Release-behaviour of tritium and its chemical forms in heating irradiated UO2(Li)-pellet

UO2-pellets containing 0.1 w/o of LiF, UO2(Li), were neutron-irradiated. Tritium released during and after the irradiation amounts to less than 1% of the total. Since the apparent activation energy for the release of tritium is 32 kcal/mole, heating the irradiated UO2(Li)from room temperature to 10500C causes almost complete release of tritium in the chemical forms HTO and HT in a proportion of roughly 10:1. The addition of a small amount of H2 or H2O leads to a drastic change in the observed distribution of tritium; in the former case more than 90% of the tritium was released as HT, while in the latter the yield of HTO reaches close to 100%. From them and other additional experimental results, it is concluded that the formation of HT is primarily related to the partial oxidation of UO2. (author)