Chinese CAP1000 units at Haiyang and Xudabao plants receive containment domes

Haiyang 4 and Xudabao 1 reactor units reached important construction milestones in February. At unit 4 of the Haiyang nuclear power plant, the outer steel dome of the double-shell containment building was installed, while the inner containment dome was lifted into place at unit 1 of the Xudabao plant.

Haiyang 4: installation of the outer steel dome

China’s State Power Investment Corporation (SPIC) said that the outer steel dome of the nuclear island at unit 4 in Shandong province was installed on 9 February.

The steel dome is a major component of the reactor building. It sits atop a steel-concrete composite structure and supports the water storage tank for passive containment cooling. The dome is conical in shape and consists of 32 main radial beams, three ring beams, 96 steel cladding panels and three steel platforms connected at the bottom. It has a diameter of approximately 41 metres, a height of around 11 metres and weighs nearly 1 000 tonnes.

According to SPIC, installation of the outer dome marks the completion of the main structure of the nuclear island and creates an important prerequisite for the project to move fully into the equipment installation and system commissioning phase.

CAP1000: China’s version of the AP1000 with modular construction

The CAP1000 design is China’s version of the Westinghouse AP1000 reactor. It uses modular construction, in which large structural modules can be manufactured in factory conditions and then installed at the construction site. This approach allows work to be carried out in parallel, shortens construction time and also brings economic benefits and advantages in quality management.

Construction of two CAP1000 units at the Haiyang nuclear power plant, where two AP1000 units are already in operation, was approved by China’s State Council in April 2022. The first concrete pour for the nuclear island at unit 3 took place in July 2022. Construction of unit 4 began in April last year. The planned construction period for units 3 and 4 is 56 months, and both units are expected to be fully operational in 2027.

Xudabao 1: construction phase completed

China National Nuclear Corporation (CNNC) announced that the inner dome—the upper part of the steel containment vessel—was lifted and installed at unit 1 of the Xudabao plant in Liaoning province on 10 February. According to CNNC, the unit’s construction is thereby moving from the construction phase to the equipment installation phase.

The CAP1000 steel containment vessel consists of six modules: the lower head, the cylindrical section (made up of four rings) and the upper head. The containment is a key barrier against the release of radioactive materials and a crucial element in implementing passive safety functions.

The upper part of the containment is assembled and welded from 64 curved steel plates, which form a semi-ellipsoidal dome once welded together. It has an internal diameter of nearly 40 metres, a total height of more than 11 metres and weighs over 820 tonnes. Selected systems and equipment, including fire sprinklers and temporary ventilation, were installed on the structure before it was lifted. CNNC says this approach reduces the amount of subsequent work in the nuclear section, improves construction efficiency and limits installation risks.

CNNC also said that the successful installation of the dome creates favourable conditions for further installation, commissioning and grid connection. According to the company, the project will support the development of China’s “northernmost nuclear base” and lay the foundation for the energy mix in Liaoning province.

Further development of the Xudabao plant

China’s Ministry of Ecology and Environment announced in November 2023 that the National Nuclear Safety Administration had decided to issue construction permits for Xudabao units 1 and 2, which are to be equipped with CAP1000 reactors with a unit capacity of 1 250 MWe. Later that month, a ceremony marking the start of construction on the first unit was held at the Xudabao site near Xingcheng (Huludao).

The Xudabao project was originally planned as a six-unit CAP1000 plant, with units 1 and 2 forming the first phase. Site preparation began in November 2010, and the National Development and Reform Commission approved the project in January 2011. Plans later changed, and construction of two Russian VVER-1200 units (Xudabao 3 and 4) began in July 2021 and May 2022, respectively. Units 5 and 6 of the plant are expected to be equipped with CAP1000 reactors once again.

The plant is owned by Liaoning Nuclear Power Company Ltd. CNNC holds a 70% stake, Datang International Power Generation Company holds 20% and the State Development and Investment Corporation holds 10%. The project’s general contractor is China Nuclear Power Engineering Company Ltd, a subsidiary of CNNC.