A little more than a half-century ago, large cask trucks, heavily shielded to provide protection against radiation, would leave the Hanford 300 Area just north of Richland with loads of highly radioactive or particularly hazardous waste that researchers did not want buried too close to town.
They’d arrive at the 618-10 Burial Ground along the main Hanford highway six miles north of Richland and back into position to drop their loads down pipes buried vertically in the ground. In between loads, each layer of waste would be topped with soil or grout to reduce the shine of radiation out of the top of the pipe.
When one pipe was filled, it would be capped with concrete and the next pipe would be filled. By the time the Department of Energy stopped using the burial ground in 1963, some 94 buried pipes had been filled with waste.
This week, weather permitting, work is expected to start to excavate the first of the pipes.
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They are referred to at Hanford as vertical pipe units, or VPUs.
The 618-10 and the similar high-hazard 618-11 farther north have been left for last among Hanford burial grounds near the Columbia River. Workers gained experience before tackling those expected to be the most hazardous.
DOE’s contractor for the work, Washington Closure Hanford, has some idea of what’s in the vertical pipe units. It has found photos and records and conducted interviews with former workers familiar with 618-10 when the vertical pipes were filled from 1956 to 1963. Washington Closure also has inserted hollow tubes into the ground around the pipes to lower instruments to take radiation readings.
But Hanford projects typically have surprises.
At 618-10, the vertical pipe units had been expected to be comprised of five 55-gallon drums, tops and bottoms cut off and welded together. That’s the case for many of them, workers found as they dug a hole next to each pipe to confirm their type and location. Some also are made from 14-inch-diameter corrugated piping.
But workers have discovered that 14 are made of steel, each about 15 to 16 feet long and 10 to 22 inches in diameter.
Those pipes will be left for last as workers proceed with a plan tested in a mockup to remove the other 80 pipes.
“We are thrilled that they are moving forward with the VPUs,” said Dennis Faulk, Hanford program manager for the Environmental Protection Agency. “We are pretty confident the processes are going to work.”
Overcasings that are 28 feet long and 4 feet in diameter have been driven into the ground around the pipes using a vibratory hammer and a crane, said Mark Buckmaster, a Washington Closure project manager.
Now workers are ready to start up an auger that will chew through the vertical pipe units, mixing up the waste, pieces of the pipe and the soil between the walls of the pipe and the overcasing. The center of the auger is hollow, allowing radiation readings as the auger mixes the waste and soil together.
Then a clamshell shovel will be used to scoop up the mixture in the overcasing and put it into a box to be mixed into grout, said Mark French, DOE project director for Hanford cleanup near the Columbia River.
Hanford workers expect to find sawdust from cutting damaged or failed irradiated reactor fuel into small pieces and metal from reactors. Much of what’s in the pipes is expected to be solid waste that was packaged in hot cells into cans with handles, but there also could be small amounts of liquid within the cans.
Mixing the liquid into the soil during augering will help stabilize it before it is lifted out of the ground, French said.
Waste will either be disposed of at the lined landfill for low-level radioactive waste in central Hanford or packaged for eventual shipment to the nation’s repository for transuranic waste, the Waste Isolation Pilot Plant in New Mexico. At Hanford, transuranic waste is typically debris contaminated with plutonium from past production for the nation’s nuclear weapons program.
A different plan will be needed for the 14 steel pipes. DOE expects a hole to be dug around them, making a bowl-shaped indentation into which liquid grout can be poured. Then everything in the hole can be crushed and mixed together, with the soupy mixture loaded out to a waste disposal box.
With Washington Closure having just a year left on its contract under the current extension granted by DOE, it’s expected to start the work and then the project will be passed to CH2M Hill Plateau Remediation Co., which is responsible for much of the central Hanford cleanup.
The 7.5-acre 618-10 site also has 12 waste trenches in an L-shape, with the vertical pipe units tucked into a corner of the burial ground.
Work that started in 2011 to dig up those trenches is nearing completion, with the exception of some waste too close to the buried pipes to excavate until the pipes are cleaned up.
The trenches, used as early as 1954, also have revealed surprises.
Workers found a decontamination cell weighing at least 20,000 pounds buried in the trenches. It’s believed to have come from Hanford’s 327 Radiometallurgy Laboratory. The chamber was used from 1948-60 to decontaminate tongs, casks and other equipment that needed to be repaired.
“It was too big to lift with an excavator,” said Dave Martin, a Washington Closure project manager. A crane was brought in to remove it from the trench. It was wrapped in plastic and disposed of in the central Hanford landfill, the Environmental Restoration Disposal Facility.
Although historical drawings of the burial ground showed a tidy grid of trenches, workers have uncovered debris throughout the burial ground and deeper than expected, French said.
Workers expected to go down 20 feet, but waste has been found down to almost 35 feet. That’s in part because of sand that has blown in to cover the burial ground since it was closed in 1963.
By the time the trenches are excavated, DOE expects 2,000 drums of waste to be removed.
More than 600 drums are expected to be unearthed that are lined with concrete, a type of waste container not found in burial grounds cleaned up earlier at Hanford. A pipe was nested inside the concrete and used to hold waste with higher levels of radioactivity.
They likely were a waste disposal container that predated the vertical pipe units, Martin said.
If radiological surveys of the drums show they may contain transuranic waste, they are stored for eventual shipment to the Waste Isolation Pilot Plant in New Mexico. Other drums are destroyed, with their waste and concrete mixed with grout before they are sent to central Hanford for disposal.
Other drums have held uranium shavings in oil, uranium oxide powders and miscellaneous debris, all of which have been unearthed at previously cleaned up Hanford burial grounds. Construction debris from tearing down some old buildings also has been unearthed.
The trenches also have contained an unexpectedly high number of laboratory bottles — thousands of them, French said.
Rather than checking each bottle individually, they are stockpiled and then an excavator bucket is used to mash them up together within a box filled with a grout mixture, breaking the bottles and releasing any liquid.
“First and foremost it is safer for the workers,” French said.
The 618-10 Burial Ground is scheduled to be cleaned up by a legal deadline of 2018. The start for cleanup of the 618-11 Burial Ground has yet to be scheduled.