San Onofre, The Nuclear Plant That Ruined Its Own Replacement Parts

The domed structures you may be able to see from the highway are the reactor containment buildings of the San Onofre Nuclear Generating Station, which sits on the beach between San Diego and Los Angeles. Unit One began producing commercial electricity in nineteen sixty-eight, making it one of the first civilian nuclear reactors to go into operation on the West Coast. Units Two and Three came online in nineteen eighty-three and nineteen eighty-four. For decades, San Onofre produced roughly twenty percent of Southern California's electricity.

In the late two-thousands, Southern California Edison made an expensive decision: it would replace the steam generators in Units Two and Three with new equipment, extending the plant's operating life through the twenty-twenties. The new generators were custom-designed for the plant and installed at substantial cost. They were supposed to be the investment that kept San Onofre running for another decade.

In January two thousand twelve, a tube inside Unit Three's new steam generator began leaking radioactive water. Eighty-two gallons per day. Regulators shut down the unit and began inspection. What they found was unexpected: the replacement generators, both of them, showed abnormal wear patterns consistent with a design error that Edison's engineers had apparently not caught before installation. The tubes inside the generator were vibrating against each other in ways the design had not accounted for, and the vibration was eroding the metal. The generators that had been installed to save the plant were destroying themselves from the inside.

Both units were shut down for investigation. Neither ever restarted. Edison announced permanent closure in June two thousand thirteen, twenty years before the plant's operating license would have expired.

Decommissioning began in twenty twenty. The estimated cost is four point four billion dollars, with completion expected sometime in the twenty-forties. The high-level radioactive waste, sealed in dry casks, will remain on the beach at San Onofre indefinitely. There is no permanent national repository for high-level nuclear waste in the United States. The waste at San Onofre, like the waste at dozens of other decommissioned reactors across the country, will be stored at the site where it was created until a solution that does not yet exist is found.

The beach next to the plant is a state beach. It is open to the public.