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Sellafield digs deep into waste storage history

by Mark Cantrell
Sellafield made history and took a significant step forward in cleaning up the site with the successful operation to remove the first batch of waste from its oldest storage vault

It’s been billed as a historic occasion, decades in the making, but Sellafield has begun the process of retrieving material from its oldest nuclear waste store.

The successful removal of the first batch from the Pile Fuel Cladding Silo marks a significant step forward in the programme to decommission Sellafield’s nuclear facilities.

Last month, after weeks of preparation and checks, the Pile Fuel Cladding Silo retrievals team gathered around the monitors in the control room of the 70-year-old plant. There, they remotely witnessed the moment a state-of-the-art robotic arm reached into the silo to remove and repackage waste for the first time.

Euan Hutton, Sellafield Ltd’s chief executive, said: “The first retrievals from the Pile Fuel Cladding Silo are a huge step towards delivering our purpose of creating a clean and safe environment for future generations.

“This achievement means that for the first time ever Sellafield is retrieving waste from all four of our legacy ponds and silos. This represents the culmination of years of effort by hundreds of people throughout our organisation and contractor community. I am enormously proud of all of them.”

History vault

Built in the 1950s to store cladding from used nuclear fuel from the Windscale Piles – the first nuclear reactors to be built at Sellafield – the vast concrete silo was designed as a ‘locked vault’ with no plan for how to retrieve its contents or decommission the building.

Cladding is the term used for the metal casing that surrounded the uranium fuel rods that were loaded into nuclear reactors. After the rods had been used in the reactors the cladding was peeled away so the fuel inside could be reprocessed. Today, this cladding is classed as intermediate-level nuclear waste.

After almost 20 years of operations the silo’s six compartments were filled and it stopped receiving waste in the early 1970s.

In the years that followed, the building underwent several upgrades to ensure it could continue to store its contents safely while a plan for retrievals was developed.

The operation to remove the waste represents “one of the most complex and difficult decommissioning challenges in the world”, Sellafield Ltd said, and one of the highest priorities for both it and the Nuclear Decommissioning Authority (NDA).

Concrete enclosure

In the last decade a giant concrete superstructure has been built around the silo and specially engineered shield doors have been installed on each of its six compartments. In 2017 holes were successfully cut in the top of each compartment, allowing access to the waste for the first time in 65 years.

Sellafield Ltd then designed, manufactured, tested, and installed nine huge modules containing the machinery needed to empty the silo. This was done in collaboration with Bechtel and Cavendish Nuclear Solutions working together as Bechtel Cavendish Nuclear Solutions.

Successful testing of the robot grab was carried out earlier in August, paving the way for the historic achievement of the first waste retrievals from the silo.

Operators used the grab to remotely reach into the silo and pick up the waste before loading it into a specially designed stainless-steel box.

Once filled the box will be loaded into a shielded flask and transported to a brand new, fit-for-purpose store called the Box Encapsulation Plant Product Store.

David Peattie, the NDA’s chief executive, said: “This is an important milestone, demonstrating tangible progress in delivering our mission and cleaning up some of our most hazardous legacy waste.

“It’s progress that has been years in the making and has been driven forward by skilled, industry leading specialists working collaboratively.

“The ability to now retrieve waste from all four legacy ponds and silos at Sellafield is a huge achievement.”

Mike Higgins, Pile Fuel Cladding Silo programme manager for Bechtel Cavendish Nuclear Solutions, said: “Getting to this position, over the last 12 years, is testament to the hard work, dedication and collaboration of the team, our joint venture partners Cavendish Nuclear, alongside our customer and all our supply chain partners.”

Main image: The six large shield doors that were attached to the side of the silo. Courtesy of Sellafield Ltd

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