|
5302 |
|
Heat treatment of cold spray copper on the weld closure zone of used nuclear fuel containers |
|
Jason Giallonardo* / Nuclear Waste Management Organization, Canada Jean-Gabriel Legoux / National Research Council, Canada Dominique Poirier/ National Research Council, Canada Caroline Hoang/ National Research Council, Canada Peter Keech/ Nuclear Waste Management Organization, Canada Dave Doyle/ Nuclear Waste Management Organization, Canada |
|
The Nuclear Waste Management Organization (NWMO) has proposed the concept of a deep geological repository (DGR) for the storage of Canadas spent nuclear fuel. A major engineered component is the used fuel container (UFC), which consists of a carbon steel core coated with copper. Since 2011, the NWMO has conducted a multi-phase development program on copper coating technologies and their application to the steel UFC structural core. The copper is required to act as the corrosion barrier when emplaced in the DGR and must be relatively pure in order to maintain performance expectations. The key mechanical attributes for the copper coating are sufficient adhesion strength to the steel substrate and ductility, both of which are necessary to satisfy the requirements for mechanical loading under DGR conditions. The NWMO has identified two coating technologies for the copper application process: electrodeposition and cold spray. Electrodeposition is utilized to coat the bulk of the UFC components (i.e., head and body). A portion of the head and body openings remain uncoated in order to facilitate the final assembly closure weld process after fuel loading. This area is then cold sprayed with copper to complete the coating on steel since it has the capability of being fully automated which will be necessary in a radioactive environment. Since the cold sprayed coating is highly strained in the as-deposited state, it requires heat treatment to impart ductility An indirect method to assess ductility is to measure the hardness of the material after the heat treatment. A recent advancement on this front included the implementation of a heat band treatment method to the UFC that was optimized and found to be capable of achieving the desired hardness value for the material that is known to have the required ductility. |