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Image: Double-shell tank
This graphic shows a cutaway view of a double-shell nuclear waste storage tank at the Hanford Site. Liquid waste has pooled up in the space between the inner and outer shell of one tank, designated AY-102. (Credit: Washington State Department of Ecology)

A long-simmering leak inside a double-walled nuclear waste storage tank at the Hanford Site in Eastern Washington got worse over the weekend, sparking an alarm, officials said today.

Online reports from the Tri-City Herald and KING-TV said that the leak detection alarm came on Sunday morning, and that radioactive waste had pooled between the inner and outer shell of Hanford’s Tank AY-102 to a depth of about 8 inches. By today, the waste level had dropped slightly, the U.S. Department of Energy said in a statement emailed to GeekWire.

The Washington State Department of Ecology said there was “no indication of waste leaking into the environment or risk to the public at this time.”

KING quoted a former Hanford worker, Mike Geffre, as saying the leak had become catastrophic. “This is probably the biggest event to ever happen in tank farm history,” he said.

Today’s statements from federal and state officials made the situation sound less dire, however.

The contractor in charge of Hanford’s 1-million-gallon capacity tanks, Washington River Protection Solutions, has been dealing with the AY-102 leak for several years. In the past, sludge containing radioactive and chemical waste seeped into the 2-foot-wide space between the tank’s two walls, known as the annulus, but quickly dried up.

Washington River Protection Solutions began pumping out the contents of AY-102 last month. About 20,000 gallons remain in the tank, and the suspicion is that the pumping activity may have disturbed the tank’s contents in a way that exacerbated the leak into the annulus.

“Additional leaking into the annulus was a known possibility during pumping and is addressed in the Department of Energy’s contingency plan that was submitted to Ecology as part of a Settlement Agreement,” the Department of Ecology said. The Energy Department said the change in the waste level had been anticipated, and that the tank’s condition was being evaluated “out of an abundance of caution.”

The waste level may have dropped after Sunday’s initial detection because some of the liquid went into the tank’s internal ventilation system, the Herald said. The pumping operation has been put on hold while engineers formulate a plan to clean up the leaked waste.

AY-102 is one of 28 underground double-shell tanks at Hanford that hold radioactive toxic waste left over from the production of plutonium for nuclear weapons. The tanks were put into service between 1971 and 1986. AY-102 is one of the oldest tanks.

In 2012 and 2013, the U.S. Department of Energy reported leaks at seven of Hanford’s 177 storage tanks, including AY-102 and six single-shell tanks. The Department of Ecology has said the tank leaks pose “no immediate or near-term health risks” but raise concerns about future groundwater problems.

Update for 7:40 p.m. PT April 18: Columbia Riverkeeper, an Oregon-based environmental group, sent along a statement from executive director Brett VandenHeuvel that noted the leak and added this comment:

“These tanks were not designed to hold waste for decades. It’s past time to get the waste out of the unsafe tanks.

“We thank the workers at Hanford for conducting this dangerous cleanup. This is another reminder of the cost of nuclear waste, and the unexpected outcomes of handling radioactive material. We will continue to push the Department of Energy for a thorough and transparent cleanup in the face of mounting challenges.”

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