Fuel behaviour modelling in accident conditions in ALCYONE fuel performance code

CEA is developing the ALCYONE fuel performance code for PWR fuel in the PLEIADES software environment. It is dedicated to normal, off-normal and accident conditions such as RIA and LOCA. CEA's participation to the IAEA FUMAC CRP led to an improvement of the fuel modelling in LOCA conditions. Specific developments of the fuel performance code for the LOCA conditions have been done regarding cladding behaviour modelling, fission gas release and stress evaluation in the pellet before and during the tests. The improved code has been used to simulate some of the experiments of interest of the FUMAC project (IFA650.10 and Studsvik 192 LOCA test), the paper summarizes the results. For IFA650.10, the cladding outer temperature profile calculated with the SOCRAT code and provided to the participants of the FUMAC CRP has been used. The results obtained with ALCYONE are in a good agreement with the experimental data. In terms of uncertainty quantification, it seems that the uncertainty on the determination of the boundary conditions like cladding outer temperature results in a large uncertainty on the cladding deformation and the burst time. Recent developments have also been done in ALCYONE to improve the modelling of fuel behaviour in RIA conditions, in particular about fuel mechanical behaviour and the consequences on fission gas release. (author)