Deep Borehole Canister Development for Norwegian High-Level Radioactive Waste - Paper 23223

Norwegian Nuclear Decommissioning (NND) is currently actively running a radioactive waste management programme and developing disposal concepts for all radioactive waste types existing in Norway. The inventory of radioactive waste is characterised by high-level waste (HLW) from the research reactors in Halden and Kjeller, taken out of operation. In addition, there will be low- and intermediate-level radioactive waste (LILW) from the planned decommissioning of the research reactors and other nuclear facilities. NND is developing a comprehensive strategy for management of all these waste types. The currently planned options for the disposal are: - Intermediate depth repository for low- and intermediate-level waste, - Deep geological repository (DGR) OR deep borehole repository (DBD) for high-level waste, - Landfill-type repository for non-radioactive decommissioning waste. Of the disposal options for HLW the deep borehole disposal concept is generally on a lower maturity level compared with the DGR option. NND is therefore running projects that will bring the DBD type repository to a more equal level with the DGR, before they will make the final decision on which disposal concept will be realised in Norway. This paper presents newly developed information on the deep borehole disposal canister for crystalline host rock and, therefore, brings the concept to a more mature level. This paper provides basic information about the deep borehole disposal canister design. First, the safety functions of the canister in deep borehole disposal are described. In the work the safety functions and requirements for the canister are quantified. The safety requirements are subsequently used to prepare the canister concept design for deep borehole disposal in crystalline host rock in Norway. In addition, the manufacturing process of the canister is described. The material chosen for the canister manufacturing is discussed, including the dimensioning of the canister. Furthermore, the geochemical environment and corrosion processes are described to predict the long-term performance of the canister. The work also discusses the required encapsulation process for the canister designed. This is how the high-level waste is encapsulated in the canister, including the hot cell, welding, and inspection requirements. (authors)