Huge pools of mystery sludge, leaking silos and risk of explosions: Sellafield needs help, but the UK government has just sacked the firm running the clean-up

Sellafield holds waste dating back to the dawn of the nuclear age (Image: Sellafield Ltd)

URGENT clean-up of two of the world’s most dangerous radioactive waste stores will be delayed by at least five years, despite growing safety fears.

The waste is stored at the UK’s Sellafield nuclear reprocessing site, which holds radioactive waste dating back to the dawn of the nuclear age. An accident at the derelict site could release radioactive materials into the air over the UK and beyond.

Last week, the UK government sacked the private consortium running the £80-billion-programme to clean up Sellafield, and gave the job back to its own agency, the Nuclear Decommissioning Authority (NDA). The clean-up operation, scheduled to end by 2120, costs the government £1.9 billion a year.


The private consortium, Nuclear Management Partners, was meant to “bring in world-class expertise” and allow the government to “get to grips with the legacy after decades of inaction”, according to a 2008 statement by Mike O’Brien, energy minister at the time. But six years on, the privatisation experiment has been abandoned.

The surprise renationalisation comes after delays at two of the four waste stores prioritised for clean-up. The four ponds and silos contain hundreds of tonnes of highly radioactive material from more than 60 years of operations. The decaying structures are cracking, leaking waste into the soil, and are at risk of explosions from gases created by corrosion.

In an NDA business plan published last April, the emptying of the 100-metre Pile fuel storage pond, which holds used fuel and waste from the manufacture of the first UK nuclear bombs in the 1950s and 60s, was planned to be completed by 2025. But a timeline in a new draft plan circulated for consultation in December shows the job won’t be done until 2030. Likewise, the £750-million task of emptying the 21-metre-high Pile fuel cladding silo, which has been full since 1964, is now scheduled for completion in 2029, not 2024.

Confirming the change, an NDA spokesman told New Scientist: “Given the unique technical challenges and complexities of these plants, which were built with no thought to how they would be decommissioned… there will continue to be programme uncertainties.”

Sellafield was built on Cumbria’s coast in north-west England in the late 1940s to manufacture plutonium for the UK atomic bomb. The site also housed the world’s first commercial nuclear power station, and became a centre for storing highly radioactive waste from reactors.

Most of the highly radioactive waste was dumped into ponds, each several times the size of an Olympic pool. Constantly circulating water kept the waste cool, but also created hundreds of cubic metres of sludge from the corrosion of the metal cladding surrounding the fuel rods.

As a result, the exact contents of the ponds are unclear, says Paul Howarth, managing director of the government-owned National Nuclear Laboratory at Sellafield. “We have to do a lot of R&D just to characterise the inventory, before we can work out how to retrieve the materials.”

And the problem is just going to get worse. When plants are decommissioned in the future, waste will still be sent to Sellafield. The UK’s plants are mostly made of concrete, rather than steel, which makes them harder to dismantle, says Timothy Abram at the University of Manchester. It also means they create about 30 times more radioactive material. And with a new nuclear plant about to be built at Hinkley Point in Somerset, the amount of radioactive waste headed for Sellafield may grow.

Another unique legacy is the 90,000 tonnes of radioactive graphite stored there, used as fuel cladding. Irradiated graphite accumulates energy known as Wigner energy, which caused the UK’s worst nuclear accident in 1957. Researchers are still unsure how to make it safe for disposal.

While other Western nations have policies for dismantling old nuclear plants as soon as they can, the UK plans to mothball them for a century or more first. Nobody wants more radioactive waste until they have cleaned up what is already there.

Leader: “We’re in for the long haul in UK’s nuclear clean-up“

Danger areas Pile 1 is one of the two original reactors built to support the UK atomic bomb project. It is where the country’s worst nuclear accident took place, when the reactor core caught fire in 1957. Once the fire was extinguished the core was sealed and it is considered best left alone for now. Pile fuel storage pond took in spent fuel from both the weapons reactors and energy reactors. The radioactive waste and sludge formed from the storage process sit in a deteriorating concrete structure filled with water. Removal of the sludge is under way. This pond has sat unused since the 1970s. Pile fuel cladding silo is jammed with 3200 cubic metres of aluminium cladding, which surrounds the fuel rods, much of it from 1950s weapons reactors. It has been sealed since the mid-1960s but corrosion means there is a risk that hydrogen will form, which could lead to explosions. Magnox spent fuel storage pond is considered the most dangerous industrial building in Europe. The 150-metre-long open-air pond is visited by birds and cracks have caused radioactive material to leak into the soil. No one knows exactly what’s in there, but it may contain a tonne of plutonium. Magnox swarf storage silo is considered the second most dangerous industrial building in Europe. It stores waste magnesium fuel cladding under water. Some sludge has leaked through cracks in the concrete, and there is a risk of explosion from hydrogen released by corrosion of storage vessels.

This article appeared in print under the headline “New delays hit Sellafield clean-up”