Similarity study of large steam line break LOCA's in ROSA-III, FIST and BWR/6

Abstract Similarity of the thermal hydraulic phenomena in a 100% steam line break loss-of-coolant accident (LOCA) between the Rig-of-Safety Assessment (ROSA)-III. Full-Integral Simulation Test (FIST) and a boiling water reactor (BWR)/6 system has been studied experimentally and analytically. The experimental results of ROSA-III (RUN952) and FIST (6MSB1) showed similar LOCA phenomena except for the core cooling. The core cooling was affected by the different ECCS actuation logics used in the tests. The effects of the different test conditions and the system-inherent features on the LOCA phenomena were separately evaluated through the post-test and similarity analysis of the ROSA-III and FIST tests by using RELAP5/MOD1 code with a jet pump model. The similarity of the major events in the ROSA-III and FIST facilities to those of BWR/6 system were confirmed assuming the same ECCS actuation logic and the same sealed initial mass inventory among the three systems. Differences in vessel geometries, metal stored heat and core power curves caused slight differences in the responses of pressure and fuel surface temperatures.