Sustainability and policy - Climate Change: Biological and Human Aspects - page 475

meaningful cutting of future carbon emissions without a decline in energy supply in
this century.
However, from the perspectives of environmental science and human ecology the
question of whether we should adopt nuclear fission as part of a move towards
a sustainable-energy strategy depends on the balance of biological risk between
nuclear and fossil fuels. What should not be an issue in climate terms, although
early in the 21st century it has featured in much public discussion, is whether energy
investment is made in either nuclear or renewable energy. Such a question simply
removes investment from the development of non-fossil carbon energy resources.
The key question is whether nuclear investment should be included in investment that
displaces fossil carbon consumption. Given the time it is taking to develop significant
amounts of renewable capacity, it is very difficult (though not entirely impossible)
to dismiss the nuclear option. Indeed, some of the public may be surprised at this
human-ecology and environmental science perspective, which differs markedly from
that of the green movement.
From a political and sociological perspective, there are other (non-scientific)
problems of nuclear power to do with proliferation: that of nations acquiring nuclear
military capability through civil nuclear programmes. However, these might be
surmounted if it is possible to keep nuclear power generation quite separate from the
other parts of the nuclear epicycle (of fuel enrichment, processing and disposal). This
is especially important if the generation of nuclear power takes place in less stable
countries.
It is not often noted, but as with finite fossil fuels there are limits to nuclear
fission that depend on the finite supply of fissile uranium. As such, some fission
can be considered a finite or fund resource. The size of this fund depends on the
rate of use, which has seen periods of rapid growth up to the 1970s and which
slowed markedly after 1986 (and Chernobyl). Consequently the estimates for the
global supply of uranium vary from over three centuries at broadly current use to less
than a few decades assuming that uranium consumption grows to meet some 40%
of anticipated global electricity demand by around 2030. There is, though, a way
in which nuclear physics can be used to extend this resource's lifetime. This is by
using a more energetic reactor to produce more nuclear fuel from certain isotopes.
These reactors are called fast breeder reactors; 'fast' because they actively depend
on an energetic type of neutron (a fast neutron) and 'breeder' because they breed
fuel through fast-neutron interaction with appropriate isotopes in the reactor's core.
However, because the process relies on high-energy fast neutrons, the resulting high
thermal energy produced needs to be carried away quickly from the core and so
typically such reactors use liquid metal (sodium) coolant to conduct the heat away.
This presents significant engineering challenges that make such reactors inherently
more expensive than non-breeder reactors. Nonetheless, fast breeder reactors would
extend the global uranium resource by some 4-6-fold.
The other problem with any major global use of nuclear power to offset green-
house emissions is that of nuclear proliferation. Even without breeder reactors it is
possible to manipulate conditions in reactors and to increase reactor-core dwell times
to produce transuranic elements such as plutonium that can then be used in war-
heads. Further, those countries with nuclear-epicycle capability (primarily, isotope