6. Fusion as a future energy source
Global demand for energy continues to grow year by year as the world
population expands and society becomes more and more dependent on energy
supplies. The need to find new sources of energy becomes increasingly
important as environmental concerns mount over the emission of CO2 from
burning fossil fuels.
At a European level, future energy supply was discussed in an EU Green
Paper published in 2000 - 'Towards a European strategy for the
security of energy supply', and a progress report published
in 2005.
Of particular concern is the dependency Europe has on importing its
energy from outside the EU (50% today and predicted to be 70% in 2030).
The long term role of fusion is recognised in this report - 'Thermonuclear
fusion also bodes well for the future and could take over the reins from
some existing energy sources towards the middle of the century'.
At national, European and international levels, future energy supply
is becoming one of the key issues. Fusion offers a valuable alternative
in future energy mix scenarios.
The way ahead ...
The success of JET, in terms of optimising plasma stability and
confinement, has led to the design of the next step device - ITER.
ITER is an international collaboration with seven partners (EU, Japan,
USA, South Korea, Russia, China and India) - and is a more advanced,
larger version of JET. It will be capable of producing 500MW of fusion
power (ten times that needed to heat the plasma). In comparison, JET
can only produce fusion power that is ~70% of the power needed to heat
the plasma. The go-ahead to build ITER at
Cadarache in France was given in June 2005. ITER will take ten years
to build and should start to operate within a few years after that.
The so-called fast track to commercial fusion power is a strategy designed
to ensure that a demonstration fusion power station puts electricity
into the grid in 30 years time. During the operation of ITER, a parallel
materials testing programme will be undertaken - developing and
assessing the materials needed for a powerplant. The experience from
both these facilities will enable the first demonstration powerplant
to be operational in ~ 30 years.
Advantages of fusion
Fusion offers significant potential advantages as a future source of
energy - as just part of a varied world energy mix.
Abundant fuels
Deuterium is abundant as it can be extracted from all
forms of water. If all the world's electricity were to be provided by
fusion power stations, present deuterium supplies from water would last
for millions of years.
Tritium does not occur naturally and will be
bred from Lithium within the machine. Therefore, once the reaction is
established, even though it occurs between Deuterium and Tritium, the
external fuels required are Deuterium and Lithium.
Lithium is the lightest metallic element and
is plentiful in the earth's crust. If all the world's electricity were
to be provided by fusion, known Lithium reserves would last for at least
one thousand years.
The energy gained from a fusion reaction is enormous. To illustrate,
10 grams of Deuterium (which can be extracted from 500 litres of water)
and 15g of Tritium (produced from 30g of Lithium) reacting in a fusion
powerplant would produce enough energy for the lifetime electricity needs
of an average person in an industrialised country.
Inherent safety
The fusion process in a future power station will be inherently safe.
As the amount of Deuterium and Tritium in the plasma at any one time
is very small (just a few grammes) and the conditions required for
fusion to occur (e.g. plasma temperature and confinement) are difficult
to attain, any deviation away from these conditions will result in
a rapid cooling of the plasma and its termination. There are
no circumstances in which the plasma fusion reaction can 'run
away' or proceed into an uncontrollable or critical condition.
Environmental advantages
Like conventional nuclear (fission) power, fusion power stations will
produce no 'greenhouse' gases - and will not contribute
to global warming.
As fusion is a nuclear process the fusion powerplant structure will
become radioactive - by the action of the energetic fusion neutrons
on material surfaces. However, this activation decays rapidly and the
time span before it can be re-used and handled can be minimised (to around
50 years) by careful selection of low-activation materials. In addition,
unlike fission, there is no radioactive 'waste' product
from the fusion reaction itself. The fusion byproduct is Helium - an
inert and harmless gas. |
