Numerical assessment of PARAMETER-SF1 test on oxidation and melting of LWR fuel assembly under top flooding conditions

The paper discusses the results of numerical assessment of LWR fuel bundle degradation phenomena during heating up in a flowing steam and top flooding with water under severe accident conditions that were investigated in the PARAMETER-SF1 test. The simulation was performed with the code SOCRAT that is widely used in Russia for safety assessment of VVER-type NPP under severe accident conditions. A set of interacting processes, including heat transfer, fuel liquefaction, oxidation of fuel rods claddings, melt relocation and oxidation, hydrogen generation is discussed. PARAMETER-SF1 was the first test in the PARAMETER program that comprised several tests with different configurations of the VVER bundle flooding (top, bottom, and combined). Investigation of the phenomenology during flooding of an overheated core at the early phase of severe accident when core keeps a mainly rod-like geometry is extremely important for understanding the possibilities and conditions for implementing the measures of severe accident management at LWR NPPs.