Influence of displacement damages on deuterium retention in reduced activation ferritic/martensitic steels F82H and Eurofer97

Abstract

The F82H and Eurofer97 steel samples were irradiated at 300K with 20MeVW ions to the damage level of 0.54 displacements per atom (dpa) at the damage peak. Additionally, the F82H steel samples were irradiated at 523K with 6.4MeV Fe ions to various damage levels in the range from 0.02 to 12.5dpa. The damaged samples were exposed to D2 gas at a pressure of 100kPa and various temperatures in the range from 373 to 573K for a certain length of time sufficient to fill ion-induced defects with deuterium. Trapping of deuterium at the ion-induced defects was examined by the D(3He, p)4He nuclear reaction with 3He energies between 0.69 and 4.0MeV allowing determination of the D concentration up to a depth of 7μm. It has been found that (i) at the damage level above 0.5dpa, the concentration of the ion-induced defects responsible for trapping of diffusing D atoms does not depend practically on the numbers of displacements per atom, and (ii) the saturation value of the D concentration in the damage zone decreases with increasing D2 gas exposure temperature, Texp, and varies from about 10−1 at.% at Texp=373K to 10−3 at.% at Texp=573K. The deuterium-trap binding energy is estimated to be 0.7±0.2eV.