Core Melt Retention Capability of CANDU Reactors

Abstract

A simple molten pool heat transfer model has been set up for the CANDU reactor to perform sensitivity studies and understand the effect of differences from a LWR-like geometry. By varying important material properties of CANDU corium over the predicted range, the effect on vessel steel temperatures and heat flux to the surrounding water inherent in the CANDU design is determined. It is concluded that the melt is retained in the calandria vessel with a large margin to dryout. Comparison with the LWR-like geometry shows that steel temperatures are much higher due to the thicker vessel wall in a LWR,otherwise the results are similar, assuming external cooling is available. In both geometries, a large fraction of the core power is radiated upwards. The results of the CANDU analysis are confirmed with a more detailed transient debris melting model.