RFSP-IST/CERBERUS Simulations With Reactor Regulating System on for CANDU 6 Accident Analysis by Using Larger Time-Step Size

Abstract

The RFSP-IST/CERBERUS [1] simulations are conducted with RRS on that might be of interest for various accident analysis of CANDU 6 reactors, such as, SBLOCA, In-CORE LOCA, LOR and moderator accidents. The steady-state initial conditions are set by coupling with the thermalhydraulic code CATHENA [2] so that the initial conditions for the other important accident scenarios, e.g., LBLOCA, could also be established based upon the history of RRS actions that follow realistically the reactor operations. The representative cases studied here are selected in application to the moderator drain accidents which demand the soundness and reliability of RRS predictions that show the capability of coping with the appreciable top-to-bottom flux tilts during the progress of transients. The CANDU 6 RRS algorithm requires a minimal time-step size of 0.5 seconds that corresponds to the bulk control temporal sequences. An attempt has been made to double the time-step size to Δt=1.0 s. The results so obtained are compared against the simulation results that are obtained by using Δt=0.5 s.