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U oxide and fluorideShigekawa, Yudai*; Kasamatsu, Yoshitaka*; Yasuda, Yuki*; Kaneko, Masashi; Watanabe, Masayuki; Shinohara, Atsushi*
Physical Review C, 98(1), p.014306_1 - 014306_5, 2018/07
Times Cited Count：4 Percentile：36.08(Physics, Nuclear)The nuclear half-life of U has been reported to vary depending on the chemical environment. In this study, both the half-life and the internal-conversion (IC) electron energy spectrum were measured for U with identical chemical environments for the first time. U oxide and fluoride samples were subjected to these measurements, and clear differences in the half-life and the energy spectrum between these samples were observed. The peaks in the energy spectra were identified with the relativistic density functional theory calculation, and the molecular orbital states of the U oxide and fluoride estimated from the energy spectra and the calculation qualitatively explained the difference in the half-lives between the samples.
2016.10Horigome, Kazushi; Taguchi, Shigeo; Ishibashi, Atsushi; Inada, Satoshi; Kuno, Takehiko; Surugaya, Naoki
JAEA-Technology 2017-008, 14 Pages, 2017/05
JAEA-Technology-2017-008.pdf:1.15MB
The plutonium solution had been converted into MOX powder to mitigate the potential hazards of storage plutonium solution such as hydrogen generation at the Plutonium Conversion Development Facility. The plutonium conversion operations had been started in April, 2014, and had been finished in July, 2016. With respect to the samples taken from the conversion process, about 2,200 items of plutonium/uranium solutions and MOX powders had been analyzed for the operation control in the related analytical laboratories at the Tokai Reprocessing Plant. This paper describes the reports on analytical activities and related maintenance works in the analytical laboratories conducted from December, 2015 to October, 2016.
2015.12Horigome, Kazushi; Suzuki, Hisanori; Suzuki, Yoshimasa; Ishibashi, Atsushi; Taguchi, Shigeo; Inada, Satoshi; Kuno, Takehiko; Surugaya, Naoki
JAEA-Technology 2016-026, 21 Pages, 2016/12
JAEA-Technology-2016-026.pdf:1.14MB
In order to mitigate potential hazards of storage plutonium in solution such as hydrogen generation, conversion of plutonium solution into MOX powder has been carried out since 2014 in the Plutonium Conversion Development Facility. With respect to the samples taken from the conversion process, about 3500 items of plutonium/uranium solutions and MOX powders have been analyzed for the operation control in the related analytical laboratories at the Tokai Reprocessing Plant. This paper describes the reports on analytical activities and related maintenance works in the analytical laboratories conducted from April 2014 to December 2015.
Oshima, Takeshi; Morishita, Norio; Kamiya, Tomihiro; Isoya, Junichi*; Baba, Shinichi; Aihara, Jun; Yamaji, Masatoshi*; Ishihara, Masahiro
Proceedings of OECD/NEA 3rd Information Exchange Meeting on Basic Studies in the Field of High Temperature Engineering (OECD/NEA No.5309), p.197 - 202, 2004/00
For the application of SiC to electronic devices, it is necessary to develop the fabrication technique of high quality SiC substrates with uniform carrier concentration. Since phosphorus (P) atoms become shallow donors in SiC, nuclear transmutation doping (NTD) is thought to be a good method for the fabrication of n-type SiC substrates with uniform electron concentration. However, defects are also introduced in SiC by neutron irradiation. Although thermal annealing at high temperatures above 1500
C is carried out to remove defects after irradiation, heavy damage in SiC is hard to recover. Therefore, the process for the reduction of defects in SiC irradiated with neutrons is necessary to develop. In this study, neutron irradiation into SiC at elevated temperature was carried out to decrease radiation damage. The electrical properties of the samples are studied using Hall effect measurement. Furthermore, to establish the measurement technique for the estimation of P atoms created in SiC by NTD, P atoms in SiC were investigated using Electron Spin Resonance (ESR).
Okubo, Tsutomu; Iwamura, Takamichi; Takeda, Renzo*; Moriya, Kumiaki*; Yamauchi, Toyoaki*; Aritomi, Masanori*
Nihon Kikai Gakkai 2003-Nendo Nenji Taikai Koen Rombunshu, Vol.3, p.245 - 246, 2003/08
A design study on a 300MWe class small Reduced-Moderation Water Reactor (RMWR) has been performed, based on the experienced LWR technology. The core can be cooled by the natural circulation and can achieve a conversion ratio of 1.01, a negative void reactivity coefficient, a core average burn-up of 65 GWd/t and a cycle length of 25 months. The system has been simplified as much as possible by introducing the passive safety components, in order to reduce the construction cost per electric power output overcoming “the scale demerit" for a small reactor comparing with the large one. The results show a 1.35 times higher cost than for the ABWR case, but suggest the possible lower cost when the effects such as the mass production are taken into account.
Shimada, Shoichiro*; Kugo, Teruhiko; Okubo, Tsutomu; Iwamura, Takamichi
JAERI-Research 2003-003, 72 Pages, 2003/03
JAERI-Research-2003-003.pdf:3.82MB
As a part of the design study on PWR-type Reduced-Moderation Water Reactors (RMWRs), a light water cooled core with the seed-blanket type fuel assemblies has been investigated. An assembly with seed of 13 layers and blanket of 5 layers was selected by optimization calculations. The core was composed with the 163 assemblies. The following results were obtained by burn-up calculations with the MVP-BURN code; The cycle length is 15 months by 3-batch refueling. The discharge burn-up including the inner blanket is about 25 GWd/t. The conversion ratio is about 1.0. The void reactivity coefficient is about -26.1pcm/%void at BOC and -21.7pcm/%void at EOC. Effects of about 10% of MA or about 2 % of FP on core performances were investigated, and they were confirmred within the design margins. Capability of multi-recycling of plutonium was confirmed, using discharged plutonium for 4 cycles, if fissile plutonium of 15.5wt% is used.
Okubo, Tsutomu; Iwamura, Takamichi; Takeda, Renzo*; Yamauchi, Toyoaki*; Okada, Hiroyuki*
Proceedings of International Conference on Global Environment and Advanced Nuclear Power Plants (GENES4/ANP 2003) (CD-ROM), 8 Pages, 2003/00
A water-cooled reactor concept named Reduced-Moderation Water Reactor is under development for effective fuel utilization through plutonium multiple recycling based on the water-cooled reactor technology. The reactor aims at achievement of a high conversion ratio more than 1.0 with MOX fuel. Especially, the core performances during the Pu multiple recycling have been investigated for the advanced fuel reprocessing schemes with low decontamination factors than the current PUREX process, and are shown to achieve the conversion ratio more than 1.0 and the negative void reactivity coefficient.
Okubo, Tsutomu; Suzuki, Motoe; Iwamura, Takamichi; Takeda, Renzo*; Moriya, Kumiaki*; Kanno, Minoru*
Proceedings of International Conference on the New Frontiers of Nuclear Technology; Reactor Physics, Safety and High-Performance Computing (PHYSOR 2002) (CD-ROM), 10 Pages, 2002/10
A small scale around 300 MWe reduced-moderation water reactor (RMWR) concept has been developed. For the core, a BWR type core concept with the tight-lattice fuel rod arrangement and the high void fraction is adopted to attain a high conversion ratio over 1.0. The negative void reactivity coefficients are also required, and the very flat short core concept is adopted to make the natural circulation cooling (NC) possible. The core burn-up of 60 GWd/t and the operation cycle of 24 months are also attained. For the system, simplification of the system with the passive safety features is a basic approach to overcome the scale demerit as well as the NC. For example, the HPCF system is replaced with the passive accumulator system resulting in the expensive emergency DGs reduction. The cost evaluation for concerned NSSS components gives about 20% reduction. Since MOX fuels in the RMWR contains Pu around 30 wt% and is irradiated to a high burn-up, the fuel safety evaluation has been performed and the acceptable results have been obtained from the thermal feasibility point of view.
Yura, Kei; Go, Michiko*
Tampakushitsu Kakusan Koso, 47(8), p.1090 - 1096, 2002/06
no abstracts in English
transformation; Article reviewSaigusa, Shin*
JAERI-Review 2002-009, 43 Pages, 2002/03
JAERI-Review-2002-009.pdf:2.3MB
The mechanism of the process of radiation-induced transformation that leads normal mammalian cell to malignant feature is still not clear. However, a drastic development of molecular biological technique in medical biology research field since 1990's have progressively revealed the mechanisms of this process and recent results have been starting to incorporate in the recent radiation risk estimate procedures. This report describes the results of the survey and review of the articles concerned with experimental studies of radiation induced in vitro transformation, since 1993 to 1997.
Okubo, Tsutomu; Iwamura, Takamichi; Yamamoto, Kazuhiko*; Okada, Hiroyuki*
Nihon Kikai Gakkai Dai-8-Kai Doryoku, Enerugi Gijutsu Shimpojiumu Koen Rombunshu, p.571 - 574, 2002/00
Based on the experienced light water reactor technology, conceptual design studies on advanced water-cooled reactors have been performed. They are named “Reduced-Moderation Water Reactor" (RMWR) with the high conversion ratio more than 1.0 and the negative void reactivity coefficients. Several concepts have been successfully established for them based on the neutronics calculations. Based on these concepts, detailed investigations on such as plutonium multiple recycling and control rod planning have been performed as well as improvement on core performances. Through these detailed core design investigation, the feasibility of those designs has been confirmed step by step.
Hibi, Koki*; Shimada, Shoichiro*; Okubo, Tsutomu; Iwamura, Takamichi; Wada, Shigeyuki*
Nuclear Engineering and Design, 210(1-3), p.9 - 19, 2001/12
Times Cited Count：25 Percentile：84.31(Nuclear Science & Technology)no abstracts in English
Okubo, Tsutomu; Takeda, Renzo*; Iwamura, Takamichi
JAERI-Research 2001-021, 84 Pages, 2001/03
JAERI-Research-2001-021.pdf:11.26MB
no abstracts in English
Iwamura, Takamichi; Ochiai, Masaaki
Proceedings of 1st Asian Specialist Meeting of Future Small-Sized LWR Development, p.7_1 - 7_9, 2001/00
JAERI has developed two types of small and medium size Light Water Reactors to meet the goals of innovative nuclear reactors such as sustainability and diversification of energy utilization. One is the Reduced-Moderation light Water Reactor (RMWR) with passive safety features. The reactor core consists of MOX fuel assemblies with tight lattice arrangement to increase the conversion ratio by reducing the moderation of neutron energy. The core design of 330MWe output with the operational cycle of 26 months was accomplished. A breeding ratio of 1.01, negative void coefficient and natural circulation cooling of the core were realized under the discharged burn-up of 60GWd/t. The other is the Passive Safe small Reactor for Distributed energy systems (PSRD) to diversify the nuclear energy utilization. An innovative advanced marine reactor (MRX) is used to supply the small grid electricity or electricity and heat co-supply by installing it on a barge. A small integral LWR for underground deployment is also studied for exclusive use of heat supply to household or office.
JNC TN1400 2000-012, 250 Pages, 2000/11
JNC-TN1400-2000-012.pdf:10.18MB
no abstracts in English
Okubo, Tsutomu; Iwamura, Takamichi; Akimoto, Hajime; Araya, Fumimasa; Onuki, Akira; Yamamoto, Kazuhiko*
Dai-7-Kai Doryoku Enerugi Gijutsu Shimpojiumu Koen Rombunshu (00-11), p.250 - 253, 2000/11
no abstracts in English
; ; ; Iguchi, Yukihiro; Matsui, Yuji;
JNC TN3410 2000-014, 43 Pages, 2000/09
JNC-TN3410-2000-014.pdf:2.37MB
None
Research Group for Advanced Reactor System; Research Group for Reactor Physics; Research Group for Thermal and Fluid Engineering
JAERI-Research 2000-035, 316 Pages, 2000/09
JAERI-Research-2000-035.pdf:19.81MB
no abstracts in English
Shimada, Shoichiro*; Akie, Hiroshi; Suzaki, Takenori; Okubo, Tsutomu; Usui, Shuji*; Shirakawa, Toshihisa*; Iwamura, Takamichi; Kugo, Teruhiko; Ishikawa, Nobuyuki
JAERI-Research 2000-026, 74 Pages, 2000/06
JAERI-Research-2000-026.pdf:4.07MB
no abstracts in English
