Three more double-shell tanks at the Department of Energy’s Hanford Site contain waste with chemistry that puts them them at heightened risk of corrosion, according to a new report from tank farm contractor Washington River Protection Solutions.
The report evaluated the waste chemistry of Hanford’s oldest double-shell tank, AY-102, which developed a leak from its inner shell, and compared it to the waste chemistry in the 27 double-shell tanks at Hanford still in use. Tank AY-102 has been emptied and taken out of service.
The study, dated June 2018, found that one of Hanford’s double-shell tanks, AY-101, has held waste that puts it at greater risk of corrosion than the tank that leaked waste between its shells. Two other double-shell tanks, AZ-101 and AZ-102, also were ranked among those most at risk, according to the report. Similarities among the waste in the four tanks, including the tank that was emptied, included high heat generation, which accelerates corrosion.
The Department of Energy initially suspected that problems during construction of Tank AY-102 caused the leak from its inner shell. Construction records showed that 36 percent of the welds on the inner shell were reworked up to four times before the tank was put into service around 1971. But after as much waste as possible was emptied from the tank by 2017, pitting likely caused by corrosion was found on the floor of the inner shell, allowing waste to leak between its shells.
The Washington state Department of Ecology said the report’s findings indicate three more double-shell tanks have “very high risk factors for tank bottom corrosion.” However, the findings do not mean the three tanks are leaking or that they will, said Jeremy Johnson, deputy federal project director for the Hanford tank farms.
