Thermal-Hydraulic Analysis of the Upper Plenum in a Typical LFR During a Reactivity Insertion Accident

Abstract MYRRHA is the Gen IV liquid metal cooled fast reactor, which is a pool-type reactor system developed and designed by the Belgian Nuclear Research Center SCK·CEN. Regarding the safety assessment of the installation, the major challenge is to analyze the complex coolant flow field characteristics in the large open regions of the reactor vessel. In this paper, a coupled sub-channel/CFD multi-scale platform is developed through implementing the sub-channel code SACOS-PB to the CFD code FLUENT based on the domain decomposition and explicit numerical scheme. The flow field characteristics in the upper plenum of reactor emergency shutdown after a reactivity insertion accident (RIA) were investigated. Based on the RIA analysis, the thermal stratification effect has been observed in the upper plenum. The analysis results well demonstrated the 3D flow and local phenomenon of the fluid in the upper plenum, which is significant to reactor design and reactor safety analysis of LFRs.