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Imaizumi, Yuya; Aoyagi, Mitsuhiro; Kamiyama, Kenji; Matsuba, Kenichi; Akayev, A. S.*; Mikisha, A. V.*; Baklanov, V. V.*; Vurim, A. D.*
Dai-26-Kai Doryoku, Enerugi Gijutsu Shimpojiumu Koen Rombunshu (Internet), 4 Pages, 2022/07
The cooling of the residual core materials after the fuel discharge from the SFR core in the core disruptive accident can significantly affect the distribution fraction of the core materials which is an important factor for the in-vessel retention (IVR). The cooling of the residual core materials is called "in-place cooling". For the evaluation of the in-place cooling, behavior in a SFR core was simulated by SIMMER-III, and method of phenomena identification and ranking table (PIRT) was applied based on the analysis result. Experiment which focuses on the thermal-hydraulic phenomena which were extracted by the PIRT was conducted in the framework of EAGLE-3 project. Continuous oscillation of sodium level which can occur in the phase of in-place cooling of SFRs was observed in the experiment, and analysis by the SIMMER-III was conducted. By investigation of the analysis result, difference between the experiment and analysis results was revealed to be due to remaining and occupation of non-condensable gas above the sodium level which would be unrealistic in the experiment. Gas mixture model between non-condensable gas and sodium vapor was developed to solve this problem, and coincidence between experiment and analysis results was largely improved by this new model.
Matsuba, Kenichi; Kato, Shinya; Kamiyama, Kenji; Akayev, A. S.*; Baklanov, V. V.*
Proceedings of 28th International Conference on Nuclear Engineering (ICONE 28) (Internet), 4 Pages, 2021/08
In order to obtain experimental knowledge on fragmentation and cooling behavior of molten core material discharged into regions where the depth and volume of sodium are limited, a series of out-of-pile experiments using molten alumina as a simulant for molten core material was conducted. It was found that following mechanisms might be involved in the fragmentation and cooling behavior in a shallow sodium pool: (1) FCI which occurs at location of impingement of the molten jet on the bottom plate promotes fragmentation. (2) If there is a sufficient amount of sodium as a heat sink outside the region, heat exchange by sodium flow in and out due to vapor expansion and condensation suppresses the sodium temperature rise. (3) This temperature suppression contributes to effective cooling of molten core material. In the future study, in order to confirm the mechanisms which was clarified in this study, analytical evaluation of the experimental result will be carried out using a simulation tool.
