Seismic Uncertainty

Region IV of the Nuclear Regulatory Commission held the 2014 annual assessment meeting for Diablo Canyon Nuclear Power Plant on June 24, 2015.

Statement by Sherry Lewis, Board Member of San Luis Obispo Mothers for Peace.


I am interested as a lay person in the science of seismology and so attended numerous workshops of the Senior Seismic Hazard Analysis Committee (SSHAC) process as well as an Independent Peer Review Panel (IPRP) meeting.

The industry (PG&E) has funded these studies through us, the ratepayers.  Nevertheless, I feel they skew the sense of the results.

To PG&E reducing the range of uncertainty is the same thing as creating accuracy.

According to Stu Nishenko, the Project Manager from PG&E, there have been dramatic improvements over the Long Term Seismic Program of the 1980’s: “unprecedented accuracy developed by industry”.  A new generation of technology has created a “revolution in resolution of detail,” comparable to the revolution in medicine where X-rays reveal 2-D pictures of the body and CT scans provide 3-D imagery.

I’ve read Dr. Sam Blakeslee’s statement last December to the Senate Committee on Environment and Public Works. He disputes the methodology in the SSHAC studies, which seem to show that as the local seismology is found to be more hazardous than when the nuclear plant was first licensed, Ground Motion Prediction Equations have become increasingly robust to seemingly counteract the potential hazard of the newly discovered motion.  He claims that a single standard is not being used, and so the results are skewed.  I brought this up to the Diablo Canyon Independent Safety Committee (DCISC) in hopes that they would look at both sides of this debate.  I want to hear their take on it.

PGE has ignored questions raised by the IPRP.

At first I thought that some of the scientists were skewing the research, but I’m not so convinced of that now.  Instead, I see the spin that PG&E puts on the research results, continually downplaying the danger.

The GMPE seem to become more robust with each iteration.  Dr. Sam Blakeslee, who initiated these studies with his Senate Bill 1632 in 2006, has grave questions about how these equations are used.  There seems to be no one equation that actually compares all of the latest hazard possibilities of the faults.

More troublesome, to me, now, is not what the research has discovered—but what it has NOT discovered—and that is, the true hazard of the plant location.

I understand the value of reducing uncertainty to such a clear degree that the hazard and risk can be accommodated.  But now I see that what the scientists are after—which is a clear understanding of the seismology and ground motion at the plant—is NOT what PG&E is after.

When the science reduces the range of uncertainty, PGE declares greater certainty.  They are not the same thing.  A great amount of uncertainty is still there.

OK.  So yes.  I don’t trust PGE’s characterization of the studies.  I would like the plant to be declared “faulty” and therefore to be shut down.

But then, we still have a problem with all the highly radioactive waste stored onsite, costing ratepayers—and, indeed, maybe even the federal taxpayer, ultimately—an enormous amount of money to maintain and isolate from the environment, down the centuries, deep into the future.

As Dr. Peter Lam, a former NRC law judge, states, “Nuclear power is an unforgiving technology.”