Localized Corrosion and Stress Corrosion Cracking of Carbon Steel Tanks at Hanford

摘要

The Hanford tank reservation contains approximately 50 million gallons of liquid legacy radioactive waste from cold war weapons production, which is stored in 177 underground storage tanks. Although the wastes tend to be alkaline due to the requirement for stress corrosion cracking (SCC) mitigation requirement based on previous work, the waste chemistries, such hydroxide concentration and nitrite concentration, will change over time due to various chemical reactions. Thus, the impact of these changes on the susceptibility of the tank steel to localized corrosion and SCC are of concern. The results obtained in this research program in the waste simulants suggest that nitrate is the principal aggressive species potentially leading to both localized corrosion and SCC of tank steels in simulated Hanford wastes. Nitrite has been found to be a strong inhibitor for both pitting and SCC. Furthermore, hydroxide can provide some inhibition for localized corrosion and SCC but is only significant in going from near neutral pH values to approximately 10 or when the pH is above 13.5; in all cases the influence of hydroxide is less than that noted for nitrite.