What could have been a negative have been turned into a positive following a leak in a 60-year-old tank at Sellafield.

The lead, from a sump in the redundant settling tank area of the nuclear site, was discovered last year.

Although the issue posed no immediate risk to people, it needed urgent work to fix it.

Despite a multitude of challenges, including the Covid-19 lockdown, the job was completed in just nine months.

The work has helped accelerate decommissioning of the wider site.

Dorothy Gradden, Sellafield Ltd’s head of legacy ponds, explained "If this had happened in the 1990s, it could have taken us years to fix it.

"But because we’ve spent the last decade removing radioactive waste and sludge using remotely operated systems in other facilities, we were able to start fixing the problem in record time.

"Working with our regulators and supply chain partners The Decommissioning Alliance, we decided the safest solution was to reseal the tank.

"Simply pouring concrete in would have locked in the radioactive material, creating a decommissioning problem for future generations."

The redundant settling tank is a relic from the 1950s. It sits next to Sellafield’s First Generation Magnox Storage Pond building and was used to store radioactive sludge taken from the outdoor pond.

The pond stopped operating in 1986 and the redundant settling tank area was put into a care and maintenance regime in the 1990s, with decommissioning planned for the 2030s.

But that all changed on 19 October 2019.

Surveillance work found the level of liquor in a sump tank was reducing at a rate of approximately 80-100 litres per hour.

As there were no signs of a leak in the pipes connecting to other plants, it had to be assumed that the liquor was being lost to ground under or around the tank.

Dorothy added: "The focus was on keeping the engineering simple, fit-for-purpose and safe.

"In total, 15 cubic metres of sludge and 15 cubic metres of solid waste needed to be moved."