In February, Duke Energy announced it was shutting down the reactor at its Crystal River power station in Florida after workers discovered a crack in the containment dome. The crack was created during efforts to replace a critical component of the reactor system that transfers heat to water in order to generate steam for the plant's turbines.
In early May, the utility Dominion shuttered its single-reactor Kewaunee nuclear plant in Carleton, Wis., a casualty of cheaper sources of electricity and an inability to build additional reactors to take advantage of what the company called economies of scale.
"Nuclear economics is tenuous at best," Mr. Lochbaum says. "If you do everything right, you can make money at this. But if you stumble, there's a big price to pay, and not just from a Fukushima-type tragedy."
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.