Engineering teams have installed equipment to scoop up and remove material from Pile Fuel Cladding Silo (PFCS) at the UK Sellafield site, Sellafield Ltd said on 8 March, noting that safely decommissioning the 70-year-old facility is a priority for Sellafield Ltd and the Nuclear Decommissioning Authority (NDA).
The PFCS, built between 1950 and 1951, is 21m high housing six waste containers. By the mid-1990s, the silo was nearing the end of its intended life and needed care and maintenance. Upgrade work was completed to enable the building to continue to store waste safely, pending its retrieval and storage.
The PFCS holds more than 3200 cubic metres of intermediate-level waste including cladding materials from fuel assemblies used in some of the UK's earliest reactors at Windscale and Chapelcross. Irradiated cladding had to be removed from the fuel assemblies before they could be reprocessed.
Because the silo was originally designed to be permanently sealed, innovative ways of accessing and removing its inventory have had to be developed. The retrievals equipment is contained in nine huge modules, and was lifted into place on top of a superstructure built on the side of the building. Waste retrieval trials are expected later this year in preparation for larger scale waste removal in 2020.
Kevin Brown, Head of the PFCS programme at Sellafield Ltd, said: “It has been a real example of collaboration, working together with Bechtel Cavendish Nuclear Solutions to take us one step closer to significantly reducing the UK’s nuclear hazard.” The site is moving into a 100-year programme of environmental remediation, which means speeding up the decommissioning of old facilities and moving the waste into safe containment for centuries to come.
The PFCS was built in the 1950s when Sellafield site's purpose was to make material for nuclear weapons. In 2016, six holes were cut into the side of the silo. Six 12.4t giant stainless steel doors were then fitted into a 40t, nine-metre wide steel door frame on the side of the building. These doors, designed to open the building's 'locked vaults', will be the access point for waste retrieval machinery.
To remove the waste, a crane will extend through the hole in the side of the silo and a grabber will be lowered to scoop the waste up. This grabber then lifts and retreats back through the hole before depositing the waste in a specially-designed metal box that will be stored in modern facility currently being built at the site.
The retreival work is being carried out in collaboration with Bechtel Cavendish Nuclear Solutions, a US-UK joint venture appointed by Sellafield Ltd to help design, manufacture, test and install the machinery required to empty the silo. The equipment has been trialled at Rosyth in Scotland at a mockup model of the silo. It took 18 months to design and 18 months to manufacture, test and commission.
The first of the modules – the waste container transfer area - was lifted into place adjacent to compartment five, where the first waste retrievals will take place.
Photo: Sellafield's PFCS (Photo: Sellafield Ltd)