Could A Giant Magnet Like This Help Power The World?
Friday, April 10, 2015
This week, General Atomics unveiled the beginning of work on a magnet more than four stories tall. This magnet's job is an even taller order: making good on the clean energy promise of nuclear fusion.
San Diego-based General Atomics unveiled on Friday the beginning of work on a magnet more than four stories tall.
This magnet's job is an even taller order. It's designed to make good on the clean energy promise of nuclear fusion.
The engineer in charge of the project is John Smith. His experience in nuclear fusion runs deep, going back to the first job he took fresh out of undergrad.
"Almost 22 years I've been working in fusion," Smith said.
In his field, fusion is a kind of holy grail. In theory, it could generate nuclear power anywhere in the world without a constant flow of radioactive waste.
"And there's no carbon," Smith said. "It's a very clean source of energy, and it's almost completely renewable."
Engineers at General Atomics have been experimenting with fusion for half a century. But now, Smith and the three dozen employees he oversees are part of a major international effort to prove fusion can actually power the world.
"The big picture goal with fusion is to replicate what happens on the sun," Smith said during a tour through the Poway facility assembling this 1,000-ton piece of machinery.
Existing nuclear power plants produce energy through fission — by splitting atoms. Fusion would do the opposite. Mimicking the reactions that fuel our sun, the process would force atoms to overcome their natural repulsion, ultimately giving off two byproducts: helium and highly energetic particles that could be harnessed to create electricity.
The challenge, Smith said, is "Two atoms don't like to fuse together. You've got to force them together. That's what we're trying to do with the temperature."
The magnet, along with other heating systems within ITER, will help bring two hydrogen isotopes up to extreme temperatures 10 times hotter than the sun. It'll do that by driving current through a plasma magnetically confined within the reactor.
Building a magnet that powerful requires nearly 24 miles of conducting cable manufactured by engineers halfway around the world.
"This is a spool of conductor as it came from Japan," Smith said, pointing to a huge coil of silvery cable that looks a bit like the world's biggest Slinky.
"We've taken it, and on the shipping fixture that it came from, we've lowered it down onto our de-spooling device."
Once the cable is straightened out, a machine winds it into precise concentric spirals. Those spirals form layers. Forty of those layers will make up one cylindrical module, called a coil.
The finished magnet will consist of six of these coils.
Once each coil is tightly wound and perfectly welded, it'll weigh 250,000 pounds. By then, the only way to move it through the facility is on a cushion of air created by a heavy-duty cart.
"The simplest way to explain it is an air-hockey table, turned upside down," Smith said. "Instead of blowing air up to levitate a puck, we're actually blowing air down, and levitating the coil."
These coils will eventually be chilled to nearly absolute zero once they're inside the French reactor. But first, they need to bake inside a furnace for five weeks at 1,300 degrees Fahrenheit. All that heat forges a superconducting material capable of circulating electricity with no energy loss.
Many steps in the magnet's production are done by machine. However, some tasks are so delicate, they still need to be done by hand. For instance, insulating the pipes that pump liquid helium into the magnet.
Smith watches the engineer tasked with this job.
"It's amazing to think you have something this big that weighs this much, and here he is putting little pieces together with tweezers," he said.
It'll be 2019 before General Atomics ships the final piece of this magnet off to France. And it'll be at least 2040 before ITER paves the way for a demonstration plant aiming to actually pump fusion energy into the grid. Some experts believe even that timeline is optimistic.
ITER has been known for cost overruns, delays and management problems. Congress is even threatening to pull U.S. funding without certain reforms. But Smith said, for scientists who've dedicated so much to fusion, it's rewarding just to see these parts finally getting made.
"For physicists this is their life looking at magnetic fusion and ITER and the promise of that," Smith said.
He recently gave a tour to a fusion researcher with years of experience working on ITER.
"And he said in all that 15 years, 'this is the first component I've seen that will actually go to ITER.'"
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