JSFRにおける炉心崩壊事故の炉容器内格納に向けた事象推移評価,2; 炉心燃料早期流出過程

Evaluation of core disruptive accident for JSFR to achieve in-vessel retention, 2; Early-discharge phase

神山 健司  ; 飛田 吉春; 豊岡 淳一  ; 小西 賢介 ; 山野 秀将   

Kamiyama, Kenji; Tobita, Yoshiharu; Toyooka, Junichi; Konishi, Kensuke; Yamano, Hidemasa

ナトリウム冷却高速炉の代表的な炉停止失敗事象であるULOF事象において、炉心溶融が進展する段階での事象推移を炉内・炉外試験データに基づいて検討・評価した。内部ダクト付き燃料集合体の導入により炉心溶融進展の早期段階で溶融燃料が炉心外へ流出するため、厳しい出力バーストをもたらす大規模な溶融燃料プールの形成が回避され、炉容器バウンダリの機械的破損が回避されるとの結論を得た。

Event sequences of the core melting progression during ULOF event were considered and evaluated based on databases both of in-pile and of out of-pile experiments. The ULOF is an representative unsuccessful operation of active and passive reactor shutdown systems in the loss of flow case in sodium-cooled fast reactors. It was concluded that formation of the large-scale molten-fuel pool, which will lead severe power excursion, can be avoided and therefore mechanical failure of the reactor vessel can be avoided, since the molten fuel is discharged from the core region during the early stage of core melting progression by introduction of the fuel assembly with inner duct structure (FAIDUS).