ML19071A114

Response to 03/12/2012 Information Request, Seismic Probabilistic Risk Assessment Supplement for Recommendation 2.1

ML19071A114
Person / Time
Site:	North Anna
Issue date:	03/07/2019
From:	Mark D. Sartain Virginia Electric & Power Co (VEPCO)
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
18-086A
Download: ML19071A114 (17)

Text

VIRGINIA ELECTRIC AND POWER COMPANY RICHMOND, VIRGINIA 23261 March 7, 2019 U.S. Nuclear Regulatory Commission Serial No. 18-086A Attention: Document Control Desk* NRA/DEA RO' Washington, DC 20555 Docket Nos.: 50-338/339 License Nos.: NPF-4/7 VIRGINIA ELECTRIC AND POWER COMPANY NORTH ANNA POWER STATION UNITS 1 AND 2 RESPONSE TO MARCH 12, 2012 INFORMATION REQUEST SEISMIC PROBABILISTIC RISK ASSESSMENT SUPPLEMENT FOR RECOMMENDATION 2.1

References:

1. NRG Letter, "Request for Information Pursuant to Title 10 of the Code of Federal Regulations 50.54(f) Regarding Recommendations 2.1, 2.3, and 9.3, of the Near-Term Task Force Review of Insights from the Fukushima Dai-ichi Accident," dated March 12, 2012 [ADAMS Accession Nos. ML12056A046 and ML12053A340].

2. NRG Letter, "Final Determination of Licensee Seismic Probabilistic Risk Assessments Under the Request for Information Pursuant to Title 10 of the Code of Federal Regulations 50.54(f) Regarding Recommendation 2.1 "Seismic" of the Near-Term Task Force Review of Insights from the Fukushima Dai-ichi Accident,

dated October 27, 2015 [ADAMS Accession No. ML15194A015].

3. Virginia Electric and Power Company Letter to NRG, "North Anna Power Station Units 1 and 2 Response to March 12, 2012 Information Request - Seismic Probabilistic Risk Assessment for Recommendation 2.1," dated March 28, 2018

[ADAMS Accession No. ML18093A445].

On March 12, 2012, the Nuclear Regulatory Commission (NRG) issued a request for information pursuant to 10 CFR 50.54(f) associated with the recommendations of the Fukushima Near-Term Task Force (NTTF) (Reference 1). Enclosure 1 of Reference 1 requested each licensee to reevc:1luate the seismic hazards at their sites using present-day NRG requirements and guidance, and to identify actions taken or planned to address plant-specific vulnerabilities associated with the updated seismic hazards.

Reference 2 contains the NRG letter "Final Determination of Licensee Seismic Probabilistic Risk Assessments." In that letter (Table 1 a - Recommendation 2.1 Seismic

- lnformatiQn Requests), the NRG instructed that a Seismic Probabilistic Risk Assessment (SPRA) be submitted for North Anna Power Station (NAPS) Units 1 and 2 by March 31, 2018.

• Reference 3 provided the NAPS Units 1 and 2 SPRA Summary Report, which provided the information requested in Enclosure 1, Item (8)8 of Reference 1.

This letter supplements the SPRA Summary Report submittal.

Serial No. 18-086A Docket Nos. 50-338/339 Page 2 of 4 Based on a review of the risk insights gained from performance of the SPRA, cost-justified plant improvements to reduce the seismic risk associated with electro-mechanical relay contact chatter events have been identified and will be implemented.

The plant improvements will consist of operating procedure(s) changes and enhanced operator training to improve the plant response to potential spurious power supply breaker lockouts and spurious pump start due to relay contact chatter. These plant improvements will be implemented by March, 2020 (2 years from the SPRA Summary Report submittal date).

The attachment to this letter provides the results of a sensitivity study that evaluates the effect of increased failure rates for FLEX equipment and FLEX-related operator actions credited in the SPRA.

If you have any questions regarding this information, please contact Diane E. Aitken at (804) 273-2694.

Sincerely, Mark D. Sartain Vice President - Nuclear Engineering and Fleet Support VICKILHULL NOTARY PUBLIC REG. # 140542 COMMONWEALTH OFVIRGINIA ; *.*

• MY COMMISSlON EXPIRES 5131/2022 COMMONWEALTH OF VIRGINIA COUNTY OF HENRICO The foregoing document was acknowledged before me, in and for the County and Commonwealth aforesaid, today by Mark D. Sartain, who is Vice President - Nuclear Engineering and Fleet Support of Virginia Electric and Power Company. He has affirmed before me that he is duly authorized to execute and file the foregoing document in behalf of that company, and that the statements in the document are true to the best of his knowledge and belief.

Acknowledged before me this ] 1J" day of 0C1trt.n I 2019.

My Commission Expires: _fit=--___,,,.,_,A""'y--"3_[.,.....=rJi...,'()"--'~=Q.____ _ __

' ~*X21/llL Notary Public

Serial No. 18-086A Docket Nos. 50-338/339 Page 3 of 4 Commitments made in this letter: Implement operating procedure changes and enhanced operator training to respond to seismic event-induced relay contact chatter by March, 2020.

Attachment:

Sensitivity Study - Effect of Increased Failure Rates for FLEX Equipment and FLEX-Related Operator Actions Credited in the Seismic Probabilistic Risk Assessment

Serial No. 18-086A Docket Nos. 50-338/339 Page 4 of4 cc: U.S. Nuclear Regulatory Commission Region II Marquis One Tower 245 Peachtree Center Ave., NE Suite 1200 Atlanta, Georgia 30303-1257 Mr. Marcus Harris Old Dominion Electric Cooperative Innsbrook Corporate Center 4201 Dominion Blvd.

Suite 300 Glen Allen, Virginia 23060 Mr. James R. Hall NRC Senior Project Manager-North Anna U.S. Nuclear Regulatory Commission One White Flint North Mail Stop 0-8 B1A 11555 Rockville Pike Rockville, Maryland 20852-2738 Ms. K. R. Cotton-Gross Project Manager - Surry U.S. Nuclear Regulatory Commission One White Flint North Mail Stop 08 G-9A 11555 Rockville Pike Rockville, MD 20852-2738 NRC Senior Resident Inspector North Anna Power Station 50.54f_Seismic.Resource@nrc.gov

Serial No. 18-086A Docket Nos. 50-338/339 Page 1 of 13 ATTACHMENT Sensitivity Study - Effect of Increased Failure Rates for FLEX Equipment and FLEX-Related Operator Actions Credited in the Seismic Probabilistic Risk Assessment VIRGINIA ELECTRIC AND POWER COMPANY (DOMINION ENERGY VIRGINIA)

NORTH ANNA POWER STATION UNITS 1 AND 2

Serial No. 19-086A Docket No. 50-338/339

Attachment:

Sensitivity Study - FLEX Failure Rates Page 2 of 13 A sensitivity study has been performed using FLEX equipment (FLEX Diesel Generator and Reactor Coolant System Injection Pump) failure rates increased by a factor of 10 (probabilities multiplied by 10) and *a high FLEX-actions Human Error Probability (HEP) value (probabilities multiplied by 5).

Tables 5.4-2 (partial), 5.4-3, and 5.4-5 from the Seismic Probabilistic Risk Assessment (SPRA) submittal are provided below with the Fussel-Vesely (FV) importances from the sensitivity study inserted into the tables (shown in bold italic font) along with the base SPRA FV importances.

In general, the FV importance of the fragility groups in Table 5.4-2 indicate that the Station Blackout (SBO) sequences increased slightly due to the higher failure probabilities of the FLEX equipment and FLEX-actions HEPs. The FV importance of fragility groups that are not part of SBO *sequences decreased slightly, which is expected.

Likewise, the FV importances of the non-seismic failures in Table 5.4-3 indicate a similar change; the FLEX basic events had a higher FV importance due to their higher failure probabilities and the FV importance of basic events associated with non-SBO sequences decreased.

Table 5.4-5 shows the FV importances of HEPs. As indicated in the table, the FV importance of the FLEX HEPs increased, while the importance of HEPs not associated with SBO sequences decreased.

Serial No. 19-086A Docket No. 50-338/339

Attachment:

Sensitivity Study - FLEX Failure Rates Page3of13 (Partial) Table 5.4-2: SCDF Importance Measures Ranked by FV Fragility Groups Fragility Group Description Ul CDF FV U2 CDF FV 6.91E-01 6.90E-01 SE IS-LOOP SEISMIC-INDUCED LOSS OF OFFSITE POWER 7.31E-01 7.30E-01 9.51E-02 1.02E-01 SEIS-SSLOCA SEISMIC-INDUCED SMALL-SMALL LOCA 5.99E-02 6.44E-02 6.76E-02 6.90E-02 SEIS-EE-BKR-HJ8-RLY 4KV to 480V BUS BREAKERS - RELAY CHATIER 1.33E-01 1.37E-01 3.84E-02 3.96E-02 SEIS-SW-P-1AB-RLY SERVICE WATER PUMPS- RELAY CHATIER 2.SSE-02 2.65E-02 3.63E-02 3.75E-02 SE1S-CH-P-1ABC-RLY CHARGING PUMPS - RELAY CHATIER 2.38E-02 2.47E-02 3.33E-02 3.37E-02 SEIS-SLOCA SEISMIC-INDUCED SMALL LOCA 2.01E-02 2.06E-02 3.26E-02 3.23E-02 SEIS-VB-INV-1234 120 VAC VITAL BUS INVERTERS 1.77E-02 1.77£-02 2.83E-02 2.83E-02 SEIS-SI-P-1AB-RLY LOW HEAD SI PUMP- RELAY CHATIER 1.81E-02 1.84E-02 2.65E-02 2.65E-02 SEIS-FW-P-3AB-RLY MOTOR-DRIVEN AFW PUMPS - RELAY CHATIER 1.66E-02 1.69E-02 1.90E-02 1.94E-02 SEIS-EE-BKR-HJ2-RLY EDG OUTPUT BREAKERS - RELAY 3.65E-02 3.77E-02 1.46E-02 1.48E-02 SEIS-EP-CB-12ABCD 125 VDC DISTRIBUTION PANELS 9.36E-03 9.SSE-03 1.40E-02 1.41E-02 SEIS-EP-CB-4ABCD 120 VAC VITAL BUS DISTRIBUTION PANELS 8.93E-03 9.12E-03 EMERGENCY DIESEL GENERATORS - RELAY 1.09E-02 1.09E-02 SEIS-EDG-HJ-RLY CHATIER 8.74E-03 B.BSE-03 8.53E-03 8.38E-03 SEIS-BY-B-1-24 STATION BATIERIES 1-11 AND 1-IV 3.91£-03 3.BSE-03 7.SSE-03 7.61E-03 SEIS-EI-CB-MCR-PNL SEISMIC FAILURE OF MCR BOARDS AND PANELS 4.76E-03 4.86E-03

Serial No. 19-086A Docket No. 50-338/339

Attachment:

Sensitivity Study - FLEX Failure Rates Page 4 of 13 Table 5.4-3: SCDF Importance Measures Ranked by FV for Non-Seismic Failures Unit 1 Model Basic Events Prob SCDFFV Description 1.33E-02 DIESEL-DRIVEN FIRE PUMP 1-FP-P-2 OUT OF SERVICE FOR lFP-DDP--TM-2 3.16E-02 7.38E-03 TEST OR MAINTENANCE 7.0SE-03 OBDBEDG--FR-1A-FLEX 2.04E-01 FLEX DIESEL GENERATOR FAILS TO RUN 4.38E-02 1.84E-03 OBD BDD P--FS-3A-FLEX 5.46E-02 FLEX RCS INJECTION PUMP (OO-BDB-P-3A) FAILS TO START 9.82E-03 1.53E-03 OBDBEDG--FS-1A-FLEX 4.53E-02 FLEX DIESEL GENERATOR FAILS TO START 8.06E-03 1.43E-03 Ul TURBINE-DRIVEN AFW PUMP OUT OF SERVICE FOR lFW-TRB--TM-2 2.81E-03 8.BBE-04 TEST OR MAINTENANCE 9.63E-04 lFW-TRB--FS-2 1.92E-03 Ul TURBINE-DRIVEN AFW PUMP FAILS TO START 6.00E-04 9.59E-04 OBDBEDG--FL-1A-FLEX 2.90E-02 FLEX DIESEL GENERATOR FAILS TO LOAD 5.02E-03 8.SSE-04 lFW-TRB--FR-2 1.71E-03 Ul TURBINE-DRIVEN AFW PUMP FAILS TO RUN 5.33E-04 8.33E-04 lFP-DDP--FR-2 2.13E-03 DIESEL-DRIVEN FIRE PUMP 1-FP-P-2 FAILS TO RUN 4.64E-04 7.37E-04 OBDBDDP--FR-3A-FLEX 2.28E-02 FLEX RCS INJECTION PUMP (OO-BDB-P-3A) FAILS TO RUN 3.91E-03 Unit 2 Model Basic Events and FV Importance 1.32E-02 DIESEL-DRIVEN FIRE PUMP 1-FP-P-2 OUT OF SERVICE FOR lFP-DDP--TM-2 3.16E-02 7.41E-03 TEST OR MAINTENANCE 6.88E-03 OBDBEDG--FR-1A-FLEX 2.04E-01 FLEX DIESEL GENERATOR FAILS TO RUN 4.32E-02 1.79E-03 OBDBDDP--FS-3A-FLEX 5.46E-02 FLEX RCS INJECTION PUMP (OO-BDB-P-3A) FAILS TO START 9.66E-03 1.49E-03 OBDBEDG--FS-1A-FLEX 4.53E-02 FLEX DIESEL GENERATOR FAILS TO START 7.91E-03 1.43E-03 U2 TURBINE-DRIVEN AFW PUMP OUT OF SERVICE FOR 2FW-TRB--TM-2 2.81E-03 8.96E-04 TEST OR MAINTENANCE 9.61E-04 2FW-TRB--FS-2 1.92E-03 U2 TURBINE-DRIVEN AFW PUMP FAILS TO START 6.04E-04 9.41E-04 OBDBEDG--FL-1A-FLEX 2.90E-02 FLEX DIESEL GENERATOR FAILS TO LOAD 4.92E-04 8.53E-04 2FW-TRB--FR-2 1.71E-03 U2 TURBINE-DRIVEN AFW PUMP FAILS TO RUN 5.37E-04 8.24E-04 lFP-DDP--FR-2 2.13E-03 DIESEL-DRIVEN FIRE PUMP 1-FP-P-2 FAILS TO RUN 4.63E-04 7.24E-04 OBDBDDP--FR-3A-FLEX 2.28E-02 FLEX RCS INJECTION PUMP (OO-BDB-P-3A) FAILS TO RUN 3.83E-03

Serial No. 19-086A Docket No. 50-338/339

Attachment:

Sensitivity Study - FLEX Failure Rates Page 5 of 13 5.4-5: SCDF Importance Measures Ranked by FV for Operator Actions HEP Basic Event SCDFFV Description 6.61E-02 Restore Cooling to the Charging Pumps from Fire Protection or H EP-C-OSW-CH P-ALT 4.0SE-02 Primary Grade Water systems 2.66E-02 H EP-C-ALIGN-TDAFW Align turbine-driven AFW Pump to the Band C SGs 1.63E-02 1.SSE-02 HEP-C-FLEX-RIP Install and Start FLEX RCS Injection Pump 5.24E-02 7.87E-03 HE P-C-F LEX-LOADS HE D Load shed the vital 125vdc batteries during SBO 2.51E-02 6.71E-03 HEP-C-1SI-OPN1836 Open 1-SI-MOV-1836 to Align Alternate Flow Path for HHSI 4.23E-03 5.SOE-03 Align SW OR Fire Protection Water to AFW Pumps When ECST HEP-C-lFW-AFWSPLY 3.BSE-03 Depletes 5.36E-03 H EP-C-FLEX-VAC Install FLEX Generator to Power Vital Buses 1.91E-02 5.llE-03 Isolate SW Flood in Auxiliary Building Caused by Seismic Failure REC-SEIS-FLD-CCHX 2.81E-03 of the CCW Heat Exchangers HEP SCDF FV Importance in Unit 2 Model 6.90E-02 Restore Cooling to the Charging Pumps from Fire Protection or HEP-C-OSW-CHP-ALT 4.26E-02 Primary Grade Water systems 2.59E-02 HEP-C-ALIGN-TDAFW Align TDAFW Pump to the Band C SGs 1.61E-02 1.SlE-02 HEP-C-FLEX-RIP Install and Start FLEX RCS Injection Pump 5.25E-02 7.67E-03 HEP-C-FLEX-LOADSHED Load shed the vital 125vdc batteries during SBO 2.48E-02 6.82E-03 HEP-C-2SI-OPN2836 Open 2-SI-MOV-2836 to Align Alternate Flow Path for HHSI 4.34E-03 5.57E-03 Align SW or Fire Protection Water to AFW Pumps When ECST H EP-C-2FW-AFWSPLY 3.93E-03 Depletes 5.19E-03 H EP-C-FLEX-VAC Install FLEX Generator to Power Vital Buses 1.BBE-02 5.19E-03 Isolate SW Flood in Auxiliary Building Caused by Seismic Failure REC-SEIS-FLD-CCHX 2.89E-03 of the Component Cooling Heat Exchangers

Serial No. 19-086A Docket No. 50-338/339

Attachment:

Sensitivity Study - FLEX Failure Rates Page 6 of 13 Tables 5.5-2 (partial), 5.5-3, and 5.5-5 from the submittal are provided below with the FV importances from the sensitivity study inserted into the tables (shown in bold italic font) along with the base SPRA FV.importances.

In general, the FV importances of the fragility groups in Table 5.5-2 indicate the SBO sequences increased slightly due to the higher failure probabilities of the FLEX equipment and FLEX-actions HEPs. The FV importance of fragility groups that are not part of SBO sequences decreased slightly, which is expected.

Likewise, the FV importances of the non-seismic failures shown in Table 5.5-3 indicate a similar change; the FLEX basic events had a higher FV importance due to their higher failure probabilities and the FV importance of basic events associated with non-SBO sequences decreased. Basic events that model failures in the SBO sequences had higher FVs due to the increase in the FLEX failure rates.

Table 5.5-5 shows the FV importances of the HEPs. As shown in the table, the FV importance of the FLEX HEPs increased, while the importance of HEPs not associated with SBO sequences decreased.

Serial No. 19-086A Docket No. 50-338/339

Attachment:

Sensitivity Study - FLEX Failure Rates Page 7 of 13 (Partial) Table 5.5-2: SLERF Importance Measures Ranked by FV Fragility Groups Fragility Group Description Ul SLERF FV U2 SLERF FV 5.0lE-01 5.0SE-01 SE IS-LOOP SEISMIC-INDUCED LOSS OF OFFSITE POWER 5.21£-01 5.28E-Ol 9.07E-02 9.19E-02 SEIS-SLOCA SEISMIC-INDUCED SMALL LOCA 8.59£-02 8.62£-02 5.46E-02 5.25E-02 SEIS-RS-P-lAB-RLY INSIDE RS PUMP - RELAY CHATIER 5.13£-02 4.86£-02 4.40E-02 4.31E-02 SE IS-BLDG-RC REACTOR CONTAINMENT BUILDING 4.12£-02 3.98£-02 SEIS-RS-P-2AB- Outside RS Pumps Spuriously Start due to Relay 2.94E-02 2.81E-02 RLYSS Chatter 2.76£-02 2.61£-02 2.43E-02 1.80E-02 SEIS-FW-P-3AB-RLY MOTOR-DRIVEN AFW PUMPS - RELAY CHATIER 2.35£-02 l.70£-02 2.29E-02 2.18E-02 SEIS-RS-P-2AB OUTSIDE RECIRC SPRAY PUMPS 2.16£-02 2.03£-02 2.26E-02 2.36E-02 SEIS-FW-P-2 TURBINE-DRIVEN AUXILIARY FEEDWATER PUMP 2.16£-02 2.22£-02 SEIS-EE-BKR-HJ8- 2.18E-02 2.20E-02 4KV TO 480V BUS BREAKERS - RELAY CHATIER RLY 3.15£-02 3.25£-02 1.58E-02 1.SOE-02 SEIS-RS-E-lABCD RECIRC SPRAY HEAT EXCHANGERS l.48£-02 l.38£-02 SEIS-EI-CB-MCR- 1.42E-02 1.62E-02 SEISMIC FAILURE OF MCR BOARDS AND PANELS PNL l.33£-02 l.48£-02 SE IS-BLDG-AB- 1.42E-02 1.39E-02 AUX BLDG LOWER FLOORS FAIL LOWER l.32£-02 l.28£-02 SEIS-MS-TV-111AB MAIN STEAM TRIP.VALVE TO TURBINE DRIVEN 1.39E-02 3.18E-03 SEIS-MS-TV-211AB AFW PUMP* l.34£-02 2.97£-03 1.37E-02 1.46E-02 SEIS-SSLOCA SEISMIC-INDUCED SMALL-SMALL LOCA l.31£-02 l.38£-02 1.34E-02 1.27E-02 SEIS-LLOCA LARGE LOCA l.26£-02 1.18£-02 1.32E-02 4.07E-03 SEIS-EG-B-3 EDG lJ Battery l.38£-02 3.84£-03 1.29E-02 3.99E-03 SEIS-EG-P-lJ EDG lJ Fuel Oil Transfer Pumps l.35£-02 3.77£-03 SEIS-MOV-QSPH- MOVs in QUENCH SPRAY PUMP HOUSE - SW 1.19E-02 1.13E-02 RSHX Cooling to RS HXs l.llE-02 l.04£-02 1.19E-02 1.35E-02 SEIS-VB-INV-1234 120 VAC VITAL BUS INVERTERS 9.91£-03 l.l4E-02

Serial No. 19-086A Docket No. 50-338/339

Attachment:

Sensitivity Study - FLEX Failure Rates Page 8 of 13 (Partial) Table 5.5-2: SLERF Importance Measures Ranked by FV Fragility Groups Fragility Group Description Ul SLERF FV U2 SLERF FV 1.14E-02 1.28E-02 SEIS-EP-CB-4ABCD 120 VAC VITAL BUS DISTRIBUTION PANELS 1.04£-02 1.17£-02 1.13E-02 1.22E-02 SEIS-MLOCA MEDIUM LOCA 1.08£-02 1.14£-02 SEIS-EE-BKR-HJ2- 1.0SE-02 1.02E-02 EDG OUTPUT BREAKERS - RELAY RLY 1.67£-02 1.64£-02 9.77E-03 1.lOE-02 SEIS-QS-TK-1 REFUELING WATER STORAGE TANK (RWST}

9.30£-03 1.07£-02 SE IS-RC-CNTRL- 9.68E-03 1.09E-02 REACTOR CONTROL RODS RODS 9.33£~03 1.04£-02 EMERGENCY DIESEL GENERATOR CONTROL 8.83E-03 1.13E-02 SE IS-E I-CB-202 PANELS IN ESGR - Fails EDGs 9.32£-03 1.23£-02 8.16E-03 1.20E-02 SEIS-EP-SS-lH 1-lJl 480V LOAD CONTROL CENTERS 1H1 AND 1J1 7.75£-03 1.24£-02 EMERGENCY DIESEL GENERATOR CONTROL 7.98E-03 9.96E-03 SEIS-EI-CB-201 PANELS IN EDG ROOM - Fails EDGs 8.26£-03 1.14£-02 SEIS-CH-P-lABC- 7.47E-03 7.30E-03 CHARGING PUMPS - RELAY CHATIER RLY 7.19£-03 6.87£-03 SE IS-CV-TV- 7.llE-03 6.96E-03 Containment Vacuum Isolation Trip Valves lSOABCD 6.64£-03 6.41£-03 EMERGENCY DIESEL GENERATORS - RELAY 7.08E-03 7.13E-03 SEIS-EDG-HJ-RLY CHATIER 8.01£-03 7.53£-03 6.87E-03 1.75E-02 SEIS-EP-SS-1H-1J 480V LOAD CONTROL CENTERS 1H AND lJ 9.43£-03 2.07£-02 6.70E-03 8.21E-03 SEIS-BY-B-1-24 STATION BATIERIES 1-11 AND 1-IV 5.97£-03 7.82£-03 6.21E-03 5.97E-03 SEIS-SW-P-lAB-RLY SERVICE WATER PUMPS- RELAY CHATIER 6.34£-03 6.02£-03 6.19E-03 5.85E-03 SEIS-EP-SW-1H-1J 4160V EMERGENCY BUSES 7.73£-03 7.37£-03 6.09E-03 1.71E-02 SEIS-EG-B-4 EDG 2J Battery 5.79£-03 2.00E-02 5.78E-03 1.64E-02 SEIS-EG-P-2J EDG 2J Fuel Oil Transfer Pumps 5.50£-03 1.87£-02 S.69E-03 2.24E-03 SEIS-EG-B-1 EDG 1H Battery 5.87£-03 2.10£-03 S.67E-03 4.06E-03 SEIS-FW-P-3AB MOTOR-DRIVEN AUXILIARY FEEDWATER PUMPS 5.43£-03 3.84£-03 SE IS-BLDG-AB- 5.40E-03 5.04E-03 AUX BLDG UPPER FLOORS FAIL LIPPER . 5.17£-03 t1.80E-03

Serial No. 19-086A Docket No. 50-338/339

Attachment:

Sensitivity Study - FLEX Failure Rates Page 9 of 13 (Partial) Table 5.5-2: SLERF Importance Measures Ranked by FV Fragility Groups Fragility Group De.scription U1 SLERF FV U2 SLERF FV SEIS-RS-P-2AB- Outside RS Pumps Fail to Start due to Lockout 5.09E-03 4.64E-03 RLVLO Relay 4.98£-03 4.39£-03 4.78E-03 5.19E-03 SEIS-EI-CB-PROCESS PLANT PROCESS CABINETS 4.84£-03 5.14£-03 BEYOND DESIGN BASIS_(FLEX) DISTRIBUTION 4.lOE-03 5.71E-03 SEIS-BDB-DB-123 PANELS 3.71£-03 5.41£-03 3.73E-03 1.21E-02 SEIS-EG-B-2 EDG 2H Battery 3.48£-03 1.49£-02 3.03E-03 1.0SE-02 SEIS-EG-P-2H EDG 2H Fuel Oil Transfer Pumps 2.82£-03 1.16£-02

Serial No. 19-086A Docket No. 50-338/339

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Sensitivity Study - FLEX Failure Rates Page 10 of 13 Table 5.5-3: SLERF Importance Measures Ranked by FV for Non-Seismic Failures Model Basic Events Prob SLERF FV Description Unit 1 Model Basic Events and FV Importance 5.14E-03 DIESEL-DRIVEN FIRE PUMP 1-FP-P-2 OUT OF lFP-DDP--TM-2 3.16E-02 4.83E-03 SERVICE FOR TEST OR MAINTENANCE 2.95E-03 B SW HEADER IN OUT OF SERVICE FOR TEST OR *

• OSW-HDR--TM-B 1.52E-02 2.81E-03 MAINTENANCE 2.73E-03 OBDBEDG--FR-lA-FLEX 2.04E-01 FLEX DIESEL GENERATOR FAILS TO RUN 9.89E-03 l.99E-03 A SW HEADER IN OUT OF SERVICE FOR TEST OR OSW-HDR--TM-A l.52E-02 1.86£-03 MAINTENANCE l.43E-03 Ul 18 SW PUMP OUT OF SERVICE FOR TEST OR lSW-PAT--TM-18 8.SSE-03

. 1.33E-03 MAINTENANCE l.29E-03 lEE-EDG--FR-lH 2.79E-02 Ul H DIESEL GENERATOR FAILS TO RUN 1.40E-03 l.14E-03 lEE-EDG--FR-lJ 2.79E-02 Ul J DIESEL GENERATOR FAILS TO RUN 1.25E-03 l.OlE-03 Ul lA SW PUMP OUT OF SERVICE FOR TEST OR lSW-PAT--TM-lA 8.SSE-03 9.40E-04 MAINTENANCE 9.13E-04 Ul H DIESEL GENERATOR OUT OF SERVICE FOR lEE-EDG--TM-lH 2.25E-02 1.00E-03 TEST OR MAINTENANCE 8.65E-04 Ul J DIESEL GENERATOR OUT OF SERVICE FOR lEE-EDG--TM-lJ 2.25E-02 9.44E-04 TEST OR MAINTENANCE Unit 2 Model Basic Events and FV Importance 5.25E-03 DIESEL-DRIVEN FIRE PUMP 1-FP-P-2 OUT OF lFP-DDP--TM-2 3.16E-02 4.95E-03 SERVICE FOR TEST OR MAINTENANCE

. 2.67E-03 OBDBEDG--FR-lA-FLEX 2.04E-01 FLEX DIESEL GENERATOR FAILS TO RUN 1.14E-02 2.62E-03 A SW HEADER IN OUT OF SERVICE FOR TEST OR OSW-HDR--TM-A l.52E-02 2.42E-03 MAINTENANCE 2.31E-03 2EE-EDG--FR-2H 2.79E-02 ' U2 H DIESEL GENERATOR FAILS TO RUN 2.lOE-03 l.79E-03 U2 H DIESEL GENERATOR OUT OF SERVICE FOR 2EE-EDG--TM-2H 2.25E-02 2.04E-03 TEST OR MAINTENANCE l.SSE-03 B SW HEADER IN OUT OF SERVICE FOR TEST OR OSW-HDR--TM-8 1.52E-02

• 1.48E-03 MAINTENANCE

Serial No. 19-086A Docket No. 50-338/339

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Sensitivity Study - FLEX Failure Rates Page 11 of 13 Table 5.5-3: SLERF Importance Measures Ranked by FV for Non-Seismic Failures Model Basic Events Prob SLERF FV Description

. 1.27E-03 2EE-EDG--FR-2J 2.79E-02 U2 J DIESEL GENERATOR FAILS TO RUN 1.37£-03 1.12E-03 U2 1B SW PUMP OUT OF SERVICE FOR TEST OR 2SW-PAT--TM-1B 8.SSE-03 1.03£-03 MAINTENANCE 9.71E-04 U2 J DIESEL GENERATOR OUT OF SERVICE FOR 2EE-EDG--TM-2J 2.25E-02 1.0SE-03 TEST OR MAINTENANCE 8.63E-04 2QS-PSB--FS-1A 5.59E-03 U2 1A QS PUMP FAILS TO START 7.95£-04

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Serial No. 19-086A Docket No. 50-338/339

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Sensitivity Study - FLEX Failure Rates Page 12 of 13 5.5-5: SLERF Importance Measures Ranked by FV for Operator Actions HEP Basic Event SLERF FV Description HEP SLERF FV Importance in Unit 1 Model 2.71E-02 HEP-C-RCSDEP Depressurize the RCS Per SAMGs 2.33E-02 2.26E-02 HEP-C-ALIGN-TDAFW Align turbine-driven AFW Pump to Band C SGs 2.0SE-02 1.17E-02 HEP-C-1BAFE Initiate Bleed and Feed After AFW Fails 1.01E-02 8.28E-03 HE P-C-FLEX-RI P Install and Start FLEX RCS Injection Pump 3.84E-02 HEP-C-1HV-SFGD- 6.77E-03 Restore Safeguards Area Ventilation VENT 5.BOE-03 5.92E-03 Isolate SW Flood in Auxiliary Building Caused by Failure of the REC-SEIS-FLD-CCHX 5.11E-03 Component Cooling Heat Exchangers HEP-C-FLEX- 5.23E-03 Load shed the vital 125vdc batteries during SBO LOADSHED 1.BSE-02 HEP SLERF FV Importance in Unit 2 Model 2.56E-02 HEP-C-RCSDEP Depressurize the RCS Per SAMGs 2.15E-02 2.34E-02 HE P-C-ALI GN-TDAFW Align turbine-driven AFW Pump to B and C SGs 2.12E-02 9.27E-03 HEP-C-2BAFE Initiate Bleed and Feed After AFW Fails 7.84E-03 8.31E-03 HEP-C-FLEX-RIP Install and Start FLEX RCS Injection Pump 3.87E-02 HEP-C-2HV-SFGD- 6.73E-03 Restore Safeguards Area Ventilation VENT 5.66E-03 5.72E-03 Isolate SW Flood in Auxiliary Building Caused by Failure of the REC-SEIS-FLD-CCHX 4.83E-03 Component Cooling Heat Exchangers HEP-C-FLEX- 5.52E-03 Load shed the vital 125vdc batteries during SBO LOADSHED 1.98E-02

Serial No. 19-086A Docket No. 50-338/339

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Sensitivity Study - FLEX Failure Rates Page 13 of 13 Sensitivity Study Conclusion This sensitivity shows the effect on seismic core damage frequency (SCDF) and seismic large early release frequency (SLERF) and the impact on importances if the FLEX equipment failure rates and FLEX HEPs are increased. The results of the sensitivity showed the SCDF increases by approximately 15% and the SLERF increases by approximately 3%.

However, the SPRA does not credit deployment of the spares that are in the FLEX storage building and, therefore, the impact on seismic risk due to variabilities in the failure rates and HEPs is expected to be less than indicated by the results of this sensitivity study. For example, there are multiple spare FLEX diesel generators available that could be used if one diesel generator failed to start, load or run. If these spares were credited in the FLEX functions in the SPRA, the SCDF and SLERF are expected to decrease or remain the same as the base SCDF and SLERF even with the higher FLEX equipment failure probabilities.