PHEBUS FPT0 test: Status of interpretation of the bundle degradation using ICARE2

The aim of the international PHEBUS FP Programme is to investigate in an in-pile facility various phenomena governing degradation of fuel as well as release, transportation and deposition of fission products in LWR severe accident conditions. This paper gives a summary on the current analysis of the core degradation aspect of the first FPT0 test using the ICARE2 code. Results show a core degradation far beyond any other test that has been performed in the past. The current interpretation illustrates difficulties to analyse complex phenomena which characterize the late phase of core degradation such as loss of rod-like geometry and large molten pool formation. The overall movement of material during the test is largely understood. Weakness in current models to predict severe degradation are identified and new development efforts are launched. Lessons learnt from FPT0 are applied in preparing the next FPT1 test. (author). 9 refs, 16 figs