Results are promising from the initial testing of a system planned to clean up Hanford research waste dropped down pipes buried vertically in the ground, according to Hanford officials.
The 618-10 Burial Ground about six miles north of Richland and just off the main Hanford highway has 94 buried pipes, called vertical pipe units. It's believed to be one of the two highest-hazard burial grounds in the area not far from the Columbia River.
Some of the worst of the research waste generated at Hanford's 300 Area just north of Richland was dropped down the pipes from 1954-63 in containers ranging from the size of juice cans to buckets.
The Department of Energy and Washington Closure Hanford are planning to pound steel overcasings into the ground to surround each vertical pipe unit, essentially providing a new way to contain the waste. Then they plan to pulverize the waste and the vertical pipe unit.
To make sure the system works, Washington Closure has installed mock vertical pipe units near the 618-10 Burial Ground to test it.
Initial testing has been done on two types of the pipe unit, with work yet to be done on a third and likely the most challenging type.
As cleanup planning began, all the vertical pipe units were believed to be made of five 50-gallon drums without tops and bottoms welded together to form a pipe. But the first 27 vertical pipe units were made from corrugated pipes 12 to 14 inches in diameter buried in the ground.
Those are the two types used in the first tests of the system. But in addition, some of the pipes now are believed to be made of steel and might be different sizes.
In the tests, steel overcasings 30 feet long and 48 inches in diameter were driven into the ground with a hydraulic hammer around the vertical pipe units. Then an auger chewed up the mock waste and the original pipes, using water for dust suppression, and mixed it up with some of the soil surrounding the original pipes.
"It was very, very good size reduction," said Mark Buckmaster, project manager for the 618-10 vertical pipe units. "It comes out looking like sand and gravel."
Washington Closure plans to start work as soon as next month to learn more about the quantity of each type of vertical pipe units in the burial ground, before proceeding with more testing, which will include the first tests of the system on one of the steel vertical pipe units.
Workers will dig down enough to uncover the top of 30 of the vertical pipe units, which were sealed earlier with concrete plugs. No more than two are expected to be uncovered at a time. Photos of construction of the vertical pipe units show what type of pipes were used for the other 64 units.
Hanford officials already have some knowledge of what's in the vertical pipe units after four narrow steel cylinders were pushed into the ground around each of them, allowing radiation detectors to be lowered to take readings.
Some of the data showed that some waste likely was cesium 137, which likely indicates highly radioactive fuel or pieces of fuel from Hanford reactors. Others have indications of cobalt 60, likely from radioactive reactor parts that failed and then were brought to the 300 Area for testing.
Generally, there were one or two isolated hot spots in each pipe, Buckmaster said.
Plans call for pulling up samples of the waste after it is augered, using the hollow center of the auger, to learn more. There is no good way to sample the waste before it is crushed and mixed by the auger, according to Hanford officials.
Some of the waste is expected to be classified as low-level radioactive and hazardous chemical waste, which can be mixed with grout and sent to the Environmental Restoration Disposal Facility, a lined landfill in central Hanford.
Early plans call for injecting grout through the hollow stem of the auger and then digging up the grout and any surrounding soil or soil at the bottom of the column that might be contaminated for low-level waste.
However, some of the vertical pipe unit waste might be classified as transuranic waste -- generally waste contaminated with plutonium or americium with radioactivity that decays over thousands of years. That waste must be packed for disposal at the nation's repository for transuranic waste, the Waste Isolation Pilot Plant in New Mexico.
For vertical pipe units with transuranic waste, Washington Closure plans to build an enclosure on the ground at the top of the pipe and then use heavy equipment operated outside the enclosure to scoop out the waste. It would be packaged into drums and then taken to central Hanford for further characterization, to make sure it meets the requirements for the repository.
A Hanford Advisory Board committee heard an update on plans for the burial recently ground , and several members had concerns.
"I am concerned about releases in the environment," Shelley Cimon said.
The waste is contained in cans, but it would be released and mixed, she added.
Other members are concerned that waste that would be considered transuranic before the waste is mixed together could be reclassified as low-level waste, allowing it to be sent to the Hanford landfill.
Questions also were raised by board members about the wisdom of pulverizing containers, some of which contain liquids.
"The amount of liquids is very minor," Buckmaster said.
Plans are being made for more testing of the system on the mockup vertical pipe units. Among refinements could be work to make sure the waste is evenly spaced from top to bottom. The cleanup work on the actual vertical pipe units could start in summer of 2015. The legally binding Tri-Party Agreement calls for the cleanup to be finished in 2018.
The 618-10 Burial Ground also has 12 trenches where bottles of laboratory waste and drums of radioactive waste were buried in the soil. Work to clean up the trenches is about 80 percent complete, according to DOE.
The high-hazard 618-11 Burial Ground also was used to bury research waste, and the method developed for the vertical pipe units at the 618-10 Burial Ground also will be used there.
The 618-11 Burial Ground, which is just off the parking lot of Energy Northwest's nuclear power plant, has three 900-foot-long trenches, 50 vertical pipe units and four caissons, or underground boxes with angled chutes.
-- Annette Cary: 509-582-1533; firstname.lastname@example.org; Twitter: @HanfordNews