ML17059D129

Limerick, Units 1 and 2 - Eighth 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

ML17059D129
Person / Time
Site:	Limerick
Issue date:	02/28/2017
From:	Jim Barstow Exelon Generation Co
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
EA-12-049, RS-17-020, TAC MF0847, TAC MF0848, TAC MF0854, TAC MF0855
Download: ML17059D129 (16)

Text

Exelon RS-17-020 February 28, 2017 U.S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555-0001 Limerick Generating Station, Units 1 and 2 Renewed Facility Operating License Nos. NPF-39 and NPF-85 NRC Docket Nos. 50-352 and 50-353 Order No. EA-12-049

Subject:

Eighth Six-Month Status Report in Response to March 12, 2012 Commission Order Modifying Licenses with Regard to Requirements for Mitigation Strategies for Design-Basis External Events (Order Number EA-12-049)

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," dated March 12, 2012 2. NRC Interim Staff Guidance JLD-ISG-2012-01, "Compliance with Order EA-12-049, Order Modifying Licenses with Regard to Requirements for Mitigation Strategies for Beyond-Design-Basis External Events," Revision 0, dated August 29, 2012 3. NEI 12-06, "Diverse and Flexible Coping Strategies (FLEX) Implementation Guide," Revision 0, dated August 2012 4. Exelon Generation Company, LLC's Initial Status Report in Response to March 12, 2012 Commission Order Modifying Licenses with Regard to Requirements for Mitigation Strategies tor Beyond-Design-Basis External Events (Order Number EA-12-049), dated October 25, 2012 5. Exelon Generation Company, LLC 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), dated February 28, 2013 (RS-13-022)

6. Exelon Generation Company, LLC 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), dated August 28, 2013 (RS-13-123)

7. Exelon Generation Company, LLC 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), dated February 28, 2014 (RS-14-012)

U.S. Nuclear Regulatory Commission Integrated Plan Report to EA-12-049 February 28, 2017 Page 2 8. Exelon Generation Company, LLC 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), dated August 28, 2014 (RS-14-210)

9. Exelon Generation Company, LLC 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), dated February 27, 2015 (RS-15-021)

10. Exelon Generation Company, LLC Fifth 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), dated August 28, 2015 (RS-15-212)

11. Exelon Generation Company, LLC Sixth 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), dated February 26, 2016 (RS-16-024)

12. Exelon Generation Company, LLC Seventh 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), dated August 26, 2016 (RS-16-147)

13. NRC letter to Exelon Generation Company, LLC, Limerick Generating Station, Units 1 and 2 -Interim Staff Evaluation Relating to Overall Integrated Plan in Response to Order EA-12-049 (Mitigation Strategies) (TAC Nos. MF0847 and MF0848), dated January 10, 2014 14. NRC letter to Exelon Generation Company, LLC, Limerick Generating Station, Units 1 and 2 -Report for the Audit Regarding Implementation of Mitigating Strategies and Reliable Spent Fuel Pool Instrumentation Related to Orders EA-12-049 and EA-12-051 (TAC Nos. MF0847, MF0848, MF0854, and MF0855), dated March 17, 2015 On March 12, 2012, the Nuclear Regulatory Commission

("NRC" or "Commission")

issued an order (Reference

1) to Exelon Generation Company, LLC (EGC). Reference 1 was immediately effective and directs EGC to develop, implement, and maintain guidance and strategies to maintain or restore core cooling, containment, and spent fuel pool cooling capabilities in the event of a beyond-design-basis external event. Specific requirements are outlined in Attachment 2 of Reference

1. Reference 1 required submission of an initial status report 60 days following issuance of the final interim staff guidance (Reference

2) and an overall integrated plan pursuant to Section IV, Condition C. Reference 2 endorses industry guidance document NEI 12-06, Revision O (Reference

3) with clarifications and exceptions identified in Reference

2. Reference 4 provided the EGC initial status report regarding mitigation strategies.

Reference 5 provided the Limerick Generating Station, Units 1 and 2 overall integrated plan. Reference 1 requires submission of a status report at six-month intervals following submittal of the overall integrated plan. Reference 3 provides direction regarding the content of the status reports. References 6, 7, 8, 9, 10, 11, and 12 provided the first, second, third, fourth, fifth, sixth, and seventh six-month status reports, respectively, pursuant to Section IV, Condition C.2, of Reference 1 for Limerick Generating Station. The purpose of this letter is to provide the eighth U.S. Nuclear Regulatory Commission Integrated Plan Report to EA-12-049 February 28, 2017 Page 3 six-month status report pursuant to Section IV, Condition C.2, of Reference 1, that delineates progress made in implementing the requirements of Reference

1. The enclosed report provides an update of milestone accomplishments since the last status report, including any changes to the compliance method, schedule, or need for relief and the basis, if any. The enclosed report also addresses the NRC Interim Staff Evaluation Open and Confirmatory Items contained in Reference 13, and any NRC Audit Report open items contained in Reference

14. This letter contains no new regulatory commitments.

If you have any questions regarding this report, please contact David J. Distel at 610-765-5517.

I declare under penalty of perjury that the foregoing is true and correct. Executed on the 28 1 h day of February 2017. Respectfully submitted, JameRa:: LJ: Director -Licensing

& Regulatory Affairs Exelon Generation Company, LLC

Enclosure:

Limerick Generating Station, Units 1 and 2 Eighth Six-Month Status Report for the Implementation of Order EA-12-049, Order Modifying Licenses with Regard to Requirements for Mitigation Strategies for Beyond-Design-Basis External Events cc: NRC Regional Administrator

-Region I NRC Senior Resident Inspector

-Limerick Generating Station NRC Project Manager, NRA -Limerick Generating Station Mr. John D. Hughey, NRR/JLD/JOMB, NRC Director, Bureau of Radiation Protection

-Pennsylvania Department of Environmental Resources R.R. Janati, Chief, Division of Nuclear Safety, Pennsylvania Department of Environmental Protection, Bureau of Radiation Protection Enclosure Limerick Generating Station, Units 1 and 2 Eighth Six-Month Status Report for the Implementation of Order EA-12-049, Order Modifying Licenses with Regard to Requirements for Mitigation Strategies for Design-Basis External Events (12 pages)

Limerick Generating Station, Units 1 and 2 Eighth Six Month Status Report for the Implementation of FLEX February 28, 2017 Enclosure Limerick Generating Station, Units 1 and 2 Eighth Six Month Status Report for the Implementation of Order EA-12-049, Issuance of Order to Modify Licenses with Regard to Requirements for Mitigation Strategies for Beyond-Design-Basis External Events 1 Introduction Limerick Generating Station, Units I and 2 developed an Overall Integrated Plan (Reference 1 in Section 8), documenting the diverse and flexible strategies (FLEX), in response to NRC Order EA-12-049 (Reference 2). This enclosure provides an update of milestone accomplishments since submittal of the last status report, including any changes to the compliance method, schedule, or need for relief/relaxation and the basis, if any. 2 Milestone Accomplishments The following milestone(s) have been completed since the August 26, 2016 status report (Reference

19) and are current as of January 25, 2017.

• None. 3 Milestone Schedule Status The following provides an update to Attachment 2 of the Overall Integrated Plan (Reference I). It provides the activity status of each item, and whether the expected completion date has changed. The dates are planning dates subject to change as design and implementation details are developed.

The need for relief/ relaxation on site implementation of Order EA-12-049 is provided in Section 5 of this enclosure.

Milestone Schedule Site: Limerick Generating Station

• Target Revised Target Activity Completion Activity Status Completion Date Date Submit 60 Day Statu s Report October 2012 Complete Submit Overall Integrated Plan February 2013 Complete Contract with RRC October 2012 Complete Submit 6 Month Updates: Update 1 Augu s t 2013 Complete Update 2 February 2014 Complete Update 3 Augu s t 2014 Complete Page 1 of 12 Limerick Generating Station, Units I and 2 Eighth Six Month Status Report for the Implementation of FLEX February 28, 20 I 7 Target Activity Completion Activity Status Date Update 4 February 20 I 5 Complete Update 5 August 2015 Complete Update 6 February 20 I 6 Complete Update 7 August 2016 Complete Update 8 February 20 I 7 Complete wit h this su bmittal Update 9 August 20 17 Not Started Update IO February 20 I 8 Not Started Submit Completion Report April 2018 Not Started Modification Development

& Implementation:

Unit I Modification Development (All September 20 I 5 Complete FLEX Pha ses) Unit I Modification Impl ementation (All April 2016 Complete FLEX Phases) Unit 2 Modification Development (All November 2014 Complete FLEX Phases) Unit 2 Modification Impl ementation (All April 2015 Complete FLEX Phases) Procedures

Create Site-Specific Procedure s April 2015 Complete Validate Procedures (NEI I 2-06, Sect. March 2015 Complete I I .4.3) Create Maintenance Procedures April 2015 Complete Perform Staffing Analysis November 20 I 4 Complete Storage Plan and Construction October 20 I 5 Complete FLEX Equipment Acquisition Ap ril 2015 Complete Training Completion April 2015 Complete Regional Response Center Operational December 2014 Complete Page 2 of 12 Revised Target Completion Date Limerick Generating Station, Units 1 and 2 Eighth Six Month Status Report for the Implementation of FLEX February 28, 2017 Activity Unit I FLEX Implementation Unit 2 FLEX Implementation Full Site FLEX Implementation 4 Changes to Compliance Method None Target Completion Activity Status Date April 2018 Started See Section 5 May 2017 Started See Section 5 April 2018 Started See Section 5 5 Need for Relief/Relaxation and Basis for the Re li ef/Relaxation This section provide.., a summary of needed relief/relaxation only. Revised Target Completion Date Date aligns with end of 2R 14 Refuel Outage Limerick Generating Station is in compliance with the aspects of Reference 1 regarding Unit I and Unit 2 Mitigation Strategies that do not rely upon a Hardened Containment Vent System. Limerick Generating Station submitted the request for relaxation to the NRC by letter dated February 26, 2014 (Reference 8). The NRC approved the Limerick relaxation request for full compliance of NRC Order EA-12-049 by letter dated April 15, 2014 (Reference 9). 6 Open Items from Overall Integrated Plan and Draft Safety Evaluation The following tables provide a summary of the open items documented in the Overall Integrated Plan, the Draft Safety Evaluation (SE), or the NRC Audit Report, and the status of each item. Page 3 of 12 Limerick Generating Station, Units 1 and 2 Eighth Six Month Status Report for the Implementation of FLEX February 28, 2017 Section Reference Overall Integrated Plan Open Item Status Sequence of Events (p. 8) The times to complete actions in the Events Complete (Reference

17) Timeline are based on operating judgment, conceptual designs, and current supporting analyses.

The final timeline will be time validated once detailed designs are completed and procedures developed.

Sequence of Events (p. 7) Initial evaluations were used to determine the Complete (Reference l 0) Installed Phase 1 fuel pool timelines.

Formal calculations will Equipment (p.37) be performed to validate this information during development of the spent fuel pool cooling strategy detailed design. Sequence of Events (p. 7) Analysis of deviations between Exelon's Complete (Reference

4) engineering analyses and the analyses contained in BWROG Document NEDC-33771 P, "GEH Evaluation of FLEX Implementation Guidelines" and documentation of results was not completed and submitted with the Overall Integrated Plan (Reference l). Identify how strategies Transportation routes will be developed from Complete (Reference

17) will be deployed in all the equipment storage area to the FLEX modes staging areas. An administrative program will (p. 11) be developed to ensure pathways remain clear or compensatory actions will be implemented to ensure all strategies can be deployed during all modes of operation.

Identification of storage areas and creation of the administrative program are open items. Identify how the An administrative program for FLEX to Complete (Reference 1 7) programmatic controls establish responsibilities, and testing & will be met (p. 12) maintenance requirements will be implemented.

Sequence of Events (p. 9) Additional work will be performed during Complete (Reference

17) detailed design development to ensure Suppression Pool temperature will support RCIC operation, in accordance with approved BWROG analysis, throughout the event. Page 4 of 12 Limerick Generating Station, Units 1 and 2 Eighth Six Month Status Report for the Implementation of FLEX February 28, 2017 Section Reference Overall Integrated Plan Open Item Status Portable Equip Phase 2 Complete an evaluation of the spent fuel pool Complete (Reference

11) (p. 50) area for steam and condensation. Installed Equip Phase 1 Evaluate the habitability conditions for the Complete (Reference

17) (p.47) Main Control Room and develop a strategy to maintain habitability.

Portable Equip Phase 2 (p. 49) Installed Equip Phase 1 Develop a procedure to prop open battery Complete (Reference

17) (p.47) room doors upon energizing the battery chargers to prevent a buildup of hydrogen in Portable Equip Phase 2 the battery rooms. (p. 50) Item Number Interim Staff Evaluation (ISE) Status Open Items I Confirmatory Actions Open Item 3.1.1.2.A NEI 12-06 states that if power is required to Complete (Reference 10 ) move or deploy the equipment (e.g., to open the door from a storage location), then power supplies should be provided as part of the deployment.

The Integrated Plan did not address whether or not power would be required to move or deploy equipment and thus this evaluation mu s t be completed satisfactorily.

Open Item 3.1.1.3.A The licensee did not address actions to be Complete (Reference

17) taken if key instruments were lost due to a seismic event, as specified in NEI 12-06, section 5.3.3. Verify that this activity is completed satisfactorily. Open Item 3.1.2.2.A Further review is required regarding how the Complete (Reference

7) licensee will address NEI 12-06 Section Complete (Reference

17) N RC Audit Open Item 6.2.3.2 deployment considerations 2, 4, 5, and 8 with respect to transient floods. This review shall include an applicable procedure review. Page 5 of 12 Item Number Open Item 3.2.3.A Open Item 3.2.4.2.C Open Item 3.4.A Confirmatory Item 3.1.1.4.A Confirmatory Item 3.1.5.2.A Confirmatory Item 3.2.1.l.A Limerick Generating Station, Units I and 2 Eighth Six Month Status Report for the Implementation of FLEX February 28, 2017 Interim Staff Evaluation (ISE) Status Open Items I Confirmatory Actions With regard to maintaining containment, the Complete (Reference

17) implementation of Boiling Water Reactor Owners Group (BWROG) Emergency Procedure Guideline (EPG)/Severe Accident Guideline (SAG), Revision 3, including any associated plant-specific evaluations, must be completed in accordance with the provisions of NRC letter dated January 9, 2014. With regard to elevated temperatures in Complete (Reference

10) general, the licensee should provide an evaluation of the impact of elevated temperatures, as a result of loss of ventilation and/or cooling, on electrical equipment being credited as part of the ELAP strategies (e.g., electrical equipment in the RCIC pump rooms). The licensee should provide details that Complete (Reference

11) demon s trate the minimum capabilities for off site resources will be met, per NEI I 2-06 Section 12.2. With regard to offsite resources , confirm that Complete (Reference

17) the licensee develops a plan that will address the logistics for equipment transportation, area set up, and other needs for ensuring the equipment and commodities to sustain the site's coping strategies. The licensee stated that the design of the Complete (Reference

11) storage facilities will include provisions to ensure the equipment storage facilities are not impacted by high temperatures. Confirm that this is evaluated appropriately. Benchmarks must be identified and discussed Complete (Reference l 0) which demonstrate that Modular Accident Analysis Program (MAAP) is an appropriate code for the simulation of an ELAP event at LGS, consistent with the NRC endorsement of the industry position paper on MAAP. Page 6 of 12 Item Number Confirmatory Item 3.2.1.1.8 Confirmatory Item 3.2.1.1.C Confirmatory Item 3.2.1.1.D Confirmatory Item 3.2.1.3.A Limerick Generating Station, Units 1 and 2 Eighth Six Month Status Report for the Implementation of FLEX February 28, 2017 Interim Staff Eva l uation (ISE) Status Open Items I Confirmatory Actions Confirm that the collapsed reactor pressure Complete (Reference I 0) vessel level remains above Top of Active Fuel and the reactor coolant system cool down rate is within technical specifications limits. Confirm that MAAP is used in accordance Complete (Reference

10) with Sections 4.1, 4.2, 4.3, 4.4, and 4.5 of the June 2013 position paper. Confirm that, in using MAAP, the licensee Complete (Reference

10) identifies and justifies the subset of key modeling parameters cited from Tables 4-1 through 4-6 of the "MAAP Application Guidance, Desktop Reference for Using MAAP Software, Revision 2" (Electric Power Research Institute Report 1 020236). The licensee stated that the "times to complete Complete (Reference

17) actions in the events timeline are based on ... current supporting analyses." Confirm that NRC Audit Open Item the final timeline is validated once detailed designs are completed and procedures are developed.

Confirmatory Item The licensee stated that the detailed design Complete (Reference

17) 3.2.1.4.A will determine containment heat-up rate and the subsequent impacts on RCIC operation and the need for any modifications. Confirm that this evaluation is completed satisfactorily.

Confirmatory Item The licensee identified two RCIC room Complete (Reference

7) 3.2.1.4.B switch set points that were above the predicted maximum temperature but pointed out that the "RCIC Equipment Room Delta Temperature High" setpoint was below that temperature at 109 °F. It is not clear whether or not any of the setpoints would have an adverse impact on the planned use of the RCIC as a mitigation strategy.

Thus, further clarification is needed for this issue. Page 7 of 12 Item Number Confirmatory Item 3.2. 1.4.C Confirmatory Item 3.2.1.7.A Confirmatory Item 3.2.1.8.A Confirmatory Item 3.2. I .8.B Limerick Generating Station, Units I and 2 Eighth Six Month Status Report for the Implementation of FLEX February 28, 20 I 7 Interim Staff Evaluation (ISE) Status Open Items I Confirmatory Actions Becau se the Integrated Plan make s reference Complete (Reference I 0) to use of the Pha se 3 equipment as backup , the Integrated Plan should address the guidance of NEI 12-06 regarding site procedures for Phase 3 implementation. The licensee addressed this concern during the audit response and stated that LGS would ensure connection capabilities of the Phase 3 offsite equipment to site systems and would develop any procedural guidance required for those connections.

Confirm that the connections for the Phase 3 equipment have been properly d e termined , once the details are finalized.

The licensee stated that LGS plans to abide by Complete (Reference I 2) the generic resolution for refueling and cold Complete (Reference

17) shutdown conditions. The licen se e s tated that a review is in progre ss to develop a plan to address potential plant s pecific i ss u es associated with implementing the generic approach.

Confirm that this evaluation is completed satisfactorily.

The licensee stated that the final de s ign of the Complete (Reference I 0) FLEX pump suction will determine if additional screens are required. Confirm that the potential for entrained debris as a re s ult of extreme external hazards (e.g., suspended so lids especially during flood conditions, or from high wind debris) in the cooling water from the spray pond i s addressed. In s ufficient technical information i s pre se nted Complete (Reference I 0) or referenced in the Integrated Plan to confirm the ability of the portable FLEX pump s to deliver the required flow through the system of FLEX ho ses, couplings, valves, e le va tion changes, etc. for the configurations described. Confirm that these evaluations are completed and documented. Page 8 of 12 Limerick Generating Station, Units 1 and 2 Eighth Six Month Status Report for the Implementation of FLEX February 28, 2017 Item Number Interim Staff Evaluation (ISE) Status Open Items I Confirmatory Actions Confirmatory Item The licensee stated that formal calculations Complete (Reference l 0) 3.2.2.A will be performed to validate the timing required for supplying cooling water to the spent fuel pool. Confirm that these calculations are performed, with acceptable results. Confirmatory Item It was not clear from the information Complete (Reference

11) 3.2.4.2.A presented in the Integrated Plan what analysis or technical basis was used to conclude that NRC Audit Open Item the battery room temperature rise is inconsequential.

Also, no discussion was presented to address possible low temperature effects. Confirm the adequacy of the battery room ventilation to protect the batteries from the effects of elevated or lowered temperatures.

Confirmatory Item The licensee stated that battery room Complete (Reference

17) 3.2.4.2.B ventilation will be addressed through procedure changes and that the proposed methods of ventilation, open doors and fans, will be confirmed during the detailed design process. Confirm that this is completed sati s factori I y. Confirmatory Item Confirm that the proposed communications Complete (Reference

19) 3.2.4.4.A upgrades in the licensee's communications assessment are completed as planned. NRC Audit O p en Item Confirmatory Item The licensee stated that keys for access to the Complete (Reference l l) 3.2.4.5.A plant are available to security, the shift manager and to the radiation protection group. The licensee further stated that plant areas requiring access as part of the FLEX response, will be evaluated to determine if sufficient keys are available or if additional keys will be required.

Confirm that this evaluation is completed.

Co nfirmatory Item According to the licensee, habitability Complete (Reference

17) 3.2.4.6.A conditions will be evaluated and a strategy will be developed for the main control room. Confirm that the strategy and associated support analyses are completed.

Page 9 of 12 Limerick Generating Station, Units 1 and 2 Eighth Six Month Status Report for the Implementation of FLEX February 28, 2017 Item Number Interim Staff Evaluation (ISE) Status Open Items I Confirmatory Actions Confirmatory Item With regard to the fuel building habitability, Complete (Reference

17) 3.2.4.6.B the licensee acknowledged that the evaluation of the spent fuel pool area for steam and NRC Audit Open Item condensation has not yet been performed.

Confirm that this evaluation is completed, and its resulting conclusions satisfactorily addressed.

Confirmatory Item The Integrated Plan did not provide Complete (Reference I 0) 3.2.4.8.A information regarding the technical basis for the selection and size of the FLEX generators to be used in support of the coping strategies.

Confirm that this evaluation is satisfactorily completed.

Confirmatory Item The licensee stated minimum limit for the de Complete (Reference

7) 3.2.4.10.B bus voltage is 105 volts. More information is needed to understand if this minimum voltage provides for sufficient operating voltages at the device terminals to ensure proper operation in suooort of the strategies.

Confirmatory Item Although the licensee addressed the potential Complete (Reference

12) 3.2.4.10.C adverse impact from load shedding on main generator hydrogen control, the licensee needs to address any other potential adverse impacts to mitigation strategies resulting from the load shed plan. Item Number NRC Audit Open Item s Status (Reference

12) A Q-22 049-RAI-Limerick-22:

Support Systems Complete (Reference

17) Ventilation

-Battery Room. Provide a discussion of battery room ventilation to prevent hydrogen accumulation while recharging the batteries in phase 2 or 3. In your response, include a descripti o n of the exhaust path if it is different than the design basis. Also provide information on the adequacy of the ventilation provided in the battery room to protect the batteries from the effects of extreme high and low temperatures.

Page IO of 12 Item Number Limerick Generating Station, Units I and 2 Eighth Six Month Status Report for the Implementation of FLEX February 28, 2017 NRC Audit Open Items (Reference

12) Status OIP-4 Identify how strateg ie s will be deployed in all Complete (Reference

17) modes (OIP p. 11) Transportation routes will be developed from the equipment storage area to the FLEX staging areas. An administrative program will be developed to ensure pathways remain clear or compensatory actions will be implemented to ensure all strategies can be deployed during all modes of operation. Identification of storage areas and creation of the administrative program are open items. 7 Potential Draft Safety Evaluation Impacts There are no potential impacts to the Draft Safety Evaluation identified at this time. 8 References The following references support the updates to the Overall Integrated Plan described in this enclosure.

I. Exelon Generation Company, LLC, 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), dated February 28, 2013 (RS-13-022)

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," dated March 12,2012 3. NRC Order EA-13-109, "Issuance of Order to Modify Licenses with Regard to Reliable Hardened Containment Vents Capable of Operation Under Severe Accident Conditions," dated June 6, 2013 4. Exelon Generation Company, LLC, 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), dated August 28, 2013 (RIS13-123) 5. NRC Letter to Exelon Generation Company, LLC, Limerick Generating Station Units 1 and 2, Interim Staff Evaluation Relating to Overall Integrated Plan in Response to Order EA-12-049 (Mitigating Strategies) dated January 10, 2014 6. NEI 12-06, "Diverse and Flexible Coping Strategies (FLEX) Implementation Guide," Revision 0, dated August 2012 7. Exelon Generation Company, LLC, 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), dated February 28, 2014 (RIS 14-012) Page 11of12 Limerick Generating Station, Units 1 and 2 Eighth Six Month Status Report for the Implementation of FLEX February 28, 2017 8. Exelon Generation Company, LLC, Limerick Generating Station Units I and 2, "Request for Relaxation from NRC Order EA-12-049, "Order Modifying Licenses With Regard To Requirements For Mitigation Strategies For Beyond-Design-Basis External Events." Dated February 26, 2014 (RS-14-044)

9. NRC Letter to Exelon Generation Company, LLC, Limerick Generating Station, Units 1 and 2 -Relaxation of Certain Schedular Requirements for Order EA-12-049 "Issuance of Order to Modify Licenses with regard to Requirements for Mitigation Strategies for Beyond Design Basis External Events." Dated April 15, 2014 10. Exelon Generation Company, LLC, 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), dated August 28, 2014 (RS-14-210)

11. Exelon Generation Company, LLC, 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), dated February 27, 2015 (RS-15-021)

12. NRC Letter to Exelon Generation Company, LLC, Limerick Generating Station, Units 1 and 2-Report for the Audit Regarding Implementation of Mitigating Strategies and Reliable Spent Fuel Pool Instrumentation Related to Orders EA-12-049 and EA-12-051, dated March 17, 2015 13. Exelon Generation Company, LLC letter to USNRC, Request for Schedule Relaxation from NRC Order EA-12-049, "Order Modifying Licenses With Regard To Requirements For Mitigation Strategies For Beyond-Design-Basis External Events" dated April 2, 2015 (RS-15-101)

14. NRC Letter to Exelon Generation Company, LLC, Limerick Generating Station, Unit 2, Relaxation of Certain Schedule Requirements for Order EA-12-049, "Issuance of Order to Modify Licenses with Regard to Requirements for Mitigation Strategies for Beyond Design Basis External Events," dated April 29, 2015 15. Exelon Generation Company, LLC letter to USNRC, Request for Second Schedule Relaxation from NRC Order EA-12-049, "Order Modifying Licenses With Regard To Requirements For Mitigation Strategies For Beyond-Design-Basis External Events" dated July 9, 2015 (RS-15-183)

16. NRC Letter to Exelon Generation Company, LLC, Limerick Generating Station, Unit 2 -180 day Relaxation of Certain Schedule Requirements for Order EA-12-049, "Issuance of Order to Modify Licenses with Regard to Requirements for Mitigation Strategies for Beyond Design Basis External Events," dated July 20, 2015 17. Exelon Generation Company, LLC, 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), dated August 28, 2015 (RS-15-212)

18. Exelon Generation Company, LLC, Sixth 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), dated February 26, 2016 (RS-16-024)

19. Exelon Generation Company, LLC, Seventh 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), dated August 26, 2016 (RS-16-147) 9 Attachments

1. None Page 12 of 12