ML12180A062

Final Browns Ferry Nuclear Plant Units 1, 2, and 3 Accident Sequence Precursor (ASP) Analysis

ML12180A062
Person / Time
Site:	Browns Ferry
Issue date:	07/30/2012
From:	NRC/RES/DRA/PRB
To:
Lai S, RES/DRA 301-251-7607
Shared Package
ML12180A056	List: ML12180A059 ML12180A062
References
LER 11-001-00, LER 11-002-01, LER 11-003-01, LER 11-005-00, LER 11-006-01 IR-11-003, IR-11-004
Download: ML12180A062 (30)

Text

Enclosure 1

Final Precursor Analysis Accident Sequence Precursor Program - Office of Nuclear Regulatory Research Browns Ferry Nuclear Plant, Units 1, 2, & 3 Loss of Normal Offsite Power Due to Switchyard Damage Caused by a Tornado Event Date: 04/27/2011 LERs: 259/11-001, -002-01, -003-01,

-005, and 259/12-006-01 IRs:

50-259/11-03 and -04 Unit 1 CCDP =

Unit 2 CCDP =

Unit 3 CCDP =

1x10-5 1x10-5 1x10-5 EVENT

SUMMARY

At-Power Event Description. On April 27, 2011, at 16:36, severe weather in the Tennessee Valley Service Area caused grid instability and loss of all 500kV offsite power sources that resulted in automatic scrams of all three units. All three units were in Mode 1 at the time of the event. All scram systems were actuated, and all required systems started and functioned successfully with the exception of an indeterminate position indication for the Unit 3 inboard Main Steam Isolation Valve (MSIV) B. All onsite safe shutdown equipment was available with the exception of the Emergency Diesel Generator (EDG) 3B, which was unavailable due to planned maintenance. All three units immediately entered Mode 3 (Hot Shutdown) with their respective 4kV shutdown boards supplied by seven out of eight of the onsite EDGs. On May 2, at approximate 20:50, the Notice of Unusual Event was terminated following restoration of qualified offsite power sources to all eight 4kV shutdown boards.

In addition to the loss of offsite power event on April 27th, two loss of shutdown cooling (SDC) events occurred on April 28th (Units 1 and 2) and May 2nd (Unit 1). Additional details of these events are provided in Appendix C and References 1-5.

Sequence of Key Events. The following table provides a sequence of key events:

Date Time Event Description April 27, 2011 14:01 Operations personnel were notified that BFN was under a Tornado Warning.

The actions of Procedure 0-A01-107, Severe Weather, were addressed.

16:36 Loss of all 500kV offsite power sources. All Units automatically scram and 7 of 8 EDGs started and loaded to their respective 4kV shutdown boards. EDG 3B was unavailable due to planned maintenance. The 161kV offsite power (Athens) source remained available, but was not used until May 2nd.

17:01 BFN declared a Notification of Unusual Event, due to the loss of normal and alternate supply voltage to all unit-specific 4-kV shutdown boards.

April 28, 2011 02:43 Unit 3 entered Mode 4 (Cold Shutdown).

05:45 Unit 2 entered Mode 4 (Cold Shutdown).

13:37 Unit 1 entered Mode 4 (Cold Shutdown).

23:30 EDG C governor hydraulic oil piping leak observed by operations personnel.

Maintenance personnel notified to prepare to add oil. Operations personnel prepared to switch from RHR pumps.

LER 259/11-001 2

Date Time Event Description 23:38 Operations personnel performed emergency shutdown of EDG C due to hydraulic oil piping leak on governor. SDC lost to Unit 1 and Unit 2. Unit 1 SDC was lost due to the loss of power to 4kV Shutdown Board C (which was being powered by the EDG C) de-energized and resulted in a loss of power to the RPS Train B causing a PCIS actuation. Unit 2 SDC was lost because the running RHR Pump 2B lost power.

23:42 Unit 2 SDC was restored by starting RHR Pump 2D.

April 29, 2011 00:25 Unit 1 SDC was restored by resetting PCIS signal and establishing SDC.

April 30, 2011 10:47 EDG C was declared operable after replacement of failed hydraulic oil piping fitting and successful post maintenance testing.

May 2, 2011 06:26 The output breaker of the EDG A tripped and power was lost to 4kV Shutdown Board A, causing a loss of Unit 1 SDC. Received half-scram (due to loss of RPS A) and PCIS Group 2, 3, 6, and 8 signals.

06:43 Power was restored to 4kV Shutdown Board A from the 161kV offsite power source.

06:52 Half-scram and PCIS signals were reset.

07:23 Unit 1 SDC restored.

20:10 All shutdown boards were powered from two qualified 161kV offsite power sources, and all EDGs were secured and in standby readiness.

Additional Event Information. The following event details are provided as additional information about the event. This additional information was not factored in the modeling of this analysis due to the negligible risk impact.

On April 27, 2011, at 2120 hours0.0245 days <br />0.589 hours <br />0.00351 weeks <br />8.0666e-4 months <br />, the Unit 1 reactor water level system generated a low reactor water level scram due to a distracted operations crew allowing reactor water level to lower below +2 inches (Level 3). At the time of this event, the reactor core isolation cooling (RCIC) and control rod drive (CRD) pumps were injecting to the vessel and the reactor level band specified was +2 to +51 inches. A valid containment isolation signal was received and Groups 2, 3, 6, and 8 isolated as expected. Water level was immediately restored to the specified band using RCIC and the CRD System. See Reference 6 for further details.

On April 19, 2012, the Unit 1, high-pressure coolant injection (HPCI) system was declared inoperable for the performance of surveillance procedure when technicians attempted to trip the HPCI turbine using the manual trip pushbutton, the HPCI turbine failed to trip. The manual trip pushbutton was pressed four times with no results. The turbine stop valve was disassembled and it was determined that the valve disc was bound to valve cover guide.

The valve disc was determined to be damaged by repeated contact with the upper lip of the valve cover guide (the valve is not designed for this contact). The cause of the contact was determined to be due to incorrect adjustment of the gaps between the actuator stem valve stem. Damage to the valve was occurring since the adjustment was made in December 2008; therefore, the valve was degraded during the LOOP event on April 27, 2011. The licensee performed an operability evaluation on the valve and determined that the valve was successfully stroked 82 times after the May 30, 2011, when the valve took 45 seconds to close during testing. Therefore, it was determined that if RCIC had failed during the LOOP and plant depressurization was not available (either through operator error or hardware

LER 259/11-001 3

failure), the turbine stop valve would have properly cycled to control reactor water level for the entire 24-hour mission time.

ANALYSIS RESULTS Conditional Core Damage Probabilities. The point estimate conditional core damage probabilities (CCDP) for this event analysis for Units 1, 2, and 3 are 1.1x10-5, 1.1x10-5, and 1.3x10-5, respectively.

The Accident Sequence Precursor Program acceptance threshold is a CCDP of 1x10-6 or the CCDP equivalent of an uncomplicated reactor trip with a non-recoverable loss of secondary plant systems (e.g., feed water and condensate), whichever is greater. These CCDP equivalents for Browns Ferry are 4x10-6 (Unit 1), 3x10-6 (Unit 2), and 9x10-7 (Unit 3).

Dominant Sequences for the At-Power Analysis. The dominant accident sequence is LOOPWR (Loss of Offsite PowerWeather-related) Sequence 28-18 for all Units 1, 2 and 3. It contributes 44% (6.4x10-6) of the Unit1 total internal events CCDP; 43% (4.6x10-6) of the Unit 2 total internal events CCDP; 36% (4.6x10-6) of the Unit 3 total internal events CCDP. Additional sequences that contribute greater than 1% of the total internal events CCDP 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 LOOPWR Sequence 28-18 are:

Weather-related LOOP occurs, Reactor scram succeeds, Emergency power fails, Closure of safety relief valves succeeds, Recirculation pump seal integrity is preserved, RCIC succeeds,1 Extended operation of emergency core cooling system fails, Manual depressurization fails, Recovery offsite power in 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> fails, and Recovery of an EDG in 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> fails.

Result Tables. Appendix A provides tables that include the following:

Modified basic events and initiating event frequencies, including base and change case probabilities/frequencies.

Dominant sequences (including CCDPs).

Sequence logic for all dominant sequences.

Fault tree definitions.

Sequence cutsets.

Definitions and probabilities for key basic events.

1 In the dominant LOOPWR Sequence 28-18, RCIC initially succeeds, but the pump is assumed to fail if the batteries deplete due to the operators failing to recover either offsite power or an EDG to a safety bus.

LER 259/11-001 4

MODELING ASSUMPTIONS Analysis Type. The individual SPAR models for Browns Ferry Unit 1 (Revision 8.22), Unit 2 (Revision 8.22), and Unit 3 (Revision 8.18) were used for this event analysis. This event was modeled as a weather-related LOOP initiating event at all three units.

The losses of SDC on April 28th (Units 1 and 2) and May 2nd (Unit 1) were determined to have relatively insignificant risk impact when compared to the CCDPs of the at-power LOOP initiating event (i.e., the first 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> of the event). Therefore, a sensitivity analysis showing the results of a Unit 1 loss of SDC (a representative case for both losses of SDC) is provided in Appendix C.

Modeling Assumptions. The following modeling assumptions were determined to be vital to this event analysis:

This analysis models the April 27, 2011 multi-unit reactor trip at Browns Ferry, Units 1, 2, and 3 as weather-related LOOP initiating events.

The 161kV offsite power source was available to supply power to the sites eight 4kV shutdown boards throughout the event.

Basic Event Probability Changes. The following initiating event frequencies and basic event probabilities were modified for the at-power analysis (i.e., the first 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> of the LOOP) for all Units 1, 2 and 3 in this event analysis:

The weather-related LOOP initiating event probability (IE-LOOPWR) was set to 1.0. All other initiating events probabilities were set to zero.

The house event, HE-LOOP-WR (Loss of Offsite Power IE Has OccurredWeather-Related), was set to TRUE for this weather related LOOP event.

The basic event OEP-VCF-LP-SITEWR (Weather-Related Site LOOP) was set to TRUE, since the LOOP affected all three units.

EDG 3B was not available during the event due to planned maintenance. Therefore, basic event EDG-DGN-TM-DG3B (EDG 3B is Unavailable Due to Test or Maintenance) was set to TRUE.

Power recovery to the sites eight 4kV shutdown boards was available from the 161kV offsite power source throughout the event. Therefore, the non-recovery probabilities for the basic events OEP-XHE-XL-NR30MWR (Operator Fail to Recover Offsite Power in 30 minutes-Weather-related), OEP-XHE-XL-NR01HWR (Operator Fail to Recover Offsite Power in 1 hourWeather-related), OEP-XHE-XL-NR04HWR (Operator Fail to Recover Offsite Power in 4 hour4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br />sWeather-related), OEP-XHE-XL-NR10HWR (Operator Fail to Recover Offsite Power in 10 hour1.157407e-4 days <br />0.00278 hours <br />1.653439e-5 weeks <br />3.805e-6 months <br />sWeather-related), and OEP-XHE-XL-NR12HWR (Operator Fail to Recover Offsite Power in 12 hour1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br />sWeather-related) were adjusted based on the SPAR-H guidance (References 7 and 8).

- Description and Event Context-Recovery of offsite power to the sites eight 4kV shutdown boards was possible almost immediately after the event occurred. Operators

LER 259/11-001 5

could restore offsite power to the 4kV Shutdown Boards A, B, C, and D for Units 1 and 2; 3EA and 3EB for Unit 3 through the Athens 161kV offsite power source.

- Operator Action Success Criteria-The restoration of electrical power from the 161kV switchyard system to the 4kV shutdown boards is performed manually by the main control room (MCR) operators.

- Cues-The availability of the offsite power is communicated to the MCR operators via the load dispatcher. The operators have voltage and load indications of the offsite power sources in the MCR.

- Procedural Guidance-Abnormal Operating Instruction (AOI)-57 provides guidance on loss of offsite power and its restoration.

- Diagnosis/Action-These human failure events (HFEs) contain sufficient diagnosis activities. The nominal action component of the human error probabilities (HEPs) is 0.001. No event information is available to warrant a change in the action performance shaping factors (PSFs) for these HEPs. The table below shows the PSFs that were adjusted; all other PSFs were determined to be Nominal (i.e., x1).

- Based on the adjusted PSFs, the following HEPs were recalculated:

Basic event OEP-XHE-XL-NR30MWR was set to 4.1x10-2.

Basic event OEP-XHE-XL-NR01HWR was set to 5.0x10-3.

Basic events OEP-XHE-XL-NR04HWR, OEP-XHE-XL-NR10HWR, and OEP-XHE-XL-NR12HWR were set to 1.4x10-3.

PSF Multiplier Notes Time Available 1 / 0.1 / 0.01 The recovery of offsite power was possible almost immediately after the LOOP occurred; therefore, a minimum of 30 minutes was available for operators to recover power to a safety bus during a postulated SBO. Since the action time required to recover power to a safety bus is minimal (<5 minutes), the minimum time for diagnosis is approximately 25 minutes.

Therefore, available time for OEP-XHE-XL-NR30MWR is assigned as Nominal (i.e., x1). Available time for OEP-XHE-XL-NR01HWR is assigned as Extra Time (i.e., x0.1; time available is 1 to 2 times nominal and > 30 minutes). Available time for OEP-XHE-XL-NR04HWR, OEP-XHE-XL-NR10HWR, and OEP-XHE-XL-NR12HWR were assigned as Expansive Time (i.e., x0.01; time available >2 times nominal and >30 minutes).

Stress 2

The PSF for diagnosis stress is assigned a value of High Stress (i.e., x2) for all offsite power recovery actions due to the postulated SBO.

Complexity 2

The PSF for diagnosis complexity is assigned a value of Moderately Complex (i.e., x2) for all offsite power recovery actions because operators would have to deal with multiple equipment unavailabilities and concurrent actions with multiple procedures.

LER 259/11-001 6

REFERENCES

1. Browns Ferry Nuclear Plant Unit 1, "LER 259/11-001, Three-Unit Scram Caused by Loss of All 500-kV Offsite Power Sources, dated June 27, 2011 (ML11180A056).

2. Browns Ferry Nuclear Plant Unit 1, LER 259/11-002-01, Loss of Safety Function (SDC)

Resulting from Loss of Power from C EDG Due to Oil Leak, dated March 21, 2012 (ML12083A194).

3. Browns Ferry Nuclear Plant Unit 1, LER 259/11-003-01, Loss of Safety Function (SDC)

Resulting from Emergency Diesel Generator Output Breaker Trip, dated December 21, 2011 (ML11363A057).

4. U.S. Nuclear Regulatory Commission, Browns Ferry Nuclear Plant - NRC Integrated Inspection Report 05000259/2011003, 05000260/2011003, and 05000296/2011003, dated August 8, 2011 (ML112210368).

5. U.S. Nuclear Regulatory Commission, Browns Ferry Nuclear Plant - NRC Integrated Inspection Report 05000259/2011004, 05000260/2011004, and 05000296/2011004, dated November 14, 2011 (ML113180503).

6. Browns Ferry Nuclear Plant Unit 1, LER 259/11-005, Reactor Water Level Scram due to Distracted Operations Crew, dated June 27, 2011 (ML11180A007).

7. Browns Ferry Nuclear Plant Unit 1, LER 259/12-006-01, High Pressure Coolant Injection System Turbine Failed to Trip Using the Manual Trip Pushbutton, dated July 18, 2012 (ML12202A001).

8. Idaho National Laboratory, NUREG/CR-6883, SPAR-H Human Reliability Analysis Method, August 2005 (ML051950061).

9. Idaho National Laboratory, INL/EXT-10-18533, SPAR-H Step-by-Step Guidance, May 2011 (ML112060305).

LER 259/11-001 A-1 Appendix A: Analysis Results Unit 1 Summary of Conditional Event Changes Event Description Cond.

Value Nominal Value EPS-DGN-TM-DG3B DG B IS UNAVAILABLE BECAUSE OF MAINTENANCE TRUE 1.43E-2 HE-LOOPWR HOUSE EVENT - LOSS OF OFFSITE POWER IE HAS OCCURRED (WEATHER-RELATED)

TRUE FALSE IE-LOOPWRa LOSS OF OFFSITE POWER INITIATOR (WEATHER-RELATED) 1.00E+0 3.91E-3 OEP-VCF-LP-SITEWR SITE LOOP (WEATHER-RELATED)

TRUE 6.92E-1 OEP-XHE-XL-NR01HWR OPERATOR FAILS TO RECOVER OFFSITE POWER IN 1 HOUR (WEATHER-RELATED) 5.00E-3 6.87E-1 OEP-XHE-XL-NR04HWR OPERATOR FAILS TO RECOVER OFFSITE POWER IN 4 HOURS (WEATHER-RELATED) 1.40E-3 4.24E-1 OEP-XHE-XL-NR10HWR OPERATOR FAILS TO RECOVER OFFSITE POWER IN 10 HOURS (WEATHER-RELATED) 1.40E-3 2.62E-1 OEP-XHE-XL-NR12HWR OPERATOR FAILS TO RECOVER OFFSITE POWER IN 12 HOURS (WEATHER-RELATED) 1.40E-3 2.33E-1 OEP-XHE-XL-NR30MWR OPERATOR FAILS TO RECOVER OFFSITE POWER IN 30 MINUTES (WEATHER-RELATED) 4.10E-2 7.96E-1

a.

All other initiating event probabilities were set to zero.

Implied Event Changes as per RASP Guidance Event Description Cond.

Value Nominal Value EPS-DGN-FR-DG3B DIESEL GENERATOR 3B FAILS TO RUN 1.00E+0 2.85E-2 EPS-DGN-FS-DG3B DIESEL GENERATOR 3B FAILS TO START 1.00E+0 2.89E-3 EPS-DGN-CF-3RUN UNIT 3 DIESEL GENERATORS FAIL FROM COMMON CAUSE TO RUN 1.22E-4 5.93E-5 EPS-DGN-CF-3START UNIT 3 DIESEL GENERATORS FAIL FROM COMMON CAUSE TO START 8.01E-6 4.75E-6 Dominant Sequence Results Only items contributing at least 1.0% to the total CCDP are displayed.

Event Tree Sequence CCDP

% Contribution Description LOOPWR 28-18 4.60E-6 43.9%

/RPS, EPS, /SRV, /RPSL, /RCI01, EXT, DEP01, OPR-04H, DGR-04H LOOPWR 25 2.80E-6 26.8%

/RPS, /EPS, /SRV, HPI, DEP LOOPWR 06 8.93E-7 8.5%

/RPS, /EPS, /SRV, /HPI, SPC, /DEP, /LPI, RHR, CVS, LI LOOPWR 04 7.12E-7 6.8%

/RPS, /EPS, /SRV, /HPI, SPC, /DEP, /LPI, RHR, /CVS, LI01 LOOPWR 28-34-3 4.59E-7 4.4%

/RPS, EPS, /SRV, RPSL, /RCI01, OPR-04H, DGR-04H LOOPWR 13 3.32E-7 3.2%

/RPS, /EPS, /SRV, /HPI, SPC, DEP LOOPWR 28-30 2.76E-7 2.6%

/RPS, EPS, /SRV, /RPSL, RCI01, /HCI01, DEP01, OPR-04H, DGR-04H Total 1.05E-5 100%

Referenced Fault Trees Fault Tree Description CVS CONTAINMENT VENTING DEP MANUAL REACTOR DEPRESS

LER 259/11-001 A-2 Fault Tree Description DEP01 MANUAL REACTOR DEPRESS DGR-04H OPERATOR FAILS TO RECOVER EMERGENCY DIESEL IN 4 HOURS EPS EMERGENCY POWER EXT ACTIONS TO EXTEND ECCS OPERATION HPI HIGH PRESSURE INJECTION (RCIC or HPCI)

LI LATE INJECTION LI01 BROWNS FERRY 1 LATE INJECTION OPR-04H OFFSITE POWER RECOVERY IN 4 HRS RCI01 RCIC RHR LOSS OF RESIDUAL HEAT REMOVAL SYSTEM RPSL RECIRC PUMP SEAL INTEGRITY SPC SUPPRESSION POOL COOLING Cutset Report - LOOPWR 28-18 CCDP Total %

Cutset 4.60E-6 100 Displaying 186 of 186 Cutsets.

1 4.57E-6 99.4 IE-LOOPWR,RSW-STR-CF-ALL Cutset Report - LOOPWR 25 CCDP Total %

Cutset 2.81E-6 100 Displaying 194 of 194 Cutsets.

1 7.86E-7 28 IE-LOOPWR,ADS-XHE-XM-MDEPR,HCI-TDP-FR-TRAIN,RCI-TDP-FR-TRAIN 2

3.57E-7 12.7 IE-LOOPWR,ADS-XHE-XM-MDEPR,HCI-MOV-CC-IVFRO,HCI-MULTIPLE-INJECT,HCI-XHE-XL-INJECT,RCI-TDP-FR-TRAIN 3

2.25E-7 8.01 IE-LOOPWR,ADS-XHE-XM-MDEPR,HCI-TDP-TM-TRAIN,RCI-TDP-FR-TRAIN 4

2.17E-7 7.74 IE-LOOPWR,ADS-XHE-XM-MDEPR,HCI-TDP-FR-TRAIN,RCI-TDP-TM-TRAIN 5

1.43E-7 5.11 IE-LOOPWR,ADS-XHE-XM-MDEPR1,HPI-XHE-XL-LVL8,HPI-XHE-XO-ERROR 6

1.29E-7 4.59 IE-LOOPWR,ADS-XHE-XM-MDEPR,HCI-TDP-FR-TRAIN,RCI-TDP-FS-TRAIN 7

1.29E-7 4.59 IE-LOOPWR,ADS-XHE-XM-MDEPR,HCI-TDP-FS-TRAIN,RCI-TDP-FR-TRAIN 8

9.86E-8 3.51 IE-LOOPWR,ADS-XHE-XM-MDEPR,HCI-MOV-CC-IVFRO,HCI-MULTIPLE-INJECT,HCI-XHE-XL-INJECT,RCI-TDP-TM-TRAIN 9

5.95E-8 2.12 IE-LOOPWR,ADS-XHE-XM-MDEPR,HCI-TDP-FR-TRAIN,RCI-RESTART,RCI-TDP-FS-RSTRT,RCI-XHE-XL-RSTRT 10 5.84E-8 2.08 IE-LOOPWR,ADS-XHE-XM-MDEPR,HCI-MOV-CC-IVFRO,HCI-MULTIPLE-INJECT,HCI-XHE-XL-INJECT,RCI-TDP-FS-TRAIN 11 3.95E-8 1.41 IE-LOOPWR,ADS-XHE-XM-MDEPR,HCI-TDP-FR-TRAIN,RCI-MOV-FC-XFER,RCI-XHE-XL-XFER 12 3.68E-8 1.31 IE-LOOPWR,ADS-XHE-XM-MDEPR,HCI-TDP-TM-TRAIN,RCI-TDP-FS-TRAIN 13 3.55E-8 1.27 IE-LOOPWR,ADS-XHE-XM-MDEPR,HCI-TDP-FS-TRAIN,RCI-TDP-TM-TRAIN Cutset Report - LOOPWR 06 CCDP Total %

Cutset 8.93E-7 100 Displaying 979 of 979 Cutsets.

1 5.00E-7 56 IE-LOOPWR,CVS-XHE-XM-VENT,RHR-XHE-XM-ERROR 2

1.08E-7 12 IE-LOOPWR,DCP-BDC-TM-RMOV1B,RHR-XHE-XM-ERROR 3

1.08E-7 12 IE-LOOPWR,DCP-BDC-TM-RMOV1A,RHR-XHE-XM-ERROR 4

1.42E-8 1.59 IE-LOOPWR,DCP-XHE-XM-1ABC,EPS-DGN-FR-DG3A,RHR-XHE-XM-ERROR Cutset Report - LOOPWR 04 CCDP Total %

Cutset 7.12E-7 100 Displaying 1512 of 1512 Cutsets.

1 5.00E-7 70.3 IE-LOOPWR,OPR-XHE-XM-LI01,RHR-XHE-XM-ERROR

LER 259/11-001 A-3 CCDP Total %

Cutset 2

1.84E-8 2.58 IE-LOOPWR,CRD-MDP-TM-TRNB,CRD-SYS-FC-ARUN,RSW-MDP-CF-RUN 3

1.40E-8 1.96 IE-LOOPWR,CRD-MDP-TM-TRNB,CRD-SYS-FC-ARUN,RSW-MDP-CF-START Cutset Report - LOOPWR 28-34-3 CCDP Total %

Cutset 4.59E-7 100 Displaying 26 of 26 Cutsets.

1 4.57E-7 99.5 IE-LOOPWR,RRS-MDP-LK-SEALS,RSW-STR-CF-ALL Cutset Report - LOOPWR 13 CCDP Total %

Cutset 3.32E-7 100 Displaying 292 of 292 Cutsets.

1 2.50E-7 75.4 IE-LOOPWR,ADS-XHE-XM-MDEPR,RHR-XHE-XM-ERROR 2

1.53E-8 4.61 IE-LOOPWR,ADS-XHE-XM-MDEPR,RHR-MOV-CF-INJECT 3

4.93E-9 1.49 IE-LOOPWR,ADS-XHE-XM-MDEPR,RHR-ACT-XR-SRIB,RHR-ACT-XR-SRIIB 4

4.19E-9 1.26 IE-LOOPWR,ADS-XHE-XM-MDEPR,RHR-ACT-XR-SRIB,RHR-ACT-XR-SRIIA 5

4.19E-9 1.26 IE-LOOPWR,ADS-XHE-XM-MDEPR,RHR-ACT-XR-SRIA,RHR-ACT-XR-SRIIB 6

3.56E-9 1.07 IE-LOOPWR,ADS-XHE-XM-MDEPR,RHR-ACT-XR-SRIA,RHR-ACT-XR-SRIIA Cutset Report - LOOPWR 28-30 CCDP Total %

Cutset 2.76E-7 100 Displaying 14 of 14 Cutsets.

1 1.81E-7 65.7 IE-LOOPWR,RCI-TDP-FR-TRAIN,RSW-STR-CF-ALL 2

5.00E-8 18.1 IE-LOOPWR,RCI-TDP-TM-TRAIN,RSW-STR-CF-ALL 3

2.97E-8 10.8 IE-LOOPWR,RCI-TDP-FS-TRAIN,RSW-STR-CF-ALL 4

1.37E-8 4.97 IE-LOOPWR,RCI-RESTART,RCI-TDP-FS-RSTRT,RCI-XHE-XL-RSTRT,RSW-STR-CF-ALL Referenced Events Event Description Probability ADS-XHE-XM-MDEPR OPERATOR FAILS TO DEPRESSURIZE THE REACTOR 5.00E-4 ADS-XHE-XM-MDEPR1 OPERATOR FAILS TO DEPRESSURIZE THE REACTOR 1.43E-1 CRD-MDP-TM-TRNB CRD TRAIN B IS UNAVAILABLE BECAUSE OF MAINTENANCE 1.43E-2 CRD-SYS-FC-ARUN CRD PUMP A IS RUNNING PUMP B IS IN STANDBY 5.00E-1 CVS-XHE-XM-VENT OPERATOR FAILS TO VENT CONTAINMENT 1.00E-3 DCP-BDC-TM-RMOV1A 250 VDC RMOV BOARD 1A IS UNAVAILABLE DUE TO TM 2.15E-4 DCP-BDC-TM-RMOV1B 250 VDC RMOV BOARD 1B IS UNAVAILABLE 2.15E-4 DCP-XHE-XM-1ABC OPERATOR FAILS TO ALIGN BACKUP POWER TO DC-MOV1A B C 1.00E-3 EPS-DGN-FR-DG3A DIESEL GENERATOR 3A FAILS TO RUN 2.85E-2 HCI-MOV-CC-IVFRO HPCI INJECTION VALVE 44 FAILS TO REOPEN 1.50E-1 HCI-MULTIPLE-INJECT MULTIPLE HPCI INJECTIONS REQUIRED 1.50E-1 HCI-TDP-FR-TRAIN HPCI PUMP TRAIN FAILS TO RUN GIVEN IT STARTED 3.97E-2 HCI-TDP-FS-TRAIN HPCI PUMP FAILS TO START 6.49E-3 HCI-TDP-TM-TRAIN HPCI TRAIN IS UNAVAILABLE BECAUSE OF MAINTENANCE 1.13E-2 HCI-XHE-XL-INJECT OPERATOR FAILS TO RECOVER HPCI INJECT MOV FAILURE TO REOPEN 8.00E-1 HPI-XHE-XL-LVL8 OPERATOR FAILS TO RECOVER HPCI/RCIC AFTER LEVEL 8 1.00E-3 HPI-XHE-XO-ERROR OPERATOR FAILS TO START/CONTROL RCIC/HPCI INJECTION 1.00E-3 IE-LOOPWR LOSS OF OFFSITE POWER INITIATOR (WEATHER-RELATED) 1.00E+0 OPR-XHE-XM-LI01 OPERATOR FAILS TO START/CONTROL LATE INJECTION 1.00E-3 RCI-MOV-FC-XFER RCIC FAILS TO TRANSFER DURING RECIRCULATION 7.97E-3 RCI-RESTART RESTART OF RCIC IS REQUIRED 1.50E-1

LER 259/11-001 A-4 Event Description Probability RCI-TDP-FR-TRAIN RCIC PUMP FAILS TO RUN GIVEN THAT IT STARTED 3.97E-2 RCI-TDP-FS-RSTRT RCIC FAILS TO RESTART GIVEN START AND SHORT-TERM RUN 8.00E-2 RCI-TDP-FS-TRAIN RCIC PUMP FAILS TO START 6.49E-3 RCI-TDP-TM-TRAIN RCIC PUMP TRAIN IS UNAVAILABLE BECAUSE OF MAINTENANCE 1.10E-2 RCI-XHE-XL-RSTRT OPERATOR FAILS TO RECOVER RCIC FAILURE TO RESTART 2.50E-1 RCI-XHE-XL-XFER OPERATOR FAILS TO RECOVER SUCTN XFER FAILURE 2.50E-1 RHR-ACT-XR-SRIA UNDETECTED HUMAN ERROR AFTER SR-3 3 5 1 6 (CHANNEL A LOOP I) 2.67E-3 RHR-ACT-XR-SRIB UNDETECTED HUMAN ERROR AFTER SR-3 3 5 1 6 (CHANNEL B LOOP I) 3.14E-3 RHR-ACT-XR-SRIIA UNDETECTED HUMAN ERROR AFTER SR-3 3 5 1 6 (CHANNEL A LOOP II) 2.67E-3 RHR-ACT-XR-SRIIB UNDETECTED HUMAN ERROR AFTER SR-3 3 5 1 6 (CHANNEL B LOOP II) 3.14E-3 RHR-MOV-CF-INJECT SPC INJECTION VALVES FAIL FROM COMMON CAUSE 3.06E-5 RHR-XHE-XM-ERROR OPERATOR FAILS TO START/CONTROL RHR 5.00E-4 RRS-MDP-LK-SEALS RECIRCULATION PUMP SEALS FAIL 1.00E-1 RSW-MDP-CF-RUN RHRSW PUMPS FAIL FROM COMMON CAUSE TO RUN 2.58E-6 RSW-MDP-CF-START RHRSW PUMPS FAIL FROM COMMON CAUSE TO START 1.96E-6 RSW-STR-CF-ALL RHRSW STRAINERS FAIL FROM COMMON CAUSE 4.57E-6

LER 259/11-001 A-5 Unit 2 Summary of Conditional Event Changes Event Description Cond.

Value Nominal Value EPS-DGN-TM-DG3B DG B IS UNAVAILABLE BECAUSE OF MAINTENANCE TRUE 1.43E-2 HE-LOOPWR HOUSE EVENT - LOSS OF OFFSITE POWER IE HAS OCCURRED (WEATHER-RELATED)

TRUE FALSE IE-LOOPWRa LOSS OF OFFSITE POWER INITIATOR (WEATHER-RELATED) 1.00E+0 3.91E-3 OEP-VCF-LP-SITEWR SITE LOOP (WEATHER-RELATED)

TRUE 6.92E-1 OEP-XHE-XL-NR01HWR OPERATOR FAILS TO RECOVER OFFSITE POWER IN 1 HOUR (WEATHER-RELATED) 5.00E-3 6.87E-1 OEP-XHE-XL-NR04HWR OPERATOR FAILS TO RECOVER OFFSITE POWER IN 4 HOURS (WEATHER-RELATED) 1.40E-3 4.24E-1 OEP-XHE-XL-NR10HWR OPERATOR FAILS TO RECOVER OFFSITE POWER IN 10 HOURS (WEATHER-RELATED) 1.40E-3 2.62E-1 OEP-XHE-XL-NR12HWR OPERATOR FAILS TO RECOVER OFFSITE POWER IN 12 HOURS (WEATHER-RELATED) 1.40E-3 2.33E-1 OEP-XHE-XL-NR30MWR OPERATOR FAILS TO RECOVER OFFSITE POWER IN 30 MINUTES (WEATHER-RELATED) 4.10E-2 7.96E-1

a.

All other initiating event probabilities were set to zero.

Implied Event Changes as per RASP Guidance Event Description Cond.

Value Nominal Value EPS-DGN-FR-DG3B DIESEL GENERATOR 3B FAILS TO RUN 1.00E+0 2.85E-2 EPS-DGN-FS-DG3B DIESEL GENERATOR 3B FAILS TO START 1.00E+0 2.89E-3 EPS-DGN-CF-3RUN UNIT 3 DIESEL GENERATORS FAIL FROM COMMON CAUSE TO RUN 1.22E-4 5.93E-5 EPS-DGN-CF-3START UNIT 3 DIESEL GENERATORS FAIL FROM COMMON CAUSE TO START 8.01E-6 4.75E-6 Dominant Sequence Results Only items contributing at least 1.0% to the total CCDP are displayed.

Event Tree Sequence CCDP

% Contribution Description LOOPWR 28-18 4.60E-6 43.1%

/RPS, EPS, /SRV, /RPSL, /RCI01, EXT, DEP01, OPR-04H, DGR-04H LOOPWR 25 2.93E-6 27.5%

/RPS, /EPS, /SRV, HPI, DEP LOOPWR 04 6.86E-7 6.4%

/RPS, /EPS, /SRV, /HPI, SPC, /DEP, /LPI, RHR,

/CVS, LI01 LOOPWR 06 5.29E-7 5.0%

/RPS, /EPS, /SRV, /HPI, SPC, /DEP, /LPI, RHR, CVS, LI LOOPWR 13 4.75E-7 4.5%

/RPS, /EPS, /SRV, /HPI, SPC, DEP LOOPWR 28-34-3 4.59E-7 4.3%

/RPS, EPS, /SRV, RPSL, /RCI01, OPR-04H, DGR-04H LOOPWR 24 2.91E-7 2.7%

/RPS, /EPS, /SRV, HPI, /DEP, LPI, VA LOOPWR 28-30 2.76E-7 2.6%

/RPS, EPS, /SRV, /RPSL, RCI01, /HCI01, DEP01, OPR-04H, DGR-04H LOOPWR 12 2.31E-7 2.2%

/RPS, /EPS, /SRV, /HPI, SPC, /DEP, LPI, VA Total 1.07E-5 100%

Referenced Fault Trees Fault Tree Description CVS CONTAINMENT VENTING DEP MANUAL REACTOR DEPRESS

LER 259/11-001 A-6 Fault Tree Description DEP01 MANUAL REACTOR DEPRESS DGR-04H DIESEL GENERATOR RECOVERY IN 4 HRS EPS TRANSFER BRANCH SBO EXT ACTIONS TO EXTEND ECCS OPERATION HPI HIGH PRESSURE INJECTION (RCIC or HPCI)

LI LATE INJECTION LI01 BROWNS FERRY 2 LATE INJECTION FAULT TREE LPI LOW PRESSURE INJECTION (CS or LPCI)

OPR-04H OFFSITE POWER RECOVERY IN 4 HRS RCI01 RCIC RHR LOSS OF RESIDUAL HEAT REMOVAL SYSTEM RPSL RECIRC PUMP SEAL INTEGRITY SPC SUPPRESSION POOL COOLING (LATE)

VA ALTERNATE LOW PRESS INJECTION Cutset Report - LOOPWR 28-18 CCDP Total %

Cutset 4.60E-6 100 Displaying 192 of 192 Cutsets.

1 4.57E-6 99.4 IE-LOOPWR,RSW-STR-CF-ALL Cutset Report - LOOPWR 25 CCDP Total %

Cutset 2.93E-6 100 Displaying 184 of 184 Cutsets.

1 7.86E-7 26.9 IE-LOOPWR,ADS-XHE-XM-MDEPR,HCI-TDP-FR-TRAIN,RCI-TDP-FR-TRAIN 2

3.57E-7 12.2 IE-LOOPWR,ADS-XHE-XM-MDEPR,HCI-MOV-CC-IVFRO,HCI-MULTIPLE-INJECT,HCI-XHE-XL-INJECT,RCI-TDP-FR-TRAIN 3

2.25E-7 7.67 IE-LOOPWR,ADS-XHE-XM-MDEPR,HCI-TDP-TM-TRAIN,RCI-TDP-FR-TRAIN 4

2.17E-7 7.41 IE-LOOPWR,ADS-XHE-XM-MDEPR,HCI-TDP-FR-TRAIN,RCI-TDP-TM-TRAIN 5

1.57E-7 5.37 IE-LOOPWR,DEP-XHE-CRD-ADS,HCI-TDP-FR-TRAIN,RCI-TDP-FR-TRAIN 6

1.29E-7 4.4 IE-LOOPWR,ADS-XHE-XM-MDEPR,HCI-TDP-FS-TRAIN,RCI-TDP-FR-TRAIN 7

1.29E-7 4.4 IE-LOOPWR,ADS-XHE-XM-MDEPR,HCI-TDP-FR-TRAIN,RCI-TDP-FS-TRAIN 8

9.86E-8 3.36 IE-LOOPWR,ADS-XHE-XM-MDEPR,HCI-MOV-CC-IVFRO,HCI-MULTIPLE-INJECT,HCI-XHE-XL-INJECT,RCI-TDP-TM-TRAIN 9

7.14E-8 2.44 IE-LOOPWR,DEP-XHE-CRD-ADS,HCI-MOV-CC-IVFRO,HCI-MULTIPLE-INJECT,HCI-XHE-XL-INJECT,RCI-TDP-FR-TRAIN 10 5.95E-8 2.03 IE-LOOPWR,ADS-XHE-XM-MDEPR,HCI-TDP-FR-TRAIN,RCI-RESTART,RCI-TDP-FS-RSTRT,RCI-XHE-XL-RSTRT 11 5.84E-8 2

IE-LOOPWR,ADS-XHE-XM-MDEPR,HCI-MOV-CC-IVFRO,HCI-MULTIPLE-INJECT,HCI-XHE-XL-INJECT,RCI-TDP-FS-TRAIN 12 4.49E-8 1.53 IE-LOOPWR,DEP-XHE-CRD-ADS,HCI-TDP-TM-TRAIN,RCI-TDP-FR-TRAIN 13 4.34E-8 1.48 IE-LOOPWR,DEP-XHE-CRD-ADS,HCI-TDP-FR-TRAIN,RCI-TDP-TM-TRAIN 14 3.95E-8 1.35 IE-LOOPWR,ADS-XHE-XM-MDEPR,HCI-TDP-FR-TRAIN,RCI-MOV-FC-XFER,RCI-XHE-XL-XFER 15 3.68E-8 1.26 IE-LOOPWR,ADS-XHE-XM-MDEPR,HCI-TDP-TM-TRAIN,RCI-TDP-FS-TRAIN 16 3.55E-8 1.21 IE-LOOPWR,ADS-XHE-XM-MDEPR,HCI-TDP-FS-TRAIN,RCI-TDP-TM-TRAIN Cutset Report - LOOPWR 04 CCDP Total %

Cutset 6.86E-7 100 Displaying 1185 of 1185 Cutsets.

1 5.00E-7 72.9 IE-LOOPWR,OPR-XHE-XM-LI01,RHR-XHE-XM-ERROR 2

1.84E-8 2.68 IE-LOOPWR,CRD-MDP-TM-TRNB,CRD-SYS-FC-ARUN,RSW-MDP-CF-RUN 3

1.40E-8 2.04 IE-LOOPWR,CRD-MDP-TM-TRNB,CRD-SYS-FC-ARUN,RSW-MDP-CF-START

LER 259/11-001 A-7 CCDP Total %

Cutset 4

7.06E-9 1.03 IE-LOOPWR,DCP-BDC-TM-TURB,RSW-MDP-CF-RUN Cutset Report - LOOPWR 06 CCDP Total %

Cutset 5.29E-7 100 Displaying 86 of 86 Cutsets.

1 5.00E-7 94.4 IE-LOOPWR,CVS-XHE-XM-VENT,RHR-XHE-XM-ERROR Cutset Report - LOOPWR 13 CCDP Total %

Cutset 4.75E-7 100 Displaying 82 of 82 Cutsets.

1 2.50E-7 52.6 IE-LOOPWR,ADS-XHE-XM-MDEPR,RHR-XHE-XM-ERROR 2

1.00E-7 21 IE-LOOPWR,ACP-BAC-TM-RMOV2D,ADS-XHE-XM-MDEPR 3

5.00E-8 10.5 IE-LOOPWR,DEP-XHE-CRD-ADS,RHR-XHE-XM-ERROR 4

2.00E-8 4.21 IE-LOOPWR,ACP-BAC-TM-RMOV2D,DEP-XHE-CRD-ADS 5

1.67E-8 3.51 IE-LOOPWR,ACP-BAC-LP-RMOV2D,ADS-XHE-XM-MDEPR 6

1.53E-8 3.22 IE-LOOPWR,ADS-XHE-XM-MDEPR,RHR-MOV-CF-SPCINJEC 7

5.00E-9 1.05 IE-LOOPWR,ADS-XHE-XM-MDEPR,RHR-STR-CF-NLOCA Cutset Report - LOOPWR 28-34-3 CCDP Total %

Cutset 4.59E-7 100 Displaying 26 of 26 Cutsets.

1 4.57E-7 99.5 IE-LOOPWR,RRS-MDP-LK-SEALS,RSW-STR-CF-ALL Cutset Report - LOOPWR 24 CCDP Total %

Cutset 2.91E-7 100 Displaying 558 of 558 Cutsets.

1 3.21E-8 11 IE-LOOPWR,EPS-DGN-FR-DGB,EPS-DGN-FR-DGD,HCI-TDP-FR-TRAIN,HVC-XHE-XM-DOOR 2

1.62E-8 5.56 IE-LOOPWR,EPS-DGN-FR-DGD,EPS-DGN-TM-DGB,HCI-TDP-FR-TRAIN,HVC-XHE-XM-DOOR 3

1.62E-8 5.56 IE-LOOPWR,EPS-DGN-FR-DGB,EPS-DGN-TM-DGD,HCI-TDP-FR-TRAIN,HVC-XHE-XM-DOOR 4

1.46E-8 5.01 IE-LOOPWR,EPS-DGN-FR-DGB,EPS-DGN-FR-DGD,HCI-MOV-CC-IVFRO,HCI-MULTIPLE-INJECT,HCI-XHE-XL-INJECT,HVC-XHE-XM-DOOR 5

1.13E-8 3.88 IE-LOOPWR,EPS-DGN-FR-DGD,HCI-TDP-FR-TRAIN,HVC-CHL-CFG-1ASTANDBY,HVC-CHL-TM-1A,HVC-XHE-XM-DOOR 6

1.13E-8 3.88 IE-LOOPWR,EPS-DGN-FR-DGB,HCI-TDP-FR-TRAIN,/HVC-CHL-CFG-1ASTANDBY,HVC-CHL-TM-1B,HVC-XHE-XM-DOOR 7

9.18E-9 3.15 IE-LOOPWR,EPS-DGN-FR-DGB,EPS-DGN-FR-DGD,HCI-TDP-TM-TRAIN,HVC-XHE-XM-DOOR 8

7.35E-9 2.53 IE-LOOPWR,EPS-DGN-FR-DGB,EPS-DGN-TM-DGD,HCI-MOV-CC-IVFRO,HCI-MULTIPLE-INJECT,HCI-XHE-XL-INJECT,HVC-XHE-XM-DOOR 9

7.35E-9 2.53 IE-LOOPWR,EPS-DGN-FR-DGD,EPS-DGN-TM-DGB,HCI-MOV-CC-IVFRO,HCI-MULTIPLE-INJECT,HCI-XHE-XL-INJECT,HVC-XHE-XM-DOOR 10 5.69E-9 1.95 IE-LOOPWR,EPS-DGN-TM-DGB,HCI-TDP-FR-TRAIN,/HVC-CHL-CFG-1ASTANDBY,HVC-CHL-TM-1B,HVC-XHE-XM-DOOR 11 5.69E-9 1.95 IE-LOOPWR,EPS-DGN-TM-DGD,HCI-TDP-FR-TRAIN,HVC-CHL-CFG-1ASTANDBY,HVC-CHL-TM-1A,HVC-XHE-XM-DOOR 12 5.26E-9 1.81 IE-LOOPWR,EPS-DGN-FR-DGB,EPS-DGN-FR-DGD,HCI-TDP-FS-TRAIN,HVC-XHE-XM-DOOR 13 5.12E-9 1.76 IE-LOOPWR,EPS-DGN-FR-DGD,HCI-MOV-CC-IVFRO,HCI-MULTIPLE-INJECT,HCI-XHE-XL-INJECT,HVC-CHL-CFG-1ASTANDBY,HVC-CHL-TM-1A,HVC-XHE-XM-DOOR 14 5.12E-9 1.76 IE-LOOPWR,EPS-DGN-FR-DGB,HCI-MOV-CC-IVFRO,HCI-MULTIPLE-INJECT,HCI-XHE-XL-INJECT,/HVC-CHL-CFG-1ASTANDBY,HVC-CHL-TM-1B,HVC-XHE-XM-DOOR

LER 259/11-001 A-8 CCDP Total %

Cutset 15 4.63E-9 1.59 IE-LOOPWR,EPS-DGN-FR-DGD,EPS-DGN-TM-DGB,HCI-TDP-TM-TRAIN,HVC-XHE-XM-DOOR 16 4.63E-9 1.59 IE-LOOPWR,EPS-DGN-FR-DGB,EPS-DGN-TM-DGD,HCI-TDP-TM-TRAIN,HVC-XHE-XM-DOOR 17 3.26E-9 1.12 IE-LOOPWR,EPS-DGN-FR-DGB,EPS-DGN-FS-DGD,HCI-TDP-FR-TRAIN,HVC-XHE-XM-DOOR 18 3.26E-9 1.12 IE-LOOPWR,EPS-DGN-FR-DGD,EPS-DGN-FS-DGB,HCI-TDP-FR-TRAIN,HVC-XHE-XM-DOOR 19 3.22E-9 1.11 IE-LOOPWR,EPS-DGN-FR-DGD,HCI-TDP-TM-TRAIN,HVC-CHL-CFG-1ASTANDBY,HVC-CHL-TM-1A,HVC-XHE-XM-DOOR 20 3.22E-9 1.11 IE-LOOPWR,EPS-DGN-FR-DGB,HCI-TDP-TM-TRAIN,/HVC-CHL-CFG-1ASTANDBY,HVC-CHL-TM-1B,HVC-XHE-XM-DOOR Cutset Report - LOOPWR 28-30 CCDP Total %

Cutset 2.76E-7 100 Displaying 14 of 14 Cutsets.

1 1.81E-7 65.7 IE-LOOPWR,RCI-TDP-FR-TRAIN,RSW-STR-CF-ALL 2

5.00E-8 18.1 IE-LOOPWR,RCI-TDP-TM-TRAIN,RSW-STR-CF-ALL 3

2.97E-8 10.8 IE-LOOPWR,RCI-TDP-FS-TRAIN,RSW-STR-CF-ALL 4

1.37E-8 4.97 IE-LOOPWR,RCI-RESTART,RCI-TDP-FS-RSTRT,RCI-XHE-XL-RSTRT,RSW-STR-CF-ALL Cutset Report - LOOPWR 12 CCDP Total %

Cutset 2.31E-7 100 Displaying 274 of 274 Cutsets.

1 4.00E-8 17.3 IE-LOOPWR,ACP-BAC-TM-SB2A,ACP-BAC-TM-SB2B 2

2.39E-8 10.3 IE-LOOPWR,ACP-CRB-CC-1616,/HVC-CHL-CFG-1ASTANDBY,HVC-CHL-TM-1B,HVC-XHE-XM-DOOR 3

2.39E-8 10.3 IE-LOOPWR,ACP-CRB-CC-1724,HVC-CHL-CFG-1ASTANDBY,HVC-CHL-TM-1A,HVC-XHE-XM-DOOR 4

1.37E-8 5.91 IE-LOOPWR,ACP-CRB-CC-1616,ACP-CRB-CC-1718,ACP-CRB-CC-1724 5

1.00E-8 4.32 IE-LOOPWR,OPR-XHE-XM-ALPI,RHR-STR-CF-NLOCA 6

9.63E-9 4.16 IE-LOOPWR,LCI-MOV-CC-F067,RHR-STR-CF-NLOCA 7

9.63E-9 4.16 IE-LOOPWR,RHR-MOV-CC-F101,RHR-STR-CF-NLOCA 8

9.63E-9 4.16 IE-LOOPWR,RHR-STR-CF-NLOCA,RSW-MOV-CC-F057 9

7.32E-9 3.16 IE-LOOPWR,/HVC-CHL-CFG-1ASTANDBY,HVC-CHL-FR-1A,HVC-CHL-TM-1B,HVC-XHE-XM-DOOR 10 7.32E-9 3.16 IE-LOOPWR,HVC-CHL-CFG-1ASTANDBY,HVC-CHL-FR-1B,HVC-CHL-TM-1A,HVC-XHE-XM-DOOR 11 6.66E-9 2.88 IE-LOOPWR,ACP-BAC-LP-SB2B,ACP-BAC-TM-SB2A 12 6.66E-9 2.88 IE-LOOPWR,ACP-BAC-LP-SB2A,ACP-BAC-TM-SB2B 13 5.72E-9 2.47 IE-LOOPWR,ACP-CRB-CC-1616,ACP-CRB-CC-1724,HVC-XHE-XM-DOOR 14 5.26E-9 2.27 IE-LOOPWR,ACP-BAC-TM-SB2A,ACP-CRB-CC-1724,ACP-XHE-XM-SB2B 15 5.26E-9 2.27 IE-LOOPWR,ACP-BAC-TM-SB2B,ACP-CRB-CC-1616,ACP-XHE-XM-SB2A 16 4.94E-9 2.14 IE-LOOPWR,HVC-ACX-CF-1AR,HVC-XHE-XM-DOOR 17 2.39E-9 1.03 IE-LOOPWR,ACP-CRB-CC-1616,/HVC-CHL-CFG-1ASTANDBY,HVC-CHL-FS-1B,HVC-XHE-XM-DOOR 18 2.39E-9 1.03 IE-LOOPWR,ACP-CRB-CC-1724,HVC-CHL-CFG-1ASTANDBY,HVC-CHL-FS-1A,HVC-XHE-XM-DOOR Referenced Events Event Description Probability ACP-BAC-LP-RMOV2D BROWNS FERRY 1 480V RMOV BOARD 2D BUS IS UNAVAILABLE 3.33E-5 ACP-BAC-LP-SB2A SHUTDOWN BOARD 2A IS UNAVAILABLE 3.33E-5 ACP-BAC-LP-SB2B SHUTDOWN BOARD 2B IS UNAVAILABLE 3.33E-5

LER 259/11-001 A-9 Event Description Probability ACP-BAC-TM-RMOV2D BROWNS FERRY 2 480V RMOV BOARD 2D BUS IS UNAVAILABLE

- TM 2.00E-4 ACP-BAC-TM-SB2A 480 VAC SHUTDOWN BOARD 2A BUS IS UNAVAILABLE - TM 2.00E-4 ACP-BAC-TM-SB2B 480 VAC SHUTDOWN BOARD 2B BUS IS UNAVAILABLE - TM 2.00E-4 ACP-CRB-CC-1616 SD BOARD B OFFSITE POWER SUPPLY BREAKER FAILS TO OPEN 2.39E-3 ACP-CRB-CC-1718 SD BOARD C OFFSITE POWER SUPPLY BREAKER FAILS TO OPEN 2.39E-3 ACP-CRB-CC-1724 SD BOARD D OFFSITE POWER SUPPLY BREAKER FAILS TO OPEN 2.39E-3 ACP-XHE-XM-SB2A OPERATOR FAILS TO ALIGN ALTERNATE POWER TO SB 2A 1.10E-2 ACP-XHE-XM-SB2B OPERATOR FAILS TO ALIGN ALTERNATE POWER TO SB 2B 1.10E-2 ADS-XHE-XM-MDEPR OPERATOR FAILS TO DEPRESSURIZE THE REACTOR 5.00E-4 CRD-MDP-TM-TRNB CRD TRAIN B IS UNAVAILABLE BECAUSE OF MAINTENANCE 1.43E-2 CRD-SYS-FC-ARUN CRD PUMP A IS RUNNING, PUMP B IS IN STANDBY 5.00E-1 CVS-XHE-XM-VENT OPERATOR FAILS TO VENT CONTAINMENT 1.00E-3 DCP-BDC-TM-TURB 250 VDC BATTERY BOARD TO 4KV UNIT BOARD (2B) BUS-TM 2.74E-3 DEP-XHE-CRD-ADS DEPENDENCY ADJUSTMENT FOR CRD-XHE-XM-ERROR AND ADS-XHE-XM-MDEPR 1.00E-4 EPS-DGN-FR-DGB DIESEL GENERATOR B FAILS TO RUN 2.85E-2 EPS-DGN-FR-DGD DIESEL GENERATOR D FAILS TO RUN 2.85E-2 EPS-DGN-FS-DGB DIESEL GENERATOR B FAILS TO START 2.89E-3 EPS-DGN-FS-DGD DIESEL GENERATOR D FAILS TO START 2.89E-3 EPS-DGN-TM-DGB DG B IS UNAVAILABLE BECAUSE OF MAINTENANCE 1.43E-2 EPS-DGN-TM-DGD DG D IS UNAVAILABLE BECAUSE OF MAINTENANCE 1.43E-2 HCI-MOV-CC-IVFRO HPCI INJECTION VALVE FAILS TO REOPEN 1.50E-1 HCI-MULTIPLE-INJECT MULTIPLE HPCI INJECTIONS REQUIRED 1.50E-1 HCI-TDP-FR-TRAIN HPCI PUMP TRAIN FAILS TO RUN GIVEN IT STARTED 3.97E-2 HCI-TDP-FS-TRAIN HPCI PUMP FAILS TO START 6.49E-3 HCI-TDP-TM-TRAIN HPCI TRAIN IS UNAVAILABLE BECAUSE OF MAINTENANCE 1.13E-2 HCI-XHE-XL-INJECT OPERATOR FAILS TO RECOVER HPCI INJECT MOV FAILURE TO REOPEN 8.00E-1 HVC-ACX-CF-1AR AHU-31-88 (1A) & AHU-31-89 (1B) FAILS TO RUN DUE TO CCF 4.94E-6 HVC-CHL-CFG-1ASTANDBY WATER CHILLER 1A IN STANDBY 5.00E-1 HVC-CHL-FR-1A WATER CHILLER 1A FAILS TO RUN 7.32E-4 HVC-CHL-FR-1B WATER CHILLER 1B FAILS TO RUN 7.32E-4 HVC-CHL-FS-1A WATER CHILLER 1A FAILS TO START 2.00E-3 HVC-CHL-FS-1B WATER CHILLER 1B FAILS TO START 2.00E-3 HVC-CHL-TM-1A WATER CHILLER 1A IN T&M 2.00E-2 HVC-CHL-TM-1B WATER CHILLER 1B IN T&M 2.00E-2 HVC-XHE-XM-DOOR FAILURE TO OPEN DOORS/INSTALL FANS AFTER HVAC FAILURE 1.00E-3 IE-LOOPWR LOSS OF OFFSITE POWER INITIATOR (WEATHER-RELATED) 1.00E+0 LCI-MOV-CC-F067 LPCI LOOP B INJECTION VALVE 74-67 FAILS TO OPEN 9.63E-4 OPR-XHE-XM-ALPI OPERATOR FAILS TO START/CONTROL ALTERNATE LOW PRES INJECTION 1.00E-3 OPR-XHE-XM-LI01 OPERATOR FAILS TO START/CONTROL LATE INJECTION 1.00E-3 RCI-MOV-FC-XFER RCIC FAILS TO TRANSFER DURING RECIRCULATION 7.97E-3 RCI-RESTART RESTART OF RCIC IS REQUIRED 1.50E-1 RCI-TDP-FR-TRAIN RCIC PUMP FAILS TO RUN GIVEN THAT IT STARTED 3.97E-2 RCI-TDP-FS-RSTRT RCIC FAILS TO RESTART GIVEN START AND SHORT-TERM RUN 8.00E-2 RCI-TDP-FS-TRAIN RCIC PUMP FAILS TO START 6.49E-3

LER 259/11-001 A-10 Event Description Probability RCI-TDP-TM-TRAIN RCIC PUMP TRAIN IS UNAVAILABLE BECAUSE OF MAINTENANCE 1.10E-2 RCI-XHE-XL-RSTRT OPERATOR FAILS TO RECOVER RCIC FAILURE TO RESTART 2.50E-1 RCI-XHE-XL-XFER OPERATOR FAILS TO RECOVER SUCTN XFER FAILURE 2.50E-1 RHR-MOV-CC-F101 RHR CROSS TIE MOV 74-101 FAILS TO OPEN 9.63E-4 RHR-MOV-CF-SPCINJEC SPC INJECTION VALVES FAIL FROM COMMON CAUSE 3.06E-5 RHR-STR-CF-NLOCA SUPPRESSION POOL STRAINERS FAIL FROM COMMON CAUSE (NON-LOCA) 1.00E-5 RHR-XHE-XM-ERROR OPERATOR FAILS TO START/CONTROL RHR 5.00E-4 RRS-MDP-LK-SEALS RECIRCULATION PUMP SEALS FAIL 1.00E-1 RSW-MDP-CF-RUN RHRSW PUMPS FAIL FROM COMMON CAUSE TO RUN 2.58E-6 RSW-MDP-CF-START RHRSW PUMPS FAIL FROM COMMON CAUSE TO START 1.96E-6 RSW-MOV-CC-F057 RHRSW/RHR CROSS TIE MOV 23-57 FAILS TO OPEN 9.63E-4 RSW-STR-CF-ALL RHRSW STRAINERS FAIL FROM COMMON CAUSE 4.57E-6

LER 259/11-001 A-11 Unit 3 Summary of Conditional Event Changes Event Description Cond.

Value Nominal Value EPS-DGN-TM-DG3B DG B IS UNAVAILABLE BECAUSE OF MAINTENANCE TRUE 1.43E-2 HE-LOOPWR HOUSE EVENT - LOSS OF OFFSITE POWER IE HAS OCCURRED (WEATHER-RELATED)

TRUE FALSE IE-LOOPWRa LOSS OF OFFSITE POWER INITIATOR (WEATHER-RELATED) 1.00E+0 3.91E-3 OEP-VCF-LP-SITEWR SITE LOOP (WEATHER-RELATED)

TRUE 6.92E-1 OEP-XHE-XL-NR01HWR OPERATOR FAILS TO RECOVER OFFSITE POWER IN 1 HOUR (WEATHER-RELATED) 5.00E-3 1.00E+0 OEP-XHE-XL-NR04HWR OPERATOR FAILS TO RECOVER OFFSITE POWER IN 4 HOURS (WEATHER-RELATED) 1.40E-3 1.00E+0 OEP-XHE-XL-NR10HWR OPERATOR FAILS TO RECOVER OFFSITE POWER IN 10 HOURS (WEATHER-RELATED) 1.40E-3 1.00E+0 OEP-XHE-XL-NR12HWR OPERATOR FAILS TO RECOVER OFFSITE POWER IN 12 HOURS (WEATHER-RELATED) 1.40E-3 1.00E+0 OEP-XHE-XL-NR30MWR OPERATOR FAILS TO RECOVER OFFSITE POWER IN 30 MINUTES (WEATHER-RELATED) 4.10E-2 1.00E+0

a.

All other initiating event probabilities were set to zero.

Implied Event Changes as per RASP Guidance Event Description Cond.

Value Nominal Value EPS-DGN-FR-DG3B DIESEL GENERATOR 3B FAILS TO RUN 1.00E+0 2.85E-2 EPS-DGN-FS-DG3B DIESEL GENERATOR 3B FAILS TO START 1.00E+0 2.89E-3 EPS-DGN-CF-3START UNIT 3 DIESEL GENERATORS FAIL FROM COMMON CAUSE TO START 8.01E-6 4.75E-6 EPS-DGN-CF-3RUN UNIT 3 DIESEL GENERATORS FAIL FROM COMMON CAUSE TO RUN 1.22E-4 5.93E-5 Dominant Sequence Results Only items contributing at least 1.0% to the total CCDP are displayed.

Event Tree Sequence CCDP

% Contribution Description LOOPWR 28-18 4.62E-6 35.0%

/RPS, EPS, /SRV, /RPSL, /RCI01, EXT, DEP01, OPR-04H, DGR-04H LOOPWR 25 3.29E-6 24.9%

/RPS, /EPS, /SRV, HPI, DEP LOOPWR 24 2.52E-6 19.0%

/RPS, /EPS, /SRV, HPI, /DEP, LPI, VA LOOPWR 04 6.83E-7 5.2%

/RPS, /EPS, /SRV, /HPI, SPC, /DEP, /LPI, RHR,

/CVS, LI01 LOOPWR 06 5.43E-7 4.1%

/RPS, /EPS, /SRV, /HPI, SPC, /DEP, /LPI, RHR, CVS, LI LOOPWR 28-34-3 4.61E-7 3.5%

/RPS, EPS, /SRV, RPSL, /RCI01, OPR-04H, DGR-04H LOOPWR 12 4.54E-7 3.4%

/RPS, /EPS, /SRV, /HPI, SPC, /DEP, LPI, VA LOOPWR 13 2.79E-7 2.1%

/RPS, /EPS, /SRV, /HPI, SPC, DEP LOOPWR 28-30 2.76E-7 2.1%

/RPS, EPS, /SRV, /RPSL, RCI01, /HCI01, DEP01, OPR-04H, DGR-04H Total 1.32E-5 100%

Referenced Fault Trees Fault Tree Description CVS CONTAINMENT VENTING DEP MANUAL REACTOR DEPRESS DEP01 MANUAL REACTOR DEPRESS

LER 259/11-001 A-12 Fault Tree Description DGR-04H DIESEL GENERATOR RECOVERY IN 4 HRS EPS TRANSFER BRANCH SBO EXT ACTIONS TO EXTEND ECCS OPERATION HPI HIGH PRESSURE INJECTION (RCIC or HPCI)

LI LATE INJECTION LI01 BROWNS FERRY 3 LATE INJECTION FAULT TREE LPI LOW PRESSURE INJECTION (CS or LPCI)

OPR-04H OFFSITE POWER RECOVERY IN 4 HRS RCI01 RCIC RHR LOSS OF RESIDUAL HEAT REMOVAL SYSTEMS RPSL RECIRC PUMP SEAL INTEGRITY SPC SUPPRESSION POOL COOLING VA ALTERNATE LOW PRESS INJECTION Cutset Report - LOOPWR 28-18 CCDP Total %

Cutset 4.62E-6 100 Displaying 729 of 729 Cutsets.

1 4.57E-6 98.8 IE-LOOPWR,RSW-STR-CF-ALL Cutset Report - LOOPWR 25 CCDP Total %

Cutset 3.29E-6 100 Displaying 166 of 166 Cutsets.

1 7.86E-7 23.9 IE-LOOPWR,ADS-XHE-XM-MDEPR,HCI-TDP-FR-TRAIN,RCI-TDP-FR-TRAIN 2

3.77E-7 11.4 IE-LOOPWR,ADS-XHE-XM-MDEPR,HCI-TDP-FR-TRAIN,RCI-XHE-XE-MISCAL 3

3.57E-7 10.9 IE-LOOPWR,ADS-XHE-XM-MDEPR,HCI-MOV-CC-IVFRO,HCI-MULTIPLE-INJECT,HCI-XHE-XL-INJECT,RCI-TDP-FR-TRAIN 4

2.25E-7 6.83 IE-LOOPWR,ADS-XHE-XM-MDEPR,HCI-TDP-TM-TRAIN,RCI-TDP-FR-TRAIN 5

2.17E-7 6.6 IE-LOOPWR,ADS-XHE-XM-MDEPR,HCI-TDP-FR-TRAIN,RCI-TDP-TM-TRAIN 6

1.71E-7 5.2 IE-LOOPWR,ADS-XHE-XM-MDEPR,HCI-MOV-CC-IVFRO,HCI-MULTIPLE-INJECT,HCI-XHE-XL-INJECT,RCI-XHE-XE-MISCAL 7

1.29E-7 3.91 IE-LOOPWR,ADS-XHE-XM-MDEPR,HCI-TDP-FS-TRAIN,RCI-TDP-FR-TRAIN 8

1.29E-7 3.91 IE-LOOPWR,ADS-XHE-XM-MDEPR,HCI-TDP-FR-TRAIN,RCI-TDP-FS-TRAIN 9

1.08E-7 3.27 IE-LOOPWR,ADS-XHE-XM-MDEPR,HCI-TDP-TM-TRAIN,RCI-XHE-XE-MISCAL 10 9.86E-8 3

IE-LOOPWR,ADS-XHE-XM-MDEPR,HCI-MOV-CC-IVFRO,HCI-MULTIPLE-INJECT,HCI-XHE-XL-INJECT,RCI-TDP-TM-TRAIN 11 6.17E-8 1.87 IE-LOOPWR,ADS-XHE-XM-MDEPR,HCI-TDP-FS-TRAIN,RCI-XHE-XE-MISCAL 12 5.95E-8 1.81 IE-LOOPWR,ADS-XHE-XM-MDEPR,HCI-TDP-FR-TRAIN,RCI-RESTART,RCI-TDP-FS-RSTRT,RCI-XHE-XL-RSTRT 13 5.84E-8 1.78 IE-LOOPWR,ADS-XHE-XM-MDEPR,HCI-MOV-CC-IVFRO,HCI-MULTIPLE-INJECT,HCI-XHE-XL-INJECT,RCI-TDP-FS-TRAIN 14 3.95E-8 1.2 IE-LOOPWR,ADS-XHE-XM-MDEPR,HCI-TDP-FR-TRAIN,RCI-MOV-FC-XFER,RCI-XHE-XL-XFER 15 3.68E-8 1.12 IE-LOOPWR,ADS-XHE-XM-MDEPR,HCI-TDP-TM-TRAIN,RCI-TDP-FS-TRAIN 16 3.55E-8 1.08 IE-LOOPWR,ADS-XHE-XM-MDEPR,HCI-TDP-FS-TRAIN,RCI-TDP-TM-TRAIN 17 3.37E-8 1.02 IE-LOOPWR,ADS-XHE-XM-MDEPR,HCI-XHE-XE-MISCAL,RCI-TDP-FR-TRAIN Cutset Report - LOOPWR 24 CCDP Total %

Cutset 2.52E-6 100 Displaying 11858 of 11858 Cutsets.

1 1.07E-7 4.26 IE-LOOPWR,ACP-CRB-CC-SB3EC,EPS-DGN-FR-DG3A,HCI-TDP-FR-TRAIN,RCI-TDP-FR-TRAIN 2

5.40E-8 2.15 IE-LOOPWR,ACP-CRB-CC-SB3EC,EPS-DGN-TM-DG3A,HCI-TDP-FR-TRAIN,RCI-TDP-FR-TRAIN

LER 259/11-001 A-13 CCDP Total %

Cutset 3

5.13E-8 2.04 IE-LOOPWR,ACP-CRB-CC-SB3EC,EPS-DGN-FR-DG3A,HCI-TDP-FR-TRAIN,RCI-XHE-XE-MISCAL 4

4.86E-8 1.93 IE-LOOPWR,ACP-CRB-CC-SB3EC,EPS-DGN-FR-DG3A,HCI-MOV-CC-IVFRO,HCI-MULTIPLE-INJECT,HCI-XHE-XL-INJECT,RCI-TDP-FR-TRAIN 5

3.63E-8 1.44 IE-LOOPWR,EPS-DGN-FR-DG3A,EPS-DGN-FR-DG3C,EPS-DGN-FR-DGC,HCI-TDP-FR-TRAIN,RCI-TDP-FR-TRAIN 6

3.06E-8 1.22 IE-LOOPWR,ACP-CRB-CC-SB3EC,EPS-DGN-FR-DG3A,HCI-TDP-TM-TRAIN,RCI-TDP-FR-TRAIN 7

2.97E-8 1.18 IE-LOOPWR,ACP-CRB-CC-SB3EC,DCP-XHE-XM-BB3,EPS-DGN-FR-DG3A,RCI-TDP-FR-TRAIN 8

2.96E-8 1.18 IE-LOOPWR,ACP-CRB-CC-SB3EC,EPS-DGN-FR-DG3A,HCI-TDP-FR-TRAIN,RCI-TDP-TM-TRAIN 9

2.59E-8 1.03 IE-LOOPWR,ACP-CRB-CC-SB3EC,EPS-DGN-TM-DG3A,HCI-TDP-FR-TRAIN,RCI-XHE-XE-MISCAL Cutset Report - LOOPWR 04 CCDP Total %

Cutset 6.83E-7 100 Displaying 705 of 705 Cutsets.

1 5.00E-7 73.2 IE-LOOPWR,OPR-XHE-XM-LI01,RHR-XHE-XM-ERROR 2

3.67E-8 5.38 IE-LOOPWR,CRD-MDP-TM-TRN3B,RSW-MDP-CF-RUN 3

2.80E-8 4.09 IE-LOOPWR,CRD-MDP-TM-TRN3B,RSW-MDP-CF-START 4

7.12E-9 1.04 IE-LOOPWR,CRD-MDP-TM-TRN3B,RHR-XHE-XM-ERROR,RS1-XHE-XM-ERROR 5

6.86E-9 1.01 IE-LOOPWR,CRD-MDP-TM-TRN3B,RHR-MOV-CC-F067,RHR-XHE-XM-ERROR 6

6.86E-9 1.01 IE-LOOPWR,CRD-MDP-TM-TRN3B,RHR-MOV-CC-F100,RHR-XHE-XM-ERROR 7

6.86E-9 1.01 IE-LOOPWR,CRD-MDP-TM-TRN3B,RHR-XHE-XM-ERROR,RSW-MOV-CC-F057 Cutset Report - LOOPWR 06 CCDP Total %

Cutset 5.43E-7 100 Displaying 222 of 222 Cutsets.

1 5.00E-7 92.1 IE-LOOPWR,CVS-XHE-XM-VENT,RHR-XHE-XM-ERROR 2

7.00E-9 1.29 IE-LOOPWR,OEP-XHE-XL-NR10HWR,PCA-TNK-FC-N2TKA,RHR-XHE-XM-ERROR Cutset Report - LOOPWR 28-34-3 CCDP Total %

Cutset 4.61E-7 100 Displaying 88 of 88 Cutsets.

1 4.57E-7 99.2 IE-LOOPWR,RRS-MDP-LK-SEALS,RSW-STR-CF-ALL Cutset Report - LOOPWR 12 CCDP Total %

Cutset 4.54E-7 100 Displaying 885 of 885 Cutsets.

1 9.53E-8 21 IE-LOOPWR,ACP-CRB-CC-SB3EC,EPS-DGN-FR-DG3A,OEP-XHE-XL-NR04HWR 2

4.81E-8 10.6 IE-LOOPWR,ACP-CRB-CC-SB3EC,EPS-DGN-TM-DG3A,OEP-XHE-XL-NR04HWR 3

1.41E-8 3.11 IE-LOOPWR,EPS-DGN-FR-DG3A,EPS-DGN-FR-DG3C,EPS-DGN-FR-DGC,OEP-XHE-XL-NR04HWR,OEP-XHE-XX-NR04HWR2 4

1.37E-8 3.02 IE-LOOPWR,ACP-CRB-CC-SB3EA,ACP-CRB-CC-SB3EB,ACP-CRB-CC-SB3EC 5

1.27E-8 2.8 IE-LOOPWR,EPS-DGN-FR-DG3A,EPS-DGN-FR-DG3C,EPS-DGN-FR-DGC,OEP-XHE-XL-NR04HWR,OEP-XHE-XX-NR04HWR3 6

1.00E-8 2.2 IE-LOOPWR,OPR-XHE-XM-ALPI,RHR-STR-CF-NLOCA 7

9.68E-9 2.13 IE-LOOPWR,ACP-CRB-CC-SB3EC,EPS-DGN-FS-DG3A,OEP-XHE-XL-NR04HWR 8

9.63E-9 2.12 IE-LOOPWR,RHR-MOV-CC-F100,RHR-STR-CF-NLOCA 9

9.63E-9 2.12 IE-LOOPWR,RHR-MOV-CC-F067,RHR-STR-CF-NLOCA 10 9.63E-9 2.12 IE-LOOPWR,RHR-STR-CF-NLOCA,RSW-MOV-CC-F057 11 9.01E-9 1.99 IE-LOOPWR,EPS-DGN-FR-DG3C,EPS-DGN-FR-DGC,EPS-DGN-TM-DG3A,OEP-XHE-XL-NR04HWR,OEP-XHE-XX-NR04HWR1

LER 259/11-001 A-14 CCDP Total %

Cutset 12 9.01E-9 1.99 IE-LOOPWR,EPS-DGN-FR-DG3A,EPS-DGN-FR-DGC,EPS-DGN-TM-DG3C,OEP-XHE-XL-NR04HWR,OEP-XHE-XX-NR04HWR1 13 8.21E-9 1.81 IE-LOOPWR,EPS-DGN-FR-DG3A,EPS-DGN-TM-DG3C,EPS-DGN-TM-DGC,OEP-XHE-XL-NR04HWR 14 8.21E-9 1.81 IE-LOOPWR,EPS-DGN-FR-DG3C,EPS-DGN-TM-DG3A,EPS-DGN-TM-DGC,OEP-XHE-XL-NR04HWR 15 8.01E-9 1.77 IE-LOOPWR,ACP-CRB-CC-SB3EA,ACP-CRB-CC-SB3EC,OEP-XHE-XL-NR04HWR 16 7.12E-9 1.57 IE-LOOPWR,EPS-DGN-FR-DG3C,EPS-DGN-FR-DGC,EPS-DGN-TM-DG3A,OEP-XHE-XL-NR04HWR,OEP-XHE-XX-NR04HWR2 17 7.12E-9 1.57 IE-LOOPWR,EPS-DGN-FR-DG3A,EPS-DGN-FR-DGC,EPS-DGN-TM-DG3C,OEP-XHE-XL-NR04HWR,OEP-XHE-XX-NR04HWR2 18 7.12E-9 1.57 IE-LOOPWR,EPS-DGN-FR-DG3A,EPS-DGN-FR-DG3C,EPS-DGN-TM-DGC,OEP-XHE-XL-NR04HWR,OEP-XHE-XX-NR04HWR2 19 6.66E-9 1.47 IE-LOOPWR,ACP-BAC-LP-SB3B,ACP-BAC-TM-SB3A 20 6.40E-9 1.41 IE-LOOPWR,EPS-DGN-FR-DG3A,EPS-DGN-FR-DG3C,EPS-DGN-TM-DGC,OEP-XHE-XL-NR04HWR,OEP-XHE-XX-NR04HWR3 21 5.89E-9 1.3 IE-LOOPWR,ACP-CRB-CC-SB3EC,EPS-SEQ-FO-DG3A,OEP-XHE-XL-NR04HWR Cutset Report - LOOPWR 13 CCDP Total %

Cutset 2.79E-7 100 Displaying 44 of 44 Cutsets.

1 2.50E-7 89.7 IE-LOOPWR,ADS-XHE-XM-MDEPR,RHR-XHE-XM-ERROR 2

1.53E-8 5.49 IE-LOOPWR,ADS-XHE-XM-MDEPR,RHR-MOV-CF-SPCINJEC 3

5.00E-9 1.79 IE-LOOPWR,ADS-XHE-XM-MDEPR,RHR-STR-CF-NLOCA Cutset Report - LOOPWR 28-30 CCDP Total %

Cutset 2.76E-7 100 Displaying 39 of 39 Cutsets.

1 1.81E-7 65.6 IE-LOOPWR,RCI-TDP-FR-TRAIN,RSW-STR-CF-ALL 2

5.00E-8 18.1 IE-LOOPWR,RCI-TDP-TM-TRAIN,RSW-STR-CF-ALL 3

2.97E-8 10.7 IE-LOOPWR,RCI-TDP-FS-TRAIN,RSW-STR-CF-ALL 4

1.37E-8 4.96 IE-LOOPWR,RCI-RESTART,RCI-TDP-FS-RSTRT,RCI-XHE-XL-RSTRT,RSW-STR-CF-ALL Referenced Events Event Description Probability ACP-BAC-LP-SB3B SHUTDOWN BOARD 3B IS UNAVAILABLE 3.33E-5 ACP-BAC-TM-SB3A SHUTDOWN BOARD 3A IS UNAVAILABLE 2.00E-4 ACP-CRB-CC-SB3EA SD BOARD 3EA OFFSITE POWER SUPPLY BREAKER FAILS TO OPEN 2.39E-3 ACP-CRB-CC-SB3EB SD BOARD 3EB OFFSITE POWER SUPPLY BREAKER FAILS TO OPEN 2.39E-3 ACP-CRB-CC-SB3EC SD BOARD 3EC OFFSITE POWER SUPPLY BREAKER FAILS TO OPEN 2.39E-3 ADS-XHE-XM-MDEPR OPERATOR FAILS TO DEPRESSURIZE THE REACTOR 5.00E-4 CRD-MDP-TM-TRN3B CRD TRAIN B IS UNAVAILABLE BECAUSE OF MAINTENANCE 1.43E-2 CVS-XHE-XM-VENT OPERATOR FAILS TO VENT CONTAINMENT 1.00E-3 DCP-XHE-XM-BB3 OPERATOR FAILS TO ALIGN BACKUP POWER TO DC-BATBD3 1.10E-2 EPS-DGN-FR-DG3A DIESEL GENERATOR 3A FAILS TO RUN 2.85E-2 EPS-DGN-FR-DG3C DIESEL GENERATOR 3C FAILS TO RUN 2.85E-2 EPS-DGN-FR-DGC DIESEL GENERATOR C FAILS TO RUN 2.85E-2 EPS-DGN-FS-DG3A DIESEL GENERATOR 3A FAILS TO START 2.89E-3 EPS-DGN-TM-DG3A DG A IS UNAVAILABLE BECAUSE OF MAINTENANCE 1.43E-2

LER 259/11-001 A-15 Event Description Probability EPS-DGN-TM-DG3C DG C IS UNAVAILABLE BECAUSE OF MAINTENANCE 1.43E-2 EPS-DGN-TM-DGC DG C IS UNAVAILABLE BECAUSE OF MAINTENANCE 1.43E-2 EPS-SEQ-FO-DG3A DG 3A LOAD SEQUENCER FAILS TO OPERATE 1.76E-3 HCI-MOV-CC-IVFRO HPCI INJECTION VALVE FAILS TO REOPEN 1.50E-1 HCI-MULTIPLE-INJECT MULTIPLE HPCI INJECTIONS REQUIRED 1.50E-1 HCI-TDP-FR-TRAIN HPCI PUMP TRAIN FAILS TO RUN GIVEN IT STARTED 3.97E-2 HCI-TDP-FS-TRAIN HPCI PUMP FAILS TO START 6.49E-3 HCI-TDP-TM-TRAIN HPCI TRAIN IS UNAVAILABLE BECAUSE OF MAINTENANCE 1.13E-2 HCI-XHE-XE-MISCAL MISCALIBRATION OF HPCI EXHAUST PRESSURE INSTRUMENTATION 1.70E-3 HCI-XHE-XL-INJECT OPERATOR FAILS TO RECOVER HPCI INJECT MOV FAILURE TO REOPEN 8.00E-1 IE-LOOPWR LOSS OF OFFSITE POWER INITIATOR (WEATHER-RELATED) 1.00E+0 OEP-XHE-XL-NR04HWR OPERATOR FAILS TO RECOVER OFFSITE POWER IN 4 HOURS (WEATHER-RELATED) 1.40E-3 OEP-XHE-XL-NR10HWR OPERATOR FAILS TO RECOVER OFFSITE POWER IN 10 HOURS (WEATHER-RELATED) 1.40E-3 OEP-XHE-XX-NR04HWR1 CONVOLUTION FACTOR FOR 1FTR-OPR (4HR-WR AVAIL) 5.53E-1 OEP-XHE-XX-NR04HWR2 CONVOLUTION FACTOR FOR 2FTR-OPR (4HR-WR AVAIL) 4.37E-1 OEP-XHE-XX-NR04HWR3 CONVOLUTION FACTOR FOR 3FTR-OPR (4HR-WR AVAIL) 3.93E-1 OPR-XHE-XM-ALPI OPERATOR FAILS TO START/CONTROL ALTERNATE LOW PRES INJECTION 1.00E-3 OPR-XHE-XM-LI01 OPERATOR FAILS TO START/CONTROL LATE INJECTION 1.00E-3 PCA-TNK-FC-N2TKA NITROGEN SUPPLY TANK A IS UNAVAILABLE 1.00E-2 RCI-MOV-FC-XFER RCIC FAILS TO TRANSFER DURING RECIRCULATION 7.97E-3 RCI-RESTART RESTART OF RCIC IS REQUIRED 1.50E-1 RCI-TDP-FR-TRAIN RCIC PUMP FAILS TO RUN GIVEN THAT IT STARTED 3.97E-2 RCI-TDP-FS-RSTRT RCIC FAILS TO RESTART GIVEN START AND SHORT-TERM RUN 8.00E-2 RCI-TDP-FS-TRAIN RCIC PUMP FAILS TO START 6.49E-3 RCI-TDP-TM-TRAIN RCIC PUMP TRAIN IS UNAVAILABLE BECAUSE OF MAINTENANCE 1.10E-2 RCI-XHE-XE-MISCAL RCIC FAILS FROM MISCALIBRATION OF RUPTURE DISC 1.90E-2 RCI-XHE-XL-RSTRT OPERATOR FAILS TO RECOVER RCIC FAILURE TO RESTART 2.50E-1 RCI-XHE-XL-XFER OPERATOR FAILS TO RECOVER SUCTN XFER FAILURE 2.50E-1 RHR-MOV-CC-F067 LPCI LOOP B INJECTION VALVE 74-67 FAILS TO OPEN 9.63E-4 RHR-MOV-CC-F100 RHR CROSS TIE MOV 74-100 FAILS TO OPEN 9.63E-4 RHR-MOV-CF-SPCINJEC SPC INJECTION VALVES FAIL FROM COMMON CAUSE 3.06E-5 RHR-STR-CF-NLOCA SUPPRESSION POOL STRAINERS FAIL FROM COMMON CAUSE (NON-LOCA) 1.00E-5 RHR-XHE-XM-ERROR OPERATOR FAILS TO START/CONTROL RHR 5.00E-4 RRS-MDP-LK-SEALS RECIRCULATION PUMP SEALS FAIL 1.00E-1 RS1-XHE-XM-ERROR OPERATOR FAILS TO ALIGN RHRSW INJECTION 1.00E-3 RSW-MDP-CF-RUN RHRSW PUMPS FAIL FROM COMMON CAUSE TO RUN 2.58E-6 RSW-MDP-CF-START RHRSW PUMPS FAIL FROM COMMON CAUSE TO START 1.96E-6 RSW-MOV-CC-F057 RHRSW/RHR CROSS TIE MOV 23-57 FAILS TO OPEN 9.63E-4 RSW-STR-CF-ALL RHRSW STRAINERS FAIL FROM COMMON CAUSE 4.57E-6

LER 259/11-001 B-1 Appendix B: Key Event Trees Figure B-1. Browns Ferry LOOP Event Tree (Weather-Related).

IE-LOOPWR LOSS OF OFFSITE POWER INITIATOR (WEATHER-RELATED)

RPS REACTOR SHUTDOWN FTF-SBO EPS TRANSFER BRANCH SBO SRV SRV'S CLOSE HPI HIGH PRESSURE INJECTION (RCIC or HPCI)

SPC SUPPRESSION POOL COOLING DEP MANUAL REACTOR DEPRESS LPI LOW PRESSURE INJECTION (CS or LPCI)

VA ALTERNATE LOW PRESS INJECTION RHR LOSS OF RESIDUAL HEAT REMOVAL SYSTEMS CVS CONTAINMENT VENTING LI LATE INJECTION End State (Phase - CD) 1 OK 2

OK 3

OK LI01 4

CD 5

OK 6

CD 7

OK RH1 8

OK LI02 9

CD 10 OK 11 CD 12 CD 13 CD 14 OK 15 OK LI01 16 CD 17 OK 18 CD 19 OK RH1 20 OK LI02 21 CD 22 OK 23 CD 24 CD 25 CD P1 26 LOOP-1 P2 27 LOOP-2 28 SBO 29 ATWS 30 CD

LER 259/11-001 B-2 Figure B-2. Browns Ferry SBO Event Tree.

FTF-SBO EPS TRANSFER BRANCH SBO SRV SRV'S CLOSE RPSL RECIRC PUMP SEAL INTEGRITY RCI RCIC HCI HPCI EXT ACTIONS TO EXTEND ECCS OPERATION FTF-SBO DEP01 MANUAL REACTOR DEPRESS FWS FIREWATER INJECTION OPR OFFSITE POWER RECOVERY DGR DIESEL GENERATOR RECOVERY CVS CONTAINMENT VENTING LI LATE INJECTION End State (Phase - CD) 1

@SBO-OP OPR-12H 2

OK DGR-12H 3

OK LI-EXT 4

CD CVS01 5

OK 6

CD 7

@SBO-OP OPR-12H 8

OK DGR-12H 9

OK LI02 10 CD CVS01 11 OK 12 CD 13

@SBO-OP OPR-04H 14 OK DGR-04H 15 CD 16

@SBO-OP OPR-04H 17 OK DGR-04H 18 CD RCI01 19

@SBO-OP OPR-12H 20 OK DGR-12H 21 OK LI02 22 CD CVS01 23 OK 24 CD 25

@SBO-OP OPR-04H 26 OK DGR-04H 27 CD 28

@SBO-OP OPR-04H 29 OK DGR-04H 30 CD HCI01 31

@SBO-OP OPR-30M 32 OK DGR-30M 33 CD 34 SBO-1 P1 35 SBO-1 P2 36 SBO-2

LER 259/11-001 C-1 Appendix C: Sensitivity Analysis for Losses of SDC Shutdown Events Description. On April 28, 2011, at 23:38, with all three units in Mode 4 (Cold Shutdown) and power supplied to the 4kV shutdown boards by onsite EDGs, operators observed a small leak on the governor hydraulic oil system piping for the EDG C. The leak rapidly progressed from one drop per minute to a steady stream/spray. Operators shut down the EDG C, due to worsening voltage and frequency fluctuations. The 4kV Shutdown Board C, which was being powered by the EDG C, de-energized and resulted in a loss of power to the RPS Train B causing a PCIS actuation. The Group 2 PCIS isolation caused the loss of SDC on Unit 1 for 47 minutes. In addition, the loss of power to the 4kV Shutdown Board C also caused the loss of the RHR Pump 2B leading to a momentary suspension of SDC for Unit 2. Shutdown Cooling for Unit 2 was immediately restored using the RHR Pump 2D. Unit 3 was not affected by this event. Additional details are provided in Reference 3.

On May 2, 2011, at approximately 06:26, the EDG A Output Breaker tripped interrupting power to 4kV Shutdown Board A, causing a loss of power to a portion of the Unit 1 RPS leading to PCIS Group 2, 3, 6, and 8 isolations. The Group 2 isolation caused the loss of SDC on Unit 1 for approximately 57 minutes. Power was restored to 4kV Shutdown Board A at 06:43. Units 2 and 3 were not affected by this event. Additional details are provided in Reference 4.

Sensitivity Analysis Assumptions. The two losses of SDC on April 28th (Units 1 and 2) and May 2nd (Unit 1 only) are expected to have similar CCDPs because both events were the result of losses of power to a shutdown board, similar durations of the loss of SDC, and similar operator actions to restore SDC. Therefore, for the purposes of the sensitivity analysis, the loss of SDC on April 28th for Unit 1 was analyzed as a representative case for both losses of SDC.

For this analysis, a loss of SDC event tree (IESD-LOSDC-M4) for Browns Ferry Unit 1 SPAR model was created and is shown below.

IESD-LOSDC-M4 INITIATOR OF LOSDC IN MODE 4 SD-LPI-CS LP INJECTION OR CORE SPRAY SD-HPI HI PRESSURE INJECTION SYSTEMS SD-SPC SUPPERESSION POOL COOLING SD-ALT-HEAT ALTERNATE HEAT REMOVAL PATHS SD-CVS CONTAINMENT VENTING SD-LI LATE INJECTION SD-REC-SDC-LT ESTABLLISH SDC/SPC COOLIING End State (Phase - CD) 1 OK 2

OK 3

OK SD-LI03 4

OK 12H 5

CD-SD 6

OK 12H 7

CD-SD 8

OK 9

OK SD-LI02 10 OK 2D 11 CD-SD 12 OK 2D 13 CD-SD 14 OK SD-LI02 15 OK 5H 16 CD-SD 17 OK SD-LI02 18 OK 5H 19 CD-SD 20 OK 5H 21 CD-SD

LER 259/11-001 C-2 In addition, the following modeling assumptions were made for the analysis of the Unit 1 loss of SDC on April 28th:

A truncation of 1x10-13 was used to ensure the low HEPs in the loss of SDC event tree were preserved in the cutsets.

The loss of SDC cooling initiating event probability (IESD-LOSDC-M4) was set to 1.0. All other shutdown initiating events probabilities were set to zero.

The following house events were set to TRUE for this weather related LOOP event.

- HE-LOOP (Loss of Offsite Power IE Has Occurred)

- HE-LOOP-A (Loss of Offsite Power to 4kV AC Shutdown Board A)

- HE-LOOP-B (Loss of Offsite Power to 4kV AC Shutdown Board B)

- HE-LOOP-C (Loss of Offsite Power to 4kV AC Shutdown Board C)

- HE-LOOP-D (Loss of Offsite Power to 4kV AC Shutdown Board D)

- HE-LOOP-WR (Loss of Offsite Power IE Has OccurredWeather-Related)

The basic event OEP-VCF-LP-SITEWR (Weather-Related Site LOOP) was set to TRUE, since the LOOP affected all three units.

The basic events SD-XHE-XR-SDC-5H (Operators Fail to Recover SDC in 5 Hours), SD-XHE-XR-SDC-12H (Operators Fail to Recover SDC in 12 Hours), and SD-XHE-XR-SDC-2D (Operators Fail to Recover SDC in 2 Days) were calculated based on References 6 and 7.

- Description and Event Context-Loss SDC due to the PCIS.

- Operator Action Success Criteria-The recovery of SDC requires the resetting of the PCIS and the realignment of the applicable SDC system valves.

- Cues-A loss of SDC caused by an automatic isolation (PCIS Group II or due to high discharge header pressure) would have at least one of the one of the following cues based on AOI-74-1:

RHR SYS I/II Discharge or SDC Header Pressure High at 100 psi.

1-FCV-74-47, RHR SDC Suction Outboard Isolation Valve Closed.

1-FCV-74-48, RHR SDC Suction Inboard Isolation Valve Closed.

1-FCV-74-53, RHR System I LPCI Inboard Injection Valve Closed.

1-FCV-74-67, RHR System II LPCI Inboard Injection Valve Closed.

- Diagnosis/Action-These HFEs contain sufficient diagnosis activities. The nominal action component of the HEPs is 0.001. No event information is available to warrant a change in the action PSFs for these HEPs. The table below shows the PSFs that were adjusted; all other PSFs were determined to be Nominal (i.e., x1).

- Based on the adjusted PSFs, the following HEPs were recalculated:

Therefore, basic events SD-REC-SDC-5H, SD-REC-SDC-12H, and SD-REC-SDC-2D were set to 1.4 x10-3.

LER 259/11-001 C-3 PSF Multiplier Notes Time Available 0.01 The recovery of SDC is possible by resetting the PCIS isolation signal and restoring the SDC alignment. The time required to perform these actions is estimated to be approximately 40 minutes; therefore, the minimum time for diagnosis is approximately 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br />. Thus, the available time for these HFEs were assigned as Expansive Time (i.e., x0.01; time available is >2 times nominal and >30 minutes).

Stress 2

The PSF for diagnosis stress is assigned a value of High Stress (i.e., x2) for the recovery of loss of SDC due PCIS.

Complexity 2

The PSF for diagnosis complexity is assigned a value of Moderately Complex (i.e., x2) for the multiple actions in and out of the MCR to reset the PCIS and restore the SDC alignment.

EDG C was tripped by operators due to a governor hydraulic oil leak. Therefore, basic event EPS-DGN-FR-DGC (EDG C Fails to Run) was set to TRUE.

EDG 3B was not available during the event due to planned maintenance. Therefore, basic event EDG-DGN-TM-DG3B (EDG 3B is Unavailable Due to Test or Maintenance) was set to TRUE.

Results. The point estimate CCDP for the Unit 1 loss of SDC on April 28th is 2.4x10-7. The dominant accident sequence, SD-LOSDC-M4 Sequence 11 (CCDP = 2.7x10-7) contributes 49.8% of the total internal events CCDP. The events and important component failures in SD-LOSDC-M4 Sequence 11 are:

Loss of SDC occurs, Low pressure injection or core spray fails, High pressure injection succeeds, Alternate heat removal fails, Containment venting succeeds, Residual heat removal service water cooling fails, Operators fail to recover SDC in 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br />.

The tables below provide the following:

Modified basic events and initiating event frequencies, including base and change case probabilities/frequencies.

Dominant sequences (including CCDPs).

Sequence logic for all dominant sequences.

Fault tree definitions.

Sequence cutsets.

Definitions and probabilities for key basic events.

LER 259/11-001 C-4 Summary of Conditional Event Changes Event Description Cond.

Value Nominal Value EPS-DGN-FR-DGC DIESEL GENERATOR C FAILS TO RUN TRUE 2.85E-2 EPS-DGN-TM-DG3B DG B IS UNAVAILABLE BECAUSE OF MAINTENANCE TRUE 1.43E-2 HE-LOOP HOUSE EVENT - LOSS OF OFFSITE POWER IE HAS OCCURRED TRUE FALSE HE-LOOP-A LOSS OF OFFSITE POWER TO 4KV AC SHUTDOWN BOARD A TRUE FALSE HE-LOOP-B LOSS OF OFFSITE POWER TO 4KV AC SHUTDOWN BOARD B TRUE FALSE HE-LOOP-C LOSS OF OFFSITE POWER TO 4 KVAC SHUTDOWN BOARD C TRUE FALSE HE-LOOP-D LOSS OF OFFSITE POWER TO 4 KVAC SHUTDOWN BOARD D TRUE FALSE HE-LOOPWR HOUSE EVENT - LOSS OF OFFSITE POWER IE HAS OCCURRED (WEATHER-RELATED)

TRUE FALSE IESD-LOSDC-M4a INITIATOR OF LOSDC IN MODE 4 1.00E+0 1.00E+0 OEP-VCF-LP-SITEWR SITE LOOP (WEATHER-RELATED)

TRUE 6.92E-1 SD-XHE-XR-SDC-12H FAIL TO RECOVER SDC LATE - 12 HRS 1.40E-3 5.00E-1 SD-XHE-XR-SDC-2D FAIL TO RECOVER SDC LATE - 2 days 1.40E-3 3.10E-1 SD-XHE-XR-SDC-5H FAIL TO RECOVER SDC LATE - 5 HRS 1.40E-3 8.00E-1

a.

All other initiating event probabilities were set to zero.

Implied Event Changes as per RASP Guidance Event Description Cond.

Value Nominal Value EPS-DGN-FR-DG3B DIESEL GENERATOR 3B FAILS TO RUN 1.00E+0 2.85E-2 EPS-DGN-FS-DG3B DIESEL GENERATOR 3B FAILS TO START 1.00E+0 2.89E-3 EPS-DGN-FS-DGC DIESEL GENERATOR C FAILS TO START FALSE 2.89E-3 EPS-DGN-TM-DGC DG C IS UNAVAILABLE BECAUSE OF MAINTENANCE TRUE 1.43E-2 EPS-DGN-CF-START DIESEL GENERATORS FAIL FROM COMMON CAUSE TO START 4.71E-6 4.75E-6 EPS-DGN-CF-RUN DIESEL GENERATORS FAIL FROM COMMON CAUSE TO RUN 2.08E-3 5.93E-5 EPS-DGN-CF-3RUN UNIT 3 DIESEL GENERATORS FAIL FROM COMMON CAUSE TO RUN 1.22E-4 5.93E-5 EPS-DGN-CF-3START UNIT 3 DIESEL GENERATORS FAIL FROM COMMON CAUSE TO START 8.01E-6 4.75E-6 Dominant Sequence Results Only items contributing at least 1.0% to the total CCDP are displayed.

Event Tree Sequence CCDP

% Contribution Description SD-LOSDC-M4 11 1.90E-7 79.5%

SD-LPI-CS, /SD-HPI, SD-ALT-HEAT, /SD-CVS, SD-LI02, SD-REC-SDC-2D SD-LOSDC-M4 05 3.98E-8 16.7%

/SD-LPI-CS, SD-SPC, SD-ALT-HEAT, /SD-CVS, SD-LI, SD-REC-SDC-12H SD-LOSDC-M4 07 5.26E-9 2.2%

/SD-LPI-CS, SD-SPC, SD-ALT-HEAT, SD-CVS, SD-REC-SDC-12H SD-LOSDC-M4 13 2.94E-9 1.2%

SD-LPI-CS, /SD-HPI, SD-ALT-HEAT, SD-CVS, SD-REC-SDC-2D Total 2.39E-7 100%

Referenced Fault Trees Fault Tree Description SD-ALT-HEAT ALTERNATE HEAT REMOVAL PATHS SD-CVS CONTAINMENT VENTING

LER 259/11-001 C-5 Fault Tree Description SD-LI LATE INJECTION SD-LI02 RESIDUAL HEAT REMOVAL SERVICE WATER COOLING SD-LPI-CS LP INJECTION OR CORE SPRAY SD-REC-SDC-12H ESTABLISH NORMAL SDC LONG TERM SD-REC-SDC-2D ESTABLISH NORMAL SDC LONG TERM SD-SPC SUPPERESSION POOL COOLING Cutset Report - SD-LOSDC-M4 11 CCDP Total %

Cutset 1.90E-7 100 Displaying 7523 of 7523 Cutsets.

1 1.40E-8 7.38 IESD-LOSDC-M4,EPS-DGN-CF-ALL,SD-XHE-XR-SDC-2D 2

1.37E-8 7.23 IESD-LOSDC-M4,ACP-CRB-CF-OPSD,SD-XHE-XR-SDC-2D 3

1.25E-8 6.58 IESD-LOSDC-M4,EPS-DGN-FR-DG3A,EPS-DGN-FR-DG3C,ESW-XHE-XL-NOREC2,SD-XHE-XR-SDC-2D 4

6.40E-9 3.37 IESD-LOSDC-M4,RSW-STR-CF-ALL,SD-XHE-XR-SDC-2D 5

6.29E-9 3.32 IESD-LOSDC-M4,EPS-DGN-FR-DG3C,EPS-DGN-TM-DG3A,ESW-XHE-XL-NOREC2,SD-XHE-XR-SDC-2D 6

6.29E-9 3.32 IESD-LOSDC-M4,EPS-DGN-FR-DG3A,EPS-DGN-TM-DG3C,ESW-XHE-XL-NOREC2,SD-XHE-XR-SDC-2D 7

4.87E-9 2.57 IESD-LOSDC-M4,EPS-DGN-CF-3RUN,EPS-DGN-FR-DGB,SD-XHE-XR-SDC-2D 8

4.82E-9 2.54 IESD-LOSDC-M4,ACP-XHE-XE-ERRORC,EPS-DGN-FR-DG3A,ESW-XHE-XL-NOREC2,SD-XHE-XR-SDC-2D 9

3.17E-9 1.67 IESD-LOSDC-M4,EPS-DGN-TM-DG3A,EPS-DGN-TM-DG3C,ESW-XHE-XL-NOREC2,SD-XHE-XR-SDC-2D 10 2.92E-9 1.54 IESD-LOSDC-M4,ACP-XHE-XM-EPSXT,EPS-DGN-CF-RUN,SD-XHE-XR-SDC-2D 11 2.71E-9 1.43 IESD-LOSDC-M4,ACP-CRB-CC-1614,EPS-DGN-FR-DG3C,EPS-DGN-FR-DGB,SD-XHE-XR-SDC-2D 12 2.45E-9 1.29 IESD-LOSDC-M4,EPS-DGN-CF-3RUN,EPS-DGN-TM-DGB,SD-XHE-XR-SDC-2D 13 2.43E-9 1.28 IESD-LOSDC-M4,ACP-XHE-XE-ERRORC,EPS-DGN-TM-DG3A,ESW-XHE-XL-NOREC2,SD-XHE-XR-SDC-2D 14 2.36E-9 1.25 IESD-LOSDC-M4,EPS-DGN-CF-RUN,EPS-DGN-FR-DG3A,EPS-DGN-FR-DG3C,SD-XHE-XR-SDC-2D 15 2.36E-9 1.25 IESD-LOSDC-M4,EPS-DGN-CF-RUN,EPS-DGN-FR-DG3A,EPS-DGN-FR-DG3D,SD-XHE-XR-SDC-2D 16 2.36E-9 1.25 IESD-LOSDC-M4,EPS-DGN-CF-RUN,EPS-DGN-FR-DG3C,EPS-DGN-FR-DG3D,SD-XHE-XR-SDC-2D 17 2.26E-9 1.19 IESD-LOSDC-M4,EPS-DGN-CF-3RUN,RSW-MDP-TM-TRNC1,SD-XHE-XR-SDC-2D Cutset Report - SD-LOSDC-M4 05 CCDP Total %

Cutset 3.98E-8 100 Displaying 14405 of 14405 Cutsets.

1 4.59E-10 1.15 IESD-LOSDC-M4,CRD-SYS-FC-ARUN,EPS-DGN-FR-DG3A,EPS-DGN-FR-DG3C,EPS-DGN-FR-DGB,EPS-DGN-FR-DGD,SD-XHE-XR-SDC-12H 2

4.59E-10 1.15 IESD-LOSDC-M4,CRD-SYS-FC-BRUN,EPS-DGN-FR-DG3A,EPS-DGN-FR-DG3C,EPS-DGN-FR-DGB,EPS-DGN-FR-DGD,SD-XHE-XR-SDC-12H Cutset Report - SD-LOSDC-M4 07 CCDP Total %

Cutset 5.26E-9 100 Displaying 2810 of 2810 Cutsets.

1 3.23E-10 6.14 IESD-LOSDC-M4,CAD-TNK-FC-N2TKA,EPS-DGN-FR-DG3A,EPS-DGN-FR-DG3C,EPS-DGN-FR-DGB,SD-XHE-XR-SDC-12H 2

1.63E-10 3.09 IESD-LOSDC-M4,CAD-TNK-FC-N2TKA,EPS-DGN-FR-DG3A,EPS-DGN-FR-DGB,EPS-DGN-TM-DG3C,SD-XHE-XR-SDC-12H 3

1.63E-10 3.09 IESD-LOSDC-M4,CAD-TNK-FC-N2TKA,EPS-DGN-FR-DG3C,EPS-DGN-FR-DGB,EPS-DGN-TM-DG3A,SD-XHE-XR-SDC-12H

LER 259/11-001 C-6 CCDP Total %

Cutset 4

1.63E-10 3.09 IESD-LOSDC-M4,CAD-TNK-FC-N2TKA,EPS-DGN-FR-DG3A,EPS-DGN-FR-DG3C,EPS-DGN-TM-DGB,SD-XHE-XR-SDC-12H 5

1.25E-10 2.37 IESD-LOSDC-M4,ACP-XHE-XE-ERRORC,CAD-TNK-FC-N2TKA,EPS-DGN-FR-DG3A,EPS-DGN-FR-DGB,SD-XHE-XR-SDC-12H 6

8.21E-11 1.56 IESD-LOSDC-M4,CAD-TNK-FC-N2TKA,EPS-DGN-FR-DGB,EPS-DGN-TM-DG3A,EPS-DGN-TM-DG3C,SD-XHE-XR-SDC-12H 7

8.21E-11 1.56 IESD-LOSDC-M4,CAD-TNK-FC-N2TKA,EPS-DGN-FR-DG3C,EPS-DGN-TM-DG3A,EPS-DGN-TM-DGB,SD-XHE-XR-SDC-12H 8

8.21E-11 1.56 IESD-LOSDC-M4,CAD-TNK-FC-N2TKA,EPS-DGN-FR-DG3A,EPS-DGN-TM-DG3C,EPS-DGN-TM-DGB,SD-XHE-XR-SDC-12H 9

6.29E-11 1.2 IESD-LOSDC-M4,ACP-XHE-XE-ERRORC,CAD-TNK-FC-N2TKA,EPS-DGN-FR-DG3A,EPS-DGN-TM-DGB,SD-XHE-XR-SDC-12H 10 6.29E-11 1.2 IESD-LOSDC-M4,ACP-XHE-XE-ERRORC,CAD-TNK-FC-N2TKA,EPS-DGN-FR-DGB,EPS-DGN-TM-DG3A,SD-XHE-XR-SDC-12H 11 5.43E-11 1.03 IESD-LOSDC-M4,DCP-XHE-XM-1ABC,EPS-DGN-FR-DG3A,ESW-MDP-FS-PMPD3,SD-XHE-XR-SDC-12H 12 5.43E-11 1.03 IESD-LOSDC-M4,DCP-XHE-XM-1ABC,EPS-DGN-FR-DG3C,ESW-MDP-FS-PMPD3,SD-XHE-XR-SDC-12H Cutset Report - SD-LOSDC-M4 13 CCDP Total %

Cutset 2.94E-9 100 Displaying 2052 of 2052 Cutsets.

1 1.54E-10 5.24 IESD-LOSDC-M4,DCP-BDC-TM-RMOV1B,SD-XHE-XR-SDC-2D,SIS-ACT-CF-LRP 2

1.54E-10 5.24 IESD-LOSDC-M4,DCP-BDC-TM-RMOV1A,SD-XHE-XR-SDC-2D,SIS-ACT-CF-LRP 3

1.40E-10 4.76 IESD-LOSDC-M4,CAD-TNK-FC-N2TKA,EPS-DGN-CF-ALL,SD-XHE-XR-SDC-2D 4

1.37E-10 4.66 IESD-LOSDC-M4,ACP-CRB-CF-OPSD,CAD-TNK-FC-N2TKA,SD-XHE-XR-SDC-2D 5

1.25E-10 4.25 IESD-LOSDC-M4,CAD-TNK-FC-N2TKA,EPS-DGN-FR-DG3A,EPS-DGN-FR-DG3C,ESW-XHE-XL-NOREC2,SD-XHE-XR-SDC-2D 6

6.40E-11 2.18 IESD-LOSDC-M4,CAD-TNK-FC-N2TKA,RSW-STR-CF-ALL,SD-XHE-XR-SDC-2D 7

6.29E-11 2.14 IESD-LOSDC-M4,CAD-TNK-FC-N2TKA,EPS-DGN-FR-DG3C,EPS-DGN-TM-DG3A,ESW-XHE-XL-NOREC2,SD-XHE-XR-SDC-2D 8

6.29E-11 2.14 IESD-LOSDC-M4,CAD-TNK-FC-N2TKA,EPS-DGN-FR-DG3A,EPS-DGN-TM-DG3C,ESW-XHE-XL-NOREC2,SD-XHE-XR-SDC-2D 9

4.87E-11 1.66 IESD-LOSDC-M4,CAD-TNK-FC-N2TKA,EPS-DGN-CF-3RUN,EPS-DGN-FR-DGB,SD-XHE-XR-SDC-2D 10 4.82E-11 1.64 IESD-LOSDC-M4,ACP-XHE-XE-ERRORC,CAD-TNK-FC-N2TKA,EPS-DGN-FR-DG3A,ESW-XHE-XL-NOREC2,SD-XHE-XR-SDC-2D 11 3.17E-11 1.08 IESD-LOSDC-M4,CAD-TNK-FC-N2TKA,EPS-DGN-TM-DG3A,EPS-DGN-TM-DG3C,ESW-XHE-XL-NOREC2,SD-XHE-XR-SDC-2D Referenced Events Event Description Probability ACP-CRB-CC-1614 SD BOARD A OFFSITE POWER SUPPLY BREAKER FAILS TO OPEN 2.39E-3 ACP-CRB-CF-OPSD COMMON CAUSE FAILURE OF OFFSITE POWER FEED TO SHUTDOWN BOARDS 9.79E-6 ACP-XHE-XE-ERRORC OPERATOR FAILS TO ALIGN 3C DIESEL TO SHUTDOWN BOARD C 1.10E-2 ACP-XHE-XM-EPSXT OPERATOR FAILS TO CROSSTIE EMERGENCY BUSES 1.00E-3 CAD-TNK-FC-N2TKA N2 SUPPLY TANK A IS UNAVAILABLE (CONTAINMENT AIR DILUTION) 1.00E-2 CRD-SYS-FC-ARUN CRD PUMP A IS RUNNING PUMP B IS IN STANDBY 5.00E-1 CRD-SYS-FC-BRUN CRD PUMP B IS RUNNING PUMP A IS IN STANDBY 5.00E-1 DCP-BDC-TM-RMOV1A 250 VDC RMOV BOARD 1A IS UNAVAILABLE DUE TO TM 2.15E-4 DCP-BDC-TM-RMOV1B 250 VDC RMOV BOARD 1B IS UNAVAILABLE 2.15E-4 DCP-XHE-XM-1ABC OPERATOR FAILS TO ALIGN BACKUP POWER TO DC-MOV1A B C 1.00E-3 EPS-DGN-CF-3RUN UNIT 3 DIESEL GENERATORS FAIL FROM COMMON CAUSE TO RUN 1.22E-4

LER 259/11-001 C-7 Event Description Probability EPS-DGN-CF-ALL ALL 8 DIESEL GENERATORS FAIL FROM COMMON CAUSE 1.00E-5 EPS-DGN-CF-RUN DIESEL GENERATORS FAIL FROM COMMON CAUSE TO RUN 2.08E-3 EPS-DGN-FR-DG3A DIESEL GENERATOR 3A FAILS TO RUN 2.85E-2 EPS-DGN-FR-DG3C DIESEL GENERATOR 3C FAILS TO RUN 2.85E-2 EPS-DGN-FR-DG3D DIESEL GENERATOR 3D FAILS TO RUN 2.85E-2 EPS-DGN-FR-DGB DIESEL GENERATOR B FAILS TO RUN 2.85E-2 EPS-DGN-FR-DGD DIESEL GENERATOR D FAILS TO RUN 2.85E-2 EPS-DGN-TM-DG3A DG A IS UNAVAILABLE BECAUSE OF MAINTENANCE 1.43E-2 EPS-DGN-TM-DG3C DG C IS UNAVAILABLE BECAUSE OF MAINTENANCE 1.43E-2 EPS-DGN-TM-DGB DG B IS UNAVAILABLE BECAUSE OF MAINTENANCE 1.43E-2 ESW-MDP-FS-PMPD3 EECW PUMP D3 FAILS TO START 1.36E-3 ESW-XHE-XL-NOREC2 OPERATOR FAILS TO RECOVER EECW WITH SWING PUMP AVAILABLE 1.10E-2 IESD-LOSDC-M4 INITIATOR OF LOSDC IN MODE 4 1.00E+0 RSW-MDP-TM-TRNC1 RHRSW PUMP C1 IS UNAVAILABLE BECAUSE OF MAINTENANCE 1.32E-2 RSW-STR-CF-ALL RHRSW STRAINERS FAIL FROM COMMON CAUSE 4.57E-6 SD-XHE-XR-SDC-12H FAIL TO RECOVER SDC LATE - 12 HOURS 1.40E-3 SD-XHE-XR-SDC-2D FAIL TO RECOVER SDC LATE - 2 DAYS 1.40E-3 SIS-ACT-CF-LRP DIVISION I, II LOW RX PRESS PERMISSIVE SIGNALS FAIL FROM COMMON CAUSE 5.12E-4