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Yanagisawa, Hiroshi; Motome, Yuiko
JAEA-Research 2025-010, 197 Pages, 2025/11
JAEA-Research-2025-010.pdf:3.5MB
For understandings of nuclear criticality risks of TRIGA fuel rods and review of safety measures for handling them, nuclear criticality characteristics for infinite and finite heterogeneous lattice systems composed of the NSRR fuel rods were re-evaluated with the use of a detailed computational model for the fuel rod. The MVP version 3 code was used with the JENDL libraries including the latest version, JENDL-5, for the re-evaluation. As the criticality characteristics, variations of neutron multiplication factors of the infinite and water-reflected finite systems were examined in detail with parameters of the lattice pitch and density of moderator water. From the results of the re-evaluated criticality characteristics, the minimum critical number of fuel rods for the water-reflected hexagonal shaped lattice system was obtained to be 46.8 
0.2 using the JENDL-5 library. Moreover, the attainability of criticality without the water as moderator and reflector was examined because the zirconium hydride moderator and graphite reflector are equipped with the TRIGA fuel rod. It was found that the criticality is possible to be attained by 115.7 0.6 of the number of fuel rods, which is the smaller number of fuel rods than loaded in the NSRR standard core, even though no water exists.
Takino, Kazuo; Oki, Shigeo
JAEA-Data/Code 2023-003, 26 Pages, 2023/05
JAEA-Data-Code-2023-003.pdf:1.66MB
Since next-generation fast reactors aim to achieve a higher core discharge burn-up than conventional reactors do, core neutronics design methods must be refined. Therefore, a suitable analysis condition is required for the analysis of burn-up nuclear characteristics to accomplish sufficient estimation accuracy while maintaining a low computational cost. We investigated the effect of the analysis conditions on the accuracy of estimation of the burn-up nuclear characteristics of next-generation fast reactors in terms of neutron energy groups, neutron transport theory, and spatial mesh. This study treated the following burn-up nuclear characteristics: criticality, burn-up reactivity, control rod worth, breeding ratio, assembly-wise power distribution, maximum linear heat rate, sodium void reactivity, and Doppler coefficient for the equilibrium operation cycle. As a result, it was found that the following conditions were the most suitable: 18-energy-group structure, 6 spatial meshes per assembly with diffusion approximation. Additionally, these conditions should apply to correction factors for energy group structure, spatial mesh and transport effects.
Collaborative Laboratories for Advanced Decommissioning Science; Ibaraki University*
JAEA-Review 2019-041, 71 Pages, 2020/03
JAEA-Review-2019-041.pdf:3.38MB
JAEA/CLADS, has been conducting the Center of World Intelligence Project for Nuclear Science/Technology and Human Resource Development (hereafter referred to "the Project") since FY2018. The Project aims at solving problems in nuclear energy field represented by the decommissioning of the Fukushima Daiichi Nuclear Power Station, Tokyo Electric Power Company Holdings, Inc. For this purpose, intelligence has been collected from all over the world, and basic research and human resource development have been promoted by closely integrating/collaborating knowledge and experiences in various fields beyond the barrier of conventional organizations and research fields. Among the adopted proposals in FY2018, this report summarizes the research results of the "Contribution to Risk Reduction in Decommissioning Works by the Elucidation of Basic Property of Radioactive Microparticles". In order to establish the decommissioning procedures (recovery of the melted fuels, decontamination inside the reactors, ensuring the safety of the workers, etc.) of the Fukushima Daiichi Nuclear Power Station, radioactive microparticles released by the accident are an important information source for clarifying what had happened inside the reactors in the course of the accident. The purpose of the present study is to obtain detailed knowledge on the basic properties (particle size, composition, electrical/optical properties, etc.) of the radioactive microparticles, as well as to further elucidate the various properties of the radioactive microparticles including the quantitative evaluation of alpha-ray-emitters, through the Japan-UK synergetic research. Thus, we are conducting research and development that will contribute to the comprehensive works towards the risk reduction in the "decommissioning" plan.
Nakajima, Ken
Proceedings of International Conference on the New Frontiers of Nuclear Technology; Reactor Physics, Safety and High-Performance Computing (PHYSOR 2002) (CD-ROM), 8 Pages, 2002/10
The nuclear characteristics of TRACY, such as the criticality, the 
/
ratio, the peak power, the energy of pulse, and the total energy, have been evaluated using the experimental data. TRACY is a supercritical reactor fueled with low-enriched uranyl nitrate aqueous solution to simulate criticality accidents in a fuel processing facility, such as a spent-fuel reprocessing plant. In this evaluation, the availability of criticality calculation and the models to evaluate the power and energy have been studied.
Owada, Ken
Journal of Chemical Physics, 84(3), p.1670 - 1676, 1986/00
Times Cited Count：2 Percentile：12.76(Chemistry, Physical)no abstracts in English
Owada, Ken
Journal of Chemical Physics, 82(2), p.860 - 867, 1985/00
Times Cited Count：2 Percentile：14.80(Chemistry, Physical)no abstracts in English
; ; Aruga, T.;
JAERI-M 8519, 113 Pages, 1979/11
no abstracts in English
; ; ; ; ;
JAERI-M 8293, 101 Pages, 1979/06
no abstracts in English
S.TERASAWA*; Nozawa, Masao*; T.IWAKI*; J.TAKAHASHI*; H.SHIOZAUKA*; M.FUJITA*
ANL-7520 PART-II, p.99 - 109, 1968/00
no abstracts in English
Thwe Thwe, A.; Kadowaki, Satoshi; Katsumi, Toshiyuki
no journal, ,
The experiments of hydrogen-air lean premixtures in a closed vessel were performed to study the effects of nitrogen addition on the combustion characteristics. The behavior of spherically propagating premixed flames was caught by high-speed Schlieren photography, and the flame radius and propagation velocity were measured. At sufficiently small flame radii, smooth flame fronts were observed. At large flame radii, on the other hand, cellular flame fronts generated by the intrinsic instability of premixed flames were observed. The flame propagation velocity increased owing to the generation of cellular fronts, and then the flame acceleration appeared. Adding nitrogen to premixtures, the cell shape of flame fronts became prominent, because of the strength of intrinsic instability. The maximum pressure in a closed vessel became lower in the case of nitrogen addition, indicating the suppression of hydrogen explosions. Moreover, the maximum pressure of experiments was lower than that of calculations under the adiabatic conditions, because of heat loss from the gases in a closed vessel to the vessel wall.
