ML14182A103
| ML14182A103 | |
| Person / Time | |
|---|---|
| Site: | Watts Bar  |
| Issue date: | 07/01/2014 |
| From: | Japan Lessons-Learned Division |
| To: | Tennessee Valley Authority |
| Balazik M, NRR/JLD, 415-2856 | |
| References | |
| Download: ML14182A103 (26) | |
Text
Near Term Task Force Near-Term Task Force Recommendation 2.1 Seismic Hazard Evaluation Evaluation Tennessee Valley Authority Tennessee Valley Authority July 1, 2014
References for Meeting Licensee Presentation Slides - ML14182A099 NRC Presentation Slides - ML14182A103 P bli M ti A
d ML14167A164 Public Meeting Agenda - ML14167A164 Meeting Feedback Form (request from mfb@nrc.gov)
May 9, 2014, NRC letter regarding Seismic Screening d P i iti ti R
lt f t
l d
t US and Prioritization Results for central and eastern US Licensees (ML14111A147)
May 21, 2014, NRC memo providing preliminary staff ground motion response spectra for central and 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 have common understanding of the causes of the primary differences between the preliminary NRC and licensee seismic hazard results B
k d NRC d li i
i h d
i
Background:
NRC and licensee seismic hazard require 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 decisions and development of seismic risk evaluations, as appropriate
- Establish resolution path, including timelines and identification of potential information needs identification of potential information needs
Look-ahead:
Potential Next Steps
- NRC will consider the meeting information NRC will consider the meeting information
- Potential paths:
- Licensee submits supplemental information Licensee submits supplemental information based on public meeting dialog
- NRC staff issues a request for information q
- 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 Watts Bar Nuclear Plant Rasool Anooshehpoor Office of Research July 1, 2014 July 1, 2014
Screening
G l
Geology The site is located in the Tennessee section of Valley and Ridge Province of the Appalachian highlands and Ridge Province of the Appalachian 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, predominant with those of Cambrian and g
p Ordovician age.
Folds involving stratified Paleozoic rocks with great differences in hardness differences in 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 at elevation 664 ft.
SSE Control Point at elevation 664 ft.
Vs Profile Development NRC C
ti l
it t
Submittal Sh l
iti b
d Continuous velocity measurements at 7 boreholes in FSAR at the top 100 ft were used to develop the Vs profile.
Shear wave velocities were based on SASW and Birdwell velocity measurements (AMEC, 2013).
p Vmedian=5704 ft/s, ln=0.134 This is in general agreement with 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 NRC 30 Randomizations Using USGS A Site Conditions Submittal 30 Randomizations Using USGS A Site Conditions ln = 0.25 Upper 50 ft.
ln = 0.15 Below 50 ft.
ln = 0.25 Upper 50 ft.
ln = 0.15 Below 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 to the base case profile at the Applied a scale factor of 1.25 to the base case profile for p
top 100 ft, and 1.31 from 100 ft to 1000 ft (Reference rock) p development of the upper and lower case profiles
Watts Bar Comparison SSE Control Point Depth to VS-reference Non-Linear/Damping p
p g Licensee NRC Staff Licensee NRC Staff Licensee NRC Staff At the base of the reactor foundation At the base of the reactor foundation 1) 592 ft 2) 936 ft
~1000 ft EPRI-Rock or Linear (low-strain EPRI-
- Linear, no damping foundation (el. 664 ft) foundation (el. 664 ft) strain EPRI Rock damping)
NRC kappa, with one layer (1000 ft) over ref. rock Licensee kappa Profile kappa Base 0.007 0.010 0.016 Lower 0.007 0.011 0.018 NRC kappa, with one layer (1000 ft) over ref. rock Profile Total kappa Upper 500 ft Balanc e
P1 0.012 0.005 0.0065 Lower 0.007 0.011 0.018 Upper 0.006 0.010 0.016 P2 0.012*1.68 0.007 0.0144 P3 0.012/1.68 0.004 0.0060 P4 0.013 0.005 0.0083 P5 0 013*1 68 0 007 0 0168 P5 0.013*1.68 0.007 0.0168 P6 0.013/1.68 0.004 0.0060 Epistemic Uncertainty = 1.68
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 depth is at 592 ft in one case and 936 ft in the other.
NRC used three velocity profiles and depth of 1000 ft to reference rock.
Low strain damping:
TVA used ~3% damping in the upper 500 ft. NRC used kappa TVA used 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.
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 M1 EPRI Rock: 0 - 500 ft M1 EPRI Rock: 0 - 500 ft M2 Linear &
EPRI Rock Damping (~3%): 0 - 500 ft M2 Linear &
EPRI Rock Damping (~3%): 0 - 500 ft Reference Rock at 1000 ft below control point.
Reference Rock at 592 ft and 936 ft below control point for P1 and P4 fil Depth Randomization, ln =0.2 profiles.
Depth Randomization, ln =0.2
Kappa and Epistemic Uncertainty NRC Kappa was calculated for each base case Submittal Kappa calculated for velocity profiles P1 P2 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 kappa Profile kappa kappa (modified)
P1 0.012 0.012 P2 0.013 0.020 (0.012 x1.68)
Profile kappa Base Case 0.014 LBC 0.015
(
)
P3 0.011 0.007 (0.012 ÷1.68)
P4 0.013 0.013 P5 0.015 0.022 (0.013 x1.68)
UBC 0.012 P6 0.012 0.008 (0.013 ÷1.67)
A lifi ti F
ti Amplification Functions 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 depth is at 592 ft in one case and 936 ft in the other.
NRC used three velocity profiles and depth of 1000 ft to reference rock.
Low strain damping:
Both TVA and NRC used ~3% damping in the upper 500 ft.
Both TVA and NRC used 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 NRC calculated kappa for each of three profiles separately.
Conclusions
- GMRS are similar
- Watts Bar screens in for risk evaluation
- Due to different assumptions of depth to bedrock
- Need additional information to support licensee assumption for depth to bedrock licensee assumption for depth to bedrock
Browns Ferry Nuclear Power Plant i
l i
IPEEE Screening Evaluation Weaknesses identified in IPEEE SER/TER ea esses de t ed S
/
- Only low power injection systems selected
- Did not include high pressure systems (HPCI/RCIC) g p y
(
/
)
- Not consistent with paths suggested in EPRI Np-6041 and other IPEEE submittals as first line of defense that responds automatically that responds automatically
- Increases demand/reliance on low pressure systems
- Automatic circuitry for depressurization and
- Automatic circuitry for depressurization and initiation of low pressure injection not included
- Increases demand/reliance on operator actions
/
p
Browns Ferry Nuclear Power Plant i
l i
IPEEE Screening Evaluation Conclusion Conclusion
- Based on weaknesses identified with the IPEEE the IPEEE results are not considered IPEEE, the IPEEE results are not considered adequate for screening purposes B
F i
d i G
2 l
- Browns Ferry is screened in as a Group 2 plant