Core Liquid Level Responses Due to Secondary-Side Depressurization during PWR Small Break LOCA

Abstract

The effects of the rate of intentional secondary-side depressurization and of the break area on the core liquid level behavior during a PWR small-break LOCA with total failure of the high pressure injection (HPI) systems were studied using experimental data from the Large Scale Test Facility (LSTF) and using analysis results obtained with the REFLA/TRAC code. The LSTF is a 1/48 volumetrically scaled full-height integral model of a Westinghouse-type PWR. The code reproduced the thermal-hydraulic responses observed in the experiment for important parameters such as the primary and secondary-side pressures and core liquid level. The sensitivity of the core minimum liquid level to the depressurization rate and break area was studied by using the code assessed above. It was found that the core liquid level took a local minimum value for a given break area as a function of secondary-side depressurization rate. The core temperature was kept below about 1,000 K when the secondary depressurization rate was greater than—200 K/h in the saturation temperature for break areas smaller than 2.5%.