Rosatom’s Engineering Division (Atomstroyexport) has installed the upper part of the dome of the inner containment (VZO - Vnutrennei Zatsitnoi Obolochki) at unit 8 of the Tianwan NPP under construction in China’s Jiangsu province.
Installation work on the 210-tonne VZO dome was carried out in two stages. In March, the lower part of the dome was installed on the cylindrical part of the shell of the reactor building. Specialists will now have to carry out welding work to combine the metal structures of the lower and upper tiers after which concreting of the inner containment will continue.
“Russian and Chinese experts are implementing this project jointly,” said Alexey Bunik, Atomstroyexport Vice President for projects in China. “The Russian side is designing and supplying documentation and equipment for the nuclear island and provides copyright supervision services, installation supervision and installation supervision during the construction of power units 7&8. The Chinese customer is responsible for the construction, installation, commissioning and other work on the construction of the units.”
The agreement for construction of Tianwan 7&8 was signed by Russia and China in 1918 and commissioning is scheduled for 2026-2027. Construction of units 7&8, equipped with VVER-1200 reactors began in May 2021. Units 1-4, with VVER-1000 reactors commissioned between 2007 to 2018 are already in operation. Units 5&6 with Chinese ACPR-1000s were commissioned in 2020 and 2021.
Double containment is a feature of the VVER-1200 units. The VZO plays a pivotal role in preventing any radioactive material from leaking into the surrounding environment. The outer containment (NZO - Naruzhnoi Zatsitnoi Obolochki) is a reinforced concrete structure that protects the reactor unit from external influences and is able to withstand an earthquake, tsunami or hurricane.
The inner shell is constructed from prestressed reinforced concrete, and consists of a cylindrical part and a hemispherical dome. The inner surface of the shell is lined with metal to ensure the tightness of the internal area in all operating modes including emergencies.
Tianwan NPP is owned and operated by the Jiangsu Nuclear Power Corporation, whose shareholders are China National Nuclear Corporation (CNNC - 50% stake), China Power Investment Corporation (30%) and Jiangsu Guoxin Group (20%).
Image: The upper section of the inner containment dome being lowered into place at Tianwan 8 in China (courtesy of Atomstroyexport)
