Swedish radioactive waste management company Svensk Kärnbränslehantering (SKB has signed an agreement with Finland’s radioactive waste management company, Posiva under which SKB will weld the bottoms of Finnish used fuel capsules. The contract is for five years with an option for two more years. The work that will be carried out in the capsule Laboratory in Oskarshamn is scheduled to begin in 2025. The agreement applies to the welding of about 160 capsules.
Posiva has recently completed its final repository in Onkalo and is awaiting permission from its regulator to put it into operation. The company needs to weld bottoms to the capsules in which the used nuclear fuel will be stored.
“We have been offering our services to sister organisations all over the world for several years. Since Finland uses the final storage method developed by SKB, KBS-3, we have shared knowledge and experience with each other for a long time,” said Magnus Holmqvist, CEO of SKB International. “With this agreement, we get the opportunity to deliver a finished product and to give us further experience in exporting the technology, knowledge and experience developed by SKB over the past 40 years.”
Posiva CEO Ilkka Poikolainen said: “With this agreement, we are taking another step closer to bringing the world’s first used fuel repository into operation. In order to be time efficient, we chose to give the assignment to SKB, which has successfully welded many capsule bottoms. This means that we avoid additional costs and we know that SKB will perform the work with high quality. “
The welding method used is called friction welding, or more specifically friction stir welding, and has been specially adapted by SKB to weld copper. It is a mechanical welding technique using a rotating conical tool that is pressed into the joint between the parts to be welded. The material around the tool is heated by the friction and becomes soft. As the tool rotates, the copper material is stirred on both sides of the joint, bonding the two metal parts into a homogeneous weld joint.
Finland’s final repository is being built based on the KBS-3 system developed by. The method is based on three protective barriers: the copper capsule that encloses the used nuclear fuel, clay buffer that is placed around the capsule and protects against minor movements in the rock, with primeval rock as the outermost barrier. Since 2001, SKB and Posiva have collaborated to develop and test this system.
