Simulation Experiment of Five Percent Small Break Loss-of-Coolant Accident of Boiling Water Reactor

Five-percent small break tests have been conducted at the ROSA-HI test facility with various emergency core cooling system (ECCS) actuation conditions. Break was assumed at the main recirculation pump inlet line. The ROSA-HI facility simulated a BWR/6-251 by the volume scaling ratio of 1/424 and a 5% break area in a ROSA-IE test means 5% of 1/424 of the BWR recirculation line pipe cross section. No dryout of fuel surface was observed in the tests with high pressure core spray system (HPCS) actuation irrespective of the conditions of the other ECCS. Without HPCS the whole core was uncovered to the steam environment; however, the peak cladding temperature (PCT) was limited to 1,022 K well below the present safety criteria of 1,473 K. The results of the test with the highest PCT without HPCS actuation were analyzed by the RELAP4/Mod6 computer code. The calculated fuel surface temperatures agreed well with measured results in the blowdown phase. The calculated PCT was 930 K, 92 K below the measured PCT of 1,0...