Geoscience Reference
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enrichment) for enriched nuclear-fuel production can produce materials for nuclear
warfare. Such considerations, though beyond the scope of this topic, are of global
sociopolitical consequence. Indeed nuclear war, no matter how limited, is not without
its own biological impact.
Nuclear fusion is the process by which light elements are built up to more nuclear-
stable heavier elements (the most stable being iron) with the release of energy. As
such it is a counterpart to fission, whereby heavy elements are split into more nuclear-
stable lighter elements (again the most stable being iron). Fusion is the process that
takes place in stars (including the Sun). The attractions of fusion include that far
more energy per light atom (such as hydrogen) is released than with an atom of
fissile uranium or plutonium. Also, whereas fission converts the fuel to radioactive
isotopes, fusion can convert hydrogen to helium without the production of long-lived
radioactive isotopes. However, both fusion and fission do lead to the transmutation of
their reactors' non-fuel structural components to radioactive isotopes. (In fusion, it is
the neutral fast neutron which is not contained by the magnetic 'bottle' that does the
transmuting.) So, both fusion and fission produce waste, albeit of markedly different
natures, and it is considered that a fusion reactor would result in far less radioactive
waste per unit of energy produced than fission.
The other problem with fusion is that it is technically difficult in engineering terms
to contain a plasma of hydrogen in a magnetic bottle at a sufficient temperature and
density for fusion to take place, let alone to extract the heat on an ongoing basis.
The first serious proposal for harnessing fusion came in 1946 with the Thomson and
Blackman toroidal design: a toroidal has no ends from which a plasma may leak.
Famously the 1957 Zero Energy Thermonuclear Assembly (ZETA) was predicted
to be the forerunner of electricity that would be too cheap to meter. It failed. Over
subsequent decadesthere has been increased plasma density, temperature and duration
in various designs, including the Russian Tokamak and the Joint European Torus
(based in Culham, England). The next major experimental fusion reactor that is hoped
to demonstrate sustained net energy output will be expensive, at over US$10 billion,
so necessitating international co-operation. It will be the International Experimental
Thermonuclear Reactor (ITER), hosted in France. The final decision on constructing
this was made in 2005 and it is thought that the first ITER plasma should be possible
by 2015. However, just as underfunding of agreed budgets slowed fusion research
between the 1980s and early 21st century, so bureaucracy and administrative hurdles
slowed the construction of the ITER and added further funding difficulties.
In terms of energy sustainability and carbon the big attraction of fusion is 2-fold.
First, it imposes a low greenhouse burden. (There will always be some greenhouse
burden, if only because of the carbon dioxide generated in the cement-making process,
even if this is reduced through carbon capture.) Second, compared to human energy
needs there is an abundance of hydrogen and its more rare isotope, deuterium. If all
humanity's commercial energy production came from deuterium fusion (at current
levels) then theoretically there would be enough fuel for well over one billion years.
Indeed, should fusion become sufficiently economical (i.e. only marginally cheaper
than oil's real-term price for much of the 20th century) then, aside from the issue
of radioactive waste, a real environmental concern might become the thermal waste
from profligate energy production and consumption. (For example, consider far more
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