UPDATE 1-Wolf Creek heats up Kansas reactor

(Updates with company report to NRC)

NEW YORK, May 12 (Reuters) - Wolf Creek Nuclear Operating Corp cooled the 1,166-megawatt Wolf Creek reactor in Kansas from hot standby mode to hot shutdown mode on May 11, the company told the U.S. Nuclear Regulatory Commission in a report.

Operators said they cooled the plant due to excessive leakage from the residual heat removal system to the hot leg injection relief valve.

On May 9, the reactor started to exit a refueling outage and heated up to hot shutdown mode but had to remain there because both trains of the residual heat removal system were inoperable. At least one train is needed to start the plant.

The unit shut for refueling on March 17.

Wolf Creek last shut for refueling from Oct. 7-Nov. 13, 2006. It is on an 18-month refueling outage.

The Wolf Creek station, which entered service in 1985, is located in Burlington in Coffey County about 70 miles south of Topeka, the state capital.

One MW powers 800 homes in Kansas.

In October 2006, Wolf Creek filed with the NRC for a 20-year extension of the unit's original 40-year operating license.