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Ueki, Taro
Progress in Nuclear Energy, 159, p.104630_1 - 104630_9, 2023/05
Times Cited Count：0 Percentile：0.01(Nuclear Science & Technology)In this work, the methodology of Generalized Extreme Value (GEV) is applied to criticality tallies in Monte Carlo fission source cycles in order to evaluate the utility value of the distribution tail ends. Numerical results obtained under a sufficiently large number of particles per cycle show that the extreme value index (EVI) in GEV falls within the range of Weibull distribution including the EVI of Gumbel distribution as the role of a boundary value layer. GEV is also applied to a historically-challenging loosely-coupled system for demonstrating population diagnosis under an insufficient number of particles per cycle. It turns out that the transition from one equilibrium to other equilibrium makes the EVIs of upper and lower distribution tail ends depart from each other so that one of them falls in the range of Weibull distribution and the other in that of Frechet distribution.
Tada, Kenichi
JAEA-Data/Code 2020-014, 30 Pages, 2020/10
JAEA-Data-Code-2020-014.pdf:2.84MB
The decommissioning of TEPCO's Fukushima Daiichi Nuclear Power Plant accident is one of the most important issues in Japan. In the process of the decommissioning, preventing radiation exposure of workers is imperative originating in nuclear criticality of fuel debris. This study provides the handy tool enabling the analysis on nuclear criticality of fuel debris. The developed analysis tool named as HAND enables estimation of the criticality of fuel debris in short time. HAND deduces the range of parameters such as the size and composition, in which the criticality of fuel debris is specified. By selecting the range of the parameters using HAND in advance, total calculation time of the detail analysis will be reduced. Since the input data of HAND is designed to be simple and the output of HAND is to be user friendly, this tool is expected to be also an intuitive tool to study the criticality of fuel debris. This report explains the outline of the HAND and input instructions for HAND.
Ueki, Taro
Nuclear Science and Engineering, 194(6), p.422 - 432, 2020/06
Times Cited Count：0 Percentile：0.01(Nuclear Science & Technology)In Monte Carlo criticality calculation, the convergence-in-distribution check of the sample mean of tallies can be approached in terms of the influence range of autocorrelation. In this context, it is necessary to evaluate the attenuation of autocorrelation coefficients over lags. However, in just one replica of calculation, it is difficult to accurately estimate small ACCs at large lags because of the comparability with statistical uncertainty. This paper proposes a method to overcome such an issue. Its essential component is the transformation of a standardized time series of tallies so that the resulting series asymptotically converges in distribution to Brownian motion. The convergence-in-distribution check is constructed based on the independent increment property of Brownian motion. The judgment criterion is set by way of the spectral analysis of fractional Brownian motion. Numerical results are demonstrated for extreme and standard types of criticality calculation.
Yamamoto, Toshihiro; Miyoshi, Yoshinori
Journal of Nuclear Science and Technology, 41(2), p.99 - 107, 2004/02
Times Cited Count：38 Percentile：90.12(Nuclear Science & Technology)A new algorithm of Monte Carlo criticality calculations for implementing Wielandt's method is developed. In this algorithm, part of fission neutrons emitted during random walk processes are tracked within the same generation, and thus a fission source distribution in the next generation spread more widely. Applying this method intensifies a neutron interaction effect even in a loosely-coupled array where conventional Monte Carlo criticality calculation methods have difficulties, and a converged fission source distribution can be obtained with fewer generations. Computing time spent for one generation, however, increases because of tracking fission neutrons within the same generation, which eventually results in an increase of total computing time up to convergence. However, since a fission source convergence is attained with fewer source iterations, a reliable determination of convergence can easily be made even in a system with a slow convergence.
Nomura, Yasushi; Mochizuki, Hiroki*
JAERI-Tech 2002-068, 131 Pages, 2002/11
JAERI-Tech-2002-068.pdf:5.59MB
no abstracts in English
Nuclear Code Evaluation Special Committee of Nuclear Code Research Committee
JAERI-Review 2002-003, 97 Pages, 2002/03
JAERI-Review-2002-003.pdf:8.64MB
no abstracts in English
Miyoshi, Yoshinori; Yamamoto, Toshihiro
Transactions of the American Nuclear Society, 87, p.149 - 150, 2002/00
no abstracts in English
Yamamoto, Toshihiro; Nakamura, Takemi*; Miyoshi, Yoshinori
JAERI-Data/Code 2001-001, 30 Pages, 2001/02
JAERI-Data-Code-2001-001.pdf:1.53MB
no abstracts in English
Nakahara, Yoshinori; Suyama, Kenya; Suzaki, Takenori
JAERI-Tech 2000-071, 381 Pages, 2000/10
JAERI-Tech-2000-071.pdf:17.6MB
no abstracts in English
Yamamoto, Toshihiro; Nakamura, Takemi*; Miyoshi, Yoshinori
Journal of Nuclear Science and Technology, 37(1), p.41 - 52, 2000/01
no abstracts in English
J.Anno*; G.Poullot*; P.Grivot*; Yamamoto, Toshihiro; Miyoshi, Yoshinori
Proceedings of 6th International Conference on Nuclear Criticality Safety (ICNC '99), 3, p.1065 - 1074, 1999/00
no abstracts in English
Suzaki, Takenori; Kurosawa, Masayoshi; Hirose, Hideyuki; Yamamoto, Toshihiro; Nakajima, Ken; ; *; *
ICNC 95: 5th Int. Conf. on Nuclear Criticality Safety, Vol. I, 0, p.1B.11 - 1B.18, 1995/00
no abstracts in English
; C.A.Brebbia*
Boundary Elements XIV, Vol.1; Field Problems and Applications, p.25 - 38, 1992/00
no abstracts in English
Shimooke, Takanori; ;
Nihon Genshiryoku Gakkai-Shi, 22(4), p.223 - 230, 1980/00
Times Cited Count：0 Percentile：0.02(Nuclear Science & Technology)no abstracts in English
; ; ; ; Katsuragi, Satoru
JAERI 1247, 78 Pages, 1976/10
no abstracts in English
; Katsuragi, Satoru; Tone, Tatsuzo
JAERI-M 4953, 72 Pages, 1972/08
no abstracts in English
; Katsuragi, Satoru
JAERI 1210, 17 Pages, 1972/02
no abstracts in English
JAERI-M 4472, 26 Pages, 1971/06
no abstracts in English
-concrete system under randomizationUeki, Taro
no journal, ,
Analysis framework under indeterminate material distribution is investigated for the Monte Carlo (MC) criticality calculation of continuously mixed media formed via molten core concrete interaction. Randomized Weierstrass functions (RWF) are utilized to represent the volume fractions of constituent materials. The possibility of several percent fluctuation of effective multiplication factor is shown by the MC simulation with delta-tracking.
Ueki, Taro
no journal, ,
In Monte Carlo criticality calculation, the convergence judgment tool for the sample mean of tallies is not established yet within the framework of convergence-in-distribution in probability theory. In this presentation, we report a convergence criterion based on stochastic differential equation. Its efficacy is demonstrated by the power spectrum of tallies.
