Application-and Validation of the Pheonics Code for Moderator System Conditions in a CANDU Nuclear Generating Station

Abstract

To demonstrate the capability of the CANDU moderator to act as an alternate heat sink far postulated accidents when other conventional heat sinks are not available, local moderator temperatures must be known as these temperatures affect the amount of subcooling available. In the search for an analytical computing tool capable of modelling the somewhat intricate features of moderator flaw for both steady state and transient scenarios, the general purpose fluid-flow, heat transfer code PHOENICS was selected. POENICS can be used in transient or steady state mode and incorporates most of the physical models necessary to model the basic phenomena occurring within the moderator. Those which are not available can be easily implemented due to the codes versatile structure. The code has recently been used to calculate three-dimensional steady state temperature and flow distributions in a CANDU 6 moderator. The credibility of results using analytic computer tools ultimately rests on the verification of the code against the problem being modelled or to some smaller scale experimental base. To date, PHOENICS has been benchmarked against the SPEL and STERN small scale moderator test results. Both of these experimental programs were based on two-dimensional representation.