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, NRR/JLD, 415-2856
References
Download: ML14182A103 (26)
v • d • e


Text

Near-Term Near Term Task Force Recommendation 2.1 Seismic Hazard Evaluation Tennessee Valley Authority July 1, 2014

References for Meeting

  • Meeting Feedback Form (request from mfb@nrc.gov)
  • May 9, 2014, NRC letter regarding Seismic Screening anddP Prioritization i iti ti R Results lt ffor central t l and d eastern t US Licensees (ML14111A147)
  • May 21, 2014, NRC memo providing preliminary staff 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 have common understanding of the causes of the primary differences between the preliminary NRC and licensee seismic hazard results B k

Background:

d NRC and d lilicensee seismic i i h hazard d require i

resolution to support a final seismic screening decision and to support related follow-on submittals Outcomes:

  • Begin NRC and licensee resolution to support regulatory decisions and development of seismic risk evaluations evaluations, as appropriate
  • Establish resolution path, including timelines and identification of potential information needs

Look-ahead:

Potential Next Steps

  • NRC will consider the meeting information
  • Potential paths:

- Licensee submits supplemental information based on public meeting dialog

- NRC staff issues a request q for information

- Licensee sends a revision or supplement to the seismic hazard report

  • NRC completes screening review and issues the final screening determination l tt letter

Watts Bar Nuclear Plant Rasool Anooshehpoor Office of Research July 1, 2014

Screening G l Geology

  • The site is located in the Tennessee section of Valley and Ridge Province of the Appalachian highlands highlands.
  • In Tennessee, the Rome Formation and Conasauga, Knox and Chickamuga groups make up the majority of b d k bedrock.
  • Sedimentary rocks from Pennsylvanian to Cambrian age, g p predominant with those of Cambrian and Ordovician age.
  • Folds involving stratified Paleozoic rocks with great differences in hardness hardness.
  • At Watts Bar the bedrock is 2000ft thick Middle Cambrian Conasauga Group (alternating shale and limestone).

limestone)

Site Geology

~706 ft Control Point at 664 ft

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

Vs Profile Development NRC Submittal Continuous C ti velocity l it measurements t Shear Sh wave velocities l iti were bbasedd at 7 boreholes in FSAR at the top on SASW and Birdwell velocity 100 ft were used to develop the Vs measurements (AMEC, 2013).

profile.

p Vmedian=5704 ft/s, ln=0.134 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)

Vs Profiles Aleatory Uncertainty in Vs Profiles NRC Submittal 30 Randomizations Using USGS 30 Randomizations Using USGS A Site Conditions A Site Conditions ln = 0.25 Upper 50 ft. ln = 0.25 Upper 50 ft.

ln = 0.15 Below 50 ft. ln = 0.15 Below 50 ft.

Epistemic Uncertainty in Vs Profiles NRC Submittal Applied a scale factors of 1.14 Applied a scale factor of 1.25 to to the base case pprofile at the the base case p profile for top 100 ft, and 1.31 from 100 ft development of the upper and to 1000 ft (Reference rock) lower case profiles

Watts Bar Comparison SSE Control Point Depth p to VS-reference Non-Linear/Damping p g Licensee NRC Staff Licensee NRC Staff Licensee NRC Staff At the base of At the base of 1) 592 ft ~1000 ft EPRI-Rock or Linear, the reactor the reactor 2) 936 ft Linear (low- no damping foundation foundation strain EPRI EPRI-(el. 664 ft) (el. 664 ft) Rock damping)

Licensee kappa NRC kappa, with one layer (1000 ft) over ref. rock Total Upper Balanc Profile kappa Profile kappa 500 ft e Base 0.007 0.010 0.016 P1 0.012 0.005 0.0065 Lower 0.007 0.011 0.018 P2 0.012*1.68 0.007 0.0144 Upper 0.006 0.010 0.016 P3 0.012/1.68 0.004 0.0060 P4 0.013 0.005 0.0083 P5 0 013*1 68 0.013*1.68 0 007 0.007 0 0168 0.0168 Epistemic Uncertainty = 1.68 P6 0.013/1.68 0.004 0.0060

Primary Differences Velocity profiles:

TVA used two sets of 3-velocity profiles. The reference rock depth is at 592 ft in one case and 936 ft in the other other.

NRC used three velocity profiles and depth of 1000 ft to reference rock.

Low strain damping:

TVA used ~3% 3% damping in the upper 500 ft. NRC used kappa in the upper 1000ft to account for damping TVA used a factor of 1.68 about P1 and P4 total kappas to account for epistemic uncertainty.

NRC calculated kappa for each of three profiles separately.

Sensitivity Test Epistemic Uncertainty in Shear Modulus and Damping Curves NRC Submittal M1 M1 EPRI Rock: 0 - 500 ft EPRI Rock: 0 - 500 ft M2 M2 Linear & Linear &

EPRI Rock Damping (~3%): 0 - 500 ft EPRI Rock Damping (~3%): 0 - 500 ft Reference Rock at 1000 ft below control Reference Rock at 592 ft and 936 ft point. below control point for P1 and P4 fil profiles.

Depth Randomization, ln =0.2 Depth Randomization, ln =0.2

Kappa and Epistemic Uncertainty NRC Submittal Kappa was calculated for each base case Kappa calculated for velocity profiles P1P1, P2 P2, profile. P3, P4, P5, and P6. Range of these kappas do not reflect epistemic uncertainty.

Profile kappa Profile kappa kappa (modified)

Base Case 0.014 P1 0.012 0.012 LBC 0.015 P2 0.013 0.020 ((0.012 x1.68))

UBC 0.012 P3 0.011 0.007 (0.012 ÷1.68)

P4 0.013 0.013 P5 0.015 0.022 (0.013 x1.68)

P6 0.012 0.008 (0.013 ÷1.67)

A Amplification lifi ti F Functions ti Rock PGA = 0.3 g

Comparison of Total Mean Soil Hazard by Spectral Frequency GMRS Comparison Primary Differences in Sensitivity Test Velocity profiles:

TVA used two sets of 3-velocity profiles. The reference rock depth is at 592 ft in one case and 936 ft in the other other.

NRC used three velocity profiles and depth of 1000 ft to reference rock.

Low strain damping:

Both TVA and NRC used ~3% 3% damping in the upper 500 ft.

TVA used a factor of 1.68 about P1 and P4 total kappas to account for epistemic uncertainty.

NRC calculated kappa for each of three profiles separately separately.

Conclusions

  • Watts Bar screens in for risk evaluation
  • Control Point hazard curves similar at 10 Hz and PGA, differ at 1 Hz

- Due to different assumptions of depth to bedrock

  • Need additional information to support licensee assumption for depth to bedrock

Browns Ferry Nuclear Power Plant IPEEE Screening i Evaluationl i Weaknesses ea esses identified de t ed in IPEEE SER/TER S /

  • Only low power injection systems selected

- Did not include high g pressure p systems y (HPCI/RCIC)

( / )

- Not consistent with paths suggested in EPRI Np-6041 and other IPEEE submittals as first line of defense that responds automatically

- Increases demand/reliance on low pressure systems

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

- Increases demand/reliance

/ on operator p actions

Browns Ferry Nuclear Power Plant IPEEE Screening i Evaluation l i Conclusion

  • Based on weaknesses identified with the IPEEE the IPEEE results are not considered IPEEE, adequate for screening purposes
  • Browns B Ferry F iis screened d iin as a G Group 2 plant l
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