation of multi-phase flow [2], [3] and hydrodynamic dispersion and molecular propagator distributions for solute transport in homogeneous and heterogeneous porous media using LB simulations [4]. It turns out that the hybrid simulation model is a suitable tool to study reactive flow processes at the pore scale. This is of great importance for CO2 storage and

A porous silica rock ("tripoli") in the footwall of the Jurassic Úrkút manganese deposit, Hungary: composition, and origin through carbonate dissolution

Science.gov (United States)

Polgari, Marta; Szabo, Zoltan; Szabo-Drubina, Magda; Hein, James R.; Yeh, Hsueh-Wen

2005-01-01

The mineralogical, chemical, and isotopic compositions were determined for a white tripoli from the footwall of the Jurassic Úrkút Mn-oxide ore deposit in the Bakony Mountains, Hungary. The tripoli consists of quartz and chalcedony, with SiO2 contents up to 100 wt.%; consequently, trace-element contents are very low. Oxygen isotopes and quartz crystallinity indicate a low-temperature diagenetic origin for this deposit. The tripoli was formed by dissolution of the carbonate portion of the siliceous (sponge spicules) Isztimér Limestone. Dissolution of the carbonate was promoted by inorganic and organic acids generated during diagensis and left a framework composed of diagenetic silica that preserved the original volume of the limestone layer. The relative enrichment of silica and high porosity is the result of that carbonate dissolution. The silty texture of this highly friable rock is due to the structurally weak silica framework.

Deciphering fluid inclusions in high-grade rocks

Directory of Open Access Journals (Sweden)

Alfons van den Kerkhof

2014-09-01

Full Text Available The study of fluid inclusions in high-grade rocks is especially challenging as the host minerals have been normally subjected to deformation, recrystallization and fluid-rock interaction so that primary inclusions, formed at the peak of metamorphism are rare. The larger part of the fluid inclusions found in metamorphic minerals is typically modified during uplift. These late processes may strongly disguise the characteristics of the “original” peak metamorphic fluid. A detailed microstructural analysis of the host minerals, notably quartz, is therefore indispensable for a proper interpretation of fluid inclusions. Cathodoluminescence (CL techniques combined with trace element analysis of quartz (EPMA, LA-ICPMS have shown to be very helpful in deciphering the rock-fluid evolution. Whereas high-grade metamorphic quartz may have relatively high contents of trace elements like Ti and Al, low-temperature re-equilibrated quartz typically shows reduced trace element concentrations. The resulting microstructures in CL can be basically distinguished in diffusion patterns (along microfractures and grain boundaries, and secondary quartz formed by dissolution-reprecipitation. Most of these textures are formed during retrograde fluid-controlled processes between ca. 220 and 500 °C, i.e. the range of semi-brittle deformation (greenschist-facies and can be correlated with the fluid inclusions. In this way modified and re-trapped fluids can be identified, even when there are no optical features observed under the microscope.

Numerical modelling of fluid-rock interactions: Lessons learnt from carbonate rocks diagenesis studies

Science.gov (United States)

Nader, Fadi; Bachaud, Pierre; Michel, Anthony

2015-04-01

Quantitative assessment of fluid-rock interactions and their impact on carbonate host-rocks has recently become a very attractive research topic within academic and industrial realms. Today, a common operational workflow that aims at predicting the relevant diagenetic processes on the host rocks (i.e. fluid-rock interactions) consists of three main stages: i) constructing a conceptual diagenesis model including inferred preferential fluids pathways; ii) quantifying the resulted diagenetic phases (e.g. depositing cements, dissolved and recrystallized minerals); and iii) numerical modelling of diagenetic processes. Most of the concepts of diagenetic processes operate at the larger, basin-scale, however, the description of the diagenetic phases (products of such processes) and their association with the overall petrophysical evolution of sedimentary rocks remain at reservoir (and even outcrop/ well core) scale. Conceptual models of diagenetic processes are thereafter constructed based on studying surface-exposed rocks and well cores (e.g. petrography, geochemistry, fluid inclusions). We are able to quantify the diagenetic products with various evolving techniques and on varying scales (e.g. point-counting, 2D and 3D image analysis, XRD, micro-CT and pore network models). Geochemical modelling makes use of thermodynamic and kinetic rules as well as data-bases to simulate chemical reactions and fluid-rock interactions. This can be through a 0D model, whereby a certain process is tested (e.g. the likelihood of a certain chemical reaction to operate under specific conditions). Results relate to the fluids and mineral phases involved in the chemical reactions. They could be used as arguments to support or refute proposed outcomes of fluid-rock interactions. Coupling geochemical modelling with transport (reactive transport model; 1D, 2D and 3D) is another possibility, attractive as it provides forward simulations of diagenetic processes and resulting phases. This

Clay shale as host rock. A geomechanical contribution about Opalinus clay

International Nuclear Information System (INIS)

Lempp, Christof; Menezes, Flora; Sachwitz, Simon

2016-01-01

The Opalinuston is a prominent rock representing the type of organic clay shales or clay stones within the sequence of Triassic and Jurassic marine sediments in Southern Germany. The rock forms a homogenous unit some ten meters thick. The degree of consolidation of this type of pelitic rock depends mainly on the former load conditions, but is also dependent on the long-term weathering and even on the present exposition. The geomechanical parameters such as shear strength, tensional strength and permeability vary with the state of consolidation and become important when the use is discussed of such rocks for radioactive waste disposal. A tunneling project at the northern escarpment of the Swabian Alb (Southwest Germany) within the Opalinus clay offered the rare opportunity to obtain fresh unweathered rock samples in greater amounts compared to fresh drilling cores from which geomechanical investigations are usually undertaken. Consequently, the results of geomechanical laboratory testings are presented in order to compare here the results of multistep triaxial compression tests, of hydraulic fracturing laboratory tests and of some other tests for rock characterization with the corresponding results of Opalinus clay sites in Switzerland that were investigated by the Swiss Nagra Company for host rock characterization. After a discussion of the relevant state of fresh Opalinus clay, especially of suction pressure conditions and saturation state, the results of triaxial shear tests are presented. Increasing shear deformation at increasing pressure and unchanged water saturation do not result in a significant strength reduction of the Opalinus clay. The rock shows increasing cohesion and stiffness, if multiple loading has repeatedly reached the failure point. Thus there is no increased permeability with continued shearing. Only at the beginning of the shearing process is a temporarily increased permeability to be expected due to dilatation processes. An increased

Development of a method for the comparison of final repository sites in different host rock formations; Weiterentwicklung einer Methode zum Vergleich von Endlagerstandorten in unterschiedlichen Wirtsgesteinsformationen

Energy Technology Data Exchange (ETDEWEB)

Fischer-Appelt, Klaus; Frieling, Gerd; Kock, Ingo; and others

2017-10-15

The report on the development of a method for the comparison of final repository sites in different host rock formations covers the following issues: influence of the requirement of retrievability on the methodology, study on the possible extension of the methodology for repository sites with crystalline host rocks: boundary conditions in Germany, final disposal concept for crystalline host rocks, generic extension of the VerSi method, identification, classification and relevance weighting of safety functions, relevance of the safety functions for the crystalline host rock formation, review of the methodological need for changes for crystalline rock sites under low-permeability covering; study on the applicability of the methodology for the determination of site regions for surface exploitation (phase 1).

Evaluation of dissolution of nonconventional phosphate fertilizers in ...

African Journals Online (AJOL)

Dissolution of phosphate rock (PR) depends on inherent chemical and physical properties of the rock and on external factors such as soils and plants. The objective of this study was to investigate, with a soil incubation experiment, the relationship between selected soil factors and extractable phosphorus (P) in order to ...

Geochemical tracing and hydrogeochemical modelling of water-rock interactions during salinization of alluvial groundwater (Upper Rhine Valley, France)

Energy Technology Data Exchange (ETDEWEB)

Lucas, Y., E-mail: yann.lucas@eost.u-strasbg.fr [Universite de Strasbourg et CNRS, Laboratoire d' Hydrologie et de Geochimie de Strasbourg, Ecole et Observatoire des Sciences de la Terre, 1, rue Blessig, 67084 Strasbourg Cedex (France); Schmitt, A.D., E-mail: anne-desiree.schmitt@univ-fcomte.fr [Universite de Strasbourg et CNRS, Laboratoire d' Hydrologie et de Geochimie de Strasbourg, Ecole et Observatoire des Sciences de la Terre, 1, rue Blessig, 67084 Strasbourg Cedex (France)] [Universite de Franche-Comte et CNRS-UMR 6249, Chrono-Environnement, 16, Route de Gray, 25030 Besancon Cedex (France); Chabaux, F., E-mail: francois.chabaux@eost.u-strasbg.fr [Universite de Strasbourg et CNRS, Laboratoire d' Hydrologie et de Geochimie de Strasbourg, Ecole et Observatoire des Sciences de la Terre, 1, rue Blessig, 67084 Strasbourg Cedex (France); Clement, A.; Fritz, B. [Universite de Strasbourg et CNRS, Laboratoire d' Hydrologie et de Geochimie de Strasbourg, Ecole et Observatoire des Sciences de la Terre, 1, rue Blessig, 67084 Strasbourg Cedex (France); Elsass, Ph. [BRGM, GEODERIS, 1, rue Claude Chappe, 57070 Metz (France); Durand, S. [Universite de Strasbourg et CNRS, Laboratoire d' Hydrologie et de Geochimie de Strasbourg, Ecole et Observatoire des Sciences de la Terre, 1, rue Blessig, 67084 Strasbourg Cedex (France)

2010-11-15

Research highlights: {yields} Major and trace elements along with strontium and uranium isotopic ratios show that groundwater geochemical characteristics along the saline plumes cannot reflect a conservative mixing. {yields} A coupled hydrogeochemical model demonstrates that cationic exchange between alkalis from polluted waters and alkaline-earth elements from montmorillonite present in the host rock of the aquifer is the primary process. {yields} The model requires only a small amount of montmorillonite. {yields} It is necessary to consider the pollution history to explain the important chloride, sodium and calcium concentration modifications. {yields} The model shows that the rapidity of the cationic exchange reactions insures a reversibility of the cation fixation on clays in the aquifer. - Abstract: In the southern Upper Rhine Valley, groundwater has undergone intensive saline pollution caused by the infiltration of mining brines, a consequence of potash extraction carried out during the 20th century. Major and trace elements along with Sr and U isotopic ratios show that groundwater geochemical characteristics along the saline plumes cannot reflect conservative mixing between saline waters resulting from the dissolution of waste heaps and one or more unpolluted end-members. The results imply the occurrence of interactions between host rocks and polluted waters, and they suggest that cationic exchange mechanisms are the primary controlling process. A coupled hydrogeochemical model has been developed with the numerical code KIRMAT, which demonstrates that cationic exchange between alkalis from polluted waters and alkaline-earth elements from montmorillonite present in the host rock of the aquifer is the primary process controlling the geochemical evolution of the groundwater. The model requires only a small amount of montmorillonite (between 0.75% and 2.25%), which is in agreement with the observed mineralogical composition of the aquifer. The model also proves

Dissolution of the Mors salt dome

International Nuclear Information System (INIS)

Lindstroem Jensen, K.E.

1982-01-01

Regardless of the interpretation of the measured salinity profiles above the Mors salt dome, they can at most be the result of dissolution rates of about 0.004 mm per year. This means that it would take more than 2.5 mill. years to dissolve 10 m of salt. Variations in groun water velocity and cap rock porosity will not significantly change this condition. The stability of the Mors salt dome is therefore not affected by dissolution of the dome. (EG)

Damage-plasticity model of the host rock in a nuclear waste repository

Energy Technology Data Exchange (ETDEWEB)

Koudelka, Tomáš; Kruis, Jaroslav, E-mail: kruis@fsv.cvut.cz [Department of Mechanics, Faculty of Civil Engineering, Czech Technical University in Prague, Thákurova 7, 166 29 Prague (Czech Republic)

2016-06-08

The paper describes damage-plasticity model for the modelling of the host rock environment of a nuclear waste repository. Radioactive Waste Repository Authority in Czech Republic assumes the repository to be in a granite rock mass which exhibit anisotropic behaviour where the strength in tension is lower than in compression. In order to describe this phenomenon, the damage-plasticity model is formulated with the help of the Drucker-Prager yield criterion which can be set to capture the compression behaviour while the tensile stress states is described with the help of scalar isotropic damage model. The concept of damage-plasticity model was implemented in the SIFEL finite element code and consequently, the code was used for the simulation of the Äspö Pillar Stability Experiment (APSE) which was performed in order to determine yielding strength under various conditions in similar granite rocks as in Czech Republic. The results from the performed analysis are presented and discussed in the paper.

Host-guest complexes of 2-hydroxypropyl-β-cyclodextrin/β-cyclodextrin and nifedipine: 1H NMR, molecular modeling, and dissolution studies

Science.gov (United States)

de Araújo, Márcia Valéria Gaspar; Vieira, João Victor Francisco; da Silva, Caroline W. P.; Barison, Andersson; Andrade, George Ricardo Santana; da Costa, Nivan Bezerra; Barboza, Fernanda Malaquias; Nadal, Jessica Mendes; Novatski, Andressa; Farago, Paulo Vitor; Zawadzki, Sônia Faria

2017-12-01

Nifedipine (NIF) is a hydrophobic drug widely used for treating cardiovascular diseases. This calcium channel blocker can present a higher apparent solubility by its inclusion into different cyclodextrins (CDs) as host-guest complexes. This paper focused on the structural investigation and dissolution behavior of inclusion complexes prepared with 2-hydroxypropyl-β-cyclodextrin (HPβCD) or β-cyclodextrin (βCD) and NIF. Drug amorphization was observed for HPβCD/NIF and βCD/NIF inclusion complexes by X-ray diffractometry (XRD). The sharp endothermic peak of NIF was not observed for these both host-guest complexes by differential scanning calorimetry (DSC). These results of XRD and DSC provide evidences of complexation between drug and the investigated CDs. 1H and saturation transfer difference nuclear magnetic resonance studies revealed the enhancement in the signal at 2.27 ppm for HPβCD/NIF and βCD/NIF inclusion complexes that corresponded to the methyl groups of NIF from the non-aromatic ring. This result suggested that non-aromatic ring of NIF was inserted into HPβCD and βCD cavities. Considering the mathematical simulations, it was observed that the inclusion process can occur in the both NH-in or NH-out forms. However, since it was used aqueous medium, it is possible to indicate that the obtained host-guest complexes HPβCD/NIF and βCD/NIF are in NH-in form which corresponded to the previous results obtained by 1H NMR experiments. Dissolution assays demonstrated that NIF inclusion complexes improved the drug release nevertheless without changing its biexponential release behavior. These host-guest complexes can be further used as feasible NIF carriers in solid dosage forms.

Nature of parent rocks, mineralization styles and ore genesis of regolith-hosted REE deposits in South China: An integrated genetic model

Science.gov (United States)

Li, Yan Hei Martin; Zhao, Wen Winston; Zhou, Mei-Fu

2017-10-01

Regolith-hosted rare earth element (REE) deposits, also called ion-adsorption or weathered crust elution-deposited REE deposits are distributed over Jiangxi, Guangdong, Fujian, Hunan, Guangxi and Yunnan provinces in South China. In general, these deposits can be categorized into the HREE-dominated type, for example the famous Zudong deposit in southern Jiangxi province and the LREE-dominated type, such as the Heling and Dingnan deposits in southern Jiangxi province. Most of these deposits form from weathering of biotite and muscovite granites, syenites, monzogranites, granodiorites, granite porphyries, and rhyolitic tuffs. The parent rocks are generally peraluminous, siliceous, alkaline and contain a variety of REE-bearing minerals. Mostly, REE patterns of regolith are inherited from the parent rocks, and therefore, characteristics of the parent rocks impose a significant control on the ore formation. Data compilation shows that autometasomatism during the latest stage of granite crystallization is likely essential in forming the HREE-enriched granites, whereas LREE-enriched granites could form through magmatic differentiation. These deposits are normally two- to three-fold, but could be up to ten-fold enrichment in REE compared to the parent granites, where the maximum enrichment usually occurs from the lower B to the upper C horizon. Ce shows different behavior with the other REEs. Strongly positive Ce anomalies commonly occur at the upper part of weathering profiles, likely due to oxidation of Ce3+ to Ce4+ and removal of Ce from soil solutions through precipitation of cerianite. Vertical pH and redox gradients in weathering crusts facilitate dissolution of REE-bearing minerals at shallow level and fixation of REE at depth through either adsorption on clay minerals or precipitation of secondary minerals. At the same time, mass removal of major elements plays an important role in concentrating REE in regolith. Combination of mass removal and eluviation

Chrysotile dissolution rates: Implications for carbon sequestration

International Nuclear Information System (INIS)

Thom, James G.M.; Dipple, Gregory M.; Power, Ian M.; Harrison, Anna L.

2013-01-01

Highlights: • Uncertainties in serpentine dissolution kinetics hinder carbon sequestration models. • A pH dependent, far from equilibrium dissolution rate law for chrysotile. • F chrysotile (mol/m 2 /s) = 10 −0.21pH−10.57 at 22 °C over pH 2–10. • Laboratory dissolution rates consistent with mine waste weathering observations. • Potential for carbon sequestration in mine tailings and aquifers is assessed. - Abstract: Serpentine minerals (e.g., chrysotile) are a potentially important medium for sequestration of CO 2 via carbonation reactions. The goals of this study are to report a steady-state, far from equilibrium chrysotile dissolution rate law and to better define what role serpentine dissolution kinetics will have in constraining rates of carbon sequestration via serpentine carbonation. The steady-state dissolution rate of chrysotile in 0.1 m NaCl solutions was measured at 22 °C and pH ranging from 2 to 8. Dissolution experiments were performed in a continuously stirred flow-through reactor with the input solutions pre-equilibrated with atmospheric CO 2 . Both Mg and Si steady-state fluxes from the chrysotile surface, and the overall chrysotile flux were regressed and the following empirical relationships were obtained: F Mg =-0.22pH-10.02;F Si =-0.19pH-10.37;F chrysotile =-0.21pH-10.57 where F Mg , F Si , and F chrysotile are the log 10 Mg, Si, and molar chrysotile fluxes in mol/m 2 /s, respectively. Element fluxes were used in reaction-path calculations to constrain the rate of CO 2 sequestration in two geological environments that have been proposed as potential sinks for anthropogenic CO 2 . Carbon sequestration in chrysotile tailings at 10 °C is approximately an order of magnitude faster than carbon sequestration in a serpentinite-hosted aquifer at 60 °C on a per kilogram of water basis. A serpentinite-hosted aquifer, however, provides a larger sequestration capacity. The chrysotile dissolution rate law determined in this study has

In vitro DISSOLUTION OF ACIDULATED ROCK PHOSPHATE BY PHOSPHATE SOLUBILIZING MICROORGANISMS

Directory of Open Access Journals (Sweden)

Ángela Patricia Moreno Quevedo

2015-05-01

Full Text Available The low availability of phosphorus (P in the soil and the high cost of P fertilization are factors that limit agricultural productivity. A biotechnological alternative for to handle this problem is to use soil microorganisms capable of dissolving rock phosphate (RP, thus improving its effectiveness as a P fertilizer. This study was carried out with the objective of determining the effectiveness of Aspergillus niger –As-, Penicillium sp. –Pn-, Bacillus sp –B-. and an unidentified actinomycete –At- in the in vitro dissolution of two partially acidulated rock phosphates. The treatments consisted of 2x16 factorial arrangement [2 levels of RP: either Boyaca RP or Norte de Santander RP; 16 levels of inoculum: an uninoculated control, individual inoculations (with As, Pn, B, At, dual inoculations (AsPn, AsB, AsAt, PnB, PnAt, BAt, triple inoculations (AsPnB, AsPnAt, AsBAt, PnBAt, and quadruple inoculation (AsPnBAt]. Each treatment was replicated three times. Each treatment was replicated three times. It was found that the microbial effectiveness in the in vitro dissolution of RP depended on the type of RP, the composition of the inoculum used and the interaction of both factors. The best results were obtained with the Norte de Santander RP and A. niger used alone. When this fungus combined with the other microorganisms, its capacity to dissolve RP was significantly reduced. RESUMEN La baja disponibilidad de fósforo (P en el suelo y el costo de la fertilización fosfórica son limitantes para la productividad agrícola. Una alternativa biotecnológica para manejar este problema es mediante el uso de microorganismos del suelo capaces de disolver rocas fosfóricas (RP y así mejorar su efectividad como fertilizante fosfórico. Con este fin se realizó un ensayo para determinar la efectividad microbial en la disolución in vitro de dos RP (Norte de Santander y Boyacá parcialmente aciduladas. Los tratamientos consistieron en un arreglo factorial 2x

Tourmaline occurrences within the Penamacor-Monsanto granitic pluton and host-rocks (Central Portugal): genetic implications of crystal-chemical and isotopic features

Science.gov (United States)

da Costa, I. Ribeiro; Mourão, C.; Récio, C.; Guimarães, F.; Antunes, I. M.; Ramos, J. Farinha; Barriga, F. J. A. S.; Palmer, M. R.; Milton, J. A.

2014-04-01

Tourmalinization associated with peraluminous granitic intrusions in metapelitic host-rocks has been widely recorded in the Iberian Peninsula, given the importance of tourmaline as a tracer of granite magma evolution and potential indicator of Sn-W mineralizations. In the Penamacor-Monsanto granite pluton (Central Eastern Portugal, Central Iberian Zone), tourmaline occurs: (1) as accessory phase in two-mica granitic rocks, muscovite-granites and aplites, (2) in quartz (±mica)-tourmaline rocks (tourmalinites) in several exocontact locations, and (3) as a rare detrital phase in contact zone hornfels and metapelitic host-rocks. Electron microprobe and stable isotope (δ18O, δD, δ11B) data provide clear distinctions between tourmaline populations from these different settings: (a) schorl-oxyschorl tourmalines from granitic rocks have variable foititic component (X□ = 17-57 %) and Mg/(Mg + Fe) ratios (0.19-0.50 in two-mica granitic rocks, and 0.05-0.19 in the more differentiated muscovite-granite and aplites); granitic tourmalines have constant δ18O values (12.1 ± 0.1 ‰), with wider-ranging δD (-78.2 ± 4.7 ‰) and δ11B (-10.7 to -9.0 ‰) values; (b) vein/breccia oxyschorl [Mg/(Mg + Fe) = 0.31-0.44] results from late, B- and Fe-enriched magma-derived fluids and is characterized by δ18O = 12.4 ‰, δD = -29.5 ‰, and δ11B = -9.3 ‰, while replacement tourmalines have more dravitic compositions [Mg/(Mg + Fe) = 0.26-0.64], close to that of detrital tourmaline in the surrounding metapelitic rocks, and yield relatively constant δ18O values (13.1-13.3 ‰), though wider-ranging δD (-58.5 to -36.5 ‰) and δ11B (-10.2 to -8.8 ‰) values; and (c) detrital tourmaline in contact rocks and regional host metasediments is mainly dravite [Mg/(Mg + Fe) = 0.35-0.78] and oxydravite [Mg/(Mg + Fe) = 0.51-0.58], respectively. Boron contents of the granitic rocks are low (<650 ppm) compared to the minimum B contents normally required for tourmaline saturation in

Self-sealing of excavation induced fractures in clay host rock

Energy Technology Data Exchange (ETDEWEB)

Zhang, Chun-Liang [Gesellschaft fuer Anlagen- und Reaktorsicherheit (GRS) mbH, Braunschweig (Germany)

2015-07-01

magnitude down to very low levels of 10{sup -19} to 10{sup -21} m{sup 2} even at low confining stresses of 2-4 MPa within short periods of months to years, compared with the long post-closure phase of tens of thousands of years. The very low water permeabilities reached are the same order as that of the intact claystones, indicating that the fractures in the claystones can be completely resealed. The very low water permeabilities do not change significantly during heating and cooling within a temperature range between 20 C and 90 C. This suggests no negative thermal impact on the sealing of the fractures. Before water saturation, the fractures act as conduits for preferential gas flow. However, after water saturation, gas entry and penetration into the resealed fractures in claystone needs certain driving forces to overcome the capillary thresholds. The gas entry/breakthrough pressure is determined by the sealing intensity of the fractures and the confining stress. The gas tests carried out on the highly-resealed claystones show that the gas breakthrough pressures increase with confining stress from low levels of 0.2-1.0 MPa at a low stress of 2 MPa up to 8.3-11.3 MPa at high stresses of 12.7-15.0 MPa corresponding to the rock stress state at a depth of ∝500 m. It is obvious that the breakthrough pressures are still below the applied confining stresses. This important finding implies that the EDZ, even when highly-resealed, will still have the capacity for gas migration with moderate pressures and thus contribute to avoid high pressure build up for fracturing the host rock. Generally speaking, the significant sealing capacities of the claystones hinder water transport and thus radionuclides migration through the fractures, but allow gas migration at moderate pressures without fracturing the host rock. These significant advantages guarantee the long-term integrity and barrier function of the host rock.

Interaction between clay-based sealing components and crystalline host rock

Science.gov (United States)

Priyanto, D. G.; Dixon, D. A.; Man, A. G.

The results of hydraulic-mechanical (H-M) numerical simulation of a shaft seal installed at a fracture zone (FZ) in a crystalline host rock using the finite element method are presented. The primary function of a shaft seal is to limit short-circuiting of the groundwater flow regime via the shaft in a deep geological repository. Two different stages of system evolution were considered in this numerical modelling. Stage 1 simulates the groundwater flow into an open shaft, prior to seal installation. Stage 2 simulates the groundwater flow into the shaft seal after seal installation. Four different cases were completed to: (i) evaluate H-M response due to the interaction between clay-based sealing material and crystalline host rock in the shaft seal structure; (ii) quantify the effect of the different times between the completion of the shaft excavation and the completion of shaft seal installation on the H-M response; and (iii) define the potential effects of different sealing material configurations. Shaft sealing materials include the bentonite-sand mixture (BSM), dense backfill (DBF), and concrete plug (CP). The BSM has greater swelling capacity and lower hydraulic conductivity ( K) than the DBF. The results of these analyses show that the decrease of the pore water pressure is concentrated along the fracture zone (FZ), which has the greatest K. As the time increases, the greatest decrease in pore water pressure is found around the FZ. Following FZ isolation and the subsequent filling of the shaft with water as it floods, the pore water pressure profile tends to recover back to the initial conditions prior to shaft excavation. The majority of the fluids that ultimately saturate the centre of the shaft seal flow radially inwards from the FZ. The time between the completion of the shaft excavation and the completion of shaft seal installation has a significant effect on the saturation time. A shorter time can reduce the saturation time. Since most of the inflow

Age, sedimentary environments, and other aspects of sandstone and related host rocks for uranium deposits

International Nuclear Information System (INIS)

1983-01-01

Project II of the Uranium Geology Working Group was assigned to the study of sedimentary basins and sandstone - type uranium deposits. About 40% of the worlds's uranium resources are contained in sandstone-type deposits, which has led to extensive research. The research was carried out mainly by correspondence, and the results reported by 21 geologists from 10 nations are summarized in this report. It investigated five topics dealing with important aspects of the geology of uranium ores in sandstone host formations: age of host rock; partitioning of uranium between continental and marine sediments; latitude limitation on formation of sandstone deposits; effect of rock formation dip on sandstone ores; usefulness of stable isotope and fluid inclusion studies. The results of studies on these subjects form part of a wider programme of the Working Group, whose final results will be presented at the 27th International Geological Congress in Moscow in 1984

The RRP Project: investigating radionuclide retardation in the host rock

International Nuclear Information System (INIS)

Alexander, W.R.; Frieg, B.; Ota, K.; Bossart, P.

1996-01-01

The Radionuclide Retardation Project (RRP), which is a joint Nagra/PNC (Power Reactor and Nuclear Fuel Development Corp.) project, has two components: the first (the Excavation Project, EP) looks at the behaviour of radionuclides which are so strongly retarded in the experimental shear zone that they cannot pass through the zones in experimentally reasonable times. In order to determine where radionuclide retardation has occurred in the pore space, as well as the flowpath geometry in the shear zone, the entire injection zone has to be excavated and taken back to the laboratory for analysis of the sites of retardation of the radionuclides. This approach has the advantage of allowing a detailed 3D description of the experimental shear zone. The aim of the second component of the project (Connected Porosities, CP) is to examine the fate of those radionuclides which diffuse out of the main water-conducting features in the shear zone and into the pore spaces of the rock matrix, where they become trapped. This represents a potentially significant retardation mechanism in a repository host rock. (author) 8 figs., refs

Redox front penetration in the fractured Toki Granite, central Japan: An analogue for redox reactions and redox buffering in fractured crystalline host rocks for repositories of long-lived radioactive waste

International Nuclear Information System (INIS)

Yamamoto, Koshi; Yoshida, Hidekazu; Akagawa, Fuminori; Nishimoto, Shoji; Metcalfe, Richard

2013-01-01

Highlights: • Deep redox front developed in orogenic granitic rock have been studied. • The process was controlled by the buffering capacity of minerals. • This is an analogue of redox front penetration into HLW repositories in Japan. - Abstract: Redox buffering is one important factor to be considered when assessing the barrier function of potential host rocks for a deep geological repository for long-lived radioactive waste. If such a repository is to be sited in fractured crystalline host rock it must be demonstrated that waste will be emplaced deeper than the maximum depth to which oxidizing waters can penetrate from the earth’s surface via fractures, during the assessment timeframe (typically 1 Ma). An analogue for penetration of such oxidizing water occurs in the Cretaceous Toki Granite of central Japan. Here, a deep redox front is developed along water-conducting fractures at a depth of 210 m below the ground surface. Detailed petrographical studies and geochemical analyses were carried out on drill core specimens of this redox front. The aim was to determine the buffering processes and behavior of major and minor elements, including rare earth elements (REEs), during redox front development. The results are compared with analytical data from an oxidized zone found along shallow fractures (up to 20 m from the surface) in the same granitic rock, in order to understand differences in elemental migration according to the depth below the ground surface of redox-front formation. Geochemical analyses by XRF and ICP-MS of the oxidized zone at 210 m depth reveal clear changes in Fe(III)/Fe(II) ratios and Ca depletion across the front, while Fe concentrations vary little. In contrast, the redox front identified along shallow fractures shows strong enrichments of Fe, Mn and trace elements in the oxidized zone compared with the fresh rock matrix. The difference can be ascribed to the changing Eh and pH of groundwater as it flows downwards in the granite, due to

Effects of Host-rock Fracturing on Elastic-deformation Source Models of Volcano Deflation.

Science.gov (United States)

Holohan, Eoghan P; Sudhaus, Henriette; Walter, Thomas R; Schöpfer, Martin P J; Walsh, John J

2017-09-08

Volcanoes commonly inflate or deflate during episodes of unrest or eruption. Continuum mechanics models that assume linear elastic deformation of the Earth's crust are routinely used to invert the observed ground motions. The source(s) of deformation in such models are generally interpreted in terms of magma bodies or pathways, and thus form a basis for hazard assessment and mitigation. Using discontinuum mechanics models, we show how host-rock fracturing (i.e. non-elastic deformation) during drainage of a magma body can progressively change the shape and depth of an elastic-deformation source. We argue that this effect explains the marked spatio-temporal changes in source model attributes inferred for the March-April 2007 eruption of Piton de la Fournaise volcano, La Reunion. We find that pronounced deflation-related host-rock fracturing can: (1) yield inclined source model geometries for a horizontal magma body; (2) cause significant upward migration of an elastic-deformation source, leading to underestimation of the true magma body depth and potentially to a misinterpretation of ascending magma; and (3) at least partly explain underestimation by elastic-deformation sources of changes in sub-surface magma volume.

Interaction between clay-based shaft seal components and crystalline host rock

International Nuclear Information System (INIS)

Priyanto, D.; Dixon, D.; Man, A.

2010-01-01

Document available in extended abstract form only. The Government of Canada has accepted the Nuclear Waste Management Organization's (NWMO) recommendation of Adaptive Phased Management (APM) as the long-term management approach for Canada's used nuclear fuel. APM ultimately involves the isolation and containment of used nuclear fuel deep in a Deep Geological Repository (DGR). On completion of waste emplacement operation and during repository closure, shaft seals, comprising clay-based shaft seal components, will be installed at strategic locations, such as where significant fracture zones (FZs) are located. The primary function of a shaft seal is to limit and prevent short-circuiting of the groundwater flow regime via the shaft. Currently, at Atomic Energy of Canada Limited's Underground Research Laboratory (URL) a full-scale shaft seal is being constructed at the intersection of a low dipping thrust fault called FZ 2 as part of the overall URL decommissioning activities. Both crystalline rock and sedimentary rock are considered potentially suitable host rocks formations for a DGR. This paper presents the results of numerical simulation of a shaft seal installed in moderately to sparsely fractured crystalline rock (MFR). The shape and thickness of the shaft seal modelled for a DGR in this exercise are similar to the shaft seal at the URL, but in the modelling exercise it is given a larger diameter (i.e. 7.30 m) equal to the assumed diameter of a production shaft of a repository. The seal consists of a blended bentonite-sand (BS) component that is constrained between two massive concrete seals. Dense backfill (DBF) materials are installed above and below the concrete seals (CS). The concrete seals are keyed into the access shaft to better anchor the concrete units in place and in order to restrain the swelling of the bentonite-sand component of the seal as it hydrates. The reference geosphere in the proposed work is MFR similar to the rock conditions

ENSI - Evaluation of NAGRA’s planned investigation of Brown Dogger host rock - Expert report

International Nuclear Information System (INIS)

Bitterli-Dreher, P; Burkhalter, R.

2011-06-01

This report published by the Swiss National Safety Inspectorate ENSI discusses the reports published on the Brown Dogger host rock formations and the investigations planned as part of Phase 2 of the planning process for deep repositories for low and medium-active nuclear wastes. After a review of the tasks to be carried out, two expert reports are introduced. In the first report, Dr. Peter Bitterli-Dreher looks at the geological situation in central Europe and rock conditions in northern Switzerland. The situation in the Dogger formations with their calcium carbonate and clay-like components in various locations in northern Switzerland are discussed, including water flow in the rocks. The second report from Dr. Reto Burkhalter also discusses the Brown Dogger formations and comments on the investigations proposed by NAGRA in detail. Work yet to be planned is looked at

Review of potential host rocks for radioactive waste disposal in the Piedmont province of North Carolina

International Nuclear Information System (INIS)

Butler, J.R.

1980-10-01

This report reviews the geology of the Piedmont province in North Carolina, emphasizing those features most pertinent to selection of potential host rocks for radioactive waste disposal. Discussion of criteria for selection indicates that the outcrop area of the rock body, probable homogeneity, low incidence of fractures, and low permeability are among the prime considerations. Application of the criteria leads to the selection of three large granite batholiths (Castalia, Churchland, and Rolesville) as potential field study areas. The report has an extensive bibliography

Chemical buffering capacity of clay rock

International Nuclear Information System (INIS)

Beaucaire, C.; Pearson, F.J.; Gautschi, A.

2004-01-01

The long-term performance of a nuclear waste repository is strongly dependent on the chemical properties of the host rock. The host rock establishes the chemical environment that determines such important performance attributes as radionuclide solubilities from the waste and the transport rates from the repository to the accessible environment. Clay-rich rocks are especially favourable host rocks because they provide a strong buffering capacity to resist chemical changes prompted either internally, by reactions of the waste itself and emplacement materials, or externally, by changes in the hydrologic systems surrounding the host rock. This paper will focus on three aspects of the stability of clay-rich host rocks: their ability to provide pCO 2 and redox buffering, and to resist chemical changes imposed by changes in regional hydrology and hydro-chemistry. (authors)

Thermal Analysis of a Nuclear Waste Repository in Argillite Host Rock

Science.gov (United States)

Hadgu, T.; Gomez, S. P.; Matteo, E. N.

2017-12-01

Disposal of high-level nuclear waste in a geological repository requires analysis of heat distribution as a result of decay heat. Such an analysis supports design of repository layout to define repository footprint as well as provide information of importance to overall design. The analysis is also used in the study of potential migration of radionuclides to the accessible environment. In this study, thermal analysis for high-level waste and spent nuclear fuel in a generic repository in argillite host rock is presented. The thermal analysis utilized both semi-analytical and numerical modeling in the near field of a repository. The semi-analytical method looks at heat transport by conduction in the repository and surroundings. The results of the simulation method are temperature histories at selected radial distances from the waste package. A 3-D thermal-hydrologic numerical model was also conducted to study fluid and heat distribution in the near field. The thermal analysis assumed a generic geological repository at 500 m depth. For the semi-analytical method, a backfilled closed repository was assumed with basic design and material properties. For the thermal-hydrologic numerical method, a repository layout with disposal in horizontal boreholes was assumed. The 3-D modeling domain covers a limited portion of the repository footprint to enable a detailed thermal analysis. A highly refined unstructured mesh was used with increased discretization near heat sources and at intersections of different materials. All simulations considered different parameter values for properties of components of the engineered barrier system (i.e. buffer, disturbed rock zone and the host rock), and different surface storage times. Results of the different modeling cases are presented and include temperature and fluid flow profiles in the near field at different simulation times. Sandia National Laboratories is a multimission laboratory managed and operated by National Technology and

Study on high-resolution sequence stratigraphy framework of uranium-hosting rock series in Qianjiadian sag

International Nuclear Information System (INIS)

Chen Fanghong; Zhang Mingyu

2005-01-01

The ore-hosting Yaojia Formation is composed of a set of braided stream medium-fine grained sediments. Guided by the basic theory of high-resolution sequence stratigraphy, and based on the core observation, the analysis of chemical composition of rocks, and data of natural potential logging and apparent resistivity logging, the authors have set up the high-resolution sequence stratigraphy framework of the ore-hosting Yaojia Formation, and discussed the relation of the stratigraphic structure of the middle cycle, as well as the paleotopography, the micro-facies to the formation of uranium deposit. (authors)

Theoretical and Numerical Investigation of the Cavity Evolution in Gypsum Rock

Science.gov (United States)

Li, Wei; Einstein, Herbert H.

2017-11-01

When water flows through a preexisting cylindrical tube in gypsum rock, the nonuniform dissolution alters the tube into an enlarged tapered tube. A 2-D analytical model is developed to study the transport-controlled dissolution in an enlarged tapered tube, with explicit consideration of the tapered geometry and induced radial flow. The analytical model shows that the Graetz solution can be extended to model dissolution in the tapered tube. An alternative form of the governing equations is proposed to take advantage of the invariant quantities in the Graetz solution to facilitate modeling cavity evolution in gypsum rock. A 2-D finite volume model was developed to validate the extended Graetz solution. The time evolution of the transport-controlled and the reaction-controlled dissolution models for a single tube with time-invariant flow rate are compared. This comparison shows that for time-invariant flow rate, the reaction-controlled dissolution model produces a positive feedback between the tube enlargement and dissolution, while the transport-controlled dissolution does not.

The Ypresian clays as alternative host rock for radioactive waste disposal in Belgium. A transferability study

International Nuclear Information System (INIS)

Van Baelen, Herve; Wouters, Laurent; Brassinnes, Stephane; Van Geet, Maarten; Vandenberghe, Noel

2012-01-01

Document available in extended abstract form only. For the long-term management of high-level and/or long-lived radioactive waste, ONDRAF/NIRAS advises deep geological repository in a plastic clay host rock. Since the seventies, Oligocene Boom Clay has been extensively studied for this purpose and is, in the Belgian context, considered as the reference host rock with Mol as the reference site for the RD and D. The alternative host rock, the Ypresian clays, has been studied for their basic properties, from the late nineties onwards, with Doel as reference site. This study aims at determining to which extent methodologies, knowledge and know-how can be transferred from Boom Clay to the Ypresian clays, in order to enhance the knowledge of this alternative without excessive research efforts. It evaluates the present knowledge of the Ypresian clays and figures out which elements are sufficiently known and understood, which elements of the Boom Clay can be reused and which need additional research. The Ypresian clays refer to a nearly continuous sequence of non-indurated, clayey layers, deposited early in the Eocene, in an open marine basin. It has a total thickness of 100 m or more and, in the area of interest, it occurs at a few hundreds of meters depth. Apart from a very slight tilt to the north, no major structures are known to affect the Ypresian clays in the investigated area. The lateral continuity inside the Ypresian clays might, however, be compromised by the potential occurrence of small-scale intra-formational faults. Two drilling campaigns, carried out in the framework of potential radioactive waste disposal, allowed to collect new data and describe and compare the Ypresian clays relative to Boom Clay. The grain size distribution of both clays is comparable. Although the minerals they are composed of are the same, the relative proportions within the clay fraction are significantly different, the Ypresian clays containing more smectite and swelling mixed

Microbiologically mediated processes in a repository sited in a clay host rock

International Nuclear Information System (INIS)

Schwyn, B.; Leupin, O. X.; Bagnoud, A.; Bernier-Latmani, R.

2012-01-01

Document available in extended abstract form only. Because of their favourable retention properties for radionuclides, clay-rich sediments are being considered in Switzerland as host rocks for the geological disposal of high, intermediate- and low-level radioactive waste. Compacted bentonite is foreseen as backfill material in the high level waste repository whereas for intermediate- and low-level waste the near field will mainly consist of cementitious material. The evolution of both types of repositories, which includes re-saturation, heat generation (only high level waste), near field degradation, gas production and radionuclide release may be impacted by microbial activity and vice versa. In this respect questions arise such as: - Are microorganisms present in a repository and its host rock? - Under which condition are microorganisms active in and around a repository? - In which processes are microorganisms involved? Various in situ experiments in a wide range of geological environments have evidenced the presence of microorganisms. Whether the microorganisms found in these in situ experiments are indigenous or introduced by drilling or/and excavation activities is still controversial. However, recent findings suggest the presence of indigenous microorganisms in Opalinus Clay. To conclusively answer the question about the origin of microorganisms, an international investigation programme has been launched to probe rock samples from the Underground Rock Laboratory at Mont Terri. So far, no metabolic activity has been observed in undisturbed clay rocks. Such activity may have ceased during diagenetic compaction of the sediment as suggested by the pore water composition measured in the Callovian-Oxfordian clayey formation of Bure (France). For the safety case of a repository the origin of microorganisms is of minor importance compared to the understanding of the conditions under which they might be metabolically active. Pore size distribution and connectivity can

The Effect of Micrite on Velocity, Its Sensitivity to Pressure, and Dissolution of Carbonates

Science.gov (United States)

El Husseiny, A.; Vanorio, T.

2014-12-01

This study investigates the effect of micrite on the acoustic properties of well-controlled microstructures created in the laboratory to closely mimic carbonate rocks. In particular, we examine the effect of micrite content on the elastic stiffness rock, its sensitivity to pressure, and induced dissolution upon saturation with a reactive fluid. We followed Dunham's classification and fabricated the samples by mixing coarse (sand size) and very fine (micrite size) calcite grains in different ratios, with the addition of cement and then cold-compressing the mixture. The acoustic velocities were measured under bench-top conditions and as functions of confining pressure before and after the injection of a CO2aqueous solution. Our bench-top measurements indicated that micrite makes the frame of the carbonate samples stiffer. Since the sensitivity of the elastic stiffness to pressure decreases as the content of micrite increases (see figure 1), we hypothesize a stiffer pore structure (i.e., rounder pores) in micrite-richer fabrics. Furthermore, the presence of micrite makes the carbonate sample more reactive upon dissolution. The concentration of Ca+2 cations in the fluid measured at the outlet after the injection of the CO2 aqueous solution shows larger dissolution in the micrite-rich samples likely due to the higher surface area of the micrite aggregates. The content of micrite also seems to affect the evolution of stiffness as dissolution proceeds. As the content of micrite increases, the enhanced dissolution translates into a marked softening of the rock frame. We conclude that the content of micrite can play an important role in the complex rock-fluid interaction of carbonates as well as when comparing Gassmann's predictions to velocity measurements of saturated carbonates.

Kinetics of carbonate dissolution in CO2-saturated aqueous system at reservoir conditions

Science.gov (United States)

Peng, Cheng; Crawshaw, John P.; Maitland, Geoffrey; Trusler, J. P. Martin

2014-05-01

In recent years, carbon capture and storage (CCS) has emerged as a key technology for limiting anthropogenic CO2 emissions while allowing the continued utilisation of fossil fuels. The most promising geological storage sites are deep saline aquifers because the capacity, integrity and injection economics are most favourable, and the environmental impact can be minimal. Many rock-fluid chemical reactions are known to occur both during and after CO2 injection in saline aquifers. The importance of rock-fluid reactions in the (CO2 + H2O) system can be understood in terms of their impact on the integrity and stability of both the formation rocks and cap rocks. The chemical interactions between CO2-acidified brines and the reservoir minerals can influence the porosity and permeability of the formations, resulting in changes in the transport processes occurring during CO2 storage. Since carbonate minerals are abundant in sedimentary rocks, one of the requirements to safely implement CO2 storage in saline aquifers is to characterise the reactivity of carbonate minerals in aqueous solutions at reservoir conditions. In this work, we reported measurements of the intrinsic rate of carbonate dissolution in CO2-saturated water under high-temperature high-pressure reservoir conditions extending up to 373 K and 14 MPa. The rate of carbonate dissolution in CO2-free HCl(aq) was also measured at ambient pressure at temperatures up to 353 K. Various pure minerals and reservoir rocks were investigated in this study, including single-crystals of calcite and magnesite, and samples of dolomite, chalks and sandstones. A specially-designed batch reactor system, implementing the rotating disc technique, was used to obtain the intrinsic reaction rate at the solid/liquid interface, free of mass transfer effects. The effective area and mineralogy of the exposed surface was determined by a combination of surface characterisation techniques including XRD, SEM, EDX and optical microscopy. The

Impact of grain size and rock composition on simulated rock weathering

Science.gov (United States)

Israeli, Yoni; Emmanuel, Simon

2018-05-01

Both chemical and mechanical processes act together to control the weathering rate of rocks. In rocks with micrometer size grains, enhanced dissolution at grain boundaries has been observed to cause the mechanical detachment of particles. However, it remains unclear how important this effect is in rocks with larger grains, and how the overall weathering rate is influenced by the proportion of high- and low-reactivity mineral phases. Here, we use a numerical model to assess the effect of grain size on chemical weathering and chemo-mechanical grain detachment. Our model shows that as grain size increases, the weathering rate initially decreases; however, beyond a critical size no significant decrease in the rate is observed. This transition occurs when the density of reactive boundaries is less than ˜ 20 % of the entire domain. In addition, we examined the weathering rates of rocks containing different proportions of high- and low-reactivity minerals. We found that as the proportion of low-reactivity minerals increases, the weathering rate decreases nonlinearly. These simulations indicate that for all compositions, grain detachment contributes more than 36 % to the overall weathering rate, with a maximum of ˜ 50 % when high- and low-reactivity minerals are equally abundant in the rock. This occurs because selective dissolution of the high-reactivity minerals creates large clusters of low-reactivity minerals, which then become detached. Our results demonstrate that the balance between chemical and mechanical processes can create complex and nonlinear relationships between the weathering rate and lithology.

Waste dissolution with chemical reaction, diffusion and advection

International Nuclear Information System (INIS)

Chambre, P.L.; Kang, C.H.; Lee, W.W.L.; Pigford, T.H.

1987-06-01

This paper extends the mass-transfer analysis to include the effect of advective transport in predicting the steady-state dissolution rate, with a chemical-reaction-rate boundary condition at the surface of a waste form of arbitrary shape. This new theory provides an analytic means of predicting the ground-water velocities at which dissolution rate in a geologic environment will be governed entirely to the chemical reaction rate. As an illustration, we consider the steady-state potential flow of ground water in porous rock surrounding a spherical waste solid. 3 refs., 2 figs

Hydrothermal alteration of deep fractured granite: Effects of dissolution and precipitation

Science.gov (United States)

Nishimoto, Shoji; Yoshida, Hidekazu

2010-03-01

This paper investigates the mineralogical effects of hydrothermal alteration at depth in fractures in granite. A fracture accompanied by an alteration halo and filled with clay was found at a depth of 200 m in a drill core through Toki granite, Gifu, central Japan. Microscopic observation, XRD, XRF, EPMA and SXAM investigations revealed that the microcrystalline clays consist of illite, quartz and pyrite and that the halo round the fracture can be subdivided into a phyllic zone adjacent to the fracture, surrounded by a propylitic zone in which Fe-phyllosilicates are present, and a distinctive outer alteration front characterized by plagioclase breakdown. The processes that result in these changes took place in three successive stages: 1) partial dissolution of plagioclase with partial chloritization of biotite; 2) biotite dissolution and precipitation of Fe-phyllosilicate in the dissolution pores; 3) dissolution of K-feldspar and Fe-phyllosilicate, and illite precipitation associated with development of microcracks. These hydrothermal alterations of the granite proceed mainly by a dissolution-precipitation process resulting from the infiltration of hydrothermal fluid along microcracks. Such infiltration causes locally high mobility of Al and increases the ratio of fluid to rock in the alteration halo. These results contribute to an understanding of how granitic rock becomes altered in orogenic fields such as the Japanese island arc.

Rock suitability classification RSC 2012

Energy Technology Data Exchange (ETDEWEB)

McEwen, T. (ed.) [McEwen Consulting, Leicester (United Kingdom); Kapyaho, A. [Geological Survey of Finland, Espoo (Finland); Hella, P. [Saanio and Riekkola, Helsinki (Finland); Aro, S.; Kosunen, P.; Mattila, J.; Pere, T.

2012-12-15

This report presents Posiva's Rock Suitability Classification (RSC) system, developed for locating suitable rock volumes for repository design and construction. The RSC system comprises both the revised rock suitability criteria and the procedure for the suitability classification during the construction of the repository. The aim of the classification is to avoid such features of the host rock that may be detrimental to the favourable conditions within the repository, either initially or in the long term. This report also discusses the implications of applying the RSC system for the fulfilment of the regulatory requirements concerning the host rock as a natural barrier and the site's overall suitability for hosting a final repository of spent nuclear fuel.

Rock suitability classification RSC 2012

International Nuclear Information System (INIS)

McEwen, T.; Kapyaho, A.; Hella, P.; Aro, S.; Kosunen, P.; Mattila, J.; Pere, T.

2012-12-01

This report presents Posiva's Rock Suitability Classification (RSC) system, developed for locating suitable rock volumes for repository design and construction. The RSC system comprises both the revised rock suitability criteria and the procedure for the suitability classification during the construction of the repository. The aim of the classification is to avoid such features of the host rock that may be detrimental to the favourable conditions within the repository, either initially or in the long term. This report also discusses the implications of applying the RSC system for the fulfilment of the regulatory requirements concerning the host rock as a natural barrier and the site's overall suitability for hosting a final repository of spent nuclear fuel

Surface controlled dissolution rates of gypsum in aqueous solutions exhibit nonlinear dissolution kinetics

Science.gov (United States)

Jeschke, Alexander A.; Vosbeck, Katrin; Dreybrodt, Wolfgang

2001-01-01

The effective dissolution rates of gypsum are determined by mixed kinetics, where the rate constants of dissolution at the surface and the transport constant of molecular diffusion of dissolved material are similar. To obtain the surface reaction rate law it is necessary to know the transport constant. We have determined the surface rate law for monocrystalline selenite by using a rotating disc set-up, where the transport coefficients are well known. As a result, up to a calcium concentration of 0.6 · ceq, we find a nearly linear rate law Rs = ksl (1- cs/ ceq) n1, where cs is the total calcium concentration at the surface and ceq the equilibrium concentration with respect to gypsum, n1 = 1.2 ± 0.2, and ksl = 1.1 · 10 -4 mmol cm -2 s -1 ± 15%. We also employed batch-experiments for selenite, alabaster and gypsum rock samples. The result of these experiments were interpreted by using a transport constant determined by NaCl dissolution experiments under similar physical conditions. The batch experiments reveal a dissolution rate law Rs = ksl (1- cs/ ceq) n1, ksl = 1.3 · 10 -4 mmol · cm -2 s -1, n1 = 1.2 ± 0.2 for c ≤ 0.94 · ceq. Close to equilibrium a nonlinear rate law, Rs = ks2 (1- cs/ ceq) n2, is observed, where ks2 is in the order of 10 mmol · cm -2 s -1 and n2 ≈ 4.5. The experimentally observed gypsum dissolution rates from the batch experiments could be accurately fitted, with only minor variations of the surface reaction constant obtained from the rotating disk experiment and the transport coefficient from the NaCl dissolution batch experiment. Batch experiments on pure synthetic gypsum, reveal a linear rate law up to equilibrium. This indicates inhibition of dissolution in natural samples close to equilibrium, as is known also for calcite minerals.

Basic investigation and analysis for preferred host rocks and natural analogue study area with reference to high level radioactive waste disposal

Energy Technology Data Exchange (ETDEWEB)

Seo, Jeong Ryul; Park, J. K.; Hwang, D. H.; Lee, J. H.; Yun, H. S.; Kim, D. Y.; Park, H. S.; Koo, S. B.; Cho, J. D.; Kim, K. E. [Korea Inst. of Geology, Mining and Materials, Taejon (Korea, Republic of)

1997-12-01

The purpose of this study is basic investigation and analysis for preferred host rocks and natural analogue study area to develope underground disposal technique of high level radioactive waste in future. The study has been done for the crystalline rocks(especially granitic rocks) with emphasis of abandoned metallic mines and uranium ore deposits, and for the geological structure study by using gravity and aeromagnetic data. 138 refs., 54 tabs., 130 figs. (author)

Evaluation of possible host rocks for China's high level radioactive waste repository and the progress in site characterization at the Beishan potential site in NW China's Gansu province

International Nuclear Information System (INIS)

Wang Ju; Jin Yuanxin; Chen Zhangru; Chen Weiming; Wang Wenguang

2000-01-01

Evaluation of possible host rocks for China's high level radioactive waste repository is summarized in this paper. The distribution and characteristics of granite, tuff, clay stone, salt and loess in China are described, while maps showing the distribution of host rocks are presented. Because of the wide distribution, large scale, good heat conductivity and suitable mechanical properties, granite is considered as the most potential host rock. Some granite bodies distributed in NW China, SW China, South China and Inner Mongolia have been selected as potential areas. Detailed site characterization at Beishan area, Gansu Province NW China is in progress

Nagra technical report 14-02, Geological basics - Dossier VI - Barrier properties of proposed host rock sediments and neighbouring rock; SGT Etappe 2: Vorschlag weiter zu untersuchender geologischer Standortgebiete mit zugehörigen Standortarealen für die Oberflächenanlage -- Geologische Grundlagen -- Dossier VI -- Barriereneigenschaften der Wirt- und Rahmengesteine

Energy Technology Data Exchange (ETDEWEB)

Gautschi, A.; Deplazes, G.; Traber, D.; Marschall, P. [National Cooperative for the Disposal of Radioactive Waste (NAGRA), Wettingen (Switzerland); Mazurek, M.; Gimmi, T.; Maeder, U. [Institute of Geological Sciences, University of Berne, Berne (Switzerland)

2014-12-15

This dossier is the sixth of a series of eight reports concerning the safety and technical aspects of locations for the disposal of radioactive wastes in Switzerland. It discusses the barrier properties of the proposed host rock sediments and neighbouring rock layers. The mineralogical composition of the host rocks are discussed as are their pore densities and hydrological properties. Diffusion aspects are discussed. The aquifer systems in the proposed depository areas and their classification are looked at. The barrier properties of the host rocks and those of neighbouring sediments are discussed. Finally, modelling concepts and parameters for the transport of radionuclides in the rocks are discussed.

Hydro-mechanical modelling of a shaft seal in crystalline and sedimentary host rock media using COMSOL

Energy Technology Data Exchange (ETDEWEB)

Priyanto, D.G. [Atomic Energy of Canada Limited, Pinawa, MB (Canada)

2011-07-01

Shaft seals are components of the engineered barriers system considered for closure of a Deep Geological Repository (DGR). These seals would be installed in strategic locations of the shafts, where significant fracture zones (FZ) are located and would serve to limit upward flow of groundwater from the repository level towards the surface. This paper presents the results of hydro-mechanical (HM) numerical modelling exercises to evaluate the performance of a shaft seal using a finite element computer code, COMSOL. This study considered a variety of host geological media as part of generic assessments of system evolution in a variety of environments including five hypothetical sedimentary and crystalline host rock conditions. Four simulations of a shaft seal in different sedimentary rocks were completed, including: shale with isotropic permeability; shale with anisotropic permeability; limestone with isotropic permeability; and limestone with anisotropic permeability. The other simulation was a shaft seal in crystalline rock with isotropic permeability. Two different stages were considered in these HM simulations. Stages 1 and 2 simulated the groundwater flow into an open shaft and after installation of shaft sealing components, respectively. As expected, the models were able to simulate that installation of the shaft seal limits groundwater flow through the shaft. Based on the conditions and assumptions defined for the host media and fracture features examined in this study, the following conclusions can be drawn from the results of the numerical modelling exercises. A shaft that remained open for a longer time was beneficial with respect to delaying of seal saturation because it could reduce the groundwater flow rate around the fracture zone. Delaying saturation time indicates slower movement of the groundwater or other substances that may be transported with the groundwater. The core of the shaft seal (i.e., the bentonite-sand mixture (BSM)) became fully saturated

Effects of bioleaching on the mechanical and chemical properties of waste rocks

Science.gov (United States)

Yin, Sheng-Hua; Wu, Ai-Xiang; Wang, Shao-Yong; Ai, Chun-Ming

2012-01-01

Bioleaching processes cause dramatic changes in the mechanical and chemical properties of waste rocks, and play an important role in metal recovery and dump stability. This study focused on the characteristics of waste rocks subjected to bioleaching. A series of experiments were conducted to investigate the evolution of rock properties during the bioleaching process. Mechanical behaviors of the leached waste rocks, such as failure patterns, normal stress, shear strength, and cohesion were determined through mechanical tests. The results of SEM imaging show considerable differences in the surface morphology of leached rocks located at different parts of the dump. The mineralogical content of the leached rocks reflects the extent of dissolution and precipitation during bioleaching. The dump porosity and rock size change under the effect of dissolution, precipitation, and clay transportation. The particle size of the leached rocks decreased due to the loss of rock integrity and the conversion of dry precipitation into fine particles.

Conceptual and safety-related questions in the final storage of radioactive waste - a comparison of various types of host rock

International Nuclear Information System (INIS)

Kleemann, U.

2005-01-01

The German Federal Office for Radiation Protection (BfS) in early November published the synthesis report (BfS 2005) about the conceptual and safety-related specific questions associated with the final storage of radioactive waste. In addition to a condensed version of twelve individual projects, the report contains a description of the results of the peer review and the workshops carried out, in particular an evaluation comparing different types of host rock in Germany. The whole project constitutes a comprehensive documentation of the current state of the art. Findings are expressed at a general level referring neither to the suitability of any specific repository site nor to that of salts as a repository formation, but covering all potential repository formations in deep geologic strata in Germany. The limits to and possibilities of, generic comparisons of various types of host rock are shown. It si seen that, in principle, none of the host rock varieties in Germany would be preferable to others. Numerous problems can be solved only for specific sites, thus requiring site comparisons. While some questions indicate a need for regulatory treatment, the need for basic research is considered to be low. The contribution presents the main findings made in each of the specific projects and the evaluations by the Office. (orig.)

Physical properties of uranium host rocks and experimental drilling at Long Park, Montrose County, Colorado. Final report

International Nuclear Information System (INIS)

Manger, G.E.; Gates, G.L.; Cadigan, R.A.

1975-01-01

A core-drilling study in uranium host rocks of the Jurassic Morrison Formation in southwestern Colorado attempted to obtain samples of host rock in its natural state. Three holes were drilled, holes and core were logged for radioactivity and electrical properties. Samples were analyzed for physical and chemical properties. Drilling results suggest that drilling with dried air yields core with least contamination at least cost. Drilling with oil results in maximum core recovery but also maximum cost and significant core contamination. Drilling with water results in contamination and loss of original pore water. A factor group of variables present are: Those positively related to uranium mineralization are poor sorting, percent by weight clay, percent of pore space containing water; negatively related variables are median grain size (mm), electrical resistivity, permeability. Optimum depth to locate ore seems to be at the top of the pore water capillary circulation zone, below the dehydrated no-capillary-circulation zone

Dissolution-Enlarged Fractures Imaging Using Electrical Resistivity Tomography (ERT)

Science.gov (United States)

Siami-Irdemoosa, Elnaz

In recent years the electrical imaging techniques have been largely applied to geotechnical and environmental investigations. These techniques have proven to be the best geophysical methods for site investigations in karst terrain, particularly when the overburden soil is clay-dominated. Karst is terrain with a special landscape and distinctive hydrological system developed by dissolution of rocks, particularly carbonate rocks such as limestone and dolomite, made by enlarging fractures into underground conduits that can enlarge into caverns, and in some cases collapse to form sinkholes. Bedding planes, joints, and faults are the principal structural guides for underground flow and dissolution in almost all karstified rocks. Despite the important role of fractures in karst development, the geometry of dissolution-enlarged fractures remain poorly unknown. These features are characterized by an strong contrast with the surrounding formations in terms of physical properties, such as electrical resistivity. Electrical resistivity tomography (ERT) was used as the primary geophysical tool to image the subsurface in a karst terrain in Greene County, Missouri. Pattern, orientation and density of the joint sets were interpreted from ERT data in the investigation site. The Multi-channel Analysis of Surface Wave (MASW) method and coring were employed to validate the interpretation results. Two sets of orthogonal visually prominent joints have been identified in the investigation site: north-south trending joint sets and west-east trending joint sets. However, most of the visually prominent joint sets are associated with either cultural features that concentrate runoff, natural surface drainage features or natural surface drainage.

Far-field sorption data bases for performance assessment of a L/ILW repository in an undisturbed Palfris marl host rock

International Nuclear Information System (INIS)

Bradbury, M.H.; Baeyens, B.

1997-12-01

A Palfris marl formation at Wellenberg (Gemeinde Wolfenschiessen, NW) has been chosen by NAGRA as a potential repository site for low- and intermediate-level radioactive waste, L/ILW. In the coming years a series of performance assessment studies will be performed for this site. One set of key data required for such safety analysis calculations is sorption data bases (SDB) for safety relevant radionuclides in the far-field. The purpose of this report is to describe the procedures used to generate sorption data bases appropriate for the in situ conditions existing along the different potential flow paths in an undisturbed marl host rock formation. An important aim was to document the sources of sorption data used and, in particular, the processes by which data selections were mad.e. The main guiding principles here were 'transparency' and 'traceability'. Inherent within this whole process is also the justification for, and defensibility of, the selected values. Much of the sorption data used to generate the SDB for marl came from the open literature. A major part of this report is concerned with describing the procedures whereby these initial literature values are modified so that they apply to the actual marl mineralogies and groundwater chemistries. The resulting 'reference R d values' are then further modified using so called Lab -> Field transfer factors to produce sorption values which are appropriate to the in situ bulk rock conditions. The Lab -> Field transfer factors attempt to correct for the differences in sorption site availability between the crushed rock state used in batch tests and the intact rock state existing in reality in the host rock. There are two main groundwater chemistries and five characteristic mineralogical compositions which cover the three broad types of flow paths which have been identified in the Palfris marl formation. In principle the methodology described here to construct sorption data bases for marl is applicable to any type of

Far-field sorption data bases for performance assessment of a L/ILW repository in an undisturbed Palfris marl host rock

Energy Technology Data Exchange (ETDEWEB)

Bradbury, M.H.; Baeyens, B. [Paul Scherrer Inst. (PSI), Villigen (Switzerland)

1997-12-01

A Palfris marl formation at Wellenberg (Gemeinde Wolfenschiessen, NW) has been chosen by NAGRA as a potential repository site for low- and intermediate-level radioactive waste, L/ILW. In the coming years a series of performance assessment studies will be performed for this site. One set of key data required for such safety analysis calculations is sorption data bases (SDB) for safety relevant radionuclides in the far-field. The purpose of this report is to describe the procedures used to generate sorption data bases appropriate for the in situ conditions existing along the different potential flow paths in an undisturbed marl host rock formation. An important aim was to document the sources of sorption data used and, in particular, the processes by which data selections were mad.e. The main guiding principles here were `transparency` and `traceability`. Inherent within this whole process is also the justification for, and defensibility of, the selected values. Much of the sorption data used to generate the SDB for marl came from the open literature. A major part of this report is concerned with describing the procedures whereby these initial literature values are modified so that they apply to the actual marl mineralogies and groundwater chemistries. The resulting `reference R{sub d} values` are then further modified using so called Lab -> Field transfer factors to produce sorption values which are appropriate to the in situ bulk rock conditions. The Lab -> Field transfer factors attempt to correct for the differences in sorption site availability between the crushed rock state used in batch tests and the intact rock state existing in reality in the host rock. There are two main groundwater chemistries and five characteristic mineralogical compositions which cover the three broad types of flow paths which have been identified in the Palfris marl formation. In principle the methodology described here to construct sorption data bases for marl is applicable to any

THM-coupled modeling of selected processes in argillaceous rock relevant to rock mechanics

International Nuclear Information System (INIS)

Czaikowski, Oliver

2012-01-01

Scientific investigations in European countries other than Germany concentrate not only on granite formations (Switzerland, Sweden) but also on argillaceous rock formations (France, Switzerland, Belgium) to assess their suitability as host and barrier rock for the final storage of radioactive waste. In Germany, rock salt has been under thorough study as a host rock over the past few decades. According to a study by the German Federal Institute for Geosciences and Natural Resources, however, not only salt deposits but also argillaceous rock deposits are available at relevant depths and of extensions in space which make final storage of high-level radioactive waste basically possible in Germany. Equally qualified findings about the suitability/unsuitability of non-saline rock formations require fundamental studies to be conducted nationally because of the comparatively low level of knowledge. The article presents basic analyses of coupled mechanical and hydraulic properties of argillaceous rock formations as host rock for a repository. The interaction of various processes is explained on the basis of knowledge derived from laboratory studies, and open problems are deduced. For modeling coupled processes, a simplified analytical computation method is proposed and compared with the results of numerical simulations, and the limits to its application are outlined. (orig.)

Jarosite dissolution rates in perchlorate brine

Science.gov (United States)

Legett, Carey; Pritchett, Brittany N.; Elwood Madden, Andrew S.; Phillips-Lander, Charity M.; Elwood Madden, Megan E.

2018-02-01

Perchlorate salts and the ferric sulfate mineral jarosite have been detected at multiple locations on Mars by both landed instruments and orbiting spectrometers. Many perchlorate brines have eutectic temperatures bearing rocks and sediments may have been altered by perchlorate brines. Here we measured jarosite dissolution rates in 2 M sodium perchlorate brine as well as dilute water at 298 K to determine the effects of perchlorate anions on jarosite dissolution rates and potential reaction products. We developed a simple method for determining aqueous iron concentrations in high salinity perchlorate solutions using ultraviolet-visible spectrophotometry that eliminates the risk of rapid oxidation reactions during analyses. Jarosite dissolution rates in 2 M perchlorate brine determined by iron release rate (2.87 × 10-12 ±0.85 × 10-12 mol m-2 s-1) were slightly slower than the jarosite dissolution rate measured in ultrapure (18.2 MΩ cm-1) water (5.06 × 10-12 mol m-2 s-1) using identical methods. No additional secondary phases were observed in XRD analyses of the reaction products. The observed decrease in dissolution rate may be due to lower activity of water (ɑH2O = 0.9) in the 2 M NaClO4 brine compared with ultrapure water (ɑH2O = 1). This suggests that the perchlorate anion does not facilitate iron release, unlike chloride anions which accelerated Fe release rates in previously reported jarosite and hematite dissolution experiments. Since dissolution rates are slower in perchlorate-rich solutions, jarosite is expected to persist longer in perchlorate brines than in dilute waters or chloride-rich brines. Therefore, if perchlorate brines dominate aqueous fluids on the surface of Mars, jarosite may remain preserved over extended periods of time, despite active aqueous processes.

Electrochemical dissolution of surface alloys in acids: Thermodynamic trends from first-principles calculations

DEFF Research Database (Denmark)

Greeley, Jeffrey Philip; Nørskov, Jens Kehlet

2007-01-01

A simple procedure is introduced to use periodic Density Functional Theory calculations to estimate trends in the thermodynamics of surface alloy dissolution in acidic media. With this approach, the dissolution potentials for solute metal atoms embedded in the surface layer of various host metals...

Effect of Callovo-Oxfordian clay rock on the dissolution rate of the SON68 simulated nuclear waste glass

Energy Technology Data Exchange (ETDEWEB)

Neeway, James J., E-mail: James.Neeway@pnnl.gov [SUBATECH, Unité Mixte de Recherche 6457, École des Mines de Nantes, CNRS/IN2P3, Université de Nantes, BP 20722, 44307 Nantes cedex 3 (France); Abdelouas, Abdesselam; Ribet, Solange; El Mendili, Yassine [SUBATECH, Unité Mixte de Recherche 6457, École des Mines de Nantes, CNRS/IN2P3, Université de Nantes, BP 20722, 44307 Nantes cedex 3 (France); Schumacher, Stéphan [ANDRA, Parc de la Croix Blanche, 1/7 rue Jean Monnet, 92298 Châtenay-Malabry (France); Grambow, Bernd [SUBATECH, Unité Mixte de Recherche 6457, École des Mines de Nantes, CNRS/IN2P3, Université de Nantes, BP 20722, 44307 Nantes cedex 3 (France)

2015-04-15

Long-term storage of high-level nuclear waste glass in France is expected to occur in an engineered barrier system (EBS) located in a subsurface Callovo-Oxfordian (COx) clay rock formation in the Paris Basin in northeastern France. Understanding the behavior of glass dissolution in the complex system is critical to be able to reliably model the performance of the glass in this complex environment. To simulate this multi-barrier repository scenario in the laboratory, several tests have been performed to measure glass dissolution rates of the simulated high-level nuclear waste glass, SON68, in the presence of COx claystone at 90 °C. Experiments utilized a High-Performance Liquid Chromatography (HPLC) pump to pass simulated Bure site COx pore water through a reaction cell containing SON68 placed between two COx claystone cores for durations up to 200 days. Silicon concentrations at the outlet were similar in all experiments, even the blank experiment with only the COx claystone (∼4 mg/L at 25 °C and ∼15 mg/L at 90 °C). The steady-state pH of the effluent, measured at room temperature, was roughly 7.1 for the blank and 7.3–7.6 for the glass-containing experiments demonstrating the pH buffering capacity of the COx claystone. Dissolution rates for SON68 in the presence of the claystone were elevated compared to those obtained from flow-through experiments conducted with SON68 without claystone in silica-saturated solutions at the same temperature and similar pH values. Additionally, through surface examination of the monoliths, the side of the monolith in direct contact with the claystone was seen to have a corrosion thickness 2.5× greater than the side in contact with the bulk glass powder. Results from one experiment containing {sup 32}Si-doped SON68 also suggest that the movement of Si through the claystone is controlled by a chemically coupled transport with a Si retention factor, K{sub d}, of 900 mL/g.

The dissolution of high-FeO olivine rock from the Lovasjaervi intrusion (SE-Finland) at 25 deg. C as a function of pH

International Nuclear Information System (INIS)

Duro, Lara; El Aamrani, Fatima; Rovira, Miquel; Gimenez, Javier; Casas, Ignasi; Pablo, Joan de; Bruno, Jordi

2005-01-01

The high-FeO olivine-rich rock from the Lovasjaervi intrusion (65% olivine, 20% plagioclase, 8% magnetite, 4% pyroxene and 3% serpentine) has been proposed as a potential redox-active backfill-additive in deep high level nuclear waste repositories. In this work, the authors report on kinetic dissolution studies of this solid under different pH and redox conditions performed by using a flow-through methodology. Assuming that silicon is mainly released to solution from the olivine contained in the solid, the experimental results have been adjusted to an empirical rate law as a function of proton concentration. The proton concentration reaction orders agree with results found in the literature for both acidic and alkaline pH ranges. The calculations conducted with the reactive transport code RETRASO show that at alkaline pH, the olivine rock might have a lower redox buffer capacity than expected

Review of potential host rocks for radioactive wasste disposal in the southeast United States: Triassic basin subregion

International Nuclear Information System (INIS)

1980-10-01

Based on an evaluation of existing information, areas were identified within the Triassic basins of the southeastern United States with geologic properties considered favorable for containment of radioactive waste. The study region included both exposed and buried Triassic basins from Maryland to Georgia. These basins are long, narrow northeast-trending troughs filled with continental deposits derived from Paleozoic and Precambrian metamorphic and igneous rocks bordering the basins. The rocks are predominantly red in color and consist mainly of fanglomerates, conglomerates, arkosic sandstones, siltstones, claystones, shales, and argillites. The investigation identified 14 exposed and 5 buried basins within the study region. Candidate areas for further investigation were identified which meet the broad general criteria for tectonic stability, slow ground water movement, and long flow paths to the biosphere. These include: the Danville Triassic Basin in Virginia; the Dan River, Durham, and Wadesboro Triassic Basins in North Carolina; and the buried Florence and Dunbarton Triassic Basins in South Carolina. Other rock types in the southeast may prove more or less suitable as host rocks for a repository, but the available data suggest that the argillaceous Triassic rocks offer sufficient promise to be considered for additional study

Hydro-chemo-mechanical coupling in sediments: Localized mineral dissolution

KAUST Repository

Cha, Minsu; Santamarina, Carlos

2016-01-01

Mineral dissolution is inherently a chemo-hydro-mechanical coupled process. Field evidence and laboratory results show that dissolution may localize and form open conduits in cohesive media such as carbonate rocks. This study focuses on the evolution of localized dissolution in soils (i.e., frictional and non-cohesive granular materials) under effective confining stresses. Experimental results show the development of localized dissolution (“pipe”) when a carbonate-quartz sand is subjected to reactive fluid flow: only loosely packed quartz grains remain within pipes, and the number of pipes decreases away from the inlet port. Concurrent shear wave velocity measurements show a decrease in stiffness during dissolution due to stress and fabric changes, and more complex signal codas anticipate the development of internal heterogeneity. The discrete element method is used to simulate localized vertical dissolution features in granular materials, under constant vertical stress and zero lateral strain far-field boundaries. As porosity increases along dissolution pipes, vertical load is transferred to the surrounding soils and marked force chains develop. In terms of equivalent stress, principal stress rotation takes place within pipes and the sediment reaches the Coulomb failure condition inside pipes and in the surrounding medium. Dissolution pipes alter the geo-plumbing of the subsurface, enhance fluid transport but limit the long term performance of storage systems, alter the fluid pressure and effective stress fields, soften the sediment and may trigger shear failures.

Hydro-chemo-mechanical coupling in sediments: Localized mineral dissolution

KAUST Repository

Cha, Minsu

2016-06-11

Mineral dissolution is inherently a chemo-hydro-mechanical coupled process. Field evidence and laboratory results show that dissolution may localize and form open conduits in cohesive media such as carbonate rocks. This study focuses on the evolution of localized dissolution in soils (i.e., frictional and non-cohesive granular materials) under effective confining stresses. Experimental results show the development of localized dissolution (“pipe”) when a carbonate-quartz sand is subjected to reactive fluid flow: only loosely packed quartz grains remain within pipes, and the number of pipes decreases away from the inlet port. Concurrent shear wave velocity measurements show a decrease in stiffness during dissolution due to stress and fabric changes, and more complex signal codas anticipate the development of internal heterogeneity. The discrete element method is used to simulate localized vertical dissolution features in granular materials, under constant vertical stress and zero lateral strain far-field boundaries. As porosity increases along dissolution pipes, vertical load is transferred to the surrounding soils and marked force chains develop. In terms of equivalent stress, principal stress rotation takes place within pipes and the sediment reaches the Coulomb failure condition inside pipes and in the surrounding medium. Dissolution pipes alter the geo-plumbing of the subsurface, enhance fluid transport but limit the long term performance of storage systems, alter the fluid pressure and effective stress fields, soften the sediment and may trigger shear failures.

Dynamic Pore-Scale Imaging of Reactive Transport in Heterogeneous Carbonates at Reservoir Conditions Across Multiple Dissolution Regimes

Science.gov (United States)

Menke, H. P.; Bijeljic, B.; Andrew, M. G.; Blunt, M. J.

2014-12-01

Sequestering carbon in deep geologic formations is one way of reducing anthropogenic CO2 emissions. When supercritical CO2 mixes with brine in a reservoir, the acid generated has the potential to dissolve the surrounding pore structure. However, the magnitude and type of dissolution are condition dependent. Understanding how small changes in the pore structure, chemistry, and flow properties affect dissolution is paramount for successful predictive modelling. Both 'Pink Beam' synchrotron radiation and a Micro-CT lab source are used in dynamic X-ray microtomography to investigate the pore structure changes during supercritical CO2 injection in carbonate rocks of varying heterogeneity at high temperatures and pressures and various flow-rates. Three carbonate rock types were studied, one with a homogeneous pore structure and two heterogeneous carbonates. All samples are practically pure calcium carbonate, but have widely varying rock structures. Flow-rate was varied in three successive experiments by over an order of magnitude whlie keeping all other experimental conditions constant. A 4-mm carbonate core was injected with CO2-saturated brine at 10 MPa and 50oC. Tomographic images were taken at 30-second to 20-minute time-resolutions during a 2 to 4-hour injection period. A pore network was extracted using a topological analysis of the pore space and pore-scale flow modelling was performed directly on the binarized images with connected pathways and used to track the altering velocity distributions. Significant differences in dissolution type and magnitude were found for each rock type and flowrate. At the highest flow-rates, the homogeneous carbonate was seen to have predominately uniform dissolution with minor dissolution rate differences between the pores and pore throats. Alternatively, the heterogeneous carbonates which formed wormholes at high flow rates. At low flow rates the homogeneous rock developed wormholes, while the heterogeneous samples showed evidence

Revisiting classical silicate dissolution rate laws under hydrothermal conditions

Science.gov (United States)

Pollet-Villard, Marion; Daval, Damien; Saldi, Giuseppe; Knauss, Kevin; Wild, Bastien; Fritz, Bertrand

2015-04-01

In the context of geothermal energy, the relative intensities of primary mineral leaching and secondary mineral precipitation can affect porosity and permeability of the reservoir, thereby influencing its hydraulic performance and the efficiency of the geothermal power station. That is why the prediction of reaction kinetics of fluid/rock interactions represents a critical issue in this context. Moreover, in several geothermal systems such as the one of Soultz-sous-Forêts (Alsace, France), the circulation of aqueous fluids induces only modest modifications of their chemical composition. Therefore, fluid-rock interactions take place at close-to-equilibrium conditions, where the rate-affinity relations are poorly known and intensively debated [1]. To describe more precisely the dissolution processes, our strategy consists in investigating the dissolution of the main cleavages of K-spar minerals (one of the prevalent primary minerals in the reservoir of Soultz-sous-Forêts geothermal system) over a wide range of Gibbs free energy (ΔG) conditions. The aims are to decipher the impact of crystallographic orientation and microstructural surface modifications on the dissolution kinetics and to propose a relation between K-spar dissolution rate and ΔG. Our experimental work relies on a coupled approach which combines classical experiments of K-spar dissolution monitored by aqueous chemical analyses (ICP-AES) and innovative techniques of nm- to μm-scale characterization of solid surface (SEM, AFM, VSI) [2]. Our results confirm that K-spar dissolution is an anisotropic process: we measure a tenfold factor between the slowest and the fastest-dissolving surfaces. Moreover, the formation of etch pits on surfaces during their alteration has been evidenced on all of the different faces that have been studied. This complex evolution of the surface topography casts doubt of the relevance of a surface model based on shrinking particles and represents a possible cause of an

Basic feature of host rock and its relation to the formation of leachable sandstone type uranium deposit in Shihongtan

International Nuclear Information System (INIS)

Quan Zhigao; Zhang Jiamin; Ji Haijun; Sun Yanhuan; Zhang Fa

2012-01-01

Basic feature of sedimentology and petrology and lithogeochemistry of middle Jurassic Xishanyao formation were discussed for Shihongtan uranium deposit in the paper. The relation between host rock and ore formation was analysed. It is indicated that the formation of Shihongtan uranium deposit de-ponds on the following host features in sedimentology, petrology, lithogeochemistry and the intense oxidized epigenetic alteration under hot dry climate condition during the formation of peneplain caused by the slow tilting uplift. (authors)

Experimental study of kinetic and mechanism of dissolution of apatite structured minerals. Application to the prediction of the long term behavior of an actinides storage host matrix

International Nuclear Information System (INIS)

Chairat, C.

2005-11-01

The motivation for this study is to assess the potential of using apatite structured ceramics as long-lived actinide storage hosts. To assess their ability to resist aqueous corrosion, the dissolution of natural fluoro-apatite and synthetic Nd-britholite (neodymium is a proxy for the trivalent actinides) was studied. Mineral surfaces were characterized using a combined spectrometric, electrokinetic and potentiometric approach and dissolution rates were measured in closed and open system reactors as a function of solution composition. Experimental results suggest apatitic minerals dissolve via distinct step sequence: 1) fluoride release, 2) release of the calcium situated in the M1, and 3) the simultaneous removal of phosphate and calcium II via the breaking of only Ca-O bonds. TST based rate equations based in this mechanism accurately describe fluoro-apatite and synthetic britholite dissolution rates as a function of solution composition. Nd release rates are limited by precipitation of Nd-rhabdophane. (author)

Biogeochemical weathering of serpentinites: An examination of incipient dissolution affecting serpentine soil formation

International Nuclear Information System (INIS)

Baumeister, Julie L.; Hausrath, Elisabeth M.; Olsen, Amanda A.; Tschauner, Oliver; Adcock, Christopher T.; Metcalf, Rodney V.

2015-01-01

Highlights: • Dissolution of primary minerals is important to porosity generation in serpentinites. • Mineral weathering extent in serpentinites follows the order Fe > Mg > Al rich minerals. • Fe-oxidizing bacteria may mediate Fe-rich primary and serpentine mineral alteration. • Serpentinite weathering is strongly impacted by degree of serpentinization. - Abstract: Serpentinite rocks, high in Mg and trace elements including Ni, Cr, Cd, Co, Cu, and Mn and low in nutrients such as Ca, K, and P, form serpentine soils with similar chemical properties resulting in chemically extreme environments for the biota that grow upon them. The impact of parent material on soil characteristics is most important in young soils, and therefore the incipient weathering of serpentinite rock likely has a strong effect on the development of serpentine soils and ecosystems. Additionally, porosity generation is a crucial process in converting rock into a soil that can support vegetation. Here, the important factors affecting the incipient weathering of serpentinite rock are examined at two sites in the Klamath Mountains, California. Serpentinite-derived soils and serpentinite rock cores were collected in depth profiles from each sampling location. Mineral dissolution in weathered serpentinite samples, determined by scanning electron microscopy, energy dispersive spectrometry, electron microprobe analyses, and synchrotron microXRD, is consistent with the order, from most weathered to least weathered: Fe-rich pyroxene > antigorite > Mg-rich lizardite > Al-rich lizardite. These results suggest that the initial porosity formation within serpentinite rock, impacting the formation of serpentine soil on which vegetation can exist, is strongly affected both by the presence of non-serpentine primary minerals as well as the composition of the serpentine minerals. In particular, the presence of ferrous Fe appears to contribute to greater dissolution, whereas the presence of Al within the

Fully automated dissolution and separation methods for inductively coupled plasma atomic emission spectrometry rock analysis. Application to the determination of rare earth elements

International Nuclear Information System (INIS)

Govindaraju, K.; Mevelle, G.

1987-01-01

In rock analysis laboratories, sample preparation is a serious problem, or even an enormous bottleneck. Because this laboratory is production-oriented, this problem was attacked by automating progressively, different steps in rock analysis for major, minor and trace elements. This effort has been considerably eased by the fact that all sample preparation schemes in this laboratory for the past three decades have been based on an initial lithium borate fusion of rock samples and all analytical methods based on multi-element atomic emission spectrometry, with switch-over from solid analysis by arc/spark excitation to solution analysis by plasma excitation in 1974. The sample preparation steps which have been automated are: weighing of samples and fluxes, lithium borate fusion, dissolution and dilution of fusion products and ion-exchange separation of difficult trace elements such as rare earth elements (REE). During 1985 and 1986, these different unit operations have been assembled together as peripheral units in the form of a workstation, called LabRobStation. A travelling robot is the master of LabRobStation, with all peripheral units at its reach in 10 m 2 workspace. As an example of real application, the automated determination of REE, based on more than 8000 samples analysed during 1982 and 1986, is presented. (author)

Theoretical study on crystalline rock for evaluating of long-term behavior (Contract research)

International Nuclear Information System (INIS)

Ichikawa, Yasuaki; Seno, Yasuhiro; Sato, Toshinori; Nakama, Shigeo

2008-03-01

The Japan Atomic Energy Agency (JAEA) is working on the Project of Mizunami Underground Research Laboratory (MIU). The project aims at developing comprehensive techniques of geological investigation and of construction of deep underground space for a repository of HLW and/or TRU. This study contributes to an estimation of long-term stability of underground spaces. Rock materials commonly show time-dependent behavior such as creep and relaxation. The underground structures for geological disposal of radioactive wastes must keep stable not only during construction and operation but also after closing, and then the long-term stability of rock structures (over thousands of years) is essentially important for designing the structures. The true mechanism of time-dependent behavior of rock materials is not yet clearly understood, though the phenomena are widely known. This study aims at elucidating the scientific truth involved in the time-dependent behavior of rock showing creep and relaxation. We used samples of Toki granite and performed precise tests under laser microscope observation, and then developed theories representing the experimental results. These experimental and theoretical results will be served for the design and construction of the Phase III (Operation Phase) of the MIU Project. This is the report worked out in the fiscal year 2006. In this work we performed the following subjects: 1) Uniaxial and stress relaxation tests under observation of a confocal laser scanning microscope (CLSM) by using granite specimens of MIU. 2) Pressure dissolution experiment by using specimens of single crystal quartz and glass beads. 3) Development of the rate of pressure dissolution of quartz and a homogenization analysis for quartz dissolution. In Chapter 2 CLSM was used to acquire clear three-dimensional images of Mizunami granite specimens for uniaxial and stress relaxation tests, and observed the change of microscale structure including the mineral configuration under

Use of radioactive 32P technique to study phosphate rock dissolution in acid soils

International Nuclear Information System (INIS)

Mahisarakul, J.; Mullins, G.L.; Chien, S.H.

2002-01-01

A laboratory experiment was conducted to evaluate the dissolution of six sources of phosphate rock in two acid soils (Ultisols): a sandy soil and a red clay soil. Labile P was determined using the radioactive 32 P technique for Pi extractable P and resin extractable P. Incubations were conducted for 0, 1, 2, 3, 4 and 5 weeks for 32 P exchangeable technique, 0 and 5 weeks for Pi technique and 5 weeks for resin technique. Rates of PR were 0 and 400 mgP/ha. The results showed that labile P in the sandy soil decreased from 0-1 weeks for all the PRs except Hahotoe PR and Hazara PR's. Between 1 and 5 weeks labile P remained relatively constant. The ranking of labile P from PRs was: North Carolina = Kouribga > Matam > Hahotoe = Hazara> Patos de Minas. In the red soil, labile P from all PRs appeared to be relatively unchanged during the 0-5 week incubation. Pi extractable P in sandy soil showed no significant differences due to incubation time. In the red clay soil, there was a significant decrease in Pi-P extracted from soil mixtures with PRs after 5 weeks as compared to 0 weeks. Results of the Resin-extractable P in both sandy and red soils were in agreement with labile P as measured by 32 P exchange technique. (author)

Lithology, microstructures, fluid inclusions, and geochemistry of rock salt and of the cap-rock contact in Oakwood Dome, East Texas: significance for nuclear waste storage. Report of investigations No. 120

International Nuclear Information System (INIS)

Dix, O.R.; Jackson, M.P.A.

1982-01-01

Oakwood salt dome in Leon and Freestone Counties, Texas, has a core composed of a diapiric salt stock at a depth of 355 m. A vertical borehole in the center of the salt stock yielded 57.3 m of continuous rock-salt core overlain by 137 m of anhydrite-calcite cap rock. The lower 55.3 m of rock salt exhibits a strong, penetrative schistosity and parallel cleavage dipping at 30 to 40 0 and more than 60 variably dipping layers of disseminated anhydrite. Anhydrite constitutes 1.3 +- 0.7 percent of the rock-salt core. The upper 2 m of rock salt is unfoliated, comprising a lower 1.4-m interval of medium-grained granoblastic rock salt and an upper 0.6-m interval of coarse-grained granoblastic rock salt. An abrupt, cavity-free contact separates rock salt from laminated cap rock consisting of granoblastic-polygonal anhydrite virtually devoid of halite or pore space. Microstructures and concentration gradients of fluid inclusions suggest that the unfoliated rock salt at the crest of the salt stock was once strongly foliated, but that this fabric was destroyed by solid-state recrystallization. Downward movement of brine from the rock-salt - cap-rock contact was apparently accompanied by two recrystallization fronts. Dissolution of halite at the contact released disseminated anhydrite that presumably accumulated as sand on the floor of the dissolution cavity. Renewed rise of the salt stock closed the cavity, and the anhydrite sand was accreted against the base of the cap rock. Much, if not all, of the lamination in the 80 m of anhydrite cap rock may result from cycles of dissolution, recrystallization, and upward movement in the salt stock, followed by accretion of anhydrite residuum as laminae against the base of the cap rock. These processes, which are strongly influenced by fluids, act both to breach waste repositories and to geologically isolate them

Representation and judgement of possible host rock formations and areas under consideration of geology and safety

International Nuclear Information System (INIS)

2005-08-01

This comprehensive report issued by the Swiss National Cooperative for the Disposal of Radioactive Waste NAGRA takes a look at the representation and judgement of possible host rock formations and areas as far as safety and geological aspects are concerned. Nagra has to demonstrate the basic feasibility of the safe disposal of spent fuel (SF), vitrified high-level waste (HLW) and long-lived intermediate-level waste (ILW) in a deep geological repository, The report shows which possibilities for the disposal of SF, HLW and ILW exist in Switzerland and summarises the current state of general academic and applied geo-scientific research as well as the project-specific knowledge base that has been developed by Nagra over the past 30 years. The descriptions and assessments of the potential host rocks and areas are based on attributes that take into account experience gained both in Switzerland and abroad and are in agreement with international practice. An assessment of potential siting areas is looked at, in view of the preparation of a General Licence application, Nagra will also have to consider land-use planning and socio-economic aspects. This will be carried out in the next step according to the Sectoral Plan for Geological Disposal under the guidance of the relevant Swiss authorities

Study on the dissolution of uranium dibutyl phosphate deposits

International Nuclear Information System (INIS)

Rufus, A.L.; Sathyaseelan, V.S.; Velmurugan, S.; Narasimhan

2008-01-01

An insoluble sticky complex of uranium dibutyl phosphate (U-DBP) formed on the inner surfaces of a reprocessing facility can host radioactive nuclides resulting in radiation exposure hazard. Removal of this layer will greatly result in the reduction of radiation field. Hence, dissolution studies with synthetically prepared U-DBP were carried out. A two-step dissolution process consisting of an initial oxidation with acid permanganate followed by reduction with NAC (NTA, Ascorbic acid and Citric acid) was used. Oxidation kinetics of DBP by permanganate, dissolution of synthetic U-DBP complex as a powder and also as a film over SS surface was studied. XRF and SEM techniques were used to monitor the process of dissolution. Material compatibility of welded SS-304 specimens was also studied. It was found that the two-step process was more efficient when compared to either permanganate or NAC treatment alone. (author)

Study on the dissolution of uranium dibutyl phosphate deposits

Energy Technology Data Exchange (ETDEWEB)

Rufus, A.L.; Sathyaseelan, V.S.; Velmurugan, S.; Narasimhan [Bhabha Atomic Research Centre Facilities, Water and Steam Chemistry Div., Kalpakkam (India)], E-mail: svn@igcar.gov.in

2008-07-01

An insoluble sticky complex of uranium dibutyl phosphate (U-DBP) formed on the inner surfaces of a reprocessing facility can host radioactive nuclides resulting in radiation exposure hazard. Removal of this layer will greatly result in the reduction of radiation field. Hence, dissolution studies with synthetically prepared U-DBP were carried out. A two-step dissolution process consisting of an initial oxidation with acid permanganate followed by reduction with NAC (NTA, Ascorbic acid and Citric acid) was used. Oxidation kinetics of DBP by permanganate, dissolution of synthetic U-DBP complex as a powder and also as a film over SS surface was studied. XRF and SEM techniques were used to monitor the process of dissolution. Material compatibility of welded SS-304 specimens was also studied. It was found that the two-step process was more efficient when compared to either permanganate or NAC treatment alone. (author)

Current results of an arachnological survey of some sandstone rock sites in Bohemia (so-called "rock cities"

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Růžička, Vlastimil

1992-07-01

Full Text Available The spider fauna of the Adrspach-Teplice rockswas investigated. Some records on spider fauna of other nine sandstone rock areas are included. The phenomenon of "rock cities" manifests itself in three aspects: (1 In the bottom parts are microclimatically cold spaces, frequently hosting northern ot mountain species of invertebrates, which here have an azonal occurence. (2 the sun exposed tops of rocks can host thermophilous species. (3 Some species are limited to the surface of rocks and boulders. These are referred to as lithophilous or lithobiont species.

Factor analysis of geochemical data from ore and host rocks of the uranium mineralization at Mika, N. E. Nigeria

International Nuclear Information System (INIS)

Funtua, I. I.

1997-01-01

The Mika uranium occurrence is located in one of a series of NW-NE trending shear zones which host uraniferous Jurassic rhyolitic dykes located in Pan-African brecciated granites within peraluminous granite complex of NE Nigeria. The bodies of mineralization are about 100 metres long and up to 4 metres thick. The U mineralization associated with the rhyolite dykes contains predominantly meta-autunite and apatite, while that of the brecciated granites displays variable mineralogy with meta-autunite, one or two generations of coffinite and colloformic, pitch blend in open veins. The mineralization is thought to be related to bimodel magmatism of the Burashika group and the reactivation of regional structures. Multivariate statistical evaluation of geochemical data of 28 elements/oxides in 296 host rock and mineralized samples from the surface and drill cores display a coherent association of [(U, Pb, Zn, Cu, P 2 O 5 , Fe 2 O 3 ) + Mo], [(CaO, Zr, Sr) +(Y, Mo, V, As)] and [(MgO, K 2 O) + (TiO 2 , Rb)] in the mineralized rocks; reflecting the presence of hamatized phosphate bearing ores in association with sulphide minerals and apatite in the granite rhyolites. A link of the mineralizing fluids with the emplacement of the rhyolites is implied from the striking resemblance between the above element association in mineralized rocks to those of the unmineralized rhyolites. A source of ore fluids over saturated in uranium and silica emanating from crystallizing rhyolitic melts which were expelled into faults and/or shear zones in the surrounding country rock is inferred

Evolution of permeability in diatomaceous rocks mediated by pressure solution

International Nuclear Information System (INIS)

Yasuhara, Hideaki; Kinoshita, Naoki; Kurikami, Hiroshi; Kishida, Kiyoshi

2007-01-01

A conceptual model is presented to follow the evolution of permeability in diatomaceous rocks mediated by pressure solution. The progress of compaction and the evolution of permeability may be followed with time. Specifically, the main minerals of diatomaceous rocks that are quartz, cristobalite, and amorphous silica, are focused to examine differences of the permeability evolutions among them at effective stresses of 5, and 10 MPa, and temperatures of 20 and 90degC. The rates and magnitudes of permeability reduction increase with increase of the dissolution rate constants. Ultimate permeabilities reduce to the order of 90% at the completion of dissolution-mediated compaction. (author)

The TIMODAZ project: Thermal impact on the damaged zone around a radioactive waste disposal in clay host rocks

International Nuclear Information System (INIS)

XiangLing, L.

2009-01-01

The management of spent nuclear fuel and other long-lived radio active waste is an important environmental issue today. Disposal in deep clay geological formations is one of the promising options to dispose of these wastes. In this context, the related research activities in the Euratom Framework Programme of European Commission are continually taking on an enhanced significance. The TIMODAZ is one of the STREP projects (Specific Targeted Research Project) in the Sixth EURATOM Framework Programme and contributes to the research related to the geological disposal of radioactive waste. The consortium is composed of a strong multidisciplinary team involving both European radioactive waste management organizations and nuclear research institutes, universities, industrial partners as well as consultancy companies (SME's). Totally, 15 partners coming from 8 countries are involved with a total budget of about 4000k EURO. Being the coordinator (through the EURIDICE expertise group), SCK-CEN plays the leading role in the project. Meanwhile, SCK-CEN participates the research in different work packages covering the laboratory tests, in-situ tests as well as the integration of TIMODAZ results within the safety case. An important item for the long-term safety of underground disposal is the proper evaluation of the DZ (damaged zone) in the clay host rock. The DZ is defined here as the zone of host rock that experiences THMC (Thermo-Hydro-Mechanical-Chemical) modifications induced by the repository, with potential major changes in the transport properties for radionuclides. The DZ is first initiated during the repository construction. Its behaviour is dynamic, dependent on changing conditions that vary from the open-drift period, to initial closure period and to the entire heating-cooling cycle of the decaying waste. The early THMC disturbances created by the excavation, the operational phase and the thermal load might be the most severe transient that the repository will undergo

The Changes of P-fractions and Solubility of Phosphate Rock in Ultisol Treated by Organic Matter and Phosphate Rock

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Heru Bagus Pulunggono

2012-09-01

Full Text Available Phosphorus (P is one of the essential elements for plant, however, its availability is mostly very low in acid soils. It is well documented that application of phosphate rock and organic matter are able to change the level of availability of P-form in acid soils. The objective of the research were to evaluate the changes of P-fractions ( resin-P, NaHCO3-Pi, and NaHCO3-Po and phosphate rock dissolution which were induced by application of organic matter (Imperata cylindrica, Pueraria javanica, dan Colopogonium mucunoides and phosphate rock in Utisol Lampung. The experiment was designed in a completely randomized design with three factors and three replications. The first factor was the types of organic matter (I. cylindrica, P. javanica, and C. mucunoides, the second factor was the rate of organic matter (0, 2.5, and 5%, and the third factor was the rate of phosphate rock (0, 40, and 80 mg P kg-1. The results showed that in the rate of 0 and 1% organic matter, the type of organic matter did not affect P-fraction of NaHCO3-Pi, but in the rate of 2.5 and 5%, NaHCO3-Pi due to application of P. javanica, and C. mucunoides higher than due to application of I. cylindrica. However, the increasing rate of organic matter increased NaHCO3-Pi. Then, P-fraction of Resin-Pi was affected by the type of organic matter, the rate of organic matter, and the rate of phosphate rock, respectively. P-fraction of resin-Pi due to application of P. javanica, and C. mucunoides was higher than due to application of I. cylindrica, but the effect of P. javanica, and C. mucunoides was not different. Increasing the rate of organic matter and phosphate rock increased P-fraction of resin-Pi and NaHCO3-Pi, but P-fraction of NaHCO3-Po was not affected by all treatments. Meanwhile, dissolution of phosphate rock was affected by the kind of organic matter and soil reaction. In the rate of 5% organic matter, dissolution of phosphate rock by application of I. cylindrica (70% was higher

Modeling gas migration experiments in repository host rocks for the MEGAS project

International Nuclear Information System (INIS)

Worgan, K.; Impey, M.; Volckaert, G.; DePreter, P.

1993-01-01

In response to concerns over the possibility of hydrogen gas generation within an underground repository for high-level radioactive waste, and its implications for repository safety, a joint European research study (MEGAS) is underway. Its aims are to understand and characterize the behavior of gas migration within an argillacious, host-rock. Laboratory experiments are being carried out by SCK/CEN, BGS and ISMES. SCK/CEN are also conducting in situ experiments at the underground laboratory at Mol, Belgium. Modeling of gas migration is being done in parallel with the experiments, by Intera Information Technologies. A two-phase flow code, TOPAZ, has been developed specifically for this work. In this paper the authors report on the results of some preliminary calculations performed with TOPAZ, in advance of the in situ experiments

Stable isotope reactive transport modeling in water-rock interactions during CO2 injection

Science.gov (United States)

Hidalgo, Juan J.; Lagneau, Vincent; Agrinier, Pierre

2010-05-01

Stable isotopes can be of great usefulness in the characterization and monitoring of CO2 sequestration sites. Stable isotopes can be used to track the migration of the CO2 plume and identify leakage sources. Moreover, they provide unique information about the chemical reactions that take place on the CO2-water-rock system. However, there is a lack of appropriate tools that help modelers to incorporate stable isotope information into the flow and transport models used in CO2 sequestration problems. In this work, we present a numerical tool for modeling the transport of stable isotopes in groundwater reactive systems. The code is an extension of the groundwater single-phase flow and reactive transport code HYTEC [2]. HYTEC's transport module was modified to include element isotopes as separate species. This way, it is able to track isotope composition of the system by computing the mixing between the background water and the injected solution accounting for the dependency of diffusion on the isotope mass. The chemical module and database have been expanded to included isotopic exchange with minerals and the isotope fractionation associated with chemical reactions and mineral dissolution or precipitation. The performance of the code is illustrated through a series of column synthetic models. The code is also used to model the aqueous phase CO2 injection test carried out at the Lamont-Doherty Earth Observatory site (Palisades, New York, USA) [1]. References [1] N. Assayag, J. Matter, M. Ader, D. Goldberg, and P. Agrinier. Water-rock interactions during a CO2 injection field-test: Implications on host rock dissolution and alteration effects. Chemical Geology, 265(1-2):227-235, July 2009. [2] Jan van der Lee, Laurent De Windt, Vincent Lagneau, and Patrick Goblet. Module-oriented modeling of reactive transport with HYTEC. Computers & Geosciences, 29(3):265-275, April 2003.

Experimental hydrothermal dissolution of forsterite, enstatite, diopside, and labradorite

Energy Technology Data Exchange (ETDEWEB)

Ponader, H.B.

1989-01-01

Natural hydrothermal water/rock interactions such as those which occur during mineral dissolution and serpentinization were experimentally duplicated using a flow-through apparatus. Labradorite, forsterite, enstatite, diopside, and lherzolite powders were reached with flowing aqueous fluids ({approximately} 10 ml/day) at 300 C and 300 bars for up to 58 days in order to quantify mineral stabilities and dissolution rates, and to characterize dissolution textures and mechanisms. The principal methods for characterization of the solids included surface sensitive spectroscopies (SAM and SPS), SEM, and XRD; reacted fluids were analyzed for major element chemistry and pH. Chapters 1 and 2 investigate labradorite dissolution by deionized water. The labradorite powder dissolved extensively while boehmite and halloysite precipitated. The SAM results show that, in general, the reacted surfaces are enriched in Al and depleted in Si, Na, and Ca. Chapter 3 describes the experiments that reacted deionized water with diopside, enstatite, forsterite, and lherzolite, from which lizardite {plus minus} chrysotile {plus minus} Fe-oxides precipitated. The reacted diopside and enstatite surfaces appeared highly corroded; their crystal structures, in part, control the mechanisms by which they dissolve. The stabilities of the minerals decrease in the order: lherzolite > diopside > enstatite > forsterite. At near neutral pH, the degree to which total surface areas influence dissolution rates appears greater that the effect of mineral composition and interaction of the primary minerals within the lherzolite.

Carbonate mineral dissolution kinetics in high pressure experiments

Science.gov (United States)

Dethlefsen, F.; Dörr, C.; Schäfer, D.; Ebert, M.

2012-04-01

The potential CO2 reservoirs in the North German Basin are overlain by a series of Mesozoic barrier rocks and aquifers and finally mostly by Tertiary and Quaternary close-to-surface aquifers. The unexpected rise of stored CO2 from its reservoir into close-to-surface aquifer systems, perhaps through a broken well casing, may pose a threat to groundwater quality because of the acidifying effect of CO2 dissolution in water. The consequences may be further worsening of the groundwater quality due to the mobilization of heavy metals. Buffer mechanisms counteracting the acidification are for instance the dissolution of carbonates. Carbonate dissolution kinetics is comparably fast and carbonates can be abundant in close-to-surface aquifers. The disadvantages of batch experiments compared to column experiments in order to determine rate constants are well known and have for instance been described by v. GRINSVEN and RIEMSDIJK (1992). Therefore, we have designed, developed, tested, and used a high-pressure laboratory column system to simulate aquifer conditions in a flow through setup within the CO2-MoPa project. The calcite dissolution kinetics was determined for CO2-pressures of 6, 10, and 50 bars. The results were evaluated by using the PHREEQC code with a 1-D reactive transport model, applying a LASAGA (1984) -type kinetic dissolution equation (PALANDRI and KHARAKA, 2004; eq. 7). While PALANDRI and KHARAKA (2004) gave calcite dissolution rate constants originating from batch experiments of log kacid = -0.3 and log kneutral = -5.81, the data of the column experiment were best fitted using log kacid = -2.3 and log kneutral = -7.81, so that the rate constants fitted using the lab experiment applying 50 bars pCO2 were approximately 100 times lower than according to the literature data. Rate constants of experiments performed at less CO2 pressure (pCO2 = 6 bars: log kacid = -1.78; log kneutral = -7.29) were only 30 times lower than literature data. These discrepancies in the

Combining water-rock interaction experiments with reaction path and reactive transport modelling to predict reservoir rock evolution in an enhanced geothermal system

Science.gov (United States)

Kuesters, Tim; Mueller, Thomas; Renner, Joerg

2016-04-01

Reliably predicting the evolution of mechanical and chemical properties of reservoir rocks is crucial for efficient exploitation of enhanced geothermal systems (EGS). For example, dissolution and precipitation of individual rock forming minerals often result in significant volume changes, affecting the hydraulic rock properties and chemical composition of fluid and solid phases. Reactive transport models are typically used to evaluate and predict the effect of the internal feedback of these processes. However, a quantitative evaluation of chemo-mechanical interaction in polycrystalline environments is elusive due to poorly constrained kinetic data of complex mineral reactions. In addition, experimentally derived reaction rates are generally faster than reaction rates determined from natural systems, likely a consequence of the experimental design: a) determining the rate of a single process only, e.g. the dissolution of a mineral, and b) using powdered sample materials and thus providing an unrealistically high reaction surface and at the same time eliminating the restrictions on element transport faced in-situ for fairly dense rocks. In reality, multiple reactions are coupled during the alteration of a polymineralic rocks in the presence of a fluid and the rate determining process of the overall reactions is often difficult to identify. We present results of bulk rock-water interaction experiments quantifying alteration reactions between pure water and a granodiorite sample. The rock sample was chosen for its homogenous texture, small and uniform grain size (˜0.5 mm in diameter), and absence of pre-existing alteration features. The primary minerals are plagioclase (plg - 58 vol.%), quartz (qtz - 21 vol.%), K-feldspar (Kfs - 17 vol.%), biotite (bio - 3 vol.%) and white mica (wm - 1 vol.%). Three sets of batch experiments were conducted at 200 ° C to evaluate the effect of reactive surface area and different fluid path ways using (I) powders of the bulk rock with

The Metamorphic Rocks-Hosted Gold Mineralization At Rumbia Mountains Prospect Area In The Southeastern Arm of Sulawesi Island, Indonesia

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Hasria Hasria

2017-09-01

Full Text Available Recently, in Indonesia gold exploration activities  are not only focused along volcanic-magmatic belts, but also starting to shift along metamorphic and sedimentary terrains. The study area is located in Rumbia mountains, Bombana Regency, Southeast Sulawesi Province. This paper is aimed to describe characteristics of alteration and ore mineralization associated  with metamorphic rock-related gold deposits.  The study area is found the placer and  primary gold hosted by metamorphic rocks. The gold is evidently derived from gold-bearing quartz veins hosted by Pompangeo Metamorphic Complex (PMC. These quartz veins are currently recognized in metamorphic rocks at Rumbia Mountains. The quartz veins are mostly sheared/deformed, brecciated, irregular vein, segmented and  relatively massive and crystalline texture with thickness from 1 cm to 15.7 cm. The wallrock are generally weakly altered. Hydrothermal alteration types include sericitization, argillic, inner propylitic, propylitic, carbonization and carbonatization. There some precious metal identified consist of native gold and ore mineralization including pyrite (FeS2, chalcopyrite (CuFeS2, hematite (Fe2O3, cinnabar (HgS, stibnite (Sb2S3 and goethite (FeHO2. The veins contain erratic gold in various grades from below detection limit <0.0002 ppm to 18.4 ppm. Based on those characteristics, it obviously indicates that the primary gold deposit present in the study area is of orogenic gold deposit type. The orogenic gold deposit is one of the new targets for exploration in Indonesia

Life in a rock pool: Radiation and population genetics of myxozoan parasites in hosts inhabiting restricted spaces.

Science.gov (United States)

Bartošová-Sojková, Pavla; Lövy, Alena; Reed, Cecile C; Lisnerová, Martina; Tomková, Tereza; Holzer, Astrid S; Fiala, Ivan

2018-01-01

Intertidal rock pools where fish and invertebrates are in constant close contact due to limited space and water level fluctuations represent ideal conditions to promote life cycles in parasites using these two alternate hosts and to study speciation processes that could contribute to understanding the roles of parasitic species in such ecosystems. Gall bladder and liver samples from five clinid fish species (Blenniiformes: Clinidae) were morphologically and molecularly examined to determine the diversity, prevalence, distribution and host specificity of Ceratomyxa parasites (Cnidaria: Myxozoa) in intertidal habitats along the coast of South Africa. Phylogenetic relationships of clinid ceratomyxids based on the SSU rDNA, LSU rDNA and ITS regions were assessed additionally to the investigation of population genetic structure of Ceratomyxa cottoidii and subsequent comparison with the data known from type fish host Clinus cottoides. Seven Ceratomyxa species including previously described Ceratomyxa dehoopi and C. cottoidii were recognized in clinids. They represent a diverse group of rapidly evolving, closely related species with a remarkably high prevalence in their hosts, little host specificity and frequent concurrent infections, most probably as a result of parasite radiation after multiple speciation events triggered by limited host dispersal within restricted spaces. C. cottoidii represents the most common clinid parasite with a population structure characterized by young expanding populations in the south west and south east coast and by older populations in equilibrium on the west coast of its distribution. Parasite and fish host population structures show overlapping patterns and are very likely affected by similar oceanographic barriers possibly due to reduced host dispersal enhancing parasite community differentiation. While fish host specificity had little impact on parasite population structure, the habitat preference of the alternate invertebrate host as

Ground deformation at collapse calderas: influence of host rock lithology and reservoir multiplicity

Energy Technology Data Exchange (ETDEWEB)

Geyer, A; Gottsmann, J [Department of Earth Sciences, University of Bristol, Wills Memorial Building, Queen' s Road, BS8 1RJ, Bristol (United Kingdom)], E-mail: A.GeverTraver@bristol.ac.uk

2008-10-01

A variety of source mechanisms have been proposed to account for observed caldera deformation. Here we present a systematic set of new results from numerical forward modelling using a Finite Element Method. which provides a link between measured ground deformation and the inaccessible deformation source. We simulate surface displacements due to pressure changes in a shallow oblate reservoir overlain by host rock with variable mechanical properties. We find that the amplitude and wavelength of resultant ground deformation is dependent on the distribution of mechanically stiff and soft lithologies and their relative distribution above a reservoir. In addition, we note an influence of layering on the critical ratio of horizontal over vertical displacements, a criterion employed to discriminate between different finite source geometries.

Salt dissolution and collapse at the Wink Sink in West Texas

International Nuclear Information System (INIS)

Johnson, K.S.

1986-06-01

The Wink Sink, in Winkler County, Texas, is a collapse feature that formed in June 1980 when an underground dissolution cavity migrated upward by successive roof failures until it breached the land surface. The original cavity developed in the Permian Salado Formation salt beds more than 1300 feet below ground level. Natural dissolution of salt occurred in the vicinity of the Wink Sink in several episodes that began as early as Salado time and recurred in later Permian, Triassic, and Cenozoic time. Although natural dissolution cavity and resultant collapse were influenced by petroleum production activity in the immediate area. Drilling, completion, and plugging procedures used on an abandoned oil well at the site of the sink appear to have created a conduit that enabled water to circulate down the borehole and dissolve the salt. When the dissolution cavity became large enough, the roof failed and the overlying rocks collapsed into the cavity. Similar collapse features exist where underground salt beds have been intentionally dissolved during solution mining or accidentally dissolved as a result of petroleum production activities

OPTIMAL METHOD FOR PREPARATION OF SILICATE ROCK SAMPLES FOR ANALYTICAL PURPOSES

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Maja Vrkljan

2004-12-01

Full Text Available The purpose of this study was to determine an optimal dissolution method for silicate rock samples for further analytical purposes. Analytical FAAS method of determining cobalt, chromium, copper, nickel, lead and zinc content in gabbro sample and geochemical standard AGV-1 has been applied for verification. Dissolution in mixtures of various inorganic acids has been tested, as well as Na2CO3 fusion technique. The results obtained by different methods have been compared and dissolution in the mixture of HNO3 + HF has been recommended as optimal.

Carbon dioxide generation and drawdown during active orogenesis of siliciclastic rocks in the Southern Alps, New Zealand

Science.gov (United States)

Menzies, Catriona D.; Wright, Sarah L.; Craw, Dave; James, Rachael H.; Alt, Jeffrey C.; Cox, Simon C.; Pitcairn, Iain K.; Teagle, Damon A. H.

2018-01-01

Collisional mountain building influences the global carbon cycle through release of CO2 liberated by metamorphic reactions and promoting mechanical erosion that in turn increases chemical weathering and drawdown of atmospheric CO2. The Southern Alps is a carbonate-poor, siliciclastic mountain belt associated with the active Australian Pacific plate boundary. On-going, rapid tectonic uplift, metamorphism and hydrothermal activity are mobilising carbon. Here we use carbon isotope measurements of hot spring fluids and gases, metamorphic host rocks, and carbonate veins to establish a metamorphic carbon budget. We identify three major sources for CO2 within the Southern Alps: (1) the oxidation of graphite; (2) consumption of calcite by metamorphic reactions at the greenschist-amphibolite facies boundary, and (3) the dissolution of groundmass and vein-hosted calcite. There is only a minor component of mantle CO2 arising on the Alpine Fault. Hot springs have molar HCO3-/Ca2+ ∼9, which is substantially higher than produced by the dissolution of calcite indicating that deeper metamorphic processes must dominate. The total CO2 flux to the near surface environment in the high uplift region of the Southern Alps is estimated to be ∼6.4 × 108 mol/yr. Approximately 87% of this CO2 is sourced from coupled graphite oxidation (25%) and disseminated calcite decarbonation (62%) reactions during prograde metamorphism. Dissolution of calcite and mantle-derived CO2 contribute ∼10% and ∼3% respectively. In carbonate-rich orogens CO2 production is dominated by metamorphic decarbonation of limestones. The CO2 flux to the atmosphere from degassing of hot springs in the Southern Alps is 1.9 to 3.2 × 108 mol/yr, which is 30-50% of the flux to the near surface environment. By contrast, the drawdown of CO2 through surficial chemical weathering ranges between 2.7 and 20 × 109 mol/yr, at least an order of magnitude greater than the CO2 flux to the atmosphere from this orogenic belt

Heterogeneity of uranium host rocks in Zhiluo formation in Dongsheng area and its relation to uranium mineralization

International Nuclear Information System (INIS)

Yi Chao; Zheng Yunlong; Wang Mingtai

2013-01-01

Numbers of uranium deposits have be found in Dongsheng area. The major ore-bearing layer is the sub member of the lower member of the Zhiluo Formation, the heterogeneity of host rocks plays an important role during the process of uranium mineralization. This paper sorted and counted up the data of sand body and the impermeable bed in Dongsheng area to study the heterogeneity characteristic of host rock and its relationship to uranium mineralization in horizontal and vertical directions. The thickness of sand body in Dongsheng area decreases gradually from northwest to southeast. The uranium mineralization is mainly distributed in the place where the thickness of sand body changed from the thick to the thin. Statistics shows that the best uranium mineralization occurred in sand body thickness between 20 m to 40 m and the sand rate over 60% in the eastern part of Dongsheng area. And the best uranium mineralization in the western part occurred in area of sand body thickness between 60 m to 70 m and the sand rate over 70%. In vertical direction, the numbers and the thickness of the impermeable beds have negative relation to sand rate. Moreover, uranium deposits generally exist in the area of less number impermeable bed and small thickness. The uranium mineralization grade decreased with the increase of number and thickness of the impermeable beds. (authors)

Geochronology of the Swift Current granite and host volcanic rocks of the Love Cove group, southwestern Avalon zone, Newfoundland

International Nuclear Information System (INIS)

Dallmeyer, R.D.; O'Driscoll, C.F.; Hussey, E.M.

1981-01-01

Zircon fractions from the variably deformed and metamorphosed Swift Current granite and host volcanic rocks of the Love Cove Group record individually discordant U-Pb ages with well-defined upper concordia intercept ages of 580 +- 20 and 590 +- 30 Ma, respectively. These are interpreted to be crystallization dates and indicate a late Proterozoic cogmagmatic relationship. Primary hornblende from the pluton record disturbed 40 Ar/ 39 Ar age spectra that suggest postcrystallization argon loss, probably during Acadian (Devonian) regional metamorphism. 40 Ar/ 39 Ar plateau ages of 560-566 Ma are well defined for the hornblende and are interpreted to date times of postmagmatic cooling. The similarity between zircon and hornblende dates suggests relatively rapid postmagmatic cooling. A six-point, Rb-Sr whole-rock isochron age of 548 +- 11 Ma is defined for the pluton. The slight discordancy of this date in comparison with the zircon and hornblende ages may reflect a minor disturbance of whole-rock isotopic systems during Acadian regional metamorphism. (author)

Phosphine from rocks: mechanically driven phosphate reduction?

Science.gov (United States)

Glindemann, Dietmar; Edwards, Marc; Morgenstern, Peter

2005-11-01

Natural rock and mineral samples released trace amounts of phosphine during dissolution in mineral acid. An order of magnitude more phosphine (average 1982 ng PH3 kg rock and maximum 6673 ng PH3/kg rock) is released from pulverized rock samples (basalt, gneiss, granite, clay, quartzitic pebbles, or marble). Phosphine was correlated to hardness and mechanical pulverization energy of the rocks. The yield of PH3 ranged from 0 to 0.01% of the total P content of the dissolved rock. Strong circumstantial evidence was gathered for reduction of phosphate in the rock via mechanochemical or "tribochemical" weathering at quartz and calcite/marble inclusions. Artificial reproduction of this mechanism by rubbing quartz rods coated with apatite-phosphate to the point of visible triboluminescence, led to detection of more than 70 000 ng/kg PH3 in the apatite. This reaction pathway may be considered a mechano-chemical analogue of phosphate reduction from lightning or electrical discharges and may contribute to phosphine production via tectonic forces and processing of rocks.

Quantifying Rock Weakening Due to Decreasing Calcite Mineral Content by Numerical Simulations.

Science.gov (United States)

Wetzel, Maria; Kempka, Thomas; Kühn, Michael

2018-04-01

The quantification of changes in geomechanical properties due to chemical reactions is of paramount importance for geological subsurface utilisation, since mineral dissolution generally reduces rock stiffness. In the present study, the effective elastic moduli of two digital rock samples, the Fontainebleau and Bentheim sandstones, are numerically determined based on micro-CT images. Reduction in rock stiffness due to the dissolution of 10% calcite cement by volume out of the pore network is quantified for three synthetic spatial calcite distributions (coating, partial filling and random) using representative sub-cubes derived from the digital rock samples. Due to the reduced calcite content, bulk and shear moduli decrease by 34% and 38% in maximum, respectively. Total porosity is clearly the dominant parameter, while spatial calcite distribution has a minor impact, except for a randomly chosen cement distribution within the pore network. Moreover, applying an initial stiffness reduced by 47% for the calcite cement results only in a slightly weaker mechanical behaviour. Using the quantitative approach introduced here substantially improves the accuracy of predictions in elastic rock properties compared to general analytical methods, and further enables quantification of uncertainties related to spatial variations in porosity and mineral distribution.

The effect of precipitation on contaminant dissolution and transport: Analytic solutions

International Nuclear Information System (INIS)

Light, W.B.; Chambre, P.L.; Pigford, T.H.; Lee, W.W.L.

1988-09-01

We analysed the effect of precipitation on the dissolution and transport rates of a nondecaying contaminant. Precipitation near the waste surface can have a profound effect on dissolution and transport rates. The mass-transfer rate at the waste surface is controlled by the solid-liquid reaction rate to an extent determined by the modified reaction-rate modulus, α. At later times extending to steady state, the mass-transfer rate depends on the location of the precipitation front r/sub p/ and on the solubility ratio C/sub o//C/sub p/. A precipitation front very near the waste surface can change the dissolution mechanism from solubility-diffusion-controlled to chemical-reaction-rate controlled. Precipitation limits the concentration of the contaminant at r > r/sub p/ to C/sub p/, steepening the concentration gradient for dissolution on the waste package side of the front and flattening the gradient for transport in the region outside the front. This increases the rate of contaminant transport from the waste to the front while decreasing the rate of transport away from the front, when compared to the situation without precipitation. The difference in the transport rates at the front is the rate of precipitation. For large changes in solubility, most of the contaminant is immobilized by precipitation, as was observed in a parallel study. The effect of a precipitation front located nearby in surrounding rock is to increase the release rate at the waste surface/rock interface. The increase in release rate at the waste surface is greater the closer the precipitation and the larger the ratio C/sub o//C/sub p/, also observed by others. The release rates of other waste constituents that dissolve congruently with the solubility-controlling matrix can be increased by a local high-solubility region between the waste surface and the precipitation front. 10 refs., 5 figs

Clay shale as host rock. A geomechanical contribution about Opalinus clay; Tonstein als Wirtsgestein. Ein geomechanischer Beitrag ueber Opalinuston

Energy Technology Data Exchange (ETDEWEB)

Lempp, Christof; Menezes, Flora; Sachwitz, Simon [Halle-Wittenberg Univ., Halle (Saale) (Germany). Inst. fuer Geowissenschaften und Geographie

2016-12-15

The Opalinuston is a prominent rock representing the type of organic clay shales or clay stones within the sequence of Triassic and Jurassic marine sediments in Southern Germany. The rock forms a homogenous unit some ten meters thick. The degree of consolidation of this type of pelitic rock depends mainly on the former load conditions, but is also dependent on the long-term weathering and even on the present exposition. The geomechanical parameters such as shear strength, tensional strength and permeability vary with the state of consolidation and become important when the use is discussed of such rocks for radioactive waste disposal. A tunneling project at the northern escarpment of the Swabian Alb (Southwest Germany) within the Opalinus clay offered the rare opportunity to obtain fresh unweathered rock samples in greater amounts compared to fresh drilling cores from which geomechanical investigations are usually undertaken. Consequently, the results of geomechanical laboratory testings are presented in order to compare here the results of multistep triaxial compression tests, of hydraulic fracturing laboratory tests and of some other tests for rock characterization with the corresponding results of Opalinus clay sites in Switzerland that were investigated by the Swiss Nagra Company for host rock characterization. After a discussion of the relevant state of fresh Opalinus clay, especially of suction pressure conditions and saturation state, the results of triaxial shear tests are presented. Increasing shear deformation at increasing pressure and unchanged water saturation do not result in a significant strength reduction of the Opalinus clay. The rock shows increasing cohesion and stiffness, if multiple loading has repeatedly reached the failure point. Thus there is no increased permeability with continued shearing. Only at the beginning of the shearing process is a temporarily increased permeability to be expected due to dilatation processes. An increased

Bioremediation in fractured rock: 2. Mobilization of chloroethene compounds from the rock matrix

Science.gov (United States)

Shapiro, Allen M.; Tiedeman, Claire; Imbrigiotta, Thomas; Goode, Daniel J.; Hsieh, Paul A.; Lacombe, Pierre; DeFlaun, Mary F.; Drew, Scott R.; Curtis, Gary P.

2018-01-01

A mass balance is formulated to evaluate the mobilization of chlorinated ethene compounds (CE) from the rock matrix of a fractured mudstone aquifer under pre- and postbioremediation conditions. The analysis relies on a sparse number of monitoring locations and is constrained by a detailed description of the groundwater flow regime. Groundwater flow modeling developed under the site characterization identified groundwater fluxes to formulate the CE mass balance in the rock volume exposed to the injected remediation amendments. Differences in the CE fluxes into and out of the rock volume identify the total CE mobilized from diffusion, desorption, and nonaqueous phase liquid dissolution under pre- and postinjection conditions. The initial CE mass in the rock matrix prior to remediation is estimated using analyses of CE in rock core. The CE mass mobilized per year under preinjection conditions is small relative to the total CE mass in the rock, indicating that current pump-and-treat and natural attenuation conditions are likely to require hundreds of years to achieve groundwater concentrations that meet regulatory guidelines. The postinjection CE mobilization rate increased by approximately an order of magnitude over the 5 years of monitoring after the amendment injection. This rate is likely to decrease and additional remediation applications over several decades would still be needed to reduce CE mass in the rock matrix to levels where groundwater concentrations in fractures achieve regulatory standards.

Phosphate Rock Dissolution and Availability in Some Soils of Semi ...

African Journals Online (AJOL)

Fiifi Baidoo

crop production with less expensive indigenous phosphate rocks (PRs) merits the attention of ... spectrophoto-meter at 712 nm following the procedure of Murphy & Riley (1962). Laboratory analyses ..... L. M. and Goh K. M. (1989). Effects of ...

Estimation of Carbon Sink in Surface Carbonate Rocks of Guangxi Province by Using Remote Sensing Images

Science.gov (United States)

Jia, B.; Zhou, G.; Wang, H.; Yue, T.; Huang, W.

2018-04-01

Studies of the imbalance of source sinks in the carbon cycle show that CO2 absorbed during rock weathering is part of the "miss carbon" of the global carbon cycle. The carbon sink contribution of carbonate rocks obviously plays a very important role in the absorption of atmospheric CO2. Estimation of carbon sinks in karst dynamic system of Guangxi province has great significance for further understanding of global karst carbon cycle and global climate research. This paper quotes the rock data from Tao Xiaodong's paper, which is obtained using RS and GIS techniques. At the same time, the dissolution rate model studied by Zhou Guoqing and others was used to estimate the dissolution rate of carbonate rocks in Guangxi Province. Finally, the CO2 content consumed by carbonate karstification in Guangxi Province was 1342910.447 t a-1. The results obtained are in the same order of magnitude as the CO2 content consumed by carbonate rock karstification in Guangxi Province calculated by Tao Xiaodong.

Application of Ga-Al discrimination plots in identification of high strength granitic host rocks for deep geological repository of high level radioactive waste

International Nuclear Information System (INIS)

Bajpai, R.K.; Narayan, P.K.; Trivedi, R.K.; Purohit, M.K.

2010-01-01

The permanent disposal of vitrified high level wastes and in some cases even spent fuel, is being planned in specifically designed and built deep geological repository located in the depth range of 500-600m in appropriate host rock at carefully selected sites. Such facilities are expected to provide very long term isolation and confinement to the disposed waste by means of long term mechanical stability of such structures that results from very high strength and homogeneity of the chosen rock, geochemical compatible environment around the disposed waste and general lack of groundwater. In Indian geological repository development programme, granites have been selected as target host rock and large scale characterization studies have been undertaken to develop database of mineralogy, petrology, geochemistry and rock mechanical characteristics. The paper proposes a new approach for demarcation of high strength homogeneous granite rocks from within an area of about 100 square kilometres wherein a cocktail of granites of different origins with varying rock mass characteristics co exists. The study area is characterised by the presence of A, S and I type granites toughly intermixed. The S type granites are derived from sedimentary parent material and therefore carry relics of parent fabric and at times undigested material with resultant reduction in their strength and increased inhomogeneity. On the other hand I type varieties are derived from igneous parents and are more homogeneous with sufficient strength. The A type granites are emplaced as molten mass in a complete non-tectonic setting with resultant homogeneous compositions, absence of tectonic fabric and very high strength. Besides they are silica rich with less vulnerability to alterations with time. Thus A type granites are most suited for construction of Deep Geological Repository. For developing a geochemical approach for establishing relation between chemical compositions and rock strength parameters, a

Transport of soluble species in backfill and rock

International Nuclear Information System (INIS)

Chambre, P.L.; Lee, W.W.L.; Light, W.B.; Pigford, T.H.

1992-03-01

In this report we study the release and transport of soluble species from spent nuclear fuel. By soluble species we mean a fraction of certain fission product species. Our previously developed methods for calculating release rates of solubility-limited species need to be revised for these soluble species. Here we provide methods of calculating release rates of soluble species directly into rock and into backfill and then into rock. Section 2 gives a brief discussion of the physics of fission products dissolution from U0 2 spent fuel. Section 3 presents the mathematics for calculating release rates of soluble species into backfill and then into rock. The calculation of release rates directly into rock is a special case. Section 4 presents numerical illustrations of the analytic results

Dissolution processes

International Nuclear Information System (INIS)

Silver, G.L.

1976-01-01

This review contains more than 100 observations and 224 references on the dissolution phenomenon. The dissolution processes are grouped into three categories: methods of aqueous attack, fusion methods, and miscellaneous observations on phenomena related to dissolution problems

THM-coupled modeling of selected processes in argillaceous rock relevant to rock mechanics; THM-Gekoppelte Modellierung ausgewaehlter gesteinsmechanisch relevanter Prozesse im Tongestein

Energy Technology Data Exchange (ETDEWEB)

Czaikowski, Oliver [Gesellschaft fuer Anlagen- und Reaktorsicherheit (GRS) mbH, Braunschweig (Germany). Repository Safety Research Div.

2012-08-15

Scientific investigations in European countries other than Germany concentrate not only on granite formations (Switzerland, Sweden) but also on argillaceous rock formations (France, Switzerland, Belgium) to assess their suitability as host and barrier rock for the final storage of radioactive waste. In Germany, rock salt has been under thorough study as a host rock over the past few decades. According to a study by the German Federal Institute for Geosciences and Natural Resources, however, not only salt deposits but also argillaceous rock deposits are available at relevant depths and of extensions in space which make final storage of high-level radioactive waste basically possible in Germany. Equally qualified findings about the suitability/unsuitability of non-saline rock formations require fundamental studies to be conducted nationally because of the comparatively low level of knowledge. The article presents basic analyses of coupled mechanical and hydraulic properties of argillaceous rock formations as host rock for a repository. The interaction of various processes is explained on the basis of knowledge derived from laboratory studies, and open problems are deduced. For modeling coupled processes, a simplified analytical computation method is proposed and compared with the results of numerical simulations, and the limits to its application are outlined. (orig.)

Preoperational assessment of solute release from waste rock at proposed mining operations

International Nuclear Information System (INIS)

Lapakko, Kim A.

2015-01-01

Highlights: • Modeling to estimate solute release from waste rock at proposed mines is described. • Components of the modeling process are identified and described. • Modeling inputs required are identified and described. • Examples of data generated and their application are presented. • Challenges inherent to environmental review are identified. - Abstract: Environmental assessments are conducted prior to mineral development at proposed mining operations. Among the objectives of these assessments is prediction of solute release from mine wastes projected to be generated by the proposed mining and associated operations. This paper provides guidance to those engaged in these assessments and, in more detail, provides insights on solid-phase characterization and application of kinetic test results for predicting solute release from waste rock. The logic guiding the process is consistent with general model construction practices and recent publications. Baseline conditions at the proposed site are determined and a detailed operational plan is developed and imposed upon the site. Block modeling of the mine geology is conducted to identify the mineral assemblages present, their masses and compositional variations. This information is used to select samples, representative of waste rock to be generated, that will be analyzed and tested to describe characteristics influencing waste rock drainage quality. The characterization results are used to select samples for laboratory dissolution testing (kinetic tests). These tests provide empirical data on dissolution of the various mineral assemblages present as waste rock. The data generated are used, in conjunction with environmental conditions, the proposed method of mine waste storage, and scientific and technical principles, to estimate solute release rates for the operational scale waste rock. Common concerns regarding waste rock are generation of acidic drainage and release of heavy metals and sulfate. Key solid

Surface studies of feldspar dissolution using surface replication combined with electron microscopic and spectroscopic techniques

Energy Technology Data Exchange (ETDEWEB)

Fung, P C [Petro-Canada, Calgary, Alberta; Sanipelli, G G

1982-04-01

The replica of a microcline cleavage surface was examined before and at various stages of interaction with water and acid solutions at 70/sup 0/C, as part of basic geochemical research for the Canadian Nuclear Fuel Waste Management Program to investigate the feasibility of disposal of these wastes in repositories mined in crystalline rocks. The objective of the report presented was to investigate the mechanism for Al and Si removal during incongruent dissolution of feldspars and its effect on dissolution rate. It was found that phase transformation, like dissolution occured preferentially along crystal defects on the surfaces of the feldspars. Secondary minerals always occured as discrete particles occupying only a very small fraction of the total parent surface, and hence, their presence would not affect the bulk composition or, in this regard, the overall dissolution rate of the feldspars by the formation of diffusion barriers.

The dissolution rate of silicate glasses and minerals: an alternative model based on several activated complexes

International Nuclear Information System (INIS)

Berger, G.

1997-01-01

Most of the mineral reactions in natural water-rock systems progress at conditions close to the chemical equilibrium. The kinetics of these reactions, in particular the dissolution rate of the primary minerals, is a major constrain for the numerical modelling of diagenetic and hydrothermal processes. In the case of silicates, recent experimental studies have pointed out the necessity to better understand the elementary reactions which control the dissolution process. This article presents several models that have been proposed to account for the observed dissolution rate/chemical affinity relationships. The case of glasses (R7T7), feldspars and clays, in water, in near neutral pH aqueous solutions and in acid/basic media, are reviewed. (A.C.)

Potency of Agroindustrial Wastewaters to Increase the Dissolution of Phosphate Rock Fertilizers

Directory of Open Access Journals (Sweden)

Ainin Niswati

2014-06-01

Full Text Available The used of agroindustrial wastewaters are not maximum yet in Lampung Province, althought it can be used as an acid solvent because of its acidic properties. This study was aimed to explore the most potential agroindustrial wastewaters in dissolving phosphate rock through acidulation in the laboratory scale. The experiment was arranged in a factorial. The first factor was origined of phosphate rock (Sukabumi, west Java and Selagailingga, central Lampung and the second factor was solvent types (agroindustrial wastewaters which were pineapple, tapioca, tofu industry, and palm oil as well as conventional acid solvents which were HCl, H2SO4, and CH3COOH. The incubation processes were 0, 1, 2, and 3 months. The results showed that agroindustrial wastewaters that have the highest potency to solubize phosphate rock was industrial tofu wastewaters and followed by industrial wastewaters of tapioca, palm oil, and pineapple. Both the conventional acid and agroindustrial wastewaters solvent had a big potency to solubilize phosphate rock, however, its highest soluble P-value did not match with the ISO criteria for phosphate fertilizers Quality I (SNI because it did not reach the solubility of 80% of its total P2O5, but it has been qualified as a fertilizer both the quality phosphate A, B, and C (SNI.

Acid rock drainage and climate change

Science.gov (United States)

Nordstrom, D. Kirk

2009-01-01

Rainfall events cause both increases and decreases in acid and metals concentrations and their loadings from mine wastes, and unmined mineralized areas, into receiving streams based on data from 3 mines sites in the United States and other sites outside the US. Gradual increases in concentrations occur during long dry spells and sudden large increases are observed during the rising limb of the discharge following dry spells (first flush). By the time the discharge peak has occurred, concentrations are usually decreased, often to levels below those of pre-storm conditions and then they slowly rise again during the next dry spell. These dynamic changes in concentrations and loadings are related to the dissolution of soluble salts and the flushing out of waters that were concentrated by evaporation. The underlying processes, pyrite oxidation and host rock dissolution, do not end until the pyrite is fully weathered, which can take hundreds to thousands of years. These observations can be generalized to predict future conditions caused by droughts related to El Ni??o and climate change associated with global warming. Already, the time period for dry summers is lengthening in the western US and rainstorms are further apart and more intense when they happen. Consequently, flushing of inactive or active mine sites and mineralized but unmined sites will cause larger sudden increases in concentrations that will be an ever increasing danger to aquatic life with climate change. Higher average concentrations will be observed during longer low-flow periods. Remediation efforts will have to increase the capacity of engineered designs to deal with more extreme conditions, not average conditions of previous years.

Mineralogical and geochemical studies on apatites and phosphate host rocks of Esfordi deposit, Yazd province, to determine the origin and geological setting of the apatite

Directory of Open Access Journals (Sweden)

Mohammad Ali Rajabzadeh

2014-10-01

recognized. Petrographic data represent three apatite generations: stage 1 which is recognized in the massive and disseminated ore types, stage 2 occurred in brecciated zones and stage 3 which is formed by dissolution and redeposition of the 1 and 2 apatite types in vein-shaped bodies. The correlations among major elements and SiO2 correspond to magmatic differentiation. Cerium is the most abundant REE in the studied samples. Similar REE distribution patterns were observed in the apatite, magnetite and host rhyolite. Electron Probe Micro Analysis (EPMA shows that the apatites are of fluoroapatite type, enriched in LREE. Low content of Sr was detected in apatites of Esfordi. Low Cd and Na concentrations but high U and Th values were also detected in the studied ore samples. Discussion Esfordi iron-apatite deposit is located NE of Bafq, Yazd Province, and in the Central Iran structural zone hosted by mainly Infracambrian rhyolites. Field evidence such as flow structure of ore and dendritic texture of some minerals, e.g., actinolite reveal the magmatic origin of iron-apatite deposit. The trends of major element concentrations in ores from different rocks are consistent with magmatic origin of the ores. The absence of sulfides shows an oxidized condition of magma at the time of ore formation. Low Sr in the apatite however, rejects any carbonatitic magma at Esfordi (Belousova et al., 2002. Similar REE distribution patterns in the apatite, magnetite and host rhyolite indicates the same origin for them. Cerium concentration in the ores from Esfordi is also consistent with magmatic ore types and negatively sloped REE distribution pattern and negative Eu anomaly resemble to the Kiruna type iron-apatite deposits (Hsieh et al., 2008. Low Cd and variable Th/U in the apatite along with low Na are contradicting with sedimentary environment (Jami, 2005; Alves, 2008. The Esfordi deposit probably formed in an extensional arc-related setting associated with syn-collision granitoids

Bioremediation in Fractured Rock: 2. Mobilization of Chloroethene Compounds from the Rock Matrix.

Science.gov (United States)

Shapiro, Allen M; Tiedeman, Claire R; Imbrigiotta, Thomas E; Goode, Daniel J; Hsieh, Paul A; Lacombe, Pierre J; DeFlaun, Mary F; Drew, Scott R; Curtis, Gary P

2018-03-01

A mass balance is formulated to evaluate the mobilization of chlorinated ethene compounds (CE) from the rock matrix of a fractured mudstone aquifer under pre- and postbioremediation conditions. The analysis relies on a sparse number of monitoring locations and is constrained by a detailed description of the groundwater flow regime. Groundwater flow modeling developed under the site characterization identified groundwater fluxes to formulate the CE mass balance in the rock volume exposed to the injected remediation amendments. Differences in the CE fluxes into and out of the rock volume identify the total CE mobilized from diffusion, desorption, and nonaqueous phase liquid dissolution under pre- and postinjection conditions. The initial CE mass in the rock matrix prior to remediation is estimated using analyses of CE in rock core. The CE mass mobilized per year under preinjection conditions is small relative to the total CE mass in the rock, indicating that current pump-and-treat and natural attenuation conditions are likely to require hundreds of years to achieve groundwater concentrations that meet regulatory guidelines. The postinjection CE mobilization rate increased by approximately an order of magnitude over the 5 years of monitoring after the amendment injection. This rate is likely to decrease and additional remediation applications over several decades would still be needed to reduce CE mass in the rock matrix to levels where groundwater concentrations in fractures achieve regulatory standards. © 2017, National Ground Water Association.

Characterization of Geologic Structures and Host Rock Properties Relevant to the Hydrogeology of the Standard Mine in Elk Basin, Gunnison County, Colorado

Science.gov (United States)

Caine, Jonathan S.; Manning, Andrew H.; Berger, Byron R.; Kremer, Yannick; Guzman, Mario A.; Eberl, Dennis D.; Schuller, Kathryn

2010-01-01

The Standard Mine Superfund Site is a source of mine drainage and associated heavy metal contamination of surface and groundwaters. The site contains Tertiary polymetallic quartz veins and fault zones that host precious and base metal sulfide mineralization common in Colorado. To assist the U.S. Environmental Protection Agency in its effort to remediate mine-related contamination, we characterized geologic structures, host rocks, and their potential hydraulic properties to better understand the sources of contaminants and the local hydrogeology. Real time kinematic and handheld global positioning systems were used to locate and map precisely the geometry of the surface traces of structures and mine-related features, such as portals. New reconnaissance geologic mapping, field and x-ray diffraction mineralogy, rock sample collection, thin-section analysis, and elemental geochemical analysis were completed to characterize hydrothermal alteration, mineralization, and subsequent leaching of metallic phases. Surface and subsurface observations, fault vein and fracture network characterization, borehole geophysical logging, and mercury injection capillary entry pressure data were used to document potential controls on the hydrologic system.

Dissolution of aluminium

International Nuclear Information System (INIS)

Uriarte Hueda, A.; Berberana Eizmendi, M.; Pereira Sanchez, G.

1968-01-01

The dissolution of aluminum with acid solutions ( nitric acid-mercuric nitrate) and alkaline solutions (sodium hydroxide-sodium nitrate) has been studied. The instantaneous dissolution rate (IDR) has been studied in function of the concentration of the used reagents and the dissolution temperature. The complete dissolution has been included in the second part of this report, to know the total dissolution time, the consume of reagents and the stability of the resultant solutions. (Author)

Low temperature geomicrobiology follows host rock composition along a geochemical gradient in Lau Basin

Directory of Open Access Journals (Sweden)

Jason B Sylvan

2013-03-01

Full Text Available The East Lau Spreading Center (ELSC and Valu Fa Ridge (VFR comprise a ridge segment in the southwest Pacific Ocean where rapid transitions in the underlying mantle chemistry manifest themselves as gradients in seafloor rock geochemistry. We studied the geology and microbial diversity of three silicate rock samples and three inactive sulfide chimney samples collected, from north to south, at the vent fields Kilo Moana, ABE, Tui Malila and Mariner. This is the first study of microbial populations on basaltic andesite, which was sampled at Mariner vent field. Silicate rock geochemistry exhibits clear latitudinal trends that are mirrored by changes in bacterial community composition. α-proteobacteria, ε-proteobacteria and Bacteroidetes are most common on a silicate collected from Kilo Moana and their proportions decrease linearly on silicates collected further south. Conversely, a silicate from Mariner vent field hosts high proportions of a unique lineage of Chloroflexi unrelated (<90% sequence similarity to previously recovered environmental clones or isolates, which decrease at ABE and are absent at Kilo Moana. The exteriors of inactive sulfide structures are dominated by lineages of sulfur oxidizing α-proteobacteria, γ-proteobacteria and ε-proteobacteria while the interior of one chimney is dominated by putative sulfur-reducing δ-proteobacteria. A comparison of bacterial communities on inactive sulfides from this and previous studies reveals the presence of a clade of uncultured Bacteroidetes exclusive to sulfidic environments, and a high degree of heterogeneity in bacterial community composition from one sulfide structure to another. In light of the heterogeneous nature of bacterial communities observed here and in previous studies of both active and inactive hydrothermal sulfide structures, the presence of numerous niches may be detected on these structures in the future by finer scale sampling and analysis.

The Rock Characterization Facility

International Nuclear Information System (INIS)

Holmes, J.

1994-01-01

In 1989, UK Nirex began a programme of surface-based characterization of the geology and hydrogeology of a site at Sellafield to evaluate its suitability to host a deep repository for radioactive waste. The next major stage in site characterization will be the construction and operation of a Rock Characterization Facility (RCF). It will be designed to provide rock characterization information and scope for model validation to permit firmer assessment of long-term safety. It will also provide information needed to decide the detailed location, design and orientation of a repository and to inform repository construction methods. A three-phase programme is planned for the RCF. During each phase, testwork will steadily improve our geological, hydrogeological and geotechnical understanding of the site. The first phase will involve sinking two shafts. That will be preceded by the establishment of a network of monitoring boreholes to ensure that the impact of shaft sinking can be measured. This will provide valuable data for model validation. In phase two, initial galleries will be excavated, probably at a depth of 650 m below Ordnance datum, which will host a comprehensive suite of experiments. These galleries will be extended in phase three to permit access to most of the rock volume that would host the repository. (Author)

Hydrological evaluation of five sedimentary rocks for high-level waste disposal

International Nuclear Information System (INIS)

Lomenick, T.F.; Kanehiro, B.Y.

1986-01-01

Utilizing performance criteria that are based upon siting guidelines issued by DOE for postclosure as well as preclosure conditions, a preliminary hydrologic evaluation and ranking is being conducted to determine the suitability of five sedimentary rocks as potential host rocks for a high-level radioactive waste repository. Based upon both quantitative and qualitative considerations, the hydrological ranking of the rocks in order of their potential as a host rock for the disposal of radioactive wastes would be shale, anhydrock, sandstone, chalk, and carbonates, with the first three rocks being significantly better than the remaining two types

Proceedings of the scientific visit on crystalline rock repository development.

Energy Technology Data Exchange (ETDEWEB)

Mariner, Paul E.; Hardin, Ernest L.; Miksova, Jitka [RAWRA, Czech Republic

2013-02-01

A scientific visit on Crystalline Rock Repository Development was held in the Czech Republic on September 24-27, 2012. The visit was hosted by the Czech Radioactive Waste Repository Authority (RAWRA), co-hosted by Sandia National Laboratories (SNL), and supported by the International Atomic Energy Agency (IAEA). The purpose of the visit was to promote technical information exchange between participants from countries engaged in the investigation and exploration of crystalline rock for the eventual construction of nuclear waste repositories. The visit was designed especially for participants of countries that have recently commenced (or recommenced) national repository programmes in crystalline host rock formations. Discussion topics included repository programme development, site screening and selection, site characterization, disposal concepts in crystalline host rock, regulatory frameworks, and safety assessment methodology. Interest was surveyed in establishing a %E2%80%9Cclub,%E2%80%9D the mission of which would be to identify and address the various technical challenges that confront the disposal of radioactive waste in crystalline rock environments. The idea of a second scientific visit to be held one year later in another host country received popular support. The visit concluded with a trip to the countryside south of Prague where participants were treated to a tour of the laboratory and underground facilities of the Josef Regional Underground Research Centre.

Factors affecting the differences in reactivity and dissolution rates between UO2 and spent nuclear fuel

International Nuclear Information System (INIS)

Shoesmith, D.W.; Tait, J.C.; Sunder, S.; Steward, S.; Russo, R.E.; Rudnicki, J.D.

1996-08-01

Strategies for the permanent disposal of spent nuclear fuel are being investigated by the U.S. Department of Energy at the Yucca Mountain site and by Atomic Energy of Canada Limited (AECL) in plutonic rock formations in the Canadian Shield. Uranium dioxide is the primary constituent of spent nuclear fuel and dissolution of the matrix is regarded as a necessary step for the release of radionuclides to repository groundwaters. In order to develop models to describe the dissolution of the U0 2 fuel matrix and subsequent release of radionuclides, it is necessary to understand both chemical and oxidative dissolution processes and how they can be affected by parameters such as groundwater composition, pH, temperature, surface area, radiolysis and redox potential. This report summarizes both published and on-going dissolution studies of U0 2 and both LWR and CANDU spent fuels being conducted at the Pacific Northwest Laboratory, Lawrence Livermore National Laboratory and Lawrence Berkeley Laboratory in the U.S. and at AECL's Whiteshell Laboratories in Canada. The studies include both dissolution tests and electrochemical experiments to measure uranium dissolution rates. The report focuses on identifying differences in reactivity towards aqueous dissolution between U0 2 and spent fuel samples as well as estimating bounding values for uranium dissolution rates. This review also outlines the basic tenets for the development of a dissolution model that is based on electrochemical principles. (author). 49 refs., 2 tabs., 11 figs

Thermal effects of the Santa Eulália Plutonic Complex (southern Portugal on the meta-igneous and metasedimentary host rocks

Directory of Open Access Journals (Sweden)

Cruz, C.

2014-12-01

Full Text Available The Santa Eulália Plutonic Complex (SEPC is a late-Variscan granitic body located in the northern part of the Ossa Morena Zone, a inner zone of the Variscan Iberian Massif. The SEPC host rocks are composed of meta-igneous and metasedimentary units, from Upper Proterozoic to Paleozoic ages, with a NW-SE structure, cross-cut by the SEPC. The SEPC host rocks, with low grade metamorphism show well preserved primary sedimentary or igneous mineralogical, textural and structural features. The thermal effect induced by the SEPC is restricted to the roof pendants. At N and NE of the SEPC, textures and paragenesis resulting from thermal metamorphism, are not related to the SEPC intrusion but to a previous magmatism, controlled by the NW-SE regional anisotropies. The restriction of the thermal effects to the pluton roof may be caused by a combination of several interrelated factors: higher volume of granitic mass, thermal effect by advection of fluids and longer period of prevalence of high thermal conditions. The geochemical study of SEPC host rocks shows the heterogeneous character and diversity of metasedimentary, igneous and meta-igneous rocks. The whole rock geochemical data indicate that all the metasedimentary lithologies derived from an upper continental crustal source and the igneous and meta-igneous rocks show no evidence of metasomatic effects by the SEPC emplacement.El Complejo Plutónico de Santa Eulalia (CPSE es un cuerpo granítico tardi-Varisco situado en la parte norte de la Zona de Ossa Morena, en la zona interior del Macizo Ibérico Varisco. Las rocas encajantes del CPSE están compuestas por unidades meta-ígneas y metasedimentarias, de edades que van desde el Proterozoico Superior hasta el Paleozoico, con una estructura de dirección NW-SE, cortada por el CPSE. Las rocas encanjantes del CPSE, con metamorfismo de bajo grado conservan estructuras, mineralogía y textura primarias. El efecto térmicoinducido por el CPSE se limita a los

Hosting Early Evolution in Heated Pores of Rock

Science.gov (United States)

Mast, C. B.; Möller, F.; Lanzmich, S.; Keil, L.; Braun, D.

2017-07-01

Recent experiments with non-equilibrium micro­systems suggest that porous rock conditions drive early molecular evolution in many ways, including accumulation, polymerization, replication, length selection and gelation.

Origin and evolution of formation water at the Jujo-Tecominoacan oil reservoir, Gulf of Mexico. Part 1: Chemical evolution and water-rock interaction

Energy Technology Data Exchange (ETDEWEB)

Birkle, Peter, E-mail: birkle@iie.org.mx [Instituto de Investigaciones Electricas (IIE), Gerencia de Geotermia, Av. Reforma 113, Cuernavaca, Morelos 62490 (Mexico); Garcia, Bernardo Martinez; Milland Padron, Carlos M. [PEMEX Exploracion y Produccion, Region Sur, Activo Integral Bellota-Jujo, Diseno de Explotacion, Cardenas, Tabasco (Mexico)

2009-04-15

The origin and evolution of formation water from Upper Jurassic to Upper Cretaceous mudstone-packstone-dolomite host rocks at the Jujo-Tecominoacan oil reservoir, located onshore in SE-Mexico at a depth from 5200 to 6200 m.b.s.l., have been investigated, using detailed water geochemistry from 12 producer wells and six closed wells, and related host rock mineralogy. Saline waters of Cl-Na type with total dissolved solids from 10 to 23 g/L are chemically distinct from hypersaline Cl-Ca-Na and Cl-Na-Ca type waters with TDS between 181 and 385 g/L. Bromine/Cl and Br/Na ratios suggest the subaerial evaporation of seawater beyond halite precipitation to explain the extreme hypersaline components, while less saline samples were formed by mixing of high salinity end members with surface-derived, low salinity water components. The dissolution of evaporites from adjacent salt domes has little impact on present formation water composition. Geochemical simulations with Harvie-M{phi}ller-Weare and PHRQPITZ thermodynamic data sets suggest secondary fluid enrichment in Ca, HCO{sub 3} and Sr by water-rock interaction. The volumetric mass balance between Ca enrichment and Mg depletion confirms dolomitization as the major alteration process. Potassium/Cl ratios below evaporation trajectory are attributed to minor precipitation of K feldspar and illitization without evidence for albitization at the Jujo-Tecominoacan reservoir. The abundance of secondary dolomite, illite and pyrite in drilling cores from reservoir host rock reconfirms the observed water-rock exchange processes. Sulfate concentrations are controlled by anhydrite solubility as indicated by positive SI-values, although anhydrite deposition is limited throughout the lithological reservoir column. The chemical variety of produced water at the Jujo-Tecominoacan oil field is related to a sequence of primary and secondary processes, including infiltration of evaporated seawater and original meteoric fluids, the subsequent

Origin and evolution of formation water at the Jujo-Tecominoacan oil reservoir, Gulf of Mexico. Part 1: Chemical evolution and water-rock interaction

International Nuclear Information System (INIS)

Birkle, Peter; Garcia, Bernardo Martinez; Milland Padron, Carlos M.

2009-01-01

The origin and evolution of formation water from Upper Jurassic to Upper Cretaceous mudstone-packstone-dolomite host rocks at the Jujo-Tecominoacan oil reservoir, located onshore in SE-Mexico at a depth from 5200 to 6200 m.b.s.l., have been investigated, using detailed water geochemistry from 12 producer wells and six closed wells, and related host rock mineralogy. Saline waters of Cl-Na type with total dissolved solids from 10 to 23 g/L are chemically distinct from hypersaline Cl-Ca-Na and Cl-Na-Ca type waters with TDS between 181 and 385 g/L. Bromine/Cl and Br/Na ratios suggest the subaerial evaporation of seawater beyond halite precipitation to explain the extreme hypersaline components, while less saline samples were formed by mixing of high salinity end members with surface-derived, low salinity water components. The dissolution of evaporites from adjacent salt domes has little impact on present formation water composition. Geochemical simulations with Harvie-Mφller-Weare and PHRQPITZ thermodynamic data sets suggest secondary fluid enrichment in Ca, HCO 3 and Sr by water-rock interaction. The volumetric mass balance between Ca enrichment and Mg depletion confirms dolomitization as the major alteration process. Potassium/Cl ratios below evaporation trajectory are attributed to minor precipitation of K feldspar and illitization without evidence for albitization at the Jujo-Tecominoacan reservoir. The abundance of secondary dolomite, illite and pyrite in drilling cores from reservoir host rock reconfirms the observed water-rock exchange processes. Sulfate concentrations are controlled by anhydrite solubility as indicated by positive SI-values, although anhydrite deposition is limited throughout the lithological reservoir column. The chemical variety of produced water at the Jujo-Tecominoacan oil field is related to a sequence of primary and secondary processes, including infiltration of evaporated seawater and original meteoric fluids, the subsequent mixing of

Age and geochemistry of host rocks of the Cobre Panama porphyry Cu-Au deposit, central Panama: Implications for the Paleogene evolution of the Panamanian magmatic arc

Science.gov (United States)

Baker, Michael J.; Hollings, Peter; Thompson, Jennifer A.; Thompson, Jay M.; Burge, Colin

2016-04-01

The Cobre Panama porphyry Cu-Au deposit, located in the Petaquilla district of central Panama, is hosted by a sequence of medium- to high-K calc-alkaline volcanic and sub-volcanic rocks. New crystallisation ages obtained from a granodiorite Petaquilla batholith and associated mineralised diorite to granodiorite porphyry stocks and dikes at Cobre Panama indicate that the batholith was emplaced as a multi-phase intrusion, over a period of 4 million years from 32.20 ± 0.76 Ma to 28.26 ± 0.61 Ma, while the porphyritic rocks were emplaced over a 2 million year period from 28.96 ± 0.62 Ma to 27.48 ± 0.68 Ma. Both the volcanic to sub-volcanic host rocks and intrusive rocks of the Cobre Panama deposit evolved via fractional crystallisation processes, as demonstrated by the major elements (e.g. Al2O3, Fe2O3, TiO2 and MgO) displaying negative trends with increasing SiO2. The Petaquilla intrusive rocks, including the diorite-granodiorite porphyries and granodiorite batholith, are geochemically evolved and appear to have formed from more hydrous magmas than the preceding host volcanic rocks, as evidenced by the presence of hornblende phenocrysts, higher degrees of large-ion lithophile element (LILE) and light rare earth element (LREE) enrichment and heavy rare earth element (HREE) depletion, and higher Sr/Y and La/Yb values. However, the degree of LREE enrichment, HREE depletion and La/Yb values are insufficient for the intrusive rocks to be considered as adakites. Collectively, the volcanic and intrusive rocks have LILE, REE and mobile trace element concentrations similar to enriched Miocene-age Cordilleran arc magmatism found throughout central and western Panama. Both the Petaquilla and Cordilleran arc magmatic suites are geochemically more evolved than the late Cretaceous to Eocene Chagres-Bayano arc magmas from northeastern Panama, as they display higher degrees of LILE and LREE enrichment. The geochemical similarities between the Petaquilla and Cordilleran arc magmas

Dissolution of crystalline ceramics

International Nuclear Information System (INIS)

White, W.B.

1982-01-01

The present program objectives are to lay out the fundamentals of crystalline waste form dissolution. Nuclear waste ceramics are polycrystalline. An assumption of the work is that to the first order, the release rate of a particular radionuclide is the surface-weighted sum of the release rates of the radionuclide from each crystalline form that contains it. In the second order, of course, there will be synergistic effects. There will be also grain boundary and other microstructural influences. As a first approximation, we have selected crystalline phases one at a time. The sequence of investigations and measurements is: (i) Identification of the actual chemical reactions of dissolution including identification of the solid reaction products if such occur. (ii) The rates of these reactions are then determined empirically to give what may be called macroscopic kinetics. (iii) Determination of the rate-controlling mechanisms. (iv) If the rate is controlled by surface reactions, the final step would be to determine the atomic kinetics, that is the specific atomic reactions that occur at the dissolving interface. Our concern with the crystalline forms are in two areas: The crystalline components of the reference ceramic waste form and related ceramics and the alumino-silicate phases that appear in some experimental waste forms and as waste-rock interaction products. Specific compounds are: (1) Reference Ceramic Phases (zirconolite, magnetoplumbite, spinel, Tc-bearing spinel and perovskite); (2) Aluminosilicate phases (nepheline, pollucite, CsAlSi 5 O 12 , Sr-feldspar). 5 figures, 1 table

Characterisation of gas transport properties of the Opalinus clay, a potential host rock formation for radioactive waste disposal

International Nuclear Information System (INIS)

Marschall, P.; Horseman, S.; Gimmi, T.

2005-01-01

The Opalinus Clay in Northern Switzerland has been identified as a potential host rock formation for the disposal of radioactive waste. Comprehensive understanding of gas transport processes through this low-permeability formation forms a key issue in the assessment of repository performance. Field investigations and laboratory experiments suggest an intrinsic permeability of the Opalinus Clay in the order of 10 -20 to 10 -21 m 2 and a moderate anisotropy ratio ≤ 10. Porosity depends on clay content and burial depth; values of ∼ 0.12 are reported for the region of interest. Porosimetry indicates that about 10-30% of voids can be classed as macro-pores, corresponding to an equivalent pore radius > 25 nm. The determined entry pressures are in the range of 0.4-10 MPa and exhibit a marked dependence on intrinsic permeability. Both in situ gas tests and gas permeameter tests on drill-cores demonstrate that gas transport through the rock is accompanied by pore water displacement, suggesting that classical flow concepts of immiscible displacement in porous media can be applied when the gas entry pressure (i.e. capillary threshold pressure) is less than the minimum principal stress acting within the rock. Essentially, the pore space accessible to gas flow is restricted to the network of connected macro-pores, which implies a very low degree of desaturation of the rock during the gas imbibition process. At elevated gas pressures (i.e. when gas pressure approaches the level of total stress that acts on the rock body), evidence was seen for dilatancy controlled gas transport mechanisms. Further field experiments were aimed at creating extended tensile fractures with high fracture transmissivity (hydro- or gas-fractures). The test results lead to the conclusion that gas fracturing can be largely ruled out as a risk for post-closure repository performance. (authors)

Calcite Dissolution Kinetics

Science.gov (United States)

Berelson, W.; Subhas, A.; Dong, S.; Naviaux, J.; Adkins, J. F.

2016-12-01

A geological buffer for high atmospheric CO2 concentrations is neutralization via reaction with CaCO3. We have been studying the dissolution kinetics of carbonate minerals using labeled 13C calcite and Picarro-based measurements of 13C enrichments in solution DIC. This methodology has greatly facilitated our investigation of dissolution kinetics as a function of water carbonate chemistry, temperature and pressure. One can adjust the saturation state Omega by changing the ion activity product (e.g. adjusting carbonate ion concentration), or by changing the solubility product (e.g. adjusting temperature or pressure). The canonical formulation of dissolution rate vs. omega has been refined (Subhas et al. 2015) and shows distinct non-linear behavior near equilibrium and rates in sea water of 1-3 e-6 g/cm2day at omega = 0.8. Carbonic anhydrase (CA), an enzyme that catalyzes the hydration of dissolved CO2 to carbonic acid, was shown (in concentrations 500x. This result points to the importance of carbonic acid in enhancing dissolution at low degrees of undersaturation. CA activity and abundance in nature must be considered regarding the role it plays in catalyzing dissolution. We also have been investigating the role of temperature on dissolution kinetics. An increase of 16C yields an order of magnitude increase in dissolution rate. Temperature (and P) also change Omega critical, the saturation state where dissolution rates change substantially. Increasing pressure (achieved in a pressure reaction chamber we built) also shifts Omega critical closer to equilibrium and small pressure increases have large impact on dissolution kinetics. Dissolution rates are enhanced by an order of magnitude for a change in pressure of 1500 psi relative to the dissolution rate achieved by water chemistry effects alone for an omega of 0.8. We've shown that the thermodynamic determination of saturation state does not adequately describe the kinetics of dissolution. The interplay of mineral

Repository for high level radioactive wastes in Brazil: the importance of geochemical (Micro thermometric) studies and fluid migration in potential host rocks; Repositorios para rejeitos radioativos de alto nivel (RANR) no Brasil: a importancia de estudos geoquimicos (microtermometricos) e de migracao de fluidos em rochas potenciamente hospedeiras

Energy Technology Data Exchange (ETDEWEB)

Rios, Francisco Javier; Fuzikawa, Kazuo; Alves, James Vieira; Neves, Jose Marques Correia [Centro de Desenvolvimento da Tecnologia Nuclear (CDTN-CNEN-MG), Belo Horizonte, MG (Brazil). Lab. de Inclusoes Fluidas e Metalogenese]. E-mail: javier@cdtn.br

2003-04-15

A detailed fluid inclusion study of host rocks, is of fundamental importance in the selection of geologically suitable areas for high level nuclear waste repository constructions (HLRW). The LIFM-CDTN is enabled to develop studies that confirm: the presence or not, of corrosive fluid in minerals from host rocks of the repository and the possible presence of micro fractures (and fluid leakage) when these rocks are submitted to high temperatures. These fluid geochemistry studies, with permeability determinations by means of pressurized air injection must be carried out in rocks hosting nuclear waste. Micro fracture determination is of vital importance since many naturally corrosive solutions, present in the mineral rocks, could flow out through these plans affecting the walls of the repository. (author)

Mathematical simulation of a waste rock heap

International Nuclear Information System (INIS)

Scharer, J.M.; Pettit, C.M.; Chambers, D.B.; Kwong, E.C.

1994-01-01

A computer model has been developed to simulate the generation of acidic drainage in waste rock piles. The model considers the kinetic rates of biological and chemical oxidation of sulfide minerals (pyrite, pyrrhotite) present as fines and rock particles, as well as chemical processes such as dissolution (kinetic or equilibrium controlled), complexation (from equilibrium and stoichiometry of several complexes), and precipitation (formation of complexes and secondary minerals). Through mass balance equations and solubility constraints (e.g., pH, phase equilibria) the model keeps track of the movement of chemical species through the waste pile and provides estimates of the quality of seepage (pH, sulfate, iron, acidity, etc.) leaving the heap. The model has been expanded to include the dissolution (thermodynamic and sorption equilibrium), adsorption and coprecipitation of uranium and radium. The model was applied to simulate waste rock heaps in British Columbia, Canada and in Thueringia, Germany. To improve the accuracy and confidence of long-term predictions of seepage quality, the entire history of the heaps was simulated. Cumulative acidity loads and water treatment considerations were used as a basis for evaluation of various decommissioning alternatives. Simulation of the technical leaching history of a heap in Germany showed it will generate contaminated leachate requiring treatment for acidity and radioactivity for several hundred years; cover installation was shown to provide a significant reduction of potential burdens, although chemical treatment would still be required beyond 100 years

10 CFR 960.5-2-9 - Rock characteristics.

Science.gov (United States)

2010-01-01

... 10 Energy 4 2010-01-01 2010-01-01 false Rock characteristics. 960.5-2-9 Section 960.5-2-9 Energy... Rock characteristics. (a) Qualifying condition. The site shall be located such that (1) the thickness and lateral extent and the characteristics and composition of the host rock will be suitable for...

Microbial Fluid-Rock Interactions in Chalk Samples and Salinity Factor in Divalent Ca2+ ions Release for Microbial Enhanced Oil Recovery Purposes

DEFF Research Database (Denmark)

Jimoh, Ismaila Adetunji; Rudyk, Svetlana Nikolayevna; Søgaard, Erik Gydesen

2011-01-01

In this study, laboratory experiments were performed on chalk samples from Danish sector of the North Sea to study microbial fluid-rock interactions with carbonate rock and to evaluate the dissolution of rock matrix (CaCO3). Result showed that the average concentration of Ca2+ ions after microbia...

Experimental Rock Deformation under micro-CT: ERDμ

Science.gov (United States)

Tisato, Nicola; Zhao, Qi; Biryukov, Anton; Grasselli, Giovanni

2015-04-01

Typically, the static elastic moduli of a rock differ from the corresponding dynamic rock-moduli. Such frequency-dependent characteristic, called modulus dispersion, implies also velocity dispersion (i.e. Vp- and Vs-dispersion). Velocity dispersion can be seen, in fact, as the result of a viscoelastic response of the geo-material to the externally imposed stress (e.g. seismic wave). Viscoelasticity can be conveniently expressed as attenuation (1/Q), which describes the loss of elastic energy for each stress cycle and comprises the measurement of the complex elastic modulus. As 1/Q at frequencies important seismic attribute as it can aid the subsurface imaging accuracy. For instance, the study of 1/Q is fundamental for the oil and gas industry as valuable natural resources, such as oil-sands or gas-shales, exhibit significant attenuation (e.g. 1/Q ~ 0.3 at 1 Hz), or for volcanic and earthquake related studies as fluids are often involved in those natural processes. In the last five years, employing the Broad Band Attenuation Vessel (BBAV), the attenuation of partially saturated rocks has been investigated along with the fluid pressure transient caused by a sudden increase of stress. In particular, those studies shed light on the relationships between 1/Q and i) saturation, ii) confining pressure, and iii) strain. The combination of laboratory and numerical results helped demonstrating that wave induced fluid flow (WIFF) on the mesoscopic scale is responsible for the large and frequency-dependent attenuation observed in the laboratory measurements of a partially saturated sandstone. However, these studies lay bare limitations: the behavior of attenuation as a function of i) the distribution of fluids in the pore space and ii) the role of dissolution-precipitation of new mineral phases are still unclear. For instance, when CO2 is injected in the Earth's crust to pursuit carbon sequestration it would be extremely useful understanding the impact of the gas-water-rock

Lattice Boltzmann simulation of dissolution-induced changes in permeability and porosity in 3D CO2 reactive transport

Science.gov (United States)

Tian, Zhiwei; Wang, Junye

2018-02-01

Dissolution and precipitation of rock matrix are one of the most important processes of geological CO2 sequestration in reservoirs. They change connections of pore channels and properties of matrix, such as bulk density, microporosity and hydraulic conductivity. This study builds on a recently developed multi-layer model to account for dynamic changes of microporous matrix that can accurately predict variations in hydraulic properties and reaction rates due to dynamic changes in matrix porosity and pore connectivity. We apply the model to simulate the dissolution and precipitation processes of rock matrix in heterogeneous porous media to quantify (1) the effect of the reaction rate on dissolution and matrix porosity, (2) the effect of microporous matrix diffusion on the overall effective diffusion and (3) the effect of heterogeneity on hydraulic conductivity. The results show the CO2 storage influenced by factors including the matrix porosity change, reaction front movement, velocity and initial properties. We also simulated dissolution-induced permeability enhancement as well as effects of initial porosity heterogeneity. The matrix with very low permeability, which can be unresolved on X-ray CT, do contribute to flow patterns and dispersion. The concentration of reactant H+ increases along the main fracture paths where the flow velocity increases. The product Ca++ shows the inversed distribution pattern against the H+ concentration. This demonstrates the capability of this model to investigate the complex CO2 reactive transport in real 3D heterogeneous porous media.

Location-Related Differences in Weathering Behaviors and Populations of Culturable Rock-Weathering Bacteria Along a Hillside of a Rock Mountain.

Science.gov (United States)

Wang, Qi; Wang, Rongrong; He, Linyan; Sheng, Xiafang

2017-05-01

Bacteria play important roles in rock weathering, elemental cycling, and soil formation. However, little is known about the weathering potential and population of bacteria inhabiting surfaces of rocks. In this study, we isolated bacteria from the top, middle, and bottom rock samples along a hillside of a rock (trachyte) mountain as well as adjacent soils and characterized rock-weathering behaviors and populations of the bacteria. Per gram of rock or surface soil, 10 6 -10 7 colony forming units were obtained and total 192 bacteria were isolated. Laboratory rock dissolution experiments indicated that the proportions of the highly effective Fe (ranging from 67 to 92 %), Al (ranging from 40 to 48 %), and Cu (ranging from 54 to 81 %) solubilizers were significantly higher in the top rock and soil samples, while the proportion of the highly effective Si (56 %) solubilizers was significantly higher in the middle rock samples. Furthermore, 78, 96, and 6 % of bacteria from the top rocks, soils, and middle rocks, respectively, significantly acidified the culture medium (pH bacteria (79 %) from the rocks were different to those from the soils and most of them (species level) have not been previously reported. Furthermore, location-specific rock-weathering bacterial populations were found and Bacillus species were the most (66 %) frequently isolated rock-weathering bacteria in the rocks based on cultivation methods. Notably, the top rocks and soils had the highest and lowest diversity of rock-weathering bacterial populations, respectively. The results suggested location-related differences in element (Si, Al, Fe, and Cu) releasing effectiveness and communities of rock-weathering bacteria along the hillside of the rock mountain.

Requirements of actual final repository concepts for different host rock formations. Final report; Anforderungen an aktuelle Endlagerkonzepte fuer unterschiedliche Wirtsgesteinsformationen. Abschlussbericht

Energy Technology Data Exchange (ETDEWEB)

Fass, Thorsten; Hartwig-Thurat, Eva; Krischer, Angelika; Lambers, Ludger; Larue, Juergen; Uhlmann, Stephan; Weyand, Torben

2017-08-15

In the frame of the research project the basic requirements and technical safety specifications with respect to the retrievability of stored radioactive wastes for the different final repository concepts based on the host rock formations occurring in Germany are presented. Existing international disposal concepts for clay/claystone, granite and salt are described and compared to the actual German regulatory requirements. The safety engineering relations between stock piling and possible retrieval are described and evaluated.

Reservoir Space Evolution of Volcanic Rocks in Deep Songliao Basin, China

Science.gov (United States)

Zheng, M.; Wu, X.; Zheng, M.; HU, J.; Wang, S.

2015-12-01

Recent years, large amount of natural gas has been discovered in volcanic rock of Lower Crataceous of Songliao basin. Volcanic reservoirs have become one of the important target reservoir types of eastern basin of China. In order to study the volcanic reservoirs, we need to know the main factors controlling the reservoir space. By careful obsercation on volcanic drilling core, casting thin sections and statistical analysis of petrophysical properties of volcanic reservoir in Songliao basin, it can be suggested that the igneous rock reservoir in Yingcheng formation of Lower Crataceous is composed of different rock types, such ad rohylite, rohylitic crystal tuff, autoclastic brecciation lava and so on. There are different reservoirs storage space in in various lithological igneous rocks, but they are mainly composed of primary stoma, secondary solution pores and fractures.The evolution of storage space can be divided into 3 stage: the pramary reservoir space,exogenic leaching process and burial diagenesis.During the evolution process, the reservoir space is effected by secondary minerals, tectonic movement and volcanic hydrothermal solution. The pore of volcanic reservoirs can be partially filled by secondary minerals, but also may be dissoluted by other chemical volcanic hydrothermal solution. Therefore, the favorable places for better-quality volcanic reservoirs are the near-crater facies of vocanic apparatus and dissolution zones on the high position of paleo-structures.

Rock-fluid chemical interactions at reservoir conditions: The influence of brine chemistry and extent of reaction

Science.gov (United States)

Anabaraonye, B. U.; Crawshaw, J.; Trusler, J. P. M.

2016-12-01

Following carbon dioxide injection in deep saline aquifers, CO2 dissolves in the formation brines forming acidic solutions that can subsequently react with host reservoir minerals, altering both porosity and permeability. The direction and rates of these reactions are influenced by several factors including properties that are associated with the brine system. Consequently, understanding and quantifying the impacts of the chemical and physical properties of the reacting fluids on overall reaction kinetics is fundamental to predicting the fate of the injected CO2. In this work, we present a comprehensive experimental study of the kinetics of carbonate-mineral dissolution in different brine systems including sodium chloride, sodium sulphate and sodium bicarbonate of varying ionic strengths. The impacts of the brine chemistry on rock-fluid chemical reactions at different extent of reactions are also investigated. Using a rotating disk technique, we have investigated the chemical interactions between the CO2-saturated brines and carbonate minerals at conditions of pressure (up to 10 MPa) and temperature (up to 373 K) pertinent to carbon storage. The changes in surface textures due to dissolution reaction were studied by means of optical microscopy and vertical scanning interferometry. Experimental results are compared to previously derived models.

Dissolution and secondary mineral precipitation in basalts due to reactions with carbonic acid

Science.gov (United States)

Kanakiya, Shreya; Adam, Ludmila; Esteban, Lionel; Rowe, Michael C.; Shane, Phil

2017-06-01

One of the leading hydrothermal alteration processes in volcanic environments is when rock-forming minerals with high concentrations of iron, magnesium, and calcium react with CO2 and water to form carbonate minerals. This is used to the advantage of geologic sequestration of anthropogenic CO2. Here we experimentally investigate how mineral carbonation processes alter the rock microstructure due to CO2-water-rock interactions. In order to characterize these changes, CO2-water-rock alteration in Auckland Volcanic Field young basalts (less than 0.3 Ma) is studied before and after a 140 day reaction period. We investigate how whole core basalts with similar geochemistry but different porosity, permeability, pore geometry, and volcanic glass content alter due to CO2-water-rock reactions. Ankerite and aluminosilicate minerals precipitate as secondary phases in the pore space. However, rock dissolution mechanisms are found to dominate this secondary mineral precipitation resulting in an increase in porosity and decrease in rigidity of all samples. The basalt with the highest initial porosity and volcanic glass volume shows the most secondary mineral precipitation. At the same time, this sample exhibits the greatest increase in porosity and permeability, and a decrease in rock rigidity post reaction. For the measured samples, we observe a correlation between volcanic glass volume and rock porosity increase due to rock-fluid reactions. We believe this study can help understand the dynamic rock-fluid interactions when monitoring field scale CO2 sequestration projects in basalts.

A dissolution-precipitation mechanism is at the origin of concrete creep in moist environments

Energy Technology Data Exchange (ETDEWEB)

Pignatelli, Isabella [Laboratory for the Chemistry of Construction Materials (LC2), Department of Civil and Environmental Engineering, University of California, Los Angeles, California 90095 (United States); Kumar, Aditya [Materials Science and Engineering Department, Missouri University of Science and Technology, Rolla, Missouri 65409 (United States); Alizadeh, Rouhollah [Giatec Scientific, Ottawa, Ontario K2H 9C4 (Canada); Le Pape, Yann [Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831 (United States); Bauchy, Mathieu, E-mail: bauchy@ucla.edu, E-mail: gsant@ucla.edu [Physics of AmoRphous and Inorganic Solids Laboratory (PARISlab), Department of Civil and Environmental Engineering, University of California, Los Angeles, California 90095 (United States); Sant, Gaurav, E-mail: bauchy@ucla.edu, E-mail: gsant@ucla.edu [Laboratory for the Chemistry of Construction Materials (LC2), Department of Civil and Environmental Engineering, University of California, Los Angeles, California 90095 (United States); California Nanosystems Institute (CNSI), University of California, Los Angeles, California 90095 (United States)

2016-08-07

Long-term creep (i.e., deformation under sustained load) is a significant material response that needs to be accounted for in concrete structural design. However, the nature and origin of concrete creep remain poorly understood and controversial. Here, we propose that concrete creep at relative humidity ≥ 50%, but fixed moisture content (i.e., basic creep), arises from a dissolution-precipitation mechanism, active at nanoscale grain contacts, as has been extensively observed in a geological context, e.g., when rocks are exposed to sustained loads, in liquid-bearing environments. Based on micro-indentation and vertical scanning interferometry data and molecular dynamics simulations carried out on calcium–silicate–hydrate (C–S–H), the major binding phase in concrete, of different compositions, we show that creep rates are correlated with dissolution rates—an observation which suggests a dissolution-precipitation mechanism as being at the origin of concrete creep. C–S–H compositions featuring high resistance to dissolution, and, hence, creep are identified. Analyses of the atomic networks of such C–S–H compositions using topological constraint theory indicate that these compositions present limited relaxation modes on account of their optimally connected (i.e., constrained) atomic networks.

Properties of uranium and thorium in host rocks of multi-metal (Ag, Pb, U, Cu, Bi, Z, F) Big Kanimansur deposit (Tajikistan)

International Nuclear Information System (INIS)

Fayziev, A.R.

2007-01-01

Multi-metal Big Kanimansur Deposit host rocks contain high averages of uranium and thorium which are more than clark averages by 7 and 2.5 times accordingly. The second property of radio-active elements distribution are low ratio of thorium to uranium. That criteria can be used as prospecting sings for flanks and depth of know ore fields as well as for new squares of multi-metal mineralisation

Kaolinite, illite and quartz dissolution in the karstification of Paleozoic sandstones of the Furnas Formation, Paraná Basin, Southern Brazil

Science.gov (United States)

Melo, Mário Sérgio de; Guimarães, Gilson Burigo; Chinelatto, Adilson Luiz; Giannini, Paulo César Fonseca; Pontes, Henrique Simão; Chinelatto, Adriana Scoton Antonio; Atencio, Daniel

2015-11-01

Karstification processes in sandstones of the Furnas Formation, Silurian to Devonian of the Paraná Basin, have been described since the mid-twentieth century. However, some geologists still doubt the idea of true karst in sandstones. Studies carried out in the Campos Gerais region, Paraná State, Southern Brazil, aimed at investigating the nature of erosion processes in Furnas Formation and the role of the dissolution in the development of their notorious erosive features and underground cavities. These studies have led to the recognition of dissolution macro to micro features ('furnas', caves, ponds, sinks, ruiniform relief on cliffs and rocky surfaces, grain corrosion, speleothems, mineral reprecipitation and incrustation). The analysis (scanning electron microscopy, energy dispersive spectrometry and x-ray diffractometry) of sandstones and their alterites has indicated significant dissolution of clay cement along with discrete quartz grain dissolution. This mesodiagenetic cement (kaolinite and illite) is dissolved and reprecipitated as clay minerals with poorly developed crystallinity along with other minerals, such as variscite and minerals of the alunite supergroup, suggesting organic participation in the processes of dissolution and incrustation. The mineral reprecipitation usually forms centimetric speleothems, found in cavities and sheltered rocky surfaces. The cement dissolution associated with other factors (fractures, wet weather, strong hydraulic gradient, antiquity of the landforms) leads to the rock arenisation, the underground erosion and the appearance of the karst features. Carbonate rocks in the basement may locally be increasing the karst forms in the overlying Furnas Formation. The recognition of the karst character of the Furnas Formation sandstones has important implications in the management of underground water resources (increasingly exploited in the region), in the use of the unique geological heritage and in the prevention of geo

Moessbauer and XRD Comparative Study of Host Rock and Iron Rich Mineral Samples from Paz del Rio Iron Ore Mineral Mine in Colombia

International Nuclear Information System (INIS)

Fajardo, M.; Perez Alcazar, G. A.; Moreira, A. M.; Speziali, N. L.

2004-01-01

A comparative study between the host rock and the iron rich mineral samples from the Paz del Rio iron ore mineral mine in Colombia was performed using X-ray diffraction and Moessbauer spectroscopy. Diffraction results of the iron rich mineral sample show that goethite, hematite, quartz, kaolinite and siderite are the main phases, and that a small amount of illite is also present. By Moessbauer spectroscopy at room temperature (RT) the presence of all the above mentioned phases was detected except quartz as well as an additional presence of small amount of biotite. The goethite, which appears as four sextets with hyperfine fields of 33.5, 30.5, 27.5 and 18.5 T, respectively, is the majority phase. This result shows the different grades of formation of this oxyhydroxide. The Moessbauer spectrum of this sample at 80 K presents the same phases obtained at RT without any superparamagnetic effect. In this case the goethite appears as two sextets. Diffraction results of the host rock sample show a large amount of quartz and kaolinite and small amounts of illite and biotite, whereas by Moessbauer spectroscopy illite, kaolinite and biotite were detected.

Electrokinetic mechanism of wettability alternation at oil-water-rock interface

Science.gov (United States)

Tian, Huanhuan; Wang, Moran

2017-12-01

Design of ions for injection water may change the wettability of oil-brine-rock (OBR) system, which has very important applications in enhanced oil recovery. Though ion-tuned wettability has been verified by various experiments, the mechanism is still not clear. In this review paper, we first present a comprehensive summarization of possible wettability alteration mechanisms, including fines migration or dissolution, multicomponent ion-exchange (MIE), electrical double layer (EDL) interaction between rock and oil, and repulsive hydration force. To clarify the key mechanism, we introduce a complete frame of theories to calculate attribution of EDL repulsion to wettability alteration by assuming constant binding forces (no MIE) and rigid smooth surface (no fines migration or dissolution). The frame consists of three parts: the classical Gouy-Chapman model coupled with interface charging mechanisms to describe EDL in oil-brine-rock systems, three methods with different boundary assumptions to evaluate EDL interaction energy, and the modified Young-Dupré equation to link EDL interaction energy with contact angle. The quantitative analysis for two typical oil-brine-rock systems provides two physical maps that show how the EDL interaction influences contact angle at different ionic composition. The result indicates that the contribution of EDL interaction to ion-tuned wettability for the studied system is not quite significant. The classical and advanced experimental work using microfabrication is reviewed briefly on the contribution of EDL repulsion to wettability alteration and compared with the theoretical results. It is indicated that the roughness of real rock surface may enhance EDL interaction. Finally we discuss some pending questions, perspectives and promising applications based on the mechanism.

Kinetics and reversibility of radionuclide sorption reactions with rocks. Progress report for fiscal year 1979

International Nuclear Information System (INIS)

Barney, G.S.; Brown, G.E.

1979-01-01

Sorption-desorption reactions of cesium, strontium, neptunium, americium, and plutonium on basalt, granite, and argillite were observed for 218 days. Equilibrium in batch experiments was not reached for most radionuclides even after this long time. Reactions of the crushed rock with ground waters (dissolution, hydrolysis, precipitation, etc.) also did not reach equilibrium after 150 days. The dissolution of basalt is accompanied by the formation of colloidal particles which contain Si, Fe, Ca, and Al. These colloids sorb Cs, Sr, Am, and Pu during equilibration. Some of the colloids pass through 0.3-μm flters, are not retained even on 0.01-μm filters and, therefore, cause calculated K/sub d/ values to be too low. Samples of crushed basalt, granite, and argillite were artificially weathered by continuous leaching with distilled water for 6 months both in air and in an oxygen-free stream of nitrogen gas. The weathered rock was then characterized for surface area, surface structure, cation exchange capacity, and composition of weathered surface on the rock. Comparisons were made of radionuclide sorption (after 14 days) on fresh rock, rock weathered in air, and rock weathered in N 2 . Sorption on rocks weathered in N 2 generally is less than on rock weathered in air. This is possibly due to the lack of an Fe(OH) 3 coating on the rock weathered in N 2 . The Fe(OH) 3 is known to scavenge cations and silica from solution. Sorption of Cs, Si, Am, and Pu is strongly affected by weathering basalt and argillite. However, the cation exchange capacity is changed very little, suggesting that ion exchange plays a minor role in sorption of these radionuclides

Ultramafic-derived arsenic in a fractured bedrock aquifer

International Nuclear Information System (INIS)

Ryan, Peter C.; Kim, Jonathan; Wall, Andrew J.; Moen, Jonathan C.; Corenthal, Lilly G.; Chow, Daniel R.; Sullivan, Colleen M.; Bright, Kevin S.

2011-01-01

Highlights: → Arsenic is elevated in groundwater from a fractured bedrock aquifer system in northern Vermont, USA. → The arsenic source is serpentinized ultramafic rock. → Antigorite, magnetite (MgCO 3 ) and magnetite (Fe 3 O 4 ) appear to be the main mineralogical hosts of arsenic in the ultramafic rock. → Arsenic appears to be introduced to the ultramafic rock when As-bearing fluids are driven out of sediments during subduction. → The occurrence of serpentinized ultramafic rocks in many orogenic belts suggests that similar arsenic anomalies may occur in geologically-similar terranes globally. - Abstract: In the fractured bedrock aquifer of northern Vermont, USA, As concentrations in groundwater range from 3 ) with lesser amounts in magnetite (Fe 3 O 4 ). Hydrochemistry of monitoring wells drilled into fractured ultramafic rock in a groundwater recharge area with no anthropogenic As source reveals above background As (2-9 μg/L) and an Mg-HCO 3 hydrochemical signature that reflects dissolution of antigorite and magnesite, confirming that As in groundwater can be derived from ultramafic rock dissolution. Arsenic mobility in groundwater affected by ultramafic rock dissolution may be enhanced by alkaline pH values and relatively high HCO 3 - concentrations.

Pore water colloid properties in argillaceous sedimentary rocks

Energy Technology Data Exchange (ETDEWEB)

Degueldre, Claude, E-mail: c.degueldre@lancaster.ac.uk [Engineering Department, University of Lancaster, LA1 4YW Lancaster (United Kingdom); ChiAM & Institute of Environment, University of Geneva, 1211 Genève 4, Swizerland (Switzerland); Earlier, NES, Paul Scherrer Institute, 5232 Villigen (Switzerland); Cloet, Veerle [NAGRA, Hardstrasse 73, 5430 Wettingen (Switzerland)

2016-11-01

The focus of this work is to evaluate the colloid nature, concentration and size distribution in the pore water of Opalinus Clay and other sedimentary host rocks identified for a potential radioactive waste repository in Switzerland. Because colloids could not be measured in representative undisturbed porewater of these host rocks, predictive modelling based on data from field and laboratory studies is applied. This approach allowed estimating the nature, concentration and size distributions of the colloids in the pore water of these host rocks. As a result of field campaigns, groundwater colloid concentrations are investigated on the basis of their size distribution quantified experimentally using single particle counting techniques. The colloid properties are estimated considering data gained from analogue hydrogeochemical systems ranging from mylonite features in crystalline fissures to sedimentary formations. The colloid concentrations were analysed as a function of the alkaline and alkaline earth element concentrations. Laboratory batch results on clay colloid generation from compacted pellets in quasi-stagnant water are also reported. Experiments with colloids in batch containers indicate that the size distribution of a colloidal suspension evolves toward a common particle size distribution independently of initial conditions. The final suspension size distribution was found to be a function of the attachment factor of the colloids. Finally, calculations were performed using a novel colloid distribution model based on colloid generation, aggregation and sedimentation rates to predict under in-situ conditions what makes colloid concentrations and size distributions batch- or fracture-size dependent. The data presented so far are compared with the field and laboratory data. The colloid occurrence, stability and mobility have been evaluated for the water of the considered potential host rocks. In the pore water of the considered sedimentary host rocks, the clay

Mineralogy and geochemistry of Skarn Fe orebody and syenodioritic intrusive host rock in Zeber Kuh prospect area (SW Bardaskan, South Khorasan province

Directory of Open Access Journals (Sweden)

Hossein Narooie

2017-11-01

Full Text Available The Zeber Kuh prospect area is located southwest of Bardaskan, South Khorasan province, in the northeastern Iran. Lithologically, the area includes Rizu and Soltanieh Formations metamorphosed carbonate rocks, which were intruded by syenogranitic and syenodioritic intrusions. Field observations and laboratory studies such as structural controls of orebody, metasomatic replacement and formation of low temperature H2O-bearing minerals, and the occurrence of magnetite and pyrite associated with chlorite, epidote, calcite, and quartz indicate that  the iron mineralization is low temperature skarn-type. The source of Fe mineralization is probably a younger intrusive rock at depth. Hydrothermal ore fluid was ascended within fault zone and/or contact between the intrusive rock and the  carbonate unit and generated orebody. Iron grade ranges from 54 to 65 wt.% and sulfur value is > 3 wt.%. Magnetite chemistry and Ti, V, Al, Mn, Ni, and Cr contents are similar to skarn deposit. Biotite syenodiorite host rock has hypidiomorphic granular texture and it consists of plagioclase, K-feldspar, biotite, and apatite minerals. Chemically, this intrusive rock is K-series alkaline type, which was generated in within plate zone. This magma is characterized by strong enrichment in LREE, LILE (Rb, Cs, Ba, and K, HFSE (Nb, Zr, and Ti, and P elements. The primary magma is produced by low degree partial melting of garnet lherzolite from asthenospheric to boundary of asthenospheric-lithospheric mantle.

Characterization of calculation of in-situ retardation factors of contaminant transport using naturally-radionuclides and rock/water interaction occurring U-Series disequilibria timescales. 1997 annual progress report

International Nuclear Information System (INIS)

Goldstein, S.; Ku, T.L.; Luo, S.; Murrel, M.; Roback, R.

1997-01-01

'The research is directed toward a quantitative assessment of contaminant transport rates in fracture-rock systems using uranium-series radionuclides. Naturally occurring uranium-and thorium-series radioactive disequilibria will provide information on the rates of adsorption-desorption and transport of radioactive contaminants as well as on fluid transport and rock dissolution in a natural setting. This study will also provide an improved characterization of preferential flow and contaminant transport at the Idaho Environmental and Engineering Lab. (INEEL) site. To a lesser extent, the study will include rocks in the unsaturated zone. The authors will produce a realistic model of radionuclide migration under unsaturated and saturated field conditions at the INEEL site, taking into account the retardation processes involved in the rock/water interaction. The major tasks are to (1) determine the natural distribution of U, Th, Pa and Ra isotopes in rock minerals. sorbed phases on the rocks, and in fluids from both saturated and unsaturated zones at the site, and (2) study rock/water interaction processes using U/Th series disequilibrium and a statistical analysis-based model for the Geologic heterogeneity plays an important role in transporting contaminants in fractured rocks. Preferential flow paths in the fractured rocks act as a major pathway for transport of radioactive contaminants in groundwaters. The weathering/dissolution of rock by groundwater also influences contaminant mobility. Thus, it is important to understand the hydrogeologic features of the site and their impact on the migration of radioactive contaminants. In this regard, quantification of the rock weathering/dissolution rate and fluid residence time from the observed decay-series disequilibria will be valuable. By mapping the spatial distribution of the residence time of groundwater in fractured rocks, the subsurface preferential flow paths (with high rock permeability and short fluid residence

10 CFR 960.3-1-2 - Diversity of rock types.

Science.gov (United States)

2010-01-01

... 10 Energy 4 2010-01-01 2010-01-01 false Diversity of rock types. 960.3-1-2 Section 960.3-1-2... NUCLEAR WASTE REPOSITORY Implementation Guidelines § 960.3-1-2 Diversity of rock types. Consideration... sites for characterization shall have different types of host rock. ...

Interim rock mass properties and conditions for analyses of a repository in crystalline rock

International Nuclear Information System (INIS)

Tammemagi, H.Y.; Chieslar, J.D.

1985-03-01

A summary of rock properties for generic crystalline rock is compiled from literature sources to provide the input data for analyses of a conceptual repository in crystalline rock. Frequency histograms, mean values and ranges of physical, mechanical, thermal, and thermomechanical properties, and the dependence of these properties on temperature are described. A description of the hydrogeologic properties of a crystalline rock mass and their dependence on depth is provided. In addition, the temperature gradients, mean annual surface temperature, and in situ stress conditions are summarized for the three regions of the United States currently under consideration to host a crystalline repository; i.e., the North Central, Northeastern, and Southeastern. Brief descriptions of the regional geology are also presented. Large-scale underground experiments in crystalline rock at Stripa, Sweden, and in Climax Stock in Nevada, are reviewed to assess whether the rock properties presented in this report are representative of in situ conditions. The suitability of each rock property and the sufficiency of its data base are described. 110 refs., 27 figs., 4 tabs

Solubility limits on radionuclide dissolution

Energy Technology Data Exchange (ETDEWEB)

Kerrisk, J.F.

1984-12-31

This paper examines the effects of solubility in limiting dissolution rates of a number of important radionuclides from spent fuel and high-level waste. Two simple dissolution models were used for calculations that would be characteristics of a Yucca Mountain repository. A saturation-limited dissolution model, in which the water flowing through the repository is assumed to be saturated with each waste element, is very conservative in that it overestimates dissolution rates. A diffusion-limited dissolution model, in which element-dissolution rates are limited by diffusion of waste elements into water flowing past the waste, is more realistic, but it is subject to some uncertainty at this time. Dissolution rates of some elements (Pu, Am, Sn, Th, Zr, Sm) are always limited by solubility. Dissolution rates of other elements (Cs, Tc, Np, Sr, C, I) are never solubility limited; their release would be limited by dissolution of the bulk waste form. Still other elements (U, Cm, Ni, Ra) show solubility-limited dissolution under some conditions. 9 references, 3 tables.

Pore water colloid properties in argillaceous sedimentary rocks.

Science.gov (United States)

Degueldre, Claude; Cloet, Veerle

2016-11-01

The focus of this work is to evaluate the colloid nature, concentration and size distribution in the pore water of Opalinus Clay and other sedimentary host rocks identified for a potential radioactive waste repository in Switzerland. Because colloids could not be measured in representative undisturbed porewater of these host rocks, predictive modelling based on data from field and laboratory studies is applied. This approach allowed estimating the nature, concentration and size distributions of the colloids in the pore water of these host rocks. As a result of field campaigns, groundwater colloid concentrations are investigated on the basis of their size distribution quantified experimentally using single particle counting techniques. The colloid properties are estimated considering data gained from analogue hydrogeochemical systems ranging from mylonite features in crystalline fissures to sedimentary formations. The colloid concentrations were analysed as a function of the alkaline and alkaline earth element concentrations. Laboratory batch results on clay colloid generation from compacted pellets in quasi-stagnant water are also reported. Experiments with colloids in batch containers indicate that the size distribution of a colloidal suspension evolves toward a common particle size distribution independently of initial conditions. The final suspension size distribution was found to be a function of the attachment factor of the colloids. Finally, calculations were performed using a novel colloid distribution model based on colloid generation, aggregation and sedimentation rates to predict under in-situ conditions what makes colloid concentrations and size distributions batch- or fracture-size dependent. The data presented so far are compared with the field and laboratory data. The colloid occurrence, stability and mobility have been evaluated for the water of the considered potential host rocks. In the pore water of the considered sedimentary host rocks, the clay

Studies on the recovery of REEY from a hard-rock deposit of Rajasthan

International Nuclear Information System (INIS)

Karan, Ram; Giri, Nitai; Anand Rao, K.; Sreenivas, T.

2017-01-01

Dantala area in Banner district of Rajasthan is endowed with poly metallic mineralization hosted in tuffaceous rocks consisting of REE, Zr, Nb, U Th, Zn and Ag. The region has potential to become a hardrock rare earth resource in India. The chemical and XRF analysis of a representative borehole sample revealed that the ore has about 68% SiO_2, 7.7% Al_2O_3, 7.4% Fe_2O_3, 4.75% CaO along with 305 ppm Nb, 109 ppm Th, 3738 ppm TREE of which, 2580 ppm is LREE and 1158 ppm is HREE including 777 ppm Y. The deportment profile of REEY in the sample determined by sequential chemical extraction technique. Major distribution of REEY is dissolvable only under highly acidic conditions as the REEY are bound to iron oxides and are associated with refractory phases (zircon?). Heavy media separation of coarsely crushed material showed presence of about 90% of REEY values in specific gravity d'' 2.8. Therefore, the REEY values could not be preconcentrated by conventional physical beneficiation techniques. Direct 'whole ore' leaching using HCL and H_2SO_4 in 'pug cure leaching' mode with H_2SO_4 yielded about 50% dissolution of REEY values. The paper discusses the process complexities in the recovery of REEY from this hard rock ore sample

Thermodynamic stability and kinetic dissolution of perovskite in natural waters

International Nuclear Information System (INIS)

Nesbitt, H.W.; Bancroft, G.M.; Fyfe, W.S.; Karkhanis, S.; Melling, P.; Nishijima, A.

1981-01-01

Ringwood and coworkers have recently proposed using titanates and zirconates as hosts for nuclear waste in the Synroc B process. Three minerals are used as hosts: perovskite (CaTiO 3 ), Ba-hollandite (BaAl 2 Ti 6 O 16 ), and zirconolite (CaZrTi 2 O 7 ). The Synroc philosophy relies heavily on geological and geochemical observations in selecting stable host minerals. Although it has been recognized that the Synroc minerals are not thermodynamically compatible with siliceous rocks, the minerals are considered to be thermodynamically stable in the presence of water, and it has been reported that these minerals are kinetically stable under high-temperature (up to 900 0 C) hydrothermal conditions. Detailed thermodynamic calculations and leach tests have been performed which demonstrate: first, that perovskite is thermodynamically unstable in all known natural waters; and second, that pervoskite leaches at a significant rate even at 100 0 C. Hydrothermal leach tests have been made on natural and synthetic perovskite and perovskite analogues between 100 0 C and 300 0 C. Weight losses and solution concentrations were monitored. The results reported previously in the literature also show that perovskite is kinetically unstable in the presence of common silicates. Our results show that perovskite may be no more stable than siliceous glasses, such as rhyolite, which have been studied previously. Geologic evidence from common alkaline rocks also indicates that hollandite and zirconolite probably will not survive in common rock matrices

Mechanism for calcite dissolution and its contribution to development of reservoir porosity and permeability in the Kela 2 gas field,Tarim Basin,China

Institute of Scientific and Technical Information of China (English)

2008-01-01

This study is undertaken to understand how calcite precipitation and dissolution contributes to depth-related changes in porosity and permeability of gas-bearing sandstone reservoirs in the Kela 2 gas field of the Tarim Basin, Northwestern China. Sandstone samples and pore water samples are col-lected from well KL201 in the Tarim Basin. Vertical profiles of porosity, permeability, pore water chem-istry, and the relative volume abundance of calcite/dolomite are constructed from 3600 to 4000 m below the ground surface within major oil and gas reservoir rocks. Porosity and permeability values are in-versely correlated with the calcite abundance, indicating that calcite dissolution and precipitation may be controlling porosity and permeability of the reservoir rocks. Pore water chemistry exhibits a sys-tematic variation from the Na2SO4 type at the shallow depth (3600-3630 m), to the NaHCO3 type at the intermediate depth (3630―3695 m),and to the CaCl2 type at the greater depth (3728―3938 m). The geochemical factors that control the calcite solubility include pH, temperature, pressure, Ca2+ concen-tration, the total inorganic carbon concentration (ΣCO2), and the type of pore water. Thermodynamic phase equilibrium and mass conservation laws are applied to calculate the calcite saturation state as a function of a few key parameters. The model calculation illustrates that the calcite solubility is strongly dependent on the chemical composition of pore water, mainly the concentration difference between the total dissolved inorganic carbon and dissolved calcium concentration (i.e., [ΣCO2] -[Ca2+]). In the Na2SO4 water at the shallow depth, this index is close to 0, pore water is near the calcite solubility. Calcite does not dissolve or precipitate in significant quantities. In the NaHCO3 water at the intermedi-ate depth, this index is greater than 0, and pore water is supersaturated with respect to calcite. Massive calcite precipitation was observed at this depth

10 CFR 960.4-2-3 - Rock characteristics.

Science.gov (United States)

2010-01-01

... DEPARTMENT OF ENERGY GENERAL GUIDELINES FOR THE PRELIMINARY SCREENING OF POTENTIAL SITES FOR A NUCLEAR WASTE REPOSITORY Postclosure Guidelines § 960.4-2-3 Rock characteristics. (a) Qualifying condition. The present and... the waste could significantly decrease the isolation provided by the host rock as compared with pre...

Predicting dissolution patterns in variable aperture fractures: 1. Development and evaluation of an enhanced depth-averaged computational model

Energy Technology Data Exchange (ETDEWEB)

Detwiler, R L; Rajaram, H

2006-04-21

Water-rock interactions within variable-aperture fractures can lead to dissolution of fracture surfaces and local alteration of fracture apertures, potentially transforming the transport properties of the fracture over time. Because fractures often provide dominant pathways for subsurface flow and transport, developing models that effectively quantify the role of dissolution on changing transport properties over a range of scales is critical to understanding potential impacts of natural and anthropogenic processes. Dissolution of fracture surfaces is controlled by surface-reaction kinetics and transport of reactants and products to and from the fracture surfaces. We present development and evaluation of a depth-averaged model of fracture flow and reactive transport that explicitly calculates local dissolution-induced alterations in fracture apertures. The model incorporates an effective mass transfer relationship that implicitly represents the transition from reaction-limited dissolution to transport-limited dissolution. We evaluate the model through direct comparison to previously reported physical experiments in transparent analog fractures fabricated by mating an inert, transparent rough surface with a smooth single crystal of potassium dihydrogen phosphate (KDP), which allowed direct measurement of fracture aperture during dissolution experiments using well-established light transmission techniques [Detwiler, et al., 2003]. Comparison of experiments and simulations at different flow rates demonstrate the relative impact of the dimensionless Peclet and Damkohler numbers on fracture dissolution and the ability of the computational model to simulate dissolution. Despite some discrepancies in the small-scale details of dissolution patterns, the simulations predict the evolution of large-scale features quite well for the different experimental conditions. This suggests that our depth-averaged approach to simulating fracture dissolution provides a useful approach for

Alteration of national glass in radioactive waste repository host rocks: A conceptional review

International Nuclear Information System (INIS)

Apps, J.A.

1987-01-01

The storage of high-level radioactive wastes in host rocks containing natural glass has potential chemical advantages, especially if the initial waste temperatures are as high as 250 0 C. However, it is not certain how natural glasses will decompose when exposed to an aqueous phase in a repository environment. The hydration and devitrification of both rhyolitic and natural basaltic natural glasses are reviewed in the context of hypothetical thermodynamic phase relations, infrared spectroscopic data and laboratory studies of synthetic glasses exposed to steam. The findings are compared with field observations and laboratory studies of hydrating and devitrifying natural glasses. The peculiarities of the dependence of hydration and devitrification behavior on compositional variation is noted. There is substantial circumstantial evidence to support the belief that rhyolitic glasses differ from basaltic glasses in their thermodynamic stability and their lattice structure, and that this is manifested by a tendency of the former to hydrate rather than devitrify when exposed to water. Further research remains to be done to confirm the differences in glass structure, and to determine both physically and chemically dependent properties of natural glasses as a function of composition

Mineral chemistry of magnetite from magnetite-apatite mineralization and their host rocks: examples from Kiruna, Sweden, and El Laco, Chile

Science.gov (United States)

Broughm, Shannon G.; Hanchar, John M.; Tornos, Fernando; Westhues, Anne; Attersley, Samuel

2017-12-01

Interpretation of the mineralizing environment of magnetite-apatite deposits remains controversial with theories that include a hydrothermal or magmatic origin or a combination of those two processes. To address this controversy, we have analyzed the trace element content of magnetite from precisely known geographic locations and geologic environments from the Precambrian magnetite-apatite ore and host rocks in Kiruna, Sweden, and the Pliocene-Holocene El Laco volcano in the Atacama desert of Chile. Magnetite samples from Kiruna have low trace element concentrations with little chemical variation between the ore, host, and related intrusive rocks. Magnetite from andesite at El Laco, and dacite from the nearby Láscar volcano, has high trace element concentrations typical of magmatic magnetite. El Laco ore magnetite have low trace element concentrations and displays growth zoning in incompatible elements (Si, Ca, and Ce), compatible elements (Mg, Al, and Mn), large-ion lithophile element (Sr), and high field strength element (Y, Nb, and Th). The El Laco ore magnetite are similar in composition to magnetite that has been previously interpreted to have crystallized from hydrothermal fluids; however, there is a significant difference in the internal zoning patterns. At El Laco, each zoned element is either enriched or depleted in the same layers, suggesting the magnetite crystallized from a volatile-rich, iron-oxide melt. In general, the compositions of magnetite from these two deposits plot in very wide fields that are not restricted to the proposed fields in published discriminant diagrams. This suggests that the use of these diagrams and genetic models based on them should be used with caution.

Programme for repository host rock characterisation in the ONKALO (ReRoC)

International Nuclear Information System (INIS)

Aalto, P.; Aaltonen, I.; Kemppainen, K.

2009-04-01

The excavation of the ONKALO is now entering the deep bedrock regime, where the ambient rock conditions are representative of those to be found in the vicinity of future deposition tunnels and deposition holes. It is proposed to study the properties of the rock under these conditions using specially-excavated rock rooms, investigation niches or stations and characterisation holes. This report provides an overview of these plans, which are designed to obtain the relevant site-specific knowledge. This report summarises the outstanding issues of the site modelling that are driving the deep rock investigations. It also lists the main long-term safety needs from the site characterisation and presents a short description of the data needs raised by the RSC (Rock Suitability Criteria) programme. The report presents the general characterisation programme of the ONKALO access tunnel. It includes geological mapping in the tunnel and the shafts and investigations in pilot, probe and characterisation hole. It also presents a programme for the pre-grouting hole studies in the shafts. The main aim of the report is to present the experimental studies that are to be carried out in the niches and studies that will be carried out below hydrogeological zone HZ20 at different locations in the tunnel, in order to obtain information on rock properties that are comparable to the rock at the disposal depth. This document provides a detailed discussion of the following experiments: (1) the sulphate reduction experiment at a depth of between 300-350 m to investigate the production, presence and effects of sulphide in the groundwater; (2) the hydrogeological interference experiment at tunnel chainage 3620 or 3748 for a detailed characterisation of connected fracture networks in the rock mass, representative of those in the near field of the deposition holes; (3) the rock matrix diffusion experiment(s) below chainage 4000 to determine the bedrock's essential retention properties for

Characteristics of a Low-Sulfidation Epithermal Deposit in the River Reef Zone and the Watuputih Hill, the Poboya Gold Prospect, Central Sulawesi, Indonesia: Host Rocks and Hydrothermal Alteration

Directory of Open Access Journals (Sweden)

Syafrizal

2017-07-01

Full Text Available Systematic exploration has delineated significant gold mineralization in the River Reef Zone and the presence of a siliceous body at Watuputih Hill, which is a Poboya gold prospect in Central Sulawesi, Indonesia. The mineralization is hosted within the Palu Metamorphic Complex. The host rocks consist of granite, biotite gneiss, and biotite schist, which is intercalated by feldspar porphyroblastic biotite schist and amphibolitic schist. The X-ray fluorescence (XRF analysis of the granite and biotite gneiss suggests that the granitic rocks can be characterized as magnesian arc calc-alkaline rocks, with a weakly peraluminous composition. Alteration minerals were analyzed by a combination of petrographic and X-ray diffraction (XRD. In the River Reef Zone, the hydrothermal alteration zones can be sorted by their proximity to the primary fluid conduit and divided into inner, high-T, and low-T propylitic zones. In Watuputih Hill, the hydrothermal alteration can be divided into advanced argillic and argillic zones. The hydrothermal alteration assemblages indicated that the fluid was at a near-neutral pH in the River Reef Zone, whereas the fluid was acidic within Watuputih Hill. Because the hill is relatively distant from the River Reef Zone, the presence of these zones at Watuputih Hill may be indicative of another mineralization system beneath the hill.

GRS' research on clay rock in the Mont Terri underground laboratory

Energy Technology Data Exchange (ETDEWEB)

Wieczorek, Klaus; Czaikowski, Oliver [Gesellschaft fuer Anlagen- und Reaktorsicherheit gGmbH, Braunschweig (Germany)

2016-07-15

For constructing a nuclear waste repository and for ensuring the safety requirements are met over very long time periods, thorough knowledge about the safety-relevant processes occurring in the coupled system of waste containers, engineered barriers, and the host rock is indispensable. For respectively targeted research work, the Mont Terri rock laboratory is a unique facility where repository research is performed in a clay rock environment. It is run by 16 international partners, and a great variety of questions are investigated. Some of the work which GRS as one of the Mont Terri partners is involved in is presented in this article. The focus is on thermal, hydraulic and mechanical behaviour of host rock and/or engineered barriers.

Dissolution Methods Database

Data.gov (United States)

U.S. Department of Health & Human Services — For a drug product that does not have a dissolution test method in the United States Pharmacopeia (USP), the FDA Dissolution Methods Database provides information on...

Simulation of CO2–water–rock interactions on geologic CO2 sequestration under geological conditions of China

International Nuclear Information System (INIS)

Wang, Tianye; Wang, Huaiyuan; Zhang, Fengjun; Xu, Tianfu

2013-01-01

Highlights: • We determined the feasibilities of geologic CO 2 sequestration in China. • We determined the formation of gibbsite suggested CO 2 can be captured by rocks. • We suggested the mechanisms of CO 2 –water–rock interactions. • We found the corrosion and dissolution of the rock increased as temperature rose. -- Abstract: The main purpose of this study focused on the feasibility of geologic CO 2 sequestration within the actual geological conditions of the first Carbon Capture and Storage (CCS) project in China. This study investigated CO 2 –water–rock interactions under simulated hydrothermal conditions via physicochemical analyses and scanning electron microscopy (SEM). Mass loss measurement and SEM showed that corrosion of feldspars, silica, and clay minerals increased with increasing temperature. Corrosion of sandstone samples in the CO 2 -containing fluid showed a positive correlation with temperature. During reaction at 70 °C, 85 °C, and 100 °C, gibbsite (an intermediate mineral product) formed on the sample surface. This demonstrated mineral capture of CO 2 and supported the feasibility of geologic CO 2 sequestration. Chemical analyses suggested a dissolution–reprecipitation mechanism underlying the CO 2 –water–rock interactions. The results of this study suggested that mineral dissolution, new mineral precipitation, and carbonic acid formation-dissociation are closely interrelated in CO 2 –water–rock interactions

Haw-glass dissolution and radionuclide release: mechanism - modelling - source term

Energy Technology Data Exchange (ETDEWEB)

Grambow, B [Forschungszentrum Karlsruhe, Institut fur Nukleare, Karlsruhe (Germany)

1997-07-01

Important release controlling processes are: 1) kinetics of glass matrix dissolution (leaching), 2) formation of secondary alteration products (controlling thermodynamic solubility), 3) sorption on surfaces in the engineered barrier system and 4) formation of mobile species. Quantification of these processes requires assessment of the energetics and dynamics of the various reversible and irreversible processes within an overall open non-equilibrium system. Corrosion/dissolution of the waste matrices is not necessarily associated with a proportional release of radionuclides. The formation of new secondary phases, such as silicates, molybdates, uranates, carbonates... establishes a new geochemical barrier for re-immobilization of radionuclides dissolved from the waste matrices. The presence of iron (corroding canisters during glass alteration) reduces the solution concentration of redox sensitive radionuclides. Consequently, the container, after being corroded, constitutes an important geochemical barrier for radionuclide re-immobilization. Geochemical modelling of the long-term behaviour of glasses must be performed in an integrated way, considering simultaneous reactions of the glass, of container corrosion, of repository rock and of backfill material. Until now, only few attempts were made for integral systems modelling. (A.C.)

An Experimental Study of the Carbonation of Serpentinite and Partially Serpentinised Peridotites

Directory of Open Access Journals (Sweden)

Alicja M. Lacinska

2017-06-01

Full Text Available In situ sequestration of CO2 in mantle peridotites has been proposed as a method to alleviate the amount of anthropogenic CO2 in the atmosphere. This study presents the results of 8-month long laboratory fluid-rock experiments on representative mantle rocks from the Oman-United Arab Emirates ophiolite to investigate this process. Small core samples (3 cm long were reacted in wet supercritical CO2 and CO2-saturated brine at 100 bar and 70°C. The extent of carbonate formation, and hence the degree of carbon sequestration, varied greatly depending on rock type, with serpentinite (lizardite-dominated exhibiting the highest capacity, manifested by the precipitation of magnesite MgCO3 and ferroan magnesite (Mg,FeCO3. The carbonate precipitation occurred predominantly on the surface of the core and subordinately within cross-cutting fractures. The extent of the CO2 reactions appeared to be principally controlled by the chemical and mineralogical composition of the rock, as well as the rock texture, with all these factors influencing the extent and rate of mineral dissolution and release of Mg and Fe for subsequent reaction with the CO2. It was calculated that ≈0.7 g of CO2 was captured by reacting ≈23 g of serpentinite, determined by the mass of magnesite formed. This equates to ≈30 kg CO2 per ton of host rock, equivalent to ≈3% carbonation in half a year. However, recycling of carbonate present in veins within the original rock sample could mean that the overall amount is around 2%. The increased reactivity of serpentinite was associated with preferential dissolution of more reactive types of serpentine minerals and brucite that were mainly present in the cross-cutting veins. The bulk of the serpentinite rock was little affected. This study, using relatively short term experiments, suggests that serpentinite might be a good host rock for CO2 sequestration, although long term experiments might prove that dunite and harzburgite could be as

Seismic response of rock joints and jointed rock mass

International Nuclear Information System (INIS)

Ghosh, A.; Hsiung, S.M.; Chowdhury, A.H.

1996-06-01

Long-term stability of emplacement drifts and potential near-field fluid flow resulting from coupled effects are among the concerns for safe disposal of high-level nuclear waste (HLW). A number of factors can induce drift instability or change the near-field flow patterns. Repetitive seismic loads from earthquakes and thermal loads generated by the decay of emplaced waste are two significant factors. One of two key technical uncertainties (KTU) that can potentially pose a high risk of noncompliance with the performance objectives of 10 CFR Part 60 is the prediction of thermal-mechanical (including repetitive seismic load) effects on stability of emplacement drifts and the engineered barrier system. The second KTU of concern is the prediction of thermal-mechanical-hydrological (including repetitive seismic load) effects on the host rock surrounding the engineered barrier system. The Rock Mechanics research project being conducted at the Center for Nuclear Waste Regulatory Analyses (CNWRA) is intended to address certain specific technical issues associated with these two KTUs. This research project has two major components: (i) seismic response of rock joints and a jointed rock mass and (ii) coupled thermal-mechanical-hydrological (TMH) response of a jointed rock mass surrounding the engineered barrier system (EBS). This final report summarizes the research activities concerned with the repetitive seismic load aspect of both these KTUs

Assessment of fluoride contaminations in groundwater of hard rock aquifers in Madurai district, Tamil Nadu (India)

Science.gov (United States)

Thivya, C.; Chidambaram, S.; Rao, M. S.; Thilagavathi, R.; Prasanna, M. V.; Manikandan, S.

2017-05-01

The fluoride contamination in drinking water is already gone to the alarming level and it needs the immediate involvement and attention of all people to solve this problem. Fluoride problem is higher in hard rock terrains in worldwide and Madurai is such type of hard rock region. Totally 54 samples were collected from the Madurai district of Tamilnadu with respect to lithology. The samples collected were analysed for major cations and anions using standard procedures. The higher concentration of fluoride is noted in the Charnockite rock types of northern part of the study area. 20 % of samples are below 0.5 ppm and 6 % of samples are above 1.5 ppm exceeding the permissible limit. The affinity between the pH and fluoride ions in groundwater suggests that dissolution of fluoride bearing minerals in groundwater. The higher concentration of fluoride ions are observed in the lower EC concentration. The isotopic study suggests that fluoride is geogenic in nature. In factor scores, fluoride is noted in association with pH which indicates the dissolution process.

A kinetic model for borosilicate glass dissolution based on the dissolution affinity of a surface alteration layer

International Nuclear Information System (INIS)

Bourcier, W.L.; Peiffer, D.W.; Knauss, K.G.; McKeegan, K.D.; Smith, D.K.

1989-11-01

A kinetic model for the dissolution of borosilicate glass is used to predict the dissolution rate of a nuclear waste glass. In the model, the glass dissolution rate is controlled by the rate of dissolution of an alkali-depleted amorphous surface (gel) layer. Our model predicts that all components concentrated in the surface layer, affect glass dissolution rates. The good agreement between predicted and observed elemental dissolution rates suggests that the dissolution rate of the gel layer limits the overall rate of glass dissolution. The model predicts that the long-term rate of glass dissolution will depend mainly on ion concentrations in solution, and therefore on the secondary phases which precipitate and control ion concentrations. 10 refs., 5 figs., 1 tab

N2-fixing legumes are linked to enhanced mineral dissolution and microbiome modulations in Neotropical rainforests

Science.gov (United States)

Epihov, Dimitar; Batterman, Sarah; Hedin, Lars; Saltonstall, Kristin; Hall, Jefferson; Leake, Jonathan; Beerling, David

2017-04-01

Legumes represent the dominant family of many tropical forests with estimates of 120 billion legume trees in the Amazon basin alone. Many rainforest legume trees form symbioses with N2-fixing bacteria. In the process of atmospheric N2-fixation large amounts of nitrogen-rich litter are generated, supplying half of all nitrogen required to support secondary rainforest succession. However, it is unclear how N2-fixers affect the biogeochemical cycling of other essential nutrients by affecting the rates of mineral dissolution and rock weathering. Here we show that N2-fixing legumes in young Panamanian rainforests promote acidification and enhance silicate rock weathering by a factor of 2 compared to non-fixing trees. We report that N2-fixers also associate with enhanced dissolution of Al- and Fe-bearing secondary minerals native to tropical oxisols. In legume-rich neighbourhoods, non-fixers benefited from raised weathering rates relative to those of legume-free zones thus suggesting a positive community effect driven by N2-fixers. These changes in weathering potential were tracked by parallel functional and structural changes in the soil and rock microbiomes. Our findings support the view that N2-fixing legumes are central components of biogeochemical cycling, associated with enhanced release of Fe- and Al-bound P and primary mineral products (Mg, Mo). Rainforest legume services therefore bear important implications to short-term C cycling related to forest growth and the long-term C cycle related to marine carbonate deposition fuelled by silicate weathering.

Optimization of Dissolution Compartments in a Biorelevant Dissolution Apparatus Golem v2, Supported by Multivariate Analysis

Directory of Open Access Journals (Sweden)

Ivan Stupák

2017-11-01

Full Text Available Biorelevant dissolution instruments represent an important tool for pharmaceutical research and development. These instruments are designed to simulate the dissolution of drug formulations in conditions most closely mimicking the gastrointestinal tract. In this work, we focused on the optimization of dissolution compartments/vessels for an updated version of the biorelevant dissolution apparatus—Golem v2. We designed eight compartments of uniform size but different inner geometry. The dissolution performance of the compartments was tested using immediate release caffeine tablets and evaluated by standard statistical methods and principal component analysis. Based on two phases of dissolution testing (using 250 and 100 mL of dissolution medium, we selected two compartment types yielding the highest measurement reproducibility. We also confirmed a statistically ssignificant effect of agitation rate and dissolution volume on the extent of drug dissolved and measurement reproducibility.

Metamorphic Rock-Hosted Orogenic Gold Deposit Type as a Source of Langkowala Placer Gold, Bombana, Southeast Sulawesi

Directory of Open Access Journals (Sweden)

Arifudin Idrus

2014-06-01

Full Text Available DOI: 10.17014/ijog.v6i1.114In 2008, placer gold was discovered in Langkowala area (Bombana Regency, Southeast Sulawesi, Indonesia, and more than 60,000 traditional gold miners in the early 2009 have been operating by digging vertical pits and panning active stream sediments. The grade of placer gold ranges from 50 to 140 g/t. Local geological framework indicates that the placer gold is not related to volcanic rock-related hydrothermal gold deposit, e.g. epithermal, skarn or porphyry. This paper describes a preliminary study on possible primary deposit type as a source of the Langkowala (Bombana secondary placer gold. A field study indicates that the Langkowala (Bombana placer/paleoplacer gold is possibly related to gold-bearing quartz veins/veinlets hosted by metamorphic rocks particularly mica schist and metasediments in the area. These quartz veins/veinlets are currently recognized in metamorphic rocks at Wumbubangka Mountains, a northern flank of Rumbia Mountain Range. Sheared, segmented quartz veins/veinlets are of 2 cm to 2 m in width and contain gold in a grade varying between 2 and 61 g/t. At least, there are two generations of the quartz veins. The first generation of quartz vein is parallel to foliation of mica schist and metasediments with general orientation of N 300oE/60o; the second quartz vein generation crosscut the first quartz vein and the foliation of the wallrock. The first quartz veins are mostly sheared/deformed, brecciated, and occasionally sigmoidal, whereas the second quartz veins are relatively massive. The similar quartz veins/veinlets types are also probably present in Mendoke Mountain Range, in the northern side of Langkowala area. This primary gold deposit is called as ‘orogenic gold type’. The orogenic gold deposit could be a new target of gold exploration in Indonesia in the future.

ONKALO rock mechanics model (RMM) - Version 2.0

International Nuclear Information System (INIS)

Moenkkoenen, H.; Hakala, M.; Paananen, M.; Laine, E.

2012-02-01

The Rock Mechanics Model of the ONKALO rock volume is a description of the significant features and parameters related to rock mechanics. The main objective is to develop a tool to predict the rock properties, quality and hence the potential for stress failure which can then be used for continuing design of the ONKALO and the repository. This is the second implementation of the Rock Mechanics Model and it includes sub-models of the intact rock strength, in situ stress, thermal properties, rock mass quality and properties of the brittle deformation zones. Because of the varying quantities of available data for the different parameters, the types of presentations also vary: some data sets can be presented in the style of a 3D block model but, in other cases, a single distribution represents the whole rock volume hosting the ONKALO. (orig.)

Dissolution and compaction instabilities in geomaterials

Science.gov (United States)

Stefanou, I.; Sulem, J.; de Sauvage, J.

2014-12-01

Compaction bands play an important role in reservoir engineering and geological storage. Their presence in geological formations may also provide useful information on various geological processes. Several mechanisms can be involved at different scales and may be responsible for compaction band instabilities [1]. Compaction bands can be seen as a particular instability of the governing mathematical system leading to localization of deformation [2-4]. In a saturated porous rock, the progressive mechanical damage of the solid skeleton during compaction, results in the increase of the interface area of the reactants and consequently in the acceleration of the dissolution rate of the solid phase [2,5]. Thus, the solid skeleton is degraded more rapidly (mass removal because of dissolution), the overall mechanical properties of the system diminish (contraction of the elastic domain - chemical softening), deformations increase and the solid skeleton is further damaged (intergranular fractures, debonding, breakage of the porous network etc.). The stability of this positive feedback process is investigated analytically through linear stability analysis by considering the strong chemo-poro-mechanical coupling due to chemical dissolution. The post bifurcation behavior is then studied analytically and numerically revealing the compaction band thickness and periodicity. The effect of various parameters is studied as for instance the influence of the hydraulic diffusivity on the compaction band thickness. [1] P. Baud, S. Vinciguerra, C. David, A. Cavallo, E. Walker and T. Reuschlé (2009), Pure Appl. Geophys., 166(5-7), 869-898 [2] I. Stefanou and J. Sulem (2014), JGR: Solid Earth, 119(2), 880-899. doi:10.1002/2013JB010342I [3] J.W. Rudnicki and J.R. Rice (1975), Journal of the Mechanics and Physics of Solids 23(6),: 371-394 [4] K.A. Issen and J.W. Rudnicki (2000), JGR, 105(B9), 21529. doi:10.1029/2000JB900185 [5] R. Nova, R. Castellanza and C. Tamagnini (2003), International

Plutonium dioxide dissolution in glass

International Nuclear Information System (INIS)

Vienna, J.D.; Alexander, D.L.; Li, Hong

1996-09-01

In the aftermath of the Cold War, the U.S. Department of Energy's (DOE) Office of Fissile Materials Disposition (OFMD) is charged with providing technical support for evaluation of disposition options for excess fissile materials manufactured for the nation's defense. One option being considered for the disposition of excess plutonium (Pu) is immobilization by vitrification. The vitrification option entails immobilizing Pu in a host glass and waste package that are criticality-safe (immune to nuclear criticality), proliferation-resistant, and environmentally acceptable for long-term storage or disposal. To prove the technical and economic feasibility of candidate vitrification options it is necessary to demonstrate that PuO 2 feedstock can be dissolved in glass in sufficient quantity. The OFMD immobilization program has set a Pu solubility goal of 10 wt% in glass. The life cycle cost of the vitrification options are strongly influenced by the rate at which PUO 2 dissolves in glass. The total number of process lines needed for vitrification of 50 t of Pu in 10 years is directly dependent upon the time required for Pu dissolution in glass. The objective of this joint Pacific Northwest National Laboratory (PNNL) - Savannah River Technology Center (SRTC) study was to demonstrate a high Pu solubility in glass and to identify on a rough scale the time required for Pu dissolution in the glass. This study was conducted using a lanthanide borosilicate (LaBS) glass composition designed at the SRTC for the vitrification of actinides

Plutonium dioxide dissolution in glass

Energy Technology Data Exchange (ETDEWEB)

Vienna, J.D.; Alexander, D.L.; Li, Hong [and others

1996-09-01

In the aftermath of the Cold War, the U.S. Department of Energy`s (DOE) Office of Fissile Materials Disposition (OFMD) is charged with providing technical support for evaluation of disposition options for excess fissile materials manufactured for the nation`s defense. One option being considered for the disposition of excess plutonium (Pu) is immobilization by vitrification. The vitrification option entails immobilizing Pu in a host glass and waste package that are criticality-safe (immune to nuclear criticality), proliferation-resistant, and environmentally acceptable for long-term storage or disposal. To prove the technical and economic feasibility of candidate vitrification options it is necessary to demonstrate that PuO{sub 2} feedstock can be dissolved in glass in sufficient quantity. The OFMD immobilization program has set a Pu solubility goal of 10 wt% in glass. The life cycle cost of the vitrification options are strongly influenced by the rate at which PUO{sub 2} dissolves in glass. The total number of process lines needed for vitrification of 50 t of Pu in 10 years is directly dependent upon the time required for Pu dissolution in glass. The objective of this joint Pacific Northwest National Laboratory (PNNL) - Savannah River Technology Center (SRTC) study was to demonstrate a high Pu solubility in glass and to identify on a rough scale the time required for Pu dissolution in the glass. This study was conducted using a lanthanide borosilicate (LaBS) glass composition designed at the SRTC for the vitrification of actinides.

Dissolution of nuclear fuels

International Nuclear Information System (INIS)

Uriarte Hueda, A.; Berberana Eizmendi, M.; Rainey, R.

1968-01-01

A laboratory study was made of the instantaneous dissolution rate (IDR) for unirradiated uranium metal rods and UO 2 , PuO 2 and PuO 2 -UO 2 pellets in boiling nitric acid alone and with additives. The uranium metal and UO 2 dissolved readily in nitric acid alone; PuO 2 dissolved slowly even with the addition of fluoride; PuO 2 -UO 2 pellets containing as much as 35% PuO 2 in UO 2 gave values of the instantaneous dissolution rate to indicate can be dissolved with nitric acid alone. An equation to calculate the time for complete dissolution has been determinate in function of the instantaneous dissolution rates. The calculated values agree with the experimental. Uranium dioxide pellets from various sources but all having a same density varied in instantaneous dissolution rate. All the pellets, however, have dissolved ved in the same time. The time for complete dissolution of PuO 2 -UO 2 pellets, having the same composition, and the concentration of the used reagents are function of the used reagents are function of the fabrication method. (Author) 8 refs

Rock fracture processes in chemically reactive environments

Science.gov (United States)

Eichhubl, P.

2015-12-01

Rock fracture is traditionally viewed as a brittle process involving damage nucleation and growth in a zone ahead of a larger fracture, resulting in fracture propagation once a threshold loading stress is exceeded. It is now increasingly recognized that coupled chemical-mechanical processes influence fracture growth in wide range of subsurface conditions that include igneous, metamorphic, and geothermal systems, and diagenetically reactive sedimentary systems with possible applications to hydrocarbon extraction and CO2 sequestration. Fracture processes aided or driven by chemical change can affect the onset of fracture, fracture shape and branching characteristics, and fracture network geometry, thus influencing mechanical strength and flow properties of rock systems. We are investigating two fundamental modes of chemical-mechanical interactions associated with fracture growth: 1. Fracture propagation may be aided by chemical dissolution or hydration reactions at the fracture tip allowing fracture propagation under subcritical stress loading conditions. We are evaluating effects of environmental conditions on critical (fracture toughness KIc) and subcritical (subcritical index) fracture properties using double torsion fracture mechanics tests on shale and sandstone. Depending on rock composition, the presence of reactive aqueous fluids can increase or decrease KIc and/or subcritical index. 2. Fracture may be concurrent with distributed dissolution-precipitation reactions in the hostrock beyond the immediate vicinity of the fracture tip. Reconstructing the fracture opening history recorded in crack-seal fracture cement of deeply buried sandstone we find that fracture length growth and fracture opening can be decoupled, with a phase of initial length growth followed by a phase of dominant fracture opening. This suggests that mechanical crack-tip failure processes, possibly aided by chemical crack-tip weakening, and distributed solution-precipitation creep in the

Solutal convection induced by dissolution. Influence on erosion dynamics and interface shaping.

Science.gov (United States)

Berhanu, Michael; Philippi, Julien; Cohen, Caroline; Derr, Julien; Courrech du Pont, Sylvain

2017-04-01

Rock fractures invaded by a water flow, are often subjected to dissolution, which let grow and evolve the initial fracture network, by evacuating the eroded minerals under a solute form. In the case of fast kinetic of dissolution, local erosion rate is set by the advection of the solute. The erosion velocity decreases indeed with the solute concentration at the interface and vanishes when this concentration reaches the saturation value. Even in absence of an imposed or external flow, advection can drive the dissolution, when buoyancy effects due to gravity induce a solutal convection flow, which controls the erosive dynamics and modifies the shape of the dissolving interface. Here, we investigate using model experiments with fast dissolving materials and numerical simulations in simplified situations, solutal convection induced by dissolution. Results are interpreted regarding a linear stability analysis of the corresponding solutal Rayleigh-Benard instability. A dissolving surface is suspended above a water height, initially at rest. In a first step, solute flux is transported through a growing diffusion layer. Then after an onset time, once the layer exceeds critical width, convection flow starts under the form of falling plumes. A dynamic equilibrium results in average from births and deaths of intermittent plumes, setting the size of the solute concentration boundary layer at the interface and thus the erosion velocity. Solutal convection can also induce a pattern on the dissolving interface. We show experimentally with suspended and inclined blocks of salt and sugar, that in a linear stage, the first wavelength of the dissolution pattern corresponds to the wavelength of the convection instability. Then pattern evolves to more complex shapes due to non-linear interactions between the flow and the eroded interface. More generally, we inquire what are the conditions to observe a such solutal convection instability in geological situations and if the properties of

Evaluation of a three compartment in vitro gastrointestinal simulator dissolution apparatus to predict in vivo dissolution.

Science.gov (United States)

Takeuchi, Susumu; Tsume, Yasuhiro; Amidon, Gregory E; Amidon, Gordon L

2014-11-01

In vitro dissolution tests are performed for new formulations to evaluate in vivo performance, which is affected by the change of gastrointestinal (GI) physiology, in the GI tract. Thus, those environmental changes should be introduced to an in vitro dissolution test. Many studies have successfully shown the improvement of in vitro-in vivo correlations (IVIVC) by introducing those physiological changes into dissolution tests. The gastrointestinal simulator (GIS), a multicompartment in vitro dissolution apparatus, was developed to evaluate in vivo drug dissolution. A gastric-emptying rate along with transit rate are key factors to evaluate in vivo drug dissolution and, hence, drug absorption. Dissolution tests with the GIS were performed with Biopharmaceutical Classification System class I drugs at five different gastric-emptying rates in the fasted state. Computational models were used to determine in vivo gastric-emptying time for propranolol and metoprolol based on the GIS dissolution results. Those were compared with published clinical data to determine the gastric half-emptying time. In conclusion, the GIS is a practical tool to assess dissolution properties and can improve IVIVC. © 2014 Wiley Periodicals, Inc. and the American Pharmacists Association.

False colour backscatter electron images and their application during electron microprobe analysis of ores and host rocks

International Nuclear Information System (INIS)

Cousens, D.R.; French, D.H.; Ramsden, A.R.

1989-01-01

The limited contrast range of conventional black and white imaging does not enable full use to be made of the dynamic range of the video signal obtained from a scanning electron microscope or microprobe. The use of false colour substantially increases the information that can be derived from such images enabling relationships to be displayed that cannot be observed in black and white. This capability is now used extensively in combination with quantitative electron microprobe analysis as a research tool for ore characterization and host rocks studies related to minerals exploration in the CSIRO Div.sion of Exploration Geoscience. Thus the CAMEBAX scanning electron microprobe has been modified to allow digital images acquisition and software (IMAGE) developed which allows false colour backscatter electron (BSE) images to be obtained during the course of routine electron microprobe analysis. 1 fig

Reactivity of micas and cap-rock in wet supercritical CO_2 with SO_2 and O_2 at CO_2 storage conditions

International Nuclear Information System (INIS)

Pearce, Julie K.; Dawson, Grant K.W.; Law, Alison C.K.; Biddle, Dean; Golding, Suzanne D.

2016-01-01

Seal or cap-rock integrity is a safety issue during geological carbon dioxide capture and storage (CCS). Industrial impurities such as SO_2, O_2, and NOx, may be present in CO_2 streams from coal combustion sources. SO_2 and O_2 have been shown recently to influence rock reactivity when dissolved in formation water. Buoyant water-saturated supercritical CO_2 fluid may also come into contact with the base of cap-rock after CO_2 injection. Supercritical fluid-rock reactions have the potential to result in corrosion of reactive minerals in rock, with impurity gases additionally present there is the potential for enhanced reactivity but also favourable mineral precipitation. The first observation of mineral dissolution and precipitation on phyllosilicates and CO_2 storage cap-rock (siliciclastic reservoir) core during water-saturated supercritical CO_2 reactions with industrial impurities SO_2 and O_2 at simulated reservoir conditions is presented. Phyllosilicates (biotite, phlogopite and muscovite) were reacted in contact with a water-saturated supercritical CO_2 containing SO_2, or SO_2 and O_2, and were also immersed in the gas-saturated bulk water. Secondary precipitated sulfate minerals were formed on mineral surfaces concentrated at sheet edges. SO_2 dissolution and oxidation resulted in solution pH decreasing to 0.74 through sulfuric acid formation. Phyllosilicate dissolution released elements to solution with ∼50% Fe mobilized. Geochemical modelling was in good agreement with experimental water chemistry. New minerals nontronite (smectite), hematite, jarosite and goethite were saturated in models. A cap-rock core siltstone sample from the Surat Basin, Australia, was also reacted in water-saturated supercritical CO_2 containing SO_2 or in pure supercritical CO_2. In the presence of SO_2, siderite and ankerite were corroded, and Fe-chlorite altered by the leaching of mainly Fe and Al. Corrosion of micas in the cap-rock was however not observed as the pH was

Plutonium oxide dissolution

International Nuclear Information System (INIS)

Gray, J.H.

1992-01-01

Several processing options for dissolving plutonium oxide (PuO 2 ) from high-fired materials have been studied. The scoping studies performed on these options were focused on PuO 2 typically generated by burning plutonium metal and PuO 2 produced during incineration of alpha contaminated waste. At least two processing options remain applicable for dissolving high-fired PuO 2 in canyon dissolvers. The options involve solid solution formation of PuO 2 With uranium oxide (UO 2 ) and alloying incinerator ash with aluminum. An oxidative dissolution process involving nitric acid solutions containing a strong oxidizing agent, such as cerium (IV), was neither proven nor rejected. This uncertainty was due to difficulty in regenerating cerium (IV) ions during dissolution. However, recent work on silver-catalyzed dissolution of PuO 2 with persulfate has demonstrated that persulfate ions regenerate silver (II). Use of persulfate to regenerate cerium (IV) or bismuth (V) ions during dissolution of PuO 2 materials may warrant further study

Effect of the size of nanoparticles on their dissolution within metal-glass nanocomposites under sustained irradiation

Energy Technology Data Exchange (ETDEWEB)

Vu, T. H. Y., E-mail: thi-hai-yen.vu@polytechnique.edu; Ramjauny, Y.; Rizza, G.; Hayoun, M. [Laboratoire des Solides Irradiés, École Polytechnique, CNRS, CEA, Université Paris-Saclay, F-91128 Palaiseau (France)

2016-01-21

We investigate the dissolution law of metallic nanoparticles (NPs) under sustained irradiation. The system is composed of isolated spherical gold NPs (4–100 nm) embedded in an amorphous silica host matrix. Samples are irradiated at room temperature in the nuclear stopping power regime with 4 MeV Au ions for fluences up to 8 × 10{sup 16 }cm{sup −2}. Experimentally, the dependence of the dissolution kinetics on the irradiation fluence is linear for large NPs (45–100 nm) and exponential for small NPs (4–25 nm). A lattice-based kinetic Monte Carlo (KMC) code, which includes atomic diffusion and ballistic displacement events, is used to simulate the dynamical competition between irradiation effects and thermal healing. The KMC simulations allow for a qualitative description of the NP dissolution in two main stages, in good agreement with the experiment. Moreover, the perfect correlation obtained between the evolution of the simulated flux of ejected atoms and the dissolution rate in two stages implies that there exists an effect of the size of NPs on their dissolution and a critical size for the transition between the two stages. The Frost-Russell model providing an analytical solution for the dissolution rate, accounts well for the first dissolution stage but fails in reproducing the data for the second stage. An improved model obtained by including a size-dependent recoil generation rate permits fully describing the dissolution for any NP size. This proves, in particular, that the size effect on the generation rate is the principal reason for the existence of two regimes. Finally, our results also demonstrate that it is justified to use a unidirectional approximation to describe the dissolution of the NP under irradiation, because the solute concentration is particularly low in metal-glass nanocomposites.

Spent fuel dissolution mechanisms

International Nuclear Information System (INIS)

Ollila, K.

1993-11-01

This study is a literature survey on the dissolution mechanisms of spent fuel under disposal conditions. First, the effects of radiolysis products on the oxidative dissolution mechanisms and rates of UO 2 are discussed. These effects have mainly been investigated by using electrochemical methods. Then the release mechanisms of soluble radionuclides and the dissolution of the UO 2 matrix including the actinides, are treated. Experimental methods have been developed for measuring the grain-boundary inventories of radionuclides. The behaviour of cesium, strontium and technetium in leaching tests shows different trends. Comparison of spent fuel leaching data strongly suggests that the release of 90 Sr into the leachant can be used as a measure of the oxidation/dissolution of the fuel matrix. Approaches to the modelling UO 2 , dissolution are briefly discussed in the next chapter. Lastly, the use of natural material, uraninite, in the evaluation of the long-term performance of spent fuel is discussed. (orig.). (81 ref., 37 figs., 8 tabs.)

Natural analogue studies in crystalline rock: the influence of water-bearing fractures on radionuclide immobilisation in a granitic rock repository

International Nuclear Information System (INIS)

Alexander, W.R.; MacKenzie, A.B.; Scott, R.D.; McKinley, I.G.

1990-06-01

Current Swiss concepts for the disposal of radioactive waste involve disposal in deep mined repositories to ensure that only insignificant quantities of radionuclides will ever reach the surface and so enter the biosphere. The rock formations presently considered as potential candidates for hosting radwaste repositories have thus been selected on the basis of their capacity to isolate radionuclides from the biosphere. An important factor in ensuring such containment is a very low solute transport rate through the host formation. However, it is considered likely that, in the formations of interest in the Swiss programme (eg. granites, argillaceous sediments, anhydrite), the rocks will be fractured to some extent even at repository depth. In the instance of the cumulative failure of near-field barriers in the repository, these hydraulically connected fractures in the host formation could be very important far-field routes of migration (and possible sites of retardation) of radionuclides dissolved in the groundwaters. In this context, the so-called 'matrix diffusion' mechanism is potentially very important for radionuclide retardation. This report is the culmination of a programme which has attempted to assess the potential influence of these water-bearing fractures on radionuclide transport in a crystalline rock radwaste repository. 162 refs., 36 figs., 16 tabs

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 .

Research on Dynamic Dissolving Model and Experiment for Rock Salt under Different Flow Conditions

Directory of Open Access Journals (Sweden)

Xinrong Liu

2015-01-01

Full Text Available Utilizing deep rock salt cavern is not only a widely recognized energy reserve method but also a key development direction for implementing the energy strategic reserve plan. And rock salt cavern adopts solution mining techniques to realize building cavity. In view of this, the paper, based on the dissolving properties of rock salt, being simplified and hypothesized the dynamic dissolving process of rock salt, combined conditions between dissolution effect and seepage effect in establishing dynamic dissolving models of rock salt under different flow quantities. Devices were also designed to test the dynamic dissolving process for rock salt samples under different flow quantities and then utilized the finite-difference method to find the numerical solution of the dynamic dissolving model. The artificial intelligence algorithm, Particle Swarm Optimization algorithm (PSO, was finally introduced to conduct inverse analysis of parameters on the established model, whose calculation results coincide with the experimental data.

Interactions between wall rocks around magma and hot water. Magma shuhen no hekigan/nessui sogo sayo

Energy Technology Data Exchange (ETDEWEB)

Fujimoto, K.

1992-12-01

This paper describes interactions between wall rocks around magma and hot water. The paper discusses effects of hydrothermal environments on dynamic properties of rock minerals with respect to hydrolytic weakening (decrease in dynamic strength of a mineral under presence of water) and reaction enhanced deformation (deformation accelerated by chemical change occurring in a mineral itself). It also explains chemical reactivity of minerals under hydrothermal enviroments with respect to four types of chemical changes in minerals, factors governing mineral dissolution rates, and importance of equilibrium and non-equilibrium in main components in reactions between minerals and waters. These statements quote mainly results of indoor experiments. The paper indicates the following matters as problems to be discussed on interactions between wall rocks around intrusive rocks and hot waters: Deviation from chemical equilibrium in reactions between rocks and waters; change in permeability as a result of reactions between rocks and waters; and possibilities of hydrolytic weakening in rocks around intrusive rock bodies. 52 refs., 6 figs.

Dissolution of aluminium; Disolucion de aluminio

Energy Technology Data Exchange (ETDEWEB)

Uriarte Hueda, A; Berberana Eizmendi, M; Pereira Sanchez, G

1968-07-01

The dissolution of aluminum with acid solutions ( nitric acid-mercuric nitrate) and alkaline solutions (sodium hydroxide-sodium nitrate) has been studied. The instantaneous dissolution rate (IDR) has been studied in function of the concentration of the used reagents and the dissolution temperature. The complete dissolution has been included in the second part of this report, to know the total dissolution time, the consume of reagents and the stability of the resultant solutions. (Author)

Mineralogical controls on porosity and water chemistry during O_2-SO_2-CO_2 reaction of CO_2 storage reservoir and cap-rock core

International Nuclear Information System (INIS)

Pearce, Julie K.; Golab, Alexandra; Dawson, Grant K.W.; Knuefing, Lydia; Goodwin, Carley; Golding, Suzanne D.

2016-01-01

Reservoir and cap-rock core samples with variable lithology's representative of siliciclastic reservoirs used for CO_2 storage have been characterized and reacted at reservoir conditions with an impure CO_2 stream and low salinity brine. Cores from a target CO_2 storage site in Queensland, Australia were tested. Mineralogical controls on the resulting changes to porosity and water chemistry have been identified. The tested siliciclastic reservoir core samples can be grouped generally into three responses to impure CO_2-brine reaction, dependent on mineralogy. The mineralogically clean quartzose reservoir cores had high porosities, with negligible change after reaction, in resolvable porosity or mineralogy, calculated using X-ray micro computed tomography and QEMSCAN. However, strong brine acidification and a high concentration of dissolved sulphate were generated in experiments owing to minimal mineral buffering. Also, the movement of kaolin has the potential to block pore throats and reduce permeability. The reaction of the impure CO_2-brine with calcite-cemented cap-rock core samples caused the largest porosity changes after reaction through calcite dissolution; to the extent that one sample developed a connection of open pores that extended into the core sub-plug. This has the potential to both favor injectivity but also affect CO_2 migration. The dissolution of calcite caused the buffering of acidity resulting in no significant observable silicate dissolution. Clay-rich cap-rock core samples with minor amounts of carbonate minerals had only small changes after reaction. Created porosity appeared mainly disconnected. Changes were instead associated with decreases in density from Fe-leaching of chlorite or dissolution of minor amounts of carbonates and plagioclase. The interbedded sandstone and shale core also developed increased porosity parallel to bedding through dissolution of carbonates and reactive silicates in the sandy layers. Tight interbedded cap-rocks

The process of ghost-rock karstification and its role in the formation of cave systems

Czech Academy of Sciences Publication Activity Database

Dubois, C.; Quinif, Y.; Baele, J.-M.; Barriquand, L.; Bini, A.; Bruxelles, L.; Dandurand, G.; Havron, C.; Kaufmann, O.; Lans, B.; Maire, R.; Martin, J.; Rodet, J.; Rowberry, Matthew David; Tognini, P.; Vergari, A.

2014-01-01

Roč. 131, APR (2014), s. 116-148 ISSN 0012-8252 Institutional support: RVO:67985891 Keywords : chemical weathering * ghost-rock * karstification * limestone dissolution * speleogenesis Subject RIV: DE - Earth Magnetism, Geodesy, Geography Impact factor: 7.885, year: 2014 http://www.sciencedirect.com/science/article/pii/S0012825214000154

Study on effect of L-arginine on solubility and dissolution of Zaltoprofen: Preparation and characterization of binary and ternary cyclodextrin inclusion complexes

Science.gov (United States)

Sherje, Atul P.; Patel, Forum; Murahari, Manikanta; Suvarna, Vasanti; Patel, Kavitkumar

2018-02-01

The present study demonstrated the binary and ternary complexes of Zaltoprofen (ZPF) with β-CD and HP-β-CD. The products were characterized using solubility, in vitro dissolution, and DSC studies. The mode of interaction of guest and host was revealed through 1H NMR and FT-IR studies. A significant increase was noticed in the stability constant (Kc) and complexation efficiency (CE) of β-CD and HP-β-CD due to addition of L-Arg in ternary complexes. The ternary complexes showed greater increase in solubility and dissolution of ZPF than binary complexes. Thus, ternary system of ZPF could be an innovative approach for its solubility and dissolution enhancement.

Some Key Features and Possible Origin of the Metamorphic Rock-Hosted Gold Mineralization in Buru Island, Indonesia

Directory of Open Access Journals (Sweden)

Arifudin Idrus

2014-07-01

Full Text Available DOI: 10.17014/ijog.v1i1.172This paper discusses characteristics of some key features of the primary Buru gold deposit as a tool for a better understanding of the deposit genesis. Currently, about 105,000 artisanal and small-scale gold miners (ASGM are operating in two main localities, i.e. Gogorea and Gunung Botak by digging pits/shafts following gold-bearing quartz vein orientation. The gold extraction uses mercury (amalgamation and cyanide processing. The field study identifies two types/generations of quartz veins namely (1 Early quartz veins which are segmented, sigmoidal, dis­continous, and parallel to the foliation of host rock. The quartz vein is lack of sulfides, weak mineralized, crystalline, relatively clear, and maybe poor in gold, and (2 Quartz veins occurred within a ‘mineralized zone’ of about 100 m in width and ~1,000 m in length. The gold mineralization is strongly overprinted by an argillic alteration zone. The mineralization-alteration zone is probably parallel to the mica schist foliation and strongly controlled by N-S or NE-SW-trending structures. The gold-bearing quartz veins are characterized by banded texture particularly colloform following host rock foliation and sulphide banding, brecciated, and rare bladed-like texture. The alteration types consist of propylitic (chlorite, calcite, sericite, argillic, and carbonation represented by graphite banding and carbon flakes. The ore mineralization is characterized by pyrite, native gold, pyrrhotite, and arsenopyrite. Cinnabar, stibnite, chalcopyrite, galena, and sphalerite are rare or maybe absent. In general, sulphide minerals are rare (<3%. Fifteen rock samples were collected in Wamsaid area for geochemical assaying for Au, Ag, As, Sb, Hg, Cu, Pb, and Zn. Eleven of fifteen samples yielded more than 1.00 g/t Au, in which six of them are in excess of 3.00 g/t Au. It can be noted that all high-grade samples are originally or containing limonitic materials, that suggest

Experimental thermomechanical damage as first approach to understand the petrophysical behavior of the granitic host-rocks from an active fractured-geothermal system (Liquiñe, Chile - 39º S)

Science.gov (United States)

Molina Piernas, E.; Sepúlveda, J.; Arancibia, G.; Roquer, T.; Morata, D.; Bracke, R.; Vázquez, P.

2017-12-01

Chile's location along an active subduction zone has endowed it with a high geothermal potential. However, a better understanding of the thermomechanical and fluid transport properties of rocks is required to assess the potential of geothermal systems and thereby enhance the possibilities for their use. We have focused in the area surrounding Liquiñe, in the Southern Andean Volcanic Zone (Chile, 39º S). This area hosts several recent thermal manifestations, predominantly hot springs, and it is affected by the Liquiñe-Ofqui Fault Zone (LOFZ), which controls the position of the modern volcanic arc in southern Chile and cuts the Patagonian batholith. We have carried out experimental analyzes in order to understand this geothermal system and the influence of the thermomechanical features over the granitic host-rocks (low-porous crystalline rocks). To do this, physical properties such as capillary water absorption coefficient, Vp-wave velocity and compressive resistance were evaluated before and after heating rock samples at 150 ºC and 210 ºC (at ambient pressure) in an oven at a heating rate of 6 °C/min and maintaining the maximum temperature for 4 hours. The cooling rate was less than 2 °C/min to avoid shrinkage phenomena. The results show that the damage by heat was greater at 210 ºC than 150 ºC, likely due to an increased capillary coefficient ( 30% and 25%). On the contrary, Vpvelocity ( -19% and -13%) and compressive resistance ( -27% in both cases) decreased, with respect to unheated samples. Consequently, we can infer an inherent effect on the later fracture process due to the thermal stress when this granitic body was at depth. After that, and considering the local and regional strain-stress state, both factors have facilitated the fluid flow, increasing the permeability of this granitic host-rock allowing the presence of hot-springs. Future work will be to acquire complementary petrophysical parameters, such as porosity, permeability, thermal

Emplacement, petrological and magnetic susceptibility characteristics of diverse magmatic epidote-bearing granitoid rocks in Brazil, Argentina and Chile

Science.gov (United States)

Sial, A. N.; Toselli, A. J.; Saavedra, J.; Parada, M. A.; Ferreira, V. P.

1999-03-01

Magmatic epidote (mEp)-bearing granitoids from five Neoproterozoic tectonostratigraphic terranes in Northeastern (NE) Brazil, Early Palaeozoic calc-alkalic granitoids in Northwestern (NW) Argentina and from three batholiths in Chile have been studied. The elongated shape of some of these plutons suggests that magmas filled fractures and that dyking was probably the major mechanism of emplacement. Textures reveal that, in many cases, epidote underwent partial dissolution by host magma and, in these cases, may have survived dissolution by relatively rapid upward transport by the host magma. In plutons where such a mechanism is not evident, unevenly distributed epidote at outcrop scale is armoured by biotite or near-solidus K-feldspar aggregates, which probably grew much faster than epidote dissolution, preventing complete resorption of epidote by the melt. Al-in-hornblende barometry indicates that, in most cases, amphibole crystallized at P≥5 kbar. Kyanite-bearing thermal aureoles surrounding plutons that intruded low-grade metamorphic rocks in NE Brazil support pluton emplacement at intermediate to high pressure. mEp show overall chemical variation from 20 to 30 mol% (mole percent) pistacite (Ps) and can be grouped into two compositional ranges: Ps 20-24 and Ps 27-30. The highest Ps contents are in epidotes of plutons in which hornblende solidified under Pcorrosion of individual epidote crystals included in plagioclase in high-K calc-alkalic granitoids in NE Brazil, emplaced at 5-7 kbar pressure, yielded estimates of magma transport rate from 70 to 350 m year -1. Most of these plutons lack Fe-Ti oxide minerals and Fe +3 is mostly associated with the epidote structure. Consequently, magnetic susceptibility (MS) in the Neoproterozoic granitoids in NE Brazil, as well as Early Palaeozoic plutons in Argentina and Late Palaeozoic plutons in Chile, is usually low (3.0×10 -3 SI, typical of magnetite-series granitoids crystallized under higher oxygen fugacity. In NE

Effect of sodium lauryl sulfate in dissolution media on dissolution of hard gelatin capsule shells.

Science.gov (United States)

Zhao, Fang; Malayev, Vyacheslav; Rao, Venkatramana; Hussain, Munir

2004-01-01

Sodium lauryl sulfate (SLS) is a commonly used surfactant in dissolution media for poorly water soluble drugs. However, it has occasionally been observed that SLS negatively impacts the dissolution of drug products formulated in gelatin capsules. This study investigated the effect of SLS on the dissolution of hard gelatin capsule shells. The USP paddle method was used with online UV monitoring at 214 nm (peptide bond). Empty size #0 capsule shells were held to the bottom of the dissolution vessel by magnetic three-prong sinkers. SLS significantly slowed down the dissolution of gelatin shells at pH < 5. Visually, the gelatin shells transformed into some less-soluble precipitate under these conditions. This precipitate was found to contain a higher sulfur content than the gelatin control sample by elemental analysis, indicating that SLS is part of the precipitate. Additionally, the slowdown of capsule shell dissolution was shown to be dependent on the SLS concentration and the ionic strength of the media. SLS interacts with gelatin to form a less-soluble precipitate at pH < 5. The use of SLS in dissolution media at acidic pH should be carefully evaluated for gelatin capsule products.

Geochemistry of vanadium in an epigenetic, sandstone-hosted vanadium- uranium deposit, Henry Basin, Utah

Science.gov (United States)

Wanty, R.B.; Goldhaber, M.B.; Northrop, H.R.

1990-01-01

The epigenetic Tony M vanadium-uranium orebody in south-central Utah is hosted in fluvial sandstones of the Morrison Formation (Upper Jurassic). Measurements of the relative amounts of V+3 and V +4 in ore minerals show that V+3 is more abundant. Thermodynamic calculations show that vanadium was more likely transported to the site of mineralization as V+4. The ore formed as V+4 was reduced by hydrogen sulfide, followed by hydrolysis and precipitation of V+3 in oxide minerals or chlorite. Uranium was transported as uranyl ion (U+6), or some complex thereof, and reduced by hydrogen sulfide, forming coffinite. Detrital organic matter in the rocks served as the carbon source for sulfate-reducing bacteria. Vanadium most likely was derived from the dissolution of iron-titanium oxides. Uranium probably was derived from the overlying Brushy Basin Member of the Morrison Formation. Previous studies have shown that the ore formed at the density-stratified interface between a basinal brine and dilute meteoric water. The mineralization processes described above occurred within the mixing zone between these two fluids. -from Authors

Carbonation by fluid-rock interactions at high-pressure conditions: Implications for carbon cycling in subduction zones

Science.gov (United States)

Piccoli, Francesca; Vitale Brovarone, Alberto; Beyssac, Olivier; Martinez, Isabelle; Ague, Jay J.; Chaduteau, Carine

2016-07-01

Carbonate-bearing lithologies are the main carbon carrier into subduction zones. Their evolution during metamorphism largely controls the fate of carbon, regulating its fluxes between shallow and deep reservoirs. Recent estimates predict that almost all subducted carbon is transferred into the crust and lithospheric mantle during subduction metamorphism via decarbonation and dissolution reactions at high-pressure conditions. Here we report the occurrence of eclogite-facies marbles associated with metasomatic systems in Alpine Corsica (France). The occurrence of these marbles along major fluid-conduits as well as textural, geochemical and isotopic data indicating fluid-mineral reactions are compelling evidence for the precipitation of these carbonate-rich assemblages from carbonic fluids during metamorphism. The discovery of metasomatic marbles brings new insights into the fate of carbonic fluids formed in subducting slabs. We infer that rock carbonation can occur at high-pressure conditions by either vein-injection or chemical replacement mechanisms. This indicates that carbonic fluids produced by decarbonation reactions and carbonate dissolution may not be directly transferred to the mantle wedge, but can interact with slab and mantle-forming rocks. Rock-carbonation by fluid-rock interactions may have an important impact on the residence time of carbon and oxygen in subduction zones and lithospheric mantle reservoirs as well as carbonate isotopic signatures in subduction zones. Furthermore, carbonation may modulate the emission of CO2 at volcanic arcs over geological time scales.

Uranium mobility in mine areas: evaluation of the water-rock interaction

Energy Technology Data Exchange (ETDEWEB)

Zuddas, P. [UFR Sciences de la Terre. PEPS. Universite Claude Bernard. Lyon (France); Rocha Scislewski, A.; Faivre, D.; Lopez, O. [Institut de Physique du Globe de Paris (France)

2005-07-01

Full text of publication follows: Toxicity and natural radioactivity of uranium are among the main environmental concerns for exploitation and processing of uranium ore. Weathering processes and potential contamination paths of these areas have to be identified to preserve the water resources. In this work, leaching experiments were carried out in flow-through reactors. Approximately 750 g of crushed rock of selected grain size between 0.35 and 0.80 mm were introduced into a Pyrex column. Distilled and deionized water, saturated with 5% CO{sub 2}/95% air mixture, was introduced through a glass inlet fitted at the base of the column. Input solution pH was constantly equal to 4.2 while the low flow rate was obtained from a peristaltic pump. The output solution was sampled periodically for about 1 year. Three different rock samples were used: an untreated granite rock with high levels of uranium minerals, a rock with low uranium content and a rock rejected after the lixiviation process for uranium industrial extraction. For untreated rocks pH and silica decrease by 1-2 orders of magnitude while sodium decreases by 2-3 orders of magnitude. This indicates the strong albitite dissolution. Total dissolved uranium has a rather constant level indicating the constant dissolution rate of the uranium mineral assemblage. Thermodynamic modelling of the interacting output solutions indicates that 80% of the dissolved uranium content is under the form of two main carbonate complexes (i.e. UO{sub 2}(CO{sub 3}){sub 2}{sup 2-} and UO{sub 2}(CO{sub 3}){sub 3}{sup 4-}), while solutions are saturated on chalcedony, kaolinite and calcium clay minerals. Solutions are under saturated with respect to uraninite and low-temperature albite. In experiments where material was treated with sulphuric acid in the plant, pH is constantly equal to 4 indicating the lack of rock buffering properties. Na, Ca, and SO{sub 4} decrease by several orders of magnitude (from some initial mmol/kg) reaching

Aqueous Alteration of Endeavour Crater Rim Apron Rocks

Science.gov (United States)

Ming, D. W.; Mittlefehldt, D. W.; Gellert, R.; Clark, B. C.; Morris, R. V.; Yen, A. S.; Arvidson, R. E.; Crumpler, L. S.; Farrand, W. H.; Grant, J. A., III; Jolliff, B. L.; Parker, T. J.; Peretyazhko, T.

2014-12-01

Mars Exploration Rover Opportunity is exploring Noachian age rocks of the rim of 22 km diameter Endeavour crater. Overlying the pre-impact lithologies and rim breccias is a thin apron of fine-grained sediments, the Grasberg fm, forming annuli on the lower slopes of rim segments. Hesperian Burns fm sandstones overly the Grasberg fm. Grasberg rocks have major element compositions that are distinct from Burns fm sandstones, especially when comparing interior compositions exposed by the Rock Abrasion Tool. Grasberg rocks are also different from Endeavour rim breccias, but have general compositional similarities to them. Grasberg sediments are plausibly fine-grained materials derived from the impact breccias. Veins of CaSO4 transect Grasberg fm rocks demonstrating post-formation aqueous alteration. Minor/trace elements show variations consistent with mobilization by aqueous fluids. Grasberg fm rocks have low Mn and high Fe/Mn ratios compared to the other lithologies. Manganese likely was mobilized and removed from the Grasberg host rock by redox reactions. We posit that Fe2+ from acidic solutions associated with formation of the Burns sulfate-rich sandstones acted as an electron donor to reduce more oxidized Mn to Mn2+. The Fe contents of Grasberg rocks are slightly higher than in other rocks suggesting precipitation of Fe phases in Grasberg materials. Pancam spectra show that Grasberg rocks have a higher fraction of ferric oxide minerals than other Endeavour rim rocks. Solutions transported Mn2+ into the Endeavour rim materials and oxidized and/or precipitated it in them. Grasberg has higher contents of the mobile elements K, Zn, Cl, and Br compared to the rim materials. Similar enrichments of mobile elements were measured by the Spirit APXS on West Spur and around Home Plate in Gusev crater. Enhancements in these elements are attributed to interactions of hydrothermal acidic fluids with the host rocks. Interactions of fluids with the Grasberg fm postdate the genesis

Mathematical modeling of drug dissolution.

Science.gov (United States)

Siepmann, J; Siepmann, F

2013-08-30

The dissolution of a drug administered in the solid state is a pre-requisite for efficient subsequent transport within the human body. This is because only dissolved drug molecules/ions/atoms are able to diffuse, e.g. through living tissue. Thus, generally major barriers, including the mucosa of the gastro intestinal tract, can only be crossed after dissolution. Consequently, the process of dissolution is of fundamental importance for the bioavailability and, hence, therapeutic efficacy of various pharmaco-treatments. Poor aqueous solubility and/or very low dissolution rates potentially lead to insufficient availability at the site of action and, hence, failure of the treatment in vivo, despite a potentially ideal chemical structure of the drug to interact with its target site. Different physical phenomena are involved in the process of drug dissolution in an aqueous body fluid, namely the wetting of the particle's surface, breakdown of solid state bonds, solvation, diffusion through the liquid unstirred boundary layer surrounding the particle as well as convection in the surrounding bulk fluid. Appropriate mathematical equations can be used to quantify these mass transport steps, and more or less complex theories can be developed to describe the resulting drug dissolution kinetics. This article gives an overview on the current state of the art of modeling drug dissolution and points out the assumptions the different theories are based on. Various practical examples are given in order to illustrate the benefits of such models. This review is not restricted to mathematical theories considering drugs exhibiting poor aqueous solubility and/or low dissolution rates, but also addresses models quantifying drug release from controlled release dosage forms, in which the process of drug dissolution plays a major role. Copyright © 2013 Elsevier B.V. All rights reserved.

Research on geochronology and uranium source of sandstone-hosted uranium ore-formation in major uranium-productive basins, Northern-China

International Nuclear Information System (INIS)

Xia Yuliang; Liu Hanbin; Lin Jinrong; Fan Guang; Hou Yanxian

2004-12-01

A method is developed for correcting uranium content in uranium ore samples by considering the U-Ra equilibrium coefficient, then a U-Pb isochron is drawn up. By performing the above correction ore-formation ages of sandstone-hosted uranium mineralization which may be more realistic have been obtained. The comparative research on U-Pb isotopic ages of detritic zircon in ore-hosting sandstone and zircon in intermediate-acid igneous rocks in corresponding provenance area indicates that the ore-hosting sandstone is originated from the erosion of intermediate-acid igneous rocks and the latters are the material basis for the formation of the uranium-rich sandstone beds. On the basis of the study on U-Pb isotopic system evolution of the provenance rocks and sandstones from ore-hosting series, it is verified that the uranium sources of the sandstone-hosted uranium deposit are: the intermediate-acid igneous rocks with high content of mobile uranium, and the sandstone bodies pre-concentrated uranium. (authors)

Dissolution of two NWCF calcines: Extent of dissolution and characterization of undissolved solids

International Nuclear Information System (INIS)

Brewer, K.N.; Herbst, R.S.; Tranter, T.J.

1995-01-01

A study was undertaken to determine the dissolution characteristics of two NWCF calcine types. A two-way blended calcine made from 4 parts nonradioactive aluminum nitrate and one part WM-102 was studied to determine the extent of dissolution for aluminum-type calcines. A two-way blend of 3.5 parts fluorinel waste from WM-187 and 1 part sodium waste from WM-185 was used to determine the extent of dissolution for zirconium-type calcines. This study was necessary to develop suitable aqueous separation flowsheets for the partitioning of actinides and fission products from ICPP calcines and to determine the disposition of the resulting undissolved solids (UDS). The dissolution flowsheet developed by Herbst was used to dissolve these two NWCF calcine types. Results show that greater than 95 wt% of aluminum and zirconium calcine types were dissolved after a single batch contact with 5 M HNO 3 . A characterization of the UDS indicates that the weight percent of TRU elements in the UDS resulting from both calcine type dissolutions increases by approximately an order of magnitude from their concentrations prior to dissolution. Substantial activities of cesium and strontium are also present in the UDS resulting from the dissolution of both calcine types. Multiple TRU, Cs, and Sr analyses of both UDS types show that these solids are relatively homogeneous. From this study, it is estimated that between 63.5 and 635 cubic meters of UDS will be generated from the dissolution of 3800 M 3 of calcine. The significant actinide and fission product activities in these UDS will preclude their disposal as low-level waste. If the actinide and fission activity resulting from the UDS is the only considered source in the dissolved calcine solutions, an estimated 99.9 to 99.99 percent of the solids must be removed from this solution for it to meet non-TRU Class A low-level waste

Leaching of boron, arsenic and selenium from sedimentary rocks: II. pH dependence, speciation and mechanisms of release

Energy Technology Data Exchange (ETDEWEB)

Tabelin, Carlito Baltazar, E-mail: carlito@trans-er.eng.hokudai.ac.jp [Laboratory of Soil Environment Engineering, Faculty of Engineering, Hokkaido University, Sapporo (Japan); Hashimoto, Ayaka, E-mail: a.hashimoto@diaconsult.co.jp [DIA Consultants Co. Ltd., Sapporo (Japan); Igarashi, Toshifumi, E-mail: tosifumi@eng.hokudai.ac.jp [Laboratory of Groundwater and Mass Transport, Faculty of Engineering, Hokkaido University, Sapporo (Japan); Yoneda, Tetsuro, E-mail: yonet@eng.hokudai.ac.jp [Laboratory of Soil Environment Engineering, Faculty of Engineering, Hokkaido University, Sapporo (Japan)

2014-03-01

Sedimentary rocks excavated in Japan from road- and railway-tunnel projects contain relatively low concentrations of hazardous trace elements like boron (B), arsenic (As) and selenium (Se). However, these seemingly harmless waste rocks often produced leachates with concentrations of hazardous trace elements that exceeded the environmental standards. In this study, the leaching behaviors and release mechanisms of B, As and Se were evaluated using batch leaching experiments, sequential extraction and geochemical modeling calculations. The results showed that B was mostly partitioned with the residual/crystalline phase that is relatively stable under normal environmental conditions. In contrast, the majority of As and Se were associated with the exchangeable and organics/sulfides phases that are unstable under oxidizing conditions. Dissolution of water-soluble phases controlled the leaching of B, As and Se from these rocks in the short term, but pyrite oxidation, calcite dissolution and adsorption/desorption reactions became more important in the long term. The mobilities of these trace elements were also strongly influenced by the pH of the rock-water system. Although the leaching of Se only increased in the acidic region, those of B and As were enhanced under both acidic and alkaline conditions. Under strongly acidic conditions, the primarily release mechanism of B, As and Se was the dissolution of mineral phases that incorporated and/or adsorbed these elements. Lower concentrations of these trace elements in the circumneutral pH range could be attributed to their strong adsorption onto minerals like Al-/Fe-oxyhydroxides and clays, which are inherently present and/or precipitated in the rock-water system. The leaching of As and B increased under strongly alkaline conditions because of enhanced desorption and pyrite oxidation while that of Se remained minimal due to its adsorption onto Fe-oxyhydroxides and co-precipitation with calcite. - Highlights: • The bulk of

UO2 dissolution rates: A review

International Nuclear Information System (INIS)

McKenzie, W.F.

1992-09-01

This report reviews literature data on UO 2 dissolution kinetics and provides a framework for guiding future experimental studies as well as theoretical modeling studies. Under oxidizing conditions, UO 2 dissolution involves formation of an oxidized surface layer which is then dissolved by formation of aqueous complexes. Higher oxygen pressures or other oxidants are required at higher temperatures to have dissolution rates independent of oxygen pressure. At high oxygen pressures (1-5 atm, 25-70 C), the dissolution rate has a one-half order dependence on oxygen pressure, whereas at oxygen pressures below 0.2 atm, Grandstaff (1976), but nobody else, observed a first-order dependence on dissolution rate. Most people found a first-order dependence on carbonate concentration; Posey-Dowty (1987) found independence of carbonate at pH 7 to 8.2. Dissolution rates increase with temperature except in experiments involving granitic groundwater. Dissolution rates were generally greater under acid or basic conditions than near neutral pH

The initial stages of NaCl dissolution: Ion or ion pair solvation?

Science.gov (United States)

Klimes, Jiri; Michaelides, Angelos

2009-03-01

The interaction of water with rock salt (NaCl) is important in a wide variety of natural processes and human activities. A lot is known about NaCl dissolution at the macroscopic level but we do not yet have a detailed atomic scale picture of how salt crystals dissolve. Here we report an extensive series of density functional theory, forcefield and molecular dynamics studies of water clusters at flat and defective NaCl surfaces and NaCl clusters. The focus is on answering seemingly elementary questions such as how many water molecules are needed before it becomes favorable to extract an ion or a pair of ions from the crystal or the cluster. It turns out, however, that the answers to these questions are not so straightforward: below a certain number of water molecules (˜ 12) solvation of individual ions is less costly and above this number solvation of ion pairs is favored. These results reveal a hitherto unknown complexity in the NaCl dissolution process born out of a subtle interplay between water-water and water-ion interactions.

Processes of water rock interaction in the Turonian aquifer of Oum Er-Rabia Basin, Morocco

Science.gov (United States)

Ettazarini, Said

2005-12-01

Possible water rock interaction processes, in the Moroccan basin of Oum Er-Rabia, were discussed by a geochemical study of groundwater from the Turonian limestone aquifer, the most important water resource in the region. Different types of water according to the classification of Piper were defined. Waters have shown an evolution from dominant CHO3 Ca Mg type through mixed to SO4 Cl Ca Mg type. The use of geochemical diagrams and chemical speciation modeling method has shown that water rock interaction is mainly controlled by carbonate and anhydrite dissolution, ion exchange and reverse ion exchange processes. Water rock equilibrium conditions are favorable for the precipitation of calcite, dolomite, kaolinite and magnesian smectite.

Nectonema zealandica n. sp. (Nematomorpha: Nectonematoidea) parasitising the purple rock crab Hemigrapsus edwardsi (Brachyura: Decapoda) in New Zealand, with notes on the prevalence of infection and host defence reactions.

Science.gov (United States)

Poinar, G; Brockerhoff, A M

2001-10-01

A new species of marine hairworm, Nectonema zealandica (Nematomorpha: Nectonematoidea), is described from the purple rock crab Hemigrapsus edwardsi Hilgendorf from the South Island, New Zealand. This is the first record of Nectonema in the South Pacific Ocean and the southernmost locality for the genus. The description is based on juveniles and pre-adults taken from crabs. The new species is characterised by its stomal structure, presence of four cephalic papillae, mesenchyme arranged in eight lobes in pre-adults, insertion of muscle layer increasing body diameter at the septum and translucent anterior chamber. Data on the prevalence of infection over a three-year period, rates of parasitism in relation to host sex and size, and host defence reactions are presented. A list of all reported hosts of nectonematids is included.

Metamorphic rock-hosted orogenic gold deposit style at Bombana (Southeast Sulawesi and Buru Island (Maluku: Their key features and significances for gold exploration in Eastern Indonesia

Directory of Open Access Journals (Sweden)

Arifudin Idrus

2017-06-01

Full Text Available In Indonesia, gold is commonly mined from epithermal-, porphyry-, and skarn-type deposits that are commonly found in volcanic belts along island arcs or active continental margin settings. Numerous gold prospects, however, were recently discovered in association with metamorphic rocks. This paper focuses on metamorphic rock-hosted gold mineralization in Eastern Indonesia, in particular the Bombana (SE Sulawesi and Buru Island (Maluku prospects. At Bombana, gold-bearing quartz-veins are hosted by the Pompangeo metamorphic complex. Sheared, segmented veins vary in thickness from 2 cm to 2 m. Gold is mainly present in the form of ‘free gold’ among silicate minerals and closely related to cinnabar, stibnite, tripuhyite, and in places, minor arsenopyrite. The gold distribution is erratic, however, ranging from below detection limit up to 134 g/t. At least three generations of veins are identified. The first is parallel to the foliation, the second crosscuts the first generation of veins as well as the foliation, and the late-stage laminated deformed quartz-calcite vein represents the third mineralization stage. The early veins are mostly massive to crystalline, occasionally brecciated, and sigmoidal, whereas the second-stage veins are narrower than the first ones and less subjected to brecciation. Gold grades in the second- and third-stage veins are on average higher than that in the earlier veins. Microthermometric and Raman spectrometric studies of fluid inclusions indicate abundant H2O-NaCl and minor H2O-NaCl-CO2 fluids. Homogenization temperatures and salinities vary from 114 to 283 ºC and 0.35 to 9.08 wt.% NaCl eq., respectively. Crush-leach analysis of fluid inclusions suggests that the halogen fluid chemistry is not identical to sea water, magmatic or epithermal related fluids, but tends to be similar to fluids in mesothermal-type gold deposits. In Buru Island (Gunung Botak and Gogorea prospects, two distinct generations of quartz veins

Fracture characteristics in Japanese rock

International Nuclear Information System (INIS)

Ijiri, Yuji; Sawada, Atsushi; Akahori, Kuniaki

1999-11-01

It is crucial for the performance assessment of geosphere to evaluate the characteristics of fractures that can be dominant radionuclide migration pathways from a repository to biosphere. This report summarizes the characteristics of fractures obtained from broad literature surveys and the fields surveys at the Kamaishi mine in northern Japan and at outcrops and galleries throughout the country. The characteristics of fractures described in this report are fracture orientation, fracture shape, fracture frequency, fracture distribution in space, transmissivity of fracture, fracture aperture, fracture fillings, alteration halo along fracture, flow-wetted surface area in fracture, and the correlation among these characteristics. Since granitic rock is considered the archetype fractured media, a large amount of fracture data is available in literature. In addition, granitic rock has been treated as a potential host rock in many overseas programs, and has JNC performed a number of field observations and experiments in granodiorite at the Kamaishi mine. Therefore, the characteristics of fractures in granitic rock are qualitatively and quantitatively clarified to some extent in this report, while the characteristics of fractures in another rock types are not clarified. (author)

Formation of chemical gardens on granitic rock. A new type of alteration for alkaline systems

Energy Technology Data Exchange (ETDEWEB)

Satoh, Hisao [Mitsubishi Materials Corporation, Naka (Japan). Energy Project and Technology Center; Tsukamoto, Katsuo [Tohoku Univ. Aramaki, Sendai (Japan). Dept. of Earth and Planetary Materials Science; Garcia-Ruiz, Juan Manuel [Granada Univ., Armilla (Spain). Lab. de Estudios Cristalograficos

2014-06-15

In order to understand the groundwater flow at near-underground facilities such as waste repositories, we have studied the effects of flowing an alkaline solution leached from cementitious building materials through the fractures of low-porosity granitic rocks under laboratory conditions. The results show that silica released from the dissolution of sodium-rich plagioclase and quartz reacts with the calcium leached from cementitious buildings to form calcium silicate hydrates (C-S-H) phases in the form of hollow tubular structures. These tubular structures form selectively on the surface of plagioclase in a similar way to reverse silica gardens structures. It was found that the rate of precipitation of C-S-H phases is faster than the rate of dissolution of plagioclase. This selftriggered dissolution/precipitation phenomenon may be an important factor controlling groundwater permeation in natural alkaline underground systems.

Formation of chemical gardens on granitic rock. A new type of alteration for alkaline systems

International Nuclear Information System (INIS)

Satoh, Hisao; Tsukamoto, Katsuo; Garcia-Ruiz, Juan Manuel

2014-01-01

In order to understand the groundwater flow at near-underground facilities such as waste repositories, we have studied the effects of flowing an alkaline solution leached from cementitious building materials through the fractures of low-porosity granitic rocks under laboratory conditions. The results show that silica released from the dissolution of sodium-rich plagioclase and quartz reacts with the calcium leached from cementitious buildings to form calcium silicate hydrates (C-S-H) phases in the form of hollow tubular structures. These tubular structures form selectively on the surface of plagioclase in a similar way to reverse silica gardens structures. It was found that the rate of precipitation of C-S-H phases is faster than the rate of dissolution of plagioclase. This selftriggered dissolution/precipitation phenomenon may be an important factor controlling groundwater permeation in natural alkaline underground systems.

The dissolution phenomenon of lysozyme crystals

Energy Technology Data Exchange (ETDEWEB)

Mueller, C.; Ulrich, J. [Martin Luther University Halle-Wittenberg, Department of Thermal Separation Processes, Centre of Engineering Science, Halle/Saale (Germany)

2012-02-15

Dissolution studies on lysozyme crystals were carried out since the observed dissolution pattern look different from non-protein dissolved crystals. The Tetragonal, High Temperature and Low Temperature Orthorhombic morphologies, crystallized using sodium chloride, were chosen and the influence of different pH, salt and protein concentration on their dissolution was investigated. An increase in pH and/or salt concentration can modify the dissolution behaviour. The pattern of the crystals during the dissolution process will, therefore, develop differently. Frequently a skeleton like crystal pattern followed by a falling apart of the crystals is observed. The multi-component character of the lysozyme crystal (protein, water, buffer, salt) as well as ''solvatomorphism'' gives first insights in the phenomena happening in the dissolution process. (copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

Rock mass mechanical property estimations for the Yucca Mountain Site Characterization Project

International Nuclear Information System (INIS)

Lin, M.; Hardy, M.P.; Bauer, S.J.

1993-06-01

Rock mass mechanical properties are important in the design of drifts and ramps. These properties are used in evaluations of the impacts of thermomechanical loading of potential host rock within the Yucca Mountain Site Characterization Project. Representative intact rock and joint mechanical properties were selected for welded and nonwelded tuffs from the currently available data sources. Rock mass qualities were then estimated using both the Norwegian Geotechnical Institute (Q) and Geomechanics Rating (RMR) systems. Rock mass mechanical properties were developed based on estimates of rock mass quality, the current knowledge of intact properties, and fracture/joint characteristics. Empirical relationships developed to correlate the rock mass quality indices and the rock mass mechanical properties were then used to estimate the range of rock mass mechanical properties

Rocks and geology in the San Francisco Bay region

Science.gov (United States)

Stoffer, Philip W.

2002-01-01

The landscape of the San Francisco Bay region is host to a greater variety of rocks than most other regions in the United States. This introductory guide provides illustrated descriptions of 46 common and important varieties of igneous, sedimentary, and metamorphic rock found in the region. Rock types are described in context of their identification qualities, how they form, and where they occur in the region. The guide also provides discussion about of regional geology, plate tectonics, the rock cycle, the significance of the selected rock types in relation to both earth history and the impact of mineral resources on the development in the region. Maps and text also provide information where rocks, fossils, and geologic features can be visited on public lands or in association with public displays in regional museums, park visitor centers, and other public facilities.

Assessing the effect of dissolved organic ligands on mineral dissolution rates: An example from calcite dissolution

International Nuclear Information System (INIS)

DeMaio, T.; Grandstaff, D.E.

1997-01-01

Experiments suggest that dissolved organic ligands may primarily modify mineral dissolution rates by three mechanisms: (1) metal-ligand (M-L) complex formation in solution, which increases the degree of undersaturation, (2) formation of surface M-L complexes that attack the surface, and (3) formation of surface complexes which passivate or protect the surface. Mechanisms (1) and (2) increase the dissolution rate and the third decreases it compared with organic-free solutions. The types and importance of these mechanisms may be assessed from plots of dissolution rate versus degree of undersaturation. To illustrate this technique, calcite, a common repository cementing and vein-filling mineral, was dissolved at pH 7.8 and 22 C in Na-Ca-HCO 3 -Cl solutions with low concentrations of three organic ligands. Low citrate concentrations (50 microM) increased the dissolution rate consistent with mechanism (1). Oxalate decreased the rate, consistent with mechanism (3). Low phthalate concentration (<50 microM) decreased calcite dissolution rates; however, higher concentrations increased the dissolution rates, which became faster than in inorganic solutions. Thus, phthalate exhibits both mechanisms (2) and (3) at different concentrations. In such cases linear extrapolations of dissolution rates from high organic ligand concentrations may not be valid

Climax Granite, Nevada Test Site, as a host for a rock mechanics test facility related to the geologic disposal of high level nuclear wastes

International Nuclear Information System (INIS)

Heuze, F.E.

1981-02-01

This document discusses the potential of the Climax pluton, at the Nevada Test Site, as the host for a granite mechanics test facility related to the geologic disposal of high-level nuclear waste. The Climax granitic pluton has been the site of three nuclear weapons effects tests: Hard Hat, Tiny Tot, and Piledriver. Geologic exploration and mapping of the granite body were performed at the occasion of these tests. Currently, it is the site Spent Fuel Test (SFT-C) conducted in the vicinity of and at the same depth as that of the Piledriver drifts. Significant exploration, mapping, and rock mechanics work have been performed and continue at this Piledriver level - the 1400 (ft) level - in the context of SFT-C. Based on our technical discussions, and on the review of the significant geological and rock mechanics work already achieved in the Climax pluton, based also on the ongoing work and the existing access and support, it is concluded that the Climax site offers great opportunities for a rock mechanics test facility. It is not claimed, however, that Climax is the only possible site or the best possible site, since no case has been made for another granite test facility in the United States. 12 figures, 3 tables

Engineering rock mass classification of the Olkiluoto investigation site

Energy Technology Data Exchange (ETDEWEB)

Aeikaes, K. [ed.; Hagros, A.; Johansson, E. [Saanio and Riekkola Consulting Engineers, Helsinki (Finland)] [and others

2000-06-01

Olkiluoto in Eurajoki is being investigated as a possible site for the final disposal of spent nuclear fuel from the Finnish nuclear power plants. The selection of the depth, placement and layout of the repository is affected by the constructability of the bedrock. The constructability, in turn, is influenced by several properties of the host rock, such as its Ethology, the extent of fracturing, its hydrogeological properties and rock engineering characteristics and also by the magnitude and orientation of the in situ stresses and the chemistry of the groundwater. The constructability can be evaluated by the application of a rock classification system in which the properties of the host rock are assessed against common rock engineering judgements associated with underground construction. These judgements are based partly on measurements of in situ stresses and the properties of the bedrock determined from rock samples, but an important aspect is also the practical experience which has been gained during underground excavation in similar conditions and rock types. The aim of the engineering rock mass classification was to determine suitable bedrock volumes for the construction of the repository and has used data from the site characterisation programme carried out at Olkiluoto, which consisted of both surface studies and borehole investigations. The classification specifies three categories of constructability - normal, demanding and very demanding. In addition, rock mass quality has also been classified according to the empirical Q-system to enable a comparison to be made. The rock mass parameters that determine the constructability of the bedrock at Olkiluoto depend primarily on the depth and the Ethology, as well as on whether construction takes place in intact or in fractured rock. The differences in the characteristics of intact rock within a single rock type have been shown to be small. The major lithological unit at Olkiluoto, the mica gneiss, lies in the

Note: CO₂-mineral dissolution experiments using a rocking autoclave and a novel titanium reaction cell.

Science.gov (United States)

Purser, Gemma; Rochelle, Christopher A; Wallis, Humphrey C; Rosenqvist, Jörgen; Kilpatrick, Andrew D; Yardley, Bruce W D

2014-08-01

A novel titanium reaction cell has been constructed for the study of water-rock-CO2 reactions. The reaction cell has been used within a direct-sampling rocking autoclave and offers certain advantages over traditional "flexible gold/titanium cell" approaches. The main advantage is robustness, as flexible cells are prone to rupture on depressurisation during gas-rich experiments. The reaction cell was tested in experiments during an inter-laboratory comparison study, in which mineral kinetic data were determined. The cell performed well during experiments up to 130 °C and 300 bars pressure. The data obtained were similar to those of other laboratories participating in the study, and also to previously published data.

Evaluation of CO2-Fluid-Rock Interaction in Enhanced Geothermal Systems: Field-Scale Geochemical Simulations

Directory of Open Access Journals (Sweden)

Feng Pan

2017-01-01

Full Text Available Recent studies suggest that using supercritical CO2 (scCO2 instead of water as a heat transmission fluid in Enhanced Geothermal Systems (EGS may improve energy extraction. While CO2-fluid-rock interactions at “typical” temperatures and pressures of subsurface reservoirs are fairly well known, such understanding for the elevated conditions of EGS is relatively unresolved. Geochemical impacts of CO2 as a working fluid (“CO2-EGS” compared to those for water as a working fluid (H2O-EGS are needed. The primary objectives of this study are (1 constraining geochemical processes associated with CO2-fluid-rock interactions under the high pressures and temperatures of a typical CO2-EGS site and (2 comparing geochemical impacts of CO2-EGS to geochemical impacts of H2O-EGS. The St. John’s Dome CO2-EGS research site in Arizona was adopted as a case study. A 3D model of the site was developed. Net heat extraction and mass flow production rates for CO2-EGS were larger compared to H2O-EGS, suggesting that using scCO2 as a working fluid may enhance EGS heat extraction. More aqueous CO2 accumulates within upper- and lower-lying layers than in the injection/production layers, reducing pH values and leading to increased dissolution and precipitation of minerals in those upper and lower layers. Dissolution of oligoclase for water as a working fluid shows smaller magnitude in rates and different distributions in profile than those for scCO2 as a working fluid. It indicates that geochemical processes of scCO2-rock interaction have significant effects on mineral dissolution and precipitation in magnitudes and distributions.

Review of potential host rocks for radioactive waste disposal in the Piedmont Province of South Carolina

International Nuclear Information System (INIS)

Secor, D.T. Jr.

1980-10-01

This report reviews the geology of the Piedmont Province of South Carolina with the aim of designating rock units favorable for field exploration for a potential underground repository for the storage of radioactive waste. Most of the rocks in the South Carolina Piedmont are metamorphosed sedimentary volcanic or igneous rocks that have experienced at least one episode of strong deformation. As a consequence of this deformation, they have irregular shapes, making it difficult to predict their subsurface extent. In evaluating the suitability of the rock units for radioactive waste storage, certain criteria were found to be particularly useful. The requirements that the storage site be located in a large volume of homogeneous, impermeable, relatively unfractured rock was the most important criteria in eliminating most of the Piedmont rock units for consideration as field study areas. Six large late- to post-tectonic igneous plutons (Winnsboro, Liberty Hill, Ogden, Newberry, Lowrys, and Bald Rock) are recommended as field study areas

Modelling of the UO2 dissolution mechanisms in synthetic groundwater solutions. Dissolution experiments carried out under oxic conditions

International Nuclear Information System (INIS)

Cera, E.; Grive, M.; Bruno, J.; Ollila, K.

2001-02-01

The analytical data generated during the last three years within the 4th framework program of the European Community at VTT Chemical Technology concerning UO 2 dissolution under oxidising conditions have been modelled in the present work. The modelling work has been addressed to perform a kinetic study of the dissolution data generated by Ollila (1999) under oxidising conditions by using unirradiated uranium dioxide as solid sample. The average of the normalised UO 2 dissolution rates determined by using the initial dissolution data generated in all the experimental tests is (6.06 ± 3.64)* 10 -7 mol m -2 d -1 . This dissolution rate agrees with most of the dissolution rates reported in the literature under similar experimental conditions. The results obtained in this modelling exercise show that the same bicarbonate promoted oxidative dissolution processes operate for uranium dioxide, as a chemical analogue of the spent fuel matrix, independently of the composition of the aqueous solution used. (orig.)

Shaft sealing concepts for high-level radioactive waste repositories based on the host-rock options rock salt and clay stone; Schachtverschlusskonzepte fuer zukuenftige Endlager fuer hochradioaktive Abfaelle fuer die Wirtsgesteinsoptionen Steinsalz und Ton

Energy Technology Data Exchange (ETDEWEB)

Kudla, Wolfram; Gruner, Matthias [TU Bergakademie Freiberg (Germany). Inst. fuer Erdbau und Spezialtiefbau; Herold, Philipp; Jobmann, Michael [DBE Technology GmbH, Peine (Germany)

2015-07-01

Unlike the shaft barriers used for the dry preservation of former mine workings and underground storage sites, shaft seals designed for radioactive-waste repositories must also fulfil additional requirements associated with the design diversity of the sealing system. This diversity makes use of the simple redundancy principle in order to prevent the proliferation of defects. In practice this means combining several sealing elements made from different materials or from materials with different properties. The R and D project, Shaft sealing systems for final repositories for high-level radioactive waste (ELSA) - phase 2: concept design for shaft seals and testing of the functional elements of shaft seals', which was funded by the Federal Ministry for Economic Affairs and Energy (BMWi), set out to investigate potential sealing elements for the two host-rock options rock salt and mudstone. This paper combines the text that the authors presented at the First International Freiberg Shaft Colloquium held at the Freiberg University of Mining and Technology on 01.10.2014 with a presentation on the sealing elements that were investigated as part of the R and D project.

Propagation of a hyperalkaline plume into the geological barrier surrounding a radioactive waste repository

International Nuclear Information System (INIS)

Lichtner, P.C.; Eikenberg, J.

1995-01-01

A coupled geochemical transport model (MPATH) which includes chemical reaction kinetics is used to evaluate the alteration of Swiss argillaceous sediments in a high-pH environment and to predict the spatial propagation of the hyperalkaline plume with time. The calculations predict dissolution of quartz, clay minerals and chlorite, and precipitation of zeolite minerals such as analcime and natrolite as well as he feldspars K-feldspar and albite. In addition, Portland cement-hydrates such as calcium silicate and aluminate hydrates, ettringite and friedel-salt are also predicted to form, depending on the composition of the inlet fluid and the host rock. The dissolution of clay minerals reduces the pH of the hyperalkaline plume to levels between approximately 8 and 10, depending on the composition of the inlet fluid and the host rock. For pure advective transport through porous medium, neglecting changes in porosity and permeability, the migration velocity of the high-pH front is calculated to be approximately one to two orders of magnitude less than that of the infiltrating groundwater. However, due to precipitation of secondary phases, in the present model concept a rapid decrease in porosity of the marl occurs several meters from the repository. At the interface between the marl host rock and cement the porosity increases as a consequence of the low silica concentration of the cement pore fluid. (author) 10 figs., 7 tabs., refs

Dissolution of minerals with rough surfaces

Science.gov (United States)

de Assis, Thiago A.; Aarão Reis, Fábio D. A.

2018-05-01

We study dissolution of minerals with initial rough surfaces using kinetic Monte Carlo simulations and a scaling approach. We consider a simple cubic lattice structure, a thermally activated rate of detachment of a molecule (site), and rough surface configurations produced by fractional Brownian motion algorithm. First we revisit the problem of dissolution of initial flat surfaces, in which the dissolution rate rF reaches an approximately constant value at short times and is controlled by detachment of step edge sites. For initial rough surfaces, the dissolution rate r at short times is much larger than rF ; after dissolution of some hundreds of molecular layers, r decreases by some orders of magnitude across several time decades. Meanwhile, the surface evolves through configurations of decreasing energy, beginning with dissolution of isolated sites, then formation of terraces with disordered boundaries, their growth, and final smoothing. A crossover time to a smooth configuration is defined when r = 1.5rF ; the surface retreat at the crossover is approximately 3 times the initial roughness and is temperature-independent, while the crossover time is proportional to the initial roughness and is controlled by step-edge site detachment. The initial dissolution process is described by the so-called rough rates, which are measured for fixed ratios between the surface retreat and the initial roughness. The temperature dependence of the rough rates indicates control by kink site detachment; in general, it suggests that rough rates are controlled by the weakest microscopic bonds during the nucleation and formation of the lowest energy configurations of the crystalline surface. Our results are related to recent laboratory studies which show enhanced dissolution in polished calcite surfaces. In the application to calcite dissolution in alkaline environment, the minimal values of recently measured dissolution rate spectra give rF ∼10-9 mol/(m2 s), and the calculated rate

Contribution in the study of the stability of Callovo-Oxfordian clay rock minerals in the presence of iron at 90 deg C

International Nuclear Information System (INIS)

Rivard, Camille

2011-01-01

In the context of underground disposal of high-level radioactive waste, it is of prime importance to understand the interaction mechanisms between Callovo-Oxfordian clay rock (COx), selected as a potential host-rock by Andra (French national radioactive waste management agency) and metallic iron, that enters the composition of containers and disposal cells. Interactions between metallic iron and COx clay-rock, COx Callovo-Oxfordian clay fraction (SCOx) and pure clay phases (kaolinite, illite, smectites) were investigated at 90 deg. C under anoxic atmosphere in chlorine solution. In order to study the role of COx non clay minerals, the reactivity of mixtures between SCOx and quartz, calcite, dolomite or pyrite, was also studied. Liquid and solid by-products were characterised by chemical analyses, mineralogical and morphometric techniques, at different scales. In our experimental conditions, major evolutions were observed during the first month, which shows that the oxidation of metallic iron is rapid. The release of iron cations in solution, pH increase (8-10) and Eh decrease (reductive conditions) are responsible for the partial dissolution of initial clay phases. Released iron is involved in the crystallization of Fe-serpentines (odinite or berthierite mainly) or precipitates under the form of magnetite in low amount. Fe-serpentine stability is controlled by the redox conditions as the introduction of dioxygen into the system leads to iron exsolution under the form of iron oxides and hydroxides and precipitation of clay particles with composition close to the initial ones. Whereas carbonates and pyrite do not significantly influence SCOx-metallic iron interactions, reaction pathways are modified in the presence of quartz. Indeed, in such conditions one observes a slight decrease of pH, an increase in Eh, the absence of magnetite and differences in the crystal chemistry of Fe-serpentines that are silica enriched, in comparison with those formed without any quartz

Dissolution process for advanced-PWR-type fuels

International Nuclear Information System (INIS)

Black, D.E.; Decker, L.A.; Pearson, L.G.

1979-01-01

The new Fluorinel Dissolution Process and Fuel Storage (FAST) Facility at ICPP will provide underwater storage of spent PWR fuel and a new head-end process for fuel dissolution. The dissolution will be two-stage, using HF and HNO 3 , with an intermittent H 2 SO 4 dissolution for removing stainless steel components. Equipment operation is described

Affinity functions for modeling glass dissolution rates

Energy Technology Data Exchange (ETDEWEB)

Bourcier, W.L. [Lawrence Livermore National Lab., CA (United States)

1997-07-01

Glass dissolution rates decrease dramatically as glass approach ''saturation'' with respect to the leachate solution. Most repository sites are chosen where water fluxes are minimal, and therefore the waste glass is most likely to dissolve under conditions close to ''saturation''. The key term in the rate expression used to predict glass dissolution rates close to ''saturation'' is the affinity term, which accounts for saturation effects on dissolution rates. Interpretations of recent experimental data on the dissolution behaviour of silicate glasses and silicate minerals indicate the following: 1) simple affinity control does not explain the observed dissolution rate for silicate minerals or glasses; 2) dissolution rates can be significantly modified by dissolved cations even under conditions far from saturation where the affinity term is near unity; 3) the effects of dissolved species such as Al and Si on the dissolution rate vary with pH, temperature, and saturation state; and 4) as temperature is increased, the effect of both pH and temperature on glass and mineral dissolution rates decrease, which strongly suggests a switch in rate control from surface reaction-based to diffusion control. Borosilicate glass dissolution models need to be upgraded to account for these recent experimental observations. (A.C.)

The dissolution of chalcopyrite in chloride media

International Nuclear Information System (INIS)

Ibanez, T.; Velasquez, L.

2013-01-01

The aim of this investigation is to determinate the effects of parameters and additives on the kinetics of dissolution of chalcopyrite on moderated conditions by means of dissolutions test with chalcopyrite concentrate and pure chalcopyrite in shake flasks and instrumented stirred reactors. A study of the dissolution of chalcopyrite in chloride solutions has demonstrated that the rate of dissolution of chalcopyrite is strongly dependent on the potential of the solution within a range of 540 to 630 mV (versus SHE). Leaching at pH around 2.5 results in increased rates of copper dissolution suggesting the possibility to keep the solution potential within the range. Both pyrite and silver ions enhance the dissolution of chalcopyrite and this effect increases when both species are present. The MnO 2 has a negative effect on the dissolution increasing the solution potential to values where the rate decreases considerably. (Author)

Phosphorus availability in an acid tropical soil amended with phosphate rocks

International Nuclear Information System (INIS)

Zaharah, A.R.; Sharifuddin, H.A.H.

2002-01-01

The fate of P from phosphate rocks applied to Malaysian soils has not been studied in detail. Since the plantation sector is the major consumer of phosphate rock (PR) in Malaysia, studies on the dissolution and agronomic effectiveness of PR are of great interest to the country. Thus a series of greenhouse and laboratory experiments involving conventional chemical extractants and 32 P isotopic techniques was carried out to evaluate the agronomic effectiveness of PR sources of different reactivity. Phosphorus and other chemical properties of the soil and PRs studied were determined. The P solubility tests by 2% formic acid, 2% citric acid and neutral ammonium citrate gave positive correlation with P uptake by one-year old oil palm seedlings. Neutral ammonium citrate proved to be a better indicator of PR solubility and its correlation coefficient with P uptake improved by expressing citrate solubility as a percentage of the rock rather than as a percentage of total P 2 0 5 content. The agronomic effectiveness of TSP and 6 PR sources was evaluated in glasshouse conditions with oil palm seedlings for one year-period. The percentage of PR dissolution varied greatly among PR sources. The PR dissolution was assessed by 0.5 M NaOH, Pi strip, L-value and 1 M ammonium citrate-dissolved Ca. Irrespective of the methods used, the more reactive PR such as North Carolina and Tunisia dissolved more P than the lower reactive sources such as Christmas Island and China PR. All the four methods used gave positive correlation with plant P uptake, with 0.5M NaOH being the best indirect method for determining PR dissolution. Less than 30% of the applied P was dissolved during the one-year period, with only about 15 to 40% of the dissolved P being taken up by the oil palm seedlings. A laboratory 32 P isotopic exchange method was also carried out in this acid soil to assess the soil P status parameters. A low water soluble P concentration (Cp) was found for all PRs used. The ratio of the

Dissolution glow curve in LLD

International Nuclear Information System (INIS)

Haverkamp, U.; Wiezorek, C.; Poetter, R.

1990-01-01

Lyoluminescence dosimetry is based upon light emission during dissolution of previously irradiated dosimetric materials. The lyoluminescence signal is expressed in the dissolution glow curve. These curves begin, depending on the dissolution system, with a high peak followed by an exponentially decreasing intensity. System parameters that influence the graph of the dissolution glow curve, are, for example, injection speed, temperature and pH value of the solution and the design of the dissolution cell. The initial peak does not significantly correlate with the absorbed dose, it is mainly an effect of the injection. The decay of the curve consists of two exponential components: one fast and one slow. The components depend on the absorbed dose and the dosimetric materials used. In particular, the slow component correlates with the absorbed dose. In contrast to the fast component the argument of the exponential function of the slow component is independent of the dosimetric materials investigated: trehalose, glucose and mannitol. The maximum value, following the peak of the curve, and the integral light output are a measure of the absorbed dose. The reason for the different light outputs of various dosimetric materials after irradiation with the same dose is the differing solubility. The character of the dissolution glow curves is the same following irradiation with photons, electrons or neutrons. (author)

Influence of pH and temperature on alunite dissolution rates and products

Science.gov (United States)

Acero, Patricia; Hudson-Edwards, Karen

2015-04-01

, leading to dissolved Al/K ratios between 0.5 and 2.5. This depletion of Al in the solution is especially clear for the experiments at pH 4.5-4.8 and 8 and it is consistent with the results of elemental quantifications of the same proportions in the reacted alunite surfaces using X-ray Photoelectron Spectroscopy (XPS). REFERENCES Flaten, T.P. (2001): Aluminium as a risk factor in Alzheimzer's disease, with emphasis on drinking water. Brain Research Bulletin 55: 187-196. Nordstrom, D.K. (2011): Hydrogeochemical processes governing the origin, transport and fate of major and trace elements from mine wastes and mineralized rock to surface waters. Applied Geochemistry 26: 1777-1791. Prietzel, J., & Hirsch, C. (1998). Extractability and dissolution kinetics of pure and soil-added synthesized aluminium hydroxy sulphate minerals. European journal of soil science, 49(4), 669-681. Swayze, G.A., Ehlmann, B.L., Milliken, R.E., Poulet, F., Wray, J.J., Rye, R.O., Clark, R.N., Desborough, G.A., Crowley, J.K., Gondet, B., Mustard, J.F., Seelos, K.D. and Murchie, S.L., 2008. Discovery of the Acid-Sulfate Mineral Alunite in Terra Sirenum, Mars, Using MRO CRISM: Possible Evidence for Acid-Saline Lacustrine Deposits?, American Geophysical Union, Fall Meeting 2008, abstract #P44A-04. Welch, S. A., Kirste, D., Christy, A. G., Beavis, F. R., & Beavis, S. G. (2008): Jarosite dissolution II'Reaction kinetics, stoichiometry and acid flux. Chemical Geology, 254(1), 73-86.

The carbonaceous phyllite rock-hosted Pedra Verde copper mine, Borborema Province, Brazil: Stable isotope constraints, structural controls and metallogenic evolution

Science.gov (United States)

da Silva Nogueira de Matos, José Henrique; Saraiva dos Santos, Ticiano José; Virgínia Soares Monteiro, Lena

2017-12-01

The Pedra Verde Copper Mine is located in the Viçosa do Ceará municipality, State of Ceará, NE Brazil. The copper mineralization is hosted by the Pedra Verde Phyllite, which is a carbonaceous chlorite-calcite phyllite with subordinate biotite. It belongs to the Neoproterozoic Martinópole Group of the Médio Coreaú Domain, Borborema Province. The Pedra Verde deposit is stratabound and its ore zoning is conspicuous, according to the following sequence, from bottom to top: marcasite/pyrite, native silver, chalcopyrite, bornite, chalcocite, native copper and hematite. Barite and carbonaceous material are reported in ore zones. Zoning reflects the ore formation within a redox boundary developed due to the interaction between oxidized copper- and sulfate-bearing fluids and the reduced phyllite. Structural control on mineralization is evidenced by the association of the ore minerals with veins, hinge folds, shadow pressures, and mylonitic foliation. It was mainly exercised by a dextral transcurrent shear zone developed during the third deformational stage identified in the Médio Coreaú Domain between 590 Ma and 570 Ma. This points to the importance of epigenetic, post-metamorphic deformational events for ore formation. Oxygen isotopic composition (δ18OH2O = 8.94 to 11.28‰, at 250 to 300 °C) estimated for the hydrothermal fluids in equilibrium with calcite indicates metamorphic or evolved meteoric isotopic signatures. The δ13CPDB values (-2.60 to -9.25‰) obtained for hydrothermal calcite indicate mixing of carbon sources derived from marine carbonate rocks and carbonaceous material. The δ34SCDT values (14.88 to 36.91‰) of sulfides suggest evaporites as sulfate sources or a closed system in relation to SO42- availability to form H2S. Carbonaceous matter had a key role in thermochemical sulfate processes and sulfide precipitation. The Pedra Verde Copper Mine is considered the first stratabound meta-sedimentary rock-hosted copper deposit described in Brazil

Small mammals as hosts of immature ixodid ticks

Directory of Open Access Journals (Sweden)

I.G. Horak

2005-09-01

Full Text Available Two hundred and twenty-five small mammals belonging to 16 species were examined for ticks in Free State, Mpumalanga and Limpopo Provinces, South Africa, and 18 ixodid tick species, of which two could only be identified to genus level, were recovered. Scrub hares, Lepus saxatilis, and Cape hares, Lepus capensis, harboured the largest number of tick species. In Free State Province Namaqua rock mice, Aethomys namaquensis, and four-striped grass mice, Rhabdomys pumilio, were good hosts of the immature stages of Haemaphysalis leachi and Rhipicephalus gertrudae, while in Mpumalanga and Limpopo Provinces red veld rats, Aethomys chrysophilus, Namaqua rock mice and Natal multimammate mice, Mastomys natalensis were good hosts of H. leachi and Rhipicephalus simus. Haemaphysalis leachi was the only tick recovered from animals in all three provinces.

Uranium in waters and aquifer rocks at the Nevada Test Site, Nye County, Nevada

International Nuclear Information System (INIS)

Zielinski, R.A.; Rosholt, J.N.

1978-01-01

Previous chemical, geological, and hydrological information describing the physical and chemical environment of the Nevada Test Site has been combined with new radiochemical and isotope data for water and rock samples in order to explain the behavior of uranium during alteration of thick sequences of rhyolitic volcanic rocks and associated volcanielastic sediments. A model is proposed in which uranium mobility is controlled by two competing processes. Uranium is liberated from the volcanic rocks through dissolution of the glassy constituents and is carried in solution as a uranyl carbonate complex. Uranium is subsequently removed from solution by adsorption on secondary oxides of iron, titanium, and manganese, as observed in fission-track maps of aquifer rocks. The model explains the poor correlation of dissolved uranium with depth within tuffaceous sequences in which percolation of ground water is predominantly downward. Good positive correlation of dissolved uranium with dissolved Na, total dissolved solids, and total carbonate supports the glass dissolution model, while inverse correlation of dissolved uranium with 234 U/ 238 U ratios of water implies uranium is being absorbed by a relatively insoluble, surficial phase. Alpha radioactivity of Test Site water is primarily caused by high 234 U contents, and beta activity is highly correlated with dissolved K ( 40 K). Smallamounts of dissolved radium, 216 Pb, and 210 Po are present but no evidence was found for alpha activity sources related to nuclear testing (Pu, 235 U). A filtered but unacidified carbonate solution of uranium was found to be stable (+-10 percent of original U concentration) for years when stored in acid-washed polyethylene bottles. 5 tables, 2 figs

The behavior during water-mineral interaction of britholite, an analogue of an apatite structured potential long-term actinide host phase

Energy Technology Data Exchange (ETDEWEB)

Chairat, C.; Oelkers, E.H.; Schott, J.; Harouiya, N.; Lartigue, J-E.; Guy, C.; Audubert, F

2004-07-01

Neodymium britholite (Ca{sub 9}Nd(PO{sub 4}){sub 5}SiO{sub 2}F{sub 2}) dissolution rates have been studied because it is an analogue for potential actinide waste hosts; it is believed that the behavior of Nd is representative of that of the actinide elements. Steady-state dissolution rates of britholite were measured in closed and open system reactors as a function of aqueous solution composition at 25 to 90 deg C. Measured britholite dissolution rates based on Ca, P, and F release are found to be close to corresponding apatite dissolution rates; these rates at 25 deg C decrease from 10-8 to 10-11 mol/m{sup 2}/s with increasing pH from 4 to 12. Measured Nd release rates are far slower than those of these other elements; Nd concentrations in solution appear to be in equilibrium with NdPO{sub 4}, which limits aqueous Nd concentrations to less than 10-12 mol/kg at near neutral conditions. By analogy, it appears likely that aqueous actinide release from analogous waste hosts will be similarly limited by the precipitation of sparingly soluble AcPO{sub 4} phases. (authors)

Loading History Effect on Creep Deformation of Rock

Directory of Open Access Journals (Sweden)

Wendong Yang

2018-06-01

Full Text Available The creep characteristics of rocks are very important for assessing the long-term stability of rock engineering structures. Two loading methods are commonly used in creep tests: single-step loading and multi-step loading. The multi-step loading method avoids the discrete influence of rock specimens on creep deformation and is relatively time-efficient. It has been widely accepted by researchers in the area of creep testing. However, in the process of multi-step loading, later deformation is affected by earlier loading. This is a key problem in considering the effects of loading history. Therefore, we intend to analyze the deformation laws of rock under multi-step loading and propose a method to correct the disturbance of the preceding load. Based on multi-step loading creep tests, the memory effect of creep deformation caused by loading history is discussed in this paper. A time-affected correction method for the creep strains under multi-step loading is proposed. From this correction method, the creep deformation under single-step loading can be estimated by the super-position of creeps obtained by the dissolution of a multistep creep. We compare the time-affected correction method to the coordinate translation method without considering loading history. The results show that the former results are more consistent with the experimental results. The coordinate translation method produces a large error which should be avoided.

The use of commercial microwave dissolution equipment for the fast and reliable dissolution of high-fired POX and MOX samples

International Nuclear Information System (INIS)

Tushingham, J.; McInnes, C.; Firkin, S.

1998-09-01

The use of commercially available microwave dissolution equipment for the fast and reliable dissolution of high-fired plutonium dioxide (POX) and mixed oxide (MOX) samples has been evaluated for application to Safeguards Analysis. Under the auspices of the UK R and D Support Programme to the IAEA, equipment has been purchased and tested for the high-pressure microwave dissolution of POX samples fired to 1250 deg. C and MOX samples fired to 1600 deg. C, in concentrated nitric acid and hydrofluoric acid mixture. Considerable problems were encountered during development of procedures for microwave dissolution, resulting largely from sudden changes in pressure within dissolution vessels, which resulted in actuation of safety interlocks designed to prevent overpressurisation. These difficulties were alleviated by controlling the microwave power to reduce the reaction temperature and pressure, and also by introducing additional safety valves into the digestion vessels. Using microwave digestion, dissolution times for high fired POX and MOX samples were substantially reduced. Samples which required ca. 10 hours to dissolve by conventional means could be dissolved in ca. 80 minutes by microwave digestion. Whilst a similar performance in terms of plutonium recovery was achieved for some materials by microwave and conventional dissolution, for other materials microwave dissolution gave higher plutonium recoveries but with poorer precision. This suggests the possible presence of some plutonium oxide within high-fired materials which is more difficult to dissolve than the bulk, and which is perhaps dissolved to an additional but variable degree by the current microwave dissolution procedure. Microwave dissolution has been demonstrated to increase the speed of dissolution of high-fired POX and MOX materials, compared with conventional dissolution. However, the technique has not yet proved satisfactory for the complete dissolution of all high-fired materials tested because of

Development of Dissolution Test Method for Drotaverine ...

African Journals Online (AJOL)

Development of Dissolution Test Method for Drotaverine ... Methods: Sink conditions, drug stability and specificity in different dissolution media were tested to optimize a dissolution test .... test by Prism 4.0 software, and differences between ...

Mechanistic Basis of Cocrystal Dissolution Advantage.

Science.gov (United States)

Cao, Fengjuan; Amidon, Gordon L; Rodríguez-Hornedo, Naír; Amidon, Gregory E

2018-01-01

Current interest in cocrystal development resides in the advantages that the cocrystal may have in solubility and dissolution compared with the parent drug. This work provides a mechanistic analysis and comparison of the dissolution behavior of carbamazepine (CBZ) and its 2 cocrystals, carbamazepine-saccharin (CBZ-SAC) and carbamazepine-salicylic acid (CBZ-SLC) under the influence of pH and micellar solubilization. A simple mathematical equation is derived based on the mass transport analyses to describe the dissolution advantage of cocrystals. The dissolution advantage is the ratio of the cocrystal flux to drug flux and is defined as the solubility advantage (cocrystal to drug solubility ratio) times the diffusivity advantage (cocrystal to drug diffusivity ratio). In this work, the effective diffusivity of CBZ in the presence of surfactant was determined to be different and less than those of the cocrystals. The higher effective diffusivity of drug from the dissolved cocrystals, the diffusivity advantage, can impart a dissolution advantage to cocrystals with lower solubility than the parent drug while still maintaining thermodynamic stability. Dissolution conditions where cocrystals can display both thermodynamic stability and a dissolution advantage can be obtained from the mass transport models, and this information is useful for both cocrystal selection and formulation development. Copyright © 2018 American Pharmacists Association®. Published by Elsevier Inc. All rights reserved.

Aluminosilicate Dissolution and Silicate Carbonation during Geologic CO2 Sequestration

Science.gov (United States)

Min, Yujia

Geologic CO2 sequestration (GCS) is considered a promising method to reduce anthropogenic CO2 emission. Assessing the supercritical CO2 (scCO2) gas or liquid phase water (g, l)-mineral interactions is critical to evaluating the viability of GCS processes. This work contributes to our understanding of geochemical reactions at CO 2-water (g, l)-mineral interfaces, by investigating the dissolution of aluminosilicates in CO2-acidified water (l). Plagioclase and biotite were chosen as model minerals in reservoir rock and caprock, respectively. To elucidate the effects of brine chemistry, first, the influences of cations in brine including Na, Ca, and K, have been investigated. In addition to the cations, the effects of abundant anions including sulfate and oxalate were also examined. Besides the reactions in aqueous phase, we also examine the carbonation of silicates in water (g)-bearing supercritical CO2 (scCO2) under conditions relevant to GCS. For the metal carbonation, in particular, the effects of particle sizes, water, temperature, and pressure on the carbonation of wollastonite were systematically examined. For understanding the cations effects in brine, the impacts of Na concentrations up to 4 M on the dissolution of plagioclase and biotite were examined. High concentrations of Na significantly inhibited plagioclase dissolution by competing adsorption with proton and suppressing proton-promoted dissolution. Ca has a similar effect to Na, and their effects did not suppress each other when Na and Ca co-existed. For biotite, the inhibition effects of Na coupled with an enhancing effect due to ion exchange reaction between Na and interlayer K, which cracked the basal surfaces of biotite. The K in aqueous phase significantly inhibited the dissolution. If the biotite is equilibrated with NaCl solutions initially, the biotite dissolved faster than the original biotite and the dissolution was inhibited by Na and K in brine. The outcomes improve our current knowledge of

Magnesite dissolution and precipitation rates at hydrothermal conditions

International Nuclear Information System (INIS)

Saldi, Giuseppe

2009-01-01

Magnesite (MgCO 3 ) is the stable anhydrous member of a series of Mg-carbonates with different degrees of hydration. Despite its relative scarcity in the natural environments, it constitutes an important mineral phase for the permanent sequestration of CO 2 as carbonate minerals. Experimental determination of magnesite precipitation and dissolution rates at conditions representative of the storage sites is therefore fundamental for the assessment of magnesite sequestration potential in basaltic and ultramafic rocks and the optimization of the techniques of CO 2 storage. Magnesite precipitation rates have been measured using mixed-flow and batch reactors as a function of temperature (100 ≤ T ≤ 200 deg. C), solution composition and CO 2 partial pressure (up to 30 bar). Rates were found to be independent of aqueous solution ionic strength at 0.1 M 3 2- activity at pH > 8. All rates obtained from mixed flow reactor experiments were found to be consistent with the model of Pokrovsky et al. (1999) where magnesite precipitation rates are proportional to the concentration of the >MgOH 2 + surface species. The study of magnesite crystallization using hydrothermal atomic force microscopy (HAFM) demonstrated the consistency of the rates derived from microscopic measurements with those obtained from bulk experiments and showed that these rates are also consistent with a spiral growth mechanism. According to AFM observations this mechanism controls magnesite growth over a wide range of temperatures and saturation states (15≤ Ω ≤200 for 80 ≤T 2 to accelerate the rate of the overall carbonation process, avoiding the inhibiting effect of carbonate ions on magnesite precipitation and increasing the rates of Mg-silicate dissolution via acidification of reacting solutions. Determination of magnesite dissolution rates by mixed flow reactor at 150 and 200 deg. C and at neutral to alkaline conditions allowed us to improve and extend to high temperatures the surface

The impact of a (hyper)alkaline plume on (fractured) crystalline rock

International Nuclear Information System (INIS)

Alexander, Russell

2012-01-01

Russell Alexander from Bedrock Geosciences, Switzerland, gave a presentation on the possible effects of cement pore waters on a crystalline host rock. Field, laboratory and natural analogue studies as well as geochemical modelling indicate that cement leachates tend to induce the sealing of fractures in the rock. These studies also indicate that strongly alkaline waters might: - Accelerate the dissolution of vitrified waste, but probably not affect the dissolution rate of spent fuel. - Degrade bentonite to some degree. To avoid some of the effects associated with the use of concrete, several approaches may be used: - Minimisation and tracking/monitoring of the concrete masses. - Development and use of low-pH cements and alternative grouting materials. - The selection of less fractured rock volumes for a repository location. The sealing of fractures evidenced in the Maquarin natural analogue study might contribute to limiting the extent of perturbations caused by an alkaline plume and is likely to create a hydraulic barrier that affects groundwater flow. The effects of these processes should be analysed in a safety case since they may support the idea of a self-sealing repository. Uncertainties in the treatment of an alkaline plume in fractured rock include: - The possible formation of colloids. - Thermodynamic data for cement components and secondary mineral stability. - Cement carbonation. - The effects of super-plasticisers. Given these uncertainties, current assessments of perturbations around a HLW or spent fuel repository caused by cementitious materials are often conservative and provide a pessimistic view of disposal system performance. Discussion of the paper included: Will groundwater flows in deep systems be fast enough to cause pervasive sealing of fractures? The process of how a network of fractures may be sealed over time is uncertain. The flow field will be altered as fractures are sealed and this may cause flow rates in other parts of the fracture

Mercury isotope constraints on the source for sediment-hosted lead-zinc deposits in the Changdu area, southwestern China

Science.gov (United States)

Xu, Chunxia; Yin, Runsheng; Peng, Jiantang; Hurley, James P.; Lepak, Ryan F.; Gao, Jianfeng; Feng, Xinbin; Hu, Ruizhong; Bi, Xianwu

2018-03-01

The Lanuoma and Cuona sediment-hosted Pb-Zn deposits hosted by Upper Triassic limestone and sandstone, respectively, are located in the Changdu area, SW China. Mercury concentrations and Hg isotopic compositions from sulfide minerals and potential source rocks (e.g., the host sedimentary rocks and the metamorphic basement) were investigated to constrain metal sources and mineralization processes. In both deposits, sulfide minerals have higher mercury (Hg) concentrations (0.35 to 1185 ppm) than the metamorphic basement rocks (0.05 to 0.15 ppm) and sedimentary rocks (0.02 to 0.08 ppm). Large variations of mass-dependent fractionation (3.3‰ in δ202Hg) and mass-independent fractionation (0.3‰ in Δ199Hg) of Hg isotopes were observed. Sulfide minerals have Hg isotope signatures that are similar to the hydrothermal altered rocks around the deposit, and similar to the metamorphic basement, but different from barren sedimentary rocks. The variation of Δ199Hg suggests that Hg in sulfides was mainly derived from the underlying metamorphic basement. Mercury isotopes could be a geochemical tracer in understanding metal sources in hydrothermal ore deposits.

Accelerated dissolution of iron oxides in ice

Directory of Open Access Journals (Sweden)

D. Jeong

2012-11-01

Full Text Available Iron dissolution from mineral dusts and soil particles is vital as a source of bioavailable iron in various environmental media. In this work, the dissolution of iron oxide particles trapped in ice was investigated as a new pathway of iron supply. The dissolution experiments were carried out in the absence and presence of various organic complexing ligands under dark condition. In acidic pH conditions (pH 2, 3, and 4, the dissolution of iron oxides was greatly enhanced in the ice phase compared to that in water. The dissolved iron was mainly in the ferric form, which indicates that the dissolution is not a reductive process. The extent of dissolved iron was greatly affected by the kind of organic complexing ligands and the surface area of iron oxides. The iron dissolution was most pronounced with high surface area iron oxides and in the presence of strong iron binding ligands. The enhanced dissolution of iron oxides in ice is mainly ascribed to the "freeze concentration effect", which concentrates iron oxide particles, organic ligands, and protons in the liquid like ice grain boundary region and accelerates the dissolution of iron oxides. The ice-enhanced dissolution effect gradually decreased when decreasing the freezing temperature from −10 to −196 °C, which implies that the presence and formation of the liquid-like ice grain boundary region play a critical role. The proposed phenomenon of enhanced dissolution of iron oxides in ice may provide a new pathway of bioavailable iron production. The frozen atmospheric ice with iron-containing dust particles in the upper atmosphere thaws upon descending and may provide bioavailable iron upon deposition onto the ocean surface.

Fluids and the evolution of rock mechanical properties

International Nuclear Information System (INIS)

Reuschle, Thierry

1989-01-01

This research thesis reports the study of the various phenomena of fluid-solid interaction (mechanical or chemical interaction with fracturing by fluid overpressure, slow crack propagation, and pore deformation by transfer in solution) which may occur in the interaction of fluids with rocks. The author first presents the formalism of slow crack propagation based on the generalisation of the Griffith criterion. The model results are compared with experimental results obtained on four materials (glass, quartz, sandstone, and micrite) by using the double-torsion test. In the second part, the author addresses the issue of pore deformation by transfer in solution: dissolution and crystallisation under stress. The Gibbs chemical potential equation is firstly generalised to the case of a circular pore, and a formalism combining mechanics and thermodynamics is then proposed. A set of simulations highlights important parameters. In the third part, the author addresses the problem of fluid-rock mechanical interaction by studying the mechanical role of fluid pressure in crack initiation and propagation [fr

In vitro dissolution methodology, mini-Gastrointestinal Simulator (mGIS), predicts better in vivo dissolution of a weak base drug, dasatinib.

Science.gov (United States)

Tsume, Yasuhiro; Takeuchi, Susumu; Matsui, Kazuki; Amidon, Gregory E; Amidon, Gordon L

2015-08-30

USP apparatus I and II are gold standard methodologies for determining the in vitro dissolution profiles of test drugs. However, it is difficult to use in vitro dissolution results to predict in vivo dissolution, particularly the pH-dependent solubility of weak acid and base drugs, because the USP apparatus contains one vessel with a fixed pH for the test drug, limiting insight into in vivo drug dissolution of weak acid and weak base drugs. This discrepancy underscores the need to develop new in vitro dissolution methodology that better predicts in vivo response to assure the therapeutic efficacy and safety of oral drug products. Thus, the development of the in vivo predictive dissolution (IPD) methodology is necessitated. The major goals of in vitro dissolution are to ensure the performance of oral drug products and the support of drug formulation design, including bioequivalence (BE). Orally administered anticancer drugs, such as dasatinib and erlotinib (tyrosine kinase inhibitors), are used to treat various types of cancer. These drugs are weak bases that exhibit pH-dependent and high solubility in the acidic stomach and low solubility in the small intestine (>pH 6.0). Therefore, these drugs supersaturate and/or precipitate when they move from the stomach to the small intestine. Also of importance, gastric acidity for cancer patients may be altered with aging (reduction of gastric fluid secretion) and/or co-administration of acid-reducing agents. These may result in changes to the dissolution profiles of weak base and the reduction of drug absorption and efficacy. In vitro dissolution methodologies that assess the impact of these physiological changes in the GI condition are expected to better predict in vivo dissolution of oral medications for patients and, hence, better assess efficacy, toxicity and safety concerns. The objective of this present study is to determine the initial conditions for a mini-Gastrointestinal Simulator (mGIS) to assess in vivo

Alteration of fault rocks by CO2-bearing fluids with implications for sequestration

Science.gov (United States)

Luetkemeyer, P. B.; Kirschner, D. L.; Solum, J. G.; Naruk, S.

2011-12-01

Carbonates and sulfates commonly occur as primary (diagenetic) pore cements and secondary fluid-mobilized veins within fault zones. Stable isotope analyses of calcite, formation fluid, and fault zone fluids can help elucidate the carbon sources and the extent of fluid-rock interaction within a particular reservoir. Introduction of CO2 bearing fluids into a reservoir/fault system can profoundly affect the overall fluid chemistry of the reservoir/fault system and may lead to the enhancement or degradation of porosity within the fault zone. The extent of precipitation and/or dissolution of minerals within a fault zone can ultimately influence the sealing properties of a fault. The Colorado Plateau contains a number of large carbon dioxide reservoirs some of which leak and some of which do not. Several normal faults within the Paradox Basin (SE Utah) dissect the Green River anticline giving rise to a series of footwall reservoirs with fault-dependent columns. Numerous CO2-charged springs and geysers are associated with these faults. This study seeks to identify regional sources and subsurface migration of CO2 to these reservoirs and the effect(s) faults have on trap performance. Data provided in this study include mineralogical, elemental, and stable isotope data for fault rocks, host rocks, and carbonate veins that come from two localities along one fault that locally sealed CO2. This fault is just tens of meters away from another normal fault that has leaked CO2-charged waters to the land surface for thousands of years. These analyses have been used to determine the source of carbon isotopes from sedimentary derived carbon and deeply sourced CO2. XRF and XRD data taken from several transects across the normal faults are consistent with mechanical mixing and fluid-assisted mass transfer processes within the fault zone. δ13C range from -6% to +10% (PDB); δ18O values range from +15% to +24% (VSMOW). Geochemical modeling software is used to model the alteration

Passive detection of Pb in water using rock phosphate agarose beads.

Science.gov (United States)

Edenborn, Harry M; Howard, Bret H; Sams, James I; Vesper, Dorothy J; Edenborn, Sherie L

2017-08-15

In this study, passive detectors for Pb were prepared by immobilizing powdered rock phosphate in agarose beads. Rock phosphate has been used to treat Pb-contaminated waters and soil by fixing the metal as an insoluble pyromorphite mineral. Under lab conditions, Pb was rapidly adsorbed from aqueous solution by the beads over time, consistent with the acidic dissolution of rock phosphate, the precipitation of pyromorphite within the pore space of the agarose gel matrix, and surface exchange reactions. Net accumulation of Pb occurred when beads were exposed to simulated periodic releases of Pb over time. Under field conditions, beads in mesh bags were effective at detecting dissolved Pb being transported as surface runoff from a site highly contaminated with Pb. Rates of Pb accumulation in beads under field conditions appeared to be correlated with the frequency of storm events and total rainfall. The rock phosphate agarose bead approach could be an inexpensive way to carry out source-tracking of Pb pollution, to verify the successful remediation of sites with Pb-contaminated soil, and to routinely monitor public water systems for potential Pb contamination. Published by Elsevier B.V.

Thermal conductivity of the rocks in the Bureau of Mines Standard Rock Suite

International Nuclear Information System (INIS)

Morgan, M.T.; West, G.A.

1980-01-01

Thermal conductivities of eight rocks from the Bureau of Mines Standard Rock Suite were measured in air over the temperature range 373 to 533 0 K (100 to 260 0 C). The thermal conductivities of these rocks were measured to furnish standards for future comparisons with host rock from prospective nuclear waste repository sites. The thermal conductivity at a given temperature decreased by as much as 9% after a specimen had been heated to the maximum temperature (533 0 K), but additional heating cycles had no further effect. This decrease was smallest in the igneous rocks and largest in the sedimentary types. Variations due to orientation were within the precision of measurements (+- 5%). In most cases the thermal conductivities were linear with the reciprocal of the temperature and were within 14% of published data obtained by other methods. Measurements were made by a cut-bar comparison method in which the sample was sandwiched between two reference or metering bars made of Pyroceram 9606 glass-ceramic. The apparatus consisted of a Dynatech Model TCFCM-N20 comparative thermal conductivity analyzer controlled by a Hewlett Packard Model 3052A data acquisition system. A program was written to increment and cycle the temperature in steps between predetermined initial and maximum values. At each step the thermal conductivity was measured after steady-state conditions were established. The rocks furnished by the Bureau of Mines were quarried in large and fairly homogeneous lots for use by researchers at various laboratories. To investigate any anisotropy, cores were taken from each rock cube perpendicular to each of the cube faces. Samples 2 in. in diameter and approx. 0.75 in. thick were prepared from the cores and were dried in a vacuum oven for at least one month prior to taking measurements

Geochemistry of two pressurized brines from the Castile Formation in the vicinity of the Waste Isolation Pilot Plant (WIPP) site

International Nuclear Information System (INIS)

Faith, S.; Spiegler, P.; Rehfeldt, K.R.

1983-04-01

The major and minor element data and isotopic data from the ERDA-6 and WIPP-12 testing indicate that the brine reservoirs encountered in the Upper Castile Formation are largely in equilibrium with their surrounding host rock environment. This contention is supported by thermodynamic and stable isotope data. It is not possible to assign an absolute age to the brine based on uranium disequilibrium considerations, but the data do indicate that the brine reequilibrated with a new rock environment at least two million years ago. Information and data evaluated herein indicate the likelihood that the brines encountered are predominantly, if not entirely, derived from a trapped seawater source subsequently modified by diagenesis. Major ion/bromide ratios indicate that halite dissolution has occurred to some extent subsequent to deposition of the Castile anhydrites and entrapment of the seawater brine. Mechanisms for additional halite dissolution are discussed. Based on the degree of present halite saturation, it is concluded that the potential for future dissolution of halite is minimal

Review of Studies of Clay Minerals as Significant Component of Potential Host Rocks or Engineering Barriers for Radioactive Waste Disposals Performed at Comenius University in Bratislava

International Nuclear Information System (INIS)

Peter, Uhlik; Vladimir, Sucha; Maria, Caplovicova; Igor, Stricek

2013-01-01

About 50 % of electric power is produced by nuclear power plants in Slovakia. In spite of the significant production of nuclear waste, Slovakia has not defined basic strategy of radioactive-waste isolation. However, some pilot projects and studies have been carried out. Five areas were determined as prospective sites for construction of deep geological repository (DGR). Two of them are situated in the south of Slovakia. Szecseny schlier (mixture of siltstones and Clay-stones) of Lucenec Formation (Egerian) is one of the most prospective host rocks from lithological, structural and spatial perspective. Besides the investigation of potential host rock for DGR the studies of bentonite properties as important part of engineering barriers for radioactive waste disposals were performed. Detailed mineral and structural analyses of smectites from the bentonitic material exposed to laboratory Mock-Up test were realised. Particular interest has been focused on interaction between Fe and smectites. Other field of interest is investigation of sorption of Cs and Sr on natural and modified bentonites, including irradiation. Purpose of this work is to present a short review of other studies done by our group with partial focusing to interaction of organic dye (Rhoda-mine 6G) with smectite that is connected with changes of layer charge after treatment; possibilities to measure preferential orientation of clays after compaction by TEM and to effort to use X-ray micro-tomography for inner structure of sediments. (authors)

Dissolution of metallic uranium and its alloys. Part 1. Review of analytical and process-scale metallic uranium dissolution

International Nuclear Information System (INIS)

Laue, C.A.; Gates-Anderson, D.; Fitch, T.E.

2004-01-01

This review focuses on dissolution/reaction systems capable of treating uranium metal waste to remove its pyrophoric properties. The primary emphasis is the review of literature describing analytical and production-scale dissolution methods applied to either uranium metal or uranium alloys. A brief summary of uranium's corrosion behavior is included since the corrosion resistance of metals and alloys affects their dissolution behavior. Based on this review, dissolution systems were recommended for subsequent screening studies designed to identify the best system to treat depleted uranium metal wastes at Lawrence Livermore National Laboratory (LLNL). (author)

Reactive Transport in a Pipe in Soluble Rock: a Theoretical and Experimental Study

Science.gov (United States)

Li, W.; Opolot, M.; Sousa, R.; Einstein, H. H.

2015-12-01

Reactive transport processes within the dominant underground flow pathways such as fractures can lead to the widening or narrowing of rock fractures, potentially altering the flow and transport processes in the fractures. A flow-through experiment was designed to study the reactive transport process in a pipe in soluble rock to serve as a simplified representation of a fracture in soluble rock. Assumptions were made to formulate the problem as three coupled, one-dimensional partial differential equations: one for the flow, one for the transport and one for the radius change due to dissolution. Analytical and numerical solutions were developed to predict the effluent concentration and the change in pipe radius. The positive feedback of the radius increase is captured by the experiment and the numerical model. A comparison between the experiment and the simulation results demonstrates the validity of the analytical and numerical models.

Used Fuel Disposal in Crystalline Rocks. FY15 Progress Report

Energy Technology Data Exchange (ETDEWEB)

Wang, Yifeng [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)

2015-08-20

The objective of the Crystalline Disposal R&D Work Package is to advance our understanding of long-term disposal of used fuel in crystalline rocks and to develop necessary experimental and computational capabilities to evaluate various disposal concepts in such media. Chapter headings are as follows: Fuel matrix degradation model and its integration with performance assessments, Investigation of thermal effects on the chemical behavior of clays, Investigation of uranium diffusion and retardation in bentonite, Long-term diffusion of U(VI) in bentonite: dependence on density, Sorption and desorption of plutonium by bentonite, Dissolution of plutonium intrinsic colloids in the presence of clay and as a function of temperature, Laboratory investigation of colloid-facilitated transport of cesium by bentonite colloids in a crystalline rock system, Development and demonstration of discrete fracture network model, Fracture continuum model and its comparison with discrete fracture network model.

Dissolution of uranium oxide TBP-HNO3 complex

International Nuclear Information System (INIS)

Mizuno, Mineo; Kosaka, Yuji; Mori, Yukihide; Shimada, Takashi

2002-12-01

As a head end process for the pulverization of the spent fuel, the mechanical method (the shredder method) and the pyro-chemical method (oxidisation heat-treatment) have been examined. UO 2 is a main ingredient of Uranium oxide powder by the mechanical method, and U 3 O 8 is that by the pyro-chemical method. Moreover, the particle size of the pulverized powder depend on the conditions of the pulverizing process. As it was considered that the difference of dissolution rates of samples was caused by the difference of sample chemical forms and dissolution temperature, parametric surveys on chemical form and particle size of powder and dissolution temperature were carried out, and the following results were obtained. 1) The remarkable difference of dissolution rate between U 3 O 8 powder (average particle size 3.7 μm) and UO 2 powder (average particle size 2.4 μm) which have comparatively similar particle size was not observed. 2) It was confirmed that the dissolution rate became lower according to the particle size increase (average particle size 2.4 μm-1 mm). And it was considered that dissolution rate had strong dependency on particle size, according to the results that the powder with 1 mm particle size did not dissolute completely after 5 hours test. 3) The temperature dependency of the dissolution rate was confirmed by dissolution test with UO 2 powder (average particle size 2.4 μm-1 mm). The higher dissolution rate was obtained in the higher dissolution temperature, and 11 kcal/mol was obtained as activation energy of dissolution. 4) In the dissolution test of UO 2 powder, the nitric acid concentration started to change earlier than that of U 3 O 8 powder and concentration change range became larger compared with that in the dissolution test of U 3 O 8 powder. It was considered that those differences were caused by difference in mole ratio of Uranium and nitric acid which are consumed in the dissolution reaction (3:7 for U 3 O 8 , 3:8 for UO 2 ). 5) In case

Dissolution rate enhancement of piroxicam by ordered mixing.

Science.gov (United States)

Saharan, Vikas Anand; Choudhury, Pratim Kumar

2012-07-01

Micronized piroxicam was mixed with lactose, mannitol, sorbitol, maltitol and sodium chloride to produce ordered mixture in a glass vial by manual hand shaking method. The effect of excipients, surfactant, superdisintegrant, drug concentration and carrier particle size on dissolution rate was investigated. Dissolution rate studies of the prepared ordered mixtures revealed that all water soluble excipients increased the dissolution rate of piroxicam when compared to the dissolution rate of piroxicam or its suspension. Ordered mixture formulation PLF4, consisting of lactose as water soluble excipient, SSG (8% w/s) and SLS (1% w/w), released piroxcam at a very fast rate so much so that about 90% of the composition had passed into solution within 2 min. The order of the dissolution rate enhancement for ordered mixtures of various water soluble excipients was: lactose > mannitol > maltitol > sorbitol > sodium chloride. Carrier granules of size 355-710 µm were most effective in increasing the dissolution rate of drug from ordered mixtures. Decreasing the carrier particle size reduced drug dissolution from ordered mixtures. The dissolution rate of ordered mixtures consisting of 1-5% w/w piroxicam was superior to dissolution rate of piroxicam suspension. The dissolution data fitting and the resulting regression parameters indicated Hixson Crowell, cube root law, as the best fit to drug release data of ordered mixtures.

Diffusion-controlled cementation experiments in porous rock analogues using potash alum and halite

Energy Technology Data Exchange (ETDEWEB)

Hufe, A.; Hilgers, C. [RWTH Aachen Univ. (Germany). Inst. of Reservoir-Petrology; Stanjek, H. [RWTH Aachen Univ. (Germany). Inst. of Interface and Clay Mineralogy

2013-08-01

A good understanding of cementation is critical for reservoir quality predictions. However, studies of core material have shown that cementation may be driven by variations in pore size of the host rock. To better understand the underlying process, we developed a transparent microreactor for diffusion-controlled cementation experiments under the microscope. We studied the effect of different pore sizes and surface charges of solid material at different pH, using rock analogs. High-resolution videos allowed to analyze the nucleation from solution, pore cementation and growth rates of cements. Diffusion - considered the major mass transport during burial diagenesis - was driven along a temperature gradient across the microreactor. Pores were cemented with salt, which is well known to form pore-size dependent seals in silicilastic reservoirs. While halite precipitated primarily in pores bigger than 200 {mu}m, alum nucleated in smaller pores. The growth rate of alum (10{sup -5} mm/s) was one order of magnitude higher than that of halite. However, the dissolution rates of both minerals was similar at about 10{sup -6} mm/s. Authigenic euhdral halite migrated against the bulk diffusion transport and towards the higher-temperature reservoir. Halite growth rates increased by one order of magnitude to 1.8 x 10{sup -5} mm/s, if the phase boundary was vapor-liquid. A comparison nucleation in a 2-phase porous rock analog showed no difference in cementation pattern at a pH 7. However, at a pH of 10.5 the surface energies of the two different solids are altered, and porosity was reduced 60% more by cements in the phase-1 porous layers. Our experiments showed that pore size dependent nucleation and cementation is a process, which may also take place in complex reservoirs. With the successful pore clogging of halite we can now bring our experimental setup to reservoir conditions and establish the processes at elevated p-T conditions. (orig.)

Improvement of database on glass dissolution

International Nuclear Information System (INIS)

Hayashi, Maki; Sasamoto, Hiroshi; Yoshikawa, Hideki

2008-03-01

In geological disposal system, high-level radioactive waste (HLW) glass is expected to retain radionuclide for the long term as the first barrier to prevent radionuclide release. The advancement of its performance assessment technology leads to the reliability improvement of the safety assessment of entire geological disposal system. For this purpose, phenomenological studies for improvement of scientific understanding of dissolution/alteration mechanisms, and development of robust dissolution/alteration model based on the study outcomes are indispensable. The database on glass dissolution has been developed for supporting these studies. This report describes improvement of the prototype glass database. Also, this report gives an example of the application of the database for reliability assessment of glass dissolution model. (author)

Impact of weathering on slope stability in soft rock mass

Directory of Open Access Journals (Sweden)

Predrag Miščević

2014-06-01

Full Text Available Weathering of soft rocks is usually considered as an important factor in various fields such as geology, engineering geology, mineralogy, soil and rock mechanics, and geomorphology. The problem of stability over time should be considered for slopes excavated in soft rocks, in case they are not protected against weathering processes. In addition to disintegration of material on slope surface, the weathering also results in shear strength reduction in the interior of the slope. Principal processes in association with weathering are discussed with the examples of marl hosted on flysch formations near Split, Croatia.

Formation, transformation and dissolution of phases formed on surfaces

International Nuclear Information System (INIS)

Shoesmith, D.W.

1983-03-01

The basic mechanisms of film growth, transformation, and dissolution of phases formed on surfaces are discussed. Film growth can occur via solid-state processes or via substrate (usally metal or alloy) dissolution, followed by local supersaturation and precipitation of an insoluble phase. The phase(s) formed may be metastable and transform to a more stable phase, via either solid-state or dissolution-reprecipitation processes. Film dissolution reactions can also occur via a variety of mechanisms, including: (i) direct chemical dissolution when no oxidation state change occurs; (ii) redox dissolution when the film dissolves via a redox reaction involving a reducing or oxidizing agent in solution; and (iii) autoreduction, where film dissolution is coupled to metal dissolution. Such film-growth and dissolution processes, which often produce complex multilayer films, are common in the nuclear industry. A number of examples are discussed

Dissolution of UO2 in redox conditions

International Nuclear Information System (INIS)

Casas, I.; Pablo de, J.; Rovira, M.

1998-01-01

The performance assessment of the final disposal of the spent nuclear fuel in geological formations is strongly dependent on the spent fuel matrix dissolution. Unirradiated uranium (IV) dioxide has shown to be very useful for such purposes. The stability of UO 2 is very dependent on vault redox conditions. At reducing conditions, which are expected in deep groundwaters, the dissolution of the UO 2 -matrix can be explained in terms of solubility, while under oxidizing conditions, the UO 2 is thermodynamically unstable and the dissolution is kinetically controlled. In this report the parameters which affect the uranium solubility under reducing conditions, basically pH and redox potential are discussed. Under oxidizing conditions, UO 2 dissolution rate equations as a function of pH, carbonate concentration and oxidant concentration are reported. Dissolution experiments performed with spent fuel are also reviewed. The experimental equations presented in this work, have been used to model independent dissolution experiments performed with both unirradiated and irradiated UO 2 . (Author)

The RCF [Rock Characterisation Facility]: engineering issues. Proof of evidence

International Nuclear Information System (INIS)

Allison, J.A.

1996-01-01

Proof of Evidence by an expert witness is presented in support of the case by Friends of the Earth (FOE) against the proposed construction by UK Nirex Ltd of an underground Rock Characterisation Facility (RCF) at a site in the Sellafield area. The RCF is part of an investigation by Nirex into a suitable site for an underground repository for the disposal of radioactive waste. The objections were raised at a Planning Inquiry in 1995. The evidence focuses on the engineering issues in key areas of uncertainty which Nirex claim can only be resolved through the construction of an RCF. These are: groundwater flow and radionuclide transport; natural and induced changes in the geological barrier; the design and construction of the repository. Particular attention is drawn to the uncertainties regarding the groundwater pathway due to the dominant influence of fractures and variability in the host rock. Significant uncertainties about the host rock performance will remain after the construction of the RCF and associated tests are complete. (5 figures; 28 references). (UK)

Potential for leaching of arsenic from excavated rock after different drying treatments.

Science.gov (United States)

Li, Jining; Kosugi, Tomoya; Riya, Shohei; Hashimoto, Yohey; Hou, Hong; Terada, Akihiko; Hosomi, Masaaki

2016-07-01

Leaching of arsenic (As) from excavated rock subjected to different drying methods is compared using sequential leaching tests and rapid small-scale column tests combined with a sequential extraction procedure. Although the total As content in the rock was low (8.81 mg kg(-1)), its resulting concentration in the leachate when leached at a liquid-to-solid ratio of 10 L kg(-1) exceeded the environmental standard (10 μg L(-1)). As existed mainly in dissolved forms in the leachates. All of the drying procedures applied in this study increased the leaching of As, with freeze-drying leading to the largest increase. Water extraction of As using the two tests showed different leaching behaviors as a function of the liquid-to-solid ratio, and achieved average extractions of up to 35.7% and 25.8% total As, respectively. Dissolution of As from the mineral surfaces and subsequent re-adsorption controlled the short-term release of As; dissolution of Fe, Al, and dissolved organic carbon played important roles in long-term As leaching. Results of the sequential extraction procedure showed that use of 0.05 M (NH4)2SO4 underestimates the readily soluble As. Long-term water extraction removed almost all of the non-specifically sorbed As and most of the specifically sorbed As. The concept of pollution potential indices, which are easily determined by the sequential leaching test, is proposed in this study and is considered for possible use in assessing efficacy of treatment of excavated rocks. Copyright © 2016 Elsevier Ltd. All rights reserved.

Site-specific evaluation of safety issues for high-level waste disposal in crystalline rocks. Final report

Energy Technology Data Exchange (ETDEWEB)

Jobmann, M. (ed.) [DBE Technology GmbH, Peine (Germany)

2016-03-31

In the past, German research and development (R and D) activities regarding the disposal of radioactive waste, including spent nuclear fuel, focused mainly on domal rock salt because rock salt was the preferred host rock formation. In addition, generic R and D work regarding alternative host rocks (crystalline rocks and claystones) had been performed as well for a long time but with lower intensity. Around the year 2000, as a consequence of the moratorium on the Gorleben site, the Federal Government decided to have argillaceous rocks and crystalline rocks investigated in more detail. As Germany does not have any underground research and host rock characterization facilities, international cooperation received a high priority in the German R and D programme for high-level waste (HLW) disposal in order to increase the knowledge regarding alternative host rocks. Major cornerstones of the cooperation are joint projects and experiments conducted especially in underground research laboratories (URL) in crystalline rocks at the Grimsel Test Site (Switzerland) and the Hard Rock Laboratory (HRL) Aespoe(Sweden) and in argillaceous rocks at the URL Mont Terri (Switzerland) and Bure (France). In 2001, the topic of radioactive waste disposal was integrated into the agreement between the former Russian Ministry of Atomic Energy (Minatom, now Rosatom) and the German Ministry of Labor (BMWA), now Ministry of Economic Affairs and Energy (BMWi), on cooperation regarding R and D on the peaceful utilization of nuclear power (agreement on ''Wirtschaftlich-Technische Zusammenarbeit'' WTZ). The intention was to have a new and interesting opportunity for international R and D cooperation regarding HLW disposal in crystalline rocks and the unique possibility to perform site-specific work, to test the safety demonstration tools available, and to expand the knowledge to all aspects specific to these host rocks. Another motivation for joining this cooperation was the

Kinetics of oxidic phase dissolution in acids

International Nuclear Information System (INIS)

Gorichev, I.G.; Kipriyanov, N.A.

1981-01-01

The critical analysis of the experimental data on dissolution kinetics of metal oxides (BeO, V 2 O 5 , UO 2 , Nb 2 O 5 , Ta 2 O 5 etc.) in acid media is carried out. Kinetic peculiarities of oxide dissolution are explained on the basis of the notions of electron- proton theory. It is established that the surface nonstoichiometric ccomposition of oxide phase and potential jump, appearing on the interface of the oxide-electrolyte phase are the important factors, determining the dissolution rate of a solid phase. The dissolution rate of metal oxides is limited by the transition of protons into the solid oxide phase. Morphological models of heterogeneous kinetics are used when explaining kinetic regularities of oxide dissolution process [ru

Dissolution rate of BTEX contaminants in water

International Nuclear Information System (INIS)

Njobuenwu, D.O.; Amadi, S.A.; Ukpaka, P.C.

2005-01-01

Benzene, toluene, ethylbenzene and xylenes (BTEX) and substituted benzenes are the most common aromatic compounds in petroleum. BTEX components are the most soluble and mobile fraction of crude oil and many petroleum products, and frequently enter soil, sediments and aquatic environments because of accidental spills, leaks and improper oil waste disposal practices. The mass transfer process of hydrocarbons in aquatic mediums has received considerable attention in the literature. This paper focused on the molecular mass transfer rate of BTEX in water, with the aim of understanding and predicting contaminant fate and transport. A comprehensive model was developed to simulate the molecular dissolution rate of BTEX in a natural water stream. The model considered the physicochemical properties of the BTEX compounds and physical processes relevant to the spreading of contaminants in the sea. The dissolution rate was a function of oil slick area, dissolution mass transferability and oil solubility in water. The total dissolution rate N was calculated and the dissolution mass transfer coefficient K was given as the point value of mass transfer coefficient. Results for the dissolution rate based on the solubility of the components in the water were compared with analytical solutions from previous studies and showed good agreement. The model showed that benzene had the largest dissolution rate, while o-xylene had the lowest rate because of its lower fraction. Benzene dissolution rate was approximately 2.6, which was 20.6 times that of toluene and ethylbenzene. It was concluded that the model is useful in predicting and monitoring the dissolution rate of BTEX contaminants in soil and water systems. 22 refs., 2 tabs., 3 figs

Dissolution along faults-fractures and hypogenic karst in carbonates: examples from Brazil

Science.gov (United States)

Ennes-Silva, Renata; Cazarin, Caroline; Bezerra, Francisco; Auler, Augusto; Klimchouk, Alexander

2015-04-01

Dissolution along faults-fractures and hypogenic karst in carbonates: examples from Brazil Ennes-Silva, R.A; Cazarin, C.L.; Bezerra, F.H.; Auler, A.S.; Klimchouk, A.B. Dissolution along zones of preferential flow enhances anisotropy in geological media and increases its complexity. Changes in parameters such as porosity and permeability due to diagenesis and presence of ascendant fluids along fractures and faults can be responsible for hypogenic karstic system. The present study investigates the relationship between lithofacies, tectonics and karstification in the Neoproterozoic Salitre Formation, located in the central-eastern Brazil. This unit comprises several systems of caves including the Toca da Boa Vista and da Barriguda hypogenic caves, the largests in South America, and focus of this study. We focused on cave mapping and morphogenetic analysis, determination of petrophysical properties, thin-section description, micro-tomography, and isotopic analysis. The Salitre Formation, deposited in an epicontinental sea, comprises mud/wakestones, grainstones, microbial facies, and fine siliciclastic rocks. Passages occur in several levels within ca. 60 m thick cave-forming section, limited at the top by lithofacies with low permeability and fractures. Cave development occurred in phreatic sluggish-flow environment with overall upwelling flow. Fluids rise via cross-formational fractures and were distributed laterally within the cave-forming section using geological heterogeneities to eventually discharge up through outlets breaching across the upper confining beds. Maps of conduits show preferred directions for development of conduits: NNE-SSW and E-W. These two directions represents a relation between structures and hypogenic morphology. Joints, axis fold and fractures allowed pathways to the fluid rises, and then development of channels of entrance (feeders), outputs (outlets) and some cupolas, which are clearly aligned to fractures. Our data indicate several events

Heterogeneous redox conditions, arsenic mobility, and groundwater flow in a fractured-rock aquifer near a waste repository site in New Hampshire, USA

Science.gov (United States)

Anthropogenic sources of carbon from landfill or waste leachate can promote reductive dissolution of in situ arsenic (As) and enhance the mobility of As in groundwater. Groundwater from residential-supply wells in a fractured crystalline-rock aquifer adjacent to a Superfund site ...

Shear-flow coupling in non-planar rock joints

International Nuclear Information System (INIS)

Makurat, A.; Barton, N.

1985-01-01

Crystalline rock masses are regarded as a possible host rock for permanent nuclear waste disposal. During the excavation of the required shafts and tunnels, the initial state of stress will be changed and cause a deformation of the rock mass and discontinuities. During the lifetime of the nuclear repository joint apertures may change due to thermally induced stress variations during the heating and cooling phase. As the conductivity of a joint is very sensitive to its aperture, fluid flow from and towards a repository, as well as the potential transport times of radionuclides are highly dependent on the deformability of the joints. Theoretical calculations of coupled flow in rock joints (Barton et al. 1984) predict an increase of conductivity of several orders of magnitude for the first few millimeters for shear displacement. The shear-dilation-conductivity coupling for two block sizes at two effective stress levels is shown

Intercalation of paracetamol into the hydrotalcite-like host

Science.gov (United States)

Kovanda, František; Maryšková, Zuzana; Kovář, Petr

2011-12-01

Hydrotalcite-like compounds are often used as host structures for intercalation of various anionic species. The product intercalated with the nonionic, water-soluble pharmaceuticals paracetamol, N-(4-hydroxyphenyl)acetamide, was prepared by rehydration of the Mg-Al mixed oxide obtained by calcination of hydrotalcite-like precursor at 500 °C. The successful intercalation of paracetamol molecules into the interlayer space was confirmed by powder X-ray diffraction and infrared spectroscopy measurements. Molecular simulations showed that the phenolic hydroxyl groups of paracetamol interact with hydroxide sheets of the host via the hydroxyl groups of the positively charged sites of Al-containing octahedra; the interlayer water molecules are located mostly near the hydroxide sheets. The arrangement of paracetamol molecules in the interlayer is rather disordered and interactions between neighboring molecules cause their tilting towards the hydroxide sheets. Dissolution tests in various media showed slower release of paracetamol intercalated in the hydrotalcite-like host in comparison with tablets containing the powdered pharmaceuticals.

Review of potential host rocks for radioactive waste disposal in the Piedmont Province of Georgia

International Nuclear Information System (INIS)

Wenner, D.B.; Gillon, K.A.

1980-10-01

A literature study was conducted on the Piedmont province of Georgia to designate areas that may be favorable for field exploration for consideration of a repository for storage of radioactive waste. The criteria utilized in such a designation was based upon consideration of the rock unit having favorable geological, geotechnical, and geohydrological features. The most important are that the rock unit have: (1) satisfactory unit dimensions (> 100 km 2 outcrop area and at least 1500 meters (approx. 5000 feet) depth of a continuous rock type); and (2) acceptable geohydrological conditions. Among all rock types, it is concluded that the granites of the large post-metamorphic plutons and large, homogeneous orthogneissic units offer the most favorable geologic settings for exploration for siting a radioactive waste repository. Virtually all other rock types, including most metavolcanic and metasedimentary lithologies have unacceptable unit dimensions, generally unfavorable geohydrologic settings, and deleterious mechanical and physical geotechnical properties. After consideration of all major lithologies that comprise the Georgia Piedmont, the following units were deemed favorable: (1) the Elberton Pluton; (2) the Siloam Pluton; (3) the Sparta Pluton; (4) two unnamed plutons adjacent to the Snelson body of S.W. Georgia; (5) the Lithonia Gneiss; (6) basement orthogneisses and charnockites of the Pine Mountain Belt

Formalization of the kinetics for autocatalytic dissolutions. Focus on the dissolution of uranium dioxide in nitric medium

International Nuclear Information System (INIS)

Charlier, F.; Canion, D.; Gravinese, A.; Magnaldo, A.; Lalleman, S.; Borda, G.; Schaer, E.

2017-01-01

Uranium dioxide dissolution in nitric acid is a complex reaction. On the one hand, the dissolution produces nitrous oxides (NOX), which makes it a triphasic reaction. On the other hand, one of the products accelerates the kinetic rate; the reaction is hence called autocatalytic.The kinetics for these kinds of reactions need to be formalized in order to optimize and design innovative dissolution reactors. In this work, the kinetics rates have been measured by optical microscopy using a single particle approach. The advantages of this analytical technique are an easier management of species transport in solution and a precise following of the dissolution rate. The global rate is well described by a mechanism considering two steps: a non-catalyzed reaction, where the catalyst concentration has no influence on the dissolution rate, and a catalyzed reaction. The mass transfer rate of the catalyst was quantified in order to discriminate when the reaction was influenced by catalyst accumulated in the boundary layer or uncatalyzed. This first approximation described well the sigmoid dissolution curve profile. Moreover, experiments showed that solutions filled with catalyst proved to lose reactivity over time. Results pointed out that the higher the liquid-gas exchanges, the faster the kinetic rate decreases with time. Thus, it was demonstrated, for the first time, that there is a link between catalyst and nitrous oxides. The outcome of this study leads to new ways for improving the design of dissolvers. Gas-liquid exchanges are indeed a lever to impact dissolution rates. Temperature and catalyst concentration can be optimized to reduce residence times in dissolvers. (authors)

Fully coupled modeling of radionuclide migration in a clayey rock disturbed by alkaline plume

International Nuclear Information System (INIS)

Pellegrni, D.; Windt, L. de; Lee, J.V.D.

2002-03-01

The disposal of radioactive wastes in clayey formations may require the use of large amounts of concrete and cement as a barrier to minimize corrosion of steel containers and radionuclide migration and for supporting drifts and disposal vaults. In this context, reactive transport modeling of the interactions between cement or concrete and the argillaceous host rock aims at estimating the evolution in time of the containment properties of the multi-barriers system. The objectives of the paper are to demonstrate that integrating radionuclides migration in the modeling of strongly coupled geochemical processes of cement-clay stone interactions is feasible and that it represents an efficient way to assess the sensitivity and modification of the classical Kd and solubility parameters with respect to the chemical evolutions. Two types of modeling are considered in the paper: i): calculation of intrinsic solubility limits and Kd values backing up on the results of modeling of cement/clay stone interactions (radionuclides are assumed to be present over the whole domain at any time whatever the scenario), ii) full mechanistic modeling which explicitly introduces radionuclides in the calculation with ad hoc assumptions on radionuclide inventory, canister failure, migration pathway, etc. The reactive transport code HYTEC, based on the geochemical code CHESS, is used to simulate both the cement-clay stone interaction processes and the radionuclide migration in 1-D and 2-D configurations. Convective/dispersive and diffuse transport can be simulated for solutes and colloids. A wide range of processes such as aqueous chemistry, redox, dissolution/precipitation, surface complexation and ion exchange can be modeled at equilibrium or with kinetic control. In addition, HYTEC is strongly coupled, i.e. the hydrology (flow and diffusion) may change when mineral precipitation or dissolution changes the local porosity. (authors)

Conditions promoting and restraining agronomic effectiveness of water-insoluble phosphate sources, in particular phosphate rock (PR): I. Indices of phosphate rock use opportunity (PRUOIS) and of phosphate rock suitability for direct use (PRSIDU)

International Nuclear Information System (INIS)

Borlan, Z.; Gavriluta, I.; Soare, M.; Stefanescu, D.; Alexandrescu, A.

2002-01-01

Several issues of phosphate rock (PR) use are discussed in this paper. Maize for green fodder (Zea mays L) and ryegrass (Lolium multiflorum Lam.) were grown in 7 kg of dry soil and in small pots of 1.25 kg dry soil capacity, respectively, on several base unsaturated soils belonging to Hapludoll and Hapludalf soil groups. The amount of phosphate rock (PR) to apply was based on experimental data considering soil adsorbed acidity (Ah), humus content (H 2 ), cation exchange capacity (T), sum of exchangeable bases (SEB) and mobile (easily soluble) phosphate content (P A L) in the soil. The factors were combined in a rock phosphate use, opportunity index of the soil (PRUOIS): PRUOIS=(A h *H 2 *100)/SEB*10 0.0245*P AL Rock phosphate suitability for direct use was evaluated by means of the rate of PR-P dissolution (PRPRS) in a 0.6% ammonium heptamolybdate in 0.01M calcium chloride solution (ppm P) and by carbonate content (%CaCO 3 ) in PR. Both of these parameters combined provided a phosphate rock suitability index for direct use (PRSIDU): PRSIDU [ppmP/min]=PRPRS*(1-0.03*CaCO 3 ) Water insoluble P sources studied were PR from Kola-Russia, Morocco, Kneifiss-Siria, El Hassa-Jordan, Gafsa- Tunisia, North-Carolina (USA), and Arad-Israel. All PRs were compared with TSP applied at the same rate of P. Neither PRUOIS or PRSIDU considered separately could satisfactorily explain the variance of PR efficiency. An index obtained by multiplicative combination of PRUOIS x PRSIDU did correlate significantly with indices on the agronomic efficiency of PR. (author)

Mineral storage of CO2/H2S gas mixture injection in basaltic rocks

Science.gov (United States)

Clark, D. E.; Gunnarsson, I.; Aradottir, E. S.; Oelkers, E. H.; Sigfússon, B.; Snæbjörnsdottír, S. Ó.; Matter, J. M.; Stute, M.; Júlíusson, B. M.; Gíslason, S. R.

2017-12-01

Carbon capture and storage is one solution to reducing CO2 emissions in the atmosphere. The long-term geological storage of buoyant supercritical CO2 requires high integrity cap rock. Some of the risk associated with CO2 buoyancy can be overcome by dissolving CO2 into water during its injection, thus eliminating its buoyancy. This enables injection into fractured rocks, such as basaltic rocks along oceanic ridges and on continents. Basaltic rocks are rich in divalent cations, Ca2+, Mg2+ and Fe2+, which react with CO2 dissolved in water to form stable carbonate minerals. This possibility has been successfully tested as a part of the CarbFix CO2storage pilot project at the Hellisheiði geothermal power plant in Iceland, where they have shown mineralization occurs in less than two years [1, 2]. Reykjavik Energy and the CarbFix group has been injecting a mixture of CO2 and H2S at 750 m depth and 240-250°C since June 2014; by 1 January 2016, 6290 tons of CO2 and 3530 tons of H2S had been injected. Once in the geothermal reservoir, the heat exchange and sufficient dissolution of the host rock neutralizes the gas-charged water and saturates the formation water respecting carbonate and sulfur minerals. A thermally stable inert tracer was also mixed into the stream to monitor the subsurface transport and to assess the degree of subsurface carbonation and sulfide precipitation [3]. Water and gas samples have been continuously collected from three monitoring wells and geochemically analyzed. Based on the results, mineral saturation stages have been defined. These results and tracer mass balance calculations are used to evaluate the rate and magnitude of CO2 and H2S mineralization in the subsurface, with indications that mineralization of carbon and sulfur occurs within months. [1] Gunnsarsson, I., et al. (2017). Rapid and cost-effective capture and subsurface mineral storage of carbon and sulfur. Manuscript submitted for publication. [2] Matter, J., et al. (2016). Rapid

On-line monitoring of lithium carbonate dissolution

Energy Technology Data Exchange (ETDEWEB)

Sun, Yuzhu; Song, Xingfu; Wang, Jin; Luo, Yan; Yu, Jianguo [National Engineering Research Center for Integrated Utilization Salt Lake Resources, East China University of Science and Technology, Shanghai (China)

2009-11-15

Dissolution of lithium carbonate (Li{sub 2}CO{sub 3}) in aqueous solution was investigated using three on-line apparatuses: the concentration of Li{sub 2}CO{sub 3} was measured by electrical conductivity equipment; CLD (Chord Length Distribution) was monitored by FBRM (Focused Beam Reflectance Measurement); crystal image was observed by PVM (Particle Video Microscope). Results show dissolution rate goes up with a decrease of particle size, and with an increase in temperature; stirring speed causes little impact on dissolution; ultrasound facilitates dissolution obviously. The CLD evolution and crystal images of Li{sub 2}CO{sub 3}powders in stirred fluid were observed detailedly by FBRM and PVM during dissolution. Experimental data were fitted to Avrami model, through which the activation energy was found to be 34.35 kJ/mol. PBE (Population Balance Equation) and moment transform were introduced to calculate dissolution kinetics, obtaining correlation equations of particle size decreasing rate as a function of temperature and undersaturation. (copyright 2009 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

Study of scenario 'mistake in determination of adsorbing properties of radionuclides on the materials of engineering barriers and host rock'

International Nuclear Information System (INIS)

Amosov, P.V.; Novozhilova, N.V.

2008-01-01

During investigations within the framework of this ASE of a storage facility, conceptual and mathematical models remained the same, as in SNE. Basic provisions of models, a solution 'tool' for diffusion equation taking into account radioactive decay and the chosen boundary conditions are presented in paper. The 79 Se isotope is chosen as basic analyzed radionuclide within the framework of the accepted ASE. The selection of this isotope can be substantiated by the following reasons: 1) Migration parameters of this radionuclide, in particular, the distribution coefficient of 79 Se isotope has specific enough values. For example, in granitoid formations (according to different research groups from Sweden, Finland, Switzerland during rather a small time range of experiments carrying out) the values of distribution coefficient vary within 20 times and thus its numerical value is small enough (0.0005 - 0.01 m 3 /kg). At the same time, the situation is reverse with cement materials: from references accessible to us only in one the value of this parameter is cited. 2) Performing calculations for the full list of radio-nuclides (in the SNE there were 8 of them) will require considerable labor expenditures and computer facilities resources: much processor time and much memory on a hard disk to store information. Since, when considering the selected ASE of facility there are accepted 4 areas of materials (the source, concrete, bentonite, the host rock) generally, it means practically a fourfold increase of all specified expenses in comparison with similar expenses for a SNE of facility. The main conclusions are: There are considered possible variants of error, which consequence is the 79 Se isotope transition in the category of a non-sorbing one in respective barrier of the near field that can conservatively lead to an increase of the facility hazard. If there is an error in selection of sorption parameters of 79 Se isotope in the host rock an increase in pollution of the

Simulation of anions diffusion in Callovo-Oxfordian argillite by description of the rock microstructure

International Nuclear Information System (INIS)

Diaz, N.

2008-01-01

The Callovo-Oxfordian argillite has been proposed as host rock for deep underground radioactive wastes storage. The aim of this study is to determine the report of effective diffusion coefficients De(anion)/De(water) at the micrometer scale considering the spatial distribution of minerals in the rock. (A.L.B.)

Sorption data bases for generic Swiss argillaceous rock systems

International Nuclear Information System (INIS)

Bradbury, M. H.; Baeyens, B.; Thoenen, T.

2010-09-01

In Switzerland the site selection procedure for both high level waste (HLW) and low and intermediate level waste (L/ILW) repositories is specified by the Swiss Federal Office of Energy in the Sectoral Plan for Deep Geological Repositories. In the forthcoming stage 2 of this plan, potential sites will be identified within regions previously selected based on the presence of suitable host rocks, namely Opalinus Clay, 'Brauner Dogger', Effingen Member and Helvetic Marl. Preliminary safety analyses are an integral part of this procedure, and require, amongst other information, the radionuclide sorption properties of the host rock. This report describes a methodology to develop a Generic Rock Sorption Data Base (GR-SDB) for argillaceous rocks. The method will be used to compile specific SDBs for the above mentioned host rocks. Arguments are presented that the main factor influencing sorption on argillaceous rocks is the phyllosilicate mineral content. These minerals are particularly effective at binding metals to their surfaces by cation exchange and surface complexation. Generally, the magnitude of sorption is directly correlated with the phyllosilicate content (2:1 type clays: illite/smectite/illitesmectite mixed layers), and this parameter best reflects the sorption potential of a given mineral assembly. Consequently, sorption measurements on illite were preferably used as source data for the GR-SDB. The second component influencing radionuclide sorption is the porewater chemistry. In the present report, generic water compositions were extracted from the analytical ranges of deep ground waters in various sedimentary formations in Switzerland. In order to cover the range of ionic strength (I) and pH values of Swiss ground waters in argillaceous rocks, five types of generic water compositions were defined, combining low, intermediate and high values of ionic strength and pH. The GR-SDB for in situ conditions was derived using conversion factors (CF). As the name

Ectoparasite diversity in the eastern rock sengis ( Elephantulus ...

African Journals Online (AJOL)

Ectoparasite diversity in the eastern rock sengis ( Elephantulus myurus ): the effect of seasonality and host sex. ... The ectoparasite assemblage comprised 11 groups of tick species, a single mite family, one louse and two flea species, with ticks and mites being the most numerous ectoparasites recovered. The prevalence ...

Monitoring the hydrolyzation of aspirin during the dissolution testing for aspirin delayed-release tablets with a fiber-optic dissolution system

Directory of Open Access Journals (Sweden)

Yan Wang

2012-10-01

Full Text Available The purpose of this study was to investigate the hydrolyzation of aspirin during the process of dissolution testing for aspirin delayed-release tablets. Hydrolysis product of salicylic acid can result in adverse effects and affect the determination of dissolution rate assaying. In this study, the technique of differential spectra was employed, which made it possible to monitor the dissolution testing in situ. The results showed that the hydrolyzation of aspirin made the percentage of salicylic acid exceed the limit of free salicylic acid (4.0, and the hydrolyzation may affect the quality detection of aspirin delayed-release tablets. Keywords: Aspirin delayed-release tablets, Drug dissolution test, Fiber-optic dissolution system, UV–vis spectrum

Basic processes and factors determining the evolution of collapse sinkholes: a sensitivity study

Science.gov (United States)

Romanov, Douchko; Kaufmann, Georg

2017-04-01

Collapse sinkholes appear as closed depressions at the surface. The origin of these karst features is related to the continuous dissolution of the soluble rock caused by a focussed sub-surface flow. Water flowing along a preferential pathway through fissures and fractures within the phreatic part of a karst aquifer is able to dissolve the rock (limestone, gypsum, anhydrite). With time, the dissolved void volume increases and part of the ceiling above the stream can become unstable, collapses, and accumulates as debris in the flow path. The debris partially blocks the flow and thus activates new pathways. Because of the low compaction of the debris (high hydraulic conductivity), the flow and the dissolution rates within this crushed zone remain high. This allows a relatively fast dissolutional and erosional removal of the crushed material and the development of new empty voids. The void volume expands upwards towards the surface until a collapse sinkhole is formed. The collapse sinkholes exhibit a large variety of shapes (cylindrical, cone-, bowl-shaped), depths (from few to few hundred meters) and diameters (meters up to hundreds of meters). Two major processes are responsible for this diversity: a) the karst evolution of the aquifer - responsible for the dissolutional and erosional removal of material; b) the mechanical evolution of the host rock and the existence of structural features, faults for example, which determine the stability and the magnitude of the subsequent collapses. In this work we demonstrate the influence of the host rock type, the hydrological and geological boundary conditions, the chemical composition of the flowing water, and the geometry and the scale of the crushed zone, on the location and the evolution of the growing sinkhole. We demonstrate the ability of the karst evolution models to explain, at least qualitatively, the growth and the morphology of the collapse sinkholes and to roughly predict their shape and location. Implementing

Microbial- and Thiosulfate-Mediated Dissolution of Mercury Sulfide Minerals and Transformation to Gaseous Mercury

Directory of Open Access Journals (Sweden)

Adiari eVázquez-Rodríguez

2015-06-01

Full Text Available Mercury (Hg is a toxic heavy metal that poses significant human and environmental health risks. Soils and sediments, where Hg can exist as the Hg sulfide mineral metacinnabar (β-HgS, represent major Hg reservoirs in aquatic environments. Metacinnabar has historically been considered a sink for Hg in all but severely acidic environments, and thus disregarded as a potential source of Hg back to aqueous or gaseous pools. Here, we conducted a combination of field and laboratory incubations to identify the potential for metacinnabar as a source of dissolved Hg within near neutral pH environments and the underpinning (abiotic mechanisms at play. We show that the abundant and widespread sulfur-oxidizing bacterium Thiobacillus extensively colonized metacinnabar chips incubated within aerobic, near neutral pH creek sediments. Laboratory incubations of axenic Thiobacillus cultures lead to the release of metacinnabar-hosted Hg(II and subsequent volatilization to Hg(0. This dissolution and volatilization was greatly enhanced in the presence of the sulfur intermediate, thiosulfate, which served a dual role by enhancing HgS dissolution and providing an additional metabolic substrate for Thiobacillus. These findings reveal a new coupled abiotic-biotic pathway for the transformation of metacinnabar-bound Hg(II to Hg(0, while expanding the sulfide substrates available for neutrophilic chemosynthetic bacteria to Hg-laden sulfides. They also point to mineral-hosted Hg as an underappreciated source of gaseous elemental Hg to the environment.

Uranium migration and retention during weathering of a granitic waste rock pile

International Nuclear Information System (INIS)

Boekhout, F.; Gérard, M.; Kanzari, A.; Michel, A.; Déjeant, A.; Galoisy, L.; Calas, G.; Descostes, M.

2015-01-01

Highlights: • We investigate the environmental impact of the granitic waste rock piles. • The majority of the waste rocks in the pile is barren- or overburden rock. • The main neo-formed U-bearing phases are (Ca) and (Cu) uranyl phosphates. • Under circum-neutral pH conditions they do not pose an environment threat. - Abstract: This study investigates the post-mining evolution of S-type granitic waste rocks around a former uranium mine, Vieilles Sagnes (Haute Vienne, NW Massif Central, France). This mine was operated between 1957 and 1965 in the La Crouzille former world-class uranium mining district and is representative of intra-granitic vein-type deposits. 50 years after mine closure and the construction and subsequent re-vegetation of the granitic waste rock pile, we evaluate the environmental evolution of the rock pile, including rock alteration, neo-formation of U-bearing phases during weathering, and U migration. Vertical trenches have been excavated through the rock pile down to an underlying paleo-soil, allowing the investigation of the vertical differentiation of the rock pile and its influence on water pathways, weathering processes and U migration and retention. Arenization dominantly drives liberation of U, by dissolution of uraninite inclusions in the most alterable granitic minerals (i.e. K-feldspar and biotite). Retention of U in the matrix at the base of the waste rock pile, and in the underlying paleo-soil most likely occurs by precipitation of (nano-) uranyl phosphates or a combination of co-precipitation and adsorption reactions of U onto Fe (oxy)hydroxides and/or clay minerals. Even though U-migration was observed, U is retained in stable secondary mineral phases, provided the current conditions will not be modified

Use of partial dissolution techniques in geochemical exploration

Science.gov (United States)

Chao, T.T.

1984-01-01

Application of partial dissolution techniques to geochemical exploration has advanced from an early empirical approach to an approach based on sound geochemical principles. This advance assures a prominent future position for the use of these techniques in geochemical exploration for concealed mineral deposits. Partial dissolution techniques are classified as single dissolution or sequential multiple dissolution depending on the number of steps taken in the procedure, or as "nonselective" extraction and as "selective" extraction in terms of the relative specificity of the extraction. The choice of dissolution techniques for use in geochemical exploration is dictated by the geology of the area, the type and degree of weathering, and the expected chemical forms of the ore and of the pathfinding elements. Case histories have illustrated many instances where partial dissolution techniques exhibit advantages over conventional methods of chemical analysis used in geochemical exploration. ?? 1984.

Water-rock interaction and chemistry of groundwaters from the Canadian Shield

International Nuclear Information System (INIS)

Frape, S.K.; Fritz, P.; McNutt, R.H.

1984-01-01

The chemical and isotopic compositions of groundwaters in the crystalline rocks of the Canadian Shield reflect different degrees of rock-water interactions. The chemistry of the shallow, geochemically immature ground waters and especially of the major cations is controlled by local rock compositions, whereby dissolution reactions dominate. Conservative constituents, such as chloride and bromide, however, are not entirely a result of such reactions but appear to be readily added from leachable salts during the initial stages of the geochemical evolution of these waters. Their concentration changes little as major cations increase, until concentrations of Total Dissolved Solids (TDS) reach 3000 to 5000 mg l -1 . The isotopic composition of these shallow waters reflects local, present day precipitations. In contrast to the shallow groundwaters, the isotopic and chemical compositions of the deep, saline waters and brines are determined by extensive, low-temperature rock-water interactions. This is documented in major ion chemistries, 18 O contents and strontium isotopic compositions. These data indicate that the deep brines have been contained in hydrologically isolated pockets. The almost total loss of primary compositions make discussions on the origin of these brines very speculative. However, all brines from across the Canadian Shield have a very similar chemical composition, which probably reflects a common geochemical history. (author)

Experimental study of kinetic and mechanism of dissolution of apatite structured minerals. Application to the prediction of the long term behavior of an actinides storage host matrix; Etude experimentale de la cinetique et des mecanismes d'alteration de mineraux apatitiques. Application au comportement d'une ceramique de confinement d'actinides mineurs

Energy Technology Data Exchange (ETDEWEB)

Chairat, C

2005-11-15

The motivation for this study is to assess the potential of using apatite structured ceramics as long-lived actinide storage hosts. To assess their ability to resist aqueous corrosion, the dissolution of natural fluoro-apatite and synthetic Nd-britholite (neodymium is a proxy for the trivalent actinides) was studied. Mineral surfaces were characterized using a combined spectrometric, electrokinetic and potentiometric approach and dissolution rates were measured in closed and open system reactors as a function of solution composition. Experimental results suggest apatitic minerals dissolve via distinct step sequence: 1) fluoride release, 2) release of the calcium situated in the M1, and 3) the simultaneous removal of phosphate and calcium II via the breaking of only Ca-O bonds. TST based rate equations based in this mechanism accurately describe fluoro-apatite and synthetic britholite dissolution rates as a function of solution composition. Nd release rates are limited by precipitation of Nd-rhabdophane. (author)

Effect of mineral constituents in the bioleaching of uranium from uraniferous sedimentary rock samples, Southwestern Sinai, Egypt.

Science.gov (United States)

Amin, Maisa M; Elaassy, Ibrahim E; El-Feky, Mohamed G; Sallam, Abdel Sattar M; Talaat, Mona S; Kawady, Nilly A

2014-08-01

Bioleaching, like Biotechnology uses microorganisms to extract metals from their ore materials, whereas microbial activity has an appreciable effect on the dissolution of toxic metals and radionuclides. Bioleaching of uranium was carried out with isolated fungi from uraniferous sedimentary rocks from Southwestern Sinai, Egypt. Eight fungal species were isolated from different grades of uraniferous samples. The bio-dissolution experiments showed that Aspergillus niger and Aspergillus terreus exhibited the highest leaching efficiencies of uranium from the studied samples. Through monitoring the bio-dissolution process, the uranium grade and mineralogic constituents of the ore material proved to play an important role in the bioleaching process. The tested samples asserted that the optimum conditions of uranium leaching are: 7 days incubation time, 3% pulp density, 30 °C incubation temperature and pH 3. Both fungi produced the organic acids, namely; oxalic, acetic, citric, formic, malonic, galic and ascorbic in the culture filtrate, indicating an important role in the bioleaching processes. Copyright © 2014 Elsevier Ltd. All rights reserved.

Aqueous dissolution rates of uranium oxides

International Nuclear Information System (INIS)

Steward, S.A.; Mones, E.T.

1994-10-01

An understanding of the long-term dissolution of waste forms in groundwater is required for the safe disposal of high level nuclear waste in an underground repository. The main routes by which radionuclides could be released from a geological repository are the dissolution and transport processes in groundwater flow. Because uranium dioxide is the primary constituent of spent nuclear fuel, the dissolution of its matrix in spent fuel is considered the rate-limiting step for release of radioactive fission products. The purpose of our work has been to measure the intrinsic dissolution rates of uranium oxides under a variety of well-controlled conditions that are relevant to a repository and allow for modeling. The intermediate oxide phase U 3 O 8 , triuranium octaoxide, is quite stable and known to be present in oxidized spent fuel. The trioxide, UO 3 , has been shown to exist in drip tests on spent fuel. Here we compare the results of essentially identical dissolution experiments performed on depleted U 3 O 8 and dehyrated schoepite or uranium trioxide monohydrate (UO 3 ·H 2 O). These are compared with earlier work on spent fuel and UO 2 under similar conditions

Dissolution of rock phosphate in animal manure soil amendment and lettuce growth

Directory of Open Access Journals (Sweden)

Kofi Agyarko

2016-04-01

Full Text Available A study was conducted in pots on the field to assess the effect of different quantities of poultry manure (PM, cattle manure (CM and pig manure (PG on the release of available phosphorus from Togo rock phosphate (RP and lettuce growth. There were eleven (11 treatments which were: Control (soil only; 2.5g RP; 2.5g CM; 2.5gRP + 2.5g CM; 2.5gRP + 5gCM; 2.5gPM; 2.5gRP + 2.5gPM; 2.5gRP + 5gPM; 2.5gPG; 2.5gRP + 2.5gPG; 2.5gRP + 5gPG, applied per kg soil, using the Completely Randomized Design (CRD with three replications. Available phosphorus and other parameters were assessed using standard methods. Results were statistically analyzed using the the GenStat (11th Edition statistical software package. The amount and type of animal manure in the amendment affected the amount of the available P released. The addition of 2.5g manure to 2.5g RP in a kg of soil significantly (P<0.05 increased available P by 4 to 7 times over the sole 2.5g RP/kg soil treatment. Doubling the amount of manure in the amendment (5g manure + 2.5g RP almost doubled the amount of P released, with the poultry manure combinations being more significant. The amount of available P in the soil positively related to the plant height (R2=63, leaf area (R2=0.55, dry weight (R2=0.73 and the percentage P in the leaf (R2=0.88 of lettuce. The PM at 2.5gRP + 5gPM recorded the highest significant (P<0.05 values. The study has provided further basis for manure selection and quantities to be used in enhancing the release of P from rock phosphate. However, investigations need to be continued using nuclear techniques.

Comparative geology and geochemistry of sedimentary-rock-hosted (Carlin Type) gold deposits in the People's Republic of China and in Nevada, USA

Science.gov (United States)

Li, Zhiping; Peters, Stephen G.

1998-01-01

Sedimentary-rock-hosted (Carlin-type) gold deposits have been considered economically significant and geologically distinct since the early 1960's. This report consists of a nine-part text and an interactive database. This small database is to help Western companies get more information about these gold deposits in China, and to help geologists who are interested in world Carlin-type deposits conduct research on them. Because of their economic significance and geological distinctiveness, these deposits have caught the interest of economic geologists all over the world since the early 1960's. Similar deposits have been discovered in China, Australia, Dominican Republic, Spain, and Russia besides Nevada. Perhaps most significant are the 165 Carlin-type gold deposits that were found in southwest China during the past 15 years. Of these, at least 19 deposits have proven to be of substantial tonnage, making China the second leading country to exploit such deposits. With the increasing interest in Chinese Carlin-type gold deposits, some western companies and geologists desire to get more information about these Chinese deposits. This seems to have been very difficult because the literature was in Chinese. It is estimated that several hundred scientific publications (including papers, books, and technical reports) have been published. This database of Chinese Carlin-type Gold deposits is built on the documentation published during the most recent 10 years and includes six subjects, which consist of 165 records and 30 fields. A new Proterozoic-age sedimentary-rock-hosted gold deposit in northeastern P.R. China also is described. Note that for the old version 1.1 on the CD-ROM, the latitude and longitude locations of the mineral occurrences have been estimated from sketch maps and journal articles and are not intended for digital analysis. One of the improvements in this version 1.2 is the accuracy of geographic data. Version 1.3 updates to the database and includes maps

Dissolution of metallic uranium in alkalis

International Nuclear Information System (INIS)

Mondino, Angel V.; Wilkinson, Maria V.; Manzini, Alberto C.

1999-01-01

The dissolution of U metallic foils has been studied in the framework of the development of an improved 99 Mo-production process. The best conditions for the dissolution of uranium foils of approximately 150 μm are the following: a) NaClO concentrations of 0.20 and 0.23 M with NaOH of 0.27 and 0.31 M respectively; b) temperature of the solution, 70 C degrees; c) volume of the solution, 15 ml / cm 2 of uranium foil; d) dissolution time, 30 minutes. (author)

Development and Validation of a Dissolution Test Method for ...

African Journals Online (AJOL)

Purpose: To develop and validate a dissolution test method for dissolution release of artemether and lumefantrine from tablets. Methods: A single dissolution method for evaluating the in vitro release of artemether and lumefantrine from tablets was developed and validated. The method comprised of a dissolution medium of ...

Low temperature dissolution flowsheet for plutonium metal

Energy Technology Data Exchange (ETDEWEB)

Daniel, W. E. [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL); Almond, P. M. [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL); Rudisill, T. S. [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL)

2016-05-01

The H-Canyon flowsheet used to dissolve Pu metal for PuO₂ production utilizes boiling HNO₃. SRNL was requested to develop a complementary dissolution flowsheet at two reduced temperature ranges. The dissolution and H₂ generation rates of Pu metal were investigated using a dissolving solution at ambient temperature (20-30 °C) and for an intermediate temperature of 50-60 °C. Additionally, the testing included an investigation of the dissolution rates and characterization of the off-gas generated from the ambient temperature dissolution of carbon steel cans and the nylon bags that contain the Pu metal when charged to the dissolver.

Petrographic and geochemical data for Cenozoic volcanic rocks of the Bodie Hills, California and Nevada

Science.gov (United States)

du Bray, Edward A.; John, David A.; Box, Stephen E.; Vikre, Peter G.; Fleck, Robert J.; Cousens, Brian L.

2013-04-23

Petrographic and geochemical data for Cenozoic volcanic rocks of the Bodie Hills, California and Nevada // // This report presents petrographic and geochemical data for samples collected during investigations of Tertiary volcanism in the Bodie Hills of California and Nevada. Igneous rocks in the area are principally 15–6 Ma subduction-related volcanic rocks of the Bodie Hills volcanic field but also include 3.9–0.1 Ma rocks of the bimodal, post-subduction Aurora volcanic field. Limited petrographic results for local basement rocks, including Mesozoic granitoid rocks and their metamorphic host rocks, are also included in the compilation. The petrographic data include visual estimates of phenocryst abundances as well as other diagnostic petrographic criteria. The geochemical data include whole-rock major oxide and trace element data, as well as limited whole-rock isotopic data.

Physical heterogeneity control on effective mineral dissolution rates

Science.gov (United States)

Jung, Heewon; Navarre-Sitchler, Alexis

2018-04-01

Hydrologic heterogeneity may be an important factor contributing to the discrepancy in laboratory and field measured dissolution rates, but the governing factors influencing mineral dissolution rates among various representations of physical heterogeneity remain poorly understood. Here, we present multiple reactive transport simulations of anorthite dissolution in 2D latticed random permeability fields and link the information from local grid scale (1 cm or 4 m) dissolution rates to domain-scale (1m or 400 m) effective dissolution rates measured by the flux-weighted average of an ensemble of flow paths. We compare results of homogeneous models to heterogeneous models with different structure and layered permeability distributions within the model domain. Chemistry is simplified to a single dissolving primary mineral (anorthite) distributed homogeneously throughout the domain and a single secondary mineral (kaolinite) that is allowed to dissolve or precipitate. Results show that increasing size in correlation structure (i.e. long integral scales) and high variance in permeability distribution are two important factors inducing a reduction in effective mineral dissolution rates compared to homogeneous permeability domains. Larger correlation structures produce larger zones of low permeability where diffusion is an important transport mechanism. Due to the increased residence time under slow diffusive transport, the saturation state of a solute with respect to a reacting mineral approaches equilibrium and reduces the reaction rate. High variance in permeability distribution favorably develops large low permeability zones that intensifies the reduction in mixing and effective dissolution rate. However, the degree of reduction in effective dissolution rate observed in 1 m × 1 m domains is too small (equilibrium conditions reduce the effective dissolution rate by increasing the saturation state. However, in large domains where less- or non-reactive zones develop, higher

Dissolution rates of DWPF glasses from long-term PCT

International Nuclear Information System (INIS)

Ebert, W.L.; Tam, S.W.

1996-01-01

We have characterized the corrosion behavior of several Defense Waste Processing Facility (DWPF) reference waste glasses by conducting static dissolution tests with crushed glasses. Glass dissolution rates were calculated from measured B concentrations in tests conducted for up to five years. The dissolution rates of all glasses increased significantly after certain alteration phases precipitated. Calculation of the dissolution rates was complicated by the decrease in the available surface area as the glass dissolves. We took the loss of surface area into account by modeling the particles to be spheres, then extracting from the short-term test results the dissolution rate corresponding to a linear decrease in the radius of spherical particles. The measured extent of dissolution in tests conducted for longer times was less than predicted with this linear dissolution model. This indicates that advanced stages of corrosion are affected by another process besides dissolution, which we believe to be associated with a decrease in the precipitation rate of the alteration phases. These results show that the dissolution rate measured soon after the formation of certain alteration phases provides an upper limit for the long-term dissolution rate, and can be used to determine a bounding value for the source term for radionuclide release from waste glasses. The long-term dissolution rates measured in tests at 20,000 per m at 90 degrees C in tuff groundwater at pH values near 12 for the Environmental Assessment glass and glasses made with SRL 131 and SRL 202 frits, respectively

Hydrothermal modification of host rock geochemistry within Mo-Cu porphyry deposits in the Galway Granite, western Ireland

Science.gov (United States)

Tolometti, Gavin; McCarthy, Will

2016-04-01

Hydrothermal alteration of host rock is a process inherent to the formation of porphyry deposits and the required geochemical modification of these rocks is regularly used to indicate proximity to an economic target. The study involves examining the changes in major, minor and trace elements to understand how the quartz vein structures have influenced the chemistry within the Murvey Granite that forms part of the 380-425Ma Galway Granite Complex in western Ireland. Molybdenite mineralisation within the Galway Granite Complex occurred in close association with protracted magmatism at 423Ma, 410Ma, 407Ma, 397Ma and 383Ma and this continues to be of interest to active exploration. The aim of the project is to characterize hydrothermal alteration associated with Mo-Cu mineralisation and identify geochemical indicators that can guide future exploration work. The Murvey Granite intrudes metagabbros and gneiss that form part of the Connemara Metamorphic complex. The intrusion is composed of albite-rich pink granite, garnetiferous granite and phenocrytic orthoclase granite. Minor doleritic dykes post-date the Murvey Granite, found commonly along its margins. Field mapping shows that the granite is truncated to the east by a regional NW-SE fault and that several small subparallel structures host Mo-Cu bearing quartz veins. Petrographic observations show heavily sericitized feldspars and plagioclase and biotite which have undergone kaolinization and chloritisation. Chalcopyrite minerals are fine grained, heavily fractured found crystallized along the margins of the feldspars and 2mm pyrite crystals. Molybdenite are also seen along the margins of the feldspars, crystallized whilst the Murvey Granite cooled. Field and petrographic observations indicate that mineralisation is structurally controlled by NW-SE faults from the selected mineralization zones and conjugate NE-SW cross cutting the Murvey Granite. Both fault orientations exhibit quartz and disseminated molybdenite

Simfuel dissolution studies in granitic groundwater

International Nuclear Information System (INIS)

Casas, I.; Caceci, M.S.; Bruno, J.; Sandino, A.; Ollila, K.

1991-09-01

The dissolution behavior of an unirradiated chemical analogue of spent nuclear fuel (SIMFUEL) has been studied in the presence of two different synthetic groundwater at 25 deg C and under both oxic and anoxic conditions. The release of U, Mo, Ba, Y and Sr was monitored during static (batch) leaching experiments of long duration (about 250 days). Preliminary results from continuous flow-through reactor experiments are also reported. The results obtained indicate the usefulness and limitations of SIMFUEL in the study of the kinetics and mechanism of dissolution of the minor components of spent nuclear fuel. Molybdenum, barium and strontium have shown a trend to congruent dissolution with the SIMFUEL matrix after a higher initial fractional release. Yttrium release has been found to be solubility controlled under the experimental conditions. A clear dependence on the partial pressure of O 2 of the rates of dissolution of uranium has been observed

SIMFUEL dissolution studies in granitic groundwater

International Nuclear Information System (INIS)

Casas, I.; Caceci, M.S.; Bruno, J; Sandino, A.

1991-09-01

The dissolution behavior of an unirradiated chemical analogue of spent nuclear fuel (SIMFUEL) has been studied in the presence of two different synthetic groundwaters at 25 degrees C and under both oxic and anoxic conditions. The release of U, Mo, Ba, Y and Sr was monitored during static (batch) leaching experiments of long duration (about 250 days). Preliminary results from continuous flow-through reactor experiments are also reported. The results obtained indicate the usefulness and limitations of SIMFUEL in the study of the kinetics and mechanism of dissolution of the minor components of spent nuclear fuel. Molybdenum, barium and strontium have shown a trend of congruent dissolution with the SIMFUEL matrix after a higher initial fractional release has been found to be solubility controlled under the experimental conditions. A clear dependence on the partial pressure of O 2 of the rate of dissolution of uranium has been observed. (au)

Overview of chemical modeling of nuclear waste glass dissolution

International Nuclear Information System (INIS)

Bourcier, W.L.

1991-02-01

Glass dissolution takes place through metal leaching and hydration of the glass surface accompanied by development of alternation layers of varying crystallinity. The reaction which controls the long-term glass dissolution rate appears to be surface layer dissolution. This reaction is reversible because the buildup of dissolved species in solution slows the dissolution rate due to a decreased dissolution affinity. Glass dissolution rates are therefore highly dependent on silica concentrations in solution because silica is the major component of the alteration layer. Chemical modeling of glass dissolution using reaction path computer codes has successfully been applied to short term experimental tests and used to predict long-term repository performance. Current problems and limitations of the models include a poorly defined long-term glass dissolution mechanism, the use of model parameters determined from the same experiments that the model is used to predict, and the lack of sufficient validation of key assumptions in the modeling approach. Work is in progress that addresses these issues. 41 refs., 7 figs., 2 tabs

THE STUDY OF GAS MIGRATION IN CRYSTALLINE ROCK USING INJECTION TESTS

Directory of Open Access Journals (Sweden)

Jiří Svoboda

2012-07-01

Full Text Available The study of gas migration in crystalline rock using injection tests is being carried out in the frame of the FORGE (Fate of Repository Gases project. The Czech Technical University in Prague (CTU, Centre of Experimental Geotechnics (CEG is participating in WP4 which is focused on disturbed host rock formations with respect to radioactive waste deep repositories. A series of in-situ tests is being conducted at the Josef Underground Laboratory. The aim of the testing is to simulate and study phenomena that might lead to gas-driven radionuclide transport in fractured crystalline rock. The in-situ tests combine migration and large-scale gas injection measurements; gas injection tests are being employed for the study of gas transport. For the purposes of comparison of the behaviour of the rock mass with regard to air and water a series of water pressure tests are also being carried out. The quality of the rock mass is assessed using rock mass classification systems.

Reactive transport simulations of the evolution of a cementitious repository in clay-rich host rocks

Science.gov (United States)

Kosakowski, Georg; Berner, Urs; Kulik, Dmitrii A.

2010-05-01

that the clay mineral is represented by a X- '(solute) ligand' initially occupied with e.g. Na+. Our representation of cation exchange is based on a multi end-member ideal solid solution model for the clay which at the same time considers the chemical reactivity of the clay phase in the high pH cement environment. As a first application, we will present the results of calculations of the interaction between a cement compartment in contact with a clay-rich host rock. References: Bradbury, M. & Baeyens, B. (2002). Porewater chemistry in compacted re-saturated MX-80 bentonite: Physico-chemical characterisation and geochemical modelling. PSI-Report 02-10, Paul Scherrer Institut, Villigen, Switzerland. Lothenbach, B. & Wieland, E. (2006). A thermodynamic approach to the hydration of sulphate-resisting Portland cement. Waste Management, 26, 706-719. Shao, H., Dmytrieva, S.V., Kolditz, O., Kulik, D.A., Pfingsten, W. & Kosakowski, G. (2009). Modeling reactive transport in non-ideal aqueous-solid solution system. Applied Geochemistry, 24(7), 1287-1300.

Development and validation of dissolution test for Metoprolol ...

African Journals Online (AJOL)

The dissolution method which uses USP apparatus I (Basket) with rotating at 100 rpm, 900 ml of different dissolution medium, ultra violet spectroscopy for quantification was demonstrated to be robust, discriminating and transferable. Dissolution tests conditions were selected after it was demonstrated that the Metoprolol ...

Interactions between a poorly soluble cationic drug and sodium dodecyl sulfate in dissolution medium and their impact on in vitro dissolution behavior.

Science.gov (United States)

Huang, Zongyun; Parikh, Shuchi; Fish, William P

2018-01-15

In the pharmaceutical industry, in vitro dissolution testing ofsolid oral dosage forms is a very important tool for drug development and quality control. However, ion-pairing interaction between the ionic drugand surfactants in dissolution medium often occurs, resulting in inconsistent and incomplete drug release. The aim of this study is toevaluate the effects ofsodium dodecyl sulfate (SDS) mediated medium onthe dissolution behaviors of a poorly soluble cationic drug (Drug B). The study was carried out by measuring solubility of Drug B substance and dissolution rate of Drug B product in media containing SDS.Desolubilization of Drug B substance was observed at pH 4.5 in the presence of SDS at concentrations below critical micelle concentration (CMC) which is attributed to the formation of an insoluble di-dodecyl sulfate salt between SDS and Drug B. This ion-pairing effect is less significant with increasing medium pH where Drug B is less ionized and CMC of SDS is lower. In medium at pH 4.5, dissolution of Drug B product was found incomplete with SDS concentration below CMC due to the desolubilization of Drug B substance. In media with SDS level above CMC, the dissolution rate is rather slower with higher inter-vessel variations compared to that obtained in pH 4.5 medium without SDS. The dissolution results demonstrate that the presence of SDS in medium generates unexpected irregular dissolution profiles for Drug B which are attributed to incompatible dissolution medium for this particular drug. Therefore, non-ionic surfactant was selected for Drug B product dissolution method and ion-pairing effect in SDS mediated medium should be evaluated when developing a dissolution method for any poorly soluble cationic drugs. Copyright © 2017 Elsevier B.V. All rights reserved.

Geochemistry of silicate-rich rocks can curtail spreading of carbon dioxide in subsurface aquifers.

Science.gov (United States)

Cardoso, S S S; Andres, J T H

2014-12-11

Pools of carbon dioxide are found in natural geological accumulations and in engineered storage in saline aquifers. It has been thought that once this CO2 dissolves in the formation water, making it denser, convection streams will transport it efficiently to depth, but this may not be so. Here, we assess theoretically and experimentally the impact of natural chemical reactions between the dissolved CO2 and the rock formation on the convection streams in the subsurface. We show that, while in carbonate rocks the streaming of dissolved carbon dioxide persists, the chemical interactions in silicate-rich rocks may curb this transport drastically and even inhibit it altogether. These results challenge our view of carbon sequestration and dissolution rates in the subsurface, suggesting that pooled carbon dioxide may remain in the shallower regions of the formation for hundreds to thousands of years. The deeper regions of the reservoir can remain virtually carbon free.

Dissolution studies of spent nuclear fuels

International Nuclear Information System (INIS)

1991-02-01

To obtain quantitative data on the dissolution of high burnup spent nuclear fuel, dissolution study have been carried out at the Department of Chemistry, JAERI, from 1984 under the contract with STA entitled 'Reprocessing Test Study of High Burnup Fuel'. In this study PWR spent fuels of 8,400 to 36,100 MWd/t in averaged burnup were dissolved and the chemical composition and distribution of radioactive nuclides were measured for insoluble residue, cladding material (hull), off-gas and dissolved solution. With these analyses basic data concerning the dissolution and clarification process in the reprocessing plant were accumulated. (author)

Dissolution testing of orally disintegrating tablets.

Science.gov (United States)

Kraemer, Johannes; Gajendran, Jayachandar; Guillot, Alexis; Schichtel, Julian; Tuereli, Akif

2012-07-01

For industrially manufactured pharmaceutical dosage forms, product quality tests and performance tests are required to ascertain the quality of the final product. Current compendial requirements specify a disintegration and/or a dissolution test to check the quality of oral solid dosage forms. These requirements led to a number of compendial monographs for individual products and, at times, the results obtained may not be reflective of the dosage form performance. Although a general product performance test is desirable for orally disintegrating tablets (ODTs), the complexity of the release controlling mechanisms and short time-frame of release make such tests difficult to establish. For conventional oral solid dosage forms (COSDFs), disintegration is often considered to be the prerequisite for subsequent dissolution. Hence, disintegration testing is usually insufficient to judge product performance of COSDFs. Given the very fast disintegration of ODTs, the relationship between disintegration and dissolution is worthy of closer scrutiny. This article reviews the current status of dissolution testing of ODTs to establish the product quality standards. Based on experimental results, it appears that it may be feasible to rely on the dissolution test without a need for disintegration studies for selected ODTs on the market. © 2012 The Authors. JPP © 2012 Royal Pharmaceutical Society.

Importance of surface structure on dissolution of fluorite

DEFF Research Database (Denmark)

Godinho, Jose; Piazolo, Sandra; Balic Zunic, Tonci

2014-01-01

forming the initial surface and its inclination to the closest stable planes, which are specific for each surface orientation. During an initial dissolution regime dissolution rates decrease significantly, even though the total surface area increases. During a second dissolution regime, some surfaces...... by the relative stability of the planes and type of edges that constitute a surface needs to be considered. Significant differences between dissolution rates calculated based on surface area alone, and based on surface reactivity are expected for materials with the fluorite structure....

Measured sections and analyses of uranium host rocks of the Dockum Group, New Mexico and Texas

International Nuclear Information System (INIS)

Dickson, R.E.; Drake, D.P.; Reese, T.J.

1977-02-01

This report presents 27 measured sections from the Dockum Group of Late Triassic age, in the southern High Plains of eastern New Mexico and northwestern Texas. Many of the measured sections are only partial; the intent in those cases was to measure the parts of sections that had prominent sandstone/conglomerate beds or that had uranium deposits. No attempt was made to relate rock color to a rock color chart; rock colors are therefore approximate. Modal analyses (by thin-section examination) of sandstone and conglomerate samples and gamma-ray spectrometric analyses of the samples are presented in appendices

In vivo in vitro correlations for a poorly soluble drug, danazol, using the flow-through dissolution method with biorelevant dissolution media

DEFF Research Database (Denmark)

Sunesen, Vibeke Hougaard; Pedersen, Betty Lomstein; Kristensen, Henning Gjelstrup

2005-01-01

The purpose of the study was to design dissolution tests that were able to distinguish between the behaviour of danazol under fasted and fed conditions, by using biorelevant media. In vitro dissolution of 100mg danazol capsules was performed using the flow-through dissolution method. Flow rates w...

Experimental Investigation of Mechanical Properties of Black Shales after CO2-Water-Rock Interaction

OpenAIRE

Lyu, Qiao; Ranjith, Pathegama Gamage; Long, Xinping; Ji, Bin

2016-01-01

The effects of CO2-water-rock interactions on the mechanical properties of shale are essential for estimating the possibility of sequestrating CO2 in shale reservoirs. In this study, uniaxial compressive strength (UCS) tests together with an acoustic emission (AE) system and SEM and EDS analysis were performed to investigate the mechanical properties and microstructural changes of black shales with different saturation times (10 days, 20 days and 30 days) in water dissoluted with gaseous/supe...

Experimental simulation of the geological storage of CO2: particular study of the interfaces between well cement, cap-rock and reservoir rock

International Nuclear Information System (INIS)

Jobard, Emmanuel

2013-01-01

The geological storage of the CO 2 is envisaged to mitigate the anthropogenic greenhouse gas emissions in the short term. CO 2 is trapped from big emitters and is directly injected into a reservoir rock (mainly in deep salty aquifers, depleted hydrocarbon oil fields or unexploited charcoal lodes) located at more than 800 m deep. In the framework of the CO 2 storage, it is crucial to ensure the integrity of the solicited materials in order to guarantee the permanent confinement of the sequestrated fluids. Using experimental simulation the purpose of this work is to study the mechanisms which could be responsible for the system destabilization and could lead CO 2 leakage from the injection well. The experimental simulations are performed under pressure and temperature conditions of the geological storage (100 bar and from 80 to 100 deg. C). The first experimental model, called COTAGES (for 'Colonne Thermoregulee A Grains pour Gaz a Effet de Serre') allows studying the effects of the thermal destabilisation caused by the injection of a fluid at 25 deg. C in a hotter reservoir (submitted to the geothermal gradient). This device composed of an aqueous saline solution (4 g.L -1 of NaCl), crushed rock (Lavoux limestone or Callovo-Oxfordian argillite) and gas (N 2 or CO 2 ) allows demonstrating an important matter transfer from the cold area (30 deg. C) toward the hot area (100 deg. C). The observed dissolution/precipitation phenomena leading to changes of the petro-physical rocks properties occur in presence of N 2 or CO 2 but are significantly amplified by the presence of CO 2 . Concerning the experiments carried out with Lavoux limestone, the dissolution in the cold zone causes a raise of porosity of about 2% (initial porosity of 8%) due to the formation of about 500 pores/mm 2 with a size ranging between 10 and 100 μm 2 . The precipitation in the hot zone forms a micro-calcite fringe on the external part of the grains and fills the intergrain porosity

Burial history of two potential clay host formations in Belgium

International Nuclear Information System (INIS)

Mertens, J.; Wouters, L.; Van Marcke, Ph.

2004-01-01

When dealing with long term stability of repository host rocks, it is important to consider and learn from all past geological events since the deposition of the formations. The burial history of the Boom Clay and Ypresian Clays, both considered as potential host rocks in Belgium, illustrates that the North Belgian region was tectonically relatively stable since deposition. In Northern Belgium, where both formations are located at a few hundreds meters of depth, tectonic movements were relatively small and no significant uplifts took place. The burial history of the Boom Clay in Mol, where the HADES underground research facility is located illustrates this. On the poster, the burial history for both formations is presented at two locations each: one location in the outcrop region and one research site location, where the formation is currently buried under a few 100 metres of sediment. (authors)

Conditions and processes affecting radionuclide transport

Science.gov (United States)

Simmons, Ardyth M.; Neymark, Leonid A.

2012-01-01

Characteristics of host rocks, secondary minerals, and fluids would affect the transport of radionuclides from a previously proposed repository at Yucca Mountain, Nevada. Minerals in the Yucca Mountain tuffs that are important for retarding radionuclides include clinoptilolite and mordenite (zeolites), clay minerals, and iron and manganese oxides and hydroxides. Water compositions along flow paths beneath Yucca Mountain are controlled by dissolution reactions, silica and calcite precipitation, and ion-exchange reactions. Radionuclide concentrations along flow paths from a repository could be limited by (1) low waste-form dissolution rates, (2) low radionuclide solubility, and (3) radionuclide sorption onto geological media.

Dissolution of FFTF vendor fuel

International Nuclear Information System (INIS)

Lerch, R.E.

1979-08-01

Dissolution experiments were performed on FFTF vendor fuel (both mechanically mixed and coprecipitated) during 1974, 1975, and 1976. A marked improvement was noted in the completeness of fuel dissolution from 1974 to 1976. The reason for this is unknown but may have been attributable to slight changes in fuel fabrication conditions. In general, the bulk of the fuel pellets tested dissolved to greater than 99.9% in nitric acid alone

Dissolution of FFTF vendor fuel

Energy Technology Data Exchange (ETDEWEB)

Lerch, R.E.

1979-08-01

Dissolution experiments were performed on FFTF vendor fuel (both mechanically mixed and coprecipitated) during 1974, 1975, and 1976. A marked improvement was noted in the completeness of fuel dissolution from 1974 to 1976. The reason for this is unknown but may have been attributable to slight changes in fuel fabrication conditions. In general, the bulk of the fuel pellets tested dissolved to greater than 99.9% in nitric acid alone.

Dissolution studies with pilot plant and actual INTEC calcines

International Nuclear Information System (INIS)

Herbst, R.S.; Garn, T.G.

1999-01-01

The dissolution of Idaho Nuclear Technology and Engineering Center (INTEC) pilot plant calcines was examined to determine solubility of calcine matrix components in acidic media. Two representatives pilot plant calcine types were studied: Zirconia calcine and Zirconia/Sodium calcine. Dissolution of these calcines was evaluated using lower initial concentrations of nitric acid than used in previous tests to decrease the [H+] concentration in the final solutions. Lower [H+] concentrations contribute to more favorable TRUEX/SREX solvent extraction flowsheet performance. Dissolution and analytical results were also obtained for radioactive calcines produced using high sodium feeds blended with non-radioactive Al(NO 3 ) 3 solutions to dilute the sodium concentration and prevent bed agglomeration during the calcination process. Dissolution tests indicated >95 wt.% of the initial calcine mass can be dissolved using the baseline dissolution procedure, with the exception that higher initial nitric acid concentrations are required. The higher initial acid concentration is required for stoichiometric dissolution of the oxides, primarily aluminum oxide. Statistically designed experiments using pilot plant calcine were performed to determine the effect of mixing rate on dissolution efficiency. Mixing rate was determined to provide minimal effects on wt.% dissolution. The acid/calcine ratio and temperature were the predominate variables affecting the wt.% dissolution, a result consistent with previous studies using other similar types of pilot plant calcines

DISSOLUTION OF IRRADIATED MURR FUEL ASSEMBLIES

Energy Technology Data Exchange (ETDEWEB)

Kyser, E.

2010-06-17

A literature survey on the dissolution of spent nuclear fuel from the University of Missouri Research Reactor (MURR) has been performed. This survey encompassed both internal and external literature sources for the dissolution of aluminum-clad uranium alloy fuels. The most limiting aspect of dissolution in the current facility configuration involves issues related to the control of the flammability of the off-gas from this process. The primary conclusion of this work is that based on past dissolution of this fuel in H-Canyon, four bundles of this fuel (initial charge) may be safely dissolved in a nitric acid flowsheet catalyzed with 0.002 M mercuric nitrate using a 40 scfm purge to control off-gas flammability. The initial charge may be followed by a second charge of up to five bundles to the same dissolver batch depending on volume and concentration constraints. The safety of this flowsheet relies on composite lower flammability limits (LFL) estimated from prior literature, pilot-scale work on the dissolution of site fuels, and the proposed processing flowsheet. Equipment modifications or improved LFL data offer the potential for improved processing rates. The fuel charging sequence, as well as the acid and catalyst concentrations, will control the dissolution rate during the initial portion of the cycle. These parameters directly impact the hydrogen and off-gas generation and, along with the purge flowrate determine the number of bundles that may be charged. The calculation approach within provides Engineering a means to determine optimal charging patterns. Downstream processing of this material should be similar to that of recent processing of site fuels requiring only minor adjustments of the existing flowsheet parameters.

Did the Kiruna iron ores form as a result of a metasomatic or igneous process? New U-Pb and Nd data for the iron oxide apatite ores and their host rocks in the Norrbotten region of northern Sweden

Science.gov (United States)

Westhues, A.; Hanchar, J. M.; Whitehouse, M. J.; Fisher, C. M.

2012-12-01

A number of iron deposits near Kiruna in the Norrbotten region of northern Sweden are of the iron oxide apatite (IOA) type of deposits; also referred to as Kiruna-type deposits. They are commonly considered a subgroup or end-member of iron oxide copper gold (IOCG) deposits, containing no economic grades of copper or gold. Both IOCG and IOA deposits are characterized by abundant low-Ti Fe oxides, an enrichment in REE, and intense sodium and potassium wall-rock alteration adjacent to the ores. Deposits of these types are of a great economic importance, not only for iron, but also for other elements such as rare earth elements (REE) or uranium. Kiruna, the type locality of the IOA type of mineral deposits, is the focus of this study. Despite a century-long mining history and 2500 Mt of iron ore produced in the region to date (with grades of 30 to 70 wt.% Fe), the genesis of these deposits is poorly understood: theories of a magmatic vs. a hydrothermal or metasomatic origin have been debated, and the timing of mineralization of the ores in the Norbotten region has never been directly dated. The results anticipated from this study will provide a better understanding of the nature of the IOA type of mineral deposits and their relation to IOCG deposits such as Olympic Dam in Australia. An array of geochemical methods is used in order to gain insights on the emplacement history of the host rocks, their subsequent alteration, and the ore genesis of these deposits. This includes in situ U/Pb geochronology of zircon, monazite, and titanite to constrain the timing between host rock emplacement, alteration and mineralization. Isotopic data from whole rocks and in situ at mineral scale will provide constraints on the involvement of hydrothermal fluids and their possible sources, as well as on the sources of Fe, U, and the REE. Newly obtained Sm-Nd isotopic data points to distinct source differences between host rocks, ore and alteration related samples. Preliminary in situ U

Dissolution of ion exchange resin by hydrogen peroxide

International Nuclear Information System (INIS)

Lee, S.C.

1981-08-01

The resin dissolution process was conducted successfully in full-scale equipment at the SRL Semiworks. A solution containing 0.001M Fe 2+ , or Fe 3+ , and 3 vol % H 2 O 2 in 0.1M HNO 3 is sufficient to dissolve up to 40 vol % resin slurry (Dowex 50W-X8). Foaming and pressurization can be eliminated by maintaining the dissolution temperature below 99 0 C. The recommended dissolution temperature range is 85 to 90 0 C. Premixing hydrogen peroxide with all reactants will not create a safety hazard, but operating with a continual feed of hydrogen peroxide is recommended to control the dissolution rate. An air sparging rate of 1.0 to 1.5 scfm will provide sufficient mixing. Spent resin from chemical separation contains DTPA (diethylenetriaminepentaacetic acid) residue, and the resin must be washed with 0.1M NH 4 OH to remove excess DTPA before dissolution. Gamma irradiation of resin up to 4 kW-hr/L did not change the dissolution rate significantly

Dissolution of mixed oxide spent fuel from FBR

International Nuclear Information System (INIS)

Sanyoshi, H.; Nishina, H.; Toyota, O.; Yamamoto, R.; Nemoto, S.; Okamoto, F.; Togashi, A.; Kawata, T.; Hayashi, S.

1991-01-01

At the Tokai Works of the Power Reactor and Nuclear Fuel Development Corporation (PNC), the Chemical Processing Facility (CPF) has been continuing operation since 1982 for laboratory scale hot experiments on reprocessing of FBR mixed oxide fuel. As a part of these experiments, dissolution experiments have been performed to define the key parameters affecting dissolution rates such as concentration of nitric acid, temperature and burnup and also to confirm the amount of insoluble residue. The dissolution rate of the irradiated fuel was determined to be in proportion to the 1.7 power of the nitric acid concentration. The activation energy determined from the experiments varied from 6 to 11 kcal/mol depending on the method of dissolution. The dissolution rate decreased as the fuel burnup increased in low nitric acid media below 5 mol/l. However, it was found that the effect of the burnup became negligible in a high concentration of nitric acid media. The amount of insoluble residue and its constituents were evaluated by changing the dissolution condition. (author)

Mathematical methods for quantification and comparison of dissolution testing data.

Science.gov (United States)

Vranić, Edina; Mehmedagić, Aida; Hadzović, Sabira

2002-12-01

In recent years, drug release/dissolution from solid dosage forms has been the subject of intense and profitable scientific developments. Whenever a new solid dosage form is developed or produced, it is necessary to ensure that drug dissolution occurs in an appropriate manner. The pharmaceutical industry and the registration authorities do focus, nowadays, on drug dissolution studies. The quantitative analysis of the values obtained in dissolution/release tests is easier when mathematical formulas that express the dissolution results as a function of some of the dosage forms characteristics are used. This work discusses the analysis of data obtained for dissolution profiles under different media pH conditions using mathematical methods of analysis described by Moore and Flanner. These authors have described difference factor (f1) and similarity factor (f2), which can be used to characterise drug dissolution/release profiles. In this work we have used these formulas for evaluation of dissolution profiles of the conventional tablets in different pH of dissolution medium (range of physiological variations).

Clay club catalogue of characteristics of argillaceous rocks

International Nuclear Information System (INIS)

2005-01-01

The OECD/NEA Working Group on the Characterisation, the Understanding and the Performance of Argillaceous Rocks as Repository Host Formations, namely the Clay Club, examines the various argillaceous rocks that are being considered for the deep geological disposal of radioactive waste, i.e. from plastic, soft, poorly indurated clays to brittle, hard mud-stones or shales. The Clay Club considered it necessary and timely to provide a catalogue to gather in a structured way the key geo-scientific characteristics of the various argillaceous formations that are - or were - studied in NEA member countries with regard to radioactive waste disposal. The present catalogue represents the outcomes of this Clay Club initiative. (author)

Olivine Dissolution in Seawater: Implications for CO2 Sequestration through Enhanced Weathering in Coastal Environments

Science.gov (United States)

2017-01-01

Enhanced weathering of (ultra)basic silicate rocks such as olivine-rich dunite has been proposed as a large-scale climate engineering approach. When implemented in coastal environments, olivine weathering is expected to increase seawater alkalinity, thus resulting in additional CO2 uptake from the atmosphere. However, the mechanisms of marine olivine weathering and its effect on seawater–carbonate chemistry remain poorly understood. Here, we present results from batch reaction experiments, in which forsteritic olivine was subjected to rotational agitation in different seawater media for periods of days to months. Olivine dissolution caused a significant increase in alkalinity of the seawater with a consequent DIC increase due to CO2 invasion, thus confirming viability of the basic concept of enhanced silicate weathering. However, our experiments also identified several important challenges with respect to the detailed quantification of the CO2 sequestration efficiency under field conditions, which include nonstoichiometric dissolution, potential pore water saturation in the seabed, and the potential occurrence of secondary reactions. Before enhanced weathering of olivine in coastal environments can be considered an option for realizing negative CO2 emissions for climate mitigation purposes, these aspects need further experimental assessment. PMID:28281750

Review of potential host rocks for radioactive waste disposal in the Piedmont Province of Virginia and Maryland

International Nuclear Information System (INIS)

Brown, W.R.

1980-10-01

This study is a detailed follow-up of a broad study of the Southeastern Piedmont by Acres American, Inc. (1978) based upon literature and existing knowledge. The purpose is to designate broad areas in which the rock type is favorable for field exploration for the possible designation of a site for disposal of solidified radioactive waste. The Acres study classified rock units as favorable, potentially favorable, and unfavorable. The objective of the present study is: (1) to review the criteria used in this classification, and (2) on the basis of a detailed knowledge of local rock units to reassign the rock types in the potentially favorable category to either the favorable or the unfavorable categories. As in the Acres study, the objective is to designate field study areas, not potential sites. This study was based entirely upon a literature study, discussions with persons knowledgeable of the region, and a personal acquaintance with the rocks and structures. No field work was done specifically for this project. No consideration was given to sociological, economic, or non-technical factors

Oxidation and dissolution of UO{sub 2} in bicarbonate media: Implications for the spent nuclear fuel oxidative dissolution mechanism

Energy Technology Data Exchange (ETDEWEB)

Gimenez, J. [Department of Chemical Engineering, Universitat Politecnica de Catalunya, Diagonal 647, 08028 Barcelona (Spain)]. E-mail: francisco.javier.gimenez@upc.edu; Clarens, F. [Department of Chemical Engineering, Universitat Politecnica de Catalunya, Diagonal 647, 08028 Barcelona (Spain); Casas, I. [Department of Chemical Engineering, Universitat Politecnica de Catalunya, Diagonal 647, 08028 Barcelona (Spain); Rovira, M. [CTM Centre Tecnologic, Avda. Bases de Manresa 1. 08240 Manresa (Spain); Pablo, J. de [Department of Chemical Engineering, Universitat Politecnica de Catalunya, Diagonal 647, 08028 Barcelona (Spain); Bruno, J. [Enresa-Enviros Environmental Science and Waste Management Chair, UPC, Jordi Girona 1-3 B2, 08034 Barcelona (Spain)

2005-10-15

The objective of this work is to study the UO{sub 2} oxidation by O{sub 2} and dissolution in bicarbonate media and to extrapolate the results obtained to improve the knowledge of the oxidative dissolution of spent nuclear fuel. The results obtained show that in the studied range the oxygen consumption rate is independent on the bicarbonate concentration while the UO{sub 2} dissolution rate does depend on. Besides, at 10{sup -4} mol dm{sup -3} bicarbonate concentration, the oxygen consumption rate is almost two orders of magnitude higher than the UO{sub 2} dissolution rate. These results suggest that at low bicarbonate concentration (<10{sup -2} mol dm{sup -3}) the alteration of the spent nuclear fuel cannot be directly derived from the measured uranium concentrations in solution. On the other hand, the study at low bicarbonate concentrations of the evolution of the UO{sub 2} surface at nanometric scale by means of the SFM technique shows that the difference between oxidation and dissolution rates is not due to the precipitation of a secondary solid phase on UO{sub 2}.

Frogging It: A poetic Analysis of Relationship Dissolution

Directory of Open Access Journals (Sweden)

Sandra L. Faulkner

2012-10-01

Full Text Available Often, themes in work and life intertwine; the author recognized that a cadre of poems she had written during the past several years were about relationship dissolution. The poems concerned romantic and friendship dissolution and the aspects of identity creation and loss this entails. The author presents the poems and makes an explicit connection to interpersonal relationship dissolution literature through the technique of poetic analysis. This analysis serves as an exemplar for how poetry as performative writing offers a valuable addition to interpersonal communication research through the poeticizing of relational dissolution as an everyday relational challenge.

Change in cap rock porosity triggered by pressure and temperature dependent CO2–water–rock interactions in CO2 storage systems

Directory of Open Access Journals (Sweden)

Christina Hemme

2017-03-01

Full Text Available Carbon capture and storage in deep geological formations is a method to reduce greenhouse gas emissions. Supercritical CO2 is injected into a reservoir and dissolves in the brine. Under the impact of pressure and temperature (P–T the aqueous species of the CO2-acidified brine diffuse through the cap rock where they trigger CO2–water–rock interactions. These geochemical reactions result in mineral dissolution and precipitation along the CO2 migration path and are responsible for a change in porosity and therefore for the sealing capacity of the cap rock. This study focuses on the diffusive mass transport of CO2 along a gradient of decreasing P–T conditions. The process is retraced with a one-dimensional hydrogeochemical reactive mass transport model. The semi-generic hydrogeochemical model is based on chemical equilibrium thermodynamics. Based on a broad variety of scenarios, including different initial mineralogical, chemical and physical parameters, the hydrogeochemical parameters that are most sensitive for safe long-term CO2 storage are identified. The results demonstrate that P–T conditions have the strongest effect on the change in porosity and the effect of both is stronger at high P–T conditions because the solubility of the mineral phases involved depends on P–T conditions. Furthermore, modeling results indicate that the change in porosity depends strongly on the initial mineralogical composition of the reservoir and cap rock as well as on the brine compositions. Nevertheless, a wide range of conditions for safe CO2 storage is identified.

Uranium carbide dissolution in nitric solution: Sonication vs. silent conditions

International Nuclear Information System (INIS)

Virot, Matthieu; Szenknect, Stéphanie; Chave, Tony; Dacheux, Nicolas; Moisy, Philippe; Nikitenko, Sergey I.

2013-01-01

The dissolution of uranium carbide (UC) in nitric acid media is considered by means of power ultrasound (sonication) or magnetic stirring. The induction period required to initiate UC dissolution was found to be dramatically shortened when sonicating a 3 M nitric solution (Ar, 20 kHz, 18 W cm −2 , 20 °C). At higher acidity, magnetic stirring offers faster dissolution kinetics compared to sonication. Ultrasound-assisted UC dissolution is found to be passivated after ∼60% dissolution and remains incomplete whatever the acidity which is confirmed by ICP–AES, LECO and SEM–EDX analyses. In general, the kinetics of UC dissolution is linked to the in situ generation of nitrous acid in agreement with the general mechanism of UC dissolution; the nitrous acid formation is reported to be faster under ultrasound at low acidity due to the nitric acid sonolysis. The carbon balance shared between the gaseous, liquid, and solid phases is strongly influenced by the applied dissolution procedure and HNO 3 concentration

Uranium carbide dissolution in nitric solution: Sonication vs. silent conditions

Science.gov (United States)

Virot, Matthieu; Szenknect, Stéphanie; Chave, Tony; Dacheux, Nicolas; Moisy, Philippe; Nikitenko, Sergey I.

2013-10-01

The dissolution of uranium carbide (UC) in nitric acid media is considered by means of power ultrasound (sonication) or magnetic stirring. The induction period required to initiate UC dissolution was found to be dramatically shortened when sonicating a 3 M nitric solution (Ar, 20 kHz, 18 W cm-2, 20 °C). At higher acidity, magnetic stirring offers faster dissolution kinetics compared to sonication. Ultrasound-assisted UC dissolution is found to be passivated after ∼60% dissolution and remains incomplete whatever the acidity which is confirmed by ICP-AES, LECO and SEM-EDX analyses. In general, the kinetics of UC dissolution is linked to the in situ generation of nitrous acid in agreement with the general mechanism of UC dissolution; the nitrous acid formation is reported to be faster under ultrasound at low acidity due to the nitric acid sonolysis. The carbon balance shared between the gaseous, liquid, and solid phases is strongly influenced by the applied dissolution procedure and HNO3 concentration.

In vitro Dissolution Studies on Solid Dispersions of Mefenamic Acid.

Science.gov (United States)

Rao, K R S Sambasiva; Nagabhushanam, M V; Chowdary, K P R

2011-03-01

Solid dispersions of mefanamic acid with a water-soluble polymer polyvinyl pyrrolidine and a super disintegrant, primojel were prepared by common solvent and solvent evaporation methods employing methanol as the solvent. The dissolution rate and dissolution efficiency of the prepared solid dispersions were evaluated in comparison to the corresponding pure drug. Solid dispersions of mefenamic acid showed a marked enhancement in dissolution rate and dissolution efficiency. At 1:4 ratio of mefenamic acid-primojel a 2.61 fold increase in the dissolution rate of mefenamic acid was observed with solid dispersion. The solid dispersions in combined carriers gave much higher rates of dissolution than super disintegrants alone. Mefanamic acid-primojel-polyvinyl pyrrolidine (1:3.2:0.8) solid dispersion gave a 4.11 fold increase in the dissolution rate of mefenamic acid. Super disintegrants alone or in combination with polyvinyl pyrrolidine could be used to enhance the dissolution rate of mefenamic acid.

TANK 12 SLUDGE CHARACTERIZATION AND ALUMINUM DISSOLUTION DEMONSTRATION

International Nuclear Information System (INIS)

Reboul, S.; Hay, Michael; Zeigler, Kristine; Stone, Michael

2009-01-01

A 3-L sludge slurry sample from Tank 12 was characterized and then processed through an aluminum dissolution demonstration. The dominant constituent of the sludge was found to be aluminum in the form of boehmite. The iron content was minor, about one-tenth that of the aluminum. The salt content of the supernatant was relatively high, with a sodium concentration of ∼7 M. Due to these characteristics, the yield stress and plastic viscosity of the unprocessed slurry were relatively high (19 Pa and 27 cP), and the settling rate of the sludge was relatively low (∼20% settling over a two and a half week period). Prior to performing aluminum dissolution, plutonium and gadolinium were added to the slurry to simulate receipt of plutonium waste from H-Canyon. Aluminum dissolution was performed over a 26 day period at a temperature of 65 C. Approximately 60% of the insoluble aluminum dissolved during the demonstration, with the rate of dissolution slowing significantly by the end of the demonstration period. In contrast, approximately 20% of the plutonium and less than 1% of the gadolinium partitioned to the liquid phase. However, about a third of the liquid phase plutonium became solubilized prior to the dissolution period, when the H-Canyon plutonium/gadolinium simulant was added to the Tank 12 slurry. Quantification of iron dissolution was less clear, but appeared to be on the order of 1% based on the majority of data (a minor portion of the data suggested iron dissolution could be as high as 10%). The yield stress of the post-dissolution slurry (2.5 Pa) was an order of magnitude lower than the initial slurry, due most likely to the reduced insoluble solids content caused by aluminum dissolution. In contrast, the plastic viscosity remained unchanged (27 cP). The settling rate of the post-dissolution slurry was higher than the initial slurry, but still relatively low compared to settling of typical high iron content/low salt content sludges. Approximately 40% of the

Uranium and thorium abundances in some graphite-bearing precambrian rocks of India and implications

International Nuclear Information System (INIS)

Pandey, U.K.; Krishnamurthy, P.

1995-01-01

Graphite schists from parts of Gujarat in the Aravalli supergroup show maximum contents of uranium (70-95 ppm), hosted mainly in the graphites, whereas such schists from the Tamil Nadu granulite terrain contain distinctly lower amounts of uranium (7-9 ppm). Graphite-bearing hornblende gneiss and calc-granulites from Madurai, Tamil Nadu, contain higher amounts of uranium (12-28 ppm) than the schists, and uranium is mainly hosted by the magnetite and allanite occurring as independent grains with flaky graphite and also as inclusions within quartz. Khondalites from Andhra Pradesh are depleted in uranium (0.9-1.3 ppm) compared to Th (17.5-20.2 ppm). Except for the khondalites, which have high Th/U ratio (13.5-22.4), all the other samples have very low Th/U ratios (0.10-0.80) compared to the crustal average (3-4). Such variations among similar rock types, may in part be related to uranium and thorium abundances inherited from parental rocks, modified later by hydrothermal and/or metasomatic processes. Graphites from such rock types can provide both in situ and migrant reductants for hosting a variety of uranium and other metallic deposits. (author). 12 refs., 1 tab., 1 fig

Dissolution behaviour of silicon nitride coatings for joint replacements

Energy Technology Data Exchange (ETDEWEB)

Pettersson, Maria [Materials in Medicine Group, Div. of Applied Materials Science, Dept. of Engineering Sciences, Uppsala University, Uppsala (Sweden); Bryant, Michael [Institute of Functional Surfaces (iFS), School of Mechanical Engineering, University of Leeds, Leeds (United Kingdom); Schmidt, Susann [Thin Film Physics, Department of Physics, Chemistry and Biology (IFM), Linköping University, Linköping (Sweden); Engqvist, Håkan [Materials in Medicine Group, Div. of Applied Materials Science, Dept. of Engineering Sciences, Uppsala University, Uppsala (Sweden); Hall, Richard M. [Institute of Medical and Biological Engineering (iMBE), School of Mechanical Engineering, University of Leeds, Leeds (United Kingdom); Neville, Anne [Institute of Functional Surfaces (iFS), School of Mechanical Engineering, University of Leeds, Leeds (United Kingdom); Persson, Cecilia, E-mail: cecilia.persson@angstrom.uu.se [Materials in Medicine Group, Div. of Applied Materials Science, Dept. of Engineering Sciences, Uppsala University, Uppsala (Sweden)

2016-05-01

In this study, the dissolution rate of SiN{sub x} coatings was investigated as a function of coating composition, in comparison to a cobalt chromium molybdenum alloy (CoCrMo) reference. SiN{sub x} coatings with N/Si ratios of 0.3, 0.8 and 1.1 were investigated. Electrochemical measurements were complemented with solution (inductively coupled plasma techniques) and surface analysis (vertical scanning interferometry and x-ray photoelectron spectroscopy). The dissolution rate of the SiN{sub x} coatings was evaluated to 0.2–1.4 nm/day, with a trend of lower dissolution rate with higher N/Si atomic ratio in the coating. The dissolution rates of the coatings were similar to or lower than that of CoCrMo (0.7–1.2 nm/day). The highest nitrogen containing coating showed mainly Si–N bonds in the bulk as well as at the surface and in the dissolution area. The lower nitrogen containing coatings showed Si–N and/or Si–Si bonds in the bulk and an increased formation of Si–O bonds at the surface as well as in the dissolution area. The SiN{sub x} coatings reduced the metal ion release from the substrate. The possibility to tune the dissolution rate and the ability to prevent release of metal ions encourage further studies on SiN{sub x} coatings for joint replacements. - Graphical abstract: Dissolution rates of SiN{sub 0.3}, SiN{sub 0.8}, and SiN{sub 1.1} coatings on CoCrMo compared to uncoated CoCrMo. Dissolution rates were obtained from i) electrochemical measurements of I{sub corr}, ii) the step height between covered and solution-exposed surfaces, measured using VSI, and iii) the ion concentration in the solution, measured with ICP. - Highlights: • The dissolution of SiN{sub x} coatings was investigated in comparison to (bulk) CoCrMo. • The coatings gave a lower or similar dissolution rate to CoCrMo, of 0.2–1.2 nm/day. • An increased nitrogen content in the coatings gave lower dissolution rates. • SiN{sub x} coatings on CoCrMo reduced the metal ion release

Weathering Profiles in Phosphorus-Rich Rocks at Gusev Crater, Mars, Suggest Dissolution of Phosphate Minerals into Potentially Habitable Near-Neutral Waters.

Science.gov (United States)

Adcock, Christopher T; Hausrath, Elisabeth M

2015-12-01

Abundant evidence indicates that significant surface and near-surface liquid water has existed on Mars in the past. Evaluating the potential for habitable environments on Mars requires an understanding of the chemical and physical conditions that prevailed in such aqueous environments. Among the geological features that may hold evidence of past environmental conditions on Mars are weathering profiles, such as those in the phosphorus-rich Wishstone-class rocks in Gusev Crater. The weathering profiles in these rocks indicate that a Ca-phosphate mineral has been lost during past aqueous interactions. The high phosphorus content of these rocks and potential release of phosphorus during aqueous interactions also make them of astrobiological interest, as phosphorus is among the elements required for all known life. In this work, we used Mars mission data, laboratory-derived kinetic and thermodynamic data, and data from terrestrial analogues, including phosphorus-rich basalts from Idaho, to model a conceptualized Wishstone-class rock using the reactive transport code CrunchFlow. Modeling results most consistent with the weathering profiles in Wishstone-class rocks suggest a combination of chemical and physical erosion and past aqueous interactions with near-neutral waters. The modeling results also indicate that multiple Ca-phosphate minerals are likely in Wishstone-class rocks, consistent with observations of martian meteorites. These findings suggest that Gusev Crater experienced a near-neutral phosphate-bearing aqueous environment that may have been conducive to life on Mars in the past. Mars-Gusev Crater-Wishstone-Reactive transport modeling-CrunchFlow-Aqueous interactions-Neutral pH-Habitability.

Dissolution of nuclear fuels; Disolucion de combustibles Nucleares

Energy Technology Data Exchange (ETDEWEB)

Uriarte Hueda, A; Berberana Eizmendi, M; Rainey, R

1968-07-01

A laboratory study was made of the instantaneous dissolution rate (IDR) for unirradiated uranium metal rods and UO{sub 2}, PuO{sub 2} and PuO{sub 2}-UO{sub 2} pellets in boiling nitric acid alone and with additives. The uranium metal and UO{sub 2} dissolved readily in nitric acid alone; PuO{sub 2} dissolved slowly even with the addition of fluoride; PuO{sub 2}-UO{sub 2} pellets containing as much as 35% PuO{sub 2} in UO{sub 2} gave values of the instantaneous dissolution rate to indicate can be dissolved with nitric acid alone. An equation to calculate the time for complete dissolution has been determinate in function of the instantaneous dissolution rates. The calculated values agree with the experimental. Uranium dioxide pellets from various sources but all having a same density varied in instantaneous dissolution rate. All the pellets, however, have dissolved ved in the same time. The time for complete dissolution of PuO{sub 2}-UO{sub 2} pellets, having the same composition, and the concentration of the used reagents are function of the used reagents are function of the fabrication method. (Author) 8 refs.

Fifteen years of microbiological investigation in Opalinus Clay at the Mont Terri rock laboratory (Switzerland)

Energy Technology Data Exchange (ETDEWEB)

Leupin, O.X. [National Cooperative for the Disposal of Radioactive Waste (NAGRA), Wettingen (Switzerland); Bernier-Latmani, R.; Bagnoud, A. [Swiss Federal Office of Technology EPFL, Lausanne (Switzerland); Moors, H.; Leys, N.; Wouters, K. [Belgian Nuclear Research Centre SCK-CEN, Mol (Belgium); Stroes-Gascoyne, S. [University of Saskatchewan, Saskatoon (Canada)

2017-04-15

Microbiological studies related to the geological disposal of radioactive waste have been conducted at the Mont Terri rock laboratory in Opalinus Clay, a potential host rock for a deep geologic repository, since 2002. The metabolic potential of microorganisms and their response to excavation-induced effects have been investigated in undisturbed and disturbed claystone cores and in pore- (borehole) water. Results from nearly 15 years of research at the Mont Terri rock laboratory have shown that microorganisms can potentially affect the environment of a repository by influencing redox conditions, metal corrosion and gas production and consumption under favourable conditions. However, the activity of microorganisms in undisturbed Opalinus Clay is limited by the very low porosity, the low water activity, and the largely recalcitrant nature of organic matter in the claystone formation. The presence of microorganisms in numerous experiments at the Mont Terri rock laboratory has suggested that excavation activities and perturbation of the host rock combined with additional contamination during the installation of experiments in boreholes create favourable conditions for microbial activity by providing increased space, water and substrates. Thus effects resulting from microbial activity might be expected in the proximity of a geological repository i.e., in the excavation damaged zone, the engineered barriers, and first containments (the containers). (authors)

Fifteen years of microbiological investigation in Opalinus Clay at the Mont Terri rock laboratory (Switzerland)

International Nuclear Information System (INIS)

Leupin, O.X.; Bernier-Latmani, R.; Bagnoud, A.; Moors, H.; Leys, N.; Wouters, K.; Stroes-Gascoyne, S.

2017-01-01

Microbiological studies related to the geological disposal of radioactive waste have been conducted at the Mont Terri rock laboratory in Opalinus Clay, a potential host rock for a deep geologic repository, since 2002. The metabolic potential of microorganisms and their response to excavation-induced effects have been investigated in undisturbed and disturbed claystone cores and in pore- (borehole) water. Results from nearly 15 years of research at the Mont Terri rock laboratory have shown that microorganisms can potentially affect the environment of a repository by influencing redox conditions, metal corrosion and gas production and consumption under favourable conditions. However, the activity of microorganisms in undisturbed Opalinus Clay is limited by the very low porosity, the low water activity, and the largely recalcitrant nature of organic matter in the claystone formation. The presence of microorganisms in numerous experiments at the Mont Terri rock laboratory has suggested that excavation activities and perturbation of the host rock combined with additional contamination during the installation of experiments in boreholes create favourable conditions for microbial activity by providing increased space, water and substrates. Thus effects resulting from microbial activity might be expected in the proximity of a geological repository i.e., in the excavation damaged zone, the engineered barriers, and first containments (the containers). (authors)

Characterizing Excavation Damaged Zone and Stability of Pressurized Lined Rock Caverns for Underground Compressed Air Energy Storage

Science.gov (United States)

Kim, Hyung-Mok; Rutqvist, Jonny; Jeong, Ju-Hwan; Choi, Byung-Hee; Ryu, Dong-Woo; Song, Won-Kyong

2013-09-01

In this paper, we investigate the influence of the excavation damaged zone (EDZ) on the geomechanical performance of compressed air energy storage (CAES) in lined rock caverns. We conducted a detailed characterization of the EDZ in rock caverns that have been excavated for a Korean pilot test program on CAES in (concrete) lined rock caverns at shallow depth. The EDZ was characterized by measurements of P- and S-wave velocities and permeability across the EDZ and into undisturbed host rock. Moreover, we constructed an in situ concrete lining model and conducted permeability measurements in boreholes penetrating the concrete, through the EDZ and into the undisturbed host rock. Using the site-specific conditions and the results of the EDZ characterization, we carried out a model simulation to investigate the influence of the EDZ on the CAES performance, in particular related to geomechanical responses and stability. We used a modeling approach including coupled thermodynamic multiphase flow and geomechanics, which was proven to be useful in previous generic CAES studies. Our modeling results showed that the potential for inducing tensile fractures and air leakage through the concrete lining could be substantially reduced if the EDZ around the cavern could be minimized. Moreover, the results showed that the most favorable design for reducing the potential for tensile failure in the lining would be a relatively compliant concrete lining with a tight inner seal, and a relatively stiff (uncompliant) host rock with a minimized EDZ. Because EDZ compliance depends on its compressibility (or modulus) and thickness, care should be taken during drill and blast operations to minimize the damage to the cavern walls.

Dissolution Model Development: Formulation Effects and Filter Complications

DEFF Research Database (Denmark)

Berthelsen, Ragna; Holm, Rene; Jacobsen, Jette

2016-01-01

This study describes various complications related to sample preparation (filtration) during development of a dissolution method intended to discriminate among different fenofibrate immediate-release formulations. Several dissolution apparatus and sample preparation techniques were tested. The fl....... With the tested drug–formulation combination, the best in vivo–in vitro correlation was found after filtration of the dissolution samples through 0.45-μm hydrophobic PTFE membrane filters....

Multi-element analysis of emeralds and associated rocks by k0 neutron activation analysis

International Nuclear Information System (INIS)

Acharya, R.N.; Mondal, R.K.; Burte, P.P.; Nair, A.G.C.; Reddy, N.B.Y.; Reddy, L.K.; Reddy, A.V.R.; Manohar, S.B.

2000-01-01

Multi-element analysis was carried out in natural emeralds, their associated rocks and one sample of beryl obtained from Rajasthan, India. The concentrations of 21 elements were assayed by Instrumental Neutron Activation Analysis using the k 0 method (k 0 INAA method) and high-resolution gamma ray spectrometry. The data reveal the segregation of some elements from associated (trapped and host) rocks to the mineral beryl forming the gemstones. A reference rock standard of the US Geological Survey (USGS BCR-1) was also analysed as a control of the method

Catalysed electrolytic metal oxide dissolution processes

International Nuclear Information System (INIS)

Machuron-Mandard, X.

1994-01-01

The hydrometallurgical processes designed for recovering valuable metals from mineral ores as well as industrial wastes usually require preliminary dissolution of inorganic compounds in aqueous media before extraction and purification steps. Unfortunately, most of the minerals concerned hardly or slowly dissolve in acidic or basic solutions. Metallic oxides, sulfides and silicates are among the materials most difficult to dissolve in aqueous solutions. They are also among the main minerals containing valuable metals. The redox properties of such materials sometimes permit to improve their dissolution by adding oxidizing or reducing species to the leaching solution, which leads to an increase in the dissolution rate. Moreover, limited amounts of redox promoters are required if the redox agent is regenerated continuously thanks to an electrochemical device. Nuclear applications of such concepts have been suggested since the dissolution of many actinide compounds (e.g., UO 2 , AmO 2 , PuC, PuN,...) is mainly based on redox reactions. In the 1980s, improvements of the plutonium dioxide dissolution process have been proposed on the basis of oxidation-reduction principles, which led a few years later to the design of industrial facilities (e.g., at Marcoule or at the french reprocessing plant of La Hague). General concepts and well-established results obtained in France at the Atomic Energy Commission (''Commissariat a l'Energie Atomique'') will be presented and will illustrate applications to industrial as well as analytical problems. (author)

Understanding the roles of ligand promoted dissolution, water column saturation and hydrological properties on intense basalt weathering using reactive transport and watershed-scale hydrologic modeling

Science.gov (United States)

Perez Fodich, A.; Walter, M. T.; Derry, L. A.

2016-12-01

The interaction of rocks with rainwater generates physical and chemical changes, which ultimately culminates in soil development. The addition of catalyzers such as plants, atmospheric gases and hydrological properties will result in more intense and/or faster weathering transformations. The intensity of weathering across the Island of Hawaii is strongly correlated with exposure age and time-integrated precipitation. Intense weathering has resulted from interaction between a thermodynamically unstable lithology, high water/rock ratios, atmospheric gases (O2, CO2) and biota as an organic acid and CO2 producer. To further investigate the role of different weathering agents we have developed 1-D reactive transport models (RTM) to understand mineralogical and fluid chemistry changes in the initially basaltic porous media. The initial meso-scale heterogeneity of porosity makes it difficult for RTMs to capture changes in runoff/groundwater partitioning. Therefore, hydraulic properties (hydraulic conductivity and aquifer depth) are modeled as a watershed parameter appropriate for this system where sub-surface hydraulic data is scarce(1). Initial results agree with field data in a broad sense: different rainfall regimes and timescales show depletion of mobile cations, increasingly low pH, congruent dissolution of olivine and pyroxene, incongruent dissolution of plagioclase and basaltic glass, precipitation of non-crystalline allophane and ferrihydrite, and porosity changes due to dissolution and precipitation of minerals; ultimately Al and Fe are also exported from the system. RTM is used to examine the roles of unsaturation in the soil profile, ligand promoted dissolution of Al- and Fe-bearing phases, and Fe-oxide precipitation at the outcrop scale. Also, we aim to test the use of recession flow analysis to model watershed-scale hydrological properties to extrapolate changes in the runoff/groundwater partitioning. The coupling between weathering processes and hydrologic

Etching of semiconductor cubic crystals: Determination of the dissolution slowness surfaces

Science.gov (United States)

Tellier, C. R.

1990-03-01

Equations of the representative surface of dissolution slowness for cubic crystals are determined in the framework of a tensorial approach of the orientation-dependent etching process. The independent dissolution constants are deduced from symmetry considerations. Using previous data on the chemical etching of germanium and gallium arsenide crystals, some possible polar diagrams of the dissolution slowness are proposed. A numerical and graphical simulation method is used to obtain the derived dissolution shapes. The influence of extrema in the dissolution slowness on the successive dissolution shapes is also examined. A graphical construction of limiting shapes of etched crystals appears possible using the tensorial representation of the dissolution slowness.

Effect of alteration phase formation on the glass dissolution rate

International Nuclear Information System (INIS)

Ebert, W.L.

1997-01-01

The dissolution rates of many glasses have been observed to increase upon the formation of certain alteration phases. While simulations have predicted the accelerating effect of formation of certain phases, the phases predicted to form in computer simulations are usually different than those observed to form in experiments. This is because kinetically favored phases form first in experiments, while simulations predict the thermodynamically favored phases. Static dissolution tests with crushed glass have been used to measure the glass dissolution rate after alteration phases form. Because glass dissolution rates are calculated on a per area basis, an important effect in tests conducted with crushed glass is the decrease in the surface area of glass that is available for reaction as the glass dissolves. This loss of surface area must be taken into account when calculating the dissolution rate. The phases that form and their effect on the dissolution rate are probably related to the glass composition. The impact of phase formation on the glass dissolution rate also varies according to the solubility products of the alteration phases and how the orthocilicic acid activity is affected. Insight into the relationship between the glass dissolution rate, solution chemistry and alteration phase formation is provided by the results of accelerated dissolution tests

Dissolution studies on Nickel ferrite in dilute chemical decontamination formulations

Energy Technology Data Exchange (ETDEWEB)

Ranganathan, S. [New Brunswick Univ., Fredericton, NB (Canada). Dept. of Chemical Engineering; Srinivasan, M.P. [Bhabha Atomic Research Centre (BARC) (India). Water and Steam Chemistry Laboratory; Raghavan, P.S. [Madras Christian College, Chennai (India); Narasimhan, S.V. [Bhabha Atomic Research Centre, Bombay (India); Gopalan, R. [Madras Christian College, Chennai (India). Department of Chemistry

2004-09-01

Nickel ferrite is one of the important corrosion products in the pipeline surfaces of water-cooled nuclear reactors. The dissolution of the nickel ferrite by chelating agents is very sensitive to the nature of the chelant, the nature of the reductant used in the formulation and the temperature at which the dissolution studies are performed. The dissolution is mainly controlled by the reductive dissolution of the ferrite particles, but complexing agents also play a significant role in the dissolution process. This study deals with the leaching of iron and nickel from nickel ferrite prepared by the solid-state method. The dissolution studies are performed in pyridine-2,6-dicarboxylic acid (PDCA), nitrilotriacetic acid (NTA), and ethylenediaminetetraacetic acid (EDTA) formulations containing organic reductants like ascorbic acid and low oxidation state transition metal ion reductants like Fe(II)-L (where L = PDCA, NTA, EDTA) at 85 C. The dissolution of nickel ferrite in PDCA, NTA and EDTA formulations is influenced by the presence of reductants in the formulations. The addition of Fe(II)-L in the formulation greatly enhances the dissolution of nickel ferrite. The preferential leaching of nickel over iron during the dissolution of nickel ferrite was observed in all the formulations. (orig.)

Dissolution studies on Nickel ferrite in dilute chemical decontamination formulations

International Nuclear Information System (INIS)

Ranganathan, S.; Narasimhan, S.V.; Gopalan, R.

2004-01-01

Nickel ferrite is one of the important corrosion products in the pipeline surfaces of water-cooled nuclear reactors. The dissolution of the nickel ferrite by chelating agents is very sensitive to the nature of the chelant, the nature of the reductant used in the formulation and the temperature at which the dissolution studies are performed. The dissolution is mainly controlled by the reductive dissolution of the ferrite particles, but complexing agents also play a significant role in the dissolution process. This study deals with the leaching of iron and nickel from nickel ferrite prepared by the solid-state method. The dissolution studies are performed in pyridine-2,6-dicarboxylic acid (PDCA), nitrilotriacetic acid (NTA), and ethylenediaminetetraacetic acid (EDTA) formulations containing organic reductants like ascorbic acid and low oxidation state transition metal ion reductants like Fe(II)-L (where L = PDCA, NTA, EDTA) at 85 C. The dissolution of nickel ferrite in PDCA, NTA and EDTA formulations is influenced by the presence of reductants in the formulations. The addition of Fe(II)-L in the formulation greatly enhances the dissolution of nickel ferrite. The preferential leaching of nickel over iron during the dissolution of nickel ferrite was observed in all the formulations. (orig.)

Effect of alteration phase formation on the glass dissolution rate

Energy Technology Data Exchange (ETDEWEB)

Ebert, W L [Argonne National Laboratory, Chemical Technology Div. (United States)

1997-07-01

The dissolution rates of many glasses have been observed to increase upon the formation of certain alteration phases. While simulations have predicted the accelerating effect of formation of certain phases, the phases predicted to form in computer simulations are usually different than those observed to form in experiments. This is because kinetically favored phases form first in experiments, while simulations predict the thermodynamically favored phases. Static dissolution tests with crushed glass have been used to measure the glass dissolution rate after alteration phases form. Because glass dissolution rates are calculated on a per area basis, an important effect in tests conducted with crushed glass is the decrease in the surface area of glass that is available for reaction as the glass dissolves. This loss of surface area must be taken into account when calculating the dissolution rate. The phases that form and their effect on the dissolution rate are probably related to the glass composition. The impact of phase formation on the glass dissolution rate also varies according to the solubility products of the alteration phases and how the orthocilicic acid activity is affected. Insight into the relationship between the glass dissolution rate, solution chemistry and alteration phase formation is provided by the results of accelerated dissolution tests.

Natural analogs in the host rock salt. Pt. 1. General study (2011). Pt. 2. Detail studies (2012-2013); Natuerliche Analoga im Wirtsgestein Salz. T. 1. Generelle Studie (2011). T. 2. Detailstudien (2012-2013)

Energy Technology Data Exchange (ETDEWEB)

Brasser, Thomas; Fahrenholz, Christine; Kull, Herbert; Meleshyn, Artur; Moenig, Heike; Noseck, Ulrich; Schoenwiese, Dagmar; Wolf, Jens

2014-12-15

The first part of the project ISIBELII on natural analogs in the host rock salt included a summary of available studies on the topic to be used in a safety analysis for a final repository for heat generating radioactive waste. In 2012 the results of the preliminary safety analysis Gorleben was available, including results on the fracturing of anhydrite, the formation of cryogenic gaps and the influence of earthquakes. The requirements for the barrier system have been modified due to the safety requirements for the final disposal of heat-generating radioactive wastes valid since 2010. For containers the functionality gas to be demonstrated for 500 years. The following issues are covered: natural analogs for the integrity demonstration of the geological barrier, natural analogs for the integrity demonstration of geotechnical barriers, natural analogs for the evaluation of release scenarios. The detail studies include anhydrite fracturing, salt grit compaction, chemical composition of fluid inclusions, thermal stability of salt rock, mechanical stability of salt rock, influence of earthquakes, qualified closures, iron corrosion, and microbial processes.

Chemical Dissolution of Simulant FCA Cladding and Plates

Energy Technology Data Exchange (ETDEWEB)

Daniel, G. [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL); Pierce, R. [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL); O' Rourke, P. [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL)

2017-11-08

The Savannah River Site (SRS) has received some fast critical assembly (FCA) fuel from the Japan Atomic Energy Agency (JAEA) for disposition. Among the JAEA FCA fuel are approximately 7090 rectangular Stainless Steel clad fuel elements. Each element has an internal Pu-10.6Al alloy metal wafer. The thickness of each element is either 1/16 inch or 1/32 inch. The dimensions of each element ranges from 2 inches x 1 inch to 2 inches x 4 inches. This report discusses the potential chemical dissolution of the FCA clad material or stainless steel. This technology uses nitric acid-potassium fluoride (HNO₃-KF) flowsheets of H-Canyon to dissolve the FCA elements from a rack of materials. Historically, dissolution flowsheets have aimed to maximize Pu dissolution rates while minimizing stainless steel dissolution (corrosion) rates. Because the FCA cladding is made of stainless steel, this work sought to accelerate stainless steel dissolution.

Montmorillonite dissolution kinetics: Experimental and reactive transport modeling interpretation

Science.gov (United States)

Cappelli, Chiara; Yokoyama, Shingo; Cama, Jordi; Huertas, F. Javier

2018-04-01

The dissolution kinetics of K-montmorillonite was studied at 25 °C, acidic pH (2-4) and 0.01 M ionic strength by means of well-mixed flow-through experiments. The variations of Si, Al and Mg over time resulted in high releases of Si and Mg and Al deficit, which yielded long periods of incongruent dissolution before reaching stoichiometric steady state. This behavior was caused by simultaneous dissolution of nanoparticles and cation exchange between the interlayer K and released Ca, Mg and Al and H. Since Si was only involved in the dissolution reaction, it was used to calculate steady-state dissolution rates, RSi, over a wide solution saturation state (ΔGr ranged from -5 to -40 kcal mol-1). The effects of pH and the degree of undersaturation (ΔGr) on the K-montmorillonite dissolution rate were determined using RSi. Employing dissolution rates farthest from equilibrium, the catalytic pH effect on the K-montmorillonite dissolution rate was expressed as Rdiss = k·aH0.56±0.05 whereas using all dissolution rates, the ΔGr effect was expressed as a non-linear f(ΔGr) function Rdiss = k · [1 - exp(-3.8 × 10-4 · (|ΔGr|/RT)2.13)] The functionality of this expression is similar to the equations reported for dissolution of Na-montmorillonite at pH 3 and 50 °C (Metz, 2001) and Na-K-Ca-montmorillonite at pH 9 and 80 °C (Cama et al., 2000; Marty et al., 2011), which lends support to the use of a single f(ΔGr) term to calculate the rate over the pH range 0-14. Thus, we propose a rate law that also accounts for the effect of pOH and temperature by using the pOH-rate dependence and the apparent activation energy proposed by Rozalén et al. (2008) and Amram and Ganor (2005), respectively, and normalizing the dissolution rate constant with the edge surface area of the K-montmorillonite. 1D reactive transport simulations of the experimental data were performed using the Crunchflow code (Steefel et al., 2015) to quantitatively interpret the evolution of the released cations

Criticality safety in high explosives dissolution

International Nuclear Information System (INIS)

Troyer, S.D.

1997-01-01

In 1992, an incident occurred at the Pantex Plant in which the cladding around a fissile material component (pit) cracked during dismantlement of the high explosives portion of a nuclear weapon. Although the event did not result in any significant contamination or personnel exposures, concerns about the incident led to the conclusion that the current dismantlement process was unacceptable. Options considered for redesign, dissolution tooling design considerations, dissolution tooling design features, and the analysis of the new dissolution tooling are summarized. The final tooling design developed incorporated a number of safety features and provides a simple, self-contained, low-maintenance method of high explosives removal for nuclear explosive dismantlement. Analyses demonstrate that the tooling design will remain subcritical under normal, abnormal, and credible accident scenarios. 1 fig

Waste form dissolution in bedded salt

International Nuclear Information System (INIS)

Kaufman, A.M.

1980-01-01

A model was devised for waste dissolution in bedded salt, a hydrologically tight medium. For a typical Spent UnReprocessed Fuel (SURF) emplacement, the dissolution rate wll be diffusion limited and will rise to a steady state value after t/sub eq/ approx. = 250 (1+(1-epsilon 0 ) K/sub D//epsilon 0 ) (years) epsilon 0 is the overpack porosity and K/sub d/ is the overpack sorption coefficient. The steady state dissolution rate itself is dominated by the solubility of UO 2 . Steady state rates between 5 x 10 -5 and .5 (g/year) are achievable by SURF emplacements in bedded salt without overpack, and rates between 5 x 10 -7 and 5 x 10 -3 (g/year) with an overpack having porosity of 10 -2

Characterizing 3-D flow velocity in evolving pore networks driven by CaCO3 precipitation and dissolution

Science.gov (United States)

Chojnicki, K. N.; Yoon, H.; Martinez, M. J.

2015-12-01

Understanding reactive flow in geomaterials is important for optimizing geologic carbon storage practices, such as using pore space efficiently. Flow paths can be complex in large degrees of geologic heterogeneities across scales. In addition, local heterogeneity can evolve as reactive transport processes alter the pore-scale morphology. For example, dissolved carbon dioxide may react with minerals in fractured rocks, confined aquifers, or faults, resulting in heterogeneous cementation (and/or dissolution) and evolving flow conditions. Both path and flow complexities are important and poorly characterized, making it difficult to determine their evolution with traditional 2-D transport models. Here we characterize the development of 3-D pore-scale flow with an evolving pore configuration due to calcium carbonate (CaCO3) precipitation and dissolution. A simple pattern of a microfluidic pore network is used initially and pore structures will become more complex due to precipitation and dissolution processes. At several stages of precipitation and dissolution, we directly visualize 3-D velocity vectors using micro particle image velocimetry and a laser scanning confocal microscope. Measured 3-D velocity vectors are then compared to 3-D simulated flow fields which will be used to simulate reactive transport. Our findings will highlight the importance of the 3-D flow dynamics and its impact on estimating reactive surface area over time. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000. This material is based upon work supported as part of the Center for Frontiers of Subsurface Energy Security, an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences under Award Number DE-SC0001114.

Emotional and Cognitive Coping in Relationship Dissolution

Science.gov (United States)

Wrape, Elizabeth R.; Jenkins, Sharon Rae; Callahan, Jennifer L.; Nowlin, Rachel B.

2016-01-01

Dissolution of a romantic relationship can adversely affect functioning among college students and represents one primary reason for seeking campus counseling. This study examined the associations among common coping strategies and distress following relationship dissolution. Avoidance and repetitive negative thinking (RNT) were significantly…

CALCIUM CARBONATE DISSOLUTION RATE IN LIMESTONE CONTACTORS

Science.gov (United States)

The rate of carbonate mineral dissolution from limestone was studied using a rotating disk apparatus and samples of limestone of varied composition. The purpose of this study was to determine the effect of limestone composition on the kinetics of carbonate mineral dissolution. Th...

Colloid-facilitated effects on migration of radionuclides in fractured rock with a kinetic solubility-limited dissolution model

International Nuclear Information System (INIS)

Jen Chunping; Tien Nengchuan

2010-01-01

Nuclides can move with groundwater either as solutes or colloids, where the latter mechanism generally results in much shorter traveling time as the nuclides interact strongly with solid phases, such as actinides. In the performance assessment, it is therefore essential to assess the relative importance of these two transport mechanisms for different nuclides. The relative importance of colloids depends on the nature and concentration of the colloids in groundwater. Plutonium (Pu), neptunium (Np), uranium (U) and americium (Am) are four nuclides of concern for the long-term emplacement of nuclear wastes at potential repository sites. These four actinides have a high potential for migrating if attached to iron oxide, clay or silica colloids in the groundwater.Strong sorption of the actinides by colloids in the groundwater may facilitate the transport of these nuclides along potential flow paths. The solubility-limited dissolution model can be used to assess the safety of the release of nuclear waste in geological disposal sites. Usually, it has been assumed that the solubility of the waste form is constant. If a nuclide reaches its solubility limit at an inner location near the waste form, it is unlikely that the same nuclide will reach its solubility limit at an outer location unless this nuclide has a parent nuclide. It is unlikely that the daughter nuclides will exceed their solubility limit due to decay of their parent nuclide. The present study investigates the effect of colloids on the transport of solubility-limited nuclides under the kinetic solubility-limited dissolution (KSLD) boundary condition in fractured media. The release rate of the nuclides is proportional to the difference between the saturation concentration and the inlet aqueous concentration of the nuclides. The presence of colloids decreases the aqueous concentration of nuclides and, thus, increases the release flux of nuclides from the waste form. (authors)

Mineralogical and structural transformations related to alterations in hydrothermal and climatological conditions of basic vulcanic rocks from northern Parana (Ribeirao Preto region, SP, Brazil)

International Nuclear Information System (INIS)

Goncalves, N.M.M.

1987-01-01

Detailed studies of the basic vulcanic rocks of northern Parana basin (Region of Ribeirao Preto, SP) reveled that these rocks were affected by pre-meteoric activity (hydrothermal alteration) before being exposed to the supergene system of alteration linked to the lithosphere/atmosphere interface. Mineralogical and structural transformation are studied. The appearance of sequential crystalline-chemical paragenesis in zones suggest that the hydrothermal activity occurred during two successives processes of alteration: the expulsion of the water from the rock during the later stages of magma cooling and the continous process of dissolution of the rock wall and the ionic diffusion involving the rock sistem of structural voids. The hydro-thermal action was followed by weathering action developing a thin 'front' of superficial alteration. This alteration system, can lead to the formation of three major levels of alteration horizons and superficial accumulations: alterites, glebular and suil surface materials. (C.D.G.) [pt

Dissolution mechanisms of CO2 hydrate droplets in deep seawaters

International Nuclear Information System (INIS)

Gabitto, Jorge; Tsouris, Costas

2006-01-01

Carbon dioxide dissolution at intermediate ocean depths was studied using physical and mass transfer models. Particle density and hydrate layer thickness were determined using existing field data. Pseudo-homogeneous and heterogeneous mass transfer models were proposed to study the dissolution process. Pseudo-homogeneous models do not seem to represent the dissolution process well. Although heterogeneous models interpret the physical behavior better, unresolved issues related to hydrate dissolution still remain. For example, solid hydrate forms on one side of the hydrate film while it dissolves on the other. Dissolution is a complex process that comprises at least two sequential steps. The global process is controlled by mass transfer inside the hydrate layer or by a dissolution reaction at the hydrate-water interface

Study of the water-rock interactions of spring waters in the Northern Apennines

International Nuclear Information System (INIS)

Venturelli, G.; Toscani, L.

2000-01-01

Forty three spring waters have been investigated in the Apennine area of Reggio Emilia province (Parco Regionale del Gigante, Italy). On the basis of the Langelier-Ludwig diagram, the (Na+K+Cl) vs (Ca+Mg) plot and the Cl content, the waters have been divided in five main groups. The chemical composition of the waters suggests that calcite is practically the only source of Ca and alkalinity for group D and E reflect ion exchange and calcite and minor silicate dissolution during a strong water-rock interaction at depth [it

Dissolution Threats and Legislative Bargaining

DEFF Research Database (Denmark)

Becher, Michael; Christiansen, Flemming Juul

2015-01-01

Chief executives in many parliamentary democracies have the power to dissolve the legislature. Despite a well-developed literature on the endogenous timing of parliamentary elections, political scientists know remarkably little about the strategic use of dissolution power to influence policymaking....... To address this gap, we propose and empirically evaluate a theoretical model of legislative bargaining in the shadow of executive dissolution power. The model implies that the chief executive's public support and legislative strength, as well as the time until the next constitutionally mandated election...

Sodium tetraphenylborate solubility and dissolution rates

International Nuclear Information System (INIS)

Barnes, M.J.; Peterson, R.A.; Swingle, R.F.; Reeves, C.T.

1995-01-01

The rate of solid sodium tetraphenylborate (NaTPB) dissolution in In-Tank Precipitation salt solutions has been experimentally determined. The data indicates that the dissolution rate of solid NaTPB is a minor contributor the lag time experienced in the 1983 Salt Decontamination Demonstration Test and should not be considered as the rate determining step. Current analytical models for predicting the time to reach the composite lower flammability limit assume that the lag time is not more than 6 hours, and the data supports this assumption (i.e., dissolution by itself requires much less than 6 hours). The data suggests that another step--such as mass transport, the reaction of a benzene precursor or the mixing behavior--is the rate determining factor for benzene release to the vapor space in Tank 48H. In addition, preliminary results from this program show that the degree of agitation employed is not a significant parameter in determining the rate of NaTPB dissolution. As a result of this study, an improved equation for predicting equilibrium tetraphenylborate solubility with respect to temperature and sodium ion concentration has been determined

Mathematical methods for quantification and comparison of dissolution testing data

Directory of Open Access Journals (Sweden)

Edina Vranić

2002-02-01

Full Text Available In recent years, drug release/dissolution from solid dosage forms has been the subject of intense and profitable scientific developments. Whenever a new solid dosage form is developed or produced, it is necessary to ensure that drug dissolutionoccurs in an appropriate manner. The pharmaceutical industry and the registration authorities do focus, nowadays, on drug dissolution studies. The quantitative analysis of the values obtained in dissolution/release tests is easier when mathematicalformulas that express the dissolution results as a function of some of the dosage forms characteristics are used. This work discusses the analysis of data obtained for dissolution profiles under different media pH conditions using mathematical methodsof analysis described by Moore and Flanner. These authors have described difference factor (f1 and similarity factor (f2, which can be used to characterise drug dissolution/release profiles. In this work we have used these formulas for evaluation of dissolution profiles of the conventional tablets in different pH of dissolution medium (range of physiological variations.

On thermal properties of hard rocks as a host environment of an underground thermal energy storage

Science.gov (United States)

Novakova, L.; Hladky, R.; Broz, M.; Novak, P.; Lachman, V.; Sosna, K.; Zaruba, J.; Metelkova, Z.; Najser, J.

2013-12-01

With increasing focus on environmentally friendly technologies waste heat recycling became an important issue. Under certain circumstances subsurface environment could be utilized to accommodate relatively large quantity of heat. Industrial waste heat produced during warm months can be stored in an underground thermal energy storage (UTES) and used when needed. It is however a complex task to set up a sustainable UTES for industrial scale. Number of parameters has to be studied and evaluated by means of thermohydromechanical and chemical coupling (THMC) before any UTES construction. Thermal characteristics of various rocks and its stability under thermal loading are amongst the most essential. In the Czech Republic study two complementary projects THMC processes during an UTES operation. The RESEN project (www.resen.cz) employs laboratory tests and experiments to characterise thermal properties of hard rocks in the Bohemian Massif. Aim of the project is to point out the most suitable rock environment in the Bohemian Massif for moderate to ultra-high temperature UTES construction (Sanyal, 2005). The VITA project (www.geology.cz/mokrsko) studies THM coupling in non-electrical temperature UTES using long term in-situ experiment. In both projects thermal properties of rocks were studied. Thermal conductivity and capacity were measured on rock samples. In addition an influence of increasing temperature and moisture content was considered. Ten hard rocks were investigated. The set included two sandstones, two ignibrites, a melaphyr, a syenite, two granites, a gneiss and a serpentinite. For each rock there were measured thermal conductivity and capacity of at least 54 dried samples. Subsequently, the samples were heated up to 380°C in 8 hours and left to cool down. Thermal characteristics were measured during the heating period and after the sample reached room temperature. Heating and cooling cycle was repeated 7 to 10 times to evaluate possible UTES-like degradation of

Dissolution of covalent adaptable network polymers in organic solvent

Science.gov (United States)

Yu, Kai; Yang, Hua; Dao, Binh H.; Shi, Qian; Yakacki, Christopher M.

2017-12-01

It was recently reported that thermosetting polymers can be fully dissolved in a proper organic solvent utilizing a bond-exchange reaction (BER), where small molecules diffuse into the polymer, break the long polymer chains into short segments, and eventually dissolve the network when sufficient solvent is provided. The solvent-assisted dissolution approach was applied to fully recycle thermosets and their fiber composites. This paper presents the first multi-scale modeling framework to predict the dissolution kinetics and mechanics of thermosets in organic solvent. The model connects the micro-scale network dynamics with macro-scale material properties: in the micro-scale, a model is developed based on the kinetics of BERs to describe the cleavage rate of polymer chains and evolution of chain segment length during the dissolution. The micro-scale model is then fed into a continuum-level model with considerations of the transportation of solvent molecules and chain segments in the system. The model shows good prediction on conversion rate of functional groups, degradation of network mechanical properties, and dissolution rate of thermosets during the dissolution. It identifies the underlying kinetic factors governing the dissolution process, and reveals the influence of different material and processing variables on the dissolution process, such as time, temperature, catalyst concentration, and chain length between cross-links.

Status report on dissolution model development

International Nuclear Information System (INIS)

Jackson, D.D.

1983-07-01

The computer program PROTOCOL models the dissolution reactions of chemical species in water. It is being developed particularly to study the dissolution of proposed nuclear waste forms and related phases. Experimentally derived leaching rate functions are coupled to thermochemical equilibrium calculations and water flow rates. The program has been developed over a period of years. This report describes improvements that have been done in the past year

Intercalation of paracetamol into the hydrotalcite-like host

International Nuclear Information System (INIS)

Kovanda, František; Maryšková, Zuzana; Kovář, Petr

2011-01-01

Hydrotalcite-like compounds are often used as host structures for intercalation of various anionic species. The product intercalated with the nonionic, water-soluble pharmaceuticals paracetamol, N-(4-hydroxyphenyl)acetamide, was prepared by rehydration of the Mg–Al mixed oxide obtained by calcination of hydrotalcite-like precursor at 500 °C. The successful intercalation of paracetamol molecules into the interlayer space was confirmed by powder X-ray diffraction and infrared spectroscopy measurements. Molecular simulations showed that the phenolic hydroxyl groups of paracetamol interact with hydroxide sheets of the host via the hydroxyl groups of the positively charged sites of Al-containing octahedra; the interlayer water molecules are located mostly near the hydroxide sheets. The arrangement of paracetamol molecules in the interlayer is rather disordered and interactions between neighboring molecules cause their tilting towards the hydroxide sheets. Dissolution tests in various media showed slower release of paracetamol intercalated in the hydrotalcite-like host in comparison with tablets containing the powdered pharmaceuticals. - Graphical abstract: Molecular simulations showed disordered arrangement of paracetamol molecules in the interlayer; most of the interlayer water molecules are located near the hydroxide sheets.▪ Highlights: ► Paracetamol was intercalated in Mg–Al hydrotalcite-like host by rehydration/reconstruction procedure. ► Paracetamol phenolic groups interact with positively charged sites in hydroxide sheets. ► Molecular simulations showed disordered arrangement of guest molecules in the interlayer. ► Slower release of paracetamol intercalated in the hydrotalcite-like host was observed.

8 Dissolution Kinetics

African Journals Online (AJOL)

user

Experiments measuring the dissolution rates of stilbite (NaCa [Al Si O ].14H O) in pH-buffered ... The rate law was established as R = k (a ) , where k is ... crystalline hydrated aluminosilicate minerals ..... from the crushing process, thin edges or.

Dissolution studies of synthetic soddyite and uranophane

International Nuclear Information System (INIS)

Casas, I.; Perez, I.; Torrero, E.; Bruno, J.; Cera, E.; Duro, L.

1997-09-01

The dissolution of synthetically obtained soddyite and uranophane has been studied in solutions of low ionic strength. These are the likely final phases of the oxidative alternation pathway of uranium dioxide. The thermodynamic and kinetic dissolution properties of these phases have been determined at different bicarbonate concentrations. The solubilities determined in the experiments with soddyite correspond fairly well to the theoretical model calculated with a log K 0 s0 =3.9±0.7. For uranophane, the best fitting was obtained for a log K 0 s0 =11.7±0.6. The dissolution rate in the presence of bicarbonate gave for soddyite an average value of 6.8(±4.4) 10 -10 mol m -2 s -1 . For uranophane, under the same experimental conditions, the following dissolution rate equation has been derived: r 0 (mol m -2 s -1 )=10 -9±2. [HCO 3 - ] 0.69±0.09 2

Basic rock properties for the thermo-hydro-mechanical analysis of a high-level radioactive waste repository

Energy Technology Data Exchange (ETDEWEB)

Kim, Jhin Wung; Kang, Chul Hyung

1999-04-01

Deep geological radioactive waste disposal is generally based on the isolation of the waste from the biosphere by multiple barriers. The host rock is one of these barriers which should provide a stable mechanical and chemical environment for the engineered barriers. In the evaluation of the safety of the high-level radioactive waste disposal systems, an important part of the safety analysis is an assessment of the coupling or interaction between thermal, hydrological, and mechanical effects. In order to do this assessment, adequate data on the characteristics of different host rocks are necessary. The properties of the rock and rock discontinuity are very complex and their values vary in a wide range. The accuracy of the result of the assessment depends on the values of these properties used. The present study is an attempt to bring together and condense data for the basic properties of various rock masses, which are needed in the thermo-hydro-mechanical analysis for the deep geological radioactive waste repository. The testing and measurement methods for these basic properties are also presented. Domestic data for deep geological media should be supplemented in the future, due to the insufficiency and the lack of accuracy of the data available at present. (author). 28 refs., 21 figs.

Basic rock properties for the thermo-hydro-mechanical analysis of a high-level radioactive waste repository

International Nuclear Information System (INIS)

Kim, Jhin Wung; Kang, Chul Hyung

1999-04-01

Deep geological radioactive waste disposal is generally based on the isolation of the waste from the biosphere by multiple barriers. The host rock is one of these barriers which should provide a stable mechanical and chemical environment for the engineered barriers. In the evaluation of the safety of the high-level radioactive waste disposal systems, an important part of the safety analysis is an assessment of the coupling or interaction between thermal, hydrological, and mechanical effects. In order to do this assessment, adequate data on the characteristics of different host rocks are necessary. The properties of the rock and rock discontinuity are very complex and their values vary in a wide range. The accuracy of the result of the assessment depends on the values of these properties used. The present study is an attempt to bring together and condense data for the basic properties of various rock masses, which are needed in the thermo-hydro-mechanical analysis for the deep geological radioactive waste repository. The testing and measurement methods for these basic properties are also presented. Domestic data for deep geological media should be supplemented in the future, due to the insufficiency and the lack of accuracy of the data available at present. (author). 28 refs., 21 figs

Does the dose-solubility ratio affect the mean dissolution time of drugs?

Science.gov (United States)

Lánský, P; Weiss, M

1999-09-01

To present a new model for describing drug dissolution. On the basis of the new model to characterize the dissolution profile by the distribution function of the random dissolution time of a drug molecule, which generalizes the classical first order model. Instead of assuming a constant fractional dissolution rate, as in the classical model, it is considered that the fractional dissolution rate is a decreasing function of the dissolved amount controlled by the dose-solubility ratio. The differential equation derived from this assumption is solved and the distribution measures (half-dissolution time, mean dissolution time, relative dispersion of the dissolution time, dissolution time density, and fractional dissolution rate) are calculated. Finally, instead of monotonically decreasing the fractional dissolution rate, a generalization resulting in zero dissolution rate at time origin is introduced. The behavior of the model is divided into two regions defined by q, the ratio of the dose to the solubility level: q 1 (saturation of the solution, saturation time). The singular case q = 1 is also treated and in this situation the mean as well as the relative dispersion of the dissolution time increase to infinity. The model was successfully fitted to data (1). This empirical model is descriptive without detailed physical reasoning behind its derivation. According to the model, the mean dissolution time is affected by the dose-solubility ratio. Although this prediction appears to be in accordance with preliminary application, further validation based on more suitable experimental data is required.

Kinetics of Inorganic Calcite Dissolution in Seawater under Pressure

Science.gov (United States)

Dong, S.; Subhas, A.; Rollins, N.; Berelson, W.; Adkins, J. F.

2016-02-01

While understanding calcium carbonate dissolution is vital in constructing global carbon cycles and predicting the effect of seawater acidification as a result of increasing atmospheric CO2, there is still a major debate over the basic formulation of a dissolution rate law. The kinetics of calcium carbonate dissolution are typically described by the equation: Rate=k(1-Ω)n, while Ω=[Ca2+][CO32-]/Ksp. In this study, 13C-labeled calcite is dissolved in unlabeled seawater and the evolving d13C composition of the fluid is traced over time to establish dissolution rate. Instead of changing ion concentration to obtain varying Ω (as in our previous study; Subhas et al. 2015), we changed Ksp by conducting experiments under different pressures (described in theory as ∂lnKsp/∂P=-ΔV/RT, where ΔV is partial molal volume). This involved the construction of a pressure vessel that could hold our sample bag and provide aliquots while remaining pressurized. Pressure experiments were conducted between 0-2000PSI. Results support the conclusion in our previous study that near-equilibrium dissolution rates are highly nonlinear, but give a disparate relationship between undersaturation and dissolution rate if Ω is calculated assuming the specific ΔV embedded in CO2SYS. A revised ΔV from -37cm3 to -65cm3 would make the dissolution formulation equation agree, but clearly appears unreasonable. Our results are explained by a pressure effect on carbonate dissolution kinetics over and above the influence of pressure on Ω. If this is a phenomenon that occurs in nature, then we would predict that dissolution should be occurring shallower in the water column (as sometimes observed) than indicated by standard Ω calculations.

Rock mechanics in the National Waste Terminal Storage Program

International Nuclear Information System (INIS)

Monsees, J.E.; Wigley, M.R.

1982-01-01

The overall objective of the rock mechanics program of the Office of Nuclear Waste Isolation is to predict the response of a rock mass hosting a waste repository during its construction, operation, and postoperational phases. The operational phase is expected to be 50 to 100 yr; the postoperational phase will last until the repository no longer poses any potential hazard to the biosphere, a period that may last several thousand years. The rock mechanics program is concerned with near-field effects on mine stability, as well as far-field effects relative to the overall integrity of the geologic waste isolation system. To accomplish these objectives, the rock mechanics program has established interactive studies in numerical simulation, laboratory testing, and field testing. The laboratory and field investigations provide input to the numerical simulations and give an opportunity for verification and validation of the predictive capabilities of the computer codes. Ultimately the computer codes will be used to predict the response of the geologic system to the development of a repository. 3 references, 5 figures

Mechanisms and kinetics laws of inactive R7T7 reference glass dissolution in water at 90 deg C: initial dissolution rate measurements

International Nuclear Information System (INIS)

Advocat, T.; Ghaleb, D.; Vernaz, E.

1993-02-01

The initial dissolution rate of inactive R7T7 reference glass was measured at 90 deg C in dilute aqueous solutions first at unspecified pH, then with imposed pH values. In distilled water, R7T7 glass corrosion initially involved preferential extraction of boron and network modifier elements (Li, Na, Ca) as long as the solution pH remained acid. When the solution pH became alkaline, glass dissolution was stoichiometric. These two mechanisms were confirmed by dissolution tests in aqueous solutions at imposed pH values under acid and alkaline conditions. The initial dissolution rate r 0 in mole.cm -3 .s -1 also increased significantly in alkaline media when the pH of the aqueous phase increased: in slightly acid media, selective glass dissolution formed a residual, de-alkalinized, hydrated glass that was characterized by transmission electron microscopy and secondary ion mass spectrometry. Under steady-state dissolution conditions, the initial glass corrosion rate (in mole.cm -3 .s -1 ) was: in acid and alkaline media, amorphous and crystallized alteration products formed after complete dissolution of the silicated glass network. The first products formed consisted mainly of Zr, Rare Earths, Fe and Al. (author). 67 refs., 29 figs., 26 tabs., 21 plates

Actor bonds after relationship dissolution

DEFF Research Database (Denmark)

Skaates, Maria Anne

2000-01-01

Most of the presented papers at the 1st NoRD Workshop can be classified as belonging to the business marketing approach to relationship dissolution. Two papers were conceptual, and the remaining six were empirical studies. The first conceptual study by Skaates (2000) focuses on the nature...... of the actor bonds that remain after a business relationship has ended. The study suggests that an interdisciplinary approach would provide a richer understanding of the phenomenon; this could be achieved by using e.g. Bourdieu's sociological concepts in dissolution research....

Multi-element analysis of emeralds and associated rocks by k{sub 0} neutron activation analysis

Energy Technology Data Exchange (ETDEWEB)

Acharya, R.N.; Mondal, R.K.; Burte, P.P.; Nair, A.G.C.; Reddy, N.B.Y.; Reddy, L.K.; Reddy, A.V.R.; Manohar, S.B

2000-12-15

Multi-element analysis was carried out in natural emeralds, their associated rocks and one sample of beryl obtained from Rajasthan, India. The concentrations of 21 elements were assayed by Instrumental Neutron Activation Analysis using the k{sub 0} method (k{sub 0} INAA method) and high-resolution gamma ray spectrometry. The data reveal the segregation of some elements from associated (trapped and host) rocks to the mineral beryl forming the gemstones. A reference rock standard of the US Geological Survey (USGS BCR-1) was also analysed as a control of the method.

Damage Features of Altered Rock Subjected to Drying-Wetting Cycles

Directory of Open Access Journals (Sweden)

Zhe Qin

2018-01-01

Full Text Available An abandoned open pit was used as a tailing pond for a concentrating mill, with the height of the water surface subject to cyclic fluctuation. The effects of drying and wetting cycles on the mechanical parameters of pit rock were tested. Interactions of the hydrochemical environment, due to the dissolution of tailings, and drying and wetting cycles caused degradation of mechanical properties in the rock. It was found that uniaxial compressive strength and elastic modulus decreased as the number of dry/wet cycles increased. The quantitative relationship between the mechanical parameters and the number of dry/wet cycles was indicated by an exponential function. In addition to uniaxial testing, cohesion and the internal friction angle were determined through triaxial testing. The shear strength index deteriorated under the drying and wetting cycles. The hydrochemical environment also negatively affected the mechanical parameters. Potential effects between drying and wetting cycles and slope displacement were analyzed by on-site monitoring. The results show that the displacement increased because of the drying and wetting cycles, which may lead to sudden failure of the slope.

Laboratory simulation of salt dissolution during waste removal

International Nuclear Information System (INIS)

Wiersma, B.J.; Parish, W.R.

1997-01-01

Laboratory experiments were performed to support the field demonstration of improved techniques for salt dissolution in waste tanks at the Savannah River Site. The tests were designed to investigate three density driven techniques for salt dissolution: (1) Drain-Add-Sit-Remove, (2) Modified Density Gradient, and (3) Continuous Salt Mining. Salt dissolution was observed to be a very rapid process as salt solutions with densities between 1.38-1.4 were frequently removed. Slower addition and removal rates and locating the outlet line at deeper levels below the top of the saltcake provided the best contact between the dissolution water and the saltcake. It was observed that dissolution with 1 M sodium hydroxide solution resulted in salt solutions that were within the current inhibitor requirements for the prevention of stress corrosion cracking. This result was independent of the density driven technique. However, if inhibited water (0.01 M sodium hydroxide and 0.011 M sodium nitrite) was utilized, the salt solutions were frequently outside the inhibitor requirements. Corrosion testing at conditions similar to the environments expected during waste removal was recommended

Final workshop proceedings of the collaborative project ''Crystalline ROCK retention processes''

Energy Technology Data Exchange (ETDEWEB)

Rabung, Thomas; Garcia, David; Montoya Vanessa; Molinero, Jorge (eds.)

2014-07-01

The present document is the proceedings of the Final Workshop of the EURATOM FP7 Collaborative Project CROCK (Crystalline Rock Retention Processes). The key driver for initiation the CP CROCK, identified by national Waste Management Organizations, is the undesired high uncertainty and the associated conservatism with respect to the radionuclide transport in the crystalline host-rock far-field around geological disposal of high-level radioactive wastes.

Investigation of dissolution kinetics of a Nigerian columbite in ...

African Journals Online (AJOL)

Investigation of dissolution kinetics of a Nigerian columbite in hydrofluoric acid using the shrinking core model. ... Experimental results indicate that the dissolution rate is chemical reaction controlled, with reaction order of 0.57. Dissolution of over 90 % of the columbite was achieved in 5 h, using 20 M HF at 90 oC with 100 ...

Dissolution behavior of PFBR MOX fuel in nitric acid

International Nuclear Information System (INIS)

Kelkar, Anoop; Kapoor, Y.S.; Singh, Mamta; Meena, D.L.; Pandey, Ashish; Bhatt, R.B.; Behere, P.G.

2017-01-01

Present paper describes the dissolution characteristics of PFBR MOX fuel (U,Pu)O 2 in nitric acid. An overview of batch dissolution experiments, studying the percentage dissolution of uranium and plutonium in (U, Pu)O 2 MOX sintered pellets with different percentage of PuO 2 with reference to time and nitric acid concentration are described. 90% of uranium and plutonium of PFBR MOX gets dissolves in 2 hrs and amount of residue increases with the decrease in nitric acid concentration. Overall variation in percentage residue in PFBR MOX fuel after dissolution test also described. (author)

Do Workplace Sex Ratios Affect Partnership Formation and Dissolution?

DEFF Research Database (Denmark)

Svarer, Michael

In this paper, I analyse the association between workplace sex ratios and partnership formation and dissolution. I find that the risk of dissolution increases with the fraction of coworkers of the opposite sex at both the female and male workplace. On the other hand, workplace sex ratios are not ......In this paper, I analyse the association between workplace sex ratios and partnership formation and dissolution. I find that the risk of dissolution increases with the fraction of coworkers of the opposite sex at both the female and male workplace. On the other hand, workplace sex ratios...

Dissolution enhancement of a model poorly water-soluble drug, atorvastatin, with ordered mesoporous silica: comparison of MSF with SBA-15 as drug carriers.

Science.gov (United States)

Maleki, Aziz; Hamidi, Mehrdad

2016-01-01

The purpose of this study was to develop mesoporous silica materials incorporated with poorly water-soluble drug atorvastatin calcium (AC) in order to improve drug dissolution, and intended to be orally administrated. A comparison between 2D-hexagonal silica nanostructured SBA-15 and mesocellular siliceous foam (MSF) with continuous 3D pore system on drug release rate was investigated. AC-loaded mesoporous silicas were characterized thorough N2 adsorption-desorption analysis, Fourier transform infrared (FT-IR) spectroscopy, powder X-ray diffraction (PXRD), differential scanning calorimetry (DSC) and dynamic light scattering (DLS). Results demonstrated a successful incorporation of AC into the silica-based hosts. The results taken from the drug release tests were also analyzed using different parameters, namely similarity factor (f2), difference factor (f1), dissolution efficiency (DE%), mean dissolution rate (MDR) and dissolution time (tm%). It confirmed a significant enhancement in the release profile of atorvastatin calcium with SBA-15, and MSF as drug carrier. Moreover, in comparison with SBA-15, MSF showed faster release rate of AC in enzyme-free simulated gastric fluid (pH 1.2). We believed that our findings can help the use of mesoporous silica materials in improving bioavailability of poorly water-soluble drugs.

The complexity of nanoparticle dissolution and its importance in nanotoxicological studies

International Nuclear Information System (INIS)

Misra, Superb K.; Dybowska, Agnieszka; Berhanu, Deborah; Luoma, Samuel N.; Valsami-Jones, Eugenia

2012-01-01

Dissolution of nanoparticles (NPs) is an important property that alters their abundance and is often a critical step in determining safety of nanoparticles. The dissolution status of the NPs in exposure media (i.e. whether they remain in particulate form or dissolve — and to what extent), strongly affects the uptake pathway, toxicity mechanisms and the environmental compartment in which NPs will have the highest potential impact. A review of available dissolution data on NPs demonstrates there is a range of potential outcomes depending on the NPs and the exposure media. For example two nominally identical nanoparticles, in terms of size and composition, could have totally different dissolution behaviours, subject to different surface modifications. Therefore, it is imperative that toxicological studies are conducted in conjunction with dissolution of NPs to establish the true biological effect of NPs and hence, assist in their regulation. -- Graphical abstract: Various physicochemical factors affecting dissolution of nanoparticles. Highlights: ► In this study we discuss dissolution of nanoparticles. ► Physicochemical properties of nanoparticles influence dissolution. ► Measuring dissolution of nanoparticles can help to understand their biological response.

Dissolution Flowsheet for High Flux Isotope Reactor Fuel

Energy Technology Data Exchange (ETDEWEB)

Daniel, W. E. [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL); Rudisill, T. S. [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL); O' Rourke, P. E. [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL); Karay, N. S [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL)

2016-09-27

As part of the Spent Nuclear Fuel (SNF) processing campaign, H-Canyon is planning to begin dissolving High Flux Isotope Reactor (HFIR) fuel in late FY17 or early FY18. Each HFIR fuel core contains inner and outer fuel elements which were fabricated from uranium oxide (U₃O₈) dispersed in a continuous Al phase using traditional powder metallurgy techniques. Fuels fabricated in this manner, like other SNF’s processed in H-Canyon, dissolve by the same general mechanisms with similar gas generation rates and the production of H₂. The HFIR fuel cores will be dissolved and the recovered U will be down-blended into low-enriched U. HFIR fuel was previously processed in H-Canyon using a unique insert in both the 6.1D and 6.4D dissolvers. Multiple cores will be charged to the same dissolver solution maximizing the concentration of dissolved Al. The objective of this study was to identify flowsheet conditions through literature review and laboratory experimentation to safely and efficiently dissolve the HFIR fuel in H-Canyon. Laboratory-scale experiments were performed to evaluate the dissolution of HFIR fuel using both Al 1100 and Al 6061 T6 alloy coupons. The Al 1100 alloy was considered a representative surrogate which provided an upper bound on the generation of flammable (i.e., H₂) gas during the dissolution process. The dissolution of the Al 6061 T6 alloy proceeded at a slower rate than the Al 1100 alloy, and was used to verify that the target Al concentration in solution could be achieved for the selected Hg concentration. Mass spectrometry and Raman spectroscopy were used to provide continuous monitoring of the concentration of H₂ and other permanent gases in the dissolution offgas, allowing the development of H₂ generation rate profiles. The H₂ generation rates were subsequently used to evaluate if a full HFIR core could be dissolved in an H-Canyon dissolver without exceeding 60% of the

Improved RMR Rock Mass Classification Using Artificial Intelligence Algorithms

Science.gov (United States)

Gholami, Raoof; Rasouli, Vamegh; Alimoradi, Andisheh

2013-09-01

Rock mass classification systems such as rock mass rating (RMR) are very reliable means to provide information about the quality of rocks surrounding a structure as well as to propose suitable support systems for unstable regions. Many correlations have been proposed to relate measured quantities such as wave velocity to rock mass classification systems to limit the associated time and cost of conducting the sampling and mechanical tests conventionally used to calculate RMR values. However, these empirical correlations have been found to be unreliable, as they usually overestimate or underestimate the RMR value. The aim of this paper is to compare the results of RMR classification obtained from the use of empirical correlations versus machine-learning methodologies based on artificial intelligence algorithms. The proposed methods were verified based on two case studies located in northern Iran. Relevance vector regression (RVR) and support vector regression (SVR), as two robust machine-learning methodologies, were used to predict the RMR for tunnel host rocks. RMR values already obtained by sampling and site investigation at one tunnel were taken into account as the output of the artificial networks during training and testing phases. The results reveal that use of empirical correlations overestimates the predicted RMR values. RVR and SVR, however, showed more reliable results, and are therefore suggested for use in RMR classification for design purposes of rock structures.

Host-rock controlled epigenetic, hydrothermal metasomatic origin of the Bayan Obo REEFe-Nb ore deposit, Inner Mongolia, P.R.C.

Science.gov (United States)

Chao, E.C.T.; Back, J.M.; Minkin, J.A.; Yinchen, R.

1992-01-01

Bayan Obo, a complex rare earth element (REE)FeNb ore deposit, located in Inner Mongolia, P.R.C. is the world's largest known REE deposit. The deposit is chiefly in a marble unit (H8), but extends into an overlying unit of black shale, slate and schist unit (H9), both of which are in the upper part of the Middle Proterozoic Bayan Obo Group. Based on sedimentary structures, the presence of detrital quartz and algal fossil remains, and the 16-km long geographic extent, the H8 marble is a sedimentary deposit, and not a carbonatite of magmatic origin, as proposed by some previous investigators. The unit was weakly regionally metamorphosed (most probably the lower part of the green schist facies) into marble and quartzite prior to mineralization. Tectonically, the deposit is located on the northern flank of the Sino-Korean craton. Many hypotheses have been proposed for the origin of the Bayan Obo deposit; the studies reported here support an epigenetic, hydrothermal, metasomatic origin. Such an origin is supported by field and laboratory textural evidence; 232Th/208Pb internal isochron mineral ages of selected monazite and bastnaesite samples; 40Ar/39Ar incremental heating minimum mineral ages of selected alkali amphiboles; chemical compositions of different generations of both REE ore minerals and alkali amphiboles; and evidence of host-rock influence on the various types of Bayan Obo ores. The internal isochron ages of the REE minerals indicate Caledonian ages for various episodes of REE and Fe mineralization. No evidence was found to indicate a genetic relation between the extensive biotite granitic rocks of Hercynian age in the mine region and the Bayan Obo are deposit, as suggested by previous workers. ?? 1992.

Linking geology, fluid chemistry, and microbial activity of basalt- and ultramafic-hosted deep-sea hydrothermal vent environments.

Science.gov (United States)

Perner, M; Hansen, M; Seifert, R; Strauss, H; Koschinsky, A; Petersen, S

2013-07-01

Hydrothermal fluids passing through basaltic rocks along mid-ocean ridges are known to be enriched in sulfide, while those circulating through ultramafic mantle rocks are typically elevated in hydrogen. Therefore, it has been estimated that the maximum energy in basalt-hosted systems is available through sulfide oxidation and in ultramafic-hosted systems through hydrogen oxidation. Furthermore, thermodynamic models suggest that the greatest biomass potential arises from sulfide oxidation in basalt-hosted and from hydrogen oxidation in ultramafic-hosted systems. We tested these predictions by measuring biological sulfide and hydrogen removal and subsequent autotrophic CO2 fixation in chemically distinct hydrothermal fluids from basalt-hosted and ultramafic-hosted vents. We found a large potential of microbial hydrogen oxidation in naturally hydrogen-rich (ultramafic-hosted) but also in naturally hydrogen-poor (basalt-hosted) hydrothermal fluids. Moreover, hydrogen oxidation-based primary production proved to be highly attractive under our incubation conditions regardless whether hydrothermal fluids from ultramafic-hosted or basalt-hosted sites were used. Site-specific hydrogen and sulfide availability alone did not appear to determine whether hydrogen or sulfide oxidation provides the energy for primary production by the free-living microbes in the tested hydrothermal fluids. This suggests that more complex features (e.g., a combination of oxygen, temperature, biological interactions) may play a role for determining which energy source is preferably used in chemically distinct hydrothermal vent biotopes. © 2013 John Wiley & Sons Ltd.

Crystal modifications and dissolution rate of piroxicam.

Science.gov (United States)

Lyn, Lim Yee; Sze, Huan Wen; Rajendran, Adhiyaman; Adinarayana, Gorajana; Dua, Kamal; Garg, Sanjay

2011-12-01

Piroxicam is a nonsteroidal anti-inflammatory drug with low aqueous solubility which exhibits polymorphism. The present study was carried out to develop polymorphs of piroxicam with enhanced solubility and dissolution rate by the crystal modification technique using different solvent mixtures prepared with PEG 4000 and PVP K30. Physicochemical characteristics of the modified crystal forms of piroxicam were investigated by X-ray powder diffractometry, FT-IR spectrophotometry and differential scanning calorimetry. Dissolution and solubility profiles of each modified crystal form were studied and compared with pure piroxicam. Solvent evaporation method (method I) produced both needle and cubic shaped crystals. Slow crystallization from ethanol with addition of PEG 4000 or PVP K30 at room temperature (method II) produced cubic crystal forms. Needle forms produced by method I improved dissolution but not solubility. Cubic crystals produced by method I had a dissolution profile similar to that of untreated piroxicam but showed better solubility than untreated piroxicam. Cubic shaped crystals produced by method II showed improved dissolution, without a significant change in solubility. Based on the XRPD results, modified piroxicam crystals obtained by method I from acetone/benzene were cube shaped, which correlates well with the FTIR spectrum; modified needle forms obtained from ethanol/methanol and ethanol/acetone showed a slight shift of FTIR peak that may be attributed to differences in the internal structure or conformation.

Dissolution of cellulose in ionic liquid: A review