energy science technology

Science fiction, or the future of clean energy – what is nuclear fusion?

It is either the miracle energy source of the future, or the most expensive wild goose chase in the history of science. If it succeeds, it could solve climate change and resource depletion at one stroke. It would be an endless source of cheap power, and our energy-intensive lifestyles could continue with impunity. If it fails, decades of research and billions of dollars will have been wasted. This is the great gamble of nuclear fusion, and since it’s been in the news again this week, I thought it was worth exploring in a little depth.

The limits of nuclear power

Nuclear power is an incredible achievement, and being low-carbon, it is often hailed as an important energy source for the future. However, even putting the expense to one side,  there are major drawbacks. The biggest problems are the issue of radioactive waste, and the limited stocks of uranium. At current rates of use, we have around 59 years of uranium left, but that will quickly reduce if nuclear power grows much beyond the 16% of the world’s electricity that it currently provides.

Thorium reactors or ‘breeder reactors’ are much more efficient, but despite decades of development, it is still experimental technology. There is just one fully functioning breeder reactor, the thirty year old and much studied Russian BN-600. A more modern prototype in Japan began transmission in 1994, reported a fire just months later, and has been in repair for 15 years. It came back online in May this year – things move slowly in the world of nuclear power. India has also developed the technology and plans to build a series of ‘second-generation’ reactors that will run off the spent fuel from its conventional nuclear programme. The first of these has been delayed, but is expected to open in 2011.

Despite the potential of breeder reactors, they are subject to the same dangers as any other nuclear reactor, and we don’t yet have a foolproof solution to nuclear waste. Decommissioned power stations are dangerous for decades, and the waste products for thousands of years. Options include burying it in the ground, burying it in deep-sea trenches or, more imaginatively, firing it into space. But some high level radioactive materials have a half life of over a million years – there is simply no safe way of handling something like that, no hole in the ground deep enough or container strong enough.

In the UK we mix nuclear waste into glass, and seal it in steel containers. Eventually, it will be buried deep underground, but we haven’t decided quite where yet. In fact, almost nobody has decided where to put their waste. Russia is stacking it up in the Ural mountains until it finds a safe long-term location for it. The US plan to create a national disposal site under Yucca Mountain has stalled. France has identified a site, but it won’t be ready until 2025, and there have been a series of incidents in the meantime. A proposal to create an international site in the desert in Australia never got off the ground, but it is probably only a matter of time before someone suggests burying it in the desert in a poor and sparsely populated African country.

The promise of nuclear fusion

So what we need is a new generation of nuclear power stations that doesn’t run off a rapidly depleting resource, and that doesn’t produce radioactive waste. And that’s where nuclear fusion comes in. You can run it off the hydrogen isotope deuterium, which is easy to come by – you just extract it from water, meaning you could fuel your power station with the boundless resource of seawater. As for waste, the most harmful by-products such as tritium could be burnt off, leaving some helium emissions and a small amount of solid waste. These solids would be more radioactive, but for a much shorter time – even the most toxic of them would degrade to harmless ash within 300 years.

Nuclear fusion is the counterpart to nuclear fission, the current form of nuclear power. Fission splits atoms to release energy, while fusion bonds them together, creating intense heat. It is the process that takes place inside a star, or the sun. It’s also what happens when you set off a hydrogen bomb. A nuclear fusion power station would fuse hydrogen atoms and generate that intense heat, and then simply use that heat to run steam-driven turbines and create electricity. It’s a beautiful theory.

When you stop and think about it, it gets a little more complicated. You are essentially creating a miniature sun inside the reactor, and while making a sun is one thing, working out what to put it in is another problem altogether. The sun burns under unfathomably enormous pressure, and fuses hydrogen at 15 million degrees. Unable to create that pressure, a fusion reactor would need to push the heat to 100 million degrees to release the energy, and there’s just nothing that can contain anything that hot.  “An unearthly kind of fire needs an unearthly kind of furnace,” as Marek Kohn puts it. The solution is really quite astonishing – rather than trying to box it in with exotic composites of metal and ceramic, the reactor contains the charged particles (or plasma) within a magnetic field.

Inside the JET tokamak

Progress in researching nuclear fusion

This magnetic field is generated in a donut-shaped chamber called a Tokamak, and the process has been successfully trialled in Oxfordshire. In 1991 the Joint European Torus, shown here in its space-age glory, managed to generate a 2MW of power for a matter of seconds. That was after 8 years of experimentation, and after a further 6 years they had got that up to 16MW. That remains the world record for fusion power, set in 1997.

Work at JET continues, trying to stabilise plasma within the magnetic field, and the facilities are currently being upgraded. Meanwhile, the next test facility is being built. The technology is considered so important, it has marshalled a quite unique degree of international cooperation. Mikhael Gorbachev suggested the initial idea to Ronald Reagan, bucking the cold war competition. The resulting project is joint funded between Russia, Japan, India, Korea, China, the US and the EU, and is called the International Thermonuclear Expermental Reactor (Iter).

So far, the reactor amounts to an enormous clearing in the woods near Caradache, a kilometre across and 400 metres wide. Given the number of parties involved, perhaps it is unsurprising that it has taken 25 years to get this far, but it doesn’t bode well. The 37 metre wide Tokamak will be ready by 2019, and you can explore the designs on the rather good Iter website. If the following years of experimentation are successful, the first energy-generating experiments are expected by 2026. A pilot commercially scaled fusion power station could then be built, coming online sometime around 205o. At this point, you will begin to see the problems for climate change.

The Iter construction site

Another problem is funding. Iter will cost $21 billion to build, three times the original estimate. As the budget has slowly ballooned, there has been a lot of quibbling over who pays for what. The latest dispute was just solved this week, with an EU bailout of the project and a new director. The cost is now becoming controversial, with European budgets being squeezed. French scientists have pointed out that national support for Iter is equivalent to all government support for biology and physics research for 20 years. If it doesn’t pay off, that’s a lot of research funding that could have been directed elsewhere, and there is mounting pressure to scrap Iter altogether.

Iter isn’t the only project working on it. China, not content with funding Iter, claims to have a working fusion reactor but isn’t sharing any details. North Korea also claims to have produced a nuclear fusion reaction, and Iran has recently declared its intention to research it.

In conclusion

It is too early to tell if fusion power will ever be commercially viable. If it is, it will be a truly remarkable achievement, but it is more likely to be the miracle energy source of the next century rather not this one. In that sense, fusion as a solution to climate change or peak oil is a misplaced hope. Only time will tell if Iter’s machine is a pioneering prototype or a $21 billion white elephant in the French woods – and time is one thing we don’t have. A new generation of nuclear fusion power stations simply will not be ready in any time frame that realistically slows CO2 emissions, nor would it come online in time to replace fossil fuels. In the short term, there is still no alternative to renewable energy, and a drastic reduction in the amount of energy we use in the first place.

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  1. Nuclear fusion won’t help to solve the underlying issue of economic growth and energy coupling. If we had limitless amounts of CO2-free energy and would follow through with a path of perpetual exponential economic growth, the Earth would at one point suffocate from our heat exhaust, the point being that ultimately economic growth and energy consumption remain coupled for physical reasons, no matter how efficient the technology becomes. The incentives in our economic system also do not encourage efficiency – on the contrary. Ultimately it is impossible to envision a sustainable economic system that is based upon the perpetual exponential growth requirement. Any efficiency or energy revolution then will only buy some time, postpone the collapse, but never solve the main problem.

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