The U.S. Nuclear Regulatory Commission chief made her first visit Monday to the troubled San Onofre nuclear plant since taking office in July, offering assurance that the facility will remain closed until its safety is certain.

NRC Chairwoman Allison Macfarlane traveled to California to visit the closed plant and meet with local elected officials, environmentalists and plant workers' union representatives to hear their concerns.

The plant has been shut down for nearly a year because of unexpected deterioration of tubes in its four giant steam generators, replaced less than two years earlier. Officials learned of the unusual wear after a tube sprang a leak last January, releasing a small amount of radioactive steam.

The NRC is reviewing a restart proposal that plant operator Southern California Edison submitted for one of the plant's two reactor units, which entails running that unit at 70% capacity for five months in hopes that operating at reduced power would alleviate the conditions that caused the tubes to vibrate excessively and rub against support structure and adjacent tubes.

Macfarlane reiterated assurances that the commission will not allow the plant to restart unless its staff is certain that Edison's plan is safe.

"We aren't doing this as an experiment. We would want to make sure that the plant can operate safely, period," she said in a meeting with reporters after touring the plant.

Although the ultimate decision on the plant's fate will be made by commission staff based on technical analysis of the restart proposal, Macfarlane said she wanted to hear from the public.

"We need to hear everybody's concerns and make sure that we take account of them," she said. "We have to be open minded, and maybe we'll learn something new."

The commission may make a decision on the restart proposal for the plant's Unit 2 as early as March. The timeline depends in part on whether Edison is able to answer a long list of questions on the plan to the satisfaction of NRC staff.

Continue reading "San Onofre to stay dark."