A three-judge panel of the Nuclear Regulatory Commission’s (NRC’s) Atomic Safety Licensing Board (ASLB) on Tuesday ruled that Southern California Edison (SCE) cannot restart Unit 2 of its shuttered San Onofre Nuclear Generating Station (SONGS) until the NRC holds a formal license amendment proceeding with full public participation.

The ASLB’s decision, which granted a petition from environmental group Friends of the Earth, puts in limbo SCE’s plans to restart the reactor at 70% for a five-month test period. The utility had in March 2012 asked the NRC for permission to restart the reactor this summer—a request the agency had considered granting without a public hearing. The judge’s ruling on Tuesday prohibits the commission from taking that step, however.

The twin-reactor plant’s Unit 2 has remained shut down since Jan. 9, 2012, when it was taken out of service for a planned outage. SCE operators performed a rapid shutdown of Unit 3 on Jan. 31, 2012, after a leak was detected at one of that unit’s steam generator tubes. Later investigations revealed premature tube wear in Unit 3 and indications of wear in Unit 2.

“The ASLB has announced that the restart plan is an ‘experiment’ and calls the tube wear at San Onofre’s defective steam generators ‘unprecedented,’ as we have asserted all along,” said Damon Moglen, energy and climate director for Friends of the Earth. Moglen explained that the ASLB’s ruling requires a license amendment because the restart plan is “experimental” under Section 5090(ii) of NRC regulations, which would allow the unit to operate beyond the scope of the existing license and without complying with applicable technical specifications.

Senator Barbara Boxer in a statement said the ASLB’s order sets “a legal framework for a full public hearing before any final decision on the restart of the San Onofre nuclear power plant is made by the NRC.”

SCE said earlier this month that it might have to retire the plant if the restart plan is not approve d. The California Independent System Operator on May 6 said that the continuing shutdown of the San Onofre units heightens reliability concerns for areas of Southern California this summer.

Sources: POWERnews, NRC, SCE, Friends of the Earth

NOTE: This story was originally published on May 14