ナトリウム冷却高速炉における3次元自然循環除熱特性評価

Evaluation of the three-dimensional natural circulation heat removal characteristics in sodium-cooled fast reactor

遠藤 淳二*; 大山 一弘*; 渡辺 収*; 堂田 哲広  

Endo, Junji*; Oyama, Kazuhiro*; Watanabe, Osamu*; Doda, Norihiro

ナトリウム冷却高速炉では自然循環による崩壊熱除去系の採用が指向されている。本研究では、自然循環除熱時に原子炉容器や1次冷却系各部で生じる温度成層化や自然対流現象が崩壊熱除去へ与える影響を検討するため、外部電源喪失事象を対象に炉心を含む1次冷却系から崩壊熱除去系までを模擬したCFD解析を実施した。その結果、自然循環への移行時にコールドレグ配管に偏流がみられるものの、炉心は安定して冷却されることが確認された。

Adoption of natural circulation decay heat removal system is being investigated for commercialized sodium-cooled fast reactors. In this study, CFD simulations of primary heat transport systems including a core and decay heat removal systems in a loss-of-offsite-power event were conducted to evaluate the influence of thermal stratification and natural convection phenomena in the core upper plenum primary and the heat transport piping on the decay heat removal. From the simulation results, it was confirmed that the core is stably cooled by natural circulation, although drift occurs in the flow in the cold led pipes during the transition from forced to natural circulation.