Post-test analysis performed by RELAP5/MOD2 code of the LOBI/MOD2 small break test BL-34 counterpart to LSTF, SPES and BETHSY Experiments

The document deals with the description of results obtained by the Relap5 code in the post test analysis of the Counterpart Test (CT) BL-34 performed in the Pressurized Water Reactor (PWR) experimental simulator LOBI installed at the EURATOM JRC Research Center of Ispra 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 LOBI loop is an Integral Test Facility (ITF) simulating with full height, full pressure, full linear power a German type 4-loop KWU-Siemens PWR. The concerned test is the low power CT of experiments performed in SPES, BETHSY and LSTF ITF. Because of the maximum power limitations of BETHSY and LSTF, the test BL-34 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 subsequently performed at high power and called BL-44. The present document discusses the results of code application to the analysis of measured data in BL-34