DF-4 Analysis Using SCDAP/RELAP5

Abstract

In this paper the SCDAP/RELAPS severe accident analysis computer code, developed at the Idaho National Engineering Laboratory, is used to analyze the fourth in a series of debris formation experiments. The debris formation-four (DF-4) experiment deals with heatup and meltdown of a boiling water reactor (BWR)-representative fuel and control blade assembly segment, performed in the Annular Core Research Reactor at Sandia National Laboratories. The DF-4 experiment provides data that are used to validate core damage progression and BWR-specific models to gain an understanding of the phenomena occurring in the bundle during a severe BWR accident and to identify additional modeling needed in severe accident codes. The SCDAP/RELAPS model used for this analysis accurately predicts the key damage events, which include control blade melting, channel box relocation and runaway oxidation, the order and timing of these events, and the maximum bundle temperature. From these analytical calculations, an accident scenario and insights into phenomena occurring during a severe BWR accident are developed.