We oversee the safe storage, retrieval, and treatment of the dangerous waste in Hanford's underground tanks. There are 149 single-shell tanks and 28 double-shell tanks at Hanford. These 177 tanks hold the most dangerous radioactive and chemical wastes from decades of plutonium production activities.
For the past few decades, the most dangerous radioactive and chemical waste has been and continues to be moved from single-shell tanks to safer double-shell tanks at Hanford. The waste will remain in the double-shell tanks until it can be moved to the Waste Treatment and Immobilization Plant (WTP)
, which is under construction.
Once it's completed, the WTP will turn the high-level waste into glass, through a process called vitrification, that will then be stored in high-grade stainless steel casks. While it will still be radioactive, the vitrified waste will no longer be able to seep into or pollute the air, water, and soil. Without the retrieval and treatment of the tank waste, any leakage would eventually reach the Columbia River. WTP is critical in helping to clean up Hanford and in reducing the possibility of further threats to the environment and all who live and work near the Columbia River.
The single-shell tanks contain a mixture of saltcake and slurry (we call it sludge), that is both radioactive and chemically hazardous. Similar to wet beach sand in consistency, the sludge comprises liquid mixed with solids. Some tanks have more waste than others, and the radioactive and chemical content can vary widely from tank to tank.
Liquid that rises to the top is called supernatant. It's present in about 35 single-shell tanks. The total volume in those 35 tanks is about 117,500 gallons. An estimated 2.5 million gallons of combined saltcake, slurry, and supernatant waste remain in the single-shell tanks.
The single-shell tanks are storing waste generated in the last century and do not meet the minimum state requirements for storage. Therefore, we are overseeing active waste removal (retrieval) of these tanks. As it's removed from the single-shell tanks, the waste is transferred to double-shell tanks for safer storage and waste management.
The U.S. Department of Energy keeps an estimate of inventory in all the single-shell and double-shell tanks.
Two tanks are actively leaking, Tank B-109 and Tank T-111. We recently issued an Agreed Order with the U.S. Department of Energy to both address these active leaks and future leaks from single-shell tanks. You can learn more about the Agreed Order here.
If existing problems aren't addressed and the waste isn't removed from the tanks, the tanks will continue to corrode and develop leaks, and contaminants could eventually reach the Columbia River at very high concentrations. The Tri-Party Agreement requires 99 percent of waste be retrieved, or as much as can be, using multiple techniques.
However, a more immediate concern is the waste that has already leaked from the tanks, contaminating the soil underneath. We must find ways to prevent that contamination from reaching the river.
Waste at the treatment plant will be mixed with a glass-forming substance and melted into robust stainless steel casks where it will be unable to pollute the air or water. These casks will hold one of two types of waste: low-activity waste and high-level waste. The low-activity casks will be transported for permanent disposal at an engineered disposal facility located on the Hanford site. The high-level waste canisters will be stored at Hanford until a national repository is identified for high-level waste.