Development of a program to calculate the amount of steam leakage from nuclear reactor piping under the leak before break event

The Central Research Institute of Electric Power Industry (CRIEPI) has developed a probabilistic fracture mechanics (PFM) code 'PEDESTRIAN' for nuclear reactor piping. Unfortunately, the current code does not have a function to calculate the amount of steam leakage at the time of an event, that is one of effective indicators to determine the severity of the event. On the other hand, some foreign PFM codes developed for similar purpose have the function to evaluate the amount of steam leakage in the form of subroutines or dedicated subprograms. Therefore, we originally developed 'LEECPIPE' to calculate the amount of steam leakage during an event with reference to similar foreign code LEAPOR. Then, verification analyses were performed for both LEAPOR and LEECPIPE to reproduce the experiment described in the reference for another program, SQUIRT, and those were compared with the experimental results and the SQUIRT calculations. As a result, the maximum relative error was approximately 33% for SQUIRT and for LEAPOR, whereas the maximum relative error was approximately 17% for LEECPIPE. (author)