Investigation outlines lax oversight at San Onofre

U.S. nuclear safety regulators missed red flags in 2009 when they agreed to pre-approve steam generators at the San Onofre nuclear plant without a thorough review, leading to the installation of faulty equipment, according to federal inquiry released Tuesday.

San Onofre was permanently shut down last year by plant operator Southern California Edison because of the rapid degradation of newly replaced steam generators.