The primary qualification of the welding process for double-walled dry shielded canisters (DSC) is underway at Chernobyl NPP ISF-2 site. The process envisages automated and manual TIG welding.
Qualification is carried out in two stages, first one was performed at the end of the last year and the second one is performed currently. In particular, the first stage was characterized by weld testing and nondestructive inspection techniques. The test laboratory of Paton Electric Welding Institute of the National Academy of Sciences of Ukraine carried out the destructive inspection of weld samples.
The welding is carried out on the basis of welding procedures and in compliance with the requirements of approved Welding Qualification Program.
During testing, the Commission consisting of Holtec (the developer of DSC welding process), SNRIU, State Scientific and Technical Center for Nuclear and Radiation Safety, Paton Electric Welding Institute of the National Academy of Sciences of Ukraine and Chernobyl NPP representatives assessed the preparation to the welding process, carried out visual and dimensional inspection and penetrant layer-by-layer examination of the welds, metallographic examination and mechanical testing of samples cut off the welds. The results of examination confirmed the compliance of the welds with the requirements of regulations, rules and standards on nuclear and radiation safety current in Ukraine.
In the framework of the second stage, it is planned to implement the practical part envisaged by the Qualification Program – welding by Chernobyl NPP experts with the help of DSC full-scale simulator.
Additional training of Chernobyl NPP operators of automated and manual welding facility was carried out in the framework of qualification and prior to welding with the help of DSC full-scale simulator supervised by Holtec experts.
The double-walled dry shielded canister is a key element of NUHOMS® interim dry storage system to be used at ISF-2 for long-term interim storage of Chornobyl NPP RBMK-1000 spent nuclear fuel.
DSC system includes the leak-tight volume that consists of two leak-tight all-welded canisters that form two separate isolation barriers, arranged on the way of possible spreading of radioactive materials, internal basket and fuel cartridges and envisages horizontal arrangement of each DSC inside of separate compartment of the concrete storage module.