Executives with the Rosemead-based parent of the Southern California Edison utility said on Thursday that the troubled San Onofre nuclear power plant will remain shut down at least through August, leaving the region facing potential power shortages this summer.

Theodore Craver, chief executive of Edison International, acknowledged in an interview with the Los Angeles Times that the troubled nuclear plant in northern San Diego County would remain offline beyond the original estimate of June.

The plant has been shut down since Jan. 31 when cracks were discovered in newly installed steam generator tubes that carry radioactive water at one of the plant’s reactors. During subsequent inspections, many more cracks were discovered in tubes in both reactors. The federal Nuclear Regulatory Commission then ordered the plant to remain offline until the full extent of the problem is diagnosed and repaired.

Craver said Thursday that the utility intends to submit its plan to the NRC by the end of July to reopen at least one of the reactors for partial operation. The NRC will need at least a month to review the plan before giving its approval, pushing the earliest date for a partial restart back to September. Edison has not indicated when – or even if – the plant would resume full operation.

The San Onofre plant had been the largest single source of electricity for Southern California, generating roughly 9 percent of the region’s total power. To offset some of the interruption, SCE has reached an agreement with AES Corp. to restart two recently retired generators in Huntington Beach and accelerate some transmission upgrades to relieve bottlenecks. The AES plants came online last month.

However, the region is still susceptible this summer to power shortages during a heat wave. In that event, major manufacturers will be called on to shut down operations for the first time since 2006.