Tritium and helium release from beryllium pebbles neutron-irradiated up to 230Â appm tritium and 3000Â appm helium

Study of tritium and helium release from beryllium pebbles with diameters of 0.5 and 1 mm after high-dose neutron irradiation at temperatures of 686-968 K was performed. The release rate always has a single peak, and the peak temperatures at heating rates of 0.017 K/s and 0.117 K/s lie in the range of 1100-1350 K for both tritium and helium release. The total tritium release from 1 mm pebbles decreases considerably by increasing the irradiation temperature. The total tritium release from 0.5 mm pebbles is less than that from 1 mm pebbles and remains constant regardless of the irradiation temperature. At high irradiation temperatures, open channels are formed which contribute to the enhanced tritium release.