Arizona nuclear plant normal after small fire

PHOENIX, Dec 26 (Reuters) - Firefighters put out a small blaze at the Palo Verde nuclear power plant, the largest in the United States, although operations were not affected, officials said on Wednesday.

The fire broke out during scheduled refurbishment at one of the cooling towers at the plant, about 50 miles (80 km) west of Phoenix, operator Arizona Public Service said in a statement.

"During maintenance work on the Unit 3 cooling tower, grinding work began to cause a fiber glass shroud to smolder," APS said. "A small fire developed but was quickly extinguished by the Palo Verde plant fire department."

Palo Verde staff called for assistance from the Tonopah Fire Department, although it proved unnecessary.

The unit is currently out of service for refueling, maintenance and replacement of the steam generators, APS said.

Damage from the fire was limited to the fiber glass shroud and would not delay the unit's return to service, which is expected on, or shortly after, Jan. 1.

The cooling tower is located outside the fence and about a quarter-mile (400 meters) from the generating unit.

In early November, the nuclear plant was locked down for part of a day after guards found a pipe bomb in a worker's truck as he tried to enter the facility.

Palo Verde's three reactors have a combined capacity of about 3,900 megawatts, and can serve 1.5 million to 2 million homes in Arizona, California, New Mexico and Texas.

APS, the principal subsidiary of Pinnacle West Capital Corp (PNW.N), has the biggest share of Palo Verde, at 29.1 percent, followed by the Salt River Project with 17.5 percent.

Edison International (EIX.N) unit Southern California Edison Co and El Paso Electric Co (EE.N) each hold 15.8 percent of Palo Verde and PNM Resources Inc's (PNM.N) Public Service Co of New Mexico subsidiary has 10.2 percent. (Reporting by Tim Gaynor; Editing by Braden Reddall)