5th RTD Framework Programme

The COLOSS programme complies with the ’Nuclear Fission Programme’ on Severe Accident and Management Measures. The objective of the project is to improve the safety of European reactors. Therefore additional research is carried out combining experiments, model developments and severe accident code improvement packages that address uncertainities, which significantly limit the understanding of both existing or future plant behaviour (PWR, BWR, VVER and EPR reactor types) under severe accident conditions. Risk-relevant topics are selected: boron-carbide oxidation and control rod degradation, high burnup fuel and MOX behaviour, oxidation of U-O-Zr mixtures and liquefaction-collapse of fuel rods. The specific objectives are:

• Experiments on selected topics at different scales for code developments and validation.
• Model development and coupling in SA codes used by utilities, industry and safety authorities.
• Evaluation of the consequences of results of safety, feedback on severe accident measures for different plant designs.

The Hungarian activites in the project cover experimental work with VVER and PWR type fuel treated under high temperature severe accident conditions and are expected to provide important information on the behaviour of control rods and fuel rods.