The retrieval of mixed waste from the underground chambers at the UK's decommissioned Berkeley NPP will enable the two Magnox units to enter a period of long-term passive storage. The Berkeley site housed some 620t of metallic fuel element debris (FED) and 6,665 containers - some of which are sludge cans - in three underground vaults. A single silo houses charge rods and the chutes used to discharge fuel from the site's two Magnox reactors.
The Nuclear Decommissioning Authority (NDA) said on 14 June that it achieved its first major milestone in March when the chute silos were declared empty. "Although we originally anticipated that all the material would be intermediate-level waste (ILW), a campaign of innovative retrieval techniques and segregation enabled some of it to be disposed of as low-level waste and very low-level waste, diverting over 50t away from the site's interim storage facility and saving millions of pounds," said Paul Oswald, Berkeley site head of projects.
This was followed by the active commissioning of the retrieval and process equipment at the vault containing FED. The design of the retrieval equipment began in 2010, while fabrication, installation and testing of the equipment has been carried out since 2013. So far, 10 shielded Ductile Cast Iron Containers (DCICs) have been filled and dried in the conditioning facility before being transferred to the on-site Interim Storage Facility (ISF). The first container holding ILW (debris from the fuel elements, resins, sludges and graphite) was placed inside the ISF at Berkeley in May 2014.
Berkeley's two Magnox units were shut down in the late 1980s after more than 25 years of operation. In 1992, Berkeley was the first Magnox site to complete defuelling and later became the first to decommission its fuel storage ponds.
In 2010, after 21 years of decommissioning work, the units became the first to be sealed up and placed in 'safestor', and they will be monitored and maintained until the site is completely cleared in about 65 years' time. Once the waste vaults are cleared, Berkeley will enter a period of 'care and maintenance', the NDA said. The units will be placed in long-term passive storage to allow time for residual radioactive materials to decay before final site clearance work begins in 2074.