The outer steel dome of the containment building has been installed at unit 1 of China’s Xudabao NPP in Liaoning province, China National Nuclear Corporation (CNNC) announced. Unit 1 is a CAP1000 design, which is the domestic Chinese adaptation of the Westinghouse AP1000 pressurised water reactor. It relies on modular construction techniques where components are prefabricated in factories and assembled on-site. The inner dome (top head of the steel containment vessel) was hoisted into place in February.
The CAP1000 relies heavily on steel for structural containment and passive heat exchange. The inner containment is entirely a free-standing steel cylinder. It is not anchored to or backed by concrete above its foundation. This allows the steel to act as a massive heat conductor. The gap between the inner steel wall and outer steel-concrete (SC) composite wall is specifically designed to function like a natural draft cooling tower.
The steel dome is the core load-bearing structure of the nuclear island. It is located on top of the steel plate concrete outer containment structure and has to bear the full load of the passive cooling water storage tank which is installed ion top of it. It is conical in shape and consists of radial main beams, ring beams, steel cladding panels and bottom steel platforms ready to hold the tank. It has a diameter of about 41 metres, a height of 11 metres, and an overall lifting weight of nearly 1,000 tonnes.
Before lifting the dome Liaoning Nuclear Power studied past projects, ran computer simulations, organised all the different teams, and carefully balanced the weight too prevent the dome from bending, tilting, or smashing into anything as it went up. The workers achieved precise positioning of the nuclear island steel dome in a single lifting operation.
The Xudabao project was originally expected to comprise six CAP1000 reactors with units 1&2 as the first phase. However, plans changed, and two Russian-supplied VVER-1200 reactors were instead designated for Xudabao 3&4 with construction starting in July 2021 and May 2022 for commissioning in 2027 and 2028. In November 2023, the Ministry of Ecology & Environment announced that the National Nuclear Safety Administration had decided to issue a construction licence for Xudabao 1&2 with 1250 MWe CAP1000 reactors – the Chinese version of the Westinghouse AP1000. Two further CAP1000 reactors are proposed for units 5&6.
Xudabao NPP is invested and controlled by CNNC subsidiary China Nuclear Power. CNNC Liaoning Nuclear Power Co, a localised joint venture created specifically to fund, build, and operate the plant, is owned by China Nuclear Power (70%), Datang International Power Generation Company (20%) and State Development and Investment Corporation (10%).
Once fully completed, the Xudabao project will provide nearly 54 TWh of power, saving 19.2m tonnes of standard coal and reducing carbon dioxide emissions by 56.7m tonnes a year million tons annually, equivalent to the annual absorption of 360,000 hectares of forest.
