Development of a Packaging to Transport the new Standardised range of Disposal Canisters to a Geological Disposal Facility in the UK

The UK’s Radioactive Waste Management Directorate (RWMD) of the Nuclear Decommissioning Authority (NDA) is developing concepts to demonstrate the viability of using a standardised range of Disposal Canister designs for geological disposal of High Level Waste (HLW) and spent fuel in the UK. The standardised Disposal Canisters (DC) are designed for disposal in a Geological Disposal Facility (GDF) with integrity requirements in the range 10000 to 100000years. International Nuclear Services (INS), is also a subsidiary of the NDA, and working with RWMD to develop a design of packaging for transporting these Disposal Canisters which is called the Disposal Canister Transport Container (DCTC). Initial studies undertaken by INS focused on optimising payload and geometry for the canister designs. Subsequent studies focused on achieving Criticality Safety Requirements for transport which established the use of Multiple Water Barriers (MWBs) were required for higher enriched spent fuels. The results of this initial work were presented at the International Nuclear Engineering (INE) society conference at London in 2012. Subsequently, RWMD commissioned INS to develop the design of DCTC to a level where it would be viable for licensing as a transport package with appropriate level of technical understanding. A specific requirement of RWMD was that the loaded DCTC should be capable of transportation on an existing design of four axle rail wagon, within a gross mass of 90 tonnes, this giving considerable logistic and overall cost benefits. Recent development work has focused on detailed impact, thermal and shielding analysis and how these influence the DCTC transport mass and the position of that mass in relation to the four axle rail wagon, both of which influence its capability for the required transport. In terms of meeting mass limits, achieving the specified radiation shielding performance (Neutron and Gamma) for the spent fuel was found to be a major challenge. However, of equal challenge was to accommodate the high forces generated under impact accident conditions due to the high mass ratio of contents to container. In order to mitigate these forces, the shock absorber designs needed to be carefully judged because their dimensions were restricted by the rail wagon design. This paper describes the DCTC development work, how the design challenges were addressed and the conclusions reached.