MELISSA BLOCK, HOST:
One power plant in particular is on the minds of many here in Southern California. It's the San Onofre nuclear plant, roughly 60 miles south of Los Angeles. The plant was shut down back in January because of a leak that released a small amount of radioactive steam. It's been off-line ever since. And this week, nuclear regulators called what led to the leak, a significant, serious safety issue.
With San Onofre out of commission, officials are scrambling to find alternative sources of energy to keep from plunging Southern California into a summer of rolling blackouts. For more, I'm joined by Abby Sewell. She's been covering the story for the Los Angeles Times. And, Abby, let's start with the leak. I gather that tubes carrying radioactive water were vibrating excessively that led to the leak. What happened? What led up to this?
ABBY SEWELL: That's correct. Southern California Edison, the operator of the plant, had, within the last couple of years, replaced the steam generators, which are these massive pieces of equipment that have thousands of tubes carrying this radioactive water.
The steam generators were replaced in an effort to extend the life of the plant. But apparently, the tubes had been knocking against each other, as you said, and that was causing them to wear out much more quickly than expected. And this led to the leak that released a small amount of radiation.
BLOCK: How much of a health risk did that pose?
SEWELL: Officials are saying that it did not pose any health threat. But obviously, you don't want any radiation escaping. Once they discovered the leak, they did power the plant down so that no more would escape.
BLOCK: The nuclear regulators say they have not seen extensive tube failure to failure like this before. And your reporting says that the computer modeling by the manufacturer of this generator, Mitsubishi, didn't predict this.
SEWELL: Right. That was the upshot of a meeting on Monday where the U.S. Nuclear Regulatory Commission gave their preliminary findings on the cause of the steam wire. And they say that Mitsubishi Heavy Industries, the manufacturer of the steam generators, inaccurately modeled the velocity of the flow of water and steam. And because the velocity was higher than expected, it caused the tubes to vibrate and knock against each other.
BLOCK: Well, what do they say about how difficult it will be to fix this and to get this plant back online and running?
(LAUGHTER)
SEWELL: Well, that's the big question on everyone's minds right now. And at this point, Edison has said that they expect it to remain shut down at least through the summer. But it's not really clear at this point what the ultimate solution is going to be, whether they're going to be able to repair this, whether they might have to completely replace the steam generators or whether it's possible that the plant might not operate again.
BLOCK: And how many people does this affect?
SEWELL: When the plant's running at full power, it supplies power for about 1.4 million homes in Southern California.
BLOCK: So we raise the specter of rolling blackouts. How likely is that to happen? What are you hearing?
SEWELL: Energy officials are saying that under most circumstances we should be fine for the summer. In the event that there was an extremely unusual heat wave or some issue with another power plant, we could potentially face issues.
BLOCK: And in the meantime, are rates expected to go up to cover this mess that they're having to fix?
SEWELL: Well, that's undoubtedly going to be a fight. Ratepayers are going to be paying for the cost of the replacement steam generators. Certainly there are a lot of advocacy out there who are promising to challenge any attempts to make ratepayers foot the bill for the repairs, or the replacement, if necessary, of the steam generators now.
BLOCK: And there are environmental groups who are saying this plant should never come back online, right? The nuclear plant should be shut down.
SEWELL: Absolutely. There are number of groups out there that are saying this shows that San Onofre simply isn't safe. And they're saying we should just cut our losses and keep the plant down.
BLOCK: Now, this problem we were talking about with the tube vibration, is it unique to this plant here in Southern California? Or is it something that nuclear power plant operators all over the country are now going and checking and making sure they don't have the same problem.
SEWELL: Tube vibration is not unique to this plant. What is unique is that in this case, the tubes are knocking against other tubes as opposed to against the support structures. The other thing that we haven't seen before is that eight tubes at the plant failed pressure tests. Which means that they could potentially have ruptured in an accident, which the NRC has said is the first time any plant that we've seen more than one to fail pressure testing.
BLOCK: OK, Abby Sewell, thanks so much for coming in.
SEWELL: Thanks for having me
BLOCK: Abby Sewell is a reporter with the Los Angeles Times.
(SOUNDBITE OF MUSIC) Transcript provided by NPR, Copyright NPR.