Experimental interpretation and code validation based on the PHEBUS-FP programme: Lessons learnt from the analysis of the containment scenario of FPT1 and FPT2 tests

The phenomenological scenario of a severe accident is extremely complex. Its simulation requires specific models of phenomena of different nature (i.e., materials behavior, thermal–hydraulics, aerosols, etc.) and their adequate coupling in safety computer codes. Therefore, an exhaustive and extensive validation against representative databases is mandatory. PHEBUS-FP project is, beyond any doubt, one of the more valuable data sources for this purpose.The main lessons learnt from the containment simulations of FPT1 and FPT2 tests were summarized. Several safety computer codes: CONTAIN 2.0, MELCOR 1.8.5 and ASTEC 1.1 have been used. This diversity has allowed a “user-independent” cross comparison of codes and data. Overall, codes estimates have reproduced properly experimental trends and no variable has shown major discrepancies. By means of parametric studies, it has been demonstrated that the minor discrepancies found did not come from the hypotheses and approximations adopted. In addition, the analyses of codes results have assisted in the interpretation of experiments by showing potential experimental uncertainties (i.e., steam injection in FPT1) or even by crediting data from a specific measurement technique over other data sources (i.e., samplings over γ-spec in FPT1).