Federal regulators have no firm timeline for restarting two California reactors that have been shuttered for months over safety concerns, the Nuclear Regulatory Commission chairman said today.

NRC Chairman Gregory Jaczko said in a statement that media reports of a timetable for restarting the San Onofre nuclear plant near San Clemente are inaccurate.

The commission hasn't received a report from plant operator Southern California Edison Co. explaining safety issues that affected the facility's steam generators in January (Greenwire, Feb. 1).

"Any discussion of a date for the restart of Unit 2 or Unit 3 is clearly premature" without that report, Jaczko said.

The plant was quickly shut down at the end of January after a leak in a tube carrying radioactive water was detected on Unit 3. Unit 2 had been shut down since Jan. 9 for a planned refueling and maintenance outage.

The NRC has since said that tubes on Unit 2 and Unit 3 that were replaced in January 2010 and January 2011, respectively, quickly deteriorated.

The utility later explained that wear on the tubes was caused by their vibrating and rubbing against adjacent tubes and support structures inside the steam generators. Tests are ongoing, the company said.

At least eight tubes failed pressure testing on Unit 3, indicating that "these tubes could have failed under some accident conditions," according to the NRC. Six other tubes required plugging and 186 more tubes were plugged as a precautionary measure, the NRC said.

A Southern California Edison spokesman said Friday that the plant could come back online as soon as June but added that problems at the plant are serious enough that the reactors may never again reach full capacity (Greenwire, May 4).

The NRC sent the utility a letter in March outlining steps the utility agreed to take related to unusual wear of the tubes attached to the steam generators.

The company hasn't yet written the NRC to confirm that all those steps have been taken, Jaczko said.

"Once we receive their response, we will take whatever time is necessary to conduct a thorough safety review," he added.