Long-time tritium release from irradiated beryllium (SIBELIUS irradiation)

Tritium is produced in beryllium, which is used as neutron-multiplier in ceramic fusion blankets, by fast neutrons. Although the production rate is about two to three orders of magnitude smaller than that of the breeder ceramic, initial tritium release tests with beryllium samples from the SIBELIUS irradiation indicated that, because of the very slow release at typical blanket temperatures (400 - 700 C), the inventory might become large during the DEMO blanket lifetime (≅ 3 y). An extrapolation of the short-time (several days) tritium release tests to longer times is difficult because the inventory decrease with time is not exponential. Therefore a long-time annealing test with beryllium samples from the SIBELIUS irradiation has been started February 1993. Samples are purged and annealed up to 12 months at 380, 450, 550 and 650 C. Residual inventories after annealing are determined by purging and heating to 850 C. Results for not-annealed and 3-, respectively 6-month annealed samples are presented. (orig.)