DEBATE about America’s energy supply is heating up: gas prices are rising, ethanol is under attack and nuclear power continues to struggle in the shadow of the Fukushima disaster in Japan.
But an abundant, safe and clean energy source once thought to be the stuff of science fiction is closer than many realize: nuclear fusion. Making it a reality, however, will take significant investment from the government at a time when spending on scientific research is under threat.
Harnessing nuclear fusion, the energy that powers the sun and the stars, has been a goal of physicists worldwide since the 1950s. It is essentially inexhaustible and it can be created using hydrogen isotopes — chemical cousins of hydrogen, like deuterium — that can readily be extracted from seawater.
Fusion energy is created by fusing two atomic nuclei, in the process converting mass to energy, which appears as heat. The heat, as in conventional nuclear fission reactors, turns water into steam, which drives turbines to generate electricity, or is used to produce fuels for transportation or other uses.
Fusion energy generates zero greenhouse gases. It offers no chance of a catastrophic accident. It can be available to all nations, relying only on the Earth’s oceans. When commercialized, it will transform the world’s energy supply.
There’s a catch. The development of fusion energy is one of the most difficult science and engineering challenges ever undertaken. Among other challenges, it requires production and confinement of a hot gas — a plasma — with a temperature around 100 million degrees Celsius.
But potential solutions to these daunting technical challenges are emerging. In one approach, known as magnetic fusion, hot plasma is confined by powerful magnets. A second approach uses large, intense lasers to bombard a frozen pellet of fusion fuel (deuterium and tritium nuclei) to heat the pellet and cause fusion to occur in a billionth of a second. Whereas magnetic fusion holds a hot plasma indefinitely, like a sun, the second approach resembles an internal combustion engine, with multiple mini-explosions (about five per second).
Once a poorly understood area of research, plasma physics has become highly developed. Scientists not only produce 100 million-degree plasmas routinely, but they control and manipulate such “small suns” with remarkable finesse. Since 1970 the power produced by magnetic fusion in the lab has grown from one-tenth of a watt, produced for a fraction of a second, to 16 million watts produced for one second — a billionfold increase in fusion energy.