A Study on ROSA/LSTF SB-CL-09 test simulating PWR 10% cold leg break LOCA; Loop-seal clearing and 3D core heat-up phenomena

Suzuki, Mitsuhiro; Nakamura, Hideo  

This report presents major results observed in LOCA test (SB-CL-09) conducted at the ROSA/LSTF test facility simulating 10% cold leg break in a 4-loop Westinghouse-type PWR. Following are found in this test with an assumption of high pressure injection system. (1) The relatively large break size resulted in pressure inverse within 2 minutes between the primary and steam generator secondary sides. (2) During a loop-seal clearing (LSC) process started at about 1 minutes after the break, the core water level was suppressed to almost lower end and then it recovered to the middle core height. The water level remained at the middle height was due to remained water levels in the SG U-tube inlet sides which were higher than their outlet sides. (3) Significant core heat-up was observed above the water level at the middle height and core power was tripped off at 111s. (4) The effects of fall-back water from the intact loop hot leg was observed by the local core cooling.