Monday, 26 March 2012

Nuclear Fusion Now Seen As A Real Possibility

Computer simulations show we might one day use power source that makes stars shine

A prototype of the nuclear fusion system that relies on coils and compressing magnetic fields to produce energy

If new computer simulations pan out in the real world, nuclear fusion, the power source that makes stars shine, may be a practical possibility here on Earth, scientists say.

Simulations at Sandia National Laboratories in New Mexico revealed a fusion reactor that surpasses the "break-even" point of energy input versus energy output, indicating a self-sustaining fusion reaction. (This doesn't break any laws of physics for the same reason that starting a fire with a match doesn't).

Extremely high temperatures and pressures are needed to spark nuclear fusion, a process in which atomic nuclei — the protons and neutrons of atoms — literally fuse together to create a heavier element. And if the conditions are right, that fusion can release massive amounts of energy.

The results of the new study have applications in weapons testing (it's feasible to test the effects of nuclear weapons in the lab, but not in the real world) and for clean energy, as the experiment relied on deuterium, which could be extracted from seawater.

In stars, the mass of hydrogen is so large that its own gravity keeps the hydrogen and helium at the center in a small area, and the temperatures are in the millions of degrees. Essentially, the plasma (gas that has had its atoms stripped of electrons) is confined forever, and the protons can't escape and take their energy with them. So hydrogen fuses into helium, producing a lot of energy in the form of light and heat.

But that's a lot more difficult to do in a lab. For years, scientists and engineers have been looking for ways to confine plasma that is so hot it would melt the walls of any container and force atoms together to make them fuse.

A video clip explaining how nuclear fusion works:

Real-world tests

Even at Sandia, there isn't a machine that can generate such a huge pulse of energy. The Z machine, a powerful X-ray generator, can hit about 26 million amperes. That might be enough, though, to prove the concept works by hitting the break-even point, where the energy put into the reaction is the same as that which comes out.

Sandia scientists are currently testing the different components of the new machine; right now, they are working on the coils, but a full-scale test should happen in 2013, they say.

Sandia spokesperson Neal Singer noted that one purpose of this work is to study the effects of nuclear explosions without actually exploding a bomb. The United States currently abides by a moratorium on underground nuclear tests. But testing warheads in some manner is essential because the nuclear stockpile is aging. Being able to create fusion reactions in a laboratory setting will go a long way toward making nuclear explosions unnecessary.

Of course, it is still uncertain whether the reaction will work the way the researchers hope. Instabilities that appear in the magnetic fields that contain the plasma, for instance, have been an obstacle to working fusion power plants. Those instabilities allow the plasma to escape, so it doesn't fuse. But the work at Sandia is a step in the right direction, said Stephen O. Dean, president of Fusion Power Associates, an advocacy group that has pushed for development of fusion energy.

"They are working at a higher density than other fusion experiments," Dean told LiveScience. "So there's more classical physics … it's better understood." Other approaches, he said, such as using lasers to force deuterium nuclei together, produce interactions that have not been studied as extensively.

Though this work is ostensibly to test weapons, Singer acknowledged its application to power generation, and that it would be a big step.

Dean was more emphatic. "Even though it's a weapons program, (power) is in the back of everyone's mind," he said.

Taken from Science on (27/3/2012)

No comments:

Post a Comment