ML14176A092

6/25/2014, Dominion Public Meeting Presentation for Surry GMRS Profile

ML14176A092
Person / Time
Site:	Millstone, Surry
Issue date:	06/25/2014
From:	Dominion, Nuclear Management Co, Virginia Electric & Power Co (VEPCO)
To:	Division of Inspection and Regional Support
References
Download: ML14176A092 (19)

Text

NRC Public Meeting Fukushima Near-Term Task Force Recommendation 2.1 Seismic Re-evaluation and Screening Results Surry Power Station - Units 1 and 2 Mill t Millstone Unit U it 2 Dominion June 25, 2014

Agenda

• Surry GMRS Differences

• Introduction

• NRC and EPRI GMRS and Surry SSE Comparison

• Velocity Profiles

• Basis for Kappa

• Basis for Depth to Hard Rock

• Summary S

• Conclusion

• Millstone Mill t U Unit it 2 - Draft D ft RAIs RAI 2

Introduction

• Dominion followed the NRC-endorsed industry guidance (EPRI 1025287 - SPID) to develop the Surry ground motion response spectrum (GMRS) in response to the NRC 10CFR 50.54(f) request for information letter

• Dominion submitted the GMRS/hazard curves and screening results for Surry Power Station Units 1 and 2 on March 3131, 2014

• The objective of this meeting is to discuss the identified differences between the Surry submittal and NRC confirmatory results, i.e., shear wave velocity profiles, total effective kappa and depth to hard rock

• Dominion will present the basis for the information provided in the submittal related to these differences 3

Surry GMRS and SSE C

Comparison i

• Surry is a low seismic hazard site (SSE spectral peak < 0.23g at 5% damping)

• GMRS (Dominion) enveloped by SSE

• GMRS (NRC) <0.29g (est.) spectral peak

• NRC GMRS confirmatory analysis differences

- Shear Wave Velocity (Vs) Profiles

- Total Kappa Value (0.027s [NRC] vs. 0.034s [Dominion])

- Depth to Hard Rock (1460 [NRC] vs. 1700 [Dominion])

4

GMRS and SSE C

Comparison i

5

Vs Profiles

• Basis for Shear Wave Velocity (Vs) Profiles

- Site-specific geotechnical profile data from Report Table 2.3.2-1

- SSE control point at surface (266 (26 6 El El.))

- Vs values

• Compacted fill - 16 16 - 1000 fps

• Upper 140 - based on sampler penetration tests (hammer blows)

• Uncertainty factor of 1 1.57 57 applied based on limited data

- Profiles reflect site-specific estimated Vs values

- No gradient applied since soft soil site (consistent with SPID) 6

Vs Profiles 7

Vs Profiles 8

Calculation of Kappa

• Basis For Estimate of Total Effective Kappa

- Kappa = 0.034s based on SPID Appendix B.5.1.3.1 guidance for soil site with <3,000 ft depth to hard rock

- Contributions from soil ( 1,600 ft) plus underlying hard rock

- Soil contribution from empirical relation based on soil depth

- Hard rock contribution 0.006s 9

Depth to Hard Rock

• Surry Screening Report: Hard rock (i.e., shear wave velocity, l it V Vs, >9200 9200 ft/sec) ft/ ) elevation l ti reported t d as -17001700

• Based on review of USGS Professional Paper No. 1612 (Feb 22, 2000)1

• Extrapolation of borehole 60 (Hog Island) [Plate 4] -

indicates crystalline basement rocks reached at approximately -1600

• Additional 100 depth to Vs=9200 ft/sec was assumed in order to account for likely weathering effects during the period the Potomac formation was being deposited 1 USGS Professional Paper No. 1612, The Effects of the Chesapeake Bay Impact Crater on the Geological Framework and Correlation of Hydrogeologic y g g Units of the Lower York-James Peninsula,, Virginia.

g 10

Depth to Hard Rock 11

Depth to Hard Rock 12

Summary

• Surry GMRS and screening results developed based on the NRC-endorsed EPRI SPID Guidance

• Surry Vs profiles are based on site-specific data and developed p consistent with SPID

• Surry site kappa value consistent with SPID Appendix pp B methodology gy

• Surry site depth to hard rock is based on a reasonable interpretation p of available data 13

Conclusion

• Surry GMRS and screening results are consistent with industry guidance

• Surry screens out from performance of further seismic risk assessment, high frequency confirmation, and spent p fuel p pool evaluation

• Expedited Seismic Evaluation Process (ESEP) is not required q p per the Augmented g Approach pp guidance (EPRI 3002000704) 14

Millstone Unit 2

• The Millstone Unit 2 GMRS and screening submittal provided the screening results based on comparison of the GMRS to the IPEEE HCLPF spectrum (IHS) per the SPID guidance

• NRC has drafted two requests q for additional information related to the Millstone Unit 2 submittal

• Dominion has reviewed these requests and is providing information for discussion 15

Millstone Unit 2

• Request q 1

- In the IPEEE adequacy review supporting IHS screening, HCLPF capacity calculations could not be located for resolution of two items: ((1)) Batteryy Racks DB1 and DB2,, and (2)

( ) Chilled Water Surge Tank. The submittal indicates that calculations were subsequently reconstituted for these components with acceptable results.

- Provide a detailed description of the methods and inputs for the evaluation of the battery racks and chilled water surge tank performed for the submittal p

- Provide a detailed description of any modifications to these components performed to support the reconstitution of the calculations 16

Millstone Unit 2

• Request q 1 Discussion

- The calculations were reconstituted for these components to resolve comments from the IPEEE adequacy review.

- The methods used in these two recent calculations are consistent with the Seismic Margin Assessment (SMA) methodology in EPRI NP-6041 SL, Rev. 1 and were independently reviewed reviewed. The capacities of both items are

>0.25g, therefore plant HCLPF remains unchanged.

- There were no new modifications to improve the HCLPF of the battery racks or the chilled water surge tank components after the IPEEE submittal and closure of IPEEE open issues.

17

Millstone Unit 2

• Request 2

- The Millstone Unit 2 IPEEE submittal included Opportunities for Safety Enhancements and identified valve 2-CHW-11 as an item to be resolved.

This air operated valve has a heavy yoke that is independently p y braced.

- Provide a detailed description of how this item was resolved and its safety significance related to the plant l HCLPF off 0.25g 02 18

Millstone Unit 2

• Request 2 Discussion

- The vital chilled water system y ((CHW)) p provides chilled water for the DC Switchgear Room HVAC system, which is a support system. Valve 2-CHW-11 provides isolation from the non-seismic portion of the system.

- The CHW system is a two-train system and failure of 2-CHW-11 only affects one train. The room cooling support function is maintained by y the redundant train. Therefore, valve 2-CHW-11 has low safety significance.

- Valve 2-CHW-11 is top-braced at the valve actuator. The top g, and pipe bracing, p p supports pp in the vicinity y of the valve,, are anchored to the same structure and stresses due to differential displacement are minimal.

- The valve was analyzed in this configuration and confirmed to meet the design basis requirements as part of the USI A-46 program. 19