Hanford contractor beats DOE expectations on waste-filled buried pipes.
Work on the landfill, considered among Hanford's most hazardous, had been scheduled as one of the last environmental cleanup tasks along the Columbia River. It's the final high-hazard project undertaken by Washington Closure before its DOE contract expires at the September's end after 11 years.
Because the contractor didn't know exactly what the pipes might contain, the goal had been to finish augering just 28 of the buried pipes by the contract's end. Instead, it finished the work on all 80 pipes for which augering could be done.
The 618-10 Burial Ground was one of just two burial grounds at Hanford to use vertically buried pipes, called vertical pipe units, to dispose of radioactive and hazardous chemical waste.
Work on the other one, the 618-11 Burial Ground by the parking lot of Energy Northwest's nuclear power plant, has yet to start. But less waste is expected to be buried there.
From 1954-63, large cask trucks, heavily shielded to provide protection from radiation, carried highly radioactive laboratory waste to the 618-10 Burial Ground about six miles north of Richland along the main highway to the Hanford Wye Barricade. There the trucks would back up to the pipes and drop their cargo down.
Washington Closure came up with a cleanup method that called for driving overcasings that are 28 feet long and 4 feet in diameter vertically into the ground around the pipes, isolating them.
In September, workers started using an auger to chew through the vertical pipe units, mixing up the waste they hold, pieces of the pipe and the band of soil between the walls of the vertical pipe units and the overcasings.
The process was used on 80 of the 94 vertical pipe units. The last 14 vertical pipe units were discovered to be made of thick-walled steel, a surprise not revealed in historical records. Those 14 will require a different cleanup technique.
The 80 vertical pipe units that Washington Closure has augered were made from 14-inch-diameter corrugated piping or from five 55-gallon drums, tops and bottoms cut off and then the drums welded together.
Some of the waste at 618-10 came out of hot cells where workers handled materials that were so radioactive that crews stood outside to manipulate tools inside the cells and watched their work through thick leaded-glass windows.
Full-scale mockups of vertical pipe units filled with waste to mimic the nonradioactive waste showed that augering could mix the waste into the soil well. Any chemical reactions from the mix of research waste would be contained within the soil.
Washington Closure started digging up the augered waste this spring, using a clamshell shovel lowered into the overcasing to bring up the waste and soil mixture, then deposit it in a nearby steel box to be mixed with grout for disposal.
Workers have loaded out the waste from 27 of the 80 augered vertical pipe units, with more expected to be finished this month.
The 7.5-acre burial ground also had trenches where waste--including about 1,900 drums, some with uranium shavings in oil or other radioactive material surrounded with concrete shielding--was buried in the ground up to 35 feet deep.
Washington Closure has finished digging up all of the waste except for some that's close to vertical pipe units. It is being cleaned up as the pipe units are removed. Once Washington Closure leaves Hanford, CH2M Hill Plateau Remediation Co. will finish up the work at the 618-10 Burial Ground.
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|Publication:||Nuclear Waste News|
|Date:||Aug 12, 2016|
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