Safeguards Verification Concept For Disposal Of Spent Nuclear Fuel

Finland is developing a national safeguards concept for disposal of spent nuclear fuel in a geological repository, taking into account inputs from EC and IAEA SG inspectorates. The disposal is planned to start around 2025. It is imperative that the fuel will be verified before disposal, since after disposal the fuel will be inaccessible forever. An NDA verification system with two simultaneous methods, PGET (Passive Gamma Emission Tomography) and PNAR (Passive Neutron Albedo Reactivity), has been built and tested. The measurement time needed is about 5 minutes. The selected methods may complement each other which greatly enhances the verification performance of the system as a whole. The measurements will initially be conducted at the shipping facility in the intermediate storage pools, before transfer of the fuel to the encapsulation plant. The verification process aims to be unattended by the inspectorates and automated, so it needs to be under continuous remote surveillance. The measurements shall create credible assurance that the declaration of the fuel is correct and complete. To ensure that the preservation of knowledge is maintained, the collected data will be stored for future generations who will not have access to the fuel itself. The data analysis shall be concluded before the transfer of the fuel from the wet storage to the encapsulation plant, so the verification process shall be designed to consider operational requirements of the nuclear operators as well as of the inspectorates. This paper describes the verification process envisaged and identifies the processes which need to be developed.