More than two decades after construction of the Hanford nuclear site’s massive vitrification plant began, the plant has taken one of the final steps to begin treating waste for disposal as soon as this summer.
Bechtel National workers have begun operating the plant using chemicals that simulate the radioactive and hazardous chemical waste that will be treated there.
The plant will initially turn some of the least radioactive waste stored in underground tanks for as long as 81 years into a stable glass form.
“Beginning nitrate feed is the next crucial step in starting environmental testing of the Low-Activity Waste Facility and ensuring operations are protective of human health and the environment,” said Suzanne Dahl, section manager of tank waste treatment at the Washington state Department of Ecology’s Nuclear Waste Program.
Ammonia and nitrous oxide-producing chemicals are being added to plant’s melters along with glass-forming material that is heated to 2,100 degrees Fahrenheit. The molten mixture will then be poured into stainless-steel containers for disposal at a lined landfill at Hanford after cooling.
Turning the waste simulant into a stable glass form tests the glassmaking system and its components, including demonstrating that its exhaust system works as designed to filter off-gases released through its stack.
The plant will next need to pass a state Department of Ecology environmental performance demonstration and then a federal operational readiness review.
If work proceeds as planned, Bechtel National could start making glass that incorporates radioactive waste as soon as late July and have a full 4 foot-by-7.5 foot canister of glassified waste in August.
That will be 23 years after ground was broken to build the Hanford Waste Treatment Plant, commonly called the vitrification plant.
The radioactive waste is left from chemically processing uranium fuel irradiated in Hanford reactors to produce nearly two-thirds of the plutonium from World War II through the Cold War.
The work left 56 million gallons of a mix of radioactive and hazardous chemical waste stored in underground tanks, some of them prone to leaking, until the waste could be treated for disposal.
The Low-Activity Waste Facility will have two 300-ton melters for heating up the waste mixture, making them the largest waste glass melters in the world at three times or more larger than any others, including those used in France, England and at the Department of Energy’s Savannah River, S.C., site.
Once the first radioactive waste is glassified at the vitrification plant in a step called hot commissioning, Bechtel National will continue treating radioactive waste for six to 18 months before the work transitions to the new Hanford tank waste contractor, said Mat Irwin, the DOE assistant manager for the vitrification plant, at the May meeting of the Hanford Advisory Board.
Hanford Tank Waste Operations and Closure, or H2C as it is called at Hanford, was awarded the contract to manage radioactive tank waste.
H2C — a joint venture of BWX Technologies, Amentum and Fluor — in February completed a four-month transition period with the outgoing contractor to manage the Hanford waste storage tank farms and then take over vitrification plant operations for low-activity waste treatment.
DOE will pick the right time for H2C to start the transition for vitrification plant operations from Bechtel National, based on what tank projects H2C is working on and unrelated activities at the vitrification plant to prepare for treating the most radioactive waste, Irwin said.
The High Level Waste Facility is still under construction at the vitrification plant to treat the most radioactive waste in Hanford’s underground storage tanks. A federal court consent decree requires that treatment to begin in 2033.
Vit plant safety issue addressed
One of the last hurdles DOE had to clear to begin operating the plant with simulated waste was an unexpected need to inspect and repair the ammonia system for the low-activity waste treatment portion of the plant.
The plant has two tanks, each approximately 24 feet long and 7 feet in diameter, with a capacity of 6,000 gallons of ammonia each.
When the vitrification plant is treating waste, it will release oxides of nitrogen into the Low-Activity Waste Facility’s exhaust system.
Ammonia will be used to cause a chemical reaction that significantly reduces the level of oxides of nitrogen to meet air permit levels.
There were two incidents where workers were told to take cover indoors after ammonia was added to the system and leaks were detected.
The first take-cover order was in December for part of central Hanford and the second take-cover incident was in the spring and was for workers only on the 65-acre vitrification plant site.
Degraded gaskets were replaced and the valves were rebuilt in the ammonia system.
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