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Sample records for surrounding graphite trunnions

  1. Flexibility of trunnion piping elbows

    International Nuclear Information System (INIS)

    Lewis, G.D.; Chao, Y.J.

    1987-01-01

    Flexibility factors and stress indices for piping component such as straight pipe, elbows, butt-welding tees, branch connections, and butt-welding reducers are contained in the code, but many of the less common piping components, like the trunnion elbow, do not have flexibility factors or stress indices defined. The purpose of this paper is to identify the in-plane and out-of-plane flexibility factors in accordance with code procedures for welded trunnions attached to the tangent centerlines of long radius elbows. This work utilized the finite element method as applicable to plates and shells for calculating the relative rotations of the trunnion elbow-ends for in-plane and out-of-plane elbow moment loadings. These rotations are used to derive the corresponding in-plane and out-of-plane flexibility factors. (orig./GL)

  2. Modern trunnions are more flexible: a mechanical analysis of THA taper designs.

    Science.gov (United States)

    Porter, David A; Urban, Robert M; Jacobs, Joshua J; Gilbert, Jeremy L; Rodriguez, José A; Cooper, H John

    2014-12-01

    There is renewed concern surrounding the potential for corrosion at the modular head-neck junction to cause early failure in contemporary THAs. Although taper corrosion involves a complex interplay of many factors, a previous study suggested that a decrease in flexural rigidity of the femoral trunnion may be associated with an increased likelihood of corrosion at retrieval. By analyzing a large revision retrieval database of femoral stems released during a span of three decades, we asked: (1) how much does flexural rigidity vary among different taper designs; (2) what is the contribution of taper geometry alone to flexural rigidity of the femoral trunnion; and (3) how have flexural rigidity and taper length changed with time in this group of revised retrievals? A dual-center retrieval analysis of 85 modular femoral stems released between 1983 and 2012 was performed, and the flexural rigidity and length of the femoral trunnions were determined. These stems were implanted between 1991 and 2012 and retrieved at revision or removal surgery between 2004 and 2012. There were 10 different taper designs made from five different metal alloys from 16 manufacturers. Digital calipers were used to measure taper geometries by two independent observers. Median flexural rigidity was 228 N-m(2); however, there was a wide range of values among the various stems spanning nearly an order of magnitude between the most flexible (80 N-m(2)) and most rigid (623 N-m(2)) trunnions, which was partly attributable to the taper geometry and to the material properties of the base alloy. There was a negative correlation between flexural rigidity and length of the trunnion and release date of the stem. There is wide variability in flexural rigidity of various taper designs, with a trend toward trunnions becoming shorter and less rigid with time. This temporal trend may partly explain why taper corrosion is being seen with increasing frequency in modern THAs.

  3. Trunnion Collar Removal Machine - Gap Analysis Table

    International Nuclear Information System (INIS)

    Johnson, M.

    2005-01-01

    The purpose of this document is to review the existing the trunnion collar removal machine against the ''Nuclear Safety Design Bases for License Application'' (NSDB) [Ref. 10] requirements and to identify codes and standards and supplemental requirements to meet these requirements. If these codes and standards can not fully meet these requirements then a ''gap'' is identified. These gaps will be identified here and addressed using the ''Trunnion Collar Removal Machine Design Development Plan'' [Ref. 15]. The codes and standards, supplemental requirements, and design development requirements for the trunnion collar removal machine are provided in the gap analysis table (Appendix A, Table 1). Because the trunnion collar removal machine is credited with performing functions important to safety (ITS) in the NSDB [Ref. 10], design basis requirements are applicable to ensure equipment is available and performs required safety functions when needed. The gap analysis table is used to identify design objectives and provide a means to satisfy safety requirements. To ensure that the trunnion collar removal machine performs required safety functions and meets performance criteria, this portion of the gap analysis tables supplies codes and standards sections and the supplemental requirements and identifies design development requirements, if needed

  4. Trunnions for spent fuel element shipping casks

    International Nuclear Information System (INIS)

    Cooke, B.

    1989-01-01

    Trunnions are used on spent fuel element shipping casks for one or more of a combination of lifting, tilting or securing to a transport vehicle. Within the nuclear transportation industry there are many different philosophies on trunnions, concerning the shape, manufacture, attachment, inspection, maintenance and repair. With the volume of international transport of spent fuel now taking place, it is recognized that problems are occurring with casks in international traffic due to the variance of the philosophies, national standards, and the lack of an international standard. It was agreed through the ISO that an international standard was required to harmonize. It was not possible to evolve an international standard. It was only possible to evolve an international guide. To evolve a standard would mean superseding any existing national standards which already cover particular aspects of trunnions i.e. deceleration forces imposed on trunnions used as tie down features. Therefore the document is a guide only and allows existing national standards to take precedence where they exist. The guide covers design, manufacture, maintenance, repair and quality assurance. The guide covers trunnions used on spent fuel casks transported by road, rail and sea. The guide details the considerations which should be taken account of by cask designers, i.e. stress intensity, design features, inspection and test methods etc. Manufacture, attachment and pre-service testing is also covered. The guide details user requirements which should also be taken account of, i.e. servicing frequency, content, maintenance and repair. The application of quality assurance is described separately although the principles are used throughout the guide

  5. Graphite

    Science.gov (United States)

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

    2017-12-19

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

  6. Replacement screws valve operating under Trunnion; Substituicao de parafusos de valvulas Trunnion em regime de operacao

    Energy Technology Data Exchange (ETDEWEB)

    Souza Netto, Charles de; Santos, Rogerio Andre Zolin dos; Arnhold, Diego [Companhia de Gas do Estado do Rio Grande do Sul (SULGAS), Porto Alegre, RS (Brazil); Jacques, Rodrigo das Neves [Guidotti e Vieira Manutencao Industrial Ltda., Canoas, RS (Brazil)

    2012-07-01

    The report shows the process created for the substitution and extraction of bearing screws of the Trunnion valves, in operation. The methodology was developed at the 'Companhia de Gas do Estado do Rio Grande do Sul - SULGAS', with the objective of avoiding failure emergency situations, and or sudden breaking of the screws of fixation of the lid of the inferior bearing of the Trunnion valves. it is a preventive process of substitution of these screws, that after a great period of use in atmospheres with high potential of oxidation present structural failure. The breaking of these components creates a leaking process by the inferior lid of the valves, fact that is intended to be avoided with the application of the technical procedure of this report, guaranteeing the integrity of the valves that are vital components for the continuous operation of the gas pipe line. (author)

  7. 49 CFR 236.335 - Dogs, stops and trunnions of mechanical locking.

    Science.gov (United States)

    2010-10-01

    ... 49 Transportation 4 2010-10-01 2010-10-01 false Dogs, stops and trunnions of mechanical locking..., AND APPLIANCES Interlocking Rules and Instructions § 236.335 Dogs, stops and trunnions of mechanical locking. Driving pieces, dogs, stops and trunnions shall be rigidly secured to locking bars. Swing dogs...

  8. 21 CFR 888.3380 - Hip joint femoral (hemi-hip) trunnion-bearing metal/polyacetal cemented prosthesis.

    Science.gov (United States)

    2010-04-01

    ... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Hip joint femoral (hemi-hip) trunnion-bearing... Devices § 888.3380 Hip joint femoral (hemi-hip) trunnion-bearing metal/polyacetal cemented prosthesis. (a) Identification. A hip joint femoral (hemi-hip) trunnion-bearing metal/polyacetal cemented prosthesis is a two...

  9. LH2 on-orbit storage tank support trunnion design and verification

    Science.gov (United States)

    Bailey, W. J.; Fester, D. A.; Toth, J. M., Jr.

    1985-01-01

    A detailed fatigue analysis was conducted to provide verification of the trunnion design in the reusable Cryogenic Fluid Management Facility for Shuttle flights and to assess the performance capability of the trunnion E-glass/S-glass epoxy composite material. Basic material property data at ambient and liquid hydrogen temperatures support the adequacy of the epoxy composite for seven-mission requirement. Testing of trunnions fabricated to the flight design has verified adequate strength and fatigue properties of the design to meet the requirements of seven Shuttle flights.

  10. LH2 on-orbit storage tank support trunnion design and verification

    International Nuclear Information System (INIS)

    Bailey, W.J.; Fester, D.A.; Toth, J.M.

    1986-01-01

    A subcritical liquid hydrogen orbital storage and transfer experiment is being designed for flight in the shuttle cargo bay. The Cryogenic Fluid Management Facility (CFMF) includes a liquid hydrogen storage tank supported in a vacuum jacket by two fiberglass epoxy composite trunnion mounts. The capability of the CFMF to meet a seven mission requirement is extremely sensitive to the fatigue life of the composite trunnions at cryogenic temperatures. An E-glass/S-glass epoxy composite material was selected for the trunnions since it provided desirable strength, weight and thermal characteristics. Because of the limited extent of analytical or experimental treatment of the fatigue life of this composite at cryogenic temperature, an experimental program was conducted to provide verification of the trunnion design and performance capability at ambient and liquid hydrogen temperatures. Basic material fatigue property data were obtained for the laminate of interest using specifically prepared test specimens. Full-scale trunnions were manufactured and subjected to cyclic load testing to verify fatigue life. An analytical evaluation of the thermal performance of the trunnions was conducted, and a test setup is being manufactured to correlate analytical predictions with test results

  11. Russian RSC Energia employees attach trunnions to DM

    Science.gov (United States)

    1995-01-01

    Employees of the Russian aerospace company RSC Energia attach trunnions to the Russian-built docking module in the Space Station Processing Facility at KSC so that it can be mounted in the payload bay of the Space Shuttle orbiter Atlantis. The module will fly as a primary payload on the second Space Shuttle/Mir space station docking mission, STS-74, which is now scheduled for liftoff in the fall of 1995. During the mission, the module will first be attached with the orbiter's robot arm to the Orbiter Docking System (ODS) in the payload bay of the orbiter Atlantis and then be docked with the Mir. When Atlantis undocks from the Mir, it will leave the new docking module permanently attached to the space station for use during future Shuttle Mir docking missions. The new module will simplify future Shuttle linkups with Mir by improving orbiter clearances when it serves as a bridge between the two space vehicles.

  12. Brazing graphite to graphite

    International Nuclear Information System (INIS)

    Peterson, G.R.

    1976-01-01

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

  13. Guided-Wave Testing of Trunnion Rods at Greenup Lock and Dam, Kentucky

    Science.gov (United States)

    2014-04-01

    fatigue cracks which go through opening and closing periods during their progression, microcracks in post-tension trunnion anchor rods are believed to be...produce undesired interference effects. A new 1.5 in. diameter, medium-damped lead zirconate titanate ( PZT ), ceramic-based crystal (i.e., an Accuscan

  14. Special graphites; Graphites speciaux

    Energy Technology Data Exchange (ETDEWEB)

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

    1964-07-01

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

  15. Impaction Force Influences Taper-Trunnion Stability in Total Hip Arthroplasty.

    Science.gov (United States)

    Danoff, Jonathan R; Longaray, Jason; Rajaravivarma, Raga; Gopalakrishnan, Ananthkrishnan; Chen, Antonia F; Hozack, William J

    2018-01-31

    This study investigated the influence of femoral head impaction force, number of head strikes, the energy sequence of head strikes, and head offset on the strength of the taper-trunnion junction. Thirty titanium-alloy trunnions were mated with 36-mm zero-offset cobalt-chromium femoral heads of corresponding taper angle. A drop tower impacted the head with 2.5J or 8.25J, resulting in 6 kN or 14 kN impaction force, respectively, in a single strike or combinations of 6 kN + 14 kN or 14 kN + 14 kN. In addition, ten 36-mm heads with -5 and +5 offset were impacted with sequential 14 kN + 14 kN strikes. Heads were subsequently disassembled using a screw-driven mechanical testing frame, and peak distraction force was recorded. Femoral head pull-off force was 45% the strike force, and heads struck with a single 14 kN impact showed a pull-off force twice that of the 6 kN group. Two head strikes with the same force did not improve pull-off force for either 6 kN (P = .90) or 14 kN (P = .90). If the forces of the 2 impactions varied, but either impact measured 14 kN, a 51% higher pull-off force was found compared to impactions of either 6 kN or 6 kN + 6 kN. Femoral head offset did not significantly change the pull-off force among -5, 0, and +5 heads (P = .37). Femoral head impaction force influenced femoral head trunnion-taper stability, whereas offset did not affect pull-off force. Multiple head strikes did not add additional stability, as long as a single strike achieved 14 kN force at the mallet-head impactor interface. Insufficient impaction force may lead to inadequate engagement of the trunnion-taper junction. Copyright © 2018 Elsevier Inc. All rights reserved.

  16. Special graphites

    International Nuclear Information System (INIS)

    Leveque, P.

    1964-01-01

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

  17. Stress index development for piping with trunnion attachment under pressure and moment loading

    International Nuclear Information System (INIS)

    Lee, D. H.; Kim, J. M.; Park, S. H.

    1997-01-01

    A finite element analysis of a trunnion pipe anchor is presented. The structure is analyzed for the case of internal pressure and moment loadings. The stress results are categorized into the average (membrane) stress, the linearly varying (bending) stress and the peak stress through the thickness. The resulting stresses are interpreted per section III of the ASME boiler and pressure vessel code from which the Primary (B 1 ), Secondary (C 1 ) and Peak (K 1 ) stress indices for pressure, the Primary (B 2 ), Secondary (C 2 ) and Peak (K 2 ) stress indices for moment are developed. Based on the comparison between stress value by stress indices derived in this paper and stress value represented by the ASME Code Case N-391-1, the empirical equations for stress indices are effectively used in the piping stress analysis. Therefore, the use of empirical equations can simplify the procedure of evaluating the local stress in the piping design stage. (author)

  18. Smart Surroundings

    NARCIS (Netherlands)

    Havinga, Paul J.M.; Jansen, P.G.; Lijding, M.E.M.; Scholten, Johan

    2004-01-01

    Ambient systems are networked embedded systems integrated with everyday environments and supporting people in their activities. These systems will create a Smart Surrounding for people to facilitate and enrich daily life and increase productivity at work. Such systems will be quite different from

  19. Artificial graphites

    International Nuclear Information System (INIS)

    Maire, J.

    1984-01-01

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

  20. Identification of β-SiC surrounded by relatable surrounding diamond ...

    Indian Academy of Sciences (India)

    β-SiC is identified in the presence of a relatable surrounding diamond medium using subtle, but discernible Raman ... Change in the nature of the surrounding material structure and its .... intensity implies very low graphite content in thin film. In.

  1. Graphite materials for nuclear reactors

    International Nuclear Information System (INIS)

    Oku, Tatsuo

    1991-01-01

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

  2. A graphite foam reinforced by graphite particles

    Energy Technology Data Exchange (ETDEWEB)

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

    2007-11-15

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

  3. Trunnion Failure of the Recalled Low Friction Ion Treatment Cobalt Chromium Alloy Femoral Head.

    Science.gov (United States)

    Urish, Kenneth L; Hamlin, Brian R; Plakseychuk, Anton Y; Levison, Timothy J; Higgs, Genymphas B; Kurtz, Steven M; DiGioia, Anthony M

    2017-09-01

    Gross trunnion failure (GTF) is a rare complication in total hip arthroplasty (THA) reported across a range of manufacturers. Specific lots of the Stryker low friction ion treatment (LFIT) anatomic cobalt chromium alloy (CoCr) V40 femoral head were recalled in August 2016. In part, the recall was based out of concerns for disassociation of the femoral head from the stem and GTF. We report on 28 patients (30 implants) with either GTF (n = 18) or head-neck taper corrosion (n = 12) of the LFIT CoCr femoral head and the Accolade titanium-molybdenum-zirconium-iron alloy femoral stems. All these cases were associated with adverse local tissue reactions requiring revision of the THA. In our series, a conservative estimate of the incidence of failure was 4.7% (n = 636 total implanted) at 8.0 ± 1.4 years from the index procedure. Failures were associated with a high-offset 127° femoral stem neck angle and increased neck lengths; 43.3% (13 of 30) of the observed failures included implant sizes outside the voluntary recall (27.8% [5 of 18] of the GTF and 75.0% [8 of 12] of the taper corrosion cases). Serum cobalt and chromium levels were elevated (cobalt: 8.4 ± 7.0 μg/mL; chromium: 3.4 ± 3.3 μ/L; cobalt/chromium ratio: 3.7). The metal artifact reduction sequence magnetic resonance imaging demonstrated large cystic fluid collections typical with adverse local tissue reactions. During revision, a pseudotumor was observed in all cases. Pathology suggested a chronic inflammatory response. Impending GTF could be diagnosed based on aspiration of black synovial fluid and an oblique femoral head as compared with the neck taper on radiographs. In our series of the recalled LFIT CoCr femoral head, the risk of impending GTF or head-neck taper corrosion should be considered as a potential diagnosis in a painful LFIT femoral head and Accolade titanium-molybdenum-zirconium-iron alloy THA with unknown etiology. Almost half of the failures we observed included sizes outside of the

  4. Thermally exfoliated graphite oxide

    Science.gov (United States)

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

    2011-01-01

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

  5. Graphite crystals grown within electromagnetically levitated metallic droplets

    International Nuclear Information System (INIS)

    Amini, Shaahin; Kalaantari, Haamun; Mojgani, Sasan; Abbaschian, Reza

    2012-01-01

    Various graphite morphologies were observed to grow within the electromagnetically levitated nickel–carbon melts, including primary flakes and spheres, curved surface graphite and eutectic flakes, as well as engulfed and entrapped particles. As the supersaturated metallic solutions were cooled within the electromagnetic (EM) levitation coil, the primary graphite flakes and spheres formed and accumulated near the periphery of the droplet due to EM circulation. The primary graphite islands, moreover, nucleated and grew on the droplet surface which eventually formed a macroscopic curved graphite crystal covering the entire liquid. Upon further cooling, the liquid surrounding the primary graphite went under a coupled eutectic reaction while the liquid in the center formed a divorced eutectic due to EM mixing. This brought about the formation of graphite fine flakes and agglomerated particles close to the surface and in the center of the droplet, respectively. The graphite morphologies, growth mechanisms, defects, irregularities and growth instabilities were interpreted with detailed optical and scanning electron microscopies.

  6. Bridged graphite oxide materials

    Science.gov (United States)

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

    2010-01-01

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

  7. Process for purifying graphite

    International Nuclear Information System (INIS)

    Clausius, R.A.

    1985-01-01

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

  8. Trunnion Corrosion and Early Failure in Monolithic Metal-on-Polyethylene TMZF Femoral Components: A Case Series

    Directory of Open Access Journals (Sweden)

    Peter Walker

    2016-09-01

    Full Text Available We describe four patients who were treated with primary total hip arthroplasty (THA at two tertiary academic Australian teaching hospitals that experienced premature failure of head-neck trunnions through dissociation of the head-neck taper junction. This retrospective case series have similar clinical presentations and macroscopic pathology with severe head-neck taper junction loss of material, corrosion and early catastrophic failure. It is proposed that the accelerated wear is related to use of varus offset neck in a proprietary beta titanium alloy (Ti-12Mo-6Zr-2Fe  or TMZFÒ Stryker Osteonics, Mahwah NJ, USA TMZF femoral stem, longer head-neck combination in a relatively active, older, male patient population. In this limited case series presentation was on average 80 months (range 53-92 following index procedure. In three of the four patients, a prodromal period of groin or buttock pain was reported for between 1 week and 2 months prior to acute presentation. Significant metallosis and local tissue damage including gluteal muscle insufficiency was evident. Each stem revised was well fixed. An extended trochanteric osteotomy was required in two of the four cases for stem extraction. We recommend caution and further evaluation on the relationship between TMZF metal alloy and its longevity in higher demand patients with high neck offset, varus stem geometry and large CoCr bearing heads.

  9. Phonon scattering in graphite

    International Nuclear Information System (INIS)

    Wagner, P.

    1976-04-01

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

  10. Monte Carlo calculation of standard graphite block

    International Nuclear Information System (INIS)

    Ljubenov, V.

    2000-01-01

    This paper presents results of calculation of neutron flux space and energy distribution in the standard graphite block (SGB) obtained by the MCNP TM code. VMCCS nuclear data library, based on the ENDF / B-VI release 4 evaluation file, is used. MCNP model of the SGB considers detailed material, geometric and spectral properties of the neutron source, source carrier, graphite moderator medium, aluminium foil holders and proximate surrounding of SGB Geometric model is organised to provide the simplest homogeneous volume cells in order to obtain the maximum acceleration of neutron history tracking (author)

  11. Actinides in irradiated graphite of RBMK-1500 reactor

    Energy Technology Data Exchange (ETDEWEB)

    Plukienė, R., E-mail: rita@ar.fi.lt; Plukis, A.; Barkauskas, V.; Gudelis, A.; Gvozdaitė, R.; Duškesas, G.; Remeikis, V.

    2014-10-01

    Highlights: • Activation of actinides in the graphite of the RBMK-1500 reactor was analyzed. • Numerical modeling using SCALE 6.1 and MCNPX was used for actinide calculation. • Measurements of the irradiated graphite sample were used for model validation. • Results are important for further decommissioning process of the RBMK type reactors. - Abstract: The activation of graphite in the nuclear power plants is the problem of high importance related with later graphite reprocessing or disposal. The activation of actinide impurities in graphite due to their toxicity determines a particular long term risk to waste management. In this work the activation of actinides in the graphite constructions of the RBMK-1500 reactor is determined by nuclear spectrometry measurements of the irradiated graphite sample from the Ignalina NPP Unit I and by means of numerical modeling using two independent codes SCALE 6.1 (using TRITON-VI sequence) and MCNPX (v2.7 with CINDER). Both models take into account the 3D RBMK-1500 reactor core fragment with explicit graphite construction including a stack and a sleeve but with a different simplification level concerning surrounding graphite and construction of control roads. The verification of the model has been performed by comparing calculated and measured isotope ratios of actinides. Also good prediction capabilities of the actinide activation in the irradiated graphite have been found for both calculation approaches. The initial U impurity concentration in the graphite model has been adjusted taking into account the experimental results. The specific activities of actinides in the irradiated RBMK-1500 graphite constructions have been obtained and differences between numerical simulation results, different structural parts (sleeve and stack) as well as comparison with previous results (Ancius et al., 2005) have been discussed. The obtained results are important for further decommissioning process of the Ignalina NPP and other RBMK

  12. A graphite nanoeraser

    DEFF Research Database (Denmark)

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

    2011-01-01

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

  13. Oxidation Resistant Graphite Studies

    Energy Technology Data Exchange (ETDEWEB)

    W. Windes; R. Smith

    2014-07-01

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

  14. Determination of thermal neutrons diffusion length in graphite

    International Nuclear Information System (INIS)

    Garcia Fite, J.

    1959-01-01

    The diffusion length of thermal neutrons in graphite using the less possible quantity of material has been determined. The proceeding used was the measurement in a graphite pile which has a punctual source of rapid neutrons inside surrounded by a reflector medium (paraffin or water). The measurement was done in the following conditions: a) introducing an aluminium plate between both materials. b) Introducing a cadmium plate between both materials. (Author) 91 refs

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

    Science.gov (United States)

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

    2012-05-08

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

  16. Graphite targets at LAMPF

    International Nuclear Information System (INIS)

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

    1983-01-01

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

  17. Electrochemical treatment of graphite

    Energy Technology Data Exchange (ETDEWEB)

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

    1983-01-01

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

  18. Electrochemical treatment of graphite

    International Nuclear Information System (INIS)

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

    1983-01-01

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

  19. Asymptomatic Intracorneal Graphite Deposits following Graphite Pencil Injury

    OpenAIRE

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

    2012-01-01

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

  20. Trunnion Rod Microcrack Detection

    Science.gov (United States)

    2013-08-01

    Richard W. Haskins, Joseph A. Padula , and John E. Hite BACKGROUND: Post-tensioned rods are used to anchor spillway gates and transfer the forces...email: James.A.Evans@usace.army.mil). This technical note should be cited as follows: Evans, J. A., Haskins, R. W., Padula , J. A., and Hite, J. E. 2013

  1. Recent developments in graphite

    International Nuclear Information System (INIS)

    Cunningham, J.E.

    1983-01-01

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

  2. Graphite for fusion energy applications

    International Nuclear Information System (INIS)

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

    1987-03-01

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

  3. Carbon-14 Graphitization Chemistry

    Science.gov (United States)

    Miller, James; Collon, Philippe; Laverne, Jay

    2014-09-01

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

  4. Melting temperature of graphite

    International Nuclear Information System (INIS)

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

    2001-01-01

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

  5. Nuclear graphite ageing and turnaround

    International Nuclear Information System (INIS)

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

    2001-01-01

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

  6. Recompressed exfoliated graphite articles

    Science.gov (United States)

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

    2013-08-06

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

  7. Tunable Graphitic Carbon Nano-Onions Development in Carbon Nanofibers for Multivalent Energy Storage

    Energy Technology Data Exchange (ETDEWEB)

    Schwarz, Haiqing L. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)

    2016-01-01

    We developed a novel porous graphitic carbon nanofiber material using a synthesis strategy combining electrospinning and catalytic graphitization. RF hydrogel was used as carbon precursors, transition metal ions were successfully introduced into the carbon matrix by binding to the carboxylate groups of a resorcinol derivative. Transition metal particles were homogeneously distributed throughout the carbon matrix, which are used as in-situ catalysts to produce graphitic fullerene-like nanostructures surrounding the metals. The success design of graphitic carbons with enlarged interlayer spacing will enable the multivalent ion intercalation for the development of multivalent rechargeable batteries.

  8. Bromine intercalated graphite for lightweight composite conductors

    KAUST Repository

    Amassian, Aram; Patole, Archana

    2017-01-01

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

  9. Cesium diffusion in graphite

    International Nuclear Information System (INIS)

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

    1980-05-01

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

  10. Irradiation Creep in Graphite

    Energy Technology Data Exchange (ETDEWEB)

    Ubic, Rick; Butt, Darryl; Windes, William

    2014-03-13

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

  11. Intercomparison of graphite irradiations

    Energy Technology Data Exchange (ETDEWEB)

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

    1959-07-01

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

  12. Graphite-based photovoltaic cells

    Science.gov (United States)

    Lagally, Max; Liu, Feng

    2010-12-28

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

  13. Electronic properties of graphite

    International Nuclear Information System (INIS)

    Schneider, J.

    2010-10-01

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

  14. Harwell Graphite Calorimeter

    International Nuclear Information System (INIS)

    Linacre, J.K.

    1970-01-01

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

  15. A standard graphite block

    Energy Technology Data Exchange (ETDEWEB)

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

    1966-04-15

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

  16. A standard graphite block

    International Nuclear Information System (INIS)

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

    1966-04-01

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

  17. Structural disorder of graphite and implications for graphite thermometry

    Science.gov (United States)

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

    2018-02-01

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

  18. Structural disorder of graphite and implications for graphite thermometry

    Directory of Open Access Journals (Sweden)

    M. Kirilova

    2018-02-01

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

  19. Bromine intercalated graphite for lightweight composite conductors

    KAUST Repository

    Amassian, Aram

    2017-07-20

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

  20. Chemical stabilization of graphite surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Bistrika, Alexander A.; Lerner, Michael M.

    2018-04-03

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

  1. Heat exchanger using graphite foam

    Science.gov (United States)

    Campagna, Michael Joseph; Callas, James John

    2012-09-25

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

  2. Purification and preparation of graphite oxide from natural graphite

    Energy Technology Data Exchange (ETDEWEB)

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

    2016-03-11

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

  3. Management of UKAEA graphite liabilities

    International Nuclear Information System (INIS)

    Wise, M.

    2001-01-01

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

  4. Graphite in Science and Nuclear Technique

    OpenAIRE

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

    2013-01-01

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

  5. Tables of formulae for calculating the mechanics of stacks in gas-graphite reactors

    International Nuclear Information System (INIS)

    1968-01-01

    This collection of formulae only gives, for nuclear graphite stacks. The mechanical effects due to the strains, thermal or not, of steel structures supporting or surrounding graphite blocks. Equations have been established by mean of experiments made at Chinon with large pile models. Thus, it is possible to calculate displacement, strain and stress in the EDF type stacks of horizontal triangular block lattice. (authors) [fr

  6. Modification of structural graphite machining

    International Nuclear Information System (INIS)

    Lavrenev, M.M.

    1979-01-01

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

  7. Glass-Graphite Composite Materials

    International Nuclear Information System (INIS)

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

    2016-01-01

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

  8. Graphite reactor physics; Physique des piles a graphite

    Energy Technology Data Exchange (ETDEWEB)

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

    1964-07-01

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

  9. Hypervelocity impacts into graphite

    Science.gov (United States)

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

    2011-03-01

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

  10. Hypervelocity impacts into graphite

    International Nuclear Information System (INIS)

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

    2011-01-01

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

  11. Acoustic emission from polycrystalline graphites

    International Nuclear Information System (INIS)

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

    1987-01-01

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

  12. Radiolytic graphite oxidation revisited

    International Nuclear Information System (INIS)

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

    1996-01-01

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

  13. Chemisputtering of interstellar graphite grains

    International Nuclear Information System (INIS)

    Draine, B.T.

    1979-01-01

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

  14. Obtention of nuclear grade graphite

    International Nuclear Information System (INIS)

    Ferreira, M.L.

    1984-01-01

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

  15. Characterization of Ignalina NPP RBMK Reactors Graphite

    International Nuclear Information System (INIS)

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

    2001-01-01

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

  16. Circumstances surrounding aneurysmal subarachnoid hemorrhage

    NARCIS (Netherlands)

    Schievink, W. I.; Karemaker, J. M.; Hageman, L. M.; van der Werf, D. J.

    1989-01-01

    The circumstances surrounding aneurysmal subarachnoid hemorrhage were investigated in a group of 500 consecutive patients admitted to a neurosurgical center. Subarachnoid hemorrhage occurred during stressful events in 42.8% of the patients, during nonstrenuous activities in 34.4%, and during rest or

  17. Graphite in Science and Nuclear Technology

    OpenAIRE

    Zhmurikov, Evgenij

    2015-01-01

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

  18. Mesostructure of graphite composite and its lifetime

    OpenAIRE

    Zhmurikov, Evgenij

    2015-01-01

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

  19. Graphite surveillance in N Reactor

    International Nuclear Information System (INIS)

    Woodruff, E.M.

    1991-09-01

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

  20. Graphite oxidation in HTGR atmosphere

    International Nuclear Information System (INIS)

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

    1982-01-01

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

  1. Graphite selection for the PBMR reflector

    International Nuclear Information System (INIS)

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

    2000-01-01

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

  2. Mechanical Degradation of Graphite/PVDF Composite Electrodes: A Model-Experimental Study

    Energy Technology Data Exchange (ETDEWEB)

    Takahashi, K; Higa, K; Mair, S; Chintapalli, M; Balsara, N; Srinivasan, V

    2015-12-11

    Mechanical failure modes of a graphite/polyvinylidene difluoride (PVDF) composite electrode for lithium-ion batteries were investigated by combining realistic stress-stain tests and mathematical model predictions. Samples of PVDF mixed with conductive additive were prepared in a similar way to graphite electrodes and tested while submerged in electrolyte solution. Young's modulus and tensile strength values of wet samples were found to be approximately one-fifth and one-half of those measured for dry samples. Simulations of graphite particles surrounded by binder layers given the measured material property values suggest that the particles are unlikely to experience mechanical damage during cycling, but that the fate of the surrounding composite of PVDF and conductive additive depends completely upon the conditions under which its mechanical properties were obtained. Simulations using realistic property values produced results that were consistent with earlier experimental observations.

  3. High temperature soldering of graphite

    International Nuclear Information System (INIS)

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

    1977-01-01

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

  4. Experience with graphite in JET

    International Nuclear Information System (INIS)

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

    1987-01-01

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

  5. Porous (Swiss-Cheese Graphite

    Directory of Open Access Journals (Sweden)

    Joseph P. Abrahamson

    2018-05-01

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

  6. Opportunity's Surroundings on Sol 1818

    Science.gov (United States)

    2009-01-01

    NASA's Mars Exploration Rover Opportunity used its navigation camera to take the images combined into this full-circle view of the rover's surroundings during the 1,818th Martian day, or sol, of Opportunity's surface mission (March 5, 2009). South is at the center; north at both ends. The rover had driven 80.3 meters (263 feet) southward earlier on that sol. Tracks from the drive recede northward in this view. The terrain in this portion of Mars' Meridiani Planum region includes dark-toned sand ripples and lighter-toned bedrock. This view is presented as a cylindrical projection with geometric seam correction.

  7. Estimation of Graphite Dust Production in ITER TBM

    International Nuclear Information System (INIS)

    Kang, Ji Ho; Kim, Eung Seon

    2013-01-01

    This scheme uses simple equations and the calculation time is much less than others. However, the contact equation requires a specially tuned material properties and instability of system matrix were reported. Second, only a couple of pebbles were modeled using FEM(Finite Element Method) and appropriate boundary and loading conditions are imposed. This scheme gives a detailed information of stress distribution of the pebbles and the stability of calculation is well established. However, the calculation cost is fairly high and only a few pebble can be analyzed in detail at a time with specifically assigned contact conditions. In this study, a prediction model of graphite dust production in ITER(International Thermonuclear Experimental Reactor) TBM(Test Blanket Module) using FEM was introduced and the amount of dust production for an operation cycle was estimated. In this study, graphite dust generation in the reflector zone of ITER TBM was estimated using FE analysis. A unit-cell model was defined to simulate normal contact forces and slip distances on contact points between the center pebble and the surrounding pebbles. The dust production was calculated using Archard equation. The simulation was repeated with different friction coefficient of graphite material to investigate the effect of friction on the dust production. The calculation result showed that the amount of dust production was 2.22∼3.67e-4 g/m 3 which was almost linearly proportional to the friction coefficient of graphite material. The amount of graphite dust production was considered too much small for a dust explosion

  8. Diffusion of graphite. The effect of cylindrical canals

    International Nuclear Information System (INIS)

    Carle, R.; Clouet d'Orval, C.; Martelly, J.; Mazancourt, T. de; Sagot, M.; Lattes, R.; Teste du Bailler, A.

    1957-01-01

    Experiments on thermal neutron diffusion in the graphite used as moderator in the pile G1 have been carried out. The object of these experiments is to determine: - the intrinsic quality of this graphite, characterised by its diffusion length L or its Laplacian 1/L 2 - the effect of the canals, which modifies anisotropically the macroscopic diffusion equation and is characterized by two principal diffusion regions (or two principal Laplacian), valid respectively for the diffusion in the direction of the canals and in a perpendicular direction. In order to determine them two experiments are necessary, in which the second derivatives of the flux in relation to the space coordinates are very different. These experiments form the object of the first two parts. Part 1: Diffusion along the axis of a flux coming from the pile source, and limited radially by a quasi cylindrical screen of cadmium bars. This screen, or Faraday cage is designed to give to the thermal flux produced the same radius of extrapolation to zero as that of the pile source. The determination of L (with the graphite full) has been made under the same conditions. The measurements have been interpreted in two ways. The influence of the brackets holding the detectors is discussed. Part 2: Radial diffusion in the graphite surrounding the 'long' cylindrical pile. This is well described by a sum of Bessel functions. Part 3: Results (valid for d = 1.61 t = 17 deg. C). For the graphite without cavity L = 52.7 ± 0.4 cm. The effect of the canals on the diffusion area and its anisotropy are in excellent agreement with the theory of Behrens: L(parallel) = 64.6 cm and L(perpendicular) 62.2 cm. Appendix: Theory of the Faraday cage. (author) [fr

  9. Thermal Pyrolytic Graphite Enhanced Components

    Science.gov (United States)

    Hardesty, Robert E. (Inventor)

    2015-01-01

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

  10. Determination of thermal neutrons diffusion length in graphite; Determinacion de la Longitud de Difusion de los Neutrones Termicos en Grafito

    Energy Technology Data Exchange (ETDEWEB)

    Garcia Fite, J

    1959-07-01

    The diffusion length of thermal neutrons in graphite using the less possible quantity of material has been determined. The proceeding used was the measurement in a graphite pile which has a punctual source of rapid neutrons inside surrounded by a reflector medium (paraffin or water). The measurement was done in the following conditions: a) introducing an aluminium plate between both materials. b) Introducing a cadmium plate between both materials. (Author) 91 refs.

  11. Friction anisotropy in boronated graphite

    International Nuclear Information System (INIS)

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

    2015-01-01

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

  12. Friction anisotropy in boronated graphite

    Energy Technology Data Exchange (ETDEWEB)

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

    2015-01-01

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

  13. Raman characterization of bulk ferromagnetic nanostructured graphite

    International Nuclear Information System (INIS)

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

    2012-01-01

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

  14. Fabrication of Graphene by Cleaving Graphite Chemically

    Institute of Scientific and Technical Information of China (English)

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

    2011-01-01

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

  15. Method of Joining Graphite Fibers to a Substrate

    Science.gov (United States)

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

    2014-01-01

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

  16. Opportunity's Surroundings on Sol 1687

    Science.gov (United States)

    2009-01-01

    NASA's Mars Exploration Rover Opportunity used its navigation camera to take the images combined into this 360-degree view of the rover's surroundings on the 1,687th Martian day, or sol, of its surface mission (Oct. 22, 2008). Opportunity had driven 133 meters (436 feet) that sol, crossing sand ripples up to about 10 centimeters (4 inches) tall. The tracks visible in the foreground are in the east-northeast direction. Opportunity's position on Sol 1687 was about 300 meters southwest of Victoria Crater. The rover was beginning a long trek toward a much larger crater, Endeavour, about 12 kilometers (7 miles) to the southeast. This view is presented as a cylindrical projection with geometric seam correction.

  17. Opportunity's Surroundings on Sol 1798

    Science.gov (United States)

    2009-01-01

    NASA's Mars Exploration Rover Opportunity used its navigation camera to take the images combined into this 180-degree view of the rover's surroundings during the 1,798th Martian day, or sol, of Opportunity's surface mission (Feb. 13, 2009). North is on top. The rover had driven 111 meters (364 feet) southward on the preceding sol. Tracks from that drive recede northward in this view. For scale, the distance between the parallel wheel tracks is about 1 meter (about 40 inches). The terrain in this portion of Mars' Meridiani Planum region includes dark-toned sand ripples and lighter-toned bedrock. This view is presented as a cylindrical projection with geometric seam correction.

  18. Photoemission study of K on graphite

    NARCIS (Netherlands)

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

    1999-01-01

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

  19. Separation medium containing thermally exfoliated graphite oxide

    Science.gov (United States)

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

    2012-01-01

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

  20. NMR studies on graphite-methanol system

    International Nuclear Information System (INIS)

    El-Akkad, T.M.

    1977-01-01

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

  1. Superconductivity in graphite intercalation compounds

    Energy Technology Data Exchange (ETDEWEB)

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

    2015-07-15

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

  2. Superconductivity in graphite intercalation compounds

    International Nuclear Information System (INIS)

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

    2015-01-01

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

  3. Graphite oral tattoo: case report.

    Science.gov (United States)

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

    2015-10-16

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

  4. 'In situ' expanded graphite extinguishant

    International Nuclear Information System (INIS)

    Cao Qixin; Shou Yuemei; He Bangrong

    1987-01-01

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

  5. Graphite nanoreinforcements in polymer nanocomposites

    Science.gov (United States)

    Fukushima, Hiroyuki

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

  6. Graphite suspension in carbon dioxide

    International Nuclear Information System (INIS)

    Roche, R.

    1965-01-01

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

  7. Characterisation of Chlorine Behavior in French Graphite

    International Nuclear Information System (INIS)

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

    2016-01-01

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

  8. Binaural Rendering in MPEG Surround

    Directory of Open Access Journals (Sweden)

    Kristofer Kjörling

    2008-04-01

    Full Text Available This paper describes novel methods for evoking a multichannel audio experience over stereo headphones. In contrast to the conventional convolution-based approach where, for example, five input channels are filtered using ten head-related transfer functions, the current approach is based on a parametric representation of the multichannel signal, along with either a parametric representation of the head-related transfer functions or a reduced set of head-related transfer functions. An audio scene with multiple virtual sound sources is represented by a mono or a stereo downmix signal of all sound source signals, accompanied by certain statistical (spatial properties. These statistical properties of the sound sources are either combined with statistical properties of head-related transfer functions to estimate “binaural parameters” that represent the perceptually relevant aspects of the auditory scene or used to create a limited set of combined head-related transfer functions that can be applied directly on the downmix signal. Subsequently, a binaural rendering stage reinstates the statistical properties of the sound sources by applying the estimated binaural parameters or the reduced set of combined head-related transfer functions directly on the downmix. If combined with parametric multichannel audio coders such as MPEG Surround, the proposed methods are advantageous over conventional methods in terms of perceived quality and computational complexity.

  9. AGC-2 Graphite Preirradiation Data Package

    Energy Technology Data Exchange (ETDEWEB)

    David Swank; Joseph Lord; David Rohrbaugh; William Windes

    2012-10-01

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

  10. Progress in radioactive graphite waste management

    International Nuclear Information System (INIS)

    2010-07-01

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

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

    Science.gov (United States)

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

    2017-09-11

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

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

    Czech Academy of Sciences Publication Activity Database

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

    2017-01-01

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

  13. Diffusion of graphite. The effect of cylindrical canals; Longueur de diffusion du graphite effet des canaux cylindriques

    Energy Technology Data Exchange (ETDEWEB)

    Carle, R; Clouet d' Orval, C; Martelly, J; Mazancourt, T de; Sagot, M; Lattes, R; Teste du Bailler, A [Commissariat a l' Energie Atomique, Dir. Industrielle, Saclay (France). Centre d' Etudes Nucleaires; Robert, C [Ecole Normale Superieure, 75 - Paris (France)

    1957-07-01

    Experiments on thermal neutron diffusion in the graphite used as moderator in the pile G1 have been carried out. The object of these experiments is to determine: - the intrinsic quality of this graphite, characterised by its diffusion length L or its Laplacian 1/L{sup 2} - the effect of the canals, which modifies anisotropically the macroscopic diffusion equation and is characterized by two principal diffusion regions (or two principal Laplacian), valid respectively for the diffusion in the direction of the canals and in a perpendicular direction. In order to determine them two experiments are necessary, in which the second derivatives of the flux in relation to the space coordinates are very different. These experiments form the object of the first two parts. Part 1: Diffusion along the axis of a flux coming from the pile source, and limited radially by a quasi cylindrical screen of cadmium bars. This screen, or Faraday cage is designed to give to the thermal flux produced the same radius of extrapolation to zero as that of the pile source. The determination of L (with the graphite full) has been made under the same conditions. The measurements have been interpreted in two ways. The influence of the brackets holding the detectors is discussed. Part 2: Radial diffusion in the graphite surrounding the 'long' cylindrical pile. This is well described by a sum of Bessel functions. Part 3: Results (valid for d = 1.61 t = 17 deg. C). For the graphite without cavity L = 52.7 {+-} 0.4 cm. The effect of the canals on the diffusion area and its anisotropy are in excellent agreement with the theory of Behrens: L(parallel) = 64.6 cm and L(perpendicular) 62.2 cm. Appendix: Theory of the Faraday cage. (author) [French] Des experiences de diffusion des neutrons thermiques dans le graphite constituant le moderateur de la pile G1 ont ete effectuees. Elles ont pour objet de determiner: - la qualite intrinseque de ce graphite, caracterisee par sa longueur de diffusion L ou son

  14. Graphite moderated 252Cf source

    International Nuclear Information System (INIS)

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

    2014-08-01

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

  15. Fission Product Sorptivity in Graphite

    Energy Technology Data Exchange (ETDEWEB)

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

    2015-04-01

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

  16. Graphite for high-temperature reactors

    International Nuclear Information System (INIS)

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

    1976-01-01

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

  17. AGC-3 Graphite Preirradiation Data Analysis Report

    Energy Technology Data Exchange (ETDEWEB)

    William Windes; David Swank; David Rohrbaugh; Joseph Lord

    2013-09-01

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

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

    Science.gov (United States)

    Zhamu, Aruna; Jang, Bor Z.

    2014-06-17

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

  19. Electrochemical Ultracapacitors Using Graphitic Nanostacks

    Science.gov (United States)

    Marotta, Christopher

    2012-01-01

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

  20. Pyrolytic graphite gauge for measuring heat flux

    Science.gov (United States)

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

    2002-01-01

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

  1. Attenuation of thermal neutron through graphite

    International Nuclear Information System (INIS)

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

    2004-01-01

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

  2. Uranium Oxide Aerosol Transport in Porous Graphite

    Energy Technology Data Exchange (ETDEWEB)

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

    2012-01-23

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

  3. Charge storage in mesoscopic graphitic islands fabricated using AFM bias lithography

    Energy Technology Data Exchange (ETDEWEB)

    Kurra, Narendra; Basavaraja, S; Kulkarni, G U [Chemistry and Physics of Materials Unit and DST Unit on Nanoscience, Jawaharlal Nehru Centre for Advanced Scientific Research, Jakkur PO, Bangalore 560 064 (India); Prakash, Gyan; Fisher, Timothy S; Reifenberger, Ronald G, E-mail: kulkarni@jncasr.ac.in, E-mail: reifenbr@purdue.edu [Birck Nanotechnology Center, Purdue University, West Lafayette, IN 47907 (United States)

    2011-06-17

    Electrochemical oxidation and etching of highly oriented pyrolytic graphite (HOPG) has been achieved using biased atomic force microscopy (AFM) lithography, allowing patterns of varying complexity to be written into the top layers of HOPG. The graphitic oxidation process and the trench geometry after writing were monitored using intermittent contact mode AFM. Electrostatic force microscopy reveals that the isolated mesoscopic islands formed during the AFM lithography process become positively charged, suggesting that they are laterally isolated from the surrounding HOPG substrate. The electrical transport studies of these laterally isolated finite-layer graphitic islands enable detailed characterization of electrical conduction along the c-direction and reveal an unexpected stability of the charged state. Utilizing conducting-atomic force microscopy, the measured I(V) characteristics revealed significant non-linearities. Micro-Raman studies confirm the presence of oxy functional groups formed during the lithography process.

  4. Dynamics of graphite flake on a liquid

    Science.gov (United States)

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

    2006-11-01

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

  5. Sealing nuclear graphite with pyrolytic carbon

    International Nuclear Information System (INIS)

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

    2013-01-01

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

  6. Nanostructured carbon films with oriented graphitic planes

    International Nuclear Information System (INIS)

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

    2011-01-01

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

  7. Production of nuclear graphite in France

    International Nuclear Information System (INIS)

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

    1955-01-01

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

  8. AC induction field heating of graphite foam

    Science.gov (United States)

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

    2017-08-22

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

  9. Nuclear graphite for high temperature reactors

    International Nuclear Information System (INIS)

    Marsden, B.J.

    2001-01-01

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

  10. Structural analysis of polycrystalline (graphitized) materials

    International Nuclear Information System (INIS)

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

    1993-01-01

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

  11. Principle design and data of graphite components

    International Nuclear Information System (INIS)

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

    2004-01-01

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

  12. Low temperature vapor phase digestion of graphite

    Energy Technology Data Exchange (ETDEWEB)

    Pierce, Robert A.

    2017-04-18

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

  13. The Fracture Toughness of Nuclear Graphites Grades

    Energy Technology Data Exchange (ETDEWEB)

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

    2017-04-01

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

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

    NARCIS (Netherlands)

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

    1969-01-01

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

  15. Hydrogen storage in graphitic nanofibres

    OpenAIRE

    McCaldin, Simon Roger

    2007-01-01

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

  16. Mixed graphite cast iron for automotive exhaust component applications

    OpenAIRE

    De-lin Li

    2017-01-01

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

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

    International Nuclear Information System (INIS)

    2001-05-01

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

  18. Development and testing of nuclear graphite for the German pebble-bed high temperature reactor

    International Nuclear Information System (INIS)

    Haag, G.; Delle, W.; Nickel, H.; Theymann, W.; Wilhelmi, G.

    1987-01-01

    Several types of high temperature reactors have been developed in the Federal Republic of Germany. They are all based on spherical fuel elements being surrounded by graphite as reflector material. As an example, HTR-500 developed by the Hochtemperatur Reaktorbau GmbH is shown. The core consists of the top reflector, the side reflector with inner and outer parts, the bottom reflector and the core support columns. The most serious problem with respect to fast neutron radiation damage had to be solved for the materials of those parts near the pebble bed. Regarding the temperature profile in the core, the top reflector is at 300 deg C, and as cooling gas flows from the top downward, the temperature of the inner side reflector rises to about 700 deg C at the bottom. Fortunately, the highest fast neutron load accumulated during the life time of a reactor corresponds to the lowest temperature. This makes graphite components easier to survive neutron exposure without being mechanically damaged, although the maximum fast neutron fluence is as high as 4 x 10 22 /cm 2 at about 400 deg C. HTR graphite components are divided into four classes according to loading. The raw materials for nuclear graphite, the development of pitch coke nuclear graphite, the irradiation behavior of ATR-2E and ASR-IRS and others are reported. (Kako, I.)

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

    OpenAIRE

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

    2015-01-01

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

  20. Mixed graphite cast iron for automotive exhaust component applications

    Directory of Open Access Journals (Sweden)

    De-lin Li

    2017-11-01

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

  1. Methodology of characterization of radioactive graphite

    International Nuclear Information System (INIS)

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

    2014-01-01

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

  2. Significance of primary irradiation creep in graphite

    CSIR Research Space (South Africa)

    Erasmus, C

    2013-05-01

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

  3. Inhibition of oxidation in nuclear graphite

    International Nuclear Information System (INIS)

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

    2015-01-01

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

  4. Metal/graphite - composites in fusion engineering

    International Nuclear Information System (INIS)

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

    1989-01-01

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

  5. Metal/graphite - composites in fusion engineering

    International Nuclear Information System (INIS)

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

    1995-01-01

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

  6. Tire containing thermally exfoliated graphite oxide

    Science.gov (United States)

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

    2011-01-01

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

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

    Science.gov (United States)

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

    2018-05-01

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

  8. Hydrogen storage in graphite nanofibers

    Energy Technology Data Exchange (ETDEWEB)

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

    1998-08-01

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

  9. Methane generated from graphite--tritium interaction

    International Nuclear Information System (INIS)

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

    1979-01-01

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

  10. Chemical sputtering of graphite by H+ ions

    International Nuclear Information System (INIS)

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

    1976-01-01

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

  11. Graphite selection for the FMIT test cell

    International Nuclear Information System (INIS)

    Morgan, W.C.

    1982-06-01

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

  12. AGC-2 Graphite Preirradiation Data Analysis Report

    Energy Technology Data Exchange (ETDEWEB)

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

    2013-08-01

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

  13. Modeling Fission Product Sorption in Graphite Structures

    International Nuclear Information System (INIS)

    Szlufarska, Izabela; Morgan, Dane; Allen, Todd

    2013-01-01

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

  14. Utilizing the slowing-down-time technique for benchmarking neutron thermalization in graphite

    International Nuclear Information System (INIS)

    Zhou, T.; Hawari, A. I.; Wehring, B. W.

    2007-01-01

    Graphite is the moderator/reflector in the Very High Temperature Reactor (VHTR) concept of Generation IV reactors. As a thermal reactor, the prediction of the thermal neutron spectrum in the VHTR is directly dependent on the accuracy of the thermal neutron scattering libraries of graphite. In recent years, work has been on-going to benchmark and validate neutron thermalization in 'reactor grade' graphite. Monte Carlo simulations using the MCNP5 code were used to design a pulsed neutron slowing-down-time experiment and to investigate neutron slowing down and thermalization in graphite at temperatures relevant to VHTR operation. The unique aspect of this experiment is its ability to observe the behavior of neutrons throughout an energy range extending from the source energy to energies below 0.1 eV. In its current form, the experiment is designed and implemented at the Oak Ridge Electron Linear Accelerator (ORELA). Consequently, ORELA neutron pulses are injected into a 70 cm x 70 cm x 70 cm graphite pile. A furnace system that surrounds the pile and is capable of heating the graphite to a centerline temperature of 1200 K has been designed and built. A system based on U-235 fission chambers and Li-6 scintillation detectors surrounds the pile. This system is coupled to multichannel scaling instrumentation and is designed for the detection of leakage neutrons as a function of the slowing-down-time (i.e., time after the pulse). To ensure the accuracy of the experiment, careful assessment was performed of the impact of background noise (due to room return neutrons) and pulse-to-pulse overlap on the measurement. Therefore, the entire setup is surrounded by borated polyethylene shields and the experiment is performed using a source pulse frequency of nearly 130 Hz. As the basis for the benchmark, the calculated time dependent reaction rates in the detectors (using the MCNP code and its associated ENDF-B/VI thermal neutron scattering libraries) are compared to measured

  15. Graphite Oxidation Thermodynamics/Reactions

    International Nuclear Information System (INIS)

    Propp, W.A.

    1998-01-01

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

  16. Religion's relationship with social boundaries surrounding gender ...

    African Journals Online (AJOL)

    Religion's relationship with social boundaries surrounding gender. ... is associated with segregation, marginalization and differentiation between men and women. ... are necessary in the society it should not be mistaken for gender inequality.

  17. Low cost sic coated erosion resistant graphite

    International Nuclear Information System (INIS)

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

    2007-01-01

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

  18. Channel uranium-graphite reactor mounting

    International Nuclear Information System (INIS)

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

    1981-01-01

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

  19. Synthesis of soluble graphite and graphene.

    Science.gov (United States)

    Kelly, K F; Billups, W E

    2013-01-15

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

  20. Adsorption of lead over graphite oxide.

    Science.gov (United States)

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

    2014-01-24

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

  1. Interface structure between tetraglyme and graphite

    Science.gov (United States)

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

    2017-09-01

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

  2. Status of Chronic Oxidation Studies of Graphite

    Energy Technology Data Exchange (ETDEWEB)

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

    2016-05-01

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

  3. Tables of formulae for calculating the mechanics of stacks in gas-graphite reactors; Formulaire pour le calcul de la mecanique des empilements des reacteurs graphite-gaz

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1968-07-01

    This collection of formulae only gives, for nuclear graphite stacks. The mechanical effects due to the strains, thermal or not, of steel structures supporting or surrounding graphite blocks. Equations have been established by mean of experiments made at Chinon with large pile models. Thus, it is possible to calculate displacement, strain and stress in the EDF type stacks of horizontal triangular block lattice. (authors) [French] Le domaine de ce formulaire est strictement limite aux effets mecaniques, pour les empilements, des deformations, thermiques ou autres, des structures metalliques de soutien (aire - support et corset). On propose un ensemble de relations qui ont ete etablies a la suite des essais de CHINON sur des maquettes de grande taille. Ces relations permettent le calcul des mouvements, des deformations et des contraintes dans les empilements du type EDF, a reseau horizontal triangulaire regulier. (auteurs)

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2013-08-14

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

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2008-03-01

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

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

    International Nuclear Information System (INIS)

    Anfimov, S.S.

    2001-01-01

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

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

    International Nuclear Information System (INIS)

    Gesh, Christopher J.

    2004-01-01

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

  8. Synthesis of graphene nanoplatelets from peroxosulfate graphite intercalation compounds

    OpenAIRE

    MELEZHYK A.V.; TKACHEV A.G.

    2014-01-01

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

  9. Seismic research on graphite reactor core

    International Nuclear Information System (INIS)

    Lai Shigang; Sun Libin; Zhang Zhengming

    2013-01-01

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

  10. Review: BNL Tokamak graphite blanket design concepts

    International Nuclear Information System (INIS)

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

    1976-01-01

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

  11. Immobilization of Rocky Flats Graphite Fines Residue

    International Nuclear Information System (INIS)

    Rudisill, T.S.

    1999-01-01

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

  12. Optical motion control of maglev graphite.

    Science.gov (United States)

    Kobayashi, Masayuki; Abe, Jiro

    2012-12-26

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

  13. Study on graphite samples for nuclear usage

    International Nuclear Information System (INIS)

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

    1994-01-01

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

  14. Collective modes in superconducting rhombohedral graphite

    Energy Technology Data Exchange (ETDEWEB)

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

    2015-07-01

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

  15. Large Scale Reduction of Graphite Oxide

    Data.gov (United States)

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

  16. Analysis of picosecond pulsed laser melted graphite

    International Nuclear Information System (INIS)

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

    1986-01-01

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

  17. Enhancement of Afterimage Colors by Surrounding Contours

    Directory of Open Access Journals (Sweden)

    Takao Sato

    2011-05-01

    Full Text Available Presenting luminance contours surrounding the adapted areas in test phase enhances color afterimages in both duration and color appearance. The presence of surrounding contour is crucial to some color phenomenon such as van Lier's afterimage, but the contour-effect itself has not been seriously examined. In this paper, we compared the contour-effect to color afterimages and to actually colored patches to examine the nature of color information subserving color-aftereffect. In the experiment, observers were adapted for 1 sec to a small colored square (red, green, yellow, or blue presented on a gray background. Then, a test field either with or without surrounding contour was presented. Observers matched the color of a test-patch located near the afterimage to the color of afterimage. It was found that the saturation of negative afterimage was almost doubled by the presence of surrounding contours. There was no effect of luminance contrast or polarity of contours. In contrast, no enhancement of saturation by surrounding contours was observed for actually colored patches even though the colors of patches were equalized to that of afterimage without contours. This dissociation in the contour-effect demonstrates the crucial difference between the color information for aftereffects and for ordinary bottom-up color perception.

  18. Vapour pressure of caesium over nuclear graphite

    International Nuclear Information System (INIS)

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

    1976-01-01

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

  19. Elastic properties of graphite and interstitial defects

    International Nuclear Information System (INIS)

    Ayasse, J.-B.

    1977-01-01

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

  20. Energy evaluations, graphite corrosion in Bugey I

    International Nuclear Information System (INIS)

    Brisbois, J.; Fiche, C.

    1967-01-01

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

  1. High temperature tests for graphite materials

    OpenAIRE

    Zhmurikov, Evgenij

    2015-01-01

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

  2. Graphite Composite Panel Polishing Fixture

    Science.gov (United States)

    Hagopian, John; Strojny, Carl; Budinoff, Jason

    2011-01-01

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

  3. Structure and functionality of bromine doped graphite.

    Science.gov (United States)

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

    2013-04-28

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

  4. Explaining preferences for home surroundings and locations

    DEFF Research Database (Denmark)

    Andersen, Hans Skifter

    2011-01-01

    This article is based on a survey carried out in Denmark that asked a random sample of the population about their preferences for home surroundings and locations. It shows that the characteristics of social surroundings are very important and can be divided into three independent dimensions......: avoiding social nuisances, preferring social homogeneity and living close to one’s social network and place of origin. The study shows that most people have many detailed preferences, whereas some have very few. This confirms an earlier theory that some people are very connected to certain places...... with given characteristics and thus do not have priorities regarding home surroundings and locations. For others, mostly young people and singles, home is just a place to sleep and relax, whereas life is lived elsewhere. For this group, there are only preferences for location and there are few specific...

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

    Energy Technology Data Exchange (ETDEWEB)

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

    1955-07-01

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

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

    International Nuclear Information System (INIS)

    Oliveira Avila, C.R. de.

    1989-01-01

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

  7. Smart Chips for Smart Surroundings -- 4S

    NARCIS (Netherlands)

    Schuler, Eberhard; König, Ralf; Becker, Jürgen; Rauwerda, G.K.; van de Burgwal, M.D.; Smit, Gerardus Johannes Maria; Cardoso, João M.P.; Hübner, Michael

    2011-01-01

    The overall mission of the 4S project (Smart Chips for Smart Surroundings) was to define and develop efficient flexible, reconfigurable core building blocks, including the supporting tools, for future Ambient System Devices. Reconfigurability offers the needed flexibility and adaptability, it

  8. Childhood Suicide and Myths Surrounding It.

    Science.gov (United States)

    Greene, Dorothea B.

    1994-01-01

    Dispels five misconceptions surrounding the suicide of children: that children under the age of six do not commit suicide; that suicide in latency years is extremely rare; that psychodynamically and developmentally true depression is not possible in childhood; that child cannot understand finality of death; and that children are cognitively and…

  9. Graphitic encapsulation of MgO and Fe3C nanoparticles in the reaction of iron pentacarbonyl with magnesium

    International Nuclear Information System (INIS)

    Dyjak, Sławomir; Cudziło, Stanisław; Polański, Marek; Budner, Bogusław; Bystrzycki, Jerzy

    2013-01-01

    A simple method to produce highly ordered carbon nanostructures by combustion synthesis is presented. Graphite-encapsulated magnesium oxide, iron carbide nanoparticles and carbon nanobelts were synthesized by the one-step reduction of iron pentacarbonyl with magnesium. High-resolution transmission electron microscopy analysis of the products revealed nanocrystalline MgO and Fe 3 C particles surrounded by a well-crystallized, tight graphite film. The possible formation mechanism is presented and discussed. - Highlights: • We present a simple method to produce highly ordered carbon nanostructures by combustion synthesis. • The cubic MgO particles are completely coated by tight graphitic shells. • The mechanism of formation a distant carbon film on MgO surface has been discussed. • The presented method can be applied to synthesis of other core-shell structures

  10. Graphite matrix materials for nuclear waste isolation

    International Nuclear Information System (INIS)

    Morgan, W.C.

    1981-06-01

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

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

    Science.gov (United States)

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

    2010-11-02

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

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

    International Nuclear Information System (INIS)

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

    2006-01-01

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

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

    International Nuclear Information System (INIS)

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

    2014-01-01

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

  14. Gas transport in graphitic materials

    International Nuclear Information System (INIS)

    Hoinkis, E.

    1995-02-01

    The characterization of the gas transport properties of porous solids is of interest in several fields of science and technology. Many catalysts, adsorbents, soils, graphites and carbons are porous. The gas transport through most porous solids can be well described by the dusty gas model invented by Evans, Watson and Mason. This model includes all modes of gas tranport under steady-state conditions, which are Knudsen diffusion, combined Knudsen/continuum diffusion and continuum diffusion, both for gas pairs with equal and different molecular weights. In the absence of a pressure difference gas transport in a pore system can be described by the combined Knudsen/continuum diffusion coefficient D 1 for component 1 in the pores, the Knudsen diffusion coefficient D 1K in the pores, and the continuum diffusion coefficient D 12 for a binary mixture in the pores. The resistance to stationary continuum diffusion of the pores is characterized by a geometrical factor (ε/τ) 12 = (ε/τ)D 12 , were D 12 is the continuum diffusion coefficient for a binary mixture in free space. The Wicke-Kallenbach method was often used to measure D 1 as function of pressure. D 12 and D 1K can be derived from a plot 1/D 1 νs P, and ε/τcan be calculated since D 12 is known. D 1K and the volume of dead end pores can be derived from transient measurements of the diffusional flux at low pressures. From D 1K the expression (ε/τ c ) anti l por may be calculated, which characterizes the pore system for molecular diffusion, where collisions with the pore walls are predominant. (orig.)

  15. Influence of Metal-Coated Graphite Powders on Microstructure and Properties of the Bronze-Matrix/Graphite Composites

    Science.gov (United States)

    Zhao, Jian-hua; Li, Pu; Tang, Qi; Zhang, Yan-qing; He, Jian-sheng; He, Ke

    2017-02-01

    In this study, the bronze-matrix/x-graphite (x = 0, 1, 3 and 5%) composites were fabricated by powder metallurgy route by using Cu-coated graphite, Ni-coated graphite and pure graphite, respectively. The microstructure, mechanical properties and corrosive behaviors of bronze/Cu-coated-graphite (BCG), bronze/Ni-coated-graphite (BNG) and bronze/pure-graphite (BPG) were characterized and investigated. Results show that the Cu-coated and Ni-coated graphite could definitely increase the bonding quality between the bronze matrix and graphite. In general, with the increase in graphite content in bronze-matrix/graphite composites, the friction coefficients, ultimate density and wear rates of BPG, BCG and BNG composites all went down. However, the Vickers microhardness of the BNG composite would increase as the graphite content increased, which was contrary to the BPG and BCG composites. When the graphite content was 3%, the friction coefficient of BNG composite was more stable than that of BCG and BPG composites, indicating that BNG composite had a better tribological performance than the others. Under all the values of applied loads (10, 20, 40 and 60N), the BCG and BNG composites exhibited a lower wear rate than BPG composite. What is more, the existence of nickel in graphite powders could effectively improve the corrosion resistance of the BNG composite.

  16. Glassy carbon coated graphite for nuclear applications

    International Nuclear Information System (INIS)

    Delpeux S; Cacciaguerra T; Duclaux L

    2005-01-01

    Taking into account the problems caused by the treatment of nuclear wastes, the molten salts breeder reactors are expected to a great development. They use a molten fluorinated salt (mixture of LiF, BeF 2 , ThF 4 , and UF 4 ) as fuel and coolant. The reactor core, made of graphite, is used as a neutrons moderator. Despite of its compatibility with nuclear environment, it appears crucial to improve the stability and inertness of graphite against the diffusion of chemicals species leading to its corrosion. One way is to cover the graphite surface by a protective impermeable deposit made of glassy carbon obtained by the pyrolysis of phenolic resin or polyvinyl chloride precursors. The main difficulty in the synthesis of glassy carbon is to create exclusively, in the primary pyrolysis product, a micro-porosity of about twenty Angstroms which closes later at higher temperature. Therefore, the evacuation of the volatile products occurring mainly between 330 and 600 C, must progress slowly to avoid the material to crack. In this study, the optimal parameters for the synthesis of glassy carbon as well as glassy carbon deposits on nuclear-type graphite pieces are discussed. Both thermal treatment of phenolic and PVC resins have been performed. The structure and micro-texture of glassy carbon have been investigated by X-ray diffraction, scanning and transmission electron microscopies and helium pycno-metry. Glassy carbon samples (obtained at 1200 C) show densities ranging from 1.3 to 1.55 g/cm 3 and closed pores with nano-metric size (∼ 5 to 10 nm) appear clearly on the TEM micrographs. Then, a thermal treatment to 2700 C leads to the shrinkage of the entangled graphene ribbons, in good agreement with the proposed texture model for glassy carbon. Glassy carbon deposits on nuclear graphite have been developed by an impregnation method. The uniformity of the deposit depends clearly on the surface texture and the chemistry of the graphite substrate. The deposit regions where

  17. Glassy carbon coated graphite for nuclear applications

    Energy Technology Data Exchange (ETDEWEB)

    Delpeux, S.; Cacciaguerra, T.; Duclaux, L. [Orleans Univ., CRMD, CNRS, 45 (France)

    2005-07-01

    Taking into account the problems caused by the treatment of nuclear wastes, the molten salts breeder reactors are expected to a great development. They use a molten fluorinated salt (mixture of LiF, BeF{sub 2}, ThF{sub 4}, and UF{sub 4}) as fuel and coolant. The reactor core, made of graphite, is used as a neutrons moderator. Despite of its compatibility with nuclear environment, it appears crucial to improve the stability and inertness of graphite against the diffusion of chemicals species leading to its corrosion. One way is to cover the graphite surface by a protective impermeable deposit made of glassy carbon obtained by the pyrolysis of phenolic resin [1,2] or polyvinyl chloride [3] precursors. The main difficulty in the synthesis of glassy carbon is to create exclusively, in the primary pyrolysis product, a micro-porosity of about twenty Angstroms which closes later at higher temperature. Therefore, the evacuation of the volatile products occurring mainly between 330 and 600 C, must progress slowly to avoid the material to crack. In this study, the optimal parameters for the synthesis of glassy carbon as well as glassy carbon deposits on nuclear-type graphite pieces are discussed. Both thermal treatment of phenolic and PVC resins have been performed. The structure and micro-texture of glassy carbon have been investigated by X-ray diffraction, scanning and transmission electron microscopies and helium pycno-metry. Glassy carbon samples (obtained at 1200 C) show densities ranging from 1.3 to 1.55 g/cm{sup 3} and closed pores with nano-metric size ({approx} 5 to 10 nm) appear clearly on the TEM micrographs. Then, a thermal treatment to 2700 C leads to the shrinkage of the entangled graphene ribbons (Fig 1), in good agreement with the proposed texture model for glassy carbon (Fig 2) [4]. Glassy carbon deposits on nuclear graphite have been developed by an impregnation method. The uniformity of the deposit depends clearly on the surface texture and the chemistry

  18. Safety implications of a graphite oxidation accident in the compact ignition tokamak device

    International Nuclear Information System (INIS)

    Merrill, B.J.; O'Brien, M.H.

    1989-01-01

    This paper addresses the possible safety consequences of an air ingress accident for the Compact Ignition Tokamak (CIT) device. An experimental program was undertaken to determine oxidation rates of four nuclear grade graphites in air at temperatures ranging from 800 to 1800 C and flow velocities from 3 to 7 m/s. On the basis of these test results, an analytic model was developed to assess the extent of first wall/divertor protective tile oxidation and the amount of energy released from this oxidation. For CIT, a significant restriction to vacuum vessel air inflow will be provided by the air seals and walls of the surrounding test cells. Under these conditions, the graphite oxidation reaction inside the vacuum vessel will become oxygen starved within minutes of the onset of this event. Since significant oxidation rates were not achieved, the heat release did not elevate structural temperatures to levels of concern with regard to activated material release. 7 refs., 9 figs

  19. Studies of physicochemical properties of graphite oxide and thermally exfoliated/reduced graphene oxide

    Directory of Open Access Journals (Sweden)

    Drewniak Sabina Elżbieta

    2015-12-01

    Full Text Available The aim of the experimental research studies was to determine some electrical properties of graphite oxide and thermally exfoliated/reduced graphene oxide. The authors tried to interpret the obtained physicochemical results. For that purpose, both resistance measurements and investigation studies were carried out in order to characterize the samples. The resistance was measured at various temperatures in the course of composition changes of gas atmospheres (which surround the samples. The studies were also supported by such methods as: scanning electron microscopy (SEM, Raman spectroscopy (RS, atomic force microscopy (AFM and thermogravimetry (TG. Moreover, during the experiments also the elemental analyses (EA of the tested samples (graphite oxide and thermally exfoliated/reduced graphene oxide were performed.

  20. Hydrogen adsorption on and solubility in graphites

    International Nuclear Information System (INIS)

    Kanashenko, S.L.; Wampler, W.R.

    1996-01-01

    The experimental data on adsorption and solubility of hydrogen isotopes in graphite over a wide range of temperatures and pressures are reviewed. Langmuir adsorption isotherms are proposed for the hydrogen-graphite interaction. The entropy and enthalpy of adsorption are estimated, allowing for effects of relaxation of dangling sp 2 bonds. Three kinds of traps are proposed: edge carbon atoms of interstitial loops with an adsorption enthalpy relative to H 2 gas of -4.4 eV/H 2 (unrelaxed, Trap 1), edge carbon atoms at grain surfaces with an adsorption enthalpy of -2.3 eV/H 2 (relaxed, Trap 2), and basal plane adsorption sites with an enthalpy of +2.43 eV/H 2 (Trap 3). The adsorption capacity of different types of graphite depends on the concentration of traps which depends on the crystalline microstructure of the material. The number of potential sites for the 'true solubility' (Trap 3) is assumed to be about one site per carbon atom in all types of graphite, but the endothermic character of this solubility leads to a negligible H inventory compared to the concentration of hydrogen in type 1 and type 2 traps for temperatures and gas pressures used in the experiments. Irradiation with neutrons or carbon atoms increases the concentration of type 1 and type 2 traps from about 20 and 200 appm respectively for unirradiated (POCO AXF-5Q) graphite to about 1500 and 5000 appm, respectively, at damage levels above 1 dpa. (orig.)

  1. Irradiation-induced amorphization process in graphite

    Energy Technology Data Exchange (ETDEWEB)

    Abe, Hiroaki [Japan Atomic Energy Research Inst., Takasaki, Gunma (Japan). Takasaki Radiation Chemistry Research Establishment

    1996-04-01

    Effects of the element process of irradiation damage on irradiation-induced amorphization processes of graphite was studied. High orientation thermal decomposed graphite was cut about 100 nm width and used as samples. The irradiation experiments are carried out under the conditions of electronic energy of 100-400 KeV, ion energy of 200-600 KeV, ionic species Xe, Ar, Ne, C and He and the irradiation temperature at from room temperature to 900 K. The critical dose ({phi}a) increases exponentially with increasing irradiation temperature. The displacement threshold energy of graphite on c-axis direction was 27 eV and {phi}a{sup e} = 0.5 dpa. dpa is the average number of displacement to atom. The critical dose of ion irradiation ({phi}a{sup i}) was 0.2 dpa at room temperature, and amorphous graphite was produced by less than half of dose of electronic irradiation. Amorphization of graphite depending upon temperature is discussed. (S.Y.)

  2. Graphite Carbon-Supported Mo2C Nanocomposites by a Single-Step Solid State Reaction for Electrochemical Oxygen Reduction.

    Science.gov (United States)

    Huang, K; Bi, K; Liang, C; Lin, S; Wang, W J; Yang, T Z; Liu, J; Zhang, R; Fan, D Y; Wang, Y G; Lei, M

    2015-01-01

    Novel graphite-molybdenum carbide nanocomposites (G-Mo2C) are synthesized by a typical solid state reaction with melamine and MoO3 as precursors under inert atmosphere. The characterization results indicate that G-Mo2C composites are composed of high crystallization and purity of Mo2C and few layers of graphite carbon. Mo2C nanoparticles with sizes ranging from 5 to 50 nm are uniformly supported by surrounding graphite layers. It is believed that Mo atom resulting from the reduction of MoO3 is beneficial to the immobilization of graphite carbon. Moreover, the electrocatalytic performances of G-Mo2C for ORR in alkaline medium are investigated by cyclic voltammetry (CV), rotating disk electrode (RDE) and chronoamperometry test with 3M methanol. The results show that G-Mo2C has a considerable catalytic activity and superior methanol tolerance performance for the oxygen reduction reaction (ORR) benefiting from the chemical interaction between the carbide nanoparticles and graphite carbon.

  3. Dislocation density and graphitization of diamond crystals

    International Nuclear Information System (INIS)

    Pantea, C.; Voronin, G.A.; Zerda, T.W.; Gubicza, J.; Ungar, T.

    2002-01-01

    Two sets of diamond specimens compressed at 2 GPa at temperatures varying between 1060 K and 1760 K were prepared; one in which graphitization was promoted by the presence of water and another in which graphitization of diamond was practically absent. X-ray diffraction peak profiles of both sets were analyzed for the microstructure by using the modified Williamson-Hall method and by fitting the Fourier coefficients of the measured profiles by theoretical functions for crystallite size and lattice strain. The procedures determined mean size and size distribution of crystallites as well as the density and the character of the dislocations. The same experimental conditions resulted in different microstructures for the two sets of samples. They were explained in terms of hydrostatic conditions present in the graphitized samples

  4. Capacitive behavior of highly-oxidized graphite

    Science.gov (United States)

    Ciszewski, Mateusz; Mianowski, Andrzej

    2014-09-01

    Capacitive behavior of a highly-oxidized graphite is presented in this paper. The graphite oxide was synthesized using an oxidizing mixture of potassium chlorate and concentrated fuming nitric acid. As-oxidized graphite was quantitatively and qualitatively analyzed with respect to the oxygen content and the species of oxygen-containing groups. Electrochemical measurements were performed in a two-electrode symmetric cell using KOH electrolyte. It was shown that prolonged oxidation causes an increase in the oxygen content while the interlayer distance remains constant. Specific capacitance increased with oxygen content in the electrode as a result of pseudo-capacitive effects, from 0.47 to 0.54 F/g for a scan rate of 20 mV/s and 0.67 to 1.15 F/g for a scan rate of 5 mV/s. Better cyclability was observed for the electrode with a higher oxygen amount.

  5. Reactivity of lithium exposed graphite surface

    International Nuclear Information System (INIS)

    Harilal, S.S.; Allain, J.P.; Hassanein, A.; Hendricks, M.R.; Nieto-Perez, M.

    2009-01-01

    Lithium as a plasma-facing component has many attractive features in fusion devices. We investigated chemical properties of the lithiated graphite surfaces during deposition using X-ray photoelectron spectroscopy and low-energy ion scattering spectroscopy. In this study we try to address some of the known issues during lithium deposition, viz., the chemical state of lithium on graphite substrate, oxide layer formation mechanisms, Li passivation effects over time, and chemical change during exposure of the sample to ambient air. X-ray photoelectron studies indicate changes in the chemical composition with various thickness of lithium on graphite during deposition. An oxide layer formation is noticed during lithium deposition even though all the experiments were performed in ultrahigh vacuum. The metal oxide is immediately transformed into carbonate when the deposited sample is exposed to air.

  6. Reduced graphite oxide in supercapacitor electrodes.

    Science.gov (United States)

    Lobato, Belén; Vretenár, Viliam; Kotrusz, Peter; Hulman, Martin; Centeno, Teresa A

    2015-05-15

    The current energy needs have put the focus on highly efficient energy storage systems such as supercapacitors. At present, much attention focuses on graphene-like materials as promising supercapacitor electrodes. Here we show that reduced graphite oxide offers a very interesting potential. Materials obtained by oxidation of natural graphite and subsequent sonication and reduction by hydrazine achieve specific capacitances as high as 170 F/g in H2SO4 and 84F/g in (C2H5)4NBF4/acetonitrile. Although the particle size of the raw graphite has no significant effect on the physico-chemical characteristics of the reduced materials, that exfoliated from smaller particles (materials may suffer from a drop in their specific surface area upon fabrication of electrodes with features of the existing commercial devices. This should be taken into account for a reliable interpretation of their performance in supercapacitors. Copyright © 2015 Elsevier Inc. All rights reserved.

  7. Graphite core design in UK reactors

    International Nuclear Information System (INIS)

    Davies, M.W.

    1996-01-01

    The cores in the first power producing Magnox reactors in the UK were designed with only a limited amount of information available regarding the anisotropic dimensional change behaviour of Pile Grade graphite. As more information was gained it was necessary to make modifications to the design, some minor, some major. As the cores being built became larger, and with the switch to the Advanced Gas-cooled Reactor (AGR) with its much higher power density, additional problems had to be overcome such as increased dimensional change and radiolytic oxidation by the carbon dioxide coolant. For the AGRs a more isotropic graphite was required, with a lower initial open pore volume and higher strength. Gilsocarbon graphite was developed and was selected for all the AGRs built in the UK. Methane bearing coolants are used to limit radiolytic oxidation. (author). 5 figs

  8. Sensing capabilities of graphite based MR elastomers

    International Nuclear Information System (INIS)

    Tian, T F; Li, W H; Deng, Y M

    2011-01-01

    This paper presents both experimental and theoretical investigations of the sensing capabilities of graphite based magnetorheological elastomers (MREs). In this study, eight MRE samples with varying graphite weight fractions were fabricated and their resistance under different magnetic fields and external loadings were measured with a multi-meter. With an increment of graphite weight fraction, the resistance of MRE sample decreases steadily. Higher magnetic fields result in a resistance increase. Based on an ideal assumption of a perfect chain structure, a mathematical model was developed to investigate the relationship between the MRE resistance with external loading. In this model, the current flowing through the chain structure consists of both a tunnel current and a conductivity current, both of which depend on external loadings. The modelling parameters have been identified and reconstructed from comparison with experimental results. The comparison indicates that both experimental results and modelling predictions agree favourably well

  9. Cluster Ion Implantation in Graphite and Diamond

    DEFF Research Database (Denmark)

    Popok, Vladimir

    2014-01-01

    Cluster ion beam technique is a versatile tool which can be used for controllable formation of nanosize objects as well as modification and processing of surfaces and shallow layers on an atomic scale. The current paper present an overview and analysis of data obtained on a few sets of graphite...... and diamond samples implanted by keV-energy size-selected cobalt and argon clusters. One of the emphases is put on pinning of metal clusters on graphite with a possibility of following selective etching of graphene layers. The other topic of concern is related to the development of scaling law for cluster...... implantation. Implantation of cobalt and argon clusters into two different allotropic forms of carbon, namely, graphite and diamond is analysed and compared in order to approach universal theory of cluster stopping in matter....

  10. Graphite based Schottky diodes formed semiconducting substrates

    Science.gov (United States)

    Schumann, Todd; Tongay, Sefaattin; Hebard, Arthur

    2010-03-01

    We demonstrate the formation of semimetal graphite/semiconductor Schottky barriers where the semiconductor is either silicon (Si), gallium arsenide (GaAs) or 4H-silicon carbide (4H-SiC). The fabrication can be as easy as allowing a dab of graphite paint to air dry on any one of the investigated semiconductors. Near room temperature, the forward-bias diode characteristics are well described by thermionic emission, and the extracted barrier heights, which are confirmed by capacitance voltage measurements, roughly follow the Schottky-Mott relation. Since the outermost layer of the graphite electrode is a single graphene sheet, we expect that graphene/semiconductor barriers will manifest similar behavior.

  11. Graphite moderated reactor for thermoelectric generation

    International Nuclear Information System (INIS)

    Akazawa, Issei; Yamada, Akira; Mizogami, Yorikata

    1998-01-01

    Fuel rods filled with cladded fuel particles distributed and filled are buried each at a predetermined distance in graphite blocks situated in a reactor core. Perforation channels for helium gas as coolants are formed to the periphery thereof passing through vertically. An alkali metal thermoelectric power generation module is disposed to the upper lid of a reactor container while being supported by a securing receptacle. Helium gas in the coolant channels in the graphite blocks in the reactor core absorbs nuclear reaction heat, to be heated to a high temperature, rises upwardly by the reduction of the specific gravity, and then flows into an upper space above the laminated graphite block layer. Then the gas collides against a ceiling and turns, and flows down in a circular gap around the circumference of the alkali metal thermoelectric generation module. In this case, it transfers heat to the alkali metal thermoelectric generation module. (I.N.)

  12. Nondestructive evaluation of nuclear-grade graphite

    Science.gov (United States)

    Kunerth, D. C.; McJunkin, T. R.

    2012-05-01

    The material of choice for the core of the high-temperature gas-cooled reactors being developed by the U.S. Department of Energy's Next Generation Nuclear Plant Program is graphite. Graphite is a composite material whose properties are highly dependent on the base material and manufacturing methods. In addition to the material variations intrinsic to the manufacturing process, graphite will also undergo changes in material properties resulting from radiation damage and possible oxidation within the reactor. Idaho National Laboratory is presently evaluating the viability of conventional nondestructive evaluation techniques to characterize the material variations inherent to manufacturing and in-service degradation. Approaches of interest include x-ray radiography, eddy currents, and ultrasonics.

  13. Electrostatic Manipulation of Graphene On Graphite

    Science.gov (United States)

    Untiedt, Carlos; Rubio-Verdu, Carmen; Saenz-Arce, Giovanni; Martinez-Asencio, Jesús; Milan, David C.; Moaied, Mohamed; Palacios, Juan J.; Caturla, Maria Jose

    2015-03-01

    Here we report the use of a Scanning Tunneling Microscope (STM) under ambient and vacuum conditions to study the controlled exfoliation of the last layer of a graphite surface when an electrostatic force is applied from a STM tip. In this work we have focused on the study of two parameters: the applied voltage needed to compensate the graphite interlayer attractive force and the one needed to break atomic bonds to produce folded structures. Additionally, we have studied the influence of edge structure in the breaking geometry. Independently of the edge orientation the graphite layer is found to tear through the zig-zag direction and the lifled layer shows a zig-zag folding direction. Molecular Dinamics simulations and DFT calculations have been performed to understand our results, showing a strong correlation with the experiments. Comunidad Valenciana through Prometeo project.

  14. THE EFFECT OF APPLIED STRESS ON THE GRAPHITIZATION OF PYROLYTIC GRAPHITE

    Energy Technology Data Exchange (ETDEWEB)

    Bragg, R H; Crooks, D D; Fenn, Jr, R W; Hammond, M L

    1963-06-15

    Metallographic and x-ray diffraction studies were made of the effect of applied stress at high temperature on the structure of pyrolytic graphite (PG). The dominant factor was whether the PG was above or below its graphitization temperature, which, in turn, was not strongly dependent on applied stress. Below the graphitization temperature, the PG showed a high proportion of disordered layers (0.9), a fairly large mean tilt angle (20 deg ) and a small crystailite size (La --150 A). Fracture occurred at low stress and strain and the materiai exhibited a high apparent Young's modulus ( approximates 4 x 10/sup 6/ psi). Above the graphitization temperature, graphitization was considerably enhanced by strain up to about 8%. The disorder parameter was decreased from a zero strain value of 0.3 to 0.l5 with strain, the mean tilt angle was decreased to 4 deg , and a fivefold increase in crystallite size occurred. When the strainenhanced graphitization was complete, the material exhibited a low apparent modulus ( approximates 0.5 x 10/sup 6/ psi) and large plastic strains (>100%) for a constant stress ( approximates 55 ksi). Graphitization was shown to be a spontaneous process that is promoted by breaking cross-links thermally, and the process is furthered by chemical attack and plastic strain. (auth)

  15. Cementation of Nuclear Graphite Using Geopolymers

    International Nuclear Information System (INIS)

    Girke, N.A.; Steinmetz, H-J.; Bukaemsky, A.; Bosbach, D.; Hermann, E.; Griebel, I.

    2016-01-01

    Geopolymers are solid aluminosilicate materials usually formed by alkali hydroxide or alkali silicate activation of solid precursors such as coal fly ash, calcined clay and/or metallurgical slag. Today the primary application of geopolymer technology is in the development of alternatives to Portland-based cements. Variations in the ratio of aluminium to silicon, and alkali to silicon or addition of structure support, produce geopolymers with different physical and mechanical properties. These materials have an amorphous three-dimensional structure that gives geopolymers certain properties, such as fire and acid resistance, low leach rate, which make them an ideal substitute for ordinary Portland cement (OPC) in a wide range of applications especially in conditioning and storage of radioactive waste. Therefore investigations have been initiated on how and to which amount graphite as a hydrophobic material can be mixed with cement or concrete to form stable waste products and which concretes fulfil the necessary specifications best. As a result, geopolymers have been identified as a promising matrix for graphite containing nuclear wastes. With geopolymers, both favourable properties in the cementation process and a high long time structural stability of the products can be achieved. Investigations include: • direct mixing of graphite with geopolymers with or without sand as a mechanically stabilizing medium; • production of cement-graphite granulates as intermediate products and embedding of these granulates in geopolymer; • coating of formed graphite pieces with geopolymer.The report shows that carbon in the form of graphite can both be integrated with different grain size spectra as well as shaped in the hydraulic binder geopolymer and meets the requirements for a stable long-term immobilisation. (author)

  16. Structures, origin and evolution of various carbon phases in the ureilite Northwest Africa 4742 compared with laboratory-shocked graphite

    Science.gov (United States)

    Le Guillou, C.; Rouzaud, J. N.; Remusat, L.; Jambon, A.; Bourot-Denise, M.

    2010-07-01

    Mineralogical structures of carbon phases within the ureilite North West Africa 4742, a recent find, are investigated at various scales by high-resolution transmission electron microscopy (HRTEM), Raman microspectrometry and X-ray diffraction. Ureilites are the most carbon-rich of all meteorites, containing up to 6 wt.% carbon. Diamond, graphite and so-called "amorphous carbon" are typically described, but their crystallographic relationships and respective thermal histories remain poorly constrained. We especially focus on the origin of "amorphous carbon" and graphite, as well as their relationship with diamond. Two aliquots of carbon-bearing material were extracted: the insoluble organic matter (IOM) and the diamond fraction. We also compare the observed structures with those of laboratory-shocked graphite. Polycrystalline diamond aggregates with mean coherent domains of about 40 nm are reported for the first time in a ureilite and TEM demonstrates that all carbon phases are crystallographically related at the nanometre scale. Shock features show that diamond is produced from graphite through a martensitic transition. This observation demonstrates that graphite was present when the shock occurred and is consequently a precursor of diamond. The structure of what is commonly described as the "amorphous carbon" has been identified. It is not completely amorphous but only disordered and consists of nanometre-sized polyaromatic units surrounding the diamond. Comparison with laboratory-shocked graphite, partially transformed into diamond, indicates that the disordered carbon could be the product of diamond post-shock annealing. As diamond is the carrier of noble gases, whereas graphite is noble gas free, graphite cannot be the sole diamond precursor. This implies a multiple-stage history. A first generation of diamond could have been synthesized from a noble gas rich precursor or environment by either a shock or a condensation process. Thermally-induced graphitization

  17. Expansion and exfoliation of graphite to form graphene

    KAUST Repository

    Patole, Shashikan P.; Da Costa, Pedro M. F. J.

    2017-01-01

    Graphene production methods are described based on subjecting non- covalent graphite intercalated compounds, such as graphite bisulfate, to expansion conditions such as shocks of heat and/or microwaves followed by turbulence-assisted exfoliation

  18. A 2-D nucleation-growth model of spheroidal graphite

    International Nuclear Information System (INIS)

    Lacaze, Jacques; Bourdie, Jacques; Castro-Román, Manuel Jesus

    2017-01-01

    Analysis of recent experimental investigations, in particular by transmission electron microscopy, suggests spheroidal graphite grows by 2-D nucleation of new graphite layers at the outer surface of the nodules. These layers spread over the surface along the prismatic direction of graphite which is the energetically preferred growth direction of graphite when the apparent growth direction of the nodules is along the basal direction of graphite. 2-D nucleation-growth models first developed for precipitation of pure substances are then adapted to graphite growth from the liquid in spheroidal graphite cast irons. Lateral extension of the new graphite layers is controlled by carbon diffusion in the liquid. This allows describing quantitatively previous experimental results giving strong support to this approach.

  19. Coordinated Isotopic and TEM Studies of Presolar Graphites from Murchison

    Science.gov (United States)

    Croat, T. K.; Stadermann, F. J.; Zinner, E.; Bernatowicz, T. J.

    2004-03-01

    TEM and NanoSIMS investigations of the same presolar Murchison KFC graphites revealed high Zr, Mo, and Ru content in refractory carbides within the graphites. Along with isotopically light carbon, these suggest a low-metallicity AGB source.

  20. Thermal Properties of G-348 Graphite

    Energy Technology Data Exchange (ETDEWEB)

    McEligot, Donald M. [Idaho National Lab. (INL), Idaho Falls, ID (United States); Swank, W. David [Idaho National Lab. (INL), Idaho Falls, ID (United States); Cottle, David L. [Idaho National Lab. (INL), Idaho Falls, ID (United States); Valentin, Francisco I. [City Univ. (CUNY), NY (United States)

    2017-04-01

    Fundamental measurements have been obtained in the INL Graphite Characterization Laboratory to deduce the temperature dependence of thermal conductivity for G-348 isotropic graphite, which has been used by City College of New York in thermal experiments related to gas-cooled nuclear reactors. Measurements of thermal diffusivity, mass, volume and thermal expansion were converted to thermal conductivity in accordance with ASTM Standard Practice C781-08 (R-2014). Data are tabulated and a preliminary correlation for the thermal conductivity is presented as a function of temperature from laboratory temperature to 1000C.

  1. London forces in highly oriented pyrolytic graphite

    Directory of Open Access Journals (Sweden)

    L.V. Poperenko

    2017-07-01

    Full Text Available Surface of highly oriented pyrolytic graphite with terrace steps was studied using scanning tunneling microscopy with high spatial resolution. Spots with positive and negative charges were found in the vicinity of the steps. Values of the charges depended both on the microscope needle scan velocity and on its motion direction. The observed effect was theoretically explained with account of London forces that arise between the needle tip and the graphite surface. In this scheme, a terrace step works as a nanoscale diode for surface electric currents.

  2. Large Scale Reduction of Graphite Oxide Project

    Science.gov (United States)

    Calle, Carlos; Mackey, Paul; Falker, John; Zeitlin, Nancy

    2015-01-01

    This project seeks to develop an optical method to reduce graphite oxide into graphene efficiently and in larger formats than currently available. Current reduction methods are expensive, time-consuming or restricted to small, limited formats. Graphene has potential uses in ultracapacitors, energy storage, solar cells, flexible and light-weight circuits, touch screens, and chemical sensors. In addition, graphite oxide is a sustainable material that can be produced from any form of carbon, making this method environmentally friendly and adaptable for in-situ reduction.

  3. Chemical atomization of graphite by H+ ions

    International Nuclear Information System (INIS)

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

    A simple model of the mechanism of chemical atomization is given, on whose basis a decrease in chemical atomization is qualitatively predicted for high temperatures. Mass spectrometric investigations of the atomization products cited, which found CH 4 and CH 3 molecules during the irradiation of graphite and H + ions thereby confirmed the presence of chemical atomization. A relationship of S and temperature of graphite T during irradiation was obtained which showed a decrease in the coefficient of atomization of a high temperature. (U.S.)

  4. The electrochemical properties of graphite and carbon

    International Nuclear Information System (INIS)

    Yeager, E.; Gupta, S.; Molla, J.A.

    1983-01-01

    Carbon and graphite are often used as supports for electrocatalysts, but also have an electrocatalytic function in such electrode reactions as O 2 reduction in alkaline electrolytes, Cl 2 generation in brine and SOCl 2 reduction in lithium-thionyl chloride batteries. These catalytic functions involve specific chemical functional groups bound to the carbon and graphite surfaces. The factors controlling O 2 reduction with various types of carbon electrodes of both low and high surface area are reviewed. Of particular importance is the role of hydrogen peroxide. The role of the functionality of the carbon in the electrocatalysis will be discussed

  5. Radiation creep of graphite. An introduction

    Energy Technology Data Exchange (ETDEWEB)

    Blackstone, R [Commission of the European Communities, Petten (Netherlands). Joint Nuclear Research Center

    1977-03-01

    Graphite, a class of materials with many unique and unusual properties, shows a remarkably high creep ductility under irradiation. As this behaviour compensates to some extent some of the more worrying radiation effects, such as dimensional changes and their strong temperature dependence, it is a property of large technological interest. There are various ways of observing and measuring in-pile creep of graphite, varying in degree of sophistication and in cost, in accuracy and in the type of data that is generated. This paper attempts to review briefly the various experimental methods, and the knowledge generated so far. An indication is given of the areas in which further knowledge is wanted.

  6. Radiation creep of graphite. An introduction

    International Nuclear Information System (INIS)

    Blackstone, R.

    1977-01-01

    Graphite, a class of materials with many unique and unusual properties, shows a remarkably high creep ductility under irradiation. As this behavior compensates to some extent some of the more worrying radiation effects, such as dimensional changes and their strong temperature dependence, it is a property of large technological interest. There are various ways of observing and measuring in-pile creep of graphite, varying in degree of sophistication and in cost, in accuracy and in the type of data that is generated. This paper attempts to review briefly the various experimental methods, and the knowledge generated so far. An indication is given of the areas in which further knowledge is wanted

  7. Radiation creep of graphite. An introduction

    International Nuclear Information System (INIS)

    Blackstone, R.

    1977-01-01

    Graphite, a class of materials with many unique and unusual properties, shows a remarkably high creep ductility under irradiation. As this behaviour compensates to some extent some of the more worrying radiation effects, such as dimensional changes and their strong temperature dependence, it is a property of large technological interest. There are various ways of observing and measuring in-pile creep of graphite, varying in degree of sophistication and in cost, in accuracy and in the type of data that is generated. This paper attempts to review briefly the various experimental methods, and the knowledge generated so far. An indication is given of the areas in which further knowledge is wanted. (Auth.)

  8. Electrical properties of Egyptian natural graphite

    International Nuclear Information System (INIS)

    El-Shazly, O.; El-Wahidy, E.F.; Elanany, N.; Saad, N.A.

    1992-06-01

    The electrical properties of Egyptian natural graphite flakes, obtained from the graphite schists of Wadi Bent, Eastern Desert, were measured. The flakes were ground and compressed into pellets. The standard four probe dc method was used to measure the temperature dependence of the electric resistivity from room temperature down to 12 K. The transverse and longitudinal magnetoresistance were measured in the low magnetic field range at temperatures 300 K, 77 K and 12 K. The transverse magnetoresistance data was used to estimate the average mobility, assuming a simple two-band model. (author). 20 refs, 4 figs, 1 tab

  9. Direct reading spectrochemical analysis of nuclear graphite

    International Nuclear Information System (INIS)

    Roca Adell, M.; Becerro Ruiz, E.; Alvarez Gonzalez, F.

    1964-01-01

    A description is given about the application of a direct-reading spectrometer the Quantometer, to the determination of boron. calcium, iron, titanium and vanadium in nuclear grade graphite. for boron the powdered sample is mixed with 1% cupric fluoride and excited in a 10-amperes direct current arc and graphite electrodes with a crater 7 mm wide and 10 mm deep. For the other elements a smaller crater has been used and dilution with a number of matrices has been investigated; the best results are achieved by employing 25% cupric fluoride. The sensitivity limit for boron is 0,15 ppm. (Author) 21 refs

  10. Graphite target for the spiral project

    International Nuclear Information System (INIS)

    Putaux, J.C.; Ducourtieux, M.; Ferro, A.; Foury, P.; Kotfila, L.; Mueller, A.C.; Obert, J.; Pauwels, N.; Potier, J.C.; Proust, J.; Loiselet, M.

    1996-01-01

    A study of the thermal and physical properties of graphite targets for the SPIRAL project is presented. The main objective is to develop an optimized set-up both mechanically and thermally resistant, presenting good release properties (hot targets with thin slices). The results of irradiation tests concerning the mechanical and thermal resistance of the first prototype of SPIRAL target with conical geometry are presented. The micro-structural properties of the graphite target is also studied, in order to check that the release properties are not deteriorated by the irradiation. Finally, the results concerning the latest pilot target internally heated by an electrical current are shown. (author)

  11. STS Observations of Landau Levels at Graphite Surfaces

    OpenAIRE

    Matsui, T.; Kambara, H.; Niimi, Y.; Tagami, K.; Tsukada, M.; Fukuyama, Hiroshi

    2004-01-01

    Scanning tunneling spectroscopy measurements were made on surfaces of two different kinds of graphite samples, Kish graphite and highly oriented pyrolytic graphite (HOPG), at very low temperatures and in high magnetic fields. We observed a series of peaks in the tunnel spectra, which grow with increasing field, both at positive and negative bias voltages. These are associated with Landau quantization of the quasi two-dimensional electrons and holes in graphite in magnetic fields perpendicular...

  12. Electronic structure of incident carbon ions on a graphite surface

    International Nuclear Information System (INIS)

    Kiuchi, Masato; Takeuchi, Takae; Yamamoto, Masao.

    1997-01-01

    The electronic structure of an incident carbon ion on a graphite surface is discussed on the basis of ab initio molecular orbital calculations. A carbon cation forms a covalent bond with the graphite, and a carbon nonion is attracted to the graphite surface through van der Waals interaction. A carbon anion has no stable state on a graphite surface. The charge effects of incident ions become clear upon detailed examination of the electronic structure. (author)

  13. Effect of thermal annealing on property changes of neutron-irradiated non-graphitized carbon materials and nuclear graphite

    International Nuclear Information System (INIS)

    Matsuo, Hideto

    1991-06-01

    Changes in dimension of non-graphitized carbon materials and nuclear graphite, and the bulk density, electrical resistivity, Young's modulus and thermal expansivity of nuclear graphite were studied after neutron irradiation at 1128-1483 K and the successive thermal annealing up to 2573 K. Carbon materials showed larger and anisotropic dimensional shrinkage than that of nuclear graphite after the irradiation. The irradiation-induced dimensional shrinkage of carbon materials decreased during annealing at temperatures from 1773 to 2023 K, followed by a slight increase at higher temperatures. On the other hand, the irradiated nuclear graphite hardly showed the changes in length, density and thermal expansivity under the thermal annealing, but the electrical resistivity and Young's modulus showed a gradual decrease with annealing temperature. It has been clarified that there exists significant difference in the effect of thermal annealing on irradiation-induced dimensional shrinkage between graphitized nuclear graphite and non-graphitized carbon materials. (author)

  14. Fracture behavior of nuclear graphites under tensile impact loading

    International Nuclear Information System (INIS)

    Ugachi, Hirokazu; Ishiyama, Shintaro; Eto, Motokuni

    1994-01-01

    Impact tensile strength test was performed with two kinds of HTTR graphites, fine grained isotropic graphite, IG-11 and coarse grained near isotropic graphite, PGX and deformation and fracture behavior under the strain rate of over 100s -1 was measured and the following results were derived: (1) Tensile strength for IG-11 graphite does not depend on the strain rate less than 1 s -1 , but over 1 s -1 , tensile strength for IG-11 graphite increase larger than that measured under 1 s -1 . At the strain rate more than 100 s -1 , remarkable decrease of tensile strength for IG-11 graphite was found. Tensile strength of PGX graphite does not depend on the strain rate less than 1 s -1 , but beyond this value, the sharp tensile strength decrease occurs. (2) Under 100 s -1 , fracture strain for both graphites increase with increase of strain rate and over 100 s -1 , drastic increase of fracture strain for IG-11 graphite was found. (3) At the part of gage length, volume of specimen increase with increase of tensile loading level and strain rate. (4) Poisson's ratio for both graphites decrease with increase of tensile loading level and strain rate. (5) Remarkable change of stress-strain curve for both graphites under 100 s -1 was not found, but over 100 s -1 , the slope of these curve for IG-11 graphite decrease drastically. (author)

  15. Oxidation behavior of IG and NBG nuclear graphites

    Energy Technology Data Exchange (ETDEWEB)

    Choi, Woong-Ki; Kim, Byung-Joo [Jeonju Institute of Machinery and Carbon Composites Palbokdong-2ga, 817, Jeonju, Jeollabuk-do 561-844 (Korea, Republic of); Kim, Eung-Seon; Chi, Se-Hwan [Dept. of Nuclear Hydrogen Project, Korea Atomic Energy Research Institute, Daejeon 305-353 (Korea, Republic of); Park, Soo-Jin, E-mail: sjpark@inha.ac.k [Dept. of Chemistry, Inha Univ., 253, Nam-gu, Incheon 402-751 (Korea, Republic of)

    2011-01-15

    Graphical abstract: Water contact angles on nuclear graphite before and after oxidation treatments: the pictures show the contact angles obtained under deionized water on oxidation-treated and untreated nuclear graphite. The water contact angles are decreased after oxidation due to the increase in the hydrophilic. Display Omitted Research highlights: The average pore size of graphites shows an increase after the oxidation treatments. They also show that oxidation produces the surface functional groups on the graphite surfaces. The surface area of each graphite behaves in a unique manner. - Abstract: This work studies the oxidation-induced characteristics of four nuclear graphites (NBG-17, NBG-25, IG-110, and IG-430). The oxidation characteristics of the nuclear graphites were measured at 600 {sup o}C. The surface properties of the oxidation graphites were characterized by means of scanning electron microscopy, X-ray photoelectron spectroscopy, and contact angle methods. The N{sub 2}/77 K adsorption isotherm characteristics, including the specific surface area and micropore volume, were investigated by means of BET and t-plot methods. The experimental results show an increase in the average pore size of graphites; they also show that oxidation produces the surface functional groups on the graphite surfaces. The surface area of each graphite behaves in a unique manner. For example the surface area of NBG-17 increases slightly whereas the surface area of IG-110 increases significantly. This result confirms that the original surface state of each graphite is unique.

  16. Influence of irradiation on high-strength graphites

    International Nuclear Information System (INIS)

    Virgil'ev, Yu.S.; Grebennik, V.N.; Kalyagina, I.P.

    1989-01-01

    To ensure efficiency of the graphite elements of the construction of the masonry of reactors, the graphite must possess high radiation stability, strength, and heat resistance. In this connection, the physical properties of graphites based on uncalcined petroleum coke with a binder - high-temperature hard coal pitch - the amount of which reaches 40% are considered in this paper

  17. Porous graphite electrodes for rechargeable ion-transfer batteries

    Energy Technology Data Exchange (ETDEWEB)

    Novak, P; Scheifele, W; Haas, O [Paul Scherrer Inst. (PSI), Villigen (Switzerland)

    1997-06-01

    The influence of preparation pressure and pore-forming additives on the properties of graphite-based, Li{sup +}-intercalating electrodes for ion-transfer batteries have been investigated. The electrochemical performance of graphite electrodes could be improved by adjusting the porosity. Specific charge of >300 Ah/kg (with respect to the graphite mass) could be achieved. (author) 4 figs., 2 refs.

  18. Opportunity's Surroundings on Sol 1818 (Vertical)

    Science.gov (United States)

    2009-01-01

    NASA's Mars Exploration Rover Opportunity used its navigation camera to take the images combined into this full-circle view of the rover's surroundings during the 1,818th Martian day, or sol, of Opportunity's surface mission (March 5, 2009). South is at the center; north at both ends. This view is presented as a vertical projection with geometric seam correction. North is at the top. The rover had driven 80.3 meters (263 feet) southward earlier on that sol. Tracks from the drive recede northward in this view. The terrain in this portion of Mars' Meridiani Planum region includes dark-toned sand ripples and lighter-toned bedrock.

  19. Opportunity's Surroundings on Sol 1818 (Polar)

    Science.gov (United States)

    2009-01-01

    NASA's Mars Exploration Rover Opportunity used its navigation camera to take the images combined into this full-circle view of the rover's surroundings during the 1,818th Martian day, or sol, of Opportunity's surface mission (March 5, 2009). South is at the center; north at both ends. This view is presented as a polar projection with geometric seam correction. North is at the top. The rover had driven 80.3 meters (263 feet) southward earlier on that sol. Tracks from the drive recede northward in this view. The terrain in this portion of Mars' Meridiani Planum region includes dark-toned sand ripples and lighter-toned bedrock.

  20. Preparation of graphite derivatives by selective reduction of graphite oxide and isocyanate functionalization

    Czech Academy of Sciences Publication Activity Database

    Kumar, A. R. S. S.; Piana, Francesco; Mičušík, M.; Pionteck, J.; Banerjee, S.; Voit, B.

    2016-01-01

    Roč. 182, 1 October (2016), s. 237-245 ISSN 0254-0584 Institutional support: RVO:61389013 Keywords : graphite oxide * surface modification * conductive nanoparticles Subject RIV: CD - Macromolecular Chemistry Impact factor: 2.084, year: 2016

  1. Ion irradiation to simulate neutron irradiation in model graphites: Consequences for nuclear graphite

    Science.gov (United States)

    Galy, N.; Toulhoat, N.; Moncoffre, N.; Pipon, Y.; Bérerd, N.; Ammar, M. R.; Simon, P.; Deldicque, D.; Sainsot, P.

    2017-10-01

    Due to its excellent moderator and reflector qualities, graphite was used in CO2-cooled nuclear reactors such as UNGG (Uranium Naturel-Graphite-Gaz). Neutron irradiation of graphite resulted in the production of 14C which is a key issue radionuclide for the management of the irradiated graphite waste. In order to elucidate the impact of neutron irradiation on 14C behavior, we carried out a systematic investigation of irradiation and its synergistic effects with temperature in Highly Oriented Pyrolitic Graphite (HOPG) model graphite used to simulate the coke grains of nuclear graphite. We used 13C implantation in order to simulate 14C displaced from its original structural site through recoil. The collision of the impinging neutrons with the graphite matrix carbon atoms induces mainly ballistic damage. However, a part of the recoil carbon atom energy is also transferred to the graphite lattice through electronic excitation. The effects of the different irradiation regimes in synergy with temperature were simulated using ion irradiation by varying Sn(nuclear)/Se(electronic) stopping power. Thus, the samples were irradiated with different ions of different energies. The structure modifications were followed by High Resolution Transmission Electron Microscopy (HRTEM) and Raman microspectrometry. The results show that temperature generally counteracts the disordering effects of irradiation but the achieved reordering level strongly depends on the initial structural state of the graphite matrix. Thus, extrapolating to reactor conditions, for an initially highly disordered structure, irradiation at reactor temperatures (200 - 500 °C) should induce almost no change of the initial structure. On the contrary, when the structure is initially less disordered, there should be a "zoning" of the reordering: In "cold" high flux irradiated zones where the ballistic damage is important, the structure should be poorly reordered; In "hot" low flux irradiated zones where the ballistic

  2. Polyphase diffusion of fission products in graphite

    International Nuclear Information System (INIS)

    Dannert, V.

    1989-05-01

    The report attempts to give an introduction into the subject of fission product transport in nuclear graphite and results in an extended proposal of a transport-model. Beginning with a rough description of the graphite in question, an idea about the physical transport-phenomena in graphite is developed. Some of the basic experimental methods, especially techniques of porosimetry, determination of sorption-isotherms and of course several transport-experiments, are briefly described and their results are discussed. Some of the most frequent transport models are introduced and assessed with the criteria emphasized in this report. An extended model is proposed including the following main ideas: The transport of the fission-products is regarded as a two-phase-diffusion process through the open pores of the graphite. The two phases are: surface-diffusion and gas-diffusion. A time-dependent coupling of the two diffusion-phases by sorption-isotherms and a concentration-dependence of the surface diffusion coefficient, also related to the physical behaviour of the sorption-isotherms, are the basic properties of the proposed model. (orig./HP) [de

  3. US graphite reactor D ampersand D experience

    International Nuclear Information System (INIS)

    Garrett, S.M.K.; Williams, N.C.

    1997-02-01

    This report describes the results of the U.S. Graphite Reactor Experience Task for the Decommissioning Strategy Plan for the Leningrad Nuclear Power Plant (NPP) Unit 1 Study. The work described in this report was performed by the Pacific Northwest National Laboratory (PNNL) for the Department of Energy (DOE)

  4. Analysis of a T-10 graphite limiter

    International Nuclear Information System (INIS)

    Hildebrandt, D.; Laux, M.; Lingertat, J.; Pech, P.; Reiner, H.D.; Strusny, H.; Wolff, H.

    1981-01-01

    Parts of a T-10 graphite limiter used during ohmic heated discharges have been investigated. Erosion and deposition phenomena have been studied by morphological and elemental surface analysis methods. From the results estimates of the plasma parameters near the limiter surface have been made. (orig.)

  5. Raw materials for reflector graphite (for reactors)

    International Nuclear Information System (INIS)

    Wilhelmi, G.; Mindermann, D.

    1992-01-01

    The manufacturing concept for the core components of German high temperature reactor (HTR) types of graphite was previously entirely directed to the use of German tar coke (St coke). As the plants for producing this material no longer complied technically with the current environmental protection requirements, one had to assume that they would soon be shut down. To prevent bottlenecks in the erection of future HTR plants, alternative cokes produced by modern processes by Japanese manufacturers were checked for their suitability for the manufacture of reactor graphite. This report describes the investigations carried out on these materials from the safe delayed coking process. The project work, apart from analysis of the main data of the candidate coke considered, included the processing of the raw materials into directly and secondarily extruded graphite rods on the laboratory scale, including characterisation. As the results show, the material data achieved with the previous raw material can be reproduced with Japanese St coke. The tar coke LPC-A from the Nippon Steel Chemical Co., Ltd was decided on as the new standard coke for manufacturing reflector graphite. (orig.) With 15 tabs., 2 figs [de

  6. Formation of dislocation dipoles in irradiated graphite

    International Nuclear Information System (INIS)

    Niwase, Keisuke

    2005-01-01

    Recently, we have proposed a dislocation dipole accumulation model to explain the irradiation-induced amorphization of graphite. However, the structure of dislocation dipole in the hexagonal networks is still an open question at the atomic-level. In this paper, we propose a possible formation process of the dislocation dipole

  7. Functional interface of polymer modified graphite anode

    Energy Technology Data Exchange (ETDEWEB)

    Komaba, S.; Ozeki, T.; Okushi, K. [Department of Applied Chemistry, Tokyo University of Science, 1-3 Kagurazaka, Shinjuku, Tokyo 162-8601 (Japan)

    2009-04-01

    Graphite electrodes were modified by polyacrylic acid (PAA), polymethacrylic acid (PMA), and polyvinyl alcohol (PVA). Their electrochemical properties were examined in 1 mol dm{sup -3} LiClO{sub 4} ethylene carbonate:dimethyl carbonate (EC:DMC) and propylene carbonate (PC) solutions as an anode of lithium ion batteries. Generally, lithium ions hardly intercalate into graphite in the PC electrolyte due to a decomposition of the PC electrolyte at ca. 0.8 V vs. Li/Li{sup +}, and it results in the exfoliation of the graphene layers. However, the modified graphite electrodes with PAA, PMA, and PVA demonstrated the stable charge-discharge performance due to the reversible lithium intercalation not only in the EC:DMC but also in the PC electrolytes since the electrolyte decomposition and co-intercalation of solvent were successfully suppressed by the polymer modification. It is thought that these improvements were attributed to the interfacial function of the polymer layer on the graphite which interacted with the solvated lithium ions at the electrode interface. (author)

  8. Functional interface of polymer modified graphite anode

    Science.gov (United States)

    Komaba, S.; Ozeki, T.; Okushi, K.

    Graphite electrodes were modified by polyacrylic acid (PAA), polymethacrylic acid (PMA), and polyvinyl alcohol (PVA). Their electrochemical properties were examined in 1 mol dm -3 LiClO 4 ethylene carbonate:dimethyl carbonate (EC:DMC) and propylene carbonate (PC) solutions as an anode of lithium ion batteries. Generally, lithium ions hardly intercalate into graphite in the PC electrolyte due to a decomposition of the PC electrolyte at ca. 0.8 V vs. Li/Li +, and it results in the exfoliation of the graphene layers. However, the modified graphite electrodes with PAA, PMA, and PVA demonstrated the stable charge-discharge performance due to the reversible lithium intercalation not only in the EC:DMC but also in the PC electrolytes since the electrolyte decomposition and co-intercalation of solvent were successfully suppressed by the polymer modification. It is thought that these improvements were attributed to the interfacial function of the polymer layer on the graphite which interacted with the solvated lithium ions at the electrode interface.

  9. Removal of iron from impure graphites

    International Nuclear Information System (INIS)

    Growcock, F.B.; Heiser, J.

    1979-01-01

    Iron-impregnated and ash-rich graphites have been purified by leaching with gaseous I 2 at 900 0 C. With addition of H 2 , the rate of removal of impurity iron can be markedly increased and becomes comparable to that obtained with Cl 2 . I 2 has an advantage in that it can also volatilize Ca and perhaps Ba and Sr

  10. Structural strength of core graphite bars

    International Nuclear Information System (INIS)

    Kikuchi, K.; Futakawa, M.

    1987-01-01

    A HTR core consists of fuel, hot plenum, reflector and thermal barrier blocks. Each graphite block is supported by three thin cylindrical graphite bars called support post. Static and dynamic core loads are transmitted by the support posts to the thermal barrier blocks and a support plate. These posts are in contact with the blocks through hemispherical post seats to absorb the relative displacement caused by seismic force and the difference of thermal expansion of materials at the time of the start-up and shutdown of a reactor. The mixed fracture criterion of principal stress and modified Mohr-Coulomb's theory as well as the fracture criterion of principal stress based on elastic stress analysis was discussed in connection with the application to HTR graphite components. The buckling fracture of a support post was taken in consideration as one of the fracture modes. The effect that the length/diameter ratio of a post, small rotation and the curvature of post ends and seats exerted on the fracture strength was studied by using IG-110 graphite. Contacting stress analysis was carried out by using the structural analysis code 'COSMOS-7'. The experimental method, the analysis of buckling strength and the results are reported. The fracture of a support post is caused by the mixed mode of bending deformation, split fracture and shearing fracture. (Kako, I.)

  11. Thermoexpanded graphite modification by titanium dioxide

    International Nuclear Information System (INIS)

    Semko, L.S.; Gorbik, P.P.; Chujko, O.O.; Kruchek, Ya.Yi.; Dzyubenko, L.S.; Orans'ka, O.Yi.

    2006-01-01

    A method of the synthesis of thermoexpanded graphite (TEG) powders coated by titanium dioxide is developed. The conversion of n-buthylorthotitanate into TiO 2 on the TEG surface is investigated. The optimal parameters of the synthesis and the structure of titanium dioxide clusters on the TEG surface are determined

  12. GRAPHITIZED STEELS IN MACHINE-BUILDING

    Directory of Open Access Journals (Sweden)

    I. V. Akimov

    2010-01-01

    Full Text Available It is shown that graphitized steels in some cases due to its intermediate disposition by structure and characteristics among low-carbon steels and cast irons, can provide the necessary combination of characteristics of construction material and consequently to increase safety and durability of details of metallurgical and machinebuilding industry machines.

  13. Crust Structure Data of Seas Surrounding Turkey

    International Nuclear Information System (INIS)

    Maden, N.; Gelisli, K.

    2007-01-01

    Black Sea, Aegean, Mediterranean and Marmara Sea, which surround the Turkey, have not been examined with respect to the Geological, Geophysical and other natural sciences sufficiently. In fact, it is not attach importance the Turkish seas adequately and abandoned with respect to the scientific researches. The most important reason of this situation is the lack of the education of the Marine Sciences in the Turkish Universities. In this study, it is tried to construct a crustal structure data base of the surrounding seas of the Turkey by collecting crustal structure data sets done by different authors in different times so far. The data acquired in the base are collected from different data base sources by dragging. The Moho depth in the eastern and western basin of the Black sea is 22 km and 19 km, respectively. In the Marmara Sea the Moho depth is 24 km. The moho value in the southern Aegean is 20 km, in the northern Aegean the moho depth is 30 km. on the other hand, the moho depth value in the eastern and western basin of the Mediterranean Sea are 15-20 km and 25-30 km, respectively

  14. Metal/graphite-composite materials for fusion device

    International Nuclear Information System (INIS)

    Kneringer, G.; Kny, E.; Fischer, W.; Reheis, N.; Staffler, R.; Samm, U.; Winter, J.

    1995-01-01

    The utilization of graphite as a structural material depends to an important extent on the availability of a joining technique suitable for the production of reliable large scale metal/graphite-composites. This study has been conducted to evaluate vacuum brazes and procedures for graphite and metals which can be used in fusion applications up to about 1500 degree C. The braze materials included: AgCuTi, CuTi, NiTi, Ti, ZrTi, Zr. Brazing temperatures ranged from 850 degree C to 1900 degree C. The influence of graphite quality on wettability and pore-penetration of the braze has been investigated. Screening tests of metal/graphite-assemblies with joint areas exceeding some square-centimeters have shown that they can only successfully be produced when graphite is brazed to a metal, such as tungsten or molybdenum with a coefficient of thermal expansion closely matching that of graphite. Therefore all experimental work on evaluation of joints has been concentrated on molybdenum/graphite brazings. The tensile strength of molybdenum/graphite-composites compares favorably with the tensile strength of bulk graphite from room temperature close to the melting temperature of the braze. In electron beam testing the threshold damage line for molybdenum/graphite-composites has been evaluated. Results show that even composites with the low melting AgCuTi-braze are expected to withstand 10 MW/m 2 power density for at least 10 3 cycles. Limiter testing in TEXTOR shows that molybdenum/graphite-segments with 3 mm graphite brazed on molybdenum-substrate withstand severe repeated TEXTOR plasma discharge conditions without serious damage. Results prove that actively cooled components on the basis of a molybdenum/graphite-composite can sustain a higher heat flux than bulk graphite alone. (author)

  15. Acceptance test for graphite components and construction status of HTTR

    International Nuclear Information System (INIS)

    Iyoku, T.; Ishihara, M.; Maruyama, S.; Shiozawa, S.; Tsuji, N.; Miki, T.

    1996-01-01

    In March, 1991, the Japan Atomic Energy Research Institute (JAERI) started to constructed the High Temperature engineering Test Reactor(HTTR) which is a 30-MW(thermal) helium gas-cooled reactor with a core composed of prismatic graphite blocks piled on the core support graphite structures. Two types of graphite materials are used in the HTTR. One is the garde IG-110, isotropic fine grain graphite, another is the grade PGX, medium-to-fine grained molded graphite. These materials were selected on the basis of the appropriate properties required by the HTTR reactor design. Industry-wide standards for an acceptance test of graphite materials used as main components of a nuclear reactor had not been established. The acceptance standard for graphite components of the HTTR, therefore, was drafted by JAERI and reviewed by specialists outside JAERI. The acceptance standard consists of the material testing, non-destructive examination such as the ultrasonic and eddy current testings, dimensional and visual inspections and assembly test. Ultrasonic and eddy current testings are applied to graphite logs to detect an internal flaw and to graphite components to detect a surface flaw, respectively. The assembly test is performed at the works, prior to their installation in the reactor pressure vessel, to examine fabricating precision of each component and alignment of piled-up structures. The graphite components of the HTTR had been tested on the basis of the acceptance standard. It was confirmed that the graphite manufacturing process was well controlled and high quality graphite components were provided to the HTTR. All graphite components except for the fuel graphite blocks are to be installed in the reactor pressure vessel of the HTTR in September 1995. The paper describes the construction status of the HTTR focusing on the graphite components. The acceptance test results are also presented in this paper. (author). Figs

  16. Quantifying microstructural dynamics and electrochemical activity of graphite and silicon-graphite lithium ion battery anodes

    Science.gov (United States)

    Pietsch, Patrick; Westhoff, Daniel; Feinauer, Julian; Eller, Jens; Marone, Federica; Stampanoni, Marco; Schmidt, Volker; Wood, Vanessa

    2016-09-01

    Despite numerous studies presenting advances in tomographic imaging and analysis of lithium ion batteries, graphite-based anodes have received little attention. Weak X-ray attenuation of graphite and, as a result, poor contrast between graphite and the other carbon-based components in an electrode pore space renders data analysis challenging. Here we demonstrate operando tomography of weakly attenuating electrodes during electrochemical (de)lithiation. We use propagation-based phase contrast tomography to facilitate the differentiation between weakly attenuating materials and apply digital volume correlation to capture the dynamics of the electrodes during operation. After validating that we can quantify the local electrochemical activity and microstructural changes throughout graphite electrodes, we apply our technique to graphite-silicon composite electrodes. We show that microstructural changes that occur during (de)lithiation of a pure graphite electrode are of the same order of magnitude as spatial inhomogeneities within it, while strain in composite electrodes is locally pronounced and introduces significant microstructural changes.

  17. Nuclear graphite wear properties and estimation of graphite dust production in HTR-10

    Energy Technology Data Exchange (ETDEWEB)

    Luo, Xiaowei, E-mail: xwluo@tsinghua.edu.cn; Wang, Xiaoxin; Shi, Li; Yu, Xiaoyu; Yu, Suyuan

    2017-04-15

    Highlights: • Graphite dust. • The wear properties of graphite. • Pebble bed. • High Temperature Gas-cooled Reactor. • Fuel element. - Abstract: The issue of the graphite dust has been a research focus for the safety of High Temperature Gas-cooled Reactors (HTGRs), especially for the pebble bed reactors. Most of the graphite dust is produced from the wear of fuel elements during cycling of fuel elements. However, due to the complexity of the motion of the fuel elements in the pebble bed, there is no systematic method developed to predict the amount the graphite dust in a pebble bed reactor. In this paper, the study of the flow of the fuel elements in the pebble bed was carried out. Both theoretical calculation and numerical analysis by Discrete Element Method (DEM) software PFC3D were conducted to obtain the normal forces and sliding distances of the fuel elements in pebble bed. The wearing theory was then integrated with PFC3D to estimate the amount of the graphite dust in a pebble bed reactor, 10 MW High Temperature gas-cooled test Reactor (HTR-10).

  18. Graphite oxidation and structural strength of graphite support column in VHTR

    International Nuclear Information System (INIS)

    Park, Byung Ha; No, Hee Cheno; Kim, Eung Soo; Oh, Chang H.

    2009-01-01

    The air-ingress event by a large pipe break is an important accident considered in design of very high-temperature gas-cooled reactors (VHTR). Core-collapse prediction is a main safety issue. Structural failure model are technically required. The objective of this study is to develop structural failure model for the supporting graphite material in the lower plenum of the GT-MHR (gas-turbine-modular high temperature reactor). Graphite support column is important for VHTR structural integrity. Graphite support columns are under the axial load. Critical strength of graphite column is related to slenderness ratio and bulk density. Through compression tests for fresh and oxidized graphite columns we show that compressive strength of IG-110 was 79.46 MPa. And, the buckling strength of IG-110 column was expressed by the empirical formula: σ 0 =σ straight-line - C L/r, σ straight-line =91.31 MPa, C=1.01. The results of uniform and non-uniform oxidation tests show that the strength degradation of oxidized graphite column is expressed in the following non-dimensional form: σ/σ 0 =exp(-kd), k=0.111. Also, from the results of the uniform oxidation test with a complicated-shape column, we found out that the above non-dimensional equation obtained from the uniform oxidation test is applicable to a uniform oxidation case with a complicated-shape column. (author)

  19. Graphite Oxidation Simulation in HTR Accident Conditions

    Energy Technology Data Exchange (ETDEWEB)

    El-Genk, Mohamed

    2012-10-19

    Massive air and water ingress, following a pipe break or leak in steam-generator tubes, is a design-basis accident for high-temperature reactors (HTRs). Analysis of these accidents in both prismatic and pebble bed HTRs requires state-of-the-art capability for predictions of: 1) oxidation kinetics, 2) air helium gas mixture stratification and diffusion into the core following the depressurization, 3) transport of multi-species gas mixture, and 4) graphite corrosion. This project will develop a multi-dimensional, comprehensive oxidation kinetics model of graphite in HTRs, with diverse capabilities for handling different flow regimes. The chemical kinetics/multi-species transport model for graphite burning and oxidation will account for temperature-related changes in the properties of graphite, oxidants (O2, H2O, CO), reaction products (CO, CO2, H2, CH4) and other gases in the mixture (He and N2). The model will treat the oxidation and corrosion of graphite in geometries representative of HTR core component at temperatures of 900°C or higher. The developed chemical reaction kinetics model will be user-friendly for coupling to full core analysis codes such as MELCOR and RELAP, as well as computational fluid dynamics (CFD) codes such as CD-adapco. The research team will solve governing equations for the multi-dimensional flow and the chemical reactions and kinetics using Simulink, an extension of the MATLAB solver, and will validate and benchmark the model's predictions using reported experimental data. Researchers will develop an interface to couple the validated model to a commercially available CFD fluid flow and thermal-hydraulic model of the reactor , and will perform a simulation of a pipe break in a prismatic core HTR, with the potential for future application to a pebble-bed type HTR.

  20. Graphite waste incineration in a fluidized bed

    International Nuclear Information System (INIS)

    Guiroy, J.J.

    1996-01-01

    French gas-cooled reactors belonging to the Atomic Energy Commission (CEA), Electricite de France (EDF), Hifrensa (Spain), etc., commissioned between the 1950s and 1970s, have generated large quantities of graphite wastes, mainly in the form of spent fuel sleeves. Furthermore, some of these reactors scheduled for dismantling in the near future (such as the G2 and G3 reactors at Marcoule) have cores consisting of graphite blocks. Consequently, a fraction of the contaminated graphite, amounting to 6000 t in France for example, must be processed in the coming years. For this processing, incineration using a circulating fluidized bed combustor has been selected as a possible solution and validated. However, the first operation to be performed involves recovering this graphite waste, and particularly, first of all, the spent fuel sleeves that were stored in silos during the years of reactor operation. Subsequent to the final shutdown of the Spanish gas-cooled reactor unit, Vandellos 1, the operating utility Hifrensa awarded contracts to a Framatome Iberica SA/ENSA consortium for removing, sorting, and prepackaging of the waste stored in three silos on the Vandellos site, essentially graphite sleeves. On the other hand, a program to validate the Framatome fluidized bed incineration process was carried out using a prototype incinerator installed at Le Creusot, France. The validation program included 22 twelve-hour tests and one 120-hour test. Particular attention was paid to the safety aspects of this project. During the performance of the validation program, a preliminary safety assessment was carried out. An impact assessment was performed with the help of the French Institute for Protection and Nuclear Safety, taking into account the preliminary spectra supplied by the CEA and EDF, and the activities of the radionuclides susceptible of being released into the atmosphere during the incineration. (author). 4 refs, 11 figs, 1 tab

  1. Graphitization in Carbon MEMS and Carbon NEMS

    Science.gov (United States)

    Sharma, Swati

    Carbon MEMS (CMEMS) and Carbon NEMS (CNEMS) are an emerging class of miniaturized devices. Due to the numerous advantages such as scalable manufacturing processes, inexpensive and readily available precursor polymer materials, tunable surface properties and biocompatibility, carbon has become a preferred material for a wide variety of future sensing applications. Single suspended carbon nanowires (CNWs) integrated on CMEMS structures fabricated by electrospinning of SU8 photoresist on photolithographially patterned SU8 followed by pyrolysis are utilized for understanding the graphitization process in micro and nano carbon materials. These monolithic CNW-CMEMS structures enable the fabrication of very high aspect ratio CNWs of predefined length. The CNWs thus fabricated display core---shell structures having a graphitic shell with a glassy carbon core. The electrical conductivity of these CNWs is increased by about 100% compared to glassy carbon as a result of enhanced graphitization. We explore various tunable fabrication and pyrolysis parameters to improve graphitization in the resulting CNWs. We also suggest gas-sensing application of the thus fabricated single suspended CNW-CMEMS devices by using the CNW as a nano-hotplate for local chemical vapor deposition. In this thesis we also report on results from an optimization study of SU8 photoresist derived carbon electrodes. These electrodes were applied to the simultaneous detection of traces of Cd(II) and Pb(II) through anodic stripping voltammetry and detection limits as low as 0.7 and 0.8 microgL-1 were achieved. To further improve upon the electrochemical behavior of the carbon electrodes we elucidate a modified pyrolysis technique featuring an ultra-fast temperature ramp for obtaining bubbled porous carbon from lithographically patterned SU8. We conclude this dissertation by suggesting the possible future works on enhancing graphitization as well as on electrochemical applications

  2. Highly Enriched Uranium Metal Cylinders Surrounded by Various Reflector Materials

    International Nuclear Information System (INIS)

    Bernard Jones; J. Blair Briggs; Leland Monteirth

    2007-01-01

    A series of experiments was performed at Los Alamos Scientific Laboratory in 1958 to determine critical masses of cylinders of Oralloy (Oy) reflected by a number of materials. The experiments were all performed on the Comet Universal Critical Assembly Machine, and consisted of discs of highly enriched uranium (93.3 wt.% 235U) reflected by half-inch and one-inch-thick cylindrical shells of various reflector materials. The experiments were performed by members of Group N-2, particularly K. W. Gallup, G. E. Hansen, H. C. Paxton, and R. H. White. This experiment was intended to ascertain critical masses for criticality safety purposes, as well as to compare neutron transport cross sections to those obtained from danger coefficient measurements with the Topsy Oralloy-Tuballoy reflected and Godiva unreflected critical assemblies. The reflector materials examined in this series of experiments are as follows: magnesium, titanium, aluminum, graphite, mild steel, nickel, copper, cobalt, molybdenum, natural uranium, tungsten, beryllium, aluminum oxide, molybdenum carbide, and polythene (polyethylene). Also included are two special configurations of composite beryllium and iron reflectors. Analyses were performed in which uncertainty associated with six different parameters was evaluated; namely, extrapolation to the uranium critical mass, uranium density, 235U enrichment, reflector density, reflector thickness, and reflector impurities. In addition to the idealizations made by the experimenters (removal of the platen and diaphragm), two simplifications were also made to the benchmark models that resulted in a small bias and additional uncertainty. First of all, since impurities in core and reflector materials are only estimated, they are not included in the benchmark models. Secondly, the room, support structure, and other possible surrounding equipment were not included in the model. Bias values that result from these two simplifications were determined and associated

  3. Method of manufacturing a graphite coated fuel can

    International Nuclear Information System (INIS)

    Saito, Koichi; Uchida, Shunsuke.

    1984-01-01

    Purpose: To improve the close bondability and homogeneity of a graphite coating formed at the inner surface of a fuel can. Method: A coating containing graphite dispersed in a volatile organic solvent is used and a graphite coating is formed to the inner surface of a fuel can by way of a plunger method. After applying graphite coating, an inert gas is caused to flow at a certain flow rate to the inside of the fuel can horizontally rotaged so that gassification and evaporation of the volatile organic solvent contained in the graphite coating may be promoted. Since drying of the graphite coating coated to the inner surface of the fuel can thus be controlled, a graphite coating with satisfactory close bondability and homogeneity can be formed. (Kawakami, Y.)

  4. Ion irradiated graphite exposed to fusion-relevant deuterium plasma

    International Nuclear Information System (INIS)

    Deslandes, Alec; Guenette, Mathew C.; Corr, Cormac S.; Karatchevtseva, Inna; Thomsen, Lars; Ionescu, Mihail; Lumpkin, Gregory R.; Riley, Daniel P.

    2014-01-01

    Graphite samples were irradiated with 5 MeV carbon ions to simulate the damage caused by collision cascades from neutron irradiation in a fusion environment. The ion irradiated graphite samples were then exposed to a deuterium plasma in the linear plasma device, MAGPIE, for a total ion fluence of ∼1 × 10 24 ions m −2 . Raman and near edge X-ray absorption fine structure (NEXAFS) spectroscopy were used to characterize modifications to the graphitic structure. Ion irradiation was observed to decrease the graphitic content and induce disorder in the graphite. Subsequent plasma exposure decreased the graphitic content further. Structural and surface chemistry changes were observed to be greatest for the sample irradiated with the greatest fluence of MeV ions. D retention was measured using elastic recoil detection analysis and showed that ion irradiation increased the amount of retained deuterium in graphite by a factor of four

  5. 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 .

  6. Hydrophilization of graphite using plasma above/in a solution

    Science.gov (United States)

    Hoshino, Shuhei; Kawahara, Kazuma; Takeuchi, Nozomi

    2018-01-01

    A hydrophilization method for graphite is required for applications such as conductive ink. In typical chemical oxidation methods for graphite have the problems of producing many defects in graphite and a large environmental impact. In recent years, the plasma treatment has attracted attention because of the high quality of the treated samples and the low environmental impact. In this study, we proposed an above-solution plasma treatment with a high contact probability of graphite and plasma since graphite accumulates on the solution surface due to its hydrophobicity, which we compared with a so-called solution plasma treatment. Graphite was hydrophilized via reactions with OH radicals generated by the plasma. It was confirmed that hydroxyl and carboxyl groups were modified to the graphite and the dispersibility was improved. The above-solution plasma achieved more energy-efficient hydrophilization than the solution plasma and it was possible to enhance the dispersibility by increasing the plasma-solution contact area.

  7. Crystallization degree change of expanded graphite by milling and annealing

    International Nuclear Information System (INIS)

    Tang Qunwei; Wu Jihuai; Sun Hui; Fang Shijun

    2009-01-01

    Expanded graphite was ball milled with a planetary mill in air atmosphere, and subsequently thermal annealed. The samples were characterized by using X-ray diffraction spectroscopy (XRD), scanning electron microscopy (SEM) and thermal gravimetric analysis (TGA). It was found that in the milling initial stage (less than 12 h), the crystallization degree of the expanded graphite declined gradually, but after milling more than 16 h, a recrystallization of the expanded graphite toke place, and ordered nanoscale expanded graphite was formed gradually. In the annealing initial stage, the non-crystallization of the graphite occurred, but, beyond an annealing time, recrystallizations of the graphite arise. Higher annealing temperature supported the recrystallization. The milled and annealed expanded graphite still preserved the crystalline structure as raw material and hold high thermal stability.

  8. Opportunity's Surroundings on Sol 1798 (Polar)

    Science.gov (United States)

    2009-01-01

    NASA's Mars Exploration Rover Opportunity used its navigation camera to take the images combined into this 180-degree view of the rover's surroundings during the 1,798th Martian day, or sol, of Opportunity's surface mission (Feb. 13, 2009). North is on top. This view is presented as a polar projection with geometric seam correction. The rover had driven 111 meters (364 feet) southward on the preceding sol. Tracks from that drive recede northward in this view. For scale, the distance between the parallel wheel tracks is about 1 meter (about 40 inches). The terrain in this portion of Mars' Meridiani Planum region includes dark-toned sand ripples and lighter-toned bedrock.

  9. Opportunity's Surroundings After Sol 1820 Drive (Polar)

    Science.gov (United States)

    2009-01-01

    NASA's Mars Exploration Rover Opportunity used its navigation camera to take the images combined into this full-circle view of the rover's surroundings during the 1,820th to 1,822nd Martian days, or sols, of Opportunity's surface mission (March 7 to 9, 2009). This view is presented as a polar projection with geometric seam correction. North is at the top. The rover had driven 20.6 meters toward the northwest on Sol 1820 before beginning to take the frames in this view. Tracks from that drive recede southwestward. For scale, the distance between the parallel wheel tracks is about 1 meter (about 40 inches). The terrain in this portion of Mars' Meridiani Planum region includes dark-toned sand ripples and small exposures of lighter-toned bedrock.

  10. Opportunity's Surroundings on Sol 1798 (Vertical)

    Science.gov (United States)

    2009-01-01

    NASA's Mars Exploration Rover Opportunity used its navigation camera to take the images combined into this 180-degree view of the rover's surroundings during the 1,798th Martian day, or sol, of Opportunity's surface mission (Feb. 13, 2009). North is on top. This view is presented as a vertical projection with geometric seam correction. The rover had driven 111 meters (364 feet) southward on the preceding sol. Tracks from that drive recede northward in this view. For scale, the distance between the parallel wheel tracks is about 1 meter (about 40 inches). The terrain in this portion of Mars' Meridiani Planum region includes dark-toned sand ripples and lighter-toned bedrock.

  11. Opportunity's Surroundings on Sol 1687 (Vertical)

    Science.gov (United States)

    2009-01-01

    NASA's Mars Exploration Rover Opportunity used its navigation camera to take the images combined into this 360-degree view of the rover's surroundings on the 1,687th Martian day, or sol, of its surface mission (Oct. 22, 2008). Opportunity had driven 133 meters (436 feet) that sol, crossing sand ripples up to about 10 centimeters (4 inches) tall. The tracks visible in the foreground are in the east-northeast direction. Opportunity's position on Sol 1687 was about 300 meters southwest of Victoria Crater. The rover was beginning a long trek toward a much larger crater, Endeavour, about 12 kilometers (7 miles) to the southeast. This view is presented as a vertical projection with geometric seam correction.

  12. Opportunity's Surroundings After Sol 1820 Drive (Vertical)

    Science.gov (United States)

    2009-01-01

    NASA's Mars Exploration Rover Opportunity used its navigation camera to take the images combined into this full-circle view of the rover's surroundings during the 1,820th to 1,822nd Martian days, or sols, of Opportunity's surface mission (March 7 to 9, 2009). This view is presented as a vertical projection with geometric seam correction. North is at the top. The rover had driven 20.6 meters toward the northwest on Sol 1820 before beginning to take the frames in this view. Tracks from that drive recede southwestward. For scale, the distance between the parallel wheel tracks is about 1 meter (about 40 inches). The terrain in this portion of Mars' Meridiani Planum region includes dark-toned sand ripples and small exposures of lighter-toned bedrock.

  13. Opportunity's Surroundings on Sol 1687 (Polar)

    Science.gov (United States)

    2009-01-01

    NASA's Mars Exploration Rover Opportunity used its navigation camera to take the images combined into this 360-degree view of the rover's surroundings on the 1,687th Martian day, or sol, of its surface mission (Oct. 22, 2008). Opportunity had driven 133 meters (436 feet) that sol, crossing sand ripples up to about 10 centimeters (4 inches) tall. The tracks visible in the foreground are in the east-northeast direction. Opportunity's position on Sol 1687 was about 300 meters southwest of Victoria Crater. The rover was beginning a long trek toward a much larger crater, Endeavour, about 12 kilometers (7 miles) to the southeast. This view is presented as a polar projection with geometric seam correction.

  14. Opportunity's Surroundings After Sol 1820 Drive

    Science.gov (United States)

    2009-01-01

    NASA's Mars Exploration Rover Opportunity used its navigation camera to take the images combined into this full-circle view of the rover's surroundings during the 1,820th to 1,822nd Martian days, or sols, of Opportunity's surface mission (March 7 to 9, 2009). South is at the center; north at both ends. The rover had driven 20.6 meters toward the northwest on Sol 1820 before beginning to take the frames in this view. Tracks from that drive recede southwestward. For scale, the distance between the parallel wheel tracks is about 1 meter (about 40 inches). The terrain in this portion of Mars' Meridiani Planum region includes dark-toned sand ripples and small exposures of lighter-toned bedrock. This view is presented as a cylindrical projection with geometric seam correction.

  15. Towards Semantic Understanding of Surrounding Vehicular Maneuvers

    DEFF Research Database (Denmark)

    Kristoffersen, Miklas Strøm; Dueholm, Jacob Velling; Satzoda, Ravi K.

    2016-01-01

    This paper proposes the use of multiple low-cost visual sensors to obtain a surround view of the ego-vehicle for semantic understanding. A multi-perspective view will assist the analysis of naturalistic driving studies (NDS), by automating the task of data reduction of the observed sequences...... into events. A user-centric vision-based framework is presented using a vehicle detector and tracker in each separate perspective. Multi-perspective trajectories are estimated and analyzed to extract 14 different events, including potential dangerous behaviors such as overtakes and cut-ins. The system...... is tested on ten sequences of real-world data collected on U. S. highways. The results show the potential use of multiple low-cost visual sensors for semantic understanding around the ego-vehicle....

  16. Lovelock black holes surrounded by quintessence

    Energy Technology Data Exchange (ETDEWEB)

    Ghosh, Sushant G. [University of KwaZulu-Natal, Astrophysics and Cosmology Research Unit, School of Mathematics, Statistics and Computer Science, Durban (South Africa); Centre for Theoretical Physics, Multidisciplinary Centre for Advanced Research and Studies (MCARS), New Delhi (India); Maharaj, Sunil D.; Baboolal, Dharmanand; Lee, Tae-Hun [University of KwaZulu-Natal, Astrophysics and Cosmology Research Unit, School of Mathematics, Statistics and Computer Science, Durban (South Africa)

    2018-02-15

    Lovelock gravity consisting of the dimensionally continued Euler densities is a natural generalization of general relativity to higher dimensions such that equations of motion are still second order, and the theory is free of ghosts. A scalar field with a positive potential that yields an accelerating universe has been termed quintessence. We present exact black hole solutions in D-dimensional Lovelock gravity surrounded by quintessence matter and also perform a detailed thermodynamical study. Further, we find that the mass, entropy and temperature of the black hole are corrected due to the quintessence background. In particular, we find that a phase transition occurs with a divergence of the heat capacity at the critical horizon radius, and that specific heat becomes positive for r{sub h} < r{sub c} allowing the black hole to become thermodynamically stable. (orig.)

  17. Lovelock black holes surrounded by quintessence

    Science.gov (United States)

    Ghosh, Sushant G.; Maharaj, Sunil D.; Baboolal, Dharmanand; Lee, Tae-Hun

    2018-02-01

    Lovelock gravity consisting of the dimensionally continued Euler densities is a natural generalization of general relativity to higher dimensions such that equations of motion are still second order, and the theory is free of ghosts. A scalar field with a positive potential that yields an accelerating universe has been termed quintessence. We present exact black hole solutions in D-dimensional Lovelock gravity surrounded by quintessence matter and also perform a detailed thermodynamical study. Further, we find that the mass, entropy and temperature of the black hole are corrected due to the quintessence background. In particular, we find that a phase transition occurs with a divergence of the heat capacity at the critical horizon radius, and that specific heat becomes positive for r_h

  18. Nuclear quadrupole interaction measurements of 19F* and 22Na* on Graphite

    International Nuclear Information System (INIS)

    Djoko-Surono, Th; Martin, Peter W

    1996-01-01

    Time differential perturbed angular distribution (TDPAD) technique has been used to investigate nuclear quadrupole interactions of 19 F * and 22 Na * in graphite. We concentrated the measurements on pseudo single crystal graphite called Highly Oriented Pyrolytic Graphite for it has an ordered structure in which the c-axes of the microcrystals aligned in a certain direction with the mosaic spread less than 1 o , while the a- and b-axes randomly oriented on a plane perpendicular to the c-axes. Interactions between quadrupole moment of 19 F * and 22 Na * with its surroundings electric field gradient were studied by detecting the γ-rays distribution, W(Θ,t). For 1 9F * we found one static interaction. The corresponding electric field gradient was V zz =3.24(19)x10 22 V/m 2 . In the case of 22 Na * we found no evidence of nuclear quadrupole interaction, however, we were able to conclude that |QV 22 | 19 bV/m 2 . Using theoretical calculation Q=0.06 barn, we find that |V zz | 20 V/m 2 . These results indicate that the value efg depend on two factors, the host crystal and the core electrons. The core electrons contribution to the total efg is considerably large

  19. Progress in radioactive graphite waste management. Additional information

    International Nuclear Information System (INIS)

    2010-06-01

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

  20. Nucleation and growth characteristics of graphite spheroids in bainite during graphitization annealing of a medium carbon steel

    International Nuclear Information System (INIS)

    Gao, J.X.; Wei, B.Q.; Li, D.D.; He, K.

    2016-01-01

    The evolution of microstructure in bainite during graphitization annealing at 680 °C of Jominy-quenched bars of an Al-Si bearing medium carbon (0.4C wt%) steel has been studied and compared with that in martensite by using light, scanning and transmission electron microscopy. The results show that the graphitization process in bainite is different from that in martensite in many aspects such as the initial carbon state, the behavior of cementite, the nucleation-growth feature and kinetics of formation of graphite spheroids during graphitization annealing, and the shape, size and distribution of these graphite spheroids. The fact that the graphitization in bainite can produce more homogeneous graphite spheroids with more spherical shape and finer size in a shorter annealing time without the help of preexisting coring particles implies that bainite should be a better starting structure than martensite for making graphitic steel. - Highlights: • This article presents a microstructural characterization of formation of graphite spheroids in bainite. • Nucleation and growth characteristics of graphite spheroids formed in bainite and martensite are compared. • Bainite should be a better starting structure for making graphitic steel as results show.

  1. Erosion of pyrolytic graphite and Ti-doped graphite due to high flux irradiation

    International Nuclear Information System (INIS)

    Ohtsuka, Yusuke; Ohashi, Junpei; Ueda, Yoshio; Isobe, Michiro; Nishikawa, Masahiro

    1997-01-01

    The erosion of pyrolytic graphite and titanium doped graphite RG-Ti above 1,780 K was investigated by 5 keV Ar beam irradiation with the flux from 4x10 19 to 1x10 21 m -2 ·s -1 . The total erosion yields were significantly reduced with the flux. This reduction would be attributed to the reduction of RES (radiation enhanced sublimation) yield, which was observed in the case of isotropic graphite with the flux dependence of RES yield of φ -0.26 (φ: flux) obtained in our previous work. The yield of pyrolytic graphite was roughly 30% higher than that of isotropic graphite below the flux of 10 20 m -2 ·s -1 whereas each yield approached to very close value at the highest flux of 1x10 21 m -2 ·s -1 . This result indicated that the effect of graphite structure on the RES yield, which was apparent in the low flux region, would disappear in the high flux region probably due to the disordering of crystal structure. In the case of irradiation to RG-Ti at 1,780 K, the surface undulations evolved with a mean height of about 3 μm at 1.2x10 20 m -2 ·s -1 , while at higher flux of 8.0x10 20 m -2 ·s -1 they were unrecognizable. These phenomena can be explained by the reduction of RES of graphite parts excluding TiC grains. (author)

  2. Electrochemical behaviour of rhenium-graphite electrode

    International Nuclear Information System (INIS)

    Varypaev, V.N.; Krasikov, V.L.

    1980-01-01

    Electrochemical behaviour of combination electrode from graphite with electrodeposited thin coating of electrolytic rhenium is studied. Solution of 0.5 m NaCl+0.04 m AlCl 3 served as an electrolite. Polarization galvanostatic curves of hydrogen evolution upon electrodes with conditional rhenium thickness of 3.5 and 0.35 μm, 35 and 3.5 nm are obtained. Possibility of preparation of rhenium-graphite cathode with extremely low rhenium consume, electro-chemical properties of which are simu-lar to purely rhenium cathode is shown. Such electrode is characterized with stable in time low cathode potential of hydrogen evolution in chloride electrolyte and during cathode polarization it is not affected by corrosion

  3. Graphite moderated {sup 252}Cf source

    Energy Technology Data Exchange (ETDEWEB)

    Sajo B, L.; Barros, H.; Greaves, E. D. [Universidad Simon Bolivar, Nuclear Physics Laboratory, Apdo. 89000, 1080A Caracas (Venezuela, Bolivarian Republic of); Vega C, H. R., E-mail: fermineutron@yahoo.com [Universidad Autonoma de Zacatecas, Unidad Academica de Estudios Nucleares, Cipres No. 10, Fracc. La Penuela, 98068 Zacatecas (Mexico)

    2014-08-15

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

  4. Magnetic response of certain curved graphitic geometries

    International Nuclear Information System (INIS)

    Wang, L.; Davids, P.S.; Saxena, A.; Bishop, A.R.

    1992-01-01

    The quasi-particle energy spectra associated with some members of buckyfamily (curved graphitic geometries), in particular C 50 , C 60 , C 70 and related fullerenes as well as coaxial helical microtubules of graphite, are obtained analytically within the mean-field approximation. These energy spectra are then used to calculate various response functions. Specifically, we calculate the specific heat, magnetization and magnetic susceptibility in the presence of an external magnetic field at low temperatures. For a single microtubule an extra peak superimposed on the first de Haas van Alphen (dHvA) oscillation in magnetic susceptibility is found in the 50--170 Tesla range depending on the radius which is possibly accessible in special (explosive flux compression) experiments. Finally, we point to important potential applications of these novel mesoscopic structures in nanotechnology

  5. Imaging of tritium implanted into graphite

    International Nuclear Information System (INIS)

    Malinowski, M.E.; Causey, R.A.

    1988-01-01

    The extensive use of graphite in plasma-facing surfaces of tokamaks such as the Tokamak Fusion Test Reactor, which has planned tritium discharges, makes two-dimensional tritium detection techniques important in helping to determine torus tritium inventories. We have performed experiments in which highly oriented pyrolytic graphite (HOPG) samples were first tritium implanted with fluences of ∼10 16 T/cm 2 at energies approx. 0 C resulted in no discernible motion of tritium along the basal plane, but did show that significant desorption of the implanted tritium occurred. The current results indicate that tritium in quantities of 10 12 T/cm 2 in tritiated components could be readily detected by imaging at lower magnifications

  6. Preparation of nanoporous carbons from graphite nanofibres

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Byung-Joo [Department of Green Chemistry and Environmental Biotechnology, University of Science and Technology, PO Box 107, Yuseong, Daejeon 305-600 (Korea, Republic of); Park, Soo-Jin [Department of Chemistry, Inha University, 253, Nam-gu, Incheon 402-751 (Korea, Republic of)

    2006-09-14

    In this study we manufactured highly porous graphite nanofibres (GNFs) by physical activation in order to develop promising energy storage materials. The activation was performed at activation temperatures in the range of 800-1050 deg. C. The pore structures of the porous GNFs were analysed using N{sub 2}/77 K adsorption isotherms. After the activation, the porous GNFs showed a decrease in diameter and scratches on their surfaces, resulting from surface oxidation and the opening of the graphitic layers, respectively. It was found that the specific surface area of the porous GNFs prepared at 1050 deg. C was more than 2000 m{sup 2} g{sup -1} without loss of their fibre shape or serious increase in electrical resistivity. This result indicates that porous GNFs prepared under optimal conditions can have a much higher specific surface area and are promising materials for energy storage technologies.

  7. Spectroscopical determination of impurities in nuclear graphite

    International Nuclear Information System (INIS)

    Lordello, A.R.; Tognini, R.P.

    1975-01-01

    A spectrochemical method for the direct determination of B, Cd, Si, Hg, Fe, Mg, Mn, Cr, Ni, Al, Mo, Ti, Sr, Na, Zn, and As in nuclear grade graphite is described. A 9:1 ratio of graphite to copper difluoride is used in the preparation of samples and standards. The excitation is carried out in a d-c at 10 amperes. The copper fluoride used as spectrographic buffer serves to increase the volatilization rate of the impurities and to diminish the differences in the nature of the analytical and calibration samples. The relative standard deviations for the determination of the 16 trace elements, except Sr, Fe, Cd, Al and Si, are in the range of 8 - 20% in their appropriate calibration levels. For the latter five elements they are approximately 20-40%

  8. Effect of total pressure on graphite oxidation

    International Nuclear Information System (INIS)

    Burnette, R.D.; Hoot, C.G.

    1983-04-01

    Graphite corrosion in the high-temperature gas-cooled reactor (HTGR) is calculated using two key assumptions: (1) the kinetic, catalysis, and transport characteristics of graphite determined by bench-scale tests apply to large components at reactor conditions and (2) the effects of high pressure and turbulent flow are predictable. To better understand the differences between laboratory tests and reactor conditions, a high-pressure test loop (HPTL) has been constructed and used to perform tests at reactor temperature, pressure, and flow conditions. The HPTL is intended to determine the functional dependence of oxidation rate and characteristics on total pressure and gas velocity and to compare the oxidation results with calculations using models and codes developed for the reactor

  9. Plastic strain caused by contraction of pores in polycrystalline graphites

    International Nuclear Information System (INIS)

    Ioka, Ikuo; Yoda, Shinichi; Konishi, Takashi.

    1989-01-01

    The effects of porosity on mechanical properties and deformation behavior of four isotropic polycrystalline graphites were studied. The pore size distributions of the graphites were measured using a conventional mercury penetration technique. The average pore radius of ISO-88 graphite was about one-tenth of that of ISEM-1, IG-11 or IG-15 graphites. Young's modulus of the graphites decreased with increasing porosity. The stress-strain curve of each graphite was measured in its lateral and axial directions. Young's modulus of graphite decreased with increasing load. The plastic strain at a given compressive load was calculated from the stress-strain curve and the initial gradient of the unloading curve at the load. The ratio of lateral plastic strain to axial plastic strain for the graphites was less than 0.5, indicating that the volume of the graphites decreased during compressive loading. By assuming that the volume change was caused by contraction of pores, plastic strain associated with contraction of pores was calculated from the axial plastic strain and lateral plastic strain by slips along the basal planes. The plastic strain increased with increasing axial plastic strain and porosity of graphite. (author)

  10. Effect of graphite reflector on activation of fusion breeding blanket

    International Nuclear Information System (INIS)

    Lee, Cheol Woo; Lee, Young-Ouk; Lee, Dong Won; Cho, Seungyon; Ahn, Mu-Young

    2016-01-01

    Highlights: • The graphite reflector concept has been applied in the design of the Korea HCCR TBM for ITER and this concept is also a candidate design option for Korea Demo. • In the graphite reflector, C-14, B-11 and Be-10 are produced after an irradiation. Impurities in both case of beryllium and graphite is dominant in the shutdown dose after an irradiation. • Based on the evaluation, the graphite reflector is a good alternative of the beryllium multiplier in the view of induced activity and shutdown dose. But C-14 produced in the graphite reflector should be considered carefully in the view of radwaste management. - Abstract: Korea has proposed a Helium-Cooled Ceramic Reflector (HCCR) breeding blanket concept relevant to fusion power plants. Here, graphite is used as a reflector material by reducing the amount of beryllium multiplier. In this paper, activity analysis was performed and the effect of graphite reflector in the view of activation was compared to the beryllium multiplier. As a result, it is expected that using the graphite reflector instead of the beryllium multiplier decreases total activity very effectively. But the graphite reflector produces C-14 about 17.2 times than the beryllium multiplier. Therefore, C-14 produced in the graphite reflector is expected as a significant nuclide in the view of radwaste management.

  11. Theoretical analysis of the graphitization of a nanodiamond

    Energy Technology Data Exchange (ETDEWEB)

    Kwon, S Joon; Park, Jae-Gwan [Nano Science and Technology Division, Korea Institute of Science and Technology (KIST), PO Box 131, Cheongryang, Seoul, 130-650 (Korea, Republic of)

    2007-09-26

    We report on a theoretical analysis of the graphitization of a nanosize diamond (nanodiamond) in the metastable state. A nanodiamond annealed at a relatively lower temperature suffers morphological transition into a nanodiamond-graphite core-shell structure. Thermodynamic stability analysis of the nanodiamond showed that the phase diagram (relationship between the annealing temperature and radius) of the nanodiamond-graphite has three regimes: smaller nanodiamond, nanodiamond-graphite, and larger nanodiamond. These regimes of nanodiamond-graphite are due to an additional phase boundary from finding the maximum size of the nanodiamond which can be graphitized. In the theoretical analysis, the most probable and the maximum volume fractions of graphite in the nanodiamond were 0.76 and 0.84 respectively, which were independent of the annealing temperature and the initial radius of the nanodiamond. Therefore, the nanodiamond is not completely transformed into graphite by simple annealing at relatively lower process temperature and pressure. The highest graphitization probability decreased with increasing annealing temperature. Raman spectra for the F{sub 2g} vibration mode of nanodiamond were also calculated, and we found that the variation in properties of the spectral line was strongly dependent on the graphitization temperature and the initial size of the nanodiamond.

  12. Theoretical analysis of the graphitization of a nanodiamond

    International Nuclear Information System (INIS)

    Kwon, S Joon; Park, Jae-Gwan

    2007-01-01

    We report on a theoretical analysis of the graphitization of a nanosize diamond (nanodiamond) in the metastable state. A nanodiamond annealed at a relatively lower temperature suffers morphological transition into a nanodiamond-graphite core-shell structure. Thermodynamic stability analysis of the nanodiamond showed that the phase diagram (relationship between the annealing temperature and radius) of the nanodiamond-graphite has three regimes: smaller nanodiamond, nanodiamond-graphite, and larger nanodiamond. These regimes of nanodiamond-graphite are due to an additional phase boundary from finding the maximum size of the nanodiamond which can be graphitized. In the theoretical analysis, the most probable and the maximum volume fractions of graphite in the nanodiamond were 0.76 and 0.84 respectively, which were independent of the annealing temperature and the initial radius of the nanodiamond. Therefore, the nanodiamond is not completely transformed into graphite by simple annealing at relatively lower process temperature and pressure. The highest graphitization probability decreased with increasing annealing temperature. Raman spectra for the F 2g vibration mode of nanodiamond were also calculated, and we found that the variation in properties of the spectral line was strongly dependent on the graphitization temperature and the initial size of the nanodiamond

  13. Graphite-graphite oxide composite electrode for vanadium redox flow battery

    International Nuclear Information System (INIS)

    Li Wenyue; Liu Jianguo; Yan Chuanwei

    2011-01-01

    Highlights: → A new composite electrode is designed for vanadium redox flow battery (VRB). → The graphite oxide (GO) is used as electrode reactions catalyst. → The excellent electrode activity is attributed to the oxygen-containing groups attached on the GO surface. → A catalytic mechanism of the GO towards the redox reactions is presumed. - Abstract: A graphite/graphite oxide (GO) composite electrode for vanadium redox battery (VRB) was prepared successfully in this paper. The materials were characterized with X-ray diffraction, X-ray photoelectron spectroscopy and scanning electron microscopy. The specific surface area was measured by the Brunauer-Emmett-Teller method. The redox reactions of [VO 2 ] + /[VO] 2+ and V 3+ /V 2+ were studied with cyclic voltammetry and electrochemical impedance spectroscopy. The results indicated that the electrochemical performances of the electrode were improved greatly when 3 wt% GO was added into graphite electrode. The redox peak currents of [VO 2 ] + /[VO] 2+ and V 3+ /V 2+ couples on the composite electrode were increased nearly twice as large as that on the graphite electrode, and the charge transfer resistances of the redox pairs on the composite electrode are also reduced. The enhanced electrochemical activity could be ascribed to the presence of plentiful oxygen functional groups on the basal planes and sheet edges of the GO and large specific surface areas introduced by the GO.

  14. Determining the future for irradiated graphite disposal

    International Nuclear Information System (INIS)

    Neighbour, G.B.; Wickham, A.J.; Hacker, P.J.

    2000-01-01

    In recent years, proposals have been made for the long-term treatment of radioactive graphite waste which have ranged from sea dumping through incineration to land-based disposal, sometimes preceded by a variable period of 'safe storage' within the original reactor containment. Nuclear regulators are challenging the proposed length of 'safe storage' on the basis that essential knowledge may be lost. More recently, political constraints have further complicated the issue by eliminating disposal at sea and imposing a 'near-zero release' philosophy, while public opinion is opposed to land-based disposal and has induced a continual drive towards minimizing radioactivity release to the environment from disposal. This paper proposes that, despite various international agreements, it is time to review technically all options for disposal of irradiated graphite waste as a framework for the eventual decision-making process. It is recognized that the socio-economic and political pressures are high and therefore, given that all currently identified options satisfy the present safety limits, the need to minimize the objective risk is shown to be a minor need in comparison to the public's want of demonstrable control, responsiveness and ability to reverse/change the disposal options in the future. Further, it is shown that the eventual decision-making process for a post-dismantling option for graphite waste must optimize the beneficial attributes of subjective risk experienced by the general public. In addition, in advocating and preferred option to the general public, it is recommended that the industry should communicate at a level commensurate with the public understanding and initiate a process of facilitation which enables the public to arrive at their own solution and constituting a social exchange. Otherwise it is concluded that if the indecision over disposal options is allowed to continue then, by default, graphite will remain in long-term supervised storage. (author)

  15. Graphite-to-Graphene: Total Conversion.

    Science.gov (United States)

    Buzaglo, Matat; Bar, Ilan Pri; Varenik, Maxim; Shunak, Liran; Pevzner, Svetlana; Regev, Oren

    2017-02-01

    The rush to develop graphene applications mandates mass production of graphene sheets. However, the currently available complex and expensive production technologies are limiting the graphene commercialization. The addition of a protective diluent to graphite during ball-milling is demonstrated to result in a game-changer yield (>90%) of defect-free graphene, whose size is controlled by the milling energy and the diluent type. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  16. Electron oxidation of graphite by fluorospecies

    International Nuclear Information System (INIS)

    Rosenthal, G.L.

    1984-09-01

    The fluoride-ion affinity (A/sub F - /) of phosphorus pentafluoride was determined to be 100 kcal/mole from the heats of reaction of the Lewis bases SF 4 and ClO 2 F with PF 5 near room temperature. The fluoride-ion affinity of boron trifluoride was determined to be 92 kcal/mole from the heat of reaction of ClO 2 F with BF 3 . The crystal structure of ClO 2 BF 4 was determined and a precise lattice energy was calculated from this structure and used to determined A/sub F - /. Both PF 5 and BF 3 were found to react with graphite in the presence of fluorine gas to yield a variety of non-stoichiometric compounds. The fluoride-ion affinity of silicon tetrafluoride is not known, but it does not react with graphite and F 2 except at high pressures. These and previous results suggested a threshold in oxidizing power of intercalating species below which the oxidative intercalation reaction would not occur. The reduction of C/sub x/PF 6 by PF 3 proved that the reaction is thermodynamically controlled to some extent. The displacement of PF 5 in C/sub x/PF 6 by BF 3 (with a smaller A/sub F - /) suggested that two BF 3 molecules may have a larger fluoride-ion affinity than one PF 5 and that B 2 F 7 - may be a stable anion in graphite. Conductivity studies of PF/sub x/ and BF/sub y/ salts showed that a large drop in conductivity when the reaction reaches first stage is due in the most part to direct fluorination of carbon in graphite

  17. Temperature dependence of phonons in pyrolitic graphite

    International Nuclear Information System (INIS)

    Brockhouse, B.N.; Shirane, G.

    1977-01-01

    Dispersion curves for longitudinal and transverse phonons propagating along and near the c-axis in pyrolitic graphite at temperatures between 4 0 K and 1500 0 C have been measured by neutron spectroscopy. The observed frequencies decrease markedly with increasing temperature (except for the transverse optical ''rippling'' modes in the hexagonal planes). The neutron groups show interesting asymmetrical broadening ascribed to interference between one phonon and many phonon processes

  18. Atomic resolution images of graphite in air

    Energy Technology Data Exchange (ETDEWEB)

    Grigg, D.A.; Shedd, G.M.; Griffis, D.; Russell, P.E.

    1988-12-01

    One sample used for proof of operation for atomic resolution in STM is highly oriented pyrolytic graphite (HOPG). This sample has been imaged with many different STM`s obtaining similar results. Atomic resolution images of HOPG have now been obtained using an STM designed and built at the Precision Engineering Center. This paper discusses the theoretical predictions and experimental results obtained in imaging of HOPG.

  19. High thermoelectric performance of graphite nanofibers

    OpenAIRE

    Tran, Van-Truong; Saint-Martin, Jérôme; Dollfus, Philippe; Volz, Sebastian

    2017-01-01

    Graphite nanofibers (GNFs) have been demonstrated to be a promising material for hydrogen storage and heat management in electronic devices. Here, by means of first-principles and transport simulations, we show that GNFs can also be an excellent material for thermoelectric applications thanks to the interlayer weak van der Waals interaction that induces low thermal conductance and a step-like shape in the electronic transmission with mini-gaps, which are necessary ingredients to achieve high ...

  20. Increase of the density of commercial graphite

    International Nuclear Information System (INIS)

    Tobias, H.; Meyerstein, D.

    1977-12-01

    The increase of the density of commercial graphite of the type ATJ by polymerization of an impregnated monomer, followed by pyrolysis, is described. The monomer which was either styrene or acrylonitrile, was irradiated by a 60 Co source and pyrolized in a standard vacuum system. The irradiation dose for the polymerization of the monomer was determined. Suggestions for the establishment of the optimum conditions are offered

  1. Characterization of graphite dust produced by pneumatic lift

    Energy Technology Data Exchange (ETDEWEB)

    Shen, Ke [Guangdong Provincial Key Laboratory of Thermal Management Engineering and Materials, Graduate School at Shenzhen, Tsinghua University, Shenzhen 518055, Guangdong (China); Peng, Wei; Liu, Bing [Institute of Nuclear and New Energy Technology of Tsinghua University, Advanced Nuclear Energy Technology Cooperation Innovation Center, The Key Laboratory of Advanced Nuclear Engineering and Safety, Ministry of Education, Beijing 100084 (China); Kang, Feiyu [Guangdong Provincial Key Laboratory of Thermal Management Engineering and Materials, Graduate School at Shenzhen, Tsinghua University, Shenzhen 518055, Guangdong (China); Yang, Xiaoyong; Li, Weihua [Institute of Nuclear and New Energy Technology of Tsinghua University, Advanced Nuclear Energy Technology Cooperation Innovation Center, The Key Laboratory of Advanced Nuclear Engineering and Safety, Ministry of Education, Beijing 100084 (China); Yu, Suyuan, E-mail: suyuan@tsinghua.edu.cn [Center for Combustion Energy, The Key Laboratory for Thermal Science and Power Engineering, Ministry of Educations, Tsinghua University, Beijing 100084 (China)

    2016-08-15

    Highlights: • Generation of graphite dust by pneumatic lift. • Determination of morphology and particle size distribution of graphite dust. • The size of graphite dust in this study is compared to AVR and THTR-300 results. • Graphite dust originates from both filler and binder of the matrix graphite. - Abstract: Graphite dust is an important safety concern of high-temperature gas-cooled reactor (HTR). The graphite dust could adsorb fission products, and the radioactive dust is transported by the coolant gas and deposited on the surface of the primary loop. The simulation of coagulation, aggregation, deposition, and resuspension behavior of graphite dust requires parameters such as particle size distribution and particle shape, but currently very limited data on graphite dust is available. The only data we have are from AVR and THTR-300, however, the AVR result is likely to be prejudiced by the oil ingress. In pebble-bed HTR, graphite dust is generally produced by mechanical abrasion, in particular, by the abrasion of graphite pebbles in the lifting pipe of the fuel handling system. Here we demonstrate the generation and characterization of graphite dust that were produced by pneumatic lift. This graphite dust could substitute the real dust in HTR for characterization. The dust, exhibiting a lamellar morphology, showed a number-weighted average particle size of 2.38 μm and a volume-weighted average size of 14.62 μm. These two sizes were larger than the AVR and THTR results. The discrepancy is possibly due to the irradiation effect and prejudice caused by the oil ingress accident. It is also confirmed by the Raman spectrum that both the filler particle and binder contribute to the dust generation.

  2. Opportunity's Surroundings on Sol 1798 (Stereo)

    Science.gov (United States)

    2009-01-01

    [figure removed for brevity, see original site] Left-eye view of a color stereo pair for PIA11850 [figure removed for brevity, see original site] Right-eye view of a color stereo pair for PIA11850 NASA's Mars Exploration Rover Opportunity used its navigation camera to take the images combined into this stereo 180-degree view of the rover's surroundings during the 1,798th Martian day, or sol, of Opportunity's surface mission (Feb. 13, 2009). North is on top. This view combines images from the left-eye and right-eye sides of the navigation camera. It appears three-dimensional when viewed through red-blue glasses with the red lens on the left. The rover had driven 111 meters (364 feet) southward on the preceding sol. Tracks from that drive recede northward in this view. For scale, the distance between the parallel wheel tracks is about 1 meter (about 40 inches). The terrain in this portion of Mars' Meridiani Planum region includes dark-toned sand ripples and lighter-toned bedrock. This view is presented as a cylindrical-perspective projection with geometric seam correction.

  3. Opportunity's Surroundings on Sol 1818 (Stereo)

    Science.gov (United States)

    2009-01-01

    [figure removed for brevity, see original site] Left-eye view of a color stereo pair for PIA11846 [figure removed for brevity, see original site] Right-eye view of a color stereo pair for PIA11846 NASA's Mars Exploration Rover Opportunity used its navigation camera to take the images combined into this full-circle view of the rover's surroundings during the 1,818th Martian day, or sol, of Opportunity's surface mission (March 5, 2009). South is at the center; north at both ends. This view combines images from the left-eye and right-eye sides of the navigation camera. It appears three-dimensional when viewed through red-blue glasses with the red lens on the left. The rover had driven 80.3 meters (263 feet) southward earlier on that sol. Tracks from the drive recede northward in this view. The terrain in this portion of Mars' Meridiani Planum region includes dark-toned sand ripples and lighter-toned bedrock. This view is presented as a cylindrical-perspective projection with geometric seam correction.

  4. Opportunity's Surroundings on Sol 1687 (Stereo)

    Science.gov (United States)

    2009-01-01

    [figure removed for brevity, see original site] Left-eye view of a color stereo pair for PIA11739 [figure removed for brevity, see original site] Right-eye view of a color stereo pair for PIA11739 NASA's Mars Exploration Rover Opportunity used its navigation camera to take the images combined into this stereo, 360-degree view of the rover's surroundings on the 1,687th Martian day, or sol, of its surface mission (Oct. 22, 2008). The view appears three-dimensional when viewed through red-blue glasses. Opportunity had driven 133 meters (436 feet) that sol, crossing sand ripples up to about 10 centimeters (4 inches) tall. The tracks visible in the foreground are in the east-northeast direction. Opportunity's position on Sol 1687 was about 300 meters southwest of Victoria Crater. The rover was beginning a long trek toward a much larger crater, Endeavour, about 12 kilometers (7 miles) to the southeast. This panorama combines right-eye and left-eye views presented as cylindrical-perspective projections with geometric seam correction.

  5. Opportunity's Surroundings After Sol 1820 Drive (Stereo)

    Science.gov (United States)

    2009-01-01

    [figure removed for brevity, see original site] Left-eye view of a color stereo pair for PIA11841 [figure removed for brevity, see original site] Right-eye view of a color stereo pair for PIA11841 NASA's Mars Exploration Rover Opportunity used its navigation camera to take the images combined into this full-circle view of the rover's surroundings during the 1,820th to 1,822nd Martian days, or sols, of Opportunity's surface mission (March 7 to 9, 2009). This view combines images from the left-eye and right-eye sides of the navigation camera. It appears three-dimensional when viewed through red-blue glasses with the red lens on the left. The rover had driven 20.6 meters toward the northwest on Sol 1820 before beginning to take the frames in this view. Tracks from that drive recede southwestward. For scale, the distance between the parallel wheel tracks is about 1 meter (about 40 inches). The terrain in this portion of Mars' Meridiani Planum region includes dark-toned sand ripples and small exposures of lighter-toned bedrock. This view is presented as a cylindrical-perspective projection with geometric seam correction.

  6. The lithosphere-asthenosphere: Italy and surroundings

    International Nuclear Information System (INIS)

    Panza, G.F.; Aoudia, A.; Pontevivo, A.; Chimera, G.; Raykova, R.

    2003-02-01

    The velocity-depth distribution of the lithosphere-asthenosphere in the Italian region and surroundings is imaged, with a lateral resolution of about 100 km, by surface wave velocity tomography and non-linear inversion. Maps of the Moho depth, of the thickness of the lithosphere and of the shear-wave velocities, down to depths of 200 km and more, are constructed. A mantle wedge, identified in the uppermost mantle along the Apennines and the Calabrian Arc, underlies the principal recent volcanoes, and partial melting can be relevant in this part of the uppermost mantle. In Calabria a lithospheric doubling is seen, in connection with the subduction of the Ionian lithosphere. The asthenosphere is shallow in the Southern Tyrrhenian Sea. High velocity bodies, cutting the asthenosphere, outline the Adria-lonian subduction in the Tyrrhenian Sea and the deep-reaching lithospheric root in the Western Alps. Less deep lithospheric roots are seen in the Central Apennines. The lithosphere-asthenosphere properties delineate a differentiation between the northern and the southern sectors of the Adriatic Sea, likely attesting the fragmentation of Adria. (author)

  7. The lithosphere-asthenosphere Italy and surroundings

    CERN Document Server

    Panza, G F; Chimera, G; Pontevivo, A; Raykova, R

    2003-01-01

    The velocity-depth distribution of the lithosphere-asthenosphere in the Italian region and surroundings is imaged, with a lateral resolution of about 100 km, by surface wave velocity tomography and non-linear inversion. Maps of the Moho depth, of the thickness of the lithosphere and of the shear-wave velocities, down to depths of 200 km and more, are constructed. A mantle wedge, identified in the uppermost mantle along the Apennines and the Calabrian Arc, underlies the principal recent volcanoes, and partial melting can be relevant in this part of the uppermost mantle. In Calabria a lithospheric doubling is seen, in connection with the subduction of the Ionian lithosphere. The asthenosphere is shallow in the Southern Tyrrhenian Sea. High velocity bodies, cutting the asthenosphere, outline the Adria-lonian subduction in the Tyrrhenian Sea and the deep-reaching lithospheric root in the Western Alps. Less deep lithospheric roots are seen in the Central Apennines. The lithosphere-asthenosphere properties delineat...

  8. INTERSTELLAR MAGNETIC FIELD SURROUNDING THE HELIOPAUSE

    International Nuclear Information System (INIS)

    Whang, Y. C.

    2010-01-01

    This paper presents a three-dimensional analytical solution, in the limit of very low plasma β-ratio, for the distortion of the interstellar magnetic field surrounding the heliopause. The solution is obtained using a line dipole method that is the integration of point dipole along a semi-infinite line; it represents the magnetic field caused by the presence of the heliopause. The solution allows the variation of the undisturbed magnetic field at any inclination angle. The heliosphere is considered as having blunt-nosed geometry on the upwind side and it asymptotically approaches a cylindrical geometry having an open exit for the continuous outflow of the solar wind on the downwind side. The heliopause is treated as a magnetohydrodynamic tangential discontinuity; the interstellar magnetic field lines at the boundary are tangential to the heliopause. The interstellar magnetic field is substantially distorted due to the presence of the heliopause. The solution shows the draping of the field lines around the heliopause. The magnetic field strength varies substantially near the surface of the heliopause. The effect on the magnetic field due to the presence of the heliopause penetrates very deep into the interstellar space; the depth of penetration is of the same order of magnitude as the scale length of the heliosphere.

  9. The roles of geometry and topology structures of graphite fillers on thermal conductivity of the graphite/aluminum composites

    Energy Technology Data Exchange (ETDEWEB)

    Zhou, C.; Chen, D.; Zhang, X.B. [State Key Laboratory of Metal Matrix Composites, Shanghai Jiao Tong University, Shanghai 200240 (China); Chen, Z., E-mail: zhe.chen@sjtu.edu.cn [State Key Laboratory of Metal Matrix Composites, Shanghai Jiao Tong University, Shanghai 200240 (China); Zhong, S.Y.; Wu, Y. [State Key Laboratory of Metal Matrix Composites, Shanghai Jiao Tong University, Shanghai 200240 (China); Ji, G. [Unité Matériaux et Transformations, CNRS UMR 8207, Université Lille 1, Villeneuve d' Ascq 59655 (France); Wang, H.W. [State Key Laboratory of Metal Matrix Composites, Shanghai Jiao Tong University, Shanghai 200240 (China)

    2015-02-20

    Various graphite fillers, such as graphite particles, graphite fibers, graphite flakes and porous graphite blocks, have been successfully incorporated into an Al alloy by squeeze casting in order to fabricate graphite/Al composites with enhanced thermal conductivity (TC). Microstructural characterization by X-ray diffraction and scanning electron microscopy has revealed a tightly-adhered, clean and Al{sub 4}C{sub 3}-free interface between the graphite fillers and the Al matrix in all the as-fabricated composites. Taking the microstructural features into account, we generalized the corresponding predictive models for the TCs of these composites with the effective medium approximation and the Maxwell mean-field scheme, which both show good agreement with the experimental data. The roles of geometry and topology structures of graphite fillers on the TCs of the composites were further discussed. - Highlights: • The thermal enhancement of various graphite fillers with different topology structures. • Predictive models for the thermal conductivity of different topology structures. • Oriented flakes alignment has the high potentials for thermal enhancement.

  10. The utilization of a pressurized-graphite/water/oxygen mixture for irradiated graphite incineration

    International Nuclear Information System (INIS)

    Antonini, G.; Perotin, J.P.; Charlot, P.

    1992-01-01

    The authors demonstrate the interest of the utilization of a pressurized-graphite/water/oxygen mixture in the incineration of irradiated graphite. The aqueous phase comes in the form of a three-dimensional system that traps pressurized oxygen, the pulverulent solid being dispersed at the liquid/gas interfaces. These three-phasic formulations give the following advantages: reduction of the apparent viscosity of the mixture in comparison with a solid/liquid mixture at the same solid concentration; reduction of the solid/liquid interactions; self-pulverizability. thus promoting reduction of the flame length utilization of conventional burners; reduction of the flue gas flow rate; complete thermal destruction of graphite. (author)

  11. 77 FR 51581 - Request for a License To Export Nuclear Grade Graphite

    Science.gov (United States)

    2012-08-24

    ... NUCLEAR REGULATORY COMMISSION Request for a License To Export Nuclear Grade Graphite Pursuant to... 27, 2012, graphite for of nuclear grade graphite to the XMAT424, 11006032. nuclear end use. graphite. Shanghai Institute of Applied Physics in China to test various types of nuclear grade graphite material in...

  12. Preparation of graphite derivatives by selective reduction of graphite oxide and isocyanate functionalization

    Energy Technology Data Exchange (ETDEWEB)

    Santha Kumar, Arunjunai Raja Shankar [Materials Science Centre, Indian Institute of Technology, Kharagpur, 721302, West Bengal (India); Leibniz-Institut für Polymerforschung Dresden e.V., Hohe Straße 6, 01069, Dresden (Germany); Piana, Francesco [Leibniz-Institut für Polymerforschung Dresden e.V., Hohe Straße 6, 01069, Dresden (Germany); Organic Chemistry of Polymers, Technische Universität Dresden, 01062, Dresden (Germany); Mičušík, Matej [Polymer Institute, Slovak Academy of Sciences, Dúbravská cesta 9, 845 41, Bratislava (Slovakia); Pionteck, Jürgen, E-mail: pionteck@ipfdd.de [Leibniz-Institut für Polymerforschung Dresden e.V., Hohe Straße 6, 01069, Dresden (Germany); Banerjee, Susanta [Materials Science Centre, Indian Institute of Technology, Kharagpur, 721302, West Bengal (India); Voit, Brigitte [Leibniz-Institut für Polymerforschung Dresden e.V., Hohe Straße 6, 01069, Dresden (Germany); Organic Chemistry of Polymers, Technische Universität Dresden, 01062, Dresden (Germany)

    2016-10-01

    Heavily oxidized and ordered graphene nanoplatelets were produced from natural graphite by oxidation using a mixture of phosphoric acid, sulphuric acid, and potassium permanganate (Marcano's method). The atomic percentage of oxygen in the graphite oxide produced was more than 30% confirmed by XPS studies. The graphite oxide produced had intact basal planes and remains in a layered structure with interlayer distance of 0.8 nm, analyzed by WAXS. The graphite oxide was treated with 4,4′-methylenebis(phenyl isocyanate) (MDI) to produce grafted isocyanate functionalization. Introduction of these bulky functional groups widens the interlayer distance to 1.3 nm. In addition, two reduction methods, namely benzyl alcohol mediated reduction and thermal reduction were carried out on isocyanate modified and unmodified graphite oxides and compared to each other. The decrease in the oxygen content and the sp{sup 3} defect-repair were studied with XPS and RAMAN spectroscopy. Compared to the thermal reduction process, which is connected with large material loss, the benzyl alcohol mediated reduction process is highly effective in defect repair. This resulted in an increase of conductivity of at least 9 orders of magnitude compared to the graphite oxide. - Highlights: • Preparation of GO by Marcano's method results in defined interlayer spacing. • Treatment of GO with diisocyanate widens the interlayer spacing to 1.3 nm. • Chemical reduction of GO with benzyl alcohol is effective in defect repair. • Electrical conductivity increases by 9 orders of magnitude during chemical reduction. • The isocyanate functionalization is stable under chemical reducing conditions.

  13. Understanding community norms surrounding tobacco sales.

    Directory of Open Access Journals (Sweden)

    Patricia A McDaniel

    Full Text Available In the US, denormalizing tobacco use is key to tobacco control; less attention has been paid to denormalizing tobacco sales. However, some localities have placed limits on the number and type of retailers who may sell tobacco, and some retailers have abandoned tobacco sales voluntarily. Understanding community norms surrounding tobacco sales may help accelerate tobacco denormalization.We conducted 15 focus groups with customers of California, New York, and Ohio retailers who had voluntarily discontinued tobacco sales to examine normative assumptions about where cigarettes should or should not be sold, voluntary decisions to discontinue tobacco sales, and government limits on such sales.Groups in all three states generally agreed that grocery stores that sold healthy products should not sell tobacco; California groups saw pharmacies similarly, while this was a minority opinion in the other two states. Convenience stores were regarded as a natural place to sell tobacco. In each state, it was regarded as normal and commendable for some stores to want to stop selling tobacco, although few participants could imagine convenience stores doing so. Views on government's role in setting limits on tobacco sales varied, with California and New York participants generally expressing support for restrictions, and Ohio participants expressing opposition. However, even those who expressed opposition did not approve of tobacco sales in all possible venues. Banning tobacco sales entirely was not yet normative.Limiting the ubiquitous availability of tobacco sales is key to ending the tobacco epidemic. Some limits on tobacco sales appear to be normative from the perspective of community members; it may be possible to shift norms further by problematizing the ubiquitous presence of cigarettes and drawing connections to other products already subject to restrictions.

  14. Understanding community norms surrounding tobacco sales.

    Science.gov (United States)

    McDaniel, Patricia A; Malone, Ruth E

    2014-01-01

    In the US, denormalizing tobacco use is key to tobacco control; less attention has been paid to denormalizing tobacco sales. However, some localities have placed limits on the number and type of retailers who may sell tobacco, and some retailers have abandoned tobacco sales voluntarily. Understanding community norms surrounding tobacco sales may help accelerate tobacco denormalization. We conducted 15 focus groups with customers of California, New York, and Ohio retailers who had voluntarily discontinued tobacco sales to examine normative assumptions about where cigarettes should or should not be sold, voluntary decisions to discontinue tobacco sales, and government limits on such sales. Groups in all three states generally agreed that grocery stores that sold healthy products should not sell tobacco; California groups saw pharmacies similarly, while this was a minority opinion in the other two states. Convenience stores were regarded as a natural place to sell tobacco. In each state, it was regarded as normal and commendable for some stores to want to stop selling tobacco, although few participants could imagine convenience stores doing so. Views on government's role in setting limits on tobacco sales varied, with California and New York participants generally expressing support for restrictions, and Ohio participants expressing opposition. However, even those who expressed opposition did not approve of tobacco sales in all possible venues. Banning tobacco sales entirely was not yet normative. Limiting the ubiquitous availability of tobacco sales is key to ending the tobacco epidemic. Some limits on tobacco sales appear to be normative from the perspective of community members; it may be possible to shift norms further by problematizing the ubiquitous presence of cigarettes and drawing connections to other products already subject to restrictions.

  15. Determination of Cl-36 in Irradiated Reactor Graphite

    International Nuclear Information System (INIS)

    Beer, H.-F.; Schumann, D.; Stowasser, T.; Hartmann, E.; Kramer, A.

    2016-01-01

    Two of the three research reactors at the Paul Scherrer Institute (PSI), the reactors DIORIT and PROTEUS, contained reactor graphite. Whereas the former research reactor DIORIT has been dismantled completely the PROTEUS is subject to a future decommissioning. In case of the DIORIT the reactor graphite was conditioned applying a procedure developed at PSI. In this case the 36 Cl content had to be determined after the conditioning. The result is reported in this paper. The radionuclide inventory including 36 Cl of the graphite used in PROTEUS was measured and the results are reported in here. It has been proven that the graphite from PROTEUS has a radionuclide inventory near the detection limits. All determined radionuclide activities are far below the Swiss exemptions limits. The graphite from PROTEUS therefore poses no radioactive waste. In contrast, the 36 Cl content of graphite from DIORIT is well above the exemption limits. (author)

  16. Calculated bond properties of K adsorbed on graphite

    International Nuclear Information System (INIS)

    Hjortstam, O.; Wills, J.M.; Johansson, B.; Eriksson, O.

    1998-01-01

    The properties of the chemical bond of K adsorbed on a graphite(0001) surface have been studied for different coverages, by means of a full-potential slab method. Specific modifications of the Hamiltonian are performed in order to make it possible to study K on graphite in the disperse phase (dilute limit). It is found that K forms a metallic state when covering a graphite surface with a (2x2) coverage. For a (3x3) coverage as well as in the disperse phase K is found to form an ionic bond with graphite. It is shown that in the disperse phase, the hybridization between the K 4s level and graphite is weak. Our findings are consistent with recent experiments. Furthermore the cohesive energies of K adsorption on graphite are found to be larger in the (2x2) coverage compared to the (3x3) coverage. copyright 1998 The American Physical Society

  17. Modeling of irradiated graphite {sup 14}C transfer through engineered barriers of a generic geological repository in crystalline rocks

    Energy Technology Data Exchange (ETDEWEB)

    Poskas, Povilas; Grigaliuniene, Dalia, E-mail: Dalia.Grigaliuniene@lei.lt; Narkuniene, Asta; Kilda, Raimondas; Justinavicius, Darius

    2016-11-01

    There are two RBMK-1500 type graphite moderated reactors at the Ignalina nuclear power plant in Lithuania, and they are under decommissioning now. The graphite cannot be disposed of in a near surface repository, because of large amounts of {sup 14}C. Therefore, disposal of the graphite in a geological repository is a reasonable solution. This study presents evaluation of the {sup 14}C transfer by the groundwater pathway into the geosphere from the irradiated graphite in a generic geological repository in crystalline rocks and demonstration of the role of the different components of the engineered barrier system by performing local sensitivity analysis. The speciation of the released {sup 14}C into organic and inorganic compounds as well as the most recent information on {sup 14}C source term was taken into account. Two alternatives were considered in the analysis: disposal of graphite in containers with encapsulant and without it. It was evaluated that the maximal fractional flux of inorganic {sup 14}C into the geosphere can vary from 10{sup −} {sup 11} y{sup −} {sup 1} (for non-encapsulated graphite) to 10{sup −} {sup 12} y{sup −} {sup 1} (for encapsulated graphite) while of organic {sup 14}C it was about 10{sup −} {sup 3} y{sup −} {sup 1} of its inventory. Such difference demonstrates that investigations on the {sup 14}C inventory and chemical form in which it is released are especially important. The parameter with the highest influence on the maximal flux into the geosphere for inorganic {sup 14}C transfer was the sorption coefficient in the backfill and for organic {sup 14}C transfer – the backfill hydraulic conductivity. - Highlights: • Graphite moderated nuclear reactors are being decommissioned. • We studied interaction of disposed material with surrounding environment. • Specifically {sup 14}C transfer through engineered barriers of a geological repository. • Organic {sup 14}C flux to geosphere is considerably higher than inorganic

  18. Physics experiments in graphite lattices (1962); Experiences sur les reseaux a graphite (1962)

    Energy Technology Data Exchange (ETDEWEB)

    Bacher, P; Cogne, F [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

    1962-07-01

    A review is made of the various experimental methods used to determine the physics of graphite, natural uranium lattices: integral lattice experiments; both absolute and differential, effective cross section measurements, both by activation methods and by analysis of irradiated fuels, fine structure measurements. A number of experimental results are also given. (authors) [French] On decrit les differentes methodes experimentales utilisees pour determiner les parametres physiques de reseaux a uranium-graphite. Il s'agit d'experiences globales: mesures absolues et relatives de laplaciens, mesures de sections efficaces effectives par activation et par analyses de combustibles irradies, mesures de structures fines. Un certain nombre de resultats experimentaux sont communiques. (auteurs)

  19. Mode II interlaminar fracture of graphite/epoxy and graphite/PEEK

    Science.gov (United States)

    Carlsson, L. A.; Gillespie, J. W.; Trethewey, B. R.

    1986-01-01

    The end notched flexure (ENF) specimen is employed in an investigation of the interlaminar fracture toughness in Mode II (skew symmetric shear) loading of unidirectional graphite/epoxy and graphite/PEEK composites. Important experimental parameters such as the influence of precracking and the data reduction scheme for the Mode II toughness are discussed. Nonlinear load-deflection response is significant for the tough thermoplastic resin composite but is also present for the brittle thermoset composite. The observed nonlinearities, which are highly rate dependent, are attributed to a combination of slow stable crack growth preceding unstable crack growth and material inelastic behavior in the process zone around the crack tip.

  20. Change in properties of graphite on stake of Obninsk NPP

    International Nuclear Information System (INIS)

    Virgul'ev, Yu.S.; Gundorov, V.V.; Kalyagina, I.P.; Belinskaya, N.T.; Dolgov, V.V.; Komissarov, O.V.; Stuzhnev, Yu.A.

    1997-01-01

    The results of testing the graphite from the AM-1 reactor masonry at the Obninsk NPP for its operation period are discussed. It is shown that the masonry graphite state after 42 years of the reactor operation remains satisfactory in the most cells inspected. Separate cells requiring a repair resulted from oxidation are characterized by strength decreased by several times. The laws of radiation changes in graphite properties are analyzed. The conclusion on possibility of the further masonry operation is drawn

  1. A systematic study of acoustic emission from nuclear graphites

    International Nuclear Information System (INIS)

    Neighbour, G.B.; McEnaney, B.

    1996-01-01

    Acoustic emission (AE) monitoring has been identified as a possible method to determine internal stresses in nuclear graphites using the Kaiser effect, i.e., on stressing a graphite that has been subject to a prior stress, the onset of AE occurs at the previous peak stress. For three nuclear graphites (PGA, IM1-24 and VNEC), AE was monitored during both monotonic and cyclic loading to failure in tensile, compressive and flexural test modes. For unirradiated graphites, the Kaiser effect was not found in cyclic loading, but a Felicity effect was observed, i.e., the onset of AE occurred below the previously applied peak stress. The Felicity effect was attributed to time-dependent relaxation and recovery processes and was characterized using a new parameter, the Recovery ratio. It was shown that AE can be used to monitor creep strain and creep recovery in graphites at zero load. The AE-time responses from these experiments were fitted to equations similar to those used for creep strain-time at elevated temperatures. The number of AE counts from irradiated graphites were greater than those from unirradiated graphites, subject to similar stresses, due to increases in porosity caused by radiolytic oxidation. A Felicity effect was also observed on cyclic loading of irradiated graphites, but no evidence for a Kaiser effect was found for irradiated graphites loaded monotonically to failure. Thus internal stresses in irradiated graphites could not be measured using AE. This was attributed to relaxation and recovery processes that occur between removing the irradiated graphite from the reactor and AE testing. This work indicated that AE monitoring is not a suitable technique for measuring internal stresses in irradiated graphite. (author). 19 refs, 6 figs, 6 tabs

  2. Huge magnetoresistance effect of highly oriented pyrolytic graphite

    International Nuclear Information System (INIS)

    Du Youwei; Wang Zhiming; Ni Gang; Xing Dingyu; Xu Qingyu

    2004-01-01

    Graphite is a quasi-two-dimensional semimetal. However, for usual graphite the magnetoresistance is not so high due to its small crystal size and no preferred orientation. Huge positive magnetoresistance up to 85300% at 4.2 K and 4950% at 300 K under 8.15 T magnetic field was found in highly oriented pyrolytic graphite. The mechanism of huge positive magnetoresistance is not only due to ordinary magnetoresistance but also due to magnetic-field-driven semimetal-insulator transition

  3. Development of integrated waste management options for irradiated graphite

    Directory of Open Access Journals (Sweden)

    Alan Wareing

    2017-08-01

    Full Text Available The European Treatment and Disposal of Irradiated Graphite and other Carbonaceous Waste project sought to develop best practices in the retrieval, treatment, and disposal of irradiated graphite including other irradiated carbonaceous waste such as structural material made of graphite, nongraphitized carbon bricks, and fuel coatings. Emphasis was given on legacy irradiated graphite, as this represents a significant inventory in respective national waste management programs. This paper provides an overview of the characteristics of graphite irradiated during its use, primarily as a moderator material, within nuclear reactors. It describes the potential techniques applicable to the retrieval, treatment, recycling/reuse, and disposal of these graphite wastes. Considering the lifecycle of nuclear graphite, from manufacture to final disposal, a number of waste management options have been developed. These options consider the techniques and technologies required to address each stage of the lifecycle, such as segregation, treatment, recycle, and ultimate disposal in a radioactive waste repository, providing a toolbox to aid operators and regulators to determine the most appropriate management strategy. It is noted that national waste management programs currently have, or are in the process of developing, respective approaches to irradiated graphite management. The output of the Treatment and Disposal of Irradiated Graphite and other Carbonaceous Waste project is intended to aid these considerations, rather than dictate them.

  4. Surface coating of graphite pebbles for Korean HCCR TBM

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Youngmin [National Fusion Research Institute, Daejeon (Korea, Republic of); Yun, Young-Hoon, E-mail: yunh2@dsu.ac.kr [Dongshin University, Naju (Korea, Republic of); Park, Yi-Hyun; Ahn, Mu-Young; Cho, Seungyon [National Fusion Research Institute, Daejeon (Korea, Republic of)

    2014-10-15

    Highlights: • A CVR-SiC coating was successfully formed on graphite pebbles for neutron reflector. • Dense and fine-grained surface morphologies of the SiC coatings were observed. • Oxidation resistance of the CVR-SiC-coated graphite pebbles was improved. - Abstract: The new concept of the recently modified Helium-Cooled Ceramic Reflector (HCCR) Test Blanket Module (TBM) is to adopt a graphite reflector in the form of a pebble bed. A protective SiC coating is applied to the graphite pebbles to prohibit their reaction with steam or air as well as dust generation during TBM operation. In this research, the chemical vapor reaction (CVR) method was applied to fabricate SiC-coated graphite pebbles in a silica source. Relatively dense CVR-SiC coating was successfully formed on the graphite pebbles through the reduction of the graphite phase with SiO gas that was simply created from the silica source at 1850 °C (2 h). The microstructural features, XRD patterns, pore-size distribution and oxidation behavior of the SiC-coated graphite pebbles were investigated. To develop the practical process, which will be applied for mass production hereafter, a novel alternative method was applied to form the layer of SiC coating on the graphite pebbles over the silica source.

  5. Characteristics of first loaded IG-110 graphite in HTTR core

    International Nuclear Information System (INIS)

    Sumita, Junya; Shibata, Taiju; Iyoku, Tatsuo; Sawa, Kazuhiro; Hanawa, Satoshi; Ishihara, Masahiro

    2006-10-01

    IG-110 graphite is a fine-grained isotropic and nuclear-grade graphite with excellent resistivity on both irradiation and corrosion and with high strength. The IG-110 graphite is used for the graphite components of High Temperature Engineering Test Reactor (HTTR) such as fuel and control rod guide blocks and support posts. In order to design and fabricate the graphite components in the HTTR, the Japan Atomic Energy Research Institute (the Japan Atomic Energy Agency at present) had established the graphite structural design code and design data on the basis of former research results. After the design code establishment, the IG-110 graphite components were fabricated and loaded in the HTTR core. This report summarized the characteristics of the first loaded IG-110 graphite as basic data for surveillance test, measuring material characteristics changed by neutron irradiation and oxidation. By comparing the design data, it was shown that the first loaded IG-110 graphite had excellent strength properties and enough safety margins to the stress limits in the design code. (author)

  6. Dependence of strength on particle size in graphite

    International Nuclear Information System (INIS)

    Kennedy, E.P.; Kennedy, C.R.

    The strength to particle size relationship for specially fabricated graphites has been demonstrated and rationalized using fracture mechanics. In the past, similar studies have yielded empirical data using only commercially available material. Thus, experimental verification of these relationships has been difficult. However, the graphites of this study were fabricated by controlling the particle size ranges for a series of isotropic graphites. All graphites that were evaluated had a constant 1.85 g/cm 3 density. Thus, particle size was the only variable. This study also considered the particle size effect on other physical properties; coefficient of thermal expansion (CTE), electrical resistivity, fracture strain, and Young's modulus

  7. Graphite moderator lifecycle behaviour. Proceedings of a specialists meeting

    International Nuclear Information System (INIS)

    1996-08-01

    The meeting provided the forum for graphite specialists representing operating and research organizations worldwide to exchange information in the following areas: the status of graphite development; operation and safety procedures for existing and future graphite moderated reactors; graphite testing techniques; review of the experiences gained and data acquired on the influence of neutron irradiation and oxidizing conditions on key graphite properties; and to exchange information useful for decommissioning activities. The participants provided twenty-seven papers on behalf of their countries and respective technical organizations. An open discussion followed each of the presentations. A consistently reoccurring theme throughout the specialists meeting was the noticeable reduction in the number of graphite experts remaining the nuclear power industry. Graphite moderated power reactors have provided a significant contribution to the generation of electricity throughout the past forty years and will continue to be a prominent energy source for the future. Yet, many of the renowned experts in the field of nuclear graphites are nearing the end of their careers without apparent replacement. This, coupled with changes in the focus on nuclear power by some industrialized countries, has prompted the IAEA to initiate an evaluation on the feasibility and interest by Member States of establishing a central archive facility for the storage of data on irradiated graphites. Refs, figs, tabs

  8. A study on wear behaviour of Al/6101/graphite composites

    Directory of Open Access Journals (Sweden)

    Pardeep Sharma

    2017-03-01

    Full Text Available The current research work scrutinizes aluminium alloy 6101-graphite composites for their mechanical and tribological behaviour in dry sliding environments. The orthodox liquid casting technique had been used for the manufacturing of composite materials and imperilled to T6 heat treatment. The content of reinforcement particles was taken as 0, 4, 8, 12 and 16 wt.% of graphite to ascertain it is prospective as self-lubricating reinforcement in sliding wear environments. Hardness, tensile strength and flexural strength of cast Al6101 metal matrix and manufactured composites were evaluated. Hardness, tensile strength and flexural strength decreases with increasing volume fraction of graphite reinforcement as compared to cast Al6101 metal matrix. Wear tests were performed on pin on disc apparatus to assess the tribological behaviour of composites and to determine the optimum volume fraction of graphite for its minimum wear rate. Wear rate reduces with increase in graphite volume fraction and minimum wear rate was attained at 4 wt.% graphite. The wear was found to decrease with increase in sliding distance. The average co-efficient of friction also reduces with graphite addition and its minimum value was found to be at 4 wt.% graphite. The worn surfaces of wear specimens were studied through scanning electron microscopy. The occurrence of 4 wt.% of graphite reinforcement in the composites can reveal loftier wear possessions as compared to cast Al6101 metal matrix.

  9. Preparation of in-house graphite reference material for boron

    International Nuclear Information System (INIS)

    Kumar, Sanjukta A.; Venkatesh, K.; Swain, Kallola K.; Manisha, V.; Kamble, Granthali S.; Pandey, Shailaja P.; Remya Devi, P.S.; Ghosh, M.; Verma, R.

    2016-05-01

    Graphite is extensively used in nuclear technology. Boron concentration in graphite is one of the important parameters that decide its acceptability for nuclear applications. Reliable analytical methods are essential for the determination of boron in graphite at concentration about 5 mg kg -1 . Reference materials are used for validation of existing analytical methods and developing new methodologies. In view of the importance of determination of boron in graphite and unavailability of graphite reference material, an In-house graphite reference material was prepared in Analytical Chemistry Division. Graphite source material was procured, processed to obtain powder of ≤ 75 μm (200 mesh) and bottled. Procedures were developed for the determination of boron in graphite using inductively coupled plasma optical emission spectrometry (ICPOES) and inductively coupled plasma mass spectrometry (ICPMS) techniques. Homogeneity testing was carried out on the bottled units and boron content along with the combined and expanded uncertainties were established. The assigned boron concentration in the In-house graphite reference material is (7.3±0.46) mg kg -1 . (author)

  10. Effect of gamma radiation on graphite - PTFE dry lubrication system

    Science.gov (United States)

    Singh, Sachin; Tyagi, Mukti; Seshadri, Geetha; Tyagi, Ajay Kumar; Varshney, Lalit

    2017-12-01

    An effect of gamma radiation on lubrication behavior of graphite -PTFE dry lubrication system has been studied using (TR-TW-30L) tribometer with thrust washer attachment in plane contact. Different compositions of graphite and PTFE were prepared and irradiated by gamma rays. Gamma radiation exposure significantly improves the tribological properties indicated by decrease in coefficient of friction and wear properties of graphite -PTFE dry lubrication system. SEM and XRD analysis confirm the physico-chemical modification of graphite-PTFE on gamma radiation exposure leading to a novel dry lubrication system with good slip and anti friction properties.

  11. Graphite moderator lifecycle behaviour. Proceedings of a specialists meeting

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1996-08-01

    The meeting provided the forum for graphite specialists representing operating and research organizations worldwide to exchange information in the following areas: the status of graphite development; operation and safety procedures for existing and future graphite moderated reactors; graphite testing techniques; review of the experiences gained and data acquired on the influence of neutron irradiation and oxidizing conditions on key graphite properties; and to exchange information useful for decommissioning activities. The participants provided twenty-seven papers on behalf of their countries and respective technical organizations. An open discussion followed each of the presentations. A consistently reoccurring theme throughout the specialists meeting was the noticeable reduction in the number of graphite experts remaining the nuclear power industry. Graphite moderated power reactors have provided a significant contribution to the generation of electricity throughout the past forty years and will continue to be a prominent energy source for the future. Yet, many of the renowned experts in the field of nuclear graphites are nearing the end of their careers without apparent replacement. This, coupled with changes in the focus on nuclear power by some industrialized countries, has prompted the IAEA to initiate an evaluation on the feasibility and interest by Member States of establishing a central archive facility for the storage of data on irradiated graphites. Refs, figs, tabs.

  12. Release enhancement of tritium from graphite by addition of hydrogen

    International Nuclear Information System (INIS)

    Saeki, Masakatsu; Masaki, N.M.

    1989-01-01

    The release behavior of tritium from graphite was studied in pure He and He + H 2 atmosphere. The release from powdered graphite was significantly enhanced in hydrogen environment. Apparent diffusion coefficients of tritium in graphite also became much higher in an atmosphere containing hydrogen than values obtained in pure helium atmosphere. A careful investigation of the release processes resulted in the conclusion that the most important process of tritium behaviour in graphite was diffusion, but the desorption process of tritium from the surface played a significant role. The enhancement of the desorption process was controlled by atomic hydrogen. (orig.)

  13. Development of integrated waste management options for irradiated graphite

    Energy Technology Data Exchange (ETDEWEB)

    Wareing, Alan; Abrahamsen-Mills, Liam; Fowler, Linda; Jarvis, Richard; Banford, Anthony William [National Nuclear Laboratory, Warrington (United Kingdom); Grave, Michael [Doosan Babcock, Gateshead (United Kingdom); Metcalfe, Martin [National Nuclear Laboratory, Gloucestershire (United Kingdom); Norris, Simon [Radioactive Waste Management Limited, Oxon (United Kingdom)

    2017-08-15

    The European Treatment and Disposal of Irradiated Graphite and other Carbonaceous Waste project sought to develop best practices in the retrieval, treatment, and disposal of irradiated graphite including other irradiated carbonaceous waste such as structural material made of graphite, nongraphitized carbon bricks, and fuel coatings. Emphasis was given on legacy irradiated graphite, as this represents a significant inventory in respective national waste management programs. This paper provides an overview of the characteristics of graphite irradiated during its use, primarily as a moderator material, within nuclear reactors. It describes the potential techniques applicable to the retrieval, treatment, recycling/reuse, and disposal of these graphite wastes. Considering the lifecycle of nuclear graphite, from manufacture to final disposal, a number of waste management options have been developed. These options consider the techniques and technologies required to address each stage of the lifecycle, such as segregation, treatment, recycle, and ultimate disposal in a radioactive waste repository, providing a toolbox to aid operators and regulators to determine the most appropriate management strategy. It is noted that national waste management programs currently have, or are in the process of developing, respective approaches to irradiated graphite management. The output of the Treatment and Disposal of Irradiated Graphite and other Carbonaceous Waste project is intended to aid these considerations, rather than dictate them.

  14. Forming gas treatment of lithium ion battery anode graphite powders

    Science.gov (United States)

    Contescu, Cristian Ion; Gallego, Nidia C; Howe, Jane Y; Meyer, III, Harry M; Payzant, Edward Andrew; Wood, III, David L; Yoon, Sang Young

    2014-09-16

    The invention provides a method of making a battery anode in which a quantity of graphite powder is provided. The temperature of the graphite powder is raised from a starting temperature to a first temperature between 1000 and 2000.degree. C. during a first heating period. The graphite powder is then cooled to a final temperature during a cool down period. The graphite powder is contacted with a forming gas during at least one of the first heating period and the cool down period. The forming gas includes H.sub.2 and an inert gas.

  15. Floatability study of graphite ore from southeast Sulawesi (Indonesia)

    Science.gov (United States)

    Florena, Fenfen Fenda; Syarifuddin, Fahmi; Hanam, Eko Sulistio; Trisko, Nici; Kustiyanto, Eko; Enilisiana, Rianto, Anton; Arinton, Ghenadi

    2016-02-01

    Graphite ore obtained from Kolaka Regency, South East Sulawesi, Indonesia have been succesfully investigated for beneficiation by froth flotation technique. Preliminary study have been done to determine the minerals types, fixed carbon content and liberation size of the graphite. Graphite is naturally floatable due to its hydrophobic property. Some suitable reagents are usually added to increase effectiveness of recovery. In this article, enrichment of graphite by froth flotation was studied by investigating the effect of reagents concentrations, rotation speed and particle size on the carbon grade and recovery of the concentrate. The carbon grade increased from 3.00% to 60.00% at the optimum flotation conditions.

  16. Surface coating of graphite pebbles for Korean HCCR TBM

    International Nuclear Information System (INIS)

    Lee, Youngmin; Yun, Young-Hoon; Park, Yi-Hyun; Ahn, Mu-Young; Cho, Seungyon

    2014-01-01

    Highlights: • A CVR-SiC coating was successfully formed on graphite pebbles for neutron reflector. • Dense and fine-grained surface morphologies of the SiC coatings were observed. • Oxidation resistance of the CVR-SiC-coated graphite pebbles was improved. - Abstract: The new concept of the recently modified Helium-Cooled Ceramic Reflector (HCCR) Test Blanket Module (TBM) is to adopt a graphite reflector in the form of a pebble bed. A protective SiC coating is applied to the graphite pebbles to prohibit their reaction with steam or air as well as dust generation during TBM operation. In this research, the chemical vapor reaction (CVR) method was applied to fabricate SiC-coated graphite pebbles in a silica source. Relatively dense CVR-SiC coating was successfully formed on the graphite pebbles through the reduction of the graphite phase with SiO gas that was simply created from the silica source at 1850 °C (2 h). The microstructural features, XRD patterns, pore-size distribution and oxidation behavior of the SiC-coated graphite pebbles were investigated. To develop the practical process, which will be applied for mass production hereafter, a novel alternative method was applied to form the layer of SiC coating on the graphite pebbles over the silica source

  17. Graphite structure and its relation to mechanical engineering design

    International Nuclear Information System (INIS)

    Brocklehurst, J.E.; Kelly, B.T.

    1980-01-01

    The inhomogeneous nature of polycrystalline graphite requires property measurements to be made over dimensions large enough to average the local variations in the structure. This is particularly true for mechanical integrity, and experimental data are presented which illustrate the importance of the real aggregate structure of graphite and the difficulties of interpreting strength data from different tests. The classical statistical treatments do not hold generally, and the problem of defining a failure criterion for graphite is discussed. It is suggested that the stress conditions in graphite components might be classified in terms of the dimensions and stress gradients related to the characteristic flaw size of the material as determined experimentally. (author)

  18. Final report on graphite irradiation test OG-2

    International Nuclear Information System (INIS)

    Price, R.J.; Beavan, L.A.

    1975-01-01

    Results are presented of dimensional, thermal expansivity, thermal conductivity, Young's modulus, and tensile strength measurements on specimens of nuclear graphites irradiated in capsule OG-2. About half the irradiation space was allocated to H-451 near-isotropic petroleum-coke-based graphite or its subsized prototype grade H-429. Most of these specimens had been previously irradiated. Virgin specimens of another near-isotropic graphite, grade TS-1240, were irradiated. Some previously irradiated specimens of needle-coke-based H-327 graphite and pitch-coke-based P 3 JHAN were also included

  19. Impacts of Artificial Reefs on Surrounding Ecosystems

    Science.gov (United States)

    Manoukian, Sarine

    Artificial reefs are becoming a popular biological and management component in shallow water environments characterized by soft seabed, representing both important marine habitats and tools to manage coastal fisheries and resources. An artificial reef in the marine environment acts as an open system with exchange of material and energy, altering the physical and biological characteristics of the surrounding area. Reef stability will depend on the balance of scour, settlement, and burial resulting from ocean conditions over time. Because of the unstable nature of sediments, they require a detailed and systematic investigation. Acoustic systems like high-frequency multibeam sonar are efficient tools in monitoring the environmental evolution around artificial reefs, whereas water turbidity can limit visual dive and ROV inspections. A high-frequency multibeam echo sounder offers the potential of detecting fine-scale distribution of reef units, providing an unprecedented level of resolution, coverage, and spatial definition. How do artificial reefs change over time in relation to the coastal processes? How accurately does multibeam technology map different typologies of artificial modules of known size and shape? How do artificial reefs affect fish school behavior? What are the limitations of multibeam technology for investigating fish school distribution as well as spatial and temporal changes? This study addresses the above questions and presents results of a new approach for artificial reef seafloor mapping over time, based upon an integrated analysis of multibeam swath bathymetry data and geoscientific information (backscatter data analysis, SCUBA observations, physical oceanographic data, and previous findings on the geology and sedimentation processes, integrated with unpublished data) from Senigallia artificial reef, northwestern Adriatic Sea (Italy) and St. Petersburg Beach Reef, west-central Florida continental shelf. A new approach for observation of fish

  20. Characterization of un-irradiated and irradiated reactor graphite; Karakterizacija neozracenog i ozracenog reaktorskog grafita

    Energy Technology Data Exchange (ETDEWEB)

    Marinkovic, S [Institute of Nuclear Sciences Boris Kidric, Vinca, Beograd (Yugoslavia)

    1965-11-15

    This report contains three parts: characterization of Yugoslav nuclear graphite development of methods and obtained results, characterization of un-irradiated and irradiated domestic nuclear graphite; calculation of electrical conductivity changes due to vacancies in the graphite crystal lattice.

  1. Carbon-14 in neutron-irradiated graphite for graphite-moderated reactors. Joint research

    Energy Technology Data Exchange (ETDEWEB)

    Fujii, Kimio [Japan Atomic Energy Research Inst., Tokai, Ibaraki (Japan). Tokai Research Establishment; Matsuo, Hideto [Radioactive Waste Management and Nuclear Facility Decommissioning Technology Center, Tokyo (Japan)

    2002-12-01

    The graphite moderated gas cooled reactor operated by the Japan Atomic Power Company was stopped its commercial operation on March 1998, and the decommissioning process has been started. Graphite material is often used as the moderator and the reflector materials in the core of the gas cooled reactor. During the operation, a long life nuclide of {sup 14}C is generated in the graphite by several transmutation reactions. Separation of {sup 14}C isotope and the development of the separation method have been recognized to be critical issues for the decommissioning of the reactor core. To understand the current methodologies for the carbon isotope separation, literature on the subject was surveyed. Also, those on the physical and chemical behavior of {sup 14}C were surveyed. This is because the larger part of the nuclides in the graphite is produced from {sup 14}N by (n,p) reaction, and the location of them in the material tends to be different from those of the other carbon atoms. This report summarizes the result of survey on the open literature about the behavior of {sup 14}C and the separation methods, including the list of the literature on these subjects. (author)

  2. Misorientations in spheroidal graphite: some new insights about spheroidal graphite growth in cast irons

    International Nuclear Information System (INIS)

    Lacaze, J; Theuwissen, K; Laffont, L; Véron, M

    2016-01-01

    Local diffraction patterning, orientation mapping and high resolution transmission electron microscopy imaging have been used to characterize misorientations in graphite spheroids of cast irons. Emphasis is put here on bulk graphite, away from the nucleus as well as from the outer surface of the spheroids in order to get information on their growth during solidification. The results show that spheroidal graphite consists in conical sectors made of elementary blocks piled up on each other. These blocks are elongated along the prismatic a direction of graphite with the c axes roughly parallel to the radius of the spheroids. This implies that the orientation of the blocks rotates around the spheroid centre giving low angle tilting misorientations along tangential direction within each sector. Misorientations between neighbouring sectors are of higher values and their interfaces show rippled layers which are characteristic of defects in graphene. Along a radius of the spheroid, clockwise and anticlockwise twisting between blocks is observed. These observations help challenging some of the models proposed to explain spheroidal growth in cast ions. (paper)

  3. Bioinspired photonic nanoarchitectures from graphitic thin films

    Energy Technology Data Exchange (ETDEWEB)

    Tamaska, I.; Dobrik, G.; Nemes-Incze, P.; Kertesz, K.; Horvath, E.; Mark, G.I.; Jaszi, T.; Neumann, P.; Horvath, Z.E.; Biro, L.P., E-mail: biro@mfa.kfki.h

    2011-04-01

    Bioinspired, regular, rectangular (with periodicities of 600 nm and 700 nm), and random (with average characteristic distances of 600 nm and 750 nm) two dimensional (2D) photonic nanoarchitectures of 60 nm thickness were produced in graphite by Focused Ion Beam (FIB) nanomachining and subsequent controlled oxidation. The color of the nanoarchitectures was modified by the conformal deposition of 90 nm Al{sub 2}O{sub 3}. The regular patterns generate iridescent colors, while the random ones exhibit a remarkably constant color with the variation of the illumination and viewing conditions.

  4. Bioinspired photonic nanoarchitectures from graphitic thin films

    International Nuclear Information System (INIS)

    Tamaska, I.; Dobrik, G.; Nemes-Incze, P.; Kertesz, K.; Horvath, E.; Mark, G.I.; Jaszi, T.; Neumann, P.; Horvath, Z.E.; Biro, L.P.

    2011-01-01

    Bioinspired, regular, rectangular (with periodicities of 600 nm and 700 nm), and random (with average characteristic distances of 600 nm and 750 nm) two dimensional (2D) photonic nanoarchitectures of 60 nm thickness were produced in graphite by Focused Ion Beam (FIB) nanomachining and subsequent controlled oxidation. The color of the nanoarchitectures was modified by the conformal deposition of 90 nm Al 2 O 3 . The regular patterns generate iridescent colors, while the random ones exhibit a remarkably constant color with the variation of the illumination and viewing conditions.

  5. Magnetic order in graphite: Experimental evidence, intrinsic and extrinsic difficulties

    International Nuclear Information System (INIS)

    Esquinazi, P.; Barzola-Quiquia, J.; Spemann, D.; Rothermel, M.; Ohldag, H.; Garcia, N.; Setzer, A.; Butz, T.

    2010-01-01

    We discuss recently obtained data using different experimental methods including magnetoresistance measurements that indicate the existence of metal-free high-temperature magnetic order in graphite. Intrinsic as well as extrinsic difficulties to trigger magnetic order by irradiation of graphite are discussed in view of recently published theoretical work.

  6. Modeling the pinning of Au and Ni clusters on graphite

    NARCIS (Netherlands)

    Smith, R.; Nock, C.; Kenny, S.D.; Belbruno, J.J.; Di Vece, M.; Paloma, S.; Palmer, R.E.

    2006-01-01

    The pinning of size-selected AuN and NiN clusters on graphite, for N=7–100, is investigated by means of molecular dynamics simulations and the results are compared to experiment and previous work with Ag clusters. Ab initio calculations of the binding of the metal adatom and dimers on a graphite

  7. Design of the Graphite Reflectors in Research Reactors

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Jin Haeng; Cho, Yeong Garp; Kim, Tae Kyu; Kim, Jong In [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

    2012-05-15

    Graphite is often used as one of reflector materials for research reactors because of its low neutron absorption cross-section, good moderating properties, and relatively low and stable price. In addition, graphite has excellent properties at high temperatures, so it is widely used as a core material in high temperature reactors. However, its material characteristics such as strength, elastic modulus, thermal expansion coefficient, dimensional change, and thermal conductivity sensitively depend on neutron fluence, temperature, and its manufacturing process. In addition, the Wigner energy and the treatment of the graphite waste such as C-14 should also be considered. For the design of the graphite reflectors, it is therefore essential to understand the material characteristics of chosen graphite materials at given conditions. Especially, the dimensional changes and the thermal conductivity are very important factors to design the nuclear components using graphite as a nonstructural material. Hence, in this study, the material characteristics of graphite are investigated via some experiments in literature. Improving design methods for graphite reflectors in research reactors are then suggested to minimize the problems, and the advantages and disadvantages of each method are also discussed

  8. The role of graphite morphology and matrix structure on low ...

    Indian Academy of Sciences (India)

    R. Narasimhan (Krishtel eMaging) 1461 1996 Oct 15 13:05:22

    Thermal cycling resistance; graphite morphology; grey cast iron; austempered ductile iron; compacted/vermicular graphite iron; matrix decompo- sition. 1. Introduction. When a material is subjected to a temperature gradient, it tends to expand differentially. During this process, thermal stresses are induced. The source of ...

  9. USE OF GRANULAR GRAPHITE FOR ELECTROLYTIC DECHLORINATION OF TRICHLOROETHYLENE

    Science.gov (United States)

    Granular graphite is a potential electrode material for the electrochemical remediation of refractory chlorinated organic compounds such as trichloroethylene (TCE). However, the use of granular graphite can complicate the experimental results. On one hand, up to 99% of TCE was re...

  10. Automotive body panel containing thermally exfoliated graphite oxide

    Science.gov (United States)

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

    2011-01-01

    An automotive body panel containing a polymer composite formed of at least one polymer and a modified graphite oxide material, which is a thermally exfoliated graphite oxide with a surface area of from about 300 m.sup.2/g to 2600 m.sup.2/g.

  11. Development of synthetic graphite resistive elements for sintering furnace

    International Nuclear Information System (INIS)

    Otani, C.; Rezende, Mirabel C.; Polidoro, H.A.; Otani, S.

    1987-01-01

    The synthetic graphites have been produced using lignin coke, natural graphite and phenolic resin. The bulk density, porosity, flexural strength and eletrical resistivity measurements have been performed on specimens at about 2400 0 C. The performance of these materials, as heating elements, was evaluated in a sintering furnace prototype. This paper reports the fabrication process and the experimental results. (Author) [pt

  12. Measurement of the specific heat capacity of graphite

    Energy Technology Data Exchange (ETDEWEB)

    Picard, S.; Burns, D.T.; Roger, P

    2006-01-15

    With the objective of implementing graphite calorimetry at the BIPM to measure absorbed dose, an experimental assembly has recently been constructed to measure the specific heat capacity of graphite. A status description of the apparatus and results from the first measurements are given. The outcome is discussed and the experimental uncertainty is reviewed. (authors)

  13. Computer Package for Graphite Total Cross-Section Calculations

    International Nuclear Information System (INIS)

    Adib, M.; Fathalla, M.

    2008-01-01

    An additive formula is given which allows calculating the contribution of the total neut.>neutron transmission through crystalline graphite. The formula takes into account the graphite form of poly or pyrolytic crystals and its parameters. Computer package Graphite has been designed in order to provide the required calculations in the neutron energy range from 0.1 MeV to 10 eV. The package includes three codes: PCG (Polycrystalline Graphite), PG (Pyrolytic Graphite) and HOPG (Highly Oriented Pyrolytic Graphite) for calculating neutron transmission through fine graphite powder (polycrystalline), neutron transmission and removal coefficient of PG crystal in terms of its mosaic spread for neutrons incident along its c-axis and the transmission of neutrons incident on HOPG crystal at different angles, respectively. For comparison of the experimental neutron transmission data with the calculated values, the program takes into consideration the effect of both wavelength and neutron beam divergence in either 2 constant wavelength spread mode (δλ=constant) or constant wavelength resolution mode (δλ/λ=constant). In order to check the validity for application of computer package Graphite in cross-section calculations, a comparison between calculated values with the available experimental data were carried out. An overall agreement is indicated with an accuracy sufficient for determine the neutron transmission characteristics

  14. Measurements of anomalous neutron transport in bulk graphite

    International Nuclear Information System (INIS)

    Bowman, C.D.; Smith, G.A.; Vogelaar, B.; Howell, C.R.; Bilpuch, E.G.; Tornow, W.

    2003-01-01

    The neutron absorption of bulk granular graphite has been measured in a classical exponential diffusion experiment. Our first measurements of April 2002 implementing both exponential decay and pulsed die-away experiments and using the TUNL pulsed accelerator at Duke University as a neutron source indicated a capture cross section for graphite a striking factor of three lower than the measured value for carbon of 3.4 millibarns. Therefore a new exponential experiment with an improved geometry enabling greater accuracy has been performed giving an apparent cross section for carbon in the form of bulk granular graphite of less than 0.5 millibarns. This result confirms our first result and is also consistent with less than one part per million of boron in our graphite. The bulk density of the graphite is 1.02 compared with the actual particle density of 1.60 indicating a packing fraction of 0.64 or a void fraction of 0.36. We suspect that the apparent suppression of absorption in bulk graphite may be associated with the strong coherent diffraction of neutrons that dominates neutron transport in graphite. Coherent diffraction has never been taken into account in graphite reactor design and no neutron transport code including general use codes such as MCNP incorporate diffraction effects even though diffraction dominates many practical thermal neutron transport problems. (orig.)

  15. Structural and Kinetic Properties of Graphite Intercalation Compounds

    Science.gov (United States)

    1983-04-29

    The exfoliation of graphite-FeCl 3NH has been used for making blankets for the extinction of metal fires [12). In addition. exfoliated graphite is...FeCl3-oH3 has been used (Aerotech GCma, 0.5 MHz wideband) equipped with for making blankets for the extinction of metal fires (3). In addition

  16. Graphite-based extinguishants for liquid metal fires

    International Nuclear Information System (INIS)

    Simpson, J.M.; Gardener, N.J.L.

    1987-01-01

    Effective extinguishants for liquid alkali metal fires must be provided for all LMFBRs. Traditional sodium salt based extinguishants have disadvantages. An intercalation compound of graphite was identified as a possible alternative. Following successful tests on fires of up to 25 m 2 area the graphite based extinguishant has been introduced by the UKAEA at Dounreay. (author)

  17. Technical development of graphite waste treatment in NUPEC

    International Nuclear Information System (INIS)

    Saishu, S.; Inoue, T.

    2001-01-01

    In Japan, Tokai Power Station, which is a Gas Cooled Reactor and uses graphite as moderator, ceased operation at the end of March in 1998 and it is planned to transfer to decommissioning stage. In this decommissioning stage it is very important to be able to treat and dispose the graphite waste in order to carry out the decommissioning safely and economically. NUPEC has been developing the graphite treatment and disposal technology since 1997 and we introduce the outline of the technical development. For the technology on high density packing into disposal container, the high density packing method and the assessment method on nuclide leaching characteristics were developed, and the cementing test for graphite powder by using Tokai spare graphite was performed and the hydrophobic characteristics between graphite and cement was grasped and the accelerator candidature for affinity was selected. From the view point of economical treatment, the incinerating technology was selected as candidature, and the methods for incinerating graphite and treating off gas are developed. The method of collecting C-14 in off gas was selected for reducing the off gas radiation level. The applicability of actual graphite treatment technology was considered from the view point of safety, economics and preparation of technical standard; the technical theme appeared, the developing planning items were established, and the detailed and actual scale tests will be carried out according to the planning. (author)

  18. Measurement of the specific heat capacity of graphite

    International Nuclear Information System (INIS)

    Picard, S.; Burns, D.T.; Roger, P.

    2006-01-01

    With the objective of implementing graphite calorimetry at the BIPM to measure absorbed dose, an experimental assembly has recently been constructed to measure the specific heat capacity of graphite. A status description of the apparatus and results from the first measurements are given. The outcome is discussed and the experimental uncertainty is reviewed. (authors)

  19. A TEM Study on the Microstructure of Fine Flaky Graphite

    DEFF Research Database (Denmark)

    Moumeni, Elham; Tiedje, Niels Skat; Horsewell, Andy

    In this investigation the microstructure of the graphite flakes in titanium alloyed cast iron is studied using electron microscopy techniques. Based on this information, growth models for the platelets in the fine graphite flakes in cast iron are considered. Detailed crystallographic analysis...... of the defects observed such as multiple twin boundaries and possible spiral growth configurations are required...

  20. Linear expansion of products out of thermal splitting graphite

    International Nuclear Information System (INIS)

    Tishina, E.A.; Kurnevich, G.I.

    1994-01-01

    Linear expansion of thermally split graphite in the form of foil and pressed items of different density was studied. It is ascertained that the extreme character of temperature dependence of linear expansion factor of pressed samples of thermally split graphite is determined by the formation of closed pores containing air in the course of their production. 3 refs., 2 figs

  1. Measurements of anomalous neutron transport in bulk graphite

    Energy Technology Data Exchange (ETDEWEB)

    Bowman, C.D.; Smith, G.A. [ADNA Corp., Los Alamos, NM (United States); Vogelaar, B. [Virginia Tech., Blacksburg, VA (United States); Howell, C.R.; Bilpuch, E.G.; Tornow, W. [Triangle Univ. Nuclear Lab., Duke Univ., Durham, NC (United States)

    2003-07-01

    The neutron absorption of bulk granular graphite has been measured in a classical exponential diffusion experiment. Our first measurements of April 2002 implementing both exponential decay and pulsed die-away experiments and using the TUNL pulsed accelerator at Duke University as a neutron source indicated a capture cross section for graphite a striking factor of three lower than the measured value for carbon of 3.4 millibarns. Therefore a new exponential experiment with an improved geometry enabling greater accuracy has been performed giving an apparent cross section for carbon in the form of bulk granular graphite of less than 0.5 millibarns. This result confirms our first result and is also consistent with less than one part per million of boron in our graphite. The bulk density of the graphite is 1.02 compared with the actual particle density of 1.60 indicating a packing fraction of 0.64 or a void fraction of 0.36. We suspect that the apparent suppression of absorption in bulk graphite may be associated with the strong coherent diffraction of neutrons that dominates neutron transport in graphite. Coherent diffraction has never been taken into account in graphite reactor design and no neutron transport code including general use codes such as MCNP incorporate diffraction effects even though diffraction dominates many practical thermal neutron transport problems. (orig.)

  2. Evaluation of ac conductivity behaviour of graphite filled

    Indian Academy of Sciences (India)

    Composites of epoxy resin having different amounts of graphite particles have been prepared by solution casting method. Temperature dependence of dielectric constant, tan and a.c. conductivity was measured in the frequency range, 1–20 kHz, temperature range, 40–180°C for 0.99, 1.96 and 2.91 wt% graphite filled ...

  3. Neutron transmission through pyrolytic graphite crystals

    Energy Technology Data Exchange (ETDEWEB)

    Adib, M. [Reactor Physics Department NRC, Reactor Physics Division, Nuclear Research Center, Egyptian Atomic Energy Authority, Cairo 13759 (Egypt); Habib, N. [Reactor Physics Department NRC, Reactor Physics Division, Nuclear Research Center, Egyptian Atomic Energy Authority, Cairo 13759 (Egypt)]. E-mail: nadiahabib15@yahoo.com; Fathaalla, M. [Reactor Physics Department NRC, Reactor Physics Division, Nuclear Research Center, Egyptian Atomic Energy Authority, Cairo 13759 (Egypt)

    2006-05-15

    Calculation of the total cross-section, neutron transmission and removal coefficient of pyrolytic graphite (PG) for thermal neutron energies were carried out using an additive formula. The formula takes into account the variation of thermal diffuse and Bragg scattering cross-sections in terms of PG temperature and mosaic spread for neutron energies in the range 1 meV to 1 eV. A computer code PG has been developed which allow calculations for the graphite in its hexagonal close-packed structure, when its c-direction is parallel with incident neutron beam (parallel orientation). The calculated total neutron cross-sections for PG in parallel orientation at different mosaic spreads were compared with the measured values. An overall agreement is indicated between the formula fits and experimental data at room and liquid nitrogen temperatures. A feasibility study for use of PG crystals as second-order neutron filter is detailed in terms of mosaic spread, optimum thickness and temperature. The calculated removal coefficients of PG crystals show that such crystals are high efficiency second-order filter within neutron energy intervals (4-7 meV) and (10-15 meV)

  4. Multiscale modeling of polyisoprene on graphite

    International Nuclear Information System (INIS)

    Pandey, Yogendra Narayan; Brayton, Alexander; Doxastakis, Manolis; Burkhart, Craig; Papakonstantopoulos, George J.

    2014-01-01

    The local dynamics and the conformational properties of polyisoprene next to a smooth graphite surface constructed by graphene layers are studied by a multiscale methodology. First, fully atomistic molecular dynamics simulations of oligomers next to the surface are performed. Subsequently, Monte Carlo simulations of a systematically derived coarse-grained model generate numerous uncorrelated structures for polymer systems. A new reverse backmapping strategy is presented that reintroduces atomistic detail. Finally, multiple extensive fully atomistic simulations with large systems of long macromolecules are employed to examine local dynamics in proximity to graphite. Polyisoprene repeat units arrange close to a parallel configuration with chains exhibiting a distribution of contact lengths. Efficient Monte Carlo algorithms with the coarse-grain model are capable of sampling these distributions for any molecular weight in quantitative agreement with predictions from atomistic models. Furthermore, molecular dynamics simulations with well-equilibrated systems at all length-scales support an increased dynamic heterogeneity that is emerging from both intermolecular interactions with the flat surface and intramolecular cooperativity. This study provides a detailed comprehensive picture of polyisoprene on a flat surface and consists of an effort to characterize such systems in atomistic detail

  5. High thermoelectric performance of graphite nanofibers.

    Science.gov (United States)

    Tran, Van-Truong; Saint-Martin, Jérôme; Dollfus, Philippe; Volz, Sebastian

    2018-02-22

    Graphite nanofibers (GNFs) have been demonstrated to be a promising material for hydrogen storage and heat management in electronic devices. Here, by means of first-principles and transport simulations, we show that GNFs can also be an excellent material for thermoelectric applications thanks to the interlayer weak van der Waals interaction that induces low thermal conductance and a step-like shape in the electronic transmission with mini-gaps, which are necessary ingredients to achieve high thermoelectric performance. This study unveils that the platelet form of GNFs in which graphite layers are perpendicular to the fiber axis can exhibit outstanding thermoelectric properties with a figure of merit ZT reaching 3.55 in a 0.5 nm diameter fiber and 1.1 in a 1.1 nm diameter one. Interestingly, by introducing 14 C isotope doping, ZT can even be enhanced up to more than 5, and more than 8 if we include the effect of finite phonon mean free path, which demonstrates the amazing thermoelectric potential of GNFs.

  6. Evaluation of the significance of inverse oxidation for HTGR graphites

    International Nuclear Information System (INIS)

    Lee, B.S.; Heiser, J. III; Sastre, C.

    1983-01-01

    The inverse oxidation refers to a higher mass loss inside the graphite than the outside. In 1980, Wichner et al reported this phenomenon (referred to as inside/out corrosion) observed in some H451 graphites, and offered an explanation that a catalyst (almost certainly Fe) is activated by the progressively increasing reducing conditions found in the graphite interior. Recently, Morgan and Thomas (1982) investigated this phenomenon is PGX graphites, and agreed on the existing mechanism to explain this pheomenon. They also called for attention to the possibility that this phenomenon may occur under HTGR (High Temperature Gas-Cooled Reactor) operating conditions. The purpose of this paper is to confirm the above mentioned explanation for this phenomenon and to evaluate the significance of this effect for HTGR graphites under realistic reactor conditions

  7. Structures and Performance of Graphene/Polyimide Composite Graphite Fibers

    Directory of Open Access Journals (Sweden)

    LI Na

    2017-09-01

    Full Text Available Dry-wet spinning process was used to gain graphene oxide/polyimide composite fibers, then graphene/polyimide composite carbon and graphite fibers were obtained through carbonized and graphitized. Different graphene oxide contents of the composite carbon and graphite fibers were measured by thermal gravimetric analysis, Raman, mechanical properties, electrical properties,SEM and so on. The results show that when the GO content is 0.3%(mass fraction,the same below, the thermal property of the graphene oxide/polyimide composite fibers is the best. The mechanical and electrical properties are obriously improved by the addition of GO, graphitization degree also increases. When the composite carbon fibers are treated at 2800℃, GO content increases to 2.0%, the thermal conductivity of the composite graphite fibers reaches 435.57W·m-1·K-1 and cross-section structures of carbon fibers are more compact.

  8. Chemical vapor deposition of TiB2 on graphite

    International Nuclear Information System (INIS)

    Pierson, H.O.; Randich, E.; Mattox, D.M.

    1978-01-01

    This study is an experimental investigation of the coating of graphite with TiB 2 by chemical vapor deposition (CVD) using the hydrogen reduction of BCl 3 and TiCl 4 at 925 0 C and 1 atm. Reasonable matching of the thermal expansion of TiB 2 and graphite was necessary to eliminate cracking. A suitable graphite was POCO DFP-1. Adhesion was improved by having a slightly rough graphite surface. Heat treatment at 2000 0 C and above resulted in a certain degree of diffusion. No melting or solid phases other than TiB 2 and graphite were detected up to 2400 0 C. The coatings showed no failure when repeatedly submitted to an electron beam pulse of 2 KW/cm 2 for 0.8 sec

  9. Lithium isotope effect accompanying electrochemical intercalation of lithium into graphite

    CERN Document Server

    Yanase, S; Oi, T

    2003-01-01

    Lithium has been electrochemically intercalated from a 1:2 (v/v) mixed solution of ethylene carbonate (EC) and methylethyl carbonate (MEC) containing 1 M LiClO sub 4 into graphite, and the lithium isotope fractionation accompanying the intercalation was observed. The lighter isotope was preferentially fractionated into graphite. The single-stage lithium isotope separation factor ranged from 1.007 to 1.025 at 25 C and depended little on the mole ratio of lithium to carbon of the lithium-graphite intercalation compounds (Li-GIC) formed. The separation factor increased with the relative content of lithium. This dependence seems consistent with the existence of an equilibrium isotope effect between the solvated lithium ion in the EC/MEC electrolyte solution and the lithium in graphite, and with the formation of a solid electrolyte interfaces on graphite at the early stage of intercalation. (orig.)

  10. Effect of Graphite on the Properties of Natural Rubber

    Directory of Open Access Journals (Sweden)

    Auda jabber Braihi

    2016-09-01

    Full Text Available Natural rubber-graphite composites (0, 1, 2, 3, 4 pphr graphite were prepared on a laboratory two-roll mill. Swelling measurements were used to evaluate the impacts of graphite on the properties of natural rubber. Swelling results showed that the volume fraction of natural rubber in the swollen gel, the interaction parameter, and the cross-link density decreased by increasing graphite loadings, while the average molecular weight of natural rubber between cross-links increased. Vulcanization results showed that only scorch time parameter increased with increasing graphite loadings, while other parameters (Max. torque, Min. torque, cure rate and cure rate index decreased. Both thermal and AC conductivities increased.

  11. Variation of the properties of siliconized graphite during neutron irradiation

    International Nuclear Information System (INIS)

    Virgil'ev, Y.S.; Chugunova, T.K.; Pikulik, R.G.

    1986-01-01

    The authors evaluate the radiation-induced property changes in siliconized graphite of the industrial grades SG-P and SG-M. The authors simultaneously tested the reference (control) specimens of graphite that are used as the base for obtaining the SG-M siliconized graphite by impregnating with silicon. The suggested scheme (model) atributes the dimensional changes of the siliconized graphite specimens to the effect of the quantitative ratio of the carbide phase and carbon under different conditions of irradiation. If silicon is insufficient for the formation of a dense skeleton, graphite plays a devisive role, and it may be assumed that at an irradiation temperature greater than 600 K, the material shrinks. The presence of isolated carbide inclusions also affects the physicomechanical properties (including the anitfriction properties)

  12. Graphitization of diamond with a metallic coating on ferritic matrix

    International Nuclear Information System (INIS)

    Cabral, Stenio Cavalier; Oliveira, Hellen Cristine Prata de; Filgueira, Marcello

    2010-01-01

    Iron is a strong catalyst of graphitization of diamonds. This graphitization occurs mainly during the processing of composites - conventional sintering or hot pressing, and during cutting operations. Aiming to avoid or minimize this deleterious effect, there is increasing use of diamond coated with metallic materials in the production of diamond tools processed via powder metallurgy. This work studies the influence of Fe on diamond graphitization diamond-coated Ti after mixing of Fe-diamonds, hot pressing parameters were performed with 3 minutes/35MPa/900 deg C - this is the condition of pressing hot used in industry for production of diamond tools. Microstructural features were observed by SEM, diffusion of Fe in diamond was studied by EDS. Graphitization was analyzed by X-ray diffraction and Raman spectroscopy. It was found that Fe not activate graphitization on the diamond under the conditions of hot pressing. (author)

  13. Fort St. Vrain graphite site mechanical separation concept selection

    International Nuclear Information System (INIS)

    Berry, S.M.

    1993-09-01

    One of the alternatives to the disposal of the Fort St. Vrain (FSV) reactor spent nuclear fuel involves the separation of the fuel rods composed of compacts from the graphite fuel block assembly. After the separation of these two components, the empty graphite fuel blocks would be disposed of as a low level waste (provided the appropriate requirements are met) and the fuel compacts would be treated as high level waste material. This report deals with the mechanical separation aspects concerning physical disassembly of the FSV graphite fuel element into the empty graphite fuel blocks and fuel compacts. This report recommends that a drilling technique is the preferred choice for accessing the, fuel channel holes and that each hole is drilled separately. This report does not cover any techniques or methods to separate the triso fuel particles from the graphite matrix of the fuel compacts

  14. Impermeable Graphite: A New Development for Embedding Radioactive Waste

    International Nuclear Information System (INIS)

    Fachinger, Johannes

    2016-01-01

    Irradiated graphite has to be handled as radioactive waste after the operational period of the reactor. However, the waste management of irradiated graphite e.g. from the Spanish Vandellos reactor shows, that waste management of even low contaminated graphite could be expensive and requires special retrieval, treatment and disposal technologies for safe long term storage as low or medium radioactive waste. FNAG has developed an impermeable graphite matrix (IGM) as nuclear waste embedding material. This IGM provides a long term stable enclosure of radioactive waste and can reuse irradiated graphite as feedstock material. Therefore, no additional disposal volume is required if e.g. concrete waste packages were replaced by IGM waste packages. The variability of IGM as embedding has been summarized in the following paper usable for metal scraps, ion exchange resins or debris from buildings. Furthermore the main physical, chemical and structural properties are described. (author)

  15. Rate-dependent mode I interlaminar crack growth mechanisms in graphite/epoxy and graphite/PEEK

    Science.gov (United States)

    Gillespie, J. W., Jr.; Carlsson, L. A.; Smiley, A. J.

    1987-01-01

    In this paper the mode I fracture behavior of graphite/epoxy and graphite/PEEK composites is examined over four decades of crosshead rates (0.25-250 mm/min). Straight-sided double-cantilever-beam specimens consisting of unidirectional laminates were tested at room temperature. For graphite/epoxy the load-deflection response was linear to fracture, and stable slow crack growth initiating at the highest load level was observed for all rates tested. In contrast, mode I crack growth in the graphite/PEEK material was often unstable and showed stick-slip behavior. Subcritical crack growth occurring prior to the onset of fracture was observed at intermediate displacement rates. A mechanism for the fracture behavior of the graphite/PEEK material (based on viscoelastic, plastic, and microcrack coalescence in the process zone) is proposed and related to the observed rate-dependent phenomena.

  16. Graphite content and isotopic fractionation between calcite-graphite pairs in metasediments from the Mgama Hills, Southern Kenya

    International Nuclear Information System (INIS)

    Arneth, J.D.; Schidlowski, M.; Sarbas, B.; Goerg, U.; Amstutz, G.C.

    1985-01-01

    Amphibolite-grade metasediments from the Mgama Hills region, Kenya, contain conspicuous quantities of graphite, most probably derived from organic progenitor materials,. The highest graphite contents are found in schists whereas calcite marbles intercalated in the sequence contain relatively low amounts. The graphitic constituents are consistently enriched in 13 C relative to common sedimentary organic material, with the highest isotopic ratios in graphite from the marbles. Carbon isotope fractionations between calcite and graphite mostly vary between 3.3 and 7.1 per mille, which comes close to both empirically recorded and thermodynamically calculated fractionations in the temperature range of the upper amphibolite facies. However, larger values occasionally encountered in the marbles suggest that complete isotopic equilibrium is not always attained in amphibolite-facies metamorphism. (author)

  17. Deployment of Smart 3D Subsurface Contaminant Characterization at the Brookhaven Graphite Research Reactor

    International Nuclear Information System (INIS)

    Sullivan, T.; Heiser, J.; Kalb, P.; Milian, L.; Newson, C.; Lilimpakas, M.; Daniels, T.

    2002-01-01

    The Brookhaven Graphite Research Reactor (BGRR) Historical Site Assessment (BNL 1999) identified contamination inside the Below Grade Ducts (BGD) resulting from the deposition of fission and activation products from the pile on the inner carbon steel liner during reactor operations. Due to partial flooding of the BGD since shutdown, some of this contamination may have leaked out of the ducts into the surrounding soils. The baseline remediation plan for cleanup of contaminated soils beneath the BGD involves complete removal of the ducts, followed by surveying the underlying and surrounding soils, then removing soil that has been contaminated above cleanup goals. Alternatively, if soil contamination around and beneath the BGD is either non-existent/minimal (below cleanup goals) or is very localized and can be ''surgically removed'' at a reasonable cost, the BGD can be decontaminated and left in place. The focus of this Department of Energy Accelerated Site Technology Deployment (DOE ASTD) project was to determine the extent (location, type, and level) of soil contamination surrounding the BGD and to present this data to the stakeholders as part of the Engineering Evaluation/Cost Analysis (EE/CA) process. A suite of innovative characterization tools was used to complete the characterization of the soil surrounding the BGD in a cost-effective and timely fashion and in a manner acceptable to the stakeholders. The tools consisted of a tracer gas leak detection system that was used to define the gaseous leak paths out of the BGD and guide soil characterization studies, a small-footprint Geoprobe to reach areas surrounding the BGD that were difficult to access, two novel, field-deployed, radiological analysis systems (ISOCS and BetaScint) and a three-dimensional (3D) visualization system to facilitate data analysis/interpretation. All of the technologies performed as well or better than expected and the characterization could not have been completed in the same time or at

  18. Development of fracture toughness test method for nuclear grade graphite

    Energy Technology Data Exchange (ETDEWEB)

    Chang, C. H.; Lee, J. S.; Cho, H. C.; Kim, D. J.; Lee, D. J. [Korea Advanced Institute of Science and Technology, Daejeon (Korea, Republic of)

    2006-02-15

    Because of its high strength and stability at very high temperature, as well as very low thermal neutron absorption cross-section, graphite has been widely used as a structural material in Gas Cooled Reactors (GCR). Recently, many countries are developing the Very High Temperature gas cooled Reactor (VHTR) because of the potentials of hydrogen production, as well as its safety and viable economics. In VHTR, helium gas serves as the primary coolant. Graphite will be used as a reflector, moderator and core structural materials. The life time of graphite is determined from dimensional changes due to neutron irradiation, which closely relates to the changes of crystal structure. The changes of both lattice parameter and crystallite size can be easily measured by X-ray diffraction method. However, due to high cost and long time of neutron irradiation test, ion irradiation test is being performed instead in KAERI. Therefore, it is essential to develop the technique for measurement of ion irradiation damage of nuclear graphite. Fracture toughness of nuclear grade graphite is one of the key properties in the design and development of VHTR. It is important not only to evaluate the various properties of candidate graphite but also to assess the integrity of nuclear grade graphite during operation. Although fracture toughness tests on graphite have been performed in many laboratories, there have been wide variations in values of the calculated fracture toughness, due to the differences in the geometry of specimens and test conditions. Hence, standard test method for nuclear graphite is required to obtain the reliable fracture toughness values. Crack growth behavior of nuclear grade graphite shows rising R-curve which means the increase in crack growth resistance as the crack length increases. Crack bridging and microcracking have been proposed to be the dominant mechanisms of rising R-curve behavior. In this paper, the technique to measure the changes of crystallite size and

  19. Study of hot corrosion of flakes of non purified graphite and of purified graphite

    International Nuclear Information System (INIS)

    Boule, Michel

    1967-01-01

    The author reports the study of hot corrosion of the Ticonderoga graphite. He reports the study of the defects of graphite flakes (structure defects due to impurities), the dosing of these impurities, and then their removal by purification. Flakes have then been oxidised by means of a specially designed apparatus. Based on photographs taken by optical and electronic microscopy, the author compares the oxidation features obtained in dry air and in humid air, between purified and non purified flakes. He also reports the study of the evolution of oxidation with respect to the initial rate of impurities, and the study of the evolution of oxidation features in humid air during oxidation. All these comparisons are made while taking the oxidation rate into account [fr

  20. HIV behavioural surveillance among refugees and surrounding host ...

    African Journals Online (AJOL)

    We used a standardised behavioural surveillance survey (BSS), modified to be directly relevant to populations in conflict and post-conflict settings as well as to their surrounding host populations, to survey the populations of a refugee settlement in south-western Uganda and its surrounding area. Two-stage probability ...

  1. Investigation of the readout electronics of DELPHI surround muon chamber

    International Nuclear Information System (INIS)

    Khovanskij, N.; Krumshtejn, Z.; Ol'shevskij, A.; Sadovskij, A.; Sedykh, Yu.; Molnar, J.; Sicho, P.; Tomsa, Z.

    1995-01-01

    The characteristics of the readout electronics of the DELPHI surround muon chambers with various AMPLEX chips (AMPLEX 16 and AMPLEX-SICAL) are presented. This electronics is studied in a cosmic rays test of the real surround muon chamber model. 4 refs., 6 figs., 1 tab

  2. Graphitic structure formation in ion implanted polyetheretherketone

    Energy Technology Data Exchange (ETDEWEB)

    Tavenner, E., E-mail: tazman1492@gmail.com [Creative Polymers Pty. Ltd., 41 Wilkinson Street, Toowoomba, Queensland 4350 (Australia); Chemical Committee, Surface Chemical Analysis, Standards (Australia); Wood, B. [Centre for Microscopy and Microanalysis, University of Queensland, St. Lucia, Queensland 4072 (Australia); Chemical Committee, Surface Chemical Analysis, Standards (Australia); Curry, M.; Jankovic, A.; Patel, R. [Center for Applied Science and Engineering, Missouri State University, 524 North Boonville Avenue, Springfield, MO 65806 (United States)

    2013-10-15

    Ion implantation is a technique that is used to change the electrical, optical, hardness and biocompatibility of a wide range of inorganic materials. This technique also imparts similar changes to organic or polymer based materials. With polymers, ion implantation can produce a carbon enriched volume. Knowledge as to the nature of this enrichment and its relative concentration is necessary to produce accurate models of the physical properties of the modified material. One technique that can achieve this is X-ray photoelectron spectroscopy. In this study the formation of graphite like structures in the near surface of polyetheretherketone by ion implantation has been elucidated from detailed analysis of the C 1s and valence band peak structures generated by X-ray photoelectron spectroscopy. Further evidence is given by both Rutherford backscatter spectroscopy and elastic recoil detection.

  3. Graphite Foam Heat Exchangers for Thermal Management

    Energy Technology Data Exchange (ETDEWEB)

    Klett, J.W.

    2004-06-07

    Improved thermal management is needed to increase the power density of electronic and more effectively cool electronic enclosures that are envisioned in future aircraft, spacecraft and surface ships. Typically, heat exchanger cores must increase in size to more effectively dissipate increased heat loads, this would be impossible in many cases, thus improved heat exchanger cores will be required. In this Phase I investigation, MRi aimed to demonstrate improved thermal management using graphite foam (Gr-foam) core heat exchangers. The proposed design was to combine Gr-foams from POCO with MRi's innovative low temperature, active metal joining process (S-Bond{trademark}) to bond Gr-foam to aluminum, copper and aluminum/SiC composite faceplates. The results were very favorable, so a Phase II SBIR with the MDA was initiated. This had primarily 5 tasks: (1) bonding, (2) thermal modeling, (3) cooling chip scale packages, (4) evaporative cooling techniques and (5) IGBT cold plate development. The bonding tests showed that the ''reflow'' technique with S-Bond{reg_sign}-220 resulted in the best and most consistent bond. Then, thermal modeling was used to design different chip scale packages and IGBT cold plates. These designs were used to fabricate many finned graphite foam heat sinks specifically for two standard type IC packages, the 423 and 478 pin chips. These results demonstrated several advantages with the foam. First, the heat sinks with the foam were lighter than the copper/aluminum sinks used as standards. The sinks for the 423 design made from foam were not as good as the standard sinks. However, the sinks made from foam for the 478 pin chips were better than the standard heat sinks used today. However, this improvement was marginal (in the 10-20% better regime). However, another important note was that the epoxy bonding technique resulted in heat sinks with similar results as that with the S-bond{reg_sign}, slightly worse than the S

  4. (Fuel, fission product, and graphite technology)

    Energy Technology Data Exchange (ETDEWEB)

    Stansfield, O.M.

    1990-07-25

    Travel to the Forschungszentrum (KFA) -- Juelich described in this report was for the purpose of participating in the annual meeting of subprogram managers for the US/DOE Umbrella Agreement for Fuel, Fission Product, and Graphite Technology. At this meeting the highlights of the cooperative exchange were reviewed for the time period June 1989 through June 1990. The program continues to contribute technology in an effective way for both countries. Revision 15 of the Subprogram Plan will be issued as a result of the meeting. There was interest expressed by KFA management in the level of support received from the NPR program and in potential participation in the COMEDIE loop experiment being conducted at the CEA.

  5. Intercalation of lanthanide trichlorides in graphite

    International Nuclear Information System (INIS)

    Stumpp, E.; Nietfeld, G.

    1979-01-01

    The reactions of the whole series of lanthanide trichlorides with graphite have been investigated. Intercalation compounds have been prepared with the chlorides of Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Sc, Y whereas LaCl 3 , CeCl 3 , PrCl 3 and NdCl 3 do not intercalate. The compounds were characterized by chemical and X-ray analysis. The amount of c-axis increase is consistent with the assumption that the chlorides are intercalated in form of a chloride layer sandwich resmbling the sheets in YCl 3 . The chlorides which do not intercalate crystallize in the UCl 3 structure having 3 D arrangements of ions. Obviously, these chlorides cannot form sheets between the carbon layers. The ability of AlCl 3 to volatilize lanthanide chlorides through complex formation in the gas phase can be used to increase the intercalation rate strikingly. (author)

  6. Chemical analysis of high purity graphite

    International Nuclear Information System (INIS)

    1993-03-01

    The Sub-Committee on Chemical Analysis of Graphite was organized in April 1989, under the Committee on Chemical Analysis of Nuclear Fuels and Reactor Materials, JAERI. The Sub-Committee carried out collaborative analyses among eleven participating laboratories for the certification of the Certified Reference Materials (CRMs), JAERI-G5 and G6, after developing and evaluating analytical methods during the period of September 1989 to March 1992. The certified values were given for ash, boron and silicon in the CRM based on the collaborative analysis. The values for ten elements (Al, Ca, Cr, Fe, Mg, Mo, Ni, Sr, Ti, V) were not certified, but given for information. Preparation, homogeneity testing and chemical analyses for certification of reference materials were described in this paper. (author) 52 refs

  7. Absorption spectra of AA-stacked graphite

    International Nuclear Information System (INIS)

    Chiu, C W; Lee, S H; Chen, S C; Lin, M F; Shyu, F L

    2010-01-01

    AA-stacked graphite shows strong anisotropy in geometric structures and velocity matrix elements. However, the absorption spectra are isotropic for the polarization vector on the graphene plane. The spectra exhibit one prominent plateau at middle energy and one shoulder structure at lower energy. These structures directly reflect the unique geometric and band structures and provide sufficient information for experimental fitting of the intralayer and interlayer atomic interactions. On the other hand, monolayer graphene shows a sharp absorption peak but no shoulder structure; AA-stacked bilayer graphene has two absorption peaks at middle energy and abruptly vanishes at lower energy. Furthermore, the isotropic features are expected to exist in other graphene-related systems. The calculated results and the predicted atomic interactions could be verified by optical measurements.

  8. High-Temperature Graphite/Phenolic Composite

    Science.gov (United States)

    Seal, Ellis C.; Bodepudi, Venu P.; Biggs, Robert W., Jr.; Cranston, John A.

    1995-01-01

    Graphite-fiber/phenolic-resin composite material retains relatively high strength and modulus of elasticity at temperatures as high as 1,000 degrees F. Costs only 5 to 20 percent as much as refractory materials. Fabrication composite includes curing process in which application of full autoclave pressure delayed until after phenolic resin gels. Curing process allows moisture to escape, so when composite subsequently heated in service, much less expansion of absorbed moisture and much less tendency toward delamination. Developed for nose cone of external fuel tank of Space Shuttle. Other potential aerospace applications for material include leading edges, parts of nozzles, parts of aircraft engines, and heat shields. Terrestrial and aerospace applications include structural firewalls and secondary structures in aircraft, spacecraft, and ships. Modified curing process adapted to composites of phenolic with other fiber reinforcements like glass or quartz. Useful as high-temperature circuit boards and electrical insulators.

  9. Nanodiamond graphitization: a magnetic resonance study

    International Nuclear Information System (INIS)

    Panich, A M; Shames, A I; Sergeev, N A; Olszewski, M; McDonough, J K; Mochalin, V N; Gogotsi, Y

    2013-01-01

    We report on the first nuclear magnetic resonance (NMR) and electron paramagnetic resonance (EPR) study of the high-temperature nanodiamond-to-onion transformation. 1 H, 13 C NMR and EPR spectra of the initial nanodiamond samples and those annealed at 600, 700, 800 and 1800 ° C were measured. For the samples annealed at 600 to 800 ° C, our NMR data reveal the early stages of the surface modification, as well as a progressive increase in sp 2 carbon content with increased annealing temperature. Such quantitative experimental data were recorded for the first time. These findings correlate with EPR data on the sensitivity of the dangling bond EPR line width to air content, progressing with rising annealing temperature, that evidences consequent graphitization of the external layers of the diamond core. The sample annealed at 1800 ° C shows complete conversion of nanodiamond particles into carbon onions. (paper)

  10. Analysis of electrochemical disintegration process of graphite matrix

    International Nuclear Information System (INIS)

    Tian Lifang; Wen Mingfen; Chen Jing

    2010-01-01

    The electrochemical method with ammonium nitrate as electrolyte was studied to disintegrate the graphite matrix from the simulative fuel elements for high temperature gas-cooled reactor. The influences of process parameters, including salt concentration, system temperature and current density, on the disintegration rate of graphite fragments were investigated in the present work. The experimental results showed that the disintegration rate depended slightly on the temperature and salt concentration. The current density strongly affected the disintegration rate of graphite fragments. Furthermore, the content of introduced oxygen in final graphite fragments was independent of the current density and the concentration of electrolyte. Moreover, the structural evolution of graphite was analyzed based on the microstructural parameters determined by X-ray diffraction profile fitting analysis using MAUD (material analysis using diffraction) before and after the disintegration process. It may safely be concluded that the graphite disintegration can be ascribed to the influences of the intercalation of foreign molecules in between crystal planes and the partial oxidation involved. The disintegration process was described deeply composed of intercalate part and further oxidation part of carbon which effected together to lead to the collapse of graphite crystals.

  11. Adsorption behavior of bisphenol A on CTAB-modified graphite

    Science.gov (United States)

    Wang, Li-Cong; Ni, Xin-jiong; Cao, Yu-Hua; Cao, Guang-qun

    2018-01-01

    In this work, the adsorption behavior of BPA on CTAB-modified graphite was investigated thoroughly to develop a novel absorbent material. Atomic force microscopy revealed that conical admicelles formed on the surface of graphite. The surface area of graphite decreased significantly from 1.46 to 0.95 m2 g-1, which confirmed the formation of the larger size admicelle instead of the original smaller particle on the surface. CTAB concentration and incubation time affected the progress of admicelle formation on the surface of graphite. Adsolubilization is key in BPA adsorption by CTAB-modified graphite. An extraordinary cation-π electron interaction between CTAB and BPA, revealed by a red-shift in the ultraviolet spectrum, as well as a hydrophobic interaction contribute substantially to BPA adsolubilization. The equilibrium adsorption capacity of the modified graphite for BPA was 125.01 mg g-1. The adsorption kinetic curves of BPA on modified graphite were shown to follow a pseudosecond-order rate. The adsorption process was observed to be both spontaneous and exothermic complied with the Freundlich model.

  12. Assessment of management modes for graphite from reactor decommissioning

    International Nuclear Information System (INIS)

    White, I.F.; Smith, G.M.; Saunders, L.J.; Kaye, C.J.; Martin, T.J.; Clarke, G.H.; Wakerley, M.W.

    1984-01-01

    A technological and radiological assessment has been made of the management options for irradiated graphite wastes from the decommissioning of Magnox and advanced gas-cooled reactors. Detailed radionuclide inventories have been estimated, the main contribution being from activation of the graphite and its stable impurities. Three different packaging methods for graphite have been described; each could be used for either sea or land disposal, is logistically feasible and could be achieved at reasonable cost. Leaching tests have been carried out on small samples of irradiated graphite under a variety of conditions including those of the deep ocean bed; the different conditions had little effect on the observed leach rates of radiologically significant radionuclides. Radiological assessments were made of four generic options for disposal of packaged graphite: on the deep ocean bed, in deep geologic repositories at two different types of site, and by shallow land burial. Incineration of graphite was also considered, though this option presents logistical problems. With appropriate precautions during the lifetime of the Cobalt-60 content of the graphite, any of the options considered could give acceptably low doses to individuals, and all would merit further investigation in site-specific contexts

  13. Immobilization of individual nanotubes in graphitic layers for electrical characterization

    International Nuclear Information System (INIS)

    Roy, Debmalya; Tiwari, Neeru; Mukhopadhyay, K; Saxena, A K

    2014-01-01

    A simple route is followed to produce an abundance of individual carbon nanotubes (CNTs) immobilized in graphitic layers to counter the challenge of locating individual CNTs and restrict the lateral displacement of CNTs due to the high electrostatic force exerted by a scanning tunnelling microscope tip for electrical characterization. Graphitic layers are selected for the embedding matrix as graphite and the nanotubes have a similar work function and hence would not perturb the electrical configuration of the nanotube. Solvent mediated exfoliation of graphite layers to insert the nanotubes was preferred over oxidative expansion, as oxidation could perturb the electrical configuration of graphite. During the exfoliation of graphite the optimized amount of nanotubes was introduced into the medium such that an individual nanotube could be immobilized in few-layer graphene followed by precipitation and centrifugation. The dose and the time of sonication were optimized to ensure that damage to the walls of the nanotubes is minimized, although the ultrasonication causes scissoring of the nanotube length. This procedure for immobilizing nanotubes in graphitic layers would be equally applicable for functionalized CNTs as well. The capability of embedding individual nanotubes into a similar work function material in an organic solvent, which could then be transferred onto a substrate by simple drop casting or spin coating methods, has an added advantage in sample preparation for the STM characterization of CNTs. (paper)

  14. Characterization of nuclear graphite elastic properties using laser ultrasonic methods

    Science.gov (United States)

    Zeng, Fan W.; Han, Karen; Olasov, Lauren R.; Gallego, Nidia C.; Contescu, Cristian I.; Spicer, James B.

    2015-05-01

    Laser ultrasonic methods have been used to characterize the elastic behaviors of commercially-available and legacy nuclear graphites. Since ultrasonic techniques are sensitive to various aspects of graphite microstructure including preferred grain orientation, microcrack orientation and porosity, laser ultrasonics is a candidate technique for monitoring graphite degradation and structural integrity in environments expected in high-temperature, gas-cooled nuclear reactors. Aspects of materials texture can be assessed by studying ultrasonic wavespeeds as a function of propagation direction and polarization. Shear wave birefringence measurements, in particular, can be used to evaluate elastic anisotropy. In this work, laser ultrasonic measurements of graphite moduli have been made to provide insight into the relationship between the microstructures and the macroscopic stiffnesses of these materials. In particular, laser ultrasonic measurements have been made using laser line sources to produce shear waves with specific polarizations. By varying the line orientation relative to the sample, shear wave birefringence measurements have been recorded. Results from shear wave birefringence measurements show that an isostatically molded graphite, such as PCIB, behaves isotropically, while an extruded graphite, such as H-451, displays significant ultrasonic texture. Graphites have complicated microstructures that depend on the manufacturing processes used, and ultrasonic texture in these materials could originate from grain orientation and preferred microcrack alignment. Effects on material isotropy due to service related microstructural changes are possible and the ultimate aim of this work is to determine the degree to which these changes can be assessed nondestructively using laser ultrasonics measurements.

  15. Design Procedure of Graphite Components by ASME HTR Codes

    International Nuclear Information System (INIS)

    Kang, Ji-Ho; Jo, Chang Keun

    2016-01-01

    In this study, the ASME B and PV Code, Subsection HH, Subpart A, design procedure for graphite components of HTRs was reviewed and the differences from metal materials were remarked. The Korean VHTR has a prismatic core which is made of multiple graphite blocks, reflectors, and core supports. One of the design issues is the assessment of the structural integrity of the graphite components because the graphite is brittle and shows quite different behaviors from metals in high temperature environment. The American Society of Mechanical Engineers (ASME) issued the latest edition of the code for the high temperature reactors (HTR) in 2015. In this study, the ASME B and PV Code, Subsection HH, Subpart A, Graphite Materials was reviewed and the special features were remarked. Due the brittleness of graphites, the damage-tolerant design procedures different from the conventional metals were adopted based on semi-probabilistic approaches. The unique additional classification, SRC, is allotted to the graphite components and the full 3-D FEM or equivalent stress analysis method is required. In specific conditions, the oxidation and viscoelasticity analysis of material are required. The fatigue damage rule has not been established yet

  16. Design Procedure of Graphite Components by ASME HTR Codes

    Energy Technology Data Exchange (ETDEWEB)

    Kang, Ji-Ho; Jo, Chang Keun [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

    2016-10-15

    In this study, the ASME B and PV Code, Subsection HH, Subpart A, design procedure for graphite components of HTRs was reviewed and the differences from metal materials were remarked. The Korean VHTR has a prismatic core which is made of multiple graphite blocks, reflectors, and core supports. One of the design issues is the assessment of the structural integrity of the graphite components because the graphite is brittle and shows quite different behaviors from metals in high temperature environment. The American Society of Mechanical Engineers (ASME) issued the latest edition of the code for the high temperature reactors (HTR) in 2015. In this study, the ASME B and PV Code, Subsection HH, Subpart A, Graphite Materials was reviewed and the special features were remarked. Due the brittleness of graphites, the damage-tolerant design procedures different from the conventional metals were adopted based on semi-probabilistic approaches. The unique additional classification, SRC, is allotted to the graphite components and the full 3-D FEM or equivalent stress analysis method is required. In specific conditions, the oxidation and viscoelasticity analysis of material are required. The fatigue damage rule has not been established yet.

  17. Effect of various dopant elements on primary graphite growth

    International Nuclear Information System (INIS)

    Valle, N; Theuwissen, K; Lacaze, J; Sertucha, J

    2012-01-01

    Five spheroidal graphite cast irons were investigated, a usual ferritic grade and four pearlitic alloys containing Cu and doped with Sb, Sn and Ti. These alloys were remelted in a graphite crucible, leading to volatilization of the magnesium added for spheroidization and to carbon saturation of the liquid. The alloys were then cooled down and maintained at a temperature above the eutectic temperature. During this step, primary graphite could develop showing various features depending on the doping elements added. The largest effects were that of Ti which greatly reduces graphite nucleation and growth, and that of Sb which leads to rounded agglomerates instead of lamellar graphite. The samples have been investigated with secondary ion mass spectrometry to enlighten distribution of elements in primary graphite. SIMS analysis showed almost even distribution of elements, including Mg and Al (from the inoculant) in the ferritic grade, while uneven distribution was evident in all doped alloys. Investigations are going on to clarify if the uneven distribution is associated with structural defects in the graphite precipitates.

  18. New insights into canted spiro carbon interstitial in graphite

    Science.gov (United States)

    EL-Barbary, A. A.

    2017-12-01

    The self-interstitial carbon is the key to radiation damage in graphite moderator nuclear reactor, so an understanding of its behavior is essential for plant safety and maximized reactor lifetime. The density functional theory is applied on four different graphite unit cells, starting from of 64 carbon atoms up to 256 carbon atoms, using AIMPRO code to obtain the energetic, athermal and mechanical properties of carbon interstitial in graphite. This study presents first principles calculations of the energy of formation that prove its high barrier to athermal diffusion (1.1 eV) and the consequent large critical shear stress (39 eV-50 eV) necessary to shear graphite planes in its presence. Also, for the first time, the gamma surface of graphite in two dimensions is calculated and found to yield the critical shear stress for perfect graphite. Finally, in contrast to the extensive literature describing the interstitial of carbon in graphite as spiro interstitial, in this work the ground state of interstitial carbon is found to be canted spiro interstitial.

  19. Neutron transmission through pyrolytic graphite crystal II

    Energy Technology Data Exchange (ETDEWEB)

    Adib, M., E-mail: mamdouhshihata@yahoo.com [Reactor Physics Department, NRC, AEAE, Cairo (Egypt); Habib, N. [Reactor Physics Department, NRC, AEAE, Cairo (Egypt); Bashter, I.; Saleh, A. [Faculty of Science, Zagazig University (Egypt)

    2011-04-15

    The measured neutron transmissions through 6.7 mm thick pyroletic graphite (PG) crystal set at different take-off-angles with respect to the beam, as a function of wavelength, were compared with the calculated values using a general formula. An adapted version of the computer package graphite was developed in order to provide the required calculations in the neutron energy range from 0.1 MeV to 10 eV. An overall agreement was obtained between the formula fits and the measured data at different take-off-angles. The major dips in transmission caused by various reflections were identified. From the shape of the dips due to 0 0 l reflections, the mosaic spread of the used PG crystal has been determined within an accuracy of 0.12{sup o}. A feasibility study is carried out on using two PG crystals to select from the reactor spectrum a neutron monochromatic beam with wavelengths longer than 0.3 nm and almost free from accompanying higher-order reflections. Calculation shows that 2 mm thick highly oriented PG (0.5{sup o} FWHM on mosaic spread) crystal set at glancing angle 20.0{sup o} reflects first-order monochromatic neutrons with 0.3 nm wavelengths. When 6.0 cm thick PG crystal (2{sup o} FWHM on mosaic spread) set at 60.63{sup o} take-off-angle is inserted on the way of the reflected neutrons, it transmits more than 70% of the first-order neutrons while attenuating the high- order ones by more than 20 times. Similar results were obtained when the selected monochromatic neutrons had wavelengths longer than 0.3 nm.

  20. Stimulus size dependence of hue changes induced by chromatic surrounds.

    Science.gov (United States)

    Kellner, Christian Johannes; Wachtler, Thomas

    2016-03-01

    A chromatic surround induces a change in the perceived hue of a stimulus. This shift in hue depends on the chromatic difference between the stimulus and the surround. We investigated how chromatic induction varies with stimulus size and whether the size dependence depends on the surround hue. Subjects performed asymmetric matching of color stimuli with different sizes in surrounds of different chromaticities. Generally, induced hue shifts decreased with increasing stimulus size. This decrease was quantitatively different for different surround hues. However, when size effects were normalized to an overall induction strength, the chromatic specificity was largely reduced. The separability of inducer chromaticity and stimulus size suggests that these effects are mediated by different neural mechanisms.

  1. Effects of Oxidation on Oxidation-Resistant Graphite

    Energy Technology Data Exchange (ETDEWEB)

    Windes, William [Idaho National Lab. (INL), Idaho Falls, ID (United States); Smith, Rebecca [Idaho National Lab. (INL), Idaho Falls, ID (United States); Carroll, Mark [Idaho National Lab. (INL), Idaho Falls, ID (United States)

    2015-05-01

    The Advanced Reactor Technology (ART) Graphite Research and Development Program is investigating doped nuclear graphite grades that exhibit oxidation resistance through the formation of protective oxides on the surface of the graphite material. In the unlikely event of an oxygen ingress accident, graphite components within the VHTR core region are anticipated to oxidize so long as the oxygen continues to enter the hot core region and the core temperatures remain above 400°C. For the most serious air-ingress accident which persists over several hours or days the continued oxidation can result in significant structural damage to the core. Reducing the oxidation rate of the graphite core material during any air-ingress accident would mitigate the structural effects and keep the core intact. Previous air oxidation testing of nuclear-grade graphite doped with varying levels of boron-carbide (B4C) at a nominal 739°C was conducted for a limited number of doped specimens demonstrating a dramatic reduction in oxidation rate for the boronated graphite grade. This report summarizes the conclusions from this small scoping study by determining the effects of oxidation on the mechanical strength resulting from oxidation of boronated and unboronated graphite to a 10% mass loss level. While the B4C additive did reduce mechanical strength loss during oxidation, adding B4C dopants to a level of 3.5% or more reduced the as-fabricated compressive strength nearly 50%. This effectively minimized any benefits realized from the protective film formed on the boronated grades. Future work to infuse different graphite grades with silicon- and boron-doped material as a post-machining conditioning step for nuclear components is discussed as a potential solution for these challenges in this report.

  2. Recent developments in graphite. [Use in HTGR and aerospace

    Energy Technology Data Exchange (ETDEWEB)

    Cunningham, J.E.

    1983-01-01

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

  3. Isotropic nuclear graphites; the effect of neutron irradiation

    International Nuclear Information System (INIS)

    Lore, J.; Buscaillon, A.; Mottet, P.; Micaud, G.

    1977-01-01

    Several isotropic graphites have been manufactured using different forming processes and fillers such as needle coke, regular coke, or pitch coke. Their properties are described in this paper. Specimens of these products have been irradiated in the fast reactor Rapsodie between 400 to 1400 0 C, at fluences up to 1,7.10 21 n.cm -2 PHI.FG. The results show an isotropic behavior under neutron irradiation, but the induced dimensional changes are higher than those of isotropic coke graphites although they are lower than those of conventional extruded graphites made with the same coke

  4. Graphite development for gas-cooled reactors in the USA

    International Nuclear Information System (INIS)

    Burchell, T.D.

    1991-01-01

    This document discusses Modular High-Temperature Gas-Cooled Reactor (MHTGR) graphite activities in the USA which currently include the following research and development tasks: coke examination; effects of irradiation; variability of physical properties (mechanical, thermal-physical, and fracture); fatigue behavior, oxidation behavior; NDE techniques; structural design criteria; and carbon-carbon composite control rod clad materials. These tasks support nuclear grade graphite manufacturing technology including nondestructive examination of billets and components. Moreover, data shall be furnished to support design and licensing of graphite components for the MHTGR

  5. Measurements of print-through in graphite fiber epoxy composites

    Science.gov (United States)

    Jaworske, Donald A.; Jeunnette, Timothy T.; Anzic, Judith M.

    1989-01-01

    High-reflectance accurate-contour mirrors are needed for solar dynamic space power systems. Graphite fiber epoxy composites are attractive candidates for such applications owing to their high modulus, near-zero coefficient of thermal expansion, and low mass. However, mirrors prepared from graphite fiber epoxy composite substrates often exhibit print-through, a distortion of the surface, which causes a loss in solar specular reflectance. Efforts to develop mirror substrates without print-through distortion require a means of quantifying print-through. Methods have been developed to quantify the degree of print-through in graphite fiber epoxy composite specimens using surface profilometry.

  6. Development and engineering plan for graphite spent fuels conditioning program

    International Nuclear Information System (INIS)

    Bendixsen, C.L.; Fillmore, D.L.; Kirkham, R.J.; Lord, D.L.; Phillips, M.B.; Pinto, A.P.; Staiger, M.D.

    1993-09-01

    Irradiated (or spent) graphite fuel stored at the Idaho Chemical Processing Plant (ICPP) includes Fort St. Vrain (FSV) reactor and Peach Bottom reactor spent fuels. Conditioning and disposal of spent graphite fuels presently includes three broad alternatives: (1) direct disposal with minimum fuel packaging or conditioning, (2) mechanical disassembly of spent fuel into high-level waste and low-level waste portions to minimize geologic repository requirements, and (3) waste-volume reduction via burning of bulk graphite and other spent fuel chemical processing of the spent fuel. A multi-year program for the engineering development and demonstration of conditioning processes is described. Program costs, schedules, and facility requirements are estimated

  7. An analysis of irradiation creep in nuclear graphites

    International Nuclear Information System (INIS)

    Neighbour, G.B.; Hacker, P.J.

    2002-01-01

    Nuclear graphite under load shows remarkably high creep ductility with neutron irradiation, well in excess of any strain experienced in un-irradiated graphite (and additional to any dimensional changes that would occur without stress). As this behaviour compensates, to some extent, some other irradiation effects such as thermal shutdown stresses, it is an important property. This paper briefly reviews the approach to irradiation creep in the UK, described by the UK Creep Law. It then offers an alternative analysis of irradiation creep applicable to most situations, including HTR systems, using AGR moderator graphite as an example, to high values of neutron fluence, applied stress and radiolytic weight loss. (authors)

  8. Manufacturing of a graphite calorimeter at Yazd Radiation Processing Center

    International Nuclear Information System (INIS)

    Ziaie, F.

    2004-01-01

    In this work, a few quasi-adiabatic graphite calorimeters of different dimensions are described. The calorimeters have been manufactured by ourselves and studied for accurate absorbed dose measurements in 10 MeV electron beam. In order to prove the accuracy and reliability of dose measurements with the use of self designed graphite calorimeters (SCD), an inter comparison study was performed on these calorimeters and Risoe graphite calorimeters (SC,standard calorimeter) at different doses by using Rhodothron accelerator. The comparison shows conclusively of the optimal size, the results agreeing with those obtained with the Sc within 1%. (author)

  9. Corrosion-induced microstructural changes in a US core graphite

    International Nuclear Information System (INIS)

    Eatherly, W.P.; Lee, D.A.

    1981-01-01

    The results reported here apply to Great Lakes grade H-451 graphite, the core graphite specified for the US HTGR. This graphite is structurally similar to the German reflector grades we have investigated at ORNL, and hence should be applicable to them if similar impurity levels are obtained. Moreover, these results extend and confirm the behavior pattern exhibited by the fuel matrix material A3-3 reported in the previous paper, although the effects are more pronounced in A3-3 presumably due to its resin-type binder and low heat-treatment temperatures

  10. Graphite suspension in carbon dioxide; Suspension de graphite dans le gaz carbonique

    Energy Technology Data Exchange (ETDEWEB)

    Roche, R [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires; Moussez, C; Rouvillois, X; Brevet, R [Societe Nationale d' Etude et de Construction de Moteurs d' Aviation (SNECMA), 75 - Paris (France)

    1965-07-01

    Since 1963 the Atomic Division of SNECMA has been conducting, under a contract with the CEA, an experimental work with a two-component fluid comprised of carbon dioxide and small graphite particles. The primary purpose was the determination of basic engineering information pertaining to the stability and the flowability of the suspension. The final form of the experimental loop consists mainly of the following items: a light-phase compressor, a heavy-phase pump, an electrical-resistance type heater section, a cooling heat exchanger, a hairpin loop, a transparent test section and a separator. During the course of the testing, it was observed that the fluid could be circulated quite easily in a broad range of variation of the suspension density and velocity - density from 30 to 170 kg/m{sup 3} and velocity from 2 to 24 m/s. The system could be restarted and circulation maintained without any difficulty, even with the heavy-phase pump alone. The graphite did not have a tendency to pack or agglomerate during operation. No graphite deposition was observed on the wall of the tubing. A long period run (250 hours) has shown the evolution of the particle dimensions. Starting with graphite of surface area around 20 m{sup 2}/g (graphite particles about 1 {mu}), the powder surface area reaches an asymptotic value of 300 m{sup 2}/g (all the particles less than 0.3 {mu}). Moisture effect on flow stability, flow distribution between two parallel channels, pressure drop in straight tubes, recompression ratio in diffusers were also investigated. (author) [French] Depuis 1963 la Division Atomique de la SNECMA conduit, dans le cadre d'un contrat avec le Commissariat A l'Energie Atomique, l'etude experimentale d'une suspension de fines particules de graphite dans le gaz carbonique. L'objectif principal est d'obtenir des informations d'ordre mecanique et technologique sur la mise en oeuvre de l'ecoulement de ce fluide diphase. Le circuit experimental comprend principalement: un

  11. Changes in unique hues induced by chromatic surrounds.

    Science.gov (United States)

    Klauke, Susanne; Wachtler, Thomas

    2016-03-01

    A chromatic surround can have a strong influence on the perceived hue of a stimulus. We investigated whether chromatic induction has similar effects on the perception of colors that appear pure and unmixed (unique red, green, blue, and yellow) as on other colors. Subjects performed unique hue settings of stimuli in isoluminant surrounds of different chromaticities. Compared with the settings in a neutral gray surround, unique hue settings altered systematically with chromatic surrounds. The amount of induced hue shift depended on the difference between stimulus and surround hues, and was similar for unique hue settings as for settings of nonunique hues. Intraindividual variability in unique hue settings was roughly twice as high as for settings obtained in asymmetric matching experiments, which may reflect the presence of a reference stimulus in the matching task. Variabilities were also larger with chromatic surrounds than with neutral gray surrounds, for both unique hue settings and matching of nonunique hues. The results suggest that the neural representations underlying unique hue percepts are influenced by the same neural processing mechanisms as the percepts of other colors.

  12. Study by electronic microscopy of corrosion features of graphite after hot oxidation (air, 620 C)

    International Nuclear Information System (INIS)

    Jodon de Villeroche, Suzanne

    1968-01-01

    The author reports the study of corrosion features of graphite after hot oxidation in the air at 620 C. It is based on observations made by electronic microscopy. This study comes after another one dedicated to oxidation features obtained by hot corrosion of natural graphite, and aims at comparing pyrolytic graphite before and after irradiation in an atomic pile, and at performing tests on a graphite processed with ozone. After a recall of generalities about natural graphite and of some issues related to hot corrosion of natural graphite, the author presents some characteristics and features of irradiated and non-irradiated pyrolytic graphite. He reports the study of the oxidation of samples of pyrolytic graphite: production of thin lamellae, production of glaze-carbon replicates, oxidation of irradiated and of non-irradiated graphite, healing of irradiation defects, and oxidation of ozone-processed natural graphite [fr

  13. Selection, rejection and optimisation of pyrolytic graphite (PG) crystal analysers for use on the new IRIS graphite analyser bank

    International Nuclear Information System (INIS)

    Marshall, P.J.; Sivia, D.S.; Adams, M.A.; Telling, M.T.F.

    2000-01-01

    This report discusses design problems incurred by equipping the IRIS high-resolution inelastic spectrometer at the ISIS pulsed neutron source, UK with a new 4212 piece pyrolytic graphite crystal analyser array. Of the 4212 graphite pieces required, approximately 2500 will be newly purchased PG crystals with the remainder comprising of the currently installed graphite analysers. The quality of the new analyser pieces, with respect to manufacturing specifications, is assessed, as is the optimum arrangement of new PG pieces amongst old to circumvent degradation of the spectrometer's current angular resolution. Techniques employed to achieve these criteria include accurate calliper measurements, FORTRAN programming and statistical analysis. (author)

  14. Highly conductive bridges between graphite spheres to improve the cycle performance of a graphite anode in lithium-ion batteries

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Hongyu [IM and T Ltd., Advanced Research Center, Saga University, Yoga-machi 1341, Saga 840-0047 (Japan); Umeno, Tatsuo; Mizuma, Koutarou [Research Center, Mitsui Mining Co. Ltd., Hibiki-machi 1-3, Wakamatsu-ku, Kitakyushu 808-0021 (Japan); Yoshio, Masaki [Advanced Research Center, Saga University, Yoga-machi 1341, Saga 840-0047 (Japan)

    2008-01-10

    Spherical carbon-coated natural graphite (SCCNG) is a promising anode material for lithium-ion batteries, but the smooth surface of graphite spheres is difficult to wet with an aqueous binder solution, and lacks electrical contacts. As a result, the cycle performance of such a graphite anode material is not satisfactory. An effective method has been introduced to tightly connect adjacent SCCNG particles by a highly conductive binder, viz. acetylene black bridges. The effect of the conductive bridges on the cyclability of SCCNG electrode has been investigated. (author)

  15. Graphite limiter and armour damage in Doublet III

    International Nuclear Information System (INIS)

    McKelvey, T.; Taylor, T.; Trester, P.

    1983-01-01

    Graphite coated with TiC has been used extensively in Doublet III for limiters and neutral beam armour. Performance of these components has been superior to that of the metal components previously used. Damage to the coated graphite has occurred and can be classified into three categories: (1) gross failure of the graphite due to thermal stresses induced by the combination of high applied energy fluxes and mechanical restraint, (2) surface failure of the graphite due to runaway electron impingement, and (3) loss of TiC coating due to arcing, sputtering, vaporization and spalling, primarily during plasma disruptions and other abnormal plasma conditions. Design improvements are being continually implemented to minimize this damage and its consequences. (author)

  16. Graphene-graphite oxide field-effect transistors.

    Science.gov (United States)

    Standley, Brian; Mendez, Anthony; Schmidgall, Emma; Bockrath, Marc

    2012-03-14

    Graphene's high mobility and two-dimensional nature make it an attractive material for field-effect transistors. Previous efforts in this area have used bulk gate dielectric materials such as SiO(2) or HfO(2). In contrast, we have studied the use of an ultrathin layered material, graphene's insulating analogue, graphite oxide. We have fabricated transistors comprising single or bilayer graphene channels, graphite oxide gate insulators, and metal top-gates. The graphite oxide layers show relatively minimal leakage at room temperature. The breakdown electric field of graphite oxide was found to be comparable to SiO(2), typically ~1-3 × 10(8) V/m, while its dielectric constant is slightly higher, κ ≈ 4.3. © 2012 American Chemical Society

  17. Design development of graphite primary structures enables SSTO success

    Science.gov (United States)

    Biagiotti, V. A.; Yahiro, J. S.; Suh, Daniel E.; Hodges, Eric R.; Prior, Donald J.

    1997-01-01

    This paper describes the development of a graphite composite wing and a graphite composite intertank primary structure for application toward Single-Stage to Orbit space vehicles such as those under development in NASA's X-33/Reusable Launch Vehicle (RLV) Program. The trade study and designs are based on a Rockwell vertical take-off and horizontal landing (VTHL) wing-body RLV vehicle. Northrop Grumman's approach using a building block development technique is described. Composite Graphite/Bismaleimide (Gr/BMI) material characterization test results are presented. Unique intertank and wing composite subcomponent test article designs are described and test results to date are presented. Wing and intertank Full Scale Section Test Article (FSTA) objectives and designs are outlined. Trade studies, supporting building block testing, and FSTA demonstrations combine to develop graphite primary structure composite technology that enables developing X-33/RLV design programs to meet critical SSTO structural weight and operations performance criteria.

  18. PNGS-A unit 4 composite graphite valve packing program

    International Nuclear Information System (INIS)

    Meaney, F.

    1992-01-01

    During the outage of Pickering 4 for retubing and rehabilitation, a composite graphite packing program was completed on 100 conventional valves and 50 nuclear valves. This paper describes component refurbishment, related maintenance, and manpower requirements. 2 figs

  19. Graphitic Carbon Foam Structural Cores and Multifunctional Applications

    Data.gov (United States)

    National Aeronautics and Space Administration — Graphitic carbon foams include a family of material forms and products with mechanical, thermal, and electrical properties that are tailor-able over a wide range....

  20. The preliminary feasibility of intercalated graphite railgun armatures

    International Nuclear Information System (INIS)

    Gaier, J.R.; Yashan, D.; Naud, S.

    1991-01-01

    This paper reports on graphite intercalation compounds which may provide an excellent material for the fabrication of electro-magnetic railgun armatures. As a pulse of power is fed into the armature the intercalate could be excited into the plasma state around the edges of the armature, while the bulk of the current would be carried through the graphite block. Such an armature would have desirable characteristics of both diffuse plasma armatures and bulk conduction armatures. In addition, the highly anisotropic nature of these materials could enable the electrical and thermal conductivity to be tailored to meet the specific requirements of electromagnetic railgun armatures. Preliminary investigations have been performed in an attempt to determine the feasibility of using graphite intercalation compounds as railgun armatures. Issues of fabrication, resistivity, stability, and electrical current spreading have been addressed for the case of highly oriented pyrolytic graphite

  1. Graphite behaviour in relation to the fuel element design

    Energy Technology Data Exchange (ETDEWEB)

    Everett, M. R. [OECD High Temperature Reactor Project Dragon, Winfrith (United Kingdom); Manzel, R. [OECD High Temperature Reactor Project Dragon, Winfrith (United Kingdom); Blackstone, R. [Reactor Centrum, Petten (Netherlands); Delle, W. [Kernforschungsanlage, Juelich (Germany); Lungagnani, V. [Joint Nuclear Research Centre, Euratom, Petten (Netherlands); Krefeld, R. [Joint Nuclear Research Centre, Euratom, Petten (Netherlands)

    1969-09-01

    The first designs of H.T.R. power reactors will probably use a Gilsocarbon based graphite for both the moderator/carrier blocks and for the fuel tubes. The initial physical properties and changes of dimensions, thermal expansion coefficient, Young*s modulus, and thermal conductivity on irradiation of Gilsocarbon graphites to typical reactor dwell-time fast neutron doses of 4 * 1021 cm -2 Ni dose Dido equivalent are given and values for the irradiation creep constant are presented. The influence of these property changes and those of chemical corrosion are considered briefly in relation to the present fuel element designs. The selection of an eventual less costly replacement graphite for Gilsocarbon graphite is discussed in terms of materials properties.

  2. Direct brazing of ceramics, graphite, and refractory metals

    International Nuclear Information System (INIS)

    Canonico, D.A.; Cole, N.C.; Slaughter, G.M.

    1976-03-01

    ORNL has been instrumental in the development of brazing filler metals for joining ceramics, graphite, and refractory metals for application at temperatures above 1000 0 C. The philosophy and techniques employed in the development of these alloys are presented. A number of compositions are discussed that have been satisfactorily used to braze ceramics, graphite, and refractory metals without a prior surface treatment. One alloy, Ti--25 percent Cr--21 percent V, has wet and flowed on aluminum oxide and graphite. Further, it has been utilized in making brazes between different combinations of the three subject materials. The excellent flowability of this alloy and alloys from the Ti--Zr--Ge system is evidenced by the presence of filler metal in the minute pores of the graphite and ceramics

  3. Determination of chlorine in graphite by combustion-ion chromatography

    International Nuclear Information System (INIS)

    Chen Lianzhong; Watanabe, Kazuo; Itoh, Mitsuo.

    1995-09-01

    A combustion/ion chromatographic method has been studied for the sensitive determination of chlorine in graphite. A graphite sample was burnt at 900degC in a silica reaction tube at an oxygen flow rate of 200 ml/min. Chlorine evolved was absorbed in 20 ml of a 0.1 mM sodium carbonate solution. The solution was evaporated to dryness. The residue was dissolved with a small volume of water. Chlorine in the solution was determined using ion chromatography. The method was applied to JAERI graphite certified reference materials and practical graphite materials. The detection limit was about 0.8 μgCl/g for a 2.0 g sample. The precision was about 2.5% (relative standard deviation) for samples with chlorine content of 70 μg/g level. The method is also usable for coal samples. (author)

  4. On estimating the fracture probability of nuclear graphite components

    International Nuclear Information System (INIS)

    Srinivasan, Makuteswara

    2008-01-01

    The properties of nuclear grade graphites exhibit anisotropy and could vary considerably within a manufactured block. Graphite strength is affected by the direction of alignment of the constituent coke particles, which is dictated by the forming method, coke particle size, and the size, shape, and orientation distribution of pores in the structure. In this paper, a Weibull failure probability analysis for components is presented using the American Society of Testing Materials strength specification for nuclear grade graphites for core components in advanced high-temperature gas-cooled reactors. The risk of rupture (probability of fracture) and survival probability (reliability) of large graphite blocks are calculated for varying and discrete values of service tensile stresses. The limitations in these calculations are discussed from considerations of actual reactor environmental conditions that could potentially degrade the specification properties because of damage due to complex interactions between irradiation, temperature, stress, and variability in reactor operation

  5. Impact-Contact Analysis of Prismatic Graphite Blocks Using Abaqus

    International Nuclear Information System (INIS)

    Kang, Ji Ho; Kim, Gyeong Ho; Choi, Woo Seok

    2010-12-01

    Graphite blocks are the important core components of the high temperature gas-cooled reactor. As these blocks are simply stacked in array, collisions among neighboring components may occur during earthquakes or accidents. The final objective of the research project is to develop a reliable seismic model of the stacked graphite blocks from which their behavior can be predicted and, thus, they are designed to have sufficient strength to maintain their structural integrity during the anticipated occurrences. The work summarized in this report is a first step toward the big picture and is dedicated to build a realistic impact-contact dynamics model of the graphite block using a commercial FEM package, Abaqus. The developed model will be further used to assist building a reliable lumped dynamics model of these stacked graphite components

  6. Reliability of graphite furnace atomic absorption spectrometry as ...

    African Journals Online (AJOL)

    spectrometry as alternative method for trace analysis of ... Purpose: To evaluate the comparative efficiency of graphite furnace atomic absorption spectrometry .... Methods comparison and validation .... plasma-optical emission spectrometry.

  7. Evaluation of coke microstructure and its effects on graphite fabrication

    International Nuclear Information System (INIS)

    Fotourehchian, S.; Ahmadi, S.

    2001-01-01

    A variety of applications for cokes (metallurgy, petroleum, etc.) have been defined in parallel to the new industrial technology growth. Coke is rich in carbon and has the main role in manufacturing carbonaceous materials such as graphite, steel, silicon carbide, titanium carbide, etc. Among the most important applications of different variety of cokes is their usage for different graphite fabrications. The crystalline structure of graphite (hexagonal with sp 2 hybrid) is based upon the microstructure of coke and it causes anisotropy in properties of produced graphite. Thus, the study of macrostructure and anisotropy degree of cokes is of importance. There are several theoretical and experimental methods to determine the Coke's microstructure and anisotropy. Numerous tests have been conducted on different variety of cokes based on the used method. Here, it is attempted to introduce an applied method to determine the microstructure and anisotropy degree of cokes based upon the kind of application

  8. Structural performance of a graphite blanket in fusion reactors

    International Nuclear Information System (INIS)

    Wolfer, W.G.; Watson, R.D.

    1978-01-01

    Irradiation of graphite in a fusion reactor causes dimensional changes, enhanced creep, and changes in elastic properties and fracture strength. Temperature and flux gradients through the graphite blanket structure produce differential distortions and stress gradients. An inelastic stress analysis procedure is described which treats these variations of the graphite properties in a consistent manner as dictated by physical models for the radiation effects. Furthermore, the procedure follows the evolution of the stress and fracture strength distributions during the reactor operation as well as for possible shutdowns at any time. The lifetime of the graphite structure can be determined based on the failure criterion that the stress at any location exceeds one-half of the fracture strength. This procedure is applied to the most critical component of the blanket module in the SOLASE design

  9. TAPIR, Thermal Analysis of HTGR with Graphite Sleeve Fuel Elements

    International Nuclear Information System (INIS)

    Weicht, U.; Mueller, W.

    1983-01-01

    1 - Nature of the physical problem solved: Thermal analysis of a reactor core containing internally and/or externally gas cooled prismatic fuel elements of various geometries, rating, power distribution, and material properties. 2 - Method of solution: A fuel element in this programme is regarded as a sector of a fuelled annulus with graphite sleeves of any shape on either side and optional annular gaps between fuel and graphite and/or within the graphite. It may have any centre angle and the fuelled annulus may become a solid cylindrical rod. Heat generation in the fuel is assumed to be uniform over the cross section and peripheral heat flux into adjacent sectors is ignored. Fuel elements and coolant channels are treated separately, then linked together to fit a specified pattern. 3 - Restrictions on the complexity of the problem: Maxima of: 50 fuel elements; 50 cooled channels; 25 fuel geometries; 25 coolant channel geometries; 10 axial power distributions; 10 graphite conductivities

  10. Measurement of the diffusion length of thermal neutrons inside graphite

    International Nuclear Information System (INIS)

    Ertaud, A.; Beauge, R.; Fauquez, H.; De Laboulay, H.; Mercier, C.; Vautrey, L.

    1948-11-01

    The diffusion length of thermal neutrons inside a given industrial graphite is determined by measuring the neutron density inside a parallelepipedal piling up of graphite bricks (2.10 x 2.10 x 2.442 m). A 3.8 curies (Ra α → Be) source is placed inside the parallelepipedal block of graphite and thin manganese detectors are used. Corrections are added to the unweighted measurements to take into account the effects of the damping of supra-thermal neutrons in the measurement area. These corrections are experimentally deduced from the differential measurements made with a cadmium screen interposed between the source and the first plane of measurement. An error analysis completes the report. The diffusion length obtained is: L = 45.7 cm ± 0.3. The average density of the graphite used is 1.76 and the average apparent density of the piling up is 1.71. (J.S.)

  11. Theoretical basis for graphite stress analysis in BERSAFE

    International Nuclear Information System (INIS)

    Harper, P.G.

    1980-03-01

    The BERSAFE finite element computer program for structural analysis has been extended to deal with structures made from irradiated graphite. This report describes the material behaviour which has been modelled and gives the theoretical basis for the solution procedure. (author)

  12. carbonaceous phyllite/graphitic schist in the Archean Kundarkocha

    Indian Academy of Sciences (India)

    rocks of noble metals (Meyers et al. 1990). Such complexes host gold deposits in North–East. Russia (Natalka, Mayskoe ..... carbonic phases using Laser Raman Spectrometry ... Graphite was formed by the reaction between CH4 and CO2.

  13. Surface Modification of Exfoliated Graphite Nano-Reinforcements, Phase I

    Data.gov (United States)

    National Aeronautics and Space Administration — Nano forms of graphite and carbon, such as flakes, worms, and tubes, can significantly modify the properties of polymers when used as reinforcements. Challenges...

  14. Modelling property changes in graphite irradiated at changing irradiation temperature

    CSIR Research Space (South Africa)

    Kok, S

    2011-01-01

    Full Text Available A new method is proposed to predict the irradiation induced property changes in nuclear; graphite, including the effect of a change in irradiation temperature. The currently used method; to account for changes in irradiation temperature, the scaled...

  15. Stable Cycling Of Graphite In An Ionic Liquid Based Electrolyte

    Energy Technology Data Exchange (ETDEWEB)

    Holzapfel, M.; Jost, C. [Degussa(Georgia); Novak, P.

    2005-03-01

    1-Ethyl-3-methylimidazolium-bis(trifluor methylsulfonyl)-imide (EMI-TFSI) has been shown to reversibly permit lithium intercalation into standard graphite when vinylene carbonate is used in small amounts as additive. (author)

  16. Spin-density wave state in simple hexagonal graphite

    Science.gov (United States)

    Mosoyan, K. S.; Rozhkov, A. V.; Sboychakov, A. O.; Rakhmanov, A. L.

    2018-02-01

    Simple hexagonal graphite, also known as AA graphite, is a metastable configuration of graphite. Using tight-binding approximation, it is easy to show that AA graphite is a metal with well-defined Fermi surface. The Fermi surface consists of two sheets, each shaped like a rugby ball. One sheet corresponds to electron states, another corresponds to hole states. The Fermi surface demonstrates good nesting: a suitable translation in the reciprocal space superposes one sheet onto another. In the presence of the electron-electron repulsion, a nested Fermi surface is unstable with respect to spin-density-wave ordering. This instability is studied using the mean-field theory at zero temperature, and the spin-density-wave order parameter is evaluated.

  17. Thermal strain measurements in graphite using electronic speckle pattern interferometry

    International Nuclear Information System (INIS)

    Tamulevicius, S.; Augulis, L.; Augulis, R.; Zabarskas, V.; Levinskas, R.; Poskas, P.

    2001-01-01

    Two 1500 MW(e) RBMK Units are operated at Ignalina NPP in Lithuania. Due to recent decision of the Parliament on the earlier closure of Unit 1, preparatory work for decommissioning have been initiated. Preferred decommissioning strategy is based on delayed dismantling after rather long safe enclosure period. Since graphite is one of the basic and probably the most voluminous components of the reactor internals, a sufficient information on status and behaviour of graphite moderator and reflector during long time safe enclosure period is of special significance. In this context, thermal strain in graphite is one of the parameters requiring particular interest. Electronic speckle pattern interferometry has been proposed and successfully tested to control this parameter using the real samples of graphite from Ignalina NPP Units. (author)

  18. Internal Grains Within KFC Graphites: Implications for Their Stellar Source

    Science.gov (United States)

    Croat, T. K.; Stadermann, F. J.; Bernatowicz, T. J.

    2005-03-01

    TEM and NanoSIMS investigations find high s-process element enrichments in internal carbides, suggesting an AGB origin for most Murchison KFC presolar graphites. Other rare phases (iron phases and metallic osmium) are consistent with a SN origin.

  19. Technique for production of graphite-carbon products

    Energy Technology Data Exchange (ETDEWEB)

    Antonov, A.N.; Bentsianovskaya, I.A.; Filatova, V.A.; Nabokov, V.S.; Nestor, V.P.; Zil' bergleyt, I.M.

    1982-01-01

    The technique for producing carbon-graphite products that includes filtration under a pressure of 0.1-015 MPa (through graphite stock) of an aqueous carbon material with the addition of surfactant, drying, and subsequent thermal treatment, is simplified and made less lengthy. Oxidized graphite is utilized with a prior addition of 1-10% water-soluble organic substance into the suspension -molasses, hemicellulose, sugar or polyacrylamide. A 0.03-1.5% suspension of oxidized graphite is utilized, with a particle size of 0.02-0.1 mkm. Thermal processing is done in a carbon fill, at a rate of 10-20 degrees/hour to 700-800/sup 0/, maintained 2-3 hours.

  20. Pyrolysis and its potential use in nuclear graphite disposal

    International Nuclear Information System (INIS)

    Mason, J.B.; Bradbury, D.

    2001-01-01

    Graphite is used as a moderator material in a number of nuclear reactor designs, such as MAGNOX and AGR gas cooled reactors in the United Kingdom and the RBMK design in Russia. During construction the moderator of the reactor is usually installed as an interlocking structure of graphite bricks. At the end of reactor life the graphite moderator, weighing typically 2,000 tonnes, is a radioactive waste which requires eventual management. Radioactive graphite disposal options conventionally include: In-situ SAFESTORE for extended periods to permit manual disassembly of the graphite moderator through decay of short-lived radionuclides. Robotic or manual disassembly of the reactor core followed by disposal of the graphite blocks. Robotic or manual disassembly of the reactor core followed by incineration of the graphite and release of the resulting carbon dioxide Studsvik, Inc. is a nuclear waste management and waste processing company organised to serve the US nuclear utility and government facilities. Studsvik's management and technical staff have a wealth of experience in processing liquid, slurry and solid low level radioactive waste using (amongst others) pyrolysis and steam reforming techniques. Bradtec is a UK company specialising in decontamination and waste management. This paper describes the use of pyrolysis and steam reforming techniques to gasify graphite leading to a low volume off-gas product. This allows the following options/advantages. Safe release of any stored Wigner energy in the graphite. The process can accept small pieces or a water-slurry of graphite, which enables the graphite to be removed from the reactor core by mechanical machining or water cutting techniques, applied remotely in the reactor fuel channels. In certain situations the process could be used to gasify the reactor moderator in-situ. The low volume of the off-gas product enables non-carbon radioactive impurities to be efficiently separated from the off-gas. The off-gas product can

  1. High-temperature annealing of graphite: A molecular dynamics study

    Science.gov (United States)

    Petersen, Andrew; Gillette, Victor

    2018-05-01

    A modified AIREBO potential was developed to simulate the effects of thermal annealing on the structure and physical properties of damaged graphite. AIREBO parameter modifications were made to reproduce Density Functional Theory interstitial results. These changes to the potential resulted in high-temperature annealing of the model, as measured by stored-energy reduction. These results show some resemblance to experimental high-temperature annealing results, and show promise that annealing effects in graphite are accessible with molecular dynamics and reactive potentials.

  2. Calculation of reactivity of control rods in graphite moderated reactors

    International Nuclear Information System (INIS)

    Nakata, H.

    1978-01-01

    A study about the method of calculation for the reactivity of control rods in graphite-moderated critical assemblies, is presented. The result of theoretical calculation, developed by super celles and Nordheim-Scalettar methods are compared with experimental results for the critical Assembly of General Atomic. The two methods are then applicable to reactivity calculation of the control rods of graphite moderated critical assemblies [pt

  3. Fabrication and testing of fire resistant graphite composite panels

    Science.gov (United States)

    Roper, W. D.

    1986-01-01

    Eight different graphite composite panels were fabricated using four different resin matrices. The resin matrices included Hercules 71775, a blend of vinylpolystyrpyridine and bismaleimide, H795, a bismaleimide, Cycom 6162, a phenolic, and PSP 6022m, a polystyrylpyridine. Graphite panels were fabricated using fabric or unidirectional tape. Described are the processes for preparing these panels and some of their mechanical, thermal and flammability properties. Panel properties are compared with state-of-the-art epoxy fiberglass composite panels.

  4. Exit Presentation: Infrared Thermography on Graphite/Epoxy

    Science.gov (United States)

    Comeaux, Kayla

    2010-01-01

    This slide presentation reports on the internship project that was accomplished during the summer of 2010. The objectives of the project were to: (1) Simulate Flash Thermography on Graphite/Epoxy Flat Bottom hole Specimen and thin void specimens, (2) Obtain Flash Thermography data on Graphite/Epoxy flat bottom hole specimens, (3) Compare experimental results with simulation results, Compare Flat Bottom Hole Simulation with Thin Void Simulation to create a graph to determine size of IR Thermography detected defects

  5. Features of spherical uranium-graphite HTGR fuel elements control

    International Nuclear Information System (INIS)

    Kreindlin, I.I.; Oleynikov, P.P.; Shtan, A.S.

    1985-01-01

    Control features of spherical HTGR uranium-graphite fuel elements with spherical coated fuel particles are mainly determined by their specific construction and fabrication technology. The technology is chiefly based on methods of ceramic fuel (fuel microspheres fabrication) and graphite production practice it is necessary to deal with a lot of problems from determination of raw materials properties to final fuel elements testing. These procedures are described

  6. Fracture toughness testing of a reactor grade graphite

    Energy Technology Data Exchange (ETDEWEB)

    Roeding, M.; Klein, G.; Schiffers, H.; Nickel, H.

    1976-03-15

    Fracture mechanics is a well established tool for the assessment of brittle fracture in metallic structural materials. In this paper an attempt is made to apply fracture mechanics to a reactor-grade graphite. The effect of several test parameters on the stress intensity factor was measured; this was found to lie in the range 25 and 50 N/mm/sup -3/2/. The results are discussed in terms of the well known mechanical characteristics of graphite.

  7. Features of spherical uranium-graphite HTGR fuel elements control

    Energy Technology Data Exchange (ETDEWEB)

    Kreindlin, I I; Oleynikov, P P; Shtan, A S

    1985-07-01

    Control features of spherical HTGR uranium-graphite fuel elements with spherical coated fuel particles are mainly determined by their specific construction and fabrication technology. The technology is chiefly based on methods of ceramic fuel (fuel microspheres fabrication) and graphite production practice it is necessary to deal with a lot of problems from determination of raw materials properties to final fuel elements testing. These procedures are described.

  8. Feasibility study of fusion breeding blanket concept employing graphite reflector

    International Nuclear Information System (INIS)

    Cho, Seungyon; Ahn, Mu-Young; Lee, Cheol Woo; Kim, Eung Seon; Park, Yi-Hyun; Lee, Youngmin; Lee, Dong Won

    2015-01-01

    Highlights: • A Helium-Cooled Ceramic Reflector (HCCR) breeding blanket concept adopts graphite as a reflector material by reducing the amount of beryllium multiplier. • Its feasibility was investigated in view point of the nuclear performance as well as material-related issues. • A nuclear analysis is performed under the fusion reactor condition to address the feasibility of graphite reflector in breeding blanket. • Also, the chemical stability of the graphite is investigated considering the chemical stability under accident conditions. • In conclusion, the adaptation of graphite reflector in breeding blanket is intrinsically safe and plausible under fusion reactor condition. - Abstract: To obtain high tritium breeding performance with limited blanket thickness, most of solid breeder blanket concepts employ a combination of lithium ceramic as a breeder and beryllium as a multiplier. In this case, considering that huge amount of beryllium are needed in fusion power plants, its handling difficulty and cost can be a major factor to be accounted for commercial use. Korea has proposed a Helium-Cooled Ceramic Reflector (HCCR) breeding blanket concept relevant to fusion power plants. Here, graphite is used as a reflector material by reducing the amount of beryllium multiplier. Its feasibility has been investigated in view point of the nuclear performance as well as material-related issues. In this paper, a nuclear analysis is performed under the fusion reactor condition to address the feasibility of graphite reflector in breeding blanket, considering tritium breeding capability and neutron shielding and activation aspects. Also, the chemical stability of the graphite is investigated considering the chemical stability under accident conditions, resulting in that the adaptation of graphite reflector in breeding blanket is intrinsically safe and plausible under fusion reactor condition.

  9. Feasibility study of fusion breeding blanket concept employing graphite reflector

    Energy Technology Data Exchange (ETDEWEB)

    Cho, Seungyon, E-mail: sycho@nfri.re.kr [National Fusion Research Institute, Daejeon (Korea, Republic of); Ahn, Mu-Young [National Fusion Research Institute, Daejeon (Korea, Republic of); Lee, Cheol Woo; Kim, Eung Seon [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of); Park, Yi-Hyun; Lee, Youngmin [National Fusion Research Institute, Daejeon (Korea, Republic of); Lee, Dong Won [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

    2015-10-15

    Highlights: • A Helium-Cooled Ceramic Reflector (HCCR) breeding blanket concept adopts graphite as a reflector material by reducing the amount of beryllium multiplier. • Its feasibility was investigated in view point of the nuclear performance as well as material-related issues. • A nuclear analysis is performed under the fusion reactor condition to address the feasibility of graphite reflector in breeding blanket. • Also, the chemical stability of the graphite is investigated considering the chemical stability under accident conditions. • In conclusion, the adaptation of graphite reflector in breeding blanket is intrinsically safe and plausible under fusion reactor condition. - Abstract: To obtain high tritium breeding performance with limited blanket thickness, most of solid breeder blanket concepts employ a combination of lithium ceramic as a breeder and beryllium as a multiplier. In this case, considering that huge amount of beryllium are needed in fusion power plants, its handling difficulty and cost can be a major factor to be accounted for commercial use. Korea has proposed a Helium-Cooled Ceramic Reflector (HCCR) breeding blanket concept relevant to fusion power plants. Here, graphite is used as a reflector material by reducing the amount of beryllium multiplier. Its feasibility has been investigated in view point of the nuclear performance as well as material-related issues. In this paper, a nuclear analysis is performed under the fusion reactor condition to address the feasibility of graphite reflector in breeding blanket, considering tritium breeding capability and neutron shielding and activation aspects. Also, the chemical stability of the graphite is investigated considering the chemical stability under accident conditions, resulting in that the adaptation of graphite reflector in breeding blanket is intrinsically safe and plausible under fusion reactor condition.

  10. The effective neutron temperature in heated graphite sleeves

    Energy Technology Data Exchange (ETDEWEB)

    Shaw, J A; Small, V G [General Reactor Physics Division, Atomic Energy Establishment, Winfrith, Dorchester, Dorset (United Kingdom)

    1963-08-15

    In a series of oscillator measurements carried out in the reactor NERO the variation of the relative reaction rates of cadmium and boron absorbers has been used to determine the effective neutron temperature inside heated graphite sleeves. This work extends the scope of similar oscillator measurements previously carried out in DIMPLE, in that the bulk moderator is now graphite as opposed to D{sub 2}O in the former case. (author)

  11. Developments in natural uranium - graphite reactors

    International Nuclear Information System (INIS)

    Bourgeois, J.

    1964-01-01

    The French natural uranium-graphite power-reactor programme has been developing - from EDF 1 to EDF 4 - in the direction of an increase of the unit power of the installations, of the specific and volume powers, and of an improvement in the operational security conditions. The high power of EDF 4 (500 MWe) and the integration of the primary circuit into the reactor vessel, which is itself made of pre-stressed concrete, make it possible to make the most of the annular fuel elements already in use in EDF 1, and to arrive thus at a very satisfactory solution. The use of an internally cooled fuel element (an annular element) has led to a further step forward: it now becomes possible to increase the pressure of the cooling gas without danger of causing creep in the uranium tube. The use of a pre-stressed concrete vessel makes this pressure increase possible, and the integration of the primary circuit avoids the risk of a rapid depressurization which would be in this case a major danger. This report deals with the main problems presented by this new type of nuclear power station, and gives the main lines of research and studies now being carried out in France. - Neutronic and thermal research has made it possible to consider using large size fuel elements (internal diameter = 77 mm, external diameter 95 mm) while still using natural uranium. - The problems connected with the production of these elements and with their in pile behaviour are the subject of a large programme, both out of pile and in power reactors (EDF 2) and test reactors (Pegase). - The increase in the size of the element leads to a large lattice pitch (35 to 40 cm). This makes it possible to consider having one charging aperture per channel or for a small number of channels, whether the charge machine be inside or outside the pressure vessel. In conclusion are given the main characteristics of a project for a 500 MWe power station using such a fuel element. In particular this project is compared to EDF 4

  12. A synchronous surround increases the motion strength gain of motion.

    Science.gov (United States)

    Linares, Daniel; Nishida, Shin'ya

    2013-11-12

    Coherent motion detection is greatly enhanced by the synchronous presentation of a static surround (Linares, Motoyoshi, & Nishida, 2012). To further understand this contextual enhancement, here we measured the sensitivity to discriminate motion strength for several pedestal strengths with and without a surround. We found that the surround improved discrimination of low and medium motion strengths, but did not improve or even impaired discrimination of high motion strengths. We used motion strength discriminability to estimate the perceptual response function assuming additive noise and found that the surround increased the motion strength gain, rather than the response gain. Given that eye and body movements continuously introduce transients in the retinal image, it is possible that this strength gain occurs in natural vision.

  13. Surrounding Moving Obstacle Detection for Autonomous Driving Using Stereo Vision

    Directory of Open Access Journals (Sweden)

    Hao Sun

    2013-06-01

    Full Text Available Detection and tracking surrounding moving obstacles such as vehicles and pedestrians are crucial for the safety of mobile robotics and autonomous vehicles. This is especially the case in urban driving scenarios. This paper presents a novel framework for surrounding moving obstacles detection using binocular stereo vision. The contributions of our work are threefold. Firstly, a multiview feature matching scheme is presented for simultaneous stereo correspondence and motion correspondence searching. Secondly, the multiview geometry constraint derived from the relative camera positions in pairs of consecutive stereo views is exploited for surrounding moving obstacles detection. Thirdly, an adaptive particle filter is proposed for tracking of multiple moving obstacles in surrounding areas. Experimental results from real-world driving sequences demonstrate the effectiveness and robustness of the proposed framework.

  14. Contamination of nebulisers and surrounding air at the bedside of ...

    African Journals Online (AJOL)

    An air sampler was used to collect air samples from the surrounding bedside environment. .... individualised resealable plastic bags and stored upside down in a cooler .... conventional and mesh technology nebulisers used at home by adults.

  15. Glow phenomenon surrounding the vertical stabilizer and OMS pods

    Science.gov (United States)

    1994-01-01

    This 35mm frame, photographed as the Space Shuttle Columbia was orbiting Earth during a 'night' pass, documents the glow phenomenon surrounding the vertical stabilizer and the Orbital Maneuvering System (OMS) pods of the spacecraft.

  16. Strength degradation of oxidized graphite support column in VHTR

    International Nuclear Information System (INIS)

    Park, Byung Ha; No, Hee Cheon

    2010-01-01

    Air-ingress events caused by large pipe breaks are important accidents considered in the design of Very High Temperature Gas-Cooled Reactors (VHTRs). A main safety concern for this type of event is the possibility of core collapse following the failure of the graphite support column, which can be oxidized by ingressed air. In this study, the main target is to predict the strength of the oxidized graphite support column. Through compression tests for fresh and oxidized graphite columns, the compressive strength of IG-110 was obtained. The buckling strength of the IG-110 column is expressed using the following empirical straight-line formula: σ cr,buckling =91.34-1.01(L/r). Graphite oxidation in Zone 1 is volume reaction and that in Zone 3 is surface reaction. We notice that the ultimate strength of the graphite column oxidized in Zones 1 and 3 only depends on the slenderness ratio and bulk density. Its strength degradation oxidized in Zone 1 is expressed in the following nondimensional form: σ/σ 0 =exp(-kd), k=0.114. We found that the strength degradation of a graphite column, oxidized in Zone 3, follows the above buckling empirical formula as the slenderness of the column changes. (author)

  17. Large-scale preparation of hollow graphitic carbon nanospheres

    International Nuclear Information System (INIS)

    Feng, Jun; Li, Fu; Bai, Yu-Jun; Han, Fu-Dong; Qi, Yong-Xin; Lun, Ning; Lu, Xi-Feng

    2013-01-01

    Hollow graphitic carbon nanospheres (HGCNSs) were synthesized on large scale by a simple reaction between glucose and Mg at 550 °C in an autoclave. Characterization by X-ray diffraction, Raman spectroscopy and transmission electron microscopy demonstrates the formation of HGCNSs with an average diameter of 10 nm or so and a wall thickness of a few graphenes. The HGCNSs exhibit a reversible capacity of 391 mAh g −1 after 60 cycles when used as anode materials for Li-ion batteries. -- Graphical abstract: Hollow graphitic carbon nanospheres could be prepared on large scale by the simple reaction between glucose and Mg at 550 °C, which exhibit superior electrochemical performance to graphite. Highlights: ► Hollow graphitic carbon nanospheres (HGCNSs) were prepared on large scale at 550 °C ► The preparation is simple, effective and eco-friendly. ► The in situ yielded MgO nanocrystals promote the graphitization. ► The HGCNSs exhibit superior electrochemical performance to graphite.

  18. Statistical considerations of graphite strength for assessing design allowable stresses

    International Nuclear Information System (INIS)

    Ishihara, M.; Mogi, H.; Ioka, I.; Arai, T.; Oku, T.

    1987-01-01

    Several aspects of statistics need to be considered to determine design allowable stresses for graphite structures. These include: 1) Statistical variation of graphite material strength. 2) Uncertainty of calculated stress. 3) Reliability (survival probability) required from operational and safety performance of graphite structures. This paper deals with some statistical considerations of structural graphite for assessing design allowable stress. Firstly, probability distribution functions of tensile and compressive strengths are investigated on experimental Very High Temperature candidated graphites. Normal, logarithmic normal and Weibull distribution functions are compared in terms of coefficient of correlation to measured strength data. This leads to the adaptation of normal distribution function. Then, the relation between factor of safety and fracture probability is discussed on the following items: 1) As the graphite strength is more variable than metalic material's strength, the effect of strength variation to the fracture probability is evaluated. 2) Fracture probability depending on survival probability of 99 ∼ 99.9 (%) with confidence level of 90 ∼ 95 (%) is discussed. 3) As the material properties used in the design analysis are usually the mean values of their variation, the additional effect of these variations on the fracture probability is discussed. Finally, the way to assure the minimum ultimate strength with required survival probability with confidence level is discussed in view of statistical treatment of the strength data from varying sample numbers in a material acceptance test. (author)

  19. Analysis of graphite gasification by water vapor at different conversions

    International Nuclear Information System (INIS)

    Xiaowei, Luo; Xiaoyu, Yu; Suyuan, Yu; Jean-Charles, Robin

    2014-01-01

    Highlights: • Graphite was gasified at different conversions. • The reaction temperature influences on the dimensionless the reaction rate. • The thickness or radius influence on the dimensionless reaction rate. - Abstract: The gasification rate of porous solids varies with the conversions with the rate increasing to a maximum and then decreasing. Many graphite gasification experiments have illustrated that the maximum gasification rates occur at different conversions for different temperatures and sample geometries. Thus, the gasification rate is related to the conversion, temperature and geometry of the graphite. The influences of those factors were studied for the graphite gasification by water vapor. A theoretical analysis was done on the basis of several logical assumptions. The influence of temperatures on the reaction rate was investigated for plate-like and cylindrical graphite. The effects of thickness for a plate-like graphite sample and of radius for a cylindrical sample on the reaction rate were also studied theoretically. The results reveal that the maximum dimensionless reaction rate decreases with reaction temperature. The plate thickness or the cylinder radius also affects the maximum dimensionless reaction rate

  20. Ionic liquids at the surface of graphite: Wettability and structure

    Science.gov (United States)

    Bordes, Emilie; Douce, Laurent; Quitevis, Edward L.; Pádua, Agílio A. H.; Costa Gomes, Margarida

    2018-05-01

    The aim of this work is to provide a better understanding of the interface between graphite and different molecular and ionic liquids. Experimental measurements of the liquid surface tension and of the graphite-liquid contact angle for sixteen ionic liquids and three molecular liquids are reported. These experimental values allowed the calculation of the solid/liquid interfacial energy that varies, for the ionic liquids studied, between 14.5 mN m-1 for 1-ethyl-3-methylimidazolium dicyanamide and 37.8 mN m-1 for 3-dodecyl-1-(naphthalen-1-yl)-1H-imidazol-3-ium tetrafluoroborate. Imidazolium-based ionic liquids with large alkyl side-chains or functionalized with benzyl groups seem to interact more favourably with freshly peeled graphite surfaces. Even if the interfacial energy seems a good descriptor to assess the affinity of a liquid for a carbon-based solid material, we conclude that both the surface tension of the liquid and the contact angle between the liquid and the solid can be significant. Molecular dynamics simulations were used to investigate the ordering of the ions near the graphite surface. We conclude that the presence of large alkyl side-chains in the cations increases the ordering of ions at the graphite surface. Benzyl functional groups in the cations lead to a large affinity towards the graphite surface.

  1. Evaluation of Accelerated Graphitic Corrosion Test of Gray Cast Iron

    International Nuclear Information System (INIS)

    Kim, Jeong Hyeon; Hong, Jong Dae; Chang Heui; Na, Kyung Hwan; Lee, Jae Gon

    2011-01-01

    In operating nuclear power plants, gray cast iron is commonly used as materials for various non-safety system components including pipes in fire water system, valve bodies, bonnets, and pump castings. In such locations, operating condition does not require alloy steels with excellent mechanical properties. But, a few corrosion related degradation, or graphitic corrosion is frequently occurred to gray cast iron during the long-term operation in nuclear power plant. Graphitic corrosion is selective leaching of iron from gray cast iron, where iron gets removed and graphite grains remain intact. In U.S.A., one-time visual inspection and hardness measurement are required from regulatory body to detect the graphitic corrosion for the life extension evaluation of the operating nuclear power plant. In this study, experiments were conducted to make accelerated graphitic corrosion of gray cast iron using electrochemical method, and hardness was measured for the specimens to establish the correlation between degree of graphitic corrosion and surface hardness of gray cast iron

  2. Electrical and thermal properties of graphite/polyaniline composites

    Energy Technology Data Exchange (ETDEWEB)

    Bourdo, Shawn E., E-mail: sxbourdo@ualr.edu [Center for Integrative Nanotechnology Sciences, University of Arkansas at Little Rock, 2801 South University Avenue, Little Rock, AR 72204 (United States); Warford, Brock A.; Viswanathan, Tito [Department of Chemistry, University of Arkansas at Little Rock, 2801 South University Avenue, Little Rock, AR 72204 (United States)

    2012-12-15

    A composite of a carbon allotrope (graphite) and an inherently conducting polymer, polyaniline (PANI), has been prepared that exhibits an electrical conductivity greater than either of the two components. An almost 2-fold increase in the bulk conductivity occurs when only a small mass fraction of polyaniline exists in the composite (91% graphite/ 9% polyaniline, by mass). This increase in dc electrical conductivity is curious since in most cases a composite material will exhibit a conductivity somewhere between the two individual components, unless a modification to the electronic nature of the material occurs. In order to elucidate the fundamental electrical properties of the composite we have performed variable temperature conductivity measurements to better understand the nature of conduction in these materials. The results from these studies suggest a change in the mechanism of conduction as the amount of polyaniline is increased in the composite. Along with superior electrical properties, the composites exhibit an increase in thermal stability as compared to the graphite. - Graphical abstract: (Left) Room temperature electrical conductivity of G-PANI composites at different mass ratios. (Right) Electrical conductivity of G-PANI composites at temperatures from 5 K to 300 K. Highlights: Black-Right-Pointing-Pointer Composites of graphite and polyaniline have been synthesized with unique electrical and thermal properties. Black-Right-Pointing-Pointer Certain G-PANI composites are more conductive and more thermally stable than graphite alone. Black-Right-Pointing-Pointer G-PANI composites exhibit a larger conductivity ratio with respect to temperature than graphite alone.

  3. Large-scale preparation of hollow graphitic carbon nanospheres

    Energy Technology Data Exchange (ETDEWEB)

    Feng, Jun; Li, Fu [Key Laboratory for Liquid-Solid Structural Evolution and Processing of Materials, Ministry of Education, Shandong University, Jinan 250061 (China); Bai, Yu-Jun, E-mail: byj97@126.com [Key Laboratory for Liquid-Solid Structural Evolution and Processing of Materials, Ministry of Education, Shandong University, Jinan 250061 (China); State Key laboratory of Crystal Materials, Shandong University, Jinan 250100 (China); Han, Fu-Dong; Qi, Yong-Xin; Lun, Ning [Key Laboratory for Liquid-Solid Structural Evolution and Processing of Materials, Ministry of Education, Shandong University, Jinan 250061 (China); Lu, Xi-Feng [Lunan Institute of Coal Chemical Engineering, Jining 272000 (China)

    2013-01-15

    Hollow graphitic carbon nanospheres (HGCNSs) were synthesized on large scale by a simple reaction between glucose and Mg at 550 Degree-Sign C in an autoclave. Characterization by X-ray diffraction, Raman spectroscopy and transmission electron microscopy demonstrates the formation of HGCNSs with an average diameter of 10 nm or so and a wall thickness of a few graphenes. The HGCNSs exhibit a reversible capacity of 391 mAh g{sup -1} after 60 cycles when used as anode materials for Li-ion batteries. -- Graphical abstract: Hollow graphitic carbon nanospheres could be prepared on large scale by the simple reaction between glucose and Mg at 550 Degree-Sign C, which exhibit superior electrochemical performance to graphite. Highlights: Black-Right-Pointing-Pointer Hollow graphitic carbon nanospheres (HGCNSs) were prepared on large scale at 550 Degree-Sign C Black-Right-Pointing-Pointer The preparation is simple, effective and eco-friendly. Black-Right-Pointing-Pointer The in situ yielded MgO nanocrystals promote the graphitization. Black-Right-Pointing-Pointer The HGCNSs exhibit superior electrochemical performance to graphite.

  4. Thermal shock test of TiC and graphite

    International Nuclear Information System (INIS)

    Shirakawa, H.; Okamura, J.; Son, P.; Miyake, M.

    1989-01-01

    Thermal shock tests were performed by pulse electron beam heating on chemically vapor deposited coatings of TiC on Poco graphite, bulk TiC, and several kinds of isotropic graphite. The specimens were heated at various power densities (10-45 MW/m 2 ) for various pulse durations (1-2 s) to examine the dependence of thermal failures on heating conditions. The TiC coating on graphite suffered cracking, surface melting and evaporation by the thermal pulse. The surface melting limit, defined as F τ 1/2 , where F is the minimum power density that causes surface melting for a specified pulse duration τ, was approximately 48 MWs 1/2 /m 2 for the TiC coating. The combined-Carbon/Titanium ratio of the coating after electron beam heating decreased with increasing power density and pulse duration. The bulk TiC specimens were so brittle that they fractured at heat load conditions where the coating showed no damage. The graphite specimens showed sublimation as a principal damage mechanism by the thermal pulse, and the sublimation weight loss decreased with increasing the thermal conductivity of the specimen. It was confirmed that the TiC coating on graphite had favorable resistance to thermal shock as compared to the bulk TiC and that graphite with high thermal conductivity is promising material as a high heat flux component. (orig.)

  5. Porosity effects in the neutron total cross section of graphite

    International Nuclear Information System (INIS)

    Santisteban, J. R; Dawidowski, J; Petriw, S. N

    2009-01-01

    Graphite has been used in nuclear reactors since the birth of the nuclear industry due to its good performance as a neutron moderator material. Graphite is still an option as moderator for generation IV reactors due to its good mechanical and thermal properties at high operation temperatures. So, there has been renewed interest in a revision of the computer libraries used to describe the neutron cross section of graphite. For sub-thermal neutron energies, polycrystalline graphite shows a larger total cross section (between 4 and 8 barns) than predicted by existing theoretical models (0.2 barns). In order to investigate the origin of this discrepancy we measured the total cross section of graphite samples of three different origins, in the energy range from 0.001 eV to 10 eV. Different experimental arrangements and sample treatments were explored, to identify the effect of various experimental parameters on the total cross section measurement. The experiments showed that the increase in total cross section is due to neutrons scattered around the forward direction. We associate these small-angle scattered neutrons (SANS) to the porous structure of graphite, and formulate a very simple model to compute its contribution to the total cross section of the material. This results in an analytic expression that explicitly depends on the density and mean size of the pores, which can be easily incorporated in nuclear library codes. [es

  6. Correlation between some mechanical and physical properties of polycrystalline graphites

    International Nuclear Information System (INIS)

    Yoda, Shinichi; Fujisaki, Katsuo

    1982-01-01

    Mechanical and physical properties of polycrystalline graphites, tensile strength, compressive strength, flexural strength, Young's modulus, thermal expansion coefficient, electrical resistivity, volume fraction of porosity, and graphitisation were measured for ten brand graphites. Correlation between the mechanical and physical properties of the graphites were studied. Young's modulus and thermal expansion coefficient of the graphites depend on volume fraction of porosity. The Young's modulus of the graphites tended to increase with increasing the thermal expansion coefficient. For an anisotropic graphite, an interesting relationship between the Young's modulus E and the thermal expansion coefficient al pha was found in any specimen orientations; alpha E=constant. The value of alphah E was dependent upon the volume fraction of porosity. It should be noted here that the electrical resistivity increased with decreasing grain size. The flexural and the compressive strength were related with the volume fraction of porosity while the tensile strength was not, The relationships between the tensile, the compressive and the flexural strength can be approximately expressed as linear functions over a wide range of the stresses. (author)

  7. Monitoring program of surrounding of the NPP SE-EBO

    International Nuclear Information System (INIS)

    Dobis, L.; Kostial, J.

    1997-01-01

    The paper dealt with monitoring program of radiation control of surrounding of the NPP Bohunice, which has the aim: (1) to ensure the control of influence of work of the NPP Bohunice on the environment in their surrounding; (2) to ensure the back-ground for regular brief of control and supervisory organs about condition of the environment in surrounding of the NPP Bohunice; (3) to maintain the expected technical level of control of the NPP Bohunice and to exploit optimally the technical means; (4) to solicit permanently the data about the radioactivity of environment in surrounding of the NPP Bohunice for forming of files of the data; (5) to exploit purposefully the technical equipment, technical workers and to maintain their in permanent emergency and technical eligibility for the case of the breakdown; (6) to obtain permanently the files of the values for qualification of the reference levels. This program of monitoring includes the radiation control of surrounding of the NPP Bohunice, in the time of normal work of power-station's blocks, inclusively of all types of trouble-shooting and repairer works in surrounding of the NPP Bohunice, up to distance 20 km from power-station. The monitoring includes: outlets from the NPP Bohunice, monitoring of radiation characteristics in surrounding of the NPP Bohunice, (aerosols, fall-outs, soil), the links of food chains: (grass and fodder, milk, agriculture products), hydrosphere in surrounding (surface waters, drink water, bores of radiation control in complex of the NPP Bohunice, components of the hydrosphere), measurement of radiation from external sources (measurement of the dose rates, measurement of the doses [sk

  8. Chromatic induction from surrounding stimuli under perceptual suppression.

    Science.gov (United States)

    Horiuchi, Koji; Kuriki, Ichiro; Tokunaga, Rumi; Matsumiya, Kazumichi; Shioiri, Satoshi

    2014-11-01

    The appearance of colors can be affected by their spatiotemporal context. The shift in color appearance according to the surrounding colors is called color induction or chromatic induction; in particular, the shift in opponent color of the surround is called chromatic contrast. To investigate whether chromatic induction occurs even when the chromatic surround is imperceptible, we measured chromatic induction during interocular suppression. A multicolor or uniform color field was presented as the surround stimulus, and a colored continuous flash suppression (CFS) stimulus was presented to the dominant eye of each subject. The subjects were asked to report the appearance of the test field only when the stationary surround stimulus is invisible by interocular suppression with CFS. The resulting shifts in color appearance due to chromatic induction were significant even under the conditions of interocular suppression for all surround stimuli. The magnitude of chromatic induction differed with the surround conditions, and this difference was preserved regardless of the viewing conditions. The chromatic induction effect was reduced by CFS, in proportion to the magnitude of chromatic induction under natural (i.e., no-CFS) viewing conditions. According to an analysis with linear model fitting, we revealed the presence of at least two kinds of subprocesses for chromatic induction that reside at higher and lower levels than the site of interocular suppression. One mechanism yields different degrees of chromatic induction based on the complexity of the surround, which is unaffected by interocular suppression, while the other mechanism changes its output with interocular suppression acting as a gain control. Our results imply that the total chromatic induction effect is achieved via a linear summation of outputs from mechanisms that reside at different levels of visual processing.

  9. Data Report on the Newest Batch of PCEA Graphite for the VHTR Baseline Graphite Characterization Program

    Energy Technology Data Exchange (ETDEWEB)

    Carroll, Mark Christopher [Idaho National Lab. (INL), Idaho Falls, ID (United States); Cottle, David Lynn [Idaho National Lab. (INL), Idaho Falls, ID (United States); Rohrbaugh, David Thomas [Idaho National Lab. (INL), Idaho Falls, ID (United States)

    2016-08-01

    This report details a comparison of mechanical and physical properties from the first billet of extruded PCEA nuclear-grade graphite from the newest batch of PCEA procured from GrafTech. Testing has largely been completed on three of the billets from the original batch of PCEA, with data distributions for those billets exhibiting a much wider range of values when compared to the distributions of properties from other grades. A higher propensity for extremely low values or specimens that broke while machining or handling was also characteristic of the billets from the first batch, owing to unusually large fissures or disparate flaws in the billets in an as-manufactured state. Coordination with GrafTech prior to placing the order for a second batch of PCEA included discussions on these large disparate flaws and how to prevent them during the manufacturing process. This report provides a comparison of the observed data distributions from properties measured in the first billet from the new batch of PCEA with those observed in the original batch, in order that an evaluation of tighter control of the manufacturing process and the outcome of these controls on final properties can be ascertained. Additionally, this billet of PCEA is the first billet to formally include measurements from two alternate test techniques that will become part of the Baseline Graphite Characterization database – the three-point bend test on sub-sized cylinders and the Brazilian disc splitting tensile strength test. As the program moves forward, property distributions from these two tests will be based on specimen geometries that match specimen geometries being used in the irradiated Advanced Graphite Creep (AGC) program. This will allow a more thorough evaluation of both the utility of the test and expected variability in properties when using those approaches on the constrained geometries of specimens irradiated in the Advanced Test Reactor as part of the AGC experiment.

  10. Magnetic susceptibilities and thermal expansion of artificial graphites; Susceptibilites magnetiques et dilatation thermique des graphites artificiels

    Energy Technology Data Exchange (ETDEWEB)

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

    1960-07-01

    Starting from measurements of the magnetic susceptibility made in the two principal directions of a graphite bar, the distribution function of the normals to the carbon planes in the crystallites has been evaluated. The effect of different variation in the manufacturing process on this crystalline anisotropy has been studied. From this crystalline anisotropy we have calculated the thermal expansion coefficient possessed by a compact mass of crystallites having exactly the same orientational anisotropy as the porous body consideration. The difference between this and the observed expansion coefficient leads to the determination of the expansion of the non-graphitic part of the mass which turns out to have a negative value and is also anisotropic. We have attempted to draw some conclusions from this result. (author) [French] En partant des mesures de la susceptibilite magnetique faites dans les directions des axes principaux d'un barreau de graphite, on a calcule la fonction de distribution des perpendiculaires aux plans graphitiques dans les cristallites. On a etudie les effets que pouvaient provoquer des modifications dans le procede de fabrication sur l'anisotropie cristalline. En considerant cette anisotropie cristalline, nous avons calcule le coefficient de dilatation thermique pour un bloc compact de cristallites ayant exactement la meme anisotropie d'orientation que le corps poreux en question. La difference entre cette valeur et celle mesuree du coefficient de dilatation, nous permet de calculer la dilatation pour la partie non-graphitique du bloc, en l'occurence, on trouve une valeur negative du coefficient pour cette partie, qui est egalement anisotropique. On a essaye d'en tirer quelques conclusions. (auteur)

  11. Graphite as negative electrode in Li-ion batteries; Le graphite comme electrode negative dans les accumulateurs Li-ion

    Energy Technology Data Exchange (ETDEWEB)

    Fischer, F.; Monnier, A. [Timcal SA (France)

    1996-12-31

    The last developments in lithium batteries design have demonstrated the advantages of graphite: competitive cost, flat output curve, high capacity thanks to the obtention of a final compound close to LiC{sub 6}, good behaviour during cycling and a high mass energy. However, these advantages are slightly tarnished by parasite secondary reactions during the evolution of the element. Two different cases are encountered: the formation of a passivation layer (loss of Li ions and formation of irreversible bounds) and the formation of a passivation layer with a reaction between graphite and the solvent (partial destruction of the graphite crystal lattice). In the first case, the theoretical graphite insertion capacity remains at 372 mAh/g while in the second case the insertion capacity is greatly reduced. Abstract only. (J.S.)

  12. Graphite as negative electrode in Li-ion batteries; Le graphite comme electrode negative dans les accumulateurs Li-ion

    Energy Technology Data Exchange (ETDEWEB)

    Fischer, F; Monnier, A [Timcal SA (France)

    1997-12-31

    The last developments in lithium batteries design have demonstrated the advantages of graphite: competitive cost, flat output curve, high capacity thanks to the obtention of a final compound close to LiC{sub 6}, good behaviour during cycling and a high mass energy. However, these advantages are slightly tarnished by parasite secondary reactions during the evolution of the element. Two different cases are encountered: the formation of a passivation layer (loss of Li ions and formation of irreversible bounds) and the formation of a passivation layer with a reaction between graphite and the solvent (partial destruction of the graphite crystal lattice). In the first case, the theoretical graphite insertion capacity remains at 372 mAh/g while in the second case the insertion capacity is greatly reduced. Abstract only. (J.S.)

  13. Low-energy electron observation of graphite and molybdenite crystals. Application to the study of graphite oxidation

    International Nuclear Information System (INIS)

    David, G.

    1969-01-01

    The LEED study of cleaved (0001) faces of crystals having a layered structure allowed to investigate flakes free of steps on graphite and molybdenite, to show twinning on natural graphite. By intensity measurements and computation in the case of a kinematical approximation it has been possible to determine an inner potential of 19 eV for graphite and to identify the direction of the Mo-S bond of the surface layer of molybdenite. The oxidation of graphite has been studied by observing changes, in symmetry of the diffraction patterns and by mass spectrometry of the gases evolved during the oxidation. No surface compounds have been detected and the carbon layers appeared to be peeled off one after the other. The oxidation took place at temperatures higher than 520 C under an oxygen pressure of 10 -5 torr. (author) [fr

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

    International Nuclear Information System (INIS)

    Anfimov, S.S.

    2000-01-01

    As a result of decommissioning of water-cooled graphite-moderated reactors, a large amount of rad-waste in the form of graphite stack fragments is generated (on average 1500-2000 tons per reactor). That is why it is essentially important, although complex from the technical point of view, to develop advanced technologies based on up-to-date remotely-controlled systems for unmanned dismantling of the graphite stack containing highly-active long-lived radionuclides and for conditioning of irradiated graphite (IG) for the purposes of transportation and subsequent long term and ecologically safe storage either on NPP sites or in special-purpose geological repositories. The main characteristics critical for radiation and nuclear hazards of the graphite stack are as follows: the graphite stack is contaminated with nuclear fuel that has gotten there as a result of the accidents; the graphite mass is 992 tons, total activity -6?104 Ci (at the time of unit shutdown); the fuel mass in the reactor stack amounts to 100-140 kg, as estimated by IPPE and RDIPE, respectively; γ-radiation dose rate in the stack cells varies from 4 to 4300 R/h, with the prevailing values being in the range from 50 to 100 R/h. In this paper the traditional methods of rad-waste handling as bituminization technology, cementing technology are discussed. In terms of IG handling technology two lines were identified: long-term storage of conditioned IG and IG disposal by means of incineration. The specific cost of graphite immobilization in a radiation-resistant polymeric matrix amounts to -2600 USD per 1 t of graphite, whereas the specific cost of immobilization in slag-stone containers with an inorganic binder (cement) is -1400 USD per 1 t of graphite. On the other hand, volume of conditioned IG rad-waste subject for disposal, if obtained by means of the first technology, is 2-2.5 times less than the volume of rad-waste generated by means of the second technology. It can be concluded from the above that

  15. Graphite epoxy composite degradation by space radiation

    International Nuclear Information System (INIS)

    Taheri, M.; Sandquist, G.M.; Slaughter, D.M.; Bennion, J.

    1991-01-01

    The radiation environment in space is a critical consideration for successful operation in space. All manned space missions with a duration of more than a few days are subjected to elevated ionizing radiation exposures, which are a threat to both personnel and structures in space. The increasing demands for high-performance materials as structural components in the aerospace, aircraft, and defense industries have led to the development of materials such as graphite fiber-reinforced, epoxy resin matrix composites (Gr/Ep). These materials provide important advantages over conventional structural materials, such as ultrahigh specific strength, enhanced specific moduli, and better fatigue resistance. The fact that most advanced composite materials under cyclic fatigue loading evidence little or no observable crack growth prior to rapid fracture suggests that for fail-safe considerations of parts subject to catastrophic failure, a detailed evaluation of radiation damage from very energetic particle is crucial. The Gr/Ep components are believed to suffer severe degradation in space due to highly penetrating secondary radiation, mainly from neutrons and protons. Investigation into the performance and stability of Gr/Ep materials are planned

  16. Pyrolytic Graphite as a Selective Neutron Filter

    International Nuclear Information System (INIS)

    Adib, M.; Habib, N.; Fathalla, M.

    2006-01-01

    The transmission of neutrons through pyrolytic graphite (PG) crystals, set at different angles with respect to incident beam, were calculated using an additive formula. A computer program HOPG was developed to provide the required calculation. An overall agreement between the calculated neutron transmissions through a slab of 1,85 mm thick PG crystal with an angular spread of c-axes of 0,4 degree, set at different angles to the incident beam, and the available experimental ones in the wavelength range from (0,02 to 1,4) nm were obtained. A feasibility study for use of PG crystal as an efficient second-order neutron filter is detailed in terms of crystal thickness, angular spread of c-axes and its operation with respect to the neutron beam. It was shown that a PG crystal with an angular spread of c-axes and its orientation with respect to the neutron beam. It was shown that a PG crystal with an angular spread of 0,8 degree is sufficient for optimum scattering of second-order neutrons in the wavelength band (0,384-0,183) nm, by adjusting the filter in an appropriate orientation

  17. Reflectivity and filtering characteristics of pyrolytic graphite

    International Nuclear Information System (INIS)

    Adib, M.; Abdel-Kawy, A.; Ashry, A.; Abbas, Y.; Wahba, W.

    1988-01-01

    The neutron transmission measurements through oriented pyrolytic graphite (P.G. crystal) were carried out in the wavelength band from 0.15 nm to 6.5 nm at different orientations of the (002) plane of the crystal w.r.t. the neutron beam direction. It was found that the P.G. crystal may be tuned for optimum scattering of second-order neutrons in the wavelength ranging between 0.112 nm and 0.425 nm, by adjusting the filter in an appropriate orientation. The reflectivity of (002), (004) and (006) planes of P.G. were measured and the following results are obtained: the reflectivity of (002) plane was found to be 99% by (transmission method). The ratio of the integrated intensity of the reflected neutrons from (004) and (006) is 3.14+-0.25 and is found to be in agreement with the calculated ratio. The measurements were performed using the fixed scattering angle spectrometer installed in front of the ET-RR-1 reactor horizontal channel

  18. The behavior of interstitials in irradiated graphite

    International Nuclear Information System (INIS)

    Pedraza, D.F.

    1991-01-01

    A computer model is developed to simulate the behavior of self-interstitials with particular attention to clustering. Owing to the layer structure of graphite, atomistic simulations can be performed using a large parallelepipedic supercell containing a few layers. In particular, interstitial clustering is studied here using a supercell that contains two basal planes only. Frenkel pairs are randomly produced. Interstitials are placed at sites between the crystal planes while vacancies are distributed in the two crystal planes. The size of the computational cell is 20000 atoms and periodic boundary conditions are used in two dimensions. Vacancies are assumed immobile whereas interstitials are given a certain mobility. Two point defect sinks are considered, direct recombination of Frenkel pairs and interstitial clusters. The clusters are assumed to be mobile up to a certain size where they are presumed to become loop nuclei. Clusters can shrink by emission of singly bonded interstitials or by recombination of a peripheral interstitial with a neighboring vacancy. The conditions under which interstitial clustering occurs are reported. It is shown that when clustering occurs the cluster size population gradually shifts towards the largest size cluster. The implications of the present results for irradiation growth and irradiation-induced amorphization are discussed

  19. Moessbauer study of small amounts of iron in graphite, around the diamond-graphite pressure-temperature stability region

    International Nuclear Information System (INIS)

    Oliveira, C.L.S. de; Silva, M.T.X.; Vasquez, A.; Jornada, J.A.H. da

    1991-01-01

    An exploratory Moessbauer spectroscopy study of the Fe-C system in the C rich region, prepared by high pressure-high temperature treatment near the graphite-diamond stability line, was made. The results obtained for the different processing conditions give no evidence of Fe intercalation in graphite. The presence of some water in the cell produced hydrated Fe complexes, which can explain the deleterious effect of water or hydrogen in the high pressure diamond synthesis. (orig.)

  20. Chemical vapor deposition of tantalum on graphite cloth for making hot pressed fiber reinforced carbide-graphite composite

    International Nuclear Information System (INIS)

    Hollabaugh, C.M.; Davidson, K.V.; Radosevich, C.L.; Riley, R.E.; Wallace, T.C.

    1977-01-01

    Conditions for the CVD of a uniform coating of Ta on fibers of a woven graphite cloth were established. The effect of gas composition, pressure, and temperature were investigated, and the conditions that gave the desired results are presented. Several layers of the coated cloth were hot pressed to produce a TaC--C composite having uniformly dispersed, fine-grained TaC in graphite. Three compositions were hot pressed: 15, 25, and 40 volume percent carbide. 8 figures, 2 tables

  1. A experimental system for the checking of the absorption of E.C.A.G. graphite; Empilement pour le controle du graphite E.C.A.G

    Energy Technology Data Exchange (ETDEWEB)

    Raievski, V; Vidal, R [Commissariat a l' Energie Atomique, Fontenay-aux-Roses (France). Centre d' Etudes Nucleaires

    1958-07-01

    A system is described for measuring the mean absorption cross section in thermal neutrons of graphite. This system consists of a graphite stack containing a Ra-Be source and a BF3 counter. A cavity in the stack receives the graphite to be studied or the graphite standard. By comparing the counting rates their absorption ratio can be deduced. The measurement is performed on graphite rods which have been machined before being placed in the pile. It provides the possibility of detecting over a batch of 1 ton of graphite, in a single measurement, a difference in absorption of 0.1 milli barn. (author) [French] On decrit un dispositif permettant de mesurer la section efficace moyenne d'absorption en neutrons thermiques du graphite. Ce dispositif est constitue par un empilement de graphite contenant une source de Ra-Be et un compteur a BF3. Une cavite menagee dans l'empilement peut recevoir le graphite a etudier ou le graphite etalon. Par comparaison des taux de comptage, on en deduit leur rapport d'absorption. La mesure est effectuee sur des barres de graphite usinees avant leur mise en place dans la pile. Elle permet de deceler sur un lot de graphite de 1 tonne, en une seule mesure, une difference d'absorption de 0,1 millibarn. (auteur)

  2. Forest Fragments Surrounded by Sugar Cane Are More Inhospitable to Terrestrial Amphibian Abundance Than Fragments Surrounded by Pasture

    Directory of Open Access Journals (Sweden)

    Paula Eveline Ribeiro D’Anunciação

    2013-01-01

    Full Text Available In recent years, there has been increasing interest in matrix-type influence on forest fragments. Terrestrial amphibians are good bioindicators for this kind of research because of low vagility and high philopatry. This study compared richness, abundance, and species composition of terrestrial amphibians through pitfall traps in two sets of semideciduous seasonal forest fragments in southeastern Brazil, according to the predominant surrounding matrix (sugar cane and pasture. There were no differences in richness, but fragments surrounded by sugar cane had the lowest abundance of amphibians, whereas fragments surrounded by pastures had greater abundance. The most abundant species, Rhinella ornata, showed no biometric differences between fragment groups but like many other amphibians sampled showed very low numbers of individuals in fragments dominated by sugar cane fields. Our data indicate that the sugar cane matrix negatively influences the community of amphibians present in fragments surrounded by this type of land use.

  3. Structural features of the adsorption layer of pentacene on the graphite surface and the PMMA/graphite hybrid surface

    Science.gov (United States)

    Fadeeva, A. I.; Gorbunov, V. A.; Litunenko, T. A.

    2017-08-01

    Using the molecular dynamics and the Monte Carlo methods, we have studied the structural features and growth mechanism of the pentacene film on graphite and polymethylmethacrylate /graphite surfaces. Monolayer capacity and molecular area, optimal angles between the pentacene molecules and graphite and PMMA/graphite surfaces as well as the characteristic angles between the neighboring pentacene molecules in the adsorption layer were estimated. It is shown that the orientation of the pentacene molecules in the film is determined by a number of factors, including the surface concentration of the molecules, relief of the surface, presence or absence of the polymer layer and its thickness. The pentacene molecules adsorbed on the graphite surface keep a horizontal position relative to the long axis at any surface coverage/thickness of the film. In the presence of the PMMA layer on the graphite, the increase of the number of pentacene molecules as well as the thickness of the PMMA layer induce the change of molecular orientation from predominantly horizontal to vertical one. The reason for such behavior is supposed to be the roughness of the PMMA surface.

  4. Elaboration of aluminum oxide-based graphite containing castables

    Science.gov (United States)

    Zhou, Ningsheng

    The aim of this work was set to develop effective and practicable new methods to incorporate natural flake graphite (FG) into the Al2O 3 based castables for iron and steel making applications. Three approaches, viz. micro-pelletized graphite (PG), crushed briquette of Al2O3-graphite (BAG) and TiO2 coated graphite (CFG), have been developed to insert flake graphite into Al2O 3 rich Al2O3-SiC based and Al2O 3-MgO based castables. These approaches were put into effect as countermeasures against the problems caused by FG in order: (1) to agglomerate the FG powders so as to decrease the specific surface area; (2) to diminish the density difference by using crushed carbon bonded compact of oxide-FG mixture; (3) to modify the surface of the flake graphite by forming hydrophilic coating; (4) to control the dispersion state of the graphite in the castable to maintain enough bonding strength; and (5) to use appropriate antioxidants to inhibit the oxidation of FG. The whole work was divided into two stages. In stage one, Al2O 3-SiC-C castables were dealt with to compare 4 modes of inserting graphite, i.e., by PG, BAG, CFG and FG. Overall properties were measured, all in correlation with graphite amount and incorporating mode. In stage two, efforts were made to reduce water demand in the Al2O3-MgO castables system. For this purpose, the matrix portion of the castable mixes was extracted and a coaxial double cylinder viscometer was adopted to investigate rheological characteristics of the matrix slurries vs. 4 kinds of deflocculants, through which the best deflocculant and its appropriate amount were found. Efforts were then made to add up to 30% MgO into the castables, using a limited amount of powders (antioxidants, Si, SiC, B4C and ZrB2, were added respectively or in combination. Overall properties of the castables, were investigated in correlation with MgO amount and graphite and antioxidant packages. Optimization work on oxidation and slag resistance was pursued. Finally

  5. Thermophysical properties estimation of paraffin/graphite composite phase change material using an inverse method

    International Nuclear Information System (INIS)

    Lachheb, Mohamed; Karkri, Mustapha; Albouchi, Fethi; Mzali, Foued; Nasrallah, Sassi Ben

    2014-01-01

    Highlights: • Preparation of paraffin/graphite composites by uni-axial compression technique. • Measurement of thermophysical properties of paraffin/graphite using the periodic method. • Measurement of the experimental densities of paraffin/graphite composites. • Prediction of the effective thermal conductivity using analytical models. - Abstract: In this paper, two types of graphite were combined with paraffin in an attempt to improve thermal conductivity of paraffin phase change material (PCM): Synthetic graphite (Timrex SFG75) and graphite waste obtained from damaged Tubular graphite Heat Exchangers. These paraffin/graphite phase change material (PCM) composites are prepared by the cold uniaxial compression technique and the thermophysical properties were estimated using a periodic temperature method and an inverse technique. Results showed that the thermal conductivity and thermal diffusivity are greatly influenced by the graphite addition

  6. Exploring the electrochemical performance of graphitic paste electrodes: graphene vs. graphite.

    Science.gov (United States)

    Figueiredo-Filho, Luiz C S; Brownson, Dale A C; Gómez-Mingot, Maria; Iniesta, Jesús; Fatibello-Filho, Orlando; Banks, Craig E

    2013-11-07

    We report the fabrication, characterisation (SEM, TEM, XPS and Raman spectroscopy) and electrochemical implementation of a graphene paste electrode. The paste electrodes utilised are constructed by simply mixing graphene with mineral oil (which acts as a binder) prior to loading the resultant paste into a piston-driven polymeric-tubing electrode-shell, where this electrode configuration allows for rapid renewal of the electrode surface. The fabricated paste electrode is electrochemically characterised using both inner-sphere and outer-sphere redox probes, namely potassium ferrocyanide(ii), hexaammine-ruthenium(iii) chloride and hexachloroiridate(iii), in addition to the biologically relevant and electroactive analytes, l-ascorbic acid (AA) and uric acid (UA). Comparisons are made with a graphite paste alternative and the benefits of graphene implementation as a paste electrode within electrochemistry are explored, as well as the characterisation of their electroanalytical performances. We reveal no observable differences in the electrochemical performance and thus suggest that there are no advantages of using graphene over graphite in the fabrication of paste electrodes. Such work is highly important and informative for those working in the field of electroanalysis where electrochemistry can provide portable, rapid, reliable and accurate sensing protocols (bringing the laboratory into the field), with particular relevance to those searching for new electrode materials.

  7. Exponential experiment on a uranium-graphite lattice; Experience exponentielle sur un reseau uranium-graphite

    Energy Technology Data Exchange (ETDEWEB)

    Leroy, J; Martelly, J

    1958-12-01

    An exponential experiment on a natural uranium and graphite lattice is described. The critical buckling for a cubic pile made with this lattice is B{sup 2} = 0.726 {+-} 0.011 m{sup -2} and the anisotropy {alpha} = (B{sub L}{sup 2}/B{sub T}{sup 2}) is 0.987 {+-} 0.006. The behavior of the neutron density in the lattice near the reflector and sources is discussed in detail. (authors) [French] Une experience exponentielle sur reseau a uranium naturel et graphite est decrite. Le Laplacien de la pile cubique nue, critique, constituee avec un tel reseau serait: B{sup 2} = 0.726 {+-} 0.011 m{sup -2} et l'anisotropie {alpha} (B{sub L}{sup 2}/B{sub T}{sup 2}) est egale a 0.987 {+-} 0.006. La perturbation apportee a la densite de neutrons dans le reseau par le voisinage du reflecteur est discutee en detail. (auteurs)

  8. Graphitic carbon nitride based nanocomposites: a review

    Science.gov (United States)

    Zhao, Zaiwang; Sun, Yanjuan; Dong, Fan

    2014-11-01

    Graphitic carbon nitride (g-C3N4), as an intriguing earth-abundant visible light photocatalyst, possesses a unique two-dimensional structure, excellent chemical stability and tunable electronic structure. Pure g-C3N4 suffers from rapid recombination of photo-generated electron-hole pairs resulting in low photocatalytic activity. Because of the unique electronic structure, the g-C3N4 could act as an eminent candidate for coupling with various functional materials to enhance the performance. According to the discrepancies in the photocatalytic mechanism and process, six primary systems of g-C3N4-based nanocomposites can be classified and summarized: namely, the g-C3N4 based metal-free heterojunction, the g-C3N4/single metal oxide (metal sulfide) heterojunction, g-C3N4/composite oxide, the g-C3N4/halide heterojunction, g-C3N4/noble metal heterostructures, and the g-C3N4 based complex system. Apart from the depiction of the fabrication methods, heterojunction structure and multifunctional application of the g-C3N4-based nanocomposites, we emphasize and elaborate on the underlying mechanisms in the photocatalytic activity enhancement of g-C3N4-based nanocomposites. The unique functions of the p-n junction (semiconductor/semiconductor heterostructures), the Schottky junction (metal/semiconductor heterostructures), the surface plasmon resonance (SPR) effect, photosensitization, superconductivity, etc. are utilized in the photocatalytic processes. Furthermore, the enhanced performance of g-C3N4-based nanocomposites has been widely employed in environmental and energetic applications such as photocatalytic degradation of pollutants, photocatalytic hydrogen generation, carbon dioxide reduction, disinfection, and supercapacitors. This critical review ends with a summary and some perspectives on the challenges and new directions in exploring g-C3N4-based advanced nanomaterials.

  9. Heat Transfer During Evaporation of Cesium From Graphite Surface in an Argon Environment

    Directory of Open Access Journals (Sweden)

    Bespala Evgeny

    2016-01-01

    Full Text Available The article focuses on discussion of problem of graphite radioactive waste formation and accumulation. It is shown that irradiated nuclear graphite being inalienable part of uranium-graphite reactor may contain fission and activation products. Much attention is given to the process of formation of radioactive cesium on the graphite element surface. It is described a process of plasma decontamination of irradiated graphite in inert argon atmosphere. Quasi-one mathematical model is offered, it describes heat transfer process in graphite-cesium-argon system. Article shows results of calculation of temperature field inside the unit cell. Authors determined the factors which influence on temperature change.

  10. Study on practical of eddy current testing of core and core support graphite components in HTTR

    International Nuclear Information System (INIS)

    Ishihara, Masahiro; Iyoku, Tatsuo; Ooka, Norikazu; Shindo, Yoshihisa; Kawae, Hidetoshi; Hayashi, Motomitsu; Kambe, Mamoru; Takahashi, Masaaki; Ide, Akira.

    1994-01-01

    Core and core support graphite components in the HTTR (High Temperature Engineering Test Reactor) are mainly made of nuclear-grade IG-110 and PGX graphites. Nondestructive inspection with Eddy Current Testing (ECT) is planned to be applied to these components. The method of ECT has been already established for metallic components, however, cannot be applied directly to the graphite ones, because the characteristics of graphite are quite different in micro-structure from those of metals. Therefore, ECT method and condition were studied for the application of the ECT to the graphite components. This paper describes the study on practical method and conditions of ECT for above mentioned graphite structures. (author)

  11. A experimental system for the checking of the absorption of E.C.A.G. graphite

    International Nuclear Information System (INIS)

    Raievski, V.; Vidal, R.

    1958-01-01

    A system is described for measuring the mean absorption cross section in thermal neutrons of graphite. This system consists of a graphite stack containing a Ra-Be source and a BF3 counter. A cavity in the stack receives the graphite to be studied or the graphite standard. By comparing the counting rates their absorption ratio can be deduced. The measurement is performed on graphite rods which have been machined before being placed in the pile. It provides the possibility of detecting over a batch of 1 ton of graphite, in a single measurement, a difference in absorption of 0.1 milli barn. (author) [fr

  12. Placental vascular responses are dependent on surrounding tissue

    DEFF Research Database (Denmark)

    Brøgger, Torbjørn Halle

    -depth understanding of the mechanism regulating blood flow and perfusion is necessary if we are to come up with new ideas for intervention and treatment. Method: From fresh born placentas stem villi arteries were carefully dissected. The artery branches were divided. The surrounding tissue was removed from one end...... and was left untouched in the other end. Then using wire myography they were investigated in terms of contractility and sensitivity to physiological relevant human-like agonists. Results: Sensitivity to PGF2α, Tx-analog, 5-HT and endothelin-1 was significantly lower in arteries with intact surrounding tissue...... compared to arteries stripped of the tissue. The maximal force development was also significantly lower in arteries with surrounding tissue, when they were depolarized high extracellular [K+] or stimulated with PGF2α or endotheline-1. Conclusion: The perivascular tissue significantly alters stem villi...

  13. Placental vascular responses are dependent on surrounding tissue

    DEFF Research Database (Denmark)

    Brøgger, Torbjørn Halle

    . Materials and methods. From fresh born placentas, stem villi arteries were carefully dissected. The artery branches were divided. The surrounding tissue was removed from one end and was left untouched in the other end.Then, using wire myography, they were investigated in terms of contractility...... and sensitivity to physiological relevant human-like agonists. Results. Sensitivity to PGF2α, Tx-analog, 5-HT and endothelin-1 was significantly lower in arteries with intact surrounding tissue compared to arteries stripped of the tissue. The maximal force development was also significantly lower in arteries...... with surrounding tissue when they were depolarized high extracellular [K+] or stimulated with PGF2α or endotheline-1. Conclusion. The perivascular tissue significantly alters stem villi arteries' sensitivity and force development in a suppressive way. This implicates a new aspect of blood flow regulation...

  14. Surrounding rock stress analysis of underground high level waste repository

    International Nuclear Information System (INIS)

    Liu Wengang; Wang Ju; Wang Guangdi

    2006-01-01

    During decay of nuclear waste, enormous energy was released, which results in temperature change of surrounding rock of depository. Thermal stress was produced because thermal expansion of rock was controlled. Internal structure of surrounding rock was damaged and strength of rock was weakened. So, variation of stress was a dynamic process with the variation of temperature. BeiShan region of Gansu province was determined to be the depository field in the future, it is essential to make research on granite in this region. In the process of experiment, basic physical parameters of granite were analyzed preliminary with MTS. Long range temperature and stress filed was simulated considering the damage effect of surrounding rock, and rules of temperature and stress was achieved. (authors)

  15. Development of Nanoscale Graphitic Devices and The Transport Characterization

    International Nuclear Information System (INIS)

    Gunasekaran, Venugopal

    2011-02-01

    This dissertation describes the development of graphitic based nanoscale devices with its fabrication and transport characterization results. It covers graphite nano-scale stacked-junctions fabricated using focused ion beam (FIB) 3-D etching technique, a single layer graphite layer (graphene) preparation and its electrical transport characterization results and the synthesis and investigation of electrical transport behavior of graphene oxide based thin film devices. The first chapter describes the basic information about the carbon family in detail in which the electronic properties and structure of graphite, graphene and graphene oxide are discussed. In addition, the necessity of developing nanoscale graphitic devices is given. The second chapter explains the experimental techniques used in this research for fabricating nanoscale devices which includes focused ion beam 3-D fabrication procedures, mechanical exfoliation technique and photolithographic methods. In third chapter, we have reported the results on temperature dependence of graphite planar-type structures fabricated along ab-plane. In the fourth and fifth chapters, the fabrication and electrical transport characteristics of large in-plane area graphite planar-type structures (fabricated along ab-plane and c-axis) were discussed and their transport anisotropy properties were investigated briefly. In the sixth chapter, we focused the fabrication of the submicron sized graphite stacked junctions and their electrical transport characterization studies. In which, FIB was used to fabricated the submicron junctions with various in-plane area (with same stack height) are and their transport characteristics were compared. The seventh chapter reports investigation of electrical transport results of nanoscale graphite stacked-junctions in which the temperature dependent transport (R-T) studies, current-voltage measurements for the various in-plane areas and for various stack height samples were analyzed. The

  16. Reinforcement of cement-based matrices with graphite nanomaterials

    Science.gov (United States)

    Sadiq, Muhammad Maqbool

    Cement-based materials offer a desirable balance of compressive strength, moisture resistance, durability, economy and energy-efficiency; their tensile strength, fracture energy and durability in aggressive environments, however, could benefit from further improvements. An option for realizing some of these improvements involves introduction of discrete fibers into concrete. When compared with today's micro-scale (steel, polypropylene, glass, etc.) fibers, graphite nanomaterials (carbon nanotube, nanofiber and graphite nanoplatelet) offer superior geometric, mechanical and physical characteristics. Graphite nanomaterials would realize their reinforcement potential as far as they are thoroughly dispersed within cement-based matrices, and effectively bond to cement hydrates. The research reported herein developed non-covalent and covalent surface modification techniques to improve the dispersion and interfacial interactions of graphite nanomaterials in cement-based matrices with a dense and well graded micro-structure. The most successful approach involved polymer wrapping of nanomaterials for increasing the density of hydrophilic groups on the nanomaterial surface without causing any damage to the their structure. The nanomaterials were characterized using various spectrometry techniques, and SEM (Scanning Electron Microscopy). The graphite nanomaterials were dispersed via selected sonication procedures in the mixing water of the cement-based matrix; conventional mixing and sample preparation techniques were then employed to prepare the cement-based nanocomposite samples, which were subjected to steam curing. Comprehensive engineering and durability characteristics of cement-based nanocomposites were determined and their chemical composition, microstructure and failure mechanisms were also assessed through various spectrometry, thermogravimetry, electron microscopy and elemental analyses. Both functionalized and non-functionalized nanomaterials as well as different

  17. Final report on graphite irradiation test OG-3

    International Nuclear Information System (INIS)

    Price, R.J.; Beavan, L.A.

    1977-01-01

    The results of dimensional, thermal expansivity, thermal conductivity, Young's modulus, and tensile strength measurements on graphite specimens irradiated in capsule OG-3 are presented. The graphite grades investigated included near-isotropic H-451 (three different preproduction lots), TS-1240, and SO818; needle coke H-327; and European coal tar pitch coke grades P 3 JHA 2 N, P 3 JHAN, and ASI2-500. Data were obtained in the temperature range 823 0 K to 1673 0 K. The peak fast neutron fluence in the experiment was 3 x 10 25 n/m 3 (E greater than 29 fJ)/sub HTGR/; the total accumulated fluence exceeded 9 x 10 25 n/m 2 on some H-451 specimens and 6 x 10 25 n/m 2 on some TS-1240 specimens. Irradiation-induced dimensional changes on H-451 graphite differed slightly from earlier predictions. For an irradiation temperature of about 1225 0 K, axial shrinkage rates at high fluences were somewhat higher than predicted, and the fluence at which radial expansion started (about 9 x 10 25 n/m 2 at 1275 0 K) was lower. TS-1240 graphite underwent smaller dimensional changes than H-451 graphite, while limited data on SO818 and ASI2-500 graphites showed similar behavior to H-451. P 3 JHAN and P 3 JHA 2 N graphites displayed anisotropic behavior with rapid axial shrinkage. Comparison of dimensional changes between specimens from three logs of H-451 and of TS-1240 graphites showed no significant log-to-log variations for H-451, and small but significant log-to-log variations for TS-1240. The thermal expansivity of the near-isotropic graphites irradiated at 865-1045 0 K first increased by 5 percent to 10 percent and then decreased. At higher irradiation temperatures the thermal expansivity decreased by up to 50 percent. Changes in thermal conductivity were consistent with previously established curves. Specimens which were successively irradiated at two different temperatures took on the saturation conductivity for the new temperature

  18. Characterization of ultra-fast deposited polycrystalline graphite by a CO{sub 2} laser-assisted combustion-flame method

    Energy Technology Data Exchange (ETDEWEB)

    McKindra, Travis, E-mail: mckindra@mst.edu [Department of Materials Science and Engineering, Missouri University of Science and Technology, Rolla, MO 65409 (United States); Patil, Sandeep; O' Keefe, Matthew J. [Department of Materials Science and Engineering, Missouri University of Science and Technology, Rolla, MO 65409 (United States); Han Yaoxuan; Ling Hao; Lu Yongfeng [Department of Electrical Engineering, University of Nebraska-Lincoln, Lincoln, NE 68588 (United States)

    2009-02-15

    High deposition rate, 750 {mu}m/min, crystalline graphite was deposited on WC substrates by a CO{sub 2} laser-assisted combustion-flame method at laser powers between 300 and 800 W. The structures, which were identified as pillars, were characterized by various methods. The pillars were cylindrical in shape and grew to a size of approximately 3 mm in length and in a few minutes. The laser power did not affect the overall length of the pillar, but caused changes in the physical shape. X-ray and electron diffraction results revealed the pillars to be crystalline graphite regardless of the laser power. Investigation of the pillars by scanning electron microscopy showed two distinct microstructural areas: an inner core of dense material surrounded by an outer shell of lamellar-like material. The core/shell microstructure was unaffected by the level of CO{sub 2} laser power.

  19. Helium generation and diffusion in graphite and some carbides

    International Nuclear Information System (INIS)

    Holt, J.B.; Guinan, M.W.; Hosmer, D.W.; Condit, R.H.; Borg, R.J.

    1976-01-01

    The cross section for the generation of helium in neutron irradiated carbon was found to be 654 mb at 14.4 MeV and 744 mb at 14.9 MeV. Extrapolating to 14.1 MeV (the fusion reactor spectrum) gives 615 mb. The diffusion of helium in dense polycrystalline graphite and in pyrographite was measured and found to be D = 7.2 x 10 -7 m 2 s -1 exp (-80 kJ/RT). It is assumed that diffusion is primarily in the basal plane direction in crystals of the graphite. In polycrystalline graphite the path length is a factor of √2 longer than the measured distance due to the random orientation mismatch between successive grains. Isochronal anneals (measured helium release as the specimen is steadily heated) were run and maximum release rates were found at 200 0 C in polycrystalline graphite, 1000 0 C in pyrographite, 1350 0 C in boron carbide, and 1350 0 and 2400 0 C (two peaks) in silicon carbide. It is concluded that in these candidates for curtain materials in fusion reactors the helium releases can probably occur without bubble formation in graphites, may occur in boron carbide, but will probably cause bubble formation in silicon carbide. 7 figures

  20. Nonlinear seismic analysis of a graphite reactor core

    International Nuclear Information System (INIS)

    Laframboise, W.L.; Desmond, T.P.

    1988-01-01

    Design and construction of the Department of Energy's N-Reactor located in Richland, Washington was begun in the late 1950s and completed in the early 1960s. Since then, the reactor core's structural integrity has been under review and is considered by some to be a possible safety concern. The reactor core is moderated by graphite. The safety concern stems from the degradation of the graphite due to the effects of long-term irradiation. To assess the safety of the reactor core when subjected to seismic loads, a dynamic time-history structural analysis was performed. The graphite core consists of 89 layers of numerous graphite blocks which are assembled in a 'lincoln-log' lattice. This assembly permits venting of steam in the event of a pressure tube rupture. However, such a design gives rise to a highly nonlinear structure when subjected to earthquake loads. The structural model accounted for the nonlinear interlayer sliding and for the closure and opening of gaps between the graphite blocks. The model was subjected to simulated earthquake loading, and the time-varying response of selected elements critical to safety were monitored. The analytically predicted responses (displacements and strains) were compared to allowable responses to assess margins of safety. (orig.)