Irradiation creep and deformation under flux of austenitic stainless steels 304 and 316

The materials constituting the PWR reactors vessels internals are submitted to a neutron flux, at a temperature between 280 and 380 C, and at mechanical solicitations. On account of the C. Pokor works, the irradiation effects are now well known; the following step is the combined study of the irradiation and the mechanical solicitation. In order to understand the mechanisms which induce the microstructural changes, irradiations have been carried out in the following experimental reactors: Osiris at 330 C until 10 dpa and BOR-60 at 330 C beyond 100 dpa. Two tests types have been studied: creep tests and deformation tests under flux. Transmission electronic microscopy analyses have allowed to quantify these microstructural changes, particularly the density and the size of the Frank loops. A behaviour law, developed by J. Besson (ENSMP) and S. Leclerq (EDF), integrating irradiation creep and plasticity of the material after irradiation, allows to describe the change of stress during the reactors tests. (O.M.)