36Cl and 14C behaviour in UNGG graphite during leaching experiments

Graphite has been used as a moderator in Natural Uranium Graphite Gas reactors. Among the radionuclides, the long-lived activation product 36Cl and 14C, which are abundant in graphite after irradiation can be the main contributors to the dose during disposal. This paper deals with the first results obtained on irradiated graphite from French G2 reactor. Both leaching and diffusion experiments have been performed in order to understand and quantify the radionuclides behaviour. Chlorine leaching seems to be controlled by diffusion transport through graphite matrix. On the contrary 14C leaching is very low, probably because after irradiation, the remaining 14C was produced from 13C activation in the crystalline structure of graphite. (authors)