Achieving an Acceptable Standard for Plant Condition and Inventory Status in Nuclear Facilities in Readiness for the Annual Physical Inventory Take

International safeguards regulations state that a physical inventory take, and subsequent verification, shall be performed in each material balance area of a facility in every calendar year. This physical inventory is the sum of all measured and derived estimates of quantities of nuclear material within a material balance area as determined by the facility operator, which is subsequently verified by the safeguards inspectorates. In order to provide the safeguards inspectorates with sufficient confidence to draw safeguards conclusions, a material balance area must be in an adequate condition and the inventory status such that it facilitates this verification. This includes minimising the quantity of nuclear material present, ensuring as much material as possible is in a measurable form and accessible for verification, and that any supporting equipment or information is available in a timely manner to the safeguards inspectors to name but a few requirements on the operator. To ensure the physical inventory verification process is as effective and as efficient as possible, Sellafield Limited has drawn upon best practice guidance for physical inventory takes and verifications as set out by the UK Office for Nuclear Regulation and the expectations and experience of the European Commission Directorate General for Energy safeguards inspectors. This collaborative approach has led to definition of these standards and their limitations for implementation in each material balance area across the Sellafield site. In order to obtain a consistent approach, this work began with a focus on ageing, legacy facilities where there were often operational constraints to obtaining optimum conditions for physical inventory takes and verification activities. The approach to plant standards in these legacy areas was successful and was therefore rolled out to the other material balance areas across the Sellafield site. This paper outlines the approach adopted by Sellafield Limited along with some of the challenges and operational constraints encountered and key learning from the exercise.