CORE LIQUID-LEVEL RESPONSES DUE TO SECONDARY-SIDE DEPRESSURIZATION DURING PWR SMALL BREAK LOCA

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 (HP I) systems were studied using experimental data from the Large Scale T est Facility (LSTF) and using analysis results obtained with the REFLA /TRAC code. The LSTF is a 1/48 volumetrically scaled full-height integ ral model of a Westinghouse-type PWR. The code reproduced the thermal- hydraulic responses observed in the experiment for important parameter s such as the primary and secondary-side pressures and core liquid lev el. The sensitivity of the core minimum liquid level to the depressuri zation rate and break area was studied by using the code assessed abov e. It was found that the core liquid level took a local minimum value for a given break area as a function of secondary-side depressurizatio n rate. The core temperature was kept below about 1,000 K when the sec ondary depressurization rate was greater than -200 K/h in the saturati on temperature for break areas smaller than 2.5%.