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Home » Cover Story, Features, In this month's issue:

REMOVING HIGH-RISK COMPONENTS FROM K-25 DEMOLITION CONTINUES

Submitted by on January 20, 2013 – 10:43 pmNo Comment

This article first appeared in the NDR January 2013 issue, Page 8, by author Fran Smith

 

In a complex task made more complicated by building conditions, historical restraints, and the fact that it was just plain hot, URS | CH2M Oak Ridge (UCOR) has safely removed the highest threat remaining at the mammoth K-25 building at the East Tennessee Technology Park (ETTP).

 

The extreme south end of the mile-long, U-shaped building’s east wing is the only part of the facility that’s still standing. The north end, which forms the bottom of the U, is being demolished. The portion still remaining consists of five segments and an additional buffer. Deactivation work is ongoing in that area and is made more difficult due to the presence of technetium-99 (Tc-99), a slow-decaying radioactive metal.

 

An aerial photo of the entire K-25 footprint. The Tc-99 area, where the NaF traps were located, is seen in the foreground. The north end demolition work is shown in the background.

 

The K-25 is a gaseous diffusion facility that was part of the Manhattan Project. It was a key piece of the infrastructure built in Oak Ridge, Tennessee, U.S., in the early 1940s that helped win World War II. K-25 was also a major player in the Cold War, producing materials integral to the maintenance and growth of the United States’ nuclear arsenal.

 

Today, the old building that served the nation so well is crumbling. There are gaping holes in the walls, floor and ceilings, and workers cannot walk on the floor without reinforcements. Original plans called for part of the building to be preserved for historical purposes, but in July 2012, federal, state and local historic preservation groups signed an agreement establishing an alternative plan that allows the north end to be demolished, while still recognizing the historic significance of the site.

UCOR expects to complete demolition by sometime in 2014, depending on funding levels.

 

UCOR arrived at ETTP in August 2011. When it bid on the contract, it didn’t know of the presence of five components known as NaF traps. The NaF traps contain a material that was used to absorb uranium from the process system, and served as a capable last line of defense before material was released to the atmosphere. When K-25 was shut down in 1987, these traps were not purged and remained with their uranium buildup still intact until Bechtel Jacobs Company, the company that held the ETTP contract before UCOR, discovered them in August 2010, after the scope of work for the Department of Energy’s Request for Proposals was already on the street.

 

Radiological Controls Technician Lavonna Kirby is seen here checking a tag in the Tc-99 area of K-25.

 

When K-25 was operational, the NaF traps were part of the final uranium removal process. Sodium fluoride pellets were used to trap the uranium, and these particular traps still contain uranium materials from when the facility was shut down decades ago. The NaF traps are each about the size of a household hot water heater and range in weight from 150 pounds to 800 pounds each, according to Todd Phillips, project manager for the NaF trap removal.

 

They are especially hazardous to workers because they contain fluorine compounds that can generate hydrogen fluoride when they come into contact with moisture in the air.

 

“We performed extensive structural analyses before doing the work and used a critical lift plan to ensure it was done safely,” said Phillips. “The original DSA [Documented Safety Analysis] didn’t allow us to work on them. The hazards hadn’t been thoroughly and appropriately evaluated and analyzed to the point where they could be safely removed. That process took about 10 months.”

 

After a thorough and meticulous implementation of all aspects of the Integrated Safety Management System, a Management Self Assessment was conducted, followed by UCOR and DOE Readiness Assessments. There were minimal findings, which were all addressed easily before lift work began. Then, the project team began work.

 

The work scope included:

  • Asbestos abatement;
  • Vent, purge and drain;
  • Piping removal;
  • Removal of roofing material; and
  • Removal of components from the facility.

 

The Hazards: Weight

While removal of the NaF traps would be a routine assignment in a modern nuclear facility, it was anything but routine at K-25. In January 2006, while conducting routine deactivation tasks, a worker had fallen through the crumbling concrete floor. This effectively shut down all work at K-25 for many months, and resulted in strict limits on the work that could be done inside the building.

 

The interior of the Tc-99 area of the K-25 building. Walkways were installed throughout the work areas in the building, placed on structural supports underneath the floor for safety

 

Workers cannot walk on the actual floor at all. They must use structures called Modular Work Platforms (MWP), which are engineered work panels that are placed on top of the concrete floor panels while spanning structural steel supports. Should the concrete panels fail, the MWP panels will remain supported by the structural steel. Daily inspections of the panels are required, to ensure they remain undamaged and that their positions have not changed. Only two people can be on a single MWP panel at a time, and limits have been established on the weight and volume of work materials and waste they may have with them on the panels. No worker weighing more than 265 pounds can access the MWP. Other limits, which were formulated by Structural Engineering using carefully weighed materials, include:

 

  • Four-wheeled carts, limited to five 5-gallon buckets of roofing material, or five bags of asbestos insulation;
  • Two-wheeled lawn carts, limited to one full load of roofing material (no mounding) or six bags of asbestos insulation;
  • Panel carts, limited to either eight pieces of pipe, maximum of 6 feet long each; seven sections of bracing angle, maximum of 6 feet long; 12 linear feet of 8-inch deep channel, with no piece longer than 4 feet; two sections of sag rod, maximum length of 6 feet; or six sections of steel tee, 6 feet long maximum; and
  • B-25 boxes, limited to either 30 five-gallon buckets of roofing material; five lawn cart loads of roofing material; 72 pieces of pipe, 6 feet long maximum; 30 bags of asbestos insulation; or all structural steel items listed in the panel cart restrictions.

 

“We enforced this to the letter, through our work control documents, area postings, and training,” says Ed Blush, K-25 operations manager. “After what happened before, with the worker falling through the floor, it was absolutely necessary to take every precaution to keep our people safe.”

 

Impacts, Drops and Flames

 

Safety planning included how to prevent any possibility of the NaF traps falling, being impacted or being exposed to fire because of the danger of hydrogen fluoride.

 

After carefully examining all options, the project team decided that the safest approach was to cut holes in the roof and lift the NaF traps directly through the roof. The three larger components were located together, as were the two smaller ones. A large hole was cut above the larger components, and a smaller one above the smaller components. An 80-ton crane safely lifted the NaF traps from the building.

 

Before the actual work took place, Phillips said, every aspect was mocked up and practiced.

 

“We simulated test vessels and lifts. We did full-scale tests of the rigging configuration. We tested the rigging fixtures and planned how to lower the NaF traps onto transfer carts and tie them down, and practiced that.”

 

Other precautions included strictly controlling access to the work area; using propane-powered equipment, which is safer than gas or diesel; and designing a stringent controlled lift plan to govern the actual lifting of the components.

 

On November 2 -3, 2012, an 80-ton crane safely and uneventfully lifted the NaF traps from the building.

 

Dealing with the Heat

When work began to remove the NaF traps, it was July and August – the heat of the East Tennessee summer – and temperatures were topping out in the 90s and 100s. Add the heat index and the considerable danger involved in wearing protective clothing and breathing protection, and the highest risks workers faced, by far, were due to heat stress.

 

Zone Supervisor Robert Johnson was there when the bulk of the work was being done.

 

“It was hot,” he says. “While we were dealing with the weight limits and the physical condition of the building, we always had to be vigilant on the heat. The crews were wearing two pairs of protective coveralls and respirators, and sometimes plastic suits as well. Each crew was accompanied by full-time industrial safety and industrial hygiene people.”

 

Workers wore heart monitors, which were closely watched. They kept a close eye on themselves and each other, and used water stations that were always nearby to stay hydrated. If they got dizzy, or noticed a co-worker showing signs of heat stress, they left the work area immediately.

 

Thanks to the rigidly controlled work practices, there were no cases of heat stress throughout the entire work evolution.

 

What’s Next?

The NaF traps are now safely contained in steel boxes in the K-25 complex outside the building structure. A berm was built to contain material in case of a spill, and a protective line of empty boxes is in place to protect against leak or impact.

 

The next step is to “mine” the components, which will involve cutting them open and determining the exact contents, then deciding the proper disposition path. But additional studies must be done to analyze hazards associated with that and develop controls for those hazards. The mining, when it is done, will be performed in the onsite segmentation shop.

 

“We expect to find that the components are high in technetium,” says Phillips, which would necessitate off-site disposition.

 

Mark Ferri, K-25 project manager, gives all the credit to the up-front planning and the workers who carried it out.

 

Zone Supervisor Robert Johnson stands at the top floor entrance to the Tc-99 area of K-25. Holes in the walls, floor and ceiling are common throughout the building, which is expected to be completely demolished in 2014.

 

“I am so proud of these crews,” he said. “They are, every day, performing new work and encountering new hazards. They know the right things to do, and they do it. It’s really hard to have a project like K-25 and have the kind of safety record we have here. It’s all because of the workers.”

 

Meanwhile, a similar work evolution is being planned at K-25’s sister facility, K-27. That building contains six NaF traps, and the same ironworkers who successfully performed the work at K-25 will also be doing the work at K-27. Lessons learned will be applied, and the work practices will likely be similar – except there are no issues with the K-27 floor, which makes things a little easier.

 

K-25 represents the largest Department of Energy demolition project in the nation. When it and K-27 are complete, other facilities will follow as part of a nine-year effort to reindustrialize and turn the property over to the Community Reuse Organization of East Tennessee for private use. A significant amount of facilities and acreage have already been transformed, and many private tenants already are located there, with more in the planning stages.

 

In addition to deactivating and demolishing the K-25 Building, UCOR is responsible for other specific scopes of work at ETTP, the Y-12 National Security Complex, and the Oak Ridge National Laboratory.

 

 

About the Author:

Fran Smith works in Public Affairs for UCOR. She has 23 years of experience in Public Affairs work at DOE sites, including 20 years at the Savannah River Site and two years at the URS Global Management and Operations Services headquarters. She has been at the East Tennessee Technology Park since UCOR took over the contract in August 2011. Smith lives in Maryville, Tennessee, with her husband, Mark, whom she met soon after she arrived in Tennessee and married in July 2012. They have five children, ranging in age from 15-21.

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