RS-14-210, 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)

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)

ML14241A285
Person / Time
Site:	Limerick
Issue date:	08/28/2014
From:	Jim Barstow Exelon Generation Co
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
EA-12-049, RS-14-210
Download: ML14241A285 (26)

Text

Exelon Generation Order No. EA-12-049 RS-14-210 August 28, 2014 U.S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555-0001 Limerick Generating Station, Units 1 and 2 Facility Operating License Nos. NPF-39 and NPF-85 NRC Docket Nos. 50-352 and 50-353

Subject:

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)

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 for 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 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 049), dated February 28, 2014 (RS-14-012)

U.S. Nuclear Regulatory Commission Integrated Plan Report to EA-12-049 August 28, 2014 Page2

8. NRG 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 On March 12, 2012, the Nuclear Regulatory Commission ("NRG" or "Commission") issued an order (Reference 1) to Exelon Generation Company, LLC (EGG). Reference 1 was immediately effective and directs EGG 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 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 0 (Reference 3) with clarifications and exceptions identified in Reference 2. Reference 4 provided the EGG 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 and 7 provided the first and second 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 third 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 NRG Interim Staff Evaluation Open and Confirmatory Items contained in Reference 8.

This letter contains no new regulatory commitments. If you have any questions regarding this report, please contact David P. Helker at 610-765-5525. '

I declare under penalty of perjury that the foregoing is true and correct. Executed on the 28th day of August 2014.

Respectfully submitted, d~~

James Barstow Director - Licensing & Regulatory Affairs Exelon Generation Company, LLC

Enclosure:

1. Limerick Generating Station, Units 1 and 2 Third 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

U.S. Nuclear Regulatory Commission Integrated Plan Report to EA-12-049 August 28, 2014 Page 3 cc: Director, Office of Nuclear Reactor Regulation NRG Regional Administrator - Region I NRG Senior Resident Inspector- Limerick Generating Station, Units 1 and 2 NRG Project Manager, NRA - Limerick Generating Station, Units 1 and 2 Ms. Jessica A. Kratchman, NRR/JLD/PMB, NRG Mr. Jack R. Davis, NRR/DPR/MSD, NRG Mr. Eric E. Bowman, NRR/DPR/MSD, NRG Mr. Jeremy S. Bowen, NRR/DPR/MSD/MSPB, NRG Mr. Robert L. Dennig, NRR/DSS/SCVB, NRG Mr. John D. Hughey, NRR/DPR/MSD/MSPB, NRG 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 Third 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 (11 pages)

Limerick Generating Station, Units 1 and 2 Third Six Month Status Report for the Implementation of FLEX August 28, 2014 Enclosure Limerick Generating Station, Units 1 and 2 Third 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 1 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 February 28, 2014 status report (Reference 7) and are current as of August OL 2014.

• A contract has been awarded for the purchase of the portable FLEX generators.

3 Milestone Schedule Status The following provides an update to Attachment 2 of the Overall Integrated Plan (Reference 1). 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 Status Report Octobet 2012 Complete Submit Overall Integrated Plan February 2013 Complete Contract with National SAFER Response October 2012 Complete Center Submit 6 Month Updates:

Update 1 August 2013 Complete Update 2 February 2014 Complete Update 3 August2014 Complete with Page 1of11

Limerick Generating Station, Units 1 and 2 Third Six Month Status Report for the Implementation of FLEX August 28, 2014 Target Revised Target Activity Completion Activity Status Completion Date Date this submittal Update 4 February 2015 Not Started Update 5 August 2015 Not Started Update 6 February 2016 Not Started Not required Update 7 August 2016 Not Started based on April 2016 second unit live date Submit Completion Report April 2016 Not Started Modification Development &

Implementation:

Unit 1 Modification Development (All February 2015 Started FLEX Phases)

Unit 1 Modification Implementation (All April 2016 Started FLEX Phases)

November 2014 Unit 2 Modification Development (All (Mod March 2014 Started FLEX Phases) implementation not affected)

Unit 2 Modification Implementation (All April 2015 Started FLEX Phases)

Procedures:

Create Site-Specific Procedures April 2015 Started Validate Procedures (NEI 12-06, Sect.

February 2015 Not Started 11.4.3)

Create Maintenance Procedures April 2015 Not Started Perform Staffing Analysis November 2014 Not Started Storage Plan and Construction April 2015 Started FLEX Equipment Acquisition April 2015 Started Training Completion April 2015 Started National SAFER Response Center Started December 2014 Operational Page 2of11

Limerick Generating Station, Units 1 and 2 Third Six Month Status Report for the Implementation of FLEX August 28, 2014 Target Revised Target Activity Completion Activity Status Completion Date Date Unit 1 FLEX Implementation April 2016 Started Unit 2 FLEX Implementation April 2015 Started Full Site FLEX Implementation April 2016 Started 4 Changes to Compliance Method There are no changes to the FLEX strategies identified at this time.

5 Need for Relief/Relaxation and Basis for the Relief/Relaxation This section provides a summary of needed relief/relaxation only. The specific details will be submitted in a separate document.

NRC Order EA-12-049 requires implementation of Mitigation Strategies to include procedures, guidance, training, and acquisition, staging, or installing of equipment needed for the strategies. The Overall Integrated Plan (Reference 1) provided the Limerick Generating Station response to NRC Order EA 049. Reference 4 identifies that delays in implementing the Hardened Containment Vent System as required by NRC Order EA-13-109 will also affect implementation of the Mitigation Strategies Order EA-12-049 actions.

The Overall Integrated Plan (Reference 1) enclosure describes the Limerick Generating Station Mitigation Strategies that are based on venting the containment using the Hardened Containment Vent System. It also describes that a modification to install a Hardened Containment Vent System (HCVS) is required.

Thus, the Limerick Generating Station NRC Order EA-12-049 response provided in Reference 1 was premised on installation and use of a Hardened Containment Vent System as required by NRC Order EA-12-050.

Upon issuance of NRC Order EA-13-109, the NRC staff changed technical and schedule requirements applicable to the Hardened Containment Vent System and rescinded the requirements of NRC Order EA-12-050.

As a result, full compliance to the Mitigation Strategies required by NRC Order EA-12-049 and described in Reference 1 for Limerick Generating Station Units 1 and 2 will not be achieved until compliance to NRC Order EA-13-109 is achieved. Relief/relaxation from the NRC Order EA-12-049 IV.A.2 requirements is required.

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Limerick Generating Station, Units 1 and 2 Third Six Month Status Report for the Implementation of FLEX August 28, 2014 Limerick Generating Station will be in compliance with the aspects of the Reference l, Unit 1 and Unit 2 Mitigation Strategies that do not rely upon a Hardened Containment Vent System unless otherwise described.

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 or the Draft Safety Evaluation (SE) and the status of each item.

Section Reference Overall Integrated Plan Open Item Status Sequence of Events (p. 8) The times to complete actions in the Events Started 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 with this Installed Phase 1 fuel pool timelines. Formal calculations will submittal - Calculation Equipment (p.37) be performed to validate this information LM-0708 documents fuel during development of the spent fuel pool pool heat up time lines and cooling strategy detailed design. has been posted on the eportal.

Sequence of Events (p. 7) Analysis of deviations between Exelon' s Completed (Reference 4) engineering analyses and the analyses contained in BWROG Document NEDC-33771P, "GEH Evaluation of FLEX Implementation Guidelines" and documentation of results was not completed and submitted with the Overall Integrated Plan (Reference 1).

Identify how strategies Transportation routes will be developed from Started will be deployed in all the equipment storage area to the FLEX Storage Building locations modes staging areas. An administrative program will for equipment have been (p. 11) be developed to ensure pathways remain clear identified and travel routes or compensatory actions will be implemented to point of use determined.

to ensure all strategies can be deployed during A contract has been all modes of operation. established for construction.

Identification of storage areas and creation of the administrative program are open items.

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Limerick Generating Station, Units 1 and 2 Third Six Month Status Report for the Implementation of FLEX August 28, 2014 Identify how the An administrative program for FLEX to Started. A corporate fleet-programmatic controls establish responsibilities, and testing & wide program has been will be met (p. 12) maintenance requirements will be developed and a template implemented. for site programs is in review.

Sequence of Events (p. 9) Additional work will be performed during Started detailed design development to ensure Suppression Pool temperature will support RCIC operation, in accordance with approved BWROG analysis, throughout the event.

Portable Equip Phase 2 Complete an evaluation of the spent fuel pool Started (p. 50) area for steam and condensation.

Installed Equip Phase 1 Evaluate the habitability conditions for the Started (p.47) Main Control Room and develop a strategy to Habitability conditions maintain habitability. within the MCR and other Portable Equip Phase 2 areas of the plant will be (p. 49) maintained with a tool box approach limiting the impact of high temperatures with methods such as supplemental cooling, personnel rotation and/or availability of fluids .

Preliminary analysis indicates that actions in the main control room will not be required until after at least 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> post event; this guidance will be included in site procedures.

Installed Equip Phase 1 Develop a procedure to prop open battery Started (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 Status Open Items I Confirmatory Actions Open Item 3 .1.1 .2.A NEI 12-06 states that if power is required to Complete *with this move or deploy the equipment (e.g., to open submittal - the storage Page 5of11

Limerick Generating Station, Units 1 and 2 Third Six Month Status Report for the Implementation of FLEX August 28, 2014 the door from a storage location), then power building design will not supplies should be provided as part of the require power to open doors deployment. The Integrated Plan did not .or move or deploy address whether or not power would be equipment. Debris required to move or deploy equipment and removal/deployment thus this evaluation must be completed vehicles will be stored in satisfactorily. each robust structure.

Open Item 3.1.1.3.A The licensee did not address actions to be Started 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 6.2.3.2 deployment considerations 2, 4, 5, and 8 with respect to transient floods. This review shall include an applicable procedure review.

Open Item 3.2.3.A With regard to maintaining containment, the Started 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.

Open Item 3.2.4.2.C With regard to elevated temperatures in Complete - calculation LM-general, the licensee should provide an 0689 previously posted on evaluation of the impact of elevated eportal documents that the temperatures, as a result of loss of ventilation currently proceduralized and/or cooling, on electrical equipment being ventilation actions during credited as part of the ELAP strategies (e.g., an SBO are adequate to electrical equipment in the RCIC pump maintain RCIC rooms). temperatures below the EQ room limits during an ELAP event.

Open Item 3.4.A The licensee should provide details that Started demonstrate the minimum capabilities for offsite resources will be met, per NEI 12-06 Section 12.2.

Confirmatory Item With regard to offsite resources, confirm that Started 3.1.1.4.A 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.

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Limerick Generating Station, Units 1 and 2 Third Six Month Status Report for the Implementation of FLEX August 28, 2014 Confirmatory Item The licensee stated that the design of the Started 3.1.5.2.A storage facilities will include provisions to ensure the equipment storage facilities are not impacted by high temperatures. Confirm that this is evaluated appropriately.

Confirmatory Item Benchmarks must be identified and discussed Complete with this 3.2.1.1.A which demonstrate that Modular Accident submittal - LG-MISC-015, Analysis Program (MAAP) is an appropriate "Use of MAAP in support code for the simulation of an ELAP event at of FLEX Implementation" LGS, consistent with the NRC endorsement of has been posted on the the industry position paper on MAAP. eportal. This information is also included as Attachment 1.

Confirmatory Item Confirm that the collapsed reactor pressure Complete with this 3.2.1.1.8 vessel level remains above Top of Active Fuel submittal - LG-MISC-015, and the reactor coolant system cool down rate "Use of MAAP in support is within technical specifications limits. of FLEX Implementation" has been posted on the eportal. This information is also included as Attachment 1.

Confirmatory Item Confirm that MAAP is used in accordance Complete with this 3.2.1.1.C with Sections 4.1, 4.2, 4.3, 4.4, and 4.5 of the submittal - LG-MISC-015, June 2013 position paper. "Use of MAAP in support of FLEX Implementation" has been posted on the eportal. This information is also included as Attachment 1.

Confirmatory Item Confirm that, in using MAAP, the licensee Complete with this 3.2.1.1.D identifies and justifies the subset of key submittal - LG-MISC-015, modeling parameters cited from Tables 4-1 "Use of MAAP in support through 4-6 of the "MAAP Application of FLEX Implementation" Guidance, Desktop Reference for Using has been posted on the MAAP Software, Revision 2" (Electric Power eportal. This information is Research Institute Report 1 020236). also included as Attachment 1.

Confirmatory Item The licensee stated that the "times to complete Future 6 month update 3.2.1.3.A actions in the events timeline are based on ...

current supporting analyses." Confirm that the final timeline is validated once detailed designs are completed and procedures are developed.

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Limerick Generating Station, Units 1 and 2 Third Six Month Status Report for the Implementation of FLEX August 28, 2014 Confirmatory Item The licensee stated that the detailed design Started 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) 3.2.1.4.8 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.

Confirmatory Item Because the Integrated Plan makes reference Complete with this 3.2.1.4.C to use of the Phase 3 equipment as backup, submittal. The hose the Integrated Plan should address the connections and electrical guidance of NEI 12-06 regarding site connections selected as part procedures for Phase 3 implementation. The of the LGS modifications licensee addressed this concern during the are compatible with the audit response and stated that LGS would Phase 3 equipment provided ensure connection capabilities of the Phase 3 by the National SAFER offsite equipment to site systems and would Response Center. This will develop any procedural guidance required for allow National SAFER those connections. Confirm that the Response Center equipment connections for the Phase 3 equipment have to be connected to the LGS been properly determined, once the details are connection points.

finalized.

Confirmatory Item The licensee stated that LGS plans to abide by Future 6 month update 3.2.1.7.A the generic resolution for refueling and cold shutdown conditions. The licensee stated that a review is in progress to develop a plan to address potential plant specific issues associated with implementing the generic approach. Confirm that this evaluation is completed satisfactorily.

Confirmatory Item The licensee stated that the final design of the Complete with this 3.2.1.8.A FLEX pump suction will determine if submittal - Calculation additional screens are required. Confirm that LM-0706 documents this the potential for entrained debris as a result of review and has been posted extreme external hazards (e.g., suspended on the eportal.

. solids especially during flood conditions, or from high wind debris) in the cooling water from the spray pond is addressed.

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Limerick Generating Station, Units 1 and 2 Third Six Month Status Report for the Implementation of FLEX August 28, 2014 Confirmatory Item Insufficient technical information is presented Complete with this 3.2.1.8.8 or referenced in the Integrated Plan to confirm submittal - Calculation the ability of the portable FLEX pumps to LM-0706 documents this deliver the required flow through the system review and has been posted of FLEX hoses, couplings, valves, elevation on the eportal.

changes, etc. for the configurations described.

Confirm that these evaluations are completed and documented.

Confirmatory Item The licensee stated that formal calculations Complete with this 3.2.2.A will be performed to validate the timing submittal - Calculation required for supplying cooling water to the LM-0708 documents this spent fuel pool. Confirm that these review and has been posted calculations are performed, with acceptable on the eportal.

results.

Confirmatory Item It was not clear from the information Started - Preliminary 3.2.4.2.A presented in the Integrated Plan what analysis analysis shows forced or technical basis was used to conclude that battery room ventilation the battery room temperature rise is actions will not be required inconsequential. Also, no discussion was for approximately 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> presented to address possible low temperature after the event.

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 Started - Based on the 3.2.4.2.8 ventilation will be addressed through computations noted above, procedure changes and that the proposed proceduralized actions are methods of ventilation, open doors and fans, being developed to address will be confirmed during the detailed design battery room ventilation.

process. Confirm that this is completed satisfactorily.

Confirmatory Item Confirm that the proposed communications Future 6 month update 3.2.4.4.A upgrades in the licensee's communications assessment are completed as planned.

Confirmatory Item The licensee stated that keys for access to the Future 6 month update 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.

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Limerick Generating Station, Units 1 and 2 Third Six Month Status Report for the Implementation of FLEX August 28, 2014 Confirmatory Item According to the licensee, habitability Started - Preliminary 3.2.4.6.A conditions will be evaluated and a strategy analysis and review will be developed for the main control room. indicates that actions will Confirm that the strategy and associated not be required during the support analyses are completed. first 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> post event.

Confirmatory Item With regard to the fuel building habitability, Started 3.2.4.6.B the licensee acknowledged that the evaluation of the spent fuel pool area for steam and 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 with this 3.2.4.8.A information regarding the technical basis for submittal - generators have the selection and size of the FLEX generators been ordered, ECR 14-to be used in support of the coping strategies. 0019, while not finalized at Confirm that this evaluation is satisfactorily this time, has been completed. completed sufficiently to confirm generator sizing.

Confirmatory Item 3.2.4.1 The licensee stated minimum limit for the de Complete (Reference 7) 0.8 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 Started 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.

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.

1. Limerick Generating Station Units 1 and 2, "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).

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Limerick Generating Station, Units 1 and 2 Third Six Month Status Report for the Implementation of FLEX August 28, 2014

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. Limerick Generating Station Units 1 and 2, "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. 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. Limerick Generating Station Units 1 and 2, "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).

8. Limerick Generating Station Units 1 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. 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 9 Attachments

1. Attachment 1- LG-MISC-015, "Use of MAAP in support of FLEX Implementation" Page 11of11

RM DOCUMENTATION NO. LG-MISC-015 REV: 0 PAGE NO. 1 STATION: Limerick UNIT(S) AFFECTED: Unit 1 and 2 TITLE: Use of MAAP In Support of FLEX Implementation

SUMMARY

(Include UREs incorporated):

MAAP 4.0.6 calculations (LG-MISC-012*R2) were performed to estimate the containment pressure and temperature response to a variety of extended Station Blackout (SBO) events.

The NRC has requested that some additional information be provided relating to the use of MAAP for FLEX analysis as part of the per1odic update to the plants response to EA-12-049.

The attached information is being provided to include in the next update to EA-12-049.

( ] Review required after periodic Update

[ X ] Internal RM Documentation [ ] Extemal RM Documentation Electronic Calculation Data Files: N/A Method g_f Review: [ X ] Detailed [ ) Alternate [ I Review of External Document This RM documentation supersedes: N/A in Its entil'8ty.

Prepared by: Jeff Gabor ~,a,,Sn/,___ -:!h~

Print Sign Date Reviewed by: Gary Hayner Print

1. ¥'file'-

G~

Approved by: Brandon Irvin Print

• Date

Use of MAAP in Support of LGS Response to EA-12-049 TABLE OF CONTENTS Section Page 1.0 PURPOSE AND SCOPE ....... ........ ... .... ....... ....... ..... ..... .. ..... .... .. .. ... ... .. ... .. ...... ..... . 3 2.0 REQUESTED INFORMATION ON THE USE OF MAAP ..... ......... .................. ..... 3 LGS-MISC-015-RO.doc 2

Use of MAAP in Support of LGS Response to EA-12-049 1.0 PURPOSE AND SCOPE The purpose of the included information is to respond to NRC questions relating to the use of MAAP in support of the plant's response to EA-12-049. The MAAP analysis is documented separately in LG-MISC-012-R2.

2.0 REQUESTED INFORMATION ON THE USE OF MAAP In response to the letter of October 3, 2013 from Jack Davis (NRR) to Joe Pollock (NEI),

the following responses have been developed regarding the use of the Modular Accident Analysis Program (MAAP) for estimating accident progression timing in support of the Overall Integrated Plan for Limerick Generating Station.

(1) From the June 2013 position paper, benchmarks must be identified and discussed which demonstrate that MAAP4 is an appropriate code for the simulation of an ELAP event at your facility.

Response to Item 1:

Generic response has been provided in EPRI Technical Report 3002002749, "Technical Basis for Establishing Success Timelines in Extended Loss of AC Power Scenarios in Boiling Water Reactors Using MAAP4 - A Guide to MAAP Thermal-Hydraulic Models".

(2) The collapsed level must remain above Top of Active Fuel (TAF) and the cool down rate must be within technical specification limits.

Response to Item 2:

Attachment 1A of the Limerick Integrated Plan (Feb 2013) states that the operators would commence a cooldown of the RPV at 20 min per E-1, SBO procedure. A controlled cooldown is identified in the SBO procedures, however, it is authorized to exceed 100 °F/hr if plant conditions require a rapid cooldown .

For the MAAP analysis used to simulate the plant response, a single SRV was assumed to be opened to perform the cooldown. The following plot of the RPV pressure from the MAAP analysis confirms this cooldown.

LGS-MISC-015-RO.doc 3

Use of MAAP in Support of LGS Response to EA-12-049 Case: Flex2 1400

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0. 400 0::

200 .. . **- - -

0 0 20 40 60 80 Time (hrs)

For the representative MAAP run (Case Flex 2), RPV water level remains well above Top of active fuel (TAF) for the duration of the analysis. The plot below shows that the lowest RPV level, calculated by MAAP, was approximately 38 ft above the bottom of the reactor vessel. TAF is located at 30.5 ft for Limerick Units 1 and 2. As shown in the following plot, the collapsed RPV water level remains approximately 8' above TAF.

Case: Flex2 60

!5..40 Qi 50

~ 30

..J ii:0:: 20 10 0

0 20 40 60 80 Time (hrs)

LGS-MISC-015-RO.doc 4

Use of MAAP in Support of LGS Response to EA-12-049 (3) MAAP4 must be used in accordance with Sections 4.1, 4.2, 4.3, 4.4, and 4.5 of the June 2013 position paper.

Response to Item 3:

MAAP analysis performed for Limerick was carried out in accordance with Sections 4.1, 4.2, 4.3, 4.4, and 4.5 of the June 2013 position paper, EPRI Technical Report 3002001785, "Use of Modular Accident Analysis Program (MAAP) in Support of Post-Fukushima Applications". Preparation and Review of the MAAP analysis is conducted under engineering training certification guide ENANRM08.

(4) In using MAAP4, the licensee must identify and justify the subset of key modeling parameters cited from Tables 4-1 through 4-6 of the "MAAP4 Application Guidance, Desktop Reference for Using MAAP4 Software, Revision 2 11 (Electric Power Research Institute Report 1020236). This should include response at a plant-specific level regarding specific coding options and parameter choices for key models that would be expected to substantially affect the ELAP analysis performed for that licensee's plant.

Although some suggested key phenomena are identified below, other parameters considered important in the simulation of the ELAP event by the vendor I licensee should also be included.

a. Nodalization

b. General two-phase flow modeling

c. Modeling of heat transfer and losses

d. Choked flow

e. Vent line pressure losses

f. Decay heat (fission products I actinides I etc.)

Response to Item 4:

a. The reactor vessel nodalization is fixed by the MAAP code and cannot be altered by the user, with the exception of the detailed core nodalization. The Limerick MAAP 4.0.6 parameter file divides the core region into 7 equal volume LGS-MISC-015-RO.doc 5

Use of MAAP in Support of LGS Response to EA-12-049 radial regions and 28 axial regions. The axial nodalization represents 25 equal-sized fueled nodes, 1 unfueled node at the top, and 2 unfueled nodes at the bottom. The figure below, taken from the MAAP User's Manual, illustrates the vessel nodalization scheme.

'SRV I

{!! © +

., LOCA

--.....LOCA f©

.3 & Key Sta~

4

© Q Palh aa:sF!ow No.

Separalois

©t ~ ~ HeatSlnk SU/face No.

5 Upper ~HeetSink Down-comer

@) GeneJ&lized

~ @) : Opetling 1.

1 care' L GenerallZed Openlng2 Generaized OpenlngS IZ _ ~

4 (Flow Pa!h 8 Not .Applicable fOr GEBWR's)

Containment nodalization is defined by the user. The standard nodalization scheme (as recommended in the MAAP4.0.6 sample parameter file) is used in the Limerick MAAP 4.0.6 parameter file and represents the following individual compartments:

1. Reactor pedestal region

2. Drywell

3. Wetwell (main pool)

4. Wetwell (under pedestal)

LGS-MISC-015-RO.doc 6

Use of MAAP in Support of LGS Response to EA-12-049 The figure below illustrates the Limerick MAAP containment nodalization along with an identification of containment flow junctions.

Junction l I

01;:!~t.Tiµtion

{ Pede$tal l:loor Node 2 Vent/failure 2 Oowncomers 3 Oram line Node 1 leakage 12 4 Vac breaker 5 Vac breaker 6 ow v enttfaaure 7 WW ven t failure 8 ,9,10 Lower Ped - WW 3

11 Doorway 12 OW leakage Vent/fa i Iure Node 4 Node3 General two-phase flow from the reactor vessel is described in the EPRI Technical Report 3002002749. In the case of the scenario outlined in the integrated plan, flow can exit the RPV via the open SRV(s) and from the assumed recirculation pump seal leakage. Flow from the SRV(s) will be single-phase steam and flow from the recirc pump seal will be single-phase liquid due to the location of the break low in the RPV with RPV level maintained above TAF.

Upon exiting the RPV, the seal leakage will flash a portion of the flow to steam based on saturated conditions in the drywall, creating a steam source and a liquid water source to the drywall. As described in the EPRI Technical Report 3002002749, "Technical Basis for Establishing Success Timelines in Extended Loss of AC Power Scenarios in Boiling Water Reactors Using MAAP4 - A Guide to MAAP Thermal-Hydraulic Models", there are two MAAP parameters that can influence the two-phase level in the RPV - FCO (void concentration factor) and FCHTUR (churn-turbulent critical velocity coefficient). The following table confirms that the parameter values match the recommended values as outlined in the EPRI Technical Report 3002002749.

LGS-MISC-015-RO.doc 7

Use of MAAP in Support of LGS Response to EA-12-049 PARAMETER NAME VALUE USED IN EPRI LIMERICK MAAP ANALYSIS RECOMMENDED VALUE FCO 1.5248 1.5248 FCHTUR 1.53 1.53

b. Modeling of heat transfer and losses from the RPV are described in the EPRI Technical Report 3002002749. The MAAP parameters that control these processes, as defined in the EPRI report, are provided below with the values selected to represent Limerick.

PARAMETER NAME VALUE USED IN COMMENT MAAP ANALYSIS QCO - not-thru-insulation 3.753E6 BTU/hr Plant specific value based on drywell heat transfer from RPV during heat removal to coolers during normal operation . normal operation . Typical values range between 1-2 MW.

FINPLT - number of plates in 8 Plant-specific value reflective insulation XTINS - average reflective 0.3346 ft Plant-specific value insulation thickness At the request of the NRC, the following information, as used in the MAAP analysis, is provided.

PARAMETER DEFINITION PARAMETER NAME IN PARAMETER VALUE MAAP IN MAAP Power level, MWth QCRO 3517 MWT Initial CST water volume, gal VCSTO (ft3) 146,887 gal Initial CST water temperature, F HCST (enthalpy) 110 °F Initial suppression pool water mass, lbm Calculated from input 7,658,000 lbm Initial suppression pool water level, ft XWRBO(i), where i is node 23 ft number for wetwell Initial suppression pool water TWRBO(i) , where i is node 95 °F temperature, F number for wetwell Drywell free volume, ft3 VOLRB(i), where I is node 243,580 ft3 number for drywell (does not include upper pedestal)

Wetwell free volume, ft3 VOLRB(i) - volume of 158,253 ft3 suppression pool water from initial pool mass LGS-MISC-015-RO.doc 8

Use of MAAP in Support of LGS Response to EA-12-049 PARAMETER DEFINITION PARAMETER NAME IN PARAMETER VALUE MAAP IN MAAP Containment vent pressure, psia Refer to MAAP analysis 27 psia document RCIC max flow rate, gpm WVRCIC 600 gpm Max FLEX pump flow rate, gpm Refer to MAAP analysis NA document Lowest set SRV flow rate, lb/hr Derived from SRV area, 933,028 lbm/hr ASRV Ref: UFSAR Table 3A-3 area 0.0993 ft2 Lowest set SRV pressure, psia PSETSV 1184.7psia Recirc pump seal leakage, gpm Value that was used to 36gpm define LOCA area, ALOCA Total leakage used in the transient, gpm Value that was used to 36gpm define LOCA area, ALOCA

c. Choked flow from the SRV and the recirculation pump seal leakage is discussed in the EPRI Technical Report 3002002749. The parameters identified that impact the flow calculation are listed below with input values identified.

PARAMETER NAME VALUE USED IN MAAP EPRI RECOMMENDED ANALYSIS VALUE ASRV - effective flow area 0.0993 ft2 Plant-specific value for relief valve (based on rated flow at pressure)

ALOCA - seal leakage area 5.7E-4 ft2 Plant-specific value (36 gpm at normal conditions)

FCDBRK - discharge 0.75 0.75 coefficient for seal leakage

d. Vent line pressure loss can be represented in two ways. The actual piping flow area can be input along with a discharge coefficient (FCDJ). An alternative method would be to calculate the effective flow area given the estimated piping losses, and input a loss coefficient of 1.0. For the Limerick analysis, the vent area is input based on a 1O" diameter pipe and a discharge coefficient of 0.75 was selected.

e. The decay heat calculation in MAAP is discussed in the EPRI Technical Report 3002002749. Input parameters used to compute the decay heat are LGS-MISC-015-RO.doc 9

Use of MAAP in Support of LGS Response to EA-12-049 identified in the EPRI report and are listed in the following table along with their values used in the Limerick analysis.

LGS-MISC-015-RO.doc 10

Use of MAAP in Support of LGS Response to EA-12-049 PARAMETER NAME VALUE USED IN EPRI RECOMMENDED MAAP ANALYSIS VALUE FENRCH - normal fuel enrichment 0.0385 Plant-specific value EXPO - average exposure 34672.4 MW-day/ton Plant-specific value FCR - total capture rate of U-238 I 0.323 Plant-specific value total absorption rate FFAF - total absorption rate I total 2.30 Plant-specific value fission rate FQFR1 - fraction of fission power due 0.510 Plant-specific value to U-235 and PU-241 FQFR2 - fraction of fission power due 0.405 Plant-specific value to PU-239 FQFR3 - fraction of fission power due 0.085 Plant-specific value to U-238 TIRRAD - average effective irradiation 30816 hours Plant-specific value time for entire core (5) The specific MAAP4 analysis case that was used to validate the timing of mitigating strategies in the integrated plan must be identified and should be available on the ePortal for NRC staff to view. Alternately, a comparable level of information may be included in the supplemental response. In either case, the analysis should include a plot of the collapsed vessel level to confirm that TAF is not reached (the elevation of the TAF should be provided) and a plot of the temperature cool down to confirm that the cool down is within tech spec limits.

Response to Item 5:

The MAAP analysis performed in support of the Limerick Integrated Plan is documented in calculation LG-MISC-012 Rev. 2 and is available on the ePortal site. Case Flex 2 was the specific MAAP run selected to represent the scenario as described in Attachment 1A of the integrated plan.

LGS-MISC-015-RO.doc 11