RS-14-208, 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)

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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)
ML14248A238
Person / Time
Site: Dresden  Constellation icon.png
Issue date: 08/28/2014
From: Kaegi G
Exelon Generation Co
To:
Document Control Desk, Office of Nuclear Reactor Regulation
References
EA-12-049, RS-14-208
Download: ML14248A238 (36)
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Text

sinw. Exelon Generation Order No. EA-12-049 RS-14-208 August 28, 2014 U.S. Nuclear Regulatory Commission ATTN: 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

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-13-020)
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. 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-14-010)

U.S. Nuclear Regulatory Commission Integrated Plan Report to EA-12-049 August 28, 2014 Page 2

8. 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 MF1047), dated November 22, 2013 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 EGO 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 EGO 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. References 6 and 7 provided the first and second six-month status reports, respectively, pursuant to Section IV, Condition 0.2, of Reference 1 for Dresden 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 NRC 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, Glen T. Kaegi Director - Licensing & Regulatory Affairs Exelon Generation Company, LLC

Enclosure:

1. Dresden Nuclear Power Station, Units 2 and 3 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 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 P. Boska, NRR/DPR/MSD/MSPB, NRC Illinois Emergency Management Agency - Division of Nuclear Safety

Enclosure Dresden Nuclear Power Station, Units 2 and 3 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 (32 pages)

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

2 Milestone Accomplishments Modification development started.

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 National SAFER Complete Response Center Submit 6 month updates August 2013 Update 1 Complete February 2014 Update 2 Complete August 2014 Update 3 Complete with this submittal February 2015 Update 4 Not started August 2015 Update 5 Not started February 2016 Update 6 Not started Page 1 of 31

Dresden Nuclear Power Station's Third Six Month Status Report for the Implementation of FLEX 8/28/2014 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 Unit 2 Unit 3 Modification Development Oct 2014 Sept 2015

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

Nov 2015

  • Maintenance procedures Note 1 Jul 2015 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 Jul 2015 National SAFER Response Center (will be a standard date Operational from National SAFER Response Center)

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, 2014 Integrated Plan update.

Page 2 of 31

Dresden Nuclear Power Station's Third Six Month Status Report for the Implementation of FLEX 8/28/2014 4 Changes to Compliance Method An update call was held with members of the Nuclear Regulatory Commission on May 28, 2014 to review current design concepts. During design development activities occurring since the February 2014 6-Month Status Report the following minor changes to the Compliance Method have been identified. The changes identified below were discussed during the May 28, 2014 update call.

Power for FLEX required loads during non-flood events will be supplied from one pre-staged diesel generator located near the Reactor Building. The pre-staged diesel generator will be housed in a robust structure to provide protection for all events except flood. This diesel generator will be a trailer mounted unit capable of supplying power to all anticipated requirements for both Units at Dresden after the event.

The change in compliance is there is now one diesel generator and it is a pre-staged trailer mounted unit. The remainder of the electrical FLEX strategy remains unaffected.

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 Unit 3 Turbine Building Trackway. This location places the pump and platform near a large roll-up door which allows for adequate ventilation and does not impact other flood event preparations. The pump suction source will be the Unit 3 Main Condenser Tube Pull Pit area which will be filled with flood waters entering the Turbine Building. Pump discharge will be routed through temporary hose to a proposed connection on the Fire Protection header located on elevation 545'. Isolation Condenser shell-side makeup can be supplied from the Fire Main through a permanently installed makeup valve. The Fire Main will also be used as a supply header for other hoses to supply makeup needs for RPV makeup and Spent Fuel Pool.

The change in compliance is the portable pump will be located in the Unit 3 Turbine Building and Fire Main piping will be used to transport water from the portable pump to the required loads The electrical strategy during a flood event is unchanged from the February 2014 6-Month Status Update Report.

5 Need for Relief/Relaxation and Basis for the Relief/Relaxation 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 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.

Page 3 of 31

Dresden Nuclear Power Station's Third Six Month Status Report for the Implementation of FLEX 8/28/2014 Section Reference Overall Integrated Plan Open Item Status Sequence of Events Analysis of deviations between Exelon's Completed. See August (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 Proposed Complete.

(page 8) fuel pool timelines. Formal calculations will be Engineering Change performed to validate this information during (EC) 31913, TIME TO development of the spent fuel pool cooling BOIL CURVES -

strategy detailed design.

DR-104-1001, Revision 2 has been completed.

The EC supports the timeline assumptions made using initial evaluations. The associate times are reflected in Attachment 1, Revised Estimated Sequence of Events Timeline.

Deployment Strategy Transportation 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 3.2.4.6.0 response.

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Dresden Nuclear Power Station's Third Six Month Status Report for the Implementation of FLEX 8/28/2014 Section Reference Overall Integrated Plan Open Item Status 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 3.2.4.2.0 response.

Item Interim Staff Evaluation OPEN Item Status number 3.1.1.1.A Each section of the Integrated Plan Completed. See February 2014 Update describing storage protection from hazards makes reference to Section 11 rather than to the specific protection requirements described in NEI 12-06 for the applicable hazard; that is Section 6.2.3.1 for floods, Section 7.3.1 for wind, 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 Completed. See February 2014 Update access to the Ultimate Heat Sink (UHS) due to flood hazard conditions, the need to provide electrical power for sump pumps, and whether or not flood barriers will be utilized.

Page 5 of 31

Dresden Nuclear Power Station's Third Six Month Status Report for the Implementation of FLEX 8/28/2014 Item Interim Staff Evaluation OPEN Item Status number 3.2.4.8.A Updated information provided by the Proposed Complete licensee as part of the 6-month update As described in Section 4, Changes to Compliance states that they are proposing to install a Method, the conceptual design has changed to prestaged generator to supply all FLEX utilize a trailer mounted generator unit pre-staged related loads for both units in a robust structure near the Reactor Building. Pre-simultaneously for Phase 2 mitigating staging in this manner allows timely strategies. This appears to be an alternative approach for satisfying the implementation of the FLEX strategies by not Mitigating Strategies order. Insufficient requiring transport of the generator prior to use.

information has been provided by the The generator is a portable (trailer mounted) unit licensee in order to determine whether that will be connected through the use of temporary this provides an equivalent level of cabling. The proposed design meets the protection as would be provided through requirements of NEI 12-06 Section 3.2.1.3.(7) and conformance with NET 12-06. Section 3.2.2.(13).

Additionally NET 12-06 Section 3.2.2 states, "It is also acceptable to have a single resource that is sized to support the required functions for multiple units at a site (e.g., a single pump capable of all water supply functions for a dual unit site)." The proposed design utilizes a single generator sized to be capable of powering the required loads of both Units after a FLEX event.

The change to the proposed design meets NEI 12-06 requirements and therefore is not an alternative approach.

Page 6 of 31

Dresden Nuclear Power Station's Third Six Month Status Report for the Implementation of FLEX 8/28/2014 Item Interim Staff Evaluation number CONFIRMATORY Item Status 3.1.1.2.A A postulated downstream dam failure Completed. See February 2014 Update from a seismic event is still being evaluated.

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 NET 12-06, Section 5.3.3, consideration 1.

3.1.1.3.B Use of, or need for ac power to Completed. See February 2014 Update mitigate ground water intrusion was not addressed.

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.

3.1.4.2.A Equipment to clear ice and snow from Completed. See February 2014 Update haul pathways is not identified in plan.

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 Started temperature impacts on FLEX equipment not yet developed.

Page 7 of 31

Dresden Nuclear Power Station's Third Six Month Status Report for the Implementation of FLEX 8/28/2014 Item Interim Staff Evaluation number CONFIRMATORY Item Status 3.2.1.1.A Need benchmarks to demonstrate Proposed Complete.

Modular Accident Analysis Program Information that validates the use of MAAP4 and that (MAAP) 4 is the appropriate code for provides response to this item is contained in Attachment simulation of ELAP. 4, MAAP Justification for ELAP Analysis Acceptability.

3.2.1.1.B For MAAP4, collapsed level must Proposed Complete.

remain above Top of Active Fuel and Information that validates the use of MAAP4 and that cool down rate must meet technical provides response to this item is contained in Attachment specifications. 4, MAAP Justification for ELAP Analysis Acceptability.

To provide a definitive time frame for worst case action points the Dresden MAAP cases assume no RPV makeup after HPCI is assumed to fail (approximately 2.5 hours5.787037e-5 days <br />0.00139 hours <br />8.267196e-6 weeks <br />1.9025e-6 months <br /> after event initiation). The Dresden strategy is to utilize Standby Liquid Control (SBLC) as a high pressure makeup source when the FLEX Generator begins supplying power to safety related electrical busses.

MAAP Case 11 (available in ePortal Document title -

Dresden FLEX - Overview of MAAP Results - MAAP Analysis DR-MISC-043, Rev. 1.doc) represents the expected plant response to the FLEX strategy most likely to be utilized. Case 11 demonstrates 37.3 hours3.472222e-5 days <br />8.333333e-4 hours <br />4.960317e-6 weeks <br />1.1415e-6 months <br /> are available to restore RPV makeup prior to water level dropping below TAF. The Dresden timeline assumes RPV makeup will be initiated prior to that time period.

3.2.1.1.0 MAAP4 use must be consistent with Proposed Complete.

June 2013 position paper. Information that validates the use of MAAP4 and that provides response to this item is contained in Attachment 4, MAAP Justification for ELAP Analysis Acceptability.

3.2.1.1.D In using MAAP4, the licensee must Proposed Complete.

identify and justify the subset of key Information that validates the use of MAAP4 and that modeling parameters cited from provides response to this item is contained in Attachment Tables 4-1 through 4-6 of the 4, MAAP Justification for ELAP Analysis Acceptability.

"MAAP4 Application Guidance, Desktop Reference for Using MAAP4 Software, Revision 2" (Electric Power Research Institute Report 1 020236).

3.2.1.1.E The specific MAAP4 analysis case Proposed Complete.

that was used to validate the timing of Information that validates the use of MAAP4 and that mitigating strategies in the integrated provides response to this item is contained in Attachment plan must be identified and should be 4, MAAP Justification for ELAP Analysis Acceptability.

available on the ePortal for NRC staff to view. Alternately, a comparable level of information may be included in the supplemental response.

Page 8 of 31

Dresden Nuclear Power Station's Third Six Month Status Report for the Implementation of FLEX 8/28/2014 Item Interim Staff Evaluation number CONFIRMATORY Item Status 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 timeline. 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 NET 12-06. To be provided in a future six (6) month update.

Page 9 of 31

Dresden Nuclear Power Station's Third Six Month Status Report for the Implementation of FLEX 8/28/2014 Item Interim Staff Evaluation number CONFIRMATORY Item Status 3.2.1.6.A Whether or not backup compressed Proposed complete.

air for valve actuation is required, is The Isolation Condenser (IC) removes decay heat with contingent on the MAAP4 analyses no loss of inventory from the reactor coolant system conclusions. The MAAP4 (although there still may be some leakage from the conclusions will determine if assumed RPV leakage into the Drywell), and with no containment venting is necessary. addition of heat to the suppression pool. As long as the shell side of the IC is replenished (phase 2) with sufficient water, the IC will remove adequate decay heat to maintain core cooling. MAAP analysis Case 11 (available in ePortal Document title - Dresden FLEX -

Overview of MAAP Results - MAAP Analysis DR-MISC-043, Rev. 1.doc) identified drywell pressure would be approximately 20 psig at 2.5 hours5.787037e-5 days <br />0.00139 hours <br />8.267196e-6 weeks <br />1.9025e-6 months <br /> from the start of the event, at which time, IC would be re-initiated and HPCI would be assumed lost. Review of the Case 11 MAAP results indicate containment pressure remains below design limits if RPV water remains above TAF and the IC is operating.

BWROG document NEDC-33771P, "GEH Evaluation of FLEX Implementation Guidelines" has been compared to the Dresden proposed strategies and Modular Accident Analysis Program (MAAP) results. The results of the BWROG document and Dresden response are consistent.

In each case at the end of 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> the peak containment values are below their respective design limits with significant margins to the limits. Therefore, containment venting to remove heat from the containment is not required. As such, backup compressed air will not be required.

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

Page 10 of 31

Dresden Nuclear Power Station's Third Six Month Status Report for the Implementation of FLEX 8/28/2014 Item Interim Staff Evaluation number CONFIRMATORY Item Status 3.2.3.A There are outstanding issues Proposed complete.

regarding the acceptability of the Information that validates the use of MAAP4 is MAAP4 analysis. The potential for contained in Attachment 4, MAAP Justification for impact of MAAP4 results on the ELAP Analysis Acceptability.

containment heat removal strategy The Isolation Condenser (IC) removes decay heat with needs to be reviewed.

no loss of inventory from the reactor coolant system (although there still may be some leakage from the assumed RPV leakage into the Drywell), and with no addition of heat to the suppression pool. As long as the shell side of the IC is replenished (phase 2) with sufficient water, the IC will remove adequate decay heat to maintain core cooling. MAAP analysis Case 11 (available in ePortal Document title - Dresden FLEX -

Overview of MAAP Results - MAAP Analysis DR-MISC-043, Rev. 1.doc) identified drywell pressure would be approximately 20 psig at 2.5 hours5.787037e-5 days <br />0.00139 hours <br />8.267196e-6 weeks <br />1.9025e-6 months <br /> from the start of the event, at which time, IC would be re-initiated and HPCI would be assumed lost. Review of the Case 11 MAAP results indicate containment pressure remains below design limits if RPV water remains above TAF and the IC is operating.

BWROG document NEDC-33771P, "GEH Evaluation of FLEX Implementation Guidelines" has been compared to the Dresden proposed strategies and Modular Accident Analysis Program (MAAP) results. The results of the BWROG document and Dresden response are consistent.

In each case at the end of 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> the peak containment values are below their respective design limits with significant margins to the limits. Therefore, containment venting to remove heat from the containment is not required. As such, a specific containment heat removal strategy beyond that identified above will not be required.

3.2.4.2.A A discussion is needed on the effects Not started of extreme low temperatures (i.e.,

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.

3.2.4.2.B Procedure will be developed to Not started address controlling battery room hydrogen concentration.

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Dresden Nuclear Power Station's Third Six Month Status Report for the Implementation of FLEX 8/28/2014 Item Interim Staff Evaluation CONFIRMATORY Item Status number 3.2.4.2.0 Evaluations to address loss of Not started ventilation in the auxiliary equipment electric room and Battery Rooms are not complete.

3.9.4.2.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.

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

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

ADAMS Accession Nos. ML12306A199 and ML13056A135.

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

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

3.2.4.6.B Final GOTHIC analysis for the HPCI Started room temperature rise is not complete.

3.2.4.6.0 Habitability of the control room Started should consider temperature limits of NUMARC 87-00 and M1L-STD-1472C.

3.2.4.8.B Detailed designs will identify Not started comprehensive load lists to confirm conceptual load assumptions.

3.2.4.8.0 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.

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Dresden Nuclear Power Station's Third Six Month Status Report for the Implementation of FLEX 8/28/2014 Item Interim Staff Evaluation number CONFIRMATORY Item Status 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).
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", NE! 12-06, Revision 0, August 2012 Page 13 of 31

Dresden Nuclear Power Station's Third Six Month Status Report for the Implementation of FLEX 8/28/2014

5. Dresden's First 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, dated August 28, 2013
6. 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, dated February 28, 2014
7. Attachment 1 Revised Estimated Sequence of Events Timeline.
8. Attachment 2, Simplified FLEX Makeup Conceptual Design
9. Attachment 3, Simplified FLEX Electrical Conceptual Design
10. Attachment 4, MAAP Justification for ELAP Analysis Acceptability Page 14 of 31

Dresden Nuclear Power Station's Third Six Month Status Report for the Implementation of FLEX 8/28/2014 Attachment 1 Revised Estimated Sequence of Events Timeline Action I Elapsed Action Time Remarks / Applicability item Time Constraint Y/N 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 Attempt to start SBO DG for either Unit N Per FLEX event initial conditions the SBO DGs are not available.

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

If yes, include technical basis discussion as requires by NE! 12-06, Section 3.2.1.7 Page 15 of 31

Dresden Nuclear Power Station's Third Six Month Status Report for the Implementation of FLEX 8/28/2014 Attachment 1 Revised Estimated Sequence of Events Timeline Action Elapsed Action Time Remarks / Applicability item Time Constraint Y/N 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 Perform 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 low Y Per UFSAR, the IC will shell-side water level without a shell- operate for approximately side makeup source. 20 minutes without shell-side makeup. It is secured when shell-side level is low to prevent possible damage.

11 30 mins 125 and 250 VDC Load Shed Y DGA 12 Step D.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 Y 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 from the Unit 3 Suppression Pool.
  • Personnel dispatched to FLEX strategy for supplying power to the FLEX Makeup Pump and station battery chargers Page 16 of 31

Dresden Nuclear Power Station's Third Six Month Status Report for the Implementation of FLEX 8/28/2014 Attachment 1 Revised Estimated Sequence of Events Timeline Action Elapsed Action Time Remarks / Applicability item Time Constraint Y/N 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 Unit 3 FLEX Makeup Pump completed. cables and connecting to the selected FLEX Makeup pump.

18 2.5 Unit 3 FLEX pump connected and Y Due to pre-staging of major hours supplying Isolation Condenser shell-side components, it is makeup. reasonable to expect the FLEX pump can be available within this time period.

Page 17 of 31

Dresden Nuclear Power Station's Third Six Month Status Report for the Implementation of FLEX 8/28/2014 Attachment 1 Revised Estimated Sequence of Events Timeline Action Elapsed Action Time Remarks / Applicability item Time Constraint Y/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 N HPCI may continue to hours pool temperature of 2140°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 3 hours3.472222e-5 days <br />8.333333e-4 hours <br />4.960317e-6 weeks <br />1.1415e-6 months <br /> Personnel dispatched to align power to a N Time is reasonable FLEX makeup pump from the Unit 2 approximation based on Suppression Pool and align hoses for operating crew assessment supplying make-up water to the Isolation of plant conditions.

Condenser shell-side.

71 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. available to supply power to battery chargers and other desired loads such as SBLC and SBGT.

Preliminary review 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.

23 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 valves sooner this is accomplished the more reactor inventory is conserved.

Page 18 of 31

Dresden Nuclear Power Station's Third Six Month Status Report for the Implementation of FLEX 8/28/2014 Attachment 1 Revised Estimated Sequence of Events Timeline Action Elapsed Action Time Remarks / Applicability item Time Constraint Y/N 1 24 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. Recirculation Loops are isolated and the Isolation Condenser is controlling reactor pressure, RPV leakage will be reduced to approximately 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).

25 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> Personnel dispatched to deploy a N Time is reasonable submersible pump from the Robust approximation based on Storage location to provide water from operating crew assessment of plant conditions.

UHS for long-term Suppression Pool makeup. Additional site resources will be available 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> after event initiation to aid in this effort including personnel to operate equipment such as mobile lifting device to deploy submersible pump in the UHS.

26 7 hours8.101852e-5 days <br />0.00194 hours <br />1.157407e-5 weeks <br />2.6635e-6 months <br /> Unit 2 FLEX pump connected and Y This action must be supplying Isolation Condenser shell-side completed prior to Unit 3 makeup. Suppression Pool inventory being reduced below 11 feet.

27 10 Personnel dispatched to establish N Further analysis is required hours temporary ventilation to the MCR and to determine if AEER (portable fans and associated supplemental ventilation is generators). needed.

Page 19 of 31

Dresden Nuclear Power Station's Third Six Month Status Report for the Implementation of FLEX 8/28/2014 Attachment 1 Revised Estimated Sequence of Events Timeline Action Elapsed Action Time Remarks / Applicability item Time Constraint Y/N 1 28 l'? 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.

29 14 Unit 2 Suppression Pool Makeup Y Long term makeup water hours available from UHS using portable source will be available equipment before the water contained in the Suppression Pools for both Units is exhausted.

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

30 24 Initial equipment from National SAFER N NEI 12-06 assumption.

hours Response Center becomes available.

31 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 National SAFER Response Center equipment in spare capacity.

Page 20 of 31

Dresden Nuclear Power Station's Third Six Month Status Report for the Implementation of FLEX 8/28/2014 Attachment 2 Shutdown Shutdown U2 Alternate ISCO Makeup 4...

Cooling Cooling 1J3 Alternate ISCO Makeup U3 SBLC F-1i 02 S8LC r---1 Flood Pump (Primary)

SFP Cleanup SFP Tank Thqr Flood Pump (Alternate Tank . Cleanup Return Diffuser L.1 (UMW, Return 001.7 Diffuser 104 C 02 SBLC Tankt-U3 Isolation Condenser 1)2 =WWI 03 SBLC Tank*--

Condenser

.74 5) psi ) Orywell Sway Dryvies Spray Orrieli Spray Cgriell SPRY 0

Del FLPV RPV TONS TORN (lea) Peal LPCI LPCI

---P4C14 Rep D Pulp 134-0144-1104 C 10,4 FLEX Pump 3A FLEX Pump 38 FLEX Pump 28 FLEX Pump 2A 3_

1: LPIVA°31-13-7. I.

--1:;.411-71 LPCI PL r.°.#1-ta-rip C 4:5-11P%V ump143A I- ..10.Z.V on1m p 1d A

LPCI Purp 0 LPG! Rep El LPCI Purip 8 LPCI Pump D 03 Reactor 02 Reactor Building Building OHS FLEX Diesel Driven Hydraulic Pump Existing FLEX CONCEPT11A1 12E1101.

July 31, 2014 Page 21 of 31

Dresden Nuclear Power Station's Third Six Month Status Report for the Implementation of FLEX 8/28/2014 Attachment 3 Flex Diesel Generator Flex Diesel Generator (non-flood scenario) (flood scenario) k G' G Temporary Power Unit (TPU) Temporary 1 Power Unit

---artPU, - -*---

(I PU)

Above U2 Diesel Reactor Gereralor Building Building Trackway Area Interlock Reactor Building I.

Bus Connection Flex Pump Devices (BCD) 2A/213:3Ai3B iffool 1 015; "1- 39 38 1- 29 28 -

---A--r Portable Cable and Devices Existing/ Pre-staged Equipment Page 22 of 31

Dresden Nuclear Power Station's Third Six Month Status Report for the Implementation of FLEX 8/28/2014 Attachment 4 MAAP JUSTIFICATION FOR ELAP ANALYSIS ACCEPTABILITY Dresden Nuclear Power Station Response 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 Dresden.

ITEM (NOTE this item corresponds to NRC Interim Staff Evaluation CONFIRMATORY action item 3.2.1.1.A of the Dresden evaluation)

(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 provided by EPRI BWR Roadmap "Technical Basis for Establishing Success Timelines in Extended Loss of AC Power Scenarios in Boiling Water Reactors Using MAAP4," (EPRI Product ID 3002002749).

ITEM (NOTE this item corresponds to NRC Interim Staff Evaluation CONFIRMATORY action item 3.2.1.1.B of the Dresden evaluation)

(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 updated Dresden Integrated Plan (Aug 2013) indicates that Dresden will utilize the isolation condenser for RPV pressure control which will not exceed the technical specifications limit for RPV cooldown of 100°F/hr. The following plots of the bulk RPV water temperature and RPV pressure from the MAAP analysis confirms this cooldown criteria for the supporting MAAP calculation. Note that the Dresden Integrated Plan does not credit external RPV injection prior to core uncovery in the MAAP analysis. This modeling assumptions leads to unrealistic spikes in RPV pressure and RPV bulk water temperature due to the core being uncovered after approximately 20 hours2.314815e-4 days <br />0.00556 hours <br />3.306878e-5 weeks <br />7.61e-6 months <br />. It is expected that successful core cooling and prevention of the RPV collapsed water level dropping below TAF would be shown when external RPV injection is included in the calculation. This would avoid these unrealistic assessments after the IC becomes ineffective.

Page 23 of 31

Dresden Nuclear Power Station's Third Six Month Status Report for the Implementation of FLEX 8/28/2014 Attachment 4 MAAP JUSTIFICATION FOR ELAP ANALYSIS ACCEPTABILITY 1400

.4 1200 T/5 0.

' 1000 a.

BOO (i) 500 IX 400 0_

ix 200 20 40 60 80 TIME, HOURS MAAP Calculation of RPV Pressure During RPV Depressurization 600 500 W 400 2

i 300

-tt 200 100 CO

a. 0 0 20 40 60 80 TIME, HOURS MAAP Calculation of RPV Bulk Water Temperature During RPV Depressurization Page 24 of 31

Dresden Nuclear Power Station's Third Six Month Status Report for the Implementation of FLEX 8/28/2014 Attachment 4 MAAP JUSTIFICATION FOR ELAP ANALYSIS ACCEPTABILITY For the representative MAAP run (Case 9), the collapsed RPV water level inside the shroud drops below TAF and remains below TAF for the duration of the analysis. The plot below shows that the lowest RPV level, calculated by MAAP, was far below instrument zero. Instrument zero is at +503" above vessel zero. TAF is located at -143" relative to instrument zero. The Dresden analysis cites the use of external FLEX pump make-up to the RPV prior to the collapsed RPV water level dropping below TAF which would prevent the core from being uncovered.

100 50 O 0 LL.

z -50 w 100

> z w w -150

_1 2 w 200 5z

> -300 a_

-350

-400 0 20 40 60 80 TIME, HOURS MAAP Calculation of Collapsed RPV Water Level Inside the Shroud ITEM (NOTE this item corresponds to NRC Interim Staff Evaluation CONFIRMATORY action item 3.2.1.1.0 of the Dresden evaluation)

(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 Dresden 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"..

Page 25 of 31

Dresden Nuclear Power Station's Third Six Month Status Report for the Implementation of FLEX 8/28/2014 Attachment 4 MAAP JUSTIFICATION FOR ELAP ANALYSIS ACCEPTABILITY ITEM (NOTE this item corresponds to NRC Interim Staff Evaluation CONFIRMATORY action item 3.2.1.1.D of the Dresden evaluation)

(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" (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 / 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 / actinides / 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 Dresden MAAP 4.0.5 parameter file divides the core region into 5 equal volume radial regions and 13 axial regions. The axial nodalization represents 10 equal-sized fueled nodes, 1 unfueled node at the top, and 2 unfueled nodes at the bottom. The figure below, taken from the MAAP Users Manual, illustrates the vessel nodalization scheme.

Page 26 of 31

Dresden Nuclear Power Station's Third Six Month Status Report for the Implementation of FLEX 8/28/2014 Attachment 4 MAAP JUSTIFICATION FOR ELAP ANALYSIS ACCEPTABILITY SRV 1.* LC-CA j* 4 Upper 4,4-4=3 to LOCA 3 Key Standpipes Gas Flow Separators O Path No.

A Heat Sink La Surface No.

5 2 Shroud Upper I= Heat Sink Head Down.

corner 0 Generalized

-- CT Opening 1 P Generalized

-10. Opening 2 1 Core 61UMW \ -... 4r .............. Generakzed Ow met co Opening 3 1,

...22 .---..

,- ,. LOCA

\ \

  • ot 7 Lower Head A Low Path 8 s.A. *., N. ',N.:\ _Ny',..
  • GE for RH944174.COR 0+

=tie Page 27 of 31

Dresden Nuclear Power Station's Third Six Month Status Report for the Implementation of FLEX 8/28/2014 Attachment 4 MAAP JUSTIFICATION FOR ELAP ANALYSIS ACCEPTABILITY Containment nodalization is defined by the user. The standard nodalization scheme is used in the Dresden MAAP 4.0.5 parameter file and represents the following individual compartments:

1. Reactor pedestal region
2. Drywell
3. Drywell vents to torus
4. Torus (Wetwell)

The figure below illustrates the Dresden containment nodalization along with an identification of containment flow junctions.

Junction Description 1 Pedestal Door to Drywell 2 Drywell to Vents/Downcomers 3 Vents/Downcomers to Suppression Pool Drywell

--> Vent 4 Drywell 4

Vent/Failure 5,6,7,8 Suppression 7--> Leakage Chamber to Vent Vacuum Breakers 9 Suppression Pedestal Chamber Vent/Failure 7> Shell Failure 10 Drywell Leakage 33 Drywell Shell 2 Failure Vents/

Down-corners Vent/Failure 5,6,7,8 9 Suppression Chamber 3

b. General two-phase flow from the reactor vessel is described in the EPRI BWR Roadmap. 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 SRV will be single-phase steam and flow from the recirc pump seal or other RPV leakage will be single-phase liquid due to the location of the break low in the RPV with Page 28 of 31

Dresden Nuclear Power Station's Third Six Month Status Report for the Implementation of FLEX 8/28/2014 Attachment 4 MAAP JUSTIFICATION FOR ELAP ANALYSIS ACCEPTABILITY RPV level continued to be maintain above TAF. Upon exiting the RPV, the seal leakage will flash a portion of the flow to steam based on saturated conditions in the drywell, creating a steam source and a liquid water source to the drywell. As described in the BWR Roadmap (EPRI Product ID 3002002749) there are two parameters that can influence the two-phase level on the RPV. The following table confirms that the parameter values match the recommended values as outlined in the roadmap.

Value Used in the EPRI Parameter Name Dresden MAAP Analysis Recommended Value FCO 1.5248 1.5248 FCHTUR 1.53 1.53

c. Modeling of heat transfer and losses from the RPV are described in the EPRI BWR Roadmap. The parameters that control these processes, as defined in the Roadmap, are provided below with the values selected to represent Dresden.

Value Used in the Parameter Name Dresden MAAP Analysis Comment QCO not-thru-insulation 4.2E6 BTU/hr Plant specific value based on heat transfer from RPV drywell heat removal to coolers during normal operation. during normal operation. Typical values range between 1-2 MW (3.4E6 to 6.8E6 BTU/hr).

FIN PLT number of plates 8 Plant-specific value in reflective insulation XTINS average reflective 0.5 ft Plant-specific value insulation thickness At the request of the NRC, the following information, as used in the MAAP analysis, is provided.

Parameter Value Used in the Parameter Definition Name in MAAP Dresden MAAP Analysis Power level, MWth QCRO 2957 MWth Initial CST water volume, gal VCSTO (ft3) 409,971 ft3 Initial CST water HCST (enthalpy) 94°F Page 29 of 31

Dresden Nuclear Power Station's Third Six Month Status Report for the Implementation of FLEX 8/28/2014 Attachment 4 MAAP JUSTIFICATION FOR ELAP ANALYSIS ACCEPTABILITY temperature, F Initial suppression pool water Calculated from input 7,264,000 Ibm mass, lbm Initial suppression pool water XWRBO(i), where i is node 14.84 ft level, ft number for wetwell Initial suppression pool water TWRBO(i), where i is node 85°F temperature, F number for wetwell Drywell free volume, ft3 VOLRB(i), where I is node 145,786.23 ft3 number for drywell Wetwell free volume, ft3 VOLRB(i) volume of 238,375.6 ft3 suppression pool water from initial pool mass Containment vent pressure, Refer to MAAP analysis N/A psia document (containment is not vented)

RCIC max flow rate, gpm WVRCIC N/A (Dresden does not have RCIC)

Max FLEX pump flow rate, Refer to MAAP analysis 500 gpm gpm document Lowest set SRV flow rate, Derived from SRV area, 540,000 lb/hr lb/hr ASRV Lowest set SRV pressure, PSETRV 1125.2 psia psia Recirc pump seal leakage, Value that was used to 61 gpm gpm define LOCA area, ALOCA Total leakage used in the Value that was used to 61 gpm transient, gpm define LOCA area, ALOCA

d. Choked flow from the SRV and the recirculation pump seal leakage is discussed in the EPRI BWR Roadmap. The parameters identified that impact the flow calculation are listed below with input values identified.

Value Used in the EPRI Parameter Name Dresden MAAP Analysis Recommended Value ASRV effective flow area for 0.062 ft2 Plant-specific value Page 30 of 31

Dresden Nuclear Power Station's Third Six Month Status Report for the Implementation of FLEX 8/28/2014 Attachment 4 MAAP JUSTIFICATION FOR ELAP ANALYSIS ACCEPTABILITY relief valve (based on rated flow at pressure)

ALOCA seal leakage area 9.55E-4 ft2 Plant-specific value (61 gpm at normal conditions)

FCDBRK discharge 0.75 0.75 coefficient for seal leakage

e. Venting of the containment was not considered in the Dresden MAAP analysis.
f. Decay heat in MAAP is discussed in the EPRI BWR Roadmap (EPRI Product ID 3002002749). Input parameters used to compute the decay heat are identified in the roadmap and are listed in the following table along with their values used in the Dresden analysis.

Value Used in the EPRI Parameter Name Dresden MAAP Analysis Recommended Value FENRCH normal fuel enrichment 0.0409 Plant-specific value EXPO average exposure 20,000 MW-day/ton Plant-specific value FCR total capture rate of U-238 / 0.324 Plant-specific value total absorption rate FFAF total absorption rate / total 2.37 Plant-specific value fission rate FQFR1 fraction of fission power 0.476 Plant-specific value due to U-235 and PU-241 FQFR2 fraction of fission power 0.437 Plant-specific value due to PU-239 FQFR3 fraction of fission power 0.087 Plant-specific value due to U-238 TIRRAD average effective 26,280 hours0.00324 days <br />0.0778 hours <br />4.62963e-4 weeks <br />1.0654e-4 months <br /> Plant-specific value irradiation time for entire core ITEM (NOTE this item corresponds to NRC Interim Staff Evaluation CONFIRMATORY action item 3.2.1.1.E of the Dresden evaluation)

(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 Page 31 of 31

Dresden Nuclear Power Station's Third Six Month Status Report for the Implementation of FLEX 8/28/2014 Attachment 4 MAAP JUSTIFICATION FOR ELAP ANALYSIS ACCEPTABILITY 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 Dresden Integrated Plan is documented in calculation DR-MISC-043 Rev. 1 and is available on the ePortal. Case 9 was the specific MAAP run selected to represent the scenario as described in Attachment 1A of the integrated plan.

Page 32 of 32

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