A concept and safety characteristics of JAERI passive safety reactor (JPSR)

Abstract

A JAERI passive safety reactor (JPSR) system has been developed for reduction of manpower in operation and maintenance and increase of safety. The major features are as follows; an inherent matching nature of core heat generation and heat removal, in-vessel control rod drive mechanism units, once-through steam generators, a large volume pressurizer, passive heat removal system, and passive safety injection system. The passive heat removal system consists of residual heat exchangers, gravity coolant injection pools and air coolers. Steady-state analysis clarified that core residual heat during the whole period from shutdown to refueling phase can be transferred by natural circulation to the gravity coolant injection pool and finally to the atmosphere. In case of a large break loss-of-coolant accident (LOCA), steam is discharged and condensed in the gravity coolant injection pool. It was evaluated that the pool water temperature remains below boiling temperature under the large break LOCA condition. In the course of the design study, probabilistic safety assessment (PSA) was used to clarify the safety features and weak points. The results indicated that loss of offsite power is the dominant initiating event. Based on the analyses, improvements of safety system design were proposed.