JINAN, Jan. 10 (Xinhua) -- The first phase of a nuclear power plant in eastern China's Shandong Province has started full commercial operation and is expected to help improve local energy mix and environment.

The No. 2 reactor unit of the Haiyang Nuclear Station in the city of Haiyang finished seven days of continuous operation at 4:30 p.m. Wednesday, marking the start of commercial operation, the Shandong Nuclear Power Co., Ltd. announced Thursday.

With this new addition, there are a total of 46 nuclear reactor units in operation in the Chinese mainland, with a total installed power generating capacity of 45 GW.

The Haiyang Nuclear Station, with a total investment of 80 billion yuan (11.7 billion U.S. dollars), is designed to have six reactor units. Its first stage includes two AP1000 reactor units with the power capacity of 1.25 GW each, with the NO. 1 unit being put into commercial operation in late October last year.

The first phase can generate 20 billion kWh of electricity a year, meeting the electricity demand of one-third of the households in Shandong, a populous Chinese province, according to the Shandong Nuclear Power Co., Ltd.

Another two reactor units in the second phase are subject to approval by the National Development and Reform Commission, the country's top planning agency.