Characterizing Melt Fuel-coolant Interaction in a NPP Context with RELAP5/SCDAP 3.2 CODE

During the progression of a severe accident in LWR, the core in absence of cooling can melt, relocate and interact with coolant in the reactor pressure vessel lower plenum or in the reactor cavity. The phenomena associated with the interaction of corium with coolant are of great safety interest as precondition to possible steam explosions and for the lower plenum debris coolability problem. Thermalhydraulic codes capable to simulate in detail the Melt Fuel Coolant Interaction (MFCI) phenomena have been developed so far but it is also interesting to illustrate the MFCI inside the general overview of a severe accident sequence (LB LOCA, in the cold leg) and inside the overall view of a generic PWR NPP (3 loops, 1000 MWe). RELAP5/SCDAP 3.2 is the code chosen to obtain the initial just before the pool of molten core material slumping into the lower plenum. These conditions could be introduced in a specific MFCI code input so a detailed MFCI study could be later performed. In that way RELAP5/SCDAP 3.2 and a detailed MFCI code can be seen as complementary tools. A further analysis on the influence of the LPIS in the sequence of the accident resulted from the calculations.

ANNUNZIATO Alessandro;  REVENTOS Frances;  PLA Patricia; 

2006-12-15

American Nuclear Society

JRC31443