CFD Modelling of Liquid Poison Injection in ACR-1000 Shutdown System

The Liquid Injection Shutdown System (LISS) is a safety system in the CANDU™-type reactor to provide rapid reactor shutdown by automatically injecting a neutron absorbing liquid (“poison”), via injection nozzles, into the moderator in the calandria. The poison distribution in the moderator plays a significant role in the shutdown performance. The Advanced CANDU Reactor (ACR-1000™) is a Generation III+ type reactor as an evolutionary extension of the proven CANDU-6 reactor. The basic design concept of the CANDU-6 LISS is adopted for the ACR-1000. The injection nozzle design has been modified to suit the ACR-1000 reactor core configuration. In this study, a Computational Fluid Dynamics (CFD) model was developed using the ANSYS-CFX software to examine the poison injection characteristics in the ACR-1000 design. The effects of calandria tubes on the poison jet growth and poison distribution in the reactor core were discussed.