The upper part of the inner containment dome weighing 210 tons has been installed in the design position in the reactor building of Tianwan NPP Unit 8, which is being constructed in China with the participation of Rosatom State Corporation Engineering Division.

“Tianwan NPP Unit 8 is being constructed strictly in accordance with the schedule. The Russian and the Chinese specialists are jointly implementing this project – the Russian Party being responsible for design and supply of documentation and equipment for the nuclear island, or designing supervision, installation and adjustment supervision during the construction of Units 7 and 8, and the Chinese Customer - for civil and erection, commissioning and other works during the Units construction”, – said Alexey Bannik, Vice President for Projects in China and Prospective Projects.

Installation of the inner containment dome was performed in two stages. Earlier, in mid-March, the lower part of the dome was installed on the cylindrical part of the reactor building. Further, the specialists will perform welding works to connect the metal structures of the lower and the upper tiers. After the completion of installation works of the dome, the builders will continue concreting of the containment.

The reactor building is the main building at the NPP, where the nuclear steam supply system and its emergency cooldown systems are located. Use of the double containment in the design ensures maximum exclusion of impact of accidental releases of radioactive products to the environment. This is a reinforced concrete structure protecting the reactor plant from external impacts and capable of sustaining an earthquake, tsunami or hurricane.

The outer containment serves as physical protection from external impacts for an inner containment. The inner containment is made of pre-stressed reinforced concrete and contains a cylindrical part and a hemispherical dome. The internal surface of the containment is lined with metal, which ensures leak-tightness of the inner containment in all operating modes of the NPS, including emergency ones. The inner containment is one of the key localizing safety systems.

For reference:
Tianwan NPS is the largest project of economic cooperation between Russia and China. Currently, two power units are being built according to the Russian design with reactor plant VVER-1200. The four units of the Russian VVER-1000 design, which have been built earlier, are successfully operating and supplying millions of kilowatts of energy to the country's power grid. On June 8, 2018, the Intergovernmental Protocol and the frame contract for construction of TNPP Units 7&8 with VVER-1200 reactors were signed in Beijing. From the Russian party, the contract was signed by the Rosatom State Corporation Engineering Division, and from the Chinese party - by CNNC companies. In accordance with these documents, the Russian side has designed the nuclear island and it will supply the key nuclear island equipment for both units. The following executive contracts were signed as well: the technical design contract for Units 7&8 and the general contract for Units 7&8. In accordance with the signed contracts, the Engineering Division is involved in designing and delivery of nuclear island documentation and equipment and provision of associated services (such as designer supervision, installation supervision, adjustment supervision). The works on construction of Units 7&8 started on May 19, 2021.