摘要
The prototype fast breeder reactor ＂MONJU＂ has an EVSS （ex-vessel fuel storage system） which consists mainly of an EVST （ex-vessel fuel storage tank） and an EVST sodium cooling system. EVST sodium cooling system consists of three independent loops. During the normal operation, the primary sodium in the EVST is circulated by natural convection and the secondary circulation in the EVST sodium cooling system is powered by electromagnetic pumps. When an SBO （station blackout） occurs, all the pumps and blowers are tripped. Therefore, it was necessary to evaluate the cooling ability by the natural circulation of sodium in the EVST sodium cooling system and air through the air cooler during the SBO. In this study, an analysis and evaluation of the plant dynamics for the spent fuel and the EVSS structural integrity during an SBO were performed. When the number of cooling loops was not changed and natural circulation occurred in only two loops, the sodium temperature in the EVST increased to approximately 450 ~C. However, the structural integrity of the EVSS was maintained. The analytical results, therefore, help clarify the number of necessary cooling loops for efficient decay heat removal and sodium temperature behavior in an SBO.
