RPT-UPDATE 1-So Cal Ed's San Onofre nuclear Unit 3 off-line

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LOS ANGELES, April 16 (Reuters) - The Southern California Edison-operated 1,110-megawatt Unit 3 went offline on Wednesday at the San Onofre Nuclear Generating Station (SONGS), the utility said.

The unit had been expected to shut for a previously announced spring maintenance. It is expected to return to service around May 24.

"Taking these steps now also achieves fuel pacing, making it possible for the unit to meet peak customer demand this August and September before it requires refueling," So Cal Ed said.

The SONGS 1,100-megawatt Unit 2 was operating normally on Wednesday afternoon.

Unit 3 is normally on a two-year refueling schedule. It underwent refueling in the fall of 2006.

Unit 1 at SONGS is no longer a working reactor.

SONGS is located on the Pacific between San Diego and Los Angeles.

The unit is owned 78.21 percent by So Cal Ed, a subsidiary of Edison International (EIX.N), 20 percent by San Diego Gas & Electric, a subsidiary of Sempra Energy (SRE.N), and 1.79 percent by the city of Riverside, California. (Reporting by Bernie Woodall; Editing by Christian Wiessner)