SIMULATION OF LIVE-L4 WITH ATHLET-CD

摘要

The test LIVE-L4 was performed at the Karlsruhe Institute of Technology (KIT) in the frame of the LIVE test series. The LIVE facility represents the lower plenum of a typical pressurized water reactor in a scale of 1:5. In order to investigate the melt behavior a substitute for corium melt is used composed of binary mixtures of sodium nitrate and potassium nitrate. The scope of the test LIVE-L4 was the investigation of the influence of external water cooling on the transient melt behavior at different power levels, while a special focus was on the examination of the crust formation and crust thickness growth. The simulation of LIVE-L4 was performed with the current development version of the severe accident code ATHLET-CD. ATHLET-CD consists of different modules to simulate the core degradation, fission product release and transport processes as well as the late phase module AIDA for the evaluation of melt pool behavior in the lower plenum. Model improvement was necessary for the internal calculation of the heat conductivity of the vessel and for the heat transfer between melt and crust. The evaluation of the simulation results of LIVE-L4 with the improved model show that the calculated temperatures during the test and the crust thickness at the end of the experiment are in good agreement to the measured values. Furthermore, the modified version of ATHLET-CD was applied on LIVE-LI and LFVE-L6, and the results show a better agreement to the experiment than previous calculations. In general, the results of these simulations indicate the improved capabilities of ATHLET-CD.