The US Hanford site vitrification plant has started heating the first of two 300-tonne melters at the $17 billion plant’s Low Activity Waste Facility with the goal of starting to treat radioactive waste by the end of 2023, according to the US Department of Energy (DOE). Construction of the first melter started 20 years ago and it must now remain hot continuously as it initially makes practice glass and then begins vitrifying low-level radioactive waste.

DOE’s goal is to start vitrifying radioactive waste stored in underground tanks, some since World War II, by the end of 2023. The 580-square-mile Hanford nuclear reservation near Richland in Eastern Washington produced about two-thirds of US plutonium for its nuclear weapons programme from World War II during the Cold War. Uranium fuel irradiated at Hanford was chemically reprocessed to remove plutonium. The mix of radioactive and other hazardous chemical waste from reprocessing has been stored in underground tanks, many of which are prone to leaking. They hold 56 million gallons of the waste until it can be treated for disposal.

“Over the last two years, the Department and its One Hanford contractors have made significant progress in the Direct-Feed Low-Activity Waste (DFLAW) Program to prepare for treating tank waste,” said Brian Vance, manager of DOE Environmental Management’s Office of River Protection and Richland Operations Office. “We are building on this progress by beginning to heat up the first WTP melter using a disciplined approach.”

The melters are expected to operate continuously for at least five years. “When we finish heating up the first melter, that will be another significant step in commissioning the Waste Treatment and Immobilisation Plant (WTP) for future operations,” said Val McCain, project director for Bechtel National. Bechtel holds the contract for building, starting up and commissioning the vitrification plant. The melters each measue about 6 metres by 9 metres and are almost 5 metres high.

“Permanently removing the waste from Hanford’s tanks and solidifying it is one of the most important elements of the entire clean-up mission, and melter heat up is an extremely important step in that process,” said David Reeploeg, the Tri-City Development Council vice president for federal programmes and the executive director for Hanford Communities, a coalition of Hanford area local governments. 

DOE and Bechtel plan a “disciplined approach” to heating up the first melter to 2,100 degrees Fahrenheit, said Brian Vance, DOE’s Hanford site manager. Workers are expected to spend about two weeks gradually heating the melter as glass beads are added in batches to be melted during the initial test run. The molten glass that results will be poured into a stainless steel container and removed from the building. Once the melter is fully commissioned and begins to treat radioactive waste, the glassified radioactive waste it produces will be buried at the Integrated Disposal Facility, a lined landfill in central Hanford.

Initially, the vitrification plant will only treat only low activity waste. Construction on the plant’s High Level Waste Facility has been mostly stalled since 2012 when technical issues caused DOE to shift its focus to treating low activity waste first. DOE faces a federal court deadline to also be treating high level radioactive waste, in addition to the initial treatment of low activity waste, by 2033 and to have the vitrification plant for that fully operating by 2036

The heating of the melter is done gradually to slowly dry out the insulation and the temperature cannot be reduced without damaging the insulation, which can harden and become ineffective if the temperature cools. Once the melter temperature reaches 2,100 degrees, there will be up to two months of evaluation and checks.  Richland company, Fluid Controls and Components, is supplying 108,000 pounds of the glass beads known as “frit” needed for the nonradioactive commissioning of the facility. It mimics waste by dissolving into a solid form at high temperatures.

“It was the first time we dealt with frit,” said Russ Watson, vice president of the Richland company, as the company worked to make the first delivery. “The chemistry and physical profile of the frit were very complex. The specifications were strict, and the monitoring process was extensive.” Lessons learned from heating up the first melter will be used to begin the same process for the second of two melters. Once both are at operating temperature, the facility next will heat up a nonradioactive simulant of tank waste with glass former as part of preparations to treat radioactive waste. Because the melters have an expected lifespan of five years, preparations have begun to assemble spare melters to have them ready when the first melters need to be replaced.

Construction was completed in early 2021 on parts of the plant that will be needed to treat low activity waste. The Low Activity Waste Facility will be supported by the vitrification plant’s Analytical Laboratory, which will ensure the quality of the glass waste form produced; the Effluent Management Facility, which will help manage waste produced during treatment; and 14 support structures that will provide services such as water purification and electrical power.

In the summer of 2021 Hanford workers finished construction of the 3,500-foot-long pipeline between the tank farms storing waste to be treated and the vitrification plant. The line uses a reinforced pipe within a pipe to guard against leaking as waste is moved to the vitrification plant in batches. Early this year, work began to pretreat tank waste to prepare it for vitrification. The Tank Side Cesium Removal System, or TSCR, started up in January, as the first industrial-scale processing of radioactive tank waste to prepare it for disposal in the Hanford site’s history. Waste that has been pretreated to remove high level radioactive waste constituents to allow it to be treated as low activity waste is being stored until the startup of the vitrification plant.

Image: A Hanford vitrification plant crew installs one of 18 startup heaters into the lid of the first melter to begin to be heated up inside the Low Activity Waste Facility (courtesy of Bechtel National)