Superheavy
Page 13
That afternoon, Ghiorso forgot to turn a valve and close the circuit. Instead of forcing the unwanted gases out, the helium became backed up and looked for an alternative exit. The weak spot in Hades’ design was a 0.1mm sheet of nickel foil. As the pressure of the helium increased, the force against the foil was so great it punctured, rupturing the system and causing the curium to ‘literally explode into a dust’. The result was like popping a balloon filled with radioactive glitter.
Hades’ outer chamber hadn’t been designed to deal with this kind of accident. A draught carried the curium dust up over the radioactive shielding and into the timber beams of the building’s roof. There, it was picked up by the ventilation system and spread out across all 1,500m2 (15,800ft2) of the building in a fine mist. Within seconds, the radioactive cloud had flooded the entire complex.
Ghiorso had heard the foil being blown and turned off the valves almost immediately. Even so, a quick check with a Geiger counter showed that the curium had scattered everywhere: on the floor, on the machine, on himself. Ghiorso hit the intercom and warned Sue Hargis, the building monitor, to start a total evacuation. He then stayed, crouched at the entrance of the Hades chamber, to shut down the machine and contain the spill. Showing a cool head and immense bravery, Hargis got everyone else out and then headed for Ghiorso to hand him the respirator and overalls.
The lab was evacuated in five minutes. Ghiorso was out in 10. An hour or so later a doctor came around and recommended that everyone provide a urine sample. Only five people bothered: the researchers knew that if they had been exposed, there was nothing modern medicine could do about it anyway.
In a small miracle, no one was seriously hurt. Hargis calculated the maximum dose anyone could have received was some 1.5 Sieverts (15 million bananas) but most of the evacuees’ exposure was far lower. Ghiorso, who had been closest to the dust, got lucky. His instinct to duck down meant the worst of the curium was blown clear above his head. He suffered no long-lasting effects. Viola, who received the highest dose, became a test case for health scientists, who provided him with a lunch pail in which to collect his poo for the next six months. ‘The results provided the health physicists with a nice paper,’ Viola recalls, ‘but I was miffed because I didn’t even get an acknowledgement.’
The HILAC laboratory was so full of radioactive particles that it took 30 people around three weeks to decontaminate it. Even so, Ghiorso recalled, ‘for many years curium continued to be found in small quantities in obscure places in the building’. Labour, materials, clean-up costs, lost equipment and – most expensive of all – lost beam time at the HILAC meant the incident had cost Berkeley $58,500 ($500,000 today). ‘It also, understandably, caused us to be quite gun-shy in the use of highly active targets,’ Ghiorso added. The search for element 102 was abandoned. Instead, Berkeley began to look for the next element in sequence.
Hades was soon rebuilt and renamed (not certain it merited the name ‘Heaven’, the team decided it was somewhere in between and called it ‘Limbo’). In 1961 it produced element 103. Ghiorso rapidly pushed for the name ‘lawrencium’ after the lab’s recently deceased leader. Photos were taken of a delighted Ghiorso, scrawling its initials (Lw, although this was later changed to Lr) into place on the periodic table.
The Americans were confident they had discovered all of the actinides, opening the path to the discovery of the superheavy elements.
They didn’t expect the Russians to get there first.
* * *
The Flerov Laboratory of Nuclear Reactions isn’t known for its interior design. Just a few corridors into its beating heart and you’ll pass hard concrete walls with warning lights in bent metal cages. Take a trip up its myriad stairs and you’ll find yourself climbing unpaved passages that feel more like a builder’s yard than a laboratory. The working ends of its machines are in rooms filled with pistons and pressure valves, sudden hisses and fluctuating needles. Signs and sirens and decontamination showers are everywhere.
Yuri Oganessian’s office, in contrast, is a thing of beauty. It is a treasure trove, built up over decades, that is crammed full of memories and ideas. Most scientists’ offices range from the clean and clinical to generic boltholes that lack personality. Oganessian’s is in another league entirely. The room is expansive. Presidential, almost; an Oval Office of science. Upon his polished desk are papers to review, notes, pens and a calculator. There is no sign of a computer. Behind his chair are the usual family photos, including a giant A3 portrait of his grandson, the proud Oganessian boasting of his exploits in a race around Manhattan. Shelves are stacked with textbooks, prizes, awards, certificates, mementos and presents – there’s even a licence plate from Roswell, New Mexico. In the corner is a blackboard, its chalk words and diagrams shielded by glass.
‘This is Flerov’s,’ Oganessian says, gesturing to the marks. He’s saved his mentor’s handwritten notes for posterity. The chalk lines, reds and oranges, shoot out violently: the Russians were discussing the idea of burying a nuclear bomb underground and setting it off to produce vast amounts of neutron-rich curium. The idea isn’t as crazy as it sounds. Throughout the 1960s, both the US and USSR set off nuclear bombs for a whole host of reasons – element discovery was just one of them. Oganessian’s voice still quavers when he speaks of his mentor. The two men were separated by almost 20 years in age. They weren’t friends, but something more – that rare bond of master and apprentice. The next room over was Flerov’s, which has been converted into a small museum full of relics. My favourite is a giant stuffed crab, caught by Flerov on an expedition to Kamchatka.
Today, Oganessian oversees the lab’s scientific programme. There’s a joke in Russia, a belief that Armenians such as Oganessian have a creative mind that can see the world differently. It might not hold true for everyone, but it certainly holds for Oganessian. ‘When you come to work for Yuri, it’s not like a lab,’ one of the Russian researchers told me before entering. ‘It’s like a theatre – and he’s the director.’ There’s another secret I was told before my visit: ‘When you meet Yuri, he’ll sit you down and talk to you about what he wants to talk about, not necessarily what you think you want to talk about. By the end, you’ll wonder why you never saw the world so clearly.’
We take our seats, thick Russian coffee in fine china at the ready. I ask him why he came into element discovery. ‘I came to the group of Flerov, and the group [work] was defined by Flerov!’ Oganessian laughs warm-heartedly at my naivety. ‘We didn’t just look at properties [of elements]. We looked at nuclear reaction, interactions, types of decay, nuclear fission, alpha emission: the wide field of nuclear physics and chemistry.’
He settles down into his chair. A grandfather telling tales. ‘All this story started, for me, in 1962,’ he recalls, four years after he first arrived at Dubna. By then the Russians had been trying to produce 102 for four years, coming tantalisingly close only for the data to contradict itself each time. ‘I was a very young guy at the time, and the other people in Flerov’s group wanted to try the experiment [for element 102] first. Then Flerov said to me: “OK, we’ll try you now.” I completely changed the apparatus for detection. It was my design.’
The reconfigured machine soon produced the first Russian breakthrough. In 1964 a trio of JINR scientists bombarded uranium with neon, discovering nobelium-256 by isolating its daughter, fermium – just as Ghiorso had attempted. Further experiments followed over the next few years. It was bad news for the Americans – the Berkeley team had made an error in their work, and while they had produced nobelium, they had misidentified the product. They had made two different isotopes, with two different half-lives, and assumed it was one thing.
This was enough for the Russians to denounce the American discovery and claim it themselves. Instead of nobelium, they decided the element would be called ‘joliotium’, after Frédéric Joliot-Curie, one-half of the dynamic wife-and-husband duo who had given the world artificial radioactivity. That Joliot-Curie had been an ardent communist
and the first person awarded the Stalin Peace Prize (think a Nobel with more Cold War cynicism) was no coincidence.
The 102 debacle highlights just how crazy the politics of element discovery had become. The Swedish had (probably) made something; the Americans had tried to claim the discovery and almost killed themselves proving it; and the Russians had pointed out an error in the Americans’ work before producing the first definitive proof of the element.
Element 102’s discovery was the flashpoint of a period remembered today as the ‘transfermium wars’: a cat’s cradle of disputes knitted by the US team at Berkeley and the USSR team at Dubna throughout the height of the Cold War.2 The ‘wars’ lasted from roughly the launch of Sputnik in 1957 to the resignation of Richard Nixon in 1974. Up until element 100, perhaps element 101, there is (today) no real debate about who discovered which element.3 Beyond, from the discovery of element 102 until the confirmation of element 108, everything is disputed.
Soon after the discovery of element 102, the Russians announced element 104. If the previous discovery had angered the Americans, the announcement of the Russians claiming the first superheavy element infuriated them. Flerov chose to name the element after his mentor, Igor Kurchatov, who had died only a few years earlier. The move was calculated to celebrate the USSR’s successes but only riled the Americans further: Kurchatov was, after all, the father of Russian nuclear science – including its first atomic bomb.
In 1967 the Soviet team claimed the discovery of element 103 from the Americans, insisting Berkeley had it wrong yet again. Instead of ‘lawrencium’, the JINR scientists decided to name their creation ‘rutherfordium’, after the discoverer of the nucleus, Ernest Rutherford. A year later, they added element 105, choosing the name ‘nielsbohrium’ after the Danish maven who had created the model of the atom (‘bohrium’, it was decided, sounded too much like the element boron, and was likely to cause confusion). The Russians had not just matched the Americans – they were in the lead.
Ghiorso’s team began to play catch-up. As they reached the elements the Russians had already created, the Berkeley scientists dismissed the Dubna team’s results and claimed the discoveries for themselves. Element 104, Ghiorso decided, would be the real ‘rutherfordium’. Element 105 wouldn’t be named ‘nielsbohrium’, but ‘hahnium’, after the German chemist Otto Hahn.
‘The big controversy was over element 104,’ recalls Matti Nurmia, a Finnish researcher who had moved to Berkeley in 1965 and had become Ghiorso’s right-hand man. ‘We were doing experiments on it, and suddenly the Russians beat us. First, there was chagrin within our group – the Russians had beaten us! We studied their work, though, and thought it was poorly documented and wasn’t the quality required [for element discovery]. The first thing you measure is the half-life of an isotope. The Russians thought they saw something that lasted 0.3 seconds. We couldn’t find that, but we found something that lasted 0.08 seconds – very short-lived. That was controversial – the Russians tried to defend their work and said they had made a mistake; we thought there was no scientific basis [for the discovery].’
If you’re lost, don’t worry; so was everyone else. By 1970 the rival periodic tables looked like this:
Element number
US name
USSR name
102
nobelium
joliotium
103
lawrencium
rutherfordium
104
rutherfordium
kurchatovium
105
hahnium
nielsbohrium
In less than 10 years of competition, Berkeley and Dubna had produced four new elements using seven different names (with one name being used for two different elements). It was chaos, with experts split on exactly which group had done what first.
The transfermium wars had left the world with two periodic tables.
* * *
You’re probably wondering how this mess could have happened. Science requires papers, data and proof. Experiments must be repeated, or they become meaningless. How could two world-class labs from two different superpowers disagree so radically about something we’re supposed to be able to prove?
Going over the research papers from that time isn’t particularly helpful. A lot of the published material is, frankly, wrong. Many of the claims didn’t have enough evidence to support them, while others had good, strong science that was dismissed out of bias. Perhaps the greatest issue was the lack of independent scientists with the expertise to understand the technical issues – with only a few labs capable of producing superheavy elements, most experts were at risk of being biased toward Berkeley or Dubna. The transfermium wars were a school-yard spat, backed by two feuding philosophies, with the history of science at stake.
For some researchers, the answer is simple. Politics. ‘It was the Cold War,’ explains JINR’s Andrey Popeko. ‘If the Americans discovered something, our first task was to show it couldn’t work at all. If we discovered something, the Americans did the same.’
Heinz Gäggeler, a Swiss chemist at the Paul Scherrer Institute who worked at both Berkeley and Dubna, agrees. ‘Physicists did good experiments in Dubna, but the Americans could always criticise part of it. Of course, the Russians also had very strict opinions of the results from Berkeley that, ah, weren’t always scientific.’
The politics of the periodic table stretched all the way to the White House, where Seaborg had the ear of the president, Nurmia recalls. ‘The word from the administration was that they were trying to build a better relationship with the Russians and it was probably best not to aggravate them too much. There was a political intervention.’ The transfermium wars had become yet another theatre of the Cold War. ‘Element discovery had become political and lost its appeal as far as I was concerned.’
While the politics overshadowed the two labs’ competition, they alone aren’t enough to explain the transfermium wars: the Americans didn’t deny that Yuri Gagarin was the first man in space, nor the Russians that the US had landed on the Moon. Beyond the Cold War drama, the transfermium wars were really over a very simple question: how do you prove you’ve discovered a new element?
Until the 1950s there wasn’t any need to have an answer. The elements were physically present, so discoveries were usually straightforward, false claims were easily disproved and mistakes were corrected. With the superheavy elements, this was impossible: their half-lives were so finite they only existed for hours or seconds.
For Georgy Flerov, the proof required was obvious. He had discovered spontaneous fission in nature, the evidence that something had broken up without being hit by a particle. If you found evidence of spontaneous fission away from the target, it could only have come from a fusion product that had been made and, while decaying radioactively, had broken apart. Spontaneous fission was easy to detect (important for the Russians, whose detectors weren’t as good as the Americans’) and gave clear evidence of something happening.
The problem with spontaneous fission, however, is that it is impossible to say for certain what has broken up. This resulted in a string of academic papers being published, often claiming different half-lives had been found as the Russians refined their experiment. For the Americans, the papers were evidence that the Russian claims were errors – Ghiorso and Seaborg dismissed them as ‘will-o’-the-wisp chases’. ‘The goal had become a moving target,’ they recalled in The Transuranium People. ‘Each time a new experiment at Berkeley showed that no such activity [for a Russian claim] existed, the Dubna team would counter with a new value or some new objection to the validity of the experiments.’
The American approach was more robust. By looking for an alpha decay chain, the Americans could match their data against a known isotope’s half-life at each step in the chain. ‘One alpha particle,’ Ghiorso declared, ‘was worth 1,000 fissions.’ But even so, the American technique wasn’t perfect; if an alpha decay chain didn’t match up with expectations, the Russians had e
very right to point out their experiment’s flaws too.
Today, the Russians are typically painted as having less solid work than their American counterparts, mainly because modern discoveries usually hinge on being able to show alpha decay chains that link up with known isotopes. But the truth is more muddied. Gäggeler points to the work of Ivo Zvara, one of the Russian team who confirmed their discovery of element 104 through chemical analysis. ‘If you go to a textbook,’ Gäggeler explains, ‘you can see there are very clear-cut chemical properties. You can run a chemical experiment and say, “OK, if something comes through, it must be 104.” But the Americans wouldn’t accept it. They wanted alpha decay, and that wasn’t fair.’
And even with alpha decay, things are rarely clear-cut. Matti Leino, who worked at Berkeley in the 1970s, explains how complicated something that appears straightforward can actually be. ‘The procedure for looking for chains is very simple. Data from the experiments come in as what we call “events”. These are time-stamped: the most important parameters are time, energy and position in the detector.’ From here there are four possible types of hit. You could get a real superheavy element, or a real decay; or you can get things that look like superheavy elements or decays, but which are just ghosts in the machine. ‘What one looks for,’ Leino continues, ‘is a chain that starts with the arrival of a nucleus and continues with at least one decay, with everything happening in the same position … in such work, one can never say with certainty that this decay event came from that nucleus, nor that it is a real nucleus and not some random background. One can only make a statistical estimation that the chain is real.’ In the superheavy field, where everything is a long shot, this can lead to some staggering calculations. ‘My rule of thumb,’ Leino says, ‘is that if it’s a probability of less than one in a million [that the thing you witnessed happened], you should seriously start to worry.’