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Journal Articles

Subcriticality determination methodology during fuel loading of accelerator-driven system

Katano, Ryota

Journal of Nuclear Science and Technology, 59(3), p.368 - 381, 2022/03

 Times Cited Count:0 Percentile:0.01(Nuclear Science & Technology)

We propose a subcriticality determination methodology to be applied during fuel loading of an accelerator-driven system (ADS). In this methodology, subcriticality is determined via the area ratio method (via the proton accelerator) in the first step and by the neutron source multiplication method (through the spontaneous fission neutrons of minor actinides) in subsequent steps; then, the number of fuel assemblies to be loaded in the next step is predicted. We performed a numerical simulation of the proposed methodology, and the estimated subcriticalities agreed well with those obtained by eigenvalue calculations. We also conducted an uncertainty assessment of the proposed methodology and deduced a value of 1000 pcm for the $$k_{eff}$$ uncertainty. The proposed methodology can be a candidate for practical subcriticality monitoring for ADS.

Journal Articles

Study of the neutron multiplication effect in an active neutron method

Komeda, Masao; Ozu, Akira; Mori, Takamasa; Nakatsuka, Yoshiaki; Maeda, Makoto; Kureta, Masatoshi; Toh, Yosuke

Journal of Nuclear Science and Technology, 54(11), p.1233 - 1239, 2017/11

 Times Cited Count:5 Percentile:54.01(Nuclear Science & Technology)

The previous active neutron method cannot remove the influence of the multiplication effect of neutrons produced by second- and subsequent fission reactions, and it might overestimate the amount of nuclear material if an item contains large amounts. In this paper, we discussed the correction method for the neutron multiplication effect on the measured data in the fast neutron direct interrogation (FNDI) method, one of the active neutron methods, supposing that the neutron multiplication effect is caused mainly by third-generation neutrons from the second-fission reactions under the condition that the forth-generation neutrons are much fewer. This paper proposed a correction method for the neutron multiplication effect in the measured data. Moreover we have shown a possibility that this correction method gives rough estimates of the effective neutron multiplication factor and the subcriticality.

Journal Articles

Criticality characteristics of MCCI products possibly produced in reactors of Fukushima Daiichi Nuclear Power Station

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.

Journal Articles

Impact of perturbed fission source on the effective multiplication factor in Monte Carlo perturbation calculations

Nagaya, Yasunobu; Mori, Takamasa

Journal of Nuclear Science and Technology, 42(5), p.428 - 441, 2005/05

 Times Cited Count:52 Percentile:95.39(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.

Journal Articles

How accurately can we calculate thermal systems?

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

JAEA Reports

Measurement of infinite multiplication factor in the mock-up core for reduced-moderation water reactor at FCA

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$$pm$$0.034. It was compared with the calculation, the ratio of the calculation to the measurement was 1.008$$pm$$0.026. The improvement in measurement accuracy was also considered.

JAEA Reports

Evaluation for the models of neutron diffusion theory in terms of power density distributions of the HTTR

Takamatsu, Kuniyoshi; Shimakawa, Satoshi; Nojiri, Naoki; Fujimoto, Nozomu

JAERI-Tech 2003-081, 49 Pages, 2003/10

JAERI-Tech-2003-081.pdf:2.6MB

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 $$gamma$$-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.

Journal Articles

A New static and dynamic one-point equation and analytic and numerical calculations for a subcritical system

Nishihara, Kenji; Iwasaki, Tomohiko*; Udagawa, Yutaka*

Journal of Nuclear Science and Technology, 40(7), p.481 - 492, 2003/07

 Times Cited Count:16 Percentile:72.31(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.

Journal Articles

Application of revised procedure on determining large excess reactivity of operating reactor; Fuel addition method

Nagao, Yoshiharu; Hosoya, Toshiaki; Kaneko, Yoshihiko*

Nihon Genshiryoku Gakkai Wabun Rombunshi, 1(2), p.153 - 163, 2002/06

no abstracts in English

Journal Articles

Revised procedure for determining large excess reactivity of reactors

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

Journal Articles

First criticality prediction of the HTTR by 1/M interposition method

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

Journal Articles

The Equivalent fundamental-mode source

G.D.Spriggs*; R.D.Busch*; Sakurai, Takeshi; Okajima, Shigeaki

Annals of Nuclear Energy, 26(3), p.237 - 264, 1999/00

 Times Cited Count:11 Percentile:64.51(Nuclear Science & Technology)

no abstracts in English

Journal Articles

International studies on burnup credit criticality safety by an OECD/NEA working group, 2; Calculation benchmarks for BWR spent fuels

; *; 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

JAEA Reports

Preliminary analyses for HTTR's start-up physics tests by Monte Carlo code MVP

Nojiri, Naoki; Nakano, Masaaki; Ando, Hiroei; Fujimoto, Nozomu; Takeuchi, Mitsuo; Fujisaki, Shingo; Yamashita, Kiyonobu

JAERI-Tech 98-032, 59 Pages, 1998/08

JAERI-Tech-98-032.pdf:2.48MB

no abstracts in English

JAEA Reports

Analytical estimation of control rod shadowing effect for excess reactivity measurement of high temperature engineering test reactor (HTTR)

Nakano, Masaaki; Yamashita, Kiyonobu; Fujimoto, Nozomu; Nojiri, Naoki; Takeuchi, Mitsuo; Fujisaki, Shingo; *; Nakata, Tetsuo*

JAERI-Tech 98-017, 61 Pages, 1998/05

JAERI-Tech-98-017.pdf:2.68MB

no abstracts in English

Journal Articles

Effects of organic solvent on infinite neutron multiplication factor of homogeneous plutonium nitrate solution system

Sakurai, Satoshi; Arakawa, Takuya*;

Journal of Nuclear Science and Technology, 35(5), p.365 - 369, 1998/05

 Times Cited Count:0 Percentile:0.01(Nuclear Science & Technology)

no abstracts in English

Journal Articles

Benchmark analysis of experiments in fast critical assemblies using a continuous-energy monte carlo code MVP

Nagaya, Yasunobu; Nakakawa, Masayuki; Mori, Takamasa

Journal of Nuclear Science and Technology, 35(1), p.6 - 19, 1998/01

 Times Cited Count:3 Percentile:32.64(Nuclear Science & Technology)

no abstracts in English

Journal Articles

Measurement of the equivalent fundamental-mode source strength

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

JAEA Reports

A Proposal of revised method for determination of large positive reactivity

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

42 (Records 1-20 displayed on this page)