Southern California Edison’s proposal to restart one of the damaged reactors at the San Onofre Nuclear Power Generating Station—and run it at 70% power to see what might shake loose—received a cold reception from the U.S. Nuclear Regulatory Commission (NRC).

The NRC told Edison in a letter this week that testing for “structural integrity” required running at full power, not 70%, and under “the full range of normal operating conditions,” according to the Associated Press.  

That might not be possible.

Two reactors at San Onofre have been closed since January when a leak of radioactive steam was discovered. Subsequent testing found hundreds of eroded steam tubes, damaged by vibration. Edison blamed manufacturer Mitsubishi, which blamed computer problems and bad math for the misdesigned equipment.

Edison replaced a bunch of the most worn tubes, but rather than take a couple years to replace the entire reactor, it proposed keeping the foot off the accelerator and running the plant that way for five months. It claims that running at 70% power fits the requirements of its license. Some scientists were skeptical.

Nuclear engineer Arnie Gundersen, who has produced independent reports on the nuclear plant for Friends of the Earth, warned that, “Restarting San Onofre without repairing the underlying problems first turns Southern California into a massive science experiment.”

An assessment by Fairewinds Associates released in July said the San Onofre generators were “significantly worse than all others nationwide.” Its study indicated that the plant “plugged 3.7 times as many steam generator tubes as the combined total of the entire number of plugged replacement steam generator tubes at all the other nuclear power plants in the US.”  

The NRC stopped short of telling Edison that San Onofre must be able to run at full-power but requested information from the utility about whether it could meet safety standards at 100%. The agency is aiming for a March decision on restarting the reactor.

Edison owns 78% of San Onofre. The rest is owned by San Diego Gas & Electric and the city of Riverside. More than 8 million people live within 50 miles of the plant, located between Los Angeles and San Diego. San Onofre supplied electricity to 1.4 million homes in Southern California before the breakdown. 

The plant originally consisted of three reactors. Unit 1 was permanently closed in 1992 because of decaying generator tubes, 12 years before its scheduled shuttering.

–Ken Broder

To Learn More:

NRC Wants More Analysis at Ailing Calif Nuke Plant (by Michael R. Blood, Associated Press)

Regulators Ask Edison Questions about San Onofre Restart Plan (by Abby Sewell, Los Angeles Times)

Maker of Nuke Generators Dinged on Repair Tests (by Morgan Lee, U-T San Diego)

Edison Lays out Case to Restart San Onofre to Nuclear Agency (by Nichola Groom, Reuters)

San Onofre Reactor Restart a Reckless Gamble with Southern Californians’ Safety (by Adam Russell, Friends of the Earth)