Abstract :
The fuels and materials testing programmes carried out at the OECD Halden Reactor Project are aimed at providing data in support of a mechanistic understanding of phenomena, especially as related to high burnup fuel. The investigations are focused on identifying long term property changes, and irradiation techniques and instrumentation have been developed over the years which enable to assess fuel behaviour and properties in-pile. The examples presented include data on thermal and mechanical behaviour, axial gas flow and pressure equilibration, fission gas release, and fuel swelling and cladding creep. The in-pile measurements can be used for understanding and modelling of phenomena such as pellet-cladding mechanical interaction, fuel thermal conductivity degradation, a possible enhancement of fission gas release and cladding lift-off at high burnup. They do not only relate to fuel performance during normal operation, but can also be applied in safety analyses to define the starting conditions of transients and to assess the further developments.
