Forward to a hybrid nuclear future?

THE IDEA of generating power using a combination of nuclear fusion (using the energy released by merging atomic nuclei) and nuclear fission (using the energy released by splitting atomic nuclei) is not new. But it has been given prominence by the development of a big new research programme in China.

Fission is the method currently used to generate nuclear power. It is fundamentally flawed, however, due to the unacceptable dangers linked both to its operation, demonstrated by the Chernobyl disaster, and to the insurmountable problem of safely storing the toxic radioactive waste generated in the fission process. This waste remains dangerous for tens of thousands of years. On the other hand, nuclear fusion does not produce significant toxic waste and promises almost limitless safe energy, but technical problems have prevented a viable reactor being developed.

Its proponents claim that a hybrid approach can solve the technical problems that have prevented fusion power taking off and simultaneously reduce the dangers linked with fission to acceptable levels. They claim that this would result in a safe power source that would be particularly welcome because it does not generate any greenhouse gasses. The urgency and seriousness of the fight against global warming means that the claims made for this hybrid approach need to be seriously considered if there is a chance it could prove acceptably safe and useful.

Nuclear fusion has been under development for more than 50 years and many scientists think that it will take another 50 to become viable, if it can be made to work at all. Two technical problems in particular are holding back the technology. Firstly, the size of even the biggest current experimental reactor under development is too small to permit a self-sustaining reaction to take place. Secondly, a material does not yet exist that can withstand the intense bombardment of high-energy particles generated by the fusion reaction.

According to professor Julian Hunt of University College London, hybrid power can potentially solve the problems associated with both fission and fusion. In a hybrid system, the ‘blanket’ that withstands the bombardment of high-energy particles has two components. The first is the fission reactor itself that absorbs some of the energy generated by the fusion reaction. This, in turn, reduces the amount of energy that has to be absorbed by the second component, the outer wall of the reactor, by a factor of 50. This means that existing materials can be used in the outer wall. Also, the hybrid reactor core can be much smaller than in a pure fusion reactor, since the energy generated by the fission reaction can be fed back into the hybrid reactor core. This would allow a core to be used that would be the same size as the one currently under development in France.

With hybrid power, the safety problems linked to nuclear fission can be reduced to acceptable levels, it is claimed, because the fusion reactor can burn the high-level nuclear waste produced in conventional nuclear fission. The reactor ‘transmutates’ this waste into radioactive materials that will be safe after 100 years, rather than tens of thousands, thus greatly reducing the problems of safe storage. Also, because the material in the fission reactor core remains well below ‘critical mass’ (the point at which a runaway reaction can occur), there is a vastly lower risk of a Chernobyl-style meltdown.

So, does the potential claimed for a hybrid approach mean opposition to nuclear power should be reconsidered? Despite its advantages, there are problems in drawing such a conclusion. The first is that the technology is still at the experimental stage, whereas renewables such as wind wave and solar power are operational, although not widely deployed. Therefore, these energy sources must be the priority given the urgent need to address global warming. Also, it will not be possible to conduct a proper risk assessment until there is a functioning prototype reactor. Ultimately it is unlikely, even with significantly reduced risks, that the balance will favour hybrid nuclear power rather than renewables. Although further research is needed, it is doubtful that governments will put sufficient resources into either of these areas, since traditional nuclear fission is already available, and the capitalist class has already clearly indicated that it is willing to run the risks linked to this technology.

Pete Dickenson