Numerical investigation on LBE-water interaction for heavy liquid metal cooled fast reactors

Abstract

Pool type Reactor Pressure Vessels (RPVs) containing steam generators with high secondary coolant pressure are adopted for a number of heavy liquid metal reactor conceptual designs. The primary side heavy liquid metal, e.g., liquid Lead-Bismuth Eutectic (LBE) with low pressure and secondary water with high pressure can come into contact in the event of Steam Generator Tube Rupture (SGTR) scenarios. Due to the pressure wave propagation and resultant sloshing of liquid LBE, the vigorous interaction between water and melt LBE can threaten the structural integrity of the reactor internals. Moreover, Reactor Pressure Vessel (RPV) pressurization, reactivity feedback as a result of steam entrance into the core as well as primary system pollution are also key concerns for SGTR accidents.The article aims to evaluate the capability of the MC3D code for LBE–water interaction in the event of SGTR scenarios. MC3D is a multidimensional numerical tool developed by IRSN for multi-phase flow studies and assessments in nuclear safety. Its field of application is mainly on Fuel-Coolant Interaction (FCI), especially the stages of premix and explosion in case of severe accidents. In order to evaluate the capability of MC3D for the Coolant-Coolant Interaction (CCI) of Liquid metal cooled Fast Reactors (LFRs), simulation of a small-scale experiment investigating water jet plunging into a pool of molten lead-bismuth alloy is carried out. Afterwards, experiments on LIFUS5/Mod2 facility at ENEA studying LBE-water interaction in the event of SGTR, for which a series of experiments have been conducted including the injection of sub-cooled water into LBE from the bottom of the test vessel, is simulated with MC3D as well. The simulation results for both facilities are then compared with those of the tests. The results predicted with MC3D for LIFUS5/Mod2 is also compared against the simulation results with SIMMER. The comparison impliesthat MC3D is generally capable for the phenomena of CCI in the event of SGTR for LFRs. Nevertheless, the potential employment of MC3D for intensive investigation of the LBE-water interaction will still need further experimental studies and improvement of physical models.