Study of High-Temperature Oxidation of the Claddings of Tolerant Fuel Elements of VVER-type Reactor

The work presents the results of a study of corrosion resistance of chrome-coated fragments of zirconium cladding of VVER-1000 reactor fuel elements. The coatings had been deposited by electrochemical deposition on the standard cladding fragments with pre-treated surfaces. Gas-dynamic treatment of the surface with chrome powder proved to have a positive effect on the surface-to-cladding adhesion. Annealing at a temperature of 400 °C contributes to relieving of the residual stresses resulting from the gas-dynamic treatment. Investigation of the durability of the coatings was performed under exposure to overheated steam at a temperature of 1200 °C and exposure period of up to 1500 s. As it has been demonstrated, the produced coatings hinder formation of ZrO₂ oxide layer at the outer surface and reduce the depth of penetration of oxygen into the metallic sublayer, in comparison with the specimens in the original condition. All this contributes to retention of the residual ductility of the tested specimens at the level of no less than 2%. (paper)