Fusion Science and Technology / Volume 54 / Number 2 / August 2008 / Pages 584-587
Technical Paper / Materials Interactions
Mineral and synthetic oils used as lubricants or operating fluids in pumps are mixtures of branched or cyclic saturated hydrocarbons. They are chemically inert but their slow partial oxidation is possible even at room temperature. Specific activity of pump oils contacted with gaseous tritium for a long time may exceed 1013 Bq/kg.
Studies of waste oils show that more than 90% of the radionuclide is bound with oxidation products. This selectivity is owned to predominant formation of quasifree tritons or 3HeT+ ions when one of the two nuclei in the T2 molecule decays. The sequence of ion-molecule triton transport reactions is the mechanism responsible for accumulation of tritium by oxidation products with higher proton affinity.
The most effective technique of oil decontamination is adsorption of tritiated species by polar adsorbents (silica gels, zeolites). The detritiation degree for these adsorbents amounts to 95%. Then complete thermal oxidative destruction can be used to convert adsorbed organic compounds into CO2 and water. Thus, adsorption, thermal oxidation and adsorbent regeneration may be proposed as the technology of tritium recycling since HTO returns to the isotope separation system. As a result, the radiation danger related with storage of high activity waste oils can be significantly decreased.