UPDATE 1-Duke shuts SC Catawba 1 reactor for refuel

(Updates with company comment)

NEW YORK, Nov 9 (Reuters) - Duke Energy Corp (DUK.N) shut the 1,129-megawatt Unit 1 at the Catawba nuclear power station in South Carolina on Nov. 6 for planned refueling and maintenance, a spokeswoman for the plant said Monday.

She could not say when the unit would return to service due to competitive reasons. She did say during this outage workers would upgrades the unit's analog cards to digital cards.

Electricity traders guessed the unit would return in about a month.

The unit last shut for refueling from about May 5 to June 23, 2008. It is on an 18-month refueling cycle.

The 2,258-MW Catawba station is located in Lake Wylie in York County about 20 miles southwest of Charlotte, North Carolina. There are two 1,129-MW Units 1 and 2 at the station, which entered service in 1985 and 1986.

The NRC renewed the units' original 40-year operating license in 2003 for another 20 years until 2043.

Unit 2 dipped to 99 percent by early Monday from full power early Friday.

One MW powers about 700 homes in the Carolinas.