£7bn fusion pact aims to harness sun's power
By Steve Connor, Science Editor
Published: 22 November 2006
The dream of unlimited clean energy came a step closer yesterday with
the signing of an international agreement to build the world's
biggest nuclear fusion reactor which aims to harness the same energy
that powers the Sun.
Six individual countries and the European Union agreed to spend about
EUR10bn (£6.75bn) over the next 20 years to construct and operate the
International Thermonuclear Experimental Reactor (Iter) at Cadarache
in the south of France.
The agreement between the US, China, the EU, India, Japan, South
Korea and Russia to build Iter - which also means "the way" in Latin -
was signed at a ceremony at the Elysée Palace in Paris.
"The growing shortage of resources and the battle against global
warming demand a revolution in our ways of production and
consumption," the French President, Jacques Chirac, said. "We have
the duty to start research that will prepare energy solutions for our
descendants".
The Iter reactor will take about eight years to build and is the
first fusion experiment designed to produce more energy than it
consumes. It is hoped that it will spawn prototype commercial
reactors that could begin to come on stream within the next 30 or 40
years.
Nuclear fusion has been a dream of scientists for many decades
because it promises to produce virtually no harmful waste. Fusion
needs only small quantities of seawater and lithium - a mineral in
plentiful supply - as its raw materials and it produces no carbon
dioxide or other greenhouse gases.
Fusion produces energy when atoms of hydrogen are collided together
under extreme pressures and temperatures - the reactor core is
several times hotter than the centre of the Sun.
Unlike existing nuclear fission reactors, which produce dangerous
high-level waste from spent fuel, nuclear fusion is expected to
produce only small quantities of moderately radioactive material from
contaminated reactor shielding, which would dissipate to safe levels
within 100 years.
However, even the most optimistic assessments suggest that nuclear
fusion may not become a routine source of energy for at least another
50 years, such are the immense difficulties of building large-scale
fusion reactors that work.
The idea for Iter came out of a superpower summit in 1985 but
negotiations became bogged down over the choice of where to build the
experimental reactor, with Japan and France vying for the privilege.
Last year it was decided that Cadarache in Provence would be the site
of the reactor, but it was agreed a Japanese civil servant, Kaname
Ikeda, would be its first director general and Japan would supply the
main components.
Martin O'Brien, the fusion programme manager at the United Kingdom
Atomic Energy Agency's Culham Laboratory, said Iter would be eight
times the volume of the Joint European Torus (Jet) in Oxfordshire,
the largest fusion machine in the world.
"The way the scaling-up works means that as the machine gets bigger,
it will result in getting more energy out of it than is put in," Mr
O'Brien said.
The temperature within the reactor's core will exceed 100 million
Celsius - about 10 times hotter than the Sun -causing atoms of
hydrogen isotopes to fuse together to form helium, an inert gas, and
releasing more energy in the process.
Experiments at Jet have achieved fusion for a few seconds at a time
but as yet it has used up more energy in heating the plasma gas
within the reactor than has been produced.
Miles Seaman, of the Institution of Chemical Engineers, said
integrating fusion with a way of storing clean energy in the form of
hydrogen could provide the breakthrough to almost unlimited
sustainable energy.
"There are undoubtedly some major technological challenges to
providing fusion power reliably and continuously. But it can and has
been done, albeit in very short bursts," Dr Seaman said.
Professor Jim Skea, the research director at the UK Energy Research
Centre, said: "Nuclear fusion could offer one of the biggest prizes
in energy: a secure, low-carbon source of electricity without
resource constraints. But it will also require a massive investment
and there is some risk that it will not pay off."
Dr Paul Howarth, the director of research at the Dalton Nuclear
Institute in the University of Manchester, said: "Great progress has
been made on fusion technology over the past few decades.
"However, it is now time to move the technology forward, scale up the
size of the experiment and investigate fusion energy conditions more
likely to found in a commercial reactor."
However, Roger Higman, the policy co-ordinator of the environmental
group Friends of the Earth, warned that efforts to limit emissions of
greenhouse gases over the next 50 years should not take a back seat
in the rush to fusion. "Isn't the money that's being spent on fusion
better spent on proven technologies rather than chasing a dream that
even its proponents say will take 100 years before it's going to
provide any of our energy answers?" Mr Higman added.
How fusion works
* Nuclear fusion is the energy source at the heart of the Sun and is
produced when two isotopes of hydrogen - deuterium and tritium -
collideunder high temperatures and pressures.
* Helium, an inert gas, is the only waste product and fusion does not
create any other emissions, such as the greenhouse gas carbon
dioxide.
* Deuterium is easily extracted from seawater and tritium can be
produced in the reactor itself with the help of lithium, a light
metal that is readily available from the ground. The intensely hot
plasma gas inside the fusion reactor is held together by a strong
magnetic field.
* Only the metal parts of the reactor close to the hot plasma gas in
the centre will become slightly radioactive, but this waste material
will be reusable within 100 years.
* Fusion does not involve a chain reaction so it is safer than
nuclear fission reactors. Only about half a gram of fuel is needed in
the Iter fusion reactor to produce a few seconds of "burn" - making
the process even safer.
* The heat generated from a fusion machine will be used to heat water
to drive steam turbines for generating electricity. If it can be
combined with a way of producing hydrogen gas from water, the
sustainable, clean energy produced could be stored for other uses.
