Seeking to improve the tokamak fusion reactor known as ITER, researchers have found a way to stop rogue tungsten atoms from shearing off the walls and messing with the plasma. The finding is another important milestone on fusion's road to success.
As the science of nuclear fusion continues to advance, tackling some of the smaller issues that arise through advancing research can have a big impact. One of the concerns scientists have about fusion reactors has to do with tungsten. The element is increasingly being explored as a way to line the inside of plasma fusion reactors known as tokamaks and stellarators because of its ability to withstand the scorching temperatures created inside of them.
But when the super hot plasma that's held inside these reactors bumps into walls lined in tungsten, some of the metal's atoms pop off and join the plasma. This has the unwanted effect of cooling the plasma and making a fusion reaction less likely.
Now, after conducting tests at three tungsten-lined tokamaks and using computer modeling, researchers at the U.S. Department of Energy's Princeton Plasma Physics Laboratory have come up with a novel solution. They found that injecting boron powder into the reactor shields the tungsten walls from the ravages of the plasma and allows it to hold on to all of its atoms.
"The boron is sprinkled into the tokamak plasma as a powder, like from a saltshaker, which is ionized at the plasma's edge and then deposited on the tokamak's inner walls and the exhaust region," said Joseph Snipes, Princeton's deputy head for Tokamak Experimental Science. "Once coated with a thin layer of boron, it will stop the tungsten from getting into the plasma and radiating away the plasma energy."
Snipes and his team found that the boron could be sprinkled from one location only to successfully coat all the walls. They are now working to develop a boron injection system that could potentially be used at the ITER reactor-scale tokamak.
ITER, which stands for the International Thermonuclear Experimental Reactor, is located in southern France and will be the world's largest nuclear fusion plant when it comes online. The system was originally scheduled to begin operations in 2025, but that timeline has been extended by about 10 years.
The researchers are presenting their findings this week at the 66th Annual Meeting of the American Physical Society Division of Plasma Physics in Atlanta, Georgia.
