Community Corner

Edison Foresaw 'Disastrous' San Onofre Design Flaws in 2004

A utility executive warned about potential damage to steam tubes.

The design flaws that sidelined San Onofre early last year were predicted eight years earlier by plant officials, according to letters released this week.

Dwight Nunn, a Southern California Edison executive, was corresponding with Mitsubishi Heavy Industries in 2004-05, as the company ramped up design and production of new steam generators for the plant. Even before the designs were fully developed, Nunn warned Mitsubishi engineers about steam tubes wearing out prematurely, the exact problem that surfaced in 2012 after a radioactive steam leak.

"I am concerned that there is the potential that design flaws could be inadvertently introduced into the steam generator design that will lead to unacceptable consequences (e.g., tube wear and eventually tube plugging)," Nunn said in a 2004 letter. "This would be a disastrous outcome for both of us and a result each of our companies desire to avoid."

The outcome has, indeed, proved disastrous for Edison. Anti-nuclear activists, already on the offensive after Japan’s 2011 tsunami and subsequent nuclear disaster in Fukushima, have used the design flaws as a rallying cry to close San Onofre for good. And, in parallel with Nuclear Regulatory Commission investigations, the California Public Utility Commission has initiated its own probe to figure out whether Edison owes its ratepayers refunds for the tens of millions the utility is spending to keep the non-functioning plant open since January 2012.

Last fall, the plant laid off more than 700 workers.

This week, the 2004 and 2005 letters led Sen. Barbara Boxer, D-Calif., to call for a criminal investigation of Edison, alleging the utility lied to the Nuclear Regulatory Commission about significant design changes to avoid a lengthy and expensive license amendment process.

She echoed accusations that anti-nuclear activists have been making for more than a year.

Edison published the letters in question and said in a press release it handled the paperwork properly, citing specific points of federal laws regulating nuclear plant upgrades and renovations. Whatever becomes of a potential investigation by the U.S. Justice Department, it will involve interpretation of intensely technical points of law.

Perhaps more interesting, however, is the level of specificity with which a 2005 letter from Nunn predicts the design flaws.

One section refers to the exact phenomenon that caused the tubes to vibrate against support structures -- a problem cited as an important factor in the 2012 leak and tube damage.

Nunn worried the small spaces between the tubes and their support structures could "dry out," meaning steam would leave the spaces intermittently, removing the pressure barrier that keep the tubes from knocking against the support structures.

When working properly, the steam tubes contain superheated radioactive steam, and they act together like a radiator to boil pure water in a separate system, creating the secondary steam that turns turbines to make electricity. The steam in the secondary system engulfs the exterior of the tubes. This was all outlined in an exhaustive December meeting between the NRC and Edison engineers during which Edison aimed to justify its restart plan.

Officials at San Onofre Nuclear Generating Station -- now headed by Chief Nuclear Officer Pete Dietrich -- have prepared a plan to restart the less damaged Unit 2 at 70 percent power for a shortened operating period.

The plan is under review by the Nuclear Regulatory Commission. A decision on whether the plant can restart doesn't appear forthcoming anytime soon, despite a request by Edison to resume operations in June, in conjunction with the peak power usage period in California.

Meanwhile, the California Independent System Operator, which is responsible for moving electricity around the state to keep the lights on, is working to make up for San Onofre's missing 2,300 megawatts this summer.


Get more local news delivered straight to your inbox. Sign up for free Patch newsletters and alerts.

We’ve removed the ability to reply as we work to make improvements. Learn more here