Oxidation induced release of deuterium from carbon based plasma facing materials

Following a description of the state of knowledge concerning cleaning of the vacuum vessel of fusion reactors From Tritium by controlled oxidation of codeposited layers of carbon and hydrogen isotopes the experimental facility Deuterium Release Experiment (DEREX) is explained. In this facility a codeposited a-C:D layer from TEXTOR (1 mu m thickness, D/C = 0.03) has been oxidised in oxygen (300-600 Pa) at 523-673 K. The results indicate, that substantial release rates, leading to complete D-release within some days, are obtained at T greater than or equal to 623 K, Surprisingly, an over proportional dependence of release rate on oxygen partial pressure was observed; this result seems worth to be examined in more detail in order to optimise the cleaning method. (C) 1998 Elsevier Science B.V. All rights reserved.