Microstructure Modeling of a 316L Stainless Steel Irradiated with Electrons

摘要

The work presented here is a first step in an effort to develop a rate theory model useful for the prediction of microstructural evolution of austenitic stainless steels in typical irradiation conditions for PWR core internals. An important difficulty associated with this type of model is the lack of well known material parameters (apparent defect migration energies, bias factors, etc.), which depend on the composition of the alloy and on the presence of impurities. The approach adopted here consists in finding an adequate set of parameters which results in a good agreement between model predictions and microstructural data after irradiating a 316L stainless steel at different temperatures in a 1 MeV electron microscope. Model results can then be compared with microstructural data corresponding to different irradiation conditions. We have chosen here to perform irradiations at low damage rate using 3 MeV electrons, which is a simpler case compared for example with neutron irradiations. We have found that calculated and measured densities of interstitial loops are in good agreement if a small fraction of the generated defects is considered to be in the form of di-interstitials, in accordance with molecular dynamics results. In the future, we intend to modify the model for the case of neutron irradiations. The same procedure as implemented here for the choice of material parameters (i. e., 1 MeV electron irradiations) will be carried out for different types of austenitic stainless steels. Model predictions will then be compared with microstructural observations obtained after irradiations of the steels up to different doses in an experimental reactor.