As Earth’s inhabitants suffer through what may wind up being the hottest year on record, there’s a Promethean spark of hope. Virtually unlimited fusion energy appears to be, if not right around the corner, at least within hailing distance.
Last December, Lawrence Livermore National Laboratory’s National Ignition Facility finally succeeded in forcing the hydrogen isotopes deuterium and tritium to undergo a self-sustained fusion reaction. It was an encouraging advancement, though not exactly a breakthrough. NIF’s small net energy gain didn’t factor in the energy it took to fire up the 192 ultraviolet lasers that initiated the reaction, which lasted “for the briefest blink of a moment,” as Dina Genkina reported for IEEE Spectrum. While there are lessons to be learned from NIF’s successes and failures, laser-based inertial confinement fusion doesn’t yet provide a practical path to commercial-scale power generation.
There’s also a lot to learn from Iter, the world’s largest fusion experiment, which is now being built in southern France. Since 1985, the project has brought together 35 countries and thousands of scientists and engineers. ITER’s magnetic-confinement fusion experiments will happen inside a giant doughnut-shaped device called a tokamak, where powerful superconducting magnets will force hydrogen isotopes to fuse.
Even if Iter succeeds in touching off a sustained fusion reaction, though, it will never harness the energy produced. That crucial engineering step will be accomplished by some other group. One team vying to take fusion energy to market is Commonwealth Fusion Systems, in Devens, Mass., whose six founders all did research at Iter. In “Tale of the Tape,” page 30, writer Tom Clynes takes us inside CFS’s Sparc pilot project to create a new kind of commercially viable, compact fusion reactor.
“So one of the questions most fusion startups are going to have to answer is where do you get tritium to keep sustaining the reaction?” –Michael Koziol
CFS’s unique design relies on thousands of kilometers of high-temperature superconducting tape, which will help provide the stunningly powerful magnetic fields necessary to confine the reactor’s superheated plasma. As Clynes explains, Sparc’s planned successor, Arc, will feature a molten salt blanket that will absorb radiated neutrons and then pump them outside the tokamak to heat water into steam to power a turbine. Crucially, the molten salt could also breed tritium, a necessary but incredibly rare fuel for magnetic-confinement fusion.
Associate Editor Michael Koziol, who follows nuclear power for Spectrum, points out that tritium does not usually form naturally. Iter alone will use a good chunk of the world’s tritium supplies, Koziol told me, “so one of the questions that CFS and most fusion startups are going to have to answer is where do you get tritium to keep sustaining the reaction?” Fortunately, tritium can be a by-product of the fusion process, says Koziol, so finding ways to funnel the tritium that’s produced back into the reactor using breeder blankets or other methods will be both an opportunity and a huge challenge to overcome in the coming years.
Two other companies, Zap Energy and Helion Energy, both with facilities in Everett, Wash., are aiming to compete with CFS. As Contributing Editor Mark Harris points out in his recent online post “Welcome to Fusion City, USA,” these startups “epitomize a new confidence that fusion power is now a solvable engineering challenge rather than an eternally elusive scientific puzzle.” That challenge can’t be met soon enough. And with billions of dollars of government funding and private investment and research from giant international projects fueling these companies, there’s real hope that within the next few years, we might start to see the technology stack necessary to help wean the world off of fossil fuels, and at a pace that could turn the rising tides of climate change.
Source: Spectrum
