The uppermost sections of the steel containment vessels of two nuclear power reactors under construction in China – Sanmen unit 3 in Zhejiang province and Haiyang unit 3 in Shandong province – have been installed, China National Nuclear Corporation announced.
The steel containment shell is an important part of the nuclear island reactor building and the third safety barrier to prevent the leakage of radioactive materials, the company noted.
The steel containment vessel of the CAP1000 – the Chinese version of the Westinghouse AP1000 – is composed of five modules: the bottom head, first cylinder ring, second cylinder ring, third cylinder ring, and the top head.
The top head of the containment vessel of Sanmen 3 was successfully hoisted into place on 6 September, China National Nuclear Corporation (CNNC) said.
The total weight of the steel containment top head was over 788 tonnes, it noted. The module is a semi-elliptical spherical head and the steel plate has a thickness of 41.3 mm. It consists of four rings comprising a total of 64 steel plates.
“This is one of the important milestones on the critical path of the installation of nuclear island equipment for unit 3 of the Sanmen nuclear power plant,” CNNC said. “It means that the civil construction of the main structure inside the reactor building of unit 3 has been basically completed, marking that the nuclear island will fully enter the stage of installation of main equipment and bulk materials.”
The following day, the containment top head was hoisted into place at Haiyang unit 3 in a process taking 1 hour and 52 minutes.
The hoisting of the top head for Haiyang 3’s containment begins (Image: CNNC)
CNNC said: “The successful hoisting marked the successful completion of the assembly of the steel containment of the Haiyang nuclear power plant unit 3, and the nuclear island construction task was fully transferred from the civil construction stage to the equipment installation stage.”
The CAP1000 reactor design 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.
“This hoisting work further practices and deepens the concept of modular construction,” said CNNC. “Before the hoisting, the installation of the attached plates, U-shaped brackets, fire sprinkler systems, temporary ventilation systems and other professional bulk materials was completed, which reduced the amount of construction work on the island, improved work efficiency, and reduced safety risks, laying a solid foundation for subsequent high-quality construction on the island.”
The construction of two new reactors at each of the Sanmen, Haiyang and Lufeng sites in China was approved by China’s State Council in April 2021. The approvals were for Sanmen units 3 and 4, Haiyang 3 and 4 and units 5 and 6 of the Lufeng plant. The Sanmen and Haiyang plants are already home to two Westinghouse AP1000 units each, and two CAP1000 units were approved for Phase II (units 3 and 4) of each plant.
The first safety-related concrete was poured for the nuclear island of Sanmen 3 on 28 June 2022, marking the official start of its construction. The first concrete for that of unit 4 was poured on 22 March last year. The units are expected to be connected to the grid in 2027 and 2028, respectively.
Construction of Haiyang 3 began in July 2022, with that of unit 4 starting in April last year. The planned construction period for Haiyang 3 and 4 is 56 months, with the two units scheduled to be fully operational in 2027.
Source: World Nuclear News