Work to empty Hanford’s oldest double-shell tank is expected to start anytime as a March 4 deadline looms.
The underground tank, AY-102, is leaking radioactive waste between its shells, and the state of Washington requires the approximately 800,000 gallons of waste it holds be removed. The waste is left from the past production of plutonium for the nation’s nuclear weapons program.
DOE has made the work a top priority over the past 18 months, said Dieter Bohrmann, spokesman for the Washington State Department of Ecology, the regulator for Hanford tanks.
“We’re encouraged by the resources they’ve committed to meet the deadline and keep on schedule,” Bohrmann said.
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Pumping the liquid portion of the waste out of the tank is expected to take a few days, with the liquid transferred by underground pipe to a sturdier double-shell tank near Hanford’s evaporator plant.
27 number of Hanford double-shell tanks that remain in service
The plant is used to evaporate liquid waste to free up more space in the 27 double-shell tanks at Hanford that remain usable. Single-shell tanks, some of which have held waste since World War II, are prone to leaking into the ground and are being emptied into double-shell tanks until the waste can be treated for disposal.
The liquid was left in place to help keep the radioactive sludge beneath it from overheating until the infrastructure was in place for the much more difficult job of retrieving the sludge.
Sludge retrieval is expected to start later this month after contractor Washington River Protection Solutions samples the sludge and positions the sluicers installed in the tank. The sluicers spray a jet of recycled liquid on the waste to dissolve it and move it toward a central pump.
The sludge will be transferred through above-ground transfer lines to a double-shell tank closer to the Hanford vitrification plant, which is planned to eventually glassify the waste for permanent disposal.
DOE has one year from this week to remove waste from Tank AY-102.
In late spring or early summer, the contractor is expected to stop retrieval long enough to replace the current sluicers with extended reach sluicers. They can reach deeper into the tank and fold out to reach more areas. They also have a high-pressure water system that may be needed to break up hardened waste at the bottom of the tank.
The state has given DOE until March 4, 2017, to have the tank emptied.
About 60 gallons of waste was believed to have leaked in three places into the 2.5-foot-wide space between the tank’s shells, as of the end of 2015. The waste is not believed to have breached the outer shell of the tank to contaminate the environment.
Emptying the tank, which has held waste since about 1970, will allow it to be inspected to learn what caused the leak. That could provide helpful information regarding Hanford’s other double-shell tanks, according to DOE.