The plant has been closed since January because of a tube leak in a reactor that caused the release of traces of radiation. That led to the discovery that hundreds of tubes carrying radioactive water were showing excessive wear.
A three-month federal probe blamed a botched computer analysis for generator design flaws that ultimately resulted in heavy wear to the alloy tubing.
Southern California Edison, which runs the plant, is expected to submit plans next month on how to restart the plant. However, the Nuclear Regulatory Commission's approval process is expected to be lengthy.
The plant serves southern Orange and San Diego counties. Edison cut 730 jobs at the plant last month.
The Associated Press contributed to this report.