ML14248A238: Difference between revisions
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: 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 | : 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 | : 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," | : 3. NEI 12-06, "Diverse and Flexible Coping Strategies (FLEX) Implementation Guide," Revision 0, dated August 2012 | ||
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 | : 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) | : 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) | ||
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==Enclosure:== | ==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) | : 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), | 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. | ||
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. | 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. | 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. | ||
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Note 1 Nov 2015 | Note 1 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 Operational (will be a standard date from National SAFER Response Center) | * 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 Operational (will be a standard date from National SAFER Response Center) | ||
Nov 2015 Unit 2 Implementation date Note 1 Nov 2016 Unit 3 Implementation date Note 1 Note(s) | 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. | ||
: 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. | 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. | 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. | ||
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Section Reference Overall Integrated Plan Open Item Status Sequence of Events (page 5-6) | Section Reference Overall Integrated Plan Open Item Status Sequence of Events (page 5-6) | ||
The times to complete actions in the Events 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. | The times to complete actions in the Events 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. | ||
Not Started 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 (page 5) | Not Started 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 (page 5) Analysis of deviations between Exelon's engineering analyses and the analyses contained 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. | ||
Analysis of deviations between Exelon's engineering analyses and the analyses contained 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. | Completed. See August 2013 Update Sequence of Events (page 8) Initial evaluations were used to determine the fuel pool timelines. Formal calculations will be performed to validate this information during development of the spent fuel pool cooling strategy detailed detailed design. | ||
Completed. See August 2013 Update Sequence of Events (page 8) | |||
Initial evaluations were used to determine the fuel pool timelines. Formal calculations will be performed to validate this information during development of the spent fuel pool cooling strategy detailed detailed design. | |||
Proposed Complete. | Proposed Complete. | ||
Engineering Change (EC) 31913, TIME TO BOIL CURVES - | Engineering Change (EC) 31913, TIME TO BOIL CURVES - | ||
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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. | 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 hours 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. | In each case at the end of 24 hours 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 of extreme low temperatures (i.e., | 3.2.4.2.A A discussion is needed on the effects 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. | ||
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. | |||
Not started 3.2.4.2.B Procedure will be developed to address controlling battery room hydrogen concentration. | Not started 3.2.4.2.B Procedure will be developed to address controlling battery room hydrogen concentration. | ||
Not started Page 11 of 31 Dresden Nuclear Power Station's Third Six Month Status Report for the Implementation of FLEX 8/28/2014 Item number Interim Staff Evaluation CONFIRMATORY Item Status 3.2.4.2.0 Evaluations to address loss of ventilation in the auxiliary equipment electric room and Battery Rooms are not complete. | Not started Page 11 of 31 Dresden Nuclear Power Station's Third Six Month Status Report for the Implementation of FLEX 8/28/2014 Item number Interim Staff Evaluation CONFIRMATORY Item Status 3.2.4.2.0 Evaluations to address loss of ventilation in the auxiliary equipment electric room and Battery Rooms are not complete. | ||
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Actions can be coordinated with personnel obtaining and staging portable generators, fans, etc. | Actions can be coordinated with personnel obtaining and staging portable generators, fans, etc. | ||
14 2 hours Establish natural air flow to HPCI room by opening doors. | 14 2 hours Establish natural air flow to HPCI room by opening doors. | ||
Y Preliminary GOTHIC analysis indicates opening doors at 2 hours will result in acceptable room temperature values to support operation of HPCI for at least 6 hours. HPCI room temperature remains below the isolation point during this time. HPCI operation is assumed for approximately 2.5 hours in Phase 1. | Y Preliminary GOTHIC analysis indicates opening doors at 2 hours will result in acceptable room temperature values to support operation of HPCI for at least 6 hours. HPCI room temperature remains below the isolation point during this time. HPCI operation is assumed for approximately 2.5 hours in Phase 1. 15 2 hours Complete actions for loss of Main Control Room Ventilation. | ||
15 2 hours Complete actions for loss of Main Control Room Ventilation. | |||
N DOA 5750-01 actions. | N DOA 5750-01 actions. | ||
16 2 hours Defeat HPCI high temperature and flow isolations N Ensure HPCI remains available during the event. | 16 2 hours Defeat HPCI high temperature and flow isolations N Ensure HPCI remains available during the event. | ||
17 2.5 hours FLEX strategy for supplying power to a Unit 3 FLEX Makeup Pump completed. | 17 2.5 hours FLEX strategy for supplying power to a Unit 3 FLEX Makeup Pump completed. | ||
Y Involves running temporary cables and connecting to the selected FLEX Makeup pump. 18 2.5 hours Unit 3 FLEX pump connected and supplying Isolation Condenser shell-side makeup. Y Due to pre-staging of major components, it is 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 Revised Estimated Sequence of Events Timeline Action item Elapsed Time Action Time Constraint Y/N 1 Remarks / Applicability 19 2.5 hours Isolation Condenser initiated for RPV pressure control Y Complete prior to loss of HPCI to ensure RPV heat removal mechanism operating prior to MAAP analysis assumed HPCI loss. 20 2.5 hours HPCI assumed to fail due to suppression pool temperature of 2140°F N HPCI may continue to 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. | Y Involves running temporary cables and connecting to the selected FLEX Makeup pump. 18 2.5 hours Unit 3 FLEX pump connected and supplying Isolation Condenser shell-side makeup. Y Due to pre-staging of major components, it is 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 Revised Estimated Sequence of Events Timeline Action item Elapsed Time Action Time Constraint Y/N 1 Remarks / Applicability 19 2.5 hours Isolation Condenser initiated for RPV pressure control Y Complete prior to loss of HPCI to ensure RPV heat removal mechanism operating prior to MAAP analysis assumed HPCI loss. 20 2.5 hours HPCI assumed to fail due to suppression pool temperature of 2140°F N HPCI may continue to 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 hours Personnel dispatched to align power to a FLEX makeup pump from the Unit 2 Suppression Pool and align hoses for supplying make-up water to the Isolation Condenser shell-side. | ||
21 3 hours Personnel dispatched to align power to a FLEX makeup pump from the Unit 2 Suppression Pool and align hoses for supplying make-up water to the Isolation Condenser shell-side. | |||
N Time is reasonable approximation based on operating crew assessment of plant conditions. | N Time is reasonable approximation based on operating crew assessment of plant conditions. | ||
71 6 hours FLEX strategy for supplying power to 480 VAC busses and associated Motor Control Centers (MCCs) completed. | 71 6 hours FLEX strategy for supplying power to 480 VAC busses and associated Motor Control Centers (MCCs) completed. | ||
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N Further analysis is required to determine if supplemental ventilation is needed. Page 19 of 31 Dresden Nuclear Power Station's Third Six Month Status Report for the Implementation of FLEX 8/28/2014 Revised Estimated Sequence of Events Timeline Action item Elapsed Time Action Time Constraint Y/N 1 Remarks / Applicability 28 l'? hours Makeup to the Spent Fuel Pools using FLEX pump strategy is available. | N Further analysis is required to determine if supplemental ventilation is needed. Page 19 of 31 Dresden Nuclear Power Station's Third Six Month Status Report for the Implementation of FLEX 8/28/2014 Revised Estimated Sequence of Events Timeline Action item Elapsed Time Action Time Constraint Y/N 1 Remarks / Applicability 28 l'? hours Makeup to the Spent Fuel Pools using FLEX pump strategy is available. | ||
Y EC 371913, Revision 2,: | Y EC 371913, Revision 2,: | ||
Time-to-Boil Curves., | Time-to-Boil Curves., identifies a time to boil of 9.54 hours, and 110.07 hours to the top of active fuel. Therefore completing the equipment line-up for initiating SFP make-up at 12 hours into the event ensures adequate cooling of the spent fuel is maintained. | ||
identifies a time to boil of 9.54 hours, and 110.07 hours to the top of active fuel. Therefore completing the equipment line-up for initiating SFP make-up at 12 hours into the event ensures adequate cooling of the spent fuel is maintained. | |||
29 14 hours Unit 2 Suppression Pool Makeup available from UHS using portable equipment Y Long term makeup water source will be available before the water contained in the Suppression Pools for both Units is exhausted. | 29 14 hours Unit 2 Suppression Pool Makeup available from UHS using portable equipment Y Long term makeup water 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. 30 24 hours Initial equipment from National SAFER Response Center becomes available. | Makeup from the UHS will not be required before this time. 30 24 hours Initial equipment from National SAFER Response Center becomes available. | ||
N NEI 12-06 assumption. | N NEI 12-06 assumption. | ||
31 24-72 hours Continue to maintain critical functions 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. | 31 24-72 hours Continue to maintain critical functions 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. | ||
N None Page 20 of 31 SFP Cleanup Return Diffuser LPCI PL--1:;.411- | N None Page 20 of 31 SFP Cleanup Return Diffuser LPCI PL--1:;.411-7 1 r.°.#1-ta-rip C 4:5-11P%V 143-ump A LPCI Purp 0 LPG! Rep El | ||
-1:LPIVA°31-13-7. I. I-*.1.0.Z. | -1: LPIVA°31-13-7. I. I-*.1.0.Z.V 1m on 1-d p A LPCI Purip 8 LPCI Pump D RPV TORN Peal U2 Alternate ISCO Makeup 4... | ||
1J3 Alternate ISCO Makeup Shutdown Cooling Cgriell SPRY Orrieli Spray SFP Cleanup Return Diffuser 02 S8LC r---1 Flood Pump (Primary) | 1J3 Alternate ISCO Makeup Shutdown Cooling Cgriell SPRY Orrieli Spray SFP Cleanup Return Diffuser 02 S8LC r---1 Flood Pump (Primary) | ||
Tank | Tank Th qr 001.7 Flood Pump (Alternate 104 C ---------- | ||
02 SBLC Tankt-1)2 =WWI 03 SBLC Tank*-- | 02 SBLC Tankt-1)2 =WWI 03 SBLC Tank*-- | ||
Condenser Del LPCI LPCI --- | Condenser Del LPCI LPCI ---P 4 C14 Rep D Pulp 13 4-0 14 4- 10 , 4 FLEX Pump 28 FLEX Pump 2A Shutdown Cooling U3 SBLC i F-1 Tank . L.1 (UMW, Dryvies Spray | ||
: 5) U3 Isolation Condenser | : 5) U3 Isolation Condenser | ||
.74 psi ) Orywell Sway 0 FLPV TONS (lea) 1104 C FLEX Pump 3A FLEX Pump 38 | .74 psi ) Orywell Sway 0 FLPV TONS (lea) 1104 C FLEX Pump 3A FLEX Pump 38 | ||
-3_ Dresden Nuclear Power Station's Third Six Month Status Report for the Implementation of FLEX 8/28/2014 OHS FLEX Diesel Driven Hydraulic Pump Existing FLEX CONCEPT11A1 12E1101. | -3_ Dresden Nuclear Power Station's Third Six Month Status Report for the Implementation of FLEX 8/28/2014 OHS FLEX Diesel Driven Hydraulic Pump Existing FLEX CONCEPT11A1 12E1101. July 31, 2014 03 Reactor Building 02 Reactor Building Page 21 of 31 Temporary Power Unit (I PU) Above U2 Reactor Building Trackway Interlock Diesel Gereralor Building Area Flex Pump 2A/213:3Ai3B Bus Connection Devices (BCD) 28 - "1- 39 iffool 38 1 015; 1- 29 ---A--r- Flex Diesel Generator (non-flood scenario) k G ' Temporary Power Unit 1 (TPU) ---artPU-*--- , - Flex Diesel Generator (flood scenario) | ||
July 31, 2014 03 Reactor Building 02 Reactor Building Page 21 of 31 Temporary Power Unit (I PU) Above U2 Reactor Building Trackway Interlock Diesel Gereralor Building Area Flex Pump 2A/213:3Ai3B Bus Connection Devices (BCD) 28 - "1- 39 iffool 38 | |||
G - Portable Cable and Devices Existing/ Pre-staged Equipment Reactor Building I. Dresden Nuclear Power Station's Third Six Month Status Report for the Implementation of FLEX 8/28/2014 Page 22 of 31 Dresden Nuclear Power Station's Third Six Month Status Report for the Implementation of FLEX 8/28/2014 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. | G - Portable Cable and Devices Existing/ Pre-staged Equipment Reactor Building I. Dresden Nuclear Power Station's Third Six Month Status Report for the Implementation of FLEX 8/28/2014 Page 22 of 31 Dresden Nuclear Power Station's Third Six Month Status Report for the Implementation of FLEX 8/28/2014 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) | ITEM (NOTE - this item corresponds to NRC Interim Staff Evaluation CONFIRMATORY action item 3.2.1.1.A of the Dresden evaluation) | ||
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Response to item 4: | 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. | : 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 SRV j* 4 Upper 4,4-4=3 to | Page 26 of 31 SRV j* 4 Upper 4,4-4=3 to o t 1.* LC-CA LOCA ___..0 Generalized P --CT Opening 1 Generalized -10. Opening 2 61 UMW \ -...4 r .............. Generakzed Ow met co Opening 3 | ||
-10. Opening 2 61 UMW \ -... | ...22 1 , .---.. -,,. LOCA \ \ | ||
... | |||
\ \ | |||
* 5 Upper Down. corner 7 Lower Head A s.A. *., N. ',N.:\ _Ny',.. | * 5 Upper Down. corner 7 Lower Head A s.A. *., N. ',N.:\ _Ny',.. | ||
* 0+ Low Path 8 GE = | * 0+ Low Path 8 GE =t for ie RH944174.COR 3 Standpipes Separators 2 Shroud Head 1 Core Key O Gas Flow Path No. A Heat Sink La Surface No. | ||
A Heat Sink La Surface No. | |||
I= Heat Sink Dresden Nuclear Power Station's Third Six Month Status Report for the Implementation of FLEX 8/28/2014 MAAP JUSTIFICATION FOR ELAP ANALYSIS ACCEPTABILITY Page 27 of 31 Junction 1 Description Pedestal Door to Drywell Drywell to Vents/Downcomers 2 3 Vents/Downcomers to Suppression Pool Drywell Vent/Failure 4 5,6,7,8 Suppression Chamber to Vent Vacuum Breakers Vent/Failure 9 Suppression Chamber --> Vent 4 7--> Leakage 7-> Shell Failure Vents/ Down- corners 3 2 5,6,7,8 9 Suppression Chamber Vent/Failure 10 Drywell Leakage 33 Drywell Shell Failure Dresden Nuclear Power Station's Third Six Month Status Report for the Implementation of FLEX 8/28/2014 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: | I= Heat Sink Dresden Nuclear Power Station's Third Six Month Status Report for the Implementation of FLEX 8/28/2014 MAAP JUSTIFICATION FOR ELAP ANALYSIS ACCEPTABILITY Page 27 of 31 Junction 1 Description Pedestal Door to Drywell Drywell to Vents/Downcomers 2 3 Vents/Downcomers to Suppression Pool Drywell Vent/Failure 4 5,6,7,8 Suppression Chamber to Vent Vacuum Breakers Vent/Failure 9 Suppression Chamber --> Vent 4 7--> Leakage 7-> Shell Failure Vents/ Down- corners 3 2 5,6,7,8 9 Suppression Chamber Vent/Failure 10 Drywell Leakage 33 Drywell Shell Failure Dresden Nuclear Power Station's Third Six Month Status Report for the Implementation of FLEX 8/28/2014 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 | : 1. Reactor pedestal region | ||
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4.2E6 BTU/hr Plant specific value based on drywell heat removal to coolers during normal operation. Typical values range between 1-2 MW (3.4E6 to 6.8E6 BTU/hr). | 4.2E6 BTU/hr Plant specific value based on drywell heat removal to coolers during normal operation. Typical values range between 1-2 MW (3.4E6 to 6.8E6 BTU/hr). | ||
FIN PLT - number of plates in reflective insulation 8 Plant-specific value XTINS - average reflective insulation thickness 0.5 ft Plant-specific value At the request of the NRC, the following information, as used in the MAAP analysis, is provided. | FIN PLT - number of plates in reflective insulation 8 Plant-specific value XTINS - average reflective insulation thickness 0.5 ft Plant-specific value At the request of the NRC, the following information, as used in the MAAP analysis, is provided. | ||
Parameter Definition Parameter Name in MAAP Value Used in the Dresden MAAP Analysis Power level, MWth QCRO 2957 MWth Initial CST water volume, gal VCSTO (ft | Parameter Definition Parameter Name in MAAP Value Used in the Dresden MAAP Analysis Power level, MWth QCRO 2957 MWth Initial CST water volume, gal VCSTO (ft 3) 409,971 ft 3 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 MAAP JUSTIFICATION FOR ELAP ANALYSIS ACCEPTABILITY temperature, F Initial suppression pool water mass, lbm Calculated from input 7,264,000 Ibm Initial suppression pool water level, ft XWRBO(i), where i is node number for wetwell 14.84 ft Initial suppression pool water temperature, F TWRBO(i), where i is node number for wetwell 85°F Drywell free volume, ft 3 VOLRB(i), where I is node number for drywell 145,786.23 ft 3 Wetwell free volume, ft 3 VOLRB(i) - volume of suppression pool water from initial pool mass 238,375.6 ft 3 Containment vent pressure, psia Refer to MAAP analysis document N/A (containment is not vented) | ||
RCIC max flow rate, gpm WVRCIC N/A (Dresden does not have RCIC) | RCIC max flow rate, gpm WVRCIC N/A (Dresden does not have RCIC) | ||
Max FLEX pump flow rate, gpm Refer to MAAP analysis document 500 gpm Lowest set SRV flow rate, lb/hr Derived from SRV area, ASRV 540,000 lb/hr Lowest set SRV pressure, psia PSETRV 1125.2 psia Recirc pump seal leakage, gpm Value that was used to define LOCA area, ALOCA 61 gpm Total leakage used in the transient, gpm Value that was used to define LOCA area, ALOCA 61 gpm 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. | Max FLEX pump flow rate, gpm Refer to MAAP analysis document 500 gpm Lowest set SRV flow rate, lb/hr Derived from SRV area, ASRV 540,000 lb/hr Lowest set SRV pressure, psia PSETRV 1125.2 psia Recirc pump seal leakage, gpm Value that was used to define LOCA area, ALOCA 61 gpm Total leakage used in the transient, gpm Value that was used to define LOCA area, ALOCA 61 gpm 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. | ||
Parameter Name Value Used in the Dresden MAAP Analysis EPRI Recommended Value ASRV - effective flow area for 0.062 | Parameter Name Value Used in the Dresden MAAP Analysis EPRI Recommended Value ASRV - effective flow area for 0.062 ft 2 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 MAAP JUSTIFICATION FOR ELAP ANALYSIS ACCEPTABILITY relief valve (based on rated flow at pressure) | ||
ALOCA - seal leakage area 9.55E-4 ft 2 (61 gpm at normal conditions) | ALOCA - seal leakage area 9.55E-4 ft 2 (61 gpm at normal conditions) | ||
Plant-specific value FCDBRK - discharge coefficient for seal leakage 0.75 0.75 e. Venting of the containment was not considered in the Dresden MAAP analysis. | Plant-specific value FCDBRK - discharge coefficient for seal leakage 0.75 0.75 e. Venting of the containment was not considered in the Dresden MAAP analysis. |
Revision as of 13:10, 9 July 2018
ML14248A238 | |
Person / Time | |
---|---|
Site: | Dresden ![]() |
Issue date: | 08/28/2014 |
From: | Kaegi G T Exelon Generation Co |
To: | Document Control Desk, Office of Nuclear Reactor Regulation |
References | |
EA-12-049, RS-14-208 | |
Download: ML14248A238 (36) | |
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 28 th 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 Completion Date Activity Status {Include date changes in this column}
Revised Target Completion Date Submit 60 Day Status Report Complete Submit Overall Integrated Implementation Plan Complete Contract with National SAFER Response Center Complete 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 Completion Date Activity Status {Include date changes in this column}
Revised Target Completion Date 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 Procedures (NET 12-06, Sect. 11.4.3)
Note 1 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 Operational (will be a standard date 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 (page 5-6)
The times to complete actions in the Events 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.
Not Started 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 (page 5) Analysis of deviations between Exelon's engineering analyses and the analyses contained 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.
Completed. See August 2013 Update Sequence of Events (page 8) Initial evaluations were used to determine the fuel pool timelines. Formal calculations will be performed to validate this information during development of the spent fuel pool cooling strategy detailed detailed design.
Proposed Complete.
Engineering Change (EC) 31913, TIME TO BOIL CURVES -
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 (pages 8-9)
Transportation routes will be developed from the equipment storage area to the FLEX staging areas. An administrative program will be developed to ensure pathways remain clear or compensatory actions will be implemented to ensure all strategies can be deployed during all modes of operation.
Identification of storage areas and creation of the administrative program are open items.
See Interim Staff Evaluation Confirmatory Item 3.1.2.2.A response.
Programmatic Controls (pages 9-
- 10) An administrative program for FLEX to establish responsibilities, and testing &
maintenance requirements will be implemented.
Not Started Spent Fuel Pool Cooling Phase 2 Discussion (page 46)
Complete an evaluation of the spent fuel pool area for steam and condensation.
See Interim Staff Evaluation Confirmatory Item 3.2.2.A response.
Safety Functions Support Phase 2 Discussion (page 57)
Evaluate the habitability conditions for the Main Control Room and develop a strategy to maintain habitability.
See Interim Staff Evaluation Confirmatory Item 3.2.4.6.0 response.
Page 4 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 Safety Functions Support Phase 2 Discussion (page 57)
Evaluate the habitability conditions for the Auxiliary Electric Equipment Room (AEER) and develop a strategy to maintain habitability.
See Interim Staff Evaluation Confirmatory Item 3.2.4.2.0 response.
Item number Interim Staff Evaluation OPEN Item Status 3.1.1.1.A Each section of the Integrated Plan 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.
Completed. See February 2014 Update 3.1.2.2. B The Plan is silent regarding loss of normal 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.
Completed. See February 2014 Update Page 5 of 31 Dresden Nuclear Power Station's Third Six Month Status Report for the Implementation of FLEX 8/28/2014 Item number Interim Staff Evaluation OPEN Item Status 3.2.4.8.A Updated information provided by the licensee as part of the 6-month update states that they are proposing to install a prestaged 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 NET 12-06.
Proposed Complete As described in Section 4, Changes to Compliance Method, the conceptual design has changed to utilize a trailer mounted generator unit pre-staged in a robust structure near the Reactor Building. Pre-staging in this manner allows timely implementation of the FLEX strategies by not requiring transport of the generator prior to use.
The generator is a portable (trailer mounted) unit that will be connected through the use of temporary cabling. The proposed design meets the requirements of NEI 12-06 Section 3.2.1.3.(7) and 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 number Interim Staff Evaluation CONFIRMATORY Item Status 3.1.1.2.A A postulated downstream dam failure from a seismic event is still being evaluated.
Completed. See February 2014 Update 3.1.1.2.B Plans for strategies did not address whether electrical power would be required to move or deploy FLEX equipment (e.g. to open a door from a storage location.)
Not started 3.1.1.3.A Development of a reference source 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.
Started 3.1.1.3.B Use of, or need for ac power to mitigate ground water intrusion was not addressed.
Completed. See February 2014 Update 3.1.1.4.A Regarding off site resources, detailed plans for local staging areas and transport of FLEX equipment to overcome hazards are to be provided in 6-month update.
Started 3.1.2.A Impact of persistence of flooding to staging of FLEX equipment not fully addressed.
Started 3.1.2.2.A Administrative program and procedures for on-site FLEX equipment storage locations and transport routes not yet established.
Started 3.1.2.3.A Administrative program and procedures related to implementation of mitigation strategies not yet developed.
Started 3.1.4.2.A Equipment to clear ice and snow from haul pathways is not identified in plan. Completed. See February 2014 Update 3.1.5.2.A Procedures to assure equipment can 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.)
Not started 3.1.5.3.A Procedures to address high temperature impacts on FLEX equipment not yet developed.
Started Page 7 of 31 Dresden Nuclear Power Station's Third Six Month Status Report for the Implementation of FLEX 8/28/2014 Item number Interim Staff Evaluation CONFIRMATORY Item Status 3.2.1.1.A Need benchmarks to demonstrate Modular Accident Analysis Program (MAAP) 4 is the appropriate code for simulation of ELAP.
Proposed Complete.
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.B For MAAP4, collapsed level must remain above Top of Active Fuel and cool down rate must meet technical specifications.
Proposed Complete.
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.
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 June 2013 position paper.
Proposed Complete.
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 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 1 020236).
Proposed Complete.
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.E 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.
Proposed Complete.
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.
Page 8 of 31 Dresden Nuclear Power Station's Third Six Month Status Report for the Implementation of FLEX 8/28/2014 Item number Interim Staff Evaluation CONFIRMATORY Item Status 3.2.1.3.A Outstanding Confirmatory Items 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. Not started 3.2.1.3.B Sequence of Events timing for compensatory actions to control temperature rise in the Main Control Room not resolved.
Started 3.2.1.4.A Detailed engineering analyses to confirm the ability of FLEX pumps to provide required flow and head capacities are not complete.
Started 3.2.1.4.B Analysis needs to be performed to 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.
Started Page 9 of 31 Dresden Nuclear Power Station's Third Six Month Status Report for the Implementation of FLEX 8/28/2014 Item number Interim Staff Evaluation CONFIRMATORY Item Status 3.2.1.6.A Whether or not backup compressed air for valve actuation is required, is contingent on the MAAP4 analyses conclusions. The MAAP4 conclusions will determine if containment venting is necessary.
Proposed complete.
The Isolation Condenser (IC) removes decay heat with 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, backup compressed air will not be required.
3.2.2.A Final analysis of fuel pool area for steam and condensation impacts regarding access is not complete.
Started Page 10 of 31 Dresden Nuclear Power Station's Third Six Month Status Report for the Implementation of FLEX 8/28/2014 Item number Interim Staff Evaluation CONFIRMATORY Item Status 3.2.3.A There are outstanding issues regarding the acceptability of the MAAP4 analysis. The potential for impact of MAAP4 results on the containment heat removal strategy needs to be reviewed.
Proposed complete.
Information that validates the use of MAAP4 is contained in Attachment 4, MAAP Justification for ELAP Analysis Acceptability.
The Isolation Condenser (IC) removes decay heat with 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 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.
Not started 3.2.4.2.B Procedure will be developed to address controlling battery room hydrogen concentration.
Not started Page 11 of 31 Dresden Nuclear Power Station's Third Six Month Status Report for the Implementation of FLEX 8/28/2014 Item number Interim Staff Evaluation CONFIRMATORY Item Status 3.2.4.2.0 Evaluations to address loss of ventilation in the auxiliary equipment electric room and Battery Rooms are not complete.
Not started 3.9.4.2.D Insufficient information to address 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.
Not started 3.2.4.4.A Provisions for portable lighting for area access not clear. More information required.
Not started 3.2.4.4.B Confirm upgrades to communication system that resulted from the licensee communications assessment.
ADAMS Accession Nos. ML 12306A 199 and ML 13056A 135.
Started 3.2.4.6.A Surface pyrometer temperature readings are required in the torus area.
The licensee needs to address habitability and access to the torus area. Started 3.2.4.6.B Final GOTHIC analysis for the HPCI room temperature rise is not complete.
Started 3.2.4.6.0 Habitability of the control room should consider temperature limits of NUMARC 87-00 and M1L-STD-1472C. Started 3.2.4.8.B Detailed designs will identify comprehensive load lists to confirm conceptual load assumptions.
Not started 3.2.4.8.0 Insufficient information provided 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.
Started Page 12 of 31 Dresden Nuclear Power Station's Third Six Month Status Report for the Implementation of FLEX 8/28/2014 Item number Interim Staff Evaluation CONFIRMATORY Item Status 3.2.4.9.A The licensee stated in its 6-month 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.
Started 3.2.4.9.B Assessing and maintaining fuel oil quality for FLEX equipment use was not addressed.
Not started 3.2.4.10.
A Final analysis for battery operation 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.
Started 3.4.A Details not provided to demonstrate the minimum capabilities for offsite resources will be met per NEI 12-06 Section 12.2.
Started 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 Revised Estimated Sequence of Events Timeline Action I item Elapsed Time Action Time Constraint Y/N 1 Remarks / Applicability 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 pressure control (or verified operating if auto initiation occurs)
N DEOP 100 will direct action based on reactor pressure.
3 2 mins Attempt to start EDGs upon identification of failure to auto start.
N Per FLEX event initial conditions the EDGs are not available.
4 3 mins Attempt to Start IC Makeup Pump for IC Shell side makeup N There are no fully qualified makeup sources for shell-side makeup.
5 5 mins Personnel dispatched to investigate EDG failure to start.
N Per FLEX event initial conditions the EDGs are not available.
6 5 mins HPCI initiated for inventory control and reactor pressure control (or verified operating if auto initiation occurs).
N DEOP 100 will direct this action. HPCI suction will 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 Revised Estimated Sequence of Events Timeline Action item Elapsed Time Action Time Constraint Y/N 1 Remarks / Applicability 8 15 mins Personnel dispatched to investigate SBO DG failure to start.
N Per FLEX event initial conditions the SBO DGs are not available.
9 15 mins Perform 125 VDC load shedding per DGA 13 N This is an immediate action 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 shell-side water level without a shell-side makeup source.
Y Per UFSAR, the IC will operate for approximately 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 Completed (actions identified in DGA 03, DGA 12 and DGA 13)
Y DGA 12 Step D.13 identifies that load 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 and plant conditions and declares an Extended Loss of AC Power (ELAP) event,
- 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 Y Time is reasonable approximation based on operating crew assessment of plant conditions Page 16 of 31 Dresden Nuclear Power Station's Third Six Month Status Report for the Implementation of FLEX 8/28/2014 Revised Estimated Sequence of Events Timeline Action item Elapsed Time Action Time Constraint Y/N 1 Remarks / Applicability 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 Ventilation N Perform DOA 5750-1 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 by opening doors.
Y Preliminary GOTHIC 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 Control Room Ventilation.
N DOA 5750-01 actions.
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 isolations N Ensure HPCI remains available during the event.
17 2.5 hours5.787037e-5 days <br />0.00139 hours <br />8.267196e-6 weeks <br />1.9025e-6 months <br /> FLEX strategy for supplying power to a Unit 3 FLEX Makeup Pump completed.
Y Involves running temporary cables and connecting to the selected FLEX Makeup pump. 18 2.5 hours5.787037e-5 days <br />0.00139 hours <br />8.267196e-6 weeks <br />1.9025e-6 months <br /> Unit 3 FLEX pump connected and supplying Isolation Condenser shell-side makeup. Y Due to pre-staging of major components, it is 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 Revised Estimated Sequence of Events Timeline Action item Elapsed Time Action Time Constraint Y/N 1 Remarks / Applicability 19 2.5 hours5.787037e-5 days <br />0.00139 hours <br />8.267196e-6 weeks <br />1.9025e-6 months <br /> Isolation Condenser initiated for RPV pressure control Y Complete prior to loss of HPCI to ensure RPV heat removal mechanism operating prior to MAAP analysis assumed HPCI loss. 20 2.5 hours5.787037e-5 days <br />0.00139 hours <br />8.267196e-6 weeks <br />1.9025e-6 months <br /> HPCI assumed to fail due to suppression pool temperature of 2140°F N HPCI may continue to 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 FLEX makeup pump from the Unit 2 Suppression Pool and align hoses for supplying make-up water to the Isolation Condenser shell-side.
N Time is reasonable approximation based on operating crew assessment of plant conditions.
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 480 VAC busses and associated Motor Control Centers (MCCs) completed.
Y When the busses are energized, power will be 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 Loops by closing suction and discharge valves N Recirc loops are isolated to reduce RPV leakage. The 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 Revised Estimated Sequence of Events Timeline Action item Elapsed Time Action Time Constraint Y/N 1 Remarks / Applicability 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 level control.
N Per MAAP analysis after 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 submersible pump from the Robust Storage location to provide water from UHS for long-term Suppression Pool makeup. N Time is reasonable approximation based on operating crew assessment of plant conditions.
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 supplying Isolation Condenser shell-side makeup. Y This action must be completed prior to Unit 3 Suppression Pool inventory being reduced below 11 feet. 27 10 hours1.157407e-4 days <br />0.00278 hours <br />1.653439e-5 weeks <br />3.805e-6 months <br /> Personnel dispatched to establish temporary ventilation to the MCR and AEER (portable fans and associated generators).
N Further analysis is required to determine if supplemental ventilation is needed. Page 19 of 31 Dresden Nuclear Power Station's Third Six Month Status Report for the Implementation of FLEX 8/28/2014 Revised Estimated Sequence of Events Timeline Action item Elapsed Time Action Time Constraint Y/N 1 Remarks / Applicability 28 l'? hours Makeup to the Spent Fuel Pools using FLEX pump strategy is available.
Y EC 371913, Revision 2,:
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 hours1.62037e-4 days <br />0.00389 hours <br />2.314815e-5 weeks <br />5.327e-6 months <br /> Unit 2 Suppression Pool Makeup available from UHS using portable equipment Y Long term makeup water 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. 30 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> Initial equipment from National SAFER Response Center becomes available.
N NEI 12-06 assumption.
31 24-72 hours Continue to maintain critical functions 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.
N None Page 20 of 31 SFP Cleanup Return Diffuser LPCI PL--1:;.411-7 1 r.°.#1-ta-rip C 4:5-11P%V 143-ump A LPCI Purp 0 LPG! Rep El
-1: LPIVA°31-13-7. I. I-*.1.0.Z.V 1m on 1-d p A LPCI Purip 8 LPCI Pump D RPV TORN Peal U2 Alternate ISCO Makeup 4...
1J3 Alternate ISCO Makeup Shutdown Cooling Cgriell SPRY Orrieli Spray SFP Cleanup Return Diffuser 02 S8LC r---1 Flood Pump (Primary)
Tank Th qr 001.7 Flood Pump (Alternate 104 C ----------
02 SBLC Tankt-1)2 =WWI 03 SBLC Tank*--
Condenser Del LPCI LPCI ---P 4 C14 Rep D Pulp 13 4-0 14 4- 10 , 4 FLEX Pump 28 FLEX Pump 2A Shutdown Cooling U3 SBLC i F-1 Tank . L.1 (UMW, Dryvies Spray
- 5) U3 Isolation Condenser
.74 psi ) Orywell Sway 0 FLPV TONS (lea) 1104 C FLEX Pump 3A FLEX Pump 38
-3_ Dresden Nuclear Power Station's Third Six Month Status Report for the Implementation of FLEX 8/28/2014 OHS FLEX Diesel Driven Hydraulic Pump Existing FLEX CONCEPT11A1 12E1101. July 31, 2014 03 Reactor Building 02 Reactor Building Page 21 of 31 Temporary Power Unit (I PU) Above U2 Reactor Building Trackway Interlock Diesel Gereralor Building Area Flex Pump 2A/213:3Ai3B Bus Connection Devices (BCD) 28 - "1- 39 iffool 38 1 015; 1- 29 ---A--r- Flex Diesel Generator (non-flood scenario) k G ' Temporary Power Unit 1 (TPU) ---artPU-*--- , - Flex Diesel Generator (flood scenario)
G - Portable Cable and Devices Existing/ Pre-staged Equipment Reactor Building I. Dresden Nuclear Power Station's Third Six Month Status Report for the Implementation of FLEX 8/28/2014 Page 22 of 31 Dresden Nuclear Power Station's Third Six Month Status Report for the Implementation of FLEX 8/28/2014 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: A 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 1400 .4 1200 T/5 0. ' 1000 a. BOO (i)
- 500 IX 400 0_ ix 200 Dresden Nuclear Power Station's Third Six Month Status Report for the Implementation of FLEX 8/28/2014 MAAP JUSTIFICATION FOR ELAP ANALYSIS ACCEPTABILITY 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 20 40 60 80 TIME, HOURS Page 24 of 31 100 50 O 0 LL. z -50 100 w >z w w -150 _1 2 200 w 5-
- z > - -300 a_ -350 -400 0 20 40 60 80 TIME, HOURS Dresden Nuclear Power Station's Third Six Month Status Report for the Implementation of FLEX 8/28/2014 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.
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 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 SRV j* 4 Upper 4,4-4=3 to o t 1.* LC-CA LOCA ___..0 Generalized P --CT Opening 1 Generalized -10. Opening 2 61 UMW \ -...4 r .............. Generakzed Ow met co Opening 3
...22 1 , .---.. -,,. LOCA \ \
- 5 Upper Down. corner 7 Lower Head A s.A. *., N. ',N.:\ _Ny',..
- 0+ Low Path 8 GE =t for ie RH944174.COR 3 Standpipes Separators 2 Shroud Head 1 Core Key O Gas Flow Path No. A Heat Sink La Surface No.
I= Heat Sink Dresden Nuclear Power Station's Third Six Month Status Report for the Implementation of FLEX 8/28/2014 MAAP JUSTIFICATION FOR ELAP ANALYSIS ACCEPTABILITY Page 27 of 31 Junction 1 Description Pedestal Door to Drywell Drywell to Vents/Downcomers 2 3 Vents/Downcomers to Suppression Pool Drywell Vent/Failure 4 5,6,7,8 Suppression Chamber to Vent Vacuum Breakers Vent/Failure 9 Suppression Chamber --> Vent 4 7--> Leakage 7-> Shell Failure Vents/ Down- corners 3 2 5,6,7,8 9 Suppression Chamber Vent/Failure 10 Drywell Leakage 33 Drywell Shell Failure Dresden Nuclear Power Station's Third Six Month Status Report for the Implementation of FLEX 8/28/2014 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.
Pedestal Drywell 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 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.
Parameter Name Value Used in the Dresden MAAP Analysis EPRI 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.
Parameter Name Value Used in the Dresden MAAP Analysis Comment QCO - not-thru-insulation heat transfer from RPV during normal operation.
4.2E6 BTU/hr Plant specific value based on drywell heat removal to coolers during normal operation. Typical values range between 1-2 MW (3.4E6 to 6.8E6 BTU/hr).
FIN PLT - number of plates in reflective insulation 8 Plant-specific value XTINS - average reflective insulation thickness 0.5 ft Plant-specific value At the request of the NRC, the following information, as used in the MAAP analysis, is provided.
Parameter Definition Parameter Name in MAAP Value Used in the Dresden MAAP Analysis Power level, MWth QCRO 2957 MWth Initial CST water volume, gal VCSTO (ft 3) 409,971 ft 3 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 MAAP JUSTIFICATION FOR ELAP ANALYSIS ACCEPTABILITY temperature, F Initial suppression pool water mass, lbm Calculated from input 7,264,000 Ibm Initial suppression pool water level, ft XWRBO(i), where i is node number for wetwell 14.84 ft Initial suppression pool water temperature, F TWRBO(i), where i is node number for wetwell 85°F Drywell free volume, ft 3 VOLRB(i), where I is node number for drywell 145,786.23 ft 3 Wetwell free volume, ft 3 VOLRB(i) - volume of suppression pool water from initial pool mass 238,375.6 ft 3 Containment vent pressure, psia Refer to MAAP analysis document N/A (containment is not vented)
RCIC max flow rate, gpm WVRCIC N/A (Dresden does not have RCIC)
Max FLEX pump flow rate, gpm Refer to MAAP analysis document 500 gpm Lowest set SRV flow rate, lb/hr Derived from SRV area, ASRV 540,000 lb/hr Lowest set SRV pressure, psia PSETRV 1125.2 psia Recirc pump seal leakage, gpm Value that was used to define LOCA area, ALOCA 61 gpm Total leakage used in the transient, gpm Value that was used to define LOCA area, ALOCA 61 gpm 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.
Parameter Name Value Used in the Dresden MAAP Analysis EPRI Recommended Value ASRV - effective flow area for 0.062 ft 2 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 MAAP JUSTIFICATION FOR ELAP ANALYSIS ACCEPTABILITY relief valve (based on rated flow at pressure)
ALOCA - seal leakage area 9.55E-4 ft 2 (61 gpm at normal conditions)
Plant-specific value FCDBRK - discharge coefficient for seal leakage 0.75 0.75 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.
Parameter Name Value Used in the Dresden MAAP Analysis EPRI 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 /
total absorption rate 0.324 Plant-specific value FFAF - total absorption rate / total fission rate 2.37 Plant-specific value FQFR1 - fraction of fission power due to U-235 and PU-241 0.476 Plant-specific value FQFR2 - fraction of fission power due to PU-239 0.437 Plant-specific value FQFR3 - fraction of fission power due to U-238 0.087 Plant-specific value TIRRAD - average effective irradiation time for entire core 26,280 hours0.00324 days <br />0.0778 hours <br />4.62963e-4 weeks <br />1.0654e-4 months <br /> Plant-specific value 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 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