As the Hanford Nuclear Waste Site in southeast Washington nears completion of the Waste Treatment and Immobilization Plant Low-Activity Waste Facility, Bechtel National Inc. revealed the successful completion of assembly of two nuclear waste melters inside the facility, each at 300 tons.

“Assembling the melters is another indication we are completing the work necessary to achieve the department’s direct feed low-activity waste approach to begin treating Hanford tank waste,” says Dept. of Energy’s Office of River Protection acting manager Ben Harp. “This approach will enable us to provide a more enduring means of protecting the Columbia River by starting treatment of the low-activity radioactive waste, the most mobile of the waste, as soon as 2022.”

The Office of River Protection has enlisted Bechtel to complete the Waste Treatment Plant, also known as the Vit Plant, which will turn 56 million gallons of radioactive liquid waste stored in 177 underground tanks into vitrified glass for long-term safe storage using the vitrification process.

The entire facility, the world’s largest radioactive waste treatment plant, will span 65 acres and includes four major nuclear facilities—Pretreatment, Low-Activity Waste Vitrification, High-Level Waste Vitrification and an Analytical Laboratory. Work is substantially complete on the laboratory and more than 20 relevant support facilities. The high-level waste portion will signify the final step in the process, even while work continues on the low-activity waste, marked by the milestone of finished installation of both the first melter in May and the second in late August.

“With the melters assembled and all major process equipment already installed, our workforce remains on pace toward the construction complete contract milestone of June 2018 for the LAW Facility,” says Peggy McCullough, Bechtel’s WTP project director.

The melters, the largest of their kind ever built in the United States, will heat Hanford’s low-activity tank waste and glass-forming material to 2,100 degrees Fahrenheit—as needed for the vitrification process—before the mixture gets poured into stainless steel containers for permanent storage. During plant operations, the LAW facility melters will produce 30 tons of glass daily, 10 times the capacity of the melter in operation at DOE Savannah River Site’s Defense Waste Processing Facility in South Carolina.

The DOE’s Hanford Site is home to 56 million gallons of chemical and radioactive waste, the result of more than four decades of plutonium production. The Office of River Protection remains responsible for the retrieval, treatment and disposal of the waste in a safe, efficient manner.

Follow Tim Newcomb on Twitter at @tdnewcomb.