Superheavy

by Kit Chapman

  The two new elements had been named only a few months earlier, in March 1942. At first, the team had used code words to throw anyone off the scent. Element 93 was ‘silver’; 94 was ‘copper’. That had worked until the group needed to talk about actual copper, which became ‘honest-to-God copper’ instead. But as the discoveries became more widely known, continuing to call them ‘silver’ and ‘copper’ became too confusing for everyone involved. They needed to come up with alternatives.1

  Seaborg and McMillan drew up a list of options. They considered ‘extremium’ or ‘ultimium’ – after all, their finds had to be the end of the periodic table, didn’t they? – but eventually took inspiration from the solar system. When uranium had been discovered in 1789 it had been named after the planet Uranus; McMillan decided to copy the idea and call element 93 ‘neptunium’, after Neptune, the next planet in sequence. Seaborg followed suit and element 94 became ‘plutonium’; never a classicist, he had no idea that the material soon to be at the heart of the atomic bomb was named after the Roman god of the afterlife.2

  Every element is given one or two letters to identify it – usually the first two letters of its name. Neptunium would be Np (Ne was taken by neon). Plutonium should have been ‘Pl’, but Seaborg couldn’t forget how much the Gilman Hall attic had reeked. In the stinkiest joke on the periodic table, he immortalised plutonium as pee-eew (Pu).

  Now in Chicago, Seaborg still needed a way to mass-produce plutonium. At the rate they were working, it would take 20,000 years to make a bomb: realistically, they needed to produce a billion times more of the world’s rarest substance. ‘A billion is a hard-to-conceive number,’ Seaborg explained in his autobiography. ‘If you took a ball an eighth of an inch in diameter and increased its diameter a billion times, it would be close to the size of the Moon.’ Worse, they then needed to make sure it was the fissile Pu-239; anything else would disrupt the chain reaction and ruin the bomb.

  Fortunately, Seaborg had a genius on hand to help. Joining him in the Windy City was Enrico Fermi. There, on a rackets court located under the bleachers of the university’s sports stadium, ‘The Pope’ was creating something only his fertile, febrile mind could imagine. On the hardwood floor, Fermi and his assistants had built a mound of graphite blocks, a ‘crude pile of black bricks and wooden timbers’. By feeding in rods of uranium into the heap to start the neutrons bouncing around, he was hoping to create a sustained, controlled neutron-capture reaction that would produce fissile material on a scale never seen before.

  It was the first nuclear reactor. But Fermi’s ‘Chicago pile’ was never going to be permanent: nobody wanted a nuclear reactor in a sports stadium in the middle of a city. They needed somewhere quieter and less populated.

  Tennessee was perfect.

  * * *

  ‘Y’all goin’ up to the lab?’ The barista beams at me as she slides my latte over, the spring in her step as effervescent as its foam, her rich Southern accent flowing mellifluously. I laugh.

  ‘What gave it away?’ I’m wearing my smartest (crumpled) charcoal grey suit and a loose shirt suited to Tennessee’s humid climes. Knoxville is a sleepy town on the main highway, tucked in the far eastern extremes of the state. Here the Great Smoky Mountains roll like ruffled green carpet into the hazy distance, a mist-shrouded heartland that gave birth to Davy Crockett, king of the wild frontier, and Jack Daniel, king of wild whiskey-soaked nights. Rising up the steep banks of a gully carved by the Tennessee River, it could be any small town on the continent, were it not for the Sunsphere – a giant golden ball on a stick left from the 1982 World’s Fair – and the university’s 100,000-seater Neyland Stadium. Currently, its main claim to fame is having a former WWE wrestler as its county mayor. I could be anyone, here for the state’s trinity of God, country music and American football.

  The barista leans forward, tapping a nail on my reading material: The Making of the Atomic Bomb. ‘That was kinda a clue,’ she winks. Sheepishly, I tuck my book away, grab my wake-up juice and head for my ride.

  It’s a conversation that couldn’t have happened 75 years ago. Until the Second World War, the area just west of Knoxville was little more than sleepy, wooded valleys and quiet farmsteads. The few families there were poor, often surviving on as little as $100 a year. There were no roads to speak of beyond the highway save a few dirt tracks. All it had in abundance was electricity: during the Great Depression of the 1930s, the government had tried to rectify the abject poverty with schemes to improve the area, including the construction of huge hydroelectric dams throughout the region.

  These factors made it the perfect site for a secret nuclear base. The region was close enough to the highway and railroad to improve the roads and transport goods but isolated enough to avoid detection. An easy, plentiful supply of power was on the doorstep. And, most importantly, the terrain meant that the different parts of the Manhattan Project based in the area could have their own valley; if the nuclear reactor happened to blow up, the different strands of uranium enrichment and plutonium separation wouldn’t all vanish, as the general in charge argued, ‘like firecrackers on a string’.

  At the end of 1942 the homesteaders of Scarboro, Wheat and other small villages along the Clinch River found eviction notices on their doors. They had up to six weeks – many less – to get what they needed and leave. In their place came the US army, occupying a stretch of land some 27km (17 miles) long. In nine months, the mud tracks and dense woods were transformed into a hidden world where, by the end of the war, 75,000 people would live and work. They ranged from some of the most famous scientists in the world to illiterate labourers, young women doing essential machine work and guard-post GIs frustrated at sitting out the war. The emerging population even had future fast food magnates: the assistant cafeteria manager Harland Sanders would go on to rebrand himself as ‘The Colonel’ and found Kentucky Fried Chicken.

  The whole thing was a mess – Seaborg described it as an ‘unfinished movie set’ of rough-hewn roads and prefab houses. Everything ended up smeared in clay from the unpaved roads. But underneath the mud was science on a scale never witnessed before. In one valley sat the largest single building in the world, the K-25 gaseous diffusion plant, its 152,000m2 (1,640,000ft2) of floor space dedicated to enriching uranium. In another was Y-12, home to the calutrons, large magnets on a racetrack for separating uranium isotopes. Finally, in a humble building of corrugated iron that looked like an old steel mill, was the X-10. This was Fermi’s pet project: the reactor that would solve Seaborg’s woes.

  The complex that had taken over the valleys was given the deliberately uninspiring title of the Clinton Engineer Works. The new settlement also needed a name, one that wouldn’t raise eyebrows with spies. In the end, the army settled on Oak Ridge.

  Today the heart of the secret city is Oak Ridge National Laboratory, one of the largest research facilities in the world. It’s home to some of the most cutting-edge science on the planet, its mission focused on clean energy, extreme materials and ambitious projects using advanced equipment no other research centre can offer. In one lab a team has 3D-printed a full-size submersible hull. In another, they’re using high-powered beams to create nanoscale circuits. A third runs the biggest carbon-fibre research facility in the US, developing space-age technologies in collaboration with commercial companies. Summit, the lab’s latest supercomputer, is the fastest in the world: the size of a basketball court, it guzzles more power than the nearest city and comfortably processes some 200,000 trillion calculations a second.3 One of the lab’s latest facilities, the most advanced neutron source in the world, cost around $1.5 billion. We’re a long way from Fermi’s Roman corridors or Seaborg’s stinky attic.

  ‘About $4.5 billion has gone into the lab in the past three years,’ says my guide, former associate laboratory director James Roberto, as we traverse the site in his car. Oak Ridge is more like a college campus than a research lab, an open plaza with manicured lawns and modern buildings. The only real difference is the n
ational-level security, the ban on alcohol, and smoking is only permitted in designated areas. The facilities are available to scientists from anywhere in the world as long as they have a good research pitch. ‘This behind-the-wall secret place transformed into a mostly open scientific lab,’ he continues, dodging past a flock of wild turkeys by the roadside. ‘We have 3,200 research guests that come and work with us every year … our mission is science and security, but to add value too. We come up with a billion-dollar innovation at least once a decade.’

  It’s only when you leave the main strip and get over the ridges that you start to see Oak Ridge’s industrial heart. ‘At the end of the war, we had the Clinton Pile, now called the Oak Ridge [X-10] Graphite Reactor,’ Roberto explains. ‘That was the best neutron source in the world. [Theoretical physicist] Eugene Wigner had a vision: why not build a national laboratory around it? The US was in the process of trying to build a commercial nuclear power industry, and we needed a reactor that could be used for fuels and separation chemistry … back then, we made iodine-131, phosphorus-32 and carbon-14 because nobody else could make them. Today we still make the isotopes nobody else can make.’ Within a year of the war ending, Oak Ridge was already shipping radioisotopes to hospitals in the US. This is the life-saving end of radiation.

  We pull up. In front of us, nestled in the woods, is a small nuclear reactor. ‘We designed and built 13 reactors. The one we’re going to is the thirteenth, completed in 1965. You won’t see us changing the fuel today, but …’

  ‘Wait, we’re going into a nuclear plant?’

  Roberto grins and leads the way. ‘Just don’t break anything.’

  * * *

  The X-10 – the Clinton Pile – still exists. Today it’s a historic landmark and museum, a chance for visitors to walk up to the reactor wall and see how things were done before safety was a priority. It still gets checked for radiation regularly, and it’s still so secret visitors aren’t allowed to take photos until they’re inside the building. But in 1943 nobody was even sure if it would work.

  The reactor was simple and elegant in design. It was a large, 7m (23ft) square chunk of graphite – the same thing you use in pencils – with 1,248 holes bored in its side. Safely behind 2m (7ft) of concrete, three men would ride an elevated platform to the holes and feed 15cm (6in) slugs of uranium as fuel, poking them through with long rods. The uranium fired off neutrons, the graphite slowed them down and the nuclear reaction started. Once a rod was used up, the team simply returned to the hole and poked in another; the used rod was pushed down a chute and into a tank of water. From there, the irradiated fuel elements would be moved through a transfer canal to an adjacent building, where the plutonium would be extracted. The whole thing even had a safety feature: several cadmium steel rods, suspended above by an electromagnet. Cadmium absorbs neutrons, so if things got out of hand all the team needed to do was kill the power and the rods would crash down to end the reaction (Fermi called it a ‘scram’ system – because if a nuclear reactor is going into meltdown, that’s what you need to do).

  Figure 3 Feeding uranium rods into the Oak Ridge X-10 Graphite Reactor.

  The reactor went critical early on 4 November 1943 and the first plutonium was produced in mid-December. The project team just needed a way to separate Pu-239 from all the other bits.

  Up in Chicago, Seaborg had spent a year assembling a team of chemists to tackle the problem. This was easier said than done. Most of the original element leaders – Lawrence, Fermi, Abelson, Segrè, McMillan – were busy working on problems of their own in a sprawling spiderweb of secret research that included the biggest names in physics. Seaborg was a virtual unknown in his early thirties who had to somehow persuade the best scientists in America to sacrifice their careers and work on something he couldn’t tell them about. He wrote in his diary his sales pitch: ‘No matter what you do with the rest of your life, nothing will be as important to the future of the world as your work on this project right now.’ Seaborg’s team blossomed to 50 scientists.

  One of the first was Stanley Thompson, Seaborg’s oldest and closest friend. Born a month apart, they had started high school together in Los Angeles and had bonded over their shared passion for science. Thompson had been rough and tumble (‘the kind of guy who would tackle you without warning and start a wrestling match’, Seaborg recalled), but had proven to be just as talented – if not more – than his classmate when it came to chemistry, and like Seaborg had gone on to study at the University of California, Los Angeles. Here, Thompson had shown he was willing to look after his friend when things got tough: when the impoverished Seaborg had almost dropped out of university, it had been Thompson who had loaned him the money to continue.

  Thompson was working for Standard Oil, but Seaborg knew he was exactly the kind of person the plutonium project required – a ‘chemist’s chemist’. In his autobiography, Seaborg recounts how he soon lured him to Chicago with a letter:

  The work here is extremely important, perhaps the number one war research project in the country, and it is of such a character that it will almost certainly have post-war significance and develop into a large industry […] unfortunately I cannot divulge to you the nature of the work but, knowing the nature of my activities in the past, you are in a fair position to guess. It is research work of the most interesting type; it is the most interesting problem upon which I have ever worked.

  Within months, Thompson blossomed into a world-class talent. His work in petrochemicals meant he had experience in scaling up reactions unmatched by his academic peers, while his intuition, patience and attention to detail made him the lab’s leading experimentalist. Seaborg later described him as ‘the best experimental chemist I have ever known’. High praise from a man who knew virtually every prominent scientist of the late twentieth century.

  A more maverick addition was a relative stranger. One of Helen Seaborg’s friends in the secretarial pool, Wilma Belt, had met a technician called Al Ghiorso, who had been hired by Berkeley Lab to wire up the intercom. The couple had married, and Al had stuck around building Geiger counters for the lab: a tedious job, but all he could get with his modest qualifications. Ghiorso cut a strange figure. He was a full head shorter than Seaborg, with hair thick with pomade, eyes hidden behind dark-rimmed glasses and a pen permanently anchored into the top pocket of his white shirt. He had grown up in Alameda, a short distance from Berkeley, on a ranch where his father bootlegged liquor during Prohibition. Living under the flight path of Oakland Airport, the young Ghiorso had taken an interest in planes, then in radio. Constantly tinkering, by the time he was in college he had boosted his ham radio to the point where he could speak with people in Ohio, some 4,000km (2,500 miles) away. This was well beyond the world record for the 5m band; characteristically, Ghiorso was operating illegally (he had never bothered to get a radio licence), so never claimed the world record prize.

  In mid-1942, as the US began to mobilise more men, Ghiorso had become concerned he’d end up drafted into the regular army, and had decided to apply for a commission in the US Navy. Lacking the required references, Wilma suggested he write to Seaborg – someone he barely knew – for a recommendation. When the letter arrived in Chicago, Glenn shared it with Helen. Realising that Ghiorso had exactly the kind of crazy, technical nous her husband needed, she looked at Glenn and said: ‘You hire this guy.’ Seaborg’s return letter had included both the recommendation and a job offer. Ghiorso chose the latter. The two wives had conspired to create one of the most successful research collaborations in history. Unlike Thompson, Ghiorso didn’t jump at the Chicago offer; he only signed up after making Seaborg swear he’d never have to make another Geiger counter again.

  Ghiorso had a stubborn, non-conformist streak and thrived on being contrary. On paper, he was the least qualified of Seaborg’s team – for his entire career, he refused to get anything higher than a bachelor’s degree in electrical engineering. He never owned a TV (convinced it would rot his brain), constantly doodled on an
ything he could find and didn’t hesitate to express his radical, liberal views. He was also compassionate and caring; in later years, when one of his colleagues, Mike Nitschke, was dying of AIDS, Ghiorso took on the role of carer – physically, mentally and financially – and established a memorial fund in his friend’s name. Ken Gregorich, a former senior staff scientist in Berkeley’s heavy element team, describes him as ‘an eccentric character … a little too enthusiastic at times … he was an inventor, not an engineer. An engineer is a real profession, and inventor is not. He just thought about the way he knew things worked and would go “well, it ought to work this way too” and he’d go and try it.’ Another Berkeley alumna, Dawn Shaughnessy, also remembers his unorthodox style to lab work: ‘You’d hear stories of Al breaking targets and not telling anyone. People would walk in the lab and say: “What’s that cloud in the sky?” And Al would reply: “Oh, that’s radioactive, don’t inhale it and you’ll be fine …”’

  The first task for Seaborg’s newly assembled team in Chicago was to work out how to get as much plutonium-239 as possible. This meant pioneering a new field called ultramicrochemistry, with its own unique apparatus. Amounts were weighed using a hair-thin quartz fibre fastened at one end; the amount the fibre bent gave you the weight of your sample. It was, Seaborg recorded, ‘an invisible material being weighed with an invisible balance’. In December 1942, while Fermi played with his pile under the bleachers, Stanley Thompson hit upon a process (using bismuth phosphate) that could extract the plutonium more effectively than before. The quantities available – and the consequences of failure – meant the team couldn’t afford to waste a single drop.