TRU oxide sample reactivity worths measured in the FCA-IX assemblies with systematically changed neutron energy spectra

Fukushima, Masahiro; Okajima, Shigeaki*; Mukaiyama, Takehiko*

Journal of Nuclear Science and Technology, 20 Pages, 2023/00

https://doi.org/10.1080/00223131.2023.2240872

A series of integral experiments was conducted to evaluate the fission and the capture cross- sections of transuranic (TRU) nuclides at the fast critical facility FCA of the Japan Atomic Energy Agency (JAEA). The experiments were carried out using seven uranium-fueled assemblies of the FCA. The neutron energy spectra of the core regions were adjusted so as to change from an intermediate neutron spectrum to a fast neutron spectrum on an assembly-by-assembly basis. The integral data measured with these experimental configurations provide some neutron energy characteristics: 1) fission rate ratios (FRRs) of Np, Pu, Pu, Am, Am, and Cm relative to Pu by using absolutely calibrated fission chambers, 2) small sample reactivity worths (SRWs) of Np, Pu, Pu, Am, and Am where oxide powders of around 15 to 20 grams were used, 3) criticalities, and 4) spectral indices such as fission rate ratios of U relative to U. In this paper, details of the SRW measurements are reported, and the latest Japanese Evaluated Nuclear Data Library JENDL-5 is tested by using the integral data obtained in systematically varied neutron energy spectra.

Benchmark tests of newly-evaluated data of U for CIELO project using integral experiments of uranium-fueled FCA assemblies

Fukushima, Masahiro; Kitamura, Yasunori*; Yokoyama, Kenji; Iwamoto, Osamu; Nagaya, Yasunobu; Leal, L. C.*

Proceedings of International Conference on the Physics of Reactors; Unifying Theory and Experiments in the 21st Century (PHYSOR 2016) (USB Flash Drive), p.605 - 619, 2016/05

A nuclear data of U has been recently evaluated for the CIELO (Collaborative International Evaluated Library Organization) project. We tested the newly-evaluated data of U using integral experiments of the Fast Critical Assembly (FCA) performed at JAEA. We selected two integral data of uranium-fueled FCA assemblies; one is the sodium-void reactivity worth of FCA XXVII-1 assembly and the other is the criticalities of the seven assemblies of FCA IX. The benchmark tests support the evaluation done in the resonance regions. However, the U capture cross section above the unresolved resonance range needs further investigation.

Benchmark models for criticalities of FCA-IX assemblies with systematically changed neutron spectra

Fukushima, Masahiro; Kitamura, Yasunori; Kugo, Teruhiko; Okajima, Shigeaki

Journal of Nuclear Science and Technology, 53(3), p.406 - 424, 2016/03

https://doi.org/10.1080/00223131.2015.1054911

Preliminary evaluation of reduction of prediction error in breeding light water reactor core performance

Kugo, Teruhiko; Kojima, Kensuke; Ando, Masaki; Okajima, Shigeaki; Mori, Takamasa; Takeda, Toshikazu*; Kitada, Takanori*; Matsuoka, Shogo*

Proceedings of 2005 International Congress on Advances in Nuclear Power Plants (ICAPP '05) (CD-ROM), 10 Pages, 2005/05

We have preliminarily evaluated the reduction of prediction errors of the core characteristics of the breeding light water reactor core based on the bias factor method by utilizing the FCA critical experiments carried out for MOX fueled tight lattice light water reactor cores. The prediction uncertainty of k is reduced from 0.62% to 0.39% by utilizing the FCA-XV-2 (65V) result. As for the reaction rate ratio of U capture and Pu fission, it is found that the FCA XXII-1 (95V) and XV (95V) results are suitable for the upper core and the upper blanket of the real core and the FCA XXII-1 (65V) and XV-2 (65V) results are suitable for the lower core and the internal blanket.

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 1.3440.034. 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.

Determination of reactivity and source intensity based on the maximum likelihood method

Nishihara, Kenji; Iwanaga, Kohei; Yamane, Tsuyoshi; Okajima, Shigeaki

JAERI-Research 2002-030, 63 Pages, 2002/12

JAERI-Research-2002-030.pdf:3.81MB

During the experiments using the critical assembly such that reactivity is added to the stationary state and the core shifts to the other stationary state, the neutron flux transitionally changes after some change of the reactivity or source. Inverse kinetics method (IK method) can generally adopted as the technique of obtaining the reactivity and/or source by analyzing the neutron flux. However, the conventional analysis method was not able to obtain the solution with the maximum likelihood considering the error of the measured neutron flux and to estimate the error of the solution. In the present research, by adopting the maximum likelihood methodology to the problem, developed is the technique to obtain the reactivity and source intensity with maximum likelihood and the errors of them. Moreover, the technique is applied to the rod drops experiment in FCA, and the validity of a technique is checked.

Adjustment of total delayed neutron yields of U, U and Pu by using results of in-pile measurements of effective delayed neutron fraction

Sakurai, Takeshi; Okajima, Shigeaki

Proceedings of International Conference on the New Frontiers of Nuclear Technology; Reactor Physics, Safety and High-Performance Computing (PHYSOR 2002) (CD-ROM), 12 Pages, 2002/10

The cross section adjustment method was applied to total delayed neutron yields of U, U and Pu of the JENDL-3.2 file by using experimental results of effective delayed neutron fraction at six cores built in two fast critical facilities of the MASURCA and FCA and a thermal critical facility of the TCA to improve these yields. The adjustment was carried out on the yields given at several incident neutron energy points in the file. Furthermore, to validate these adjusted delayed neutron yields, analyses were performed for the experiments at ZPR fast critical facility. These adjusted yields brought a reduction of uncertainty of calculated and an improvement in agreement of between experiment and calculation.

Experiments and analyses on sodium void reactivity worth in uranium-free fast reactor at FCA

Oigawa, Hiroyuki; Iijima, Susumu; Ando, Masaki

Journal of Nuclear Science and Technology, 39(7), p.729 - 735, 2002/07

https://doi.org/10.3327/jnst.39.729

no abstracts in English

Adjustment of total delayed neutron yields of U, U and Pu in JENDL-3.2 using benchmark experiments on effective delayed neutron fraction

Sakurai, Takeshi; Okajima, Shigeaki

Journal of Nuclear Science and Technology, 39(1), p.19 - 30, 2002/01

https://doi.org/10.3327/jnst.39.19

The cross section adjustment method was applied to total delayed neutron yields of U, U and Pu of the JENDL-3.2 file by using experimental results of effective delayed neutron fraction at six cores built in two fast critical facilities of the MASURCA and FCA and a thermal critical facility of the TCA to improve these yields. The adjustment was carried out on the yields given at several incident neutron energy points in the file. After the adjustment, the yield of U was almost uniformly decreased by about 3% below 7 MeV. The yield of Pu was increased by 2.6% and that of U was decreased by 0.9% at the thermal energy point, while the change of yield was less than 0.3% at the other energy points for these nuclides. By using these adjusted yields, the uncertainty of calculated was reduced and the agreement of between experiment and calculation was improved.

Experiments and analyses on reactivity worth of gas expansion module (GEM) in FCA XX-1 (Joint research)

Oigawa, Hiroyuki; Ando, Masaki; Iijima, Susumu; Takaki, Naoyuki*; Uematsu, Mari Marianne*

JAERI-Research 2001-036, 48 Pages, 2001/06

JAERI-Research-2001-036.pdf:2.38MB

no abstracts in English