Hanford single-shell tanks leak causes and locations - 15509
Historically 67 assumed and known leaking tanks in the single-shell tank (SST) system were identified at the Hanford Site. The US DOE, Washington River Protection Solutions LLC., and the State of Washington, Department of Ecology identified 25 of the 67 tanks as likely having had liner leaks by a comprehensive review of current and historical data. The remaining tanks are those with potential leaks from sources other than liner failures such as overfilling the tanks or the failure of process lines connecting SSTs. The location of the leaks was determined, based largely on logging radiological data from dry wells installed around the tank and/or radiological data from laterals installed under select tanks. The dry wells and laterals provide the best indication of the vicinity of the leak location, but not necessarily the exact location of the leak. Twenty of the 25 liner leaks appear to have occurred at or near the bottom of the tanks. Many of the tanks appeared to have multiple leak locations. Leak locations could not be determined for all tanks with the available data. Three of the tanks showed apparent sidewall leaks. Potential causes for liner leaks that were evaluated included tank design features, tank construction conditions, waste temperature, tank waste chemistry conducive to different types of corrosion (uniform corrosion, nitrate induced stress corrosion cracking, pitting, crevice, and liquid-air interface corrosion), and bulges in the tank bottom. (authors)