The first concrete has been poured for the nuclear island of unit 4 at the Sanmen nuclear power plant, China National Nuclear Corporation (CNNC) has announced. It marks the official start of construction of the second of two CAP1000 pressurised water reactors planned as Phase II of the site in China's Zhejiang province.

First concrete is poured for Sanmen unit 4 (Image: CNNC)

Following approval by the National Nuclear Safety Administration, the first tank of concrete was poured for the nuclear island of Sanmen 4 on 22 March, marking the official start of construction of the unit.

The construction of two new reactors at each of the Sanmen, Haiyang and Lufeng nuclear power plant sites in China was approved by the country's State Council in April 2021. The approvals were for Sanmen units 3 and 4, Haiyang 3 and 4 and units 5 and 6 of the Lufeng plant. The Sanmen and Haiyang plants are already home to two Westinghouse AP1000 units each, and two CAP1000 units - the Chinese version of the AP1000 - were approved for Phase II (units 3 and 4) of each plant.

Workers prepare to begin work on unit 4 (Image: CNNC)

In May 2022, CNNC signed contracts for the civil construction of the nuclear islands and installation engineering for the planned second phases of the Sanmen and Haiyang nuclear power plants. China Nuclear Industry 22 Construction Company was contracted to carry out the civil construction of the Sanmen Phase II nuclear island, while China Nuclear Industry 24 Construction Company will conduct the civil construction of the Haiyang Phase II nuclear island. Meanwhile, China Nuclear Industry Fifth Construction Company (CNI5) has been contracted to undertake the nuclear island installation work at all four units.

The first safety-related concrete was poured for the nuclear island of Sanmen 3 on 28 June last year, marking the official start of its construction.

CNNC said it has united with more than ten state-owned enterprises - including Shanghai Electric Group, Harbin Electric Group, Erzhong Group (Deyang) Heavy Equipment Company, Bohai Shipbuilding Industry Company, Dongfang Electric Company and CNNC Sufan Technology Industry Company - and more than 40 private equipment suppliers, and "will further increase the strength of localised equipment design and manufacturing applications".

After units 3 and 4 are completed and put into operation, the total installed capacity of the Sanmen nuclear power plant will reach 5 GWe, and the annual power generation will reach 40 GWh, which is equivalent to an annual reduction of 30 million tonnes of carbon dioxide emissions, CNNC noted.

Both units of Phase I of the Sanmen plant began operating in 2018. Sanmen 1 was the world's first AP1000 to start up, achieving first criticality - a sustained chain reaction - on 22 June and grid connection on 2 July. It reached full power operation for the first time on 14 August and entered commercial operation on 21 September. Sanmen 2 attained first criticality on 17 August and was connected to the grid on 24 August. The reactor entered commercial operation on 5 November.