Abstract
Aluminum-clad reactor fuels at the Savannah River Site (SRS) traditionally stored in light-water filled basins for 9-12 months, are currently undergoing extended basin storage times approaching five years. Separations facilities at the site have not processed fuels for several years due to new regulations, policy changes, and safety upgrades. With this extended water storage, pitting corrosion of the aluminum fuel is a primary concern. Component immersion tests and actual storage of irradiated fuel in the basins show that the water is aggressive toward the pitting corrosion of aluminum. Current laboratory immersion and electrochemical tests conducted at varying water conductivity levels indicate that the corrosion potential, Ecorr, of the aluminum alloy is more noble as conductivity is decreased. The pitting potentials of the 1100 and 6063 aluminum alloys were higher than the 8001 alloy. Pitting was observed only when the protective oxide coating was broken down by higher impressed voltages.
An analysis of the basin storage conditions indicates that a number of factors may be operating synergistically to cause corrosion of the aluminum-clad alloys. Among those factors playing key roles are high water conductivity, basin water chemistry, sludge on the basin floor, and galvanic couples between dissimilar metals in the basin. A basin cleanup program is in place to improve the storage conditions. The ultimate solution, is however, to remove the spent fuel from the basins and stabilize it using the SRS Separations facilities.
