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http://www.guardian.co.uk/science/story/0,,1781601,00.html

Where the dream of harnessing the sun's power could come true

 International reactor project gets go-ahead
 Commercial usage not guaranteed, say critics

James Randerson, science correspondent
Wednesday May 24, 2006
Guardian

There is a deafening, unearthly howl as if a 
jumbo jet was firing up its engines in the Albert 
Hall. On the screen in the control room a ghostly 
pinkish glow whips round the edges of the inside 
of the nuclear reactor. At its core it is 10 
times hotter than the centre of the sun.

This, according to some physicists, is the 
solution to the energy crisis - a future with 
cheap, reliable, safe and nearly waste-free 
power. Today, after years of false starts and 
political wrangling dating from the cold war, 
they will get their chance to make that dream a 
reality. A 10bn (7bn) project, called Iter, to 
build a prototype nuclear fusion reactor will be 
signed off in Brussels by the EU, Japan, China, 
South Korea, India and the US.

The prospect of virtually limitless energy is not 
merely science fiction. The haunting, screaming 
growl of matter being smashed together at 
unimaginably high speed is a daily occurrence at 
Jet in Oxfordshire, an existing experimental 
fusion reactor. Jet is by far the biggest of the 
world's 28 fusion reactors. It is the work of 
scientists here that has paved the way for the 
much bigger Iter, which, once the project is 
ratified in December, will be built in Cadarache 
in southern France.

Its advocates say nuclear fusion is the most 
promising long-term solution to the energy 
crisis, offering the possibility of abundant 
power from cheap fuel with no greenhouse gases 
and low levels of radioactive waste. But critics 
say the government is gambling huge sums of money 
- 44% of the UK's research and development budget 
for energy - on a long shot with no guarantee of 
ever producing useful energy.

Last week Tony Blair backed conventional nuclear 
power, saying in a speech to business leaders 
that not replacing Britain's ageing nuclear power 
stations would be "a serious dereliction of our 
duty to the future of this country".

He argued that only nuclear energy could prevent 
a huge hike in CO2 emissions once the current 
nuclear stations were decommissioned.

But while the debate over the future of 
conventional nuclear power continues, many 
physicists argue that fusion is the future. 
"Fusion works - it powers the sun and stars," 
said Sir Chris Llewellyn Smith, head of the UK 
Atomic Energy Authority. "In the second part of 
the century I'm optimistic it will indeed be a 
major part of the world energy portfolio."

Unlike nuclear fission, which tears atomic nuclei 
apart to release energy, fusion involves 
squeezing the nuclei of two hydrogen atoms 
together. This process releases a helium nucleus 
and a neutron plus huge quantities of energy. The 
hydrogen fuel is part heavy hydrogen or 
deuterium, which can be easily extracted from 
water, and part super-heavy hydrogen or tritium, 
which can be made from lithium, a reasonably 
abundant metal.

The energy produced is truly colossal. The 
lithium in just one laptop battery and the heavy 
hydrogen from half a bath of water could provide 
enough energy for the average European for 30 
years.

One of fusion's big advantages over fission is 
safety. Firstly, there is no chance of a runaway 
meltdown as happened at Chernobyl. If you stop 
applying the fuel or switch off the magnetic 
jacket that keeps the fuel in the reactor, the 
reaction just stops.

"It is very difficult to keep it running. It is 
like keeping honey on the back of a spoon," said 
Mathias Brix, a physicist at Jet. Also, the 
quantities of fuel involved are much smaller than 
in fission reactors. Jet contains less than a 
gram of fuel, while Chernobyl had 250 tonnes. 
Lastly, the fuel and waste from the reactor is 
much less radioactive. But although physicists 
think they understand fusion, harnessing it has 
proved extremely difficult. Research first began 
in the 1950s with claims that fusion would 
provide reliable power by the end of the century 
but even now scientists admit that a commercial 
application is at least 40 years away. The 
problem is getting two nuclei close enough to 
fuse and then controlling the reaction. This 
means putting in huge amounts of energy at the 
start to convert less than a gram of the fusion 
fuel into a super-hot gas or plasma. Hydrogen 
nuclei flying around at high speed in the plasma 
can then come close enough together to fuse.

In 1991 Jet was the first fusion reactor to do 
this using a mixture of deuterium and tritium. It 
proved that fusion reactors could work, but was 
not a viable energy option because it only pumped 
out about 70% of the energy required to start the 
process off. "The purpose of these experiments is 
not really to produce energy but to learn how to 
control the hot gas," said Sir Chris. Iter will 
be 10 times the volume of Jet and produce 10 
times the energy needed to get the reaction 
started. "It's the step where we will demonstrate 
scientifically and technically that fusion energy 
is a viable energy source," said Akko Mass, one 
of the Iter scientists. But with so many broken 
promises some involved in the project doubt it 
will yield commercial energy any time soon. Iter 
scientist John How described the billed 40-year 
timescale as "very, very, very ambitious". He 
suspects it will be nearer to a century.

Footnotes

Iter (International Thermonuclear Experimental Reactor)
10bn project to build the next generation 
experimental fusion reactor with 10 times the 
volume of Jet. Due to be built at Cadarache in 
France.

Nuclear fusion
Process in which deuterium and tritium are 
combined to produce helium, a neutron and huge 
amounts of energy.

Jet (Joint European Torus)
Experimental fusion reactor built in 1983 at 
Culham, near Oxford. It was the first fusion 
reactor in the world to use fusion fuel (in 1991).

Deuterium or heavy hydrogen
Conventional hydrogen is made up of a proton 
nucleus with an electron spinning around it. The 
nucleus of a heavy hydrogen atom contains a 
proton and a neutron.

Tritium or super-heavy hydrogen
Its nucleus contain a proton and two neutrons. It 
is moderately radioactive and can be manufactured 
from the metal lithium.

Magnetic jacket
The reaction occurs within a doughnut-shaped 
chamber surrounded by an electromagnetic jacket. 
Invented in Russia in the 1960s, it stops 
sub-atomic particles within the plasma.

Plasma
Fourth state of matter apart from solid, liquid 
and gas. When superheated, a gas becomes a 
plasma. Examples include lightning.