Unit 3 of the Changjiang nuclear power plant in China’s Hainan province has achieved first criticality: the Hualong One reactor, rated at 1,100 megawatts electric, has for the first time sustained a self-sustaining, controlled nuclear chain reaction. This is the milestone that separates a construction site from an operating power plant. From here, engineers will carry out a series of low-power physics tests, gradually raise the reactor’s output, and verify the performance of safety systems before connecting to the grid.
Changjiang Unit 3 is the first of two Hualong One reactors planned under the plant’s second expansion phase. Construction began in March 2021, with the first concrete pour for Unit 4 following in the second half of the same year. Together, the two reactors represent an investment of approximately 40 billion yuan, or around $5.9 billion, and are expected to be fully operational by early 2027. The road ahead is still long — physics tests, incremental power ascension, turbine commissioning, and then grid connection — but achieving criticality is the milestone that certifies the reactor core is performing as designed.
The HPR1000 — the technical designation for the Hualong One — is a Generation III pressurized water reactor jointly developed by CNNC and China General Nuclear. The design integrates both active and passive safety systems, a double-shell containment structure, and a design operational life of 60 years. Each unit is sized to generate roughly 10 billion kilowatt-hours of electricity per year — enough, by some estimates, to power one million people in a middle-income country. As of January 2026, the total number of Hualong One units either in operation or under construction worldwide had reached 41, making it the most widely deployed reactor model in the world by total unit count.
China’s track record with this design has been consistent. The world’s first Hualong One, Fuqing Unit 5, entered commercial operation in January 2021. By May 2025, it had logged more than 1,000 consecutive days of safe operation and delivered over 37 billion kilowatt-hours to the grid. Zhangzhou Unit 1 began commercial operation on January 1, 2025, while Unit 2 at the same site — the world’s largest Hualong One hub by installed capacity — started generating electricity in November 2025. In February 2026, Taipingling Unit 1 in the Greater Bay Area connected to the grid. Each new reactor adds operational data that strengthens the technical foundation of the entire program.
China aims to raise nuclear power’s share of its electricity generation from the current 5% to 10% by 2035. The Hualong One is the primary vehicle for this expansion, both domestically and abroad: Pakistan and Argentina are already customers, and more than twenty countries have signed cooperation agreements. With Changjiang Unit 3 advancing toward grid connection and Unit 4 under construction, the Hainan site stands as the latest demonstration that China’s nuclear program shows no signs of slowing down. The coming weeks of low-power testing will confirm whether the reactor’s actual performance matches its design specifications — and given this design’s recent track record, there is little reason to expect otherwise.
