"Post-test analysis of LOBI experiment BL-21 by RELAP5/MOD2 code", 9th Meet. of LOBI LPTF, Ispra (I), Sept. 26-28, 1988

The document deals with the post-test of an experiment to be performed in LOBI ITF in the configuration Mode2. LOBI was a Pressurized Water Reactor (PWR) simulator installed in the EC center of Ispra Italy financially supported by EURATOM. The configuration Mod2 of LOBI was designed as a consequence of the Three Mile accident in US and is the follow-up of the configuration Mod1. Mod2 was designed to simulate stratification phenomena and natural circulation which are important during Small Break Loss of Coolant Accidents (SBLOCA); as a difference Mod1 was designed to simulate phenomena expected during Large Break Loss of Coolant (LBLOCA) scenarios. Namely downcomer size in Mod2 was much smaller than in the case of Mod1 and a large number of Emergency Core Cooling Systems (ECCS) were installed in Mod2. The concerned BL-21 Steam Generator Tube Rupture (SGTR) experiment was performed to model as far as possible the PWR performance. The code application allowed to confirm the scaling criteria adopted for the design of the test. The SGTR is a safety system challenging situation where Emergency Operating Procedures must be carefully designed to avoid or minimize radioactivity release to the environment, avoid the risk of boron dilution and Pressurized Thermal Shock and maintain cooled the core. The present post-test analysis, follow-up of works to plan the experiment and to perform pre-test analysis was discussed in a specific meeting in Ispra of the so-called LPTF research group where University of Pisa represented Italy