Influence of break size on blowdown for large breaks

The transient thermal-hydraulic behaviour of a simulated pressurized water reactor (PWR) primary cooling system during the blowdown period of a loss-of-coolant accident (LOCA) is being investigated in the LOBI test facility. The overall objective of the LOBI experimental programme is to provide and/or extend data base required for assessing the capabilities of computer codes to predict integral blowdown-refill experiments for a range of system components operational conditions and for pipe ruptures of different sizes and at various locations within the primary cooling system. This paper summarizes the essential results of four loss-of-coolant experiments covering the large-to-intermediate break spectrum. These tests were cold leg breaks with intact loop cold leg emergency core coolant (ECC) injection. A comparative analysis of the essential test results shows that the influence of break size on blowdown in the LOBI facility is mainly confined to core thermal-hydraulic response