A model of Young’s modulus for Gilsocarbon graphites irradiated in oxidising environments

This paper presents the development and validation of an empirical model of combined fast neutron damage and radiolytic oxidation effects on Young’s modulus for the Gilsocarbon graphites used in advanced gas-cooled reactors. The combined irradiation and oxidation model is based on a model of fast neutron damage in an inert environment and the degree of radiolytic oxidation as measured by weight loss. The change in Young’s modulus with exposure was found to vary from one power reactor to another and with the relative contributions of oxidation and fast neutron damage in data from materials test reactors. The model was calibrated to data from material trepanned from advanced gas-cooled reactor moderator bricks after varying operating times. The model also predicts materials test reactor data that extend beyond the range of currently-available trepanned data. The model is convenient to use because it is an analytic function that eliminates the interpolation on temperature and dose that is used in an earlier model.