Hydrogen trapping by irradiation-induced defects in 316L stainless steel

Abstract : The irradiation-induced defects in stainless steel internal components of pressurized water reactors combined with hydrogen uptake during the oxidation process could be a key parameter in the mechanism for Irradiation-Assisted Stress Corrosion Cracking (IASCC). The ultimate aim of this study is to characterize the effects of irradiation defects on hydrogen uptake during the oxidation of an austenitic stainless steel (SS) in primary water. The focus was made on the interactions between hydrogen and these defects. A heat-treated 316L SS containing a low amount of defects is compared with ion implanted samples. Both materials were characterized by Transmission Electron Microscopy (TEM). Hydrogen uptake was then promoted by cathodic charging using deuterium as isotopic tracer for hydrogen. The deuterium distribution was first characterized by SIMS (Secondary Ion Mass Spectrometry) profiles. This technique highlighted some deuterium segregation in link with the localization of implantation-induced defects, i.e. dislocation loops and cavities. Using TDS (Thermal Desorption Spectrometry) experimental results and literature data, a numerical model was used to simulate the deuterium profiles, providing diffusion and trapping/detrapping information associated with irradiation defects in the 316L SS.