ML11262A260

Communication Plan for North Anna Nuclear Power Plant Earthquake Response

ML11262A260
Person / Time
Site:	North Anna
Issue date:	09/14/2011
From:	Juan Uribe NRC/NRR/DE/EMCB
To:
Uribe J
References
TAC ME7050, TAC ME7051, FOIA/PA-2011-0357
Download: ML11262A260 (11)

Text

OFFICIAL USE ONLY

- SENSITIVE INTERNAL INFORMATION 1 COMMUNICATION PLAN FOR NORTH ANNA NUCLEAR POWER PLANT EARTHQUAKE RESPONSE Last Update: November 14 , 2011 (ML11262A260)

Goal This plan will guide staff communications and activities with internal and external stakeholders of the United States Nuclear Regulatory Commission (NRC) as they relate to the August 23, 2011 earthquake and the response from the North Anna Nuclear Power Station (NAPS). Key Messages The key messages to be communicated to stakeholders based on the available information are:

1. The earthquake caused no significant damage to either operating unit. Both units automatically shutdown without any problems or release of radioactive materials to the environment. All safety systems functioned properly and the earthquake did not affect the performance of any of the safety related systems.

2. Testing, inspections, and analys es performed following the earthquake have revealed mostly non

-significant damage (cracking, missing concrete chips, etc.) to non

-safety related systems, structures, and components.

3. The current best estimate (with uncertainty) of the Peak Ground Acceleration (PGA) for the NAPS site is 0.26g, which indicates that the ground motion likely exceeded the safe shutdown earthquake (SSE) ground motion for NAPS Units 1 and 2 over a considerable frequency range. Any plant that experiences ground motion in excess of the Operating Basis Earthquake (which is of lesser magnitude than the SSE) and other alternative criteria, is required to shutdown and is not permitted to restart until authorized by the NRC, per 10 CFR Part 100 Appendix A section V (a)(2).

4. The estimated ground motion from the earthquake is generally consistent with the information developed for the combined operating license application (COLA) ground motion response spectrum for NAPS Unit 3. The event validated the current studies of the NRC's seismic hazard assessment approaches and models for new reactors, as well as the basis for GI

-199 (generic issue "Implications of Updated Probabilistic Seismic Hazard Estimates in Central and Eastern United States on Existing Plants") reviews.

Backgr ound On August 23, 2011, a magnitude 5.8 earthquake occurred approximately 1 2 miles (18km) from the NAPS located in Louisa, VA. This event resulted in a loss of offsite power and automatic reactor trip of both units. In response to this event, an Alert was declared due to significant seismic activity at the site. Almost immediately after the earthquake, both units were stabilized and offsite power was restored.

Following the event, seismic data was retrieved from the installed monitoring system and shipped to the vendor to determine the response spectrum for the event. On August 26, 2011, OFFICIAL USE ONLY

- SENSITIVE INTERNAL INFORMATION 2 initial reviews of the data determined that the seismic activity exceeded the Design Basis Earthquake. Therefore, this event was reportable per 10 CFR 50.72(b)(3)(ii) (B) for the nuclear power plant being in an unanalyzed condition that significantly degrades plant safety. On August 26, the licensee declared all safety

-related SSCs of Units 1 and 2 inoperable and issued a 10 CFR 50.72 Notification.

NAPS has two Safe Shutdown Earthquake (SSE) ground motions, one for structures, systems, and components (SSCs) located on top of rock, which is anchored at 0.12 g, and the other is for SSCs located on top of soil, which is anchored at 0.18 g.

The NAPS has two corresponding Operating Basis Earthquake (OBE), 0.09 g for soil and 0.06 g for rock.

The current best estimate of the Peak Ground Acceleration (PGA) for the NAPS site is 0.26 g, which contains uncertainty. This estimate indicates that the ground motion likely exceeded the SSE response spectra for NAPS Units 1 and 2. The vibratory motion from the 5.8 magnitude earthquake was recorded in all three orientations at several locations in the plant using two types of instruments: the Engdahl scratch plates that record 12 discrete spectral accelerations between 2 and 25.4 Hz, and the Kinemetrics analog recorders that recorded time histories of the accelerations. Based on evaluation of recorded plant data, it is concluded that ground motion from the Central Virginia earthquake of August 23, 2011, exceeded the DBE of North Anna Plant at different elevation levels

. Currently, unit 2 has been defueled as part of the planned refueling outage and unit 1 is in cold shutdown. Visual inspections were performed of the fuel during the offload and detailed physical inspections were performed in the spent fuel pool of a select number of fuel assemblies. All of the Rod Cluster Control Assembly (RCCA) from unit 2 have been drag tested and the only resistance observed was from a known issue. No significant equipment damage to Safety Related System (including Class 1 Structures) has been identified through site walk

-downs nor has equipment degradation been detected through plant performance and surveillance testing following the earthquake. The licensee is performing the plant walk downs in accordance with RG 1.167, "Restart of a Nuclear Power Plant Shutdown by a Seismic Event," which endorses EPRI's "Guidelines for Nuclear Plant Response to an Earthquake" with conditions. The licensee indicated that the Spent Fuel Pit cooling system also remains fully functional and the temperature of the Spent Fuel Pit remained unchanged during the event.

The licensee also indicated that the vendor has finished the analysis of the seismic data and this information will be utilized to address the long term actions following the earthquake.

A Confirmatory Action Letter (CAL) was issued on 09/30/11, by Region II restating the regulatory requirements in 10 CFR Part 100 Appendix A section V "SEISMIC AND GEOLOGICAL DESIGN BASES" (a)(2) "Determination of Operating Basis Event Earthquake" where: "If vibratory ground motion exceeding that of the Operating Basis Earthquake occurs , shutdown of the nuclear power plant will be required. Prior to resuming operations, the licensee will be required to demonstrate to the Commission that no functional damage has occurred to those features necessary for continued operation without undue risk to the health and safety of the public." The CAL confirms the understanding stated in the public meeting and in its September 17, 2011 correspondence that the licensee is not to enter Modes 1 through 4 until the NRC has completed its safety evaluation report and reported its conclusion to the licensee in writing.

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- SENSITIVE INTERNAL INFORMATION 3 Audience and Stakeholders Internal The Commission (SECY)

Office of the Executive Director for Operations (OEDO)

Office of Nuclear Regulatory Research (RES)

Office of Nuclear Reactor Regulation (NRR) Office of New Reactors (NRO)

Office of Nuclear Material Safety and Safeguards (NMSS)

Office of Federal and State Materials and Environmental Management Programs (FSME) Regional Offices (Regions I through IV)

Office of Public Affairs (OPA)

Advisory Committee on Reactor Safeguards (ACRS)

Office of International Programs (OIP)

Office of Congressional Affairs (OCA)

(See the "Communications Team" section for a list of specific Communication Team members.)

External Reactor Operator Licensees Energy Power Research Institute (EPRI)

Nuclear Energy Institute (NEI)

Congressional members Public interest groups, media, and the general public.

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- SENSITIVE INTERNAL INFORMATION 4 Communication Timeline Item # Milestone Completion Date Lead 1 Conduct daily conference calls with the licensee to obtain status of activities.

(C) DORL 2 Conduct audit on the effects of the earthquake on the nuclear fuel.

9/19-22 (C) SNPB 3 Prepare acceptance criteria for reviewers 9/20/2011(C)

DORL 4 Issue Communications Plan, and update as necessary 9/20/2011 (C) DE 5 Brief NRR OD of Regulatory Basis for Restart and Review Process 9/22/2011 (C) DORL 6 Provide Briefing Books to EDO (VEPCO Drop ins with Chairman and Commissioners

- 9/29 and 9/30 9/23/2011 (C) DORL 7 Provide Response to GT

-IAEA One Pager 9/23/2011 (C) DORL 8 Develop SE template for reviewers 9/28/2011 (C) DORL 9 Conduct Commissioner's TA Briefing 9/28/11 (C)

DORL 10 Applicable technical branches within DE, DSS, DCI, DIRS, DRA, and DLR identify questions and issues that the licensee should address in the short term (prior to restart) and long term initiatives (post restart) and provide to DORL.

9/28/11 (C) All 11 Meeting with Chairman to address Regulatory Process for Restart and Licensing Process 9/29 (C) DORL/DE/OGC 12 Dominion Drop in with Chairman and Commissioners 9/29 and 9/30 (C) EDO 13 Issue Confirmatory Action Letter to Licensee (after communicating CAL language to VEPCO) 9/30/2011 (C) Region II 14 Issue formal requests for additional information to licensee. 9/30/2011 (C) DORL 15 NRR OD and Region 2 RA to tour site prior to AIT exit meeting 10/3/2011 (C) NRR and Region II 16 Identify issues for regional follow

-up (walkdowns and inspections) 10/3/2011 (C) All 17 Conduct AIT public exit briefing and provide insights to DORL for their review of the restart submittal 10/3/2011 (C) Region II 18 Restart Readiness Inspection 10/5 - 11/7 (C) Region II OFFICIAL USE ONLY

- SENSITIVE INTERNAL INFORMATION 5 Item # Milestone Completion Date Lead 20 Obtain acceptance from FEMA National regarding infrastructure to support restart prior to restart.

10/11(C) NSIR 2 1 EDO Alignment/Prebrief for 10/21 Commissioner Meeting 10/12 (C) DORL/DE 22 Receive draft safety evaluation input from reviewers 1 1/7 (C) All 2 3 Determine regulatory vehicle, as necessary, to ensure long-term actions are completed 11/7 (C) DORL 2 4 Develop the language for appropriate regulatory vehicle for ensuring long

-term actions are completed, if necessary.

11/7 (C) DORL/DE 2 5 Conduct Commissioner TA Briefing 10/18 (C) DORL 2 6 Conduct Public Commission Meeting regarding North Anna Restart Initiative.

10/21 (C) DORL 2 8 Receive final safety evaluation input from reviewers 11/1 (C) DORL 2 9 Conduct Public Meeting in Louisa, VA, to communicate results of Restart Readiness Inspection and technical review regarding restart decision.

11/1 (C) Region II NRR 30 Issue letter to VEPCO on restart decision (reference inspection activities and attach NRC T E) and CAL 11/11/11 (C) NRR 31 Notify Congress of restart decision & CAL 11/11/11 (C) OCA 32 Notify Virginia of restart decision & CAL 11/11/11 (C) RII SLO 33 Issue press release (w/

Restart Letter, Technical Evaluation

& CAL appended) 11/11/11 (C) OPA 34 Issue Restart Letter, Technical Evaluation & CAL via NRR listserv 11/11/11 (C) NRR 35 Post the Restart Letter, Technical Evaluation

& CAL to public website/ADAMS 11/14/11 (C) NRR 3 6 Update 1-pager for Commissioners

. (C) DORL 3 7 Address GT 20110668 regarding 2.206 Petition 12/12 (T) DORL/DPR 3 8 Address any potential generic issues (e.g., seismic instrumentation power supplies, seismic monitor locations on structures as well as in the "free field," and seismic monitors on ISFSI pads).

TBD Region II NMSS/DE/DPR

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- SENSITIVE INTERNAL INFORMATION 6 Item # Milestone Completion Date Lead 40 Conduct ACRS Briefings, as needed. (Informational Meeting) 1/19/12 or 1/20/12 Region 2 has lead with NRR support 41 Conduct EDO and Commissioner Briefings, as needed. Ongoing DORL and DE 42 Develop SharePoint Site C DE OFFICIAL USE ONLY

- SENSITIVE INTERNAL INFORMATION 7 Communication Team

• NMSS hasdevelop ed a separate Communication Plan related to the North Anna ISFSI issues.

Name Office Telephone Number Email ID Contacts in NRR Michele Evans NRR 301-415-1453 Michele.Evans@nrc.gov Allen Howe 301-415-1351 Allen.Howe@nrc.gov Meena Khanna 301-415-2150 Meena.Khanna@nrc.gov Kenneth Karwoski 301-415-2752 Kenneth.Karwoski@nrc.gov Patrick Hiland 301-415-3298 Patrick.Hiland@nrc.gov Kamal Manoly 301-415-2765 Kamal.Manoly@nrc.gov Contacts in NRO Nilesh Chokshi NRO 301-415-1634 Nilesh.Chokshi@nrc.gov Clifford Munson 301-415-6947 Clifford.Munson@nrc.gov Rebecca Karas 301-415-7533 Rebecca.Karas@nrc.gov Christopher Cook 301-415-6397 Christopher.Cook@nrc.gov Contacts in RES Rosemary Hogan RES 301-251-7634 Rosemary.Hogan@nrc.gov Contacts in NMSS Eric Benner*

NMSS* (see footnote) 301-492-3294 Eric.Benner@nrc.gov Earl Love*

301-492-3170 Earl.Love@nrc.gov Contacts in NRC Regional Offices Wayne Schmidt Region I 601-337-5315 Wayne.Schmidt@nrc.gov Mark Franke Region II 404-997-4436 Mark.Franke@nrc.gov Gerald McCoy Region II 404-997-4551 Gerald.McCoy@nrc.gov Robert Trojanowski Region II 404-997-4427 Robert.Trojanowski@nrc.gov Vijay Meghani Region III 630-829-9751 Vijay.Meghani@nrc.gov Thomas Farnholtz Region IV 817-860-8243 Thomas.Farnholtz@nrc.gov

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- SENSITIVE INTERNAL INFORMATION 8 Communication Tools This Communication Plan and associated information will be provided to NRC management for use during planned outreach activities. Information that will be prepared and maintained by the Communication Team includes key messages, press talking points, a press release, and a bank of Questions and Answers for use in communicating with stakeholders.

Materials will be used for outreach activities and will be tailored, as needed, to effectively communicate key messages and address specific stakeholder issues.

Additional Communication Tools The staff created a Seismic Issue Fact Sheet regarding Seismic Issues for Nuclear Power Plants that can be found at: (http://www.nrc.gov/reading

-rm/doc-collections/fact

-sheets/fs-seismic-issues.html

). Updates and Revisions If major revisions are necessary to the plan or its key messages, a formal revision will be made and the revision will be placed into ADAMS.

Final Closeout The close-out will be a memorandum and will contain any lessons learned about the plan or its implementation.

Point s of Contact For any questions/comments related to this communication plan, please contact:

Juan Uribe Kamal Manoly NRR/DE/EMCB NRR/DE/SLA 301.415.3809 301.415.2765 Juan.Uribe@nrc.gov Kamal.Manoly@nrc.gov Name Office Telephone Number Email ID Communications assistant in OPA Scott Burnell OPA 301-415-8204 Scott.Burnell@nrc.gov Roger Hannah OPA RII 404-997-4417 Roger.Hannah@nrc.gov Joey Ledford OPA RII 404-997-4416 Joey.Ledford@nrc.gov Contact in OC A Tim Riley OCA 301-415-8492 Tim.Riley@nrc.gov

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- SENSITIVE INTERNAL INFORMATION 9 Questions and Answers North Anna Earthquake Response Earthquake Ground Motion s Q1. Why do estimate s of ground motion acceleration differ so much?

A1. The estimate of peak ground acceleration from the USGS is 0.26 g. NRC also ran ground motion equations based on the earthquake magnitude 5.8 and distance 18 km

, which gave a peak ground acceleration value of about 0.2g.

Both of these estimates were made for the "free

-field" at the ground surface and not directly under or on structures of interest.

A free surface and free field seismometer at the site would have provided the best recording on the ground motion level. However, Dominion has no seismic instrumentation located on the free surface in the free-field and the structures, systems and components where seismometers are located will have their influence on the input motion from the earthquake at different levels

. Q2. Why is Dominion offering an array of measurements?

A2.The shaking of the nuclear power plant from the magnitude 5.8 earthquake was strongly affected by the response of the structure, which varies considerably at different locations and elevations within the structure.

North Anna has seismic instruments of various types at different locations throughout the plant following the requirements defined in the regulatory guidance document. The readings from these instruments have been compared to the design level values for that particular location within the structure.

Many of these comparisons show that the accelerations from the earthquake are higher than the original design values at certain frequencies.

Q3. What is the direct cause of their reactors' shut

-down? Considering newspaper and press release of NRC, there are two possibilities for the shut

-down. 1. Observed actual seismic acceleration, which triggered directly shut

-down. 2. Outer line outrage triggered turbine trip followed by reactor shut

-down. A3. The root cause summary submitted on September 27, 2011 (ML11272A129) includes the statement that the automatic shutdown of the reactor occurred as a result of real physical changes affecting the reactor core heat generation and the sensitivity of the instruments monitoring the core. A combination of negative reactivity effects (causing a decrease in reactor power) with a shift in the position of the detector (if its farther away it will read a lower value) and increased shielding by reactor coolant (a thicker layer of water between the core and the reactor will cause the reading on the instrument to go down) led to the power level seen by the nuclear instrumentation to decrease rapidly, which is a negative rate

- the first trip that came in during the event.

The root cause analysis also ruled out the following potential causes: core flow increases, core bypass flow impacts, Hydrogen voiding, dropped control rods, core temperature excursion, detector voltage impacts, detector cable motion, electrical grounding impact, Electro

-magnetic interference, Motor

-Generator set output breaker opening, and reactor trip breaker failure.

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- SENSITIVE INTERNAL INFORMATION 10 Q 4. Describe what occurred at the North Anna Nuclear Power Station as a result of the earthquake, including the sequence of events that led to the shutdown of the two reactors, the failures of any safety equipment to operate following the earthquake, and any problems that may occur when the plant restarts.

A 4. Just after 2 pm on August 23, 2011, the North Anna Power Station declared an Alert condition due to significant seismic activity onsite. Both units experienced automatic reactor trips from 100% power and were stabilized in hot shutdown. All offsite electrical power to the site had been lost. All four emergency diesel generators (EDG) started automatically and provided power to the emergency buses. While operating, the one EDG developed a coolant leak and was shutdown. The corresponding emergency bus was re

-energized with another diesel-powered generator. The cause of the coolant leak has been determined to be the result of improperly performed maintenance and not the earthquake. The licensee has entered this problem into its corrective action program and they are addressing the issue with their corrective action process.

On August 29, 2011, the Nuclear Regulatory Commission dispatched an Augmented Inspection Team (AIT) to the North Anna Power Station to further review the effects of the earthquake, the operators' response and the plant staff's activities to check equipment. This team complete d its inspection on September 16, 2011 and will document its inspection results within 30 days after the Public Exit Meeting held on October 3, 2011.

Currently unit 1 is in the cold shutdown condition and the reactor fuel has been removed from unit 2 as a normal part of the planned refueling outage. Proceeding with the refueling outage has allowed Dominion to perform additional tests and inspections that could not have been done in the normal cold shutdown condition. To date, no problems have been discovered on either unit, including the additional checks on unit 2 related to the refueling operations.

Neither unit may resume operations until Dominion proves to the NRC's satisfaction that the plant can be restarted and operated safely. The restart plan being developed by Dominion will include appropriate pauses and checks as an additional precaution to verify the earthquake did not affect any equipment that is important to safely operating the plant.

Q 5. What time did North Anna report any aftershocks and an Unusual event?

A5. Due to the seismic activity, North Anna declared an Unusual Event on Aug. 25 at 0118 EDT following a reported 4.5 magnitude aftershock at approximately 0107 EDT, and the epicenter is approximately 5 miles south of Mineral, Va. Another minor quake was felt on Aug. 25 at 1149 EDT and the plant exited that Unusual Event later that week. North Anna declared a new Unusual Event on September 1 st for an aftershock at 0518 EDT, exiting the Unusual Event shortly in the afternoon. There were no personnel injuries or damage.

Q6. What time did North Anna downgrade from ALERT to an NOUE?

A 6. North Anna downgraded its original ALERT to a Notification of Unusual Event (NOUE) at 11:16 a.m. on August 24, 2011. Both units are in cold shutdown.

Q 7. What time did North Anna elevate to an Alert?

A 7. North Anna elevated to an Alert on Tuesday, Aug. 23 at 14:55.

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- SENSITIVE INTERNAL INFORMATION 11 Q 8. When was the electrical power restored at North Anna?

A 8. The plant had electrical power at 17:40 on Tuesday, Aug. 23.

Q 9. Was there any damage at the plant?

A9. The NRC is continuing its examination of the site and so far all the walkdowns and investigations indicated no significant earthquake damage, with all safety

-related equipment performing appropriately (one emergency diesel developed a coolant leak an hour later and was replaced by another diesel generator). The NRC will ensure that the plant is capable of continuing to operate safely before the agency would authorize the restart of the reactors.

Q 10. Is there anything from a reactor physics perspective that would suggest the plant experienced any unusual or unanticipated behavior during the quake?

A 10. It appears that the plant behavior before the reactor scrammed is consistent with a seismic event. Refer to question 3 for additional information on the licensee's Root Cause Analysis report. Q 11. Does the NRC staff have a safety concern from the observed behavior of the reactor during this event?

A 11. No. We do not have a safety concern from the observed behavior of the reactor. The reactor protection systems designed to ensure the safety of the reactor appeared to have operated as anticipated, shutting down the reactor in the expected and desired manner.

The staff will evaluate the licensee's Root Cause Analysis report when it is formally provided to verify this assessment.

Q1 2. Why is the NRC satisfied with Dominion only inspecting the U2 fuel and crediting those inspections for U1?

A 1 2. The NRC has assessed independently the fuel performance at North Anna from those fuel inspections performed by Dominion. NRC staff also confirmed that the Dominion fuel assessment methods and criteria were consistently applied by onsite observations of the North Anna fuel inspections.

Fundamentally, the NRC assessment evaluated the design of the North Anna fuel assemblies to determine the seismic forces present and the most likely stress failure modes and locations on the assemblies resulted from the earthquake vibration.

The staff considered fuel vendor design criteria, failure mode testing results, and measured ground motion to determine if sufficient design margin exists for all of the North Anna fuel.

Q1 3. Please provide more information on the analyses performed by the NRC, North Anna, and the fuel vendor for the North Anna Fuel.

A 1 3. At the request of the NRC, Dominion calculated the applied seismic loads on the fuel residing in the reactor on August 23 based upon measured ground motion. Each fuel vendor then performed a detailed engineering calculation that demonstrated that applied seismic loads would not result in damage or deformation of the fuel assembly components including the fuel

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- SENSITIVE INTERNAL INFORMATION 12 rods, guide tubes, and grid cages. The NRC has audited these calculations and will report its findings in its safety evaluation.

In addition, Dominion has performed detailed visual inspection of the Unit 2 fuel assemblies and RCCA drag tests to confirm no damage or deformations.

The two North Anna units are in close proximity and are oriented 180 degrees from each other.

Due to the symmetric characteristics of the core and RCCAs, directionally dependent forces or vibrations would impact the cores in the same manner.

It is the staff's understanding that the licensee will perform control rod testing and core physics testing during startup if the plant is allowed to restart

. North Anna Plant Design Q 1 4. Describe whether the North Anna plant fully addressed all inspection findings at the facility, including the problems that the NRC detailed in the May 13, 2011 report and structural integrity issues or other problems that may have occurred as a result of the August 23, 2011 earthquake. If the plant has not fully addressed all of these findings , provide a timeline by which the plant will have addressed all such problems.

A 1 4. As documented in Integrated Inspection Report 05000338, 339/2011003 of July 28, 2011, NRC inspectors reviewed Inspection Report 05000338, 339/2011010 of May 13, 2011 and conducted detailed follow

-up inspection, and there were no inspection findings identified during this follow

-up inspection. The AIT, in response to the August 23, 2011 earthquake, was dispatched to the site following the earthquake to gather the facts. The AIT inspection report is scheduled to be issued 30 days after the Public Exit Meeting, which was completed on October 3. Q 1 5. Describe the seismic hazards that the plant is designed to withstand, the date that those hazards were estimated, the basis for estimated seismic hazards, and any more recent data on seismic hazards that may differ from the information used to originally estimate the seismic hazards for the North Anna plant.

A 1 5. The North Anna Power Station (NAPS) has two Design Basis Earthquake (DBE) ground motions. The first is for structures, systems, and components (SSCs) founded on top of rock, and is anchored at 0.12g (12 percent of the force of gravity). The other DBE is for SSCs founded on top of soil, and is anchored at 0.18g, with the consideration that soil will amplify the ground motion. These seismic ground accelerations were estimated during the time that the construction licenses were issued in 1971. These design values are addressed in the NAPS Final Safety Analysis Report (FSAR). The FSAR indicates that the estimates were based on the Modified Mercalli Intensity (MMI) of VII, which is associated with the largest potential earthquake related to the Arconia Syncline occurring close to the site area. The North Anna plant was evaluated as part of the Individual Plant Examination for External Events (IPEEE) effort in response to NRC Generic Letter 88

-20, Supplement 4, and found to be capable to withstand a significantly higher seismic ground motion than the design basis earthquake, except some identified structures and components. The seismic hazard analysis that was used for the Early Site Permit Application for North Anna, Unit 3, differs from this earlier estimate, in that it provides for a higher ground acceleration, mostly with regards to the high frequency range of the response spectrum for the site, based on OFFICIAL USE ONLY

- SENSITIVE INTERNAL INFORMATION 13 the guidance in Regulatory Guide 1.208, "A Performance

-Based Approach to Define the Site

-Specific Earthquake Ground Motion," dated March 2007.

Q 1 6.There has been reports that the plant was designed to withstand a 5.9

-6.1 magnitude earthquake and the earthquake experienced was a 5.8 magnitude earthquake. Given the current understanding of the seismic risks, describe the difference in the margin of safety assumed at the time the plant was built versus when the earthquake occurred.

A 1 6. As indicated in the response to Q3 above, the design of NAPS is based on a Modified Mercalli Intensity (MMI) of VII.

This intensity does not correlate directly with the measured magnitude 5.8 experienced at the plant site. The preliminary information on the measured response spectra from the ground motion experienced by plant structures indicates that the ground motion exceeded the design spectra at certain frequencies, however, well within the IPEEE review level earthquake with exception of some structures and components whose seismic capacities are below the IPEEE Review Level Earthquake (RLE) peak ground acceleration of 0.3g

. This does not appear to appreciably encroach on the built

-in seismic design margin of safety related structures and components.

It should be noted that the ground motion response spectrum from the recent earthquake experienced at North Anna will in all likelihood be bounded by the anticipated response spectrum the licensee would be expected to use in its seismic risk evaluation in conjunction with the response to the proposed generic letter for Generic Issue 199, "Implications of Updated Probabilistic Seismic Hazard Estimates in Central and Eastern United States on Existing Plants," currently under development.

Q 1 7. What level of earthquake is the North Anna plant built to? What did the instruments show? A 1 7.North Anna's design basis earthquake ground acceleration is 0.12g for rock and 0.18g for soil. The USGS's estimate of the peak ground acceleration at the site was approximately 0.26g. Dominion's seismic instruments located on the structures at different elevation levels indicate earthquake vibration exceeded the plants design basis earthquakes at considerable frequency range. Q18. Please discuss briefly the inspections performed to assess the structural integrity of the buried piping at North Anna Units 1 and 2.

A18.The licensee performed system pressure tests on all safety

-related buried piping and found no leakage.

The licensee also excavated certain segments of buried pipes for direct inspections and found no cracking.

The inspected and/or tested buried piping are the Service water system, Quench Spray System, Recirculation Spray system, Safety injection system, and fire protection system. NRC review and responsibility Short Term Q1 9. Is the NRC satisfied with Dominion's inspections so far? Are those inspections sufficient? How does NRC guarantee that Dominion's inspections are satisfactory? A1 9. The NRC is currently assessing the acceptability of the licensee's actions following the earthquake. Immediately after the event, an Augmented Inspection Team was sent to the site in order to assess the circumstances surrounding the loss of offsite power, the reactor trips, and the emergency diesel generator failure and other seismic impact to the facility. A restart OFFICIAL USE ONLY

- SENSITIVE INTERNAL INFORMATION 14 inspection was conducted October 5

-14, 2011. The basis for determining the acceptability of Dominion's inspections will be documented in the NRC's publically available evaluation of the information. Prior to resuming operations, the plant operator, Dominion, will submit information to the NRC to demonstrate that no functional damage has occurred to those features necessary for continued operation without undue risk to the health and safety of the public. The staff issued the bulk of its RAI questions by 10/17 and is in the process of reviewing the responses received. The staff's review will be documented in a safety evaluation. At this time, the NRC has not made its determination regarding the acceptability of the licensee's actions for supporting plant restart. Q 20. What does NRC believe is a likely re

-start timeframe for North Anna

? A 20. The NRC's responsibility is to assess the licensee's determination regarding its acceptability to restart the plants. The NRC will take the appropriate amount of time necessary to be satisfied that there is reasonable assurance that public health and safety will be maintained. Dominion is continuing to perform tests, checks, and evaluations. As the information is communicated to the NRC additional questions about the details of this work are being asked and Dominion is continuing to provide updates as they continue to check the equipment and structures at the site. The actual re

-start time cannot be accurately predicted at this time.

Q21. From NRC's perspective, what happens in the process after Dominion says the plant is ready to re

-start? (I.e. what needs to happen from a regulatory perspective?)

A 21. The NRC will review the information provided by Dominion. If additional information is needed for the staff to conclude that there is reasonable assurance that public health and safety will be maintained, then additional information will be requested of the licensee. In addition to the review of information provided by Dominion, NRC will conduct the appropriate on

-site inspections to provide a measure of the completeness and effectiveness of the licensee's activities to demonstrate readiness to restart. Once sufficient information is available, the staff will document its basis for its conclusion.

Q2 2. When will North Anna nuclear plant restart?

A2 2. The NRC will only allow North Anna to restart when Dominion proves to the agency's satisfaction that all of its systems and components can meet their functional requirements to protect public health and safety.

NRC review and responsibility Long Term Q 2 3. Why isn't the NRC immediately forcing Dominion to reinforce North Anna to resist a quake like the one that occurred on August 23?

A 2 3.The NRC initiated in 2005 Generic issue (GI

-199) "Implications of Updated Probabilistic Seismic Hazard Estimates in Central and eastern US on Existing Plants" to evaluate the latest seismic hazards in the Central and Eastern United States (CEUS) because the seismic investigations for ESPs and COLAs indicated higher seismic hazards with respect to the hazards of the co

-located operating reactors.

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- SENSITIVE INTERNAL INFORMATION 15 Results from the NRC's GI 199 study show that the ground motions from earthquakes in the CEUS may likely exceed previous estimates; however, due to the large seismic safety margin in the nuclear plants' original design, the changes in seismic core damage frequency (CDF) for plants in the CEUS were in the range of 1E

-4 and 1E-5 which does not require immediate action since there is no imminent safety concern. Following the completion of the safety/risk assessment stage of GI

-199, the NRC issued Information Notice (IN) 2010

-018. Recently, NRC also issued a draft Generic Letter (for public comments) to licensees of all operating reactors to request to evaluate seismic risk using the latest estimates of seismic hazards that will be available by the end of 2011.

The draft Generic Letter is currently out for public comment.

The plant demonstrated its capability to resist a n earthquake of the magnitude experienced on 08/23/11 through many rounds of investigations and walkdowns. Based on the specific evaluation performed by the licensee in the late 1990s in conjunction with the IPEEE effort, the plant's has a potential capability to resistant to a ground motion up to 0.3 g.

Q 2 4. Why does the NRC not require Dominion to modify its licensing basis prior to restart? A 2 4: The staff may not require Dominion to modify its licensing basis prior to restart because of the following reasons:

Technical Perspective Damage intensity was determined to be "0," but for the sake of conservatism, the licensee deliberately set it to be "1." All the walkdowns and investigations conducted thus far do not indicate any significant damage to safety related SSCs.

The strong motion duration from the earthquake is of very short, about 1

-3 sec onds. North Anna NPP's reactors are designed and evaluated for a duration of 20 seconds with SSE and LOCA loads combined)

. The largest Cumulative Absolute Velocity (CAV, a damage indicator) is 0.175 g

-second (comparing safe shutdown threshold 0.16 g

-second), which is much smaller than the CAV values used in original design (> 0.58 g

-second). North Anna's beyond design evaluation for IPEEE demonstrated that the plant has a seismic capacity to resist an earthquake ground motion up to 0.3 g (with some identified exceptions).

Those SSCs did not meet the 0.3g criteria received special consideration by the licensee.

The plant High Confidence Low Probability Failure (HCLPF) under IPEEE was determined to be 0.16 g.

The licensee will have to prove operability and functionality of the plant SSC's IAW part 9900 of the inspection manual by performing walk downs, inspections and testing.

This overall evaluation of the SSC's performed by the licensee will have to be approved by the NRC staff prior to operation of the plant.

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- SENSITIVE INTERNAL INFORMATION 16 Licensing Perspective From a licensing perspective, there is no regulatory or legal basis for requiring the licensee to modify the SSE prior to restart.

If during the staff's review, an adequate protection issue is identified, the staff would then order the licensee to take such an action.

We believe North Anna, as well as the other applicable operating reactors, should re-evaluate their SSE, consistent with GI

-199 GL provisions, in the future.

One caveat is that NNTF recommended reassessment of seismic risks under the auspices of adequate protection.

Q2 5. What will happen if the ground acceleration exceeded the design basis safe shutdown for North Anna? What will NRC Do?

A2 5.The NRC initially dispatched a seismic expert and another structural expert to assist the agency's resident inspectors on site. Further reviews indicated that additional inspection is warranted.

On Aug. 29, the NRC dispatched the Augmented Inspection Team (AIT) to the North Anna nuclear power station to further review the effects the earthquake, the operators' response and the plant staff's investigations. No significant damage to safety related SSCs has been identified to date, but Dominion has reported to the NRC that initial reviews determined the plant have exceeded the ground motion for which it was designed. This determination is in line with NRC's preliminary independent analyses. The NRC will continue to carefully evaluate information to determine if additional actions may be necessary. NRC regulations require that the station not start up until it can demonstrate that no functional damage occurred to those features needed for continued safe operation.

An AIT was formed by the NRC to review more significant events or issues at NRC

-licensed facilities. The AIT incl ude d technical experts from NRC headquarters in Rockville, Md. as well as two additional inspectors from the regional office in Atlanta. The AIT w as led by NRC Region II Branch Chief Mark Franke and North Anna Senior Resident Inspector Greg Kolcum.

The AI T presented its findings at the exit meeting held on October 3, 2011. That meeting w as open to interested members of the public and the news media, and team members , Region 2 and NRR senior managers were at the site to answer questions after the results were presented. The AIT's report will be issued in 30 days after the completion of the inspection

. GI-199 Q 2 6. How does the Mineral, Va. earthquake impact what we were doing with regard to GI

-199? Was the earthquake "bounded" by the GI

-199 information or do we need to re

-assess what we need licensee's to analyze for their plants?

A 2 6.The ground motion estimates from the earthquake in VA strongly appear to validate the NRC's current seismic hazard assessment approaches and the basis for GI

-199 reviews. Whe n the new hazard estimates for performing the GI

-199 generic letter (GL) evaluations become OFFICIAL USE ONLY

- SENSITIVE INTERNAL INFORMATION 17 available, the ground motion estimate at the NAPS site will likely bound the VA earthquake response spectrum measured at the plant. Tentatively, the licensee's long

-term action will, in some fashion, refer to its future response to the GL as a means to ascertain its seismic adequacy and desired core damage frequency (CDF) of 1 E-5 (one chance in 100,000 per year) or less. Q 2 7. What is Generic Issue 199 about?

A 2 7. GI-199 investigates the safety and risk implications of updated earthquake

-related data and models. These data and models suggest that the probability for earthquake ground motion above the seismic design basis for some nuclear plants in the Central and Eastern United States (CEUS), although is still low, is larger than previous estimates.

Q 28. Where can I get current information about Generic Issue 199?

A 2 8. The public NRC Generic Issues Program (GIP) website

(http://www.nrc.gov/about

-nrc/regulatory/gen

-issues.html) contains program information and documents, background and historical information, generic issue status information, and links to related programs. The latest Generic Issue Management Control System quarterly report, which has regularly updated GI

-199 information, is publicly available at http://www.nrc.gov/reading

-rm/doc-collections/generic

-issues/quarterly/index.html. Additionally, the US Geological Survey provides data and results that are publicly available at http://earthquake.usgs.gov/hazards/products/conterminous/2008/

. Q 2 9. What are the current findings of GI

-199? A2 9. Current operating nuclear plants in the US remain safe, with no need for immediate action. This determination is based on NRC staff reviews of updated seismic hazard information and the conclusions of the first stage of GI

-199. Existing nuclear plants were designed with considerable margin to be able to withstand the ground motions from the "deterministic" or "scenario earthquake" that accounted for the largest earthquakes expected in the area around the plant. The results of the GI

-199 assessment demonstrate that the probability of exceeding the design basis ground motion may have increased at some sites, but only by a relatively small amount. In addition, the probabilities of seismic core damage are lower than the guidelines for taking immediate action. Although there is not an immediate safety concern, the NRC is focused on assuring safety during even very rare and extreme events. Therefore, the NRC has determined that assessment of updated seismic hazards and plant performance should continue.

Q 30. Does GI

-199 provide rankings of US nuclear plants in terms of safety?

A 30. The NRC does not rank nuclear plants by seismic risk. The objective of the GI

-199 Safety/Risk Assessment was to perform a conservative, screening

-level assessment to evaluate if further investigations of seismic safety for operating reactors in the CEUS are warranted, consistent with NRC directives. The results of the GI

-199 safety risk assessment 5 should not be interpreted as definitive estimates of plant

-specific seismic risk because some analyses were very conservative making the calculated risk higher than in reality. The nature of the information used (both seismic hazard data and plant

-level fragility information) make these estimates useful only as a screening assessment.

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- SENSITIVE INTERNAL INFORMATION 18 Q 31. Following up on the NRC's September 2010 Information Notice titled "Implications of Updated Probabilistic Seismic Hazard Estimates in the Eastern and Central United States on Existing Plant," describe:

a. Whether there are any new seismic

-hazard estimates that the report anticipated would be finished in late 2010 or early 2011. If so, please provide those estimates;

b. The status of implementation of the report's recommendations, including a description of the plants that have and have or recalculated their seismic core damage frequency;

c. The timeline for completing individual safety reviews at all of the nation's nuclear power plants; and

d. Steps that the NRC could take to expedite the implementation of safety reviews and the completion of any work needed to address safety issues found during such a review

.

A 31. Since the publication of this Information Notice 2010

-018, NRC issued a draft Generic Letter (GL) entitled, "Seismic Risk Evaluations for Operating Reactors," on September 1, 2011, for public comments. a) The information on updated seismic hazard estimates is expected to be available at the end of calendar year 2011.

b) According to the draft GL, addressees would start their evaluations following formal issuance of the final GL. The GL provides a proposed schedule for various milestones that they are required to follow for submitting the requested information.

c) The above mentioned milestones specify proposed completion of seismic evaluations within one or two years from the date of issuance of the GL, depending on the chosen type of seismic evaluation (i.e., seismic margin assessment or seismic probabilistic risk assessment) d) The NRC may opt to use contractors to support the review of licensees' seismic risk evaluations and proposed actions.

Q 32. Dominion has said North Anna is the "test case" for GI

-199. How important is the North Anna review to the entire GI

-199 process? Could the GI

-199 process delay re

-start for North Anna?

A 32. As discussed in response to the above questions, the NRC is currently developing its approach to evaluate those actions that the licensee is taking to demonstrate that no functional damage has occurred to those features necessary for operation and that operations may resume without undue risk to the health and safety of the public.

Q 33. What is the NRC doing on seismic risk in response to recent earthquake events?

A 33. The NRC continues its effort to have U.S. nuclear power plants better characterize seismic risk and their response to earthquakes. The NRC expects by the end of the year to issue new seismic source models for CEUS and require some individual plant analysis; the plants' responses would be available within one or two years, depending on the analysis used.

Q 34. What do you mean by "increased estimates of seismic hazards" at nuclear plant sites? A 34. Seismic hazard (earthquake hazard) represents the chance (or probability) that a specific level of ground motion could be observed or exceeded at a given location.

OFFICIAL USE ONLY

- SENSITIVE INTERNAL INFORMATION 19 Our estimates of seismic hazard at some Central and Eastern United States locations have changed based on results from recent research, indicating that earthquakes occurred more often or seismic waves propagate much farther than previously estimated.

Our estimates of seismic hazard have also changed because the models used to predict the level of ground motion, as caused by a specific magnitude earthquake at a certain distance from a site, changed.

The increased estimates of seismic hazard at some locations in the CEUS were discussed in a memorandum to the Commission, dated July 26, 2006. (The memorandum is available in the NRC Agencywide Documents Access and Management System [ADAMS] under Accession No. ML052360044).

US NPP Seismic Design Q 35. How many US reactors are located in active earthquake zones?

A3 5. Although we often think of the US as having "active" and "non

-active" earthquake zones, earthquakes can actually happen almost anywhere. Seismologists typically separate the US into low, moderate, and high seismicity zones. The NRC requires that every nuclear plant be designed for site

-specific ground motions that are appropriate for their locations. In addition, the NRC has specified a minimum ground motion level to which nuclear plants must be designed.

Q 36. What level of earthquake hazard are the US reactors designed for?

A3 6. Each reactor is designed for a different ground motion that is determined on a site

-specific basis. The existing nuclear plants were designed on a "deterministic" or "scenario earthquake" basis that accounted for the largest earthquakes expected in the area around the plant, without consideration of the likelihood of the earthquakes considered. New reactors are designed using probabilistic method that characterize s both the ground motion levels and uncertainty at the proposed site. These probabilistic metho ds account for the ground motions that may result from all potential seismic sources in the region around the site. Technically speaking, this is the ground motion with an annual frequency of exceedance of 1x10-4/year, but this can be thought of as the ground motion that occurs every 10,000 years on average. One important aspect is that probabilistic seismic hazard and risk

-assessment techniques account for beyond

-design basis events. NRC's Generic Issue 199 (GI

-199) project is using the latest probabilisti c methods used for new nuclear plants to review the safety of the existing plants. [See GI-199 Q & A section for more information about GI

-199] Q3 7. What magnitude earthquake are currently operating US nuclear plants designed to?

A3 7. Ground motion is a function of both the magnitude of an earthquake and the distance from the fault to the site. Nuclear plants, and in fact all engineered structures, are actually designed based on ground motion levels, not earthquake magnitudes. The existing nuclear plants were designed based on a "deterministic" or "scenario earthquake" basis that accounted for the largest earthquakes expected in the area around the plant. A margin is further added to the predicted ground motions to provide added robustness.

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- SENSITIVE INTERNAL INFORMATION 20 Q3 8. What is the likelihood of the design basis earthquake or "SSE" ground motions being exceeded over the life of a nuclear plant?

A3 8. The ground motion re sponse spectra that are used as seismic design bases at US nuclear plants are called the Safe Shutdown Earthquake (SSE). Because the SSEs for operating nuclear power plants were established many years ago and the current understanding on seismic hazard is somehow different from when the plants' SSEs were determined, there is likelihood that the SSE for a n operating nuclear power plant may be exceeded by an earthquake ground motion. However, each plant was designed differently according to different licensing SSEs, Therefore, the likelihood of exceedance is plant specific. The August 23 earthquake has demonstrated that NAPS SSEs have been exceeded.

Meanwhile, it shouldn't be ignored that structures, systems and components are required to have "adequate margin," meaning that they must continue be able to withstand shaking levels that are above the plant's design basis.

Q39. Has there been another reactor site that has experienced exceedance of its seismic design limit during an earthquake?

A39. This would be the first instance of an operating reactor in the United States exceeding its design limit for ground acceleration. In 1986, earthquake motions at the Perry NPP in Ohio exceeded its OBE and SSE during construction but was found acceptable for operation before its license was issued. In 1979 the VC Summer plant in South Carolina also experienced an exceedance in both OBE and SSE while under construction but was found acceptable for operation before its license was issued. In Japan, there are many incidences when design basis earthquakes were exceeded, for example , the Kashiwazaki

-Kariwa nuclear power plant in Japan exceeded its design basis earthquake on July 16, 2007. The KK event was significantly more destructive as indicated by the damage in the area.

Generic Seismic Questions Q 40. What is magnitude? What is the Richter scale? What is intensity?

A 40. An earthquake's magnitude is a measure of the strength of the earthquake as determined from seismographic observations. Magnitude is essentially an objective, quantitative measure of the size of an earthquake. The magnitude can be expressed in various ways based on seismographic records (e.g., Richter Local Magnitude, Surface Wave Magnitude, Body Wave Magnitude, and Moment Magnitude). Currently, the most commonly used magnitude measurement is the Moment Magnitude, Mw, which is based on the strength of the rock that ruptured, the area of the fault that ruptured, and the average amount of slip. Moment magnitude is, therefore, a direct measure of the energy released during an earthquake. Because of the logarithmic basis of the scale, each whole number increase in magnitude represents a tenfold increase in measured amplitude; as an estimate of energy, each whole number step in the magnitude scale corresponds to the release of about 31 times more energy than the amount associated with the preceding whole number value. The Richter magnitude scale was developed in 1935 by Charles F. Richter of the California Institute of Technology and was based on the behavior of a specific seismograph that was manufactured at that time. The instruments are no longer in use and the magnitude scale is, therefore, no longer used in the technical community.

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- SENSITIVE INTERNAL INFORMATION 21 However, the Richter scale is a term that is so commonly used by the public that scientists generally just answer questions about "Richter" magnitude by substituting moment magnitude without correcting the misunderstanding.

The intensity of an earthquake is a qualitative assessment of effects of the earthquake at a particular location. The intensity assigned is based on observed effects on humans, on human

-built structures, and on the earth's surface at a particular location. The most commonly used scale in the US is the Modified Mercalli Intensity (MMI) scale, which has values ranging from I to XII in the order of severity. MMI of I indicates an earthquake that was not felt except by a very few, whereas MMI of XII indicates total damage of all works of construction, either partially or completely. While an earthquake has only one magnitude, intensity depends on the effects at each particular location.

Q 4 1. How do magnitude and ground motion relate to each other?

A 4 1. The ground motion experienced at a particular location is a function of the magnitude of the earthquake, the distance from the earthquake generating fault to the location of interest, and other elements such as the geologic materials through which the waves pass.

Q 4 2. Does the Seismic Core Damage represent a measurement of the risk of radiation release or only the risk of core damage (not accounting for additional containment)?

A 4 2. Seismic core damage frequency is the probability of damage to the core resulting from a seismic initiating event. It does not imply either a meltdown or the loss of containment, which would be required for radiological release to occur. The likelihood of radiation release is far lower. http://earthquake.usgs.gov/hazards/products/conterminous/2008/

. Q 4 3. In the wake of the Fukushima nuclear power plant accident in Japan, what if anything has the commission or Congress done to make sure that cooling systems and backup electricity at U.S. plants are adequate?

A 4 3. Subsequent to the Fukushima event the NRC issued two temporary instructions (inspections) to gather information on the adequacy, among other things, of reactor and spent fuel cooling systems and back-up electrical power.

This information was used in the preparation of the NRC's near

-term task force report.

This report is currently be evaluated by the NRC to assess what actions should be taken and to prioritize them.

Q4 4. Where to find out more about seismic issues for nuclear power plants?

A 4 4. See the NRC Factsheet http://www.nrc.gov/reading

-rm/doc-collections/fact

-sheets/fs-seismic-issues.html Q 4 5. Are there seismic monitors on site?

A 4 5.Yes. The NRC requires nuclear power plants to maintain operating seismic monitors on site.

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- SENSITIVE INTERNAL INFORMATION 22 Q 4 6. Is there any way of verifying the ground

-motion recordings NAPS reported last month? Or does the NRC just record what they say?

A 4 6. Following any event at or near a nuclear power plant the NRC has the option to verify the information provided by the licensee depending on the significance of the event.

For example, the seismic information for North Anna was reviewed by the NRC Augmented Inspection Team

.