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On the morning of Friday October 11 1957, a terse message landed on the desk of Sir Edwin Plowden, head of the UK’s Atomic Energy Authority. A fire had broken out at Windscale, a nuclear facility situated remotely on the north-west coast of England. The missive read: “Position has been held all night but fire [is] still fierce.”
It couldn’t have come at a worse moment for Britain’s nuclear establishment. Windscale’s two “piles”, the country’s first operational reactors, had been churning out fissile material for a secretive atomic weapons programme. Scientists were scheduled to detonate the UK’s first hydrogen bomb within weeks. Now, instead of a triumph, a possible disaster was at hand.
The blaze had taken hold in the core of Pile One, a graphite structure, honeycombed with thousands of channels full of slugs of highly irradiated uranium fuel and the various toxic by-products of nuclear fission. Temperatures raged above 400C. The risk was that the fuel cans could ignite and burst, spewing radioactive contents across the Cumbrian countryside.
The one bright spot was that the worst had not happened. “Emission [sic] has not been very serious and hope to continue to hold this,” the message to Plowden continued. The challenge was to douse the flames quickly. The assistant works manager, Tom Tuohy, had tried pumping in carbon dioxide without effect. Now, he advised Plowden, he was trying a more extreme method, one that could cause an explosion. Tuohy was “injecting water above the fire and . . . watching results”.
Plowden couldn’t know it, but by the time he read these words, the danger had passed. Tuohy’s ploy had succeeded, and the fire was out. Such emissions as had leaked from the reactor were almost all captured by filters housed in a curious lantern-like structure atop its giant ventilation-stack, as Plowden would later tell a very relieved prime minister, Harold Macmillan.
The Windscale fire is generally regarded as Britain’s biggest nuclear accident. But despite its fearful reputation, it had no observable health consequences. The fire’s main legacy was the discarded reactors themselves, their chimneys visible for miles. The burnt out and contaminated Pile One never reopened, written off after just seven years of operation. Following an official inquiry, its undamaged twin followed suit.
Today those rain-stained, lantern-topped stacks no longer loom over the Cumbrian countryside. The chimney on Pile Two came down two decades ago, while its fire-contaminated neighbour is still being dismantled today. The original piles, however, are still there, cold and dark, their grimy concrete walls sequestered behind innocuous modern cladding.
Windscale is now known as Sellafield. If the name change in the 1980s was intended to erase the associations of the past, it was for naught. To scan the densely packed site is to find most of Britain’s nuclear history standing before you: the hastily constructed cold war military installations; the world’s first civil nuclear power station, Calder Hall, opened by the Queen in 1956; the experimental “golf ball” reactor from the 1960s.
The present is here too. One of the world’s biggest nuclear sites, Sellafield still handles all the material produced by Britain’s seven nuclear power plants. Almost three-quarters of the UK’s nuclear waste is stored within its 6 sq km precincts or close by. Its plutonium stockpile alone — 140 tonnes of the radioactive element extracted from nuclear fuel over the past seven decades — could make 22,000 of the bombs dropped on Nagasaki in 1945.
Sellafield is the liminal space of Britain’s atomic legacy. It is at the centre of a debate about Britain’s energy future. Many think nuclear power is vital if the country is to achieve net zero emissions by 2050, a goal to which the government is legally committed. The current energy crisis in the UK, caused by surging natural gas prices, has focused minds on the merits of non-fossil fuel and nature-dependent power.
Yet new reactors are expensive: Hinkley Point C, the giant “first of a kind” twin-reactor plant being constructed in Somerset, will cost north of £22bn and saddle consumers with elevated energy bills for decades to come. (The industry hopes the cost will fall as more are built.) Uncertain back-end costs threaten to upend the technology’s already stretched economics, while waste disposal poses even more difficult problems.
Comparatively little of Sellafield, and few of Britain’s other “first generation” nuclear plants, have yet been wholly dismantled. The full bill for dealing with these relics, and hence nuclear’s lifecycle costs, cannot yet be known. Then there is the worry about where to put all the waste, for which there is no final destination. “If you can’t get rid of it,” says one opponent, “how on earth can you justify creating any more?”
When a nuclear plant closes, there are three types of waste material. The safest is the low-level stuff, which includes items such as old protective clothing and accounts for about 90 per cent of all the waste by volume. This is the easiest to deal with as the contamination is limited and it can be buried in sites with less elaborate safety procedures.
More troublesome are the so-called intermediate wastes (7 per cent), which include items such as fuel cladding and old machinery, and the high level kind — essentially the highly irradiated spent fuel itself. Despite accounting for just 3 per cent by volume, it is responsible for 95 per cent of the radioactivity. This was what lay at the bottom of the cooling ponds in the long-closed Windscale complex at Sellafield.
Dorothy Gradden leads the project to clear the Sellafield ponds. It has been a “voyage of discovery”, she tells me, as we clamber on the gantries above the Pile Fuel Storage Pond, one of the oldest and most restricted areas on the entire Sellafield estate. Penned off behind high fences patrolled by armed guards, the area can only be entered through a room divided by a low barrier. All outer clothing worn inside the zone — shoes, overalls, helmets — must stay on the “contaminated” far side of that divide, and we’re checked by Geiger counters when we emerge.
Gradden started out in the 1980s working on new reactor projects but, like many nuclear engineers, found her career becalmed after the 1986 Chernobyl accident. She moved over to decommissioning in 1999. “No one quite knew what to do at the beginning because the emphasis had always been on building new facilities and not clearing up old ones,” she says, as we survey the ponds, our dosimeters occasionally chirruping to record radiation.
At the outset especially, decommissioning is a lottery. “There are good and bad surprises,” says Gradden. “Sometimes you only find out what you’re dealing with when you stick a robot or a scoop into it.” Materials that are already hazardous, such as asbestos, of which there are prodigious quantities across Britain’s early nuclear estate, become more complex to handle when combined with radioactive contamination.
The uncertainties were compounded by Britain’s early nuclear history after the second world war, when scientists and engineers were working at the frontiers of knowledge as they scrambled to catch up with US and Soviet weapons programmes. The 1957 Windscale fire happened mainly due to their imperfect understanding of the materials in use and a phenomenon known as “Wigner energy”, in which heat can build up in heavily irradiated graphite reactor cores. The piles had been running flat out to produce fissile material for the H-bomb tests.
When it came to clearing up, those pioneers didn’t leave much of a map for their successors. “The whole place had lain fallow since the 1960s and there were 200 skips full of contaminated material in the ponds, most of which hadn’t seen the light of day since the 1940s, so we had no idea about their condition,” recalls Gradden.
Each step was tentative, as they came to understand the materials they were working with. A special vacuum cleaner was built to filter the sludge and remove it to a containment area. Then they painstakingly removed the fuel-filled skips one by one and packed them for disposal in Sellafield’s on-site waste facility, which is designed to hold them for another hundred years. The first [skip] took three months, says Gradden, to make sure it was decontaminated and packaged securely. “We can now do four in a few weeks.” Despite this, the ponds aren’t due to be emptied of water until the 2030s.
Back in the 1990s, workers at Sellafield could spend only half an hour a day around the (then more contaminated) ponds because of fear of exceeding the permitted dosage (20 millisieverts in a single year, roughly equivalent to two CAT scans). But technology has provided work-rounds, with robotic equipment allowing teams to get into hotspots sooner. Gradden now makes extensive use of autonomous underwater vehicles to investigate still-contaminated parts of the legacy ponds.
Technology was also in evidence when I subsequently visited Trawsfynydd in mid-Wales, one of 11 first generation Magnox civil stations in various stages of decommissioning. Here contractors have entombed a six tonne Brokk 500 — a sort of electric tractor — in a contaminated area, where its robotic arm is cheerfully shovelling the twisted remains of old fuel cans that once held uranium rods from a cluster of silos where they were dropped from the 1960s to the 1990s. The waste is then moved to a conveyor belt where another robot packs it for storage.
Shifting those 94 tonnes of swarf would once have been a painfully slow task. “Now, if everything goes well, we can generally shift about a tonne a day,” says Geraint, one of the operators.
In 2019, official estimates of the liabilities attached to cleaning up 17 of Britain’s oldest nuclear sites put the cost at £124bn over the next 120 years, of which £97bn applies to Sellafield alone. Other industries, such as oil and gas, also face huge bills to clear up after themselves. But the scale of nuclear’s number has made it an existential issue.
Tim Stone, chief executive of the Nuclear Industry Association, argues that the historic bill is not representative of what may happen in future. New reactors are designed with dismantling in mind, and their longer lives (they are built to last for 60-80 years) mean their decommissioning costs should easily be covered out of operating revenue. Hinkley Point estimates that it will have to set aside roughly 3 per cent of its income as it goes along.
Meanwhile, the industry has learnt how to dismantle reactors economically and safely. “We have spent decades building experience and world-class skills,” he says, adding “extremely cautious estimates of funding for future decommissioning of new build are now routinely built in from the outset.”
Opponents, however, insist the massive historic bill highlights the folly of any more construction. “The back-end liabilities are so large and distant that there’s always a tendency to underestimate them,” says Tom Burke of the environmental group E3G. “We risk building uneconomic nuclear plants we can’t afford.”
One lesson that has been learnt is to fund decommissioning in advance and not leave old plants sitting around for years waiting for the state to cough up on a “pay-as-you-go” basis. Successive governments were slow to grasp the nettle with Sellafield and the Magnox plants, adopting over-optimistic assumptions about what the costs might be when they were finally incurred. So when decommissioning the first generation finally started in earnest, estimates ballooned alarmingly as the complexity hit home, as well as the lack of a skilled supply chain. Those for the non-Sellafield first generation sites rose from £12bn in 2005 to £37bn just four years later.
These have since stabilised, falling back to £30bn by 2019. There is a growing recognition that procrastination is unwise, as it leads to a higher overall bill in the long run. The annual “hotel cost” of Sellafield runs at more than £2bn.
Signs of this new thinking can be discerned on the Magnox estate. The old strategy had been to defuel and stabilise the stations before putting them into a 60-year suspended animation (known as “care and maintenance”). Only then would they be pulled down. Now, at Trawsfynydd, they are thinking of doing it all in one go. “This would let us retain all the skills, whereas if we just wall it up we lose all the expertise that we have built up,” says Angharad Rayner, the plant’s site closure director.
One of the biggest challenges for nuclear is to overcome decades of public mistrust; attitudes that some scientists maintain are based on a deep misunderstanding of risk.
Not far from Trawsfynydd’s brutalist Basil Spence-designed reactor complex stands an inconspicuous low structure. Stacked inside from floor to ceiling are 330 concrete-covered boxes, each with a capacity of three cubic metres. These contain solid intermediate-level waste that has been recovered from within the plant. There are also 1,941 drums, each containing 3 tonnes of resin — essentially solidified radioactive sludge.
The receptacles are there not because it’s convenient, but because there is no final resting place for them. Yet without one, Trawsfynydd and places like Sellafield can never close.
Given that plutonium and certain fission products will remain radioactive for hundreds of thousands of years, there is a need to secrete them far below the earth’s surface where no one can get to them. Neil Hyatt, professor of nuclear materials chemistry at Sheffield university, believes that, for intermediate and high level waste, this should happen 300 metres to a kilometre underground.
The waste would be put in containers with several engineered barriers and then surrounded by clay. The containers would be spaced out to allow any heat from the decaying isotopes to dissipate.
“The principle here is that we are using depth as an isolation mechanism,” says Hyatt. The packaging around the waste will corrode eventually, he concedes. “But we design the facility so that failure occurs over thousands of years and there are many barriers working together so the return of radioactivity to the surface is insignificant.”
Persuading the public that such a solution is safe has proved hard, however. Geraldine Thomas, a professor at Imperial College who has studied nuclear accidents, argues that part of the problem is “our excessive fear of one risk: radiation”.
Take the example of one of the worst radiation releases, the Chernobyl accident, and its impact on those exposed to it, including the 600,000 “liquidators” or workers who cleaned up after the disaster. According to the US oncologist and radiation expert, Robert Gale, there have been no reports of an increase in leukaemias known to be caused by radiation. That’s not to dismiss the long-term radiation consequences. Using standard risk estimators, Gale calculates the discharge might lead over 80 years to 11,000-18,000 more cancers than there would otherwise have been. However, this needs to be set against a background incidence of 200 million over the timeframe; no more than a 0.009 per cent increase.
“Every death is tragic but perspective is needed,” writes Gale. “For every terawatt hour of electricity produced, nuclear energy is 10-100 times safer than coal or gas.”
Modern reactor designs, meanwhile, bear no resemblance to Chernobyl, still less to the primitive atomic piles erected at Sellafield after the war.
Yet attempts to build a so-called geological disposal facility (GDF) in the US, UK and other European countries have stalled over concerns that such a depository could genuinely be proofed against toxic releases over a very long period. Critics such as Paul Dorfman, a senior research fellow at UCL’s Energy Institute, argue that, even now, we simply don’t know enough to give such a commitment. “We are talking about massive questions of uncertainty,” he says. “There are questions about geology and whether the cylinders designed to package the waste are safe from corrosion. Can the radiation be contained?” His preference is to see the existing waste stored on the surface, with no more being created.
One of the biggest paradoxes concerning nuclear radiation is that larger doses, and therefore larger health effects, come from isotopes with shorter half-lives that become concentrated in the body; however, these decay very quickly in the environment. Iodine-131, for instance, has a half-life of just eight days, meaning it has all but entirely dissipated after less than three months. Those that last longest, such as plutonium with a half-life of 24,000 years, may concern the public. But they don’t emit much radiation.
On a 1957 visit to the atomic research facilities at Harwell, the Queen was handed a lump of plutonium in nothing more than a plastic bag and invited to feel how warm it was. (“Like a live rabbit” as Leona Marshall Libby, Enrico Fermi’s assistant during the Manhattan Project, recorded in her diaries.) In the case of plutonium, what it does emit is alpha particles, which do not even penetrate human skin. Or as the late John Fremlin, professor of radioactivity at Birmingham university, once told a public inquiry, plutonium can be sat upon safely by someone wearing only a stout pair of jeans.
David MacKay, the late scientific adviser to the UK energy department, put it like this: “Everyone knows that midday desert sun can be harmful if one lies in it without protection. And everyone knows that moonlight is essentially harmless.” Yet moonlight and sunshine are made up of the same photons. The former is simply harmless because it is 400,000 times less bright than sunshine. “Nuclear radiation can be like sunlight, and it can be like moonlight.”
In some countries there are signs that public attitudes may be shifting. In Finland, the government is now building the world’s first GDF after a painstaking confidence-building exercise in which local communities in geologically suitable areas were invited to bid for the site. This should open by the middle of this decade. Sweden looks set to follow suit.
This is not just blind trust. As part of the safety case constructed for their proposed facility, the Finns looked at the impact of waste leaking from it after 1,000 years on someone living directly above, whose food and water all came from the most contaminated plot of land. The conclusion? That person was likely to receive a dose of 0.00018 millisieverts per year; equivalent to the radiation we ingest from eating two bananas. The environmental group Greenpeace, no friends of nuclear, subjected the report to its own scientific study. This concluded that “ . . . there is no proof so far that the planned repository is not safe and that the open problems cannot be solved . . . ”
Britain is now trying to win support for a GDF using a similar consultative approach to the Finns. Local communities have been invited to bid and two local authorities in Cumbria, Copeland and Allerdale, have registered interest. Both are close to Sellafield, which remains the area’s biggest employer and is seen as offering high quality skilled life-long jobs.
It is all very different from the top-down plans Britain promoted in the 1980s, or the military secrecy that shrouded nuclear endeavours in the 1950s. (Macmillan wouldn’t allow the official report into the Windscale fire to be published, fearing that it would dent American confidence in Britain’s nuclear prowess.)
While acknowledging that a safety case can only be made once a suitable site has been identified and investigated, Hyatt of Sheffield university sees no obstacle in principle to the UK following the Finns. “Everything we know at the moment leads us to believe we can do it safely.” Leaving waste on the surface would be a dereliction. “It’s not sustainable and, anyway, it’s not fair to future generations,” he says.
For Gwen Parry Jones, the boss of Magnox, which would be one of the first customers for a British GDF, it is all about “closing the loop” that started with the opening of the Windscale piles back in 1950 and the fire seven years later. “We are on an environmental mission to clear up after ourselves responsibly and sustainably in a way that not many other industries do,” she says. Hyatt is more succinct: “We can definitely do this.”
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