Investigation on multi-dimensional short-term behaviour through benchmark analysis of a large-volume sodium combustion experiment

Sonehara, Masateru; Okano, Yasushi; Uchibori, Akihiro; Oki, Hiroshi*

Journal of Nuclear Science and Technology, 62(5), p.403 - 414, 2025/05

https://doi.org/10.1080/00223131.2024.2441427

For sodium-cooled fast reactors, understanding sodium combustion behaviour is crucial for managing sodium leakage accidents. In this study, we perform benchmark analyses of the Sandia National Laboratories (SNL) T3 experiment using the multi-dimensional thermal hydraulic code AQUA-SF. Conducted in an enclosed space with a large vessel volume of 100 m and a sodium mass flow rate of 1 kg/s, the experiment highlighted the multi-dimensional effects of local temperature increase shortly after sodium injection. This study aims to extend the capabilities of AQUA-SF by focusing on the simulation of these multi-dimensional temperature variations, in particular the formation of high temperature regions at the bottom of the vessel. The proposed models include the temporary stopping of sodium droplet ignition and spray combustion of sodium splash on the floor. Furthermore, it has been shown that additional heat source near the floor is essential to enhance the reproduction of the high temperature region at the bottom. Therefore, case studies including sensitivity analyses of spray cone angle and prolonged combustion of droplets on the floor are conducted. This comprehensive approach provides valuable insights into the dynamics of sodium combustion and safety measures in sodium-cooled fast reactors.

Advances in the analysis and management of accidents and future challenges; The OECD/NEA WGAMA

Nakamura, Hideo; Bentaib, A.*; Adorni, M.*

Proceedings of 20th International Topical Meeting on Nuclear Reactor Thermal Hydraulics (NURETH-20) (Internet), p.5668 - 5678, 2023/08

https://doi.org/10.13182/NURETH20-40641

The OECD/NEA Working Group on the Analysis and Management of Accidents (WGAMA); Advances in codes and analyses to support safety demonstration of nuclear technology innovations

Nakamura, Hideo; Bentaib, A.*; Herranz, L. E.*; Ruyer, P.*; Mascari, F.*; Jacquemain, D.*; Adorni, M.*

Proceedings of International Conference on Topical Issues in Nuclear Installation Safety; Strengthening Safety of Evolutionary and Innovative Reactor Designs (TIC 2022) (Internet), 10 Pages, 2022/10

Development of unstructured mesh-based numerical method for sodium-water reaction phenomenon in steam generators of sodium-cooled fast reactors

Uchibori, Akihiro; Watanabe, Akira*; Takata, Takashi; Ohshima, Hiroyuki

Journal of Nuclear Science and Technology, 54(10), p.1036 - 1045, 2017/10

https://doi.org/10.1080/00223131.2017.1344155

To evaluate a sodium-water reaction phenomenon in a steam generator of sodium-cooled fast reactors, a computational fluid dynamics code SERAPHIM, in which a compressible multicomponent multiphase flow with sodium-water chemical reaction is computed, has been developed. The original SERAPHIM code is based on the difference method. In this study, unstructured mesh-based numerical method was developed to advance a numerical accuracy for the complex-shaped domain including multiple heat transfer tubes. Numerical analysis of an underexpanded jet experiment was performed as part of validation of the unstructured mesh-based numerical method. The calculated pressure profile showed good agreement with the experimental data. Applicability of the numerical method for the actual situation was confirmed through the analysis of water vapor discharging into liquid sodium. The effect of use of the unstructured mesh was also investigated by the two analyses using structured and unstructured mesh.

Event sequence assessment of deep snow in sodium-cooled fast reactor based on continuous Markov Chain Monte Carlo method with plant dynamics analysis

Takata, Takashi; Azuma, Emiko*

Journal of Nuclear Science and Technology, 53(11), p.1749 - 1757, 2016/11

https://doi.org/10.1080/00223131.2016.1155508

Margin assessment of a nuclear power plant against external hazards is one of the most important issues after Fukushima Dai-ichi Nuclear Power Plant Accident. In this paper, a new approach has been developed to assess the plant status during external hazards and countermeasures against them in operation quantitatively and stochastically. A Continuous Markov chain Monte Carlo (CMMC) method is applied and coupled with a plant dynamics analysis. In the CMMC method, a subsequence plant status is determined by the latest state (Markov chain) and the status is evaluated from the plant dynamics analysis. A failure or success of safety function of plant component is also evaluated stochastically based on a latest state of plant or hazard. A numerical investigation of plant dynamics analysis against a snow hazard is also carried out in a loop type sodium cooled fast reactor so as to assess the margin against the hazard.

Analysis of natural circulation tests in the experimental fast reactor JOYO

Nabeshima, Kunihiko; Doda, Norihiro; Ohshima, Hiroyuki; Mori, Takero; Ohira, Hiroaki; Iwasaki, Takashi*

Proceedings of 16th International Topical Meeting on Nuclear Reactor Thermal Hydraulics (NURETH-16) (USB Flash Drive), p.1041 - 1049, 2015/08

Natural circulation is one of the most important mechanisms to remove decay heat in the sodium cooled fast reactors from the viewpoint of passive safety. On the other hand, it is difficult to evaluate plant dynamics accurately under low flow natural circulation condition. In this study, Super-COPD has been validated through the application to the analysis of natural circulation tests in the experimental fast reactor JOYO. Almost all plant components in JOYO including four air-coolers were modeled in Super COPD. Furthermore, the full scale modeling of fuel subassembly was also adopted in this analysis. The natural circulation test after reactor scram from 100 MW full power at JOYO was selected and simulated by Super-COPD. The transient behaviors predicted by Super-COPD showed good agreement with the experimental data.

Monte Carlo/molecular dynamics simulation on laser melting and evaporation

Kunugi, Tomoaki; ;

Proc. of 2nd Japan-Central Europe Joint Workshop on Modelling of Materials and Combustion, 0, p.205 - 208, 1996/00

no abstracts in English

Estimation of net reactivity based on H estimation theory

Suzuki, Katsuo; Shimazaki, Junya; Shinohara, Yoshikuni

Nihon Genshiryoku Gakkai-Shi, 36(1), p.79 - 88, 1994/01

https://doi.org/10.3327/jaesj.36.79

no abstracts in English

Evaluation report on CCTF core-II reflood test C2-15(Run 75); Investigation of FLECHT-SET coupling test results

Okubo, Tsutomu; Iguchi, Tadashi; ; Murao, Yoshio

JAERI-M 91-227, 89 Pages, 1992/01

JAERI-M-91-227.pdf:1.82MB

no abstracts in English

Thermal and hydraulic tests of a standard fuel rod of HTTR with HENDEL

Takase, Kazuyuki; Hino, Ryutaro;

Nihon Genshiryoku Gakkai-Shi, 32(11), p.1107 - 1110, 1990/11

https://doi.org/10.3327/jaesj.32.1107

no abstracts in English