The Nuclear Regulatory Commission directed its staff today to determine whether owners of the crippled San Onofre plant in California should have obtained regulatory approval before making design changes that might have contributed to the plant's closure.

NRC staff should determine whether Southern California Edison and San Diego Gas & Electric, the utilities that jointly own the majority of the plant, should have amended its license before replacing damaged steam generators at the plant in San Diego County two years ago, according to the order.

Separately, the commission also ordered its three-member Atomic Safety and Licensing Board Panel to determine whether environmental groups -- Friends of the Earth and the Natural Resources Defense Council -- should be allowed to ask for a hearing in the case.

The twin reactors have been shut down since Jan. 31, when radiation escaped from a steam generator tube (Greenwire, Oct. 9).

State regulators have since launched an investigation of the outage to determine whether and how the utilities should compensate ratepayers for replacing the plant's 2,200 megawatts (Greenwire, Oct. 26).

The NRC issued the order today in response to a request from environmental groups for the agency to hold off on restarting the plant until the license amendment was addressed.

The NRC denied the groups' request, but Damon Moglen, FOE's climate and energy director, said the agency's ruling today was still a good step.

"We are encouraged by the tone and content of this decision, and will pursue the issue as suggested by the commission while exploring our other options aside from those through the agency," Moglen said in a statement.