Why nuclear batteries are making a comeback

Posted: October 31, 2025

More than half a century after Apollo 11, astronauts are finally getting ready to walk on the Moon again. 

NASA hopes to launch a crewed mission as soon as next February, sending four astronauts on a ten-day flight around the far side of the Moon. After that, the U.S. wants to send another team to walk on the lunar surface in 2027, the first time since 1969. 

As space agencies plan for longer and longer stays on the planet, one of the problems they face is energy supply: During the 14-day lunar night, when the surface is shrouded in constant darkness and temperatures can dip as low as minus 400 Fahrenheit (minus 240 Celsius), the solar panels that power many satellites and spacecraft simply don’t work. 

One solution is to employ a new generation of nuclear batteries—a decades-old technology now seeing a resurgence, and one that could also find useful applications in a range of industries back on Earth. 

How nuclear batteries work 

Nuclear batteries are nothing new. The first nuclear-powered pacemaker, containing plutonium-238 in a titanium case, was implanted in 1970. But they went out of fashion within the next two decades, not least due to regulators’ unease around the whereabouts of the devices after they reached their end of life. 

Now, a new wave of research projects and start-up companies is pushing advanced technologies that are safer and more efficient, and could be used not just in spacecraft but also in drones and sensors to monitor industrial facilities. 

Aside from the unique requirements of space missions, industry insiders say innovation is driven by the need for micro devices in the industrial internet of things, as well as the general buzz around all things nuclear—from advances in fusion power to the development of modular reactors. 

“We’re catching that wave,” says Peter Cabauy, co-founder and CEO of City Labs, a Miami-based nuclear battery company. 

Nuclear batteries don’t work like a reactor; instead of splitting atoms, they simply capture and convert the energy of radioactive isotopes as they decay. 

City Labs is one of a handful of companies and universities working on batteries that use semiconductors to absorb the radiation from these isotopes—such as tritium, carbon-14 or nickel-63—to convert it to an electric current. (Other techniques include converting the heat produced by the radiation to electricity in a thermoelectric generator, for example.) 

The big benefit of these devices is that they can work on their own for decades or even centuries, depending on the isotope’s half-life. Such longevity makes them suitable for medical implants and power in space, but also things like monitoring oil wells for leaks. 

“If, all of a sudden, you're able to have these autonomous units that can operate through any temperature [and] pressure conditions, that just changes the game,” says Cabauy. “You just drop a sensor and leave it behind, and it can just work for decades.” 

Cabauy, a physicist who started City Labs together with an engineering co-founder in 2005, picked tritium—which has a relatively short half-life of around 12 years—for several reasons. One is that the isotope is produced as a byproduct of power generation in Canada’s fleet of deuterium uranium reactors, ensuring a stable supply. Another is that it’s widely used in everyday items like watch dials and glow-in-the-dark exit signs, which lowers the regulatory complexity. 

“[Customers] can just leave them there for decades and decades,” he says of the devices. “Or they can ship it back to the supplier at end of life.” 

Diamonds—a battery’s best friend? 

Tom Scott and Neil Fox, two professors at the University of Bristol in the UK, started seriously working on nuclear batteries in 2016, after taking a meeting with a defense company looking to develop next-generation submarines with solid-state power sources. 

Fox had been working on diamond-based thermionic devices, while Scott was researching the residual radioactivity of graphite in reactor cores. “Together, we came up with the idea of a diamond battery, which at the time was just a concept,” Scott says. 

Fast forward a decade, and the pair is now working to commercialize the world's first carbon-14 diamond battery. Developed with the UK Atomic Energy Authority, its design revolves around a lab-grown diamond structure enveloping the isotope, functioning both as the semiconductor and a durable casing to contain the radioactivity. 

Other companies are also working on batteries with diamond semiconductors, which, in general, boast higher conversion efficiencies than some other approaches. One, Beijing Betavolt New Energy Technology Co., is working with a range of isotopes, including nickel-63. 

Scott and Fox’s battery has a potential lifespan of thousands of years thanks to carbon-14’s half-life—although the power density is much lower than, say, tritium. 

“We're never going to power a train or an aeroplane or even a car, right? These are micro power devices,” says Scott. “A real ambition for [the next] 10 years or so is that you could maybe get one of these to permanently power a mobile phone”—at least in theory. 

Bringing nuclear batteries to market 

More realistically, Fox and Scott envision their technology as a next-generation RFID tag to track assets both in space and on Earth. The researchers are already working on the technology with the European Space Agency, but also cite its potential use in black-box flight recorders or boreholes for carbon capture and storage projects, where temperatures could be too hot for chemical batteries to work. 

“We can't easily displace the existing lithium battery market,” Scott says. “What we can do is we can use the technology in places and spaces where it's environmentally very extreme and standard battery solutions don't work.” 

The pair has launched a spin-out company, Arkenlight, to take their technology from the research lab to commercial production, and are currently negotiating with two partners for a direct investment to scale up production. 

In Miami, City Labs is similarly looking to vertically integrate: While Cabauy has manufactured batches of his tritium battery to order thus far, he says the company is now planning to launch mass production next year. 

Both Arkenlight and City Labs are also working on heat conversion models of their respective technologies. City Labs recently secured a NASA contract to support initial research on a radioisotope heating unit that could also use the heat directly to warm up electronics or chemical batteries in space—a potential way around those long lunar nights. 

“If you're going to the Moon, you know, surviving the lunar night, which is like 14 Earth days, and it's colder than liquid nitrogen—you need some heat,” Cabauy says.