Exelon Corp's 867-megawatt Unit 1 at the Quad Cities nuclear power station in Illinois shut by early Wednesday from full power early Tuesday, the U.S. Nuclear Regulatory Commission said in a report.

The 1,734 MW Quad Cities station, which entered service in 1972, is located in Cordova in Rock Island County, about 155 miles west of Chicago. There are two 867 MW Units 1 and 2 at the station. The NRC renewed the plant's original 40-year operating licenses in 2004 for another 20 years until 2032.

Unit 2 continued to operate at full power.

One MW powers about 800 homes in Illinois.

Exelon's Exelon Generation Co LLC subsidiary operates the station for its owners, Exelon (75 percent) and Berkshire Hathaway Inc's (BRKa.N) MidAmerican Energy Co subsidiary (25 percent).

Exelon, of Chicago, owns and operates more than 38,000 MW of generating capacity, markets energy commodities, and transmits and distributes electricity to about 5.4 million customers in northern Illinois and southeast Pennsylvania and natural gas in the Philadelphia area. (Reporting by Scott DiSavino; Editing by John Picinich)