- The Pacific Gas and Electric (PG&E) Diablo Canyon nuclear facility can withstand a one-in-10,000 years earthquake of 0.8 times the force of gravity, the utility reported to the Nuclear Regulatory Commission (NRC). The plant is also safe from tsunamis and from earthquakes spreading through multiple surrounding faults, it added.
- The report was required by the NRC from all U.S. nuclear facilities in the aftermath of the 2011 Japanese earthquake-tsunami that led to the Fukushima Dai-ichi nuclear plant meltdown. U.S. Geological Survey (USGS) seismologists just raised the odds from 4.7% to 7% that California would experience a magnitude 8 or higher earthquake in the next 30 years.
- In 2013, an NRC commissioner said Diablo Canyon should be shut down until it was proved safe. This study, performed under the utility’s supervision, concludes it can.
Diablo Canyon was designed to withstand a 0.75 times-the-force-of gravity-earthquake but with a safety margin against larger events, according to PG&E. Seismologists increased the odds of a magnitude 8 event after studying how quakes become more destructive as they move across faults.
PG&E relocated its nuclear facility to Diablo Canyon when another site proved to have a fault line running through it. Federal authorities approved construction in 1968 because PG&E said there were no active faults within 18.6 miles. Oil company geologists then reported the Hosgri fault 3 miles offshore from the plant, which the USGS estimates could produce a magnitude 7.5 quake. The Shoreline Fault, which is within 2,000 feet of the reactors, was found in 2008. Several other faults have subsequently been found nearby.
Opponents, who have challenged the facility’s seismic safety since 1971, have become more aggressive since the Fukushima events and now want it shuttered like the San Onofre Nuclear Generating Station.