When its first nuclear power plant went online in 1957, America seemed poised to embrace nuclear energy. But by the 1990s, with accidents at Chernobyl and Three Mile Island souring public opinion, enthusiasm plummeted. Over the next three decades, research and construction of new reactors stalled. In recent years, however, interest in nuclear power has resurged as America’s energy demands continue to rise. But unlike the massive behemoths of the nuclear age, some of today’s reactors, called microreactors or nuclear batteries, are small, and can easily fit inside a truck. And they just might help solve America’s energy conundrum, according to experts. Several in tandem, for example, might power a college campus or a remote mining community. They could be installed on barges and serve as floating nuclear power plants, bringing power where it’s needed by ocean or sea.A microreactor’s size comes with a tradeoff, however: While nuclear power plants can generate one gigawatt of electricity per year, their tinier cousins produce a more modest 1 to 20 megawatts—still enough to power thousands of homes for a year. The flip side of that coin is a dramatic reduction in risk. “Because they’re much smaller, much simpler, with less steel and concrete, if a microreactor project fails, you’ve lost maybe 200 million dollars instead of 15 billion,” says Jacopo Buongiorno, Ph.D., a nuclear science and engineering professor at M.I.T. The easier-to-swallow price tag makes microreactors an appealing bet for companies—which range from startups like Radiant Nuclear and Oklo to established giants with decades of nuclear energy experience like Westinghouse. But the road to a viable commercial product is a complicated one, involving research and development, extensive testing, and regulatory approval. “It’s a long and rigorous process,” says Jon Ball, Ph.D., who leads Westinghouse’s eVinci microreactor effort. All nuclear reactors derive their power from nuclear fission, the process of splitting an atom (often Uranium-235) by bombarding it with neutrons, which releases energy and additional neutrons. A coolant siphons the resulting heat away from the reactor core and turns it into steam, which spins a turbine and generates electricity. To create a sustained reaction, you need a moderator to slow down the neutrons and give them a chance to collide with other uranium atoms. Most nuclear power plants in the U.S., the so-called light-water reactors, use water as both coolant and moderator. But the challenges of shrinking a nuclear reactor down to microreactor size—Westinghouse’s eVinci is 30 feet long—nudged researchers to experiment with other materials and strategies.Compared to large reactors, for example, it’s harder to sustain a chain reaction with small reactors since “their high surface-to-volume ratio means a lot of neutrons leak out,” Buongiorno says. The solution: “Make your fuel juicier,” or with a higher percentage of Uranium-235, the active ingredient in a fission reaction. Enter TRISO fuel—high-density Uranium-235 spheres encased in layers of carbon and ceramic. Its outer shells make it virtually meltdown-proof while its construction traps potentially dangerous fission byproducts.Similarly, the need to increase reactor efficiency, having reactors that operate at higher temperatures, prompted researchers to swap out water for coolants like molten salt, liquid metals, and helium gas—all of which have higher boiling points than water. In the event of an accident or unexpected shutdown, modern microreactors are also safer than previous generations of nuclear reactors, which rely on external power to operate critical safety measures. A 2011 earthquake and tsunami in Fukushima, Japan, for example, disabled electricity-reliant cooling systems meant to prevent core meltdowns. Microreactors, in contrast, “are designed to cool down passively, meaning no electricity, no pumps are needed,” says Jess Gehin, Ph.D., an Associate Laboratory Director at Idaho National Labs, where companies like Westinghouse and Radiant plan to test their microreactors. Instead, they lose heat through intervention-free mechanisms like conduction, pressure drops, or radiative heat transfer. All told, the probability of a radioactive leak is “extremely low,” Gehin says.Nuclear energy’s untapped potential is exciting to scientists like Gehin. Fossil fuels are vulnerable to market fluctuations, which impact their price; while solar and wind energy depend on weather conditions. Nuclear energy, on the other hand, “doesn’t emit carbon, can operate 24/7, and is very reliable,” Gehin says. And once they’re on, they can run for 5 to 8 years without needing to refuel.Big Tech, with its data centers and their outsized energy needs, have taken note. Universities are on board too. Both Penn State and MIT have expressed interest in adopting eVinci to power their campuses, according to Ball. Microreactors are also ideal for remote communities like military bases or mining sites, where diesel is expensive and often difficult to get. And they run autonomously, requiring a staff of one to two people to keep things on track instead of the army employed at traditional nuclear power plants.Westinghouse plans to deploy its first commercial units by 2030, Ball says. And it’s his hope that eventually we can “produce microreactors much like how Henry Ford produced automobiles in a factory.” Ball is optimistic. “This is a technology that can really help create an era where energy is abundant, accessible, secure and available essentially anywhere—both here on Earth as well as in space,” he says.