The difficulties currently being encountered in the generation of electric-power by nuclear fission, highlighted by some of the evidence being presented to the current Sizewell Inquiry, makes its long term future uncertain. From the ecological point of view, fission now stands condemned and we can safely say that it will have no part in the sane socialist society of the future. This situation is leading to a renewed interest in alternative sources of energy but current progress in one of these — nuclear fusion — has been limited by a lack of financial support, as the Scientific American reported in its July 1972 issue.
The source of energy in nuclear fusion is the same as in nuclear fission; that is. by the transformation of mass into energy. Fission takes place by the splitting of heavy elements such as uranium, and is the basis of the A-bomb. This connection with the arms trade has helped to keep fission power going despite its disappointing economic performance. In contrast, fusion involves the combination of light elements such as isotopes of hydrogen, and is the basis of the H-bomb, where the reaction is triggered by the explosion of an A-bomb. This method is obviously unsuitable for industrial use. Fusion reactions take place continuously on the sun and other large stars.
On the surface, the prospects for nuclear fusion look sky high. There is virtually an unlimited supply of low cost fuel in the form of heavy water (deuterium oxide) in the ocean. The end product of the fusion reaction is radiation free (but this does not apply to all intermediate products) unlike the hellholes where fission wastes are stored. The low mass and volume of the fuel needed makes plant layout and siting relatively problem-free. Handling and storage areas can be very small and installations need not be tied to port and railway facilities.
The nuclei of the fuel atoms are positively charged and so repel each other just as the like poles of two magnets do. In order to overcome this repulsion and put the nuclei close enough together for a fusion reaction to occur, a level of kinetic energy must be imparted to them, which requires a temperature of about 90 million degrees centigrade. In the H-bomb this is the function which the A-bomb performs. At such temperatures the gaseous state is transcended and the material becomes a charge-dominated collection of ionised matter known as plasma which at high temperature cannot be confined by material walls and has instead to be held in position by strong electromagnetic forces. In the search for a controlled fusion reaction for industrial use the crux lies in the design of a magnetic field to contain the plasma in stable equilibrium. This is the main reason why fusion research is so expensive. Attention is now being given to a laser-induced fusion technique, which requires no containment of plasma although the requirement to generate enormous temperatures remains. At the present time it is not possible to say definitely that a satisfactory solution will eventually be found, even granted adequate funding.
The radioactive intermediate product of the fusion reaction is tritium, another isotope of hydrogen. Tritium is not found in nature and has a half life of 12.3 years. It permeates metal walls at high temperature and containment will require careful detailed design. The vacuum wall and blanket structure will become radioactive during operation and require long-term disposal after the end of their working life. The internal plant structure can only be handled and repaired by complex remote control facilities. There are clearly hazards associated with high pressure, high temperature materials and high magnetic fields.
Optimistic forecasts of the nuclear fusion future should be judged against this information. The prospects of this type of work being performed in the capitalist commercial environment are not very strong, to say the least.
E C Edge
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