As temperatures are rising in Southern California, so are tensions over the future of the San Onofre nuclear generating station, also known as SONGS. It’s been nearly four months since the nuclear power plant, located 45 miles north of San Diego, was shuttered after a small amount of radiation leaked into the atmosphere from a recently installed steam-generator tube in the plant’s reactor Unit 3.

It was subsequently discovered that a large number of these tubes, which function like a car radiator and carry hot, pressurized radioactive water, were damaged in Unit 2, the other operating unit at the seaside plant, which is operated by Southern California Edison, San Diego Gas & Electric (SDG&E), and jointly owned with the city of Riverside, Calif.

Jennifer Manfre, a spokeswoman for Southern California Edison, told The Daily Beast that the company has since plugged 510 damaged tubes in Unit 2 and 807 tubes in Unit 3. But investigators with Edison and the Nuclear Regulatory Commission (NRC) still haven’t pinpointed the reason for the tubes’ erosion—other than to say it was the result of a vibration.

Meanwhile, the plant, which supplies 20 percent of San Diego County’s power, remains closed indefinitely. And many Southern California residents are growing increasingly concerned about the potential for rolling blackouts as the region heats up.

Karen Garland, a married mother of two who lives in Oceanside, 17 miles south of the plant, recalls the the blackout that affected San Diego and Orange Counties last September. “It was scary and I don’t want to go through that again,” she says. “I’m worried that without San Onofre, we won’t have enough power and this whole area will go dark again.”

Edison representatives say that is a possibility. Earlier this month, Veronica Gutierrez, a spokeswoman for Edison, told a California newspaper group, “We could have rolling blackouts if we had a heatwave and conservation efforts aren’t enough. Let’s say we get one of the units at San Onofre back up this summer. If it’s a normal summer we may not have any issues. But if something happened somewhere else in the system, like a fire that damages transmission lines ... that could start rolling blackouts.”

But Dan Hirsch, president of the Committee to Bridge the Gap, a nonprofit nuclear-policy organization founded in 1970, says the likelihood of blackouts has been greatly exaggerated by the plant operators to create a panic. “Edison clearly wants the public to be scared of not having air conditioning this summer,” he says, “so they can drum up more support for the plant to re-open.”

Hirsch doesn’t anticipate any blackouts because, he says, contingency plans are already in place, including bringing some unused generators back online at a closed natural-gas power plant in nearby Huntington Beach. “The real issue for Southern Californians isn’t blackouts, but safety,” Hirsch says.

Edison does appear eager to get the plant back online--despite not knowing the cause of the vibrations that are causing the tubes to quickly degrade. A few weeks ago, Stephen Pickett, the company’s executive vice president of external relations, told the Los Angeles Times that Edison was preparing to propose a plan to the NRC--which has final say on when or if the plant re-opens—that would put San Onofre’s Unit 2 back online in early to mid-June, and Unit 3 back in service a few weeks later.

But many were critical of this optimistic timetable, and Edison is now backing away from those earlier predictions. “Nuclear safety has no timeline,” Edison’s Manfre said last week, “and the units will only be returned to service when Edison and the Nuclear Regulatory Commission are satisfied it is safe to do so.”

Just what did happen at San Onofre, and why? An analysis of the crisis (PDF) at San Onofre by Fairewinds Associates and Arnie Gundersen, an independent nuclear engineer who’s worked in the nuclear-power industry for more than 40 years, concluded that a series of major, unreviewed design changes at the plant may have contributed to the problem.

At a news conference last week in Charlotte, N.C., NRC Chairman Gregory Jaczko, who recently announced he was resigning, said the problem with the steam-generator tubes at San Onofre could point to a weakness in federal safety regulations. Jaczko, a former aide to Senate Majority Leader Harry Reid, is the only high-ranking member of the NRC to consistently contend that American nuclear plants are not doing enough to ensure the safety of Americans in this post-Fukushima world. He said at the news conference that some people at the NRC believe design problems at San Onofre would have been identified with a better federal review procedure.

“If [Edison] did it consistent with our regulations,” he said, “then we need to think about changing our regulations.”

Sen. Barbara Boxer (D-Calif.), chairwoman of the Senate Committee on Environment and Public Works (EPW), sent a letter to Edison and the NRC on May 15 asking for documents detailing the design changes made in the plant’s steam generators beginning in 2009, and inquiring as to whether these changes were properly reviewed by federal regulators.

A committee spokesperson who asked not to be named told The Daily Beast that last Wednesday, “EPW staff had a briefing with NRC and will continue to review information. Edison will brief committee staff later this week regarding technical documents related to design changes.”

According to Manfre, one of the options being considered by Edison is to run San Onofre “at a reduced output, between 50 to 80 percent, for three to five months, and then perform follow-up inspections.”

But several sources argue that this is a bad idea. A report issued by Friends of the Earth warned that running the nuclear plant at reduced power would not resolve problems with the degrading tubing. And according to Hirsch, this plan would put the public at risk.

“The operators know something bad is happening at this plant but they don’t know exactly what, and yet they want to reopen,” he says. “Their theory is that if they reduce power, it will reduce the vibration, but they won’t know until they go back online. They don’t know what will happen. There are eight and a half million people within 50 miles of this plant.”

Bernadette Del Chiaro, director of the Clean Energy Program at Environment California, a citizen-funded environmental-advocacy organization, agrees that reopening San Onofre any time soon, even at a reduced output, could be a “recipe for disaster. It’s hard to have anything but extreme concern, since they still don’t really know what’s going on. I’m very concerned with the overall stability of these steam generators.”

As far as potential rolling blackouts, Del Chiaro agrees with Hirsch and others who say these fears have been stirred up by the plant’s operators. “I’m confident that the lights will stay on in Southern California this summer,” she says. “If Edison puts in place some energy-efficiency measures and repowers the Huntington Beach plant, which they say will be ready in a few weeks, we should be OK. It’s not the perfect solution, and it’s not long term. The Huntington plant does cause air pollution. But it’s certainly safer than restarting a damaged nuclear plant.”

Del Chiaro adds that Southern California residents should be more concerned with safety and California’s energy future. “San Onofre has one of the worst safety records of any nuclear power plant in the country,” she notes. “The time to move to renewable energy sources is now.”

Bethann Chambers, wife of James Chambers, who worked at San Onofre for 27 years and has been an outspoken critic of the plant (PDF), says that she and her husband have recently been in contact with people who still work at San Onofre.

In an interview, she says these plant employees said that no one knows what Edison is going to do about the steam-generator tube problems. “Management isn’t even telling their own workers what the plan for restarting entails,” she says. “Everyone has questions, and the company is not providing answers.”

A statement issued earlier this month from Edison said in part, “The health and safety of the public and employees is the No. 1 priority for San Onofre.”