The Latest Chapter in Diablo Canyon’s Seismic Saga
Lara Uselding
Public Affairs Officer, Region IV
Scott Burnell
Public Affairs Officer, HQ
Today, the NRC is looking over a 1,400-page report produced by the owners of the
Diablo Canyon nuclear power plant for California state officials who had asked for new seismic information about the plant.
Specifically, Pacific Gas & Electric produced the report to meet part of a 2006 California law,
California Assembly Bill 1632.
PG&E shared the report with the NRC as they’re required to do as
part of the plant’s existing long-term seismic research program.

Earlier
research examined the Shoreline fault, just offshore of Diablo Canyon.
Both PG&E and the NRC had previously concluded, in
2009 and
2012,
the fault could only generate a quake weaker than one from the Hosgri
fault, which Diablo Canyon is designed to safely withstand.
For the new report, PG&E performed state-of-the-art surveys of
faults near the plant, including the Shoreline fault. The new report’s
more detailed information and updated analysis indicates the Shoreline
fault is both longer than previously thought and able to produce a
slightly stronger earthquake.
As part of its NRC requirements, PG&E must assess the report’s
impact on plant operations. NRC Resident Inspectors and Region IV staff
experts have already looked at PG&E’s assessment and so far the
information provides confidence the plant can keep the public safe after
a seismic event.
While PG&E’s new seismic information adds detail about the faults
in the plant’s immediate vicinity, the company’s evaluation claims an
earthquake generated by movement on the Shoreline fault would not be as
energetic as previous studies say a Hosgri-generated earthquake would
be.
Just as with the earlier Shoreline fault reports, the NRC will
thoroughly review the new information through our existing oversight
methods. The agency will take whatever action is appropriate if our
review questions PG&E’s conclusions.
PG&E will also use this new information as it re-evaluates its overall seismic hazard as part of the NRC’s
response
to the 2011 Fukushima nuclear accident. PG&E’s re-evaluation is due
to the NRC in March 2015. The NRC remains committed to integrating new
information into our understanding of safety at all reactors.