Inner dome installed at Shidaowan unit 1

The Hualong One reactor design features a double-layered containment building, the main function of which is to ensure the integrity and leak tightness of the reactor building, and it plays a key role in the containment of radioactive substances.

The inner dome of Shidaowan 1 - a hyperboloid structure composed of 70 wall panels, weighing 227.9 tonnes - was hoisted into position on top of the containment walls on 25 April.

China Huaneng said that the installation of the inner dome at Shidaowan 1 "marks the project's full transition from the civil construction phase to the equipment installation phase".

_{(Image: China Huaneng)}

The company plans to construct four Hualong One reactors, in two phases, at Shidaowan with a total installed capacity of 4.8 GWe.

China's State Council approved the construction of units 1 and 2 of the Shidaowan plant in July 2023. First concrete for unit 1 was poured in July 2024 and that for unit 2 in May 2025.

"Once all four units are completed and put into operation, the base will generate 35 billion kilowatt-hours of electricity annually, enough to meet the annual electricity needs of 17 million three-person households," China Huaneng said. "This is equivalent to reducing standard coal consumption by 11.5 million tonnes and carbon dioxide emissions by 27.6 million tonnes annually."

The first of two demonstration Guohe One (CAP1400) reactors at the Shidaowan site was connected to the grid in November 2024. The CAP1400 is an enlarged version of the CAP1000 pressurised water reactor developed from the Westinghouse AP1000, with consulting input from the USA-based company. The design is intended to be deployed in large numbers across the country, as well as for export.

The Shidaowan site is already home to the demonstration High Temperature Gas-Cooled Reactor-Pebble-bed Module (HTR-PM), which entered commercial operation in early December 2023. The HTR-PM features two small reactors that drive a single 210 MWe turbine. It is owned by a consortium led by China Huaneng (47.5%), with China National Nuclear Corporation (CNNC) subsidiary China Nuclear Engineering Corporation (32.5%) and Tsinghua University's Institute of Nuclear and New Energy Technology (20%), which is the research and development leader.