The steel dome module is an important component of the shielded building, situated on top of a steel-concrete composite structure, and supporting the passive containment cooling water storage tank. The steel dome is conical in shape, consisting of 32 radial main beams, three ring beams, 96 steel cladding panels, and three steel platforms connected at the bottom. It has a diameter of about 41 metres, a height of about 11 metres, and a total lifting weight of nearly 1,000 tonnes.
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(Image: CNNC)
The installation of the outer dome marks “the near completion of the construction of the large steel structure modules of the unit and lays a solid foundation for achieving the milestone of the completion of the nuclear island plant structure”, CNNC said.
The CAP1000 reactor design – the Chinese version of the Westinghouse AP1000 – uses modular construction techniques, enabling large structural modules to be built at factories and then installed at the site. This means that more construction activities can take place at the same time, reducing the time taken to build a plant as well as offering economic and quality control benefits.
The inner dome – the top of the containment vessel – was hoisted into place at Xudabao unit 1 on 10 February this year.
The Xudabao plant
The Ministry of Ecology and Environment announced in November 2023 that the National Nuclear Safety Administration had decided to issue a construction licence for Xudabao units 1 and 2, which will both feature 1,250 MWe CAP1000 reactors. A ceremony was held later that month at the Xudabao site near Xingcheng City, Huludao, to mark the start of construction of unit 1.
The Xudabao project (also known as Xudapu) was originally expected to comprise six CAP1000 reactors, with units 1 and 2 in the first phase. Site preparation began in November 2010. The National Development and Reform Commission gave its approval for the project in January 2011. CNNC noted that the total investment in units 1 and 2 exceeds CNY48 billion (USD6.6 billion).
However, with a change in plans, construction of two Russian-supplied VVER-1200 reactors as Xudabao units 3 and 4 began in July 2021 and May 2022, respectively. Commissioning of those units is scheduled for 2027 and 2028, respectively.
The Xudabao plant is owned by Liaoning Nuclear Power Company Ltd, in which CNNC holds a 70% stake with Datang International Power Generation Company holding 20% and State Development and Investment Corporation owning 10%. The general contractor is China Nuclear Power Engineering Company Ltd, a subsidiary of CNNC.
Two further CAP1000 reactors are proposed for units 5 and 6 at the Xudabao plant.
Upon completion, the six-unit project – with a total installed capacity exceeding 7.6 MWe – will provide nearly 54 billion kilowatt-hours of clean electricity annually, saving 19.2 million tonnes of standard coal and reducing carbon dioxide emissions by 56.7 million tonnes annually, CNNC said.
