A divided county Board of Supervisors voted 3-2 Tuesday to ask the Nuclear Regulatory Commission to delay renewal of Diablo Canyon nuclear power plant’s operating licenses for three years while additional earthquake studies are conducted.
Supervisors Adam Hill, Jim Patterson and Bruce Gibson said it is common sense to delay license renewal until there is a fuller picture of the earthquake faults near the plant.“I believe we have time to do this right,” Gibson said.
Supervisors Frank Mecham and Katcho Achadjian disagreed, saying the earthquake studies could be done concurrently with license renewal. They noted that plant owner Pacific Gas and Electric Co. and the NRC continually update their seismic safety information.
“When we are talking about safety, I’m comfortable with this,” Mecham said.
NRC officials say they expect to make a decision on whether to delay the renewal application by the end of the month. PG&E opposes a delay, saying it needs to have a license renewal decision by 2014 for planning purposes.
PG&E officials and Hill, who asked that the letter be sent, downplayed any rift between them. PG&E representative John Shoals described it as a “friendly disagreement.”
In November, the utility applied to renew the plant’s two operating licenses for 20 more years. The current licenses expire in 2024 and 2025.
In a separate vote, supervisors agreed unanimously to send a letter to the California Public Utilities Commission urging that PG&E be allowed to bill its ratepayers to recover the cost of doing the additional earthquake studies.
The studies would cost more than $16 million and use three-dimensional mapping and other advanced techniques to study earthquakes near the plant over a three-year period.
PG&E officials said the 3-D mapping would be most useful in learning about the two main faults in the area, the Hosgri and Los Osos faults. It would provide less information about a recently discovered fault, the Shoreline Fault, said Loren Sharp, PG&E’s director of engineering.
The Shoreline Fault was discovered in November 2008 just offshore of Diablo Canyon. PG&E has been studying the fault and estimates that it could produce a 6.1-magnitude earthquake. Diablo Canyon is designed to withstand a 7.5-magnitude quake.
PG&E officials expect to release their study of the Shoreline Fault by the end of the year. It will determine how long the fault is, whether it connects with other faults, exactly how far offshore it is and how active it is.