The JET torus in 1996, showing a worker wearing protective clothing performing maintenance within the vessel. Photograph courtesy of EFDA-JET
It's hard to take fusion energy seriously when its proponents employ descriptors like "power of the Sun" and "energy from a star" to explain it. This kind of hyperbole—and the fact that scientists have never created a sustained fusion reaction capable of generating more electricity than it soaks up—make fusion sound like a fantastical scheme devised by Lex Luthor. But in the wake of the current energy crisis, new money and political support may finally channel enough resources into fusion to make the elusive process a reality.
On May 24, the US, EU, Russia, China, South Korea, Japan and India signed on to help build the International Thermonuclear Experimental Reactor (ITER) in Cadarache, in the south of France. ITER is the largest fusion research project to date and one of the biggest international scientific collaborations ever. Its budget is 10 billion euros over 20 years, more than three times that of the Large Hadron Collider at CERN. The reactor is scheduled to be functional by 2016.
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"[ITER] is not only a scientific and technological experiment aimed at demonstrating the scientific and technological feasibility of fusion energy, but it is also an experiment in international relations," said Ned Sauthoff, the U.S. project manager for ITER. "Never before have the governments representing more than half the population of the world gotten together and tried to solve a global problem."
Theoretically, fusion is an ideal energy source. It releases no carbon into the atmosphere and is fueled by hydrogen atoms, which can easily be derived from water. Traditional nuclear fission, on the other hand, requires uranium or plutonium, both limited and costly resources. While the radioactive byproducts of fission can linger for hundreds of thousands of years, the radioactive waste produced in fusion decays within 50 to 100 years. In addition, fusion eliminates the risk of a runaway reaction like the one that occurred at Chernobyl—a fusion reaction on Earth is so delicate that any error in operation would end the process rather than causing a meltdown.
In a fusion reactor, laser or charged-particle beams and radio waves heat hydrogen atoms, or the heavy hydrogen isotopes deuterium and tritium, to more than 100 million degrees Celsuis—nearly seven times the heat of the Sun—creating a free-flowing thermonuclear plasma. Atoms in the plasma collide with each other, fusing into helium atoms and release single neutrons and disproportionately large amounts of energy that can then be transformed into electricity through a steam turbine cycle.
The Sun, a fusion reactor, keeps hydrogen atoms colliding via the enormous pressure at its core. ITER will test a device, called a tokamak, meant to replicate the containing effect of the Sun's gravity. A tokamak is a vacuum vessel that cradles the plasma within a magnetic field generated by current-carrying coils. Scientists have used tokomaks experimentally for decades, but never one as large as the device at ITER, which will be two to three times larger than the current largest tokamak, the Joint European Torus located in England, outside Oxford.
In order for fusion to become a viable energy source, scientists must overcome a number of hurdles. For one, no one has ever managed to contain the ultra-hot plasma for long enough to sustain a fusion reaction that generates more energy than is required to keep it going. Other problems include the difficulty of finding materials suitable for reactors that need to sustain temperatures as hot as the Sun, and the prohibitive upfront costs of constructing commercial fusion plants.
"You know the joke about fusion: Fusion is thirty years away, and always will be," said John Perkins, a nuclear physicist at Lawrence Livermore National Laboratory.