The containment vessel is a critical component designed to prevent the release of radioactive material and support passive safety functions. It consists of six modules: the bottom head, four cylindrical rings, and the top head. On 6 September, the top head for Haiyang 4, manufactured by CNNC Equipment Corporation, was successfully lifted and placed onto the containment structure. The installation process, involving a component 40 meters in diameter, 11 meters in height, and weighing 658 tonnes, was completed in 3 hours and 22 minutes.
According to State Power Investment Corporation (SPIC): "With this, the initial shape of the reactor building has been realised, and the nuclear island construction has shifted from civil engineering to installation." The next step will involve placing a steel and concrete outer dome over the inner containment dome.
The CAP1000 reactor design incorporates modular construction methods, allowing large sections to be prefabricated in factories and then transported to the site for installation. This approach enables multiple construction activities to occur simultaneously, reducing overall construction time while enhancing quality control and cost efficiency.
SPIC highlighted the role of CNNC Equipment Corporation in this process: "As the contractor of the steel containment vessel, CNNC Equipment Corporation fully implements the concept of 'factory prefabrication and modular construction', prefabricates relevant sub-modules in the production workshop, and completes the assembly, hoisting and installation of the modules at the nuclear power site, greatly improving the efficiency of project construction."
The construction of Haiyang units 3 and 4 was approved by China’s State Council in April 2022. Work on unit 3 began in July 2022 with the pouring of the first safety-related concrete for the nuclear island, while construction on unit 4 started in April 2023.
Haiyang already operates two AP1000 reactors, making units 3 and 4 an expansion of the site’s nuclear capacity. The planned construction timeline for both new reactors is 56 months, with commissioning expected in 2027.
The installation of the containment vessel’s top head at Haiyang 4 underscores progress toward completing the project within schedule, while demonstrating the benefits of modular construction and domestic manufacturing capabilities in advancing nuclear power development.
