Burnup Credit for Transportation and Storage

After spent fuel has cooled for several years, its efficient transportation and storage tend to be limited by nuclear criticality safety design considerations. This differs from experience with current generation spent-fuel systems, which have been designed for short cooling times and are generally limited by heat transfer or shielding considerations. Consideration of the reduced reactivity of spent fuel due to burnup in the reactor is termed burnup credit. The use of burnup credit in nuclear criticality analysis can increase capacities of storage facilities and transport casks, resulting in reduced handling and shipments of spent fuel. These factors reduce worker and public exposure and result in decreased risk and cost. The acceptance of burnup credit for the design of transport casks and dry storage is contingent on the resolution of certain system safety issues. These issues are being addressed by using an integrated approach to reduce the uncertainties involvedandtoprovidecalculationalandoperational guidance.