Phenomena affecting mechanical and thermal behaviour of PWR fuel rods at beginning of life. Some recent experiments and modelling results

The thermal and mechanical behaviour of fuel rods is affected by pellet fragmentation and relocation effects, especially at beginning of life due to a subsequent decrease in the gap size. These phenomena are quantified here through a comparative analysis of two experimental programmes conducted at the Commissariat a l'Energie Atomique (CEA), with the co-operation of FRAMATOME Nuclear Fuels and Electricite de France (EDF). The discussion concerns the modelling of gap heat transfer and pellet clad mechanical interaction considering relocation effects. (author)