Financial setbacks can take their toll as well, he says, whether a setback comes from lost business or from hardware failures or human error that sets the stage for costly repairs.
In announcing San Onofre's closure Friday, Ted Craver, Southern California Edison's chairman and chief executive officer, noted that the station has been generating electricity for more than 40 years, "but we have concluded that the continuing uncertainty about when or if SONGS might return to service was not good for our customers, our investors, or the need to plan for our region's long-term electricity needs."
The utility first broke ground on SONGS in 1964. The plant initially hosted one nuclear reactor. Two more were added and came on line in 1983 and '84. Since then, the plant's first reactor was decomissioned, leaving units 2 and 3 to help power southern California's voracious demand for energy.
Both units sported relatively new sets of steam generators – components that along with the reactor sit inside a concrete containment building. The steam generator houses bundles of tubes through which high-pressure, superheated steam from the nuclear reactor flows. Pumps force water past the searingly hot tubes to produce the steam that drives the plant's generators.
In early January 2012, the utility took Unit 2 down for a routine refueling outage. At the end of the month, operators running Unit 3 detected a small leak in a steam generator tube that allowed radioactive steam to mix with the steam sent outside the containment building to the generators.
The utility shut down Unit 3 and began an exhaustive inspection of the steam generators for both reactors. The inspections revealed unexpected wear and tear on a significant proportion of the tubes.