The effect of neutron irradiation condition on tritium release from beryllium is described in this paper. Beryllium samples were irradiated in the SM reactor with neutron fluence (E > 0.1 MeV) of (0.37-2.0) x 1012 cm(-2) at 70-100 and 650-700 degreesC. Mass-spectrometry technique was used in out of pile tritium release experiments during stepped-temperature anneal within a temperature range from 250 to 1300 degreesC. The total amount of helium accumulated in irradiated beryllium samples varied from 521 to 3061 appm. The first signs of tritium release were detected at temperature of 406553 degreesC. It was shown that irradiation temperature and helium generation level significantly affect the tritium release. A fraction of 44-74% of tritium content in samples irradiated at low temperature (70-100 degreesC) is released from beryllium at an annealing temperature below 800 degreesC, whereas for samples after high temperature irradiation (650-700 degreesC) tritium release did not exceed 14%. Majority of tritium (similar to68%) is released within a temperature range from 800 to 920 degreesC. The increase of helium generation from 521 to 3061 appm results in lowering the temperature of maximal tritium release rate and the upper temperature of tritium release from beryllium by 100-130 and 200-240 degreesC, correspondingly. On the basis of data obtained, the diffusion coefficients of tritium in beryllium were calculated. (C) 2004 Elsevier Ltd. All rights reserved.
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