China needs to speed up building planned nuclear reactors and make quick new approvals over the next few years to meet a target for 2020 and keep projects rolling beyond that, an ex-chairman of China National Nuclear Corporation [CNNNC.UL] said.

CNNC aims to start up around November this year - nearly four years behind an original timeline - the world's first Westinghouse AP1000 reactor, said former chairman Sun Qin in an interview this week.

China currently operates 35 nuclear reactors, which supply 3 percent of China's total power use, and it is building another 31 units as part of an ambitious program to put a total of 58 gigawatts into operation by 2020.

Several former top nuclear powers, including Germany and Switzerland, announced plans to withdraw from the sector in the wake of Japan's Fukushima nuclear disaster of 2011, the world's worst since Chernobyl. With Japan and the United States also scaling back on nuclear, China could emerge in the next decade as the most significant developer of nuclear-fired power if it accelerates its building schedules.

"The successful start-up of AP1000 will boost industry morale ... and will be replicated along the coast as we've planned a series of both AP1000, and (Areva's) EPR reactors," Sun said.

Delays at so-called third-generation reactors, both the Westinghouse AP1000 and French state firm Areva's European Pressurised Reactor (EPR), have dragged on China's pace of nuclear power development for the past few years, after Beijing had already suspended new project approvals for three years following the Fukushima meltdowns.

At the world's maiden AP1000 project in the eastern province of Zhejiang, developed by Westinghouse and its struggling Japanese parent Toshiba, delays for the fine-tuning of designs have inflated costs of the first two reactors by at least 10-20 percent, said Sun, who retired last December after working in the industry for over 30 years.

Sun didn't give the initial cost estimates, but state media reported in 2009 the first two reactors then cost 40 billion yuan ($5.8 billion).

Beijing will need to approve six to eight new reactors a year between 2018 and 2020, to accelerate post-2020 development, said Sun, adding that another slowdown would waste China's recently developed nuclear equipment manufacturing capacity.

The European Pressurized Reactor (EPR) developed by French Areva and being built in South China's Guangdong province has also seen delays, similar to EPR projects in Finland and France, said Sun.

China, however, is not relying on foreign technology alone to develop its nuclear power sector. CNNC and domestic rivals China General Nuclear Power Group (CGN) and State Power Investment Corp [CPWRI.UL] all aim to export their own technologies after proving them at domestic plants.

Sun said China's own third-generation reactor Hualing-1, jointly developed by CNNC and CGN, was progressing smoothly in the southeastern city of Fuqing, where first operations are expected in 2020. China is building an identical Hualong-1 unit in Pakistan and is waiting for Argentina to finalize another Hualong-1 deal.

State Power Investment is also developing an enhanced version of AP1000, called CAP1400 with a pilot project planned in eastern Shandong province.

Sun also said CNNC remains in talks with French nuclear fuel group New Areva - a unit being spun off from parent Areva - over a potential stake of at least 10 percent and a board membership.