MAAP-CANDU Simulation of Severe Accidents in Darlington NGS

Abstract

MAAP-CANDU is an integrated computer code for the simulation of severe accident progression in a CANDU type nuclear plant. The code is designed to handle accident sequences including ones resulting in a complete core disassembly and relocation of the core material into the containment. This paper presents the results of MAAP-CANDU version 3.1 simulations of a series of severe accident sequences at Darlington NGS leading to severe core damage states. The accident scenarios presented originate from Loss of Coolant Accidents (LOCA) coincident with the loss of the Emergency Coolant Injection System (ECIS) and the unavailability of the moderator heat sink. The timing of major events and radiological consequences in terms of source term releases are discussed. It is concluded that Darlington NGS has inherent design features that prolongs the accident progression, thus, providing opportunities to mitigate the accident.