Piece of the Sun : The Quest for Fusion Energy (9781468310412) Read online

  A fusion reactor does produce some radioactive waste but, again, the amount is tiny compared to a fission plant. The ‘ash’ of fusion burning is helium, the harmless inert gas that is used to fill party balloons, lift modern-day airships, and cool NMR machines. The metal and other materials in the structure of a fusion reactor, after decades of being bombarded by high-energy neutrons from the reactions, will become mildly radioactive. So when a plant is dismantled it will need to be buried in shallow pits for a few decades, by which time it would be safe to recycle. There is none of the high-level waste that takes millennia to cool down.

  Fusion seems too good to be true and to the fusion pioneers in the late 1940s and early 1950s, although they wouldn’t have known all of these details, it was clear that fusion would be a vastly superior energy source compared to fission. There was a certain idealism to these early followers of fusion, who were almost all in the United Kingdom, the United States and the Soviet Union. All physicists had been shaken by the power unleashed in the Manhattan Project and many felt a sense of responsibility for the devastation that the atomic bombs caused. Fusion provided a way to use nuclear technology peacefully, for the benefit of everyone. Much of the early work on fusion was done in weapons laboratories because that’s where the nuclear physicists were, but many of them left the labs to pursue fusion outside the military complex.

  With the technological optimism of the time, the early pioneers expected that they would be able to master fusion in about a decade and then move on to commercial power stations – a similar timeline to fission. They knew that they would have to get their hydrogen fuel very, very hot, at least 100 million °C. At such temperatures solids, liquids and even gases cannot exist, so they would have to deal with plasma – that fourth state of matter that exists in the Sun’s core where negatively-charged electrons and positive ions move around independently. In the middle of the last century scientists didn’t know much about plasmas, especially very hot ones, and they had to come up with a system that could contain the plasma, heat it hotter than the core of the Sun and then hold it there without it touching the sides, because its extreme temperature would burn or melt almost any material.

  Undaunted by these hurdles, the early fusion enthusiasts exploited the key difference between plasma and normal gas: that it is made up of charged particles. When charged particles move around in an electric or magnetic field they feel a force pushing them in a particular direction. So researchers started building containers pierced by complicated magnetic and electric fields to push the particles of the plasma towards the centre and away from the walls. Sometimes these were straight tubes, sometimes ring-shaped doughnuts and other shapes. At first they were made of glass – the scientist’s favourite building material – small enough to sit on a lab bench and sprouting an impenetrable tangle of wires, pumps and measuring apparatuses.

  Soon researchers worked out how to create plasmas in their devices and how to heat them to high temperature, if only for a fleeting fraction of a second. No fusion yet, but success in containing and heating plasmas encouraged them to try out new ideas, build more devices and build them bigger. Their makers gave them strange names such as pinches, mirror machines, stellarators and tokamaks. One of the reasons they were not getting to fusion temperatures was that too much heat was escaping from the plasma, so they guessed that bigger was better, since it would take the heat longer to escape from the core of the plasma if there was more of it. Soon their machines were too big for lab benches and were taking up whole rooms, then filling large hangar-like buildings.

  They encountered other problems too. Using high-speed cameras to observe the plasma – it glows, just as the plasma in fluorescent lights does – they saw it wriggling and bulging as if trying to break free of its bonds. These phenomena, known as instabilities, had never been seen before, perhaps because no one had tried doing these things to plasma before. To work out how to prevent them, the researchers had to adapt or make up the theory of plasmas as they went along.

  A pattern began to emerge in fusion research: scientists would build a new machine; when it was working they would make progress towards fusion conditions but not quite as much as they had predicted; this could be because the machine underperformed or they encountered some new unforeseen type of instability; the way forward was to build another bigger and better machine, and so on. Fusion got a reputation for promising a lot but never delivering. The oft-repeated joke was, ‘Fusion is the energy of the future, and always will be.’

  By the 1980s the reactors had come a long way from the bench-top devices of the early days. During that decade the biggest fusion reactors built to date were completed: the Joint European Torus or JET, which is the size of a three-storey house, and its US counterpart, the Tokamak Fusion Test Reactor. These were meant to be the reactors that finally made it to the first great milestone of fusion: break-even. This is the situation when the power given off by the fusion reactions is equal to the power used to heat up the plasma. Thus far all reactors had been net consumers of energy. If fusion was going to be viable as a source of power it had to get over this hurdle. But despite the heroic efforts of researchers over more than a decade, neither of these great machines managed to get to break-even. JET’s best shot, made in 1997, produced 16 megawatts of fusion power but this was only around 70% of the power pumped in to heat the plasma – nearly there, but not quite.

  * * *

  Some people have spent their whole working lives researching fusion and then retired feeling bitter at what they see as a wasted career. But that hasn’t stopped new recruits joining the effort every year: optimistic young graduates keen to get to grips with a complicated scientific problem that has real implications for the world. Their numbers have been increasing in recent years, perhaps motivated by two factors: there is a new machine under construction, a huge global effort that may finally show that fusion can be a net producer of energy; and the need for fusion has never been greater, considering the twin threats of dwindling oil supplies and climate change.

  The new machine is the International Thermonuclear Experimental Reactor, or simply ITER (pronounced ‘eater’) as it now likes to be called. Many machines over the past sixty years have been billed as ‘the one’ that will make the big breakthrough, only to stumble before getting there. But considering how close JET, its direct predecessor, got to break-even, ITER has to have a good chance. Those earlier machines were almost invariably built in haste, part of a breakneck research programme. ITER, in contrast, was in development for a quarter of a century before construction began and, because of the delicate politics of building an international collaboration, was subjected to endless reviews, reappraisals, rethinks and redesigns. It may not be the perfect fusion reactor but it is the best guess of the thousands of researchers who have contributed to its design since the mid 1980s.

  ITER is not a power station; it won’t be connected to the grid and won’t even generate any electricity, but its designers are aiming to go far beyond break-even and spark enough fusion reactions to produce ten times as much heat as that pumped in to make it work. To get there is requiring a reactor of epic proportions. The building containing the reactor will be 60m tall and extend 13m underground – altogether taller than the Arc de Triomphe. The reactor inside will weigh 23,000 tonnes – continuing the Parisian theme, that’s more than three Eiffel Towers. The heart of the reactor, the empty space were the hot plasma will hopefully burn, is about four times the height of an adult and has a volume of 840m3 – dwarfing JET’s 100m3.

  At the time of writing, workers at the ITER site in Cadarache, in southern France, are laying foundations, erecting buildings, installing cables and generally preparing the ground. In factories around the world the various components that will make up the reactor are being built, ready to be shipped to France and assembled on site. The scale and the quantities are prodigious. In six different ITER member countries factories are churning out niobium-tin superconducting wires for the reactor’s magnets.
When finished, they will have made 80,000km of wire, enough to wrap around the equator twice. The giant D-shaped coils of wire that are the electromagnets used to contain the plasma are each 14m tall and weigh 360 tonnes, as much as a fully laden jumbo jet. ITER needs eighteen of these magnets. Perhaps the most mindboggling statistic about ITER, and one of the reasons it is being built by an international collaboration, is its cost: somewhere between €13 billion and €16 billion. That makes it the most expensive science experiment ever built – twice as expensive as the Large Hadron Collider at CERN. The European Union, as the host, is footing 45% of the bill; the rest is being split equally between China, India, Japan, Russia, South Korea and the United States. According to the current schedule, the reactor will be finished in 2019 or 2020.

  That huge sum of money is, for the nations involved, a gamble against a future in which access to energy will become an issue of national security. Most agree that oil production is going to decline sharply during this century. There is still plenty of coal around but burning it in large quantities increases the risk of catastrophic climate change. That doesn’t leave many options for the world’s future energy supplies. Conventional nuclear power makes people uneasy for many reasons, including safety, the problems of disposing of waste, nuclear proliferation and terrorism. The disaster at the Fukushima Daiichi nuclear plant in Japan following the earthquake and tsunami in March 2011 served to remind the world how even the most secure installation can still be vulnerable.

  Alternative energy sources such as wind, wave and solar power will undoubtedly be a part of our energy future. They are, in a sense, just harvesting energy from our local giant fusion reactor, the Sun. The cost of electricity from alternative sources is high but has declined substantially in recent decades and with continuing improvements in technology it will come down further. It would be very hard, however, for our modern energy-hungry society to function on alternative energy alone because it is naturally intermittent – sometimes the sun doesn’t shine and the wind doesn’t blow – and also diffuse – alternative technologies take up a lot of space to produce not very much power. There are ways around the intermittent nature of alternative energy, such as energy storage and backup generators, but these all add to the cost. Finding enough space for wind and solar farms is more problematic, especially since the world’s wide open spaces tend to be far from big cities where the bulk of energy is consumed and transmitting electricity over long distances causes sizable losses. The United Kingdom, as an example, has pushed heavily to build up its wind energy production and by 2011 had around 300 wind farms with a total of almost 3,500 turbines. But wind energy contributed only around 5% of the UK’s total electricity production and, given how hard it often is to overcome local opposition to building new wind farms, it is not clear how wind energy could provide a substantial fraction of Britain’s needs.

  Difficult choices lie ahead over energy and, some fear, wars will be fought in coming decades over access to energy resources, especially as the vast populations of countries such as China and India increase in prosperity and demand more energy. Anywhere that oil is produced or transported – the Strait of Hormuz, the South China Sea, the Caspian Sea, the Arctic – could be a flashpoint. Supporting fusion is like backing a long shot: it may not come through, but if it does it will pay back handsomely. No one is promising that fusion energy will be cheap; reactors are expensive things to build and operate. But in a fusion-powered world geopolitics would no longer be dominated by the oil industry, so no more oil embargoes, no wild swings in the price of crude and no more worrying that Russia will turn off the tap on its gas pipelines.

  Much expectation rides on the back of ITER but it may not even be the machine to make the breakthrough first. There is a rival fusion reactor technology that has been developed largely in nuclear weapons labs to help study the physics of nuclear explosions and it, rather than ITER, could reach break-even first. This type of reactor doesn’t confine a large volume of plasma and heat it to fusion temperatures. Instead it takes a tiny capsule no bigger than a peppercorn, filled with deuterium and tritium, and crushes it to a density a thousand times that of lead using the highest energy lasers in the world. Assuming that the compression is clean and symmetrical, the extreme temperature and pressure created will spark an explosive fusion reaction like a tiny hydrogen bomb. Each explosion produces a relatively small amount of energy, but if the process can be coaxed to give a good energy yield and a plant can be created that produces ten or more such explosions per second, then you might have a power station.

  The foremost machine attempting this type of fusion is the National Ignition Facility or NIF near San Francisco. This $3.5-billion machine was completed in 2009 and, at the time of writing, researchers there are still fine-tuning it to get the best possible compression of the capsules. Their aim is to achieve ‘ignition,’ a burning plasma that sustains itself with its own heat and generates more energy than was put into compressing it. If NIF researchers do succeed they predict that, using existing technology, they could build a prototype power plant in just twelve years. Not everyone in this branch of fusion thinks that is possible but they all passionately believe that such machines will one day provide a viable alternative to magnetic fusion machines such as ITER.

  There are other avenues too; other reactor designs that were put to one side in the headlong rush to build the one, big machine. Rather than using magnets or lasers to manipulate a plasma, these use things such as heavy ion beams, extreme electrical currents, or hydraulic rams. If ITER and NIF should fail, or not succeed well enough, then these bypassed technologies could have their day. Some of them have already been adopted by a new crop of start-up companies which, backed by venture capital, are trying to make a dash to fusion with small teams of dedicated researchers in secretive private laboratories.

  There are still many sceptics who say that fusion will never supply a single kilowatt of power to the grid because there are just too many scientific and technological uncertainties. But their views will not dent the conviction of those who have dedicated their lives to the dream of fusion energy, enduring ups and downs, dead ends, false trails and minor breakthroughs. The story of fusion is not just one of scientists toiling away in laboratories in isolation. Military expediency, international politics and historical serendipity have all boosted and buffeted the progress of fusion research. Funding for the increasingly expensive machines that fusion requires has ebbed and flowed depending on the eagerness of governments to find alternative sources of energy: the Middle East oil embargo of the 1970s led to a huge boost in funding for fusion but by the 1980s, when oil was cheap again, research money was harder to find. Atomic espionage, superpower summits, hijackings by Palestinian terrorists and the Iraq War have all impacted on fusion’s fortunes. What has kept it going is the unwavering belief among the scientists who have embraced the field that one day it will work. Fusion science is not about seeking knowledge for its own sake; it doesn’t have the intellectual appeal of the Big Bang, black holes, the human genome or the hunt for the Higgs boson; it is about hammering away at a stubborn nut in the conviction that one day it will crack. There’s unlikely to be a eureka moment but one day the operators of ITER, or some other reactor, will get their settings just right, the plasma will get hot, stay hot, and burn like a piece of the Sun.

  CHAPTER 2

  Britain:

  Thonemann

  and the Pinch

  NOBODY IS QUITE SURE WHO HAD THE IDEA FIRST. AFTER THE whirlwind of discovery that was physics in the 1920s and 1930s, all the theoretical building blocks for generating energy by thermonuclear fusion were at hand and someone was bound to put them together. As often happens in science, the same idea popped up in several disconnected places at around the same time.

  Hans Bethe, an émigré physicist from Germany who fled when the Nazis came to power in 1933 and settled at Cornell University, remembers having a conversation in Washington during 1937 with fellow émigré Leo Szilard from Hungary
. Bethe had that year written a landmark paper that finally nailed down the fusion processes in stars which produce energy, so he was well placed to address the problem of creating fusion. Fritz Houtermans was another German-born physicist who fled the Nazis, but in his case to Kharkov in the Soviet Union. He is believed to have been carrying out experiments in fusion in 1937. And Peter Thonemann, an undergraduate student at the University of Melbourne in Australia, remembers working out a basic plan for a fusion reactor in 1939.

  Although everything was ready for the pursuit of fusion to begin, the Second World War soon had physicists thinking of other things. After Nazi troops invaded Poland, Szilard drafted a letter alerting the US government that a fission chain reaction could be used to make a devastating bomb and warning that German scientists were working in this area. He persuaded his old friend and colleague Albert Einstein to co-sign the letter and they delivered it to President Franklin Roosevelt. That letter led eventually to the herculean Manhattan Project to develop an atomic bomb before the Nazis did. Bethe joined the Manhattan Project, heading the theory division at the top-secret Los Alamos laboratory in the New Mexico desert where many of America’s and Europe’s best physicists spent the latter years of the war.

  Thonemann also joined the war effort, taking a job at the Australian government’s Munitions Supply Laboratories in 1940 and later leaving to join the research department of Amalgamated Wireless near Sydney. As the war approached its conclusion, he took up his studies again at Sydney University. In Sydney, his passion for the possibilities of fusion continued. His thesis topic was how to measure the density of electrons in a plasma. Thonemann talked endlessly about fusion and at home he melted window glass in the oven in an effort to make doughnut-shaped vessels for plasma experiments.