Application of the GIF Safety Design Criteria and Safety Design Guidelines on Natural Circulation Capability to Next Generation Sodium-Cooled Fast Reactor in Japan

Abstract

This paper describes the application of safety design criteria (SDC) and safety design guidelines (SDG) developed in the Generation-IV International Forum to the natural circulation of sodium to sodium-cooled fast reactors (SFRs) recently designed in Japan. It was consequently confirmed that the SFR designs conformed to the SDC and SDG without any specific gaps. Against design-basis accidents, the decay heat removal system (DHRS) is designed to have a combination of one train of a direct reactor auxiliary cooling system (DRACS) and two trains of a primary reactor auxiliary cooling system (PRACS) in a loop-type SFR, and a combination of one train of a DRACS and four trains of an intermediate reactor auxiliary cooling system (IRACS) in a pool-type SFR. Each DHRS design has a fully passive system with natural circulation capability by adopting reduction of system pressure loss and securing the difference in height between components. The natural circulation capability was confirmed by scaled experiments, one-dimensional plant dynamics calculations, and three-dimensional computational fluid dynamics simulations.