U.SO.NRCUNiTED STA'rS NUCLEAR RMULATOM COMMISSON

Protecting People and the Envirný t

Briefing on NRC ActivitiesRelated-to the RecentJapanese Earthquake

Mary Jane Ross-Lee, Branch ChiefOperating Experience Branch

Division of Inspection and Regional SupportOffice of Nuclear Reactor Regulation

July 26, 2007

Agenda

* Key PointsEarthquake Description & Impact onJapanese Nuclear Power Plant

* United States Seismic Design for Existingand Future Nuclear Power Plants

* Lessons Learned

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Key Points

• All units at the Japanese nuclear powerplant nearest to -the earthquake shut down,and nuclear safety was not compromised.

* US plants are designed for postulatedseismic activity at each plant's specificlocation.

• NRC has established process for utilizinglessons learned from events.

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Earthquake Description

* Niigata Earthquake occurred on July 16,at 10:13 AM local time.

* Magnitude of the earthquake was 6.6.

2007

° Earthquake occurred at a depth of 1beneath the surface.

0 km

o Earthquake epicenter was about 8-10 km fromthe Kashiwazaki-Kariwa Nuclear Power Plant.

o Earthquake caused a reported 11 fatalities,multiple injuries, collapsed houses, crackedhighways.

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Kashiwazaki-Kariwa Nuclear PowerPlant Description

* World's largest nuclear power plant interms of power output capacity.

.7- Unit plant producing 8,210 MW (PaloVerde, the largest US plant, has anoutput capacity of 3,880 MW).

* Units 3, 4, and 7 operating before event.

* Unit.2 was starting up.

e Units 1'5' and 6 were shut down.

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July 26, 2007

Location of Earthquake & Plant

Source: International Herald Tribune

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Impact on Kashiwazaki-Kariwa

* Operating units automatically shut down.* Transformer fire outside Unit 3.° Small liquid and gaseous radiological

releases.

* Drums of low level solid radioactivewaste fell over.

• Minor damage to other plant equipment.

* Seven workers suffered minor injuries.

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Auxiliary Transformer Fire

Fire occurred in Unit 3 " •auxiliary transformer. ..

* Fire was extinguishedapproximately two.. hoursafter earthquake.

* Fire had no impact. on.radiological safety and noimpact to the public.

(Source: Associated Press)

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Liquid Radiological Release

* Small puddles of water found with minoramounts of~rad.ioactivity.

* Radioactive water had leaked throughpenetrations to discharge sump.

* Approximately 317 gallons of waterdischarged into Sea of Japan.

S"Total amount of radioactivity of dischargedwater was very low (estimated .dose topublic significantly less than 1 millionth ofannual limit).,

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Liquid Radiological Release Flowpath

The 1st basement floor

Discharge canal

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Radiological Gas & Particulate Release

• Radioactive iodine and other radioactiveParticulate matter found at the Unit 7ventilation stack.

* The total amount of radioactivity releasedwas estimated to be very low (estimateddose to public less than 1 millionth ofannual limit).

• No radioactivity found at otherrunits' stacks.

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Low Level Waste Drums

• Waste drums were stackedin solid radwaste storagewarehouse.,

* Over 100 low level solidwaste (e.g., rags, tools,gloves, supplies):drumsknocked over during event.

° Several found with lids off.• No- measured release of

radiation and no impact topublic.

July 26, 2007 Source: Nuclear and Industrial'Safety Agency 12

US Reactor Seismic Design

* Existing US reactors are robustlydesigned to withstand site-specificearthquakes such that systems and

,.structures necessary.for nuclear safetywill remain functional.

* US plants are designed for an earthquakethat is not likely to occur more than onceevery 10,000 years.

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US Reactor Seismic Design,,

• Only 2 US nuclear power plants withactive faults located nearby. Both willautomatically shut down during a seismicevent above a specified limit.

* Plants in the US, which are located inareas& of considerably less seismic activitythan California, have seismic instrumentsinstalled and requirements forý manualshutdown at specified levels.

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NRC Seismic Activities

* NRC focused on seismic safety since 1970s:- Seismic Safety Margins Research Program

Implemented lessons learned from earthquakeexperience at non-nuclear facilities.

- Implemented plant walk-downs and ensuredanchorages were adequate for various structures.

- Assessed the ability of plant equipment to withstandaccidents beyond the plant's design and concludedthere were large margins of safety.

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New Reactor Seismic Design in US

SN RC recently issued new seismicguidance for new reactors.

• This guidance incorporatescomprehensive, state of the art scientificmethods.

o NRC reviews new reactor applications toverify that the latest earthquake hazardinformation has been considered for eachsite.

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Lessor

* NRC will continue toinformation related t(

* NRC will evaluate thidentify any actionsimplemented at ope

* Lessons learned frorchiange to regulationguides or generic coto inspection p rograr

* IAEA and USGS ha\review data related tthis additional data tb

is Learned

collect and evaluate) this event.e lessons learned tolecessary to be-ating and future reactors.n data could lead tos, issuance of regulatorymmunicat.ions, or changens, for example.fe sent teams to Japan too event. NRC will utilize

enhance our programs.

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July 26, 2007

Differences. Between NRC &Japanese Seismic Requirements

NRC JapaneseGDC #2: "shall reflect: (1)Appropriate consideration of themost severe of the naturalphenomena that have beenhistorically reported for the siteand surrounding area, withsufficient margin for thle limitedaccuracy, quantity, and period oftime .in which the historical datahave been accumulated, (2).appropriate combinations of theeffects of normal and accidentconditions with the effects of thenatural phenomena and (3) theimportance of the safety functionsto be performed"

"the maximum design earthquakethat would have the greatest effecton the proposed site based onengineering judge following aseismological review.of pastearthquakes, the nature of anyactive faults and the- seismo-tectonic structure underlying thesite and the surrounding region"

Differences Between NRC &Japanese Seismic Requirements

Appendix A, "Seismic and GeologicSiting Criteria for Nuclear Power.Plants," describes the nature ofinvestigations required to obtainthe geologic and seismic datanecessary to determine sitesuitability and to providereasonable. assurance that anuclear power plant can beconstructed and operated at aproposed site without undue riskto the health and safety of thepublic. It describes procedures fordetermining the quantitativevibratory ground motion designbasis at a site due to earthquakesand describes information neededto .determine whether and to whatextent a nuclear power plant needbe designed to withstand theeffects of surface faulting.

In determining the design basi'searthquake ground motions, fullconsideration shall be given to thefollowing items:

(i) The magnitude, epicenter, hypocenter,aftershock area and maximumintensity of earthquake ground motion(or estimated value), and resultantdamage (including destruction rate ofstructures, overturning of tombstones,etc.) in earthquakes that have affectedthe site and the surrounding region inthe past.

ii) The statistical expectation of theintensity of the past destructiveearthquake ground motions.

(iii) The magnitude of the earthquake andthe distance between the site and itscenter of energy release.

(iv) Past observation records for thegeneral region as well as those forthe site, including any results of.bedrock property investigations.

Differences Between NRC &Japanese Seismic Requirements

* Safety-related SSCs are SeismicCategory I

• Requires dynamic analysis• Equipment qualification by analysis or

tests

* Safety classes A, B and Ci•(.E)ýýaiC ea rthq-k---re-.

' . (i) Buidlingsand-structuresJSHorizontal seismic forces shall be--,

•/ determined by multiplying the weight at{ "Cthe height and above by the followingstoA shear coefficient correspondingto thedý'jmportance of the facility.

* Class A story shear coefficient 3.OCIX

• •Class B story shear coefficient 1.5CI*Class C storyh~ear coefficient I .OCI

* •Here, CI of the stoQry shearcoefficient shall beM0.2 in thestandard case, and sihall be fixedconsidering the vibrat\"io >

/ characteristics of buildings andstructures, the category of the p '

g~roundq, and so on.

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Differences Between NRC &Japanese Seismic Requirements

Ground motion generallyapplied at the foundationlevel.

Soil-structure interactioneffects considered

Damping values based onRG 1.61

The design earthquakeground motions forseismic design of reactorfacilities shall be derivedfrom the earthquakemotions at the freesurface of the basestratum in the proposedsite.

Founded on bed rock, usedfixed base analysis

Damping values forstructures lower thanNRC

Diffe rences BEJapanese Seisr

• SEP reviews and plantupgrades

* IPEEE seismic marginsand anchorage upgrades

* PSHA implemented inPart 100.23 & RG 1.165

• Performance-based

tween NRC andnic Requirements

* New seismic criteriacloser to NRC approachbut not back fitted toexisting plants

- Use of PSHA

Higher (0.4g) minimumPGA for earthquakes nottied to faults

* Seismic scramseismic demand, RG1.208

* Seismic scram only inhigh seismicity areas

* a

Seismic Events and Experience

• Off-shore fault wasinvestigated at DiabloCanyon and plant wasbackfitted.

Humboldt Bay and GE testreactors shut down due toseismic hazard

* 2003 San Simeonrecorded at DiabloCanyon.

* Japan will investigate off-shore faults nearKashiwazaki- Seismic scram worked- Safety systems worked- Soil liquefaction at ground

Radioactive airductconnections at stacksseparated at all units7 out of 67 instruments atplant site workedDownhole records showdeamplification throughoverburden

..US-Japan Seismic CriteriaOverall View

Basic comparisons are very high level. Differences in the end resultsdepend on:

Actual design, other loads and load combinations used,differences in analytical procedures, construction procedures,codes and standards and as-built margins

- A simple top level comparisons of seismic criteria cannot give usa comprehensive picture

* For new plants we require explicit seismic margins* Fundamental approaches to seismic resistant design in both

countries are similar, but vary in details.* Designs resulting from criteria in both countries produce seismically

robust plants.* Our assessments are analytical, but Japan had a real test and came

through safely..

General Post-earthquake Shutdown Actions at Nuclear PlantsI-

" Each licensee has seismic instrumentati,with or meet the intent of RG 1.12 (1974,"Nuclear Plant Instrumentation for Earthearthquake response plan and procedur1.166 (1997) "Pre-Earthquake Planning aOperator Post Earthquake Actions" whic6695 (1989) "Guidelines for Nuclear Plan

" The threshold for a plant shutdown decibasis earthquake (OBE) ground motion cOBE is a fraction of the design basis earreactors, and one-third to one-half for ne

" A seismic instrumentation panel board i.alarm is annunciated in the Control Roofrecorded by the strong motion (> 0.01g)second alarm is annunciated later if theexceedance of the OBE.

* The earthquake response plan consistsinspections and tests, and long-term evo

n program at the site in accordance1997, previously Safety Guide 12)quakes". Each licensee also has ann-s in place that meet the intent of RGnd Immediate Nuclear Power Plant*h endorses (with exceptions) EPRI NP-t Response to an Earthquake."

;ion is exceedance of the operatingor significant plant damage occurs. Thethquake (one-half for operatingw reactors).

; located in the Control Room. An,n to indicate a seismic event is being•ccelerographs. In many plants, avent analysis software indicates

)f short-term actions, post-shutdownluations.

Short-Term Actions: Enable rapid determination of severity of earthquake anddecision with regard to readiness of the plant for continued operation or the needfor shutdown.

" Immediate operator actions to maintain plant in safe condition

" Operator walk-down inspections to identify any significant damage (~ within 8hours of event)

" Evaluate ground motion data recorded by on-site seismic instrumentation todetermine if OBE has been exceeded (Response Spectra check & CumulativeAbsolute Velocity check): - within 4 hours of the event

" Bases for shutdown decision - OBE exceedance, damage, continued operation

" Pre-shutdown inspections - confirm plant's readiness to shutdown

e Normal plant shutdown after capability is verified

Question: How are nuclear power plants (both existing and new ones in thefuture) in the U.S. designed to withstand earthquakes?

* US Nuclear Power Plants are robustly designed to withstand site-specificdesign basis earthquakes such that nuclear safety-related structures, systemsand components will remain functional without undue risk to public health andsafety.

e The site-specific design basis earthquakes for US nuclear plants have aprobability of exceedance of the order of once in 10,000 years.

* The site-specific design basis earthquake ground motion represents theconservative maximum earthquake potential for the site and is rationallydetermined based on considerations of regional and local geology, seismology,historical record of all earthquakes reported for the region and inherentuncertainties.

* The magnitudes of postulated strong earthquakes in western US (7 to 8) aresignificantly higher than those in central and eastern US (5 to low 6). Japan isamong the' most earthquake prone nations in the world and earthquakes of themagnitude of the recent Japan earthquake are not envisioned to be experiencedat nuclear plant sites in the central and eastern US.

* In the 1990s, the NRC conducted an assessment of severe accidentvulnerabilities of plant components beyond design basis earthquake fOr eachoperating reactor. The conclusion was that substantial seismic design capacityexists for safety-related components beyond the postulated seismic designdemand.

Question: What are the lessons learned from the recent earthquake inJapan and it's impact at the Kashiwazaki plant?

e Fact: The ground motion recorded at the Kashiwazaki nuclear plant from therecent Japan earthquake exceeded the design basis of the reactors.

* Fact: The plant successfully withstood the earthquake as designed withoutcompromising reactor and public safety, which indicates a conservative design.

* Lesson Learned: US nuclear power plants are conservatively designed forearthquake events based on site-specific maximum credible earthquakes.These plants are expected to perform as designed during a credible seismicevent with reasonable assurance that there will not be undue risk to reactor andpublic safety.