「もんじゅ」実測データに基づく安全裕度評価

Monju safety margin analysis based on measurements

西田 和弘; 北村 謙治*; 山田 文昭

Nishida, Kazuhiro; Kitamura, Kenji*; Yamada, Fumiaki

高速増殖原型炉「もんじゅ」の総合機能試験及び性能試験の結果を用いて、制御棒急速引抜事故及び1次主冷却系循環ポンプ軸固着事故を解析し、事故の正確な推移を把握するとともに、この事故が安全に終息することを再確認した。解析結果は、異常な過渡変化時及び事故時の判断基準、当該原子炉設置許可申請書添付書類十安全評価の同事故時の解析結果に対して十分に下回り、制御棒急速引抜事故時の原子炉最大出力は106%、1次主冷却系循環ポンプ軸固着事故時の被ふく管肉厚中心最高温度は702Cとなった。安全評価の同事故時の解析結果との差の要因を分析した結果、解析条件の制御棒特性に最も余裕があることを明らかにした。

The results of the function test and the startup test of the Prototype Fast Breeder Reactor Monju were examined for the hypothetical analysis of the rapid withdrawal of the control rod assembly and to analyze pump seizure in the Primary Heat Transport System, in order to obtain accurate transition of the plant dynamics. These analyses confirmed that both of the accidents settle down without affecting the plant structure. During the withdrawal accident, reactor power reached 106%. During the pump seizure accident, the fuel cladding mid-wall temperature reached 702C. Both of these values are sufficiently below the safety margins for anomaly transients and accidents during operation and former analyses for design safety permission. The differences between these results and the former analyses for design safety permission have mostly been attributed to the characteristics of the control rods.