Is Carbon-Free Nuclear Fusion Energy Just Around the Corner?
About 800,000 years after humans first used and controlled fire, scientists at the Lawrence Livermore National Laboratory’s National Ignition Facility (NIF) in Berkeley, Calif., ignited a new kind of fire for the first time. On December 5, a nuclear fusion reaction successfully produced more power than it took to start. Then, it flickered out. A potentially limitless source of carbon-free energy appeared on the horizon but the road to fusion power on the electric grid will take time.
The fusion process, unlike the fission reactors currently used in the energy industry, produces no radioactive waste, making it potentially the cleanest source of energy in history. Fusion reactors also present no risk of meltdowns that, though rare, are a major concern with fission reactors. Oxford, U.K.-based Philosophical Transactions of the Royal Society estimates that fusion energy could cost half what electricity generated by onshore wind facilities does. In our conversations with fusion startup executives, they describe vast generators requiring billions in capital investments as well as small-footprint facilities that would fit in a city block and cost only a half-billion dollars to build. Both approaches could augment the emerging distributed grid.
Science has worked for almost 70 years to achieve fusion ignition. By contrast, pre- and early-human use of fire took about 400,000 to become commonplace in the archeological record. To use fire as a tool, humans first had to wait for a fire to occur naturally and master transporting embers, then learn to make their own fires using flint and iron or pyrite, as well as avoid suffocating in closed caves and prevent fire from spreading beyond the hearth. We think of these as simple lessons but they took hundreds of thousands of years to propagate across our species.
In these accelerated, connected times, fusion’s slow progress since the 1950s represents immense progress; we may be more than halfway to realizing the dream. Academic researchers believe fusion will be commercially viable in the second half of the century, at the earliest.
What Happened on December 5?
Like early humans working with flint in the cold and wind to ignite tinder, fusion scientists have been trying to spark a reaction that lasts more than milliseconds. In short, they want to get more energy out of the ignited reaction than they put in before the fire goes out. Fusion reactions are ignited by lasers pointed at a small fuel pellet in the reactor, which produces energy by forcing elements to combine into another element. In the NIF’s case, two hydrogen isotopes, deuterium and tritium are fused, releasing a helium atom, a free neutron, and a lot of excess energy, which could be used to heat water to generate electricity.
“I don’t want to give you a sense that we’re going to plug the NIF into the grid: That is definitely not how this works,” said Lawrence Livermore National Laboratory Director Kim Budil at a press conference on December 13. “Ignition is a first step — a truly monumental one that sets the stage for a transformational decade in high energy density science and fusion research — and I cannot wait to see where it takes us.”
The NIF team’s December experiment used 2.05 megajoules (MJ) of energy to generate 3.15 MJ in output, or about 54% more energy than the 2.05 MJ that generated the reaction. The catch here is that powering up the banks of lasers and the loss of energy as it was transferred to the lasers required required 322 MJ of energy — 1oo times the fusion energy generated. Nevertheless, when measured on a direct input-output basis, December 5 represents a significant breakthrough, and future experiments will focus on reducing the energy needed to power the lasers.
Fusion produces a plasma, a soup of charged particles as hot as the core of the sun. Next, science must master keeping the fire lit and containing and using the heat generated by the fusion reaction.
What Happens Next?
The NIF’s mission is to simulate the energy created by a nuclear explosion, not to develop electricity-generating fusion reactors. The Department of Energy announced a 10-year plan to develop commercial fusion energy last March. Secretary of Energy Jennifer Granholm said the agency will accelerate fusion innovation by combining government research under one umbrella program, though the NIF may remain focused on weapons projects. With more than 30 private companies pursuing fusion power generation, the main action may take place outside of government and academic laboratories.
Fusion-powered electricity generation, which involves managing temperatures of as much as 150 million degrees, must solve a variety of problems to become commercially viable.
Keeping the Reaction Going
Early fusion reactors may need to be reignited frequently. Finding efficient ways to inject additional tiny pellets of deuterium and tritium, the fuel for the fusion reaction, into the reactor quickly will be key to maximizing power generation and minimizing downtime. Eventually, self-sustaining fusion, when the heat keeps the reaction going, will keep the reactor working for long periods. Extended reactions are key to generating enough electricity to maintain the baseload power levels necessary to support homes and businesses on the grid all day long.
Solving Plasma Containment
Fusion plasmas are controlled and held in place using magnetic fields. When the containment field fails or is breached, the reaction stops instantaneously, so efficient management of plasma and the containment system is key to generating energy efficiently. Several reactor configurations and different fuels are under development, and more than one combination may be successful. The most popular approach is a donut-like ring reactor like the NIF’s, known as a tokomak. Linear systems that drive energy into a central chamber where the plasma is contained from each end represent a second strategy, one led by TAE Energy, which has raised more than $800 million in funding to date.
Getting the Energy Out of the Reaction and Into an Electric Generator
Once the reaction is persistent and the plasma is manageable, the problem of getting the heat from the reactor to a generation system will be key to generating the most electricity possible. Heating water by bringing it into contact with the plasma through pipes and using a molten material — such as salt to transfer heat from the reaction chamber to a generator — are two options; others may emerge.
But here we run into the problem of radiation contamination in the environment immediately around the reactor.
Preventing Neutron-Caused Damage
Remember that in addition to the energy generated, a free neutron is produced. Neutrons, which accelerate ionization, making metals brittle increasing the likelihood of failure and potentially high maintenance costs. Parts of the reactor may need to be replaced frequently to prevent failures because the components have become brittle.
While the fusion reaction itself doesn’t produce radioactive waste, current fusion technologies, which allow some of the neutrons produced in the reaction to escape, can make the structure of the reactor equipment and building radioactive. This problem must be overcome before the technology can become ubiquitous.
Making the “Fuel”
Tritium, the hydrogen isotope used in the NIF reaction, doesn’t occur naturally in large concentrations. It must be bred in a fusion reactor, where neutrons can convert lithium into helium and tritium. And that’s expensive. Other fusion reaction fuels, such a boron, which TAE Energy uses, are available in large volumes in nature. In all cases, new processes and environmentally responsible methods of manufacturing need to be evolved to support long-term generation of electricity.
When Will Fusion Arrive?
Despite optimistic claims by fusion startups that they will be providing commercial energy by 2035, fusion is likely to take longer to reach that goal. In fact, the largest fusion reactor project aiming to generate electricity in the world, the $22 billion ITER project being built in St-Paul-lès-Durance, France, is not expected to achieve ignition until 2035. However, the pace of investment — by government and private parties — is accelerating. The Biden Administration has made fusion an anchor technology in its decarbonization plan and touts the idea that fusion could play a meaningful role in U.S. and global carbon-free electricity production in the late 2030s.
It is safe to say, because of the state of research and the time involved in building generation plants, that fusion will not be part of the energy infrastructure until the 2040s at the earliest. However, history shows that the unexpected often happens, and scientists may crack the problem sooner. In the meantime, homes and business need to continue to use electricity more efficiently so that the available supply can support new demand for power, which is expected to double by 2050.