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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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Posted by Dave Elliott on July 4, 2009 12:34 PM |

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Comments (4)

  • 1 Axil July 5, 2009 4:44 AM

    The answer to the energy revolution is an old idea whose time has come. It is best to configure a “system” of reactors in which one type produces fuel, a clean fuel, a pure fuel, and another that consumes this fuel. This is analogous to a bakery that bakes bread for a populace that hungrily consumes its loaves as they are baked.


    Hans Bethe played an important role in the development of the larger hydrogen bomb, though he had originally joined the project with the hope of proving it could not be made. His scientific research never ceased even into the later years of his life. He is one of the few scientists who can claim a major paper in his field every decade of his career, which spanned nearly sixty years. Freeman Dyson called Bethe the "supreme problem solver of the 20th century." One of the most innovative ideas was his advocacy of the fission/fusion hybrid. See this old article by Bethe as follows:


    http://www.marcobresci.it/docs/fusione_ibrida.pdf


    As a bridge technology to pure fusion, the fusion/fission hybrid is at the root of a large network of fission reactors that feed off the U233 fuel produced by the fusion reactor. Bethe thought that such fusion capability was just around the corner. But fusion took some wrong turns that slowed it down. However, certain types of fusion reactors are currently at hand. Their fusion approach has been demonstrated. As is common in fusion technology, they must show a scaling up of the neutron production rate that will make a thorium fusion hybrid effective and productive.


    My intent is to examine and describe in simple terms where the thorium fusion/fission hybrid stands and to evaluate the probability of its success in the near term.


    The basic physics of the field reverse configuration (FRC) fusion process has been demonstrated in a small test device referred to as the Inductive Plasmoid Accelerator (IPA).


    The IPC forms two packets of Tritium-deuterium plasma at each end of a beryllium tube and accelerates them at each other to collide at a central point in a fusion burn chamber. These two packets combine both their energies together to form a stable ball of high energy ions that are both well mixed and well formed.


    A surrounding large magnet compresses the ball of plasma together to reduce its size and hold it in the burn chamber for a period longer then what was expected from past experiments. That is good. When fusion experiments are scaled up (made bigger) something almost always goes wrong and the experiment does worst than expected. Much work must be done to find out what the problem is and how to fix it.


    The ball of plasma was much stronger than expected. This is great since fusion in plasmas that don’t stay together just won’t work. The fusion guys don’t really understand the way this type of FRC fusion works much better than their theoretical models predict. They think it might somehow be due to the ash produced by fusion. They just don’t understand it yet, but they surely are happy about it. Sometimes it is better to be lucky than smart.


    The equipment to do all this is simple and ordinary. It is cheap and will hold up well when operated in rapidly repeating pulses over a long timeframe.


    After fusion in the ball of plasma is completed, the fusion ash and the left over tritium and deuterium find its way into a diverter that removes it from the burn chamber. The high energy neutrons produced by fusion fly out in all directions. It will be these neutrons that will make U233 in the thorium blanket that will eventually surround the burn chamber.


    Past FRC experiments have shown that the number of high energy neutrons produced by fusion scales as a simple function of the energy in which they collide and the strength of the magnetic field that compresses the plasma. Both these values can be increased to a level that will eventually produce enough neutrons to make the fusion/fission thorium hybrid concept possible.


    The big challenge is to keep the damage to the beryllium first wall down. That is why the fusion guys must set up a component test facility to check out how much ware they can get out of the first wall. They know the thorium fission reactor technology exists having been developed and demonstrated in the 60’s and 70’s but they don’t know the details. They need to integrate this thorium stuff into their configuration. But it looks like it can integrate together really well.


    How long is this development process going to take?


    If the fusion guys get development money, just a pittance compared to ITER, they will get to a neutron production rate that can breed U233 by 2013. So the pure thorium fuel cycle could be at hand.


    Sometimes there is a dark horse in the race that could be a black swan. Let’s hope this technology gets the funding it needs to save the day.


  • 2 M. Simon July 6, 2009 12:43 AM

    The Polywell Fusion Reactor is showing a lot of promise. And yet outside the USA and Japan this type of device is hardly being looked at.

  • 3 Jim Dobbin July 6, 2009 12:08 PM

    I think Dave Elliott is missing the point here. There should be vastly increased investment in all clean energy technologies, instead of renewables and fusion fighting each other for scraps. Less than 0.1% of the energy market is going into R&D for new technology, this is the real problem.

    Diverting the fusion budget into renewables would make virtually no difference to solving our energy problems. There should be enough money to develop near-term solutions like wind and solar as well as looking further ahead to fusion, which has the best long-term potential of any energy source.

  • 4 Tug Lx July 20, 2009 6:22 PM

    I do not believe that the budget for renewables energy source development is reduced because there is a money flow going to the development of fusion. There is a simple law that say if you have few and simple projects of investment you will catch less money than if you present more projects and more reliable date. Of course there is a ceiling for public funding, but renewables are in a stage were private companies are giving a contribution for this research.

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