Text

Three Mile Island, Unit 1 - 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-12-04
	ML16057A010
Person / Time
Site:	Three Mile Island
Issue date:	02/26/2016
From:	David Helker; Exelon Generation Co
To:	; Document Control Desk, Office of Nuclear Reactor Regulation
References
	EA-12-049, RS-16-030, TMl-16-009
	Download: ML16057A010 (19)
	v • d • e

Exelon Generation

(.) RS-16-030 TMl-16-009 February 26, 2016 U.S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555-0001 Three Mile Island Nuclear Station, Unit 1 Renewed Facility Operating License No. DPR-50 NRC Docket No. 50-289 Order No. EA-12-049

Subject:

Sixth 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 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-13-026)

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-13-131)

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-14-016)

U.S. Nuclear Regulatory Commission Integrated Plan Report to EA-12-049 February 26, 2016 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-14-214)

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-15-025)

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-15-216)

11. NRC letter to Exelon Generation

Company, LLC, Three Mile Island Nuclear Station, Unit 1 -Interim Staff Evaluation Relating to Overall Integrated Plan in Response to Order EA-12-049 (Mitigation Strategies)

(TAC No. MF0803),

dated December 17, 2013 12. NRC letter to Exelon Generation

Company, LLC, Three Mile Island Nuclear Station, Unit 1 -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. MF0803 and MF0866},

dated January 11, 2016 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 Three Mile Island Nuclear Station, Unit 1 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 and 10 provided the first, second, third, fourth, and fifth six-month status reports, respectively, pursuant to Section IV, Condition C.2, of Reference 1 for Three Mile Island Nuclear Station, Unit 1. The purpose of this letter is to provide the sixth 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 11, and the NRC Audit Report open items contained in Reference

12.

U.S. Nuclear Regulatory Commission Integrated Plan Report to EA-12-049 February 26, 2016 Page 3 It is noted that open issues were identified by the NRC during the NRC on-site audit review conducted on August 10-13, 2015 that require additional follow-up with the NRC staff and could affect the final strategies.

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 26th day of February 2016. Respectfully submitted, David P. Helker Manager -Licensing

& Regulatory Affairs Exelon Generation

Company, LLC

Enclosure:

1. Three Mile Island Nuclear Station, Unit 1 Sixth 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

-Three Mile Island Nuclear Station, Unit 1 NRC Project Manager, NRR -Three Mile Island Nuclear Station, Unit 1 Mr. John D. Hughey, NRR/JLD/JOMB, NRC Director, Bureau of Radiation Protection

-Pennsylvania Department of Environmental Resources

Chairman, Board of County Commissioners of Dauphin County, PA Chairman, Board of Supervisors of Londonderry

Township, PA R. R. Janati, Chief, Division of Nuclear Safety, Pennsylvania Department of Environmental Protection, Bureau of Radiation Protection Enclosure Three Mile Island Nuclear Station, Unit 1 Sixth 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 (15 pages)

Three Mile Island Nuclear Station, Unit 1 Sixth Six Month Status Report for the Implementation of FLEX, February 26, 2016 Three Mile Island Station, Unit 1 Sixth 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 1 Introduction Three Mile Island Nuclear Station, Unit 1 (TMI) developed an Overall Integrated Plan (Reference 1 in Section 8), documenting the diverse and flexible strategies (FLEX), in response to Reference

2. This enclosure provides an update of milestone accomplishments since submittal of the last status report (August 2015), including any changes to the compliance method, schedule, or need for relief/relaxation and the basis, if any. 2 Milestone Accomplishments Many milestone(s) have been completed since August 28, 2015 and are current as of February 26, 2016:

Engineering is complete except for additional Turbine Building Structural Analysis

Modification installation is complete except for potential additional Turbine Building Structural Modifications

Portable materials to support the strategy have been procured and staged

Procedures have been validated and issued for Hot Shutdown, Hot Standby or Power Ops Modes 3 Milestone Schedule Status The following provides an update to Attachment 2 of the Overall Integrated Plan. 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 revised milestone target completion dates do not impact the order implementation date. Original Target Activity Status Completion Date Submit 60 Day Status Report Complete Submit Overall Integrated Complete Implementation Plan Contract with SNRC Complete 6 Month Updates Update 1 Aug., 2013 Complete Page 1 of 15 Three Mile Island Nuclear Station, Unit 1 Sixth Six Month Status Report for the Implementation of FLEX, February 26, 2016 Original Target Activity Status Completion Date Update 2 Feb., 2014 Complete Update 3 Aug., 2014 Complete Update 4 Feb., 2015 Complete Update 5 Aug., 2015 Complete Update 6 Feb., 2016 Complete with this submittal Modification Development Oct2014 Phase 1 modifications (1) RCP Seal Upgrade Complete Oct2014 Phase 2 modifications (1) FLEX Electrical Power Supply Complete (2) FLEX RCS & SFP Makeup Complete (3) FLEX Feedwater System Complete (4) FLEX Storage Facility Complete (5) Turbine Bldg. Structure Started (6) FLEX platform in Turbine Building Complete (7) FLEX fuel oil supply Complete (8) Spent Fuel Pool Level Complete (9) On Site Communications Complete modification (10) Reactor Building Vent Complete (11) Satellite phone storage Complete (12) Main Steam Seismic Mods Complete (13) Main Steam Missile Protection Complete Oct 2014 Phase 3 modifications None Modification Implementation Nov 2015 Phase 1 modifications (1) RCP Seal Upgrade Complete Page 2 of 15 Three Mile Island Nuclear Station, Unit 1 Sixth Six Month Status Report for the Implementation of FLEX, February 26, 2016 Original Target Activity Status Completion Date Nov 2015 Phase 2 modifications (1) FLEX Electrical Power Supply Complete (2) FLEX RCS & SFP Makeup Complete (3) FLEX Feedwater System Complete (4) FLEX Storage Facility Complete (5) Turbine Bldg. Structural Started (6) Turbine Bldg. FLEX platform Complete (7) FLEX fuel oil supply Complete (8) Spent Fuel Pool Level Complete (9) On Site Communications Complete modification (10) Reactor Building Vent Complete (11) Satellite phone storage Complete (12) Main Steam Seismic Mods Complete (13) Main Steam Missile Protection Complete Nov 2015 Phase 3 modifications None Original Target Activity Status Completion Date Procedure development Jun 2015

Create Site-Specific Procedures Hot Shutdown, Hot Standby & Power Ops Mode procedures are complete.

Heat Up-Cooldown, Cold Shutdown

& Refueling Shutdown Mode procedures are started (Complete by April 30, 2016). Jul2015

Validate Procedures (NEI 12-06, Started (Complete by April 30, Sect. 11 .4.3) 2016) Jun 2015

Create Maintenance Procedures Started (Complete by April 30, 2016) Jul2015 Staffing analysis Complete Nov 2015 Storage Plan Complete Nov 2015 FLEX equipment acquisition Complete Nov 2015 Training Complete Jun 2015 Regional Response Center Operational Complete April 30, 2016 Unit 1 Implementation date Page 3 of 15 Three Mile Island Nuclear Station, Unit 1 Sixth Six Month Status Report for the Implementation of FLEX, February 26, 2016 4 Changes to Compliance Method The following changes are the most significant changes made to the FLEX implementation strategy since the last update (August 2015): o Added contingency strategies for additional postulated failures of FLEX power supply cables, FLEX RCS Makeup Piping or the FLEX Feedwater system ("diverse flow paths") (Reference 6). o The condensate supply plan was revised based on evaluation which demonstrated tornado missile protection for CO-T-1A (Reference 5). o Additional analysis and modifications were completed to ensure the integrity of the Main Steam pressure boundary in the Turbine Building (Reference 7 & 8). 5 Need for Relief/Relaxation and Basis for the Relief/Relaxation Exelon requested and NRG approved deferment of compliance until April 30, 2016 to allow for further analysis of the Turbine Building structure and Main Steam Lines (References 12 and 13). Page 4 of 15 Three Mile Island Nuclear Station, Unit 1 Sixth Six Month Status Report for the Implementation of FLEX, February 26, 2016 6 Open Items from Interim Staff Evaluation and Audit Report Item Status Reference Item Description FEB 2016 UPDATE Provide the analysis supporting the licensee's mitigation strategy This response will be completed in the compliance (WCAP-17792-P) for NRG staff review, identify the specific calculation(s) letter. ISEOI in WCAP-17792 considered applicable to demonstrating the feasibility of 3.2.1.1.B the proposed

strategy, and justify the applicability of the calculation(s) relied upon in WCAP-17792 to TMl-1. ISEOI As applicable, provide additional analyses for core cooling, RCS This response will be completed in the compliance 3.2.1.1.C makeup, and shutdown margin that are relied upon, but not included in letter. WCAP-17792-P.

The licensee appears to use a probabilistic approach to reach a This response will be completed in the compliance ISEOI conclusion that at least one of the three tanks depended on for RCS letter. 3.2.4.7.A makeup will survive an ELAP event. NEI 12-06 guidance does not include this option. Provide further justification for this alternate approach.

The licensee stated that protection of associated portable equipment This response will be completed in the compliance from external hazards would be provided in structures that will be letter. ISECI constructed to meet the requirements of NEI 12-06 Section 11. 3.1.1.1.A However the licensee did not specify the type of configuration, how FLEX equipment would be secured, or how stored equipment and structures would be protected from all external hazards.

The licensee did not specifically address deployment considerations with This response will be completed in the compliance respect to the deployment of FLEX equipment through areas subject to letter. liquefaction, routing only through seismically robust buildings, power ISECI required to deploy or move equipment, and protection of the means to 3.1.1.2.A move equipment.

Page 5 of 15 Item Reference ISECI 3.2.1.A ISECI 3.2.1.2.A ISECI 3.2.1.2.B ISECI 3.2.1.2.C ISECI 3.2.1.4.A Three Mile Island Nuclear Station, Unit 1 Sixth Six Month Status Report for the Implementation of FLEX, February 26, 2016 Status Item Description FEB 2016 UPDATE The licensee needs to confirm that the transition to the backup This response will be completed in the compliance feedwater system will occur without a significant interruption of letter. feedwater to the steam generators.

The 1 A and 1 B ES motor control center (MCC) will be energized using This response will be completed in the compliance the FLEX diesel generators as described in Safety Functions Support letter. section and the FLEX RCS makeup pump will be started within 4 hours4.62963e-5 days 0.00111 hours 6.613757e-6 weeks 1.522e-6 months . The analysis to confirm the timeline is not yet complete.

Information should be provided to justify that the procedures are This response will be completed in the compliance effective to keep the RCS temperatures within the limits of the seal letter. design temperatures, and address the adequacy of the seal leakage rate (2 gallons per minute (gpm)/seal) used in the ELAP analysis.

For plants such as TMl-1 that credit low leakage seals to maintain the This response will be completed in the compliance initial maximum leakage rate of 2 gpm/seal for the ELAP analyses of the letter. RCS response, a discussion of the information (including seal leakage testing data) should be provided to justify the use of 2 gpm/seal in the ELAP analysis.

The licensee did not provide any further description of specific initial key This response will be completed in the compliance plant parameters specified in NEI 12-06, Sections 3.2.1.2 and 3.2.1.3 letter. except the assumption regarding SSC's [safety systems and components],

and the items from the Sequence of Events (SOE) Attachment 1 A. The licensee did not provide the initial conditions used in the RCS and SFP calculations used in the TMI Training and Reference Manual, ER-TM-TSC-0016, the TMI. Page 6 of 15 Item Reference ISECI 3.2.1.6.A ISECI 3.2.1.9.A Three Mile Island Nuclear Station, Unit 1 Sixth Six Month Status Report for the Implementation of FLEX, February 26, 2016 Item Description During the ELAP and LUHS [Loss of Ultimate Heat Sink]

basis external event, the licensee has identified that times to complete actions in the Events Timeline are based on operating

judgment, the conceptual

designs, and the current supporting analyses.

The TMI mitigation strategy is not based upon the PWROG [Pressurized Water Reactor Owners Group] WCAP-17601-P ELAP mitigation strategy.

In the audit process, the licensee stated that the current SOE is for the seismic event only and that another SOE would be developed for the flood event. Based on the information provided by the licensee, it is not possible to determine the validity of the time constraints provided in the preliminary sequence of events timeline for all hazards.

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

The results will be provided in a future 6-month update. The licensee stated that the FLEX diesel generators (FX-Y-1 A & B), fuel storage tank (FX-T-2) and FLEX MCC will be located north of the turbine pedestals on the Turbine Building 322' elevation.

The FLEX diesel generators and FLEX MCC will be designed for operation if subjected to twice the Safe Shutdown Earthquake (SSE), as part of the "augmented approach."

Protective barriers will be installed to ensure this equipment remains functional following a tornado.

Feasibility analysis has been completed which shows that the Turbine Building should be adequate to support these loads during an SSE. Further analysis is being performed to determine if any structural modifications are necessary to support that conclusion.

Page 7 of 15 Status FEB 2016 UPDATE This response will be completed in the compliance letter. This response will be completed in the compliance letter.

Item Reference ISECI 3.2.1.9.B ISECI 3.2.2.A ISECI 3.2.4.3.A ISECI 3.3.3.A Three Mile Island Nuclear Station, Unit 1 Sixth Six Month Status Report for the Implementation of FLEX, February 26, 2016 Status Item Description FEB 2016 UPDATE The Integrated Plan table titled, "PWR [Pressurized Water Reactor]

This response will be completed in the compliance Portable Equipment Phase 2," lists two diesel driven pumps. The letter. second table titled, "PWR Portable Equipment Phase 3," lists several pumps to be obtained from the RRC [NSRC]. The licensee did not discuss how the operator actions are modeled in the ELAP to determine the required flow rates of the portable pumps listed in the "PWR Portable Equipment Phase 3", or justify that the capacities of each of the above discussed pumps are adequate to maintain core cooling during phases 2 and 3 of ELAP The licensee stated that initial SFP cooling calculations were used to This response will be completed in the compliance determine the fuel pool timelines and that formal calculations will be letter. performed to validate this information during development of the detailed design. The licensee also stated that these strategies utilize a vent path for steam, and that the effects of this steam on other systems and equipment will be evaluated, and the results will be provided in a future 6-month update. The licensee specified that a strategy for extreme cold, snow and ice This response will be completed in the compliance events is being developed.

Preliminary plans include the use of heat letter. tracing for some piping and tanks, e.g. the Borated Water Storage Tank, and minimum flow paths or steam heating in other situations (e.g. the CST's). The final plans will be reviewed when complete.

The specific procedures for training, new or revised, have not yet been This response will be completed in the compliance completed.

The requirements from the analysis will be used to develop letter. and to validate the new and revised procedures.

This includes the existing design and licensing basis requirements and the new FLEX requirements.

Validation of time response is performed using a composite of field simulation and performance/simulator exercises.

Page 8 of 15 Item Reference AQ2 AQ13 AQ 19 Three Mile Island Nuclear Station, Unit 1 Sixth Six Month Status Report for the Implementation of FLEX, February 26, 2016 Status Item Description FEB 2016 UPDATE A review was conducted of Exelon's plans for the development of This response will be completed in the compliance mitigating strategies with respect to the procedural interfaces letter. considerations for seismic hazards associated with large internal flooding sources that are not seismically robust and do not require ac power, the use of ac power to mitigate ground water in critical locations, or the existence of non-seismically robust downstream dams, but it was determined that there was insufficient information in the plans to conclude that there is reasonable assurance that these aspects of the requirements of Order EA-12-049 and NEI 12-06, Section 5.3.3, consideration 2-4 will be met. Please provide a discussion of these considerations in the appropriate six-month update. The integrated plan for TMl-1 did not provide any information regarding This response will be completed in the compliance how decay heat rates were determined in the analyses for reactor core letter. and spent fuel pool cooling.

Please identify how decay heat was modeled for these analyses and provide justification for its adequacy.

The FLEX emergency feedwater pumps and two diesel generators and This response will be completed in the compliance fuel tanks are located in the Turbine Building which is apparently a non-letter. seismic Class 1 building.

As noted on page 11 of the submittal the pumps are only designed for the flood condition.

It is not clear if these pumps will be available in a seismic event due to their location.

Please clarify the availability of these pumps during a seismic event, including accessibility of any instrumentation and controls needed to support their operation, and identify how makeup to the steam generators would be provided for such an event. If the FLEX emergency feedwater pumps are credited for a seismic event, please provide adequate justification.

Please clarify whether the diesel generators and fuel tanks located in a protected enclosure in the Turbine Building (reference page 37 of submittal) will be adequately protected from damage from beyond-design-basis external events (e.g., seismic,

tornado, etc.). Please further clarify whether access to the protected enclosure could be restricted by damage to non-seismic structures and equipment.

Page 9 of 15 Item Reference AQ20 AQ40 AQ 51 Three Mile Island Nuclear Station, Unit 1 Sixth Six Month Status Report for the Implementation of FLEX, February 26, 2016 Item Description Since the FLEX Emergency Feedwater pumps and the Emergency RCS Charging Pumps are permanently installed they do not appear to qualify for portable status per NEI 12-06. The rationale for having portable equipment is that it can be stored or located in such a way that it is protected from all of the external events listed in NEI 12-06 (seismic,

flooding, high wind, extreme cold and heat). The FLEX Emergency feedwater pumps do not appear to be protected from seismic events. A justification is needed related to how these two permanently installed systems qualify as FLEX equipment under NEI 12-06, Section 3.1.2.12.

Also, a discussion of how these two systems and their respective power supplies are any more survivable than the normally installed plant equipment, is needed. Please discuss this issue. Provide a discussion on the diesel fuel oil supply (e.g., fuel oil storage tank volume, supply pathway, etc.) for the diesel driven FLEX pumps and generators and how continued operation to ensure core and spent fuel pool cooling is maintained indefinitely (i.e., Phase 2 and 3). Also, explain how fuel quality will be assured if stored for extended periods of time. The staff also requests the licensee provide a refueling strategy for the diesel driven FLEX equipment, to include fuel consumption estimates for the FLEX diesel driven FW pumps taking suction from the UHS [ultimate heat sink], and the time for refueling, and how the fuel will be provided.

Please clarify whether a single FLEX pump will be used to provide cooling flow to multiple destinations (e.g., the reactor core, steam generators, and the spent fuel pool). If so, please confirm that the FLEX pump can supply adequate flow and clarify whether the pumped flow will be split and simultaneously supplied to all destinations or whether the flow will be alternated between them. If simultaneous flow will be used, then clarify how the flow splits will be measured and controlled (i.e., whether control exists for the total flow on a common line or on lines to individual destinations) to ensure that adequate flow (i.e., sufficient but not excessive) reaches each destination.

Page 10 of 15 Status FEB 2016 UPDATE This response will be completed in the compliance letter. This response will be completed in the compliance letter. This response will be completed in the compliance letter.

Item Reference AQ56 AQ59 AQ64 OIPOl 9 Three Mile Island Nuclear Station, Unit 1 Sixth Six Month Status Report for the Implementation of FLEX, February 26, 2016 Status Item Description FEB 2016 UPDATE The licensee plans to secure the main generator seal oil pump when the This response will be completed in the compliance hydrogen pressure decreases to 15 psig. The staff requests the licensee letter. to explain why the pressure decrease is stopped at 15 psig and the main generator is not purged with C02. The licensee is also requested to describe the consequences of securing the seal oil pump with 15 psi of hydrogen remaining in the generator casing. The licensee's strategy for RCS includes using water from the spent fuel This response will be completed in the compliance pool. The staff requests the licensee provide an evaluation of the letter. consequences on the spent fuel pool using this strategy and the consequential actions required by the operators to maintain adequate spent fuel pool cooling.

The table titled, "PWR Portable Equipment Phase 2," lists two diesel This response will be completed in the compliance driven pumps. The pumps have flow rates and required head of 240 letter. gpm and 250 psid [pounds per square inch differential],

and 600 gpm and 245 psid, respectively.

The second table titled, "PWR Portable Equipment Phase 3," cites a positive displacement high pressure pumps with the specifications of 1000-3000 psi shutoff head and 60 gpm capacity and three low pressure pumps of 300 psi shutoff head and 2500 gpm max flow, 500 psi shutoff head and 500 gpm max flow, and 150 psi shutoff head and 5000 gpm max flow. Specify the required times for the operator to realign each of the above discussed pumps and confirm that the required times are consistent with the results of the ELAP analysis.

Discuss how the operator actions are modeled in the ELAP to determine the required flow rates of the portable pumps, and justify that the capacities of each of the above discussed pumps are adequate to maintain core cooling during phases 2 and 3 of ELAP. A portable refueling vehicle with a large diesel oil bladder will be This response will be completed in the compliance available on site to support refilling our portable equipment diesel tanks. letter. An additional means (river makeup is available) of delivering condensate may also be developed; details to be provided in a future 6-month update. Page 11 of 15 Item Reference OIP 0113 SE2 Three Mile Island Nuclear Station, Unit 1 Sixth Six Month Status Report for the Implementation of FLEX, February 26, 2016 Status Item Description FEB 2016 UPDATE A plan will be developed to re-supply borated water to the Borated Water I This response will be completed in the compliance Storage Tank or SFP. letter. a. Discuss the design of the suction strainers used with FLEX pumps taking suction from raw water sources, including perforation dimension(s) and approximate surface area. b. Provide reasonable assurance that the strainers will not be clogged with debris (accounting for conditions following

flooding, severe storms, earthquakes or other natural hazards),

or else that the strainers can be cleaned of debris at a frequency that is sufficient to provide the required flow. In the response, consider the following factors:

i. The timing at which FLEX pumps would take suction on raw water relative to the onset and duration of the natural hazard. ii. The timing at which FLEX pumps would take suction on raw water relative to the timing at which augmented staffing would be available onsite. iii. Whether multiple suction hoses exist for each FLEX pump taking suction on raw water, such that flow interruption would not be required to clean suction strainers.

Page 12 of 15 This response will be completed in the compliance letter.

Item Reference SE3 SE4 SE 6 SE14 Three Mile Island Nuclear Station, Unit 1 Sixth Six Month Status Report for the Implementation of FLEX, February 26, 2016 Status Item Description FEB 2016 UPDATE Discuss all areas of where local manual actions are credited in FLEX This response will be completed in the compliance strategies (e.g., SG atmospheric dump valves, auxiliary feedwater flow letter. control, making connection points, control room, etc.). Can Operators safety enter these areas to complete necessary actions during extreme hot and cold hazard during an ELAP? (Heat, cold, humidity, etc.) Are these actions feasible based on ELAP conditions and time constraint restrictions?

Will sufficient lighting be available to complete tasks (e.g., portable

lighting, headlamps, flashlights, etc.)? Is communication with the control room possible based on noise in area of local manual actions?

Will portable ventilation be established?

When will they be established?

Identification of FLEX pump (RCS makeup, FW and SFP makeup) This response will be completed in the compliance connection points and diverse flowpaths.

Confirmation that the letter. connection points are reasonably protected from all applicable, external hazards and will remain accessible when needed during an ELAP event. Verify that appropriate human factors are applied for the implementation This response will be completed in the compliance of the FLEX strategies.

letter. The licensee needs to confirm that the temperature and pressure within This response will be completed in the compliance containment, other areas within the plant (i.e., electrical switchgear letter. room), and atmospheric dump valve rooms will not exceed the qualification of electrical equipment that is being relied upon as part of the FLEX strategy.

The licensee needs to ensure that the qualification of the required electrical equipment remains bounding during the entire duration of the event (i.e., indefinitely).

Page 13 of 15 Item Reference SE18 SE20 SE 21 SE22 Three Mile Island Nuclear Station, Unit 1 Sixth Six Month Status Report for the Implementation of FLEX, February 26, 2016 Status Item Description FEB 2016 UPDATE Clarify MSIV [main steam isolation valve] behavior during ELAP at TMI. This response will be completed in the compliance Understand that MSIVs are motor-operated and that the operator cabling letter. may not be qualified during seismic event. Understand position of MSIVs during different scenarios.

Open MSIVs implies potential for cross-tied SG pressure.

Closed MSIVs implies potential for independent pressures in SGs [steam generators].

Obviously this could influence RCS loop temperatures and flows for cases where asymmetry may arise. Also, because of potential inability to close MSIVs if electrical power unavailable to valve operator, confirm whether downstream piping is robust to turbine stop valves, or whether there is potential for uncontrolled cooldown that must be addressed.

This situation could arise if downstream steam lines or connected piping is non-robust in one or more ELAP scenarios.

The licensee's strategy relies on a single connection point for the Phase This response will be completed in the compliance 2 DGs to provide power to the TMI 480 V electrical distribution system. letter. Licensee needs to provide an analysis that shows that staging the N and This response will be completed in the compliance N+ 1 Phase 2 FLEX DGs in close proximity to one another does not letter. reduce the reliability of either Phase 2 FLEX DG to perform its required function (i.e., a catastrophic failure on one Phase 2 FLEX DG will not adversely impact the other FLEX DG or its associated equipment (cabling, connections, etc.). How will seismic water sources (e.g. condensate storage tanks CO-T-1A This response will be completed in the compliance I 1 B) be protected from the impact of a seismic or tornado event on other letter. connected tanks? Page 14 of 15 Three Mile Island Nuclear Station, Unit 1 Sixth Six Month Status Report for the Implementation of FLEX, February 26, 2016 7 Potential Draft Safety Evaluation Impacts No potential impact to the Draft Safety Evaluation was identified.

8 References The following references support the updates to the Overall Integrated Plan described in this 6-month update. 1. Three Mile Island Nuclear Station, Unit 1, 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. 2. NRC Order Number EA-12-049, Order Modifying Licenses with Regard to Requirements for Mitigation Strategies for Beyond-Design-Basis External Events, dated March 12, 2012. 3. NEI 12-06, Rev. 0, Diverse and Flexible Coping Strategies (FLEX) Implementation Guide, dated August 2012. 4. TMI Station's Fifth Six Month Status Report for the Implementation of FLEX, dated August 28, 2015 5. Technical Evaluation 13-00476, "FLEX -Design Evaluation of CO-T-1A, CO-T-1 Band DW-T-2" 6. Technical Evaluation 15-00345, "FLEX -Diverse Flow Paths" 7. ECR 15-00328 "Main Steam BDBEE Tornado Missile Protection Mods" 8. ECR 15-00330 "Main Steam BDBEE Seismic Evaluation and Mods" 9. Report 990-2179 "Assessment of earthquake-induced liquefaction potential and associated ground failure hazards for Three Mile Island Unit 1 ", Geomatrix Consultants

10. Technical Evaluation 14-00126, FLEX Impact evaluation

-Turbine Building

11. Technical Evaluation 15-00142, FLEX Impact evaluation

-Non Seismic Eqpt Failures in Class I Buildings

12. Exelon letter to NRC dated October 29, 2015 (ADAMS Accession No. ML 15303A080)

13. NRC letter to Exelon dated November 18, 2015 (TAC NO MF0803).

9 Attachments None Page 15 of 15 Exelon Generation