Text

Notification of Full Compliance with Order EA-12-049 for Mitigation Strategies for Beyond Design Basis External Events and Update for Order EA-12-051 for Reliable Spent Fuel Pool Instrumentation
	ML16067A088
Person / Time
Site:	South Texas
Issue date:	02/17/2016
From:	Gerry Powell; South Texas
To:	; Document Control Desk, Office of Nuclear Reactor Regulation
References
	EA-12-049, EA-12-051, NOC-AE-15003311
	Download: ML16067A088 (129)
	v • d • e

Nuclear Operating Company South Texas Protect £1ectric Generating Station PHO.

Box 289 Wadsworth, TeXas77483 */j _

February 17, 2016 N OC-AE- 15003311 10 CER 2.202 U. S. Nuclear Regulatory Commission Attention: Document Control Desk Washington, DC 20555-0001 South Texas Project Units 1 & 2 Docket No. STN 50-498, STN 50-499 Notification of Full Compliance with Order EA-12-049 for Mitigation Strategies for Beyond Design Basis External Events and Update for Order EA-12-051 for Reliable Spent Fuel Pool Instrumentation

References:

1. NRC Order Number EA-12-049, "Issuance of Order to Modify Licenses with Regard to Requirements for Mitigation Strategies for Beyond-Design-Basis External Events",

March 12, 2012 (AE-NOC-1 2002268)(ML12073A195)

2. Letter from G.T. Powell, STPNOC, to NRC Document Control Desk, "Notification of Compliance with Orders EA-12-049 for Mitigation Strategies for Beyond-Design Basis External Events and EA-12-051 for Reliable Spent Fuel Pool Instrumentation (TAC Nos. MF0826 and MF0828)", July 2, 2015 (NOC-AE-15003257)(ML15196A031)

3. Letter from D.L. Koehl, STPNOC, to NRC Document Control Desk, "STPNOC Overall Integrated Plan in Response to March 12, 2012 Commission Order Modifying Licenses with Regard to Requirements for Mitigation Strategies for Beyond-Design-Basis External Events (Order Number EA-12-049)", February 28, 2013 (NOC-AE-1 3002963) (ML13070A011)

4. Letter from J.S. Bowen, NRC, to D.L. Koehl, STPNOC, "Interim Staff Evaluation Relating to Overall Integrated Plan in Response to Order EA-1 2-049 (Mitigation Strategies) (TAC Nos. MF0825 and MF0826)", January 29, 2014 (AE-NOC-I14002494)(M L 13339A736)

5. Letter from T. Brown, NRC, to D.L. Koehl, STPNOC, "South Texas Project, Units 1 and 2 - Report for the Onsite Audit Regarding Implementation of Mitigating Strategies and Reliable Spent Fuel Instrumentation Related to Orders EA-12-049 and EA-12-051 (TAC Nos. MF0825, MF0826, MF0827, and MF0828)", May 6, 2015 (AE-NOC-1 5002661) (ML15111A465)

6. Letter from G.T. Powell, STPNOC, to NRC Document Control Desk, "Report of Full Compliance with Order EA-12-051 Reliable Spent Fuel Pool Instrumentation,"

January 19, 2016 (NOC-AE-15003297)

STI 34239725

N OC-AE- 15003311 Page 2 of 4 The purpose of this letter is to fulfil the requirement to report to the NRC that STP Unit 1 and Unit 2 are in full compliance with Order EA-12-049 (Reference 1) regarding mitigation strategies for Beyond-Design-Basis External Events. Notification for STP Unit 2 compliance is documented in a previous submittal (Reference 2).

Section IV.A.2 of Order EA-1 2-049 requires full implementation no later than two refueling cycles after submittal of the Overall Integrated Plan (Reference 3) or December 31, 2016, whichever comes first. In addition,Section IV.C.3 of Order EA-12-049 requires that licensees report to the NRC when full compliance is achieved. On December 19, 2015, STP Unit 1 entered Mode 2 (Startup). STP Unit 1 and Unit 2 were in full compliance with both Order EA 049 and EA-12-051 at that time. Reference 6 submitted the report of full compliance for Order EA-12-051.

The Enclosure for this letter provides a brief summary of the key elements associated with compliance with Order EA-12-049 including a completed milestone accomplishment schedule. includes summary responses for the open and confirmatory items from the NRC's Interim Staff Evaluation (ISE) of STP's Overall Integrated Plan (Reference 4). The information contained in Attachment 1 is considered legacy information and may not accurately reflect the current diverse and flexible coping (FLEX) strategies. The current STP FLEX strategies are described in the Final Integrated Plan (FIP) (Attachment 4). provides a clarification related to the response to open and pending items documented in the Onsite Audit Report (Reference 5) that were provided with the STP Unit 2 Order compliance letter (Reference 2). provides responses to other NRC questions that arose after the Audit Report was issued. STPNOC considers the response items listed in Attachments 1 through-3 complete pending NRC closure. to this letter is the STP FLEX Final Integrated Plan (FIP) that includes a summary of FLEX strategies, descriptions of FLEX equipment and descriptions of applicable hazards.

NOC-AE- 15003311 Page 3 of 4 There are no regulatory commitments in this letter.

If there are any questions, please contact Wendy Brost at (361) 972-8516 or me at (361) 972-7566.

I declare under penalty of perjury that the foregoing is true and correct.

Executed on: f'¢nvi 171 o'/*

G. T. Powell Site Vice President web

Enclosure:

Summary of Compliance with NRC Order EA-12-049 Regarding Mitigation Strategies for Beyond-Design-Basis External Events and Update of Compliance Date for Order EA-12-051 Regarding Reliable Spent Fuel Pool Instrumentation Attachments: 1. Summary of Responses for the FLEX Interim Staff Evaluation Open and Confirmatory Items

2. Update to Response to Open and Pending Items from the FLEX and SFPLI Audit Report

3. Summary of Reponses for Other Issues that Arose after the Audit Report

4. STP FLEX Final Integrated Plan (FIP)

N OC-AE-1 5003311 Page 4 of 4 CC:

(paper copy)

(electronic copy)

Regional Administrator, Region IV Morgan, Lewis & Bockius LLP U.S. Nuclear Regulatory Commission Steve Frantz, Esquire 1600 East Lamar Boulevard Arlington, TX 76011-4511 U.S. Nuclear Requlatory Commission Lisa M. Regner Lisa M. Regner Milton Valentin Senior Project Manager Tony Brown U.S. Nuclear Regulatory Commission One White Flint North (08 H04) NRG South Texas LP 11555 Rockville Pike John Ragan Rockville, MD 20852 Chris O'Hara Jim von Suskil NRC Resident Inspector U. S. Nuclear Regulatory Commission CPS Energy

>* P.O. Box 289, Mail Code: MNl16 Kevin Polio Wadsworth, TX 77483 Cris Eugster L. D. Blaylock Milton Valentin Project Manager Crain Caton & James, P.C.

Orders Management Branch Peter Nemeth Japan Lessons-Learned Division U.S. Nuclear Regulatory Commission One White Flint North (MS 1 3F1 5) City of Austin 11555 Rockville Pike Elaina Ball Rockville, MD 20852 John Wester Texas Dept. of State Health Services Richard A. Ratliff Robert Free

Enclosure NOC-AE-1 5003311 ENCLOSURE Summary of Compliance with NRC Order EA-12-049 Regarding Mitigation Strategies for Beyond-Design-Basis External Events and Update of Compliance Date for Order EA-12-051 Regarding Reliable Spent Fuel Pool Instrumentation

Enclosure N OC-AE-1 5003311 Page 1 of 8

1. Introduction STP Nuclear Operating Company (STPNOC) developed an Overall Integrated Plan (OIP)

(Reference 3) to provide diverse and flexible coping (FLEX) strategies in response to Order EA-1 2-049 (Reference 1 ). The final FLEX strategies differ from the strategies described in the OIP. Strategy updates have been submitted through periodic six-month update letters (References 6 - 10).

The information provided in this submittal documents compliance with Order EA-12-049 for STP Units 1 and 2. Compliance with the related Order EA-1 2-051 (Reference 11) regarding reliable spent fuel pool level indication (SEPLI) for STP Unit 1 and Unit 2 was submitted in January 2016 (Reference 12). Additionally, a compliance letter for both Orders specific to Unit 2 was submitted in July 2015 (Reference 2).

2. Milestone Accomplishments Issues from the NRC Interim Staff Evaluation (ISE) for FLEX Order compliance (Reference

4) have been addressed by STPNO00. Responses to the ISE open and confirmatory items were provided to the NRC as part of the FLEX audit and are summarized in Attachment 1.

The issues that were identified as open and pending in the NRC Onsite Audit Report (Reference 5) are listed below. A summary of the response to each of the open and pending issues was provided in the FLEX and SFPLI Order Compliance letter for STP Unit 2 (Reference 2). The summary responses, including any revisions, are provided in Attachment

2. The open and pending items do not affect STP's compliance with Order EA-12-049:

ISE Open Item (ISE 01) - ISE 01 3.2.1.1 .B ISE Confirmatory Items (ISE Cl) - ISE Cl 3.2.1.2.C, ISE CI 3.2.1.3.A, ISE Cl 3.2.1.4.A Audit Questions (AQ) - AQ #25 Additional Safety Evaluation (SE) needed information - SE #9, SE #10, SE #11, SE #17 STPNOC has no remaining open or pending Licensee Identified Open Items.

Enclosure NOC-AE- 15003311 Page 2 of 8

3. Milestone Schedule Completion FLEX Milestones and SFPLI Update (Units 1 and 2) Completion Date Submit Overall Integrated Plan February 28, 2013 Six Month Updates 1s Update August 26, 2013 2 nd Update February 27, 2014 3 rd Update August 27, 2014 4 th Update February 26, 2015 5 th Update August 26, 2015 Walk-throughs or Demonstrations April 30, 2015 Perform Staffing Analysis Phase 1 Staffing Assessment June 3, 2013 Phase 2 Staffing Assessment November 25, 2014 Revised Phase 2 Staffing Assessment July 2, 2015 Modifications Unit 2 Modifications Design Completion April 30, 2015 Unit 2 Final Modification Implementation May 1, 2015 Unit 1 Modifications Design Completion -November 4, 2015 Unit 1 Final Modification Implementation November 11, 2015 Storage Equipment Storage Complete April 30, 2015 National SAFER Response Center (NSRC)

NSRC Plan Requirements Complete April 18, 2015 Procedures Issue Site-Specific FSGs November 10, 2015 Issue Operations/Maintenance Procedures November 10, 2015 Training Training Complete March 2015 Unit 2 FLEX & SFPLI Compliance Date May 7, 2015 Unit 1 FLEX & SFPLI Compliance Date December 19, 2015 Submit Unit 2 FLEX Compliance Letter July 2, 2015 Submit Notification of Full Compliance Letter1 February 17, 2015 1 Action completed with this submittal

Enclosure NOC-AE- 15003311 Page 3 of 8

4. Order EA-12-049 Compliance Elements - Summary STPNOC has completed implementation of Order EA-12-049 for STP Units 1 and 2 including the following elements:

Strategies- Complete STP FLEX strategies are in compliance with Order EA-1 2-049. To meet the intent of the Order, STPNOC followed the guidance provided in NEI 12-06 (Reference 13) with the exception of the Alternate Approaches listed below. These Alternate Approaches have been presented to and discussed with the NRC review staff and are noted in the Onsite Audit Report (Reference 5):

-STP pre-staged some of the FLEX response equipment including two diesel generators in protected structures on top of the Mechanical Auxiliary Building (MAB) roof, and pumps, hoses, associated equipment inside existing Class 1 plant structures protected against design-basis external events. The primary reason for pre-staging this equipment is due to difficulties in retrieving and deploying equipment following a design-basis flooding event.

-STP utilizes two pre-staged pumps with separate injection pathways for Reactor Coolant System (RCS) fill instead of a single pump with primary and alternate connection points and injection pathways supplemented by a portable pump. In the STP strategy, the failure of a pre-staged pump would render one of the two injection pathways unavailable as opposed to the two pathways that would be available using the portable pump strategy. As a compensatory measure, STP reduced the allowed out of service time for both the positive displacement pump (PDP) and FLEX RCS makeup pump and their associated connections and flowpaths. STP FLEX strategies also rely on pre-staged pumps for Steam Generator (SG) makeup and SEP makeup, however, STP also has the ability to makeup to these systems using a portable pump.

These alternate approaches are listed in Section 3.5 of the STP FLEX Final Integrated Plan (F IP) submitted as Attachment 4.

Modifications- Complete All modifications required to support the FLEX strategies for STP Units 1 and 2 have been fully implemented in accordance with station processes.

Equipment - Procuredand Maintenance and Testing Performed - Complete The equipment required to implement the FLEX strategies for STP Units 1 arid 2 has been procured, received, initially tested and performance verified as recommended in accordance with NEI 12-06 (Reference 13) and is available for use. Maintenance and testing requirements for FLEX equipment are included in the STP Preventative Maintenance Program such that equipment reliability is monitored and maintained.

Enclosure NOC-AE-1 5003311 Page 4 of 8 Procedures- Complete STPNOC has developed FLEX Support Guidelines (FSGs) and integrated them into the existing procedure framework. Other affected procedures required for FLEX implementation have also been revised. The FSGs and applicable procedures have been verified and are available for use and are being controlled in accordance with station processes.

Training - Complete All necessary training has been completed in accordance with the Systematic Approach to Training (SAT) as recommended in NEI 12-06.

Staffing - Complete The STPNOC Phase 1 Staffing Assessment (Reference 14) was completed in accordance with the 10 CFR 50.54(f) request for information with respect to Near-Term Task Force (NTTF) Recommendation 9.3 for Emergency Preparedness (Reference 15).

The STPNOC Phase 2 Staffing Assessment (Reference 16) was also completed in accordance with the 10 CFR 50.54(f) letter.

Following the development of the FSGs, STP performed a revalidation of the Phase 2 assessment to ensure the FLEX strategies could be implemented as written. STP determined that two additional maintenance personnel are required to implement the FLEX strategies for a two unit event in addition to the minimum on-shift staff required by the Emergency Plan for a single unit event. The needed personnel are currently procedurally obligated to be onsite at all times and STP has implemented administrative controls to ensure these staffing levels are maintained.

The results of the revalidation were communicated to the NRC and the Revised Phase 2 Staffing Assessment that resulted from the revalidation efforts was submitted to the NRC on July 2, 2015 (Reference 17).

Additionally, during the implementation outage for Unit 1, STP determined that an additional personnel action was needed for one of the FLEX strategies. In an event such as a flood from an embankment breach of the Main Cooling Reservoir, the site is flooded to a degree that the Trailer-Mounted Diesel-Driven Pumps (TMDDPs) cannot be used to transfer water to the Auxiliary Feedwater Storage Tank (AFWST) until later in the event.

In this case, the condensate Deaerator (DA) can be used as a makeup water source for the AFWST until flood waters recede.

STP FSG-06 (Reference 18) directs Operators to connect hoses between the DA and the Auxiliary Feed Pump Test Line Drain Valve which supplies the AFWST. Prior to opening the DA storage tank drain valve, STP determined that the DA must be vented for at least seven hours to preclude the release of two-phase water into the transfer hoses.

STP reviewed the Revised Phase 2 Staffing Assessment (Reference 17) and determined that there would be a person in each unit who could perform this task, if

Enclosure NOC-AE- 15003311 Page 5 of 8 needed, among the on-shift staffing available. Steam suits and hearing protection are staged in the Turbine Generator Building (TGB) that can be used for completing this venting action (Reference 18).

A supplement to the Revised Phase 2 Staffing Assessment will be submitted to the NRC to provide additional details (Reference 19).

National SAFER Response Center (NSRC) - Complete STPNOC has joined the Strategic Alliance for FLEX Emergency Response (SAFER)

Team Equipment Committee for off-site facility coordination. A site-specific SAFER Response Plan has been developed (Reference 20) and the requisite equipment is available at the NSRCs to support Phase 3 FLEX implementation in the event that it is needed.

Validation - Complete STPNOC has completed validation of the FLEX strategies using station processes and in accordance with industry developed guidance to assure required tasks, manual actions and decisions for FLEX strategies are feasible and may be executed within the constraints identified in the FLEX strategy timeline.

FLEX Program Document - Established STPNOC developed a FLEX Program Document (Reference 21) in accordance with the requirements of NEI 12-06. Additionally, STP developed the FLEX FIP that includes a summary of FLEX strategies, descriptions of equipment, and descriptions of applicable hazards (Attachment 4).

Enclosure NOC-AE-1 5003311 Page 6 of 8 References

1. NRC Order Number EA-12-049, "Issuance of Order to Modify Licenses with Regard to Requirements for Mitigation Strategies for Beyond-Design-Basis External Events", March 12, 2012 (AE-NOC-12002268)(ML12073A195)

2. Letter from G.T. Powell, STPNOC, to NRC Document Control Desk, "Notification of Compliance with Orders EA-12-049 for Mitigation Strategies for Beyond-Design Basis External Events and EA-12-051 for Reliable Spent Fuel Pool Instrumentation (TAC Nos. MF0826 and MF0828)", July 2, 2015 (NOC-AE-15003257)(ML15196A031)

3. Letter from D.L. Koehl, STPNOC, to NRC Document Control Desk, "STPNOC Overall Integrated Plan in Response to March 12, 2012 Commission Order Modifying Licenses with Regard to Requirements for Mitigation Strategies for Beyond-Design-Basis External Events (Order Number EA-12-049)", February 28, 2013 (NOC-AE-1 3002963)(ML13070A011)

4. Letter from J.S. Bowen, NRC, to D.L. Koehl, STPNOC, "Interim Staff Evaluation Relating to Overall Integrated Plan in Response to Order EA-12-049 (Mitigation Strategies) (TAC Nos. MF0825 and MF0826)", January 29, 2014 (AE-NOC-14002494)(ML13339A736)

5. Letter from T. Brown, NRC, to D.L. Koehl, STPNOC, "South Texas Project, Units 1 and 2 - Report for the Onsite Audit Regarding Implementation of Mitigating Strategies and Reliable Spent Fuel Instrumentation Related to Orders EA-12-049 and EA-12-051 (TAC Nos. MF0825, MF0826, MF0827, and MF0828)", May 6, 2015 (AE-NOC-15002661) (ML15111A465)

6. Letter from G.T. Powell, STPNOC, to NRC Document Control Desk, "STPNOC First Six-Month Status Report in Response to March 12, 2012 Commission Order Modifying Licenses with Regard to Requirements for Mitigating Strategies for Beyond-Design-Basis External Events (Order Number EA-12-049)", August 26, 2013 (NOC-AE-1 3003027)(ML13249A060)

7. Letter from G.T. Powell, STPNOC, to NRC Document Control Desk, "STPNOC Second Six-Month Status Report in Response to March 12, 2012 Commission Order Modifying Licenses with Regard to Requirements for Mitigating Strategies for Beyond-Design-Basis External Events (Order Number EA-12-049)", February 27, 2014 (NOC-AE-1 4003089)(ML14073A458)

8. Letter from G.T. Powell, STPNOC, to NRC Document Control Desk, "STPNOC Third Six-Month Status Report in Response to March 12, 2012 Commission Order Modifying Licenses with Regard to Requirements for Mitigating Strategies for Beyond-Design-Basis External Events (Order Number EA-12-049)(TAC Nos.

MF0825 and MF0826)", August 27, 2014 (NOC-AE-1 40031 62)(ML14251A029)

Enclosure NOC-AE-1 5003311 Page 7 of 8

9. Letter from G.T. Powell, STPNOC, to NRC Document Control Desk, "STPNOC Fourth Six-Month Status Report in Response to March 12, 2012 Commission Order Modifying Licenses with Regard to Requirements for Mitigating Strategies for Beyond-Design-Basis External Events (Order Number EA-12-049)(TAC Nos.

MF0825 and MF0826)", February 26, 2015 (NOC-AE-1 5003224)(ML15075A019)

10. Letter from G.T. Powell, STPNOC, to NRC Document Control Desk, "STPNOC Fifth Six-Month Status Report in Response to March 12, 2012 Commission Order Modifying Licenses with Regard to Requirements for Mitigating Strategies for Beyond-Design-Basis External Events (Order Number EA-12-049)(TAC Nos.

MF0825 and MF0826)", August 26, 2015 (NOC-AE-15003287)(ML15251A208)

11. NRC Order Number EA-12-051, "Issuance of Order to Modify Licenses with Regard to Requirements for Reliable Spent Fuel Pool Instrumentation," March 12, 2012 (AE-NOC-12002271) (ML12054A679)

12. Letter from G.T. Powell, STPNOC, to NRC Document Control Desk, "Report of Full Compliance with Order EA-12-051 Reliable Spent Fuel Pool Instrumentation," January 19, 2016 (NOC-AE-1 5003297)

13. Nuclear Energy Institute (NEI) Guidance 12-06, "Diverse and Flexible Coping Strategies (FLEX) Implementation Guide," Revision 0, August 21, 2012 (ML12242A378) .

14. Letter from G.T. Powell, STPNOC, to NRC Document Control Desk, "Revised Phase 1 Staffing Assessment Submitted in Response to Request for Information Pursuant to 10 CFR 50.54(f) Regarding Recommendation 9.3 of the Near-Term Task Force Review of Insights", June 3, 2013 (NOC-AE-1 3003004)(M L131 82A021 )

15. Letter from E.J. Leeds, NRC, to All Power Reactor Licensees, "Request for Information Pursuant to Title 10 of the Code of Federal Regulations 50.54(f)

Regarding Recommendations 2.1, 2.3, and 9.3 of the Near-Term Task Force Review of Insights from the Fukushima Dai-lchi Accident", March 12, 2012 (AE-NOC-1 2002269) (ML12053A340)

16. Letter from A. Capristo, STPNOC, to NRC Document Control Desk, "Response to Request for Information Pursuant to 10 CFR 50.54(f) Regarding Recommendation 9.3 of the Near-Term Task Force Review of Insights from the Fukushima Dai-Ichi Accident - Phase 2 Staffing Assessment", November 25, 2014 (NOC-AE-1 4003189)

17. Letter from G.T. Powell, STPNOC, to NRC Document Control Desk, "Supplement to Response to Request for Information Pursuant to 10 CFR 50.54(f) Regarding Recommendation 9.3 of the Near-Term Task Force Review of Insights from the Fukushima Dai-lchi Accident - Phase 2 Staffing Assessment", JulY 2, 2015 (NOC-AE-1 5003255)

18. STP FLEX Support Guideline Procedure, 0POP12-ZO-FSG06, "Alternate AFWST Makeup", Revision 1, November 10, 2015 (STI 34237577)

Enclosure NOC-AE-1 5003311 Page 8 of 8

19. STP Condition Reporting Database Action, CR 12-11657-38

20. STPNOC Vendor Technical Document, VTD-A977-0003, "SAFER Response Plan for South Texas Project Electric Generating Station", Revision 0 (STI 34077493)

21. STPNOC Document, FLEX-0001, "Diverse and Flexible Coping Strategies (FLEX) Program Document", Revision 0 (STI 33759523)

22. STPNOC Calculation, STP-CP-006, "ELAP Analysis with the South Texas Project RETRAN-02 Input Model", Revision 1, April 15, 2015 (STI 34064235)

Attachment 1 NOC-AE-1 5003311 ATTACHMENT 1 Summary of Responses for the FLEX Interim Staff Evaluation Open and Confirmatory Items

Attachment 1 NOC-AE-1 5003311 Page 1 of 15 The information summarized in this Attachment was discussed with the NRC review staff during the FLEX and SFPLI audit process and was previously provided electronically on the CERTREC Inspection Management System (IMS) portal.

Note: The information contained in this attachment is considered legacy information and may not accurately reflect the current FLEX strategies. The current STP FLEX strategies are described in the Final Integrated Plan (FIP). The intent of providing this information is to show the evolution of the STP FLEX strategies and to document some of the discussions with the NRC Review Staff following the issuance of the Interim Staff Evaluation (ISE) during the audit process.

Identifying Question/Request STP Response Number Confirmatory Item: The licensee should confirm the need for, No auxiliary power will be required to move or deploy 3.1.1 .2.A or use of, auxiliary power to facilitate moving or deploying pral LXeupet FLEX equipment. portable _______FLEX____equipment._____

Confirmatory Item: Although the Integrated Plan briefly discusses the use of portable instruments to obtain necessary instrument readings at the qualified display processing system, the plan does not fully address the guidance of NEI 3.1.1.3.A 1206, Section 5.3.3, consideration 1 regarding providingGudneicatrdnthFSs 3.1..3.A operators with adequate information to obtain these readings..GudneicatrdnthFSs During the audit process, the licensee stated that this concern would be addressed by the development and incorporation of the guidance provided in the Westinghouse Owners Group FLEX emergency response guidelines.

Confirmatory Item: The licensee's Integrated Plan did not address the development of mitigating strategies with respect See CR Action 12-11658-117. STP Engineering analysis 3.1.1 .3.B to the procedural interface for the use of ac power to mitigate determines that no impact to FLEX equipment is expected ground water in critical locations. Confirm that the corrective due to groundwater.

action initiated to address this issue is complete.

Confirmatory Item: The Integrated Plan did not confirm that, STP does not credit sump pumps or temporary flood barriers 3.1 .2.2.B for flood considerations, power is available for water extraction in their flood protection for safety related equipment or areas sump pumps, or that temporary flood barriers would beduigaELP

______employed appropriately. during ___________an_____ELAP.______

Attachment 1 NOC-AE-1 5003311 Page 2 of 15 Identifying Question/Request STP Response Number Confirmatory item: The Integrated Plan made reference to developing procedures to implement strategies as indicated The FSGs reference specific STP safety procedures. These 3.1.3.3.A by a licensee identified open item (Ol#9). Confirm that the prcdeswlenuehitm ag etpovesaf 3133A procedures address considerations for high winds such as prcduresto whillensureinshift managemseentvprovidesta codtosaf personnel protection or removing debris as well as the high drcinwiewrigi des niomna odtos temperature hazard.

The tractors and Trailer-Mounted Diesel-Driven Pumps ConfrmaoryIte:

Wth egar toa ConfrmaoryIte:

Wth egar toa cncen cncen rgaring(TMDDPs) rgaringThis are designed equipment to operate is commercial in highofheat equipment veryconditions.

good quality addressing the high heat hazard for deployment, the licensee tyialusdofrmanrnceinSthTx.Ter generated two self-identified open items (O1#4 and #9) to storiageylocationfrswlbevniated byncmean Soft neas.Tuera 3.

52A track the resolution of storage location, protection, and circulation. Transporting the equipment to the Protected Area 3.1..2.A transportation, and the administrative requirements associated will occur after offsite resources arrive (beyond 6 hours6.944444e-5 days 0.00167 hours 9.920635e-6 weeks 2.283e-6 months with those elements. Confirm that considerations for high heat floigeet;teeoe esne a oio ookr patof thEXresoutiomn. elyetadpoedritrae r for signs of overheating. There will be no problem moving partof te reolutonand operating this equipment with outside ambient temperatures around 100°F.

See CR 12-11656-12 for minimum time for RCS Reflux cooling to occur. Two phase flow at the RCP seals is Confirmatory Item: Confirm that two-phase leakage from the expected to occur prior to the transition to reflux cooling.

Limitation 1.3.4 in the RETRAN3D White Paper states that 3.2.1 .2.A reactor coolant pump (RCP) seals will not occur prior to the the results will not be used beyond the point when two phase transition to reflux cooling. flow passes through the RCP seals. The RETRAN3D analysis will demonstrate that two phase flow through the RCP seal will not occur.

The assumption of a constant seal leakage area is being Confirmatory Item: Provide confirmation of the acceptability of revised based on work being performed by the PWROG and 3.2.1.2.B assuming a constant seal leakage area in light of the potential under review by the NRC staff. The results of this work will be for increased stresses on seal materials during cooldown. factored into the RETRAN3D analysis.

Attachment 1 NOC-AE-1 5003311 Page 3 of 15 Identifying Number Question/Request STP Response Confirmatory Item: In some plant designs, such as those with 1200 to 1300 psia SG design pressures and no accumulator backing of the main steam system PORV actuators, the cold In Letter OG 13399, Westinghouse has documented the test legs could experience temperatures exceeding 580 degrees F results that demonstrate the RCP 0-rings will withstand before cooldown commences. This is beyond the qualification temperatures of 583°F for periods longer than 14 hours1.62037e-4 days 0.00389 hours 2.314815e-5 weeks 5.327e-6 months , temperature (550 degrees F) of the 0-rings used in the RCP which is beyond the conditions that will be experiencedduring 3.2.1.2.0 seals. For such Westinghouse designs, a discussion of the an ELAP event. The RCP seal leakage rate of 21 gpm is information (including the applicable analysis and relevant being revised based on work performed by the PWROG and seal leakage testing data) should be provided to justify that (1) under review by the NRC Staff. As discussed in the the integrity of the associated 0-rings will be maintained at the RETRAN3D White Paper dated August 21, 2014 the results temperature conditions experienced during the ELAP event, of this work will be applied to the RETRAN3D analysis..

and (2) the seal leakage rate of 21 gpm/seal used in the ELAP

_________is adequate and acceptable.

Confirmatory Item: The licensee should address the following issues associated with decay heat modeling: (1) specify the value of the multiplier applied to the ANS 5.1 1979 decay heat The RETRAN3D analysis applies a multiplication factor of standard for the ELAP event and its basis. (2) Clarify whether one using decay heat data for U235, Pu239 and U238 and the multiplier would be capable of accounting for the residual includes contribution to decay heat from U239 and NP239.

heat contribution from actinides (e.g., plutonium, neptunium) The resulting decay heat bounds the decay heat presented 3.2.1 .3.A and neutron absorption in fission products, or whether these on Table 6.2.1.36 of the UFSAR used for containment peak residual heat sources were accounted for explicitly. (3) Clarify pressure analysis. The RETRAN3D analysis calculates the whether the discussion applies to RETRAN3D thermal- steam generator makeup required for the at power event to hydraulic analysis or whether it applies to auxiliary the point where pressurizer level is restored and the plant is calculations (e.g., the determination of steam generator in a stable condition.

makeup required during various phases of the ELAP coping analysis).

Confirmatory Item: Confirm that the key initial plant 3.2.1.4.A parameters and assumptions used in the forthcoming The RETRAN3D analysis conforms to the requirements RETRAN3D analysis are consistent with the appropriate stated in Section 3.2.1.2 of NEI 12-06, Rev 0.

__________values from NEI 1206, Section 3.2, or justify any deviations. __________________________

Attachment 1 NOC-AE-1 5003311 Page 4 of 15 Numertfyn Question/Request STP Response Confirmatory Item: In response to a concern regarding the survivability of critical instrumentation in an adverse NAI-1786-001 Rev. 0 (STI 33945544) is the Containment containment atmosphere, the licensee provided details of the Analysis for ELAP event. This calculation confirms that 3.2.1.5.A containment analysis being used at STP. Resolution of the neither containment nor its instrumentation are challenged concern regarding survivability and proper function of when an ELAP and the subsequent loss of coolant occurs containment instrumentation is dependent on results of the from at power conditions.

containment analysis.

The RCS wide range pressure indication will not be used in Confirmatory Item: Provide adequate justification that the RCS the determination of nitrogen injection into the RCS. Instead, wide range pressure indication would not be influenced by steam generator pressure will be used consistent with the 3.2.1 .5.B containment conditions to an extent that would affect a reliable PWROG recommendations. The uncertainty associated with determination of nitrogen injection from the cold leg containment conditions has been factored into the steam accumulators. generator pressure setpoint consistent with the guidance provided by the PWROG. See PWROG EOP ECA0.0.

Provided in STPs "White Paper Demonstrating the Applicability Of The RETRAN3D Code For Analysis Of The ELAP". A.1 Boron Transport Model (SER Condition #3). NRC staff position is that the boron transport model in RETRAN3D is approved for use, with the caveat that its diffusive nature Confirmatory Item: The licensee should either (1) confirm that should not be allowed to produce misleading results (Rev. [2]

it wll bid di cusionon b ricaci miing taf bytheNRC pg 14). In this context, "diffusive" refers, for example, to the it NR illabie stffb thiscssin o boic cidmixng tendency to "wash out" or attenuate pulses or step changes under two-phase natural circulation flow conditions, or (2) in boron concentration. A simple example occurs when an 3.2..8.A identify another acceptable method for ensuring that the boric accumulator suddenly injects into the system. A local acidnecssay aciev adeuatt shtdon mrgi topulse/step in boron concentration is expected, and this pulse mitigate an ELAP event will be adequately mixed with the should propagate around the system, eventually returning to recutior clowolndtisystem voueudrtopaentrlits origination point. Along the way, it is physically expected circlaton ondtios..that low the pulse will be attenuated by mixing in various plenums. Additional nonphysical attenuation will occur due to numerical diffusion. The net effect is that the pulse will become flattened and broadened. The nonphysical portion of the attenuation will cause the leading edge of the pulse to appear earlier than physically expected.

Attachment 1 NOC-AE-15003311I Page 5 of 15 Iumenrfyn Question/Request STP Response If this change in timing is important, or if the "excess" attenuation is important, then misleading conclusions may occur. In the ELAP scenario, the total natural circulation flow is approximately 2,000 lbm/sec, the total RCS mass is approximately 600,000 Ibm, which implies a loop circulation time of approximately 300 seconds, or 12 loop circulationsin one hour. After a few circuits around the system, any boron concentration pulse/step will be washed out by plenum ConfrmaoryIte:

Te Te liense liense soul ConfrmaoryIte: soul eiher eiher 1)

1) onfrm onfrm hatmixing, hataround the andeventually theuniformity system. This boron willwill be occur mixedwith uniformly or without it will abide by the NRC staff discussion on boric acid mixing numerical diffusion; diffusion simply accelerates the effect.

under two-phase natural circulation flow conditions, or (2) UsnthgudcepoidinheNCm odad 3.2.1 .8.A identify another acceptable method for ensuring that the boric UsnthgudcepoidinheNCm odad (coninud) t cidnecssay acieveadeuat shtdon mrgi toJanuary 8, 2014 and restated in Section 1.7, not taking credit (contin mitigatedanesar ELA ahevenwilbadequatelyutow mixedgith the for boron until one hour after the target boron concentration is mitiatean ven wil EAP beadeqatey mxed iththe reached while two phase flow is greater than single phase reactor coolant system volume under two-phase natural flow will ensure that the diffusive nature of the boron circulation flow conditions.. transport model will not produce misleading results.

Therefore, the use of the boron transport model in RETRAN-3D satisfies the SER Condition #3 for ELAP analysis in PWRs. Update: Limitation 1.3.3 of the RETRAN3D White Paper (See Open Item 3.2.1.I.A) plc\ h esrcino boron mixing that abides by the NRC staff discussion on boric acid mixing under two-phase natural circulation flow conditions. The plant specific analysis abides by this

___ ___ ___ ____ ___ ___ ____ ___ ___ ___ restriction.

Confirmatory Item: Complete shutdown margin analysis for 3.2.1.8.B STP and demonstration of adequate shutdown margin during See response to 3.2.1.8.D.

an ELAP event.

Attachment 1 NOC-AE-1 5003311 Page 6 of 15 Numentryn Question/Request STP Response A review of the Nuclear Design Reports for several representative fuel cycles shows that xenon worth remains above the equilibrium value between 20 and 25 hours2.893519e-4 days 0.00694 hours 4.133598e-5 weeks 9.5125e-6 months for beginning of life and end of life conditions and between 18 Confirmatory Item: Provide adequate basis that the core and boron20from hourstheforFLEX middle of lifeexpected pumps conditions. The addition of to occur in less than 3.2.1.8.0 xenon concentration would remain above its equilibrium value 10 hours1.157407e-4 days 0.00278 hours 1.653439e-5 weeks 3.805e-6 months which will provide the boron to ensure the reactor forpst-tip.core t lest2 hous does not become critical. As an additional barrier, the Emergency Operating Procedures direct the operators to perform alternate RCS boration within 17 hours1.967593e-4 days 0.00472 hours 2.810847e-5 weeks 6.4685e-6 months of the initiation of the ELAP event, which allows a one hour operator action time to perform this evolution.

A fuel cycle specific curve of the boron requirements versus Confrmaory Cofirmtha tem shtdow maginRCS temperature for various fuel burnup similar to Figure 3..1onDfeqirementsory futuem Copeirmtatin cycleswrmarin bone y 5.8.11 in WCAP 17601-P was developed. These curves are th.18.

eqcluaioem nt forfuntur opyertn 14. s ean onddb used as part of the STP reload safety evaluation process to theUitalclaton

, Ccle14.ensure or sufficient shutdown margins will be maintained and Unit 1, Cycle 14 remains bounding.

Confirmatory Item: The licensee stated during the audit response "all these N pumps will be pre-staged in Category 1 The TMDDPs do not perform primary safety functions to structures, protected from all external events." However, the protect the core, the spent fuel, or containment. They are 3.2.1 .9.B licensee has previously stated that the storage of the trailer used as support equipment. These pumps are stored in metal mounted diesel driven pumps was in non-Category 1 building buildings that meet NEI 12-06 structural requirements.

physically separated to assure survivability of at least one pump. Confirm resolution of the apparent conflict.

Attachment 1 NOC-AE-15003311I Page 7 of 15 Identifying Qeto/eus INumber Qusin~qetSTP Response Confirmatory Item: The licensee stated that the FLEX pumps have been sized and deployment time determined to ensure that (1) reflux cooling will not occur, (2) the RCS makeup flow will exceed the RCP seal leak-off and be able to restore 3.2.1.9.0 pressurizer water level, (3) provide sufficient boron to prevent Analyses complete.

a return to power and (4) to remove decay heat. The ability of '

these pumps to provide sufficient makeup flow in the required time frame will be demonstrated by plant specific analyses, scheduled to be completed by the end of the year.

The TDAFW pump is designed to operate at steam pressures greater than 110 psig. The emergency operating procedure (0POP05-E0-EC00) will direct the operators to depressurize Confirmatory Item: Identify the minimum steam requirements the steam generator to 405 psig, thus ensuring sufficient 3..1.9E to support TDAFW operation and justify that the TDAFW steam pressure to the TDAFW pump. This pressure will be pump can perform its function until FLEX pumps can be maintained until the FLEX secondary pumps are made placed into operation, available. In the event sufficient steam pressure cannot be maintained due to low decay heat, the emergency operating procedures directs the operators to implement the FLEX secondary makeup pump (0POP12-ZO-FSG03).

Confirmatory Item: Confirm that the analysis for preventing nitrogen injection from the accumulators will use the methodology in Attachment 1 to the Pressurized Water Reactor Owners Group (PWROG) interim core cooling The methodology used to ensure that nitrogen injection from 3.2.1.A position paper ("PWROG Core Cooling Position Paper,") the accumulators used in the RETRAN-3D analysis complies Revision 0, November 2012, PAPSC0965; (withheld from the with the methodology developed by the PWROG.

public for proprietary reasons) or specify an alternate method for preventing nitrogen injection and demonstrate its

__________acceptability.____________________________

Attachment 1 NOC-AE-1500331 1 Page 8 of 15 Iumentryn Question/Request STP Response EC00 and/or the FSG that contains the RCS cooldown tell the operators the approximate value to open the SG PORVs Confirmatory Item: Confirm (1) that remote operation of the (10%). This will conserve the hydraulic pressure for SG PORVs will be implemented in a manner that will conserve etne eoeoeain ln prtr r rie n the vaiabl pessre hydaulcsch hatthe OR~ ca be have procedural direction (existing site procedures) to locally remotely operated to the extent necessary to perform the operate the SG PORVs including during an ELAP. A manual 3.2.1.B cooldown called for in the integrated plan without local hydraulic pump used for manual pressing up of the SG actions, (2) that local manual actions can be taken to increase PRVhdalcpesrisoatdnteTubeGnrtr the hydraulic pressure to permit further remote operation of Builing Becrauirssue t is location isno prteed furomn Geeall r drcloaoprtoofthe PORVs conitnawth ntegrated mplanor(3shat externalevns an additional pump will be stored inside the diretofthe lcalopertio OR~ ca be ccoplihedPower Block, protected from all external events. Procedural consistent with the integrated plan., guidance is provided in the appropriate FSGs for this operation.

Confirmatory Item: On page 41 of the Integrated Plan, in the Dsg hnePcae1-15-0adascae secton th SEPcooing iscusin or has 3 uingtheDesign Change Notices document the piping modification for portable SEP pump, the licensee stated that a pre-staged the suction of the SEP fill pump. The suction piping will come 3..2A FLEX SFP fill pump will be attached to the emergency core off of the containment spray 2B suction piping. Clarification 3.2.2.A cooling system in a manner still to be determined. The licensee later stated that the FLEX modification design Update: The discharge is hard-piped from the pakgsare scheduled for completion in May of 129' elevation of the Fuel Handling Building (FHB) to the 68' package Cofr F ilp ofgrtoelevation of the FHB, very close to the spent fuel pool.

Confirmatory Item: The licensee stated that a site specific Preliminary analysis using the GOTHIC computer code (NAI-containment analysis is being performed to ensure that1760)deosrtshatecnaim tpesusad containment integrity is not challenged by the energy release temperatur remainstwaell below dhesigntainden peqsuip esnt resutin EAP frm vente and tht evirnmetaleffcts qualification limits. The analysis is based on the mass and on equipment located inside containment relied upon to energy releases from the RETRAN3D computer code that 3.2.3.A mitigate the ELAP event, will not result in this equipmentusarecocolnpmpellakgmdlthtisil failing to perform its intended function. The licensee also under review by the NRC staff. Upon resolution of the reactor stated that the purpose of the containment analysis is to coolant pump seal leakage model issue, the GOTHIC ensure that containment integrity is not challenged by the aayi ilb eiie oesr htcnanetpesr energy release resulting from the ELAP event. Confirm temperatresvimitsaed andlsi ntoexueeded.ntimet rssr

_______completion of this analysis. n eprtrslmisaentecee.

Attachment 1 NOC-AE-1500331 1 Page 9 of 15 Identifying Question/Request STP Response Number Confirmatory Item: Confirm how long batteries will be relied The Phase 2 Staffing Assessment includes performance of upon during the mitigation strategies before charging is the additional DC load shed within two hours as required by initiated and justify that the batteries are capable of supporting the battery study, therefore credit can be taken for the load for that duration. For duration greater than 8 hours9.259259e-5 days 0.00222 hours 1.322751e-5 weeks 3.044e-6 months , and batteries performing as indicated in the study. The FLEX DG 3.24.1.A acceptable method is provided in NEI position paper entitled will be started at the 2.5 hour5.787037e-5 days 0.00139 hours 8.267196e-6 weeks 1.9025e-6 months mark and the A & C train "Battery Life Issue" and the NRC endorsement (Agencywide battery chargers will begin charging the batteries at the 4 Documents Access and Management System (ADAMS) hour mark providing ample margin for starting to charge the Accession Nos. ML13241A186 and ML1 3241Al188). batteries within 8 hours9.259259e-5 days 0.00222 hours 1.322751e-5 weeks 3.044e-6 months .

Plant Operations has procedures for the de-energizing of ConfrmaoryIte:

Povie te reult oftheaddtioal oad every AC and DC electrical bus. This additional load ConfrmaoryIte:

Povie te reult oftheaddtioal oad shedding has already been identified and can be easily shedding evaluation needed to extend the Class 1 E battery referenced in these procedures. There will be no remedial 3.2.4.10.B life that will be incorporated into the FLEX support guideline,. esrsbsdsll nd-nriigteeadtoa Inclden rmedal dicusion easres equredforde- loads. With all AC power lost, no fans or pumps will be energizing of additional loads. running so failure closed of AOVs or dampers will not adversely affect equipment.

Heat trace circuits normally maintain the 4 weight percent boric acid at approximately 850°F. When the ELAP occurs, the water temperature will slowly lower but will not reach 55°F because the tanks and piping are insulated and inside Confirmatory Item: There was no discussion in the integrated concrete Acid pumps buildings. When the will be started FLEX (hour DGand 8-10) is running, the Boric will recirculate the Plan regarding the need for heat tracing in lines with borated Boric Acid Tanks (BATs) to ensure the temperature does not coolant, and if necessary, how the heat tracing would be continue to lower where saturation could become an issue.

3.2.4.3.A powered. Provide clarification of the need for heating to By approximately hour 15, it will no longer be necessary to prevent boric acid precipitation for a duration sufficient to take suction from the BATs suction will be transferred to the support the actions in the integrated plan, and power sources Reactor Water Storage Tank (RWST) which has a much for te heaerslower boron concentration. In the very unlikely event that the boric acid did begin to solidify early, this suction source transfer (from BATs to RWST) can take place at any time because the pumps can take suction on either source at any time.

Attachment 1 NOC-AE-1 5003311 Page 10 of 15 Identifying Qetoleus Number QusinRqetSTP Response Confirmatory Item: The licensee has identified the use of temporary 480 VAC FLEX power but there was no information regarding the technical analyses performed as the basis for the size and configuration of the generator and distribution system for Phase 2 or Phase 3. The licensee addressed this See Audit Question #60 for OG sizing calculation. Drawing 3,2.4.8.A concern during the audit process and stated that the FLEX 00001 EOFRAA shows configuration of DGs and the diesel generator sizing calculation was expected to be distribution system.

completed by the end of 2013. Confirm completion of the calculation and that the calculation supports the size and configuration of the generator and distribution for Phase 2 and/or Phase 3.

Confirmatory Item: Confirm that procedures and breaker FSG-05 and FSG-1 3 provide adequate isolation and 3,2.4.8.C design will provide isolation and protection when aligning the protection for both installing and removing FLEX power from backup DGs and when restoring normal power. the plant.

The accuracy and resolution values for the FLEX generator instrumentation are provided below:

Confirmatory Item: Confirm that the FLEX generator Current (Ak) +/1.2% +/0.5digit 3248D instrumentation utilized in monitoring equipment operation, Vlae()+1.%+ . ii 3...8D has appropriate tolerances accuracies to assure proper Renpoerg (kWh, MWhGh) +/3.5% +/ 0.5 digit operation of the equipment to support the strategies. Retal power (kWA, MWA)+/ 3.5% +/ 0.5 digit Frequency (Hz) +/1 Hz +/1 Hz Time delay (sec) +11 sec +11 sec

Attachment 1 NOC-AE-1 5003311 Page 11 of 15 Identifying Question/Request STP Response Number Ultra-Low Sulfur Diesel (ULSD; Sulfur content <15 ppm) is currently the only standard type of commercial diesel fuel available and the fuel available through STP's fuel tanks.

New engines are designed for use of ULSD and Tier 4 emission engines require it. Legacy engines and those 3.2.4.9.A Confirmatory Item: Confirm proper quality of fuel oil for FLEX produced using Tier 13 standards may run it with only strategy usage. minimal impacts. The engine models we have are the John Deere 6068H (part of Gorman-Rupp Model PA6B60606H) and the MTU 1000XC6DT2 Gen Set. These are both listed as Tier 2 engines per manufacturing documentation and are designed to use ULSD from the factory.

Confirmatory Item: The lack of a means to deploy the diesel driven trailer mounted pump, relied upon as a backup SG makeup pump, during a design basis flood during the first 72 Tedee-rvnpmsaen ogrpr fteS 3.3.1A hours renders it unavailable to support mitigating strategy makeup (i.e. Core Cooling) strategy.

functions. Confirm that appropriate equipment unavailability controls will be used for the primary capability for performance of this function (i.e., the RCS Core Cooling FLEX Pump).

The TMDDPs are no longer part of the SG fill strategy. The strategy for the +1 Core Cooling (SG Makeup) pump has Open Item: The licensee does not provide for been changed. STP plans to purchase and install a pump 3.1.2.2.A transportation/deployment of the diesel-driven trailer-mounted identical to the N pump to perform this function. This second pumps relied upon as a spare SG makeup pump in the event SG Makeup pump will be installed in a different bay/train than of a design basis flood, the N pump in the same protected safety related building.

With this change in strategy, STPNOC considers this deployment issue closed.

Attachment 1 NOC-AE-1 5003311 Page 12 of 15 Identifying Question/Request STP Response Number 3.2.1.1.A Open Item: Demonstrate the applicability of the RETRAN- STP provided a revised RETRAN-3D white paper to the NRC via email on 10/8/14. Also included was a rack-up of the NRC 3Dcode for analysis of ELAP transient staff comments and their resolution.

Open item: Provide analysis of the ELAP transient that is applicable to STP and which demonstrates the adequacy of the mitigating strategy proposed for STP. This includes specification of an acceptable definition for the transition to STP has preliminary results using the RETRAN-3D code.

reflux condensation cooling to ensure that the analysis is not Results will be provided to the NRC once all comments from 3..11 B credited beyond this juncture. A sufficient number of cases the white paper submitted for O1#3.2.1 1IA have been 3.2.11 .B should be included in the analysis to demonstrate the acceptability of different strategies that may be necessary to incorporated. See Response to OI 3.2.1.1A - Revised white mitigate an ELAP (e.g., as discussed in Section 3.2.1.6, in paper submitted 10/8/14.

some cases "N" and "N+1" pumps have different capabilities, which may substantially affect the sequence of events in the integrated plan).

3.2.1.6.A Open Item: Develop the final timeline(s) and sequence(s) of Sequence of Events timeline is complete and has been events for STP. provided to the NRC review team.

Attachment 1 NOC-AE-1 5003311 Page 13 of 15 Numentryn Question/Request STP Response Pre-staging the two FLEX DGs is necessary because of the postulated flood caused by a breach of the reservoir embankment (Reference U FSAR Section 3.4.1.1 ). Although this event is not considered credible, another flooding scenario due to upstream dam failure has the potential of inundating the site with several feet of water. Staging and storing the FLEX diesels on the MAB roof would provide reasonable protection from either flooding event. NEI 12-06 Section 11.3.2 states that the mitigation strategy and support Open Item: Electric Power Sources - On page 20 of the equipment will be reasonably protected from applicable Integrated Plan, the licensee stated the strategy for mitigating external events such that the equipment could be operated in an ELAP is to use a 480 VAC air cooled diesel generator on place. Use of the existing electrical distribution system also top of roof of the MAB to provide power to an electric driven conforms to the requirements of NEI12-06. Section 3.2.1.3, SG FLEX pump, a RCS FLEX pump and a spent fuel pool Item (8) states that installed electrical distribution systems, FLEX pump. The use of pre-staged generators appears to be including inverters and battery chargers, remain available 3...8B an alternative to NEI 12-06. The licensee has not provided provided they are protected consistent with current station sufficient information to demonstrate that the approach meets design. The electrical paths for energizing the FLEX the NEI 12-06 provisions for pre-staged portable equipment. equipment will be diverse in that the currently installed Additional information is needed from the licensee to equipment will be repowered via Class 1 E motor control determine whether the proposed approach provides an centers (MO~s) and the new FLEX pumps will be powered equivalent level of flexibility for responding to an undefined via new cabling to the new pumps. Item (9) of Section 3.2.1.3 event as would be provided through conformance with NEI states that no additional events or failures are assumed to 12-06. occur immediately prior to or during the event. As stated in Section 8.1.4.2 of the STP UFSAR, the Class 1E Electrical System is designed to withstand the effects of design basis natural phenomena, assuming single active failure, without loss of onsite power to those safety-related electrical components required to shut down the plant and maintain it in a safe condition or to mitigate the consequences of postulated accidents. The two pre-staged 480VAC 1000kW DGs are capable of providing the protection called for in the Order.

Attachment 1 NOC-AE- 15003311I Page 14 of 15 Numertfyn Question/Request STP Response New cables will be run from a new FLEX distribution panel located near the new FLEX DGs either through existing electrical system pathways (cable trays) or through conduits that meet the requirements associated with initial plant construction standards. The FLEX equipment being powered from the FLEX diesel that will be used in Phase 2 of the-FLEX strategy is contained in Category I structures and protected from external events. Cabling provides power to Class 1 E MCCs so that other components can be powered to provide a variety of functions including battery charging, Open Item: Electric Power Sources - On page 20 of the Integrated Plan, the licensee stated the strategy for mitigating pumping, ventilation, lighting and communications. The new and previously installed cables that will be used for the FLEX an ELAP is to use a 480 VAC air cooled diesel generator on strategies will be protected from all external events as top of roof of the MAB to provide power to an electric driven described in NEI 12-06 as will the MCCs and the pre-staged SG FLEX pump, a RCS FLEX pump and a spent fuel pool pumps. Diversity for this strategy exists:

FLEX pump. The use of pre-staged generators appears to be

The FLEX OGs are 100% capacity, only one is required.

3.2.4.8.B an alternative to NEI 12-06. The licensee has not provided

The FLEX distribution joanel feeds three completely (continued) sufficient information to demonstrate that the approach meets Separate and independent "trains" of ESF electrical the NEI 12-06 provisions for pre-staged portable equipment.

equipment. These are separated on three different elevations Additional information is needed from the licensee to in the Electrical Auxiliary Building (EAB) and power like determine whether the proposed approach provides an components on different trains.

equivalent level of flexibility for responding to an undefined

Specific FLEX cables go directly to the new FLEX pumps event as would be provided through conformance with NEI without utilizing the "trains" of ESF electrical equipment.

12-06.

Each safety function strategy has both a permanent plant pump and a new FLEX pump with diverse power distribution.

Flexibility for this strategy exists: The FLEX cabling being run from the FLEX DGs to power ESF motor control centers for powering battery chargers, pumps, lighting, valves and other equipment can be modified to run to multiple motor control centers (MCC) to power redundant equipment in the event of a fire or disturbance to one particular "train" of ESF electrical power.

Attachment 1 NOC-AE- 15003311 Page 15 of 15 Identifying Question/Request STP Response Number

~An example would be the Boric Acid Transfer pump B is powered from the train 'A' MCC and the Boric Acid Transfer Open Item: Electric Power Sources - On page 20 of the pump A is powered from train 'C' MOO. The Reactor Makeup Integrated Plan, the licensee stated the strategy for mitigating Water pumps are powered similarly. Thus if something an ELAP is to use a 480 VAC air cooled diesel generator on disturbed the 10' elevation of the EAB electrical switchgear top of roof of the MAB to provide power to an electric driven room where the 'A' train electrical equipment is located, the SG FLEX pump, a RCS FLEX pump and a spent fuel pool 'C' train electrical equipment should not be affected because FLEX pump. The use of pre-staged generators appears to be it is on the 60' elevation of the EAB. For this reason, there is 3.2.4.8.B an alternative to NEI 12-06. The licensee has not provided capability to adapt to different scenarios. Section 3.2.1.3(6) of (continued) sufficient information to demonstrate that the approach meets NEI 12-06 states that permanent plant equipment that is the NEI 12-06 provisions for pre-staged portable equipment. contained in structures with designs that are robust with Additional information is needed from the licensee to respect to seismic events, floods, high winds and associated determine whether the proposed approach provides an missiles are available. Section 3.2.1.7 states that the priority equivalent level of flexibility for responding to an undefined for the plant response is to utilize systems or equipment that event as would be provided through conformance with NEI provides the highest probability for success. The STP 12-06. strategies that include pre-staged FLEX diesel generators and use permanent plant equipment provide the highest

_________ ___________________________________________probability of success.

Attachment 2 NOC-AE-1 5003311 ATTACHMENT 2 Update to Response to Open and Pending items from the FLEX and SEPLI Audit Report

Attachment 2 NOC-AE-1 5003311 Page 1 of 1 STPNOC provided responses to the Open and Pending items identified in the FLEX/SFPI Onsite Audit Report issued by the NRC (Reference 5) with STP's Order Compliance letter (Reference 2) for Unit 2.

STPNOC has responded to all of the follow-up questions asked by the NRC regarding RCP seals. At this time, no further work is required to validate that STP Units 1 and 2 are in compliance with Order EA-12-049 relative to ROP seal behavior and Westinghouse ELAP analyses. STP will continue to monitor the discussions between the PWROG and the NRC regarding these issues.

Attachment 3 NOC-AE-1 5003311 ATTACHMENT 3 Summary of Responses for Other Issues that Arose after the Audit Report

Attachment 3 NOC'-AE- 15003311 Page 1 of 3 The NRC asked STP to respond to two questions regarding the FLEX strategies since the issuance of the STP Onsite Audit Report. The first involved the performance of Westinghouse-style RCP seals under Extended Loss of AC Power (ELAP) conditions. The second involved the seismic surviveability of the FLEX storage buildings not designed to withstand the plant site's Safe-Shutdown Earthquake (SSE). STP's responses to these two questions are included below.

NRC Question - Plants with Westinghouse-Style Seals and with Mitigation Strategy Safety Evaluations (SEs) Outstanding The NRC asked STP the following question in August 2015 and requested that STP provide the site specific information in the table provided on the following page.

Background:

Based on a series of interactions with the PWROG, a number of issues associated with the performance of Westinghouse-style ROP seals under ELAP conditions have been resolved. However, at present, several key issues remain unresolved, and it appears that the PWROG may not be able to resolve them fully on a timescale consistent with the Mitigation Strategies Order. These issues include (1) the potential for 1st-stage seal leakoff line overpressurization, (2) vendor recommendations for an extended cooldown to ensure second-stage seal integrity (see Westinghouse Technical Bulletin 15-1), and (3) the potential for earlier initiation of the RCS cooldown and ROS makeup in light of unexpected leakage rate increases with time during the recent AREVA Karlstein tests.

STP Response STP's site specific information was provided to the NRC in the form of the table on the following page. The information contained in this table was derived from calculation STP-CP-006 (Reference 22).

The table contains revised values for STP and includes additional clarifying notes were added to explain the changes.

Attachment 3 NOC-AE-1 5003311 Page 2 of 3 Plant Seal No.1 Seal Extended Cooldown for Time to Currently -Previous Approx. Notes Leakoff Leakoff #2 Seal Integrity per Initiate Planned understanding Need Line Line Max TB 15-1(2) RCS Time for of Planned Time for Category Pressure Cooldown Cooldown Coo1down RCS Time for RCS RCS Lmt Temp Time (hrs) (hrs) Makeup Makeup (hrs) Makeup (psia)(1) (Default (Default (hrs) (hrs)

(Default Value <= Value <= (Default (Default Value >= 350 0F) 24 hrs) Value<= Value <=

2 50 0 p s ia ) 2 h rs ) 8 h rs )_ _ _ _ _ __ _ _ _ _ _

South 6 2500(3) 450° F <4 1 10 10 11.*3(4) Both units have ARE VA-Texas 1595 manufactured seals installed. Understand can

_______ ____ ________ ___ ___ tolerate > 2500 psia (1) Refers to seal leakoff line maximum tolerable internal pressure for piping and components inclusive of the flow measurement orifice. 0 (2) STP initiates a second cooldown at 10 hours1.157407e-4 days 0.00278 hours 1.653439e-5 weeks 3.805e-6 months to reduce the RCS temperature to below 350 F approximately 12 hours1.388889e-4 days 0.00333 hours 1.984127e-5 weeks 4.566e-6 months into the event.

(3) See Condition Report Engineering Evaluation (CREE) 15-15223-3. The remaining values in the table are documented in STP calculation STP-CP-006 (Reference 22).

(4) Time at which two-phase flow through RCP seals could occur.

(5) Onset of reflux cooling

Attachment 3 NOC-AE-1 5003311 Page 3 of 3 NRC Question - FLEX Storage Building Design

.Regarding the seismic design of the two STP FLEX storage buildings, if the buildings are not designed to a level commensurate with the plant SSE, provide justification that the equipment necessary to mitigate a beyond-design basis seismic event under the conditions of Order EA-12-049 can be deployed successfully. This could be demonstrated by one of the following means:

1. Evaluate the storage buildings to the SSE level and demonstrate its performance is adequate to support fulfillment of the strategies (e.g. does it collapse, fail major/minor structural members, skew doorframes, etc.)

2. Show that there is another load case (such as wind loading) which governs the building design such that the building would be functional following an SSE.

3. Show that the equipment stored in the building is not essential for the strategies to succeed following a seismic event. (This may be applicable to sites who rely heavily on pre-staged FLEX equipment already in other protected buildings.)

4. Show that the reevaluated GMRS [Ground Motion Response Spectrum] seismic hazard is equivalent to or enveloped by the ASCE 7-10 spectra which was used to design the building.

STP Response - FLEX Storage Building Design STP developed a Condition Report Engineering Evaluation (CREE) in response to this NRC question. CREE 12-11658-741 has been provided electronically via the IMS portal and is discussed in Section 3.7 of the FIP, "Protection of FLEX Equipment" (Attachment 4).

The CREE confirmed that the wind forces used in the design significantly exceed SSE seismic forces. This is a consequence of the relatively low mass of the one-story buildings, the low seismicity of the Texas Gulf Coast region, and the relatively high wind forces required by ASCE 7-10 in this region. The engineering evaluation estimated SSE seismic forces using the static equivalent method of seismic analysis and 1.5 times SSE peak acceleration. Therefore, even though SSE was not used in the design of the buildings, the higher wind forces that were used guarantee that the b~uildings will survive the STP design basis SSE earthquake.

Attachment 4 NOC-AE-1 5003311 ATTACHMENT 4 STP FLEX Final Integrated Plan (FIP)

Docket Nos. 50-498/499 Order EA-12-049 FINAL INTEGRATED PLAN Beyond Design Basis FLEX Mitigation Strategies STP Nuclear Operating Company

STP FLEX Mitigation Strategies Docket Nos. 50-498/499 Final Integrated Plan Order EA-12-049 Table of Contents

1. Introduction ......................................................................................... I

2. Background.........................................................................................I

3. Diverse and Flexible Mitigation Capability (FLEX).............................................. 3 3.1 General Elements - Assumptions ........................................................... 3 3.2 FLEX Mitigation Strategy Overview ......................................................... 5 3.2.1 Reactor Core Cooling Strategy ......................................................... 8 3.2.2 Systems, Structures, Components.................................................... 21 3.2.3 FLEX Strategy Connections ........................................................... 29 3.2.4 Key Reactor Parameters........................................................ ....... 31 3.2.5 Thermal Hydraulic Analyses ........................................................... 32 3.2.6 Shutdown Margin Analysis............................................................. 33 3.2.7 Electrical Analysis ...................................................................... 34 3.3 Spent Fuel Pool Cooling and Inventory ................................................... 34 3.3.1 Phase 1 Strategy........................................................................ 34 3.3.2 Phase 2 Strategy........................................................................ 35 3.3.3 Phase 3 Strategy........................................................................ 36 3.3.4 SFP Makeup Connections ............................................................. 36 3.3.5 Fuel Handling Building Ventilation..................................................... 37 3.3.6 Key Parameters ........................................................................ 37 3.3.7 Thermal-Hydraulic Analyses........................................................... 37 3.3.8 Pumps and Water Supplies for SFP Fill .............................................. 38 3.4 Containment Integrity ....................................................................... 138 3.4.1 Phase I ........................ ........................................................ 38 3.4.2 Phase 2.................................................................................. 39 3.4.3 Phase 3.................................................................................. 39 3.4.4 Equipment for Ventilation Cooling and Spray Strategies............................ 40 3.4.5 Key Containment Parameters ......................................................... 40 3.4.6 Thermal-Hydraulic Analyses........................................................... 40 Pagei

STP FLEX Mitigation Strategies Docket Nos. 50-498/499 Final Integrated Plan Order EA-1 2-049 3.5 Alternate Approaches........................................................................ 40 3.6 Characterization of 'External Hazards ..................................................... 41 3.6.1 Seismic .................................................................................. 41 3.6.2 External Flooding....................................................................... 42 3.6.3 Severe Storms with High Wind ........................................................ 43 3.6.4 Ice, Snow and Extreme Cold........................................................... 44 3.6.5 Extreme Heat ........................................................................... 46 3.7 Protection of FLEX Equipment......................46 3.8 Planned Deployment of FLEX Equipment ................................................ 49 3.8.1 Haul Paths................................................................................ 50 3.8.2 Accessibility.............................................................................. 50 3.8.3 Deployment Limitations for the FLEX TMDDPs Due to Flooding................... 51 3.9 Fueling of Equipment........................................................................ 51 3.10 Offsite Resources ........................................................................... 52 3.10.1 National SAFER Response Center.................................................... 52 3.10.2 Equipment List, .............................. i........................................... 56 3.11 Equipment Operating Conditions........................................................... 58 3.11.1 Ventilation and Habitability ...... *.............................................,..........58 3.11.2 Heat Tracing............................................................................. 59 3.12 Lighting................................................................... .................... 60 3.13 Communications ................................. "............................................ 62 3.14 Shutdown and Refueling Modes Analysis ....................... :.......................... 63 3.14.1 Core Cooling and ROS Inventory Control............................................. 64 3.14.2 SFP Strategy .......................................................................... . 64 3.14.3 Containment Strategy................................................................... 65 3.15 Sequence of Events......................................................................... 66 3.16 Programmatic Elements........................68 3.16.1 Overall Program Document............................................................ 68 3.16.2 Procedural Guidance................................................................... 69 Page ii

STP FLEX Mitigation Strategies Docket Nos. 50-498/499 Final Integrated Plan Order EA-12-049 3.16.3 Staffing .................................................................................. 70 3.16.4 Training.................................................................................. 71 3.16.5 Equipment List.......................................................................... 71 3.16.6 N+I- Equipment Requirement.......................................................... 75 3.16.7 Equipment Maintenance and Testing ................................................. 76 4.- References........................................................................................ 78 Page iii

STP FLEX Mitigation Strategies Docket Nos. 50-498/499 Final integrated Plan Order EA-12-049 List of Tables Table 3.2.2.2 Qualified Water Sources for FLEX .............................................. 23 Table 3.10.2 List of equipment provided by the NSRC........................................ 57 Table 3.12 Locations of Appendix R backup battle lanterns.................................. 60 Table 3.15 FLEX Sequence of Events Timeline ............................................... 67 Table 3.16.5 List of Equipment used in FLEX Strategies ..................................... 73 List of Figures Figure 3.2.1-1 Diagram of FLEX SG Makeup Strategy .............................................. 9 Figure 3.2.1-2 Diagram of FLEX RCS Makeup Strategy........................................... 10 Figure 3.2.1.2-1 - Photo of SG Makeup Pump..................................................... 14 Fig ure 3.2.1.2 Diagram of the TMDDP method for SGs Fill................................... 15 Fig ure 3.2.1.2-3 - CVCS PDP FLEX Power Transfer Switch..................................... 16 Figure 3.2.1.2 RCS Makeup Pumps (Modes *1-4 and Modes 5 & 6) ......................... 17 Figure 3.2.1.2 AWFST Makeup from the DA................................................... 19 Figure 3.2.2.2 Typical tank drain at STP........................................................ 25 Fig ure 3.2.2.2 AFWST Emergency Fill Method fire water connection ......................... 26 Figure 3.2.2.2 AFWST Emergency Fill Method through nitrogen lines ... '.................... 26 Figure 3.7 FLEX DG Enclosure, Unit 2 ......................................................... 47 Figure 3.10Q.1 Travel path from Bay City off-site staging area to STP........................ 54 Figure 3.10.1 Travel path from Wadsworth off-site staging area to STP .................... 55 Figure 3.12 FLEX lighting panel transfer switch ............................................... 61 Page iv

STP FLEX Mitigation Strategies Docket Nos. 50-498/499 Final Integrated Plan Order EA-1 2-049 List of Acronyms AC - Alternating Current FSG - FLEX Support Guideline AFW - Auxiliary Feedwater GMRS - Ground Motion Response Spectrum AFWST - Auxiliary Feedwater Storage Tank HHSI - High Head Safety Injection AOV - Air Operated Valve LLRW - Low Level Radwaste Building ATWS - Anticipated Transient Without Scram LOOP - Loss of Offsite Power BAT - Boric Acid Tank LUHS - Loss of Normal Access to the BOB - Beyond-Design-Basis Ultimate Heat Sink BDBEE - Beyond-Design-Basis External MAB - Mechanical Auxiliary Building Event MCC - Motor Control Center CCW - Component Cooling Water MCR - Main Cooling Reservoir CVCS - Chemical and Volume Control MSL - Mean Sea Level System MSSV - Main Steam Safety Valve DA - Deaerator MW - Megawatt DC - Direct Current NEI - Nuclear Energy Institute DCP - Design Change Package NRC - Nuclear Regulatory Commission DG - Diesel Generator NSRC - National SAFER Response Center DWST - Demineralized Water Storage Tank NSSS - Nuclear Steam Supply System ECP - Essential Cooling Pond NTTF - Near-Term Task Force ECW - Essential Cooling Water OBE - Operating Basis Earthquake ELAP - Extended Loss of AC Power OE - Operating Experience EOP - Emergency Operating Procedure OIP - Overall Integrated Plan ESF - Engineered Safety Feature PA - Protected Area FHB ~-Fuel Handling Building POP - Positive Displacement Pump FIP - Final Integrated Plan PEICo - Pooled Equipment Inventory FLEX - Diverse and Flexible Coping Company Strategies PORV - Power Operated Relief Valve FR - Fukushima Response PRT - Pressurizer Relief Tank Page v

STP FLEX Mitigation Strategies Docket Nos. 50-498/499 Final Integrated Plan Order EA-12-049 PRV - Pressure Relief Valve TRM - Technical Requirements Manual PWROG - Pressurized Water Reactor TS - Technical Specification Owner's Group TSC - Technical Support Center QDPS - Qualified Display Processing System UHS - Ultimate Heat Sink*

RCFC - Reactor Containment Fan Cooler WR - Wide Range RCP - Reactor Coolant Pump RCS - Reactor Coolant System RMW - Reactor Makeup Water RMWST - Reactor Makeup Water Storage Tank RVWL - Reactor Vessel Water Level RWST - Refueling Water Storage Tank SAFER - Strategic Alliance for Emergency

Response

SBO - Station Blackout SEP - Spent Fuel Pool SI - Safety Injection SMUT - Secondary Makeup Tank SPID - Screening, Prioritization and Implementation Details SSE - Safe Shutdown Earthquake STP - South Texas Project STPEGS - South Texas Project Electric Generating Station STPNOC - South Texas Project Nuclear Operating Company TDAFW Pump - Turbine-Driven Auxiliary Feedwater Pump TMDDP - Trailer-Mounted Diesel-Driven Pump Page vi

STPNOC FLEX Mitigation Strategies Docket Nos. 50-498/499 Final Integrated Plan Order EA-12-049

1. Introduction This Final Integrated Plan (FIP) defines strategies capable of mitigating a simultaneous loss of all alternating current (AC) power and loss of normal access to the ultimate heat sink (UHS) resulting from a Beyond-Design-Basis External Event (BDBEE). These strategies provide adequate capability to maintain or restore core cooling and inventory as well as containment and Spent Fuel Pool (SFP) cooling capabilities for both STP Unit I and STP Unit 2. The inability to anticipate all possible scenarios involving a BDBEE necessitates that the strategies are also diverse and flexible to encompass a wide range of possible conditions to protect the public health and safety. The impact of these strategies on the design basis capabilities of the units have been evaluated under 10 CFR 50.59.

2. Background

In 2011, an earthquake-induced tsunami caused Beyond-Design-Basis (BOB) flooding at the Fukushima Dai-ichi Nuclear Power Station in Japan. The flooding caused the emergency power supplies and electrical distribution systems to be inoperable, resulting in an extended loss of AC power (ELAP) in five of the six units on the site. The ELAP led to the loss of core cooling, loss of spent fuel pool cooling capabilities and a significant challenge to maintaining containment integrity. All direct current (DC) power was lost early in the event at Units I and 2 and after some period of time at the other units. Core damage occurred in three of the units along with a loss of containment integrity, resulting in a release of radioactive material to the surrounding environment.

Following this event, the US Nuclear Regulatory Commission (NRC) assembled a Near-Term Task Force (NTTF) to advise the Commission on actions the US nuclear industry should take to preclude core damage and a release of radioactive material after a natural disaster such as that seen at Fukushima. The NTTF report (Reference 1) contained many recommendations to fulfill this charter, including assessing extreme external event hazards and strengthening station capabilities for responding to BDBEEs.

Based on NTTF Recommendation 4.2, the NRC issued Order EA-12-049 (Reference 2) requiring licensees to implement mitigation strategies for BDBEEs including the following requirements:

Licensees shall develop, implement, and maintain guidance and strategies to maintain or restore core cooling, containment, and SFP cooling capabilities following a BDBEE.

Licensees shall develop strategies that are capable of mitigating a simultaneous loss of all AC power and loss of normal access to the ultimate heat sink (LUHS) and have adequate capacity to address challenges to core cooling, containment and SFP cooling capabilities at all units on a site.

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STPNOC FLEX Mitigation Strategies Docket Nos. 50-498/499 Final Integrated Plan Order EA-1 2-049

Licensees must provide reasonable protection for the associated equipment from external events. Such protection must demonstrate that there is adequate capacity to address challenges to core cooling, containment, and SFIp cooling capabilities at all units on a site.

Licensees must be capable of implementing the strategies in all modes.

Full compliance shall include procedures, guidance, training, and acquisition, staging or installing of equipment needed for the strategies.

Order EA-12-049 specifies a three-phase approach for strategies to mitigate BDBEEs. The initial phase, "Phase 1", requires the use of installed equipment and resources to maintain or restore core cooling, containment and SFP cooling capabilities. The transition phase, "Phase 2", requires providing sufficient, portable, onsite equipment and consumables to maintain or restore these functions until resources can be brought from off site. The final phase, "Phase 3" requires obtaining sufficient offsite resources to sustain those functions indefinitely.

Order EA-12-049 also required licensees of operating reactors to submit an Overall Integrated Plan (OIP) that included a description of how compliance with these requirements would be achieved by February 28, 2013 (Reference 3), followed by status updates submitted at six-month intervals (References 4 - 8). The Order also requires licensees to complete implementation of the requirements no later than two refueling cycles after submittal of the OIP or by December 31, 2016, whichever comes first.

The Nuclear Energy Institute (NEI) developed NEI 12-06 (Reference 9) which provides guidelines for nuclear stations to assess extreme external event hazards and implement the mitigation strategies required by Order EA-12-049. The NRC issued Interim Staff Guidance JLD-ISG-2012-01 (Reference 10) endorsing NEI 12-06 with clarifications for determining baseline coping capability and equipment quality.

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STPNOC FLEX Mitigation Strategies Docket Nos. 50-498/499 Final Integrated Plan Order EA-12-049

3. Diverse and Flexible Mitigation Capability (FLEX)

South Texas Project Nuclear Operating Company (STPNOC) has developed the following FLEX strategies to meet the requirements of Order EA-12-049.

3.1 General Elements - Assumptions STPNOC established the following plant initial conditions, boundary conditions and assumptions consistent with NEI 12-06 for the purpose of defining FLEX strategies.

Boundary Conditions

A BDBEE occurs impacting both units at the site.

All reactors on-site initially operating at power, unless site has procedural direction to shut down due to the impending event.

Each reactor is successfully shut down when required (i.e., all rods inserted, no ATWS).

On-site staff are at site administrative minimum shift staffing levels.

No independent, concurrent events, e.g., no active security threat.

All personnel on-site are available to support site response.

Spent fuel in dry storage is outside the scope of FLEX.

Initial Conditions

Prior to the event the reactors have been operating at 100 percent rated thermal power for at least 100 days or have been shut down as required by plant procedures in advance of the impending event.

The reactor and supporting plant equipment are operating within normal ranges for pressure, temperature and water level, or are available to operate from the standby state as described in the site design and licensing basis.

The initiating event is not specific. The initial condition is assumed to be a loss of offsite power (LOOP) affecting both units on the site with no prospect for recovery for an extended period.

All installed sources of emergency onsite AC power and station blackout (SBO)

Alternate AC power sources are not available and not imminently recoverable.

Cooling and makeup water inventories contained in systems or structures that are robust with respect to seismic events, floods, high winds and associated missiles are available.

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STPNOC FLEX Mitigation Strategies Docket Nos. 50-498/499 Final Integrated Plan Order EA-12-049

Normal access to the UHS is lost, but the water inventory in the UHS remains available and robust piping connecting the UHS to plant systems remains intact.

The motive force for UHS flow (i.e., pumps) is assumed to be lost with no prospect for recovery.

, Permanent plant equipment and fuel for FLEX equipment stored in structures that are robust with respect to seismic events, floods, high winds and associated missiles are available.

Other equipment, such as portable AC power sources, portable back up DC power supplies, spare batteries, and equipment for 10 CFR 50.54(hh)(2), may be used provided it is reasonably protected from the applicable external hazards, has predetermined hookup strategies with appropriate procedural guidance and the equipment is stored in a relative close vicinity of the site.

Installed electrical distribution systems, including inverters and battery chargers, remain available provided they are protected consistent with current station design.

No additional events or failures occur immediately prior to or during the event, including security events.

The portion of the fire protection system that is robust with respect to seismic events, floods, high winds and associated missiles is also available as a water source.

Reactor Transient Boundary Conditions o Following the loss of all AC power, both reactors are successfully shut down when required (i.e., all rods inserted, no ATWS).

Steam release to maintain decay heat removal upon shutdown functions normally, and Reactor Coolant System (RCS) overpressure protection valves respond normally, if required by plant conditions, and reseat.

No independent failures, other than those causing the ELAP/LUHS event, are assumed to occur in the course of the transient.

Reactor Coolant Inventory Loss Assumptions

Sources of expected reactor coolant inventory loss consist of normal system leakage from reactor coolant letdown flow (until isolated) and Reactor Coolant Pump (RCP) seal leak-off at a rate dependent on RCP seal design.

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STPNOC FLEX Mitigation Strategies Docket Nos. 50-498/499 Final Integrated Plan Order EA-1 2-049 SFP Initial Conditions

SFP boundaries and cooling system are intact, including the liner, gates, transfer canal and attached piping.

Initial loss of SFP inventory from sloshing during a seismic event does not preclude access to the refueling deck around the pool.

The SFP heat load is assumed to be the maximum design basis heat load.

3.2 FLEX Mitiqation Strateqy Overview The objective of the FLEX strategies is to establish an indefinite coping capability in order to prevent damage to the fuel in the reactors, maintain the containment function and maintain cooling and prevent damage to fuel in the SFP using installed equipment, onsite portable and pre-staged FLEX equipment, and pre-staged offsite resources.

Indefinite coping capability is attained through the implementation of pre-determined FLEX strategies that are focused on maintaining or restoring key plant safety functions.

The FLEX strategies are not tied to any specific damage state or mechanistic assessment of external events. Rather, the strategies are developed to maintain the key plant safety functions based on the evaluation of plant response to the ELAP/LUHS event. The FLEX strategies are diverse and flexible to encompass a wide range of possible conditions.

This safety function-based approach is consistent with the existing site EOPs. FLEX strategies are implemented in support of the EOPs using the procedures developed for implementing the FLEX strategies, the FLEX Support Guidelines (FSGs).

The strategies for coping with the plant conditions that result from an ELAP/LUHS event involve a three-phase approach:

Phase 1 (Initial Phase) - Initially cope by relying on installed plant equipment and onsite resources.

Phase 2 (Transition Phase) - Transition from installed plant equipment to onsite FLEX equipment.

Phase 3 (Final Phase) - Obtain additional capability and redundancy from offsite equipment until power, water, and coolant injection systems are restored.

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STPNOC FLEX Mitigation Strategies Docket Nos. 50-498/499 Final Integrated Plan Order EA-12-049 The duration of each phase is specific to the installed and portable equipment utilized for the particular FLEX strategy employed to mitigate the plant condition.

For the Phase 2 or Transition Phase coping actions, the STP FLEX strategies utilize mainly pre-staged equipment instead of portable equipment. This is primarily due to challenges presented by STPs design basis flooding event. The design basis flooding event from a breach of the Main Cooling Reservoir (MCR) embankment inundates the site with water therefore some types of strategies are not feasible (i.e. moving portable pumps from a storage location to the power block to pre-installed connections to the Steam Generators (SGs), the RCS and the SFP). This is considered an Alternate Approach to NEI 12-06.

Additional details regarding the MOR embankment breach scenario are included in Section 3.6.2, "External Flooding". Further details about all of STP's alternate approaches to the NEI 12-06 guidance are discussed in Section 3.5, "Alternate Approaches".

Narrative Summary of ELAP/LUKS Event Sequence A timeline of the overall strategy is presented in Table 3.15-1. The ROS response events in the timeline are based on analysis assuming the RCP seal leakage presented in Westinghouse Report PWROG-1 401 5-P (Reference 35).

Phase 1 begins when the ELAP occurs. The reactor trips with all control rods and shutdown rods inserted. The TDAFW pump begins to feed the D-Train SG within one minute of the start of the event. The steam generator safety relief valve provides the initial RCS temperature and pressure control. At four minutes into the event, the leakage from the #1 RCP seal increases to approximately 16.5 gpm. Within ten minutes, Operators are dispatched to restore steam generator PORV control to the Control Room and begin to cross-connect AFW flow from the TDAFW pump to the other three SGs (Reference 11). The #1 seal leak-off line containment isolation valve is also locally closed, resulting in the #1 RCP seal flow being diverted to the PRT through the #1 seal leak-off line (PSV-3200).

Thirty minutes into the event, Operators determine that an ELAP condition has Occurred and perform the initial assessment of FLEX equipment staging in accordance with FSG-05 and commence DC load shed of the non-essential equipment in accordance with FSG-04 (References 22 and 30).

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STPNOC FLEX Mitigation Strategies Docket Nos. 50-498/499 Final Integrated Pian Order EA-12-049 Forty minutes into the event, flow from the TDAFW pumps is provided to all four SGs.

One hour into the event, Operators commence a depressurization of all four SGs to a target pressure of 405 psig to reduce RCP seal leakage. Approximately 75 minutes into the event, the pressure in the Pressurizer Relief Tank (PRT) exceeds the rupture disk design pressure, resulting in the flow from the #1 seal leak-off line being released into containment. The FLEX equipment lineups and connections begin within one to two hours. Two hours into the event, the DC load shed of non-essential equipment is completed.

Within three hours, the SGs are depressurized to 405 psig, which ensures nitrogen injection from the safety injection (SI) Accumulators into the RCS does not occur.

During the depressurization of the SGs and subsequent cooldown of the RCS, the boron addition from the accumulators ensures the reactor remains sub-critical. After six hours, offsite personal resources begin to arrive onsite.

Phase 2 begins in less than eight hours when a FLEX diesel generator (DG) is started and power becomes available to the FLEX equipment. Within eight hours, the A and C battery chargers begin charging batteries. Within ten hours, power to the SI Accumulator isolation valves is made available and these valves are closed, ensuring nitrogen injection into the RCS does not occur. At this time, charging flow of 35 gpm to the RCS from the BAT or RWST using the PDP is assumed, which provides boron and RCS inventory makeup.

The FLEX steam generator (SG) makeup pump is available by this time to ensure Auxiliary Feedwater (AFW) flow is available in the event t-he SG pressure decreases to such a point the TDAFW pump can no longer be sustained. The SG Power-Operated Relief Valves (PORVs) are used to start a second depressurization of the SGs and cooldown and depressurization of the RCS.

The second SG depressurization results in a significant decrease in the #1 RCP seal leakage. The #1 RCP seal leak-off is terminated when the RCS pressure decreases below the #1 seal leak-off line relief valve reset pressure. As the RCS inventory is restored, the RCS pressure increases. The IRCS pressure is maintained at a pressure that ensures that the #1 RCP seal leak-off line relief valve does not re-open, which occurs at approximately 15 hours1.736111e-4 days 0.00417 hours 2.480159e-5 weeks 5.7075e-6 months using the reactor vessel upper head vents.

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STPNOC FLEX Mitigation Strategies Docket Nos. 50-498/499 Final Integrated Plan Order EA-12-049 At approximately 21 hours2.430556e-4 days 0.00583 hours 3.472222e-5 weeks 7.9905e-6 months into the event, the reactor vessel upper head is filled. Flow through the reactor vessel upper head vent valves continues for another 30 minutes to cool the metal in the upper head, if required. At approximately 22 hours2.546296e-4 days 0.00611 hours 3.637566e-5 weeks 8.371e-6 months into the event, the reactor vessel upper head vents are secured and the pressurizer PORV or reactor vessel upper head vents could be used to maintain RCS pressure below the #1 RCP seal leak-off line relief valve pressure. At approximately 23 hours2.662037e-4 days 0.00639 hours 3.80291e-5 weeks 8.7515e-6 months into the event, pressurizer level is restored and the FLEX RCS makeup pump is secured.

During Phase 2, preparations are made to refill the AFWST. The TMDDP used to fill the AFWST could also be used to fill the RWST.. At this point, the plant is in a stable condition. The containment pressure is less than 3 psig and containment temperature is less than 135°F. The spent fuel pool temperature is less than 212°F.

Phase 3 begins with the arrival of additional equipment from NSRC. Among this equipment are two 4160V turbine generators which can be connected to an Engineered Safety Feature (ESF) electrical bus.

3.2.1 Reactor Core Coolingq Strategqy Reactor core cooling involves the removal of decay heat through the secondary side of the Nuclear Steam Supply System (NSSS) and maintaining sufficient RCS inventory to ensure the continuation of natural circulation in the primary side of the NSSS. The FLEX strategy for reactor core cooling and decay heat removal involves releasing steam from the SGs using the SG PORVs and the addition of a corresponding amount of AFW to the SGs via the Turbine-Driven AFW (TDAFW) pump. The Auxiliary Feedwater Storage Tank (AFWST) is the water supply to the TDAFW pump. Operator actions to verify, re-align and throttle AFW flow are required by STP procedure 0POP05-EO-EC00, "Loss of All AC Power" (Reference 11) during an ELAP/LUHS event to prevent SG dryout.

Per the EC00 procedure, Operators will initiate RCS cooldown within the first hour following a BDBEE that triggers an ELAP/LUHS event.

RCS makeup and boron addition will be initiated within 10 hours1.157407e-4 days 0.00278 hours 1.653439e-5 weeks 3.805e-6 months following a BDBEE to ensure natural circulation, reactivity control, and adequate boron mixing is maintained in the RCS. See Figure 3.2.1-1 and Figure 3.2.1-2, below, for a diagrams of the FLEX SG and FLEX RCS Makeup pathways.

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STPNOC FLEX Mitigation Strategies Docket Nos. 50-498/499 Final Integrated Plan Order EA-12-049 STEAM GENCRATOR STEAM,*

OtNERATOR Figure 3.2.1-1 Diagram of Unit 2 FLEX SG Makeup Strategy Page 9 of 86

STPNOC FLEX Mitigation Strategies Docket Nos. 50-498/499 Final Integrated Plan Order EA-12-049 Figure 3.2.1-2 Diagram of Unit 2 FLEX RCS Makeup Strategy Page 10 of 86

STPNOC FLEX Mitigation Strategies Docket Nos. 50-498/499 Final Integrated Plan Order EA-1 2-049 The reactor core cooling strategies for Phases I through 3, described below, are the same for STP Unit I and Unit 2.

3.2.1.1 Phase I Stratecqy The Phase I FLEX strategy for reactor core cooling and heat removal relies on installed plant equipment and water sources for supplying AFW flow to the SGs.

Operators will respond to the ELAP/LUHS event in accordance with the EOPs. Operators will transition to the EOP for loss of all AC power, 0POP05-EO-EC00 (Reference 11), when it is determined that all AC power has been lost. This procedure directs isolation of RCS letdown pathway, verification of containment isolation, reduction of DC loads on the station Class 1E batteries, and alignment of electrical equipment in preparation for eventual power restoration. Following an ELAP/LUHS event, the reactor will trip and the plant will initially stabilize at an average RCS temperature of approximately 582°F, with reactor decay heat removal via steam release to the atmosphere through the Main Steam Safety Valves (MSSVs). The SG PORVs will fail closed on the loss of power and power must be restored to the SG PORV circuit to allow them to be opened from the Control Room. Natural circulation of the RCS will provide core cooling and the TDAFW pump will automatically provide flow from the AFWST to the D-Train SG to make up water lost due to the steam release.

During the first hour of the event, Operators will be dispatched locally to re-align AFW flow to all SGs. This will allow the SGs to cooldown symmetrically. Once the SG PORV control has been restored to the Control Room, then the SG PORVs are opened to reduce pressure to between 1130 and 1190 psig so the Main Steam safety valves will close.

This reduced RCS temperature to approximately 571°0F. A cooldown of the RCS is initiated within the first hour of the event to minimize inventory loss through the RCP seals per EC00 (Reference 11).

The TDAFW pump starts automatically on SG Low-Low level and does not require AC electrical power to provide AFW to the SGs. In the event that the TDAFW pump does not start on demand or trips after starting, an operator will restart the TDAFW pump per the EC00 procedure. The AFW system is normally aligned for the TDAFW pump to deliver flow to the D-Train SG, so the loss of all AC power EOP directs Operators to Page 11 of 86

STPNOC FLEX Mitigation Strategies Docket Nos. 50-498/499 Final Integrated Plan Order EA-12-049 manually align flow to all four SGs. Manual control of TDAFW pump flowrate to the SGs for establishing and maintaining proper water levels in the SGs will be performed locally in the Isolation Valve Cubicle (IVC) per EC00 (Reference 11).

Steam release from the SGs will be controlled remotely from the Main Control Room using hydraulically-operated SG PORVs per EC00. Local manual operation of the SG PORVs can be performed in the event that hydraulic pressure is expended.

In accordance with the EC00 procedure, RCS cooldown and depressurization is initiated at a rate of less than 100°F/hr to a minimum SG pressure of 405 psig, which corresponds to an RCS core inlet temperature of approximately 450°F. The RCS cooldown minimizes the adverse effects of high temperature RCS coolant on RCP seal performance and reduces SG pressure to allow for SG injection from one of the FLEX SG makeup pumps in the event that the TDAFW pump becomes unavailable. The minimum SG pressure of 405 psig is sufficient to prevent nitrogen gas from the SI Accumulators from entering

,the RCS.

Analysis demonstrates that the plant can maintain this condition for 10 hours1.157407e-4 days 0.00278 hours 1.653439e-5 weeks 3.805e-6 months without the RCP seals experiencing two phase flow or reflux cooling occurring as defined in the NRC endorsement letter for the use of the PWROG NOTRUMP code for ELAP events (Reference 83). STP performs fuel cycle specific analysis to demonstrate that the reactor core remains subcritical for this period of time (Reference 84).

AFW supply is provided by the AFWST. Conservatively assuming the initial water level in the AFWST is at the low level alarm, the usable volume of this tank provides a sufficient source of AFW for a minimum of 32 hours3.703704e-4 days 0.00889 hours 5.291005e-5 weeks 1.2176e-5 months of RCS decay heat removal (Reference 18).

The Phase I equipment including the TDAFW pump, SG PORVs, AFW regulating valves and the AFWST maintain the initial RCS cooling strategy. The Phase 2 FLEX equipment will be started as needed to support longer term cooldown. A FLEX RCS makeup pump for boron addition will be started to maintain adequate shutdown margin during the cooldown. A FLEX SG makeup pump will be aligned to support replacing the TDAFW pump when SG pressure will no longer support TDAFW pump operations.

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STPNOC FLEX Mitigation Strategies Docket Nos. 50-498/499 Final Integrated Plan Order EA-1 2-049 3.2.1.2 Phase 2 Stratecqy The Phase 2 FLEX strategy for reactor core cooling and heat removal continues to rely on feedwater from the AFWST using the TDAFW pump and, eventually, one of the FLEX SG makeup pumps powered by a FLEX DG.

Once the SI Accumulators have been isolated using FSG-10 (Reference 15), Operators initiate a second cooldown and depressurization of the RCS per the EC00 procedure (Reference 11), lowering the SG pressure to below the required 150 psig to run the TDAFW pump (Reference 16).

One purpose of this subsequent cooldown and depressurization is to re-seat the Pressure Relief Valve (PRV) on the RCP seal return line that opened due to the increased RCP seal leakage early in the event. At about 12 hours1.388889e-4 days 0.00333 hours 1.984127e-5 weeks 4.566e-6 months into the event, the PRV should be re-seated (Reference 14). At approximately 23 hours2.662037e-4 days 0.00639 hours 3.80291e-5 weeks 8.7515e-6 months following event start, pressurizer level will be restored and makeup to the RCS will no longer be required (Reference 14).

Prior to the completion of this second cooldown and depressurization, Operators start one of the two FLEX S'G makeup pumps (Reference 11),

fine up the pump to feed all SGs, and secure the TDAFW pump (Reference 17). The FLEX SG makeup pumps take suction on the AFWST and are pre-staged inside the IVC in each unit in the C-Train and B-Train bays.

During Phase 2, core heat removal via the SGs will be maintained continuously. These FLEX SG makeup pumps are rated for a nominal pressure of 500 psig while flowing at 300 gpm, sufficient size for use in this strategy (Reference 14). FLEX connections are provided on the suction piping from the AFWST and on the AFW discharge cross-connect piping. Plant personnel will use FSGs to remove blinds and install short hoses and spool pieces in the system to facilitate supplying water with the FLEX pumps (References 22 and 17).

See Figure 3.2.1.2-1, below, for a photo of one of the SG makeup pumps.

Page 13 of 86

STPNOC FLEX Mitigation Strategies Docket Nos. 50-498/499 Final Integrated Plan Order EA-12-049 Figure 3.2.1.2-1 - Photo of SG Makeup Pump During Phase 2, the S~s can also be filled using the portable Trailer-Mounted Diesel-Driven Pumps (TMDDPs) stored in the STP FLEX storage buildings. See Figure 3.2.1.2-2 for a diagram of the TMDDP method for S~s fill via one of the two Main Feedwater lines. Per FSG-03 (Reference 17), the TMDDPs can take suction from various water sources including outside water tanks, those containing demineralized water are the first priority, and from the Essential Cooling Pond (ECP) or Circulation Water underground piping if all water tanks have been depleted.

Page 14 of 86

STPNOC FLEX Mitigation Strategies Docket Nos. 50-498/499 Final Integrated Plan Order EA-12-049 Figure 3.2.1.2 Diagram of the TMDDP method for SGs Fill Page 15 of 86

STPNOC FLEX Mitigation Strategies Docket Nos. 50-498/499 Final Integrated Plan Order EA-1 2-049 Primary Strateqy for Phase 2 RCS Fill The primary strategy for filling the RCS utilizes a 35 gpm Chemical and Volume Control System (CVCS) Positive Displacement Pump (PDP) at 3100 psig that takes suction on either the Boric Acid Tanks (BATs) or the Refueling Water Storage Tank (RWST) and discharging into the CVCS charging line. A separate electrical power distribution system provides power from the FLEX DGs' distribution panel (DP1000) to the CVCS PDP. Locally at the PDP, a manual transfer switch is installed that permits powering the PDP from either its normal source, Motor Control Center (MCC) 1G8 (2G8), or from the FLEX DGs. See Figure 3.2.1.2-3, below.

Figure 3.2.1.2 CVCS PDP FLEX Power Transfer Switch Page 16 of 86

STPNOC FLEX Mitigation Strategies Docket Nos. 50-498/499 Final Integrated Plan Order EA-12-049 N+I Strateqy for Phase 2 RCS Fill The N+I strategy for filling the RCS utilizes a pre-staged 70 gpm FLEX RCS makeup pump at 700 psig installed in the Train 'A' SI pump bay in the Fuel Handling Building (FHB). This pump takes suction from the RWST and discharges into the SI line downstream of High Head Safety Injection (HHSI) discharge motor-operated valve (MOV) which is connected to the RCS. In the event that a bubble in the reactor head increases pressure above the FLEX RCS makeup pump's discharge head, STP has the ability to vent the reactor head using the Reactor Vessel Upper Head Vent valves as described in EC00 (Reference 11).

For the purposes of the FLEX timeline, STP conservatively assumes that operators will be able to start one of the FLEX DGs within eight hours following the ELAP event. The FLEX DG will power the FLEX RCS makeup pumps in order to provide boric acid to the RCS to maintain shutdown margin. See Figure 3.2.1.2-4, below, for a photo of the FLEX RCS makeup pumps.

Figure 3.2.1.2-4 - RCS Makeup Pumps (Modes 1-4 and Modes 5 & 6)

Page 17 of 86

STPNOC FLEX Mitigation Strategies Docket Nos. 50-498/499 Final Integrated Plan Order EA-12-049 STP has elected to use two installed RCS makeup pumps as the N and N+1 RCS fill strategies which is an alternate approach to the NEI 12-06 guidance. See Section 3.5 of this document, "Alternate Approaches", for additional details.

Considerations for Phase 2 RCS Fill Followinq a Flood Event In the event of a large flood that prohibits movement around the site, the approximately 474,000 gallons of water are available in the AFWST and 148,000 gallons of water in the Condensate Deaerator (DA) can be used until flood waters recede (Reference 18). Flow from the DA to the AFWST is accomplished by gravity feed due to the elevation differences of the two tanks. Figure 3.2.1.2-5 below provides a diagram of the AFWST fill from the DA strategy.

The AFWST has sufficient capacity to provide AFW to the steam generators for approximately 32 hours3.703704e-4 days 0.00889 hours 5.291005e-5 weeks 1.2176e-5 months after the initiation of the ELAP event. During this period, hoses are connected between the DA FLEX Feedwater Isolation Valve and the Auxiliary Feed Pump Recirculation Test Line Drain Valve which supplies the AFWST. Prior to opening the DA FLEX Feedwater Isolation Valve, the DA is vented for at least seven hours to reduce the pressure and temperature in the deaerator to atmospheric saturation conditions. As noted in FSG-06, if the DA is not allowed proper time for venting, this could result in a release of two-phase water into the transfer hoses. Steam suits and hearing protection staged in the Turbine Generator Building (TGB) can be used to support opening the valves to complete this venting action (Reference 27).

The additional water inventory from the DA extends the capacity of the AFWST to approximately 47 hours5.439815e-4 days 0.0131 hours 7.771164e-5 weeks 1.78835e-5 months . In the event additional makeup to the AFWST could not be provided, the steam generators would contain sufficient inventory for approximately 58 hours6.712963e-4 days 0.0161 hours 9.589947e-5 weeks 2.2069e-5 months before a loss of heat sink would occur.

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STPNOC FLEX Mitigation Strategies Docket Nos. 50-498/499 Final Integrated Plan Order EA-12-049 ELEVATION 109' WATER LEVEL FOR A FULL DEAERATOR STORAGE TANK #2 FLEX HOSE 2 1/2" FLEX HOSE 017 FW0488 *

-- EL. 83'- 0"TGB L.i WYE CONNECTIONS BLOWDOWN TO CONDENSER ELEVATION 64" - 4".

TOP SIDE OF AFWST 1 1/2" FIRE HOSE AUXILIARY FEEDWATER APPROXIMATE ELEVATION STORAG E TAN K . 20' OF IVC (AFWST)

C (CDI422O (02-46))

Figure 3.2.1.2-5 - AWFST Makeup from the DA Page 19 of 86

STPNOC FLEX Mitigation Strategies Docket Nos. 50-498/499 Final Integrated Plan Order EA-1 2-049 3.2.1.3 Phase 3 Strateqy The Phase 3 FLEX strategies for RCS cooling and heat removal continue to rely on the FLEX SG makeup pumps. During this phase, decay heat will eventually decrease to the point that steaming and feeding the SGs will only be periodically performed. This form of heat transfer can continue indefinitely.

As outlined in FSG-21 (Reference 19), the FLEX SG makeup pumps can be supplemented by one of the normal permanent plant AFW pumps powered from the Strategic Alliance for Emergency Response (SAFER) National Resource Center (NSRC) 4.16 KV turbine generators and AC distribution center that will arrive onsite approximately 24 hours2.777778e-4 days 0.00667 hours 3.968254e-5 weeks 9.132e-6 months following notification of the NSRC. The NSRC generator can provide power to a motor-driven AFW pump as well as other equipment on the same electrical bus.

The NSRC 4.16 KV generator provides additional defense-in-depth for temporary power options and is sized to power one of the three 4.16 KVAC ESF electrical switchgears. The cable tie-in locations for the NSRC generators are on the downstream side of the ESF transformers (Reference 19).

Note that the Phase 3 strategy does not rely on the delivery of the NSRC generator for core cooling - the site can continue to cope using the FLEX SG makeup pumps.

The NSRC will deliver other equipment that can be used for the

Phase 3 core cooling strategy including the following:

Low pressure, medium flow pump used to fill the SGs. Direction for use of this pump would come from the Emergency Response Organization (ERO).

Diesel fuel transfer tank and associated pump used for fueling diesel driven equipment.

This equipment is listed in the STP SAFER Response Plan and associated site procedure (References 95 and 20).

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STPNOC FLEX Mitigation Strategies Docket Nos. 50-498/499 Final Integrated Plan Order EA-12-049 3.2.2 Systems, Structures, Components The following Structures, Systems, and Components (SSCs) are utilized in the FLEX strategies.

3.2.2.1 Pumps Turbine-Driven Auxiliary Feedwater Pump The TDAFW pump is a safety-related, missile protected and seismically qualified pump. The TDAFW pump located in the IVC which is designed for protection from applicable design basis external hazards.

The TDAFW pump should automatically start and deliver AFW flow to the D-Train SG following an ELAP/LUHS event. Two DC powered steam supply valves supply steam to the TDAFW pump turbine. These valves are normally closed and open to admit steam to the turbine on a SG Low-Low level or SI signal. The TDAFW pump turbine steam flow will either be controlled automatically by the governor valve or manually with the overspeed trip-throttle valve.

In the event the TDAFW pump fails to start, EC00 and FSG-07 (References 11 and 21) direct the operators to manually start the pump.

A local vent fan for cooling the TDAFW pump room will be powered once the FLEX DG has been started and begins powering the designated MC~s (Reference 22).

Trailer-Mounted Diesel-Driven Pumps There are two TMDDPs stored in the FLEX storage buildings located outside the protected area (PA) and a third unprotected pump stored inside the power block that is designated for use in response to mitigate 10 CFR 50.54(hh)(2) events. The specifications for these pumps are as follows: \

John Deere powered Gorman-Rupp pump

20 ft suction lift

Approximately 1000 gpm at greater than 150 psig flowrate and pressure

130 gallon fuel tank

60 ft of 6 inch diameter suction hose including a floating strainer

3000 ft of 2.5 inch discharge hose Page 21 of 86

STPNOC FLEX Mitigation Strategies Docket Nos. 50-498/499 Final Integrated Plan Order EA-12-049 For the FLEX strategies, the primary function of the TMDDPs is to provide makeup water to the AFWST and the RWST in both units. The highest priority for use of the pump is filling the AFWSTs. The TMDDPs will not be required to makeup to either of these tanks for at least 24 hours2.777778e-4 days 0.00667 hours 3.968254e-5 weeks 9.132e-6 months . After 24 hours2.777778e-4 days 0.00667 hours 3.968254e-5 weeks 9.132e-6 months , the NSRC will begin providing additional pumps to perform the same functions.

The secondary function of the TMDDPs is to provide makeup water to the SGs and the SFP in the event that the N and N+I FLEX makeup pumps are unavailable.

The TMDDPs and hose trailers are strategically separated to increase the likelihood that one of them survives a large external event.

Additionally, the two TMDD pumps in the FLEX buildings have their wheels chocked to help ensure they are not damaged during a seismic event. The two pumps stored in the FLEX storage buildings are deployed to their needed locations by means of four wheel drive tractors stored with the pumps. The unprotected third pump and hose trailer is stored inside the PA.

FLEX SG Makeup Pumps SG water injection capability is provided using two pre-staged FLEX SG makeup pumps (N and N+I) installed inside a Category I building in each unit. The FLEX SG makeup pumps are rated for a nominal pressure of 500 psig while flowing at 300 gpm. The FLEX SG makeup pumps are 480V motor-driven Centrifugal pumps located in separate bays in the IVO. These pumps provide SG water injection in the event that the TDAFW pump can no longer perform its function (e.g. due to insufficient turbine inlet steam flow from the SG). Hydraulic analyses have confirmed that the FLEX SG makeup pumps are sized to provide the minimum required SG injection flowrate to support reactor core cooling and decay heat removal (References 23 and 24).

FLEX RCS Makeup Pumps The N and N+I FLEX RCS makeup pumps are installed in different locations inside Category 1 buildings and have different suction and discharge piping arrangements. The N pump is the CVCS POP which provides approximately 35 gpm at 3100 psig. The N+1 pump is a centrifugal pump that provides 70 gpm at 700 psig. The N+1 pump is a lower pressure pump because the reactor head can be vented to reduce pressure (Reference 11), ensuring this pump is sufficiently sized to fill Page 22 of 86

STPNOC FLEX Mitigation Strategies Docket Nos. 50-498/499 Final Integrated Plan Order EA-12-049 the RCS. Hydraulic analysis of the RCS makeup pumps with the associated hoses and installed piping systems confirm minimum flow rate and head capabilities exceed the FLEX strategy requirements for maintaining RCS inventory (References 25 and 26).

3.2.2.2 Water Sources Table 3.2.2.2-1 lists the qualified water sources (demineralized or borated) used in the STP FLEX strategies. All listed water sources are protected against environmental hazards including seismic, external flooding, high winds, low temperature, high temperature.

Water Required Normal WaeQult Sucs Minimum Volume VolumeQu(gal)

Sources ~~(gal) Vlm gl RWST 458,000 (TS limit) 518,000 Borated AFWST 485,000 (TS limit) 508,000 Demineralized BATs 27,000 (TRM limit) 60,000 Borated RMWST N/A 122,000 Demineralized ECP (shared) N/A 112 million Well water Table 3.2.2.2-1 - Qualified Water Sources for FLEX Note that the useable volume of the RWST is 398,000 gal, as defined in Section 6.3.2.2 of the UFSAR (Reference 44). The useable volume of the AFWST is 474,000 gal, as defined in STP's calculation for the time to loss of heat sink during an ELAP (Reference 18).

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STPNOC FLEX Mitigation Strategies Docket Nos. 50-498/499 Final Integrated Plan Order EA-12-049 The FSGs also list alternate water sources for use in the FLEX strategies (References 17, 27 and 41), including:

Secondary Makeup Tank (SMUT), clean water, high usage priority

Demineralized Water Storage Tank (DWST), clean water, high usage priority

Deaerator Storage Tank, SG feedwater, high usage priority

Fire Water Storage Tank, ground water, medium usage priority

Service Water Storage Tank, ground water, medium usage priority

Organics Basin, medium usage priority

Essential Cooling Water (ECW) Pond, brackish water, low usage priority

Circulating Water underground piping, brackish water, low usage priority Additional details on the qualified water sources are provided'below.

Auxiliary Feedwater Storaqe Tank The AFWST is a safety-related, seismic and tornado-missile protected structure designed to withstand the applicable design basis external hazards stated in NEI 12-06. The AFWST is normally aligned to provide emergency makeup water to the SGs and it is the preferred AFW system water source at the onset of the ELAP event. Per Technical Specification (TS) 3.7.1.3, the minimum volume of each Unit's AFWST is maintained at 485,000 gallons. As outlined in FSG-06, following the onset of an ELAP/LUHS event the AFWST will be supplied with water from a variety of sources, including the ECP in a worst-case-scenario using the TMDDPs (Reference 27). See Figure 3.2.2.2-1, below, for a photo of a typical tank drain that will be used as a source of water, if available.

Page 24 of 86

STPNOC FLEX Mitigation Strategies Docket Nos. 50-498/499 Final Integrated Plan Order EA-12-049 Figure 3.2.2.2-1 - Typical tank drain at STP Assuming RCS cooldown rate of less than 100°F per hour, the maximum cooldown rate allowed by the EC00 procedure, each Unit's AFWST would provide sufficient water for 32 hours3.703704e-4 days 0.00889 hours 5.291005e-5 weeks 1.2176e-5 months of coping time (Reference 18).

An emergency fill valve has been installed on top of each AFWST along with 100 ft of 2.5 inch diameter fire hose that will be used to fill the AWFST with firewater, if necessary. Figure 3.2.2.2-2 shows the connection point.

In the event that this valve or associated piping is damaged, the 2 inch nitrogen lines with threaded connections can be connected to the fire water connection and used to fill the AFWST. The nitrogen lines are shown in Figure 3.2.2.2-3 below.

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STPNOC FLEX Mitigation Strategies Docket Nos. 50-498/499 Final Integrated Plan Order EA-12-049 Figure 3.2.2.2 AFWST Emergency Fill Method fire water connection Figure 3.2.2.2 AFWST Emergency Fill Method through nitrogen lines Page 26 of 86

STPNOC FLEX Mitigation Strategies Docket Nos. 50-498/499 Final Integrated Plan Order EA-1 2-049 In the event of an MCR breach, the site will be flooded with water and the TMDDPs will not be able to be brought to their pumping locations before the AFWST would need to begin being refilled. In this flood-hazard specific scenario, water from the DA will be used to begin refilling the AFWST. As described in FSG-06, the DA must first be vented for at least seven hours prior to opening the FLEX FW isolation valve for the AFWST fill line (FW-0488) to begin refilling the AFWST (Reference 27).

This action is performed to ensure that there is not a release of two phase fluid (water and steam) into the transfer hoses.

Refuelinq Water Storaqe Tank The RWST is a borated water source for the FLEX RCS makeup strategies. Each unit has one RWST located inside the MAB. The tanks are stainless steel, safety-related and seismically qualified storage tanks that are completely protected from the applicable design basis external hazards. During at-power operations, each operating unit's RWST borated volume is maintained greater than 458,000 gallons as required by TS 3.5.5 at a boron concentration between 2800 and 3000 ppm.

Before the RWST is depleted, it will be refilled using a TMDD pump taking suction on an unborated tank, basin or the ECP as listed in FSG-17 (Reference 28).

Boric Acid Tanks The BATs are an additional source of borated water that provide a suction source to the CVCS POP. The BATs are protected from external events inside the MAB. Per the STP procedure for the mixing of boric acid, 0POP02-CV-0003, the BATs are typically maintained with a combined total of approximately 60,000 gallons of water with a minimum boron concentration of 7000 ppm (Reference 29). STP Technical Requirements Manual (TRM) Section 3.2.1.6 requires a minimum volume of 27,000 gallons for the Boric Acid Storage System.

Page 27 of 86

STPNOC FLEX Mitigation Strategies Docket Nos. 50-498/499 Final Integrated Plan Order EA-12-049 Essential Coolinq Water Pond The ECP is a man-made excavated below grade pond with an approximately 8 ft high embankment completely surrounding its perimeter. It is normally filled via the well water system. As stated in UFSAR Section 9.2.5.2, the ECP has a surface area of 39.2 acres at an elevation of 17 ft and 46.5 acres at elevation 25.5 ft. As stated in UFSAR Section 9.2.5.1.1.2, the ECP has approximately 112 million gallons of storage capacity. If no other water sources are available, one of the TMDD pumps can be positioned to take suction on this pond and deliver water to both Units' AFWST and RWST.

3.2.2.3 Other Components Steam Generator Power Operated Relief Valves The SG PORVs are safety-related and seismically qualified valves.

Power to the SG PORV controllers in the Main Control Room is normally provided by Class 1 E 120 VAC power and 480 VAC is supplying the hydraulic pump to maintain hydraulic pressure for normal operation.

During the ELAP event, a relay loses power in the SG PORV circuitry causing the valves to fail closed. EC00 directs Operators to manipulate SBO switches to re-energize this relay, returning control of the SG PORVs to the Main Control Room (Reference 11). This procedural action aids in minimizing field activities and maximizing SG PORV control response.

Operation of the SG PORVs from the Main Control Room will continue until hydraulic pressure is depleted, at which time manual control will be initiated via local manual controls. The SG PORVs can be cycled at least 1.5 full strokes without the hydraulic pump in operation. A manual hydraulic hand pump located in the TGB can be utilized to locally provide hydraulic pressure for additional strokes.

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STPNOC FLEX Mitigation Strategies Docket Nos. 50-498/499 Final Integrated Plan Order EA-12-049 Class 1 E Batteries The safety-related Class 1E batteries and associated DC distribution systems are located within safety-related structures designed to meet applicable design basis external hazards. During an ELAP event, these batteries are initially relied upon to power required key instrumentation and applicable DC components.

Per FSG-04 (Reference 30), Operators begin stripping all non-essential loads within one hour following a BDBEE to extend the Class I E battery life. Load stripping actions will be completed within the next hour.

These actions extend the useable Station Class I1E battery life to at least eight hours for each unit (Reference 31).

Thee FLEX DGs will be used to repower instrumentation prior to battery depletion per FSG-19, FSG-05, and FSG-04 (References 32, 22 and 30).

3.2.3 FLEX Strateqiy Connections Primary SG Makeup Pump Connection The primary connections to supply makeup water to the SGs are located on the AFW system suction and cross-connect lines in the IVO. Following the ELAP event, flexible hoses or spool pieces will be routed from the FLEX SG makeup pump suction and discharge to the primary connections in the AFW system per FSG-03 (Reference 17). Hydraulic analyses of the flowpaths confirmed that applicable performance requirements are met (References 23 and 24). IVC Train B and C bays each contain a FLEX SG makeup pump. Each train is separated by individual watertight doors. One of the two FLEX SG makeup '

pumps is the N FLEX SG makeup pump. The pump used for the primary N pump has its own independent connection points associated with that train.

Alternate SG Makeup Connection In the event that the N SG makeup pump is not available for makeup to the S~s, the N+I FLEX SO makeup pump will be used. The N+l pump is located in the other Train bay of the IVC and utilizes alternate suction and discharge connection points.

Page 29 of 86

STPNOC FLEX Mitigation Strategies Docket Nos. 50-498/499 Final Integrated Plan Order EA-1 2-049 Primary RCS Connection The primary connection for RCS makeup is via the CVCS system using the permanent plant PDP installed in the MAB. Normal CVCS piping is used for the suction and discharge flowpaths. The BATs are the primary suction source for the OVCS PDP and the RWST is available as a secondary suction source.

Alternate RCS Makeup Connection The alternate connection for RCS makeup is via the RCS makeup FLEX pump installed in the FHB. The suction connection is located on the SI suction header for the A-Train SI pump and the discharge connection is downstream of the A-Train HHSI pump discharge MOV to the RCS hot leg. As directed by FSG-08, flexible hoses are used to attach the FLEX pump to the SI suction and discharge piping (Reference 33).

480 VAC Electrical Power Connections The two 1-MW FLEX DGs provide power to both the RCS makeup and the SG makeup pumps by means of permanent power distribution circuits. The FLEX DGs are located on the MAB roof in a missile protected enclosure. Separate electric power distribution feeds from the independent FLEX DGs can provide power to the FLEX Distribution Panel. An interlock is provided to only allow one FLEX DG to be aligned to the FLEX Distribution Panel. The FLEX Distribution panel provides a direct electrical AC power source to the FLEX components independent from the site's normal electrical distribution system. FLEX electrical power circuits have been permanently installed inside Category I buildings to ensure a quick and dependable response to the ELAP event.

4160 VAC Electrical Power Connections Two 1-MW 4160 VAC generators delivered to each STP Unit from the NSRC can be connected to ESF transformers on the downstream (load) side. The deployment location for the NSRC generators is the area near the ESF transformers. The NSRC will supply 300 feet of generator cable, affording the flexibility to park the generators in a variety of locations. Operators may elect to maintain power to loads supplied by the 480V FLEX DG when the NSRC generator arrives or to de-energize one train (A, B or C) of the AC busses that the FLEX 480V DG was supplying and place this power source in service. The Emergency Director or Shift Manager will determine which of the three ESF transformers, if any, will be connected to the NSRC generators, depending on the needs of the plant and the condition of the individual transformers. This is proceduralized in the FSG-21, "NSRC Turbine Generator"' (Reference 19).

Page 30 of 86

STPNOC FLEX Mitigation Strategies Docket Nos. 50-498/499 Final Integrated Plan Order EA-12-049 3.2.4 Key Reactor Parameters Instrumentation providing the following key parameters is credited for all phases of the reactor core cooling and decay heat removal strategy with indication available in the Main Control Room:

Auxiliary Feedwater Flowrate - AFW flowrate indication will be available.

SG Water Level - SG wide range (WR) water level indication will be available.

SG Pressure - SG pressure indication will be available in the Main Control Room and locally in the IVC for all SGs.

RCS Temperature - ROS WR hot-leg and cold-leg temperature indication will be available.

RCS Pressure - RCS WR pressure indication will be available.

Core-Exit Thermocouple Temperature - Core-exit thermocouple temperature indication will be available.

AFWST Level - AFWST water level indication will be available in the Main Control Room and locally using indication installed on the tank.

Pressurizer Level - Pressurizer level indication will be available.

Reactor Vessel Water Level (RVWL) - RCS level indication from the RVWL will be available.

Ex-Core Nuclear Instruments - Indication of nuclear, instrumentation activity will be available.

FLEX equipment is also supplied with local instrumentation necessary for operating the equipment. FSG-07 and FSG-20 provide guidance for obtaining the above critical parameters locally when instrument power is unavailable (References 21 and 34).

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STPNOC FLEX Mitigation Strategies Docket Nos. 50-498/499 Final Integrated Plan Order EA-12-049 3.2.5 Thermal Hydraulic Analyses 3.2.5.1 RCS Response STP used the RETRAN-3D Input Model to determine RCS response as documented in STP calculation STP-CP-006 (Reference 14). The following conclusions were drawn from the RETRAN ELAP analysis:

The RCS can be cooled down and maintained at the target steam generator pressure.

The boron provided by the SI accumulators to the RCS combined with the boron supplied by the RCS makeup pumps from the RWST or BATs is sufficient to allow the Operators to cool-down the RCS to 300°F and ~depressurize the RCS to less than 135 psig within 24 hours2.777778e-4 days 0.00667 hours 3.968254e-5 weeks 9.132e-6 months .

Flow from the primary FLEX RCS makeup pump is sufficient to borate the RCS to Xenon-free conditions.

The SG PORVs are adequately sized to maintain the RCS temperature at or below 300°F and RCS pressure less than 135 psig.

The alternate N+1 FLEX SG makeup pump may be required to provide inventory to the SG during Phase 2 due to low steam pressure to the TDAFW pump.

Adequate boron mixing occurs under single and two-phase flow conditions to prevent a return to criticality.

3.2.5.2 Reactor Coolant Pump Seals The leakage model for the RCP No. 1 seal used in the FLEX strategy analyses is based on results presented in Westinghouse Report PWROG-1 4015-P, Revision 2 (Reference 35). STP is a Category 6 plant as defined in the Westinghouse Report, however the STP FLEX analysis conservatively assumed the higher leak rate presented in the Westinghouse report for a Category I or 6 plant. This leak rate was used in a site-specific model to determine that the time to ROP seal uncovery occurs at 11.3 hours3.472222e-5 days 8.333333e-4 hours 4.960317e-6 weeks 1.1415e-6 months and reflux cooling occurs at 15.9 hours1.041667e-4 days 0.0025 hours 1.488095e-5 weeks 3.4245e-6 months following the initiation of the ELAP event.

Page 32 of 86

STPNOC FLEX Mitigation Strategies Docket Nos. 50-498/499 Final Integrated Plan Order EA-12-049 The expected timeline to restore flow to the RCS is within four hours when using the PDP or within eight hours using the FLEX makeup pump if the PDP is not available.

While PWROG-14015-P has not yet been approved by the NRC, the following additional conservatisms provide reasonable assurance that RCP seal uncovery or reflux cooling will not occur:

The results of the analysis documented in the RETRAN-3D White Paper (Reference 36) show that the RETRAN-3D STP computer model conservatively predicts the time to RCP seal uncovery (13.1 hours1.157407e-5 days 2.777778e-4 hours 1.653439e-6 weeks 3.805e-7 months for RETRAN-3D vs. 13.5 hours5.787037e-5 days 0.00139 hours 8.267196e-6 weeks 1.9025e-6 months for RELAP5) and time to reflux cooling (17.9 hours1.041667e-4 days 0.0025 hours 1.488095e-5 weeks 3.4245e-6 months for RETRAN-3D and 24.9 hours1.041667e-4 days 0.0025 hours 1.488095e-5 weeks 3.4245e-6 months for RELAP5) when compared to a similar RELAP5 STP computer model.

The Pressurized Water Reactor Owner's Group (PWROG)

ITCHSEAL calculations used to determine ROP seal leakage contain known conservatisms when compared to the results of the generic analysis to the Montereau test data. As discussed in Westinghouse Report PWROG-14074-P, parameters within the ITCHSEAL calculations used for the STP RCP seal leakage values were adjusted to ensure significant margin when compared the Montereau test data (Reference 37).

FSG-01 and FSG-08 are used to monitor RCS inventory (e.g. reactor pressure vessel water level) during the ELAP event and direct the operators to implement primary makeup more rapidly if signs of increased RCP leakage are detected (References 38 and 33).

3.2.6 Shutdown Marqin Analysis Per the site Core Reload Design Process, STP performs an evaluation for each fuel cycle to ensure that the reactor maintains a keff of 0.99 or less (Reference 84). In addition, Operators are provided curves of the required boron concentration versus fuel cycle burnup for several RCS temperature conditions for equilibrium xenon and xenon free conditions to use as a guide to ensure the reactor core keff remains at or below 0.99 (References 85 and 86) as recommended in Westinghouse Report WCAP-1 7601 (Reference 96).

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STPNOC FLEX Mitigation Strategies Docket Nos. 50-498/499 Final Integrated Plan Order EA-1 2-049 3.2.7 Electrical Analysis The eight hour Class 1E battery duty cycle for STP was calculated in accordance with the IEEE-485 methodology using manufacturer discharge test data applicable to the FLEX strategy as outlined in the NEI white paper on extended battery duty cycles (References 40 and 97). There are approximately two hours between the calculated battery duration for use in the FLEX strategy and the expected deployment and startup time for FLEX equipment to supply the DC loads.

Within eight hours of the start of the event, the 480V FLEX DGs will begin re-powering one battery charger in each of A and C trains.

3.3 Spent Fuel Pool Coolinqi and Inventory The STP FLEX strategy for maintaining SFP cooling is to monitor SFP level using remote and local indicators and to provide sufficient makeup water to the SFP to maintain the normal SFP level. Note that STP has individual SFPs for Unit1I and Unit 2 located in their respective FHBs.

Initial actions to monitor level and, as necessary, stage makeup and spray hoses on the fuel pool deck need to be completed early in the event. FSG-11I directs plant personnel to evaluate the need to provide a ventilation pathway for water vapor to leave the FHB (Reference 41). The most time sensitive scenario occurs with a full core offloaded into the SFP.

3.3.1 Phase 1 Strateqiy During Phase 1, the loss of AC power makes the SFP Cooling and Cleanup System unable to circulate water through heat exchangers. This causes the SFP to gradually heat up from the decay heat being transferred into the water fronithe spent fuel and the water begins to evaporate. To calculate the required makeup water volume and rate required to maintain normal SFP level, STP assumed the worst-case maximum design heat load for the SFP with every SFP cell containing a spent fuel assembly.

The Phase 1 activities consist of establishing FHB vent pathways and monitoring for water accumulation. The normal fill methods would not be available with a loss of AC power. Since FLEX equipment is required for SFP inventory, a'fill strategy is established in Phase 2.

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STPNOC FLEX Mitigation Strategies Docket Nos. 50-498/499 Final Integrated Plan Order EA-12-049 3.3.2 Phase 2 Strategqy STP has a primary and alternate SEP fill strategy that is implementing using FSG-l11. The primary method for filling the SFP is to start a Reactor Makeup Water (RMW) pump and open manual valve FC-0048, the SFP RMW Supply Valve (Reference 41). The RMW pump component design parameters are listed in UFSAR Table 9.2.7-1 (Reference 44). Both RMW pumps receive power from the FLEX DGs via MOO El1B4(E2B4) or MOO El1C2(E2C2). Closing the feeder breaker to the selected RMW pump will provide control power to start the pump from the Control Room. Once FC-0048 is open and the RMW pump is started, SEP re-fill can commence at approximately 300 gpm (Reference 43). SFP level will still be well above the point at which radiation levels on the operating deck make the SEP deck uninhabitable. The water level in the pool will be monitored from the Rad Waste Control Room in the MAB.

NEI 12-06 requires a makeup method for the SEP that does not require accessing the operating deck. FC-0048 can be accessed without crossing the operating deck utilizing a travel route through the FHB truck bay. From the truck bay, valve FC-0048 can be accessed by going up the stairwell to the 53' elevation and then down another stairwell to the 21' elevation leading to the SEP Cooling and Cleanup pump 1B(2B) Room.

\

Water from the RMWST is non-borated demineralized water, however, it can be used to fill the SFP because of the design basis and construction of the Spent Fuel Storage Rack system. As stated in STP UFSAR Section 4.3, the design basis for preventing criticality in the spent fuel pool is as follows (Reference 44):

The effective neutron multiplication factor, keff, of the fuel rack array will be less than 1.00 in pure, unborated water, with a 95 percent probability at a 95 percent confidence level, including uncertainties; and,

The effective neutron multiplication factor, keff, of,the fuel rack array will be less than 0.95 in the pool, containing borated water, with a 95 percent probability at a 95 percent confidence level, including uncertainties.

In the event the primary SEP fill strategy is not available, the "hose to the pool" method will be implemented. This alternate strategy uses a 250 gpm, 150 psi pre-staged FLEX SEP makeup pump installed in the FHB in the B-Train SI bay.

The FLEX SEP. makeup pump flow also meets the NEI 12-06 requirement for exceeding the boil-off rate.

This pump discharges into a pipe that runs from the -29' elevation of the FHB up to the operating deck at the 68' elevation. Fittings are installed on the end Page 35 of 86

STPNOC FLEX Mitigation Strategies Docket Nos. 50-498/499 Final Integrated Plan Order EA-12-049 of the pipe on the operating deck and temporary hoses have been staged in the area. Plant personnel will install a short hose/spool piece between the Containment Spray suction piping and the pump suction (Reference 41). The FLEX SEP makeup pump takes suction from the RWST and relies on the FLEX DGs for power. A permanent power cable has been run though conduit from the distribution panel on the MAB roof to the bottom of the FHB to power the pre-staged FLEX SEP makeup pump.

If it becomes necessary to spray the SEP from the pre-staged SEP spray monitors, the "spray method" uses the FLEX SEP makeup pump and hoses routed from the same hard pipe on the operating deck to a spray monitor on the south end of the SEP deck. A flow of 250 gpm is required per NEI 12-06 (Revision 0) with 50 gpm included for margin for overspray (Reference' 9).

3.3.3 Phase 3 Strate~qy SEP cooling can be maintained indefinitely using the Phase 2 makeup strategy. In Phase 3, the NSRCs will provide equipment that can be used to ensure water is always provided to cool the spent fuel for operational flexibility and additional defense-in-depth. For example, the NSRC 4.16 KV generators can provide power to a LHSI pump used to makeup to the SEP in emergency situations.

Prior to the depletion of the RWST, either the ECP or an unprotected tank that survived the event will be used as the water source to makeup to the RWST or the SEP. The NSRC also provides additional TMDDPs that could be used to replenish the RWST and to makeup to the SEP.

3.3.4 SEP Makeup Connections 3.3.4.1 Primary Connection The primary, N, pump for SEP makeup is the RMW pump located on the 10, elevation of the MAB of each Unit. The suction source for this strategy is the RMWST. The RMW is one of the normal fill methods for the SEP. The RMW piping connects to the SEP piping through manual fill valve FC-0048. This strategy utilizes a different piping arrangement and connections for both the suction source and the discharge to the SEP than the alternate N+1 pump.

3.3.4.2 Alternate Connection The alternate, N+1, pump is the FLEX SEP makeup pump is located in the -29 ft elevation of the FHB of each unit in the B Train SI bays. The Page 36 of 86

STPNOC FLEX Mitigation Strategies Docket Nos. 50-498/499 Final Integrated Plan Order EA-1 2-049 suction source for this strategy is the RWST. The borated water from the RWST goes through the SI piping to the B Train Containment Spray suction where a hose/spool piece has been installed to route the water to the FLEX SFP makeup pump. The discharge of the FLEX SFP makeup pump goes through FLEX piping to the SEP deck on the 68' elevation. Then from the FLEX piping the water goes directly into the SEP through fire hoses or it is routed to a spray monitor. This discharge piping arrangement and the suction source is different from the N SEP makeup pump, as is the suction source.

3.3.5 Fuel Handling Buildinq Ventilation Ventilation requirements to prevent excessive steam accumulation in the FHB are described in FSG-11I which directs operators to open doors in the FHB and MAB to establish a natural circulation flowpath (Reference 41). Airflow through these doors provides ventilation pathways through which steam generated by SEP boiling can exit the FHB.

3.3.6 Key Parameters The key monitoring parameter for the SEP makeup strategy is SFP water level which is monitored by instrumentation installed in response to Order EA-1 2-051 for Reliable SEP Level-Instrumentation (Reference 45). STP's SEP level instrumentation consists of two separate channels of microwave pulses that are transmitted by the sensor electronics system through a waveguide pipe to a horn that is just above the water line. The waveguide pipe transports the level measurement signal to the electronic display in the Rad Waste Control Room.

3.3.7 Thermal-Hydraulic Analyses Loss of SEP cooling is assumed to occur at 30 days after core reload is complete. At this time, the SEP decay heat is the highest during power operations. Higher decay heat gives higher boil-off rate and a lower time to reach 200°F.

The SEP heat-up rate as a function of time following a loss of SEP cooling is provided in Plant Curve Book Figure 5.13A for each Unit. The time to reach 200°F as a function of time following a loss of SEP cooling is provided in Plant Curve Book Figure 5.19A for each Unit.

The SEP temperature is normally maintained at less than 100°F. Assuming a conservatively high initial SEP temperature of 100°F, the time to reach 200°F is approximately 29 hours3.356481e-4 days 0.00806 hours 4.794974e-5 weeks 1.10345e-5 months . The boil-off rate at this time is approximately 28 gpm, Page 37 of 86

STPNOC FLEX Mitigation Strategies Docket Nos. 50-498/499 Final Integrated Plan Order EA-12-049 well within the makeup capability of the RMW pump (300 gpm) and SFP makeup pump (250 gpm). Assuming the SFP level is at the Technical Specification required minimum elevation of 62.5 ft, the time for the SFP water level to boil down from the minimum level to 10 feet above the top of the active fuel is 83 hours9.606481e-4 days 0.0231 hours 1.372354e-4 weeks 3.15815e-5 months (Reference 46). Maintaining the water level greater than 10 feet above the active core should limit the maximum radiation dose to 2.5 millirem per hour for personnel in the area (Reference 102).

3.3.8 Pumps and Water Supplies for SFP Fill 3.3.8.1 Reactor Makeup Water Pump There are two RMW pumps per unit rated at 300 gpm flowrate at a pressure of 150 psig (Reference 106). For the FLEX strategies, the sole function of the RMW pumps is to add water to the SFPs. Water can be added to the SFP once the FLEX DGs begin providing power to the pumps and manual valve FC-0048 is opened (Reference 41).

3.3.8.2 FLEX SFP Makeup Pump The FLEX SFP makeup pump can provide 250 gpm of water at 150 psig (Reference 104 and 105) for either SFP fill or spray functions. This pump is located inside the FHB -29 ft elevation B-Train SI bay and takes suction from the RWST.

3.3.8.3 Trailer-Mounted Diesel-Driven Pumps The TMDDPs can be used for filling or spraying the SFP (References 43 and 87). The suction source for these pumps is either the Organic basin at the south end of the plant, the Circulating Water discharge piping, or the Fire Water header if it remained intact following the BDBEE. The hoses for the TMDDPs will be routed into the FHB truck bay on ground level and be connected to hoses staged on a platform below the SFP operating deck. The staged hoses are connected to the spray monitors located on the SFP operating deck.

3.4 Containment Integrity 3.4.1 Phase 1 For scenarios that utilize SGs to remove core heat from containment, no specific coping strategy is required for maintaining containment integrity during Phase 1, 2 or 3. In this case, the only necessary action is to monitor containment pressure and temperature to verify that RCS leakage is minimal per standard procedures.

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STPNOC FLEX Mitigation Strategies Docket Nos. 50-498/499 Final Integrated Plan Order EA-12-049 Containment conditions are monitored via the available Qualified Display Parameter System (QDPS) indications or used by FSG-20.

When an ELAP occurs while a Unit is operating in Modes 1-4, containment is isolated via normally closed or fail closed isolation valves, check valves, or valves that will be manually closed by personnel as directed in the EOPs. As stated in NEI 12-06, no valve failures are assumed to occur following the BDBEE (Reference 9).

STP performed analyses using the RETRAN-3D and GOTHIC computer models (References 14 and 47) to confirm that the containment pressure during and following an ELAP event would not challenge the design basis pressure of 56 psig and the containment temperature would not exceed the equipment qualification limits. The RETRAN-3D analysis determined the RCP seal leakage rates and RCS piping temperature while a GOTHIC analysis determined the containment pressure and temperature response using the RETRAN-3D results. The results of the analysis show that the maximum containment pressure increase is less than 2 psig and the maximum containment temperature is 144°F for Phases 1, 2, and 3, well below the limits for both containment pressure and equipment qualification temperature (Reference 47).

3.4.2 Phase 2 During Phase 2, an 'unexpected pressure rise can be addressed by venting or cooling containment. FSG-12 provides several different methods for providing containment cooling. With the support of the TSC, the containment cooling strategy will be determined based on equipment availability (Reference 48).

3.4.3 Phase 3 During Phase 3, any necessary actions to reduce containment temperature and pressure utilize existing plant systems powered by offsite equipment. Two portable 4160 VAC generators and a distribution panel for each unit will be brought in from the NSRC and can be used to supply power to one of the three Class 1E 4160 VAC buses in each unit, providing another option for powering various station pumps or fans.

As described in FSG-12, in the event it becomes necessary to cool or depressurize containment, the 4160 VAC NRSC DGs could also be used to power the Reactor Containment Fan Coolers (RCFCs) to accomplish this task.

FSG-12 also describes an option for spraying the outside shell of containment using the TMDDPs to reduce temperature and pressure.

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STPNOC FLEX Mitigation Strategies Docket Nos. 50-498/499 Final Integrated Plan Order EA-1 2-049 3.4.4 Eqiuipment for Ventilation Coolinq and Spray Strate~qies The following equipment can be used for cooling and venting Containment if deemed necessary:

Containment Spray pump powered by the NSRC generators

Containment Purge fans powered by the NSRC generators

RCFCs powered by the NSRC generators

Component Cooling Water (CCW) pump powered from the NSRC generators

TMDDPs stored on site or delivered from the NSRC The NSRC will provide a low pressure, high flow pump (nominal 5000 gpm) which can be used to provide cooling loads to various water systems. A low pressure, medium flow (nominal 2500 gpm) pump will also be provided by the NSRC, if needed. As discussed previously, water supplies are listed in the FSGs by order of preference. When the RWST is depleted, other tanks and basins will be drawn from if available and the ECP can be used as a last resort.

3.4.5 Key Containment Parameters Instrumentation providing the following key parameters is available and is credited for the Containment Integrity strategy for Phases 1 through 3:

Containment Pressure indication

Containment Temperature indication

Containment Sump Level indication 3.4.6 Thermal-Hydraulic Analyses STPs thermal-hydraulic analyses concluded that containment temperature and pressure will remain well below design limits and that equipment qualification temperatures for key parameter instruments subject to the containment environment will remain functional indefinitely. The containment temperature is monitored using FSG-05 (Reference 22).

3.5 Alternate Approaches STPNOC followed the guidance provided in NEI 12-06 with the exception of the Alternate Approaches listed below. These Alternate Approaches were discussed with the NRC review staff during the onsite audit and some are noted in the Onsite Audit Report (Reference 49):

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STPNOC FLEX Mitigation Strategies Docket Nos. 50-498/499 Final Integrated Plan Order EA-12-049 Pre-Staqiingq of FLEX Response Equipment inside Protected Structures STP pre-staged some of the FLEX response equipment including two DGs in protected structures on top of the MAB roof as well as pumps, hoses, and associated equipment inside existing Class 1 buildings protected against design-basis external events. The primary reason for pre-staging this equipment is due to difficulties in retrieving and deploying equipment following a large-scale flooding event.

Two-Separate Pumps and Iniection Pathways for RCS Fill STP utilizes two pre-staged pumps with separate injection pathways for the FLEX RCS fill strategy instead of a single pump with primary and alternate connection points and injection pathways supplemented by a portable pump. The advantage of this strategy is that the pumps are protected inside safety-related buildings, however, it limits the diversity of connection points to supply water to the pumps.

In the STP strategy, the failure of a pre-staged pump would render one of the two injection pathways unavailable as opposed to the two pathways that would be available using the portable pump strategy. As a compensatory measure, STP reduced the allowed out-of-service time for both the PDP and FLEX ROS makeup pump and their associated connections and flowpaths from 90 days to 30 days to help ensure reliability of this equipment.

The STP FLEX strategies also rely on pre-staged pumps for SG makeup and SFP makeup, however, STP has the ability to makeup to these systems using a portable TMDDP.

3.6 Characterization of External Hazards 3.6.1 Seismic The peak accelerations associated with SSE and OBE have been established based on the seismicity evaluation described in UFSAR Section 2.5. The peak horizontal acceleration at this site is less than 0.10g. Because this acceleration value is below the minimum established in Appendix A, "Reactor Site Criteria" to 10CFR1 00, a maximum horizontal acceleration was selected to be 0.10g. The peak horizontal accelerations of 0.10g for SSE and 0.05g for OBE were incorporated in the design response spectra in order to comply with Appendix A, to 10CFR1 00. The ground acceleration as represented by the spectral acceleration at 33 Hz is 0.1g for both the horizontal and the vertical directions. At 50 Hz the vertical spectral acceleration is reduced to two-thirds of the horizontal acceleration.

Page 41 of 86

STPNOC FLEX Mitigation Strategies Docket Nos. 50-498/499 Final Integrated Plan Order EA-12-049 In response to the 50.54(f) letter and following the guidance provided in the Screening, Prioritization and Implementation Details (SPID) (Reference 50), a seismic hazard reevaluation was performed for STP Units I and 2 (Reference 58). Based on the results of the screening evaluation, the reevaluation shows that the updated GMRS does not exceed the SSE, therefore no further evaluations will be performed.

As described in Section 3.7, "Protection of FLEX Equipment", FLEX storage provides adequate seismic protection.

3.6.2 External Floodinqi Section 2.4 of the UFSAR describes the flooding mechanisms evaluated for STP Units I and 2. These include local intense precipitation, flooding in streams and rivers, storm surge, seiche, tsunami, and dam breaches and failures including upstream dam failures and the breach of the Main Cooling Reservoir (MCR) embankment.

The current design basis (CDB) flood elevations for the safety-related structures, systems and components at STP 1 and 2 are governed by the maximum flood levels resulting from this postulated breach of the MCR embankment, as documented in Section 2.4.4.3.2 of the UFSAR. The MCR is a major feature of the site, which is formed by a 12.4 mile long earth-fill embankment constructed above the natural ground surface. The MCR has a surface area of 7000 acres with a normal maximum operating level of 49 ft. MSL. A postulated breach of the MCR embankment is not considered a credible event as documented in Section 2.4.4.1 .1.3 of the UFSAR. However a very conservative MCR embankment breach analysis was performed.

As a result of the MCR embankment breach, the 0DB flood elevations in the power block vary from a minimum of 44.5 ft. MSL at the Diesel Generator Building and the north face of the Mechanical Electrical Auxiliaries Building to a maximum of 50.8 ft. MSL at the south face of the Fuel Handling Building. In the Essential Cooling Pond, the 0DB flood elevation was established to be 40.8 ft.

MSL at the essential cooling water intake structure (ECWlS).

All safety-related structures and components are designed to withstand the flood levels from these postulated events.

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STPNOC FLEX Mitigation Strategies Docket Nos. 50-498/499 Final Integrated Plan Order EA-12-049 A Flooding Hazard Reevaluation was prepared in response to the March 12, 2012, 50.54(f) letter to provide information on the reevaluation of external flooding hazards at STP Units I and 2 using present day methodologies, data and guidance. The reevaluation of external flooding hazards concluded that the highly conservative MCR embankment breaching scenario remains the controlling flooding mechanism for Units I and 2, consistent with the design basis flood evaluation in UFSAR. The UFSAR design basis flood levels, between 44.5 and 50.8 ft. MSL at the plant structures (power block area) and 40.8 ft. MSL at the ECW intake structure, remain bounding. For STP Units I and 2, the current design basis flood protection measures implemented at the site will provide adequate protection against the reevaluated flood hazards. Based on the results of the reevaluated flood hazards, no interim actions or integrated assessment are necessary.

As described in Section 3.7, "Protection of FLEX Equipment", FLEX storage provides adequate flood protection.

3.6.3 Severe Storms with Hicqh Wind NEI 12-06, Section 7 provides a screening process for evaluation of high wind hazards. This screening process considers the hazard due to hurricanes, tornadoes and tornado missiles.

The screening for high wind hazards associated with hurricanes was accomplished by comparing the site location to NEI 12-06, Figure 7-1. If the resulting frequency of recurrence of hurricanes with wind speeds in excess of 130 miles per hour (MPH) exceeds 10-6 per year probability, the site should address hazards due to extreme high winds associated with hurricanes. Based on the location of STP Units 1 and 2, Figure 7-1 shows an applicable hurricane wind speed of approximately 210 mph with an annual exceedance probability of 10-6.

The screening for high wind hazards associated with tornadoes was accomplished by comparing the site location to NEI 12-06, Figure 7-2. If the resulting frequency of recurrence of tornadoes with wind speeds in excess of 130 miles per hour (MPH) exceeds 10-6 per year probability, the site should address hazards due to extreme high winds associated with tornadoes. Based on the location (latitude of slightly lower than 29 degrees and longitude 96 degrees) of STP Units 1 and 2, Figure 7-2 shows an applicable tornado wind speed of approximately 161 mph with an annual exceedance probability of 10-6.

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STPNOC FLEX Mitigation Strategies Docket Nos. 50-498/499 Final Integrated Plan Order EA-12-049 Based on these results, the STP Units I & 2 site is susceptible to high winds from hurricanes and tornadoes and associated missiles.

The design basis wind speeds for STP Units 1 & 2 safety-related structures are defined in UFSAR Section 3.3. The design tornado parameters includes winds with a. combined tangential and translation velocity of 360 mph. The associated wind pressure and tornado missiles listed in this UFSAR section govern the design of these safety-related structures.

FLEX Diesel Enclosure located on the roof of the MAB is designed to meet the maximum of design basis wind loads or wind loads computed in accordance with the latest code requirements including ASCE 7-10, Regulatory Guide 1.76 and Regulatory Guide 1.221.

FLEX Storage Buildings located outside the protected area are designed in accordance with or evaluated equivalent to ASCE 7-10. Distance separation of the buildings address impact of tornadic wind and wind generated missiles.

As described in Section 3.7, "Protection of FLEX Equipment", FLEX storage provides adequate protection from high winds generated from hurricanes arid tornadoes and associated missiles.

3.6.4 Ice, Snow and Extreme Cold STP Units I & 2 screens out for extreme cold and snowfall hazard.

o The guidance provided in NEI 12-06, Section 8.2.1, states that plants above the 3 5 th parallel must consider extreme cold and snowfall. STP Units 1 & 2 site is located below the 3 5 th parallel.

As stated in NEI 12-06, sites in the Gulf Coast do not experience extreme cold conditions, therefore extreme cold is not considered an applicable hazard for STP Units I & 2.

Section 8.2.1 of NEI 12-06 indicates that sites on the Gulf Coast are unlikely to experience extreme snow. NEI 12-06 Figure 8.1, "Record 3-Day Snowfalls", shows that for the area around STP Units 1 & 2, although snow occurs, it does not reach extreme levels. On this basis, extreme snowfall is not considered to be an applicable hazard for STP Units 1 & 2 that would adversely impact equipment deployment. UFSAR Table 2.3-4, "Site / Region Meteorological Extremes" provides information on the snowfall levels in the STP Units I & 2 site area, confirming this conclusion.

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STPNOC FLEX Mitigation Strategies Docket Nos. 50-498/499 Final Integrated Plan Order EA-12-049 NEI 12-06, Figure 8.2, "Maximum Ice Storm Severity Maps", shows that STP Units I & 2 site is located in Ice Severity Level 3 (Yellow), which is defined as low to medium damage to power lines and/or existence of considerable amount of ice. Section 8.2.1 states that plants with this Ice Severity Level should consider the effects of ice storm impacts.

The STP FLEX strategies do not rely on power lines, and the area is not likely to experience considerable amounts of ice. Per UFSAR Section 2.3.1.2.4, no ice storms were reported within a 50-mile radius of the site for the 1959 to 1972 period. The site area averages less than one day per year with glaze (1950 to 1969). The greatest thickness of ice observed on utility wires during the 1928 to 1937 period (latest data available) in the STP Units 1 & 2 site area was in the range from 0.25 inches to 0.49 inches.

More recent snow and ice storm data was prepared in support of the licensing for STP Units 3 and 4, which would be located nearby STP Units 1 and 2. The data used for Units 3 and 4 is based on the latest version of the Climatic Atlas of the United States (Reference 51), which has been developed from observations made between 1961 and 1990, and the storm events for Texas (Reference 52),

based on observations made through March 2007. These references show that any accumulation of snow is a rare occurrence on the Upper Coastal division within the Coastal Prairie region where STP is located, with normal annual totals averaging less than 0.5 in.

According to the NOAA Storm Events database, (Reference 52), the greatest snowfall on record in the STP area was measured at a Danevang, Texas weather observing station located 20 miles north-northwest of the STP site. 24-hour and monthly total station records of 10.5 inches were recorded during the Christmas Storm of 2004 (Reference 52).

Depending on the temperature characteristics of the air mass, snow events are often accompanied by or alternate between sleet and freezing rain or ice.

According to the Climatic Atlas (Reference 51), freezing precipitation occurs only approximately 2.5 to 5.4 days per year at the STP site.

The use of four-wheel drive tractors to transport the TMDDPs and associated hose trailers from the FLEX Buildings outside the protected area will handle these limited occurrences of ice. The vast majority of STP's FLEX equipment is Page 45 of 86

STPNOC FLEX Mitigation Strategies Docket Nos. 50-498/499 Final Integrated Plan Order EA-12-049 pre-staged inside protected structures and deployment of this equipment would not be impacted by ice.

As described in Section 3.7, "Protection of FLEX Equipment", FLEX storage provides adequate protection from extreme ice.

3.6.5 Extreme Heat Section 9.2 of NEI 12-06 states that all sites must consider the impact of high temperatures. UFSAR Section 2.3.2.1.5 (Table 2.3-4) provides extremes of temperature for six surrounding locations to STP Units I & 2. Extreme high temperature ranges from 101 to 107 degrees F.

The tractors and TMDDPs are designed to operate in high heat conditions.

Ventilation for the FLEX Diesel enclosure on the roof of the MAB was designed to maintain interior temperatures below 122 degrees F. All equipment protected by the enclosure can withstand this temperature. The new enclosure on top of the MAB housing the FLEX DGs will also be cooled by natural circulation.

The FLEX Storage Buildings outside the protected area contain no heat source and will be ventilated by natural circulation. The metal doors to the storage buildings can be manually opened and function well in high temperatures.

Plant procedures include considerations for personnel working in high heat conditions including the staging of cool vests. Plant personnel regularly work in areas that are greater than 110 degrees F inside the plant. Plant personnel will be monitored for signs of heat stress using current safety procedures.

As described in Section 3.7, "Protection of FLEX Equipment", FLEX storage provides adequate protection from extreme heat.

3.7 Protection of FLEX Equipment The vast majority of the equipment needed for the FLEX strategies is pre-staged and protected in safety-related concrete structures as described in Section 3.8 of the UFSAR. As discussed in Section 3.5 of this FIP as well as the STP FLEX Onsite Audit Report (Reference 49), this is considered an Alternate Approach to the NEI 12-06

guidance. However, these permanent plant safety-related structures are designed to protect the FLEX equipment from all external hazards including seismic (SSE), external flooding, high winds; missile impact, Snow, ice, extreme cold and extreme heat.

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STPNOC FLEX Mitigation Strategies Docket Nos. 50-498/499 Final Integrated Plan Order EA-1 2-049 A steel enclosure has been added in each unit on the roof of the MAB for protecting and housing the FLEX diesel generators, fuel oil tank and electrical distribution panel. The enclosure is designed to protect the FLEX equipment from all external hazards including seismic (SSE), external flooding, high winds, missile impact, snow, ice, extreme cold and extreme heat.

The specific design characteristics of the enclosures are presented in STP Calculation SC-05018 (Reference 53). The Design Change Package (DCP) for the Unit 1 enclosure is DCP 12-11658-28 (Reference 54) and DCP 12-11658-27 for the Unit 2 enclosure (Reference 55). These enclosures meet the NEI 12-06 requirements for robustness.

See Figure 3.7-1, below, for a photo of one of the FLEX DG enclosures.

Figure 3.7-1 - FLEX DG Enclosure, Unit 2 FLEX StoraQe BuildinQs The two FLEX Storage Buildings located outside the PA house four-wheel drive tractors, TMDDPs and associated hoses and trailers. The locations of the buildings are sufficiently separated so that there is assurance that at least one of the buildings would survive the applicable site hazards, such as a tornado and flood.

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STPNOC FLEX Mitigation Strategies Docket Nos. 50-498/499 Final Integrated Plan Order EA-12-049 The FLEX storage building located on the MCR embankment intermediate level is a pre-engineered metal building designed to meet the following:

ASCE 7-10 for seismic capability

Design basis for wind load

High temperature - the building contains no heat load and it will be ventilated by natural circulation

Cold temperature - addressed through use of anti-freeze in the tractors and motors for the TMDDPs

Hazards due to tornadoes and flood are addressed by separating the buildings by over a mile apart and locating them at different elevations A portion of the Low Level Radwaste (LLRW) Building serves as the FLEX storage building for the other set of equipment. It is a pre-engineered metal building designed to meet the following:

ASCE 7-05 for seismic capability - seismic protection evaluated equivalent to ASCE 7-10

Design basis for wind load

High temperature - the building contains no heat load and it will be ventilated by natural circulation

Cold temperature - addressed through use of anti-freeze in the tractors and motors for the TMDDPs

Hazards due to tornadoes and flood are addressed by separating the buildings by over a mile apart and locating them at different elevations Note that the LLRW Building was built prior to the FLEX effort under ASCE 7-05, not ASCE 7-10. An engineering review was performed to address the difference in code requirements (ASCE 7-05 versus ASCE 7-10). The study concluded that for this area of the U.S. and for this particular building, the differences will not adversely affect the structural and foundation performance (Reference 56).

Seismic Survivability of FLEX Storaqe Buildinqs NEI 12-06 was used to establish requirements for the storage of FLEX equipment.

Section 5.3.1 listed acceptable options for storage, one of which was to house the equipment in a building designed equivalent to ASCE 7-10. STP implemented this guidance for the design and analysis of the two FLEX Storage Buildings.

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STPNOC FLEX Mitigation Strategies Docket Nos. 50-498/499 Final Integrated Plan Order EA-1 2-049 The STP FLEX strategy includes storage of equipment in two non-Category 1 one-story metal buildings located outside the Protected Area. These structures were designed or evaluated equivalent to ASCE 7-10, 'Minimum Design Loads for Buildings and Other Structures", which is one of the acceptable methods identified in Section 5.3.1 of NEI 12-06.

In response to a question to the industry from the NRC regarding seismic survivability of the FLEX Storage Buildings, STP completed an engineering evaluation that determined that another load case, wind loading, governs the storage building designs such that they would be functional following an SSE (Reference 57).

The STP Engineering evaluation confirmed that the wind forces used in the design significantly exceed SSE seismic forces. This is a consequence of the relatively low mass of the one-story buildings, the low seismicity of the Texas Gulf Coast region, and the relatively high wind forces in this region. The engineering evaluation estimated SSE seismic forces using the static equivalent method of seismic analysis and 1.5 times SSE peak acceleration. Therefore, even though SSE was not used in the design of the buildings, the higher wind forces that were used guarantee that the buildings will survive the STP design basis (SSE) earthquake.

Note also that at STP the reevaluated seismic spectra (GMRS) is lower than SSE, as established in STP's Seismic Hazard and Screening Report (Reference 58).

The design of the buildings for high wind loads makes them capable of withstanding the smaller lateral forces that would occur during an earthquake characterized by SSE.

Since the SSE bounds the GMRS, both buildings are confirmed to withstand both SSE and GMRS seismic loads.

3.8 Planned Deployment of FLEX Equipment The only FLEX equipment that must be deployed into the PA are the TMDDPs and associated hoses and trailers that are primarily used to move water to the AFWST and the RWST. The TMDDPs will be deployed when personnel are available but is required when AFWST level lowers to less than 177,000 gal per EC00.

The TMDD pumps are pulled using four wheel drive tractors with front end loaders. The tractors are stored with the pumps and hose trailers in the two FLEX buildings. Two

/_

haul paths are available for the tractor stored in the LLRW Building and three haul paths are available to the tractor stored on the east side of the MCR. The front end loaders will be used for debris removal if necessary.

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STPNOC FLEX Mitigation Strategies Docket Nos. 50-498/499 Final Integrated Plan Order EA-12-049 In Phase 3, the NSRC will provide additional equipment such as pumps and generators to be used as needed. Both the site FLEX TMDDPs and the NSRC pumps will be situated near the water source to limit the length of the suction hose required.

3.8.1 Haul Paths The haul paths for transporting the TMDDPs into the PA to their deployment locations have been reviewed for potential soil liquefaction and were determined to be stable following a seismic event. Soil liquefaction is discussed in UFSAR Section 2.5.4.8.1.5, which states that liquefaction will not occur in the plant area during the SSE.

Additionally, the haul paths minimize travel through areas with trees, power lines and narrow passages to the extent practical. High winds can cause debris from distant sources to interfere with planned haul paths, so debris removal equipment (four wheel drive tractors with front end loaders) is stored inside the FLEX Storage Buildings to clear obstructions from the pathway between the storage buildings and their deployment location(s).

The haul paths from the FLEX Building located east of the MCR are as follows:

Top of reservoir embankment road that heads directly to the plant from the east

Top of reservoir embankment road that goes around the reservoir and approaches the plant from the west

Down reservoir embankment to the heavy haul road Depending on the type external event, one of these haul paths should be available.

Phase 3 of the FLEX strategies involves the receipt of equipment from offsite sources including the NSRC and various commodities such as fuel and supplies.

Delivery of this equipment is discussed in Section 3.10 of the FIP.

The ,same debris removal equipment used for the haul paths may also be used to support debris removal to facilitate road access within the site boundaries.

3.8.2 Accessibility Potential access impairments consist primarily of doors in Phases I and 2 and PA access gates in Phases 2 and 3. These doors and gates are typically controlled to maintain their function as barriers during normal operations.

Following a BDBEE and subsequent ELAP, FLEX coping strategies may require the routing of hoses and cables through normally closed barriers in order to Page 50 of 86

STPNOC FLEX Mitigation Strategies Docket Nos. 50-498/499 Final Integrated Plan Order EA-12-049 connect FLEX equipment to station water and electric systems, as well as for ingress and egress and ventilation. Certain barriers (gates and doors) will be opened and remain open for the duration of the event (Reference 21). This departure from normal administrative controls is acknowledged by Security and is acceptable during the implementation of FLEX coping strategies.

The Shift Manager will distribute keys as necessary to personnel to permit opening of Security doors during an ELAP event (Reference 21).

Vehicle access to the PA occurs via the East Gafe Entrapment. As described in FSG-06, Security is contacted to open the East Gate Entrapment to allow delivery of TMDDPs, tractors and hose trailers into the PA.

3.8.3 Deployment Limitations for the FLEX TMDDPs Due to Flooding It is clearly stated in the UFSAR that a breach of the MCR embankment is not considered a credible event. Many conservatisms were contained in the analysis including the assumption of an instantaneous removal of approximately 2000 linear feet on the embankment, as stated in UFSAR Section 2.4.4.1.1.3.

In order to get a better understanding of the site conditions that would be expected following the very unlikely event of a failure of the MCR embankment, a more realistic breach analysis was performed in 2012 by Atkins (Reference 59).

Results of this 2012 MCR embankment breach analysis were used to determine flood levels on site at various time intervals after the event.

One of the FLEX scenarios utilizes TMDDPs to pump water to the AFWST and the RWST. The input from the 2012 breach analysis was used in developing time lines for implementing the use of the TMDDPs.

3.9 Fuelingq of Equipment The diesel consumption for the first seven days of the BDBEE will not deplete our ESE DG FOSTs. The fuel oil that will be used for these strategies is compatible with all the various FLEX diesel components.

The three ESF DG FOSTs each contain at least the TS limit of 60,500 gal per unit, yielding a minimum of 181,500 gal of fuel oil per unit that is protected from external events. The fuel oil that STP uses for all FLEX diesel driven components will be stored in these tanks.

Each FLEX DG will use 54 gallons per hour at 75% load and 70 gallons per hour at full load. The FLEX DG has a protected 660 gal fuel oil tank that will allow over eight hours Page 51 of 86

STPNOC FLEX Mitigation Strategies Docket Nos. 50-498/499 Final Integrated Plan Order EA-12-049 of fully loaded run time before requiring refueling. Approximately 12 hours1.388889e-4 days 0.00333 hours 1.984127e-5 weeks 4.566e-6 months into the event, preparations will be underway to begin the refill effort. In each ESF DG bay, there is a 1 inch fuel oil sample line that will be used to install a suction hose fitting. The suction hose will be attached to a 120V FLEX fuel oil transfer pump stored in a FLEX locker on the EAB 86' elevation. A discharge hose will be lowered from the roof of the EAB and attached to the fuel oil transfer pump. The hoses will also be stored in the EAB 86' elevation. Power for the pump will come from a receptacle on the 35' elevation of the EAB in the Control Room. An extension cord for connecting the receptacle to the pump is also stored in the EAB 86' elevation. These actions are described in FSG-19 (Reference 32).

Refueling the TMDDPs will not be required until more than 24 hours2.777778e-4 days 0.00667 hours 3.968254e-5 weeks 9.132e-6 months after the start of the event. To refuel these pumps, the hose used to fill the FLEX DG FOST will need to be lowered to ground level (29 ft elevation), east of the 0GB to facilitate refueling any portable equipment (Reference 32). When the NSRC refuel equipment arrives on site, it can also be used to move fuel from the ESF DG FOSTs to the TMDDPs.

The following fuel consumption approximations are documented in the acceptance test packages in the applicable work orders:

The FLEX DG uses approximately 70 gallons per hour at full load (1,680 gallons per day) J

The TMDDPs use approximately 15 gallons per hour at full load (360 gallons per day)

Per the SAFER guideline, the two NSRC Marine turbine generators use approximately 110 gals/hr each (5280 gallons per day).

Given these fuel consumption approximations, the minimum of 181,500 gallons of fuel in the ESE DG FOSTs plus the 660 gallons of fuel in the FLEX FOST, STP will has sufficient fuel to operate under these conditions for approximately 25 days per Unit.

3.10 Offsite Resources 3.10.1 National SAFER Response Center The industry has established two NSRCs to support utilities and provide supplemental equipment during BDB events. STP has established contracts with the Pooled Equipment Inventory Company (PEICo) for support of the NSRCs, as required. Each NSRC will hold five sets of equipment, four of which will be able to be fully deployed when requested with the fifth set of equipment in a maintenance cycle. In addition, onsite BDB equipment hose and cable end Page 52 of 86

STPNOC FLEX Mitigation Strategies Docket Nos. 50-498/499 Final Integrated Plan Order EA-12-049 fittings have been standardized to be compatible with the equipment supplied from the NSRC.

In the event of a BDBEE and subsequent ELAP/LUHS condition, equipment will be moved from an NSRC directly to the STP site staging area. In the event that the onsite staging area is not available, the NSRC will be directed to send the equipment to a local assembly area established by the SAFER team. These alternate staging areas are in Bay City, approximately 30 minutes from the STP and near Wharton, approximately one hour from the STP. Equipment can be taken to the STP site from the offsite staging areas and staged at the SAFER onsite Staging Area "B" on the west side of the plant by ground or helicopter if ground transportation is unavailable.

See Figure 3.10.1-1 and Figure 3.10.1-2, below, for travel paths from the offsite staging areas to STP.

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STPNOC FLEX Mitigation Strategies Docket Nos. 50-498/499 Final Integrated Plan Order EA-1 2-049 4-Figure 3.10.1 Travel path from Bay City off-site staging area to STP Page 54 of 86

STPNOC FLEX Mitigation Strategies Docket Nos. 50-498/499 Final Integrated Plan Order EA-12-049 Figure 3.1 0.1 Travel path from Wharton off-site staging area to STP Page 55 of 86

STPNOC FLEX Mitigation Strategies Docket Nos. 50-498/499 Final Integrated Plan Order EA-12-049 Communications will be established between STP and the SAFER team using satellite phones, helping required equipment to be moved to the site as needed (Reference 22). The NSRC equipment will begin to arrive on site within 24 hours2.777778e-4 days 0.00667 hours 3.968254e-5 weeks 9.132e-6 months from the initial request.

3.10.2 Equipment List The equipment stored and maintained at the NSRC for transportation to the local assembly area to support the response to a BDB external event at STP is listed in Table 3.10.2-1, below. Table 3.10.2-1 identifies some of the equipment that will be available for backup and replacement purposes should onsite equipment be unavailable. Only the 4160 VAC generator is credited in the FLEX strategies (Reference 19). Emergency response personnel can use the backup equipment as needed to enhance implementation.

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STPNOC FLEX Mitigation Strategies Docket Nos. 50-498/499 Final Integrated Plan Order EA-12-049

~Use and (Potential / Flexibility) Diverse Uses Portable Cn.NtsPerformance Equipment Core on.RCS NtsCriteria Cooling Cooling/ Access Instrumentation Inventory integrity Medium Voltage FSG-2......

X Generators.. X X X 4160 VAC 1 MW Low Voltage for.

Potential.....backup...

............. Potential backup for High.Pressur =::=" ....... ............ "defense-in-depth 2000 psig 60 GMW pump SG Makeup X > defense-in-depthX 5000 psid 500 GPM HighPresurePotential backup for Loe suP e * ::: : 2i: ...... .. : ""... .......... defense-in-depth30 psd 2 0GP MnedtiumFow pump ;==,,:= ; ) "*

Low.....HighPressure! : *!!!: ::::*,:**Potential backup for 15psd 00GP Flowkeupump X ... defense-in-depth 50pi 0 P Lighting Towers *IPotential backup for 4,0

defense-in-depth sd Lu 50Gmen Di PeselsueTraser/ X X Refuelquipmen Diesel Fuel Transfer Refuel equipment Tank & Pump XXX Xfor 4160 VAC -- 264 gal generator Table 3.10.2-1 - List of equipment provided by the NSRC Page 57 of 86

STPNOC FLEX Mitigation Strategies Docket Nos. 50-498/499 Final Integrated Plan Order EA-12-049 3.11 Eqiuipment Operatin~q Conditions 3.11.1 Ventilation and Habitability Some plant locations where FLEX equipment is stored have heat loads and little to no ventilation until the FLEX DGs are put into operation and begin powering equipment. Natural circulation and the proceduralized propping open of doors are the initial capabilities for room cooling. There will be no forced ventilation anywhere in the plant until the FLEX OG is powering equipment. STP performed evaluations on the most critical areas and equipment to ensure equipment survivability and area habitability.

The EAB Heatup Calculation NA1-1646-001 (Reference 47) with supporting input calculation NC-07091 (Reference 93) evaluates ELAP heatup in critical portions of the EAB, primarily the QDPS and inverter rooms.

Heatup calculations for the QDPS cabinets and the Class 1 E inverters show that prior to 24 hours2.777778e-4 days 0.00667 hours 3.968254e-5 weeks 9.132e-6 months into the event the room doors will need to be opened for ventilation. After opening the room doors, the cabinets and inverters will not reach their high temperature limit for an additional three days at which point forced ventilation will have been established.

STP's calculations demonstrate that running the TDAFW pump during an ELAP event will not cause the TDAFW pump room to heat up beyond the pump Environmental Qualification temperature limit of 170°F (Reference 60). However, operators will be directed to the IVC early in the event to lineup Auxiliary Feedwater to all S~s. FSG-05 directs operators to open the door to the TDAFW pump room to allow the heat being generated in the room to dissipate into the hallway, up the stairwell and out of the IVC. Once the FLEX DG is in operation, the TDAFW Cubicle Vent fan can also be started. The FLEX SO makeup pumps in the IVC bays also have cubicle vent fans that can be started when the FLEX DO is powering DPI1000, which provides power to the cubicle vent fan MCC (Reference 22).

The rooms containing the-SG PORVs and the TDAFW pump are at elevated temperatures. STP has cool vests stored inside a FLEX storage locker in the EAB on the 86' elevation for personnel use in these rooms and for other FLEX strategies, if necessary.

Additionally, as part of STP's loss of EAB HVAC Procedure (Reference 61 ),

portable ventilation fans are pre-staged in the EAB on the 10', 60' and 86' elevations to be used if ventilation is lost. The loss of EAB HVAC procedure also

.i.......

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STPNOC FLEX Mitigation Strategies Docket Nos. 50-498/499 Final Integrated Plan Order EA-12-049 directs the placement of these fans and identifies which doors to prop open for best circulation of air (Reference 61).

During an ELAP, Control Room ventilation will be lost, however, the Control Room heat loads will be simultaneously reduced. The DC load shedding actions completed during the first two hours of the event per FSG-04 (Reference 30) de-energizes equipment in the Control Room and the adjacent relay room. The remaining heat sources in the Control Room are primarily generated by personnel, emergency lighting, and remaining QDPS instrumentation. Although the ELAP heat-up calculation performed by STP (References 47) does not specifically model heat-up in the Control Room, the calculations show that temperature response in the critical rooms is relatively slow, requiring over 24 hours2.777778e-4 days 0.00667 hours 3.968254e-5 weeks 9.132e-6 months before temperature limits are approached and action is taken to open doors. The calculation models the Control Room as an adjacent heat sink and assumes Control Room temperature starts at 78°F and increases linearly over the next eight hours to I104°F. This is a reasonable assumption based on the limited heat sources remaining in the Control Room and its relatively large air volume (approximately 91,000 ft3 ).

The FLEX DG is projected to be started three hours following the start of the ELAP event. Actions to connect cables to MCC EIA2(E2A2) are projected to start between 30 and 90 minutes following event start. After MCCs E1A2(E2A2) and E1C2(E2C2) are energized, communications equipment, lighting, and battery chargers are energized via the FLEX DG and the safety-related Control Room Return Fan 11IA(21A) may be started per FSG-05 (Reference 22). Actions to connect cables to MCC El1B4(E2B4) are projected to be performed before 4.5 hours5.787037e-5 days 0.00139 hours 8.267196e-6 weeks 1.9025e-6 months following event start. An additional Control Room Return Fan 11 B(21 B) can then be started to increase outside air flow to the Control Room.

3.11.2 Heat Tracing Heat trace circuits keep the 4-weight-percent boric acid at approximately 85°F. When the ELAP occurs, the water temperature will slowly lower but will not decrease past 55°F because the tanks and piping are insulated and inside concrete buildings. When the FLEX DG is running, the Boric Acid pumps will be started when the boric acid piping temperature is less than 65 degrees F. The pumps recirculate the solution in the BATs to ensure the temperature does not continue to lower to the point where boric acid begins to solidify. In the unlikely event that the boric acid begins to solidify early, suction source transfer from the BATs to the RWST can be started per FSG-08 or FSG.-01 (References 33 and 62).

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STPNOC FLEX Mitigation Strategies Docket Nos. 50-498/499 Final Integrated Plan Order EA-12-049 3.12 LiQhtincj Lighting for the Control Room and other vital areas is provided by Appendix R battery-powered lights for at least eight hours following the ELAP event; these lights are not qualified to operate following a design basis seismic event but they all have seismic Il/I restraints. There are over 220 such fixtures in each unit at fixed locations. In the event that the Appendix R lighting is damaged at these locations, each unit has three lanterns for a backup lighting source located in the hallway next to the Control Room.

Additionally, Operators are required to carry flashlights with them at all times and handheld navy battle lanterns are stored the EAB and MAB. The battle lanterns contain LEDs and should last approximately 32 hours3.703704e-4 days 0.00889 hours 5.291005e-5 weeks 1.2176e-5 months (Reference 88). Table 3.12-1, below, lists the locations of the hand held battle lanterns.

TA*GIPNS :==lAppendix R! !Location Roo 7E561ELG0348L Y EAB 010 7E562ELG0348L Y EAB 010 7E561ELG0309L Y EAB 212 7E562ELG0309L Y EAB 212 7E561ELG0278L Y EAB 318 7E562ELG0278L Y EAB 318 7E561 ELG0385L Y MAB 326 7E562ELG0385L Y MAB 326 Table 3.12-1 - Locations of Appendix R backup battle lanterns Other portable lighting sources are stored in a designated FLEX locker that is protected from external hazards and easily accessed in the EAB.

Six new battery-backed light fixtures have been installed in each FLEX DG enclosure to enhance visibility for personnel starting the generators. Once the FLEX DG has been started, Power from the FLEX DG Switchgear will be routed from the MAB roof to two manually operated transfer switches to allow the powering of the lighting transformers should the primary source fail during a BDBEE. The transfer switches will be located in the vicinity of the lighting panel transformers on the 35' elevation of the EAB. The cables from the FLEX Distribution Panel to Transfer Switch will be routed in conduit and existing non-Class IE cable trays. The remaining cables will be routed in conduits. A cable will be connected to provide FLEX power from both manual transfer switches. Existing cables from the MCCs to the lighting transformers will be pulled back Page 60 of 86

STPNOC FLEX Mitigation Strategies Docket Nos. 50-498/499 Final Integrated Plan Order EA-1 2-049 and routed to the new transfer switches. The downstream lighting transformers LP1 4L and LP14U (EAB Elevation 35') will be powered from the FLEX DG per FSG-05. The manual transfer switches will be located in the vicinity of the lighting transformers for the panels LPI4L and LP14U. Power from the FLEX DG Switchgear will be routed from the MAB roof to fused disconnect switches upstream of the MO~s (MCC E2C2 and MOO E2A2) for the panels LP14N and LP14M (EAB Elevation 60') to allow powering from the FLEX DG. The fused disconnect switches will be located in the vicinity of MOO E2O2 and MOO E2A2.

See Figure 3.12-1, below, for a photo of a lighting panel power transfer switch.

Figure 3.12 FLEX lighting panel transfer switch Page 61 of 86

STPNOC FLEX Mitigation Strategies Docket Nos. 50-498/499 Final Integrated Plan Order EA-12-049 There are numerous 120 VAC receptacles that will also be powered by the FLEX 0G.

At this point, Appendix R fixtures, those are fed from aforementioned lighting panels, throughout all elevations of the EAB will be re-powered and returned back to charge/standby mode. DCP 12-11685-34 and 12-11685-80 provide FLEX power to these lighting panels (Reference 63). LPE-14L provides over twenty 120 VAC power receptacle circuits for the Control Room and also a number in rooms surrounding the control room, such as such the kitchen area and briefing areas in EAB. LPE-14U provides power to a large number of Exit signs in EAB and to a large number of Appendix R light receptacles. LPE-14M and 14N provide lighting in Main Control Room and EAB switchgear rooms, hall wall and Inverter/Battery rooms for all Trains.

In Phase 3, the NSRC will bring light towers to STP which can be placed around the site as needed.

3.13 Communications As a result of the Recommendation 9.3 Communications Assessment (References 64 and 98), communications at STP were upgraded as follows:

Additional sound powered head sets and cords

Additional hand-held satellite phones and chargers

Additional radios and chargers

Bullhorns`

Replacement antennas for the hardwired satellite phones.

Modifications were made to enable the hardwired satellite phone in the Technical Support Center (TSC) to be moved into the Main Control Room (CR) during the ELAP event thereby providing two hardwired satellite phones in the CR.

Storage of this equipment is inside the power block, protected from external events.

These communication strategies are discussed in FSG-05, Initial Assessment and FLEX Equipment Staging.

In addition, the Lossy Loop amplification system can now be powered by FLEX power thus enabling radio communications throughout the plant including inside buildings on two channels.

Phase 1 STP plant communications capabilities include multiple technologies and redundant power supplies. In the event of massive system failures, onsite and offsite communication requirements will continue to be met with the combination of sound Page 62 of 86

STPNOC FLEX Mitigation Strategies Docket Nos. 50-498/499 Final Integrated Plan Order EA-12-049 powered phones, satellite phones, and radios that will work in line of sight. The sound powered phones are staged throughout the plant inside the power block.

There is one hardwired satellite phone in each Control Room and one in each TSC with hard wired antennas on the roof of the EAB. Per FSG-05, the hard wired satellite phone normally located in the TSC will be moved into the Control Room following a BDBEE (Reference 22). For the permanent satellite phone in the Control Room and the TSC, replacement antennas are stored in protected locations in the EAB in the event that both installed antennas are damaged during the event. There are also two additional hand held satellite phones in the EAB 35' elevation to be used as necessary.

During Phase 1, sufficient batteries are available to power plant radios and satellite phones until the FLEX 480V DG is available to supply power to the radio and phone chargers.

Phase 2 Once the FLEX DG has been started and begins providing power to lighting panels LPE-14M and LPE-14N, the Lossy Loop Amplifiers will be receiving power. Until the Lossy Loop is powered, the radios will only work for line-of-sight communications. Two radio channels have been modified so that they will function once the Lossy Loop is powered - One channel is designated for use by Security and the other channel is designated for Operations and Maintenance. The Control Room operators will bring a hand-held radio into the Control Room to use during the event since the Quintron system is without power. Each unit has also been provided with a bull horn stored in the FLEX storage lockers to assist with public address-type communications.

3.14 Shutdown and Refuelinq Modes Analysis The units will be at full power for the majority of any operating cycle, which is the most limiting condition for scenarios in which the SGs are available for core heat removal.

The same general FLEX approaches can also be used at reduced power and in lower modes when the SGs are intact (Modes 1-4). At reduced power, the plant thermal response will be slower and less severe. In lower-power modes, the additional time for the RCS to heat up to the point at which decay heat can be removed by the SG PORVs will not invalidate or challenge the overall FLEX strategies.

FLEX strategies are not explicitly designed for outage conditions due to the small fraction of the operating cycle that is spent in an outage condition, generally less than 10%. Requirements for FLEX strategies in outage conditions are described in a NEI position paper (Reference 65) which was subsequently endorsed by the NRC (Reference 66). Due in part to the large and diverse scope of activities and configurations for any given nuclear plant outage (planned or forced), the paper Page 63 of 86

STPNOC FLEX Mitigation Strategies Docket Nos. 50-498/499 Final Integrated Plan Order EA-12-049 concluded that a systematic approach to shutdown safety risk identification and planning is the most effective way of enhancing safety during shutdown. The NEI

position references concepts established for outage planning and control including integrated management, level of activities, defense-in-depth, contingency planning, training, and outage safety review. In particular:

Contingency plans should be available when entering a higher risk evolution.

Contingency plans should be developed when system availability drops below planned defense in depth.

Contingency plans should consider use of alternate equipment to respond to loss of dedicated safety and monitoring equipment, and should consider additional monitoring or controls to minimize the potential for unplanned equipment unavailability.

Personnel who may be required to implement a contingency plan should be familiar with the plan.

3.14.1 Core Coolinq and RCS Inventory Control With no SGs available, RCS water will begin to evaporate as a means to transfer core decay heat to the containment. The primary, N, strategy for RCS makeup is to pump water from the RWST by aligning a FLEX Shutdown RCS makeup pump (170 gpm at 100 psig) to take suction from the RWST and discharge to an RCS cold leg. The FLEX Shutdown RCS makeup pumps are located in the SI bays on the -29 ft elevation of the FHB. The alternate, N+I, strategy is identical to the primary except that the pump and connection points are located in a different SI bay and train and connects to different SI piping. The N pump and connections are located in the A-Train SI bay, and the N+1 pump and connections are located in the B-Train SI bay.

For this shutdown mode FLEX strategy, the reactor is assumed to have been shut down below Mode 3 for a minimum of 30 hours3.472222e-4 days 0.00833 hours 4.960317e-5 weeks 1.1415e-5 months following an operating cycle which represents the approximate minimum time required to cooldown the plant for normal offload of spent fuel with the SGs isolated for planned maintenance.

Additionally, both the RCS and the Containment are assumed to be vented because they are vented the majority of the time during Modes 5 and 6. Makeup requirements in this time frame are approximately 143 gpm (Reference 67) which can be supplied by one of the FLEX ROS makeup Pumps. The 170 gpm at 100 psig FLEX ROS makeup pump will provide the required 143 gpm plus an additional 27 gpm for boron flushing as required by NEI 12-06.

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STPNOC FLEX Mitigation Strategies Docket Nos. 50-498/499 Final Integrated Plan Order EA-12-049 3.14.2 SFP Strateqy During shutdown and refueling operations, the time to reach 200° F and the heat-up rate of the SFP as a function of time following a loss of SFP cooling are provided in the Plant Curve Book Figures 5.19B and 5.13B, respectively, for each Unit. The maximum heat load for a typical refueling operation occurs at the end of a full core offload, typically greater than seven days after the reactor shutdown. Assuming this full core heat load at seven days coincident with a loss of cooling, the SFP would begin to boil approximately five hours following the ELAP/LUHS event.

In this scenario the SFP boil-off rate would be about 93 gpm, well within the makeup capability of the RMW pump (300 gpm) and FLEX SFP makeup pump (250 gpm). The SFP would boil down from the normal operating level to 10 feet above the top of the active fuel in approximately 33 hours3.819444e-4 days 0.00917 hours 5.456349e-5 weeks 1.25565e-5 months following the loss of cooling (Reference 46). Maintaining the water level greater than 10 feet above the active core should limit the maximum radiation dose to 2.5 millirem per hour for personnel (Reference 102).

3.14.3 Containment Strateqy With no SGs available, once through cooling will be used to transfer core decay heat to the containment. Without containment heat removal systems available, containment pressure and temperature will rise. Containment venting may be required to prevent exceeding the containment pressure limit. During Phases 2 and 3, containment will be vented as necessary using FSG-12 (Reference 48).

Containment is usually vented during outages, but in the event it was not vented, the actual strength of the containment is considerably higher than the conservatively chosen static design pressure of 56.5 psig stated in Section 3.8.1.3.1 of the UFSAR (Reference 44). Per ASME Code, the STP containments were physically tested to 115% of design pressure (65 psig) and the calculated ultimate strength is 141 psig (Reference 89).

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STPNOC FLEX Mitigation Strategies Docket Nos. 50-498/499 Final Integrated Plan Order EA-12-049 3.15 Sequence of Events Table 3.15-1, below, presents the Sequence of Events Timeline for an ELAP/LUHS event at STP. The times listed in the Table below are approximate and were generated from the relevant FLEX calculations and EOP actions. The times below are assumed in the calculations and do not necessarily represent the minimum times that the actions can be accomplished.

Event Time Comments Loss of All AC Power 0 Reactor Trip 0 TDAFW Pump feeds D-Train SG 1 min Operators enter 0POP05-EO-EC00 2 min RCP Leakage increase to about 16.5 gpm 4 min Transfer SG PORVs to Control Room control 10 min ELAPdeciion oint30mm Determine if in an ELAP condition; initiate FSG-04 and FSG-05 Strip ESF Load Sequencers 30 min Operators complete cross connecting AFW to 40mn Required for symmetric RCS all four SGs 4mm cooldown Operators initiate SG depressurization to 1 r Minimize RCP seal damage from approximately 405 psig 1 r high temperature water PRT ruptures 1.25 hrs Releases RCS fluid to containment FLEX DC load shed completed 2 hrs Ensures at least 8 hrs of battery life Ensures no N2 injection from SGs depressurized to -405 psig 2-3 hrs acmltr Time includes 1 hr delay for boron Boron from SI Accumulator precludes criticality 5 hrs mixing under natural circulation flow for Xenon-free condition for Phase 1 conditions Offsite personnel resources begin to arrive onste> 6 hrs Provides additional manpower END PHASE 1 (relying on Design Basis Equipment) at_< 8 hrs Table 3.15 FLEX Sequence of Events Timeline (page 1 of 2)

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STPNOC FLEX Mitigation Strategies Docket Nos. 50-498/499 Final Integrated Plan Order EA-12-049 Event Time Comments FLEX DG started and power available to FLEX Operations to have the FLEX diesel Equipment 8Bhrs available within 8 hrs A and C battery chargers begin charging 8 hrs batteries Accumulator valve closure allows Power/close SI Accumulator valves < 10 hrs cniudcodw Initiate RCS Makeup 10 hrs CVCS PDP is the primary Initiate second SG cooldown 10 hrs Using SG PORVs SG makeup pump lined up and placed in 10 hrs Will be required prior to TDAFW service unavailable due to low SG pressure RCP Seal leakage terminated when RCS 1 r S-20rst pressure drops to <135 psig ____

SFP Makeup commenced using RMW pump 12 hrs depending on SFP level Open Reactor Head Vents. 15 hrs Maintain RCS pressure Reactor Head reached 100% head level, close 2 r nueuprha oln head vents 30 min later Maintain RCS pressure using pressurizer 2 r PORVs and head vents Pressurizer level restored. Secure RCS 2 r ln si taysaemd makeup pump.

Will require moving TMDDP(s) and Prepare to fill AFWST & RWST as necessary 24 hrs talr END PHASE 2 (relying on DB and FLEX equipment)

Continue coping using Phase 1 and 2 equipment and equipment from NSRCs24hr Connect NSRC 4160 V Turbine Generator to 24hr one ESF electrical bus 24+________hrs_____

Table 3.15 FLEX Sequence of Events Timeline (page 2 of 2)

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STPNOC FLEX Mitigation Strategies Docket{ Nos. 50-498/499 Final Integrated Plan Order EA-12-049 3.16 Programmatic Elements 3.16.1 Overall Program Document STP developed an overall program document that provides a historical description of the FLEX Program (Reference 68). The revised FLEX strategies and information are contained in this FIP.

The program elements provided in the Program Document include:

Description-of the FLEX strategies and basis,

Provisions for documentation of the historical record of previous strategies and the basis for changes,

The basis for the maintenance and testing programs chosen for the FLEX equipment, and

Designation of the minimum set of parameters necessary to support strategy implementation.

Existing design control procedures have been revised to ensure that future changes to the plant design, physical plant layout, roads, buildings, and miscellaneous structures will not adversely impact the approved FLEX strategies.

STP's procedure for making design changes has been updated to include screening for impacts to FLEX strategies. As stated in the procedure, all changes affecting the SSCs listed below must be evaluated to ensure that they do not affect any of the FLEX strategies and associated time estimates to complete the strategies (Reference 90):

,Fukushima Response (FR) system or components

Normal travel paths inside the, power block

Vehicle travel paths inside the PA

TSC or Control Room communications (radio or satellite phone)

Instrumentation shown on QDPS

SFP level indicators

FLEX equipment in Building 44 or the Fukushima Response Building

SAFER laydown area on the West side of the plant Future changes to the FLEX strategies may be made without prior NRC approval provided the revised FLEX strategies meet the requirements of NEI 12-06 and an engineering basis is documented that ensures that the change in FLEX strategies continues to ensure the key safety functions (core cooling, SFP cooling and containment integrity) are met.

Page 68 of 86

STPNOC FLEX Mitigation Strategies Docket Nos. 50-498/499 Final Integrated Plan Order EA-12-049 3.16.2 Procedural Guidance The FSGs provide guidance that can be employed for a variety of conditions.

Clear criteria for entry into FSGs ensures that FLEX strategies are used only as directed for BDBEE conditions and are not used inappropriately in lieu of existing procedures. When FLEX equipment is needed to supplement EOPs or abnormal operating procedures (AOP), the EOP or AOP directs the entry into and exit from the appropriate FSG procedure. FSGs are used to supplement, not replace, the existing procedure structure that establishes command and control for the event.

The STP FSGs were developed in accordance with PWROG guidelines.

Procedural interfaces have been incorporated into station procedure EC00 to include appropriate reference to FSGs and provide command and control for the

.:ELAP (Reference 11). Additionally, a new AOP for loss of all AC power while on shutdown cooling (Reference 69) was prepared to provide the command and control function for the ELAP while on RHR since EC00 does not apply in this operating mode.

In accordance with site administrative procedures, Revision 1 of NEI 96-07 (Reference 70), Guidelines for 10 CFR 50.59 Implementation, and Revision 1 of NEI 97-04 (Reference 71), Design Bases Program Guidelines, are used to evaluate changes to current procedures, including the FSGs, to determine the need for prior NRC approval. However, per the guidance and examples provided in NEI 96-07, Revision 1, changes to procedures (EOPs, AOPs, or FSGs) that perform actions in response to an event that exceeds a site's design-basis should screen out under 10 CFR.50.59 and would not require prior NRC approval.

Therefore, procedure steps which recognize the BDB ELAP/LUHS has occurred and which direct FLEX strategy actions to ensure core cooling, containment, or SFP cooling should not require prior NRC approval.

FSGs have been reviewed and validated to the extent necessary to ensure that implementation of the associated FLEX strategy is feasible. Specific FSG validation was accomplished via walk-throughs of the guidelines when appropriate, in accordance with 0PGP03-ZO-FLEX, "FLEX Support Guideline Program" (Reference 72). Revisions to the FSGs will be made in accordance with the FLEX Support Guideline Program.

The EOPs have been revised in accordance with established EOP change processes to clearly reference and identify appropriate entry and exit conditions for these pre-planned strategies.- The EOPs retain overall command and control of the actions responding to a BDB external event.

Page 69 of 86

STPNOC FLEX Mitigation Strategies Docket Nos. 50-498/499 Final Integrated Plan Order EA-12-049 3.16.3 Staffingq In December 2011, the NRC added paragraph A.9 to Section IV of 10 CER 50, Appendix E requiring Licensees to perform a detailed analysis demonstrating that on-shift personnel assigned emergency plan implementation functions are not assigned responsibilities that would prevent the timely performance of their assigned function as specified in the emergency plan (Reference 73). NEI 10-05 (Reference 74) provides guidance for completing this analysis. However, NEI 10-05 did not consider a multi-unit BDBEE with an ELAP.

In response to NTTF Recommendation 9.3, the NRC requested th'at licensees assess their current staffing levels and determine the appropriate staff to fill all necessary positions for responding to a multi-unit event during a BDBEE when all units are affected, there is an ELAP, and access to the site is impeded (Reference 94).

Using the methodology presented in NEI 12-01, "Guideline for Assessing Beyond Design Basis Accident Response Staffing and Communications Capabilities" (Reference 75), STP performed assessments of the capability of STP's on-shift staff and augmented Emergency Response Organization (ERO) to respond to a BDBEE.

The assumptions for the NEI 12-01 scenario postulate that the BDB event involves a non-specific large-scale external event that results in an ELAP and LUHS that impacts both units on the site. Additionally, the NEI 12-01 guidance assumes that access to the site by offsite responders and resources is impeded as follows:

0 to 6 hours6.944444e-5 days 0.00167 hours 9.920635e-6 weeks 2.283e-6 months post event - No site access

6 to 24 hours2.777778e-4 days 0.00667 hours 3.968254e-5 weeks 9.132e-6 months post event - Limited site access. Individuals may access the site by walking, personal vehicle, or via alternate transportation capabilities (e.g., private resource providers or public sector support)

Greater than 24 hours2.777778e-4 days 0.00667 hours 3.968254e-5 weeks 9.132e-6 months post event - Improved site access. Site access is restored to a near-normal status and/or augmented transportation resources are available to deliver equipment, supplies and large numbers of personnel STP performed a "Phase 1" staffing study to evaluate the ability to respond to a BDBEE using pre-FLEX station procedures and resources. STP also performed a "Phase 2" staffing study to evaluate the ability to respond to a BDBEE using FLEX procedures and equipment. "Phase 1" and "Phase 2" as used in this section, are not to be confused with the phase designations used in the FLEX strategies.

Page 70 of 86

STPNOC FLEX Mitigation Strategies Docket Nos. 50-498/499 Final Integrated Plan Order EA-12-049 The "Phase 1" staffing study revealed some areas for improvement in the Emergency Response Organization staffing that have been addressed (References 76 and 99).

The "Phase 2" staffing study that included staffing for FLEX strategies assessed whether or not the FLEX strategies could be performed in the required time with the current STP on-shift staffing. The "Phase 2" study concluded that STP's current on-shift staffing can implement actions required to support the FLEX strategies for the first six hours of the event (Reference 77). The assessment was verified following the completion of the FSGs and a supplement to the original staffing study "Phase 2" assessment was submitted to the NRC (Reference 78).

3.16.4 Traininq STP's Nuclear Training Program has been revised to assure personnel proficiency in utilizing FSGs and associated BDB equipment for the mitigation of BDBEEs is adequate and maintained. These programs and controls were developed and have been implemented in accordance with the Systematic Approach to Training (SAT) Process.

Initial training has been provided and periodic training will be provided to site emergency response leaders on BDB emergency response strategies and implementing guidelines. Personnel assigned to direct the execution of the FLEX mitigation strategies for BDB external events have received the necessary training to ensure familiarity with the associated tasks, considering available job aids, instructions, and mitigation strategy time constraints.

As stated in Section 11.6 of NEI 12-06, ANSI/ANS 3.5 (Reference 79) certification of simulator fidelity is considered to be sufficient for the initial stages of the BDBEE scenario until the current capability of the simulator model is exceeded.

Per Section 11.6 of NEI 12-06, where appropriate, integrated FLEX drills will be organized on a team or crew basis and conducted periodically with all time-sensitive actions to be evaluated over a period of not more than eight years. It is not required to connect or operate equipment during these drills (Reference 9).

STP plans to follow the industry guidance provided in NEI 13-06 for conducting FLEX drills (Reference 103).

3.16.5 Equipment List The equipment stored and maintained at STP for use with FLEX strategies in response to a BDBEE is listed in Table 3.16.5-1, below. Table 3.16.5-1 identifies Page 71 of 86

STPNOC FLEX Mitigation Strategies Docket Nos. 50-498/499 Final Integrated Plan Order EA-12-049 the quantity, applicable strategy, capacity/rating and various clarifying notes for the major BDB equipment components only.

Page 72 of 86

STPNOC FLEX Mitigation Strategies Docket Nos. 50-498/499 Final Integrated Plan Order EA-12-049 Use and (Potential / Flexibility) Diverse Uses Equipment Used in FLEX LoainPerformance Strategies LoainCriteria Core Containment SFP Instrumentation Accessibility SG makeup pumps (2 per Pesadinde 300 gpm @

unit) X safety-related 500 psig building RCS makeup pump (FLEX) Pre-staged inside 7 p 0 for at power modes (1 per x safety-related building pi unit) pi RCS makeup pump (CVCS Existing plant PDP) for at power modes (1 Xequipment inside 35 gpm @

per unit) safety-related 3000 psig building RCS makeup pump (FLEX) Pre-staged inside 170 gpm @

for Modes 5 and 6 (2 per unit) X ,safety-related 100 psi building Existing plant SEP makeup pump (RMW Xequipment inside 300 gpm @

pump) 2 per unit safety-related 150 psig building SEP makeup pump (FLEX) 1 Pre-staged inside 250 gpm @

per unit X safety-related 150 psig building Table 3.16.5 List of Equipment used in FLEX Strategies (page 1 of 2)

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STPNOC FLEX Mitigation Strategies Docket Nos. 50-498/499 Final Integrated Plan Order EA-12-049

?Equipment Used in FLEX Use and (Potential / Flexibility) Diverse Uses Performance StratgiesLocation Ciei StaeisCore Containment SFP Instrumentation Accessibility Ciei TMDD pumps (3 total, 2 Stored in FLEX >1000 gpm designated for FLEX and 1 X X X buildings outside the @15pi for 10 CFR 50.54(hh)(2)) PA @15pi 480 VAC generators (2 per Stored in missile unit) and associated cables, protected enclosure connectors and switchgear XXXXXon roof of safety- 1000 kW each (to power FLEX equipment related structure like pumps, battery chargers, fans, etc.)

Four-wheel drive tractor with Stored in FLEX front end loader and hose X X X X buildings outside the trailer (total of 2) PA Stored in FLEX Fuel oil pumps (2 per unit) X X X X lockers inside safety- 10gmt4 related building f Satelit phoes 2 had wredPre-staged /stored

&Sandteldt phoes2hrd unit) d X inside safety-related

& 2 and eld er uit)building Stored in FLEX Fluke 705, 712B & 114 X lockers inside safety-related building Radis & attriesforStored in FLEX Raisecu attritchnel (1oprunt X lockers inside safety-Secuitychanel 10 pr uit)related building Table 3.16.5-1 - List of Equipment used in FLEX Strategies (page 2 of 2)

Page 74 of 86

STPNOC FLEX Mitigation Strategies Docket Nos. 50-498/499 Final Integrated Plan Order EA-12-049 3.16.6 N+l Equipment Requirement NEI 12-06 requires sites to have N+1 sets of major BDB equipment that directly performs a FLEX mitigation strategy for core cooling, containment, or SFP cooling in order to assure reliability and availability of the FLEX equipment required to meet the FLEX strategies. Unit I and Unit 2 at STP are separated by over 600 feet and a significant external event is a large flood event, STP elected to provide N+1 equipment sets for each unit. Sufficient equipment has been purchased to address all functions at all units on-site, plus one additional spare per unit.

The N+1 capability applies to the portable FLEX equipment that directly supports maintenance of the key safety functions identified in Table 3-2 of NEI 12-06 for FLEX baseline capability for PWRs. Other FLEX support equipment provided for mitigation of BDB external events but not directly.supporting a credited FLEX strategy, is not required to have N+1 capability.

In the case of hoses and cables associated with FLEX equipment required for FLEX strategies, an alternate approach to meet the N+I capability has been selected. These hoses and cables are passive components being stored in a protected facility. It is postulated the most probable cause for

.degradation/damage of these components would occur during deployment of the equipment. Therefore the +1 capability is accomplished by having sufficient hoses and cables to satisfy the N capability + 10% spares or at least 1 length of hose and cable. This 10% margin capability ensures that failure of any one of these passive components would not prevent the successful deployment of a FLEX strategy. The hoses and cables that come under this requirement at STP are the following:

SG Makeup hoses/spools - because STP has two completely different sets of pumps and hoses, this satisfies the +1 requirement.

RCS Makeup hoses - because STP has two completely different means to fill the RCS, the hoses do not require duplication.

SFP Makeup hoses - because STP has two completely different means to fill the RCS, the hoses do not require duplication.

Fuel oil fill strategy - this strategy requires +1 on the pump and +1 on the hoses as discussed above. The 100 ft power cord can be replaced by ones in the MAB Hot Tool Rooms.

.P.age 75 of 86

STPNOC FLEX Mitigation Strategies Docket Nos. 50-498/499 Final Integrated Plan Order EA-12-049 All FLEX support equipment and tools are subject to inventory checks, unavailability requirements, and any maintenance and testing that are needed to ensure they can perform their required functions (References 82 and 92).

3.16.7 Equipment Maintenance and Testingi Initial component level testing that consisted of Factory Acceptance Testing and Site Acceptance Testing was conducted to ensure the FLEX equipment can perform its required FLEX strategy functions. Factory Acceptance Testing verified that the pre-staged pumps performance conformed to the manufacturers rating for the equipment as specified in the Purchase Order. Verification of the vendor test documentation was performed as part of the receipt inspection process for each of the affected pieces of equipment and included in the applicable Vendor Test Reports (References 91,100, 101 ). Site Acceptance Testing of the FLEX DGs and associated circuitry for all loads confirmed the FLEX equipment will perform in accordance with the FLEX strategy functional design requirements. The Site Acceptance Testing is documented in applicable work orders.

The BOB equipment that directly performs a FLEX mitigation strategy for the core cooling, containment, or SFP cooling is subject to periodic maintenance and testing in accordance with NEI 12-06 and INPO AP 913, "Equipment Reliability Process", (Reference 80), to verify proper function. Additional FLEX support equipment that requires maintenance and testing has Preventative Maintenance (PM) activities to ensure it will perform its required functions following a BOB external event. The PMs for FLEX equipment were developed using the templates and guidance contained in the EPRI report for the PM basis for FLEX equipment (Reference 81).

The PM procedures and test procedures are based on the templates contained within the EPRI Preventive Maintenance Basis Database or from manufacturer provided information/recommendations when templates were not available from EPRI. The corresponding maintenance strategies were developed and documented. The performance of the PMs and test procedures are controlled through the site work order process. FLEX support equipment not falling under the scope of INPO AP 913 will be maintained as necessary to ensure continued reliability. Performance verification testing of FLEX equipment is scheduled and performed as part of STP's PM process. Equipment maintenance and testing will be adjusted and modified based on internal operating experience (OE) and equipment performance per the STP PM process.

Page 76 of 86

STPNOC FLEX Mitigation Strategies Docket Nos. 50-498/499 Final Integrated Plan Order EA-12-049 A procedure was established to ensure the unavailability of equipment and applicable connections that directly perform a FLEX mitigation strategy for core cooling, containment, and SFP cooling will be managed such that risk to mitigation strategy capability is minimized (Reference 82). Maintenance/risk guidance conforms to the guidance of NEI 12-06 as follows:

FLEX equipment may be unavailable for 90 days(1 ) provided that the site FLEX capability (N) is available. The more restrictive exception to this is the 30 day unavailability time of the RCS makeup pumps at STP as previously discussed.

If FLEX equipment becomes unavailable such that the site FLEX capability (N) is not maintained, initiate actions within 24 hours2.777778e-4 days 0.00667 hours 3.968254e-5 weeks 9.132e-6 months to restore the site FLEX capability (N) and implement compensatory measures (e.g.,

use of alternate suitable equipment or supplemental personnel) within 72

(

hours.

(1) Note that the 90 day allowed out-of-service time was reduced to 30 days for both the PDP and FLEX RCS makeup pump, as described in Section 3.5 of this FIP.

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STPNOC FLEX Mitigation Strategies Docket Nos. 50-498/499 Final Integrated Plan Order EA-12-049

4. References

1. Enclosure to SECY-1 1-0093, "Recommendations for Enhancing Reactor Safety in the 2 1 st Century - The Near-Term Task Force Review of Insights from the Fukushima Dai-ichi Accident", July 12, 2011 (ML111861807)

2. NRC Order Number EA-12-049, "Issuance of Order to Modify Licenses with Regard to Requirements for Mitigation Strategies for Beyond-Design-Basis External Events", March 12, 2012 (ML12054A735)

3. Letter from D.L. Koehl, STPNOC, to NRC Document Control Desk, "STPNOC Overall Integrated Plan in Response to March 12, 2012 Commission Order Modifying Licenses with Regard to Requirements for Mitigation Strategies for Beyond-Design-Basis External Events (Order Number EA-12-049)", February 28, 2013 (NOC-AE-1 3002963)(ML13070A011)

4. Letter from G.T. Powell, STPNOC, to NRC Document Control Desk, "STPNOC First Six-Month Status Report in Response to March 12, 2012 Commission Order Modifying Licenses with Regard to Requirements for Mitigation Strategies for Beyond-Design-Basis External Events (Order Number EA-12-049)", August 26, 2013 (NOC-AE- I13003027)(ML I13249A060)

5. Letter from G.T. Powell, STPNOC, to NRC Document Control Desk, "STPNOC Second Six-Month Status Report in Response to March 12, 2012 Commission Order Modifying Licenses with Regard to Requirements for Mitigation Strategies for Beyond-Design-Basis External Events (Order Number EA-12-049)", February 27, 2014 (NOC-AE-1 4003089)(ML14073A458)

6. Letter from G.T. Powell, STPNOC, to NRC Document Control Desk, "STPNOC Third Six-Month Status Report in Response to March 12, 2012 Commission Order Modifying Licenses with Regard to Requirements for Mitigation Strategies for Beyond-Design-Basis External Events (Order Number EA-12-049) (TAC Nos.

MF0825 and MF0826)", August 27, 2014 (NOC-AE-14003162)(ML14251A029)

7. Letter from G.T. Powell, STPNOC, to NRC Document Control Desk, "STPNOC Fourth Six-Month Status Report in Response to March 12, 2012 Commission Order Modifying Licenses with Regard to Requirements for Mitigation Strategies for Beyond-Design-Basis External Events (Order Number EA-12-049) (TAC Nos.

MF0825 and MF0826)", February 26, 2015 (NOC-AE-1 5003224)(MLI15075A01 9)

8. Letter from G.T. Powell, STPNOC, to NRC Document Control Desk, "STPNOC Fifth Six-Month Status Report in Response to March 12, 2012 Commission Order Modifying Licenses with Regard to Requirements for Mitigation Strategies for Page 78 of 86

STPNOC FLEX Mitigation Strategies Docket Nos. 50-498/499 Final Integrated Plan Order EA-12-049 Beyond-Design-Basis External Events (Order Number EA-12-049) (TAC Nos.

MF0825 and MF0826)", August 26, 2015 (NOC-AE-15003287)(ML15251A208)

9. Nuclear Energy Institute Guidance Document, NEI 12-06, "Diverse and Flexible Coping Strategies (FLEX) Implementation Guide", Revision 0, August 21, 2012 (ML12242A378)

10. NRC Final Interim Staff Guidance, JLD-ISG-201 2-01, "Compliance with Order EA-12-049, Order Modifying Licenses with Regard to Requirements for Mitigation Strategies for Beyond-Design-Basis External Events", Revision 0, August 29, 2012 (ML12229A174)

11. STP Procedure, 0POP05-EO-EC00, "Loss of All AC Power", Revision 25, November 10, 2015 (STI 34238759)

12. STP Calculation,15-FR-015, "Decay Heat Curve Comparison", Revision 0, July 9, 2015 (STI 34151445)

13. South Texas Project Technical Specifications

14. STP Calculation, STP-CP-006, "ELAP Analysis with the South Texas Project RETRAN-02 Input Model", Revision 1, April 15, 2015 (STI 34064235)

15. STP FLEX Support Guideline Procedure, OPOP12-ZO-FSGIO, "RCS Accumulator Injection Isolation", Revision 1, November 10, 2015 (STI 34237570)

16. STP EOP Setpoint Document, 5Z010Z51003, Revision 7, February 3, 2015 (STI 34048625)

17. STP FLEX Support Guideline Procedure, OPOPI12-ZO-FSG03, "Alternate Low Pressure Feedwater', Revision 1, November 10, 2015 (STI 34236715)

18. STP Calculation, 15-FR-014, "Time to Loss of Heat Sink During an ELAP Event",

Revision 0, November 9, 2015 (STI 34151443)

19. STP FLEX Support Guideline Procedure, OPOPI12-ZO-FSG21, "NSRC Turbine Generator", Revision 1, November 10, 2015 (STI 34236709)

20. STP Emergency Response Desktop Guide Instruction, ZV-0028, "SAFER Response Plan", April 1, 2015 (STI 34040267)

21. STP FLEX Support Guideline Procedure, 0POP12-ZO-FSG07, "Loss of Vital Instruments or Control Power", Revision 1, November 10, 2015 (STI 34237576)

22. STP FLEX Support Guideline Procedure, 0POP12-ZO-FSG05, "Initial Assessment and FLEX Equipment Staging", Revision 1, November 10, 2015 (STI 34236725)

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STPNOC FLEX Mitigation Strategies Docket Nos. 50-498/499 Final Integrated Plan Order EA-12-049

23. STP Design Change Package, DCP 12-11658-24, "FLEX SG Make-Up Including Filling of the AFWST from the Deaerator (DA) Blowdown Line", Revision 0, October 2, 2015 (STI 33953633)

24. STP Design Change Package, DCP 12-11658-75, "FLEX SG Make-Up Including Filling of the AFWST from the Deaerator (DA) Blowdown Line", Revision 0, March 18, 2015 (STI 34079576)

25. STP Design Change Package, DCP 12-11658-23, "FLEX RCS Make-Up/Boration", Revision 5, April 25, 2015 (STI 34115885)

26. STP Design Change Package, DCP 12-11658-74, "FLEX RCS Make-up/Boration", Revision 3, October 29, 2015 (STI 34232699)

27. STP FLEX Support Guideline Procedure, 0POP1 2-ZO-FSG06, "Alternate AFWST Makeup", Revision 1, November 10, 2015 (STI 34237577)

28. STP FLEX Support Guideline Procedure, 0POP12-ZO-FSGI7, "Portable Pump Fill of RWST", Revision 1, November 10, 2015 (STI 34237394).

29. STP Procedure, 0POP02-CV-0003, "Mixing of Boric Acid", Revision 13, February 7, 2015 (STI 34051467)

30. STP FLEX Support Guideline Procedure, 0POP12-ZO-FSG04, "ELAP DC Bus Load Shed/Management", Revision 1, November 10, 2015 (STI 34237578)

31. STP Calculation, 2011-11676-EAD, "2011 Class IE Battery Coping Study",

Revision 1, February 3, 2012 (STI 3333.8842)

32. STP FLEX Support Guideline Procedure, 0POP12-ZO-FSGI9, "480V FLEX Diesel Generator Operation", Revision 1, November 10, 2015 (STI 34237393)

33. STP FLEX Support Guideline Procedure, 0POP12-ZO-FSG08, "Alternate RCS Boration", Revision 1, November 10, 2015 (STI 34237574)

34. STP FLEX Support Guideline Procedure, 0POP12-ZO-FSG20, "Alternate QDPS Parameter Monitoring", Revision 1, November 10, 2015 (STI 34237391) -

35. Westinghouse Report (Proprietary), PWROG 1401 5-P, "No-I Seal Flow Rate for Westinghouse Reactor Coolant Pumps Following Loss of All AC Power"', Revision 2, April 1, 2015 (STI 34259706)

36. STP White Paper by P. Jensen and C.R. Albury, "White Paper Demonstrating the Applicability of the RETRAN-3D Code for Analysis of the ELAP", August 21, 2014 (STI 34048769)

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STPNOC FLEX Mitigation Strategies Docket Nos. 50-498/499 Final Integrated Plan Order EA-12-049

37. Westinghouse Report (Proprietary), PWROG 14074-P, "Benchmarking the ITCHSEAL Code," April 2015

38. STP FLEX Support Guideline Procedure, 0POP12-ZO-FSG-01, "Long Term RCS Inventory Control", Revision 1, November 10, 2015 (STI 34236714)

39. Letter from J.R. Davis, NRC, to J. Stringfellow, PWROG, "Boron Mixing Endorsement Letter in Regards to Mitigation Strategies Order EA-12-049",

January 8; 2014 (ML13276A183)

40. 'Letter from J.R. Davis, NRC, to J. E. Pollock, NEI, "Battery Life White Paper Endorsement", September 16, 2013 (ML1 3241Al188)

41. STP FLEX Support Guideline Procedure, 0POP1 2-ZO-FSGll1, "Alternate SFP Makeup and Cooling", Revision 1, November 10, 2015 (STI 34237569)

42. STP Calculation, NC-71 06, "Spent Fuel Pool Heatup Analysis for 18-Month Refueling Cycles", Revision 3, March 15, 2001 (STI 31238242)

43. STP Procedure, 0POP10O-FP-0001, "Alternate Fire Protection System Operation",

Revision 4, May 23, 2012 (STI 33551601)

44. South Texas Project Updated Final Safety Analysis Report

45. NRC Order Number EA-12-051, "Issuance of Order to Modify Licenses with Regard to Requirements for Reliable Spent Fuel Pool Instrumentation", March 12, 2012 (AE-NOC-1 2002271 )(ML12054A679)

46. STP Calculation, I15-FR-01 7, Revision 0 "Spent Fuel Pool Heatup Analysis for ELAP Event" (STI 34152997)

47. STP Calculation, NA1-1646-001, "STP Electrical Auxiliary Building GOTHIC Room Heatup Analysis", Revision 1, February 10, 2015 (STI 34056329)

48. STP FLEX Support Guideline Procedure, 0POP12-ZO-FSGI2, "Alternate Containment Cooling", Revision 1, November 10, 2015 (STI 34237565)

49. Letter from T. Brown, NRC, to D.L. Koehl, STPNOC, "South Texas Project, Units 1 and 2 - Report for the Onsite Audit Regarding Implementation of Mitigating Strategies and Reliable Spent Fuel Instrumentation Related to Orders EA-12-049 and EA-12-051 (TAC Nos. MF0825, MF0826, MF0827 and MF0828)", May 6, 2015 (AE-NOC-1 5002661 )(ML15111A465)

50. EPRI Report 1025287, J. Richards, J. Hamel and R. Kassawara, "Seismic Evaluation Guidance - Screening, Prioritization and Implementation Details Page 81 of 86

STPNOC FLEX Mitigation Strategies Docket Nos. 50-498/499 Final Integrated Plan Order EA-12-049 (SPID) for the Resolution of Fukushima Near-Term Task Force Recommendation 2.1: Seismic", November 2012 (ML12333A170)

51. Climatic Atlas of the United States 'The Climatic Atlas of the United States,"

NCDC, Version 2.0 (CD-ROM), NCDC, Climate Services Division, NOAA, September 2002

52. National Oceanic and Atmospheric Administration National Climatic Data Center, Texas Storm Events, "Storm Events for Texas, Hail Event, and Snow and Ice Event Summaries," https://www. ncdc. noaa.gov/stormevents/

53. STP Calculation, SC-05018, "Design of FLEX Diesel Generator Missile Enclosure", Revision 0, July 16, 2014 (STI133835553)

54. STP Design Change Package, DCP 12-11658-28, "FLEX Modification for two Diesel Generators, and Load Distribution Panel with Enclosure and Supporting Facilities", Revision 0, December 9, 2014 (STI 33995455)

55. STP Design Change Package, DCP 12-11658-27, "FLEX Modification for two Diesel Generators, and Load Distribution Panel with Enclosure and Supporting Facilities", Revision 0, July 16, 2014 (STI 33901830)

56. STP Condition Reporting Database Action, 12-11658-652 Attachment, "Audit item

6-A, Warehouse 44"

57. STP Condition Report Engineering Evaluation, CREE 12-11658-741, December 3, 2015

58. Letter from G.T. Powell, STPNOC, to NRC Document Control Desk, "Seismic Hazard and Screening Report (CEUS Sites), Response to NRC Request for Information Pursuant to 10 CFR 50.54(f) Regarding Recommendation 2.1 of the Near Term Task Force Review of Insights from the Fukushima Dai-ichi Accident",

March 31, 2014 (NOC-AE-1 400311 4)(ML14099A235)

59. STP Vendor Report, "South Texas Project Units I and 2 Flood Analysis, Atkins",

March 29, 2012 (STI 33430176)

60. STP Calculation, MC-06506, "AFW Pump Room D Maximum Temperature During a Station Blackout", Revision 0, August 17, 2004 (STI 31767960)

61. STP Procedure, 0POPI10-HE-0001, "Loss of EAB HVAC", Revision 2, April 29, 2015 (STI 34117278)

62. STP FLEX Support Guideline Procedure, 0POP12-ZO-FSG01, "Long Term RCS Inventory Control", Revision 1, November 10, 2015 (STI 34236714)

.Page 82 of 86

STPNOC FLEX Mitigation Strategies Docket Nos. 50-498/499 Final Integrated Plan Order EA-12-049

63. STP Design Change Package, DCP 12-11685-34, "FLEX Power to Lighting, Receptacles and Communications", Revision 0, December 30, 2014 (STI 34026165)

64. Letter from D.W. Rencurrel, STPNOC, to NRC Document Control Desk, "Supplement to Revised 60-Day Response to Request for Information Pursuant to 10 CFR 50.54(f) Regarding Recommendation 9.3 of the Near-Term Task Force Review of Insights from the Fukushima Dai-ichi Accident", October 31, 2012 (N oC-AE- 1200291 8)(M L 1231 8A096)

65. NEI Position Paper, "Shutdown/Refueling Modes", September 18, 2013 (ML13273A514)

66. Letter from J.R. Davis, NRC, to J.E. Pollock, NEI, "Endorsement letter:

Mitigation Strategies Order EA-12-049, NEI Position Paper Shutdown/Refueling Modes", September 30, 2013 (ML13267A382)

67. STP Calculation, 15-FR-007, "RCS Boil-Off and RWST Refill Time for ELAP Event in Modes 5 & 6", Revision 0, April 23, 2015 (STI 34106175)

68. STP FLEX Program Document, FLEX-0001, 9Q539LFR0001, "Diverse and Flexible Coping Strategies (FLEX) Program Document, South Texas Project (STP) Units 1 & 2", Revision 0, April 14, 2014 (STI 33759523)

69. STP Abnormal Operating Procedure, 0POP04-AE-0007, "Loss of All AC Power While on Shutdown Cooling", Revision 0, April 30, 2015 (STI 34097372)

70. Letter from A.R. Pietrangelo, NEI, to D.B. Matthews, NRC, "Letter forwarding NEI 96-07 Revision 1, 'Guidelines for 10 CFR 50.59 Implementation"'", November 17, 2000 (ML003771157)

71. Nuclear Energy Institute Guidance Document, NEI 97-04, Appendix B, "Design Basis Program Guidelines", November 27, 2000 (ML003771698)

72. STP Procedure, 0PGPO3-ZO-FLEX, "FLEX Support Guideline Program", Revision 1, August 27, 2015 (STI 34175437)

73. STPEGS Emergency Plan

74. Nuclear Energy Institute Guidance Document, NEI 10-05, "Assessment of On-Shift Emergency Response Organization Staffing and Capabilities", Revision 0, September 30, 2010 (ML102730613)

75. Nuclear Energy Institute Guidance Document, NEI 12-01, "Guideline for Assessing Beyond Design Basis Accident Response Staffing and Communications Capabilities", Revision 0, May 4, 2012 (ML12125A412)

Page 83 of 86

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76. Letter from D.W. Rencurrel, STPNOC, to NRC Document Control Desk, "Response to Request for Information Pursuant to 10 CFR 50.54(f) Regarding Recommendation 9.3 of the Near-Term Task Force Review of Insights from the Fukushima Dai-Ichi Accident - Phase 1 Staffing Assessment", April 25, 2013 (NOC-AE-1 3002989)(M L 131 23A028)

77. Letter from A. Capristo, STPNOC, to NRC Document Control Desk, "Response to Request for Information Pursuant to 10 CFR 50.54(f) Regarding Recommendation 9.3 of the Near-Term Task Force Review of Insights from the Fukushima Dai-lchi Accident- Phase 2 Staffing Assessment", November 25, 2014 (NOC-AE-14003189)

78. Letter from G.T. Powell, STPNOC, to NRC Document Control Desk, "Supplement to Response to Request for Information Pursuant to 10 CFR 50.54(f) Regarding Recommendation 9.3 of the Near-Term Task Force Review of Insights from the Fukushima Dai-Ichi Accident - Phase 2 Staffing Assessment", July 2, 2015 (NOC-AE-1 5003255)

79. American Nuclear Society Standard, ANSI/ANS-3.5-2009, "Nuclear Power Plant Simulators for Use in Operator Training and Examination", September 4, 2009

80. Institute of Nuclear Power Operations, INPO AP-913, "Equipment Reliability Process Description", Revision 4, October 2013

81. Electric Power Research Institute Report, "Preventive Maintenance Basis for FLEX Equipment - Project Overview Report", September 30, 2013

82. STP FLEX Support Guideline Procedure, 0PGP03-ZO-0056, "FLEX Equipment Functionality Program", Revision 1, November 10, 2015 (STI 34237450)

83. J.R. Davis, NRC, to J. Stringfellow, NEI, "Letter to PWROG - NOTRUMP Endorsement for ELAP Events", June 16, 2015 (ML15061A442)

84. STP Procedure, 0PEP01-ZE-0003, "Core Reload Design Process", Revision 17, October 28, 2015 (STI 34230503)

85. Plant Curve Book, Figures 3.9a, "1% Subcritical Boron Concentration for ELAP Conditions with AR! and HFP Equilibrium Xenon" (STIs 34253220, 34108855)

86. Plant Curve Book, Figures 3.9b, "1% Subcritical Boron Concentration for ELAP Conditions with ARI and No Xenon" (STIs 34253221, 34108877)

87. STP Procedure, 0POP10-FC-0001, "Spent Fuel Pool Damage Mitigation Strategies", Revision 6, July 17, 2012 (STJ 33573138)

Page 84 of 86

STPNOC FLEX Mitigation Strategies Docket Nos. 50-498/499 Final Integrated Plan Order EA-12-049

88. Vendor Technical Document, Seacoast Development Group, Inc., VTD-S967-0001, "Battle Lantern, Portable, Rechargeable", Revision 1, February 4, 2010 (STI 32608918)

89. Bechtel Design Report for STP, "Reactor Containment Building Design Report, Appendix C, Calculation CC-5210", Revision 6, April 6, 1987 (STI 186)

90. STP Procedure, 0PGP04-ZE-0309, "Design Change Package", Revision 35, December 21, 2015 (STI 34254803)

91. STP Vendor Report, "Pump/Motor Performance Test Report". December 2, 2014 (STI 34037406)

92. STP Procedure, 0POP01 -ZA-0001, "Plant Operations Department Administrative Guidelines", Revision 48, November 10, 2015 (STI 34237449)

93. sTP Calculation, NC-07091, "EAB Gothic Modeling Input Parameters", Revision 0, January 8, 2013 (STI 32886314)

94. Letter from E.J. Leeds, NRC, to All Power Reactor Licensees, "Request for Information Pursuant to Title 10 of the Code of Federal Regulations 50.54(f)

Regarding Recommendations 2.1, 2.3, and 9.3, of the Near-Term Task Force Review of Insights from the Fukushima Dai-ichi Accident", March 12, 2012 (ML12053A340)

95. Vendor Technical Document, VTD-A977-0003, "SAFER Response Plan for South Texas Project Electric Generating Station", Revision 0, April 15, 2015 (STI 34077493)

96. Westinghouse Report (Proprietary), WCAP-17601-P, "Reactor Coolant System Response to the Extended Loss of AC Power Event for Westinghouse, Combustion Engineering and Babcock & Wilcox NSSS Designs", Supplement 1, (WCAP-1 7601 -P)(STI 33805251)

97. Letter from N. Pappas, NEI, to J.R. Davis, NRC, "EA-12-049 Mitigating Strategies Resolution of Extended Battery Duty Cycles Generic Concern", August 27, 2013 (MLI13241A1 86)

98. Letter from G.T. Powell, STPNOC, to NRC Document Control Desk, "STPNOC Response to January 23, 2013, Request for Additional Information Related to the Near-Term Task Force Recommendation 9.3 on Communications", February 21, 2013 (NOC-AE-1 3002958)(ML13092A258)

99. Letter from D.W. Rencurrel, STPNOC, to NRC Document Control Desk, "Revised Phase 1 Staffing Assessment Submitted in Response to Request for Information Page 85 of 86

STPNOC FLEX Mitigation Strategies Docket Nos. 50-498/499 Final Integrated Plan Order EA-1 2-049 Pursuant to 10 CFR 50.54(f) Regarding Recommendation 9.3 of the Near-Term Task Force Review of Insights", June 3, 2013 (NOC-AE-1 3003004)

(ML13182A021 )

100. STP Vendor Report, "Pump/Motor Performance Test Report", March 31, 2015 (STI 34130445) 101. STP Vendor Report, "Pump/Motor Performance Test Report", May 28, 2015 (STI 34145846) 102. Regulatory Guide 1.13, "Spent Fuel Storage Facility Design Bases", Revision 2, March 19, 2007 (ML07031003) 103. Nuclear Energy Institute Guidance Document, NEI 13-06. "Enhancements to Emergency Response Capabilities for Beyond Design Basis Events and Severe Accidents", Revision 0, September 30, 2014 (ML14269A230) 104. STP Design Change Package, DCP 12-11658-30, "FLEX Spent Fuel Pool Makeup", Revision 0, October 1, 2014 (STI 33944800) 105. STP Design Change Package, DCP 12-11658-76, "FLEX Spent Fuel Pool Makeup", Revision 0, September 9, 2015 (STI 34193889) 106. Vendor Technical Drawing, 4122--Oil126HX, "Outline Arrangement Pump Type

'N3' - Size 3 x 4 x 8" (STI 625080)

Page 86 of 86