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Today we know that in the sun light elements – mainly hydrogen –are turned
into heavier ones, such as helium. This 'thermo-nuclear' process of fusion, as it is
called, takes place at fantastically high temperatures (in the centre of the sun the
temperature is believed to be about 15 million degrees Centrigrade). The heat fuses
the nuclei, which would normally repel each other because they have the same
(positive) electrical charge; heat means violent movement of particles, in other words:
energy. Thus the hydrogen nuclei bump into each other and combine to form helium
nuclei, with a simultaneous release of energy. As in nuclear fission, some mass is
converted into energy in the fusion process, but the sun can keep up its rate of loss of
mass – five million tons per second – for some thousands of million years.
This process is only possible where light elements are concerned; hydrogen, the
lightest of them, has the smallest electrical charge, and therefore the repellent force of
its nuclei can be more easily overcome than that of heavier elements. If there was any
chance at all of producing nuclear energy from fusion – this was a point about which
scientists agreed – it could only be done by using hydrogen: in short, by emulating on
earth the process that makes the sun shine.
Again, as in the case of atomic fission, this was first achieved in the form of a
weapon, the hydrogen bomb. Even the testing of this weapon has proved to be highly
dangerous because it contaminates the atmosphere all over the world with radio-
active 'fall-out' isotopes which can produce cancer of the bone and blood. No one
doubts that a nuclear war fought with fission and fusion bombs would mean the
suicide of mankind.
As these lines are being written many scientists in at least half a dozen
countries are busy trying to find a system to tame the energy of the H-bomb for
peaceful use, but no decisive 'break-through' has been achieved. It may, however,
come at any moment. In August 1957 British physicists working with their thermo-
nuclear device called '2eta' believed they had succeeded, but this turned out to be a
mistake. Still, the scientists' efforts towards that goal are all based on the same basic
principle, and some time somewhere another Zeta will achieve the 'break-through'.
In these experiments the heavy hydrogen isotope deuterium – which has an
extra neutron in its nucleus – plays the decisive part. At very high temperatures the
protons are detached from the electrons revolving around them, and the neutrons fly
off at great speed, thus providing extra energy, i. e. heat, as the protons melt together
to form new nuclei. There are many difficult problems to overcome before the
thermo-nuclear power station based on this process can become a reality, but that of
fuel supply is the least of them: the oceans of the earth are practically inexhaustible
source of deuterium, and its extraction from sea water is neither complicated nor
expensive. One gallon of sea water may be sufficient to yield as much energy as 100
gallons of petrol, and a bucketful containing one-fifth of a gram of deuterium could
keep a five-room house warm for a whole year.
The real trouble starts when we attempt to produce the very high temperatures
required to achieve thermo-nuclear fusion. Up to 1950, the highest temperature ever
produced in a laboratory was 30,000° Centigrade. All the Zeta-type assemblies,
therefore, are machines designed to reach temperatures of many millions of degrees
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