Hanford has started up its tank waste evaporator to reduce the volume of radioactive and hazardous chemical waste stored in the nuclear reservation's underground tanks by about 500,000 gallons.
The work will free up space in Hanford's double-shell tanks as waste is emptied into them from older and leak-prone single-shell tanks.
Space in double-shell tanks is at a premium as work continues to build the $12.3 billion vitrification plant, which will treat the waste for disposal starting in 2019. Hanford has about 53 million gallons of radioactive waste stored in underground tanks, and its 28 double-shell tanks can hold just 28 million gallons of waste.
Concentrating the waste helps avoid the cost of building new double-shell tanks at Hanford, according to the Department of Energy and its contractor, Washington River Protection Solutions.
No tank is being emptied now, but Washington River Protection Solutions expects to begin retrieving the remaining waste from single-shell Tank C-111 this month.
The evaporator has not been run since 2009, which is a typical schedule. Last year it reduced waste in the double-shell tanks by about 940,000 gallons.
"The evaporator is critical to the safe and timely cleanup of Hanford's tank waste," said Stacy Charboneau, DOE assistant manager for the tank farms, in a statement.
Since the 242-A Evaporator began operating in 1977, it has reduced the total volume of tank waste by about 67 million gallons. Liquid has to be added to the waste for some of the techniques used to empty single-shell tanks, and liquid also is needed to thin some of the waste enough to allow it to be pumped from tank to tank.
The evaporator heats liquid tank waste in a vacuum to allow it to evaporate at about 125 degrees. Water vapor from the boiling waste is captured and condensed. It's then filtered and sent to the nearby Liquid Effluent Retention Facility for more treatment before it is disposed.
The concentrated waste then is returned to the double-shell tanks.
Since the evaporator last was operated, work has been under way to maintain and improve the 33-year-old facility. Federal economic stimulus money was used to improve the raw water service building, which provides the evaporator with an average of 2,500 gallons of water per minute to cool equipment and condense the water vapors during processing.
During the 2009 evaporator campaign, the raw water service building's pressure control assemblies and filters failed and brought operations to a standstill. With no replacement parts available, the equipment was repaired and rebuilt, but engineers determined that more work was required to allow long-term operation of the evaporator.
Other work at the evaporator has included decontaminating the condenser room so that it is easier for workers to do maintenance there and a complete overhaul of operating procedures, said John Britton, spokesman for Washington River Protection Solutions. A cold run was conducted in May.
The evaporator originally was expected to operate until about 1987, but its life was extended until 2018 with major upgrades between 1994 and 2004. Additional upgrades are expected to keep the evaporator running until 2040 to support the feed of radioactive waste to the vitrification plant.