Preliminary Interpretation of the PHEBUS FPT0 Test with the MFPR V1.0 Code

Interpretation of the PHEBUS FPT0 experiment with IPSN's MFPR code is presented. MFPR is a mechanistic, fission product (FP) release code where the version used in this study, version 1.0 revision 1, available early 98, is a stand-alone version which models the release of fission gases and the volatile FPs Cs, I and Te. Relatively low releases were obtained from calculations which treated the fuel as solid irrespective of the temperature or the experimental evidence of fuel degradation and relocation. This result is consistent with the fuel being only trace-irradiated in FPT0. Use of the liquefied fuel option of MFPR was therefore necessary to produce results for total releases of volatile FPs in agreement with the experiment (though the code does not allow a distinction to be made between the different FPs released from the liquid phase). Effects of grain growth were investigated as well as sensitivities to some other modelling parameters.