Linglong One has entered hot functional testing about 63 months after first concrete, roughly five months beyond the 58 month construction period set for the project. The 125 MWe reactor, developed by China National Nuclear Corporation as the ACP100, is being built at the Changjiang site on Hainan, and Chinese media reported on 1 October 2026 that the tests were under way.
What hot testing checks on Linglong One
Hot functional tests raise the temperature of the reactor coolant system to simulate operating conditions before any fuel is loaded. They verify that the coolant circuits and safety systems work as intended and that the nuclear island and conventional equipment meet design requirements. They follow cold functional tests, which were completed in October 2025 and verified the leak tightness of the primary circuit, cleaned the main circulation pipes and ran the reactor and auxiliary systems together for the first time.
The Linglong One schedule against its plan
First concrete was poured on 13 July 2021, equipment installation began in December 2022, the main internal structure of the reactor building was completed in March 2023, and the outer containment dome was hoisted into place in February 2025. Counting from first concrete, cold tests came after about 51 months and hot testing after about 63 months. The months are calculated from the reported dates.
Fuel loading is targeted within 2026, which means the 58 month plan, if measured to that milestone, has already been exceeded. The overrun is modest for a first of a kind reactor, but it is the measure that matters for the developers of competing designs, where licensing and construction schedules are also tight, as in the Clinch River BWRX-300 construction permit timeline.
Design and output
Linglong One is an integrated pressurised water reactor: the primary circuit components sit within a single vessel. Development began in 2010, the preliminary design was completed in 2014, and in 2016 it became the first SMR to pass a safety review by the International Atomic Energy Agency. The design can supply electricity, heating, steam or seawater desalination.
The reported output is about 1 billion kWh a year, enough for 526,000 households. Against a 125 MW rating running all year, which is 1.095 billion kWh, that implies a capacity factor of about 91 percent, a calculation from the reported figures.
Next step for Linglong One
The Changjiang site already has two operating CNP600 pressurised water reactors and two Hualong One units under construction, the first of which entered commercial operation in September. With hot testing under way, the remaining gate is fuel loading, which has no announced date beyond 2026.
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