Staff Reports
WC Monitor
10/2/2015
Work began this week to demolish the vertical pipe units at Hanford’s high-hazard 618-10 Burial Ground. Remediation of the burial ground and the similar 618-11 Burial Ground have been left for last in Hanford’s river corridor to let workers gain experience with other burial grounds that were expected to be easier. The 618-10 Burial Ground, which is about six miles north of Richland beside a main Hanford highway, was used from 1954 to 1963 for waste generated in the 300 Area adjacent to Richland that researchers thought too radioactive or too hazardous to dispose of at the site. It includes waste from research and development of fuels and chemical separations processes. Trucks would drive north from the 300 Area and back up to drop their loads down pipes vertically buried in the ground. Soil or grout would be added to the pipe after each load to control radiation shine until the pipe was full and it was capped with concrete.
The 618-10 Burial Ground is scheduled to be cleaned up by a Tri-Party Agreement deadline of 2018. However, work on the 618-11 Burial Ground is not expected to be completed by that point. It adjoins the parking lot of Energy Northwest’s commercial nuclear power plant on leased land at Hanford. With Washington Closure Hanford starting the final year of its extended contract for river corridor cleanup, work to complete removal of the 618-10 Burial Ground pipes is expected to be passed to CH2M Hill Plateau Remediation Co. by the end of fiscal 2016.
The 618-10 Burial Ground has 94 vertical pipe units, or VPUs, that were believed to be made by welding together five 55-gallon drums with tops and bottoms removed. But excavations down to the top of each VPU showed that some also were made of 14-inch-diameter corrugated pipe and that 14 were made of steel. The steel VPUs are about 15 to 16 feet long and range from 10 to 22 inches in diameter. There was also an effort before work started to demolish the VPUs to determine what had been disposed of in the pipes. Records were searched, former workers were interviewed, and hollow rods were inserted into the ground around each VPU to allow instruments to be dropped down to take radiation readings at different levels beneath the ground. Much of the waste in the VPUs is expected to be contained in cans with handles that were packed with waste within hot cells. Some of it could be sawdust from cutting damaged or otherwise irregular irradiated uranium fuel, and some of the containers could contain liquid waste, according to Hanford officials.
Demolition will begin on the VPUs made of lighter metal, with the steel pipes left for later. Overcasings that are 4 feet in diameter and 28 feet long have been pounded into the ground around each VPU using a vibratory hammer and crane, said Mark Buckmaster, Washington Closure Hanford project manager. An auger is being inserted in each overcasing to cut through the walls of the VPU and mix the waste and the surrounding soil. Mixing any liquid into the soil should neutralize it, said Mark French, Department of Energy project director for the river corridor. Instruments inserted through the hollow core of the auger take radiation readings as the waste is mixed. A clamshell shovel will be used to scoop the mixture from the overcasing and put it into boxes to be mixed with grout for disposal, French said.
“We are pretty confident the processes are going to work.” said Dennis Faulk, Hanford project manager for the Environmental Protection Agency, at the start of VPU remediation. The grouted waste that is characterized as transuranic will be stored for eventual shipment to the Waste Isolation Pilot Plant in New Mexico and other waste will be taken to the Environmental Restoration Disposal Facility in central Hanford. Tentative plans for the steel VPUs call for digging a hole around each pipe that will be filled with liquid grout. Then heavy equipment will be used to crush the VPUs and their contents, mixing them with grout that will be loaded out to boxes in a soupy mixture.
The 618-10 Burial Ground also has 12 waste trenches in an L-shape around the corner that contains the VPUs. Although historic plans for the burial ground show the trenches in tidy rows, excavations begun in 2011 have found waste scattered throughout the burial ground. Debris also has been deeper than expected, with workers digging down to almost 35 feet to retrieve it, rather than the 20 feet planned. Some of the difference might be due to sand that has blown in to cover the burial ground since it was last used more than 50 years ago, French said.
The burial ground, which covers about seven acres, was used to dispose of about 2,000 drums of waste, thousands of laboratory bottles, construction debris from tearing down buildings, and miscellaneous debris, including old equipment. Workers unearthed a decontamination cell from Hanford’s 327 Radiometallurgy Laboratory. It was used from 1948-1960 to decontaminate tongs, casks, and other equipment. The hot cell weighed more than 20,000 pounds and a crane had to be brought in to lift it out of the burial ground. It was wrapped in plastic and taken to the Environmental Restoration Disposal Facility.
The large number of bottles disposed of in the burial ground was not expected when excavation started, French said. Rather than characterize each individually, they have been stockpiled and then mashed together by an excavator bucket in a waste box. Any liquid or other waste they contain is neutralized by grout as they are crushed.
Drums of waste have held uranium shavings in oil, uranium oxide powders, and miscellaneous debris, all of which have been found at river corridor burial grounds previously remediated. But the 618-10 trenches are the first place where workers have found concreted drums. Dave Martin, Washington Closure project manager, said he believes they were used for high-hazard waste before the VPUs were installed at the burial ground. Waste was placed in a pipe inserted in each drum and then the pipe was surrounded with concrete. The concreted drums that are characterized as transuranic are sent to storage. But those that are characterized as low-level waste that may go to the central Hanford landfill are broken up in a grout mixture inside a box at the burial ground, similar to the process used for bottles. Washington Closure expects workers to find well over 600 concreted drums. Much of the trench remediation has been completed, but some of the trench waste is too close to the VPUs to retrieve until VPUs are removed.