The Preliminary Analysis of a Typical Fluoride-Salt-Cooled High-Temperature Reactor in the Loss of Flow Accident with the Influence of Rolling Motion

Abstract

The solid-fuel-type MSR, Fluoride-salt-cooled High-temperature Reactor presents potential advantages in the use of passive safety systems that ensure the safe response of the reactor during anticipated operational occurrences, design basis events, and beyond design basis events. The FHR applied in ocean conditions faces a strong influence on the thermal-hydraulics. Using the system analysis code, ASYST with the implementation of thermal-hydraulic models in the consideration of the ocean motions effects, the safety evaluation is performed on the typical FHR design, MK1 PB-FHR, with the proposed concept designs of Direct Reactor Auxiliary Cooling System (DRACS). The influence of rolling motion condition is explored on the safety characteristics in the protected Loss of Forced circulation Accident (LOFA).In the analyzed rolling motion condition, mass flow rates in the core pebble bed, DHX, and DRACS loop fluctuate, signifying flow direction reversals. Additionally, DRACS' passive heat removal capability declines under rolling motion. While both DRACS loops operate, core outlet and fuel maximum temperatures remain stable. However, if one DRACS loop fails due to freezing, notable differences in thermal-hydraulic parameters arise between static and rolling motion conditions.