Nuclear divers penetrate 65 years of sludge

Diver enters the Pile Fuel Storage Pond (Sellafield Ltd)
Diver enters the Pile Fuel Storage Pond (Sellafield Ltd)

It might not be everyone's idea of a dream job, but a US specialist team of nuclear divers have become the first humans in 65 years to enter a storage pond at Cumbria’s Sellafield site.

According to the plant’s records, it was in 1958 that a maintenance operator and a health physics monitor last dived into the Pile Fuel Storage Pond, their task to repair a broken winch. Since then only ROVs have ventured into its unwelcoming environment of radioactive water, sludge and debris.

The 100m-long outdoor pond, one of the oldest parts of Sellafield, was installed in the 1940s to support the operation of the site's first nuclear reactors, called the “Windscale Piles”. It was used for cooling, storing and decanning (removing metal cladding) spent fuel from the reactors, as part of the UK’s post-war atomic weapons programme.

When operations at the plant were abandoned in the 1960s, radioactive sludge was left to form from the decaying nuclear fuel, algae and other debris. Today Sellafield Ltd is responsible to the UK’s Nuclear Decommissioning Authority, and says the work to detoxify the site remains one of the world’s most complex decommissioning challenges. 

The Sellafield nuclear reactor site (Simon Ledingham)
The Sellafield site (Simon Ledingham)

It reports that “significant progress” has been made in retrieving and safely storing fuel, sludge and redundant equipment from the pond using robots and other tools, but by the end of last year it had become a matter of retrieving materials from the floor, corners and other inaccessible areas – at which point only humans were deemed capable of completing the priority project.

A replica facility was set up in 2019 so that the nuclear divers could practice the necessary working practices in uncontaminated water, especially their entry and exit protocols.

‘No ordinary divers'

Underwater Construction Corporation team-member Josh Everett was the first to dive into the murky water of the Pile Fuel Storage Pond. He and the other specialist divers enter via a specially installed access platform and position themselves on a metal dive-stand with a shielded floor, prepared to work in shifts for up to 3.5 hours at a time. They can be seen at work here.

“These are no ordinary divers,” says Sellafield Ltd. “Josh and his team have years of experience in safely diving in radioactive environments around the world, including at Dungeness A and Sizewell A in the UK.” 

Lessons learned at these sites have been applied at the Pile Fuel Storage Pond, which the company says “still presents some unique challenges owing to its age and complexity”, with the operation set in turn to influence future clean-up operations.

“The Pile Fuel Storage Pond diver project has been five years in the planning and has been a huge success,” said Sellafield Ltd head of programme delivery for legacy ponds Carl Carruthers. “The team are used to diving in toxic and hazardous environments all over the world, including inside nuclear reactor vessels, but this is a first for us.

“Safety has been our priority throughout, and the divers are monitored and communicating with the dive supervisor at all times… once all of the waste materials have been removed from the pond the water will be removed, ready for final demolition of the building.

“Current plans estimate the decommissioning work will cost around £212 million and will be completed by 2039 – an achievement almost a century in the making.”

Also on Divernet: Nuclear Divers Go To Work At Sizewell


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