Invited Lecture
Diffusion and irradiation : the paradoxes of irradiation creep

Irradiation induced creep plays an important role in relaxing stresses in bolts in nuclear power point. Beside this important industrial consequence, irradiation creep presents an interesting combination of characteristics usually associated to diffusion creep ( such as a linear dependence with temperature ) and other which are somewhat surprising such as the lack of temperature depencance, and the presence of creep like behavior at very low temperatures. The existing theories for the phenomenon will be compared to a detailed quantitative analysis of microstructural features performed on stainless steels, and their lack of succees to predict the proper order of magnitude will be discussed. A new experimental approach involving micromechanical systems will be proposed. Analysis of creep and irradiation creep in copper deposited layers will be presented and the possibility of interpretation of irradiation creep as an irradiation induced instability of the dislocation network will be discussed.