MYRRHA/FASTEF Safety Analysis in Sub-critical and Critical Mode

FP7 Central Design Team (CDT) has been launched in April 2009. CDT’s main target is to finalize a preliminary design of a new version of the MYRRHA reactor, named MYRRHA/FASTEF. The main purpose of the analysis is to verify the capability of the safety systems to bring the reactor to a safe shutdown state after a postulated accidental event. The safety analysis will focus on three different categories of transient events, including protected transients to analyze the protection system and decay heat removal (DHR) system capabilities, protected transients to analyze the overcooling risk and unprotected transients to analyze protection requirements. Safety analysis has been performed by creating a complete model of the facility based on the updated design. The model includes primary, secondary and tertiary systems and all foreseen DHR systems. The MYRRHA/FASTEF model has been made using the RELAP5 mod 3.3 system code in a specific version modified by ENEA (tested in benchmark problems through code-to-code comparisons). Despite of this, the MYRRHA/FASTEF design proved to be able to brilliantly lead the system to a safe shutdown conditions in case of protected accidents, with no risk of clad failure, and limited clad failure risk in case of unprotected accidents.