Tritium inventory of carbon dust in ITER

Abstract

In order to estimate tritium inventory of carbon dust in ITER, deuterium absorption amounts of carbon dust after D 2 gas absorption and deuterium ion irradiation were measured. In a case of D 2 gas absorption, the amount of retained deuterium was very low, D/C∼10 −3 in the atomic ratio of D/C, when the gas pressure was 1 Pa and the temperature 573 K. In a case of the deuterium ion irradiation, the amount of retained deuterium was very similar to the case for graphite. Thus, at a divertor wall temperature higher than 1073 K, the amount of retained deuterium can be regarded negligible small, D/C∼0. During the plasma discharge, carbon eroded at a divertor trace by both plasma irradiation and high heat flux co-deposits on the vacuum vessel with fuel hydrogen atoms. In order to estimate the amount of retained fuel hydrogen in the co-deposited carbon dust, D 2 arc discharge with carbon electrodes was conducted and the amount of retained deuterium in the co-deposited dust was measured. In a case that the D 2 gas pressure was approximately 1 Pa and the wall temperature approximately 400 K, the amount of retained deuterium was low, D/C∼0.06. Above results showed that fuel hydrogen inventory of the co-deposited carbon dust was largest. In a DT plasma, the corresponding tritium inventory becomes a half, T/C∼0.03, which is approximately one order of magnitude smaller than the value estimated so far.