The month of March marked the 25th year of radiological operations for the Defense Waste Processing Facility (DWPF) at the Department of Energy’s Savannah River Site in South Carolina. Radiological operations at DWPF, which is used to treat Savannah River’s high-level radioactive tank waste, began on March 12, 1996, with the first canister of vitrified waste poured on April 29 that year.
To date, more than 4,200 stainless steel canisters of vitrified waste have been poured at DWPF, according to the DOE.
The only operating waste vitrification plant in the nation, DWPF is operated by Savannah River Remediation, the DOE’s liquid waste contractor at the site. According to the DOE, DWPF operations are expected to continue for approximately 15 more years, and about 4,000 more canisters are scheduled to be produced. The DOE expects to begin hot operations at a second waste vitrification plant later this year at its Idaho National Laboratory site.
The process: Using a 75-ton melter and a sand-like borosilicate glass (called “frit”), radioactive tank waste is converted to a solid glass form at the DWPF. The vitrification process immobilizes the waste, making it suitable for safe, long-term disposal in stainless steel canisters. The canisters are being stored in an on-site facility until a permanent, federal repository is available.
The history: DWPF’s history, the DOE said, can be traced back before its 1996 startup. In the mid-1970s, the department recognized significant safety and cost advantages in immobilizing the liquid waste into a solid form. About 20 different waste forms, including synthetic rock, ceramic, and cement, were evaluated as a solution to stable, long-term storage of the liquid waste.
In 1982, the DOE selected borosilicate glass as the preferred waste form for the high-level waste at Savannah River. Research confirmed that the radioactive constituents in the waste were chemically bound in the borosilicate glass matrix, making it a highly durable waste form.
In November 1983, ground was broken for construction of DWPF. Seventy-one thousand cubic yards of concrete and 10,500 tons of steel were used in constructing the facility. The DWPF’s 10-foot-thick concrete foundation mat is reinforced by 2.25-inch-diameter reinforcing steel. After construction was completed, the facility went through a rigorous testing program prior to startup, during which 80 canisters of simulated glass were poured.
Three different melters have operated as the “heart” of DWPF, melting and pouring the waste stream into canisters. Melter 2 poured more than 10 million pounds of glass and exceeded its design life by more than 12 years. Melter 3 has been operating since 2017. DWPF has poured more than 16 million pounds of molten glass since 1996.