CFD Model of CANDU Calandria Vessel Retention During Severe Accidents

Abstract

A CFD model is developed for the calandria vessel retention of generic CANDU ®1 reactors, including the Enhanced CANDU 6 ®™2 (EC6®™2), the Advanced CANDU Reactor®3 (ACR- 1000®3), and the CANDU 6, during a postulated severe accident. The model is focused on the thermal hydraulics in a full-scale calandria vessel when terminal debris bed is formed during a loss of coolant accident, which is bounding in terms of potential challenge to calandria vessel integrity. The CFD model is benchmarked against MAAP4-CANDU analysis of ACR-1000. The results show that with ex-vessel cooling available, the core debris can be well contained inside the calandria vessel, demonstrating the successful in-vessel retention strategy in the ACR-1000 severe accident management.