Analysis of a SBO in a CANDU Using RELAP/SCDAPSIM/MOD3.6

Abstract

A new experimental version, RELAP/SCDAPSIM/MOD3.6, is being developed to support the analysis of Pressurized Heavy Water Reactors (PHWRs) under severe accident conditions. It is a derivative of RELAP/SCDAPSIM/MOD3.5, which has the most advanced fuel and severe accident modeling options for LWRs. This paper summarizes the verification and development of input models and minor changes to the code for a RELAP/SCDAPSIM/MOD3.6 analysis and the recommendations for code improvements to develop a robust code for severe accident analysis of a CANDU reactor. The CANDU-specific modeling improvements which include (a) the development of a single channel fuel bundle model, (b) improvements to the SCDAP fuel rod and shroud component models for horizontal fuel bundles, calandria tubes, and pressure tubes, and (c) improvements to the COUPLE porous media module to predict the latter stages of the accident. This paper will also discuss the verification testing of the models by comparing predicted results to LWR experiments and CANDU specific codes, and the analysis of a station blackout in a CANDU NPP.