Hanford workers have removed all the highly contaminated “pencil tanks” from the Plutonium Finishing Plant, a key step toward having the plant torn down in 2016.
“This was really a significant achievement,” said Mike Swartz, vice president in charge of work at the plant for CH2M Hill Plateau Remediation Co.
CH2M Hill started work toward removing the pencil tanks in 2008. Initially, the project was expected to be completed in spring 2012.
But the remotely operated crane needed to maneuver the long, skinny tanks has shown its age. Work has repeatedly stopped through the years for repairs to the crane.
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“The crane was never designed to handle the amount of work we put it through,” said Tom Teynor, Department of Energy project director for the Plutonium Finishing Plant.
Before work to remove the tanks started, workers repeatedly entered the contaminated four-story canyon of the plant’s Plutonium Reclamation Facility to repair the crane used in the Cold War. They wore three to four layers of protective clothing and breathed through air hoses. Each worker also carried an emergency air bottle.
The Plutonium Reclamation Facility was built in 1963 to increase the production of plutonium for the nation’s nuclear weapons program. It was used to recover plutonium from scrap material that otherwise would have been waste.
Tanks, ranging from 3 feet to 22 feet long with pointed ends, were shaped to prevent an uncontrolled nuclear reaction during the years when processing was still happening. The canyon held 52 pencil tank assemblies, made up of 196 sections, hanging on steel racks.
The same crane that was used during scrap processing for plutonium recovery was used to remove the pencil tanks from the racks and then hang them in a nearby maintenance bay. Workers reached inside the maintenance area through gloves attached to ports at different heights up and down the bay.
They cut off the bottoms of the tanks, assuring they were empty of processing liquid, as expected. Then they made further horizontal cuts to create shorter pieces. Some of the tanks included valves and piping.
Pieces that are 24 to 40 inches long were place inside a steel container, which was lowered into cardboard tube that was wrapped in a sealed, clean plastic sleeve as it was removed from the maintenance bay. That went into a tube-shaped overpack to be shipped in a waste box to the Hanford Central Waste Complex for temporary storage.
“They are out of the canyon now,” Swartz said. All the pencil tank units have been packaged in the waste boxes and should be shipped to the Central Waste Complex by mid May.
DOE has said in the past that the waste will be disposed of at the Waste Isolation Pilot Plant in New Mexico, but the waste repository will have to reopen first.
Workers were protected from radiation and had to make fewer entries into the canyon by using the remotely operated crane, with work guided by video cameras, to handle the pencil tanks. Use of the crane was picked at the beginning of the project as the safest and least expensive option.
But it was slow and frustrating work, with the DOE Office of Inspector General reporting in 2014 that the crane was out of service for half of the time since early 2010.
CH2M looked at options for the crane, including replacing it, but settled on replacing most of the electrical and mechanical components. That was done by workers using supplied air respirators. The project took much of 2013.
Since then, the crane has performed more reliably, but it still broke down once in October and again in November 2014.
Work went well since then, with workers on the project coming up with ways to increase efficiency and disassembling 25 percent of the units in the past five months.
The last pencil tank to be removed was one of the most complex of the units. It was 22 feet long and had significant piping, flanges and valves, Teynor said.
“Credit for the success goes to the workers and their willingness to work in a hostile environment to safely complete this campaign,” Teynor said.
Work still must be done to prepare the Plutonium Reclamation Facility, one of the main facilities at the Plutonium Finishing Plant, for demolition using heavy equipment.
The crane will continue to be used to load out the remaining debris in the canyon. Then workers will enter the canyon to clean up any debris the crane could not reach. They will check for radioactive hot spots and decontaminate them. Because the canyon is still highly contaminated, they will continue to do the work with supplied-air respirators.
The glove boxes also need to be cleaned out and decontaminated. The building will be opened up enough at the start of demolition to pluck some of them out.
The work completed to remove the pencil tanks is important progress toward demolishing the Plutonium Finishing Plant, which reduces risk on the Hanford nuclear reservation, Teynor said. DOE has called the plant the highest risk facility remaining at Hanford.