Post-test analysis performed by Relap5/mod2 code of the SPES small Break LOCA test SP-SB-04 high power counterpart to SPES SP-SB-03 experiment

The document deals with the description of results obtained by the Relap5 code in the post-test analysis of the Counterpart Test (CT) SP-SB-04 performed in the Pressurized Water Reactor (PWR) experimental simulator SPES installed at the Piacenza SIET Research Center in Italy. The Relap5 is the well-known computer code developed at Idaho National Laboratory in US: the code is in use at UNIPI since more than a decade. The SPES loop is an Integral Test Facility (ITF) simulating with full height, full pressure, full linear power a US type 3-loop Westinghouse PWR. The concerned test is the high power CT of experiments performed in LOBI, BETHSY and LSTF ITF. Because of the maximum power limitations of BETHSY and LSTF, the test SP-SB-03 was performed starting from a ‘low power condition’ (about 20% nominal power): thus, the initial 10-50 seconds of the experiments were ‘highly’ distorted with respect to the test scenario expected in the reference Nuclear Power Plant (NPP), the prototype. Therefore a new test was performed (in the same way in LOBI ITF, CT BL34 and Bl-44, low and high power tests were performed) and called SP-SB-04. The present document discusses the results of Relap code application to the analysis of SP-SB-04 (high power) experiment.