Development of analysis code for behavior of passive safety device in innovative sodium-cooled fast reactor

Abstract

FAST (Floating Absorber for Safety at Transient) is a passive safety device which inserts negative reactivity in the reactor core depending on the coolant temperature. To analyze the behavior of FAST, FASTAC (Floating Absorber for Safety at Transient Analysis Code) was developed in this study. In order to verify the physical model used for the FASTAC, verification procedure of the FASTAC was conducted by comparing results of CFD (Computational Fluid Dynamics) analysis. Validation of the FASTAC could be achieved by comparing terminal velocity measured by experiment. The uncertainty of results in the experimental process was analyzed for the pin diameter and guide wings. Through the computational fluid analysis, the resistance applied to the shape of FAST was analyzed. The developed code evaluated the inserted length of FAST using the results of MATRA-LMR and Monte-Carlo codes, assuming transient conditions.