Developing Design Criteria for Safeguards Seals for Spent-Fuel Transportation Casks

Current designs for spent-fuel transportation casks cannot ensure a cask’s integrity during shipment, nor is there any verifiable means of maintaining continuity of knowledge (CoK) on the contents of transportation casks - that is, spent fuel destined for encapsulation plants (EP) or geological repositories (GR) - without employing additional containment and surveillance (C/S) measures during shipment. Following final safeguards accountancy measurements on spent fuel assemblies, the shipment of verified assemblies will require unprecedented reliance on maintaining CoK on the fuel inside transport casks, as there will be no re-verification of spent fuel following encapsulation into disposal canisters, and dual C/S measures during such fuel shipments are required according to the IAEA’s Application of Safeguards to Repositories (ASTOR) expert group. By designing spent fuel transportation casks with effective seals integrated into their design, CoK can be more effectively maintained than by ad-hoc C/S measures by ensuring that a transportation cask has not been tampered with. An integrated cask seal would reveal tampering of a cask (beyond removing a bolted lid, for example, such as cutting through the unsealed end of a cask), and thereby rigorously maintain CoK on a cask’s contents during shipment. Externally applied seals may not be able to provide such assurance for currently designed spent fuel transportation casks, though some combination of seals, detectors and/or a technology that can verify canister integrity might provide this assurance. In this report, we examine design criteria for integrating safeguards seals into transportation casks as well as identify limitations of such an approach and recommendations for near-term applications.