ML11305A062

Restart Readiness, Public Meeting PR2

ML11305A062
Person / Time
Site:	North Anna
Issue date:	11/01/2011
From:	Heacock D Dominion, Virginia Electric & Power Co (VEPCO)
To:	NRC/RGN-II
References
Download: ML11305A062 (24)

Text

North Anna Power Station Restart Readiness David A. Heacock, President & Chief Nuclear Officer

North Anna Inspection Summary Process

• More than 100,000 hours0 days <br />0 hours <br />0 weeks <br />0 months <br />

• $21 million in inspection, testing, & evaluation

• Exceeded NRC endorsed guidance

• Restart readiness plan complete Findings

• No functional damage to safety systems

• Units ready for restart 2

Forecasting Seismic Damage Key factors

• Acceleration (vertical, north/south, east/west)

• Frequency of the vibration

• Duration of strong motion Seismic acceleration response spectra

• Used to conservatively design plants

• Does not account for duration Cumulative Absolute Velocity (CAV)

• Integrates all three factors

• Best indicator of energy imparted

• Best indicator of damage 3

August 23:

A strong, but very short event East-West: 3.1 sec Acceleration (g)

Vertical: 1.5 sec North-South: 1.0 sec 2 4 6 8 10 12 14 16 18 20 seconds 4

CAV Comparisons: Regulatory Guide Slightly Exceeded in One Dimension 1.4 1.2 1

0.8 g-sec 0.6 0.4 0.2 Regulatory Limit 0

Horizontal (N-S) Horizontal (E-W) Vertical August 23, 2011 Earthquake DBE - Design Basis Event IPEEE Review - 1990s updated study 5

North Anna Has Significant Design Margin

• Conservatism in analytical methods

• Conservatism in American Society of Mechanical Engineers Code

• Accident load design of greater capacity

• Conservatism in seismic test standards Previous Evaluations Established Significant Margins Beyond Design Basis 6

The Plant Tells the Story Unit 2 Turbine Building Non-Safety Related Demineralizer Tanks Base Pedestal 8

Turbine Building Hallway Crack In Unreinforced Non-Safety Related Block Wall 9

Unit 1 Containment Surface Crack In Interior Containment Wall 10

Dry Cask Storage Casks moved between 1 and 41/2 inches 11

Dominion Complied with -

and Went Beyond -

Regulatory Guidance

Regulatory Guidance Station restart readiness assessment actions based on NRC-endorsed guidance RG 1.166, Pre-earthquake Planning and Immediate Nuclear Power Plant Operator Post-earthquake Actions, March 1997 RG 1.167, Restart of a Nuclear Power Plant Shut Down by a Seismic Event, March 1997 EPRI NP-6695, Guidelines for Nuclear Plant Response to an Earthquake, December 1989 13

What is Functional Damage Significant damage to plant systems, components, and structures, either physical or other, which impairs the operability or reliability of the damaged item to perform its intended function.

Minor damage such as slight or hairline cracking of concrete elements in structures does not constitute functional damage.

(from EPRI NP-6695) 14

Let the Plant Tell the Story Recommended actions are based on the following concepts:

The plant itself, not damage information from nearby communities or recorded distant ground motion, is the best indicator of the severity of the earthquake at the plant site. (from EPRI NP-6695) 15

Inspections and Tests:

11,000+ Dominion Hours, 100,000+ Hours by Contractors, Multiple External Consultants

Investigating Components Most Likely to be Damaged Unit 2 Tunnel Inspection 17

Extensive Fuel Inspections Visual inspection of RCCA hubs Examination of underside of a mid-span mixing grid 18

Buried Piping

~ 100 ft of safety-related buried pipe visually inspected with wall thickness verified by Ultrasonic Testing 19

Next Steps Short-Term Actions Installed Key Seismic Monitoring Equipment Revised Procedure to Respond to Earthquake Complete Start-Up Surveillances 21

Long-Term Actions

• Install permanent free-field seismic monitoring instrumentation

• Re-evaluate safe shutdown equipment (components with identified lower margins)

• Perform seismic analysis of recorded event consistent with EPRI guidance

• Maintain seismic margins in future modifications

• Revise the North Anna Safety Analysis Report 22

Summary

• Acceleration criteria were briefly exceeded in certain directions and frequencies by a strong, but very short duration earthquake

• Previous evaluations establish safe shutdown systems, structures and components can handle peak accelerations above design basis

• No safety-related systems, structures or components required repair due to the earthquake

• No significant damage was found or should have been expected and results of expanded tests and inspections have confirmed expectations 23

==

Conclusion:==

The Plant Is Safe to Operate Consistent With Federal Law:

• Restart Readiness Demonstration Complete

• No Functional Damage to Safety Systems

• Units Ready For Restart 24