Hydrogen retention of carbon dust produced in JT-60

Hydrogen retention of dust produced by hydrogen discharges from June 1987 to October 1987 in JT-60 was measured to contribute for the estimation of in-vessel tritium inventory in the next generation of fusion reactor, such as ITER. After venting the vacuum chamber, several types of dust-like pieces, i.e. flake-like carbon dust, graphite, and metal pieces, were found in the vacuum vessel. The amount of retained hydrogen in flake-like carbon dust was two orders of magnitude larger than that in the graphite and metal pieces. However, the hydrogen concentration of flake-like carbon dust was 0.04 in the atomic ratio of H/C, which was one order of magnitude smaller than that of carbon flake produced in JET. One of possible explanations is the difference of the wall temperature between JT-60 and JET.