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Friday, 7 May, 1999, 17:05 GMT 18:05 UK
Fusion project sparks new hope of cheap, clean power
power plant pollution
If nuclear fusion researchers are correct, polluting scenes like this may become a thing of the past
A new type of nuclear fusion reactor holds out the possibility of unlimited, cheap, clean energy that does not involve the production of hazardous radioactive waste or the burning of fossil fuels, according to its designers.

They hope to have the power plant working within a decade. The world is preparing for the Kyoto environment summit in December. Fusion, if it works, promises to solve many of the world's energy problems. Toby Murcott of BBC Science reports.

At present virtually all electricity generation consumes limited resources of coal, oil, gas and uranium, and produces noxious effluent such as smoke, carbon dioxide and radioactive waste.

The emission of such gases may be causing global warming and will be on the agenda at the Kyoto summit to discuss ways of tackling climate change.

Meanwhile, hopes of unlimited, pollution-free energy rest at the moment with nuclear fusion, the process that powers the Sun and all stars. But this has proved extremely difficult to harness.

Current nuclear fusion reactors depend on the fusion of hydrogen isotopes, including radioactive tritium, but controlling the extreme conditions for this reaction to proceed is technologically very difficult. A commercial nuclear fusion reactor is still many years away.

Now a group of physicists in the United States have proposed a fusion reactor that works on a different principle, does not produce radioactive waste and is based largely on establised technology.

Colliding beam

The starting point is the fuel, which, as Hendrik Monkhorst of the University of Florida, United States, explains, is very different to that in conventional nuclear reactors.

"The ingredients are hydrogen and boron, a particular isotope of boron called boron 11. Boron 11 is very abundant in nature, hydrogen is very abundant as well. The hydrogen and boron will be put in accelerators and these accelerators will bring the hydrogen atoms - actually nuclei - to a very high velocity inside this cylindrically shaped device called the colliding beam fusion reactor."

It is the accelerators in this reactor that are the key to the new idea. Fusion occurs when two atomic nuclei are squeezed together. They combine to form new nuclei, releasing energy in the process.

But atomic nuclei repel each other and need to be smashed together at very high speed to overcome the repulsion. Conventional nuclear fusion reactors do this by heating the nuclei to very high temperatures. The new device uses particle accelerators. The hydrogen and boron nuclei are accelerated towards each other at very high speeds and when they collide, they fuse, producing fast moving helium nuclei.

"When the fusion reaction has taken place you get out three helium nuclei and they scatter out of [leave] the reaction chamber into two devices at the end of this reaction chamber called direct energy converters," said Mr Monkhorst.

Low-cost power

"The virtue of that device is that you can turn the kinetic energy, that is the motional energy of the helium nuclei, directly into electricity. The final result is helium gas and a lot of electricity that you can pump into the electric net. The helium gas is just helium as we know it to fill party balloons."

The system is relatively simple compared to current nuclear fusion reactors and calculations suggest that it could produce electricity more cheaply than fossil fuel powered generators. There are other advantages too.

"Our reactor for say one hundred megawatts, which would be able to power a small sized city, would be about the size of three or four big city buses standing next to each other. The other advantages are that we have no radioactivity to speak of," said Mr Monkhorst.

The colliding beam fusion reactor sounds too good to be true. It uses cheap, abundant, non-radioactive fuel and produces nothing but a harmless gas. A feasibility study is about to start and it could be in commercial service within 10 years.

But will it work? Other nuclear physicists are happy that the science behind the design is correct, but are sceptical whether it can ever be commercially exploited to produce electricity.

See also:

25 Aug 98 | Global warming
Life in the greenhouse
30 Nov 97 | Global warming
Kyoto 'will not stop the rising tide'
25 Aug 98 | Global warming
Our changing world
25 Aug 98 | Global warming
See and hear how the world could alter
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