Community Research and Development Information Service - CORDIS


Core Loss During a Severe Accident (COLOSS), Final Report

Project ID: FIKS-CT-1999-00002
Funded under: FP5-EAECTP C


The COLOSS project was a 3-year shared-cost action, which started in February 2000. The work-programme performed by 19 partners involved complementary activities aimed at improving the core degradation phase during of severe accident. Risk-relevant issues of particular interest regarding H2 production, melt generation and the source term were studied in a large number of experiments devoted to a) dissolution of fresh and high burn-up UO2 and MOX by molten Zircaloy, b) simultaneous dissolution of UO2 and ZrO2, c) oxidation of U-OZr mixtures, d) oxidation of pure B4C material and degradation-oxidation of B4C control rods.
Corresponding models were developed and implemented in severe accident computer codes. Upgraded codes were finally used to calculate key severe accident sequences occurring in different plants such as PWR-900, PWR-1300, BWR, VVER-1000, EPR and in the TMI-2 accident.
Perspectives: Remaining uncertainties and SA code weaknesses in safety-relevant phenomena of core degradation have been transmitted to the PIRT review on SA carried out in the EURSAFE thematic network (5th FP) to be addressed in the SARNET network of excellence (6th FP). In particular results on dissolution of irradiated fuel and oxidation of metal rich mixtures during core degradation and re-flooding should be consolidated. The follow-up of the COLOSS activity on plant calculations with sensitivity studies and benchmarking exercises has also been recommended. SA code weaknesses identified in the project will be addressed, the priority being put on the improvement of the European ASTEC code.

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