TN™ 81: A Challenging Design

With increasing burn-up, reprocessing of spent nuclear fuel yields higher quantities of radionuclides, with a powerful source term and high heat output. Improvement in the vitrification process and environmentally sound thinking have been drivers to reduce the number of transports of vitrified residues (High Level Waste) to interim storage facilities in their owner’s country: this results in higher concentrations of nuclides in the stable glass matrix. The challenge was to create, with almost the same allowable mass and dimensions, a transport/storage casks able to transport glass canisters with this new specifications. Improving the environmental performance of the glass canisters would be of no avail without the corresponding means of transport and storage. This is why COGEMA LOGISTICS introduced the TN™ 81 concept; a dual purpose cask able to handle the most demanding canisters from reprocessing: 56 kW instead of 41 kW, and to shield with efficiency greater gamma and neutron sources, which regulations have been made more stringent regarding the neutron quality factor. The paper will comment the choices made, the drop test campaigns run specifically, and report on the loading of the first TN 81 for KernKraftwerk Go¨sgen (KKG), Switzerland.