Long-term deuterium release from CFC NB31 in the air atmosphere

Long-term deuterium release from carbon fibre composite (CFC) NB31 irradiated with 200 eV D ions at room temperature to a fluence of ~1024 D m−1 and then stored in air was investigated with the D(3He, p)4He nuclear reaction at 3He+ energies varying from 0.69 to 4.0 MeV. The decrease of retained D from CFC NB31 with storage time was expressed by the linear combination of two exponential functions with time constants of ~440 and ~22 500 h, respectively. Accordingly, about 45% of retained D was lost after 1 year air storage. It has been concluded that the main D loss is attributed to D release from a-C:D soft layers formed on the surface and pore walls of CFC due to redeposition of chemically eroded hydrocarbons.