EDF - An important advance

The internal structures of reactor vessels are used to support and cool the reactor core, but their mechanical properties change under the effects of irradiation.

Assessing the behaviour of materials and understanding the mechanisms that are likely to degrade them are therefore essential to be able to justify keeping such equipment in service and optimise their monitoring and maintenance. This was the goal of a project led by EDF R&D, with the participation of American, Russian, Japanese and other European partners.

The results of this research programme gave us abetter understanding of the different phenomena involved and the ability to forecast changes in the mechanical characteristics of the materials concerned for up to 60 years. The mechanisms that had led to the unscrewing of certain bolts were therefore explained. The contribution of these studies to the justification of current installations and the management of the lifespan of reactors is essential and the programme is being pursued. Therefore, the GONDOLE experiment being conducted at the CEA with EDF R&D and EPRI will enable us to assess the risk of swelling of the parts most exposed to temperature and irradiation appearing at the end of their working life.

The scientific community welcomed this important result by awarding the 2005 Grand Prix of the "Société Française d'Energie Nucléaire" jointly to EDF, the CEA and FRAMATOME.