VIENNA, Oct. 7 (Xinhua) -- Nuclear energy plays an irreplaceable role in tackling climate change and building a green, low-carbon and sustainable energy system, said a Chinese delegate at a UN conference here on Monday.

"Nuclear energy is a clean, low-carbon, high efficiency, base-load energy", said Zhang Kejian, director of China Atomic Energy Authority at the International Conference on Climate Change and the Role of Nuclear Power held by the International Atomic Energy Agency (IAEA) in cooperation with the Nuclear Energy Agency of the Organization for Economic Cooperation and Development.

"It plays a very important role in the UN 2030 sustainable development agenda. It also helps China to ensure energy supply, optimize its energy mix and tackle climate change," he added.

China has always been an active player in the global efforts to combat climate change and is constantly decreasing the use of fossil fuels and developing green energy, Zhang said.

In 2018, Chinese carbon emission per unit GDP decreased 45.8 percent from the 2005 level, equivalent to cutting CO2 emission by 5.26 billion tons, Zhang said. China has also promised that by 2030 carbon emission per unit GDP will decrease by 60-65 percent compared with 2005.

Up to now China has 47 nuclear power units in operation with a capacity of 48.73 gigawatts, he said. Eleven units are under construction with a capacity of 12.18 gigawatts.

Zhang said China, supported by a complete industrial chain, has developed mature technology and abundant talents in nuclear fuel production, equipment manufacturing, project construction, waste disposal and technology application.

"No country can fight alone or stand idle. Only by joining hands can we effectively combat climate change, protect ecosystem, prevent nuclear proliferation so as to realize the 2030 Sustainable Development Goals," he advocated.

Some 550 participants representing 79 countries and 18 international organizations are taking part in the week-long conference, the first on this topic organized by the IAEA.

The event serves as "a unique forum for exchanging science-based information and conducting objective discussions on the role of nuclear power in mitigating climate change," said the IAEA on its official website.