Transient analyses of the Bethsy Integral Test Facility (ITF) 4.2b test carried out by the code Cathare 2 v1.5B r4.1

The document deals with the description of results obtained by the Cathare code in the post-test simulation of the Small Break Loss of Coolant Accident (SBLOCA) experiment performed in the Pressurized Water Reactor (PWR) experimental simulator BETHSY installed at the CEA-CENG Research Center in France. The Cathare is the well-known computer code developed at CEA-CENG (in cooperation with FRAMATOME and EdF) research center in Grenoble, France: the code is in use at UNIPI since more than a decade. The BETHSY is a medium-large scale Integral Test Facility (ITF) simulating with full height, full pressure, full linear power a French type PWR. The concerned test is the SBLOCA (Small Break Loss of Coolant Accident) test 4.2b. The document describes the results of the post-test calculation submitted (by UNIPI) to CEA (French Atomic Energy Commission) after the execution of the test. This is part of “post-test analysis”: the comparison of about 60 calculated time trends with measured data allows an evaluation of the capabilities of the computer code and of the code user team in predicting the scenario of an accident. This is relevant for demonstrating the capabilities in evaluating safety margins of existing NPP, with main reference to PWR accident management situation (in this case). The importance and the difficulty of modeling TPCF (Two Phase Critical Flow) was demonstrated (again) in this experiment