Safety Design and Evaluation in a Large-Scale Japan Sodium-Cooled Fast Reactor

Abstract EN

As a next-generation plant, a large-scale Japan sodium-cooled fast reactor (JSFR) adopts a number of innovative technologies in order to achieve economic competitiveness, enhanced reliability, and safety.

This paper describes safety requirements for JSFR conformed to the defense-in-depth principle in IAEA.

Specific design features of JSFR are a passive reactor shutdown system and a recriticality-free concept against anticipated transients without scram (ATWS) in design extension conditions (DECs).

A fully passive decay heat removal system with natural circulation is also introduced for design-basis events (DBEs) and DECs.

In this paper, the safety design accommodation in JSFR was validated by safety analyses for representative DBEs: primary pump seizure and long-term loss-of-offsite power accidents.

The safety analysis also showed the effectiveness of the passive shutdown system against a typical ATWS.

Severe accident analysis supported by safety experiments and phenomenological consideration led to the feasibility of in-vessel retention without energetic recriticality.

Moreover, a probabilistic safety assessment indicated to satisfy the risk target.