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Tag Archives: nuclear fusion

A factor of two

By Michael Banks

“A factor of two is not a small thing, it is quite a challenge,” says Robert McCory from the University of Rochester in New York.

McCory was speaking about the latest in laser-based fusion research (known as inertial confinement fusion) at the 2013 AAAS conference.

The National Ignition Facility (NIF), which began full operation in 2009, is based at the Lawrence Livermore National Laboratory in the US and is currently the world’s leading laser-based fusion device.

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A trip to MIT

By Michael Banks

It may have been the prospect of free pizza that led me to hop on a bus heading to the Massachusetts Institute of Technology (MIT).

But apart from a free lunch, we were also promised a tour of MIT’s fusion facilities, which are based at institute’s Plasma Science and Fusion Center (PSFC).

So after a few slices of pepperoni pizza, we donned the hard hats and moved on to the tour, which included a look at MIT’s main experimental fusion facility – the Alcator C-Mod fusion tokamak.

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Why fusion?

One of the big hopes for the energy future is nuclear fusion- not messy uranium fission, with all its problems, but allegedly clean and hopefully prolific hydrogen based nuclear fusion. However, it’s a long time coming – and it’s costing a lot. $20 billion so far globally, and more soon. The cost of the new ITER project at Cadarache in Southern France. has risen from £9 billion to, reportedly, around £18 billion. It’s a joint EU, Russia, US, China, Japan and S. Korea project toward which it seems the UK is contributing around £20m p.a. That’s in addition to the £26 m for nuclear fusion research in the UK through the Engineering and Physical Sciences Research Council for 2007-8.

For comparison, government expenditure on research and development for all the renewable energy sources in 2007-8 was £ 15.92 million via the Research Councils and £ 7.53m via the Technology Strategy Board, plus some related policy work via the UK Energy Research Centre and Tyndall Centre for Climate Change Research.

Fusion is clearly getting favourable treatment compared to renewables. Is this wise? After all there is a wide range of renewable technologies, a dozen or more very different systems, not just one. Why the imbalance?

The claim is that fusion offers, as the EURATOM web site says, ‘an almost limitless supply of clean energy’. And yet the UK Atomic Energy Authority say that, assuming all goes well with ITER and the follow up plants that will be needed before anything like commercial scale is reached, fusion only ‘has the potential to supply 20% of the world’s electricity by the year 2100.’ That’s not a misprint – 20%, if all goes well, in 90 years time. Renewables already supply that now globally, including hydro, and the new renewables like wind, solar, tidal and wave power, are moving ahead rapidly- and could be accelerated.

By comparison, the prospects for fusion are actually rather mixed. The physics may be sorted, up to a point. The UK’s JET experiment at Culham managed to generate 16MW briefly (but not of course net- it needed 23MW input). But the engineering is going to be complicated. How do you generate electricity from a radioactive plasma at 200 million degrees C? The answer it seems is by absorbing the neutron flux in a surrounding blanket that then gets hot, and has pipes running through to extract the heat, which is then used it to boil water and raise steam -as with traditional power plants. Not very 21st century…

As yet, few people would hazard a guess as to the economics of such systems. The ITER web site (www.iter.org) says ‘it is not yet possible to say whether nuclear fusion based on magnetic confinement will produce a competitive energy source’.

But at least there won’t be any fission products to deal with. However, the neutron flux will activate materials in the fusion reactor which will interfere with its operation, and will have to be stripped out regularly- so there will still be a radioactive waste storage problem, albeit a lesser one. The materials will only have to be kept secure for a hundred years or so, rather than thousands of years as with some fission products.

The risk of leaks and catastrophic accidents is said to be lower than with fission. Fusion reactions are difficult to sustain, so in any disturbance to normal operation the reaction would be likely to shut itself down very rapidly. But it is conceivable that some of the radioactive materials might escape. The main concern is the radioactive tritium that would be in the core of the reactor, which if accidentally released, could be dispersed in the environment as tritiated water, with potentially disastrous effects. To put it simply, it could reach parts of the body, which other isotopes couldn’t.

Finally what about the fuel source? The basic fuels in the most likely configuration to be adopted would be deuterium, an isotope of hydrogen, which is found in water, and tritium, another isotope of hydrogen, which can be manufactured from Lithium. Water is obviously plentiful while it is claimed that Lithium reserves might last for perhaps 1000 years, depending on the rate of use. That presumably depends on the competing use in Li Ion batteries in consumer electronics and possibly soon, on a much larger scale, in electric vehicles.

While that could be a problem for the future, there is a long way to go before we need worry about fuel scarcity. The ITER project is small (500 Megawatt rated) and won’t start operating until 2018, and, even assuming all goes well, it’s only a step toward a commercial pilot plant. And that at best is decades away. There could of course be breakthroughs. While the ITER magnetic constriction device is seen as the main line of attack, the US is also looking at laser fusion. But, even if it works, that too is unlikely to provide a practical energy source for some while.

We need to start responding to the climate problem now. So why then are we spending so much taxpayers money on fusion? It might eventually be useful for powering space craft. But on Earth? Wouldn’t it make more sense to speed the development and deployment of full range of renewable technologies, and make use of the free energy we get from fusion reactor we already have- the sun.

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