The final weld of the main pipeline for Unit 8 at the Tianwan nuclear power station has been successfully completed, marking a critical milestone for the facility. According to the China Nuclear Energy Association (CNEA), the last weld in the transition section of the main pipeline passed rigorous non-destructive testing (NDT) on August 10, 2025, confirming its structural integrity and clearing the path for subsequent commissioning work.
The main circulation pipeline is a vital component in a nuclear power plant's reactor coolant system. It is responsible for transporting coolant through the reactor core to absorb the immense heat generated by nuclear fission. Given its function in a high-pressure and high-temperature environment, the integrity of every weld is non-negotiable for ensuring safe and reliable operation. The successful NDT provides essential quality assurance that the weld is free of hidden defects and flaws.
The CNEA stated that the main pipeline system for each reactor unit consists of four heat transfer loops, each containing seven welds, for a total of 28 welds per unit. The completion and successful testing of all these welds represent a major accomplishment in the construction of the VVER-1200 pressurized water reactor unit.
Construction of Tianwan-8 began in February 2022. It is one of two Russian-designed VVER-1200 units under construction at the site, alongside Tianwan-7, which began construction in May 2021. The Tianwan station also has six other commercial units in operation, including four VVER-1000 units and two of China’s indigenous CNP-1000 PWR designs. The successful completion of this phase underscores the ongoing progress in expanding China’s nuclear energy infrastructure with an emphasis on rigorous quality control through advanced testing methods like NDT.
