Application of a direct-heating model to the Sandia SURTSEY tests

In the event of a severe light water reactor accident which involves fuel melting at high primary system pressures the direct heating of the containment atmosphere is an important physical process to consider. This would occur as the fuel, which has slumped from the core into vessel lower plenum, fails the reactor pressure vessel (RPV) wall and is discharged under high pressure into the reactor cavity below the vessel. As the fuel and high-pressure gases are discharged from the RPV the fuel can be entrained in the gas flow and dispersed as droplets into the containment atmosphere. The heating of the atmosphere by the sensible heat of the fuel droplets as well as possible chemical reactions of the fuel with the gases may threaten containment integrity. A series of experiments is being planned at Sandia (SURTSEY) to understand this direct heating phenomenon. In the paper the authors present a pre-test calculation of the first SURTSEY test (DCH-1) using a recently developed direct heating model (DIRHET). This model will be compared to the SURTSEY test data to verify its applicability and is being used in scoping calculations for containment direct heating.