1 - Nuclear Sciences and Applications - IAEA

IAEA-CN-50/A-0 5
ceptible to fast release in a fusion reactor in case of accident can in principle
be reduced to very low levels by adequate design, as it is not linked with the
fundamental process of energy production but only with auxiliary systems.
— The radioactivity in a DT fusion plant arises only from the intermediate tritium
fuel and from the interaction between neutrons and the structural materials of
the plant; the reaction products themselves are not radioactive. The development
of an environmentally benign DT fusion reactor is, therefore, a question
of engineering aimed at maintaining a low tritium inventory and, together with
materials development, at keeping the activation of structural materials to a low
level; it has no basic limit due to the fundamental process of energy production
itself. Moreover, one could even conceive of using, in a later stage, instead of
the DT reaction, reactions such as deuterium-helium 3 (D- 3 He) which, at the
cost of more demanding plasma parameters, would have the potential for
removing most of the environmental concerns. The availability of 3 He, once
considered an insuperable problem, might find solutions in the distant future.
These potential advantages of future fusion reactors, together with the abundance
and wide availability of the primary fuel (lithium), should, if properly understood,
be of substantial weight in determining the public attitude towards fusion.
Past achievements
Let me now briefly consider our past achievements. Fusion research has only
recently emerged from the intimacy of the laboratories into highly visible Big Science
public programmes and is still mostly in a scientific stage of development, although
a growing fraction of the R&D effort is being devoted to fusion technology.
Successive generations of tokamaks continue to occupy the forefront of magnetic
fusion research, thus contributing most of the papers at these conferences; new
devices of this kind are still under construction. Wisely, however, the major fusion
programmes have maintained the necessary breadth in the toroidal confinement
approach by experimenting with alternative configurations — stellarators, reversed
field pinches and others — which are complementary to the tokamaks and could
potentially have intrinsic advantages over them for the ultimate reactor. And then
there is the inertial approach to controlled fusion, which is also making good
progress, as will be reported at this conference, but which belongs to a slightly different
world, traditionally not covered by the Artsimovich Memorial Lectures.
The most impressive result so far in controlled thermonuclear fusion research
has been obtained with tokamaks. The value of the product of central ion temperature,
central ion density and global energy confinement time, which is the best figure
of merit on the way to the reactor, has increased by almost four orders of magnitude
during the past twenty years. It is now only a factor of four away from breakeven
and slightly more than an order of magnitude away from ignition, which is our longed
for milestone marking the achievement of the proof of the scientific feasibility of
fusion power.