The Water Detritiation System (WDS) designed for ITER is based on the combined electrolysis and catalytic exchange(CECE) process to ensure the emission of tritium to the environment is maintained below very strict limits. The CECE process is one of the processes for tritium removal that CNL (Canadian Nuclear Laboratories, formerly Atomic Energy of Canada Ltd.) has studied, developed and successfully demonstrated. In this work, CNL evaluated ITER’s design conditions of the exchange column and the electrolyser – the two key components of the CECE process (and the ITER WDS system) – to assess the effectiveness of tritium removal and investigate options to improve it. The evaluation was done using CNL’s CECE process simulation according to a protocol set out by ITER. Initially, calibration (benchmarking) of CNL’s hydrogen-water exchange column model was performed with a standard data set for a specified column to determine modeling parameters that resulted in a good match with the tritium concentration data. The model was then applied (with the same parameters) to the current WDS design. Some optimized conditions for the CECE process that could improve performance of the WDS to meet its design criteria were determined. The details of some of these assessments are presented here with particular attention to the WDS case where the feed water contains high levels of deuterium.