ML15170A454
| ML15170A454 | |
| Person / Time | |
|---|---|
| Site: | Diablo Canyon  |
| Issue date: | 06/19/2015 |
| From: | Ayres Law Group, Friends of the Earth |
| To: | Atomic Safety and Licensing Board Panel |
| SECY RAS | |
| Shared Package | |
| ML15170A450 | List: |
| References | |
| 50-275, 50-323, ASLBP 15-941-05-LA-BD01, RAS 27964 | |
| Download: ML15170A454 (27) | |
Text
Exhibit 3 Testimony of Dr. Sam Blakeslee to the U.S.
Senate Committee on Environment and Public Works (December 3, 2014)
1!
WRITTEN!STATEMENT!
BY!SAM!BLAKESLEE,!PH.D.!
CALIFORNIA!STATE!SENATOR,!FORMER!
CALIFORNIA!SEISMIC!SAFETY!COMMISSIONER,!FORMER!
TO!THE!!
SENATE!COMMITTEE!ON!ENVIRONMENT!AND!PUBLIC!WORKS!
DECEMBER!3,!2014!
Senator!Boxer,!Ranking!Member!Vitter,!and!Members!of!the!Committee,!
Thank!you!for!the!invitation!to!testify!at!todays!hearing!titled!NRCs!implementation!of!the!
Fukushima! nearDterm! task! force! recommendations! and! other! actions! to! ensure! and!
maintain! nuclear! safety.! The! Fukushima! meltdowns! raised! important! concerns! about!
nuclear!reactors!and!one!of!those!concerns!relates!to!seismic!safety.!!As!a!geophysicist!and!
former!California!State!Senator,!I!authored!AB!1632,!a!bill!that!required!PG&E!to!conduct!
seismic!hazard!research!of!the!faults!near!the!Diablo!Canyon!Nuclear!Power!Plant!(Diablo)!
housed!in!the!community!that!I!reside!in!and!represented!for!8!years!as!a!state!legislator.!!
Just! two! months! ago,! PG&E! published! the! Coastal! California! Seismic! Imaging! Project!
(CCCSIP)!Report!and!the!results!were!astonishing.!The!Report!documents!the!presence!of!a!
number!of!earthquake!faults!discovered!after!the!design!and!construction!of!the!plant!that!
have!been!found!to!be!larger!and!more!dangerous!than!previously!understood.!In!a!postD Fukushima! regulatory! environment,! it! is! important! that! policymakers! and! regulators!
understand!the!ramifications!of!these!findings.!
EXECUTIVE!
SUMMARY
PG&E!has!a!long!history!of!grappling!with!Californias!earthquake!faults!when!trying!to!site!
its!nuclear!plants.!It!had!previously!proposed!a!nuclear!power!plant!on!the!California!coast!
at!Bodega!Bay!but!abandoned!the!plan!when!it!was!discovered!that!the!site!was!to!be!built!
overtop!the!Shaft!Fault!and!within!1000!feet!of!the!San!Andreas!Fault.!!Later,!PG&E!built!a!
small!nuclear!power!plant!on!the!California!coast!at!Humboldt!Bay,!but!the!plant!was!shut!
down!after!the!discovery!of!three!faults!within!few!thousand!meters!of!the!plant.!PG&E!
selected!the!location!for!the!Diablo!plant,!representing!that!the!seismic!activity!in!the!area!
was!minimal.!!
In!the!late!1970s,!when!Diablo!was!still!under!construction,!data!surfaced!on!the!presence!
of!a!large!active!fault!(named!the!Hosgri)!located!just!three!miles!offshore!from!the!plant.!
PG&E!first!denied!its!existence.!When!that!assertion!was!disproved,!it!argued!the!fault!was!
likely!inactive.!When!PG&E!had!to!concede!it!was!active,!it!argued!it!was!not!capable!of!
producing!particularly!large!earthquakes.!It!turned!out!it!that!was!capable!of!generating!
very!large!earthquakes.!!
2!
In!a!recent!replay!of!these!events!concerning!a!newly!discovered!fault!system,!the!Shoreline!
fault!was!discovered!in!2008!and!analyzed!with!stateDofDtheDart!methods!and!found!to!be!
capable!of!generating!an!M7.3!earthquake!within!a!mere!600!meters!of!the!plant.!
There!is!no!getting!around!the!fact!that!PG&E!has!consistently!downplayed!seismic!hazards!
on!the!coast!near!its!nuclear!plants.!Especially!disturbing!is!that!during!these!past!decades!
the! NRC! has! repeatedly! relaxed! its! seismic! standards! to! accommodate! the! operation! of!
Diablo!Canyon.!
Now!that!the!data!about!the!faults!near!Diablo!is!indisputable,!PG&E!has!changed!tactics!
and!declared!the!plant!safe!on!the!basis!of!a!new!set!of!equations!it!has!developed.!PG&E!
has!undertaken!major!revisions!to!the!complex!ground!motion!equations!that!have!been!
used! to! estimate! how! much! shaking! can! be! produced! by! earthquakes.! Unsurprisingly,!
PG&Es!changes!to!its!methodologies!have!dramatically!reduced!estimated!shaking!at!the!
plant! from! all! hypothetical! earthquakes.! ! So! far,! NRC! has! largely! gone! along! with! these!
changes.!
With! PG&Es! history! of! playing! down! seismic! concerns! these! recent! developments! are!
cause!for!deep!concern.!!So!is!PG&Es!documented!history!of!coDopting!the!very!regulatory!
bodies!tasked!with!overseeing!it.!!Just!this!year:!!
- PG&E! was! found! to! be! inappropriately,! and! possibly! illegally,! lobbying! California!
Public!Utilities!Commissioners!and!staff!to!successfully!judge!shop!in!a!case!before!
the!CPUC.!!The!revelation!resulted!in!the!firings!of!three!senior!PG&E!executives,!the!
reassignment!of!the!CPUCs!chief!of!staff,!and!the!decision!by!the!President!of!the!
CPUC!to!recuse!himself!from!future!PG&E!decisions!and!to!not!seek!reDappointment.!!!
The!CPUC!was!just!fined!a!$1.05!million!for!this!backDchannel!lobbying.!
- PG&E! was! indicted! on! 12! criminal! charges! related! to! safety! violations! in! its! gas!
distribution,! including! an! accusation! that! PG&E! officials! obstructed! a! federal!
investigation!and!that!the!utility!!knowingly!relied!on!erroneous!and!incomplete!
information! to! avoid! inspections! that! would! have! exposed! risks! that! ultimately!
killed!8!people!in!a!2010!gas!pipeline!explosion!
- PG&E!was!discovered,!through!email!disclosures,!to!be!exploring!how!and!when!the!
Diablo! Canyon! Independent! Peer! Review! Panel! could! be! disbanded.! ! This! is! the!
stateDmandated!panel!tasked!with!providing!thirdDparty!quality!control!of!seismic!
risk!analysis!at!Diablo!that!is!quantified!by!the!Report,!which!is!my!subject!here.!
In!2013,!because!of!steam!generator!failures,!San!Onofre,!Californias!only!other!nuclear!
power!plant!was!permanently!shut!down!at!great!cost!to!ratepayers,!shareholders,!and!grid!
operations.! ! Last! month,! the! Office! of! the! Inspector! General! at! the! NRC! issued! a! report!
criticizing! the! NRCs! failure! to! call! for! a! license! amendment! process,! which! might! have!
identified!the!shortcomings!of!the!utilitys!technical!analysis!that!ultimately!led!to!those!
leaks.!The!safety!ramifications!of!steam!generator!leaks!at!San!Onofre,!as!serious!as!they!
were,!are!dwarfed!by!the!risks!to!the!public!should!PG&Es!Diablo!seismic!analysis!prove!to!
be! incomplete! or! inaccurate.! ! You! would! think! that! after! Fukushima! the! NRC! would! go!
beyond! a! check! the! box! review! process! when! confronted,! as! it! is! at! Diablo,! with! the!
3!
possibility!of!a!7.3!magnitude!earthquake!within!a!halfDmile!of!the!plant.!!So!far!we!have!
been!disappointed.!
Remarkably,!in!all!the!years!of!its!operation,!the!facility!has!never!gone!through!a!formal!
license! amendment! process! to! deal! with! even! the! Hosgri! Fault! discovered! in! the! 1970s.!
Instead,! its! possible! ramifications! were! more! or! less! explained! away! in! a! separate!
document.! More! significant! faults! have! been! discovered! since,! which! speaks! poorly! of!
PG&Es!original!examination!of!the!area,!and!of!the!NRCs!supervision!of!that!process.!One!
should! not! be! discovering! such! faults! after! building! a! plant.! The! potential! earthquakes!
affecting!the!plant!have!increased!with!each!major!study.!But!whats!equally!striking!is!that!
the!shaking!predicted!by!PG&E!for!these!increasing!threats!has!systematically!decreased!as!
PG&E!adopted!less!and!less!conservative!analytical!methodologies,!and!they!did!so!with!
NRC!approval.!!!
It!is!time!to!end!this!hodgeDpodge!of!licensing!rationalizations.!We!know!a!great!deal!more!
about!seismic!issues!than!we!did!when!Diablo!Canyon!was!licensed.!Its!time!for!the!NRC!to!
reassess! the! seismic! standards! for! the! plant! and! submit! them! to! a! formal! licensing!
amendment!process.!The!thing!that!both!PG&E!and!NRC!fear!most!is!a!public!hearing!in!
which!they!would!have!to!justify!what!they!have!done.!It!is!also!what!we!need!most!to!
assure!seismic!safety,!and!it!is!what!the!public!deserves.!
INTRODUCTION!
In! 2005,! as! the! elected! State! Assemblyman! representing! the! Central! Coast! and! as! a!
geophysicist,!I!became!concerned!that!PG&Es!prior!seismic!hazard!analysis!in!the!vicinity!
of! the! Diablo! Canyon! Nuclear! Power! Plant! had! failed! to! utilize! modern! stateDofDtheDart!
geophysical! techniques! that! have! proven! highly! effective! at! mapping! seismic! faults.! ! ! In!
2006,! I! authored,! the! state! legislature! passed,! and! Governor! Schwarzenegger! signed!
AB1632,! which! directed! the! California! Energy! Commission! to! assess! existing! scientific!
studies!to!determine!the!potential!threat!of!earthquakes!to!the!future!reliable!operation!of!
Diablo.!!After!extensive!review!the!California!Energy!Commission!concluded!that!significant!
seismic!uncertainty!existed!and!charged!PG&E!with!the!task!of!acquiring!new!stateDofDtheD art!geophysical!data!to!reassess!the!seismic!threats!to!Diablo.!!In!the!furtherance!of!AB1632!
the!California!Public!Utilities!Commission!provided!$64M!of!California!ratepayer!funds!to!
compensate!PG&E!for!the!Coastal!California!Seismic!Imaging!Project!that!resulted!in!the!
Report.!!!
At!the!time!of!the!bills!passage!few!appreciated!the!potential!threat!that!large!earthquake!
faults! posed! to! operating! nuclear! facilities.! ! Since! then! the! publics! awareness! of! the!
importance!of!the!issue!has!increased!significantly:!
- In!2007!the!KashiwazakiDKariwa!Nuclear!Power!Plant,!the!largest!in!the!world,!was!
severely!damaged!and!shuttered!due!to!an!M6.6!earthquake!19!kilometers!offshore!
from!the!facility.!!!
- In!2008!the!USGS!discovered!a!previously!unknown!Shoreline!Fault!only!600!meters!
from!the!Diablo!Nuclear!Power!Plant!and!only!300!meters!from!the!intake.!!
4!
- In!2011!the!Fukushima!Daiichi!nuclear!disaster!resulted!in!the!meltdown!of!three!of!
the!plants!six!reactors,!triggering!an!emergency!review!by!the!NRC!of!US!nuclear!
reactors!and!their!ability!to!withstand!shaking!from!earthquakes.!!This!tragedy!was!
caused!by!an!earthquake!and!Tsunami!far!larger!than!the!utility!believed!possible,!
which!produced!greater!shaking!than!the!plant!was!designed!to!withstand.!
Two!months!ago,!eight!years!after!the!passage!of!AB1632,!PG&E!issued!its!Report,!which!
will!likely!be!relied!upon!by!state!and!federal!regulators!in!the!course!of!their!immediately!
upcoming! deliberations! regarding! PG&Es! request! to! extend! the! operating! license! of! the!
Diablo! through! 2044D2045.! ! My! review! of! this! Report! addresses! important! historic,!
technical,! and! regulatory! issues! that! are! central! to! the! final! conclusion! of! the! Report;!
specifically,!that!the!facility!has!been!shown!to!be!safe!from!seismic!threats.!!!
PG&Es!Report!makes!a!number!of!key!findings!regarding!earthquake!threats.!In!virtually!
every!instance,!the!faults!surrounding!Diablo!are!now!understood!to!be!larger!and!more!
connected!than!previously!believed!as!recently!as!2011.!!Of!course!the!plant!was!initially!
licensed!assuming!these!seismic!threats!were!nonDexistent.!!Whereas!the!Hosgri!Fault!had!
previously! been! believed! to! be! the! most! dangerous! fault! near! Diablo,! newly! released!
research!shows!that!the!prior!Hosgri!maximum!earthquake!assumption!is!eclipsed!by!five!
other!faultDrupture!threats:!
- 1. SHORELINE! FAULT:! The! newly! discovered! Shoreline! Fault! located! within! 600!
meters!of!the!plant,!is!now!twice!as!long!as!thought!in!2011!and!almost!three!times!
as!long!as!the!lower!bound!proposed!in!2009.!!With!a!length!now!understood!to!be!
45!km!long!it!is!capable!of!generating!M6.7!strikeDslip!earthquake,!which!is!larger!
than!estimated!in!PG&Es!previous!2009!and!2011!reports.!
- 2. SAN!LUIS!BAY!FAULT:!The!newly!reinterpreted!16!km!San!Luis!Bay!Fault!located!
within! 1,900! meters! of! the! plant,! is! capable! of! generating! a! M6.4! reverse!
earthquake,!which!is!larger!than!previous!estimated!in!PG&Es!2011!report.!
- 3. LOS!OSOS!FAULT:!The!newly!reinterpreted!36!km!Los!Osos!Fault!located!within!8.1!
km!of!the!plant!is!capable!of!generating!a!M6.7!reverse!earthquake!which!is!smaller!
than!the!M6.8!estimate!in!PG&Es!2011!report,!but!still!estimated!to!produce!more!
ground!motion!than!the!Double!Design!Earthquake!(DDE),!also!known!as!the!Safe!
Shutdown!Earthquake!in!the!license.!
- 4. JOINT!SHORELINE/HOSGRI!FAULT!SYSTEM:!The!newly!reinterpreted!145!km!joint!
Shoreline/Hosgri! Fault! system! now! assumes! that! the! Hosgri! Fault! and! Shoreline!
Fault!connect,!whereas!previously!the!two!were!considered!to!be!wholly!separate!
and!incapable!of!failing!in!a!larger!single!rupture.!!A!joint!Shoreline/Hosgri!strikeD slip! rupture! within! 600! meters! of! the! plant! could! theoretically! generate!
approximately!a!M7.3!earthquake!according!to!the!Report.!
- 5. JOINT! HOSGRI/SAN! SIMEON! FAULT:! The! newly! reDinterpreted! 171! km! joint!
Hosgri/San!Simeon!Fault!system!now!assumes!that!the!Hosgri!Fault!and!San!Simeon!
Fault!connect,!whereas!previously!the!two!were!considered!to!be!wholly!separate!
5!
and! incapable! of! failing! in! a! larger! single! rupture.! ! A! joint! Hosgri/San! Simeon!
rupture! within! 4.5! km! of! the! plant! is! capable! of! generating! a! M7.3! strikeDslip!
earthquake,!which!is!larger!than!the!previously!estimated!M7.1!utilized!in!numerous!
prior! reports.! ! The! newly! defined! Hosgri! Fault! is! considerably! longer! than!
previously!presumed!by!PG&E!and!NRC.!
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.! ! This! result! is! remarkable! as! the! enormous!
Hosgri!Fault,!which!can!be!seen!easily!on!oil!company!seismic!lines!and!passes!the!plant!at!
a!distance!of!only!three!miles,!had!been!argued!for!many!years!to!be!the!greatest!threat!to!
the! facility.! ! (Note:! from! a! regulatory! perspective! the! Hosgri! Fault! had! previously! been!
treated! as! the! controlling! fault,! which! is! to! say! the! fault! posing! the! greatest! possible!
seismic!threat!to!Diablo.)!
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!reDinterpreted!faults!are!capable!of!producing!shaking!that!exceeds!
the!shaking!from!the!Hosgri,!yet!that!shaking!threat!would!be!much!reduced!from!prior!
estimates.!!!
Though!discussed!only!in!passing!in!the!Report,!the!reason!for!this!seeming!contradiction!is!
quite!important!when!assessing!whether!or!not!the!plant!is!safe!or!whether!it!is!operating!
within!its!license!conditions.!!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!lessDconservative!
than! the! prior! methodology,! essentially! deDamplifies! the! shaking! estimated! from! any!
given!earthquake!relative!to!the!prior!methodology!used!during!the!licensing!process.!
DIABLO!LICENSING!BACKGROUND!
The! Diablo! Canyon! Nuclear! Power! Plant! was! licensed! through! a! strictly! adjudicated!
process!that!defined!the!Safe!Shutdown!Earthquake!as!the!maximum!earthquake!potential!
for!which!certain!structures,!systems,!and!components,!important!to!safety,!are!designed!to!
sustain!and!remain!functional.!!In!the!unique!parlance!of!the!Diablo!Canyon!Nuclear!Power!
Plant!this!Safe!Shutdown!Earthquake!was!defined!as!the!Double!Design!Earthquake.!!The!
NRC!licensing!process!ensures!that!the!detailed!operability!requirements!of!the!American!
Society! of! Mechanical! Engineers! Boiler! and! Pressure! Vessel! Code! are! met! at! the! higher!
ground! motions. i!! The! Design! Earthquake! (DE)! for! Diablo! was! defined! during! the!
construction!permit!process!as!the!largest!of!four!possible!earthquake!scenarios.!!The!DE!
was!assumed!capable!of!generating!a!peak!ground!acceleration!of!0.2!g.!!The!Safe!Shutdown!
Earthquake!was!then!defined!for!Diablo!as!0.4g,!which!is!to!say!the!plant!must!be!able!to!
shut!down!safely!if!a!hypothetical!earthquake!generates!double!the!0.2g!of!shaking!that!
was! estimated! to! be! possible! from! known! surrounding! threats.! ! This! hypothetical! Safe!
Shutdown! Earthquake! is! known! as! the! Double! Design! Earthquake! (DDE)! and! is! a! key!
element!in!establishing!safety!standards!during!the!licensing!process.!
6!
This! formal! NRC! licensing! process,! which! defined! the! DDE! as! the! Safe! Shutdown!
Earthquake! for! enforceable! regulatory! purposes,! occurred! prior! to! the! discovery! of! the!
Hosgri!Fault.!!!!Upon!its!discovery!the!USGS!analyzed!the!Hosgri!Fault!and!determined!that!
it!could!generate!a!M7.5!earthquake!at!a!distance!of!4.5!km.!!The!NRC!negotiated!with!PG&E!
to!create!the!1977!Hosgri!Evaluation!(HE)!exception!under!the!theory!that!the!plant!could!
withstand! shaking! from! this! newly! discovered! fault! under! a! narrow! and! specific! set! of!
assumptions.!!!The!HE!used!considerably!lessDconservative!assumptions!than!those!used!
for!the!DDE,!which!was!applied!to!all!other!earthquake!threats.!!The!reduction!of!safety!
margins! by! the! use! of! these! special! assumptions! for! the! Hosgri! Fault! was! quite!
controversial,!and!was!strongly!criticized!by!NRC!Commissioners!Gilinsky!and!Bradford!in!
an! opinion! they! issued! on! the! Diablo! seismic! matters! in! 1981.ii!! The! DDE! is! the! Safe!
Shutdown!Earthquake!for!Diablo!and!applies!in!the!Current!Licensing!Basis!to!all!faults!that!
can!affect!Diablo,!with!the!exception!of!the!Hosgri!Fault,!to!which!the!1977!HE!exception!
and! its! methodology! and! assumptions! uniquely! apply.! ! Because! of! the! differing!
assumptions!the!HE!exception!did!not!and!was!never!intended!at!the!time!to!eliminate!or!
supersede!the!DDE!standard.!!!
To!operate!within!its!license!the!utility!has!been!required!to!show!that!the!plant!will!not!be!
exposed!to!shaking!beyond!either!the!DDE!basis!or!the!lessDconservative!HE!exception!for!a!
potential! Hosgri! earthquake.! ! Later,! the! 1977! HE! exception! was! modified! to! assume! a!
slightly!smaller!M7.2!earthquake!but!with!a!slightly!more!dangerous!reverse!component!of!
slip.!!The!combination!of!the!two!changes!produced!a!modified!spectrum!that!changed!only!
modestly!with!small!enhancement!at!higher!frequencies.!!That!modification!became!known!
as!the!1991!LTSP!spectrum;iii!however,!it!never!became!part!of!the!Current!Licensing!Basis.!!
(For!the!rest!of!this!letter!the!Hosgri!shaking!estimates!will!be!described!as!the!HE/LTSP!
spectrum!due!to!the!fact!that!the!HE!and!LTSP!are!used!somewhat!interchangeably!and!
differ! only! slightly,! even! though! the! differences! are! important! from! a! historic! and!
regulatory!perspective).!
In!2008!history!repeated!itself!and,!as!in!the!case!of!the!Hosgri!Fault,!another!offshore!fault!
was! discovered,! but! this! time! even! closer! to! the! plant.! ! USGS! found! the! Shoreline! Fault!
within!600!meters!of!the!reactors!and!within!300!meters!of!the!intakes.!!When!considering!
that! the! fault! runs! to! a! depth! of! 16! km,! spatially! the! nuclear! power! plant! lies! virtually!
overtop! the! new! fault.! ! In! the! immediate! aftermath! of! the! discovery,! PG&Es! data!
demonstrates! that! the! nearby! faults! could! produce! ground! motions! significantly! higher!
than!the!0.4g!peak!acceleration!permissible!under!the!DDE!standard!(see!table!below!D!note!
this!analysis!occurred!prior!to!the!seismic!studies!described!in!the!Report!which!found!that!
the!faults!were!larger!than!assumed!in!table).!
Table:!Comparison!of!Reanalysis!to!Diablo!Canyon!SSEiv!
Local!Earthquake!
Fault!
Peak!Ground!
Acceleration!
DDE!
0.40g!
Shoreline!
0.62g!
Los!Osos!!
0.60g!
San!Luis!Bay!
0.70g!
Hosgri!!
0.75g!
7!
In!the!face!of!this!conflict!with!the!license,!PG&E!began!to!compare!the!new!seismic!threats!
not!to!the!DDE!in!the!license,!but!rather!to!the!HE/LTSP!spectrum.!!If!PG&E!could!ignore!
the! DDE! Safe! Shutdown! Earthquake! standard! in! the! license,! PG&E! could! simply! seek! to!
prove!that!the!newly!discovered!seismic!threats!were!bounded!by!the!HE/LTSP!spectrum,!
with!their!less!conservative!assumptions!D!ergo,!notwithstanding!the!newly!discovered!and!
reDinterpreted!faults,!the!plant!could!be!said!to!be!operating!consistent!with!its!license.!!!
Dr.!Michael!Peck,!the!Senior!Resident!NRC!Inspector!at!the!Diablo!Canyon!Nuclear!Power!
Plant,! was! concerned! that! the! newly! discovered! and! reDinterpreted! faults! (Los! Osos,!
Shoreline,!San!Luis!Bay)!had!been!shown!by!PG&E!to!produce!greater!shaking!than!the!.04g!
peak!acceleration!DDE!design!basis.!!He!stated!that!the!only!approved!exception!to!the!DDE!
was!the!1977!HE!exception,!which!applied!only!to!the!Hosgri!Fault,!and!that!the!exception!
was!not!transferrable!to!these!other!nearby!faults!D!ergo!a!license!amendment!was!required!
to!correct!the!inconsistency!between!the!existing!license!and!the!new!seismic!threats.!!
Buttressing!Pecks!argument!that!the!less!strict!spectrum!was!not!to!supersede!or!replace!
the!DDE,!on!October!12th,!2012!the!NRC!wrote!to!PG&Ev:!The!DCPP!Final!Safety!Analysis!
Report!Update!states!in!Section!2.5,!!
the!LTSP!material!does!not!alter!the!design!bases!for!DCPP.!!In!SSER!34!the!NRC!
states,!The!Staff!notes!that!the!seismic!qualification!basis!for!Diablo!Canyon!will!
continue! to! be! the! original! design! basis! plus! the! Hosgri! evaluation! basis!
(emphasis!added).!
Faced! with! newly! estimated! ground! motions! in! excess! of! the! DDE! Safe! Shutdown!
Earthquake!license!requirement,!PG&E!proposed!revising!its!license!to!eliminate!the!DDE!
requirement! and! have! the! HE/LTSP! spectrum,! with! its! considerably! less! protective!
methodological!assumptions,!apply!not!just!to!the!Hosgri!Fault!as!an!exception!to!the!DDE,!
but!to!all!faults.!!The!NRC!declined!to!accept!the!request!for!review!because!it!failed!to!meet!
certain!required!standards.!
CRITICAL!ISSUE!EXPLORED!
I!do!not!seek!to!engage!on!Pecks!important!regulatory!issue!of!whether!the!utility!can!now!
legally! disregard! the! DDE! standard! and! instead! meet! only! the! lessDconservative! HE!
exception.!That!is!a!matter!for!the!NRC!to!determine!based!on!its!safety!and!regulatory!
standards!and,!hopefully,!informed!by!the!postDFukushima!understanding!of!the!dangers!of!
lax! regulatory! oversight.! ! In! the! aftermath! of! this! disagreement! between! the! Senior!
Resident!NRC!Inspector!at!Diablo!Canyon!Nuclear!Power!Plant!and!NRC!staff,!deliberation!
on!this!regulatory!issue!is!now!the!subject!of!a!lawsuit!filed!before!the!US!Court!of!Appeals!
for!the!District!of!Columbia.!
Instead,!this!analysis!seeks!to!explore!a!different!issue;!specifically,!is!PG&E!correct!when!it!
asserts!that!the!utility!has!shown!that!the!new!seismic!threat!is!bounded!by!the!1977!HE!
exception?!!(By!exploring!only!this!second!issue!I!do!not!mean!to!minimize!the!importance!
of!the!first!issue,!but!this!second!issue!is!central!to!the!critical!conclusion!of!the!Report).!!In!
other! words,! the! question! is! whether! or! not! the! new! seismic! threats! have! in! fact! been!
shown! to! produce! shaking! that! is! smaller! than! the! HE! basis! exception! when! the! same!
associated!analytical!methods!used!to!create!the!HE!basis!exception!are!applied!to!the!new!
seismic!threats.!!!
8!
Why! is! it! important! to! add! this! caveat! about! the! same! associated! analytical! methods?!
Because!the!rest!of!the!NRC!statement!cited!above!under!SSER!34!goes!on!to!say,!!
The!Staff!notes!that!the!seismic!qualification!basis!for!Diablo!continues!to!be!the!
original! design! basis! plus! the! Hosgri! evaluation! basis,! along) with) associated) analytical)methods,)initial)conditions,)etc.(emphasis!added).!!!
If! the! utility! seeks! to! argue! that! the! 1977! HE! exception! can! be! used! as! an! alternative!
standard! to! avoid! the! stricter! DDE! standard,! which! is! controversial! in! itself,! then! the!
methods!which!were!used!to!compute!the!HE!exception!become!of!paramount!importance.!!
This!analysis!seeks!to!document!that!the!associated!analytical!methods!used!by!the!utility!
to!analyze!the!new!seismic!threats!in!the!Report!are!markedly!lessDconservative!than!those!
used!for!the!1977!HE!exception.!!!
Why!is!this!change!in!methodology!important,!particularly!when!the!methodology!is!less!
conservative?!!Under!10!CFR!50.59,!a!license!amendment!is!required!when!the!Final!Safety!
Analysis!Report!(FSAR)!is!inadequate!to!describe!the!circumstances!at!the!plant!and!there!
is!a!!
departure!from!a!method!of!evaluation!described!in!the!FSAR!(as!updated)!used!in!
establishing!the!design!bases!or!in!the!safety!analysis.!!NRC!regulations!define!such!
a!departure!as:!!"(i)!Changing!any!of!the!elements!of!the!method!described!in!
the!FSAR!(as!updated)!unless!the!results!of!the!analysis!are!conservative!or!
essentially! the! same;! or! (ii)! Changing! from! a! method! described! in! the! FSAR! to!
another! method! unless! that! method! has! been! approved! by! NRC! for! the! intended!
application."!
The! NRC! requires! a! license! amendment! when! there! is! a! departure! from! a! method! of!
evaluation!that!established!the!design!basis!unless!that!departure!is!essentially!the!same!or!
more!conservative.!!If!the!utility!is!allowed!to!employ!lessDconservative!analytical!methods!
to!obtain!more!optimistic!results!then!prior!safety!standards!could!be!lowered!without!the!
full!understanding!or!regulatory!concurrence!of!the!NRC.!!!
It!was!this!very!problem!that!led!to!the!shutdown!of!the!San!Onofre!SONGS!plant.!!The!
failure!of!the!NRC!to!recognize!the!need!for!a!license!amendment!to!replace!San!Onofres!
steam!generators!was!identified!by!the!Office! of! the! Inspector! General!at!the!Nuclear!
Regulatory!Commission!as!a!missed!opportunity!to!identify!weakness!in!Edisons!technical!
analysesvi.!!There!is!a!marked!difference!between!NRC!staff!review!of!a!utilitys!change!in!
methodology!versus!the!rigor!and!process!associated!with!a!license!amendment.!
This!analysis!contends!that!because!a!true!applesDtoDapples!comparison!was!never!made!in!
the!Report!between!the!Hosgri!and!the!new!seismic!threats!using!analytical!methods!that!
are! conservative! or! essentially! the! same! as! those! used! for! the! Hosgri! evaluation.!!
Therefore,!it!is!inaccurate!to!assert!that!the!new!seismic!threats!are!shown!to!be!bounded!
by!the!Hosgri!evaluation!basis!-!as!that!phrase!has!any!bearing!for!regulatory!purposes.!!!
This!contention!is!important!because!D!If!PG&E!is!allowed!by!the!NRC!to!reject!both!the!
stricter!standard!of!the!DDE!and!the!conservative!analytical!methods!used!when!the!1977!
HE!exception!was!authorized,!then!the!NRCs!prior!seismic!safety!licensing!standards!will!
have!been,!for!all!practical!purposes,!circumvented.!!!
9!
Making! this! particularly! troubling! is! that! this! circumvention! will! have! been! achieved!
without! a! license! amendment! process,! which! would! ensure! a! more! robust! process! for!
including!analysis!of!differing!and!minority!findings!and!opinions!-!findings!and!opinions!
which!have!been!proven!over!time!to!be!right,!more!often!than!not.!!!
GROUND!MOTION!PREDICTION!RETROSPECTIVE!
Methodologies! employed! to! assess! potential! shaking! at! the! nuclear! power! plant! can! be!
broken!into!three!broad!categories:!
- 1) SOURCE:!Estimated!energy!released!by!a!specific!earthquake!on!a!given!fault!-!based!on!
equations! that! involve! factors! such! fault! mechanics,! stress! drop,! radiation! pattern,!
directivity,!rupture!history,!rupture!length!and!width,!etc.!
- 2) PROPAGATION:! Estimated! attenuation! and! amplification! factors! that! convert! the!
energy! released! during! the! fault! rupture! process! to! the! actual! observed! free! field!
ground!motion!at!a!particular!site,!based!on:!
- a. TRANSMISSION!EFFECTS:!Energy!transmission!involves!absorption!and!scattering,!
otherwise! known! as! attenuation,! incurred! along! the! propagation! path! from! the!
earthquake!to!the!vicinity!of!the!particular!site,!and!
- b. SITE!EFFECTS:!Site!amplification!and!deDamplification!effects!due!to!the!stiffness!of!
the!rocks!and!soils!of!the!particular!site!and!the!impedance!contrasts!that!give!rise!
to!a!variety!of!scattering!and!reverberation!effects.!
- 3) TRANSFERENCE:! Estimated! shaking! adjustments! from! reference! freeDfield! station! to!
powerDblock,!turbineDbuilding!foundation!levels,!and!then!to!structures,!systems,!and!
components! throughout! the! facility! -! based! on! certain! projection,! coherence,! and!
damping!factors.!
This!analysis!seeks!to!examine!#1!and!#2a!and!#2b!cited!above.!!
A! Ground! Motion! Prediction! Equation! (GMPE)! is! used! to! predict! shaking! at! a! particular!
distance!from!an!earthquake!based!on!a!variety!of!parameters.!!A!GMPE!represents!the!
statistical!relationship!that!best!fits!the!empirical!distanceDattenuation!observations!from!
some! database! of! earthquake! recordings.! ! Some! of! the! parameters! used! to! make! the!
estimate!include:!size!of!earthquake,!fault!mechanics,!geometry!of!the!fault!to!the!recording!
station,! and! the! velocity! of! the! rocks! immediately! below! the! recording! station.! ! GMPEs!
incorporate!a!large!range!of!phenomena!and!effects.!
Since!discovery!of!the!Shoreline!Fault!PG&E!has!significantly!changed!the!GMPE!equations!
used!to!analyze!potential!shaking!at!Diablo.!!The!following!summarizes!the!changes!and!
their!net!effect!on!seismic!hazard!estimates.!!To!help!track!the!evolution!of!GMPEs!they!are!
informally! numbered! in! the! following! retrospective.! ! (GMPE\\1,! nomenclature! for! the!
purposes!of!this!letter!would!be!the!methodology!used!for!the!DDE!and!the!HE!exception!
from!the!construction!permit).!
In! 1991,! PG&E! constructed! the! LTSP! spectrum,! which! assumed! a! M7.2! earthquake! at! a!
distance! of! 4.5! km! and! used! a! GMPE! (GMPE\\2)! derived! from! their! own! distanceD
10!
attenuation!relationship!based!on!a!database!of!strongDmotion!recordings!of!earthquakes!
at!a!range!of!distances!along!with!regression!analysis!!
In! 2008! the! Shoreline! Fault! was! discovered! which! triggered! a! requirement! that! PG&E!
assess!whether!or!not!shaking!caused!by!the!newly!discovered!fault!was!bounded!by!the!
DDE!and!the!HE!exception,!as!required!by!its!current!operating!license.!!Rather!than!use!the!
same!GMPE!to!perform!that!analysis!PG&E!began!introducing!new!methodologies!making!it!
difficult! to! perform! historical! comparisons! with! earlier! standards! approved! through! the!
NRCs!regulatory!process.!!!
PG&E,!in!an!initial!sensitivity!reportvii!to!the!NRC,!assumed!that!the!length!of!the!Shoreline!
Fault!was!as!much!as!24!km!long!with!a!depth!of!12!km!and!capable!of!generating!a!M6.5!
earthquake.!!It!then!used!an!assortment!of!different!recently!developed!GMPEs,!known!as!
the! Next! Generation! Attenuation! models,! to! create! a! new! averaged! GMPE! (GMPE\\3)! to!
compute! shaking! estimates! at! the! plant! caused! by! a! Shoreline! earthquake.! ! GMPED3!
resulted! in! a! deDamplification! effect! of! median! estimated! shaking,! relative! to! the! prior!
methodology,!i.e.!a!decrease!in!shaking,!relative!to!GMPED1!or!GMPED2.!!This!new!GMPE!
was! justified! based! on! the! use! of! the! Pacific! Earthquake! Engineering! Research! Center!
(PEER)!database!of!some!3,600!earthquake!recordings.!!Using!GMPED3!PG&E!reported!that!
the!shaking!was!substantially!lower!than,!or!bounded!by,!the!LTSP/HE!spectrum1.!
In! 2009,! NRC! staff! used! PG&Es! proposed! GMPE\\3! equations! but! then! analyzed! the!
Shoreline! Fault! assuming! it! was! 24! km! long! with! a! depth! of! 16! km,! which! was! more!
conservative! than! PG&Es! depth! of! 12! km.! ! Using! these! parameters,! and! including! a! 1!
standard!deviation!of!magnitude!estimate,!the!largest!possible!earthquake!was!computed!
to!be!M6.85!rather!than!M6.5.!!Assuming!the!somewhat!larger!earthquake!their!analysis!
found,!!
!The! motions! are! very*close! to! the! LTSP/HE! in! the! highDfrequency! range! but! fall!
below! the! LTSP/HE! in! the! longDperiod! range.! and! seismic! loading! levels!
predicted!for!a!maximum!magnitude!earthquake!on!the!Shoreline!Fault!are!slightly*
below!those!levels!for!which!the!plant!was!previously!analyzed!in!the!Diablo!Canyon!
Long!Term!Seismic!Program!(emphasis!added).!!!!!
Using!GMPED3!shaking!from!an!assumed!24!km!Shoreline!Fault!was!found!to!be!very*close*
to! and! only! slightly* below! the! LTSP/HE! spectrum! when! using! the! new! GMPED3!
methodology!!(emphasis!added).!!!!
The!five!NGA!GMPEs!which,!when!averaged,!produce!GMPED3!are!each!shown!in!figure!10!
from!the!NRC!report.!!The!NRC!staff!analysis!also!tested!the!significance!of!using!the!lowerD bound!estimate!of!rock!velocity!rather!than!the!best!estimate!(lower!velocity!corresponds!
to!higher!shaking).!!Using!a!rock!velocity!of!800!m/s!instead!of!1,100!m/s!resulted!in!a!
spectrum!that,!exceeds!the!LTSP!spectrum!by!a!small!amount!over!some!frequencies.!!In!
summary,!by!using!reasonable!but!somewhat!more!conservative!approaches!to!the!three!
available! variables! (the! NGA! model! selection,! earthquake! magnitude! estimate,! or! rock!
1 The LTSP and HE spectra are very similar and are used almost synonymously in some reports cited herein. To avoid confusion caused by switching back and forth, a single term LTSP/HE will be used in some instances even though they differ from a regulatory basis.
11!
velocity)!the!spectrum!was!found!to!be!very!close!or!exceedsby!a!small!amount.!!This!
result! was! quite! significant! because! it! showed! that,! even! in! the! early! days! when! the!
Shoreline! Fault! was! still! believed! to! be! relatively! small,! shaking! could! exceed! the! LTSP!
Spectrum!assuming!certain!models!and!certain!rock!parameters.!!!The!Chiou!&!Youngs!(08)!
GMPE!(dotted!blue!line)!exceeds!the!LTSP!Spectrum!(solid!black!line)!at!about!7!Hz!and!
above,!the!others!are!just!a!little!below,!hence!the!characterization!that!they!are!very*close!
(emphasis!added).**!
This!result!naturally!raises!important!questions!about!the!effect!of!the!new!GMPE!applied!
to! the! Shoreline.! ! For! example:! would! estimation! of! shaking! on! a! 24! km! rupture! of! the!
Shoreline!Fault!have!exceeded!the!LTSP!if!GMPED1!was!used!rather!than!GMPED3?!!Given!
what!is!shown!in!Figure!10!it!appears!that!the!answer!would!likely!be!yes!if!the!difference!
between!GMPED3!vs!GMPED1!was!anything!other!than!de!minimis,!but!that!analysis!was!not!
performed!in!the!2009!Shoreline!report.!
The!effect!of!which!GMPE!methodology!is!employed!is!highlighted!in!a!NRC!staff!remark!
when! it! wrote,! epistemic! uncertainty! in! the! GMPEs,! which! tends! to! be! higher! in! the!
magnitudeDdistance! ranges! with! sparse! available! seismological! data! (such! as! large!
magnitudes! at! short! distances).! ! Generally! the! GMPEs! are! the! largest) source) of) uncertainty!in!the!ground!motion!values!produced!in!seismic!hazard!analysis!(emphasis!
added).!Here!the!NRC!staff!acknowledges!that!the!new!GMPEs!are!the!source!of!the!greatest!
uncertainty,! and,! that! uncertainty! is! greatest! for! large! earthquakes! at! short! distances,!
which!is!exactly!the!situation!for!Diablo.!
In! 2011,! PG&E! issued! its! Report! on! the! Analysis! of! the! Shoreline! Fault! Zone,! Central!
Coastal!California!assuming!the!same!maximum!M6.5!earthquake!along!a!23!km!fault,!but!
introducing! a! number! of! new! factors! creating! yet! another! new! GMPE,! named! here! as!
12!
GMPE\\4.!!The!utility!started!with!its!2009!GMPED3!equation!but!then!added!a!new!hardD rock!effect.!!The!rationale!for!this!equation!was!inferred!from!work!by!Silva!(2008).!!The!
result! adjusted! estimated! shaking! downward! still! further! from! GMPED3.! ! Silvas! work,!
which!was!specific!to!a!particular!range!of!rock!hardness!along!with!other!factors,!did!not!
include! the! actual! rocks! at! Diablo.! ! Therefore! PG&E! extrapolated! the! findings! of! the!
published!paper!so!they!could!be!applied!to!Diablo!where!a!faster!rock!velocity!of!1,200!
m/s!was!assumed!(faster!rocks!equate!to!lower!shaking).!!!
Additionally,! PG&E! created! new! equations! to! reduce! the! standard! deviation! of! the!
estimated!shaking.!!Because!84th!percentile!shaking!estimates!are!the!sum!of!the!median!
shaking!plus!one!standard!deviation!the!total!spectrum!can!be!lowered!either!by!reducing!
the!median,!reducing!the!standard!deviation,!or!lowering!both.!!!
With! the! issuance! of! the! 2011! report! PG&E! reduced! both! the! median! and! the! standard!
deviation!used!in!the!analysis!of!the!seismic!threats!-!the!first!through!yet!another!new!
GMPE!with!hardDrock!deDamplification!effects;!and!second,!through!a!statistical!approach!
described!as!singleDstation!sigma.!!!
Using! this! new! GMPE\\4! the! resulting! spectrum! that! was! no! longer! slightly*below! and!
very* close! to! the! LTSP/HE! spectrum,! per! the! prior! NRCs! findings! of! 2009! (emphasis!
added).!!The!new!margin!was!significantly!larger!thereby!allowing!PG&Es!to!again!assert!
that! the! LTSP/HE! spectrum! was! not! at! risk! of! being! exceeded! by! shaking! on! a! M6.5!
earthquake!on!the!Shoreline!Fault.!!Note!how!the!PG&Es!methodology!to!compute!shaking!
changed!not!once!but!twice!in!the!short!period!of!time!since!the!discovery!of!the!Shoreline!
Fault!in!2008.!!Both!those!changes!produced!reduced!estimates!of!shaking!from!the!newlyD discovered!Shoreline!Fault.!
In!2012,!NRC!staff!issued!its!Confirmatory!Analysis!of!Seismic!Hazard!at!the!Diablo!Canyon!
Power! Plant! from! the! Shoreline! Fault! Zone.! ! The! report! details! staffs! review! of! PG&Es!
report.! ! NRC! staff! decided! to! lower! their! maximum! possible! earthquake! from! M6.85! to!
M6.7,!which!was!closer!to!PG&Es!figure!of!M6.5!(smaller!earthquakes!correspond!to!lower!
shaking).! ! Similarly! staff! decided! to! revise! their! estimate! of! rock! velocity! upward! from!
1,100!to!1,200!m/s!which!was!the!figure!used!by!PG&E!(faster!velocities!correspond!to!
lower!shaking).!!!
They!also!reviewed!PG&Es!new!hardDrock!deDamplification!adjustment!and!pointed!out!a!
number!of!problems!with!the!approach!including!uncertainty!in!the!estimate!of!Kappa,!a!
factor! that! describes! damping! in! basement! rock.! ! When! NRC! staff! explored! alternative!
methodologies!they!found,!the!NRC!results!are!conservative!relative!to!the!PG&E!results!at!
virtually!all!frequencies.viii!!Nonetheless,!NRC!staff!incorporated!a!new!hard!rock!effect!and!
added!that!factor!to!GMPED3.!!Staff!elected!not!to!use!add!singleDstation!sigma!effect!to!
further! lower! the! 84th! percentile! of! shaking.! ! They! did! however! agree! with! PG&Es!
conceptual!approach,!albeit!they!noted!statistical!unreliability!of!its!use!at!Diablo!due!to!
small!amounts!of!available!data.!!!
To!issue!this!report,!NRC!staff!acquiesced!to!PG&Es!use!of!the!!
- 1) Use!of!the!new!NGA!GMPEs,!
- 2) Averaging!of!NGA!GMPEs!to!eliminate!outliers,!
- 3) Smaller!earthquake!magnitude!estimate,!
13!
- 4) New!hardDrock!rock!scaling!factor,!
- 5) Increased!site!rock!velocities,!and!!
- 6) New!statistical!singleDstation!sigma.!!!
The!net!effect!of!adding!these!factors!allowed!the!NRC!to!issue!a!confirmation!in!2012!of!
PG&Es! assertion! that! the! Shoreline! Fault! would! produce! shaking! below! the! LTSP/HE!
spectrum.!!!
In! 2014,! after! the! offshore! seismic! studies! were! completed,! PG&E! issued! its! Coastal!
California! Seismic! Imaging! Project! (CCCSIP)! Report.! ! The! Report! concluded! that! the!
Shoreline!Fault!is!45!km!long!(a!tripling!of!the!utilitys!2009!lowerDbound!figure)!and!that!a!
hypothetical!joint!Hosgri/Shoreline!Fault!rupture!would!be!145!km!long!generating!a!M7.3!
earthquake! within! 0.6km! of! the! plant! (corresponding! to! a! factor! of! 30! greater! released!
energy!relative!to!the!earlier!lowerDbound!estimate).!!The!Report!also!details!the!size!and!
location!of!the!Los!Osos!and!San!Luis!Bay!Faults!and!the!potential!earthquakes!they!could!
generate.! ! Again,! all! of! these! threats! produce! shaking! that! is! greater! than! their! new!
calculations! of! shaking! from! the! Hosgri,! which! had! previously! been! identified! as! the!
controlling!fault!
In!Chapters!11!and!13!PG&E!analyzes!the!new!seismic!threats,!which!are!markedly!larger!
than!those!analyzed!in!2011!using!their!new!GMPED4!which!was!used!successfully!with!the!
Shoreline! Report! to! calculate! lower! levels! of! shaking! than! the! earlier! methodology.!!
Analyzing! the! new! threats! using! GMPED4! the! Report! finds! that! even! a! massive! M7.3!
earthquake! linking! the! Hosgri! and! Shoreline! Faults,! with! rupture! occurring! within! 600!
meters!of!the!reactors,!could!not!exceed!the!LTSP/HE!spectrum.!!Demonstrating!just!how!
effective! these! lessDconservative! methodologies! are! in! lowering! estimates! of! shaking,!
without! a! single! retrofit,! Diablo! becomes! virtually! invulnerable! to! any! imaginable!
earthquake!regardless!of!size!and!proximity.!!!
Evidence! of! the! total! cumulative! effect! of! these! new! methodologies! can! be! inferred! by!
looking!at!the!before!and!after!calculations!of!shaking!of!a!hypothetical!Hosgri!Fault!
earthquake.!!Such!a!comparison!shows!that!the!peak!acceleration!is!reduced!from!0.75g!to!
0.46g!!!The!deDamplification!effect!is!even!larger!than!suggested!by!this!38%!decrease!in!
estimated! shaking! because! the! before! Hosgri! earthquake! is! smaller! than! the! after!
Hosgri! earthquake,! which! now! assumes! a! joint! rupture! on! the! Hosgri/San! Simeon! Fault!
System.!!The!importance!of!using!a!new!methodology!that!reduces!peak!accelerations!by!at!
least!38%!is!never!singled!out!for!mention!in!the!Report,!nor!is!the!prior!lessDconservative!
methodology!applied!to!the!new!seismic!threats.!
IMPORTANCE!OF!NEW!GMPEs!
These!changes!to!GMPEs,!documented!in!the!prior!section,!are!crucial!to!the!fate!and!future!
of!Diablo!and!give!rise!to!two!important!questions.!!!
First,!from!a!technical!perspective:!!Are!these!rapidly!evolving!GMPEs!appropriate!
for! application! to! Diablo! given! the! statistics! and! science! embedded! in! their!
assumptions?!!!
Second,! from! a! regulatory! perspective:! ! Are! these! rapidly! evolving! GMPEs!
appropriate! for! application! to! Diablo! when! dealing! with! the! safety! margins! and!
14!
adjudicated! rules! that! define! how! nuclear! power! plant! licenses! are! enforced! or!
amended?!
In!this!retrospective!of!evolving!GMPEs!Ive!made!no!arguments!regarding!the!technical!or!
scientific!merit!regarding!the!halfDdozen!changes!to!GMPEs!that!have!occurred.!!This!is!a!
rapidly!evolving!field!of!research!for!which!there!is!insufficient!data!to!provide!a!simple!
yes!or!no!answer.!!Instead!it!is!more!appropriate!to!identify!concerns!and!to!point!out!
alternative!interpretations!to!the!existing!data.!!Therefore,!I!address!the!first!question!in!an!
attached!appendix,!which!can!be!read!separately!from!this!letter.!!!
However,!as!a!former!policymaker!I!do!believe!there!is!a!clearDcut!answer!to!the!second!
question,! which! I! will! address! here.! ! Making! this! GMPE! chronology! troubling! from! a!
regulatory!and!safety!perspective!is!that,!as!newly!discovered!or!reDinterpreted!faults!are!
progressively!understood!to!be!larger!and!more!dangerous!than!previously!believed!the!
newly!derived!methodologies!adjust!shaking!downward!just!sufficiently!to!accommodate!
the! new! threat.! ! In! fact,! the! safety! of! the! facility! no! longer! depends! on! whether! or! not!
dangerous!faults!actually!surround!the!nuclear!power!plant!and!are!capable!of!generating!
earthquakes! that! exceed! the! shaking! predicted! from! the! previously! defined! controlling!
fault.!That!question!has!been!answered!unequivocally!and!the!PG&E!Report!acknowledges!
the!presence!of!such!earthquake!faults.!!Instead!the!safety!of!the!facility!depends!upon!the!
reliability! of! new! lessDconservative! equations,! which! are! going! through! major! revisions!
literally!with!each!newly!issued!report.ix!!!
These! facts! raise! significant! regulatory! issues! that! need! to! be! addressed! at! the! highest!
levels!of!the!NRC.!!In!this!instance!we!see!a!nuclear!power!plant!that!is!found!to!be!exposed!
marked! greater! seismic! threats! than! ever! envisioned! during! the! licensing! process.! ! This!
increase!has!happened!not!once,!with!the!discovery!of!the!Hosgri!Fault,!but!twice.!!With!
this! years! report! an! entire! new! class! of! earthquake! threats! have! been! identified! that!
eclipse!the!prior!Hosgri!Fault!threat.!!This!fact!alone!should!galvanize!the!NRC!to!act.!!But!
what!makes!the!situation!even!more!dire!is!that!the!methodologies!used!by!the!utility!to!
analyze!the!new!threats!have!changed!as!well.!!If!the!utilitys!associated!analytical!methods!
to!compute!ground!motion!were!the!same!or!more!conservative!the!debate!would!be!solely!
on! the! scientific! questions! surrounding! the! earthquake! potential! introduced! by! the! new!
faults.!!However,!in!this!case!the!associated!analytical!methods!to!compute!ground!motion!
beneath! the! plant! are! markedly! lessDconservative! than! those! ever! used! before.! These!
methods!are!lessDconservative!than!when!the!plant!was!licensed!and!less!conservative!than!
even! six! years! ago! when! the! Shoreline! Fault! was! first! discovered.! If! the! prior!
methodologies!used!during!licensing!were!applied!to!these!new!faults!it!is!possible,!and!
perhaps!likely,!that!shaking!would!exceed!both!the!DDE!and!LTSP/HE!spectrum.!If!true,!
this!means!that!the!plant!is!currently!operating!beyond!the!tolerances!established!under!its!
license.!That!is!why!this!is!a!critical!regulatory!issue.!Threats!are!going!up!at!the!same!time!
the! utilitys! preferred! method! for! analyzing! all! such! threats! has! become! markedly! less!
conservative.!From!a!regulatory!perspective,!it!is!this!simultaneous!convergence!of!higher!
threats!and!lessDconservative!methodologies!that!requires!the!NRC!to!act!immediately.!!
15!
CONCLUSION!
In!summary:!The!geophysical!methodologies!to!locate!faults!and!assess!the!size!of!potential!
earthquakes! are! well! established! and! have! been! tested! for! innumerable! instances! over!
many!decades.!Similarly,!the!estimation!of!site!effects!when!dealing!with!relatively!simple!
geology!is!well!understood.!!This!history!has!allowed!regulators!to!rely!comfortably!on!the!
long!record!of!published!findings!on!these!important!elements!of!seismic!hazards.!
However,! the! geophysical! methodologies! for! determining! ground! motion! in! the! extreme!
nearDfield! are! in! a! rudimentary! state! of! development.! Similarly,! the! estimation! of!
broadband!site!effects!when!dealing!with!highly!complex!and!heterogeneous!3D!geology!is!
a!difficult!technical!problem!and!an!active!area!of!research!(see!appendix).!
PG&E! has! progressively! used! methodologies! that! produce! lessDconservative! results! to!
analyze! the! steadily! increasing! seismic! threat.! With! each! successive! generation! of! new!
information!about!the!threat!prior!methodologies!are!modified!and!more!sanguine!results!
are!obtained.!!!
Of!course,!from!a!research!perspective,!the!fact!that!a!whole!series!of!new!methodologies!
are! being! explored! and! new! equations! are! being! tested,! albeit! with! limited! data! (see!
appendix),! is! a! good! thing.! However,! it! is! a! quite! perilous! thing! from! a! regulatory!
perspective,!which!requires!highDlevels!of!scientific!and!statistical!certainty!based!on!large!
datasets!and!wellDvetted!methodologies.!The!regulatory!determination!of!safety!should!not!
hang!tenuously!upon!the!results!of!an!ongoing!science!experiment.!When!faced!with!such!a!
situation! nuclear! regulators! must! rely! upon! the! existing,! more! conservative,! and!
historically!accepted!methodologies!to!assess!risk.!!!
But! beyond! the! imprudence! of! relying! upon! rapidly! evolving! methodologies! to! obtain!
lower!risk!estimates!at!a!nuclear!power!plant,!there!is!a!regulatory!reason!why!such!an!
approach!is!not!allowable.!!The!NRC!stated,x!The!Staff!notes!that!the!seismic!qualification!
basis! for! Diablo! Canyon! will! continue! to! be! the! original! design! basis! plus! the! Hosgri!
evaluation! basis,! along) with) associated) analytical) methods,) initial) conditions,) etc.)
(emphasis! added).! ! Clearly! the! Hosgri! evaluation! basis,! if! it! is! to! have! any! regulatory!
meaning,!can!only!be!applied!to!a!new!seismic!threat!if!the!same,!or!more!conservative,!
analytical!methods!are!employed!to!compare!the!two.!This!however!is!not!how!the!utility!is!
treating! the! Hosgri! evaluation! basis.! Instead,! the! utility! employs! significantly! less!
conservative!analytical!methods!and!then!states!that!the!lower!shaking!produced!by!new!
seismic!threats!is!bounded!by!the!HE!exception.!
Finally,!if!altogether!lessDconservative!methodologies!are!to!be!used!to!analyze!altogether!
new!and!more!dangerous!faults!it!is!important!that!such!analysis!be!performed!at!arms!
length!through!a!transparent,!rigorous,!and!strict!license!amendment!process!so!that!the!
public!can!have!confidence!that!safety!is!the!foremost!consideration!of!the!NRC.!This!is!why!
such!analysis!should!be!performed!through!the!course!of!a!license!amendment!process.!
My!overarching!concerns!with!the!Report!include:!
- Disregard!of!DDE!basis:!In!a!postDFukushima!setting!the!NRC!must!insist!upon!the!high!
and! robust! seismic! safety! standards! at! the! nations! only! nuclear! power! plant! that! is!
16!
ringed! by! numerous! nearby! faults! capable! of! earthquakes,! each! larger! than! the!
earthquakes!envisioned!from!previously!assumed!controlling!fault.!However,!toDdate!
the!NRC!has!ignored!the!cautions!of!experts!and!even!its!own!resident!inspector!who!
has!declared!the!plant!is!operating!beyond!its!current!operating!license!based!on!the!
DDE.!
- Weakening!of!HE!basis:!The!1977!HE!basis!was!allowed!as!an!exception!that!applied!
only!for!an!earthquake!on!the!Hosgri!Fault.!However,!while!the!utility!is!ignoring!the!
DDE!standard!and!is!applying!the!HE!exception!to!all!faults,!it!is!also!simultaneously!
seeking! to! weaken! the! 1977! HE! exception! by! creating! new! associated! analytical!
methods!that!are!markedly!less!conservative.!
- Lack! of! Transparency:! Notably,! the! Report! never! makes! an! applesDtoDapples!
comparison!wherein!the!same!associated!analytical!methods!are!used!to!analyze!new!
seismic!threats!and!the!HE!exception.!Nor!are!lowerDvelocity!parameters!input!to!the!
new!analytical!methods!to!assess!their!sensitivity!to!critical!real!world!parameters!and!
uncertainties!at!the!site.!The!public!is!never!given!the!opportunity!to!see!the!cumulative!
effect! of! each! generation! of! new! GMPEs! or! the! range! of! effects! due! to! rock! velocity!
selection.! This! makes! it! impossible! for! PG&E! to! accurately! assert! in! the! Report! that,!
from!a!regulatory!perspective,!the!new!seismic!threats!are!shown!to!be!bounded!by!
the!HE!basis.!!From!what!data!are!shown!by!the!Independent!Peer!Review!Panel!such!a!
transparent!and!applesDtoDapples!analysis!would!likely!prove!the!opposite.!!!
- Rapidly! Evolving! Analytical! Methods:! The! utility! is! relying! upon! lessDconservative!
methodologies! that! are! evolving! and! changing! rapidly,! which! reduces! reliability! and!
confidence! from! a! regulatory! perspective.! The! velocity! parameters! themselves,! upon!
which!some!of!these!new!methodologies!depend,!are!in!serious!dispute.!!Furthermore,!
the!methodology!to!compute!extreme!nearDfield!ground!motion!in!a!setting!ringed!by!
large! strikeDslip! and! reverse! faults! is! nowhere! near! developed! enough! to! ascribe!
certainty!to!median!or!variance!estimates!of!probable!shaking.!
- More!Seismic!Threats!to!Come?:!!Two!future!possible!seismic!threats!remain!unknown!
due!to!data!limitations.!It!is!not!clear!that!the!poorly!imaged!faults!under!the!Irish!Hills!
have!been!properly!identified!in!the!geologic!crossDsections!which!could!mean!a!whole!
new!category!of!undiscovered!threats!may!exist!directly!under!the!plant.!The!quality!of!
the! seismic! data! obtained! onshore! just! under! the! Irish! Hills! is! poor! and! due! to! the!
virtual! absence! of! relevant! geologic! information! from! deep! wells! ! it! is! difficult! to!
differentiate! between! active! and! dormant! faults! in! the! seismic! data.! Whether! or! not!
another!class!of!active!thrust!faults!exist!under!the!plant!remains!an!open!question.!The!
current!data!cannot!be!used!to!rule!out!such!a!possibility!and!the!compressional!nature!
of!the!topography!argues!that!such!faulting!could!be!inferred.!!Additionally,!the!study!
area! used! by! PG&E! does! not! include! the! area! that! connects! the! more! northerly! San!
Simeon!Fault!with!the!San!Gregorio!Fault.!!The!Report!agrees!that!the!Hosgri!Fault!is!
connected! with! the! San! Simeon! Fault,! which! has! caused! the! maximum! possible!
earthquake!to!increase!significantly.!!If!the!San!Gregorio!Fault!to!the!north!is!similarly!
17!
connected!then!the!Report!has!underestimated!the!maximum!earthquake!that!Diablo!
might!need!to!survive.!
- Troubling!History:!!The!utility!has!a!long!and!remarkable!history!of!producing!sanguine!
technical! reports! that! get! the! seismic! hazard! analysis! at! Diablo! exactly! wrong.!!
Whenever!new!data!has!emerged!identifying!possible!new!seismic!threats!the!utility!
has!mobilized!its!internal!and!external!experts!to!sequentially!argue!that!nearby!faults!
simply!didnt!exist,!they!did!exist!but!were!inactive,!they!were!active!but!not!large,!and!
then!that!they!were!large!but!segmented!and!unconnected.!Now!that!the!evidence!about!
the!size!and!location!of!the!faults!is!indisputable!D!the!argument!has!suddenly!changed!
again.! Now! the! utility! declares! that! although! the! faults! are! quite! large,! nearby,! and!
interconnected!the!prior!equations!used!during!the!licensing!process!to!predict!shaking!
should!be!abandoned!and!replaced!with!lessDconservative!methodologies!which!allows!
the!utility!to!claim!that!the!plant!is!safeeven!from!a!M7.3!within!600!meters!of!the!
facility.!One!must!ask,!if!the!utility!has!been!proven!to!be!wrong!so!many!times!in!
the!past!on!so!many!similar!issues!and!given!the!high!stakes!of!mishandling!this!
critical!issue,!should!the!utilitys!new\\found!conclusions!be!relied!upon!without!
the! direct! regulatory! oversight! of! the! NRCs! license! amendment! process?! As!a!
scientist!and!a!policy!maker!I!believe!the!responsible!answer!is!No.!
In!conclusion,!if!the!NRC!were!to!decide!to!rely!upon!the!utilitys!assertion!that!the!facility!
is!operating!in!conformance!with!its!license!based!on!these!new!evolving!lessDconservative!
equations!the!NRC!would!be!allowing!the!HE!exception!to!be!markedly!weakened!by!the!
utility!without!the!third!party!objectivity,!regulatory!safeguards,!and!technical!rigor!of!the!
license! amendment! process.! Such! a! decision! in! the! aftermath! of! the! difficult! lessons! of!
Fukushima! could! come! back! to! haunt! the! NRC,! the! utility,! and! more! importantly! -! the!
public.!!
18!
APPENDIX!
TECHNICAL!CONCERNS!
The!following!are!some!of!the!reasons!I!believe!that!these!lessDconservative!equations!and!
evolving!GMPEs!are!still!very!much!a!work!in!progress,!making!it!premature!to!apply!the!
methodology!to!the!Diablo!Canyon!Nuclear!Power!Plant.!!If!the!only!possible!way!to!prove!
that! the! plant! is! operating! below! the! LTSP/HE! basis! is! through! the! use! of! these! new!
equations!then!a!formal!adjudicated!license!amendment!process,!especially!if!the!LTSP/HE!
exception!is!to!be!relied!upon!in!lieu!of!the!DDE!safety!standard.!!!
CONCERN! #1! -! Methodology! limitations! in! applying! PEER! derived! GMPEs! distanceD attenuation! predications! for! extreme! nearDfield! applications:! ! The! Next! Generation!
Attenuation! models,! which! is! the! basis! for! GMPED3! and! many! of! the! other! subsequent!
GMPEs,!is!derived!from!the!PEER!database!of!some!3,600!recordings.!!The!various!peerD reviewed! and! published! attenuationDdistance! equations! are! based! on! robust! statistical!
bestDfits! to! the! very! large! PEER! dataset.! ! However,! the! proximity! of! the! plant! to! the!
Shoreline!and!the!San!Luis!Bay!Faults!are!only!0.6!km!and!1.9!km.!!Out!of!this!entire!PEER!
dataset!only!a!couple!dozen!recordings!exist!within!2!km!of!the!fault!and!of!those!only!8!
recordings! occur! with! 0.6! km.! ! This! number! of! recordings! is! insufficient! to! create! a!
statistically!significant!estimate!of!ground!motion!in!this!extreme!near\\field!setting.!!Any!
statistical!estimate!of!an!empirical!distanceDattenuation!relationship!in!which!over*99%*of*
the*data!occur!in!a!range!outside!of!the!distance!where!the!relationship!will!be!applied!is!
unreliable!for!determining!a!mean!or!variance!of!shaking.!!!
The!uncertainty!in!the!extreme!nearDfield!estimates!of!ground!motion!using!NGA!GMPEs!is!
not!reduced!through!an!averaging!approach.!!All!of!the!GMPEs!constructed!from!various!
subsets!of!the!PEER!dataset!include!the!same!systematic!under!sampling!of!extreme!nearD field! recordings! and! over! sampling! of! farDfield! earthquakes.! ! Because! this! error! is!
systematic!rather!than!random!the!averaging!process!cannot!be!relied!upon!to!improve!
confidence!of!extreme!nearDfield!shaking!estimates.!!!
The! new! Next! Generation! Attenuation! models! used! for! GMPE\\3! and! the! evenDnewer!
GMPE\\4! both! suffer! from! data! limitations! that! make! them! problematic! for! reliable!
application!to!Diablo.!!Simply!adding!geologic,!site!effect,!and!statistical!correction!factors!
to! the! underlying! NGA! equations! does! not! overcome! the! statistical! problem! inherent! in!
applying!these!equations!in!the!extreme!nearDfield.!
CONCERN#2! -! Methodology! problems! in! PG&Es! siteDspecific! adjustments! to! shaking!
estimates!at!Diablo:!!As!stated!above,!the!Next!Generation!Attenuation!models,!which!is!the!
basis!for!GMPED3!and!GMPED4!is!derived!from!the!PEER!database!of!some!3,600!recordings.!!
The!vast!majority!of!these!recordings!occurred!in!rock!types!that!differed!significantly!from!
the!rocks!types!under!the!Diablo!Canyon!Nuclear!Power!Plant.!!!
The!NRC!pointed!out!in!September!2012!that!there!are,!!
only! 51! recordings! with! sites! defined! with! Vs30>=900! m/s.! ! This! is! less! than!
1.4%!of!the!database.!!There!are!only!15!recordings!with!Vs30>=1,200!m/s!(less!
than!oneDhalf!of!oneDpercent).Hence,!applying!a!Vs30!of!1,200!m/s!directly!in!the!
19!
GMPEs!increases!uncertainty,!as!this!value!is!beyond!the!range!well!constrained!by!
the!observational!data.xi!!!
To!deal!with!this!deficiency!NRC!staff!and!PG&E!began!constructing!a!variety!of!rock!type!
correction!factors!and!singleDsite!correction!factors.!!These!new!adjustments!were!derived!
from!the!utilitys!own!sparse!database.!!!
Such!an!effort!could!be!justified!if!the!proper!dataset!were!available;!however,!the!Diablo!
database!is!inadequate!for!this!purpose.!!Over!the!past!few!years!only!a!handful!of!strongD motion! instruments! at! Diablo! have! recorded! just! two! relevantDsized! earthquakes! (e.g.,!
>=M6.0).!!!These!two!earthquakes!are!the!M6.0!Parkfield!earthquake!at!a!distance!of!85!km!
and!the!M6.5!San!Simeon!earthquake!at!a!distance!of!35!km.!!It!is!simply!not!possible!to!
perform!rigorous!statistical!analysis!on!a!sample!size!of!two.!
What!makes!the!small!size!of!this!dataset!even!more!troubling!is!that!neither!of!these!two!
reference! earthquakes! occurred! to! the! west! or! south! of! the! plant,! which! is! where! the!
Hosgri,!Shoreline,!and!San!Luis!Bay!Faults!are!located.!!Any!siteDspecific!Greens!function2!
derived! from! the! small! amount! of! existing! strong! motion! data! would! not! include!
information!about!how!the!site!responds!to!energy!from!a!large!earthquake!arriving!from!
the!west!or!south.!!!
Wellbore!velocity!profiles!obtained!at!the!site!prove!that!the!underlying!soft!and!hard!rock!
environment!is!neither!homogeneous!nor!layerDcake!1Ddimensional.!!Instead!a!high!degree!
of! 3D! complexity! with! significant! impedance! heterogeneity! is! evident! in! the! geology!
underlying!the!plant.!!Therefore!a!single!azimuthallyDindependent!site!response!will!likely!
fail! to! incorporate! the! 3D! heterogeneity! at! the! site.! ! Any! empirically! calculated! Greens!
function! based! on! limitedDazimuth! data! from! the! north! and! east! will! be! unreliable! in!
predicting!strong!ground!motion!from!the!Hosgri,!Shoreline,!and!San!Luis!Bay!Faults.!!
Finally,!neither!of!these!two!reference!earthquakes!occurred!in!the!near!field.!!A!nearDfield!
earthquake!cannot!be!treated!as!a!virtual!point!source!at!a!fixed!azimuth.!!Instead!a!nearD field! earthquake! must! be! treated! as! a! distributed! source! whose! azimuth! varies! as! the!
rupture!propagates!up!to,!along!side,!and!then!past!the!nuclear!power!plant.!!This!areal!
source!propagates!signal!to!the!recording!site!from!a!range!of!azimuths!and!inclinations,!
potentially! with! different! Greens! functions.! ! Two! relatively! distant! pointDsource! signals,!
Parkfield!and!San!Simeon!earthquakes,!from!the!east!and!north!cannot!be!used!to!infer!the!
shaking!from!a!rupture!on!the!Hosgri!or!Shoreline!Faults!that!actively!propagates!in!the!
nearDfield!past!the!plant,!and/or!stops!directly!adjacent!to!the!plant!to!the!west.!!
Given! the! significant! number! of! large! active! faults! that! surround! the! plant,! a! dangerous!
neighborhood!to!be!sure,!it!is!imprudent!to!base!the!safety!of!the!plant!and!the!community!
solely!upon!reliance!on!site!effects!derived!from!this!small!dataset.!!!
Future!possible!research!designed!to!create!a!numerically!simulated!3D!site!effect!(which!is!
reportedly!underway!and!will!become!GMPE\\5)!to!get!around!the!deficiencies!of!both!the!
2 Greens Function: A mathematical term of art defining a system response to an impulse signal which can be used to describe, through convolution and superposition, a systems response to a more complex signal
20!
empirical!data!sets!identified!above,!would!face!significant!challenges.!!Accurate!numerical!
elastic! waveDequation! simulation! of! a! siteDspecific! Greens! function! would! require! a! 3DD!
velocity! and! impedance! structure! below! and! around! the! facility! that! extends! to!
considerable!depth,!includes!surficial!topographic!features,!and!accounts!for!accurate!PDS!
and! SDP! and! surfaceDwave! conversions! calculations,! complex! ray! bending,! critical!
refracting,!scattering!and!focusing!effects.!!To!construct!such!a!simulation!would!require!
higherDresolution!and!deeper!data!than!is!currently!available!from!the!wellbore!or!nearD surface!tomographic!information.!!!
If!somehow!such!difficulties!could!be!overcome,!the!numerically!simulated!site!response!
would!still!need!to!be!tested!to!determine!how!well!it!predicted!the!shaking!generated!by!
an!actual!earthquake!>=M6.0!impinging!on!the!site!from!the!west!and!originating!in!the!
nearDfield.!!A!prediction!without!a!test!to!assess!the!accuracy!of!the!prediction!would!be!
insufficient!for!regulatory!purposes.!
CONCERN! #3! -! Methodology! problems! in! estimating! shaking! caused! by! an! earthquake!
located!in!the!extreme!near!field:!!This!issue!is!different!from!the!statistical!issue!regarding!
the!paucity!of!data!available!in!the!nearDfield!recordings!or!the!lack!of!data!for!the!rockD types! in! question! D! which! were! covered! under! concerns! #1! and! #2,! respectively.! ! At!
progressively!greater!distances!from!an!earthquake!the!particulars!of!the!dynamic!rupture!
process!becomes!less!important!relative!to!the!larger!effects!of!total!energy!release!and!
energy!attenuation!during!transmission.!!However,!in!the!extreme!near!field!the!location!of!
a! recording! station! relative! to! an! earthquakes! rupture! history,! asperity! locations,!
heterogeneous! stress! drops,! and! starting! and! stopping! phases,! directivity,! and! a! host! of!
other!effects!become!very!important!-!in!some!cases!the!largest!effect!under!consideration.!!
Due!to!the!location!of!the!Shoreline,!Los!Osos,!and!San!Luis!Bay,!and!Hosgri!Faults!these!
effects! would! likely! be! significant.! ! As! more! extreme! nearDfield! recordings! have! been!
obtained,! although! still! relatively! few! in! number,! it! has! become! clear! that! a! simple!
estimation!of!an!earthquakes!magnitude!and!distance!from!a!site!may!be!insufficient!to!
make!precise!estimates!of!shaking.!!!
For!example,!in!2004,!48!strongDmotion!recordings!within!10!km!of!the!San!Andreas!Fault!
were!made!of!the!M6.0!Parkfield!earthquakexii.!!This!dataset!was!used!to!test!three!different!
attenuationDdistance! equations.! ! These! equations! are! shown! to! do! a! good! job! of! making!
accurate!predictions!for!distances!beyond!about!10!km,!but!the!observed!shaking!becomes!
highly!variable!in!close!proximity!to!the!fault.!!Rather!than!finding!accurate!predictions!of!
mean!shaking!in!the!extreme!nearDfield!the!paper!notes,!!
Peak!ground!acceleration!in!the!nearDfault!region!ranges!from!0.13!g!at!Fault!Zone!
4,!to!1.31!g!at!Fault!Zone!14,!ten!times!larger,!to!over!2.5!g!at!Fault!Zone!16!(where!
the!motion!exceeded!the!instrument!capacity!and!the!actual!maximum!value!is!still!
being!estimated).!
21!
Figure*3:*Shakal*et.*al.,*2004*showing*remarkably*high*and*low*accelerations*in*the*
extreme*nearEfield*(rupture*started*where*the*star*is*shown*and*then*propagated*to*
the*northEeast*and*southEwest*where*they*stopped)*
The!dense!strongDmotion!Parkfield!recordings!are!relevant!to!the!conclusions!of!the!Report!
for!a!number!of!reasons.!!!
- First,!these!extreme!nearDfield!areas!of!high!and!low!acceleration!are!not!well!predicted!
by!a!distantDdependent!GMPE!estimate!of!shaking.!!!In!this!extreme!nearDfield!setting!
the!particulars!of!how!ruptures!start!and!stop,!the!direction!the!rupture!propagates,!the!
potential! focusing! effect! of! the! velocity! structure! of! the! fault! zone,! the! locations! of!
specific!asperities!become!major!factors!that!affect!ground!motion.!!These!factors!are!
not! included! in! the! current! generation! of! GMPEs,! which! were! never! intended! to!
describe! these! complex! phenomena! that! are! significant! effects! principally! in! the!
extreme!nearDfield.!
- Second,!the!Parkfield!data!shows!that!the!high!degree!of!variability!in!the!extreme!nearD field!is!not!a!spatially!random!phenomenon.!Instead!the!highest!levels!of!acceleration!
are! systematically! found! near! the! ends! of! the! fault! where! stopping! phases! radiated!
22!
energy! during! the! rupture! process! of! this! specific! earthquake.! ! If! the! nuclear! power!
plant! happens! to! be! located! in! a! zone! of! focused! seismic! energy! the! 84th! percentile!
estimate!from!the!GMPE!estimate!will!likely!underestimate!the!observed!shaking.!
- Third,!PG&E!has!argued!in!the!Report!that!while!an!earthquake!on!100!km!of!the!Hosgri!
Fault!could!jump!to!the!43!km!of!the!Shoreline!Fault!creating!a!143!km!rupture,!the!
likelihood! of! such! an! event! is! purportedly! low.! ! They! contend! that! a! northDtoDsouth!
Hosgri! rupture! that! jumped! to! the! Shoreline! would! terminate! due! to! bending! and!
segmentation!before!rupturing!the!full!length!of!the!Shoreline!Fault.!!If!PG&E!is!right!in!
this!assertion!they!would!be!correct!to!reduce!the!component!of!shaking!that!is!derived!
from!the!size!of!the!earthquake.!!But!they!would!then!need!to!account!for!the!markedly!
higher! accelerations! produced! by! stopping! phases! that! would! radiate! from! the!
segments! and! asperities! associated! with! terminating! the! rupture! near! the! facility.!!
Given! the! high! accelerations! observed! in! the! Parkfield! dataset,! an! earthquake! that!
propagates! the! 100! km! length! of! the! Hosgri! and! only! 20! km! of! the! Shoreline! but!
violently! stops! directly! adjacent! to! the! nuclear! power! plant! could! in! fact! be! more!
dangerous!than!a!scenario!involving!the!full!145!km!of!propagation!
There!are!a!few!ways!to!demonstrate!the!significant!influence!of!these!new!equations.!!One!
obvious!demonstration!is!to!review!the!reduction!in!estimated!shaking!from!an!earthquake!
on! the! Hosgri! Fault! relative! to! PG&Es! earlier! estimates! when! creating! the! HE/LTSP!
spectrum.!
23!
(Figure*7a*from*IPRP*Report)*
As! seen! in! Figure! 7a! from! the! Independent! Peer! Review! Panel! (IPRP)! report! and! in! a!
number! of! other! related! reports,! the! new! lessDconservative! equations! cause! a! major!
reduction! in! shaking! across! the! entirety! of! the! frequency! spectrum! from! a! hypothetical!
earthquake!on!the!Hosgri!fault!(compare!blue!lines!which!use!the!newly!devised!methods!
with!black!lines!which!use!the!prior!methods,!in!figure!7a!above).!!In!the!frequency!range!
from! 2D10! Hz! the! lessDconservative! methodologies! have! cut! the! maximum! estimated!
acceleration!from!2!g!down!to!about!1.3!g.!!At!the!peakDfrequency!range,!from!30D100!hz,!
the!maximum!estimated!acceleration!as!been!reduced!by!a!third!from!.75!g!to!under!.50!g.!!
In!fact!the!deDamplification!effect!is!even!larger!than!this!comparison!suggests!because!the!
blue! lines,! which! represent! the! shaking! on! the! reDinterpreted! Hosgri,! assume! a! larger!
rupture!on!the!Hosgri!Fault!than!the!earthquake!that!was!used!to!initially!create!the!1977!
HE!basis!exception.!!!
More!importantly,!as!can!be!seen!in!Figure!7a!the!shaking!from!the!Los!Osos,!Shoreline,!San!
Luis!Bay!Faults!all!exceed!the!reDinterpreted!Hosgri!(red,!yellow,!green!lines!are!all!above!
the!blue!line).!!One!can!reasonably!conclude!that,!if!the!original!analytical!methods!
had!been!used!to!estimate!ground!motion,!the!new!seismic!threats!would!exceed!the!
original!HE!and!LTSP!spectra.!
This!conclusion!is!supported!by!the!sensitivity!analysis!shown!in!Figures!7b!and!7c,!which!
test!the!importance!of!various!parameters!to!the!new!GMPE!and!site!effects.!!The!same!
IPRP!report!cited!previously!states,!!
These!two!figures!also!show!that!if!DCPP!site!had!a!Vs30!value!of!760!m/s!rather!
than!1,200!m/s,!and!if!the!site!behaves!more!like!an!average!site!in!ground!motion!
amplification,! some! deterministic! spectra! would! exceed! the! 1991! LTSP!
spectrumxiii!(figure!7c!below).!!!
In!fact,!it!is!more!than!just!some.!!Under!the!scenario!shown!in!Figure!7c!the!IPRP!shows!
that!the!LTSP/HE!spectrum!is!exceeded!by!all!of!the!newly!discovered!and!reDinterpreted!
seismic!threats,!including!earthquakes!on!the!Shoreline!Fault,!the!Los!Osos!Fault,!and!the!
San!Luis!Bay!Fault!(note!that!the!red,!yellow,!and!green!lines!are!all!above!the!solid!black!
line).!!The!fourth!and!largest!hypothetical!earthquake!scenario,!a!M7.3!rupture!on!a!joint!
Hosgri/Shoreline! Fault,! is! not! shown! on! this! figure! but! could! reasonably! be! assumed! to!
exceed!the!LTSP/HE!as!well.!
24!
(Figure*7c.*from*IPRP*Report)*
This! sensitivity! analysis! shows! that! the! cumulative! effect! of! lessDconservative! fast! rock!
velocities!along!with!lessDconservative!GMPEs!is!clearly!not!a!small!issue,!nor!is!it!a!only!an!
academic!issue.!!The!IPRP!reviewed!the!limited!wellbore!data!(see!IPRP!Report!6!Figure!4)!
and!concluded!that!the!wellbore!velocities!appeared!to!be!lower!than!those!estimated!by!
PG&E,!which!could!result!in!the!conclusion!that!PG&E!has!underestimated!shaking!from!
new!seismic!threats!even!if!the!new!equations!are!allowed.!!The!IPRP!challenged!PG&Es!
use!of!wellbore!data!at!the!ISFSI!site!to!justify!the!higher!1,200!m/s!velocity!and!instead!
focused!on!the!velocities!measured!in!the!wellbore!data!closest!to!the!facility.!
!Specifically,!IPRP!Report!#6!says,!!
Consider!the!three!usable!measured!profiles,!AD2,!C,!and!D,!the!mean!value!at!10!m!
is!approximately!800m/s,!considerably!below!PG&Es!mean!of!1200m/s.!and!If!AD 2! had! the! same! velocity! as! C! at! a! depth! of! 5m,! consistent! with! the! relative!
weathering!described!in!the!borehole!logs,!the!mean!velocity!at!that!depth!would!be!
about!650m/s,!also!below!PG&Es!mean!value!of!1000m/s.!
25!
This!appendix!does!not!seek!to!weigh!in!on!the!question!of!which!velocities!are!appropriate!
to!use!when!computing!site!effects!at!Diablo.!!Instead,!these!stated!concerns!are!intended!to!
demonstrate!that:!!
First,!the!deDamplification!effects!of!moving!from!GMPED1!to!GMPED4!are!very!large!
and!likely!determinative!of!whether!or!not!the!new!seismic!threats!would!produce!
shaking!above!the!HE!exception;!and!!
Second,!even!if!one!were!to!accept!the!use!of!GMPED4,!which!is!problematic!for!the!
reasons! previously! stated,! the! critically! important! rock! velocities! upon! which! the!
deDamplification!factors!are!based!are!complex,!in!dispute,!and!arguably!lower!than!
those!used!by!PG&E,!which!would!mean!that!shaking!would!be!significantly!larger!
than!stated!in!the!Report.!!Indeed,!a!conservative!approach!toward!this!technical!
question!would!have!used!of!the!lowest!velocities!found!in!the!well!data!rather!than!
the!highest.!
26!
i!Peck!Differing!Professional!Opinion!-!Diablo!Canyon!Seismic!Issues!
ii!Opinion!of!Commissioners!Gilinsky!and!Bradford!on!Commission!Review!of!ALABD644!
(Diablo!Canyon!Proceeding,!Dockets!50D275!OL!and!50D323!OL)!
iii!Safety!Evaluation!Report!related!to!the!operation!of!Diablo!Canyon!Nuclear!Power!Plant,!
Units!1!and!2.!Docket!Nos.!50D275!and!50D323;!NUREGD0675,!Supplement!No.!34!
iv!PG&E!submitted!to!the!NRC!Report!on!the!Analysis!of!the!Shoreline!Fault,!Central!Coast!
California,!January,!7,!2011,!ML!110140400!
v!Oct!12,!2012!NRC!letter!from!Joseph!M.!Sebrosky,!Senior!Project!Manager!to!Mr.!Edward!
D.!Halpin,!Senior!Vice!President!and!Chief!Nuclear!Officer!PG&E;!
Subject:
!Diablo!Canyon!
Power!Plant,!Units!Nos.!1!and!2!-!NRC!Review!of!Shoreline!Fault!
vi!Office!of!the!Inspector!General!US!NRC:!NRC!Oversight!of!Licensees!Use!of!10!CFR!50.59!
Process!to!Replace!SONGS!Steam!Generators!Case!No.!13D006!
vii!Research!Information!Letter!09D001:!Preliminary!Deterministic!Analysis!of!Seismic!
Hazard!at!Diablo!Canyon!Nuclear!Power!Plant!from!Newly!Identified!Shoreline!Fault.!
Pages!8D10.!
viii!U.S.!Nuclear!Regulatory!Commission,!2012.!!Confirmatory!Analysis!of!Seismic!hazard!at!
the!Diablo!Canyon!Power!Plant!from!the!Shoreline!Fault,!Research!Information!Letter.!
x!Oct!12,!2012!NRC!letter!from!Joseph!M.!Sebrosky,!Senior!Project!Manager!to!Mr.!Edward!
D.!Halpin,!Senior!Vice!President!and!Chief!Nuclear!Officer!PG&E;!
Subject:
!Diablo!Canyon!
Power!Plant,!Units!Nos.!1!and!2!-!NRC!Review!of!Shoreline!Fault!
xi!NRC!Research!Information!Letter!12D01,!page!56!(September!2012)!
xii!Shakal,!A.,!Grazier,!V.,!Huang,!M.,!Borcherdt,!R.,!Haddadi,!H.,!Lin,!K.,!Stephens,!C.,!and!
Roffers,!P.:!Preliminary!Analysis!of!StrongDMotion!Recordings!from!28!September!2004!
Parkfield,!California!Earthquake.!Submitted!to!SRL!November!5,!2004!
xiii!IPRP!Report!No.!6,!August!12,!2013!