U.K. nuclear company Magnox Ltd. is using divers for underwater dismantlement of former spent nuclear fuel storage containers in retired cooling ponds at the shuttered Dungeness A nuclear power plant in Kent, the Nuclear Decommissioning Authority said Tuesday.
While it has been four years since the former nuclear power plant has contained any used fuel, the storage “skips” are classified as intermediate-level waste that must be addressed.
The 1-meter-tall skips were used to store spent fuel rods upright and securely in the site’s two cooling ponds, Magnox spokesman Sam Fox said in a telephone interview. Cutting up the containers underwater avoids the need for airborne contamination prevention measures that would be necessary if doing the work on land, according to an NDA press release.
The water will also help protect the divers from Connecticut-based Underwater Construction Corp. against radiation exposure. Nonetheless, Magnox will apply strict health and safety measures and oversight for the personnel before, during, and following the dives, NDA said. That will include regular radiation monitoring, according to Fox.
After a four-week trial period earlier this year, actual disassembly began in September, Fox said.
“It’s proceeding as we expected. The trial was really important in ensuring the project is conducted safely,” he said. “We’ve cracked on and gotten on with it.”
The disassembled skips will be placed in cast-iron waste containers at a shielded storage space at Dungeness A before being prepared for interim storage at the Bradwell site in Essex. They are likely eventually to be shipped to a planned long-term geologic repository for intermediate and high-level radioactive waste.
The project will also involve extraction and disassembly of 20 metric tons of “pond furniture,” which is classified as low-level waste. That includes handling gear such as manipulators and splitters, along with steel frameworks and other material, which will be ultimately placed at the Low-Level Waste Repository in West Cumbria.
Fox said he could not release further details about the project, including the cost and the number of skips involved, which he said are commercially sensitive and confidential.
The cooling ponds project is due to conclude early next year. Afterward, lessons learned could be applied to other reactor decommissioning sites, potentially starting with the Sizewell A site.
Dungeness A operated from 1965 to 2012, and was fully defueled in 2012. Decommissioning is ongoing, with draining and stabilizing of the cooling ponds to begin once the divers have completed their work. Additional operations include retrieving intermediate-level waste from other areas of the site and eventually demolition ahead of putting Dungeness A into the care and maintenance phase in 2027.
Care and maintenance, according to Magnox, involves remote management and close monitoring of retired nuclear plants to allow time for radiation levels to drop ahead of final site clearance. Work on that final milestone is expected to begin in 2087 and to end a decade later, Fox said.
