Hanford is home to 177 underground waste storage tanks: 149 single-shell tanks and 28 double-shell tanks located about 10 miles from the Columbia River.
One of WRPS’ priorities is to transfer waste from single-shell tanks to double-shell tanks until the waste can be permanently treated.
The first single-shell tanks were put into service in 1944, and more than 60 of the original single-shell tanks are known or suspected to have leaked waste to the surrounding soil. The tanks—consisting of a carbon steel liner surrounded by a layer of thick steel-reinforced concrete—are well past their design life but are still storing waste.
Double-shell tanks were built at Hanford beginning in 1968. The double-shell tanks have a carbon-steel inner tank with a separate steel liner surrounding it. The tank liners are separated by an air space, or annulus, of about 30 inches armed with a leak-detection system. Unlike Hanford’s single-shell tanks, the double-shell tanks still meet federal and state regulations. But even the double-shell tanks are starting to show signs of aging. In 2012, it was discovered that the oldest of Hanford’s double-shell tanks—AY-102—leaked waste into its annulus but not the environment. Preparations are underway to empty the tank and remove it from service.