INTENTIONAL DEPRESSURIZATION OF STEAM-GENERATOR SECONDARY-SIDE DURING A PWR SMALL-BREAK LOSS-OF-COOLANT ACCIDENT

The consequence of intentional depressurization of the steam generator (SG) secondary side during a small break loss-of-coolant accident (LOCA) in a pressurized water reactor (PWR) was studied using the ROSA-IV Large Scale Test Facility (LSTF). The LSTF is a 1:48 volumetrically scaled full-height model oi a Westinghouse-type PWR. The experiment simulated a 0.5% cold leg small-break LOCA with total failure of high pressure injection (HPI) system. The SG secondary-side atmospheric relief valve (ARV) was latched open after the core top region was uncovered. Then, the primary pressure closely followed the secondary pressure and dropped to the accumulator (ACC) injection pressure of 4.51 MPa before the core became severely overheated. A post test analysis, which was performed using the RELAP5/MOD2 code with modifications made by the authors, predicted well the primary and secondary side responses during this experiment.