PHEBUS FPT1 Uncertainty Application with the MELCOR 2.2 Code

During the last decades, the interest of countries employing nuclear energy as part of their national energy mix has been increasingly focused on Severe Accident (SA) mitigation strategies; several postulated unmitigated scenarios have been analyzed using state-of-art SA codes to demonstrate management strategy adequacy. Considering the complexity of phenomena taking place during a SA and the sources of uncertainty affecting the codes, the quantification of uncertainty is currently of great interest to the international nuclear technical community. In this framework, the Management and Uncertainties of Severe Accidents (MUSA) project, founded in HORIZON 2020 and coordinated by CIEMAT (Spain), aims to establish a harmonized approach for the analysis of uncertainties and sensitivities associated with SAs. The Uncertainty Quantification Methods against Integral Experiments (AUQMIE) WP4, coordinated by ENEA, is aimed at applying and testing Uncertainty Quantification (UQ) methodologies against the internationally recognized PHEBUS FPT1 test. This UQ application will train the project Partners to gain experience in the uncertainty and sensitivity analyses for SAs, in the view of the plant and spent fuel pool MUSA applications. In this paper, the simulation of the first two phases of the FPT1 test performed with the MELCOR 2.2 code, developed by Sandia National Laboratories for USNRC, is presented. The probabilistic method to propagate input uncertainty will be used coupling MELCOR with uncertainty tools (e.g. DAKOTA and RAVEN). The Figure Of Merits (FOMs) considered are related to fission products release and their behavior in the facility containment. KEYWORDS