| Fusion Future |
| Wednesday, 26 April 2006 | |
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Tom Walters talks to Chris Llewellyn-Smith about harnessing the reactions that power the stars With its potential as a non-polluting and safe source of power, nuclear fusion has been a dream of energy researchers for decades. If full-scale fusion reactors become a reality, they could provide plentiful electricity with no carbon emissions, no risk of catastrophic failure and very low running costs. With all this behind it, fusion is definitely the acceptable face of nuclear energy. So when could full-scale fusion become possible? I spoke to Chris Llewellyn- Smith, Director of UKAEA Culham, a major centre for fusion research worldwide, to find out his views on meeting the energy demands of the world.  Credit: UKAEA To the observer, fusion may seem to have taken a long time to progress, but Llewellyn-Smith is quick to defend its development. “In the early 1950s people knew the basic physics of fusion but didn’t know about the basic physics of plasmas, and they grossly underestimated the difficulties. Sorting out the basic science took the 1950s and 1960s.” The technical challenges involved were, and still are, immense. The first step in making fusion work was to find the best configuration of magnets to hold several thousand cubic metres of gas that is ten times hotter than the centre of the sun.“It wasn’t until the end of the 1960s that the basic configuration you need to do this was worked out, and from then it’s been a systematic process of scaling up in size”, says Llewellyn-Smith. This scaling up is a complex task,but he seems confident that it is not insurmountable: “things that would have seemed inconceivably complex 50 years ago, like a jumbo jet,do work routinely and we’ve learned a lot about technology, so I’m personally rather confident that the complexity problem will be mastered.” So what about the intervening period before fusion’s promises become reality? Should we invest in new fission reactors or in renewable energy? On this point, his response is simple: “probably both, actually”. “There’s a rather false debate going on at the moment: ‘do we want nuclear or renewables?’ The fact is that when you look at the size of the energy challenge,we probably need everything we can get, especially when you look on a global scale at the anticipated increase in energy use.A huge increase is not only projected but needed to lift billions of people out of poverty in the developing world.” It is unlikely that any one renewable energy source could provide more than 5% of the world’s energy needs. The only exception to this is hydroelectric power, which already stands at 6%.“But”, he suggests “we should take all those 5 percents and add them together.” Renewables are inherently variable in output, and with current technology, there is no efficient way of storing power. “To complement renewables, you need steady, base-load power around the clock. At the moment, the only options are to go on burning coal, oil and gas, or to use fission.We really need another option”, says Llewellyn-Smith. In the long term, fusion could fill this gap,but what about the intervening period? Should we build another generation of fission power stations in the UK? Llewellyn- Smith is pragmatic.“This country can easily afford to build one more generation of power stations without increasing the nuclear legacy enormously. Fission has, around the world, a pretty good safety record, it’s rather reliable and the costs are looking pretty reasonable, but I would be nervous about the world going onto a big expansion of fission forever,” he says. Llewellyn-Smith is realistic about the timescales involved in development of fusion:“With a blank cheque we could go out and build a fusion power station and it might produce a few kilowatts, but it would be very unreliable.” He believes that the real question is when it will be possible to build 20 reactors, at high reliability and low cost. This, he thinks, is still around 40 years away, “but we could get much surer about that date with more investment”. On the issue of energy research and development funding, Llewellyn-Smith is animated. “The level is pathetic”, he says. “Worldwide, the funding of energy R&D has halved in real terms since 1980. I find that absolutely staggering. In 1980 we didn’t have a problem—while we’ve learned that we have an energy problem the funding of energy R&D has halved.”The statistics he gives are telling.“Public funding of energy R&D—which is the major source for long-term work—is less than 0.3% of the [worldwide energy] market. I don’t know of any high-tech business with a looming crisis where less than 0.3% is going into R&D.We need bigger energy R&D budgets.” Tom Walters is a PhD student in the Department of Physiology, Development and Neuroscience
How Fusion Works Fusion is the reaction that powers the stars. Energy is liberated when nuclei of the lightest elements fuse together at high temperatures and pressures. The easiest fusion reaction to perform on Earth involves heating a gas of deuterium and tritium, two isotopes of hydrogen, to 100,000,000°C. The ensuing reaction releases 10 million times as much energy as an elementary chemical reaction. There is one deuterium atom for every 6,500 hydrogen atoms on the planet and tritium can easily be made from lithium, so both reactants are readily available in large quantities. |
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