Diablo Canyon: Balanced on a Fault Line
Excerpted from the prize-winning 2012 book, Nuclear Roulette (Chelsea Green)
Diablo Canyon’s 27-year-old twin reactors overlook the Pacific Ocean from Point Buchon, a coastal bluff 12 miles southwest of San Luis Obispo. This is the plant that state senator Sam Blakeslee (whose district includes the reactor station) grimly predicts could become “our Fukushima.” The plant’s demise probably would not come from a tsunami (the plant is perched atop an 85-foot-tall cliff). A catastrophic earthquake is the greater threat.
In the event of a loss of outside electric power (as happened at Fukushima), Diablo Canyon’s emergency generators are supposed to kick in within 10 seconds, and (assuming the 50,000-gallon underground fuel tanks survived the quake) there would be enough diesel fuel on hand to cool the two reactor cores for seven days. However, if the emergency generators fail to start (or if the emergency persists for more than a week), the only remaining backup is a set of 125-volt batteries.
According to a San Luis Obispo Country press release, the batteries would provide “enough power to shut the reactors and provide emergency core cooling and other necessary safety measures for two hours.” Plant engineer Rudy Ortega explained what that would mean in practical terms: “We would have two hours to get one of the six diesel generators started."
In 2011, the Union of Concerned Scientists bestowed a “Near-Miss” award on Diablo Canyon after NRC inspectors reported that plant engineers had unwittingly disabled critical valves controlling the emergency cooling system. The problem, which could have lead to a partial meltdown, had gone undiscovered for 18 months.
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