Deuterium retention in advanced steels for fusion reactor structural application☆

Reduced activation ferritic-martensitic (RAFM) steels, castable nanostructured alloys (CNA), and oxide-dispersion-strengthened (ODS) steels have been developed for the fusion reactor structural application with improved mechanical properties and radiation resistance. However, the hydrogen isotope retention in these steels is not well understood. In this study, 10 keV D₂ implantation was performed on six steels, together with pure iron and T91 as references, at room temperature. Subsequent thermal desorption spectroscopy (TDS) measurements were carried out to investigate the deuterium retention. Possible deuterium trapping sites in the studied materials were discussed in coordination with available microstructural information. The results indicated that ODS-steels have the largest deuterium retention, which is almost one order of magnitude higher than that of pure iron, ∼6 times of RAFM, and 2–4 times of CNA steels. The difference in nanoparticles and grain/lath boundaries are primarily responsible for the different deuterium retention, while other trapping sites (e.g., vacancy clusters, dislocations, etc.) are present. Deuterium retention increases with increasing sink strength of the studied materials, although they are not linear correlated.