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Yamano, Hidemasa; Kubo, Shigenobu; Tokizaki, Minako*; Nakamura, Hironori*
Proceedings of International Conference on Topical Issues in Nuclear Installation Safety; Strengthening Safety of Evolutionary and Innovative Reactor Designs (TIC 2022) (Internet), 12 Pages, 2022/10
Specific design features of advanced sodium-cooled fast reactors (SFRs) designed in Japan are a passive reactor shutdown system, a passive decay heat removal system (DHRS), and an in-vessel retention (IVR) concept against an anticipated transients without scram (ATWS) in design extension condition (DECs). The present paper describes numerical analysis methodologies for event sequences studied in Japan and some numerical analyses of DECs to show the effectiveness of the passive shutdown system against a typical ATWS and severe accident mitigation measures for the IVR of molten core. For the passive shutdown capability, the numerical analysis has demonstrated the effectiveness of a self-actuated shutdown system against a severe ATWS event, for which the temperature response time was separately evaluated by a computational fluid dynamics (CFD) code. A recently developed debris-bed cooling analysis methodology coupled with a CFD code and a debris-bed module has successfully simulated a three-dimensional coolant flow field near the debris bed with the passive DHRS capability in order to demonstrate the debris-bed coolability on a core catcher.
Li, C.-Y.; Uchibori, Akihiro; Takata, Takashi; Pellegrini, M.*; Erkan, N.*; Okamoto, Koji*
Dai-25-Kai Doryoku, Enerugi Gijutsu Shimpojiumu Koen Rombunshu (Internet), 4 Pages, 2021/07
The capability of stable cooling and avoiding re-criticality on the debris bed are the main issues for achieving IVR (In-Vessel Retention). In the actual situation, the debris bed is composed of mixed-density debris particles. Hence, when these mixed-density debris particles were launched to re-distribute, the debris bed would possibly form a density-stratified distribution. For the proper evaluation of this scenario, the multi-physics model of CFD-DEM-Monte-Carlo based neutronics is established to investigate the coolability and re-criticality on the heterogeneous density-stratified debris bed with considering the particle relocation. The CFD-DEM model has been verified by utilizing water injection experiments on the mixed-density particle bed in the first portion of this research. In the second portion, the coupled system of the CFD-DEM-Monte-Carlo based neutronics model is applied to reactor cases. Afterward, the debris particles' movement, debris particles' and coolant's temperature, and the k-eff eigenvalue are successfully tracked. Ultimately, the relocation and stratification effects on debris bed's coolability and re-criticality had been quantitatively confirmed.
Suzuki, Toru; Sogabe, Joji; Tobita, Yoshiharu; Sakai, Takaaki*; Nakai, Ryodai
Nihon Kikai Gakkai Rombunshu (Internet), 83(848), p.16-00395_1 - 16-00395_9, 2017/04
no abstracts in English
Suzuki, Toru; Sogabe, Joji; Tobita, Yoshiharu; Sakai, Takaaki*; Nakai, Ryodai
Dai-21-Kai Doryoku, Enerugi Gijutsu Shimpojiumu Koen Rombunshu (USB Flash Drive), 4 Pages, 2016/06
Suzuki, Toru; Tobita, Yoshiharu; Kawada, Kenichi; Tagami, Hirotaka; Sogabe, Joji; Matsuba, Kenichi; Ito, Kei; Ohshima, Hiroyuki
Nuclear Engineering and Technology, 47(3), p.240 - 252, 2015/04
Times Cited Count：27 Percentile：91.4(Nuclear Science & Technology)Kamiyama, Kenji; Konishi, Kensuke; Sato, Ikken; Toyooka, Junichi; Matsuba, Kenichi; Suzuki, Toru; Tobita, Yoshiharu; Pakhnits, A. V.*; Vityuk, V. A.*; Vurim, A. D.*; et al.
Proceedings of 10th International Topical Meeting on Nuclear Thermal Hydraulics, Operation and Safety (NUTHOS-10) (USB Flash Drive), 8 Pages, 2014/12
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Nuch.Eng.Des./Fusion, 1, p.243 - 253, 1984/00
no abstracts in English
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JAERI-M 8274, 53 Pages, 1979/06
no abstracts in English
Suzuki, Toru; Kamiyama, Kenji; Matsuba, Kenichi; Isozaki, Mikio; Yamano, Hidemasa; Morita, Koji*; Zhang, B.*; Guo, L.*; Tobita, Yoshiharu
no journal, ,
In Sodium-Cooled Fast Reactor (SFR), it is possible to provide appropriate design measure to achieve the In-Vessel Retention of Core Disruptive Accident (CDA). In this study, the assessment methodology of the important phenomena in the achievement of IVR, such as the discharge of molten core materials from core region, the fragmentation of molten core material into debris by coolant, and the behavior of accumulated debris bed, are developed based on the combination of experiments and validation of analytical method.
Onoda, Yuichi; Matsuba, Kenichi; Tobita, Yoshiharu
no journal, ,
no abstracts in English
Suzuki, Toru; Tobita, Yoshiharu; Sakai, Takaaki; Nakai, Ryodai
no journal, ,
no abstracts in English
Kubota, Ryuzaburo; Suzuki, Toru; Kawada, Kenichi; Kubo, Shigenobu; Yamano, Hidemasa; Koyama, Kazuya*; Moriwaki, Hiroyuki*; Yamada, Yumi*; Shimakawa, Yoshio*
no journal, ,
A new methodology to obtain SAS4A input data of power and reactivity profile more consistent with the core design for various core states was consolidated. Using this methodology, SAS4A analyses on the initiating phase during ULOF and UTOP transients from the full power state and the low power state were performed. This analysis study suggests that the power excursion with prompt criticality leading to large mechanical energy release can be prevented in the initiating phase of the current design for the medium-scale Gen-IV loop-type SFR.
Sogabe, Joji; Wada, Yusaku*; Suzuki, Toru*; Tobita, Yoshiharu
no journal, ,
no abstracts in English
Emura, Yuki; Kamiyama, Kenji; Matsuba, Kenichi; Isozaki, Mikio
no journal, ,
In case of core disruptive accident in sodium-cooled fast reactors, it is thought that molten-core material will be discharged into the lower plenum and fragmented there due to fuel-coolant interactions. To understand this fragmentation behavior, we performed the simulation test in which molten stainless steel discharged into sodium pool and fragmentation behavior was observed using a visualization system combined X-ray and high-speed camera. Both successful visualization of fragmentation behavior by above visualization system and rapid cooling of molten stainless steel due to fragmentation are presented in this study.
