ELEX process for tritium separation from aqueous effluents

Within the framework of the European Communities' indirect action program on management and storage of radioactive waste the Belgian Nuclear Research Centre, S.C.K./C.E.N., is developing the ELEX process for tritium separation from aqueous reprocessing effluents. This process is a combination of water electrolysis and tritium exchange between hydrogen and water, the exchange being promoted by a hydrophobic catalyst. For classical electrolysis under normal working conditions with elementary tritium separation factor of 11.6 with a standard deviation of 6% was obtained. As to the exchange step an appropriate hydrophobic catalyst has been developed, and overall tritium exchange rates were measured in a countercurrent packed-bed reactor. Extrapolation of these results to the 3 m3 per day scale of a reprocessing plant leads to an electrolyser capacity of about 1 MW and to an exchange volume of about 1 m3 for an ELEX installation that concentrates 90% of the original tritium in 1% of the original volume. At the moment the construction of a small integrated detritiation unit is nearly finished. A larger pilot installation will be built later on