China switched on the world’s first commercial small modular reactor

After more than a decade of design work and construction, China has moved a compact nuclear reactor on the tropical island of Hainan into its final startup, positioning it to become the world’s first land-based commercial small modular reactor. The unit, known as Linglong One, is a fraction of the size of a conventional power station yet is being connected into the grid to sell electricity like any other plant. Its arrival marks a milestone that reactor developers in the United States, Britain, and Canada have chased for years without reaching.

What a small modular reactor actually is

The phrase “small modular reactor” describes a class of designs meant to break from the tradition of building each nuclear plant as a one-off megaproject. Instead of a single gigawatt-scale unit that takes a decade and tens of billions of dollars to erect, an SMR is smaller, standardized, and intended to be manufactured in factory-built modules that can be shipped and assembled on site. The pitch is faster construction, lower upfront cost, and the flexibility to place reactors closer to cities or industrial users. Linglong One, formally the ACP100, embodies that concept at a modest scale, and its progress has been tracked as a leading example of the first commercial onshore SMR to reach operation. Whether the economics live up to the marketing is a question the industry is watching this project to answer.

The numbers behind Linglong One

The reactor is rated at 125 megawatts of electrical output, a sliver of the roughly 1,000 megawatts a large conventional unit produces, but enough to matter at a local scale. Chinese officials say it can supply electricity to more than half a million households, with figures commonly cited around 526,000 homes, while displacing the emissions of the coal plants that dominate the region’s grid. Backers estimate it will cut carbon dioxide output by hundreds of thousands of tons each year. The reactor sits at the Changjiang nuclear site on Hainan, alongside larger conventional units, and was developed by the state-owned China National Nuclear Corporation. Its expected commercial debut was reported when Chinese state media confirmed the country would begin commercial operation of its first small modular reactor in 2026.

The road to first power

Bringing a reactor online is a staged process, and Linglong One has been working through the sequence over the past year. It cleared cold functional testing in October 2025, a check that confirms the plant’s pipes, pumps, and containment can handle operating pressures before any nuclear fuel is involved. In late December 2025 it passed a non-nuclear steam start-up test, running its turbine and secondary systems on conventionally generated steam to verify they perform as designed, a step documented when the project completed its non-nuclear steam start-up test on the first attempt. Those milestones set the stage for fuel loading, first criticality, and grid connection, the final steps that transform a finished building into a working power source. The original schedule, built around a 58-month construction timeline, pointed toward completion in the first half of 2026.

Why the West has fallen behind

The significance of Linglong One is as much geopolitical as technical. For years, SMRs have been held up in Western capitals as the future of clean, dispatchable power, yet the flagship efforts have stumbled. In the United States, the most advanced licensed design saw its lead deployment project canceled after costs climbed, and no comparable reactor is under construction. Britain and Canada have designs in development but nothing yet operating. China, by contrast, has pushed its version through construction and testing while rivals remained in licensing reviews, and the contrast has become a recurring theme in analyses of how the country’s nuclear program is outpacing competitors. That momentum is part of a wider expansion charted in coverage of the year nuclear power reclaimed relevance amid China’s expansion.

The caveats that come with a first

Being first is not the same as being proven, and Linglong One carries the usual asterisks of pioneering nuclear projects. The reactor took longer to reach this stage than its original 58-month timeline implied, a reminder that even China’s fast-moving program is not immune to the delays that plague nuclear construction everywhere. Independent international data on the exact sequence of criticality and grid connection has lagged the announcements, and analysts caution that operator timelines should be read as targets rather than guarantees until each step is formally confirmed. There are also open questions about cost. Early SMRs, built as first-of-a-kind units, tend to be expensive per megawatt, and the technology’s promise of cheap factory production only materializes if many identical reactors are eventually built. For now, Linglong One stands as a genuine milestone: a working commercial-scale SMR feeding a real grid, and a demonstration that the concept can leave the drawing board, even as the harder test of whether it can be replicated cheaply still lies ahead.

This article was produced with the assistance of AI and reviewed by the Morning Overview editorial team.

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