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Yanagisawa, Hiroshi; Umeda, Miki; Motome, Yuiko; Murao, Hiroyuki
JAEA-Technology 2022-030, 80 Pages, 2023/02
JAEA-Technology-2022-030.pdf:2.57MBJAEA-Technology-2022-030(errata).pdf:0.11MB
Nuclear criticality benchmark analyses were carried out for TRIGA-type reactor systems in which uranium-zirconium hydride fuel rods are loaded by using the continuous-energy Monte Carlo code MVP with the evaluated nuclear data library JENDL-5. The analyses cover two sorts of benchmark data, the IEU-COMP-THERM-003 and IEU-COMP-THERM-013 in the International Criticality Safety Benchmark Evaluation Project (ICSBEP) Handbook, and effective neutron multiplication factors, reactivity worths for control rods etc. were calculated by JENDL-5 in comparison with those by the previous version of JENDL. As the results, it was confirmed that the effective neutron multiplication factors obtained by JENDL-5 were 0.4 to 0.6% greater than those by JENDL-4.0, and that there were no significant differences in the calculated reactivity worths by between JENDL-5 and JENDL-4.0. Those results are considered to be helpful for the confirmation of calculation accuracy in the analyses on NSRR control rod worths, which are planned in the future.
Tonoike, Kotaro; Okubo, Kiyoshi; Takada, Tomoyuki*
Proceedings of International Conference on Nuclear Criticality Safety (ICNC 2015) (DVD-ROM), p.292 - 300, 2015/09
The damaged Unit 1-3 reactors of the Fukushima Daiichi Nuclear Power Station may contain fuel debris of a significant amount that is in a form of molten-core-concrete-interaction (MCCI) product with porous structure. Such low density MCCI product including fissile material is a great concern for its criticality control, especially under submerged condition, due to its fairly good neutron moderation. This report shows computation results of basic criticality characteristics of the MCCI product, which will facilitate criticality risk assessments during decommissioning of the reactors. The results imply that water bound in concrete may raise the risk from the viewpoints of possibility of criticality events and of effectiveness of mitigation measures such as neutron poison injection into coolant water.
Nagaya, Yasunobu; Mori, Takamasa
Journal of Nuclear Science and Technology, 42(5), p.428 - 441, 2005/05
Times Cited Count：67 Percentile：96.40(Nuclear Science & Technology)A new method to estimate a change in the effective multiplication factor due to the perturbed fission source distribution has been proposed for Monte Carlo perturbation calculations with the correlated sampling and differential operator sampling techniques. The method has been implemented into the MVP code for verification. Simple benchmark problems have been set up for fast and thermal systems and the applicability of the method has been verified with the problems. In consequence, it has been confirmed that the method is very effective to estimate the change. It has been also shown that there are some cases where the perturbed source effect is significant and the change in reactivity cannot be estimated accurately without taking the effect into account. Even in such cases, the new method can estimate the perturbed source effect and the estimation of the change in reactivity has been remarkably improved.
Cullen, D. E.*; Blomquist, R. N.*; Dean, C.*; Heinrichs, D.*; Kalugin, M. A.*; Lee, M.*; Lee, Y. K.*; MacFarlane, R.*; Nagaya, Yasunobu; Trkov, A.*
UCRL-TR-203892, p.1 - 40, 2004/04
no abstracts in English
Kojima, Kensuke; Okajima, Shigeaki; Yamane, Tsuyoshi; Ando, Masaki; Kataoka, Masaharu*; Iwanaga, Kohei
JAERI-Tech 2004-016, 38 Pages, 2004/03
JAERI-Tech-2004-016.pdf:1.46MB
To investigate the void coefficient in the Reduced-Moderation Water Reactor (RMWR), an infinite multiplication factor was measured in the FCA-XXII-1 (65V) core. Axial and radial fission rate distributions were measured by micro fission chambers with four different kinds of nuclides. The infinite multiplication factor was derived from the material buckling, which was obtained from both the axial and radial fission rate distributions, and the migration area calculated. The value of it in the test region of the FCA-XXII-1 (65V) core was 1.344
0.034. It was compared with the calculation, the ratio of the calculation to the measurement was 1.0080.026. The improvement in measurement accuracy was also considered.
Takamatsu, Kuniyoshi; Shimakawa, Satoshi; Nojiri, Naoki; Fujimoto, Nozomu
JAERI-Tech 2003-081, 49 Pages, 2003/10
In the case of evaluations for the highest temperature of the fuels in the HTTR, it is very important to expect the power density distributions accurately; therefore, it is necessary to improve the analytical model with the neutron diffusion and the burn-up theory. The power density distributions are analyzed in terms of two models, the one mixing the fuels and the burnable poisons homogeneously and the other modeling them heterogeneously. Moreover these analytical power density distributions are compared wtih the ones derived from the gross 
-ray measurements and the Monte Carlo calculational code with continuous energy. As a result the homogeneous mixed model isn't enough to expect the power density distributions of the core in the axial direction; on the other hand, the heterogeneous model improves the accuracy.
Nishihara, Kenji; Iwasaki, Tomohiko*; Udagawa, Yutaka*
Journal of Nuclear Science and Technology, 40(7), p.481 - 492, 2003/07
Times Cited Count：17 Percentile：71.96(Nuclear Science & Technology)A new one-point equation is derived according to the balance of the fission neutrons. The equation has the same form as the conventional equation containing keff. The variables of the equation are the number of the fission neutrons and the delayed neutron precursors, and the coefficients are the multiplication factors of a prompt fission neutron, a delayed neutron and a source neutron. In the equation derived here, all variables and coefficients have each clear physical meaning. Analytic, deterministic and probabilistic calculations of the equation are performed for an accelerator-driven system.
Nagao, Yoshiharu; Hosoya, Toshiaki; Kaneko, Yoshihiko*
Nihon Genshiryoku Gakkai Wabun Rombunshi, 1(2), p.153 - 163, 2002/06
no abstracts in English
Kaneko, Yoshihiko*; Nagao, Yoshiharu; Shimakawa, Satoshi
Journal of Nuclear Science and Technology, 36(11), p.988 - 995, 1999/11
Times Cited Count：0 Percentile：0.01(Nuclear Science & Technology)no abstracts in English
Fujimoto, Nozomu; Nakano, Masaaki*; Nojiri, Naoki; Takeuchi, Mitsuo; Fujisaki, Shingo; Yamashita, Kiyonobu
JAERI-Conf 99-006, p.328 - 333, 1999/08
no abstracts in English
; ; Suyama, Kenya; Ando, Yoshihira*
Proceedings of 6th International Conference on Nuclear Criticality Safety (ICNC '99), 2, p.566 - 575, 1999/00
no abstracts in English
Nojiri, Naoki; Nakano, Masaaki; Ando, Hiroei; Fujimoto, Nozomu; Takeuchi, Mitsuo; Fujisaki, Shingo; Yamashita, Kiyonobu
JAERI-Tech 98-032, 59 Pages, 1998/08
no abstracts in English
Nakano, Masaaki; Yamashita, Kiyonobu; Fujimoto, Nozomu; Nojiri, Naoki; Takeuchi, Mitsuo; Fujisaki, Shingo; ; Nakata, Tetsuo*
JAERI-Tech 98-017, 61 Pages, 1998/05
no abstracts in English
Sakurai, Satoshi; Arakawa, Takuya*;
Journal of Nuclear Science and Technology, 35(5), p.365 - 369, 1998/05
Times Cited Count：0 Percentile：0.00(Nuclear Science & Technology)no abstracts in English
Nagaya, Yasunobu; Nakagawa, Masayuki; Mori, Takamasa
Journal of Nuclear Science and Technology, 35(1), p.6 - 19, 1998/01
Times Cited Count：3 Percentile：31.90(Nuclear Science & Technology)no abstracts in English
Nagao, Yoshiharu; Shimakawa, Satoshi; Kaneko, Yoshihiko*
JAERI-Research 97-048, 59 Pages, 1997/07
JAERI-Research-97-048.pdf:1.82MB
no abstracts in English
G.D.Spriggs*; R.D.Busch*; Sakurai, Takeshi; Okajima, Shigeaki
Transactions of the American Nuclear Society, 76, p.374 - 375, 1997/06
no abstracts in English
Kaneko, Yoshihiko*; Shimakawa, Satoshi; Nagao, Yoshiharu; Yamashita, Kiyonobu; ; Yamane, Tsuyoshi
JAERI-Research 97-003, 70 Pages, 1997/02
JAERI-Research-97-003.pdf:1.79MB
no abstracts in English
Nagashima, Keisuke
JAERI-Research 95-052, 14 Pages, 1995/07
JAERI-Research-95-052.pdf:0.53MB
no abstracts in English
; Yamane, Tsuyoshi; Sasa, Toshinobu
JAERI-Data/Code 94-013, 17 Pages, 1994/10
JAERI-Data-Code-94-013.pdf:0.77MB
no abstracts in English
