Grant: Collaborative Research and Development Grants

Fuel cladding tubes are manufactured using the pilgering process at the Cameco Fuel Manufacturing Plant in Cobourg, Ontario. However, customers who plan to buy these tubes requested that the surface should be further polished after the pilgering process. This additional requirement is associated with a significant increase in the cost of manufacturing and it is not known whether additional polishing process is beneficial. In this proposal, the detailed investigations will be done on Zircaloy-4, which is used, at present, for fuel cladding in CANDU reactors. This alloy is exposed to the environment of high temperature, radiation and corrosion for an extended period of time. The objective of the proposed study is to determine the influences of the surface roughness and the polishing treatment on the oxidation, structural transformation and hydrogen ingress and hydrides formation. If the polishing is beneficial, the optimum conditions of this treatment will be proposed. Although, the studies will be focused on Zircaloy-4 some experimental tests will be repeated to evaluate other alloys that are considered for fuel cladding in the Generation IV reactors. These alloys include E110, M5 and Zerlo. Based on the proposed research, a better understanding of the roles, that the surface roughness, texture, microstructure and polishing-induced changes in structure and accumulated stress play in the process of formation of oxide structure, hydrogen ingress, hydride formation and hydride orientation in fuel cladding tubes, will be accomplished. This work will not only allow us to determine whether or not the polishing of the cladding tubes is beneficial, but also help to formulate a clear recommendation on the optimum conditions of surface treatment for the manufacture of fuel cladding tubes.