Decommissioning milestone at Oak Ridge reactor

UCOR - a partnership of Amentum, Jacobs, and Honeywell, working under contract with the Department of Energy (DOE) Oak Ridge Office of Environmental Management - removed the top portion of the 32-foot (9.8-metre) tall reactor vessel in November last year.

Since then, workers have focused on filtering and draining the reactor pool water to reach irradiated materials and prepare for the lower reactor vessel removal. Rigorous safety measures were in place due to high radiation dose rates, and those rates increased as thousands of gallons of pool water were pumped into tanks outside the facility, lowering the buffer between the radioactive materials and workers.

Workers removed 127,000 gallons (480 cubic metres) of water and sediment to reach the lower portion of the reactor vessel, which sat on the pool floor. They also took out the lead brick shielding in the basement that surrounded the pool. Twenty crew members loaded 157,000 contaminated bricks into containers.

Workers have now used a 72-inch (1.8-metre) diamond wire saw to cut the final pieces that held the lower reactor vessel in place at the bottom of the reactor pool. They used a 20-tonne overhead crane to lift that equipment and load it into a 32,000-pound (14.5-tonne) protective cask to ship it for disposal offsite.

The reactor vessel is loaded into a protective shipping container for transportation and disposal offsite (Image: DOE EM)

DOE noted that removing the vessel was the first step before preparing the remainder of the facility, also known as Building 3042, for its upcoming demolition.

"Removing the reactor vessel from the Oak Ridge Research Reactor facility has been an incredibly complex task," said Jim Daffron, Oak Ridge National Laboratory (ORNL) portfolio project director. "Through an immense amount of planning and careful execution, workers were successful and completed the work safely."

Steven Reed, UCOR Oak Ridge Research Reactor project manager, added: "We faced various challenges throughout the pool reactor remediation and cleanup process with our key partner, Energy Solutions, who provided their knowledge and expertise in collaboration, helping us resolve critical issues quickly and safely."

The next steps involved in preparing the reactor for demolition consist of isolating and deactivating 6000 feet (1830 metres) of piping. Workers will also finish draining the pool water and encapsulating the 25-foot (7.6-metre) deep pool with a fixative to reduce contamination migration during demolition.

ORNL was established in 1943 - when it was known as Clinton Laboratories - to conduct pilot-scale production and separation of plutonium for the World War II Manhattan Project. It was also highly involved in reactor design and isotope research and production. The DOE Office of Environmental Management is responsible for cleanup activities related to the historic operations at ORNL, including 16 inactive research reactors and isotope facilities.