Experimental Investigation on Operational Performance of PAFS for CIV Opening Stroke

The test facility, ATLAS-PAFS was constructed to experimentally investigate the thermal hydraulic behavior in the primary and secondary systems of the APR+ during a transient when PAFS is actuated. In this study, PAFS-CIV-01 test was performed for validating the cooling rate of the reactor according to the CIV opening stroke at the FLB accident, which was analyzed as the most severe case in the APR+ SSAR (Standard Safety Analysis Report). With an aim of simulating a FLB+CIV accident of the APR+ as realistically as possible, the three-level scaling methodology was taken into account to determine the test conditions of the steady-state and the transient. The main objectives of this test were not only to provide physical insight into the system response of the APR+ during changes of CIV opening stroke but also to produce an integral effect test data to validate a thermal hydraulic safety analysis code. The initial steady-state conditions and the sequence of event in the FLB scenario for the APR+ were successfully simulated with the ATLAS-PAFS facility. The pressure and the temperature gradient of the primary system was reduced as the stroke of the CIV was decreased during the heat removal by PAFS operation. The mean temperature gradient of the core was reduced as the stroke of the CIV was decreased. The cooling rate of the core under 60% stroke (70.4 mm²) of the CIV met the criteria. The water in the PCCT was heated up to the saturation condition by the heat transfer from the PCHX tube surface. In PAFS-CIV-01 test, the major sequence of events was ended before the water level decrease in the PCCT. From the present experimental result, it could be concluded that the cooling rate of the core was controlled by the adjustment of the CIV opening stroke when the APR+ PAFS was operating