In a pressurized water reactors core, the primary environment combined with neutron irradiation promotes IASCC (Irradiation Assisted Stress Corrosion Cracking), which may lead to premature failure of internal components made of stainless steel (SS).
During stainless steel exposure to primary water, it was shown that non negligible amounts of hydrogen were incorporated and trapped under the oxide/alloy interface1. As neutron irradiation leads to the formation of defects (vacancies, interstitials, dislocation loops…) that may act as trap sites for hydrogen and favor hydrogen accumulation in the alloy, hydrogen trapping can thus be a key parameter in the IASCC mechanisms.
The aim of this study is to identify, characterize and understand the interactions between hydrogen and irradiation-induced defects. Several thermal treatments applied to a 316L SS allowed to elaborate a reference material with the least possible defects (carbides, dislocations). This reference material is then submitted to various ion implantation conditions to create irradiation defects, which are characterized by Transmission Electron Microscopy (TEM). Hydrogen uptake is then promoted on both implanted and reference specimens by room temperature cathodic charging. Hydrogen distribution and trapping are characterized by GD-OES (Glow Discharge Optical Emission Spectroscopy), SIMS (Secondary Ion Mass Spectrometry) and TDS (Thermal Desorption Spectrometry). In fine, a numerical model2 is used to determine the hydrogen trapping and detrapping kinetic constants associated with irradiation defects.