Changjiang Unit 4 outer steel dome installed, civil works near completion

The outer steel dome has been set on Changjiang Unit 4 in Hainan, a clear sign that the reactor’s second phase civil work is moving into its final stage and the build is shifting deeper into the sequence that leads toward testing and commissioning.

The dome was hoisted into place on 13 April on top of the containment building at the Changjiang nuclear power plant in Haiwei, Changjiang Li Autonomous County. It measured 52 metres across, stood 12 metres high and weighed about 415 tonnes. A 4,000-tonne crawler crane handled the lift, which took two hours and underscored how much heavy-lift work still sits at the heart of modern reactor construction even after the big structural pieces are largely in position.

For Changjiang Unit 4, the dome installation matters because it closes out one of the most visible containment-building steps and signals that the project has moved well beyond the early civil phase. The unit already passed another major containment milestone in December 2023, when CNNC reported the inner dome had been installed. In April 2025, the main circulation pipeline was completed, and the China Nuclear Energy Association said workers were ready to proceed to primary-circuit cold function testing. That sequence shows a project moving from concrete and steel into the more precise systems work that comes before fuel loading and startup preparations.

Changjiang Unit 4 is a domestic Hualong One, or HPR1000, pressurised water reactor, with a gross design capacity of 1,200 MW. Construction began in December 2021, and units 3 and 4 are scheduled to be fully operational in early 2027. The site already has two operating CNP-600 reactors, with Unit 1 entering commercial operation in December 2015 and Unit 2 following in August 2016, giving the plant a long-running role in Hainan’s power mix.

China Huaneng Group and CNNC have said the two new units are expected to generate about 18 billion kilowatt-hours a year once complete, enough to save 6.326 million tonnes of coal and cut carbon dioxide emissions by 11.68 million tonnes annually. CNNC has described Changjiang as one of China’s important nuclear power bases, and the phase-two project has been presented as the largest energy project in Hainan Free Trade Port construction since that effort began. With the outer dome now in place, the remaining work is becoming more intricate, and the schedule is moving from headline steelwork toward the long finish that turns a reactor shell into a operating unit.