Assessments of the RELAP5/MOD3.2 computer code using loss-of-coolant experiment data from the PSB facility have been performed independently by analysts at the Electrogorsk Research and Engineering Center and the Idaho National Engineering and Environmental Laboratory. The PSB experiment facility is a full height, 1/300 volume and power scale representation of a VVER-1000 reactor. The experiment modeled was an 11% break in the upper plenum, simulating the rupture of one of the hydroaccumulator injection lines. The two assessments were compared, investigating differences in the input models and explaining the resultant differences in the calculations. Both calculations agreed reasonably well with most of the significant phenomena occurring during the test. Both teams concluded that there was only minimal agreement between the calculated and measured mixture level and entrainment in the core. Some changes in input modeling can improve the prediction of the core void distribution. Application of these findings to the full size plant need to consider that PSB has only one simulated fuel bundle, and as a result there may be scaling issues that need to be addressed
