The federal cleanup contractor in Oak Ridge announced on Tuesday that it has removed one of the highest-risk parts left in the K-25 Building.
That building was once the world’s largest building under one roof, but it has been shut down for decades and is now being demolished.
In a press release Tuesday, cleanup contractor UCOR said it had used cranes to remove five sodium fluoride, or NaF, traps. The traps contain a material that was used to absorb uranium, and they were in the section of the K-25 Building known as the Tc-99 area, which is being deactivated so it can be demolished.
The K-25 Building was composed of three major sections—the east and west wings and the north end—that were aligned in a U shape that was more than a mile around. The entire west wing and the most of the east wing are already gone, and the north end, which makes the base of the U, is now undergoing demolition, the release said.
The portion of the east wing still remaining is the Tc-99 area. It has five segments and an extra buffer at the south end of the building.
“The deactivation is more difficult due to the presence of technetium-99 (Tc-99), a slow-decaying radioactive metal,” the release said.
When K-25 was operating, the NaF traps were part of the last 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 water heater and range in weight from 150 pounds to 800 pounds each, according to Todd Phillips, project manager for the NaF trap removal.
“We performed extensive structural analyses before doing the work and used a critical lift plan to ensure it was done safely,” Phillips said in the release.
The release said extensive safeguards were in place during the removal because the vessels could be dangerous if they were dropped or caught on fire.
To remove the vessels, workers cut a hole in the roof of the building, and a crane lifted them out. The entire removal activity was completed in two days, the release said.
“The NaF traps are now safely stored in the K-25 area until they can be sampled and a disposition path determined,” the release said.
“It’s a big accomplishment to remove these vessels,” said Leo Sain, UCOR president and project manager. “They represented one of the highest risks remaining in the K-25 Building. Safely removing them gets us one step closer to project completion.”
Demolition of the north end is expected to be complete in the next few months, with the Tc-99 area following.
In addition to deactivating and demolishing the K-25 Building, UCOR is responsible for other work at the East Tennessee Technology Park (the former K-25 site), the Y-12 National Security Complex, and the Oak Ridge National Laboratory.
UCOR is a partnership between URS and CH2M Oak Ridge LLC, and the company is the U.S. Department of Energy’s cleanup contractor in Oak Ridge.