A £1M contract was awarded to TWI by SKB, the Swedish nuclear fuel and waste management company. The contract was to develop special-purpose electron beam (EB) welding equipment to study canister fabrication and encapsulation methods for high level nuclear waste.
A compact 100kW in-chamber gun using the latest RF excitation technology was mounted on a purpose-built 5.5m long linear traverse inside the 150 cubic metre vacuum chamber at TWI. This allowed the first full length 0.9m diameter 60mm thick canister to be EB welded along a length of five metres.
For the next stage, extensive modifications were made to existing reduced pressure electron beam equipment, increasing the height of the vacuum chamber (located inside TWI's non-vacuum welding bay) to around six metres. This was performed to enable housing of the resulting five metre tall canisters for welding of bottoms and lids. Fully assembled, the canisters, complete with steel liners, weigh approximately 11 tonnes (17 tonnes when full of fuel elements).
A further phase of work involved lowering several of these fabrications into the reduced pressure bay through a specially constructed leaded sliding hatchway. Fabrication and sealing of four empty canisters was followed by work on modified canister designs.
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