Southern California Edison has submitted paperwork to federal regulators Monday that would allow the Unit 2 reactor at the San Onofre Nuclear Generating Station (SONG) to run at 70 percent power, down from the now-required 100 percent.
The plant between Los Angeles and San Diego has been idle since January 2012, after a small radiation leak led to the discovery of unusual damage to tubes that carry radioactive water.
Edison says running at reduced power should end vibration that damages tubing.
The company wants to start the reactor in early June, to help meet summer power demand. It is the latest step by the utility to restarting one of the twin reactors in northern San Diego County.
The Nuclear Regulatory Commission must approve a restart.
Anti-nuclear activists want the plant shut down permanently.