RELAP5 MOD3 ANALYSIS OF A ROSA-IV/LSTF LOSS-OF-RHR EXPERIMENT WITH A 5-PERCENT COLD LEG BREAK/

An analysis was performed using the RELAPS/MOD3 version 3.1.2 code for a loss of residual heat removal event during midloop operation after reactor shutdown in a Westinghouse-type pressurized water reactor. An event during a main coolant pump shaft seal removal operation was anal yzed using the data of a ROSA-IV LSTF experiment that simulated the ev ent with a 5% cold leg break. The predicted time when boiling started in the core and the peak primary system pressure showed good agreement s with the measured data. The late loop seal clearing, however, was ca lculated because the steam condensation in the U-tubes started early. A large mass error appeared in the transient calculations because of n umerical truncation errors. The influence of the mass error was insign ificant on the primary pressure prediction in this analysis. Copyright (C) 1996 Elsevier Science Ltd