Unit 2 of the Sanmen nuclear power plant in China's Zhejiang province has been connected to the electricity grid and has begun supplying power. In late-June, Sanmen 1 became the world's first AP1000 to achieve grid connection and power generation.

Sanmen units 1 and 2 (Image: SNPTC)

Sanmen 2 was connected to the grid at 5:22pm today, China National Nuclear Corporation (CNNC) and State Nuclear Power Technology Corporation announced.

The unit will now undergo gradual power ascension testing until all testing is safely and successfully completed at 100% power. On completion of these tests, CNNC will then seek approval for commercial operation of the unit.

In September 2007, Westinghouse and its partner the Shaw Group received authorisation to construct four AP1000 units in China: two at Sanmen and two more at Haiyang in Shandong province. Construction of Sanmen 1 began in April 2009, while first concrete for Sanmen 2 was poured in December 2009. Construction of Haiyang 1 and 2 began in September 2009 and June 2010, respectively.

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. Sanmen 2 attained first criticality on 17 August.

Unit 1 of the Haiyang plant attained first criticality on 8 August and was grid connected on 17 August. Haiyang 2 is expected to start up in 2019.

Four AP1000 reactors were also being built in the USA - two each at Vogtle and Summer. However, construction of the two Summer units was suspended last August. Vogtle 3 and 4 are scheduled to start operating in November 2021 and November 2022, respectively.