"OECD CSNI ISP 26: post-test analysis of a Small Break LOCA in the LSTF Facility performed by RELAP5/MOD2 code in the frame of a cooperation with University of Zagreb and ENEA", OECD CSNI Workshop on ISP 26, Grenoble (F), June 6-8, 1990

The document deals with the description of results obtained by the Relap5 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 LSTF installed at the Tokai Mura 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 is a large scale Integral Test Facility (ITF) simulating with full height, full pressure, full linear power a US type PWR. The concerned test was selected as International Standard Problem 26 (ISP 26) by OECD/NEA/CSNI (Organization for Economic Cooperation and Development / Nuclear Energy Agency / Committee on the Safety of Nuclear Installations). The document describes the results of the post-test calculation submitted (by UNIPI) to JAERI (Japan Atomic Energy Research Institute) after the execution of the test. This is called open 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 reflood (in this case).