Deuterium retention in tungsten exposed to helium-Seeded deuterium plasma. Review of recent experimental results

Abstract

Reduction of the tritium accumulation is important requirement for fusion reactor materials. Tungsten is promising material for protect a first wall of the vacuum chamber of fusion devices. The tungsten plates will be exposed to intense fluxes of accelerated of deuterium (D), tritium (T), helium (He) particles from fusion plasma. Results of recent studies (2008-2014) on deuterium retention in tungsten exposed to high flux helium-seeded deuterium plasma carried out in Japan Atomic Energy Agency (Japan), Max-Planck Institute for Plasma Physics (Germany) and NRC Kurchatov Institute (Russia) are summarized in the present review. It has been shown that addition of helium ions into the D plasma at elevated temperatures significantly reduces the D retention in tungsten, both without and with ion-induced defects, compared to that for the pure plasma exposure. It has been also found that significant part of deuterium initially retained in tungsten after deuterium plasma exposure is released during sequential exposure to protium plasma. However, exposure of the D-plasma-exposed W samples to helium-protium plasma reduces the amount of released deuterium as compared to pure protium plasma irradiation.