Since 1978 the Belgian Nuclear Research Centre, S. C. K. /C. E. N. , has been developing the ELEX process for water detritiation. The ELEX process, which looks very suitable for the detritiation of CTR cooling water and wastewater, is based on the electrolysis of water and the catalytic exchange of tritium between hydrogen and water. The exchange is carried out in a simple countercurrent packed-bed reactor and it is promoted by a proprietary hydrophobic catalyst. After a study of the single constituent steps with a. o. the development of an appropriate hydrophobic catalyst, the integrated ELEX process was succesfully demonstrated by detritiating more than 1000 dm**3 water in a 0. 18 dm**3h** minus **1 bench-scale installation.