The Department of Energy has met legal deadlines to have 77 Hanford waste sites along the Columbia River cleaned up, it announced Wednesday.
The waste sites were near the D and H plutonium-production reactors near the horn of the Columbia River as it cuts through the Hanford nuclear reservation.
DOE had two Tri-Party Agreement deadlines to get the waste sites cleaned up by the end of 2011. Previously, 45 waste sites in the two areas had been cleaned up.
Work began to clean up the sites as early as 2005, but much work remains. DOE and its contractor Washington Closure Hanford still have more than 100 waste sites, some of them newly identified, to clean up near the two former reactors, said Cameron Hardy, DOE spokesman.
The sites included debris from reactor operations that was disposed of by burial during World War II and the Cold War. The waste near the Columbia River now must be dug up to meet modern environmental standards.
"There definitely were some challenging waste sites," Hardy said.
The most dangerous waste found was irradiated fuel fragments.
Washington Closure developed new technology for the waste sites near D Reactor to detect irradiated fuel before it left the excavator bucket. The irradiated fuel looks much like thousands of spacers that also ended up in reactor debris burial grounds.
As waste is lifted out of a burial ground, the excavator operator pauses with the bucket raised halfway to allow the Compton Ratio Analysis for Testing Environmental Radioactivity, or CRATER, to run for 15 seconds to check for irradiated fuel.
The technology can detect gamma radiation from cesium 137 in irradiated fuel and distinguish it from the cobalt 60 found in most of the other irradiated and rusting metal discarded in the burial grounds. It reduces handling of the waste and the possibility of worker radiation exposure.
Cleaning up the 77 waste sites required removing 1.2 million tons of soil and debris containing heavy metals, hydrocarbons, gas, diesel, oil-based liquids and radioactive constituents, including the irradiated fuel fragments and irradiated reactor hardware.
Most of the soil and debris was taken to the Environmental Restoration Disposal Facility, a lined landfill in central Hanford. However, irradiated fuel is required to be sent to a federal repository when the nation establishes one for spent fuel.
DOE plans to have most cleanup of Hanford along the Columbia River completed in 2015.