Transport of carbon in 316 steels submitted to neutron irradiation

Carbon profiles were determined by EMPA in various irradiated and non-irradiated carburized clads. All clads were in 316 type steels. An effective diffusion coefficient (Dsub(eff)) has been calculated for each profile. The set of Dsub(eff) is shown in an Arrhenius Diagram. A comparison is drawn between our results and literature values for: true diffusion coefficient of carbon in the γ phase and effective diffusion coefficients of carbon derived from out-of-pile simulation experiments. Activation energy of Dsub(eff) coefficient (in-pile and out-of-pile) is small compared to the activation energy of carbon diffusion in austenite. Dsub(eff) values are quite insensitive to surface concentration in the range 0.9 to 4%. Dsub(eff) decreases as time increases and at given temperatures and carburization times, Dsub(eff) is smaller under irradiation. We conclude with the recommendation of a Dsub(eff) value for simple evaluations of carburization intensity in irradiated 316 steels: Dsub(eff) = 1.62 x 10-10 exp (-3850/T). (author)