Numerical Simulation of Coolant-Coolant Interaction During Sgtr Accident in Lead-Cooled Fast Reactors

Abstract

Motivated to deepen the knowledge on the interaction mechanisms between high-pressure subcooled water jet and high-temperature molten lead-based metal during Steam Generator Tube Rupture (SGTR) accident in Lead-cooled Fast Reactors (LFRs), as well as the resultant pressure build-up characteristics, a numerical investigation is conducted using the MC3D code in this study. At the first place, a 2D numerical model is established based on a previous small-scale experimental study, and the simulation results are validated against the experimental data. Through simulation, good agreement is found between the experiment and simulation results for the non-explosion cases, which shows the capability of MC3D for modeling the Coolant-Coolant Interaction (CCI) phenomenon during a LFR SGTR accident. Thereafter, to extend the application scope of the MC3D code, another 2D numerical model is built according to the design specifications of the heat exchange tube in an experimental LFR using Lead-Bismuth Eutectic (LBE) as primary coolant. A sensitivity analysis is performed and the effects of LBE temperature, water temperature, water pressure, rupture diameter as well as rupture type on pressure build-up characteristics are discussed. The simulation results reveal that all the parameters have promoting effect on pressure build-up characteristics, among which the effect of water temperature is much more remarkable than LBE temperature. Besides, as guillotine rupture occurs in SGTR accident, void spots with low water volume fraction are observed around the two tube walls, and the pressure trend in the single-wall guillotine rupture case is highly similar to the one in the double-wall guillotine rupture case. Nevertheless, more experimental data are needed for the further validation of the MC3D code, and improvement as well as development of the current calculation models are also highly anticipated in the future to enhance the overall reliability of MC3D.

Keywords: lead-cooled fast reactor, Steam generator tube rupture, Coolant-coolant interaction, Numerical study