Environmental Engineering Reference
In-Depth Information
Therein, however, lies the problem with fusion in terms of generating
electricity. Making a fusion bomb - popularly known as a hydrogen or
H-bomb - is relatively easy. It is done with the very blunt instrument of
using a fission explosion to set off a fusion explosion that only has to be
momentary. This technique is hardly appropriate if one day you want to
be able to use fusion to generate electricity for customers with any conti-
nuity. So we have the odd situation that less than ten years after the first
fission bomb we had fission-produced electricity, but that more than fifty
years after the first H-bomb, we are still decades away from obtaining
useful electricity from fusion.
Fusion is an attempt to replicate the way that the sun and stars fuse
hydrogen nuclei. But we poor earthlings can't do it in quite the same way.
The sun and stars have huge gravitational pressures upon their nuclei,
which mean they fuse at the relatively low temperature of a mere ten mil-
lion degrees centigrade. In the absence of such pressures on earth, fusion
requires temperatures as high as a hundred million degrees centigrade to
overcome the repelling forces of positively-charged hydrogen nuclei.
How do you go about achieving such high temperatures? One of the
chief difficulties is how to contain the superheated fuel particles without
letting them touch any solid container that would just leach away the heat.
The main solution being pursued uses a tokamak, a Russian-designed
doughnut-shaped machine that produces a magnetic field to contain the
hot fuel plasma, and thereby keep the fuel particles away from the toka-
mak's walls. The containment problem is not just one of preventing the
fuel particles hitting the reactor walls and dissipating heat - it is also to
keep the particles together long enough for the fusion reaction to produce
energy at a rate greater than that of the energy input.
The Iter consortium
Pursuing this solution is an international consortium known as Iter, made
up of China, the EU countries, India, Japan, Russia, South Korea and the
US. Originally Iter's name was an acronym standing for International
Thermonuclear Experimental Reactor, but some people were understand-
ably nervous about the word thermonuclear being used in close conjunc-
tion with the word experimental. So sometimes the word tokamak is used
instead of its place. Iter means “journey” in Latin - and fusion is certainly
a journey to an unknown destination.
Iter is building on previous experience with tokamaks - notably the work
achieved by an EU project, the Joint European Torus (JET), at Culham near
