Retran kinetics studies for loss of feedwater anticipated transients without scram

Results are presented for postulated loss of feedwater (LOFW) anticipated transient without scram (ATWS) analyses performed with the RETRAN-02 MOD003 computer code for a four-loop Westinghouse pressurized water reactor in order to demonstrate the capabilities of the RETRAN code to predict system transient responses similar to the Westinghouse LOFTRAN code and the Brookhaven National Laboratory RELAP code results. Differences between the RETRAN, LOFTRAN and RELAP code predictions can be attributed to differences in methodology and modelling techniques. These LOFW ATWS studies provide additional insight into the kind of detailed parametric analyses required for using RETRAN for ATWS studies or for the evaluation of any reactor transient dominated by moderator density feedback phenomena. This paper gives the results of point kinetics sensitivity studies and steam generator relief valve modelling effects. The effect of using a realistic steam generator model with multiple banked relief valve setpoints versus an ideal single plateau value is presented. The modelling of actual multiple banked opening and closing pressure setpoints result in higher primary system pressure due to the fast steam generator inventory depletion