China's first nuclear unit constructed after the 2011 Fukushima accident in Japan was put into operation on Wednesday, after 168 hours of test operation, according to China General Nuclear Power Corp, the country's largest nuclear operator.

With construction beginning in November 2012, Unit 4 of the Yangjiang nuclear power plant, China's biggest nuclear power plant located in Guangdong province, has had a good safety record, said CGN, which is also the world's fifth-biggest nuclear operator with 19 nuclear power units in operation and an installed capacity of 20.38 gigawatts at the end of 2016.

After the Fukushima disaster, nuclear power unit construction was suspended in China and all nuclear plants under planning or construction were reviewed.

However, nuclear power generation in recent years, especially in the first two months of the year, had continued to see sharp growth, said Joseph Jacobelli, a senior analyst with Asia utilities and infrastructure research at Bloomberg Intelligence.

China's nuclear energy developers will be commissioning many more reactors during the 13th Five-Year Plan (2016-20) as nuclear power is a key source of clean energy along with hydropower, he said.

"Installed nuclear capacity already more than doubled to 27.17 GW in the 12th Five-Year Plan (2011-15) and should double again by 2020 to 58 GW," said Jacobelli.

"Actual output from nuclear plants has also followed suit, with a 24.4 percent increase in 2016 alone."

The growth was coming from a low base with nuclear power accounting for just 3.6 percent of the total in 2016, he added.

Six units are planned for the Yangjiang plant, with Unit 1 entering commercial operation in March 2014, Units 2 and 3 in June 2015 and January 2016, respectively. And all six reactors will be put into operation by 2019, said the company.

The grid connection of Yangjiang's Unit 4 brings its total number of operational power reactors in operation to 20, with a combined installed capacity of more than 21.46 GW, said the company.

CGN's total annual nuclear on-grid power generation was roughly 115.58 billion kilowatt-hours in 2016, an increase of 30.8 percent year-on-year, which is equivalent to a reduction in coal consumption of 37 million metric tons and carbon dioxide emissions of 90 million tons and sulfur dioxide emissions of 880,000 tons, it said.