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Don't count on Diablo 

License renewal is not a foregone conclusion

"Pay no attention to that man behind the curtain!" bellowed an increasingly panicked Wizard of Oz after feisty Toto and his intrepid companions had blown the cover on the pugnacious imposter. Behind a fearsome façade of smoke and mirrors, this “wizard” managed to rule a mythical paradise through fear and intimidation. In a modern remake released last week—minus the Technicolor trappings—Sen. Barbara Boxer and San Luis Obispo’s former state Sen. Dr. Sam Blakeslee (also a former Exxon geophysicist who headed the Republican caucus when he served in the Assembly) pulled back the curtain on the myth of seismic safety at the Diablo Canyon nuclear plant, a charade that PG&E and the Nuclear Regulatory Commission have been casting like a spell over the Oz-like serenity of the Central Coast.

With his cogent testimony before Sen. Boxer and 26 pages of supporting documentation, Dr. Blakeslee exposed the mathematical shell game that PG&E is playing with the results of their “Final Seismic Report.” That report, released in September, was in fulfillment of Blakeslee’s AB 1632 of 2006.

Blakeslee notes PG&E’s historic neglect for the presence of earthquake faults near Diablo, which led to cost overruns and delays in the original construction of the plant. More significantly, when the major threat of the Hosgri fault was finally acknowledged, more than 80 percent of the plant had been built. Rather than re-evaluate the true danger and possibly cancel the plant, PG&E, with the NRC’s acquiescence, began a policy of reverse engineering their earthquake ground motion prediction formulas to make them fit within the mathematical boundaries of what had already been built. Often this required the use of arcane experimental “models” with little or no real world evidence or experience. As a result, PG&E was granted an exception for the Hosgri fault from the license’s conservative assumptions for soil-structure interaction and damping. PG&E has used this loophole ever since to maintain that any ground motion lower than shaking from the Hosgri fault is not a threat.

Today, with their newest report—a 13 chapter, 1,700-page data dump—PG&E takes this numerical obfuscation to dizzying heights. The first 11 chapters look at the individual faults of concern at Diablo and arrive at the conclusion that the faults are longer, more connected, nearer the plant, and more powerful in magnitude than previously known. As Blakeslee notes:


  • The predicted ground motion generated by this list of earthquake scenarios are all greater than the current ground motion estimates for a M7.3 Hosgri Fault earthquake located 4.7 kilometers from the facility …
  • However, in a seeming contradiction, rather than finding that larger or closer faults produce greater shaking and therefore a greater threat, PG&E argues in the Report that ground motion will be lower than the levels previously estimated. In other words, these newly discovered and re-interpreted faults are capable of producing shaking that exceeds the shaking from the Hosgri, yet that shaking threat would be much reduced from prior estimates … .
  • The reason the earthquake threat purportedly went down when new faults were discovered is because the utility adopted significant changes to the methodology utilized for converting earthquakes (which occur at the fault) into ground motion (which occurs at the facility). This new methodology, which is less-conservative than the prior methodology, essentially “de-amplifies” the shaking estimated from any given earthquake relative to the prior methodology used during the licensing process.


Blakeslee’s analysis reveals that PG&E’s seismic number crunchers have been re-tooling their formulas over the years to make earthquake threats disappear—on paper only—even as the actual hazard from the ground below is shown to increase. When they claim that new ground motion threats are “less than the Hosgri,” they conveniently neglect to use the same formulas that computed the Hosgri shaking in the first place. And they most certainly are not comparing them to the seismic design standards legally written into Diablo’s actual NRC licensing permit, as former NRC resident inspector Dr. Michael Peck documented in his widely circulated critique.

Thus, it’s not a surprise to attend a public seismic workshop and hear PG&E’s expert cardsharps use the phrase “Monte Carlo Method” when computing probabilities of earthquake danger. In PG&E’s probabilistic casino—where the chance of an earthquake occurring counts for more than the actual damage it could do when it occurs—the deck is stacked, the cards are marked, and the house always wins. If the roof timbers of your house—built under a towering old tree—were shown to be not up to code standards were that tree to come crashing down, would you insist that the contractor reinforce the roof, or accept his assurances that the odds of the tree falling were too low to worry about? Are you feeling lucky?

Dr. Blakeslee’s analysis also reminds us that PG&E’s recent corporate behavior should cast an ominous shadow over their seismic shell game: PG&E is being criminally prosecuted by the U.S. Justice Department for safety violations in its gas pipelines, including corruption of a federal investigation. The 28-count felony indictment states that the utility “knowingly relied on erroneous and incomplete information” to avoid inspections that would have exposed risks that ultimately killed eight people in the 2010 San Bruno gas explosion.

In light of these revelations, can anyone believe that the same financial calculus used by PG&E executives to determine whether or when pipelines require inspection or repair can also be trusted to oversee the most dangerous non-military industrial enterprise on the planet?

These stunning seismic revelations mark the fifth anniversary of PG&E’s consistently stymied attempt to relicense Diablo Canyon for an additional 20 years.

Among the other recent stumbling blocks: The State Water Resources Control Board (SWRCB) has mandated that once-through cooling be phased out at all coastal plants. A subcommittee, including the California Energy Commission and Public Utilities Commission, told the SWRCB commissioners that there is no rationale for exempting PG&E from compliance with state policy. The California Coastal Commission (CCC) weighed in on its own, commenting, “It would be fair to categorize Diablo Canyon as California’s largest marine predator.”

Further, the CCC has federal equivalency with the NRC and must sign off on PG&E’s license renewal application before the NRC process continues. To date, PG&E has not satisfied a very long list of CCC requirements—including many seismic questions—and the NRC has grown impatient with PG&E’s inability to provide a time frame for delivering the signed permit. The NRC has given PG&E an end-of-year deadline for answers, and the CCC staff reports that PG&E has yet to initiate discussion of this vital link in their license renewal chain.

All of which should put the community of San Luis Obispo on notice: License renewal of Diablo Canyon—even continued operation until the end of its current license—is not a foregone conclusion. PG&E’s promise of ongoing revenue for the county’s school districts, support for local nonprofits, and high-paying jobs with their multiplier effects are all now “uncertainties.” Abrupt plant shutdowns last year in Florida and Wisconsin have led to financial hardships in those communities. The Vermont Yankee plant will close on Dec. 31, and Vermonters have been holding workshops with planners and community members since the announcement a year ago in an attempt to get a head start on their future plans. Concerned San Luis Obispans would be wise to begin a similar process.

Read the full text of Dr. Sam Blakeslee’s analysis at

Rochelle Becker is executive director of the Alliance for Nuclear Responsibility. Send comments to the executive editor at

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