China had 20 nuclear reactors under construction at the end of March, with a total capacity of 23.11 gigawatts (GW), the China Nuclear Energy Association said on Thursday. China had 36 reactors in full commercial operation at the end of last month, with a total capacity of 34.72 GW, said association chairman Zhang Huazhu, speaking at the group’s annual assembly in Beijing. The two combined equate to just under 58 GW, in line with China’s target for capacity on line by 2020, but China also aims to have a further 30 GW of nuclear reactors under construction by the end of 2020. Zhang warned the overall target would not be easy, especially after construction of new reactors slowed following a nationwide safety review prompted by Japan’s Fukushima disaster in 2011. Half of the 20 new units under construction at end-March are advanced “third-generation” reactors, Zhang said, and include the world’s first AP1000 designed by Toshiba Corp’s Westinghouse at Sanmen on China’s eastern coast. The AP1000 reactors are designed to have new safety features and a bigger generation capacity. The first AP1000 unit is set to go into operation in the second half of this year after long delays caused by safety concerns and design flaws. Zhang said the project was now in the testing stage, with “laid foundations” in place to ensure that 2017 construction schedule was met. But China’s reliance on largely untested third-generation technologies, including French firm Areva SA’s EPR as well as home-grown reactor brands like the Hualong One and the CAP1400, could also pose serious challenges, Zhang said. “The AP1000 and Hualong One currently under construction and the CAP1400 about to go into construction will be the main models of future development, but as the first reactors (of their kind), their maturity and efficiency need further testing during the construction process,” he said. China has sought to take advantage of the global lull in nuclear project construction since the Fukushima disaster to become a world leader in the sector. It has built three out of a planned six reactors in Pakistan and is a major investor in Britain’s Hinkley Point C. Zhang said as well as its contract in Britain, China had already signed agreements with Argentina, South Africa, Turkey, Romania and Saudi Arabia, and was also improving its uranium supply network through closer cooperation with Kazakhstan, Uzbekistan, Mongolia, Niger and Namibia. Qiushi, the official Communist Party journal, said earlier this year that China now had a historical opportunity to take advantage of a market stretching to more than 20 countries and involving a potential investment more than $1 trillion by 2030.