The lower tier of liner of the inner containment dome of the reactor building has been lifted at Unit 7 of Tianwan NPS being constructed in China with participation of Rosatom’s Engineering Division.
The large-sized metal structure with diameter of 44 m and weight of 391 t has been installed in its design position on the cylindrical part of the reactor building containment. For this purpose, a crane with the maximum lifting capacity of 2,000 tons has been delivered to the construction site.
“Today marks two years from the moment when the heads of the two countries, Vladimir Putin and Xi Jinping, took part via the video conference in the ceremony of the first concrete pouring into the foundation slab of Unit 7 reactor compartment, which manifests the start of construction of the 4th stage of Tianwan NPS. This project is a bright example of successful cooperation between Russia and China. Over several decades, specialists from our countries have been constructing together the most advanced power units of the NPS, improving and optimizing production processes, moving confidently towards the technological sovereignty”, noted Alexey Bannik, Vice President for Projects in China and Prospective Projects of Atomstroyexport JSC.
At the next stage, it is anticipated to complete installation works on assembly of the top tier of the liner and installation of the required equipment and pipelines with the total weight of 214 tons on it. Upon completion of this stage, a phase of key installation works inside the reactor building will be opened for all parts of the design, including installation of the reactor pressure vessel, steam generators, emergency core cooling system tanks, pressurizer, reactor coolant pumps and other equipment, as well as welding of the main coolant pipeline.
The reactor building is the main building at the NPS, where the nuclear steam supply system and its emergency cooldown systems are located. Use of the double containment in the design ensures the 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. An 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 of 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. A double containment is a distinctive feature of the Russian design of power units with VVER-1200 reactors, ensuring the highest level of safety.
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 earlier four units of the Russian VVER-1000 design 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 TNPS Units 7&8 with VVER-1200 reactors were signed in Beijing. From the Russian side, the contract was signed by the Rosatom State Corporation Engineering Division, and from the Chinese side – by CNNC companies. In accordance with these documents, the Russian side has designed the NPS 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.