The Department of Energy has completed work to empty as much waste as possible from Hanford’s double-shell tank with an interior leak, according to a notification to the state Department of Ecology.
DOE was required by a settlement agreement with the Department of Ecology to have the tank emptied of enough waste to determine the cause of the leak by March 4.
“Preparations for tank inspections are being initiated,” the notice said.
Tank AY-102, Hanford’s oldest double-shell waste storage tank, held about 744,000 gallons of radioactive and hazardous chemical waste when work started to empty it almost a year ago on March 3.
After using two different technologies to retrieve waste from the enclosed, underground tank, DOE contractor Washington River Protection Solutions removed about 98 percent of the waste in the tank, according to a memo sent to its employees Tuesday. The contractor estimates about 19,000 gallons of sludge remain in the tank.
Tank AY-102 was slowly leaking waste into the space between its shells when a settlement agreement was reached in 2014 between the state and DOE, setting deadlines for emptying it. The waste is not believed to have breached the outer shell of the tank to contaminate the environment.
The Department of Ecology is “now awaiting confirmation from DOE demonstrating that they have in fact met the retrieval criteria set out in the settlement agreement,” Ecology said in a statement Tuesday.
A video inspection of the tank will be done next, said the memo to employees signed by Mark Lindholm, president of Washington River Protection Solutions, and Dave Molnaa, president of the Hanford Atomic Metal Trades Council. HAMTC is a coalition of unions doing work at Hanford.
“Follow-up activities to further investigate or implement additional retrieval will be planned and executed based on the result of the video inspection,” the memo said.
Information learned from inspecting the tank after removing waste may be helpful in assessing the condition of Hanford’s 27 double-shell tanks that remain in service.
Waste is being emptied from Hanford’s older, leak-prone single-shell tanks for storage in double-shell tanks until the waste can be treated for disposal. The waste is left from the past production of plutonium for the nation’s nuclear weapons program.
DOE also has not ruled out the possibility of determining if Tank AY-102 could be repaired and put back into service, although officials have said a return to service seems unlikely. The tank, which has held waste since about 1970, had documented construction issues.
Washington River Protection Solutions did an exceptional job planning, coordinating and executing the work to retrieve waste, said Kevin Smith, manager of the DOE Hanford Office of River Protection, in a statement Tuesday.
“I’m very proud of them for meeting the schedule commitment under challenging conditions, including our unpredictable winter weather,” Smith said.
More than two years of work was needed to improve infrastructure at AY-102 and the double-shell tank that now holds the waste before retrieval work began.
Some of it was high-risk work, as the memo to employees pointed out. The construction team had to use specialized long-reach tools to remove old equipment, including five obsolete pumps contaminated with radioactive waste.
The tank, which has a capacity of about 1 million gallons, had 593,000 gallons of liquid waste that was quickly pumped out when retrieval started last year. But the estimated 151,000 gallons of waste in the form of sludge it held were more difficult to remove.
Work to remove the sludge began with two standard sluicers, a technology that has been used in the past to empty tanks. But four extended-reach sluicers that are more flexible and can reach more areas within the tank also were prepared.
Work began with those sluicers in December and continued until this month, when little more waste could be retrieved with the technology. The sluicers spray liquid waste on sludge to break it up and move it toward a pump for removal from the tank.
The project shows “how critical work can be accomplished safely and effectively when labor and management work together to resolve our issues and concerns,” said the memo from Lindholm and Molnaa.
Multiple control systems were used to protect workers from hazards, including the potential exposure to chemical vapors, they said.