Relap5/mod3.2 post-test analysis and accuracy quantification of LSTF test SB-CL-21

The document deals with the description of results obtained by the Relap5 code in post-test analysis of the Counterpart Test (CT) SB-CL-21 performed in the Pressurized Water Reactor (PWR) experimental simulator LSTF installed at the Tokai-Mura JAERI Research Center in Japan. 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 LSTF loop is an Integral Test Facility (ITF) simulating with full height, full pressure, full linear power a US type 4-loop Westinghouse PWR. The concerned test is the low power CT of experiments performed in LOBI, BETHSY and SPES ITF. Because of the maximum power limitations of BETHSY and LSTF, the test SB-CL-21 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, additional a tests were performed (in the same way in LOBI and SPES ITF). The present document discusses the results of the application of the FFTBM to the analysis of the comparison between experimental and calculated data. Both the SB-CL-21 analysis and the FFTBM bases are discussed in other documents. The original activity documented here is the application of FFTBM to the concerned experiment which is needed for the application of the UMAE uncertainty method.