Investigation of break orientation effect during cold leg small-break LOCA at ROSA-IV LSTF.

Abstract

The Large Scale Test Facility (LSTF) of the Rig-of-Safety Assessment No. 4 (ROSA-IV) Program is a volumetrically scaled (1/48) pressurized water reactor (PWR) system with an electrically heated core used for integral simulation of small break loss-of-coolant accidents (SBLOCAs) and operational transients. Three 2.5% cold-leg SBLOCA experiments were conducted at LSTF. In the experiments, the break was oriented at the side, bottom and top of the horizontal cold leg, respectively. The loop seal clearing in the bottom break case was later than in the side break case since a larger amount of liquid had to be discharged until the loop seal clearing. The loop seal clearing in the top break case was later than in the side break case because of the smaller discharge flow rate. The core liquid level drop due to boiloff after the loop seal clearing in the bottom break case was earliest among three cases because of the largest mass loss before the loop seal clearing and in the top break case latest because of the lat...