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#REDIRECT [[0CAN121602, Mitigating Strategies Assessment (MSA) Report for the New Seismic Hazard Information Per Nuclear Energy Institute (NEI) 12-06, Appendix H, Revision 2, H.4.3 Path 3]]
| number = ML16365A084
| issue date = 12/30/2016
| title = Arkansas Nuclear One, Units 1 and 2 - Mitigating Strategies Assessment (MSA) Report for the New Seismic Hazard Information Per Nuclear Energy Institute (NEI) 12-06, Appendix H, Revision 2, H.4.3 Path 3
| author name = Anderson R L
| author affiliation = Entergy Operations, Inc
| addressee name =
| addressee affiliation = NRC/Document Control Desk, NRC/NRR
| docket = 05000313, 05000368
| license number = DPR-051, NPF-006
| contact person =
| case reference number = 0CAN121602, TAC MF3822, TAC MF3823
| document type = Letter, Report, Miscellaneous
| page count = 9
| project = TAC:MF3822, TAC:MF3823
| stage = Other
}}
 
=Text=
{{#Wiki_filter:0CAN121602  
 
December 30 2016
 
U.S. Nuclear Regulatory Commission
 
ATTN: Document Control Desk
 
11555 Rockville Pike
 
Rockville, MD 20852
 
==SUBJECT:==
Mitigating Strategies Assessment (MSA) Report for the New Seismic Hazard Information per Nuclear Energy Institute (NEI) 12-06, Appendix H, Revision 2, H.4.3 Path 3  
 
Arkansas Nuclear One - Units 1 and 2
 
Docket Nos. 50-313 and 50-368
 
License Nos. DPR-51 and NPF-6
 
==Dear Sir or Madam:==
 
The purpose of this letter is to provide the results of the assessment for Arkansas Nuclear One, Units 1 and 2 (ANO-1 and ANO-2, respectively) to demonstrate that an Individual Plant
 
Examination of External Events (IPEEE)-based alternate mitigating strategy can be
 
implemented considering the impacts of the r eevaluated seismic hazard. The assessment was performed in accordance with the guidance provided in Appendix H of Reference 1, which was
 
endorsed by the NRC in Reference 2.
 
The mitigating strategies seismic hazard information (MSSHI) is the licensee's reevaluated
 
seismic hazard information at ANO-1 and ANO-2 which was developed using probabilistic
 
seismic hazard analysis. The MSSHI for Path 3 includes the performance-based ground motion
 
response spectrum (GMRS) at various frequencies developed at the ANO-1 and ANO-2 control
 
point elevations. In response to Reference 7, Entergy Operations, Inc. submitted the
 
reevaluated seismic hazard information including the uniform hazard response spectra, GMRS, and the hazard curves (References 3, 5, and 6). The NRC staff concluded that the MSSHI
 
adequately characterizes the reevaluated seismic hazard for the site (Reference 4).
 
Consistent with Section H.4.3 of Reference 1, the ANO-1 and ANO-2 GMRS is bounded by the
 
high-confidence-of-low-probability-of-failure (HCLPF) spectrum developed from evaluations for
 
the IPEEE between 1 and 10 Hz - referred to as the IPEEE HCLPF spectrum (IHS). 
 
Section 6.1.2 of Reference 2 identified that the method described in Section H.4.3 of
 
Reference 1 is applicable to ANO-1 and ANO-2. The ANO-1 and ANO-2 GMRS are not
 
bounded by the IHS at frequencies greater than 10 Hz.
 
Based upon the mitigating strategies assessment in the attachment to this letter, the mitigating
 
strategies for ANO-1 and ANO-2 considering the impacts of the reevaluated seismic hazard can
 
be implemented as designed.
 
Entergy Operations, Inc.
1448 S.R. 333 Russellville, AR  72802
 
Tel  479-858-3110 Richard L. Anderson A NO Site Vice President
 
0CAN121602 Page 2 of 3
 
This letter contains no new regulatory commitments. Should you have any questions regarding
 
this submittal, please contact Stephenie Pyle at 479.858.4704.
 
I declare under penalty of perjury that the foregoing is true and correct; executed on
 
December 30, 2016.
 
Sincerely, ORIGINAL SIGNED BY TERRY A. EVANS (ACTING VP) FOR RICHARD L. ANDERSON
 
RLA/nbm
 
==Attachment:==
Mitigating Strategies Assessment for Arkansas Nuclear One
 
==REFERENCES:==
: 1. NEI 12-06, Revision 2, Diverse and Flexible Coping Strategies (FLEX) Implementation Guide , December 2015 (ML16005A625)
: 2. JLD-ISG-2012-01, Revision 1, Compliance with Order EA-12-049, Order Modifying Licenses with Regard to Requirements for Mitigation Strategies for Beyond-Design-Basis External Events , February 2016 (ML15357A163)
: 3. Entergy letter to NRC, Seismic Hazard and Screening Report (Central Eastern United States Sites), Response to NRC Request for Information Pursuant to 10 CFR 50.54(f) Regarding Recommendation 2.1 of the Near-Term Task Force (NTTF) Review of Insights from the Fukushima Dai-ichi Accident , dated March 28, 2014 (ML14092A021)
(0CAN031404)
: 4. NRC letter to ANO, Arkansas Nuclear One, Units 1 and 2- Staff Assessment of Information Provided Pursuant to 10 CFR 50.54(f), Seismic Hazard Reevaluations for Recommendation 2.1 of the NTTF Review of Insights from the Fukushima Dai-ichi Accident (TAC NOS. MF3822 and MF3823), dated December 15, 2015 (ML15344A109)
(0CNA121502)
: 5. Entergy letter to NRC, Response to Request for Additional Information Associated with NTTF Recommendation 2.1, Seismic Hazard and Screening Report Arkansas Nuclear One , dated August 21, 2014 (ML14233A275) (0CAN081401)
: 6. Entergy letter to NRC, Information Pursuant to 10 CFR 50.54(f) Regarding the Seismic Aspects of Recommendation 2.1 of the NTTF Review of Insights from the Fukushima Dai-ichi Accident , dated November 4, 2014, (ML14308A212) (0CAN111401)
: 7. NRC Letter to Entergy, Request for Information Pursuant to 10 CFR 50.54(f) Regarding Recommendations 2.1, 2.3, and 9.3, of the NTTF Review of Insights from the Fukushima Dai-ichi Accident , dated March 12, 2012 (ML12053A340) (0CNA031208)
 
0CAN121602 Page 3 of 3
 
cc: Mr. Kriss Kennedy Regional Administrator
 
U. S. Nuclear Regulatory Commission, Region IV
 
1600 East Lamar Boulevard Arlington, TX 76011-4511
 
NRC Senior Resident Inspector
 
Arkansas Nuclear One
 
P.O. Box 310
 
London, AR 72847
 
U. S. Nuclear Regulatory Commission
 
Attn: Mr. Thomas J. Wengert
 
MS O8 B1A
 
One White Flint North
 
11555 Rockville Pike
 
Rockville, MD 20852 
 
Attachment to 0CAN121602 Mitigating Strategies Assessment for Arkansas Nuclear One Attachment to 0CAN121602
 
Page 1 of 5
 
Mitigating Strategies Assessment for Arkansas Nuclear One Introduction
 
The purpose of this mitigating strategies assessment is to evaluate and demonstrate that
 
Arkansas Nuclear One, Units 1 and 2 (ANO-1 and ANO-2, respectively) can mitigate the effects
 
of the reevaluated seismic hazard information developed pursuant to the 10 CFR 50.54(f) letter
 
dated March 12, 2012 (Reference 14). The assessment was performed in accordance with the
 
guidance provided in Reference 1. Reference 1 discusses a method to develop an alternate
 
mitigating strategy (AMS) to address the mitigating strategies seismic hazard information (MSSHI). This includes a modification of the general criteria and baseline assumptions included
 
in Section 3.2.1 of Reference 1 to exclude consideration of losses such as an extended loss of
 
alternating current power (ELAP), loss of offsite power, or loss of ultimate heat sink (LUHS)
 
unless caused by the seismic hazard. Reference 2 provides an NRC staff position that the
 
method described in Section H.4.3 of Reference 1 for an AMS is acceptable for mitigating a
 
beyond-design-basis external event (BDBEE).
 
An individual plant examination of external events (IPEEE)-based AMS relies on the seismic
 
evaluation of plant equipment to demonstrat e robustness of structures, systems, and components (SSCs) to the ground motion response spectrum (GMRS). The IPEEE for ANO-1
 
and ANO-2 relied on the results of an Electric Power Research Institute (EPRI) seismic margins
 
assessment (SMA) methodology to demonstrate the capability to bring the plant to a safe-
 
shutdown condition following a review level earthquake (RLE) as described in NUREG-1407 (Reference 5). The EPRI SMA methodology approach evaluated two safe-shutdown success
 
paths. The safe-shutdown success paths provide independent means of achieving a
 
safe-shutdown condition following a severe seismic event (e.g., core cooling by heat removal
 
from the steam generators and core cooling by reactor coolant system 'feed and bleed').
 
The IPEEE high-confidence-of-low-probability-of-failure spectrum (IHS) for ANO-1 and ANO-2
 
demonstrates plant seismic capacity to levels higher than the GMRS in the 1-10 Hz range (Reference 4). Seismic evaluations performed under the IPEEE included SSCs in those two
 
safe-shutdown success paths. Therefore, based on the results of the IPEEE, safe-shutdown of
 
the plant following a seismic event can be accomplished and consequences can be mitigated
 
for a seismic event up to the plant capacity level (i.e., the IHS) for which the SSCs in the IPEEE
 
were evaluated.
 
Indefinite Coping
 
A plant-specific evaluation was performed which concluded that SSCs that limit the SMA-based
 
IPEEE coping duration to 72 hours are available for an indefinite period following a beyond-
 
design-basis seismic event at the reevaluated seismic hazard level to support continued
 
maintenance of the safe-shutdown condition. The ANO-1 and ANO-2 IPEEE was based on the
 
EPRI SMA method. This approach defined the Seismic Equipment List for evaluation of
 
safe-shutdown success paths to be comprised of those SSCs required to bring the plant to a
 
safe-shutdown condition and maintain that condition for a minimum of 72 hours. Therefore, the
 
IPEEE results have been evaluated for limitations that are based on the 72-hour coping
 
duration. Generally, the conclusions of the SM A are not sensitive to coping duration; however, certain consumable items, such as water and fuel oil inventories, have been evaluated based Attachment to 0CAN121602
 
Page 2 of 5
 
on a limited onsite supply. The ability to continue coping would potentially require re-supply of consumables.
 
Site access is assumed to be restored to a near-normal status and/or augmented transportation
 
resources are available within a few days as discussed in NEI 12-01 (Reference 6) to allow for
 
additional supplies to be delivered and allow for continuation of coping strategies and maintain
 
the plant in a safe-shutdown condition. A plant-specific evaluation has been performed to
 
identify consumables and/or SSCs that are limiting for the 72-hour coping duration assumed in
 
the development of the IPEEE and to identify methods of addressing any shortfalls.
 
The coping evaluation (Reference 11) concluded that borated and non-borated water would be
 
available indefinitely for all safety functions. Several water supplies are available to ANO-1 and
 
ANO-2 to support coping for an extended period following the beyond-design-basis seismic
 
event to support continued maintenance of the safe-shutdown condition. This includes multiple
 
large atmospheric storage tanks and the ultimate heat sink. The large atmospheric storage
 
tanks include the ANO-1 condensate storage tank (CST), both ANO-2 CSTs, the safety-related
 
condensate storage tank (QCST), the ANO-1 borated water storage tank, and the ANO-2
 
refueling water tank. These tanks would provide numerous days of continued operation for
 
reactor coolant inventory control, decay heat removal, and spent fuel pool (SFP) cooling. This
 
would provide ample coping time before inventory from the ultimate heat sink is required. The
 
ultimate heat sink is comprised of the emergency cooling pond (ECP), a large but finite source
 
of inventory, and Lake Dardanelle which can be considered an indefinite supply of water. The National Strategic Alliance for FLEX Emergency Response (SAFER) Response Centers (NSRC) would supply portable pumps and other equipment to support the indefinite coping
 
capability for both ANO-1 and ANO-2.
 
Although not determined to be limiting, fuel oil supplies supporting emergency diesel generator
 
and portable diesel-driven equipment operation were also evaluated for extended coping (Reference 11). The on-site supplies have been evaluated to last at least 3.5 days to continue the strategies evaluated under the IPEEE and the on-site FLEX strategies for SFP cooling. 
 
Consistent with the ANO Final Integrated Plan (FIP) (Reference 9), at least 72 hours of on-site
 
fuel is ample time to have additional fuel oil provided from offsite resources as necessary.
 
IPEEE Upgrade to Full Scope
 
The ANO-1 IPEEE was a modified full scope SMA and requires the performance of a detailed review of relay chatter. The ANO-2 IPEEE was a modified focused scope SMA and also
 
requires the performance a detailed review of relay chatter. ANO-2 is included in the focused
 
scope bin, and an upgrade to a full scope assessment is required as described in
 
EPRI 1025287 (Reference 7).
 
ANO-2 was binned as a 0.3g focused scope plant in NUREG-1407 (Reference 5). As stated in
 
Section 3.3.1 of the EPRI Seismic Evaluation Guidance: Screening, Prioritization, and
 
Implementation Details (SPID), focused-scope IPEEE submittals may be used for screening
 
against the GMRS provided they are enhanced to bring them in line with full scope
 
assessments. The enhancements include (1) a full scope detailed review of relay chatter and
 
(2) a full evaluation of soil failures.
Attachment to 0CAN121602
 
Page 3 of 5
 
Full Scope Relay Chatter Review Assessments of relay chatter effects in accordance with the scope and procedures described in
 
NUREG-1407 (Reference 5) were performed for ANO-1 and ANO-2. ANO-1 and ANO-2 were
 
considered A-46 plants, and the relay chatter review was conducted consistent with staff
 
recommendations outlined in NUREG-1407, Appendix D, Table 7.17.2, which includes
 
expansion of the A-46 relay scope to include IPEEE systems and evaluation of the entire
 
expanded scope at the IPEEE RLE.
 
Soil Failure Analysis As stated in NUREG 1407 (Reference 5), Section 3.2.1, a plant in the full-scope category that is
 
located on a rock site is not required to perform a soil failure evaluation. The ANO-1 and ANO-2
 
safety-related structures are founded on rock.
 
SFP Cooling Evaluation
 
The evaluation of SFP cooling for ANO was performed based on the initial conditions
 
established in NEI 12-06 (Reference 1) for SFP cooling coping in the event of an ELAP/LUHS. 
 
The evaluation also used the results of SFP heatup analyses from the ELAP evaluation as input (Reference 9).
 
The FLEX strategy for SFP cooling utilizes SFP level monitoring and makeup capability as
 
described in the ANO Final Implementation Plan (Reference 9). The permanently installed plant equipment relied on for the implementation of the SFP cooling FLEX strategy includes
 
components associated with SFP level instrumentation and the SFP makeup riser. This equipment, portable FLEX equipment availab ility (including its storage and deployment pathways) and the permanently installed plant equipment needed to accomplish SFP cooling
 
have subsequently been evaluated considering t he GMRS-consistent loading conditions in accordance with NEI 12-06, Appendix H, Section 5, and/or Seismic Qualification Utility Group (SQUG) experience-based walkdowns (Reference 12). FLEX equipment availability has been
 
demonstrated through evaluations in accordance with NEI 12-06, Appendix H, Section 5, by evaluating the SFP makeup riser pipe supports, both ANO FLEX storage buildings, sliding and rocking of FLEX equipment stored within those buildings, the onsite FLEX equipment
 
deployment path, and the NSRC equipment deployment path. In addition, Seismic Qualification Utility Group (SQUG) experience-based walkdowns were conducted to demonstrate sufficient
 
seismic adequacy of the SFP makeup riser piping, SFP level instrumentation components, operator access pathways needed to implement the FLEX SFP cooling strategies, and local
 
storage of portable flexible hoses near the SFP. Through the evaluations completed in
 
accordance with NEI 12-06, Appendix H, Section 5, and SQUG walkdowns, the means to
 
provide SFP cooling following a severe seismic event has been demonstrated to be adequate
 
for GMRS-consistent loading conditions in accordance with NEI 12-06, Appendix H.
 
High Frequency Evaluation (HFE)
 
To address high frequency exceedance above the IHS, ANO-1 and ANO-2 have conducted an
 
evaluation of high frequency motion sensitive components (relays) in accordance with the
 
guidance in EPRI 3002004396 (Reference 8). The HFE confirmed that the applicable devices
 
in the EPRI SMA methodology scope are acceptable for the high frequency motions at both Attachment to 0CAN121602
 
Page 4 of 5
 
ANO-1 and ANO-2 (Reference 13). Reliance on post-event operator actions was necessary to resolve outliers. A summary of the operator actions and associated outliers is provided in
 
Reference 13.
 
Availability of FLEX Equipment
 
With the exception of SFP cooling, the AMS described in H.4.3 does not rely upon availability of FLEX equipment. On-site FLEX equipment may be available for deployment to support the
 
maintenance of core cooling, containment, and SFP cooling functions. In order to provide additional potential mitigating capability, portable FLEX equipment not being used for the AMS
 
is stored and reasonably protected in accordance with Section 5.3.1 of NEI 12-06.
 
Additionally, ANO maintains the capability to obtain additional portable FLEX equipment from
 
offsite sources. The use of offsite equipment for ANO is documented in Reference 9. The
 
industry has established two NSRCs to support utilities during BDBEEs, of which ANO has
 
established contracts to participate in the process for support of the NSRCs as required. Each
 
NSRC holds multiple sets of equipment, capable of being fully deployed when requested. In the
 
event of a beyond-design-basis seismic even t, equipment can be moved from an NSRC to a local assembly area established by the SAFER t eam. From there, equipment can be taken to the site and staged at the SAFER onsite Staging Area by helicopter, if ground transportation is
 
unavailable. Communications would be established between the site and the SAFER team via
 
satellite phones and required equipment moved to the site as needed. Initial equipment would
 
be delivered to the site within 24 hours from the initial request. The order in which equipment is
 
delivered is identified in the ANO SAFER Response Plan and no modifications to the sequence
 
are necessary following a seismic event.
 
Summary of Modifications
 
Based on the conclusions of the seismic MSA, ANO does not require any modifications to assure SFP cooling, indefinite coping, the availability of FLEX equipment, or to support
 
components evaluated under the HFE.
 
Implementation of SFP makeup following a severe seismic event would be at the discretion of
 
Operations. The existing site procedures direct operations to restore SFP cooling utilizing
 
various methods in the event of an SFP emergency, one of which includes providing emergency
 
makeup from the respective unit's service water system. The service water system for each unit was determined to be seismically adequate as part of IPEEE, as it is required for safe-
 
shutdown. While Operations would likely utiliz e the service water systems to provide SFP cooling following a loss of normal SFP cooling, the MSA shows that the FLEX SFP hose
 
makeup strategy is capable of being implemented, providing additional flexibility following a
 
severe seismic event. As such, no procedure changes are necessary because Operations would direct the use of the FLEX SFP makeup based on the condition of the unit.
 
Attachment to 0CAN121602
 
Page 5 of 5
 
REFERENCES
: 1. NEI 12-06, Revision 2, Diverse and Flexible Coping Strategies (FLEX) Implementation Guide , December 2015 (ML16005A625)
: 2. JLD-ISG-2012-01, Revision 1, Compliance with Order EA-12-049, Order Modifying Licenses with Regard to Requirements for Mitigation Strategies for BDBEEs , February 2016 (ML15357A163)
: 3. Entergy letter to NRC, Seismic Hazard and Screening Report (Central Eastern United States Sites), Response to NRC Request for Information Pursuant to 10 CFR 50.54(f) Regarding Recommendation 2.1 of the NTTF Review of Insights from the Fukushima Dai-
 
ichi Accident , dated March 28, 2014 (ML14092A021) (0CAN031404)
: 4. NRC letter to ANO, Staff Assessment of Information Provided Pursuant to 10 CFR 50.54(f), Seismic Hazard Reevaluations for Recommendation 2.1 of the NTTF Review of Insights from the Fukushima Dai-ichi Accident (TAC NOS. MF3822 and MF3823), dated December 15, 2015 (ML15344A109) (0CNA121502)
: 5. U.S. NRC, NUREG-1407: Procedural and Submittal Guidance for the IPEEE for Severe Accident Vulnerabilities , Washington, D.C., June 1991 (ML063550238)
: 6. NEI, NEI 12-01 Revision 0: Guideline for Assessing Beyond-Design-Basis Accident Response Staffing and Communications Capabilities , Washington, D.C., May 2012
: 7. EPRI, SPID for the Resolution of Fukushima NTTF Recommendation 2.1: Seismic, Report Number 1025287 , Palo Alto, CA, November 2012
: 8. EPRI, High Frequency Program: Application Guidance for Functional Confirmation and Fragility Evaluation , Report Number 3002004396, Palo Alto, CA, July 30, 2015
: 9. Entergy letter to NRC, Notification of Full Compliance with NRC Order EA-12-049 Order Modifying Licenses with Regard to Requirements for Mitigation Strategies for BDBEEs , dated January 12, 2016 (ML16014A396) (0CAN011601)
: 10. NRC letter to NEI, Endorsement of EPRI Report 3002007148, Seismic Evaluation Guidance: SFP Integrity Evaluation , dated March 17,2016 (ML15350A158)
: 11. CALC-ANOC-CS-16-00008, Mitigating Strategies Assessment for New Seismic Hazards Information ANO , Revision 000
: 12. CALC-13-E-0005-57, HCLPF Evaluation of FLEX SFP Cooling and Instrumentation , Revision 000
: 13. Entergy Letter to NRC, High Frequency Supplement to Seismic Hazard Screening Report, Response NRC Request for Information Pursuant to 10 CFR 50.54(f) Regarding Recommendation 2.1 of the NTTF Review of Insights from the Fukushima Dai-ichi
 
Accident , dated December 30, 2016 (0CAN121603)
: 14. NRC Letter to Entergy, Request for Information Pursuant to 10 CFR 50.54(f) Regarding Recommendations 2.1, 2.3, and 9.3, of the NTTF Review of Insights from the Fukushima Dai-ichi Accident , dated March 12, 2012 (ML12053A340) (0CNA031208)}}

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