San Onofre has been shut down for almost a year following a small radiation leak and the discovery of excessive wear on tubes that carry radioactive water.
Southern California Edison, which operates the plant, has asked the Nuclear Regulatory Commission for permission to restart one of the reactors, Unit 2, and run it at reduced power.
The agency has started to draw up a list of what would need to be done before that can be considered. A decision isn't expected until at least March.
