In southeastern Washington State, Bechtel National, Inc. is designing, constructing and commissioning the world’s largest radioactive waste treatment plant for the U.S. Department of Energy (DOE). When complete, the Waste Treatment and Immobilization Plant (WTP), will process and stabilize much of the 56 million gallons of radioactive and chemical waste currently stored at the Hanford Site.
The waste, a byproduct of national defense plutonium-production efforts during World War II and the Cold War era, resides in 177 aging underground tanks. Of these, more than one-third have already leaked, contaminating the subsurface and threatening the nearby Columbia River.
The plant will use vitrification technology, which involves blending the waste with glass-forming materials and heating it to 2,100 degrees Fahrenheit (1,149 degrees Celsius). This mixture is poured into stainless steel canisters to cool and solidify. In this glass form, the waste is stable and impervious to the environment, and its radioactivity will safely dissipate over hundreds to thousands of years.
While vitrification has been employed successfully at other radioactive waste clean-up sites, it has never been attempted at the scale of or on waste as complex as that stored at Hanford. The WTP Project is a feat of engineering and construction at an unprecedented level. It is the largest undertaking of its kind and one of DOE’s most technically challenging clean-up projects.
The WTP Project is equivalent to building two nuclear power plants and is being accomplished at a time when a new nuclear facility has not been built in the U.S. for decades. The construction site spans 65 acres and includes four major nuclear facilities – Pretreatment, Low-Activity Waste Vitrification, High-Level Waste Vitrification and the Analytical Laboratory. The largest of these structures, the Pretreatment Facility, has a footprint equivalent to four football fields and will be 12 stories tall when complete. Operations and maintenance buildings, service utilities and office space complete the complex that overall requires more than 260,000 cubic yards of concrete, 40,000 tons of structural steel, and more than one million feet of piping.