ML112411358

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Final Precursor Analysis: Concurrent Unavailabilities - EDG B Inoperable Due to Failed Output Breaker and EDG a Unavailable Due to Testing and Maintenance
ML112411358
Person / Time
Site: Robinson Duke Energy icon.png
Issue date: 09/23/2011
From:
NRC/RES/DRA
To:
Hunter C, 251-7575 RES/DRA
References
IR-10-005
Download: ML112411358 (18)
v • d • e


Text

Final Precursor Analysis Accident Sequence Precursor Program - Office of Nuclear Regulatory Research Concurrent Unavailabilities- EDG B Inoperable due to Failed H. B. Robinson Output Breaker and EDG A Unavailable due to Testing and Maintenance LER: 261/10-001 Event Date: 02/22/2010 CDP = 3x10-6 IR: 50-261/10-05 EVENT

SUMMARY

Brief Event Description. At 0455 on February 22, 2010, with H. B. Robinson Steam Electric Plant, Unit 2, operating at approximately 99% power, Emergency Diesel Generator (EDG) B was removed from service for scheduled maintenance. Technical Specifications (TS) Limiting Condition for Operation 3.8.1 Condition B, was entered due one EDG inoperable. During the post-maintenance testing, EDG B Output Breaker 52/27B failed to close. The investigation for the inoperability of Breaker 52/27B determined that the shunt trip attachment (STA) had internal binding that prevented the STA from releasing the trip bar, resulting in the trip bar remaining in the "trip condition" and preventing the breaker from closing. EDG B was inoperable from January 28, 2010 to February 24, 2010, approximately 27 days. In addition, EDG A was declared inoperable on February 8, 2010 for approximately 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> and 53 minutes for scheduled maintenance. Additional details are provided in References 1 and 2.

Key Event Details. The following event details are significant to the modeling of this event analysis:

  • There were approximately 27 days that the EDG B was unavailable due to the breaker failure. During this period, EDG A was unavailable due to surveillance testing for 7 hours8.101852e-5 days <br />0.00194 hours <br />1.157407e-5 weeks <br />2.6635e-6 months <br />. Therefore, the total duration of EDG B was unavailable by itself is 27 days minus 7 hours8.101852e-5 days <br />0.00194 hours <br />1.157407e-5 weeks <br />2.6635e-6 months <br />, (i.e. 27 days x 24 hour2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />s/day - 7 hours8.101852e-5 days <br />0.00194 hours <br />1.157407e-5 weeks <br />2.6635e-6 months <br /> = 641 hours0.00742 days <br />0.178 hours <br />0.00106 weeks <br />2.439005e-4 months <br />).
  • The duration that both the EDG B was unavailable due to the failed breaker and EDG A was undergoing scheduled maintenance was approximately 7 hours8.101852e-5 days <br />0.00194 hours <br />1.157407e-5 weeks <br />2.6635e-6 months <br />.

ANALYSIS RESULTS Importance. The importance or increase in core damage probability (CDP) for this event is 3.4x10-6; therefore, this event is a precursor (i.e., CDP greater than or equal to 10-6).

Dominant Sequence. The dominant accident sequence, Loss of Offsite Power [Grid-Related]

(LOOPGR) 16-46 (CDP of this sequence from the results of Calculations 1 and 2 combined is 1.6x10-6) contributes 47% of the total internal events CDP. Additional sequences that contribute greater than 1% of the total internal events CDP are provided in Appendix A.

The dominant sequence is shown graphically in Figures B-1 and B-2 in Appendix B. The events and important component failures in LOOPGR Sequence 16-46 are:

1

LER 261/10-001

  • Emergency power system fails,
  • Operators fail to recover offsite power within 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br />, and
  • Operators fail to recover an EDG within 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br />.

SAPHIRE 8 Report. The SAPHIRE 8 Worksheets (Appendix A) provide the following:

  • Summary of conditional event changes, including base and change case probabilities/frequencies.
  • Event tree dominant results
  • Dominant sequences (including CDPs).
  • Sequence logic for all dominant sequences.
  • Referenced fault trees (including definitions).
  • Cutset report for each dominant sequence.
  • Referenced events (including definitions and probabilities for key basic events)

MODELING ASSUMPTIONS Analysis Type. The Revision 8.16 of the H. B. Robinson SPAR model was used for the analysis of this degraded condition. This analysis was completed using two SAPHIRE calculations: (1) one calculation of the CDP of the unavailability of EDG B by itself for 641 hours0.00742 days <br />0.178 hours <br />0.00106 weeks <br />2.439005e-4 months <br />, and (2) a second calculation of the CDP with both the EDGs unavailable for 7 hours8.101852e-5 days <br />0.00194 hours <br />1.157407e-5 weeks <br />2.6635e-6 months <br />.

Analysis Rules. The ASP program uses Significance Determination Process results for degraded conditions when available. However, the ASP Program performs independent analyses for unavailabilities of safety equipment that were determined to not be caused by a licensee performance deficiency. In addition, ASP analyses are performed when multiple degraded conditions exist during the same time window.

Key Modeling Assumptions. The following modeling assumptions and associated basic event modifications were required for this event analysis:

Calculation 1- EDG B Unavailable for 641 Hours

  • The basic event EPS-DGN-FS-2B (Diesel Generator 2B fails to start) was set to TRUE because EDG B failed to start and was unavailable for 641 hours0.00742 days <br />0.178 hours <br />0.00106 weeks <br />2.439005e-4 months <br />.
  • To ensure that the common cause failure probabilities were calculated within SAPHIRE the following basic events were modified as the following:

- The basic event EPS-DGN-FR-2B (Diesel Generator 2B fails to run) was set to 1.0.

- The basic event EPS-DGN-TM-2B (Diesel Generator 2B unavailable due to test and maintenance) was set to TRUE.

- The basic event EPS-DGN-CF-2ABFR (Common-cause failure of EDGs 2A and 2B to run) was set to FALSE.

2

LER 261/10-001

  • The licensee concluded (Reference 1) that several response actions to recover EDG B, such as the discovery of the manually manipulating the trip bar or replacing the affected breaker with a spare could be accomplished in an estimated time frame which ranged from one to four hours. However, during a postulated LOOP with additional EDG failures leading to a station blackout and AFW system failures, this analysis assumes that recovery of EDG B within one hour is not possible. Recovery of EDG B within 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> (the other key recovery time for H.B. Robinson) is credited in this analysis.

- The basic event EPS-XHE-XL-NR04H (Operators fail to recover an EDG in 4 Hours) was set to 5.0x10-3. This value was calculated using the SPAR-H Method (Reference 3).

This EDG recovery action contains both diagnosis and action activities.

Since operators would have enough time to perform the action, the nominal action human error probability (HEP) of 1x10-3 was applied.

The following performance shaping factors (PSF) were adjusted. All other PSFs were determined to be nominal (i.e., x1).

PSF for Multiplier Notes Diagnosis Operators would have at least 3 hours3.472222e-5 days <br />8.333333e-4 hours <br />4.960317e-6 weeks <br />1.1415e-6 months <br /> to diagnose the problem; Time Available 0.1 therefore, Extra Time (i.e., x0.1) was selected.

The PSF for diagnosis stress is assigned a value of High Stress (i.e., x2)

Stress 2 because the failure to recover the EDG would lead directly to core damage.

The PSF for diagnosis complexity is assigned a value of Moderately Complex (i.e., x2) because the recovery of the EDG required a Complexity 2 technician to determine the failure mechanism of the breaker and develop a solution to close the breaker.

Diagnosis HEP 4E-3 Action HEP 1E-3 Adjusted Total HEP 5E-3 Calculation 2- EDGs A and B Unavailable for 7 Hours

  • The basic event EPS-DGN-FS-2B was set to TRUE because EDG B failed to start and was unavailable for this 7 hours8.101852e-5 days <br />0.00194 hours <br />1.157407e-5 weeks <br />2.6635e-6 months <br /> period.
  • The basic event EPS-DGN-TM-2A (Diesel Generator 2A unavailable due to test and maintenance) was set to TRUE to because EDG A was undergoing scheduled maintenance for this 7 hour8.101852e-5 days <br />0.00194 hours <br />1.157407e-5 weeks <br />2.6635e-6 months <br /> period.
  • To ensure that the common cause failure probabilities were calculated within SAPHIRE the following basic events were modified as the following:

- The basic event EPS-DGN-FR-2B was set to 1.0.

- The basic event EPS-DGN-TM-2B was set to TRUE.

- The basic event EPS-DGN-FS-2A (Diesel Generator 2A fails to start) was set to 1.0.

- The basic event EPS-DGN-FR-2A (Diesel Generator 2A fails to run) was set to 1.0.

  • The basic event EPS-XHE-XL-NR04H was set to 5.0x10-3 to credit the potential recovery of EDG B within 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> (same as Calculation 1).

3

LER 261/10-001 REFERENCES

1. Progress Energy, "LER 261/10-001- Emergency Diesel Generator Inoperable in Excess of Technical Specifications Allowed Completion Time, dated June 10, 2010.
2. U.S. Nuclear Regulatory Commission, H. B. Robinson Steam Electric Plant- NRC Integrated Inspection Report 05000261/2010005, dated January 28, 2011.
3. Idaho National Laboratory, NUREG/CR-6883: The SPAR-H Human Reliability Analysis Method, dated August 2005.

4

LER 261/10-001 Appendix A: SAPHIRE 8 Worksheets Calculation 1- EDG B Unavailable (Failed to Start) for 641 hours0.00742 days <br />0.178 hours <br />0.00106 weeks <br />2.439005e-4 months <br /> Summary of Conditional Event Changes Event Description Cond. Nominal Value Value EPS-DGN-CF-2ABFR COMMON CAUSE FAILURE OF DIESEL False 3.282E-4 GENERATORS 2A & 2B TO RUN EPS-DGN-FR-2B DIESEL GENERATOR 2B FAILS TO RUN 1.000E+0 2.118E-2 EPS-DGN-FS-2B DIESEL GENERATOR 2B FAILS TO START True 5.000E-3 EPS-DGN-TM-2B DIESEL GENERATOR 2B UNAVAILABLE DUE TO True 1.200E-2 TEST AND MAINTENANCE EPS-XHE-XL-NR01H OPERATOR FAILS TO RECOVER EMERGENCY True 7.857E-1 DIESEL IN 1 HOUR EPS-XHE-XL-NR04H OPERATOR FAILS TO RECOVER EMERGENCY 5.000E-3 5.568E-1 DIESEL IN 4 HOURS EPS-DGN-CF-2ABFS COMMON CAUSE FAILURE OF DIESEL 1.150E-2 5.750E-5 GENERATORS 2A & 2B TO START EPS-DGN-CF-2ABDSFR CCF OF DIESEL GENERATORS 2A, 2B & DS TO RUN 6.665E-4 1.214E-4 EPS-DGN-CF-2ABDSFS CCF OF DIESEL GENERATORS 2A, 2B & DS TO 3.722E-3 1.861E-5 START Dominant Sequence Results Only items contributing at least 1.0% to the total CCDP are displayed.

EVENT TREE SEQUENCE CCDP CDP CDP DESCRIPTION LOOPGR 16-46 1.375E-6 3.242E-8 1.343E-6 /RPS, EPS, AFW-B, OPR-01H, DGR-01H LOOPSC 16-46 4.706E-7 1.047E-8 4.601E-7 /RPS, EPS, AFW-B, OPR-01H, DGR-01H LOOPWR 16-46 4.584E-7 1.158E-8 4.468E-7 /RPS, EPS, AFW-B, OPR-01H, DGR-01H LOOPGR 15 2.173E-7 1.270E-8 2.046E-7 /RPS, /EPS, AFW-L, FAB-L LOOPSC 15 1.212E-7 6.736E-9 1.145E-7 /RPS, /EPS, AFW-L, FAB-L LOOPPC 16-46 6.782E-8 1.232E-9 6.658E-8 /RPS, EPS, AFW-B, OPR-01H, DGR-01H LOOPWR 15 5.602E-8 2.821E-9 5.320E-8 /RPS, /EPS, AFW-L, FAB-L Total 3.939E-6 1.028E-6 2.911E-6 Referenced Fault Trees Fault Tree Description AFW-B AUXILIARY FEEDWATER AFW-L ROBINSON UNIT 2 PWR B AFW USING LOOP-FTF FAULT TREE FLAGS DGR-01H OPERATOR FAILS TO RECOVER EMERGENCY DIESEL IN 1 HOUR EPS EMERGENCY POWER FAB-L ROBINSON UNIT 2 PWR B FAB USING LOOP-FTF FAULT TREE FLAGS OPR-01H OPERATOR FAILS TO RECOVER OFFSITE POWER IN 1 HOUR Cutset Report - LOOPGR 16-46 Only items contributing at least 1% to the total are displayed.

  1. PROB/FREQ TOTAL% CUTSET 1.879E-5 100 Displaying 2612 of 2612 Cutsets.

1 2.115E-6 11.26 IE-LOOPGR,AFW-XHE-XM-EPP1,EPS-DGN-CF-2ABDSFS,OEP-XHE-XL-NR01HGR 2 9.546E-7 5.08 IE-LOOPGR,AFW-TDP-FS-SDP,EPS-DGN-TM-2A,OEP-XHE-XL-NR01HGR A-1

LER 261/10-001

  1. PROB/FREQ TOTAL% CUTSET 3 9.149E-7 4.87 IE-LOOPGR,AFW-TDP-FS-SDP,EPS-DGN-CF-2ABFS,OEP-XHE-XL-NR01HGR 4 6.535E-7 3.48 IE-LOOPGR,AFW-TDP-TM-SDP,EPS-DGN-CF-2ABFS,OEP-XHE-XL-NR01HGR 5 5.594E-7 2.98 IE-LOOPGR,AFW-TDP-FR-SDP,EPS-DGN-TM-2A,OEP-XHE-XL-NR01HGR 6 5.361E-7 2.85 IE-LOOPGR,AFW-TDP-FR-SDP,EPS-DGN-CF-2ABFS,OEP-XHE-XL-NR01HGR 7 4.230E-7 2.25 IE-LOOPGR,EPS-DGN-CF-2ABDSFS,FWS-EDP-TM-DDP,OEP-XHE-XL-NR01HGR 8 4.015E-7 2.14 IE-LOOPGR,AFW-XHE-XM-EPP1,EPS-DGN-TM-2A,EPS-MDP-FR-FUELDS,OEP-XHE-XL-NR01HGR 9 3.978E-7 2.12 IE-LOOPGR,AFW-TDP-FS-SDP,EPS-DGN-FS-2A,OEP-XHE-XL-NR01HGR 10 3.847E-7 2.05 IE-LOOPGR,AFW-XHE-XM-EPP1,EPS-DGN-CF-2ABFS,EPS-MDP-FR-FUELDS,OEP-XHE-XL-NR01HGR 11 2.961E-7 1.58 IE-LOOPGR,AFW-TDP-FS-SDP,EPS-DGN-CF-2ABDSFS,OEP-XHE-XL-NR01HGR 12 2.948E-7 1.57 IE-LOOPGR,AFW-TDP-FS-SDP,EPS-DGN-FR-2A,OEP-XHE-XL-NR01HGR,OEP-XHE-XX-NR01HGR1 13 2.841E-7 1.51 IE-LOOPGR,AFW-TDP-TM-SDP,EPS-DGN-FS-2A,OEP-XHE-XL-NR01HGR 14 2.728E-7 1.45 IE-LOOPGR,AFW-XHE-XM-EPP1,EPS-DGN-TM-2A,EPS-XHE-XM-DGDS,OEP-XHE-XL-NR01HGR 15 2.614E-7 1.39 IE-LOOPGR,AFW-XHE-XM-EPP1,EPS-DGN-CF-2ABFS,EPS-XHE-XM-DGDS,OEP-XHE-XL-NR01HGR 16 2.387E-7 1.27 IE-LOOPGR,AFW-TDP-FS-SDP,EPS-SEQ-FO-DG2A,OEP-XHE-XL-NR01HGR 17 2.387E-7 1.27 IE-LOOPGR,AFW-TDP-FS-SDP,EPS-FAN-FS-HVS6,OEP-XHE-XL-NR01HGR 18 2.387E-7 1.27 IE-LOOPGR,AFW-TDP-FS-SDP,EPS-FAN-FS-HVE18,OEP-XHE-XL-NR01HGR 19 2.331E-7 1.24 IE-LOOPGR,AFW-TDP-FR-SDP,EPS-DGN-FS-2A,OEP-XHE-XL-NR01HGR 20 2.115E-7 1.13 IE-LOOPGR,AFW-TDP-TM-SDP,EPS-DGN-CF-2ABDSFS,OEP-XHE-XL-NR01HGR 21 2.106E-7 1.12 IE-LOOPGR,AFW-TDP-TM-SDP,EPS-DGN-FR-2A,OEP-XHE-XL-NR01HGR,OEP-XHE-XX-NR01HGR1 22 1.989E-7 1.06 IE-LOOPGR,ACP-CRB-CC-52-18B,AFW-TDP-FS-SDP,OEP-XHE-XL-NR01HGR Cutset Report - LOOPSC 16-46 Only items contributing at least 1% to the total are displayed.
  1. PROB/FREQ TOTAL% CUTSET 6.431E-6 100 Displaying 1963 of 1963 Cutsets.

1 7.314E-7 11.37 IE-LOOPSC,AFW-XHE-XM-EPP1,EPS-DGN-CF-2ABDSFS,OEP-XHE-XL-NR01HSC 2 3.302E-7 5.13 IE-LOOPSC,AFW-TDP-FS-SDP,EPS-DGN-TM-2A,OEP-XHE-XL-NR01HSC 3 3.164E-7 4.92 IE-LOOPSC,AFW-TDP-FS-SDP,EPS-DGN-CF-2ABFS,OEP-XHE-XL-NR01HSC 4 2.260E-7 3.51 IE-LOOPSC,AFW-TDP-TM-SDP,EPS-DGN-CF-2ABFS,OEP-XHE-XL-NR01HSC 5 1.935E-7 3.01 IE-LOOPSC,AFW-TDP-FR-SDP,EPS-DGN-TM-2A,OEP-XHE-XL-NR01HSC 6 1.854E-7 2.88 IE-LOOPSC,AFW-TDP-FR-SDP,EPS-DGN-CF-2ABFS,OEP-XHE-XL-NR01HSC 7 1.463E-7 2.27 IE-LOOPSC,EPS-DGN-CF-2ABDSFS,FWS-EDP-TM-DDP,OEP-XHE-XL-A-2

LER 261/10-001

  1. PROB/FREQ TOTAL% CUTSET NR01HSC 8 1.388E-7 2.16 IE-LOOPSC,AFW-XHE-XM-EPP1,EPS-DGN-TM-2A,EPS-MDP-FR-FUELDS,OEP-XHE-XL-NR01HSC 9 1.376E-7 2.14 IE-LOOPSC,AFW-TDP-FS-SDP,EPS-DGN-FS-2A,OEP-XHE-XL-NR01HSC 10 1.331E-7 2.07 IE-LOOPSC,AFW-XHE-XM-EPP1,EPS-DGN-CF-2ABFS,EPS-MDP-FR-FUELDS,OEP-XHE-XL-NR01HSC 11 1.024E-7 1.59 IE-LOOPSC,AFW-TDP-FS-SDP,EPS-DGN-CF-2ABDSFS,OEP-XHE-XL-NR01HSC 12 9.827E-8 1.53 IE-LOOPSC,AFW-TDP-TM-SDP,EPS-DGN-FS-2A,OEP-XHE-XL-NR01HSC 13 9.433E-8 1.47 IE-LOOPSC,AFW-XHE-XM-EPP1,EPS-DGN-TM-2A,EPS-XHE-XM-DGDS,OEP-XHE-XL-NR01HSC 14 9.206E-8 1.43 IE-LOOPSC,AFW-TDP-FS-SDP,EPS-DGN-FR-2A,OEP-XHE-XL-NR01HSC,OEP-XHE-XX-NR01HSC1 15 9.040E-8 1.41 IE-LOOPSC,AFW-XHE-XM-EPP1,EPS-DGN-CF-2ABFS,EPS-XHE-XM-DGDS,OEP-XHE-XL-NR01HSC 16 8.254E-8 1.28 IE-LOOPSC,AFW-TDP-FS-SDP,EPS-FAN-FS-HVS6,OEP-XHE-XL-NR01HSC 17 8.254E-8 1.28 IE-LOOPSC,AFW-TDP-FS-SDP,EPS-FAN-FS-HVE18,OEP-XHE-XL-NR01HSC 18 8.254E-8 1.28 IE-LOOPSC,AFW-TDP-FS-SDP,EPS-SEQ-FO-DG2A,OEP-XHE-XL-NR01HSC 19 8.061E-8 1.25 IE-LOOPSC,AFW-TDP-FR-SDP,EPS-DGN-FS-2A,OEP-XHE-XL-NR01HSC 20 7.314E-8 1.14 IE-LOOPSC,AFW-TDP-TM-SDP,EPS-DGN-CF-2ABDSFS,OEP-XHE-XL-NR01HSC 21 6.879E-8 1.07 IE-LOOPSC,ACP-CRB-CC-52-18B,AFW-TDP-FS-SDP,OEP-XHE-XL-NR01HSC 22 6.576E-8 1.02 IE-LOOPSC,AFW-TDP-TM-SDP,EPS-DGN-FR-2A,OEP-XHE-XL-NR01HSC,OEP-XHE-XX-NR01HSC1 Cutset Report - LOOPWR 16-46 Only items contributing at least 1% to the total are displayed.
  1. PROB/FREQ TOTAL% CUTSET 6.265E-6 100 Displaying 1954 of 1954 Cutsets.

1 5.892E-7 9.4 IE-LOOPWR,AFW-XHE-XM-EPP1,EPS-DGN-CF-2ABDSFS,OEP-XHE-XL-NR01HWR 2 2.660E-7 4.25 IE-LOOPWR,AFW-TDP-FS-SDP,EPS-DGN-TM-2A,OEP-XHE-XL-NR01HWR 3 2.549E-7 4.07 IE-LOOPWR,AFW-TDP-FS-SDP,EPS-DGN-CF-2ABFS,OEP-XHE-XL-NR01HWR 4 1.915E-7 3.06 IE-LOOPWR,AFW-TDP-FS-SDP,EPS-DGN-FR-2A,OEP-XHE-XL-NR01HWR,OEP-XHE-XX-NR01HWR1 5 1.821E-7 2.91 IE-LOOPWR,AFW-TDP-TM-SDP,EPS-DGN-CF-2ABFS,OEP-XHE-XL-NR01HWR 6 1.558E-7 2.49 IE-LOOPWR,AFW-TDP-FR-SDP,EPS-DGN-TM-2A,OEP-XHE-XL-NR01HWR 7 1.493E-7 2.38 IE-LOOPWR,AFW-TDP-FR-SDP,EPS-DGN-CF-2ABFS,OEP-XHE-XL-NR01HWR 8 1.368E-7 2.18 IE-LOOPWR,AFW-TDP-TM-SDP,EPS-DGN-FR-2A,OEP-XHE-XL-NR01HWR,OEP-XHE-XX-NR01HWR1 9 1.314E-7 2.1 IE-LOOPWR,AFW-TDP-FS-SDP,EPS-DGN-FR-2A,OEP-XHE-XL-NR01HWR,OEP-XHE-XX-NR01HWR2 10 1.178E-7 1.88 IE-LOOPWR,EPS-DGN-CF-2ABDSFS,FWS-EDP-TM-DDP,OEP-XHE-XL-NR01HWR 11 1.122E-7 1.79 IE-LOOPWR,AFW-TDP-FR-SDP,EPS-DGN-FR-2A,OEP-XHE-XL-NR01HWR,OEP-XHE-XX-NR01HWR1 A-3

LER 261/10-001

  1. PROB/FREQ TOTAL% CUTSET 12 1.118E-7 1.79 IE-LOOPWR,AFW-XHE-XM-EPP1,EPS-DGN-TM-2A,EPS-MDP-FR-FUELDS,OEP-XHE-XL-NR01HWR 13 1.108E-7 1.77 IE-LOOPWR,AFW-TDP-FS-SDP,EPS-DGN-FS-2A,OEP-XHE-XL-NR01HWR 14 1.072E-7 1.71 IE-LOOPWR,AFW-XHE-XM-EPP1,EPS-DGN-CF-2ABFS,EPS-MDP-FR-FUELDS,OEP-XHE-XL-NR01HWR 15 9.387E-8 1.5 IE-LOOPWR,AFW-TDP-TM-SDP,EPS-DGN-FR-2A,OEP-XHE-XL-NR01HWR,OEP-XHE-XX-NR01HWR2 16 8.248E-8 1.32 IE-LOOPWR,AFW-TDP-FS-SDP,EPS-DGN-CF-2ABDSFS,OEP-XHE-XL-NR01HWR 17 8.053E-8 1.29 IE-LOOPWR,AFW-XHE-XM-EPP1,EPS-DGN-FR-2A,EPS-MDP-FR-FUELDS,OEP-XHE-XL-NR01HWR,OEP-XHE-XX-NR01HWR1 18 7.915E-8 1.26 IE-LOOPWR,AFW-TDP-TM-SDP,EPS-DGN-FS-2A,OEP-XHE-XL-NR01HWR 19 7.700E-8 1.23 IE-LOOPWR,AFW-TDP-FR-SDP,EPS-DGN-FR-2A,OEP-XHE-XL-NR01HWR,OEP-XHE-XX-NR01HWR2 20 7.599E-8 1.21 IE-LOOPWR,AFW-XHE-XM-EPP1,EPS-DGN-TM-2A,EPS-XHE-XM-DGDS,OEP-XHE-XL-NR01HWR 21 7.282E-8 1.16 IE-LOOPWR,AFW-XHE-XM-EPP1,EPS-DGN-CF-2ABFS,EPS-XHE-XM-DGDS,OEP-XHE-XL-NR01HWR 22 6.649E-8 1.06 IE-LOOPWR,AFW-TDP-FS-SDP,EPS-FAN-FS-HVS6,OEP-XHE-XL-NR01HWR 23 6.649E-8 1.06 IE-LOOPWR,AFW-TDP-FS-SDP,EPS-FAN-FS-HVE18,OEP-XHE-XL-NR01HWR 24 6.649E-8 1.06 IE-LOOPWR,AFW-TDP-FS-SDP,EPS-SEQ-FO-DG2A,OEP-XHE-XL-NR01HWR 25 6.493E-8 1.04 IE-LOOPWR,AFW-TDP-FR-SDP,EPS-DGN-FS-2A,OEP-XHE-XL-NR01HWR Cutset Report - LOOPGR 15 Only items contributing at least 1% to the total are displayed.
  1. PROB/FREQ TOTAL% CUTSET 2.970E-6 100 Displaying 2054 of 2054 Cutsets.

1 2.650E-7 8.92 IE-LOOPGR,AFW-FAN-FR-HV7B,AFW-XHE-XM-CNTRL,DCP-BAT-LP-BATB1HR,DCP-XHE-XM-BC1 2 2.232E-7 7.52 IE-LOOPGR,AFW-MDP-TM-A,AFW-XHE-XM-CNTRL,DCP-BAT-LP-BATB1HR,DCP-XHE-XM-BC1 3 1.674E-7 5.64 IE-LOOPGR,AFW-FAN-FS-HV7B,AFW-XHE-XM-CNTRL,DCP-BAT-LP-BATB1HR,DCP-XHE-XM-BC1 4 8.370E-8 2.82 IE-LOOPGR,AFW-MDP-FS-A,AFW-XHE-XM-CNTRL,DCP-BAT-LP-BATB1HR,DCP-XHE-XM-BC1 5 8.038E-8 2.71 IE-LOOPGR,AFW-FAN-FR-HV7B,AFW-TDP-FS-SDP,PPR-MOV-FC-536 6 8.038E-8 2.71 IE-LOOPGR,AFW-FAN-FR-HV7B,AFW-TDP-FS-SDP,PPR-MOV-FC-535 7 6.770E-8 2.28 IE-LOOPGR,AFW-MDP-TM-A,AFW-TDP-FS-SDP,PPR-MOV-FC-535 8 6.770E-8 2.28 IE-LOOPGR,AFW-MDP-TM-A,AFW-TDP-FS-SDP,PPR-MOV-FC-536 9 6.696E-8 2.25 IE-LOOPGR,AFW-FCV-CC-1424,AFW-XHE-XM-CNTRL,DCP-BAT-LP-BATB1HR,DCP-XHE-XM-BC1 10 5.741E-8 1.93 IE-LOOPGR,AFW-FAN-FR-HV7B,AFW-TDP-TM-SDP,PPR-MOV-FC-536 11 5.741E-8 1.93 IE-LOOPGR,AFW-FAN-FR-HV7B,AFW-TDP-TM-SDP,PPR-MOV-FC-535 12 5.078E-8 1.71 IE-LOOPGR,AFW-FAN-FS-HV7B,AFW-TDP-FS-SDP,PPR-MOV-FC-536 13 5.078E-8 1.71 IE-LOOPGR,AFW-FAN-FS-HV7B,AFW-TDP-FS-SDP,PPR-MOV-FC-535 14 4.710E-8 1.59 IE-LOOPGR,AFW-FAN-FR-HV7B,AFW-TDP-FR-SDP,PPR-MOV-FC-536 15 4.710E-8 1.59 IE-LOOPGR,AFW-FAN-FR-HV7B,AFW-TDP-FR-SDP,PPR-MOV-FC-535 16 3.967E-8 1.34 IE-LOOPGR,AFW-MDP-TM-A,AFW-TDP-FR-SDP,PPR-MOV-FC-535 A-4

LER 261/10-001

  1. PROB/FREQ TOTAL% CUTSET 17 3.967E-8 1.34 IE-LOOPGR,AFW-MDP-TM-A,AFW-TDP-FR-SDP,PPR-MOV-FC-536 18 3.627E-8 1.22 IE-LOOPGR,AFW-FAN-FS-HV7B,AFW-TDP-TM-SDP,PPR-MOV-FC-536 19 3.627E-8 1.22 IE-LOOPGR,AFW-FAN-FS-HV7B,AFW-TDP-TM-SDP,PPR-MOV-FC-535 20 3.001E-8 1.01 IE-LOOPGR,AFW-MDP-FR-A,AFW-XHE-XM-CNTRL,DCP-BAT-LP-BATB1HR,DCP-XHE-XM-BC1 21 2.975E-8 1 IE-LOOPGR,AFW-FAN-FS-HV7B,AFW-TDP-FR-SDP,PPR-MOV-FC-536 22 2.975E-8 1 IE-LOOPGR,AFW-FAN-FS-HV7B,AFW-TDP-FR-SDP,PPR-MOV-FC-535 Cutset Report - LOOPSC 15 Only items contributing at least 1% to the total are displayed.
  1. PROB/FREQ TOTAL% CUTSET 1.657E-6 100 Displaying 1563 of 1563 Cutsets.

1 1.482E-7 8.94 IE-LOOPSC,AFW-FAN-FR-HV7B,AFW-XHE-XM-CNTRL,DCP-BAT-LP-BATB1HR,DCP-XHE-XM-BC1 2 1.248E-7 7.53 IE-LOOPSC,AFW-MDP-TM-A,AFW-XHE-XM-CNTRL,DCP-BAT-LP-BATB1HR,DCP-XHE-XM-BC1 3 9.360E-8 5.65 IE-LOOPSC,AFW-FAN-FS-HV7B,AFW-XHE-XM-CNTRL,DCP-BAT-LP-BATB1HR,DCP-XHE-XM-BC1 4 4.680E-8 2.82 IE-LOOPSC,AFW-MDP-FS-A,AFW-XHE-XM-CNTRL,DCP-BAT-LP-BATB1HR,DCP-XHE-XM-BC1 5 4.494E-8 2.71 IE-LOOPSC,AFW-FAN-FR-HV7B,AFW-TDP-FS-SDP,PPR-MOV-FC-536 6 4.494E-8 2.71 IE-LOOPSC,AFW-FAN-FR-HV7B,AFW-TDP-FS-SDP,PPR-MOV-FC-535 7 3.786E-8 2.29 IE-LOOPSC,AFW-MDP-TM-A,AFW-TDP-FS-SDP,PPR-MOV-FC-535 8 3.786E-8 2.29 IE-LOOPSC,AFW-MDP-TM-A,AFW-TDP-FS-SDP,PPR-MOV-FC-536 9 3.744E-8 2.26 IE-LOOPSC,AFW-FCV-CC-1424,AFW-XHE-XM-CNTRL,DCP-BAT-LP-BATB1HR,DCP-XHE-XM-BC1 10 3.210E-8 1.94 IE-LOOPSC,AFW-FAN-FR-HV7B,AFW-TDP-TM-SDP,PPR-MOV-FC-536 11 3.210E-8 1.94 IE-LOOPSC,AFW-FAN-FR-HV7B,AFW-TDP-TM-SDP,PPR-MOV-FC-535 12 2.839E-8 1.71 IE-LOOPSC,AFW-FAN-FS-HV7B,AFW-TDP-FS-SDP,PPR-MOV-FC-536 13 2.839E-8 1.71 IE-LOOPSC,AFW-FAN-FS-HV7B,AFW-TDP-FS-SDP,PPR-MOV-FC-535 14 2.633E-8 1.59 IE-LOOPSC,AFW-FAN-FR-HV7B,AFW-TDP-FR-SDP,PPR-MOV-FC-536 15 2.633E-8 1.59 IE-LOOPSC,AFW-FAN-FR-HV7B,AFW-TDP-FR-SDP,PPR-MOV-FC-535 16 2.218E-8 1.34 IE-LOOPSC,AFW-MDP-TM-A,AFW-TDP-FR-SDP,PPR-MOV-FC-535 17 2.218E-8 1.34 IE-LOOPSC,AFW-MDP-TM-A,AFW-TDP-FR-SDP,PPR-MOV-FC-536 18 2.028E-8 1.22 IE-LOOPSC,AFW-FAN-FS-HV7B,AFW-TDP-TM-SDP,PPR-MOV-FC-536 19 2.028E-8 1.22 IE-LOOPSC,AFW-FAN-FS-HV7B,AFW-TDP-TM-SDP,PPR-MOV-FC-535 20 1.678E-8 1.01 IE-LOOPSC,AFW-MDP-FR-A,AFW-XHE-XM-CNTRL,DCP-BAT-LP-BATB1HR,DCP-XHE-XM-BC1 21 1.664E-8 1 IE-LOOPSC,AFW-FAN-FS-HV7B,AFW-TDP-FR-SDP,PPR-MOV-FC-536 22 1.664E-8 1 IE-LOOPSC,AFW-FAN-FS-HV7B,AFW-TDP-FR-SDP,PPR-MOV-FC-535 Cutset Report - LOOPPC 16-46 Only items contributing at least 1% to the total are displayed.

  1. PROB/FREQ TOTAL% CUTSET 9.268E-7 100 Displaying 1093 of 1093 Cutsets.

1 1.069E-7 11.53 IE-LOOPPC,AFW-XHE-XM-EPP1,EPS-DGN-CF-2ABDSFS,OEP-XHE-XL-NR01HPC 2 4.825E-8 5.21 IE-LOOPPC,AFW-TDP-FS-SDP,EPS-DGN-TM-2A,OEP-XHE-XL-NR01HPC 3 4.624E-8 4.99 IE-LOOPPC,AFW-TDP-FS-SDP,EPS-DGN-CF-2ABFS,OEP-XHE-XL-NR01HPC A-5

LER 261/10-001

  1. PROB/FREQ TOTAL% CUTSET 4 3.303E-8 3.56 IE-LOOPPC,AFW-TDP-TM-SDP,EPS-DGN-CF-2ABFS,OEP-XHE-XL-NR01HPC 5 2.827E-8 3.05 IE-LOOPPC,AFW-TDP-FR-SDP,EPS-DGN-TM-2A,OEP-XHE-XL-NR01HPC 6 2.709E-8 2.92 IE-LOOPPC,AFW-TDP-FR-SDP,EPS-DGN-CF-2ABFS,OEP-XHE-XL-NR01HPC 7 2.138E-8 2.31 IE-LOOPPC,EPS-DGN-CF-2ABDSFS,FWS-EDP-TM-DDP,OEP-XHE-XL-NR01HPC 8 2.029E-8 2.19 IE-LOOPPC,AFW-XHE-XM-EPP1,EPS-DGN-TM-2A,EPS-MDP-FR-FUELDS,OEP-XHE-XL-NR01HPC 9 2.010E-8 2.17 IE-LOOPPC,AFW-TDP-FS-SDP,EPS-DGN-FS-2A,OEP-XHE-XL-NR01HPC 10 1.945E-8 2.1 IE-LOOPPC,AFW-XHE-XM-EPP1,EPS-DGN-CF-2ABFS,EPS-MDP-FR-FUELDS,OEP-XHE-XL-NR01HPC 11 1.496E-8 1.61 IE-LOOPPC,AFW-TDP-FS-SDP,EPS-DGN-CF-2ABDSFS,OEP-XHE-XL-NR01HPC 12 1.436E-8 1.55 IE-LOOPPC,AFW-TDP-TM-SDP,EPS-DGN-FS-2A,OEP-XHE-XL-NR01HPC 13 1.379E-8 1.49 IE-LOOPPC,AFW-XHE-XM-EPP1,EPS-DGN-TM-2A,EPS-XHE-XM-DGDS,OEP-XHE-XL-NR01HPC 14 1.321E-8 1.43 IE-LOOPPC,AFW-XHE-XM-EPP1,EPS-DGN-CF-2ABFS,EPS-XHE-XM-DGDS,OEP-XHE-XL-NR01HPC 15 1.218E-8 1.31 IE-LOOPPC,AFW-TDP-FS-SDP,EPS-DGN-FR-2A,OEP-XHE-XL-NR01HPC,OEP-XHE-XX-NR01HPC1 16 1.206E-8 1.3 IE-LOOPPC,AFW-TDP-FS-SDP,EPS-FAN-FS-HVE18,OEP-XHE-XL-NR01HPC 17 1.206E-8 1.3 IE-LOOPPC,AFW-TDP-FS-SDP,EPS-FAN-FS-HVS6,OEP-XHE-XL-NR01HPC 18 1.206E-8 1.3 IE-LOOPPC,AFW-TDP-FS-SDP,EPS-SEQ-FO-DG2A,OEP-XHE-XL-NR01HPC 19 1.178E-8 1.27 IE-LOOPPC,AFW-TDP-FR-SDP,EPS-DGN-FS-2A,OEP-XHE-XL-NR01HPC 20 1.069E-8 1.15 IE-LOOPPC,AFW-TDP-TM-SDP,EPS-DGN-CF-2ABDSFS,OEP-XHE-XL-NR01HPC 21 1.005E-8 1.08 IE-LOOPPC,ACP-CRB-CC-52-18B,AFW-TDP-FS-SDP,OEP-XHE-XL-NR01HPC Cutset Report - LOOPWR 15 Only items contributing at least 1% to the total are displayed.
  1. PROB/FREQ TOTAL% CUTSET 7.656E-7 100 Displaying 1078 of 1078 Cutsets.

1 6.881E-8 8.99 IE-LOOPWR,AFW-FAN-FR-HV7B,AFW-XHE-XM-CNTRL,DCP-BAT-LP-BATB1HR,DCP-XHE-XM-BC1 2 5.796E-8 7.57 IE-LOOPWR,AFW-MDP-TM-A,AFW-XHE-XM-CNTRL,DCP-BAT-LP-BATB1HR,DCP-XHE-XM-BC1 3 4.347E-8 5.68 IE-LOOPWR,AFW-FAN-FS-HV7B,AFW-XHE-XM-CNTRL,DCP-BAT-LP-BATB1HR,DCP-XHE-XM-BC1 4 2.174E-8 2.84 IE-LOOPWR,AFW-MDP-FS-A,AFW-XHE-XM-CNTRL,DCP-BAT-LP-BATB1HR,DCP-XHE-XM-BC1 5 2.087E-8 2.73 IE-LOOPWR,AFW-FAN-FR-HV7B,AFW-TDP-FS-SDP,PPR-MOV-FC-536 6 2.087E-8 2.73 IE-LOOPWR,AFW-FAN-FR-HV7B,AFW-TDP-FS-SDP,PPR-MOV-FC-535 7 1.758E-8 2.3 IE-LOOPWR,AFW-MDP-TM-A,AFW-TDP-FS-SDP,PPR-MOV-FC-535 8 1.758E-8 2.3 IE-LOOPWR,AFW-MDP-TM-A,AFW-TDP-FS-SDP,PPR-MOV-FC-536 9 1.739E-8 2.27 IE-LOOPWR,AFW-FCV-CC-1424,AFW-XHE-XM-CNTRL,DCP-BAT-LP-BATB1HR,DCP-XHE-XM-BC1 10 1.491E-8 1.95 IE-LOOPWR,AFW-FAN-FR-HV7B,AFW-TDP-TM-SDP,PPR-MOV-FC-536 A-6

LER 261/10-001

  1. PROB/FREQ TOTAL% CUTSET 11 1.491E-8 1.95 IE-LOOPWR,AFW-FAN-FR-HV7B,AFW-TDP-TM-SDP,PPR-MOV-FC-535 12 1.319E-8 1.72 IE-LOOPWR,AFW-FAN-FS-HV7B,AFW-TDP-FS-SDP,PPR-MOV-FC-536 13 1.319E-8 1.72 IE-LOOPWR,AFW-FAN-FS-HV7B,AFW-TDP-FS-SDP,PPR-MOV-FC-535 14 1.223E-8 1.6 IE-LOOPWR,AFW-FAN-FR-HV7B,AFW-TDP-FR-SDP,PPR-MOV-FC-536 15 1.223E-8 1.6 IE-LOOPWR,AFW-FAN-FR-HV7B,AFW-TDP-FR-SDP,PPR-MOV-FC-535 16 1.030E-8 1.35 IE-LOOPWR,AFW-MDP-TM-A,AFW-TDP-FR-SDP,PPR-MOV-FC-535 17 1.030E-8 1.35 IE-LOOPWR,AFW-MDP-TM-A,AFW-TDP-FR-SDP,PPR-MOV-FC-536 18 9.418E-9 1.23 IE-LOOPWR,AFW-FAN-FS-HV7B,AFW-TDP-TM-SDP,PPR-MOV-FC-536 19 9.418E-9 1.23 IE-LOOPWR,AFW-FAN-FS-HV7B,AFW-TDP-TM-SDP,PPR-MOV-FC-535 20 7.794E-9 1.02 IE-LOOPWR,AFW-MDP-FR-A,AFW-XHE-XM-CNTRL,DCP-BAT-LP-BATB1HR,DCP-XHE-XM-BC1 21 7.726E-9 1.01 IE-LOOPWR,AFW-FAN-FS-HV7B,AFW-TDP-FR-SDP,PPR-MOV-FC-536 22 7.726E-9 1.01 IE-LOOPWR,AFW-FAN-FS-HV7B,AFW-TDP-FR-SDP,PPR-MOV-FC-535 Referenced Events Event Description Probability ACP-CRB-CC-52-18B CIRCUIT BREAKER 52/18B FAILS TO OPEN 2.500E-3 AFW-FAN-FR-HV7B AFW MDP-2A HVAC HVH-7B FAILS TO RUN 4.749E-3 AFW-FAN-FS-HV7B CCF OF AFW HVAC HVH-7A&B TO START 3.000E-3 AFW-FCV-CC-1424 FAILURE OF AFW MDP-A DISCHARGE PATH HYDRAULIC VALVE 1.200E-3 1424 AFW-MDP-FR-A AFW MOTOR-DRIVEN PUMP A FAILS TO RUN 5.379E-4 AFW-MDP-FS-A AFW MOTOR-DRIVEN PUMP A FAILS TO START 1.500E-3 AFW-MDP-TM-A AFW MOTOR-DRIVEN A UNAVAILABLE DUE TO T & M 4.000E-3 AFW-TDP-FR-SDP AFW TURBINE DRIVEN PUMP FAILS TO RUN 4.102E-3 AFW-TDP-FS-SDP AFW TURBINE DRIVEN PUMP FAILS TO START 7.000E-3 AFW-TDP-TM-SDP AFW TDP UNAVAILABLE DUE TO TEST AND MAINTENANCE 5.000E-3 AFW-XHE-XM-CNTRL OPERATOR FAILS TO CONTROL AFW TDP 3.000E-1 AFW-XHE-XM-EPP1 OPERATOR FAILS TO ALIGN SDP DURING SBO 5.000E-2 DCP-BAT-LP-BATB1HR DIVISION 2B BATTERY 1-B FAILS IN 1 HR 1.000E+0 DCP-XHE-XM-BC1 OPERATOR FAILS TO CLOSE BATT CHARGER BKRS ON E1/E2 1.000E-2 UV-LOOP EPS-DGN-CF-2ABDSFS CCF OF DIESEL GENERATORS 2A, 2B & DS TO START 3.722E-3 EPS-DGN-CF-2ABFS COMMON CAUSE FAILURE OF DIESEL GENERATORS 2A & 2B TO 1.150E-2 START EPS-DGN-FR-2A DIESEL GENERATOR 2A FAILS TO RUN 2.118E-2 EPS-DGN-FS-2A DIESEL GENERATOR 2A FAILS TO START 5.000E-3 EPS-DGN-TM-2A DIESEL GENERATOR 2A UNAVAILABLE DUE TO TEST AND 1.200E-2 MAINTENANCE EPS-FAN-FS-HVE18 DG-A EXHAUST FAN HVE-18 FAILS TO START 3.000E-3 EPS-FAN-FS-HVS6 DG-A SUPPLY FAN HVS-6 FAILS TO START 3.000E-3 EPS-MDP-FR-FUELDS DIESEL GENERATOR B FUEL TRANSFER PUMP DS FAILS TO 5.887E-2 RUN EPS-SEQ-FO-DG2A LOAD SEQUENCER FOR DG-2A FAILS TO OPERATE 3.000E-3 EPS-XHE-XM-DGDS OPERATOR FAILS TO START AND ALIGN DG-DS TO BUS DS 4.000E-2 FWS-EDP-TM-DDP FWP DDP UNAVAILABLE DUE TO T & M 1.000E-2 IE-LOOPGR LOSS OF OFFSITE POWER INITIATOR (GRID-RELATED) 1.860E-2 IE-LOOPPC LOSS OF OFFSITE POWER INITIATOR (PLANT-CENTERED) 2.070E-3 A-7

LER 261/10-001 Event Description Probability IE-LOOPSC LOSS OF OFFSITE POWER INITIATOR (SWITCHYARD-RELATE D) 1.040E-2 IE-LOOPWR LOSS OF OFFSITE POWER INITIATOR (WEATHER-RELATED) 4.830E-3 OEP-XHE-XL-NR01HGR OPERATOR FAILS TO RECOVER OFFSITE POWER IN 1 HOUR 6.110E-1 (GRID-RELATED)

OEP-XHE-XL-NR01HPC OPERATOR FAILS TO RECOVER OFFSITE POWER IN 1 HOUR 2.775E-1 (PLANT-CENTERED)

OEP-XHE-XL-NR01HSC OPERATOR FAILS TO RECOVER OFFSITE POWER IN 1 HOUR 3.779E-1 (SWITCHYARD)

OEP-XHE-XL-NR01HWR OPERATOR FAILS TO RECOVER OFFSITE POWER IN 1 HOUR 6.555E-1 (WEATHER-RELATED)

OEP-XHE-XX-NR01HGR1 CONVOLUTION FACTOR FOR 1FTR-OPR (1HR-GR AVAIL) 1.750E-1 OEP-XHE-XX-NR01HPC1 CONVOLUTION FACTOR FOR 1FTR-OPR (1HR-PC AVAIL) 1.430E-1 OEP-XHE-XX-NR01HSC1 CONVOLUTION FACTOR FOR 1FTR-OPR (1HR-SC AVAIL) 1.580E-1 OEP-XHE-XX-NR01HWR1 CONVOLUTION FACTOR FOR 1FTR-OPR (1HR-WR AVAIL) 4.080E-1 OEP-XHE-XX-NR01HWR2 CONVOLUTION FACTOR FOR 2FTR-OPR (1HR-WR AVAIL) 2.800E-1 PPR-MOV-FC-535 BLOCK VALVE RC-535 FOR PORV PCV-456 CLOSED DURING 1.300E-1 POWER (PSA)

PPR-MOV-FC-536 BLOCK VALVE RC-536 FOR PORV PCV-455C CLOSED DURING 1.300E-1 POWER (PSA)

A-8

LER 261/10-001 Calculation 2- EDG A in TM and EDG B Unavailable (Failed to Start) for 7 hours8.101852e-5 days <br />0.00194 hours <br />1.157407e-5 weeks <br />2.6635e-6 months <br /> Summary of Conditional Event Changes Event Description Cond. Nominal Value Value EPS-DGN-FR-2A DIESEL GENERATOR 2A FAILS TO RUN 1.000E+0 2.118E-2 EPS-DGN-FR-2B DIESEL GENERATOR 2B FAILS TO RUN 1.000E+0 2.118E-2 EPS-DGN-FS-2A DIESEL GENERATOR 2A FAILS TO START 1.000E+0 5.000E-3 EPS-DGN-FS-2B DIESEL GENERATOR 2B FAILS TO START True 5.000E-3 EPS-DGN-TM-2A DIESEL GENERATOR 2A UNAVAILABLE DUE TO True 1.200E-2 TEST AND MAINTENANCE EPS-DGN-TM-2B DIESEL GENERATOR 2B UNAVAILABLE DUE TO True 1.200E-2 TEST AND MAINTENANCE EPS-XHE-XL-NR01H OPERATOR FAILS TO RECOVER EMERGENCY True 7.857E-1 DIESEL IN 1 HOUR EPS-XHE-XL-NR04H OPERATOR FAILS TO RECOVER EMERGENCY 5.000E-3 5.568E-1 DIESEL IN 4 HOURS EPS-DGN-CF-2ABFR COMMON CAUSE FAILURE OF DIESEL 1.000E+0 3.282E-4 GENERATORS 2A & 2B TO RUN EPS-DGN-CF-2ABFS COMMON CAUSE FAILURE OF DIESEL 1.000E+0 5.750E-5 GENERATORS 2A & 2B TO START EPS-DGN-CF-2ABDSFR CCF OF DIESEL GENERATORS 2A, 2B & DS TO 2.118E-2 1.214E-4 RUN EPS-DGN-CF-2ABDSFS CCF OF DIESEL GENERATORS 2A, 2B & DS TO 3.746E-3 1.861E-5 START Dominant Sequence Results Only items contributing at least 1.0% to the total CCDP are displayed.

EVENT TREE SEQUENCE CCDP CDP CDP DESCRIPTION LOOPGR 16-46 2.638E-7 3.540E-10 2.634E-7 /RPS, EPS, AFW-B, OPR-01H, DGR-01H LOOPSC 16-46 9.126E-8 1.143E-10 9.114E-8 /RPS, EPS, AFW-B, OPR-01H, DGR-01H LOOPWR 16-46 7.700E-8 1.265E-10 7.687E-8 /RPS, EPS, AFW-B, OPR-01H, DGR-01H LOOPPC 16-46 1.331E-8 1.346E-11 1.330E-8 /RPS, EPS, AFW-B, OPR-01H, DGR-01H LOOPGR 16-43 6.016E-9 7.475E-12 6.009E-9 /RPS, EPS, /AFW-B, PORV-B, OPR-01H, DGR-01H Total 4.895E-7 1.123E-8 4.783E-7 Referenced Fault Trees Fault Tree Description AFW-B AUXILIARY FEEDWATER DGR-01H OPERATOR FAILS TO RECOVER EMERGENCY DIESEL IN 1 HOUR EPS EMERGENCY POWER OPR-01H OPERATOR FAILS TO RECOVER OFFSITE POWER IN 1 HOUR PORV-B ROBINSON UNIT 2 PWR B PORVS/SRVS CHALLENGED DURING SBO Cutset Report - LOOPGR 16-46 Only items contributing at least 1% to the total are displayed.

  1. PROB/FREQ TOTAL% CUTSET 3.301E-4 100 Displaying 383 of 383 Cutsets.

A-9

LER 261/10-001

  1. PROB/FREQ TOTAL% CUTSET 1 7.955E-5 24.1 IE-LOOPGR,AFW-TDP-FS-SDP,OEP-XHE-XL-NR01HGR 2 5.682E-5 17.21 IE-LOOPGR,AFW-TDP-TM-SDP,OEP-XHE-XL-NR01HGR 3 4.661E-5 14.12 IE-LOOPGR,AFW-TDP-FR-SDP,OEP-XHE-XL-NR01HGR 4 3.345E-5 10.13 IE-LOOPGR,AFW-XHE-XM-EPP1,EPS-MDP-FR-FUELDS,OEP-XHE-XL-NR01HGR 5 2.273E-5 6.89 IE-LOOPGR,AFW-XHE-XM-EPP1,EPS-XHE-XM-DGDS,OEP-XHE-XL-NR01HGR 6 1.364E-5 4.13 IE-LOOPGR,AFW-FCV-CC-6416,OEP-XHE-XL-NR01HGR 7 1.136E-5 3.44 IE-LOOPGR,ACP-XHE-XM-MCC5,AFW-XHE-XM-EPP1,OEP-XHE-XL-NR01HGR 8 6.819E-6 2.07 IE-LOOPGR,AFW-XHE-XM-EPP1,EPS-DGN-TM-DS,OEP-XHE-XL-NR01HGR 9 6.691E-6 2.03 IE-LOOPGR,EPS-MDP-FR-FUELDS,FWS-EDP-TM-DDP,OEP-XHE-XL-NR01HGR 10 4.546E-6 1.38 IE-LOOPGR,EPS-XHE-XM-DGDS,FWS-EDP-TM-DDP,OEP-XHE-XL-NR01HGR Cutset Report - LOOPSC 16-46 Only items contributing at least 1% to the total are displayed.
  1. PROB/FREQ TOTAL% CUTSET 1.142E-4 100 Displaying 329 of 329 Cutsets.

1 2.751E-5 24.1 IE-LOOPSC,AFW-TDP-FS-SDP,OEP-XHE-XL-NR01HSC 2 1.965E-5 17.21 IE-LOOPSC,AFW-TDP-TM-SDP,OEP-XHE-XL-NR01HSC 3 1.612E-5 14.12 IE-LOOPSC,AFW-TDP-FR-SDP,OEP-XHE-XL-NR01HSC 4 1.157E-5 10.13 IE-LOOPSC,AFW-XHE-XM-EPP1,EPS-MDP-FR-FUELDS,OEP-XHE-XL-NR01HSC 5 7.861E-6 6.88 IE-LOOPSC,AFW-XHE-XM-EPP1,EPS-XHE-XM-DGDS,OEP-XHE-XL-NR01HSC 6 4.717E-6 4.13 IE-LOOPSC,AFW-FCV-CC-6416,OEP-XHE-XL-NR01HSC 7 3.931E-6 3.44 IE-LOOPSC,ACP-XHE-XM-MCC5,AFW-XHE-XM-EPP1,OEP-XHE-XL-NR01HSC 8 2.358E-6 2.07 IE-LOOPSC,AFW-XHE-XM-EPP1,EPS-DGN-TM-DS,OEP-XHE-XL-NR01HSC 9 2.314E-6 2.03 IE-LOOPSC,EPS-MDP-FR-FUELDS,FWS-EDP-TM-DDP,OEP-XHE-XL-NR01HSC 10 1.572E-6 1.38 IE-LOOPSC,EPS-XHE-XM-DGDS,FWS-EDP-TM-DDP,OEP-XHE-XL-NR01HSC Cutset Report - LOOPWR 16-46 Only items contributing at least 1% to the total are displayed.

  1. PROB/FREQ TOTAL% CUTSET 9.636E-5 100 Displaying 324 of 324 Cutsets.

1 2.216E-5 23 IE-LOOPWR,AFW-TDP-FS-SDP,OEP-XHE-XL-NR01HWR 2 1.583E-5 16.43 IE-LOOPWR,AFW-TDP-TM-SDP,OEP-XHE-XL-NR01HWR 3 1.299E-5 13.48 IE-LOOPWR,AFW-TDP-FR-SDP,OEP-XHE-XL-NR01HWR 4 9.320E-6 9.67 IE-LOOPWR,AFW-XHE-XM-EPP1,EPS-MDP-FR-FUELDS,OEP-XHE-XL-NR01HWR 5 6.332E-6 6.57 IE-LOOPWR,AFW-XHE-XM-EPP1,EPS-XHE-XM-DGDS,OEP-XHE-XL-NR01HWR 6 3.799E-6 3.94 IE-LOOPWR,AFW-FCV-CC-6416,OEP-XHE-XL-NR01HWR 7 3.166E-6 3.29 IE-LOOPWR,ACP-XHE-XM-MCC5,AFW-XHE-XM-EPP1,OEP-XHE-XL-NR01HWR A-10

LER 261/10-001

  1. PROB/FREQ TOTAL% CUTSET 8 1.900E-6 1.97 IE-LOOPWR,AFW-XHE-XM-EPP1,EPS-DGN-TM-DS,OEP-XHE-XL-NR01HWR 9 1.864E-6 1.93 IE-LOOPWR,EPS-MDP-FR-FUELDS,FWS-EDP-TM-DDP,OEP-XHE-XL-NR01HWR 10 1.368E-6 1.42 IE-LOOPWR,AFW-XHE-XM-EPP1,EPS-DGN-CF-2ABDSFR,OEP-XHE-XL-NR01HWR,OEP-XHE-XX-NR01HWR0 11 1.368E-6 1.42 IE-LOOPWR,AFW-XHE-XM-EPP1,EPS-DGN-CF-2ABFR,EPS-DGN-FR-DS,OEP-XHE-XL-NR01HWR,OEP-XHE-XX-NR01HWR0 12 1.368E-6 1.42 IE-LOOPWR,AFW-XHE-XM-EPP1,EPS-DGN-FR-DS,OEP-XHE-XL-NR01HWR,OEP-XHE-XX-NR01HWR1 13 1.266E-6 1.31 IE-LOOPWR,EPS-XHE-XM-DGDS,FWS-EDP-TM-DDP,OEP-XHE-XL-NR01HWR Cutset Report - LOOPPC 16-46 Only items contributing at least 1% to the total are displayed.
  1. PROB/FREQ TOTAL% CUTSET 1.666E-5 100 Displaying 250 of 250 Cutsets.

1 4.021E-6 24.13 IE-LOOPPC,AFW-TDP-FS-SDP,OEP-XHE-XL-NR01HPC 2 2.872E-6 17.24 IE-LOOPPC,AFW-TDP-TM-SDP,OEP-XHE-XL-NR01HPC 3 2.356E-6 14.14 IE-LOOPPC,AFW-TDP-FR-SDP,OEP-XHE-XL-NR01HPC 4 1.691E-6 10.15 IE-LOOPPC,AFW-XHE-XM-EPP1,EPS-MDP-FR-FUELDS,OEP-XHE-XL-NR01HPC 5 1.149E-6 6.89 IE-LOOPPC,AFW-XHE-XM-EPP1,EPS-XHE-XM-DGDS,OEP-XHE-XL-NR01HPC 6 6.893E-7 4.14 IE-LOOPPC,AFW-FCV-CC-6416,OEP-XHE-XL-NR01HPC 7 5.744E-7 3.45 IE-LOOPPC,ACP-XHE-XM-MCC5,AFW-XHE-XM-EPP1,OEP-XHE-XL-NR01HPC 8 3.447E-7 2.07 IE-LOOPPC,AFW-XHE-XM-EPP1,EPS-DGN-TM-DS,OEP-XHE-XL-NR01HPC 9 3.382E-7 2.03 IE-LOOPPC,EPS-MDP-FR-FUELDS,FWS-EDP-TM-DDP,OEP-XHE-XL-NR01HPC 10 2.298E-7 1.38 IE-LOOPPC,EPS-XHE-XM-DGDS,FWS-EDP-TM-DDP,OEP-XHE-XL-NR01HPC Cutset Report - LOOPGR 16-43 Only items contributing at least 1% to the total are displayed.

  1. PROB/FREQ TOTAL% CUTSET 7.529E-6 100 Displaying 5 of 5 Cutsets.

1 3.658E-6 48.59 IE-LOOPGR,OEP-XHE-XL-NR01HGR,/PPR-MOV-FC-536,PPR-SRV-CO-SBO,PPR-SRV-OO-455C 2 3.658E-6 48.59 IE-LOOPGR,OEP-XHE-XL-NR01HGR,/PPR-MOV-FC-535,PPR-SRV-CO-SBO,PPR-SRV-OO-456 Referenced Events Event Description Probability ACP-XHE-XM-MCC5 OPERATOR FAILS TO CONNECT BUS DS TO MCC-5 2.000E-2 AFW-FCV-CC-6416 FAILURE OF AFW SDP DISCHARGE PATH HYDRAULIC VALVE 1.200E-3 6416 AFW-TDP-FR-SDP AFW TURBINE DRIVEN PUMP FAILS TO RUN 4.102E-3 AFW-TDP-FS-SDP AFW TURBINE DRIVEN PUMP FAILS TO START 7.000E-3 AFW-TDP-TM-SDP AFW TDP UNAVAILABLE DUE TO TEST AND MAINTENANCE 5.000E-3 AFW-XHE-XM-EPP1 OPERATOR FAILS TO ALIGN SDP DURING SBO 5.000E-2 A-11

LER 261/10-001 Event Description Probability EPS-DGN-CF-2ABDSFR CCF OF DIESEL GENERATORS 2A, 2B & DS TO RUN 2.118E-2 EPS-DGN-CF-2ABFR COMMON CAUSE FAILURE OF DIESEL GENERATORS 2A & 2B TO 1.000E+0 RUN EPS-DGN-FR-DS DEDICATED DIESEL GENERATOR FAILS TO RUN 2.118E-2 EPS-DGN-TM-DS DEDICATED DIESEL GENERATOR UNAVAILABLE DUE TO TEST 1.200E-2 AND MAINTENANCE EPS-MDP-FR-FUELDS DIESEL GENERATOR B FUEL TRANSFER PUMP DS FAILS TO 5.887E-2 RUN EPS-XHE-XM-DGDS OPERATOR FAILS TO START AND ALIGN DG-DS TO BUS DS 4.000E-2 FWS-EDP-TM-DDP FWP DDP UNAVAILABLE DUE TO T & M 1.000E-2 IE-LOOPGR LOSS OF OFFSITE POWER INITIATOR (GRID-RELATED) 1.860E-2 IE-LOOPPC LOSS OF OFFSITE POWER INITIATOR (PLANT-CENTERED) 2.070E-3 IE-LOOPSC LOSS OF OFFSITE POWER INITIATOR (SWITCHYARD-RELATE D) 1.040E-2 IE-LOOPWR LOSS OF OFFSITE POWER INITIATOR (WEATHER-RELATED) 4.830E-3 OEP-XHE-XL-NR01HGR OPERATOR FAILS TO RECOVER OFFSITE POWER IN 1 HOUR 6.110E-1 (GRID-RELATED)

OEP-XHE-XL-NR01HPC OPERATOR FAILS TO RECOVER OFFSITE POWER IN 1 HOUR 2.775E-1 (PLANT-CENTERED)

OEP-XHE-XL-NR01HSC OPERATOR FAILS TO RECOVER OFFSITE POWER IN 1 HOUR 3.779E-1 (SWITCHYARD)

OEP-XHE-XL-NR01HWR OPERATOR FAILS TO RECOVER OFFSITE POWER IN 1 HOUR 6.555E-1 (WEATHER-RELATED)

OEP-XHE-XX-NR01HWR0 CONVOLUTION FACTOR FOR CCF-OPR (1HR-WR Avail) 4.080E-1 OEP-XHE-XX-NR01HWR1 CONVOLUTION FACTOR FOR 1FTR-OPR (1HR-WR AVAIL) 4.080E-1 PPR-SRV-CO-SBO PORVs/SRVs OPEN DURING SBO 3.700E-1 PPR-SRV-OO-455C PORV PCV-455C FAILS TO RECLOSE AFTER OPENING 1.000E-3 PPR-SRV-OO-456 PORV PCV-456 FAILS TO RECLOSE AFTER OPENING 1.000E-3 A-12

LER 261/10-001 Appendix B: Key Event Trees LOSS OF OFFSITE POWER REACTOR TRIP EMERGENCY POWER AUXILIARY FEEDWATER PORV/SRVs ARE CLOSED LOSS OF SEAL COOLING HIGH PRESSURE INJECTION FEED AND BLEED OFFSITE POWER RECOVERY OFFSITE POWER RECOVERY COOLDOWN (PRIMARY & RESIDUAL HEAT REMOVAL HPR PRESSURE RECIRC # End State AVAILABLE IN 2 HRS IN 6 HRS SECONDARY) (Phase - CD)

IE-LOOP RPS EPS FTF-SBO AFW FTF-LOOP-RECOVERY PORV LOSC FTF-LOSC HPI FAB OPR-02H OPR-06H SSC RHR HPR 1 OK LOSC-L 2 LOOP-1 3 OK 4 OK 5 CD 6 OK PORV-L 7 CD 8 OK HPR-L 9 CD HPI-L 10 CD 11 OK 12 CD AFW-L 13 OK HPR-L 14 CD FAB-L 15 CD 16 SBO 17 ATWS 18 CD Figure B-1. H. B. Robinson LOOP event tree.

B-1

LER 261/10-001 EMERGENCY POWER AUXILIARY FEEDWATER PORV/SRVs ARE CLOSED LOSS OF SEAL COOLING RAPID SECONDARY RCP SEAL STAGE 1 RCP SEAL STAGE 1 RCP SEAL STAGE 2 RCP SEAL STAGE 2 OFFSITE POWER RECOVERY DIESEL GENERATOR # End State DEPRESS INTEGRITY INTEGRITY (O-RING INTEGRITY INTEGRITY (O-RING (IN 4 HR) RECOVERY (IN 4 HR) (Phase - CD)

(BINDING/POPPING) EXTRUSION) (BINDING/POPPING) EXTRUSION)

EPS FTF-SBO AFW-B FTF-SBO PORV LOSC-B FTF-SBO RSD-B FTF-SBO BP1 O1 BP2 O2 OPR-04H DGR-04H 1 OK 2 OK 21 gpm/rcp 3 OK 4 SBO-4 5 SBO-1 182 gpm/rcp 6 OK 7 CD 8 SBO-1 76 gpm/rcp 9 OK 10 SBO-4 11 SBO-1 480 gpm/rcp 12 OK OPR-02H DGR-02H 13 CD 14 SBO-2 21 gpm/rcp 15 OK 16 SBO-4 17 SBO-2 172 gpm/rcp 18 OK OPR-03H DGR-03H 19 CD 20 SBO-2 182 gpm/rcp 21 OK OPR-03H DGR-03H 22 CD 23 SBO-2 61 gpm/rcp 24 OK 25 SBO-4 26 SBO-2 300 gpm/rcp 27 OK OPR-02H DGR-02H 28 CD 29 SBO-2 300 gpm/rcp 30 OK OPR-02H DGR-02H 31 CD 32 SBO-2 76 gpm/rcp 33 OK 34 SBO-4 35 SBO-2 300 gpm/rcp 36 OK OPR-02H DGR-02H 37 CD 38 SBO-2 480 gpm/rcp 39 OK OPR-02H DGR-02H 40 CD 41 SBO-2 PORV-B 42 OK OPR-01H DGR-01H 43 CD 44 SBO-3 45 OK OPR-01H DGR-01H 46 CD Figure B-2. H. B. Robinson station blackout event tree.

B-2

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