Effective safeguards in a commercial reprocessing plant

Large reprocessing plants require special attention if they are to be safeguarded effectively, and since a number of new plants are under construction or being planned, it is highly important to resolve the technical and logistic issues they will present to the safeguards inspectorates. In the United Kingdom, the THORP plant, which will reprocess up to 1200 t of irradiated oxide fuel per year, is under construction and is due to commence operation in the early 1990s. The development of procedures for safeguarding this plant is of immediate concern to the owner, British Nuclear Fuels, Ltd. (BNFL), but also to the safeguards community and the nuclear power industry worldwide. Last year, BNFL published its views on the need for a fresh and imaginative approach to safeguarding reprocessing plants, and suggested ways in which a combination of technical measures, linked to a flexible application for diversion detection criteria, could provide an effective and efficient safeguards strategy. The present paper describes how that approach could be implemented in THORP with reference to specific design features, and particularly addresses the question of verification. It is a paper about practicalities; it describes materials measurement systems, inferential measurement techniques, and the use of process models, and discusses the techniques available to the inspectorates to verify the operator's data