Controlled chaos can be the key to unlimited clean energy

Controlled chaos can be the key to unlimited clean energy

nuclear fusion reactors could eventually harness the power of the sun to generate massive amounts of clean energy. But for now, they are prone to instabilities that can wreak havoc on the futuristic machines.

Now in a new study published in the journal Physical Verification LettersScientists have figured out one possible way to avoid these destructive instabilities — by deliberately boiling a few smaller ones together.

Here is the background – Nuclear fusion, the same reaction that occurs at the heart of stars, joins atomic nuclei together to form heavier nuclei. Any mass that doesn’t make it into new atoms is converted to energy, releasing an extraordinary amount of light and heat.

Scientists have long tried to create nuclear fusion in reactors on Earth because it produces far more energy than burning fossil fuels. For example, a pineapple-sized amount of hydrogen atoms provides as much energy as 10,000 tons of coal.

The tokamak could help scientists create clean fusion power.Jean-Marie HOSATT/Gamma-Rapho/Getty Images

Most experimental fusion reactors use a ring-shaped Russian design called a tokamak. These designs use powerful magnetic fields to confine a cloud of plasma or ionized gas at extremely high temperatures – high enough for atoms to fuse together.

But all magnetically confined plasmas inherently develop instabilities, or regions where small perturbations in the plasmas grow rapidly.

Instabilities that arise at the edge of the plasma ring in a tokamak are called “edge-localized modes” (ELMs) and are something like solar flares on the sun’s surface. Anyone can cast up to 20 percent of the energy stored in the reactorcausing potentially catastrophic damage to the walls of a tokamak.

Previous research suggests a possible solution: use magnets to slightly distort the plasma ring so that it forms a shape that looks a bit like a rounded triangle.

This step can expand the donut’s more stable interior and make the overall plasma more stable, says Georg Harrer, lead author of the study and plasma physicist at the Technical University of Vienna in Austria.

Previous studies have also shown that filling the ring with gas provides an increase in density and pressure at the very edge of the plasma. This triggers many small ELMS instead of large, more harmful ones.

But scientists thought such a scenario was only possible in relatively small tokamaks and not in the large ones currently being developed for research into fusion power.

This new study suggests that a barrier to nuclear fusion could actually help it succeed.MARK GARLICK/SCIENCE PHOTO LIBRARY/Science Photo Library/Getty Images

What’s new – This new work turns that theory on its head. Through a series of experiments and simulations, the researchers suggest that creating small instabilities could prevent larger ones in fusion reactors.

While researchers have previously manipulated small instabilities in the lab, they weren’t previously thought of as a tool for fusion reactors, says Saskia Mordijck, a plasma physicist at the College of William & Mary who wasn’t involved with the new research.

But the most recent study does consider that possibility.

You can compare a tokamak to a pot of boiling water with a tight lid, says Harrer. Just as the lid of a pot rattles when the pressure increases, large ELMs slam the tokamak as the pressure increases.

But scientists can offer pressure relief, like tipping a saucepan lid to let off steam: subjecting the tokamak to many small pressure surges could result in less damage.

This strategy generates several thousand small instabilities per second. It’s still unclear whether these small blasts help protect the tokamak, but “we have good reason to believe they’re much less damaging,” says Harrer.

Such bursts spread heat over a much larger area and over a longer period of time, hopefully preventing the tokamak interior from significantly melting. Furthermore, this approach shouldn’t significantly change the efficiency of a fusion reactor, he adds.

This new strategy will be tested at the Joint European Torus in England.Leon Neal/Getty Images News/Getty Images

Why it matters – This technique could be applied in reactors such as the International Thermonuclear Experimental Reactor (ITER) project, which aims to build the world’s first nuclear fusion facility.

ITER is currently being built in southern France. When operational, it could generate 10 times the energy scientists put into it.

What’s next – Future research will test this strategy on the world’s largest operational tokamak, the Joint European Torus (JET) in England, according to Harrer. JET is currently conducting experiments that could help pave the way for the International Thermonuclear Experimental Reactor.

“It’s a challenge to predict how a fusion reactor will behave at this point,” says Mordijck. “The region the authors are studying is known to be challenging for a number of reasons, and this is the region most altered in a fusion reactor.”

All in all, this new work is “just one small piece of the puzzle in a very complex problem,” Harrer warns. “As of now, people shouldn’t expect to get their power from a fusion reactor before the 2050s.”


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