Development of core hot spot evaluation method of a loop type fast reactor equipped with natural circulation decay heat removal system

Doda, Norihiro  ; Ohshima, Hiroyuki; Kamide, Hideki ; Watanabe, Osamu*

A natural circulation decay heat removal system is adopted in the design of an advanced loop type fast reactor in Japan. For the core structural integrity, we have developed a new evaluation method for the core hot spot temperature during natural circulation decay heat removal operations. In the method, safety analyses are performed with the plant dynamics models that can consider characteristic thermal-hydraulic phenomena under natural circulation conditions. In addition, the core hot spot temperature is estimated with its uncertainty quantified in the statistical manner. This paper describes the evaluation method and also the application results to a loss of offsite power event.