Deuterium retention in RAFM steels after high fluence plasma exposure

Abstract

Deuterium retention and detrapping behavior in the ferritic-martensitic steels EUROFER’97 and P92 after exposure to plasma at high fluences ≥ 1026D/m2 was studied using thermal desorption spectroscopy (TDS), supported by nuclear reaction analysis. Low-temperature irradiation at 450K and fluences ≥ 1026D/m2 with low impact energy D+ / D++He+ ions of 40eV at PSI-2 resulted in a deuterium inventory of 7–18 ×1019D/m2 predominantly at depths ≥8.6µm. Helium admixture led to a reduction of total D retention in both steels, irrespective of surface erosion and composition. The deuterium spectra of both steels displayed one D2 desorption peak at ∼ 540–570K and HD maxima at 540–590, 700–730 and 900–930K. It is suggested that deuterium is mostly retained in the bulk of steel material on interfaces of carbide precipitates and on grain boundaries. Keywords: EUROFER, RAFM, Deuterium, Retention, High fluence, Desorption