Heavy Water Physical Verification in Power Plants

This paper is a report on the Agency experience in verifying heavy water inventories in power plants. The safeguards objectives and goals for such activities are defined in the paper. The heavy water is stratified according to the flow within the power plant, including upgraders. A safeguards scheme based on a combination of records auditing, comparing records and reports, and physical verification has been developed. This scheme has elevated the status of heavy water safeguards to a level comparable to nuclear material safeguards in bulk facilities. it leads to attribute and variable verification of the heavy water inven tory in the different system components and in the store. The verification methods include volume and weight determination, sampling and analysis, non destructive assay (NDA), and criticality check. The analysis of the different, measurement methods and their limits of accuracy are discussed in the paper.