By Prudence Ho and Yvonne Lee 

HONG KONG--China's largest nuclear power plant operator has already sold 40% of its coming US$3 billion Hong Kong initial public offering to cornerstone investors, a sign that interest for what is set to be China's first listed pure nuclear play is heating up.

If the IPO kicks off next week ahead of a December listing, as scheduled, CGN Power Co. Ltd.'s IPO will be Hong Kong's biggest since January. It would also be the first pure nuclear plant operator to list anywhere in the world since British Energy Group, since delisted, went public in London in 1996, according to Dealogic.

Investors who have attended informal meetings with CGN's bankers have been enthusiastic about the firm, say people familiar with the IPO process. CGN, which will start taking orders from investors next week, has won commitments from at least 15 investors including GIC Pte Ltd., Singapore's sovereign-wealth fund, and hedge fund Och-Ziff Capital Management Group LLC.

The last time a Hong Kong IPO had so much demand before formal roadshows, or order-taking, took place was in January, when Hong Kong billionaire Li Ka-shing's electric company raised US$3.1 billion. Mr. Li's HK Electric Investments also managed to get around 40% of its IPO sold to cornerstone investors, or investors that pledge to hold their stake for a few months after a company goes public.

CGN is planning to list Dec. 10, other people familiar with the situation said earlier, adding the timetable is subject to market conditions.

While CGN's preliminary prospectus points to volatile uranium prices and protests from green groups as potential risks, fund managers say they like this company, a market leader in an industry Beijing is pushing to develop. CGN controls around 64% of China's nuclear power generation. Beijing-based China National Nuclear Power Co., the other big nuclear plant operator in China, is currently awaiting approval to list in Shanghai.

"There is a scarcity value for the company [CGN] as no other nuclear power firm has been listed currently," said Alex Wong, a director of asset management at Ample Capital Ltd., adding that his fund is likely to buy in the offering. "I won't be surprised to see CGN pricing at above 20 times forecast earnings."

Hong Kong electricity firm CLP, which is one of the cornerstone investors in CGN, trades at 16 times 2015 earnings, while China's Huaneng Renewables Corp., a big player in wind energy, is trading at 12.4 times. Japan's Tokyo Electric Power Co., which shut its reactors after the Fukushima nuclear power plant leak a few years ago, is trading at 4.5 times, while U.S. firm Duke Energy Corp. is trading at 16.8 times, according to S&P Capital IQ.

Chinese state firms that have bought into CGN include China Reinsurance (Group) Corp., China Life Insurance Co., China Development Bank Corp., China Cinda Asset Management Co., Beijing Jingneng Clean Energy and China Minmetals Corp., people with direct knowledge of the deal said, adding more names may join the list.

China is building more nuclear plants to reduce its reliance on coal, and has set a target to get nuclear power make up 2.7%, or 40,000 megawatts, of its total power capacity by 2015, up from less than 2% currently.

"With China encouraging clean energy, government policy should favor CGN, " said Ben Kwong, head of research at KGI Asia.

CGN operates 11 reactors mainly in China's southern Guangdong province, where the power grid is the company's top customer. In the first six months of the year, CGN saw net profit drop 3% to 2.57 billion yuan (US$420 million) due to higher finance costs, but its sales of electricity rose 19%, according to its prospectus. IPO proceeds will go toward buying a stake in a nuclear power station owned by its parent, CGNPC, as well as building more plants.

CLP confirmed the investment, while CGN and GIC declined to comment. Other cornerstone investors couldn't immediately be reached for comment.

P.R. Venkat contributed to this article.

Write to Prudence Ho at prudence.ho@wsj.com and Yvonne Lee at yvonne.lee@wsj.com

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