ML14182A103

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July 1, 2014 NRC Slides for Public Meeting with TVA - NTTF 2.1 - Seismic Reevaluation - GMRS
ML14182A103
Person / Time
Site: Watts Bar Tennessee Valley Authority icon.png
Issue date: 07/01/2014
From:
Japan Lessons-Learned Division
To:
Tennessee Valley Authority
Balazik M F, NRR/JLD, 415-2856
References
Download: ML14182A103 (26)


Text

NearTermTaskForce Near-Term Task Force Recommendation 2.1 Seismic Hazard Evaluation EvaluationTennesseeValley Authority Tennessee Valley Authority July 1, 2014 References for Meeting*Licensee Presentation Slides -ML14182A099*NRC Presentation Slides -ML14182A103PbliMtiAd ML14167A164

  • P u bli c M ee ti ng A gen d a -ML14167A164*Meeting Feedback Form (request from mfb@nrc.gov)
  • May 9, 2014, NRC letter regarding Seismic Screening dPiititiRltftldtUS an d P r i or iti za ti on R esu lt s for cen t ra l an d eas t ern US Licensees(ML14111A147)*May 21, 2014, NRC memo providing preliminary staff groundmotionresponsespectraforcentraland ground motion response spectra for central and eastern Licensees(ML14136A126)*Meeting Summary to be issued within 30-day Meeting Introduction Purpose: support information exchange and begin dialog to havecommonunderstandingofthecausesoftheprimary have common understanding of the causes of the primary differences between the preliminary NRC and licensee

seismic hazard resultsBkdNRCdliiihdi B ac k groun d: NRC an d licensee se i sm i c h azar d requ i re resolution to support a final seismic screening decision and to support related follow-on submittals Outcomes: *Begin NRC and licensee resolution to support regulatory decisionsanddevelopmentofseismicriskevaluations decisions and development of seismic risk evaluations , as appropriate*Establish resolution path, including timelines and identificationofpotentialinformationneeds identification of potential information needs Look-ahead:

Potential Next Steps

  • NRCwillconsiderthemeetinginformation NRC will consider the meeting information*Potential paths:

-Licenseesubmitssupplementalinformation Licensee submits supplemental information based on public meeting dialog

-NRC staff issues a re q uest for information q-Licensee sends a revision or supplement to the seismic hazard report*NRC completes screening review and issues the final screening determination ltt l e tt e r WattsBarNuclearPlant Watts Bar Nuclear Plant Rasool Anooshehpoor Office of ResearchJuly1,2014 July 1, 2014

Screening Gl G eo l ogy*The site is located in the Tennessee section of Valley andRidgeProvinceoftheAppalachianhighlands and Ridge Province of the Appalachian highlands.*In Tennessee, the Rome Formation and Conasauga, Knox and Chickamugagroups make up the majority of bdk b e d roc k.*Sedimentary rocks from Pennsylvanian to Cambrian a g e, predominant with those of Cambrian and gp Ordovician age.*Folds involving stratified Paleozoic rocks with great differencesinhardnessdifferences in hardness.*At Watts Bar the bedrock is 2000ft thick Middle Cambrian ConasaugaGroup (alternating shale and limestone) limestone)

.

Site Geology

~706 ft Control Point at 664 ft Control Point NRC Submittal SSE Control Point at elevation 664 ft.

SSE Control Point at elevation 664 ft.

V s Profile Development NRCCtilitt SubmittalShlitibd C on tinuous ve l oc it y measuremen t s at 7 boreholes in FSAR at the top 100 ftwere used to develop the V s p rofile. Shear wave ve l oc ities were b ase d on SASW and Birdwell velocity measurements (AMEC, 2013).

p V median=5704 ft/s, ln=0.134Thisisingeneralagreementwith This is in general agreement with the General Atomics (1974)

estimates.

Figure 2.5-70, FSAR (reproduced)

Shear wave velocity data from seven boreholes (FSAR)

V s Profiles Aleatory Uncertainty in V s Profiles NRC Submittal NRC30 Randomizations Using USGS "A" Site Conditions Submittal30 Randomizations Using USGS "A" Site Conditions ln= 0.25 Upper 50 ft.ln=0.15Below50ft.ln= 0.25 Upper 50 ft.ln=0.15Below50ft.ln 0.15 Below 50 ft.ln 0.15 Below 50 ft.

Epistemic Uncertainty in V s ProfilesNRCSubmittalApplied a scale factors of 1.14 to the base case profile at the Applied a scale factor of 1.25 to the base case p rofile for ptop 100 ft, and 1.31 from 100 ft to 1000 ft(Reference rock) pdevelopment of the upper and lower case profiles Watts Bar ComparisonSSE Control PointDe pth to VS-referenceNon-Linear/Dam p in g p pgLicenseeNRC StaffLicenseeNRC StaffLicenseeNRC StaffAt the base of the reactor foundationAt the base of

the reactor foundation1)592 ft 2)936 ft~1000 ftEPRI-Rock or Linear (low-strain EPRI-Linear, no damping foundation (el. 664 ft) foundation (el. 664 ft) strain EPRI Rock damping)NRCkappa,withonelayer(1000 ft)overref.rock Licensee kappa ProfilekappaBase0.0070.0100.016 Lower 0.0070.011 0.018 NRC kappa, with one layer (1000 ft) over ref. rock ProfileTotal kappa Upper500ft Balanc e P10.0120.0050.0065 Lower 0.0070.011 0.018Upper0.0060.0100.016 P20.012*1.680.0070.0144 P30.012/1.680.0040.0060 P40.0130.0050.0083 P50013*168000700168 P5 0.013*1.68 0.007 0.0168 P60.013/1.680.0040.0060Epistemic Uncertainty = 1.68

Primary DifferencesVelocity profiles:TVA used two sets of 3-velocity profiles. The reference rock depthisat592 ftinonecaseand936 ftintheother depth is at 592 ft in one case and 936 ft in the other.NRC used three velocity profiles and depth of 1000 ftto reference rock.Low strain damping: TVAused~3%dampingintheupper500ft.NRCusedkappa TVA used 3% damping in the upper 500 ft. NRC used kappa in the upper 1000ft to account for dampingTVA used a factor of 1.68 about P1 and P4 total kappasto accountforepistemicuncertainty.

account for epistemic uncertainty.

NRC calculated kappa for each of three profiles separately.

Epistemic Uncertainty in Shear Modulus and Damping Sensitivity Test Curves NRC Submittal M1EPRI Rock: 0 -500 ft M1EPRI Rock: 0 -500 ft M2 Linear &EPRI Rock Damping (~3%): 0 -500 ft M2Linear&EPRI Rock Damping (~3%): 0 -500 ftReference Rock at 1000 ftbelow control point. Reference Rock at 592 ftand 936 ftbelow control point for P1 and P4 fil Depth Randomization, ln=0.2 pro fil es.Depth Randomization, ln=0.2 Kappa and Epistemic Uncertainty NRCKappawascalculatedforeachbasecase SubmittalKappacalculatedforvelocityprofilesP1P2 Kappa was calculated for each base case profile.Kappa calculated for velocity profiles P1 , P2 , P3, P4, P5, and P6. Range of these kappas do not reflect epistemic uncertainty.

Profile kappaProfilekappa kappa (modified)

P10.0120.012 P2 0.013 0.020 (0.012 x1.68

)Profile kappa BaseCase 0.014 LBC 0.015 ()P30.011 0.007(0.012 ÷1.68)

P40.0130.013 P5 0.015 0.022(0.013 x1.68)

UBC 0.012 P6 0.012 0.008(0.013 ÷1.67)

AlifitiFti A mp lifi ca ti on F unc ti onsRock PGA = 0.3 g Comparison of Total Mean Soil Hazard by Spectral Frequency GMRS Comparison Primary Differences in Sensitivity TestVelocity profiles:TVA used two sets of 3-velocity profiles. The reference rock depthisat592 ftinonecaseand936 ftintheother depth is at 592 ft in one case and 936 ft in the other.NRC used three velocity profiles and depth of 1000 ftto reference rock.Low strain damping: BothTVAandNRCused

~3%dampingintheupper500ft.

Both TVA and NRC used 3% damping in the upper 500 ft. TVA used a factor of 1.68 about P1 and P4 total kappasto account for epistemic uncertainty. NRCcalculatedkappaforeachofthreeprofilesseparatelyNRC calculated kappa for each of three profiles separately.

Conclusions*GMRS are simila r*Watts Bar screens in for risk evaluation*Control Point hazard curves similar at 10 HzandPGA,differat1Hz Hz and PGA, differ at 1 Hz-Due to different assumptions of depth to bedrock *Need additional information to support licenseeassumptionfordepthtobedrock licensee assumption for depth to bedrock Browns Ferry Nuclear Power PlantiliIPEEE Screen ing Eva luat i on W ea kn esses i de n t ifi ed in IPEEE S ER/TEReaessesdetedS/

  • Only low power injection systems selected

-Did not include hi g h pressure s ystems (HPCI/RCIC)gpy(/)-Not consistent with paths suggested in EPRI Np-6041 and other IPEEE submittals as "first line of defense" thatrespondsautomaticallythat responds automatically

-Increases demand/reliance on low pressure systems

  • Automaticcircuitryfordepressurizationand
  • Automatic circuitry for depressurization and initiation of low pressure injection not included

-Increases demand

/reliance on o perator actions

/p Browns Ferry Nuclear Power PlantiliIPEEE Screen ing Eva luat i on Conclusion Conclusion

  • Based on weaknesses identified with the IPEEEtheIPEEEresultsarenotconsidered IPEEE , the IPEEE results are not considered adequate for screening purposesBFidiG2l*Browns Ferry is screene d i n as a Group 2 p lant