RS-14-010, 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)

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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)
ML14059A430
Person / Time
Site: Dresden  Constellation icon.png
Issue date: 02/28/2014
From: Kaegi G
Exelon Generation Co
To:
Document Control Desk, Office of Nuclear Reactor Regulation
References
EA-12-049, RS-14-010
Download: ML14059A430 (23)
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Text

1 ExelonGe Order No. EA-12-049 RS-14-010 February 28, 2014 U.S. Nuclear Regulatory Commission ATrN: Document Control Desk Washington, DC 20555-0001 Dresden Nuclear Power Station, Units 2 and 3 Renewed Facility Operating License Nos. DPR-19 and DPR-25 NRC Docket Nos. 50-237 and 50-249 Supject: Second Six-lVIonth 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-13-020)
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-13-119)
7. NRC letter to Exelon Generation Company, LLC, Dresden Nuclear Power Station, Units 2 and 3 - Interim Staff Evaluation Relating to Overall Integrated Plan in Response to Order EA-12-049 (Mitigation Strategies) (TAC Nos. MF1046 and MF1 047), dated November 22,2013

U.S. Nuclear Regulatory Commission Integrated Plan Report to EA-12-049 February 28, 2014 Page 2 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 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 EGC initial status report regarding mitigation strategies. Reference 5 provided the Dresden Nuclear Power Station, Units 2 and 3 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. Reference 6 provides the first six-month status report pursuant to Section IV, Condition C.2, of Reference 1 for Dresden Station. The purpose of this letter is to provide the second 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 7.

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 February 2014.

Respectfully submitted,

~/.¥ Glen T. Kaegi Director - Licensing & Regulatory Affairs Exelon Generation Company, LLC

Enclosure:

1. Dresden Nuclear Power Station, Units 2 and 3 Second 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 February 28, 2014 Page 3 cc: Director, Office of Nuclear Reactor Regulation NRC Regional Administrator - Region III NRC Senior Resident Inspector - Dresden Nuclear Power Station, Units 2 and 3 NRC Project Manager, NRR - Dresden Nuclear Power Station, Units 2 and 3 Ms. Jessica A. Kratchman, NRR/JLD/PMB, NRC Mr. Jack R. Davis, NRR/DPR/MSD, NRC Mr. Eric E. Bowman, NRR/DPR/MSD, NRC Mr. Jeremy S. Bowen, NRR/DPR/MSD/MSPB, NRC Mr. Robert L. Dennig, NRR/DSS/SCVB, NRC Mr. John Boska, NRRIDPR/MSD/MSPB, NRC Illinois Emergency Management Agency - Division of Nuclear Safety

Enclosure Dresden Nuclear Power Station, Units 2 and 3 Second 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 (19 pages)

Enclosure Dresden's Second 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 1 Introduction Dresden Nuclear Power Station (Dresden) developed an Overall Integrated Plan (Reference I 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 Overall Integrated Plan, including any changes to the compliance method, schedule, or need for relief/relaxation and the basis, if any.

2 Milestone Accomplishments None 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.

Original Target Activity Status Revised Target Completion Date {Include date changes in Completion Date this column}

Submit 60 Day Status Report Complete Submit Overall Integrated Complete Implementation Plan Contract with RRC Complete Submit 6 month updates August 2013 Update 1 Complete February 2014 Update 2 Complete with this submittal August 2014 Update 3 Not started February 2015 Update 4 Not started August 2015 Update 5 Not started February 2016 Update 6 Not started Page 1 of 19

Dresden Nuclear Power Station's Second Six Month Status Report for the Implementation of FLEX February 28, 2014 Original Target Activity Status Revised Target Completion Date {Include date changes in Completion Date this column}

August 2016 Update 7 Not started Submit Completion Report tumt 2 Unit 3 Modification Development bct 2014 Sept 2015

  • Phase 1 modifications Note 1 pct 2014 Sept 2015
  • Phase 2 modifications Note 1 pct 2014 Sept 2015
  • Phase 3 modifications Note 1 tunit 2 Unit 3 Modification Implementation 1N0v 2015 1N0v 2016
  • Phase 1 modifications Note 1 1N0v 2015 Nov 2016
  • Phase 2 modifications Note 1 Nov 2015 1N0v 2016
  • Phase 3 modifications Note 1 Procedure development Nov 2015
  • Strategy procedures Note 1 Nov 2015
  • Validate Strategy Note 1 Procedures (NEI 12-06, Sect. 11.4.3)

Nov 2015

  • Maintenance procedures Note 1 Ju120l5 Staffing analysis Note 1 Nov 2015 Storage Plan and construction Note 1 Nov 2015 FLEX equipment acquisition Note 1 Nov 2015 Training completion Note 1 Ju12015 Regional Response Center (will be a standard date Operational from RRC)

Nov 2015 Unit 2 Implementation date Note 1 Nov 2016 Unit 3 Implementation date Note 1 Note(s):

1. Exelon will update the status of ongoing and future milestones in the Integrated Plan for DNPS during a scheduled six (6) month update. This update will include any changes to the milestone schedule as submitted in the February 28, 2013 Integrated Plan.

Page 2 of 19

Dresden Nuclear Power Station's Second Six Month Status Report for the Implementation of FLEX February 28, 2014 4 Changes to Compliance Method A review of seismic events identified a downstream dam failure would adversely affect the FLEX strategies identified in the August 2013 update. The pumps identified in the August 2013 6-month update for FLEX strategies during worst postulated dam failure would lose suction during a downstream dam failure (Dresden UFSAR Section 9.5). The overall Dresden strategy has been modified as a result of this review. Attachment 2 provides a sketch of the conceptual design described below.

The revised strategy for all events except flooding will utilize the Suppression Pools as the initial FLEX water source. Electrically driven FLEX pumps will be pre-staged in or near each of the 4 ECCS Corner Rooms in the Reactor Building. Temporary hoses will be used to connect the pumps to existing piping which communicates with the Suppression Pools. Water from the FLEX Pumps will be directed through a combination of existing piping and temporary hoses to supply makeup needs for the Isolation Condenser (lC) Shell-side, RPV and Spent Fuel Pool of both Units. The Suppression Pools will be used in succession to supply the initial FLEX makeup requirements. Water from the Ultimate Heat Sink will subsequently be made available through pOltable submersible pumps to supply makeup after the Suppression Pools are exhausted.

Power to the pre-staged FLEX pumps will be supplied from pre-staged diesel generators located near the Reactor Building. Temporary cables will be routed from a diesel generator through proposed penetrations in the Reactor Building wall and then connected to the appropriate FLEX pump. After a FLEX pump is operating (time critical action, 2.5 hours5.787037e-5 days <br />0.00139 hours <br />8.267196e-6 weeks <br />1.9025e-6 months <br />) personnel will be able to route additional temporary cables from the generator to supply the safety related 480 VAC busses in the Reactor Building. The 480 V AC safety related busses will then be available to power desired loads such as Standby Liquid Control (SBLC) pumps for high pressure RPV injection and battery chargers. The pre-staged diesel generators will be housed in robust structures to provide protection for all events except flood.

Flood coping strategy employs a diesel driven portable FLEX pump. Because the flood event is precipitation based there is time to prepare. The pump will be placed on a floating platform inside the Reactor Building. The pump suction source will be flood waters surrounding the Reactor Building. Pump discharge will be routed through temporary hoses to the IC Makeup header. This header will be used as a supply header for other hoses to supply makeup needs for RPV makeup and Spent Fuel Pool. A portable diesel generator will be placed on the 2/3 Reactor Building Trackway Interlock roof. The output of the diesel generator will be connected to the safety related 480 V AC busses in the Reactor Building via temporary cables. The 480 VAC safety related busses will then be available to power desired loads.

5 Need for RelieflRelaxation and Basis for the RelieflRelaxation Dresden Nuclear Power Station expects to comply with the order implementation date and no relief/relaxation is required at this time.

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 Page 3 of 19

Dresden Nuclear Power Station's Second Six Month Status Report for the Implementation of FLEX February 28, 2014 Section Reference Overall Integrated Plan Open Item Status Sequence of Events The times to complete actions in the Events Not Started (page 5-6) 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 Analysis of deviations between Exelon's Completed. See Aug (page 5) engineering analyses and the analyses contained 2013 Update in BWROG Document NEDC-33771P, "GEH Evaluation of FLEX Implementation Guidelines," and documentation of results on Att. 1B, "NSSS Significant Reference Analysis Deviation Table." Planned to be completed and submitted with August 2013 Six Month Update.

Sequence of Events Initial evaluations were used to determine the Not Started (page 8) fuel pool timelines. Formal calculations will be performed to validate this information during development of the spent fuel pool cooling strategy detailed design.

Deployment Strategy TranspOltation routes will be developed from See Interim Staff (pages 8-9) the equipment storage area to the FLEX staging Evaluation Confirmatory areas. An administrative program will be Item 3 .1.2.2.A response.

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.

Programmatic Controls An administrative program for FLEX to Not Started (pages 9- establish responsibilities, and testing &

10) maintenance requirements will be implemented.

Spent Fuel Pool Cooling Complete an evaluation of the spent fuel pool See Interim Staff Phase 2 area for steam and condensation. Evaluation Confirmatory Discussion (page 46) Item 3.2.2.A response.

Safety Functions Evaluate the habitability conditions for the See Interim Staff Support Phase 2 Main Control Room and develop a strategy to Evaluation Confirmatory Discussion (page 57) maintain habitability. Item 3.2.4.6.C response.

Safety Functions Evaluate the habitability conditions for the See Interim Staff Support Phase 2 Auxiliary Electric Equipment Room (AEER) Evaluation Confirmatory Discussion (page 57) and develop a strategy to maintain habitability. Item 3.2.4.2.C response.

Page 4 of 19

Dresden Nuclear Power Station's Second Six Month Status Report for the Implementation of FLEX February 28, 2014 Item Interim Staff Evaluation OPEN Item Status number 3.1.1.1.A Each section of the Integrated Plan Proposed Complete.

describing storage protection from By reference in NEI 12-06, Section 11.3 Items hazards makes reference to Section 11 11.3.1,11.3.2 and 11.3.3, the structures will rather than to the specific protection conform to the guidance of NEI 12-06, Sections 5 requirements described in NEI 12-06 for through 9. Therefore, each applicable hazard will the applicable hazard; that is Section be evaluated and storage requirements will be 6.2.3.1 for floods, Section 7.3.1 for wind, established per NEI 12-06.

etc. As a result, the specific guidelines for each hazard are not addressed.

3.1.2.2. B The Plan is silent regarding loss of normal Proposed Complete access to the Ultimate Heat Sink (UHS) The Ultimate Heat Sink is a section of the intake due to flood hazard conditions, the need canal (Dresden UFSAR Section 9.5). The intake to provide electrical power for sump canal is connected to the Kankakee River. During pumps, and whether or not flood barriers a flood event the river will overflow its banks.

will be utili zed. Water for FLEX requirements will come from the flood waters. As a result, access specifically to the UHS is not required. During the actual flood the water in the UHS and the flood water will essentially be the same.

The FLEX Flood strategy is described in Section 4, Changes to Compliance Method, of this update.

The FLEX flood strategy acknowledges that installed sump pumps and temporary flood barriers will be in place. With the primary FLEX Flood pump being staged on a floating platform the strategy will function regardless of the status of the sump pumps or temporary flood barriers.

3.2.4.8.A Updated information provided by the Not started.

licensee as part of the 6-month update states that they are proposing to install a prest aged generator to supply all FLEX related loads for both units simultaneously for Phase 2 mitigating strategies. This appears to be an alternative approach for satisfying the Mitigating Strategies order. Insufficient information has been provided by the licensee in order to determine whether this provides an equivalent level of protection as would be provided through conformance with NEI 12-06.

Page 5 of 19

Dresden Nuclear Power Station's Second Six Month Status Report for the Implementation of FLEX February 28, 2014 Item Interim Staff Evaluation number CONFIRMATORY Item Status 3.1.1.2.A A postulated downstream dam failure Proposed Complete from a seismic event is still being The downstream dam failure during a seismic event has evaluated. been evaluated against the criteria in Section 5 of NEI 12-06 Rev 0 and this failure is applicable to Dresden for FLEX response.

As a result the Dresden FLEX strategy conceptual design has been revised as described in Section 4, Changes to Compliance Method, of this update to address this event.

Detailed design will incorporate the results of the review.

No further action required.

3.1.1.2.B Plans for strategies did not address Not started whether electrical power would be required to move or deploy FLEX equipment (e.g. to open a door from a storage location.)

3.1.1.3.A Development of a reference source Started for obtaining necessary instrument readings in the event of seismic damage to electrical equipment as described in NEI 12-06, Section 5.3.3, consideration 1.

3.1.1.3.B Use of, or need for ac power to Proposed Complete.

mitigate ground water intrusion was The Dresden FLEX Flood strategy assumes the flood not addressed. waters will eventually enter the Reactor Building.

Control of ground water intrusion is desirable but is not required. Ground water intrusion will not prevent implementation of the FLEX strategy. Therefore, AC power is not required to mitigate ground water intrusion.

See Interim Safety Evaluation OPEN Item 3.1.2.2. B response (above) for additional explanation.

3.1.1.4.A Regarding off site resources, detailed Started plans for local staging areas and transport of FLEX equipment to overcome hazards are to be provided in 6-month update.

3.1.2.A Impact of persistence of flooding to Started staging of FLEX equipment not fully addressed.

3.1.2.2.A Administrative program and Started procedures for on-site FLEX equipment storage locations and transport routes not yet established.

3.1.2.3.A Administrative program and Started procedures related to implementation of mitigation strategies not yet developed.

Page 6 of 19

Dresden Nuclear Power Station's Second Six Month Status Report for the Implementation of FLEX February 28, 2014 Item Interim Staff Evaluation number CONFIRMATORY Item Status 3.1.4.2.A Equipment to clear ice and snow from Proposed Complete.

haul pathways is not identified in Dresden has purchased an F750 Truck with a snow plow plan. for snow/ice clearing of haul paths. The plow on the F-750 is of a composite design with a steel reinforced frame.

The truck will be used for snow/ice clearing to support initial FLEX equipment deployment.

3.1.5.2.A Procedures to assure equipment can Not started be deployed in a high temperature context have not been developed.

Specifically, address high temperature effects on storage locations (e.g.

expansion of sheet metal, swollen seals, etc.)

3.1.5.3.A Procedures to address high StaIted temperature impacts on FLEX equipment not yet develQPed.

3.2.1.1.A Need benchmarks to demonstrate Started Modular Accident Analysis Program (MAAP) 4 is the appropriate code for simulation of ELAP.

3.2.1.1.B For MAAP4, collapsed level must Started remain above Top of Active Fuel and cool down rate must meet technical specifications.

3.2.1.1.C MAAP4 use must be consistent with Started June 2013 position paper.

3.2. 1. l.D In using MAAP4, the licensee must Started 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" (Electric Power Research Institute Report 1020236).

3.2.1.1.E The specific MAAP4 analysis case Started 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.

Page 7 of 19

Dresden Nuclear Power Station's Second Six Month Status Report for the Implementation of FLEX February 28, 2014 Item Interim Staff Evaluation Status number CONFIRMATORY Item  !

3.2.1.3.A Outstanding Confirmatory Items Not started regarding the use of the MAAP4 analysis may impact the sequence of events timeline. Any changes to the MAAP4 analysis results will need to be reviewed for impact on the sequence of events time line. The licensee stated that the final timeline will be time validated once detailed designs are completed, procedures are developed, and the results will be provided in a future six (6) month update.

3.2.1.3.B Sequence of Events timing for Started compensatory actions to control temperature rise in the Main Control Room not resolved.

3.2.1.4.A Detailed engineering analyses to Started confirm the ability of FLEX pumps to provide required flow and head capacities are not complete.

3.2.1.4.B Analysis needs to be performed to Started validate that the plant modifications, selected equipment, and identified mitigating strategy can satisfy the safety function requirements of NEI 12-06. To be provided in a future six (6) month update.

3.2.1.6.A Whether or not backup compressed Started air for valve actuation is required, is contingent on the MAAP4 analyses conclusions. The MAAP4 conclusions will determine if containment venting is necessary.

3.2.2.A Final analysis of fuel pool area for Started steam and condensation impacts regarding access is not complete.

3.2.3.A There are outstanding issues Started regarding the acceptability of the MAAP4 analysis. The potential for impact of MAAP4 results on the i containment heat removal strategy i needs to be reviewed. I Page 8 of 19

Dresden Nuclear Power Station's Second Six Month Status Report for the Implementation of FLEX February 28, 2014 Item Interim Staff Evaluation number CONFIRMATORY Item Status 3.2A.2.A A discussion is needed on the effects Not started of extreme low temperatures (Le.,

temperatures below those assumed in the sizing calculation for each battery) on each battery's capability to perform its function for the duration of the ELAP event.

3.2A.2.B Procedure will be developed to Not started address controlling battery room hydrogen concentration.

3.2A.2.C Evaluations to address loss of Not started I ventilation in the auxiliary equipment electric room and Battery Rooms are not complete.

3.2A.2.D Insufficient information to address Not started impact on elevated temperatures in areas critical to mitigation strategies.

For example, initial temperatures assumed in the analyses is not clear, critical components in pump rooms are not identified, etc. Detailed design information is needed.

3.2AA.A Provisions for portable lighting for Not started area access not clear. More information required.

3.2AA.B Confirm upgrades to communication Started system that resulted from the licensee communications assessment.

ADAMS Accession Nos.

ML12306A199 and ML 13056AI35.

3.2.4.6.A Surface pyrometer temperature I Started readings are required in the torus area.

The licensee needs to address habitability and access to the torus area.

3.2A.6.B Final GOTHIC analysis for the HPCI Started room temperature rise is not complete.

3.2A.6.C Habitability of the control room Started should consider temperature limits of NUMARC 87-00 and MIL-STD-1472C.

3.2A.8.B Detailed designs will identify Not started comprehensive load lists to confirm I conceptual load assumptions.

Page 9 of 19

Dresden Nuclear Power Station's Second Six Month Status Report for the Implementation of FLEX February 28, 2014 Item Interim Staff Evaluation number CONFIRMATORY Item Status 3.2.4.8.C Insufficient information provided Started regarding FLEX diesel generators and the plant Class 1 E diesel generators isolation to prevent simultaneously supplying power to the same Class 1 E bus and regarding minimum bus voltages during the use of FLEX generators.

3.2.4.9.A The licensee stated in its 6-month Started update that a modification has been proposed to allow transfer of fuel oil from the 2/3 Emergency Diesel Generator main fuel oil storage tank to the area of the proposed FLEX diesel generators. Need to confirm that the modification is installed and supplies sufficient fuel.

3.2.4.9.B Assessing and maintaining fuel oil Not started quality for FLEX equipment use was not addressed.

3.2.4.10. Final analysis for battery operation Started A with load shed not complete. Need detailed load profile for all mitigating strategies and a detailed discussion of loads that will be shed, how they will be shed, and what are the effects of the shed.

3.4.A Details not provided to demonstrate Started the minimum capabilities for offsite resources will be met per NEI 12-06 Section 12.2.

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. Dresden Nuclear Power Station's 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 (subsequently revised Aug 28, 2013).

Page 10 of 19

Dresden Nuclear Power Station's Second Six Month Status Report for the Implementation of FLEX February 28,2014

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. Dresden Nuclear Power Station Updated Final Safety Analysis Report, Revision 9
4. Diverse and Flexible Coping Strategies (FLEX) Implementation Guide", NEI 12-06, Revision 0, August 2012
5. Attachment 1 Revised Estimated Sequence of Events Timeline.
6. Attachment 2, Simplified FLEX Makeup Conceptual Design
7. Attachment 3, Simplified FLEX Electrical Conceptual Design Page 11 of 19

Dresden Nuclear Power Station's Second Six Month Status Report for the Implementation of FLEX February 28, 2014 Attachment 1 Revised Estimated Sequence of Events Timeline Action Elapsed Action Time Remarks I Applicability item Time Constraint YIN 1 0 Event Starts NA Plant @ 100% power 0 Reactor scram NA Loss of power to Reactor Protection System results in a reactor scram.

1 1 min Personnel enter DGP 02-03 and DGA 12 N These actions will provide direction for reactor control and options for loss of AC power.

2 1 min Isolation Condenser initiated for N DEOP 100 will direct pressure control (or verified operating if action based on reactor auto initiation occurs) pressure.

3 2 mins Attempt to start EDGs upon N Per FLEX event initial identification of failure to auto start. conditions the EDGs are not available.

4 3 mins Attempt to Start IC Makeup Pump for N There are no fully qualified IC Shell side makeup makeup sources for shell-side makeup.

5 5 mins Personnel dispatched to investigate EDG N Per FLEX event initial failure to start. conditions the EDGs are not available.

6 5 mins HPCI initiated for inventory control and N DEOP 100 will direct this reactor pressure control (or verified action. HPCI suction will operating if auto initiation occurs). auto swap to the Torus due to CSTs being assumed lost with the FLEX event (not missile protected).

7 10 mins I Attempt to start SBO DG for either Unit N Per FLEX event initial conditions the SBO DGs are not available.

I 1 Instructions: Provide justification if No or NA is selected in the remark column.

If yes, include technical basis discussion as requires by NEI 12-06 section 3.2.1.7 Page 12 of 19

Dresden Nuclear Power Station's Second Six Month Status Report for the Implementation of FLEX February 28, 2014 Attachment 1 Revised Estimated Sequence of Events Timeline Action Elapsed Action Time Remarks I Applicability item Time Constraint YIN 1 8 15 mins Personnel dispatched to investigate SBO N Per FLEX event initial DG failure to start. conditions the SBO DGs are not available.

9 15 mins PeIiorm 125 VDC load shedding per N This is an immediate action DGA 13 of DGA 13 to prolong battery availability. Must be completed by 30 minutes after event initiation.

10 20 mins Isolation Condenser secured due to lack Y Per UFSAR, the IC will of shell-side makeup. operate for approximately 20 minutes without shell-side makeup. It is secured to prevent possible damage.

11 30 mins 125 and 250 VDC Load Shed Y DGA 12StepD.13 Completed (actions identified in DGA identifies that load 03, DGA 12 and DGA 13) shedding to maintain battery availability must be completed if DC chargers are unavailable.

12 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br /> Control Room crew has assessed SBO N Time is reasonable and plant conditions and declares an approximation based on Extended Loss of AC Power (ELAP) operating crew assessment event. of plant conditions.

  • Personnel dispatched to FLEX strategy for supplying make-up water to the Isolation Condenser shell-side.
  • Personnel dispatched to FLEX strategy for supplying power to the FLEX Makeup Pump and station battery chargers Page 13 of 19

Dresden Nuclear Power Station's Second Six Month Status Report for the Implementation of FLEX February 28, 2014 Attachment 1 Revised Estimated Sequence of Events Timeline Action Elapsed Action Time Remarks I Applicability item Time Constraint YIN 1 13 2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br /> Complete actions for Loss of AEER N Perform DOA 5750-1 Ventilation Attachment C Step 6.

Actions can be coordinated with personnel obtaining and staging portable generators, fans, etc.

14 2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br /> Establish natural air flow to HPCI room Y Preliminary GOTHIC by opening doors. analysis indicates opening doors at 2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br /> will result in acceptable room temperature values to support operation of HPCI for at least 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br />. HPCI room temperature remains below the isolation point during this time. HPCI operation is assumed for approximately 2.5 hours5.787037e-5 days <br />0.00139 hours <br />8.267196e-6 weeks <br />1.9025e-6 months <br /> in Phase 1.

15 2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br /> Complete actions for loss of Main N DOA 5750-01 actions.

Control Room Ventilation.

16 2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br /> Defeat HPCI high temperature and flow N Ensure HPCI remains isolations available during the event.

17 2.5 FLEX strategy for supplying power to a Y Involves running temporary hours FLEX Makeup Pump completed. cables and connecting to the selected FLEX Makeup pump.

18 2.5 FLEX pump connected and supplying Y Due to pre-staging of major hours Isolation Condenser shell-side makeup. components, it is reasonable to expect the FLEX pump can be available within this time period.

Page 14 of 19

Dresden Nuclear Power Station's Second Six Month Status Report for the Implementation of FLEX February 28, 2014 Attachment 1 Revised Estimated Sequence of Events Timeline Action Elapsed Action Time Remarks I Applicability item Time Constraint V/N 1 19 2.5 Isolation Condenser initiated for RPV Y Complete prior to loss of hours pressure control HPCI to ensure RPV heat removal mechanism operating prior to MAAP analysis assumed HPCI loss.

20 2.5 HPCI assumed to fail due to suppression I N HPCI may continue to hours pool temperature of 2: 140°F operate above 140°F but it is not relied upon past this point. Restoration of the Isolation Condenser will replace the need for HPCI in terms of RPV pressure control.

21 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> FLEX strategy for supplying power to Y When the busses are 480 VAC busses and associated Motor energized, power will be Control Centers (MCCs) completed. II available to supply power I to battery chargers and I other desired loads such as SBLC and SBGT.

Preliminary review I indicates the batteries will remain available for at least 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> without chargers.

22 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> Isolate both Reactor Recirculation N Recirc loops are isolated to Loops by closing suction and discharge reduce RPV leakage. The I valves sooner this is accomplished II the more reactor inventory is conserved.

Page 15 of 19

Dresden Nuclear Power Station's Second Six Month Status Report for the Implementation of FLEX February 28, 2014 Attachment 1 Revised Estimated Sequence of Events Timeline Action Elapsed Action Time Remarks I Applicability item Time Constraint yIN 1 23 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> Initiate SBLC as necessary for RPV N Per MAAP analysis after level control. Recirc Loops are isolated and the Isolation Condenser is controlling reactor pressure, RPV leakage will be reduced to approximatel y 15 gpm at time = 6.0 hours0 days <br />0 hours <br />0 weeks <br />0 months <br />. Makeup from SBLC can be utilized to maintain RPV level above Top of Active Fuel (TAF).

24 10 Personnel dispatched to establish N Further analysis is required hours temporary ventilation to the MCR and to determine if AEER (p011able fans and associated supplemental ventilation is generators). needed.

25 12 Makeup to the Spent Fuel Pools using Y EC 371913, Revision 2, hours FLEX pump strategy is available. Time-to-Boil Curves, identifies a time to boil of 9.54 hours6.25e-4 days <br />0.015 hours <br />8.928571e-5 weeks <br />2.0547e-5 months <br />, and 110.07 hours8.101852e-5 days <br />0.00194 hours <br />1.157407e-5 weeks <br />2.6635e-6 months <br /> to the top of active fuel. Therefore completing the equipment line-up for initiating SFP make-up at 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> into the event ensures adequate cooling of the spent fuel is maintained.

26 12 Personnel dispatched to deploy portable N Additional site resources hours pump and line-up water supply from the will be available 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> Ultimate Heat Sink (UHS). after event initiation to aid in this effort. The resources include personnel to operate equipment such as mobile lifting device to deploy submersible pump in the UHS.

Page 16 of 19

Dresden Nuclear Power Station's Second Six Month Status Report for the Implementation of FLEX February 28,2014 Attachment 1 Revised Estimated Sequence of Events Timeline Action Elapsed Action Time Remarks I Applicability item Time Constraint YIN 1 27 17 Makeup available from UHS using N Long term makeup water hours portable equipment source will be available before the water contained in the Suppression Pools for both Units is exhausted.

Makeup from the UHS will not be required before this time.

28 24 Initial equipment from Regional N NEI 12-06 assumption.

hours Response Center becomes available.

29 24-72 Continue to maintain critical functions N None hours of core cooling (via IC and FLEX Pump injection), containment (via hardened vent opening) and SFP cooling (FLEX pump injection to SFP). Utilize initial RRC equipment in spare capacity.

Page 17 of 19

Dresden Nuclear Power Station's Second Six Month Status Report for the Implementation of FLEX February 28,2014 Attachment 2 Simplified FLEX Makeup Conceptual Design ShWIowI'I ShuIdcMn U21U3 ISCO Makeup Riser

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Dresden Nuclear Power Station's Second Six Month Status Report for the Implementation of FLEX February 28, 2014 Attachment 3 SWGR39 SWGR3S SWGR28 i ,SWGR2Q

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