75,000 gallons of rad-hot sludge and counting

In early 2014, evidence of radioactive pollution was discovered in the city of Oak Ridge’s sewage treatment facility on the west side of town.

sludgeThe unwelcome surprise was blamed on technetium-99 that had migrated from a demolition project at the federal government’s K-25 uranium-enrichment plant on the other side of the Clinch River.

The radioactive contaminants, which can be mobile in the environment, had infiltrated pipelines leading to the sewer system.

Although the radioactivity reportedly didn’t not pose a health threat to workers at the plant or drinking water supplies in the area, it prompted a number of cleanup actions — including efforts to remove the technetium in the sewage treatment systems.

Over the past two years, about 75,000 gallons of radioactive sludge have been removed from the city facility and shipped out west for treatment and eventual disposal. But the Oak Ridge problem still hasn’t been resolved fully, and it’s not clear when it will be.

“Overall Tc-99 levels continue to decline within the Rarity Ridge Treatment Plant, but it is premature to estimate the exact number of shipments (of sludge) or even the estimated time frame that will be needed to bring the facility back to normal operating parameters,” Anne Smith, a spokeswoman for UCOR (URS-CH2M Oak Ridge), the Department of Energy’s cleanup manager in Oak Ridge, said in an email response to questions.

On Nov. 5, UCOR made the 15th shipment — each of them 5,000 gallons — from the Oak Ridge treatment plant to a Perma-Fix Environmental treatment facility in Richland, Wash. The next shipment will likely take place in January, according to the DOE contractor.

Smith said the weather, particularly rainfall amounts, can elevate the radioactivity levels at the sewage treatment plant and have an impact on the number of sludge shipments.

“Rain events are similar to a cleansing mechanism and carry more debris through the system, which increases the suspended solids,” she said. “The Tc-99 concentrates with the solids and thus increases the levels of Tc-99 being accumulated in the sludge and, as a result, into the tanker.”

Lower levels of suspended solids typically occur when rainfall is minimal, she said.

“UCOR and the city of Oak Ridge continue to watch this correlation very closely and adjust the shipment schedules to maximize the amount of Tc-99 being removed (from the sewer treatment system) for shipment,” Smith said. Maximizing the radioactive material removed during this process will reduce the number of waste shipments necessary, she said.

Last year, after the problem was discovered, the Department of Energy and its contractor took steps to isolate the pipelines near the K-25 demolition site and prevent them from reaching the lines that lead to the sewage treatment facility.

City officials have generally praised DOE and its contractor for its response to the problem.
UCOR said it is managing the sludge for the city of Oak Ridge until the radioactivity levels “subside back to a level where they can manage it per their normal protocols.”

As part of its response, UCOR has taken steps to better contain the radioactive and hazardous contaminants associated with the demolition rubble at cleanup sites.

The contractor said it is applying lessons learned from the K-25 project — one of the biggest demolition projects in history — to upcoming work at the K-27 facility, which also has trace amounts of radioactive technetium in its old equipment.

Smith said UCOR will either remove piping contaminated with technetium-99 before demolition begins or seal the equipment with a foam to keep the contamination in place as the building is torn down.

Most of the demolition rubble will be sent to a local landfill that’s designated for Superfund cleanup wastes. However, some of the equipment won’t qualify for disposal there because of high levels of radioactivity or other reasons.

Smith said those pieces of equipment will be painted so they can be easily identified and segregated. They will later be chopped up to prepare for disposal and kept until cover to prevent the spread of contamination.

“Components pulled from the demolition debris will be shipped on an expedited schedule to minimize the time they are in the field,” Smith said.

This is another attempt to keep rainfall from carrying away loose contamination at a demolition site.

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