A Study of Corrosion and Stress Corrosion Cracking of Carbon Steel Nuclear Waste Storage Tanks

The Hanford reservation Tank Farms in Washington State houses 177 underground storage tanks containing approximately 50 million gallons of liquid legacy radioactive waste from Cold War plutonium production. This study aims to investigate the corrosion and stress corrosion cracking (SCC) of carbon steel storage tanks used for these highly alkaline pH wastes, which are specially designed to protect against corrosion. Despite these measures, localized corrosion and SCC remain significant concerns due to variations in waste chemistry across different tanks, comprising various combinations of hydroxide, nitrate, nitrite, chloride, carbonate, aluminate, and other species. The methodology includes electrochemical polarization, slow strain rate, and crack growth rate testing to assess the effects of solution chemistry, pH, temperature, and applied potential on corrosion behavior. Results indicate that certain constituents, particularly nitrates and chloride, can still render carbon steel susceptible to localized corrosion even under highly alkaline conditions, stressing the need for careful monitoring and control of tank chemistry to mitigate these risks. The findings contribute to understanding the long-term integrity of storage tanks and the safety of radioactive waste storage.