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Saito, Kenji; Sekita, Kenji; Kawasaki, Kozo; Yamamoto, Kazuhiko*; Matsuura, Makoto*
JAEA-Technology 2007-059, 36 Pages, 2007/11
JAEA-Technology-2007-059.pdf:26.24MB
The Wide-Range Monitoring neutron detectors of HTTR are used under 450 
C in normal operation and 550 C in the accidents. When the WRM detectors are used under the high temperature for a long time, characteristics of the detector might be degraded, because of the decrease of the nitrogen concentration in the ionization gas caused by adsorbtion of nitrogen into the electrode material. Consequently, the nitrogen gas adsorption test was carried out to clarify the quantity of absorbed nitrogen gas in electrode material under the high temperature. Then, the performance evaluation test of the prototype detector was carried out, and it was confirmed that degradation of the prototype detector characteristics didn't arise under the high temperature anvironment. This report describes the results of consideration about the life-extension of WRM detectors. As a result, it was confirmed that the WRM detectors are usable for 5 years under 450 C in normal operation and 550 C in the accidents.
Iwamura, Takamichi; Okubo, Tsutomu; Akie, Hiroshi; Kugo, Teruhiko; Yonomoto, Taisuke; Kureta, Masatoshi; Ishikawa, Nobuyuki; Nagaya, Yasunobu; Araya, Fumimasa; Okajima, Shigeaki; et al.
JAERI-Research 2004-008, 383 Pages, 2004/06
JAERI-Research-2004-008.pdf:21.49MB
The present report contains the achievement of "Research and Development on Reduced-Moderation Light Water Reactor with Passive Safety Features", which was performed by Japan Atomic Energy Research Institute (JAERI), Hitachi Ltd., Japan Atomic Power Company and Tokyo Institute of Technology in FY2000-2002 as the innovative and viable nuclear energy technology (IVNET) development project operated by the Institute of Applied Energy (IAE). In the present project, the reduced-moderation water reactor (RMWR) has been developed to ensure sustainable energy supply and to solve the recent problems of nuclear power and nuclear fuel cycle, such as economical competitiveness, effective use of plutonium and reduction of spent fuel storage. The RMWR can attain the favorable characteristics such as high burnup, long operation cycle, multiple recycling of plutonium (Pu) and effective utilization of uranium resources based on accumulated LWR technologies.
Iwamura, Takamichi; Okubo, Tsutomu; Kureta, Masatoshi; Nakatsuka, Toru; Takeda, Renzo*; Yamamoto, Kazuhiko*
Proceedings of 13th Pacific Basin Nuclear Conference (PBNC 2002) (CD-ROM), 7 Pages, 2002/10
In order to ensure sustainable energy supply in Japan, the reduced-moderation water reactor (RMWR) has been developed by JAERI since 1998. MOX fuel assemblies with tight lattice arrangement are used to increase the conversion ratio. In order to establish negative void reactivity coefficient, the core should be short and flat to increase neutron leakage from the core. The core designs were accomplished to a large core with 1,356MWe and a small core with 330MWe. For both cores, negative void coefficient and natural circulation cooling of the core were realized. To confirm thermal-hydraulic feasibility, critical heat flux experiments were performed using 7-rod bundles with the gap width of 1mm and 1.3mm. The results indicated that enough cooling was assured for the tight lattice core. Further R&D studies, including large scale thermal-hydraulic experiments, reactor physics experiments, development of high burn-up fuel cladding material and simplified reprocessing technology, are necessary to realize commercial introduction of RMWR by 2020's for the replacement of current generation LWRs.
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.
Kureta, Masatoshi; Akimoto, Hajime; Yamamoto, Kazuhiko*; Okada, Hiroyuki*
Proceedings of International Congress on Advanced Nuclear Power Plants (ICAPP) (CD-ROM), 7 Pages, 2002/00
no abstracts in English
Okubo, Tsutomu; Takeda, Renzo*; Iwamura, Takamichi; Yamamoto, Kazuhiko*; Okada, Hiroyuki*
Proceedings of International Conference on Back-End of the Fuel Cycle: From Research to Solutions (GLOBAL 2001) (CD-ROM), 7 Pages, 2001/09
An advanced water-cooled reactor concept named the Reduced-Moderation Water Reactor (RMWR) has been proposed to attain a high conversion ratio more than 1.0 and to achieve the negative void reactivity coefficient. At present, several types of design concepts satisfying both the design targets have been proposed based on the evaluation for the fuel without fission products and minor actinides. In this paper, the feasibility of the RMWR core is investigated and confirmed for the plutonium multiple recycling under advanced reprocessing schemes with low decontamination factors as proposed for the FBR fuel cycle.
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
Tanaka, M.*; Yamamoto, H.*; Fujisawa, O.*; Okutsu, Kazuo*; Miura, K.*; Takamura, Hisashi*
JNC TJ8400 2000-036, 196 Pages, 2000/02
JNC-TJ8400-2000-036.pdf:23.76MB
TRU waste should be isolated from biosphere for a long period of time as it includes long lived nuclides. In this study, (1) data were conected on the mechanical properties of engineered barrier materials, (2) affection on the mechanical properties of Na bentonito by salt water was studied and (3) soundness of the disposal system against changes in the volume of engineered banier was evaluated, to examine critical events related to the long-term soundness of the disposal system. Described below are the results of the studies. (1) The swelling pressure, swelling amount and permeability were obtained for a material consisting of NaCa-exchanged bentonito and silica sand with a relative weight of 30% (with a dry density of 1.6 Mgm
) by supplying saturated calcium hydroxide aqeous solution. As a result, it was confirmed that the swelling pressure and permeability were approximately estimated from the relation between these properties and the effective dry density of bentonito. (2) The swelling pressure, swelling amount and permeability were obtained for a material consisting of salty Na bentonito and silica sand with a relative weight of 30% (with a dry density of 1.6 Mgm) by supplying artifical salt water. As a result, it was confirmed that these properties were approximately these properties of NaCa-bentonito. (3) Tests were conducted as a part of the evaluation of system soundness against changes in the volume of engineered barrier. Development of a void around bentonito was assumed. Self sealing of Na and NaCa-exchanged bentonito, and theirs water cut-off capability and swelling pressure were investigated.As a result, it was confirmed that the change of permeability and swelling pressure under self sealing of bentonito. Based on the test results (i.e. the both relations between the swelling pressure and dry density, and the permeability and dry density), soundness of the system was verified against changes of the volume of engineered barrier materials.
Tanaka, M.*; Yamamoto, H.*; Fujisawa, O.*; Okutsu, Kazuo*; Miura, K.*; Takamura, Hisashi*
JNC TJ8400 2000-035, 59 Pages, 2000/02
JNC-TJ8400-2000-035.pdf:8.87MB
no abstracts in English
Hibiya, Keisuke*; ; Shiogama, Yukihiro*; ; Masumoto, Kazuhiko*; Furuichi, Mitsuaki*; Saegusa, Hiromitsu
JNC TN7400 99-004, 314 Pages, 1999/03
In order to understand groundwater flow in Japan, it is important to know the hydraulic gradient and the sea / fresh-water boundaly. In particular, the hydraulic gradient is required to estimate very slow groundwater flow at depth. Also, the location of the sea / fresh-water boundary is required to characterize groundwater flow near the coast. In this study, we obtained the above-mentioned data from a number of published papers, and tried to find the suitable method to help evaluating the groundwater flow model.
Hibiya, Keisuke*; ; Shiogama, Yukihiro*; Masumoto, Kazuhiko*; Fukazawa, E.*; Taira, K.*; Tanaka, Toshiyuki*; Kondo, Y.*; Yamamoto, M.*; Okutsu, Kazuo*; et al.
PNC TJ1100 97-004, 69 Pages, 1997/02
None
Hibiya, Keisuke*; ; Shiogama, Yukihiro*; Masumoto, Kazuhiko*; Fukazawa, E.*; Taira, K.*; Tanaka, Toshiyuki*; Kondo, Y.*; Yamamoto, M.*; Okutsu, Kazuo*; et al.
PNC TJ1100 97-003, 130 Pages, 1997/02
None
Hibiya, Keisuke*; Toida, Masaru*; Shiogama, Yukihiro*; ; Masumoto, Kazuhiko*; Furuichi, Mitsuaki*
PNC TJ1100 96-002, 85 Pages, 1996/03
None
Hibiya, Keisuke*; Toida, Masaru*; Shiogama, Yukihiro*; ; Masumoto, Kazuhiko*; Furuichi, Mitsuaki*
PNC TJ1100 96-001, 290 Pages, 1996/03
None
SRHigemoto, Wataru; Ito, Takashi; Sato, Kazuhiko*; Oishi, Kazuki*; Yamamoto, Etsuji; Haga, Yoshinori; Onuki, Yoshichika; Goko, Tatsuro*
no journal, ,
no abstracts in English
at very low temperatureHigemoto, Wataru; Sato, Kazuhiko*; Ito, Takashi; Nishida, Nobuhiko*; Oishi, Kazuki*; Heffner, R. H.; Haga, Yoshinori; Yamamoto, Etsuji; Kimura, Noriaki*; Onuki, Yoshichika; et al.
no journal, ,
The unconventional superconductivity in heavy fermion UPt attracted much interest. In recent neutron experiment, the narrowing of the AF Bragg peak at low temperature was observed, from which they suggest that a quasistatic AF long range order is realized below 20 mK. We have extended ZF-SR measurement down to 8 mK to investigate the anomalous magnetic state over the very low temperature region. In our ZF-SR, there is no significant change in the muon spinrelaxation rate down to 8 mK. The result suggests the absence of static or quasistaticmagnetic order over the relevant temperature range.
Watanabe, Shoichi; Tonoike, Kotaro; Yoshiyama, Hiroshi; Yamamoto, Toshihiro; Izawa, Kazuhiko; Miyoshi, Yoshinori
no journal, ,
no abstracts in English