Hanford

Hanford workers pump leaked radioactive waste back into tank

Hanford workers spent months preparing for the start of waste retrieval at Hanford’s double shell Tank AY-102.
Hanford workers spent months preparing for the start of waste retrieval at Hanford’s double shell Tank AY-102. Courtesy Washington River Protection Solutions

Hanford workers succeeded in their first attempt to remove leaked waste from between the shells of Hanford’s oldest double-shell tank Thursday.

They pumped some radioactive waste that had leaked out of the inner shell of Tank AY-102 back into the primary tank, following a contingency plan developed months ago with the state of Washington.

Repeated monitoring and inspections have found no evidence that any waste has breached the shell’s outer tank to contaminate the environment. The Washington State Department of Ecology has said there is no risk at this time to the public from the leak within the tank.

Workers also resumed on Thursday working toward the main goal — retrieving stored waste from the tank.

Washington River Protection Solutions had been making good progress this spring toward emptying Tank AY-102. The work was required by the state because of an interior tank leak.

The Department of Energy was working to meet the terms of a settlement agreement with the state to empty the waste into another of Hanford’s double-shell tanks so the cause of the leak can be investigated. The tank had leaked an estimated 70 gallons of waste from its inner shell into the space between the shells in recent years.

Since March 31, Washington River Protection Solutions had pumped out more than two-thirds of the estimated 151,000 gallons of sludge in the tank, working mostly on weekends when fewer people are at Hanford.

We were prepared for this event. Our workforce should be commended for their teamwork and perseverance in safely implementing the contingency plan and procedures, and resuming operations to remove waste from the tank.

Glyn Trenchard, DOE deputy assistant manager

But work stopped after an alarm sounded early Sunday. Significantly more waste had begun leaking from the inner shell, which Hanford and state officials had known was a possibility once pumping of the stored waste began.

Previously, leaked waste from the inner shell had dried in three patches in the space between the two shells, called the annulus. But Sunday the waste in that space continued to rise through the day until it reached about 8.4 inches deep. The annulus is about 30 feet high and about 30 inches wide.

The level of the newly accumulated leaked waste then began to drop, first by about three-quarters of an inch and then more later in the week until the waste in the annulus was about 6.5 inches deep.

As part of preparations to empty Tank AY-102, a pump was installed in the annulus in case the leak worsened.

“We were prepared for this event,” Glyn Trenchard, DOE’s deputy assistant manager for the tank farms, said in a statement. “Our workforce should be commended for their teamwork and perseverance in safely implementing the contingency plan and procedures, and resuming operations to remove waste from the tank.”

Washington River Protection Solutions employees had been working since Monday to prepare to pump the leaked waste from the annulus, including putting radioactive shielding around the line to be used to pump the waste.

Late Thursday morning they started pumping and dropped the waste to about 4 inches — about 1,500 gallons.

Then workers had to stop to replenish the supplied air for their respirators, according to an employee message from Rob Gregory, the Washington River Protection Solutions chief operating officer.

Monitoring and inspections show no visual or chemical indications that waste from the tank has leaked into the environment.

Department of Energy statement

Workers are required to use supplied air because of the risk of chemical vapors from Hanford waste.

As work resumed to retrieve stored waste from the tank Thursday, the level of waste in the annulus again began to rise, as Gregory had predicted it would in a message to employees earlier in the week.

The DOE contractor plans to resume annulus pumping as necessary to keep that waste level as low as possible. The annulus must have at least 5 inches of waste for pumping to start and can be pumped to as low as 2 inches.

When work resumed Thursday to empty the stored waste from the shell, officials estimated that about 46,000 gallons of waste remained, filling the 1-million-gallon capacity tank about 14 inches deep.

In early March most of the liquid waste that sat above the sludge in the tank and helped cool it was pumped into another double-shell tank, which was an easier and quicker task than removing the sludge. In all, 95 percent of the waste in the tank has been removed, according to DOE.

Checks have been made of both the leak detection pit beneath Tank AY-104 and the pH level of the pit’s contents, which includes some precipitation, since Sunday.

Repeated monitoring and inspections have found no evidence that any waste has breached the shell’s outer tank to contaminate the environment. The Washington State Department of Ecology has said there is no risk at this time to the public from the leak within the tank.

“Monitoring and inspections show no visual or chemical indications that waste from the tank has leaked into the environment,” DOE said in a statement.

The inner tank sits on a pad-like structure called a refractory that has narrow air channels to help cool the sludge.

Some of the waste in the annulus may be flowing into the channels, accounting for the drop in the depth of waste in the annulus to 6.5 inches, according to Washington River Protection Solutions. The waste also may be being absorbed into the somewhat porous refractory material.

Hanford has 56 million gallons of radioactive waste stored in underground tanks. The waste is left from the past production of plutonium for the nation’s nuclear weapons program.

Work is underway to empty the waste from leak-prone single-shell tanks into double-shell tanks. With Tank AY-102 permanently out of service, Hanford has 27 usable double-shell tanks to store waste until the vitrification plant under construction can glassify it for permanent disposal.

Annette Cary: 509-582-1533, @HanfordNews

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