Summary of the Phébus-FP Interpretation Status

B. Clément, 5th PHEBUS FP Technical Seminar, Aix-en-Provence – June 24-26th 2003

A number of synthetic or more detailed papers dealing with the interpretation of the Phébus-FP tests are presented at this seminar. Going further and giving an even more synthetic picture needs a selection of the main outcomes of the interpretation work performed so far. Doing so, the author derived twelve main conclusions and classified them into three categories. First, it should be acknowledged that the interpretation work led to reconsider the understanding and modelling of certain phenomena, denying some hypotheses that were commonly accepted within the severe accident community. This is called in the following "disproving some paradigms". Secondly, the integral nature of the Phébus-FP experiments, simulating in a coupled way a far-advanced fuel degradation together with a representative fission product behaviour allowed "exploring deeper some problem areas". Using all these results, we have improved our knowledge and understanding, and have been or are still being "improving our prediction capability", that is the third category for the main conclusions of the interpretation work. It should be noticed at that point that the prediction capability does not only depends on the quality of the tools used for calculating severe accident sequences, but also on the skilfulness of their users. Both were improved as a result of the interpretation work of the Phébus-FP tests.

A short general status of the work - where we are and where we go - is given first in this paper. Then twelve selected main conclusions are detailed. Some information is given afterwards concerning other work that is still in progress.