NEW YORK - Entergy Corp shut the 1,157-megawatt nuclear Unit 3 at the Waterford power plant in Louisiana on Oct. 19 for planned refueling and maintenance, a spokesman said Tuesday.

He could not say when the unit would return due in part to competitive reasons. Electricity traders guessed the unit would return in about a month.

The spokesman said the company would replace a reactor coolant pump in addition to the usual refueling activities.

The unit last shut from April 28 to June 2, 2008. It is on an 18-month refueling cycle.

The 1,973 MW Waterford plant is located in St Charles Parish about 30 miles west of New Orleans. There are three units at the station including the 411 MW gas/oil Unit 1, which entered service in 1975, the 405 MW gas/oil Unit 2 (1975) and the 1,157 MW nuclear reactor (1985).

One MW powers about 500 homes in Louisiana.

Entergy, of New Orleans, owns and operates about 30,000 MW of generating capacity, markets energy commodities, and transmits and distributes power to 2.7 million customers in Arkansas, Louisiana, Mississippi and Texas. (Reporting by Scott DiSavino; Editing by Walter Bagley)