Argon generation in fusion reactor materials

Abstract

Different candidate plasma facing materials (as tungsten, beryllium), the low activation structure materials (as vanadium alloys, silicon carbides), liquid breeders (lithium and lithium-lead) and some others have been suggested for future fusion power reactor cores as corresponding to maintenance, recycling and for waste disposal acceptance after 50 and 100 years of cooling. It is shown by the neutron activation analysis that a relatively short-lived Ar-41 (T1/2=1.85h), Ar-37 (T1/2=35 days) and rather long lived Ar-39 (T1/2=269yr) may appear in these materials under the fusion neutron irradiation conditions. While argon production is essentially less than helium production in irradiated materials, at other times its impact, e.g., in the inhalation dose, becomes significant. In some cases the Ar-39 activity is comparable or even exceeds the C-14 activity and may become apparent after tritium removal from plasma exhaust and dust, from the liquid breeders, during plasma-facing and structural component recycling and waste management. The main source terms of argon-39 activity for these materials are identified and the specific production rates are evaluated relative to radiation conditions of a power or DEMO fusion reactor and to electric power production.