原子炉構造レジリエンスを向上させる破損の拡大抑制技術の開発,7; 超高温時のレジリエンス向上策の有効性評価技術

Development of failure mitigation technologies for improving resilience of nuclear structures, 7; Effectiveness evaluation technology of the measures for improving resilience at ultra-high temperatures

小野田 雄一 ; 西野 裕之  ; 栗坂 健一 ; 山野 秀将   ; 出町 和之*

Onoda, Yuichi; Nishino, Hiroyuki; Kurisaka, Kenichi; Yamano, Hidemasa; Demachi, Kazuyuki*

超高温時のレジリエンス向上策の有効性を評価するため、炉心損傷頻度に着目した評価の概念を構築した。高速炉において通常であれば炉心損傷に至る炉停止後の除熱機能喪失事象を対象に、喪失した除熱機能の超高温時における回復を可能にするレジリエンス向上策として、破損の拡大抑制技術を活用した1次冷却材の保持対策、及び超高温条件下で使用可能な熱輸送系の追設を想定した。レジリエンス向上策の導入前後の炉心損傷頻度を試計算し、これらの比較から頻度の低減効果をレジリエンス向上策の有効性として見積った。

In order to evaluate the effectiveness of the measures for improving resilience at ultra-high temperatures, a concept of evaluation focusing on core damage frequency was proposed. Assuming loss of heat removal systems event after reactor shutdown which may result in core damage in sodium-cooled fast reactors, the measures for improving resilience which enable to recover the safety functions at ultra-high temperatures are identified: one is to retain the primary coolant using failure mitigation technology, and the other is to add a heat removal system that can be used under ultra-high temperature conditions. The core damage frequencies were calculated preliminarily and their reduction effect was estimated by comparing them before and after the introduction of the measures for improving resilience.