Construction landmark at Russia-designed VVER-1200 unit
The final weld of the main pipeline for Unit 8 at the Tianwan nuclear power station in Jiangsu province, eastern China, has been completed, paving the way for further commissioning work.
The China Nuclear Energy Association (CNEA) said the last weld in the transition section of the main pipeline passed non-destructive testing on 10 August 2025, marking completion of all pipeline welding for the unit.
Tianwan-8 is a Russia-designed VVER-1200 pressurised water reactor unit. Construction began in February 2022.
The main circulation pipeline at a nuclear power plant carries coolant – usually water – through the reactor core to absorb heat generated by nuclear fission.
The reactor coolant system for each unit consists of four heat transfer loops connected in parallel to the reactor pressure vessel. Each loop connects the pressure vessel, steam generator and main pump via a main pipeline, forming a closed circuit.
The CNEA said each loop has seven welds, giving a total of 28 welds per unit.
There are two Russian VVER-1200 PWR units being built at Tianwan. Construction of twin unit Tianwan-7 started in May 2021.
The Tianwan station has another six PWR units in commercial operation, with Units 1 to 4 having been built by Russia using its VVER-1000 PWR technology.
Units 5 and 6 are China’s indigenous CNP-1000 PWR design.
