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Journal Articles

Enhancement of element production by incomplete fusion reaction with weakly bound deuteron

Wang, H.*; Otsu, Hideaki*; Chiga, Nobuyuki*; Kawase, Shoichiro*; Takeuchi, Satoshi*; Sumikama, Toshiyuki*; Koyama, Shumpei*; Sakurai, Hiroyoshi*; Watanabe, Yukinobu*; Nakayama, Shinsuke; et al.

Communications Physics (Internet), 2(1), p.78_1 - 78_6, 2019/07

 Times Cited Count:5 Percentile:63.62(Physics, Multidisciplinary)

Searching for effective pathways for the production of proton- and neutron-rich isotopes through an optimal combination of reaction mechanism and energy is one of the main driving forces behind experimental and theoretical nuclear reaction studies as well as for practical applications in nuclear transmutation of radioactive waste. We report on a study on incomplete fusion induced by deuteron, which contains one proton and one neutron with a weak binding energy and is easily broken up. This reaction study was achieved by measuring directly the cross sections for both proton and deuteron for $$^{107}$$Pd at 50 MeV/u via inverse kinematics technique. The results provide direct experimental evidence for the onset of a cross-section enhancement at high energy, indicating the potential of incomplete fusion induced by loosely-bound nuclei for creating proton-rich isotopes and nuclear transmutation of radioactive waste.

Journal Articles

The Japanese approach to developing clay-based repository concepts; An Example of design studies for the assessment of sealing strategies

Sugita, Yutaka; Fujita, Tomo; Takahashi, Yoshiaki*; Kawakami, Susumu; Umeki, Hiroyuki; Yui, Mikazu; Uragami, Manabu*; Kitayama, Kazumi*

Physics and Chemistry of the Earth, 32(1-7), p.32 - 41, 2007/00

 Times Cited Count:6 Percentile:22.87(Geosciences, Multidisciplinary)

The H12 repository concept for vitrified high-level radioactive waste was developed based on a multi-barrier system with the emphasis on robust engineered barrier performance to ensure its feasibility for a wide range of geological conditions typically observed in Japan. The buffer is clay-based and plays a very important role in the engineered barrier system (EBS). The decision to use a volunteer siting process requires maximum flexibility of the repository concept to allow it to be adapted to potential sites and hence a wide range of variants of the basic H12 repository design has been developed. In order to evaluate the feasibility and the applicability of different repository options to specific siting environments, NUMO has established a set of "design factors" which classify the aspects that need to be considered when evaluating the pros and cons of different repository options. A Na-type bentonite from Japan is used as the reference material for all clay-based repository components (buffer, backfill, clay plug, etc.). The characteristics of this bentonite (thermal, mechanical, chemical, hydraulic) have been examined with consideration of various practical constraints (limitation on the repository footprint, the influence of saline water, the interaction of hyperalkaline leachates and practical working environment, etc.). Clay-based seals, which close off the tunnels after emplacement of the EBS, may also be key components for assessment of the repository. Full analyses considering all engineered barrier components (buffer, backfill, clay plug, concrete lining, tunnel, concrete plug, host rock) that may be used in a repository will be an essential future task. As a first step towards this goal, a numerical analysis focusing on hydraulic behaviour at the intersections of the disposal tunnels and the main tunnel is presented to illustrate how the design requirements of clay-based seals can be determined.

JAEA Reports

Study on the corrosion assessment of overpack welds, 2 (Joint research)

Mitsui, Hiroyuki*; Taniguchi, Naoki; Otsuki, Akiyoshi*; Kawakami, Susumu; Asano, Hidekazu*; Yui, Mikazu

JAEA-Research 2006-031, 88 Pages, 2006/06

JAEA-Research-2006-031.pdf:4.72MB

The corrosion experiments for welded carbon steel were planed to contribute to an assessment of long-term integrity of carbon steel overpack welds considering corrosion damage specific to overpack welds. Based on this plan, electrochemical tests for welded carbon steel using the samples welded by EBW and TIG were carried out, and the corrosion behavior of welded zone was compared with that of base metal. The results of anodic polarization tests in 0.01M and 0.1M carbonate aqueous solutions for base metal, heat affected zone and welded metal indicated that; -As for EBW, the anodic polarization curves were not affected by welding although the metallurgical structures vary with base metal, heat affected zone and welded metal. -As for TIG, the current density of welded metal was larger than that of base metal and of heat affected zone, and local dissolution with immediate increase in current density was observed in 0.01M-pH10 carbonate aqueous solution.

JAEA Reports

The Study plan on applicability to actual geological environment conditions of the engineering technology for geological disposal of high level nuclear-waste through the second phases in Horonobe Underground Research Project

Aoyanagi, Shigeo; Yui, Mikazu; Tanai, Kenji; Kawakami, Susumu; Fujita, Tomo; Taniguchi, Naoki; Shibata, Masahiro; Konishi, Kazuhiro; Nishimura, Mayuka; Kikuchi, Hirohito*; et al.

JAEA-Review 2006-014, 61 Pages, 2006/03

JAEA-Review-2006-014.pdf:5.03MB

no abstracts in English

JAEA Reports

Status of assessment tools on the performance guarantee contents of backfill, bulkhead, tunnel and pit

Kawakami, Susumu; Fujita, Tomo; Yui, Mikazu

JAEA-Research 2006-015, 25 Pages, 2006/03

JAEA-Research-2006-015.pdf:2.66MB

no abstracts in English

Journal Articles

Engineering technology research on the performance guarantee for the Engineered Barrier System (EBS)

Kawakami, Susumu; Fujita, Tomo; Sugita, Yutaka

Hoshasei Haikibutsu Anzen Kenkyu Nenji Keikaku (Heisei-13-Nendo$$sim$$Heisei-17-Nendo) Kenkyu Seika Hokokushu, p.216 - 223, 2006/03

no abstracts in English

Journal Articles

Development on computer system of the coupled thermo-hydro-mechanical and chemical process in the near-field of the high-level radioactive waste repository

Fujita, Tomo; Fujisaki, Kiyoshi; Suzuki, Hideaki*; Kawakami, Susumu; Yui, Mikazu; Chijimatsu, Masakazu*; Neyama, Atsushi*; Ishihara, Yoshinao*; Hishiya, Tomoyuki*

Proceedings of 2nd International Conference on Coupled T-H-M-C Processes in Geo-systems; Fundamentals, Modeling, Experiments and Applications (GeoProc 2006), p.416 - 421, 2006/00

We have initiated a research on the coupled Thermo-Hydro-Mechanical-Chemical (THMC) processes and are trying to carry out numerical experiments on the coupled THMC processes in order to predict the near-field long-term evolution. This paper describes the modified THMC model to add on the function of de-gases and gases diffusion, accumulation and dilution phenomena for mass transport analysis, and of ionic exchange, surface reaction and kinetic reaction for geochemical analysis. And also the results of demonstration study with THMC code are shown.

Journal Articles

Studies on design of the engineered barrier system and mechanical stability of rock based on surfaced-based investigation of the Horonobe URL project

Aoyagi, Shigeo; Tanai, Kenji; Matsui, Hiroya; Kawakami, Susumu; Yui, Mikazu

Proceedings of International Conference on Nuclear Energy System for Future Generation and Global Sustainability (GLOBAL 2005) (CD-ROM), 6 Pages, 2005/10

This paper presents the design of the disposal design based on surface-based investigations in Horonobe URL project with a focus on the engineered barrier system (EBS) and the estimation of mechanical stability of rock. The purpose of this study is as follows.[1]Establishment of the overall design methodology on engineered barrier system and repository based on the results of surface-based investigation in sedimentary rock.][2]Extraction of issues to be solved in the construction phase of URL through studies based on surface-based investigation.]The applied methods on this study are based on the second progress report (H12)(1999) published by JNC. As results of this study,the design flow shown in H12 report is revised under the consideration of correlation with each field. The typical specification of buffer and overpack (iron) in the geological environment in Horonobe are the same specification as H12 report. The rock around a dry pit at the depth of 450m in Horonobe is expected more stable in long-term than SR-C in H12 report.

JAEA Reports

Discussion on sealing performance required to disposal system; Hydraulic analysis considering intersections of tunnels

Sugita, Yutaka*; Fujita, Tomo; Takahashi, Yoshiaki*; Kawakami, Susumu; Umeki, Hiroyuki; Yui, Mikazu; Uragami, Manabu*

JNC TN8400 2005-016, 49 Pages, 2005/09

JNC-TN8400-2005-016.pdf:5.45MB

The sealing performance of a repository should be considered in the safety assessment of the geological disposal system of the high level radioactive waste. Nuclear Waste Management Organization of Japan and Japan Nuclear Cycle Development Institute are examining the sealing performance of the closure components (backfilling material and clay plug) to present the concept on the sealing performance required to the disposal system, and to develop the direction for the future R&D programme for the design requirements of the closure components of the presented concepts.The first step of this examination reviewed the current status of the domestic and the international sealing technologies, summarized the repository components and the repository environments, and performed the hydraulic analysis considering components on the intersections of a main tunnel and a disposal tunnel in a disposal panel and in and around the engineered barrier system (EBS). Since all tunnels connect in the underground facility, understanding of hydraulic behaviour at the intersections of the tunnels is the important issue to estimate migration of radionuclides from the EBS, and to evaluate the required sealing performance for the disposal system. The considering components in the analysis model are the intersections of the disposal tunnel and the main tunnel, the waste package, the EBS, the backfilling material, the clay plug, the concrete plug, the excavated disturbed zone, the tunnel lining and the host rock. Alteration of the concrete material (tunnel lining and concrete plug) is described as variation of the hydraulic conductivity of it. Sites of emplacement of the clay plug are the disposal tunnel and the main tunnel. No clay plug condition is also analysed. Effect of the clay plug is discussed by the results of these analyses.

JAEA Reports

Estimation of the applicability on the disposal technology under real geological environment

Matsui, Hiroya; Tanai, Kenji; Kawakami, Susumu; Sato, Toshinori; Yui, Mikazu

JNC TN5400 2005-004, 250 Pages, 2005/09

JNC-TN5400-2005-004.pdf:41.57MB

Japan Nuclear Fuel Development Institute (JNC) published the possibility of the geological disposal independent geological environment in Japan and its scientific basis in H12 progress report. The overall research and development on geological disposal after FY2000 were planned based on the review results of H12 report and initiated the two major goals ; - Demonstration of applicability of disposal technology to specific geological environments - Further understanding of long-term system behaviorThe approach to the first goal for the R&D program from FY2000 to FY2005 is to establish the methodology integrated with disposal technology and geoscitentfic research by the application of the technology developed until FY 2000 on geological environment understood in surface based investigation phase in URL project.This report is described the applicability and future subject derived from the results to apply the design methods of geological disposal developed until FY2000 to

JAEA Reports

Hydrogen Evolution Behavior in the Corrosion of Carbon Steel in Contact with Magnetite

Taniguchi, Naoki; Tateishi, Tsuyoshi*; Fukudome, Kazuyuki*; Nishimura, Tsutomu*; Kawakami, Susumu

JNC TN8400 2005-014, 36 Pages, 2005/07

JNC-TN8400-2005-014.pdf:0.44MB

It has been reported that the corrosion of carbon steel is accelerated by a contact with magnetite, which is a representative corrosion product in low oxygen environment. It is important to clear the corrosion mechanism in the presence of magnetite for long term prediction of overpack corrosion. There are two possible cathodic reactions in the presence of magnetite coupled with anodic reaction. One is reduction of Fe(III) in magnetite, and the other is hydrogen evolution reaction. If the former dominate the cathodic reaction, corrosion acceleration will be stopped with the consumption of Fe(III). While, if the latter is the main cathodic reaction, corrosion acceleration is possible to be continued for a long time. In this study, corrosion rate and hydrogen evolution behavior were investigated by the immersion test of carbon steel in contact with dummy corrosion product to contribute to understanding the corrosion mechanism.

JAEA Reports

Material test data of 316FR Steel (IX)

Odaka, Susumu; Kato, Shoichi; Yoshida, Eiichi; Kawakami, Tomohiro*; Suzuki, Takaichi*; Kawashima, Seiichi*; Ishigami, Katsuo*

JNC TN9450 2005-001, 196 Pages, 2005/03

JNC-TN9450-2005-001.pdf:6.7MB

Material test of 316FR steel, which was used for structure material of fast breeder reactor (FBR) has been preformed in New Technology Development Group. In this report, the result of test obtained up to this time was collected. Many valuable data that long time test more than 40000 hours including sodium environment test data in this report will be use for material examination of FBR in the future.Contents of the data sheet are as follows; (1) Material: 316FR Steel, (2) Test environment: In air,in sodium, (3) Test emperature: Room temperature to 800, (4) Test method: According to JIS and FBR metallic materials test manual (Revised edition), (5) Number of data:Tensile tests 234, Creep tests 408, Fatigue tests 201, Creep-fatigue tests 47, Relaxation tests 6,Total 896 This report consists of the printouts fromthe structural material data processing system, SMAT.

JAEA Reports

The Corrosion Rate and the Hydrogen Absorption Behavior of Titanium under Reducing Condition-III

Suzuki, Hiroyuki*; Taniguchi, Naoki; Kawakami, Susumu

JNC TN8400 2005-003, 76 Pages, 2005/03

JNC-TN8400-2005-003.pdf:8.31MB

Titanium is one of the candidate materials for overpacks as a high corrosion resistance metal.At the initial stage of repository,oxidizing condition will be given around the overpack because oxygen will be brought from the ground. The oxygen will be consumed by the reaction with impurities in buffer material or corrosion of overpack, and reducing condition will be achieved around the overpack. With the changing of redox condition, the water reduction becomes to dominate the cathodic reaction accompanying hydrogen generation. Crevice corrosion and hydrogen embrittlement are main causes of the damage of long term integrity of titanium overpack.However, it is not known about the corrosion resistance and hydrogen absorption behavior of titanium under reduction condition. In this study, the completely sealed ampoule test and the immersion test of titanium in aqueous solution and bentonite was carried out. In order to obtain reliable data about the hydrogen generation rate and the ratio of hydrogen absorption in titanium.From the result of 3 years immersion tests, corrosion rate of titanium were estimated to be in the order of 10$$^{-2}$$- 10$$^{-1}$$micro m / y in the aqueous solution, and 10$$^{-3}$$- 10$$^{-2}$$micro m / y in bentonaite.This value is almost the same as the last report.Almost all the hydrogen generated by corrosion was absorbed in titanium in the immersion tests in completely sealed ampoule.In the examination that changed each parameter, it was suggested that the amount of the hydrogen absorption become 2 - 3 times in 1M HCO$$_{3}$$$$^{-}$$ and pH13.

JAEA Reports

Status of Assessment Tools of Corrosion Behavior for Performance Guarantee on Overpacks

Taniguchi, Naoki; Kawakami, Susumu; Jintoku, Takashi; Yui, Mikazu

JNC TN8400 2005-002, 29 Pages, 2005/03

JNC-TN8400-2005-002.pdf:36.7MB

In order to contribute to the safety standards and guidelines for overpacks on which the administration decides, the tools for performance guarantee on overpacks were studied based on the present research products for overpack corrosion. The corrosion modes that should to be considered in repository environments were extracted, and then the assessment methods and examples for each mode was summarized based on current understandings of corrosion behavior of overpacks.The passivation, general corrosion, localized corrosion (pitting corrosion, crevice corrosion, and stress corrosion cracking) and hydrogen embrittlement were extracted and the experimental methods to evaluate the initiation and propagation behavior were presented. The assessment examples based on research products such as second progress report (H12 report) were given.

JAEA Reports

Experimental Study on Corrosion Behavior of Pure Copper in the Presence of Cement

Kawasaki, Manabu*; Taniguchi, Naoki; Kawakami, Susumu

JNC TN8400 2004-028, 37 Pages, 2005/03

JNC-TN8400-2004-028.pdf:41.12MB

In geological disposal of high-level radioactive waste in soft rock, the cement material will be used as concrete support to ensure the mechanical stability of underground tunnel. The pH in ground water becomes high by the contact with cement. Therefore, the influence of cement on the corrosion of copper which is one of the candidate materials for overpacks was investigated. The anodic polarization measurement and immersion test in reducing environment were carried out, using the solution simulating the seawater(SSW) in contact with ordinary portland cement(OPC) and low alkaline cement (HFSC). The anodic polarization curves on SSW and SSW + HFSC were active dissolution type and, the polarization curve of SSW + OPC, was active dissolution / passivation transition type. The polarization curves in bentonite were active dissolution type. These results were consistent with results that have already reported. As the results of immersion test, corrosion rates became small with time. The growth of corrosion for 90day and one year immersion test was small and the average corrosion depth was in the order 0.1um. Within the test conditions, the influence of cement materials on the corrosion of was not significant.

JAEA Reports

Corrosion Assessment of Pure Copper in Synthetic Sea Water Containing Sulfide

Kawasaki, Manabu*; Taniguchi, Naoki; Kawakami, Susumu

JNC TN8400 2004-027, 94 Pages, 2005/03

JNC-TN8400-2004-027.pdf:59.54MB

The immersion tests of pure copper which is one of the candidate overpack materials were carried out in synthetic sea water (SSW) and in bentonite under low oxygen atmosphere at 80 degrees Celsius with changing the sulfide concentration. As the results, corrosion rates became large with increase in sulfide concentration both in simple solution and in bentonite. The corrosion rates tended to be lowered with time in every cases. Assuming that the corrosion is controlled by diffusion of HS- in bentonite, the corrosion rates were calculated for experimental conditions of bentonite thickness and compared with the values obtained in the experiments. The calculated corrosion depths were larger than experimental results. And then assuming the actual thickness of the buffer material, the long-term corrosion depth was estimated based on the diffusion of HS- in bentonite. As the results, the corrosion depth in 1000 years was 0.5mm (HS- 0.001M), 1.76mm (HS- 0.005M), 14mm (HS- 0.1M). It is likely that the corrosion product film formed in solution was tightly adhere to surface and seemed to protective. On the other hand, only a thin film was observed in bentonite at low sulfide concentration condition, and the corrosion product film formed in high sulfide concentration condition was easily broken away from the surface. It is considered that corrosion product formed in bentonite was less protective. According to the X-ray diffraction measurement, Cu2O (cuprite) was detected in SSW without sulfide, and Cu2S (chalcocite) was detected in the presence of sulfide.

JAEA Reports

Experimental Studies on the Coupled THMC Processes by COUPLE Equipment -Part II-

Oda, Yoshihiro; Suzuki, Hideaki*; Kawakami, Susumu; Yui, Mikazu

JNC TN8400 2004-024, 55 Pages, 2005/02

JNC-TN8400-2004-024.pdf:1.29MB

The research for numerical experiments on the coupled Thermo -Hydro -Mechanical and Chemical (THMC) processes in the near-field of a high-level radioactive waste repository has been initiated, in order to increase reality in the near-field environmental condition adopted in the evaluation of engineered barrier design and performance assessment. As a part of this research, experimental studies on the coupled THMC processes by COUPLE equipment have been carried out. The COUPLE equipment simulates the coupled processes in the near-field after emplacement of the engineered barrier. The specimen of COUPLE equipment is composed of heater, buffer material and mortar block. In this experiment, temperature at heater and side surface of mortar block was kept at 100 and 70 Celsius's degree, respectively. And high-pH water reacted with mortar infiltrates into the buffer material. This report presents the results of measured data by Cation Exchange, X-Ray diffraction, and SEM/EDS. From these result, there is no large difference in buffer material between before and after this experiment.

JAEA Reports

Study on the corrosion assessment of overpack welds (Joint research)

Asano, Hidekazu*; Taniguchi, Naoki; Kawakami, Susumu; Yui, Mikazu

JNC TY8400 2004-008, 30 Pages, 2004/04

JNC-TY8400-2004-008.pdf:2.6MB

It is necessary to understand the corrosion behavior of welds in overpack for ensuring the quality of welding, and improving the long term reliability of overpack. In this study, the method for evaluation of corrosion of welded joint was planned by Radioactive Waste Management Funding and Research Center (RWMC) and Japan Nuclear Cycle Development Institute (JNC). RWMC has been developed the overpack welding techniques and the inspection techniques of welded joint. In this study, RWMC provided the information on current status of welding techniques for applying the overpacks. Electron Beam Welding (EBW) and Tungsten Inert Gas Welding (TIG) were prospected to be available for overpack and the results of the examinations to find adequate conditions for overpack welding were presented. JNC has been studying the corrosion behavior and lifetime of overpack, and provided the information on corrosion of welded carbon steel under repository conditions. According to immersion tests by JNC, it was shown that corrosion rates of carbon steel welded by EBW were almost equal to those of base metal under anaerobic condition, which is representative condition in repository environment. Based on the information provided by RWMC and JNC, the research subjects on the corrosion of welds were extracted and the concept of corrosion tests for overpack welds was given.

JAEA Reports

Design Studies on the Engineered Barrier System and on the in-situ Experiments under the Conditions of Geological Environment in Horonobe

Kurihara, Yuji; Yui, Mikazu; Tanai, Kenji; Kawakami, Susumu; Sugita, Yutaka; Taniguchi, Naoki; Hirai, Takashi

JNC TN8400 2004-006, 59 Pages, 2004/04

JNC-TN8400-2004-006.pdf:5.97MB

Following studies have been done in this papers in order to apply the technologies based on H12 report to the actual geological conditions of Horonobe underground research laboratory. 1.reconsidering the process of repository design, 2. arrangement of the relations between geological conditions and the performance of engineering barrier systems, 3.present the appropriate form of geological informations, 4.study on the stability of deposition hall.

JAEA Reports

Studies on the In-Situ Experiments with Respect to Disposal Engineering in Horonobe Underground Research Laboratory

Kurihara, Yuji; Yui, Mikazu; Tanai, Kenji; Kawakami, Susumu; Sugita, Yutaka; Taniguchi, Naoki; Hirai, Takashi

JNC TN8400 2004-002, 58 Pages, 2004/04

JNC-TN8400-2004-002.pdf:2.38MB

In this paper, the items of in-situ experiments at Horonobe URL with respect to the technical issues about reliability of long-term behavior of engineered barrier system were extracted. And the concepts of the experiments were studied from several points of view such as verification of models and getting the actual behavior. Extracted items of the in-situ experiments are as follows. Coupled Phenomena Test (THMC Test), Buffer & Rock Creep Test, Gas Migration Test, Over-pack Corrosion Test, High-pH Influence Test, Low Alkaline Concrete Execution Test, Engineering-Barrier Emplacement Test, Tunnel Plugging Test.

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