Tomorrow, the U.S. Department of Energy is expected to announce that the era of fusion power is finally upon us: Scientists at the Lawrence Livermore National Laboratory, in California, have generated energy with a controlled nuclear fusion reaction. It has already been hailed as a transformative moment, even as the nature and reality of that transformation are nigh-impossible to discern.
As first reported yesterday by the Financial Times, Energy Secretary Jennifer Granholm is expected to announce that researchers have ignited a small fusion reaction that produces more energy than it consumes. The federal government is calling this “a major scientific breakthrough,” and if the rumors are true, that description will in some sense be justified. For the better part of a century, scientists have been trying to use the power of fusion—the nuclear process that makes the sun shine—to provide a near-limitless source of energy. But it takes a huge amount of energy to set up the reaction: to build the tremendous heat and pressure necessary to get light atoms to stick together—to fuse—and release energy stored in their mass. Until now, physicists and engineers had managed to produce more than they’d invested only by triggering uncontrolled fusion reactions in certain types of nuclear weapons; no one has yet made a defensible claim of doing so in the lab.
How defensible the Livermore scientists’ claim will be is not yet clear. (When this story went to press, neither the Livermore lab nor the Department of Energy had responded to requests for comment.) Their fusion-energy device, the multibillion-dollar National Ignition Facility, was playing defense from the start. On paper, the plan seemed great, if ambitious: to use enormous, building-size lasers to focus light energy down onto a target roughly the size of a BB, compressing and heating it and causing its contents to fuse. However, previous laser experiments at Livermore have failed to deliver promised fusion results, and a number of scientists were skeptical that the facility would ever achieve “ignition,” defined as generating more energy from fusion than is contained in the laser beams. Advocates of NIF turned to a top-secret set of nuclear experiments from the 1980s called Halite/Centurion—in which X-rays from underground nuclear explosions shined upon similarly tiny target capsules—to back up their argument that NIF would, indeed, achieve ignition. But the results of those experiments are classified, and a few insiders with the requisite clearance have expressed their concerns. “Something that worked at the Halite/Centurion scale would not necessarily work at the NIF scale,” Ray Kidder, a weapons designer, told a historian in 2008. “They didn’t want that to be said.”
Nevertheless, the first target pellet was witness to the firepower of a fully armed and operational ignition facility in 2010. NIF scientists were confident of quick success. Siegfried Glenzer, Livermore’s plasma-physics group leader at the time, told the press to expect ignition later that year. It didn’t happen. Nor did it happen in the next fiscal year, as promised in 2011 by then–Livermore head Parney Albright. Nor did it happen in the next six to 18 months, as then–NIF head Ed Moses said “with some confidence” in 2012; at the time, the official word was that Livermore was “tantalizingly close” to this achievement.
Tantalus never got to eat, though. Success remained well out of reach, and the full-on “national ignition campaign” was a failure. Yet you wouldn’t have known that by the headlines that sprouted up around the world in 2014, when Livermore declared victory with a claim of having extracted net energy from fusion fuel. Physics World even named it one of the top 10 breakthroughs of the year. This was nothing more than an accounting trick: Instead of comparing the fusion energy produced with the energy of the incoming laser beams, NIF scientists had compared it with the small fraction of the laser-beam energy that struck the target chamber, got converted into X-rays that shined onto the target, and was eventually absorbed by the fuel—which is to say, roughly 1 percent of the total. Fiddling with the denominator turned a 99 percent failure into a 100 percent victory.
When the headlines faded, NIF kept puttering along, consuming energy and dollars. Only in the past year have its scientists come within a respectable distance of achieving ignition. In mid-2021, one shot yielded 1.3 megajoules of fusion energy, more than half of what’s contained in the roughly 2-megajoule laser beams. That, too, was touted as a breakthrough, and one that Livermore scientists would later designate an “‘existence proof’ of ignition in the lab.” Once again, though, their claim was based on a sleight of hand, using a slightly different definition of ignition to make it seem like NIF had finally lived up to its middle name. (On Twitter, NIF claimed that its criterion remained the same: “The ‘goalpost’ for ignition has never moved.”)
This brings us to tomorrow’s announcement. According to the FT, one NIF shot finally generated more energy than was contained in the laser beams—about 2.5 megajoules out, compared with 2.1 megajoules in. If true, this would meet the classic definition of ignition used for decades rather than the ad hoc ones Livermore scientists have lofted to hide their failures over the years; NIF would genuinely have succeeded at its goal, albeit more than a decade late. No more fake-it-’til-you-make-it: This would arguably be the first production of net fusion energy produced outside of a nuclear-weapons test.
However, the real implications of honest-to-god ignition at NIF are significantly more subtle than one might think. Even if NIF is able to replicate the shot, perform similar ones consistently, and eventually increase the yield by five or tenfold, the experiment is still a dead end when it comes to meaningful energy production. Two megajoules is about the amount of energy released by burning a small chunk of kindling, so thousands upon thousands of such shots a day would be required before the energy production became in any way usable. Unfortunately, NIF’s lasers use huge slabs of glass that take hours to cool down between shots; in other words, they simply aren’t up to the task. (In fact, NIF was never meant to be a fusion-energy project but one designed for weapons research—another story altogether.)
If the achievement is genuine (and NIF hasn’t moved the goalposts yet again), it means that—at the very least—NIF has achieved its nominal goal: ignition as scientists defined it a few generations ago. But this definition is untethered from the realities of power generation. The “more energy out than laser energy in” equation masks several fundamental problems. NIF’s doped glass lasers have an efficiency of about 0.5 percent, meaning that they would have sucked in roughly 400 megajoules of energy from the grid in order to produce the 2.1 megajoules of light energy that eventually yielded the 2.5 megajoules of fusion energy out. That isn’t accounted for in the “break-even” calculation. Nor is the large amount of energy (and time and money) required to manufacture each target. Even if we could collect all the fusion energy generated with perfect efficiency and convert it into usable power (which we can’t), this brings us to much, much less than 1 percent of the way to a true net production of energy from NIF’s very best fusion reaction.
This isn’t to say that the achievement is meaningless. NIF really producing 2.5 megajoules of fusion energy from a 2.1-megajoule laser beam would be a genuine victory, and not just because it’s a multibillion-dollar experiment that finally stopped failing to meet its design goal. But this would be less like a Kitty Hawk moment than a lab experiment demonstrating that air flowing over a wing can produce a little bit of lift. The work doesn’t address any of the myriad other scientific, technical, and design problems that would need to be solved before we really can take off from the ground and claim that we’ve produced more energy with fusion than we’ve consumed. Still, it’s a symbolic achievement—and symbols, too, should be celebrated.