In China, large reactors are coming together at a stunning pace. The country has nearly doubled its nuclear fleet since 2016, reaching nearly 60 gigawatts of total power capacity. The new facilities are nearly all gigawatt-scale pressurized-water reactors.
Meanwhile, the US has built just two reactors in that time—Unit 3 and Unit 4 at Plant Vogtle in Georgia. Smaller reactors are attracting a lot of excitement and investment, though. A microreactor developer just saw its reactor reach criticality in a new Department of Energy pilot program.
The world is racing to meet rising electricity demand, and many countries are interested in energy sources, like nuclear power, that don’t come with greenhouse-gas emissions. The key question: Which of these strategies will really pay off in terms of getting electrons on the grid quickly?
Today, the US and France are known as leaders in the nuclear industry. The US has the world’s largest fleet, with France coming in second. France is heavily dependent on nuclear for its grid—about two-thirds of the country’s power comes from nuclear reactors.
But they have hardly added any new reactors to their fleets in recent years. The US can point only to Vogtle, and France connected its latest reactor to the grid in December 2024—the first in over 20 years.
It’s incredibly difficult to build the massive projects that dominate the nuclear industry today. Up-front investment can run well into the billions, so investors need to wait decades to break even. Designs are complex and can often change during the regulatory process, tacking on cost and time.
Many are hoping that the key to turning things around in these countries could be smaller reactors.
The idea is that shrinking the footprint of a reactor cuts down the initial investment needed to prove out the new technology. The reactors could even be put together in a factory rather than being built on-site, allowing for a lower price over time.
These smaller reactors are the target of tons of interest and investment in the US, including a new Department of Energy pilot program. The department set a goal last year of having three test reactors reach criticality by July 4, 2026, the nation’s 250th anniversary. (Criticality is the point at which a reactor achieves a self-sustaining chain reaction that can release energy.)
Last week, California-based Antares hit the milestone with its Mark-0 reactor.
The company plans to eventually build microreactors, designed to produce between 100 kilowatts and 1 megawatt of electricity (large reactors on the grid today are at least 1,000 times that size). The core design is a sodium-cooled reactor, and it uses TRISO fuel, self-contained graphite-coated spheres of a more concentrated fuel than what most reactors use today.
But there is still a long way to go before it can actually produce power—the Mark-0 doesn’t have any power conversion or heat removal systems. The company plans to produce electricity in late 2027 and deploy in the field by 2028, CEO Jordan Bramble told the Associated Press.
The private sector is interested—and invested—too. Big Tech companies are throwing money at new reactors they hope can help power data centers.
But look to the other side of the globe, and others are sticking with the established blueprint: China is absolutely churning out large nuclear reactors. Construction started on six new reactors there in 2025, and two more got underway in the first five months of 2026. The country is on course to overtake both the US and the European Union in installed nuclear capacity by 2030.
The speed here is staggering. As of 2024, the average time to build a new reactor in China came in at between five and seven years. The global average is about nine years, and the two most recent reactors in the US took about 15 years.
One key to this speed is standardization: China has set up a uniform project management system to design, license, and build new reactors. They’re built in batches of six or more to take advantage of economies of scale.
It’s one of the ideas meant to give the edge to smaller reactors, but China is working to realize the same benefits for larger projects. A huge amount of government investment is certainly helping.
Larger reactors generally provide more electricity to the grid for a lower price, a key consideration in view of China’s steeply increasing electricity demand. While smaller reactors require less up-front investment than larger ones because of their size, they’ll actually be more expensive per unit of electricity produced.
That’s not to say China is exclusively focused on big reactors: the country is also expected to see its first operational small modular reactor, the Linglong-1, start sending power to the grid this year.
But looking ahead, it’ll be interesting to see if smaller reactors can help the West keep building new nuclear power. At the moment, with China’s quick progress, it’s looking as if bigger might just be better.
This article is from The Spark, MIT Technology Review’s weekly climate newsletter. To receive it in your inbox every Wednesday, sign up here.
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