Interpretation of the Phébus FPT0 and FPT1 Circuit Results using the SOPHAEROS/ASTEC V1 Module

Phébus FP tests study the phenomenology of severe accidents in water-cooled nuclear reactors. The first test, FPT0, was performed with fuel irradiated for only one week; the second test, FPT1, was performed with fairly similar boundary conditions but with irradiated fuel (burn-up: 23 GWd/t). The objective of this work is, on the one hand, to summarize the main experimental results of these two tests concerning the behavior and transport of fission products (FP) and structural materials (SM) in the circuit and, on the other hand, to identify any modeling weaknesses in the SOPHAEROS/ASTEC V1 module used for interpreting the experimental results. Besides comparison with available experimental data, the main results of the entire circuit analyses are compared with former SOPHAEROS/ASTEC V0 analyses and, for so-called quasi-separated steam generator tubes, with one- and two-dimensional Eulerian and Lagrangian (particle tracking) models. Concerning the transport of iodine vapor species, it is shown that the results obtained are compatible with passage of non-negligible amounts of the measured highly volatile iodine through circuit to containment. It is also shown that these results depend heavily on the considered kinetics of Cd release from the bundle.JRC.F.4-Safety of future nuclear reactor