Southern California Edison wants to restart one of the two reactors at its San Onofre nuclear plant, which has been shuttered for eight months over safety concerns, officials said Thursday.
The plant's Unit 2 reactor was offline for routine inspections and maintenance when a steam generator tube in Unit 3 sprung a leak on Jan. 31, releasing a small amount of radioactive steam. That led to the discovery that the tubes in the newly replaced steam generators were wearing out more quickly than expected, including some that showed an unusual type of wear caused by tubes rubbing against adjacent tubes.
The U.S. Nuclear Regulatory Commission dispatched a special inspection team to the plant and ordered Edison to keep the plant shut down until the company could show that it fully understood the cause of the issues and how to fix them.
In a plan submitted Thursday, Edison proposed to restart Unit 2 and run it at 70% of full power for five months before taking it offline for inspections to make sure the tube wear is not continuing. Unit 3, which had a more serious issue, would remain offline indefinitely. It is unclear when or if that reactor could start again.
Edison wrote that the unusual wear was a result of "fluid elastic instability" -- high-velocity steam flow and low moisture in certain areas that caused the tubes to vibrate excessively and rub against each other. Running the plant at reduced power would reduce the steam velocity to an acceptable level, the company said.
Out of the more than 300 tubes that showed tube-to-tube wear, only two were in Unit 2, and the rest were in Unit 3.
However, some critics have argued that it's unsafe to restart either of the reactors, since the design of the steam generators in both units is essentially the same. Environmental group Friends of the Earth surveyed people in Edison's service area and released results earlier this week showing that a majority of respondents thought the plant should stay offline.
The group released a statement calling Edison's plans to restart Unit 2 "a reckless gamble that flies in the face of the utility’s claim that it puts safety ahead of profits."
The NRC would need to sign off on Edison's plan before Unit 2 could restart, a process than NRC Chairwoman Allison Macfarlane said could take months.