Pacific Gas and Electric Company is asking the federal government to extend the utility's license to operate its Diablo Canyon nuclear power plant until 2045. The federal process is being complicated by new questions about the seismic safety at Diablo Canyon after Japan's experience with the Fukushima earthquake. 

Then  In 2008, a United States Geological Survey scientist announced research results which had startling implications.

In her Menlo Park USGS office, seismologist Jeanne Hardebeck explained the significance of red dots on a map on a computer screen.

HARDEBECK:  Looking offshore I found that a number of small earthquakes that previously had looked kind of scattered and spaced, actually lined up along a plane.

In November 2008, she confirmed there was a fault line just a few hundred yards from the reactors at Diablo Canyon. Hardebeck said knowing the significance of her findings made her all the more careful.  

BLAKESLEE: The closer the fault is, the great the accelerations will be, we know that.  So if your let's say three miles away from a fault, the level of certainty in terms of your ability to predict what the shaking will be is not great but it's better than if the fault is almost right underneath your plant.

PG&E declined to be interviewed for this series. (Read a statement by PG&E regarding Diablo Canyon, which references this NRC document)  But upon discovery of the shoreline back in 2008, the company moved quickly to tell the Nuclear Regulatory Commission that the plant remained safe.  Blakeslee says they acted way too fast.

BLAKESLEE: California, this is not a good place for hubris.  This is probably a place where you want to approach these questions with humility.

Blakeslee says one thing that concerns him most is a frightening and he says credible scenario; A combined Hosgri and Shoreline earthquake erupting together, creating a much larger event right at the plant.  At a conference last year,  a PGE's seismologist gave that same scenario a probability of zero.   

HAMILTON: Well the reaction was that nobody else there was very happy to hear that.  And you know it was obvious that this wasn't a popular concept at all.  And that was the end of it.

Twenty years after PG&E allegedly dismissed Hamilton's concerns a United States Geological Survey scientist discovered a fault no one disputes, called the shoreline fault.  It runs 600 yards from Diablo Canyon.

With that new uncertainty some were stunned by this announcement by PG&E's chief nuclear officer, John Conway in 2009.

CONWAY: I'm both pleased and excited to announce we are officially beginning the process to seek license renewal for the Diablo Canyon Facility. 

A new 20-year license for Diablo Canyon from the Nuclear Regulatory Commission would extend the plant's operation until 2045. 

James Boyd is co-chair of the California Energy Commission. He was surprised by PG&E's license renewal announcement because for the last three years his agency has told the utility it needs to conduct  advanced 3D studies of the seismic features around the plant.  PG&E maintains only the NRC can mandate such safety measures.  

Boyd says he asked the NRC to slow down the process until the studies were conducted. Boyd says the NRC told him: 

BOYD: It's not an element of the re-licensing process.  It's not one of the check boxes that we check off because we consider this as an operational issue and were anything to be brought to our attention we would immediately look into it. 

We wondered why the NRC didn't simply mandate the studies back in 2008 when California officials said they were essential. We traveled to NRC western U.S headquarters in Texas and asked the top administrator there, Elmo Collins, the same question.

COLLINS: The question the NRC has to answer is, is the facility safe today.  And we believe we have a basis for that.  And we just simply do not need the 3D studies to confirm that safety.

Collins told us, the reason for the NRC's comfort is confidence in PG&E's seismic monitoring.

In January of this year PG&E sent a report to the NRC with its conclusions about the Shoreline Fault.  The report said the plant was safe in the event of the strongest earthquake the shoreline could generate.

But  Jeanne Hardebeck of the U.S. Geological Survey says there is problem with that interpretation. 

PG&E's report is based on the assumption that two faults - the nearby Hosgri and the shoreline fault -- couldn't possibly connect.  Hardebeck says the science does not support that assumption.

HARDEBECK: The earthquakes along the Shoreline Fault very clearly go all the way to the Hosgri Fault.  So it looks very clear to me that those two are, those two faults are connected.  And so an interpretation that says that they don't connect doesn't seem to be to fit with the observations that we have.

Hardabeck says a quake involving both the Hosgri and Shoreline faults could come with a magnitude  as high as 7.2.  Such a quake would generate approximately 20 times more energy than the isolated 6.5 Shoreline, PG&E projects.

PG&E declined multiple requests for an interview. The company did issue a statement to us that said quote:

"Diablo Canyon was designed and constructed with seismic safety in mind and components of the facility were tested to withstand probable ground motions resulting from nearby faults."

Despite that statement, PG&E wrote a letter to the NRC suggesting a delay in the relicensing process.  Then, last month, the NRC ordered a 52 month hold on the relicensing. And it ordered PGE to conduct the 3-D seismic studies the State of California had been demanding for three years.