Sellafield houses more than 1,000 nuclear facilities on its six square kilometre site James Temperton/WIRED

It’s a warm August afternoon and I’m standing on a grassy scrap of land squinting at the most dangerous industrial building in western Europe. Seagulls chatter, the hum of machinery is constant, a pipe zig-zagging across the ground vents steam. “That one there, that’s the second most dangerous,” says Andrew Cooney, technical manager at Sellafield, nodding in the direction of another innocuous-looking site on the vast complex.

Earlier this year WIRED was given rare access to Sellafield, a sprawling collection of buildings dating back to the first atom-splitting flash of the nuclear age. This was where, in the early 1950s, the Windscale facility produced the Plutonium-239 that would be used in the UK’s first nuclear bomb. In 1956 this stretch of Cumbrian coast witnessed Queen Elizabeth II opening Calder Hall, the world’s first commercial nuclear power station. Both buildings, for the most part, remain standing to this day.


The site currently handles nearly all the radioactive waste generated by the UK’s 15 operational nuclear reactors. It also reprocesses spent fuel from nuclear power plants overseas, mainly in Europe and Japan – 50,000 tonnes of fuel has been reprocessed on the site to date.

This is a huge but cramped place: 13,000 people work in a 6 sq km pen surrounded by razor wire. There are more than 1,000 nuclear facilities. Sellafield is the largest nuclear site in Europe and the most complicated nuclear site in the world.

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By its own admission, it is home to one of the largest inventories of untreated waste, including 140 tonnes of civil plutonium, the largest stockpile in the world. To put that into perspective, between five and 10 kilograms of plutonium is enough to make a nuclear weapon.

Sellafield has its own train station, police force and fire service James Temperton/WIRED


Sellafield is protected by its own police force, the Civil Nuclear Constabulary (CNC), and its own fire service. It has its own railway station and, until September 11, 2001, its visitor centre was a major tourist attraction visited by an average of 1,000 people per day. The countryside around is quiet, the roads deserted. Within minutes of arriving by train at the tiny, windswept Sellafield train station the photographer I visited the site with was met by armed police.

Those officers will soon be trained at a new £39 million firearms base at Sellafield. What was once a point of pride and scientific progress is a paranoid, locked-down facility.

A recent investigation by the BBC found a catalogue of safety concerns including insufficient staffing numbers to operate safely and an allegation that radioactive materials were stored in degrading plastic bottles. Responding to the accusations, Sellafield said there was “no question” it was safe. “The programme painted a negative picture of safety that we do not recognise,” the statement continued. An anonymous whistleblower who used to be a senior manager at Sellafield told the broadcaster’s Panorama programme that he worried about the safety of the site “every day”.

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Pipes run in every direction and a lattice of scaffolding blocks out the sky. Structures that will eventually be dismantled piece-by-piece look close to collapse – but they can’t fall down. Sellafield’s isolated location, perched on the Cumbrian coast looking over to the Isle of Man, is also a slow death-warrant; the salty, corrosive sea air plays a lethal game of cat and mouse with the site’s ageing infrastructure. Some buildings are so dangerous that their collapse could be catastrophic, but the funding, expertise or equipment needed to bring them down safely isn’t immediately available. And so they must be maintained and kept standing.

Sellafield currently costs the UK taxpayer £1.9 billion a year to run. The site’s reprocessing contracts are due to expire in four years but clean-up may take more than 100 years and cost up to £162 billion. Material housed here will remain radioactive for 100,000 years. This is Sellafield’s great quandary.

In some cases, the process of decommissioning and storing nuclear waste is counterintuitively simple, if laborious. The Windscale gas-cooled reactor took nine years to decommission. Constructed in 1962 and shuttered in 1981, the ‘golf ball’ wasn’t built with decommissioning in mind.

In 2002 work began to make the site safe. An automated dismantling machine, remote-controlled manipulator arm and crane were used to take it apart piece by piece, leaving only the concrete biological shield and iconic, aluminium-clad shell. The waste, a mix of graphite, bricks, tubing and reams of metalwork – so-called low and intermediate-level radioactive waste – was then loaded into 121 concrete blocks and sealed using a grout mix of concrete and steel. Walk inside and your voice echoes, bouncing off a two-storey tall steel door that blocks entry to the core.

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Some buildings at Sellafield date back to the late-1950s when the UK was racing to build its first nuclear bomb James Temperton/WIRED

"It's not fancy technology, it's not somebody from Oxford that's come up with this,” says Richard Edmondson, operations manager at Sellafield, standing beside a looming stack of the concrete monoliths. We’ve walked a short distance from the 'golf ball' to a cavernous hangar used to store the waste. Each two-metre square box weighs up to 50 tonnes and contains around 100 sieverts of radiation. A dose of between 4.5 and six is considered deadly. But the boxes, for now, are safe. "Typical nuclear, we over-engineer everything,” Edmondson says, taking out a dosimeter and sliding it nonchalantly along the face of one box. Though the inside is highly radioactive, the shielding means you can walk right up to the boxes.

A B&Q humidity meter sits on the wall of the near-dark warehouse, installed when the boxes were first moved here to check if humidity would be an issue for storage. It wasn’t. Every month one of 13 easy-to-access boxes is lifted onto a platform and inspected on all sides for signs of damage and leakage. The towers of blocks are spaced to allow you to walk between them, but reach the end and you’re in total darkness. The only hint of what each box contains is a short serial number stamped on one side that can only be decoded using a formula held at three separate locations and printed on vellum.

Low and intermediate-level radioactive waste is temporarially being stored in 50-tonne concrete blocks James Temperton/WIRED

Not everything at Sellafield is so seemingly clean and simple. Among the site’s cramped jumble of facilities are two 60-year-old ponds filled with hundreds of highly radioactive fuel rods. It is these two sites, known as First Generation Magnox Storage Pond and the Magnox Swarf Storage Silos, that are referred to as the most hazardous in Western Europe. Leaked images of the ponds from 2014 show them in an alarming state of disrepair, riddled with cracks and rust. In one image a seagull can be seen bobbing on the water. WIRED was not given access to these facilities, but Sellafield asserts they are constantly monitored and in a better condition than previously.

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How radioactive waste ended up spending decades in open-air ponds is a story typical of Sellafield’s troubled past. As of 2014 the First Generation Magnox Storage Pond contained 1,200 cubic metres of radioactive sludge. Commissioned in 1952, waste was still being dumped into the 20 metre-long pond as recently as 1992. As well as being filled with waste during the early years of the nuclear age, Sellafield’s ponds were also overwhelmed with spent fuel during the 1974 miners’ strike.

There are four so-called legacy ponds and silo facilities at Sellafield, all containing highly contaminated waste. In March 2015 work began to pump 1,500 cubic metres of radioactive sludge from the First Generation Magnox Storage Pond, enough to fill seven double-decker buses. The clean-up operation is arduous – the Magnox pond isn’t expected to be decommissioned until 2054. It is one of several hugely necessary, and hugely complex, clean-up jobs that must be undertaken at Sellafield.

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One of of the site’s oldest buildings, constructed in the 1950s, carried out analytical chemistry and sampling of nuclear material. "This is a 60-year-old building, records are non-existent,” says Rich Davey, a mechanical responsible engineer at Sellafield. Much of the facility is now being decommissioned.

Among its labyrinth of scruffy, dilapidated rooms are dozens of glove boxes used to cut up fuel rods. But working out exactly what is in each laboratory has proven complicated. When records couldn’t be found, Sellafield staff conducted interviews with former employees. One retired worker, who now lives in nearby Seascale, thought there might be a dropped fuel rod in one of the glove boxes – a rumour that turned out to be false.

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This process, according to Davey, is about “separating fact and fiction” before work can begin. “Often we're fumbling in the dark to find out what's in there,” he says. The huge risk of contamination means human exposure can’t be risked. Endoscopes are poked through lead-clad walls before robotic demolition machines and master-slave arms are installed to break up and safely store the waste. “The air inside is so contaminated that in minutes you’d be over your total dose for the year,” Davey says of one room currently being decommissioned.

The building is so dangerous that it has been fitted with an alarm that sounds constantly to let everyone know they are safe. This tick-tock noise, emitted by Tannoys dotted throughout the facility, is the equivalent of an 'everything's okay' alarm. If the alarm falls silent, it means the criticality alarm has stopped working. Standing in a tiny control room crammed with screens and a control desk, Davey points to a grainy video feed on a CRT monitor. “This stopped operating before I was born and back then there was a Cold War mentality,” he says. The room on the screens is littered with rubbish and smashed up bits of equipment. This, he explains, is all part of the robot-led decommissioning process.

Much of Sellafield's decomissioning work is done by robots to protect humans from deadly levels of radiation James Temperton/WIRED

In Lab 188c engineers are using a combination of demolition robots and robot arms to safely demolish and store contaminated equipment. The lab operated in the 1970s and produced the Plutonium-238 used in early cardiac pacemakers and as a primary fuel source for Nasa’s deep space missions where solar energy isn’t available.

It is now home to a one-tonne BROKK-90 demolition machine which smashes up sections of the lab and loads them into plastic buckets on a conveyer belt. The buckets are then fed through an enclosed hole in the wall to a waiting RAPTOR master-slave robot arm encased in a box made of steel and 12mm reinforced glass. An operator uses the arm to sort and pack contaminated materials into 500-litre plastic drums, a form of interim storage. Some plastic drums are crushed into smaller “pucks”, placed into bigger drums and filled with grout.

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Once the room is cleared, humans can go in. Working 10-hour days, four days a week in air-fed suits, staff are tasked with cleaning every speck of dust and dirt until the room has been fully decontaminated. The process of getting suited up and into the room takes so much time that workers only spend around 90 minutes a day in contaminated areas. In other areas of Sellafield, the levels of radiation are so extreme that no humans can ever enter.

Sellafield is so big it has its own bus service. Two shuttles run clockwise and counterclockwise, ferrying employees between buildings. A drive around the perimeter takes 40 minutes. Train tracks criss-cross the ground as we pass Calder Hall and park up next to a featureless red and black building. This is Thorp, Sellafield’s Thermal Oxide Reprocessing Plant. It is here that spent fuel from the UK and overseas nuclear power plants is reprocessed and prepared for storage.

The waste comes in on rails. Flasks ranging in size from 50 tonnes to 110 tonnes, some measuring three metres high, arrive at Thorp by freight train and are lifted out remotely by a 150-tonne crane. Once in the facility, the lid bolts on the flasks are removed and the fuel is lowered into a small pool of water and taken out of the flask. The flask is then removed, washed, cleaned and tested before being returned to the sender. The highly radioactive fuel is then transferred next door into an even bigger pool where it’s stored and cooled for between three and five years.

The cavernous Thorp facility reprocesses spent nuclear fuel from the UK and overseas James Temperton/WIRED

This giant storage pool is the size of two football fields, eight metres deep and kept at a constant 20°C. Every day 10,000 litres of demineralised water is pumped in to keep the pool clean. At present the pool can hold 5.5 tonnes of advanced gas-cooled reactor (AGR) fuel, soon it will be able to hold 7.5 tonnes. Once sufficiently cooled, the spent fuel is moved by canal to Sellafield’s Head End Shear Cave where it is chopped up, dropped into a basket and dissolved in nitric acid.

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Conditions inside the Shear Cave are intense: all operations are carried out remotely using robots, with the waste producing 280 sieverts of radiation per hour - more than 60 times the deadly dose. The dissolved fuel, known as liquor, comprises 96 per cent uranium, one per cent plutonium and three per cent high-level waste containing every element in the periodic table.

On April 20, 2005 Sellafield workers found a huge leak at Thorp, which first started in July 2004. A later report found a design error caused the leak, which was allowed to continue undetected due to a complacent culture at the facility. The leak caused 83 cubic metres of nitric acid solution to seep from a broken pipe into a secondary containment chamber - a stainless steel tub encased in two-metre-thick reinforced concrete with a capacity of 250 cubic metres.

The leaked liquid was estimated to contain 20 metric tons of uranium and 160kg of plutonium. The leak was eventually contained and the liquid returned to primary storage. Thorp was closed for two years as a result of the leak, costing tens of millions of pounds in lost revenue. The facility, which opened in 1994, is due to close permanently in 2018.

Thorp’s legacy will be the highly radioactive sludge it leaves behind: the final three per cent of waste it can’t reprocess. The solution, for now, is vitrification. The remaining waste is mixed with glass and heated to 1,200°C. Once cooled, it forms a solid block of glass. This glass is placed into a waste container and welded shut. The outside of the container is decontaminated before it is moved to Sellafield’s huge vitrified product store, an air-cooled facility currently home to 6,000 containers.

Overseas reprocessing contracts signed since 1976 require that this vitrified waste is returned to the country of origin, meaning Sellafield now only has responsibility for storing the UK’s vitrified waste. The facility has an 8,000 container capacity. Sellafield says vitrification ensures safe medium-to-long-term storage, but even glass degrades over time. Where the waste goes next is controversial.

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"Nobody yet has come up with a different suggestion other than sticking it in the ground,” Davey tells me, half-jokingly. Cumbria has long been suggested as a potential site for the UK’s first, long-term underground nuclear waste storage facility - a process known as geological disposal. This burial plan is the government’s agreed solution but public and political opposition, combined with difficulties in finding a site, have seen proposals stall. Environmental campaigners argue burying nuclear waste underground is a disaster waiting to happen.

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For Sellafield, the politics are almost as complex as the clean-up operation. In January 2015, the government sacked the private consortium that had been running the Sellafield site since 2008. The site was too complex to be run privately, officials argued.

Sellafield is now completely controlled by the government-run Nuclear Decommissioning Authority. Regardless of who runs it, Sellafield could remain one of Europe’s most toxic sites for millennia. There’s currently enough high and intermediate level radioactive waste to fill 27 Olympic-sized swimming pools. And the waste keeps piling up.


The UK government’s dilemma is by no means unique. Nuclear power stations have been built in 31 countries, but only six have either started building or completed construction of geological disposal facilities. In January 2012 Cumbria County Council rejected an application to carry out detailed geological surveys in boroughs near Sellafield.

The government continues to seek volunteers for what would be one of the most challenging engineering projects ever undertaken in the UK. It might not have a home yet, but the country’s first geological disposal facility will be vast: surface buildings are expected to cover 1km sq and underground tunnels will stretch for up to 20 km sq. But who wants nuclear waste buried in their backyard? "It's all about the politics," Davey argues. "It's so political that science doesn't matter."

Updated 19/09/16, 16:00 - References to certain building names have been removed at the request of Sellafield