EXPRESSION OF INTEREST (EOI) for Subcontract - Hanford Waste Chemistry and Corrosion Testing

Double-Shell Tank (DST) waste chemistry controls were established in the 1980s in response to tank failures at the Department of Energy Savannah River Site (SRS), due to nitrate induced stress-corrosion cracking (SCC) of the carbon steel liner. Due to the limited work done at that time, and the time dependent character of SCC initiation, very conservative chemistry limits were initially set for DST waste at the Hanford Site. The establishment of a Hanford Site corrosion testing program, the subsequent testing results, and input from the Tank Integrity Expert Panel (TIEP) Corrosion Sub-Group (CSG), showed that general and pitting corrosion of carbon steel can be effectively controlled at much lower levels of caustic additions, minimizing both the cost of maintaining tank chemistry and the expensive process of conditioning the waste for vitrification. The TIEP CSG has conducted a considerable amount of work on the causes of SCC and pitting corrosion, and this work has recently led to new chemistry control limits for the DSTs based on a pitting factor model, ensuring corrosion risks in these tanks are minimized. The CSG continues to guide WRPS in maintaining the chemistry control limits and helps in identifying and addressing other corrosion mechanisms in the DST system and supporting facilities – including the Effluent Treatment Facility and 242-A Evaporator. Central to the corrosion mitigation work by WRPS and the TIEP is the on-going need for corrosion testing based on field samples obtained from the Tank Farms and the development of new tools for corrosion detection.