Study on loss-of-cooling and loss-of-coolant accidents in spent fuel pool, 8; Safety margin of spent fuel in large LOCA event by the simple assessment method

使用済み燃料プールの冷却機能不全、冷却水損失事故に関する研究,8; 使用済燃料プールLOCA時の簡易計算による安全裕度評価

染谷 崇之*; 千年 宏昌*; 渡辺 聡*; 根本 義之  ; 加治 芳行  

Someya, Takayuki*; Chitose, Hiromasa*; Watanabe, Satoshi*; Nemoto, Yoshiyuki; Kaji, Yoshiyuki

新規制基準の下、電力各社ではSFP冷却水損失事故時の安全評価を簡易な手計算で実施しているが、その安全裕度に関しては十分な議論がなされていない。そのため、本研究ではCFD解析によるSFP冷却水損失事故の詳細評価を実施し、簡易な手計算での評価結果と比較を行った。その結果、簡易な手計算ではCFD解析に比較して100C程度、事故時の燃料の最高温度を高く評価することが明らかになった。

In this study, CFD analysis has been conducted for the assessment of spent fuel integrity in large LOCA event and the maximum temperature of spent fuel assemblies has been evaluated. Then, it has been compared with the result of the simple assessment method. As a case study, additional CFD analysis has been conducted, where water level in SFP decreases to the Bottom of Active Fuel (BAF) due to boil-off. Since this scenario might be more severe than large LOCA scenario, the number of spent fuel assemblies, their decay heat and loading pattern to maintain spent fuel integrity are investigated.