INVESTIGATION OF THE CORROSIVITY OF THE VAPOR PHASE OVER HIGH-LEVEL RADIOACTIVE WASTE

摘要

Corrosion in the vapor space and at the liquid/air interface of the Department of Energy (DOE) high level waste (HLW) tanks have emerged as a potentially aggressive corrosion mechanism. Controls on the solution chemistry are in place to preclude the initiation and propagation of degradation in the tanks within the liquid space. However, recent experience has shown that steel not in contact with the bulk waste solution but exposed to the "vapor space" above the bulk waste and the liquid/air interface, may be vulnerable to the initiation and propagation of degradation. Experimentation was performed to determine the potential for vapor space corrosion and liquid/air interface corrosion in ASTM A285 and A537 steels, the materials of construction of the Savannah River Site (SRS) HLW storage tanks. Corrosion studies were performed with flat, unstressed coupons in nitrate, nitrite, and hydroxide solutions. The results suggest that the potential for vapor space and liquid/air interface general corrosion and pitting exists even with inhibited solution chemistry. Further experimentation is planned to quantify the magnitude of the corrosion and also to determine the potential for stress corrosion cracking under similar conditions.