A year after the beleaguered San Onofre Nuclear Generating Station (SONGS) was shut down owing to issues identified in the steam generator tubes of the plant’s two units, the Nuclear Regulatory Commission (NRC) announced tentative milestones for its independent review. The federal agency now projects that a possible decision regarding restart of Unit 2 could come in late April.
The NRC stressed it would continue oversight of Southern California Edison’s (SCE’s) plant in north San Diego County, Calif. "The NRC will not allow the plant to restart until we are satisfied that the licensee can operate the plant without undue risk to public health and safety. The NRC will take the time needed to determine the appropriate actions to ensure adequate protection of the public, and will continue efforts to communicate the status of its actions and the determination regarding the restart of SONGS, Units 2 and 3."
New milestones tentatively schedule a public meeting with SCE in mid-April in Southern California on the NRC’s ongoing inspection and technical evaluation. A decision regarding restart for Unit 2 is scheduled for five to 30 days after an intent to issue a decision that will determine whether or not to restart Unit 2 has been published, likely in late April.
Unit 2 has been shut down since Jan. 9, 2012, after issues were identified in its steam generator tubes during a planned refueling and maintenance outage. The plant’s Unit 3 was later shut down on Jan. 31, 2012, after leaks were also detected in the steam generator tubes of that unit.
A prior determination found that the tube-to-tube wear in both units’ steam generators was likely caused by a "fluid elastic instability," a combination of high–steam velocity and low-moisture conditions in specific locations of the tube bundles and ineffective tube supports in the same locations. If it obtained the NRC’s approval to restart, SCE proposed to run Unit 2 at 70% power for five months to prevent the vibration-causing environment by decreasing steam velocity and increasing moisture content. It would then shut down the unit for inspection.
"As we have said from the beginning, there is no timeline on safety. SCE is confident in its submitted response and restart plan and is currently working on our response to technical questions from the NRC,” SCE said in a statement.
Sources: POWERnews, NRC, SCE