Retention of Fuel Hydrogen Retention of Tungsten Plasma Facing Wall in Fusion Reactor

Abstract

In-vessel tritium inventory in fusion reactors has to be reduced from a view point of safety in fusion reactors. It is required to evaluate the amount of tritium retained in tungsten plasma facing walls. The plasma discharge with hydrogen isotope (deuterium) was conducted to evaluate the tritium retention in tungsten. The glow discharges using helium, neon and argon were performed after the deuterium discharge to reduce the deuterium retention. The use of inert gas discharge little reduced the deuterium retention. Namely, the inert gas glow discharge is not useful to reduce the tritium inventory. The deuterium glow discharge significantly replaced the hydrogen in the tungsten wall into the deuterium. Thus, the deuterium glow discharge is quite useful to reduce the tritium inventory through the hydrogen isotope exchange. The use of neon or argon glow discharge followed by deuterium discharge can more reduce the tritium inventory. In addition, the tritium inventory can be easily reduced if the wall baking with a temperature of 700-800K is conducted.