Simulation of CANDU 6 LLOCA power transients terminated by SDS1 with a full 2-energy-group coupled RFSP-IST/CATHENA approach

This paper describes a series of coupled neutronics-thermalhydraulics simulations of postulated Large Loss-of-Coolant Accident (LLOCA) transients for the Point Lepreau and Gentilly-2 generating stations, showing the sensitivity of peak reactivity, fuel-centreline temperature and peak sheath temperature to changes in side-to-side flux tilt, coolant isotopic purity, moderator isotopic purity and moderator poison concentration, over 5 seconds, for a 100% pump-suction-pipe (PSP) break. Dynamic coupling of the thermalhydraulic code CATHENA version MOD-3.5c Rev. 1 with the neutronics code RFSP-IST version REL-3-00-05HP was automated with the rfspcb script. A full 2-energy-group WIMS-IST-based Simple-Cell Model (SCM) approach was used with 2-group device incremental cross sections from DRAGON. The thermalhydraulics code calculated both full-circuit response as well as single-channel fuel sheath and centreline temperature transients. (author)