What Comes After a World’s First in Fusion Research
As soon as Kim Budil, the director of Lawrence Livermore National Laboratory, said on Tuesday that cheap, abundant electricity from nuclear fusion is still “probably decades” away, some people lost interest in the news that her lab had achieved a world’s first in fusion research. We earthlings can’t wait decades for a solution to climate change.
There are three reasons to pay attention. One, commercialization of fusion could happen sooner than Budil thinks if enough people get behind it. Two, fusion is a controlled version of what happens inside a nuclear warhead, so it can be used to test computer-aided designs for nuclear weapons. Three, the science is totally cool.
At 1:03 a.m. Pacific time on Mon., Dec. 5, scientists at Livermore, in California’s Bay Area, fired the world’s most powerful laser — 192 laser beams — at a target about the size of a peppercorn or a BB pellet. It was a perfectly round, hollow sphere made of diamond and containing supercooled deuterium and tritium, which are heavier isotopes of hydrogen. The sphere was inside a cylinder the size of a pencil eraser made of depleted uranium lined with gold. The laser beams entered the ends of the cylinder, hitting the gold and generating a bath of X-rays that vaporized the outer layer of the tiny sphere, causing the inner layer to implode and turning the fuel inside into plasma hotter than the center of the sun. Stripped of their electrons, some of the hydrogen atoms fused into helium, releasing energy in the process.
Livermore has zapped spheres of fuel for several decades, with not much to show for it until last year. The breakthrough on Dec. 5 was that for the first time the energy produced by the fusion reactions was greater than the energy directly applied to achieve them. That’s ignition in the scientific parlance.
But the energy that’s directly applied is only part of the total energy that the overall system requires. For one thing, Livermore’s monster laser isn’t 100 percent efficient. The next step — getting so much energy out of fusion that it exceeds the total energy drawn from the grid — is still a long ways off. Still, Livermore scientists were over the moon. When Tammy Ma, a plasma physicist, got word a few hours later, she was at San Francisco International Airport waiting for a flight. She told reporters on Tuesday that she burst into tears of joy.
As an interesting aside, the Livermore experiment produced a lot of power (how fast energy is used, as in weight lifting) but not much total energy (as is expended over the course of a marathon). For less than a billionth of a second, the power from fusion reactions was far greater than that of the entire U.S. power grid. But because the pulse was so brief, the total energy produced was only about enough to boil a few kettles of water.
At this point I want to stop with the superlatives and mention a prosaic number: 25 cents. Two fusion experts told me separately that for fusion to become commercially practical, the cost of the fuel targets will need to fall to around 25 cents each, since a commercial-scale plant will need to use them up at a rate of about 10 a second. We’re a long way from that. It’s not just the gold and diamond. It’s mainly the labor-intensive fabrication process, which today takes seven months. The spherical targets that Livermore uses must be almost perfectly smooth: A flaw the size of a single bacterium can degrade their implosion.
“If the target fabrication cost turns out to be a dollar or two,” rather than around 25 cents, “then that would greatly increase the size and capital cost of the power plant,” Stephen Bodner, a plasma physicist who is retired from the Naval Research Laboratory, wrote in an email. That’s based on the idea that bigger power plants would produce more electricity per shot, so a more expensive target would still be affordable.
Simon Woodruff, who has evaluated fusion plant designs for the federal government’s Advanced Research Projects Agency-Energy, wrote in an email that there are four key metrics. First is the gain — energy out versus energy in. A gain of 1.0 or more is considered ignition. The gain achieved by Livermore this month was 1.5, and the facility’s potential is about 20. To be economical, the gain needs to be 100 to 200, he wrote. Second is the efficiency with which grid power is turned into laser power. That’s around 1 percent and needs to be around 7 percent, he said.
Third is the cost of the target. Woodruff, like Bodner, said it needs to be about 25 cents, depending on plant design. “The target cannot be too complicated,” he wrote. “The more manufacturing steps that are needed, the more costly will be the target.” And fourth, he said, is the cost of the factory that makes the targets.
Of those four objectives, Livermore has put almost all its effort into maximizing the gain. That’s appropriate for a national lab, for which the science comes first. Also, one of Livermore’s main jobs is to oversee the nation’s stockpile of nuclear weapons. Creating a fusion reaction is a way to study what happens inside a nuclear weapon when it detonates. Commercialization of fusion power is not Livermore’s mission.
The other three objectives will require some science plus a lot of engineering. Woodruff, who runs Woodruff Scientific, which makes research gear in Santa Fe, N.M., wrote that Livermore, by achieving ignition, has “paved the way” for private companies working on laser fusion. He named five — Xcimer Energy, Focused Energy, Marvel Fusion, HB11 and First Light Fusion — and said “there may be more coming.” Most fusion companies use a different approach, which is to hold the plasma in place with powerful magnets. Even before Livermore’s announcement, 21 of 25 fusion companies surveyed by the Fusion Industry Association predicted fusion power would be commercially viable by 2040. Three of them predicted viability by 2030. (But you wouldn’t expect them to be pessimistic.)
“The timeline is the function of the will we have and the amount of investment that society puts forth and the number of people who get excited and want to work on these challenges. The excitement is at a level I’ve never seen,” Sam Wurzel, the technology-to-market adviser at ARPA-E, said in an interview. Scott Hsu, who is the Department of Energy’s lead fusion coordinator, said, “Don’t count fusion out as a solution to our 2050 targets” for reducing greenhouse gas emissions.
Livermore’s big blast on Dec. 5 has energized the long-suffering community of fusion scientists. True, there’s many a slip ’twixt the shot and the watt, but ignition is nevertheless an exciting advance.
Elsewhere: Supply Chains Are Still Tight
Pressure in the global supply chain increased modestly in November for a second month but remains well below its pandemic highs, according to an index maintained by the Federal Reserve Bank of New York. The biggest contributor to the November increase was delivery times in China. Delivery times in the United States improved. The worst month for the New York Fed’s index was December 2021.
Quote of the Day
“Capital, nation and state are distinct entities, each operating according to its own principles, but like a Borromean knot, they are linked in such a manner that all will fall apart if any of the three is missing.”
— Kojin Karatani, “The Structure of World History: From Modes of Production to Modes of Exchange” (2014)