ML16165A510

Final ASP Analysis - D.C. Cook 1 (LER 315-2014-003)

ML16165A510
Person / Time
Site:	Cook
Issue date:	04/21/2015
From:	Chelliah E, Keith Tetter NRC/RES/DRA/PRB
To:
Chelliah E
Shared Package
ML16165A505	List: ML16165A510
References
LER-315-2014-003
Download: ML16165A510 (17)

Text

1 Final Precursor Analysis Accident Sequence Precursor Program - Office of Nuclear Regulatory Research Donald C. Cook Nuclear Plant Unit 1 Turbine-driven auxiliary feed-water pump failed to run following a loss of main condenser event due to high wind-induced debris-damage of the circulating water system pumps Event Date: 11/01/2014 LER: 315-2014-003 IR: 05000315/2014005 and 05000315/2015001 CCDP = 1x10-6 Plant Type: Westinghouse 4-loop PWR with Wet, Ice Condenser Containment Plant Operating Mode (Reactor Power Level): Mode 1 (100% Reactor Power)

Analyst:

Erulappa Chelliah Reviewer:

Keith Tetter Contributors:

N/A BC Approved Date:

04/21/2015 EVENT

SUMMARY

Event Description. On November 1, 2014, both Unit 1 and Unit 2 of D.C. Cook Nuclear Plant were operating at 100 percent power. As the National Weather Service predicted a severe storm, a storm of lower magnitude arrived at the site. High winds, water waves of about 20-feet high in the forebay, and a water-surge of 2 feet high in the forebay, transported large amounts of dune grass and other debris to the areas of plant circulating water system (CWS) pumps.

The dune grass and debris impinged upon the trash racks (TRs) of the CWS system, causing a failure of the TRs, and subsequent rapid fouling of the traveling water screens of the CWS system. The following timeline describes the occurred sequence of events, on November 1, 2014:

0015 With forebay level lowering due to buildup of debris on the TRs, the operators of Unit 1 and Unit 2 throttled unit-specific CWS outlet valves to lower the total system flow, and to recover the forebay level. The forebay level recovered slightly, but after a very brief period, forebay level continued to lower.

0141 The Unit 2 operators stopped one of the four Unit 2 CWS pumps to recover the forebay level. The forebay level continued to lower.

0154 Due to traveling water screens failing to maintain normal screen differential pressure, Unit 2 operators entered the procedure for managing degraded conditions of the forebay level. Unit 1 operators also entered the same procedure.

Initial response actions of the procedure were to monitor the forebay level and to control the forebay level by turning off running CWS pumps.

0210 Unit 2 operators entered the forebay level control procedure for rapid reactor power reduction response and reduced power at four percent per minute to approximately fifty percent power to establish conditions to stop a second running CWS pump.

0218 Unit 2 operators stopped the second of four running CWS pumps, per the forebay level control procedure.

LER 315-2014-003 2

0242 Unit 1 operators stopped one of three running CWS pumps, per the forebay level control procedure.

0249 The forebay level conditions degraded further and met procedure-conditions, directing removal of all CWS pumps from service. The procedure required the operators to manually trip both reactors, to manually close the steam generator (SG) main steam isolation valves (MSIVs), and then to remove all CWS pumps from service. The operators of both Unit 1 and Unit 2 performed these actions successfully.

0300 Unit 1 operators observed that the turbine-driven auxiliary feedwater (TDAFW) pump throttle and trip valve (TTV) unlatched annunciator came on. The TTV is the valve which opens to let steam in to start and run the TDAFW pump. They determined that the TDAFW pump automatically started on unplanned demand, and ran successfully for a period of 16 minutes. Then, the TDAFW pump tripped for unknown reasons. The operators declared the TDAFW pump to be inoperable.

Since the TDAFW pump failed to run during the mission period, the operators used both motor-driven auxiliary feedwater (MDAFW) pumps to provide sub-cooled water to all four SGs at Unit 1.

The operators did not recover the failed TDAFW pump during the 24-hour mission time. Later, the licensee completed corrective actions to the failed TDAFW pump TTV mechanism. Unit 1 operators restored the TDAFW pump to an operable state, on 11/3/2014, at 12:17 a.m.

0323 Unit 1 operators noted that SG 1 pressure was low, approximately 980 psig. The expected SG pressure was approximately 1000 psig. The operators in the field noted that three of the five SG safety valves (SGSVs) were leaking. Then, the operators opened and cycled SG atmospheric relief valves (SGARVs) to force the failed valve seats of the leaked SGSVs to a fully closed position. Then, the operators found mechanical agitation of the SGSVs to be effective in achieving a forced-seating of the leaking SGSVs. SG 1 pressure then increased. Then, the operators controlled SG 1 pressure by again opening and cycling the SGARVs to keep SG pressure at approximately 1000 psig.

In summary, the operators observed at Unit 1:

a loss of main condenser due to high wind-induced failures of all CWS pumps, a failure of the TDAFW pump to run continuously, after the manual reactor-trip of Unit 1 (an as-found degraded-condition), and a storm-induced common cause failure (CCF) of the CWS pumps, the TWSs, and the TRs.

The licensee reported event-induced degraded-condition, in a licensee event report (LER), per 10 CFR Part 50.73(a)(2)(iii) and 50.73(a)(2)(iv)(A), as an event or condition that could have prevented the fulfillment of the safety function of a system to mitigate an accident or a transient.

See Reference 1 for additional information.

Failure Causes. The loss of main condenser event occurred due to a manual closure of the MSIVs by the operators during the storm. The licensee found a cause for the MSIV isolation

LER 315-2014-003 3

event due to an operating practice that the D.C. Cook organization did not establish aggressive preventive methodologies to identify and mitigate risks associated with storm-induced debris intrusion into the forebay, prior to changing the forebay level conditions, or to prevent a significant damage to the forebay concrete structures.

The licensee determined the cause of the TDAFW pump failure at Unit 1 to be mechanical interference, which affected the operation of the TTV during the TDAFW pump run-demand.

The licensee corrected the interference to preclude re-occurrence of further interference.

Inspection Findings. Region III evaluated as-found failures during post-trip response of the storm event at Unit 1. Region III closed the LER; see Reference 3 for additional information.

Event-Related Failures at Unit 1. In their LER, the licensee stated that the TDAFW pump failed to continuously run for a 24-hour mission period.

Inoperable Condition-Related Failure at Unit 1. In LER 315-14-003, the licensee stated that the TDAFW pump at Unit 1 failed to continuously run for a 24-hour mission time on November 1st.

Based on ASME standards-stated test intervals for standby safety-related pumps and valves, the operators tested the TDAFW pump at a test interval of 90 days. The performance findings of the last pump-test determined that the TDAFW pump ran successfully for the entire mission period of 24-hours. The operators might have conducted the technical specifications (TS)-

required test (last test prior to current failure) during sometime in early August 2014.

When a storm event arrived at the site, on November 1st, and demanded the TDAFW pump to run, after a manual reactor trip, the TDAFW pump failed to run continuously. The licensee determined an as-found failure of the TTV component of the TDAFW pump, after the storm event. The TTV failure contributed to a failure of the TDAFW pump to run for a period of 24-hours during the transient period, on November 1st. The operators did not recover the failed TTV component of the TDAFW pump of Unit 1.

Therefore, the TDAFW pump at standby position would have been inoperable due to a pre-existing failure condition of the TTV component during an inoperable condition period of 45 days. RES\\DRA\\PRB staff determined this degraded condition period of 45-days, based on the second half-portion of one full-test interval of 90 days. The plant TS approved a 90-day period.

This pre-existing failure condition of the TDAFW pump would have existed during a specific degraded TTV condition period of 45 days (9/16/2014 thru 11/01/2014).

ANALYSIS TYPE For Unit 1, the analyst conducted one event risk analysis (ERA-1) in estimating conditional core damage probability (CCDP) due to as-occurred loss of main condenser (LOCHS) event, with as-found inoperability of the TDAFW pump. See Appendix A for additional information.

For Unit 1, the analyst conducted also one condition risk analysis (CRA-1) in estimating increase in core damage probability (CDP) due to an as-found degraded condition, which involved a pre-existing inoperability of the TDAFW pump for a period of 45-days (1080-hours).

See Appendix A for additional information.

LER 315-2014-003 4

Modeling Assumptions. The following modeling assumptions were associated with this analysis.

The operators did not recover the failed TDAFW pump within a 30-minute period (SG dry-boil time for the Westinghouse-manufactured SGs) during transient mitigation period of 24-hours, on 11/01/2014. During this mission period of 24-hours, the operators could not have recovered the failed TDAFW pump to deliver sub-cooled water to all 4 SGs of Unit 1, if the MDAFW pumps would have failed with a failure probability.

This ERA-1 analysis case did not credit a recovery of the failed TDAFW pump.

ERA-1 analysis case at Unit 1 did not find any other significant simultaneous failures, or concurrent unavailability of other safety-related trains, on the event date.

CRA-1 analysis case at Unit 1 did not find any other significant overlapping and/or simultaneous failures, or unavailability of other safety-related trains during a 45-day exposure period, prior to event date.

Logic Model Changes to Recent SPAR Model of DC COOK Unit 1. Idaho National Laboratory published a recent plant probabilistic failures-model for Donald C. Cook Nuclear Plant Units 1 and 2 (SPAR PWR B, Model Version No. 8.22). Two analysis cases (ERA-1 and CRA-1) were run; no model changes were made.

Probability-Changes:

ERA-1 Initiating event, IE-LOCHS (loss of main condenser), was set to a probability value of 1.0 because a loss of main condenser event occurred due to a storm-induced failure of the CWS pumps on November 1st.

Basic Event, AFW-TDP-FR-PP4 (AFW TDP PP4 fails to run), was set to TRUE to reflect the as-found failure of the TDAFW pump to run during transient mitigation, after a manual reactor trip. The operators found the failure of the TTV component that resulted in a failure of the TDAFW pump to run continuously during the transient mitigation.

CRA-1 Basic event AFW-PMP-FR-PP4 was set to a TRUE value to reflect as-found failure of the TDAFW pump to run during a condition-affected IE mitigation mission period.

A pre-existing failure condition of the TTV component of the TDAFW pump existed during a specific degraded condition period of 45-days (9/16/2014 thru 11/01/2014).

There are 12 initiating events that could have affected the CDP due to an as-found inoperability of the TTV component of the TDAFW pump during the 45-day exposure period.

The D.C. Cook SPAR model includes industry-wide frequencies for these 12 initiating events.

An exposure period of 1080 hours0.0125 days <br />0.3 hours <br />0.00179 weeks <br />4.1094e-4 months <br /> (45 days) to estimate the CDP value.

CRA-1 analysis case determined and characterized a performance deficiency, inadequate testing of the TDAFW pump, including the TTV component during the last TS-test by the testing equipment personnel.

LER 315-2014-003 5

Results of ERA-1 (Initiating Event Analysis). Appendix A to this report documented the results of the ERA-1 analysis case (LOCHS event at Unit 1, concurrent with a failure of the TDAFW pump). A reader may note the following:

ERA-1 estimated a CCDP value of about 1x10-6 due to the occurred LOCHS event, with a concurrent failure of the TDAFW pump.

ERA-1 found a contributing dominant sequence to total CCDP to be due to LOCHS 02-02-10 (Appendix B, Figure B-1) with a CCDP of 6x10-7 (approximately 51 percent of total CCDP).

LOCHS-02-02-10 is due to the failure of the reactor coolant pump seal cooling (after the loss of condenser heat sink initiating event occurred), a failure of high pressure injection, a failure of residual heat removal, a failure of high-and low-pressure recirculation.

Results of CRA-1 (Degraded Condition Analysis). Appendix A to this report documented the results of the CRA-1 analysis case (TDAFW pump inoperability during a 45-day exposure period). A reader may note the following:

CRA-1 estimated a total CDP value of about 5x10-7 due to an as-found inoperability of the TDAFW pump during a pre-existing inoperable condition period of 1080-hours.

CRA-1 found contributing dominant sequences to be due to condition-affected sequences of the steam line break (SLB) outside containment event tree (see Appendix B, Figure B-2).

CRA-1 estimated an CDP value of 2x10-7 due to condition-affected sequences of the SLB event tree.

CRA-1 found a condition-affected dominant sequence of the SLB event tree to be due to SLB-06. CRA-1 estimated an CDP value of 2x10-7 due to dominant sequence, SLB 06 (see Appendix B, Figure B-2).

REFERENCES

1. Donald C. Cook Nuclear Plant Unit 1, Manual Reactor Trip Due To Debris Intrusion Causing Degraded Forebay Conditions - Indiana Michigan Power, LER-315-2014-003-00, Event Date of November 01, 2014, dated December 23, 2014. ML14364A023.

2. U. S. Nuclear Regulatory Commission, Donald C. Cook Nuclear Plant Unit 1 - NRC Inspection report, 05000315/2014005, Dated February 10, 2015

3. U. S. Nuclear Regulatory Commission, Donald C. Cook Nuclear Plant Unit 1 - NRC Inspection report, 05000315/2015001, Dated May 11, 2015.

LER 315-2014-003 A-1 Appendix A: SAPHIRE 8 Worksheets ERA-1 Summary of Conditional Event Changes Event Description Cond Value Nominal Value AFW-TDP-FR-PP4 AFW TDP PP4 FAILS TO RUN TRUE 3.95E-2 IE-LOCHS LOSS OF CONDENSER HEAT SINK INITIATING EVENT 1.00E+0a 5.86E-2

a.

All other initiating event probabilities were set to zero.

Dominant Sequence Results Only items contributing at least 1.0% to the total CCDP are displayed.

EVENT TREE SEQUENCE CCDP

% CONTRIBUTION DESCRIPTION LOCHS 02-02-10 5.57E-7 51.3%

/RPS, /AFW, /PORV, LOSC, /RCPT, /RSD, /BP1, BP2, HPI-S, /SSC1, /LPI, RHR, HPR, LPR LOCHS 12 2.06E-7 18.9%

/RPS, AFW, FAB LOCHS 13-10 1.41E-7 12.9%

RPS, RCSPRESS LOCHS 13-08 1.04E-7 9.6%

RPS, /RCSPRESS, /FW, BORATION LOCHS 02-03-10 3.47E-8 3.2%

/RPS, /AFW, /PORV, LOSC, /RCPT, /RSD, BP1, /BP2, HPI-S, /SSC1, /LPI, RHR, HPR, LPR LOCHS 02-02-12 1.96E-8 1.8%

/RPS, /AFW, /PORV, LOSC, /RCPT, /RSD, /BP1, BP2, HPI-S, SSC1 Total 1.09E-6 100.0%

Referenced Fault Trees Fault Tree Description AFW AUXILIARY FEEDWATER BORATION EMERGENCY BORATION BP1 RCP SEAL STAGE 1 INTEGRITY (BINDING/POPPING)

BP2 RCP SEAL STAGE 2 INTEGRITY (BINDING/POPPING)

FAB FEED AND BLEED HPI-S HIGH PRESSURE INJECTION HPR HIGH PRESSURE RECIRCULATION LOSC LOSS OF RCP SEAL COOLING LPR LOW PRESSURE RECIRCULATION RCSPRESS RCS PRESSURE LIMITED RHR RESIDUAL HEAT REMOVAL RPS REACTOR SHUTDOWN SSC1 RCS COOLDOWN TO RHR PRESSURE USING TBVs, ETC.

Cut Set Report - LOCHS 02-02-10 Only items contributing at least 1% to the total are displayed.

CCDP TOTAL%

CUT SET 5.57E-7 100 Displaying 72 Cut Sets. (72 Original) 1 5.16E-7 92.54 IE-LOCHS,ESW-MDP-CF-RUN,RCS-MDP-LK-BP2 2

3.20E-8 5.75 IE-LOCHS,ESW-STR-CF-STR,RCS-MDP-LK-BP2

LER 315-2014-003 A-2 Cut Set Report - LOCHS 12 Only items contributing at least 1% to the total are displayed.

CCDP TOTAL%

CUT SET 2.06E-7 100 Displaying 322 Cut Sets. (322 Original) 1 8.03E-8 39.04 IE-LOCHS,DCP-BAT-CF-ALL 2

3.80E-8 18.50 IE-LOCHS,AFW-MDP-CF-PP3STRT,AFW-XHE-XM-XTIEUNIT,HPI-XHE-XM-FB 3

5.98E-9 2.91 IE-LOCHS,AFW-PMP-CF-FRALL,AFW-XHE-XM-XTIEUNIT,HPI-XHE-XM-FB 4

5.30E-9 2.58 IE-LOCHS,ACP-BAC-LP-T11A,AFW-MDP-TM-PP3E,AFW-XHE-XM-XTIEUNIT 5

5.01E-9 2.44 IE-LOCHS,AFW-MDP-TM-PP3W,AFW-PMP-FR-PP3E,AFW-XHE-XM-XTIEUNIT,HPI-XHE-XM-FB 6

5.01E-9 2.44 IE-LOCHS,AFW-MDP-TM-PP3E,AFW-PMP-FR-PP3W,AFW-XHE-XM-XTIEUNIT,HPI-XHE-XM-FB 7

3.99E-9 1.94 IE-LOCHS,AFW-XHE-XM-XTIEUNIT,DCP-BAT-CF-UNIT1 8

3.20E-9 1.56 IE-LOCHS,AFW-SGN-CF-SIGNAL,AFW-XHE-XM-MANSTRT,AFW-XHE-XM-XTIEUNIT,HPI-XHE-XM-FB 9

3.02E-9 1.47 IE-LOCHS,AFW-AOV-OO-247,AFW-MDP-TM-PP3E,AFW-XHE-XM-XTIEUNIT,HPI-XHE-XM-FB 10 3.02E-9 1.47 IE-LOCHS,AFW-AOV-OO-257,AFW-MDP-TM-PP3W,AFW-XHE-XM-XTIEUNIT,HPI-XHE-XM-FB 11 3.01E-9 1.46 IE-LOCHS,AFW-MDP-FS-PP3W,AFW-MDP-TM-PP3E,AFW-XHE-XM-XTIEUNIT,HPI-XHE-XM-FB 12 3.01E-9 1.46 IE-LOCHS,AFW-MDP-FS-PP3E,AFW-MDP-TM-PP3W,AFW-XHE-XM-XTIEUNIT,HPI-XHE-XM-FB 13 2.24E-9 1.09 IE-LOCHS,AFW-MDP-TM-PP3E,AFW-XHE-XM-XTIEUNIT,DCP-BAT-LP-AB 14 2.11E-9 1.02 IE-LOCHS,AFW-MDP-CF-PP3RUN,AFW-XHE-XM-XTIEUNIT,HPI-XHE-XM-FB 15 2.10E-9 1.02 IE-LOCHS,ACP-BAC-LP-T11A,AFW-PMP-FR-PP3E,AFW-XHE-XM-XTIEUNIT Cut Set Report - LOCHS 13-10 Only items contributing at least 1% to the total are displayed.

CCDP TOTAL%

CUT SET 1.41E-7 100 Displaying 81 Cut Sets. (81 Original) 1 2.25E-8 16.02 IE-LOCHS,RCS-PHN-MODPOOR,RPS-BME-CF-RTBAB 2

1.88E-8 13.36 IE-LOCHS,RCS-PHN-MODPOOR,RPS-CBI-CF-6OF8,/RPS-CCP-TM-CHA,RPS-XHE-XE-NSGNL 3

1.69E-8 12.04 IE-LOCHS,RCS-PHN-MODPOOR,RPS-ROD-CF-RCCAS 4

1.27E-8 9.06 IE-LOCHS,RCS-PHN-MODPOOR,/RPS-CCP-TM-CHA,RPS-CCX-CF-6OF8,RPS-XHE-XE-NSGNL 5

5.70E-9 4.05 IE-LOCHS,PPR-SRV-CC-PRV151,RPS-BME-CF-RTBAB 6

5.70E-9 4.05 IE-LOCHS,PPR-SRV-CC-PRV152,RPS-BME-CF-RTBAB 7

5.70E-9 4.05 IE-LOCHS,PPR-SRV-CC-PRV153,RPS-BME-CF-RTBAB 8

4.76E-9 3.38 IE-LOCHS,PPR-SRV-CC-PRV152,RPS-CBI-CF-6OF8,/RPS-CCP-TM-CHA,RPS-XHE-XE-NSGNL 9

4.76E-9 3.38 IE-LOCHS,PPR-SRV-CC-PRV153,RPS-CBI-CF-6OF8,/RPS-CCP-TM-CHA,RPS-XHE-XE-NSGNL 10 4.76E-9 3.38 IE-LOCHS,PPR-SRV-CC-PRV151,RPS-CBI-CF-6OF8,/RPS-CCP-TM-CHA,RPS-XHE-XE-NSGNL 11 4.28E-9 3.04 IE-LOCHS,PPR-SRV-CC-PRV151,RPS-ROD-CF-RCCAS 12 4.28E-9 3.04 IE-LOCHS,PPR-SRV-CC-PRV152,RPS-ROD-CF-RCCAS 13 4.28E-9 3.04 IE-LOCHS,PPR-SRV-CC-PRV153,RPS-ROD-CF-RCCAS 14 3.22E-9 2.29 IE-LOCHS,PPR-SRV-CC-PRV152,/RPS-CCP-TM-CHA,RPS-CCX-CF-6OF8,RPS-XHE-XE-NSGNL

LER 315-2014-003 A-3 CCDP TOTAL%

CUT SET 15 3.22E-9 2.29 IE-LOCHS,PPR-SRV-CC-PRV153,/RPS-CCP-TM-CHA,RPS-CCX-CF-6OF8,RPS-XHE-XE-NSGNL 16 3.22E-9 2.29 IE-LOCHS,PPR-SRV-CC-PRV151,/RPS-CCP-TM-CHA,RPS-CCX-CF-6OF8,RPS-XHE-XE-NSGNL 17 1.46E-9 1.03 IE-LOCHS,RCS-PHN-MODPOOR,RPS-UVL-CF-UVDAB,RPS-XHE-XE-SIGNL Cut Set Report - LOCHS 13-08 Only items contributing at least 1% to the total are displayed.

CCDP TOTAL%

CUT SET 1.05E-7 100 Displaying 17 Cut Sets. (17 Original) 1 3.22E-8 30.80 IE-LOCHS,CVC-XHE-XM-BOR,RPS-BME-CF-RTBAB 2

2.69E-8 25.70 IE-LOCHS,CVC-XHE-XM-BOR,RPS-CBI-CF-6OF8,/RPS-CCP-TM-CHA,RPS-XHE-XE-NSGNL 3

2.42E-8 23.15 IE-LOCHS,CVC-XHE-XM-BOR,RPS-ROD-CF-RCCAS 4

1.82E-8 17.42 IE-LOCHS,CVC-XHE-XM-BOR,/RPS-CCP-TM-CHA,RPS-CCX-CF-6OF8,RPS-XHE-XE-NSGNL 5

2.08E-9 1.99 IE-LOCHS,CVC-XHE-XM-BOR,RPS-UVL-CF-UVDAB,RPS-XHE-XE-SIGNL Cut Set Report - LOCHS 02-03-10 Only items contributing at least 1% to the total are displayed.

CCDP TOTAL%

CUT SET 3.47E-8 100 Displaying 16 Cut Sets. (16 Original) 1 3.22E-8 92.85 IE-LOCHS,ESW-MDP-CF-RUN,RCS-MDP-LK-BP1 2

2.00E-9 5.77 IE-LOCHS,ESW-STR-CF-STR,RCS-MDP-LK-BP1 Cut Set Report - LOCHS 02-02-12 Only items contributing at least 1% to the total are displayed.

CCDP TOTAL%

CUT SET 1.96E-8 100 Displaying 15 Cut Sets. (15 Original) 1 1.03E-8 52.73 IE-LOCHS,ESW-MDP-CF-RUN,OPR-XHE-XM-DEPRCS2,RCS-MDP-LK-BP2 2

4.00E-9 20.45 IE-LOCHS,CCW-CFG-AP-UNIT1W,CCW-SYS-LK-WEST,CVC-XHE-XM-CVCSXTIE,OPR-XHE-XM-DEPRCS2,RCS-MDP-LK-BP2 3

4.00E-9 20.45 IE-LOCHS,CCW-CFG-AP-UNIT1E,CCW-SYS-LK-EAST,CVC-XHE-XM-CVCSXTIE,OPR-XHE-XM-DEPRCS2,RCS-MDP-LK-BP2 4

6.40E-10 3.28 IE-LOCHS,ESW-STR-CF-STR,OPR-XHE-XM-DEPRCS2,RCS-MDP-LK-BP2 5

2.00E-10 1.02 IE-LOCHS,CCW-CFG-AP-UNIT1E,CCW-SYS-LK-EAST,OPR-XHE-XM-DEPRCS2,RCS-MDP-LK-BP2,UNIT-2-CVCS 6

2.00E-10 1.02 IE-LOCHS,CCW-CFG-AP-UNIT1W,CCW-SYS-LK-WEST,OPR-XHE-XM-DEPRCS2,RCS-MDP-LK-BP2,UNIT-2-CVCS Referenced Events Event Description Probability ACP-BAC-LP-T11A 4160VAC T11A BUS FAILS 3.33E-5 AFW-AOV-OO-247 EMERG. LEAK OFF FRV-247 FAILS TO CLOSE: FLOW DIVERSION 9.51E-4 AFW-AOV-OO-257 EMERG. LEAK OFF FRV-257 FAILS TO CLOSE: FLOW DIVERSION 9.51E-4 AFW-MDP-CF-PP3RUN COMMON CAUSE FAILURE OF AFW MDPs TO run 2.63E-6 AFW-MDP-CF-PP3STRT COMMON CAUSE FAILURE OF AFW MDPs TO START 4.76E-5 AFW-MDP-FS-PP3E AFW MDP PP3E FAILS TO START 9.47E-4

LER 315-2014-003 A-4 Event Description Probability AFW-MDP-FS-PP3W AFW MDP PP3W FAILS TO START 9.47E-4 AFW-MDP-TM-PP3E AFW MDP PP3E UNAVAILABLE DUE TO TEST AND MAINTENANCE 3.98E-3 AFW-MDP-TM-PP3W AFW MDP 3W UNAVAILABLE DUE TO TEST AND MAINTENANCE 3.98E-3 AFW-PMP-CF-FRALL COMMON CAUSE FAILURE OF AFW PUMPS 7.47E-6 AFW-PMP-FR-PP3E FAILURE OF AFW PUMP UNIT PP3E 1.58E-3 AFW-PMP-FR-PP3W FAILURE OF AFW PUMP UNIT PP3W 1.58E-3 AFW-SGN-CF-SIGNAL CCF SG SIGNAL (PSA) 2.00E-4 AFW-XHE-XM-MANSTRT OPERATOR FAILS TO MANUALLY START AFW PUMPS 2.00E-2 AFW-XHE-XM-XTIEUNIT OPERATOR FAILS TO XTIE OPPOSITE UNIT AFW SYSTEM 4.00E-2 CCW-CFG-AP-UNIT1E FRACTION OF TIME UNIT 1 EAST CCW IS INITIALLY OPERATING TRAIN 5.00E-1 CCW-CFG-AP-UNIT1W FRACTION OF TIME UNIT 1 WEST CCW IS INITIALLY OPERATING TRAIN 5.00E-1 CCW-SYS-LK-EAST EAST HEADER LEAKAGE REQUIRES ISOLATION (PSA) 1.00E-4 CCW-SYS-LK-WEST WEST HEADER LEAKAGE REQUIRES ISOLATION (PSA) 1.00E-4 CVC-XHE-XM-BOR OPERATOR FAILS TO INITIATE EMERGENCY BORATION 2.00E-2 CVC-XHE-XM-CVCSXTIE OPERATOR FAILS TO ALIGN CVCS XTIE TO ALTERNATE UNIT 2.00E-2 DCP-BAT-CF-ALL FAILURE OF BATTERIES IN BOTH UNITS 8.03E-8 DCP-BAT-CF-UNIT1 CCF OF 250VDC BATTERYS AB AND CD 9.97E-8 DCP-BAT-LP-AB FAILURE OF 250VDC BATTERY AB 1.41E-5 ESW-MDP-CF-RUN CCF U1&2 ESW PUMPS FAIL TO RUN 2.58E-6 ESW-STR-CF-STR CCF OF ESW MDP DISCHARGE STRAINERS 1.60E-7 HPI-XHE-XM-FB OPERATOR FAILS TO INITIATE FEED AND BLEED COOLING 2.00E-2 IE-LOCHS LOSS OF CONDENSER HEAT SINK INITIATING EVENT 1.00E+0 OPR-XHE-XM-DEPRCS2 OPERATOR FAILS TO DEPRESSURIZE RCS/SECONDARY SIDE (RAPID) 2.00E-2 PPR-SRV-CC-PRV151 PORV 151 FAILS TO OPEN ON DEMAND 3.54E-3 PPR-SRV-CC-PRV152 PORV 152 FAILS TO OPEN ON DEMAND 3.54E-3 PPR-SRV-CC-PRV153 PORV 153 FAILS TO OPEN ON DEMAND 3.54E-3 RCS-MDP-LK-BP1 RCP SEAL STAGE 1 INTEGRITY (BINDING/POPPING OPEN) FAILS 1.25E-2 RCS-MDP-LK-BP2 RCP SEAL STAGE 2 INTEGRITY (BINDING/POPPING OPEN) FAILS 2.00E-1 RCS-PHN-MODPOOR MODERATOR TEMP COEFFICIENT NOT ENOUGH NEGATIVE 1.40E-2 RPS-BME-CF-RTBAB CCF OF RTB-A AND RTB-B (MECHANICAL) 1.61E-6 RPS-CBI-CF-6OF8 CCF 6 BISTABLES IN 3 OF 4 CHANNELS 2.70E-6 RPS-CCX-CF-6OF8 CCF 6 ANALOG PROCESS LOGIC MODULES IN 3 OF 4 CHANNELS 1.83E-6 RPS-ROD-CF-RCCAS CCF 10 OR MORE RCCAS FAIL TO DROP 1.21E-6 RPS-UVL-CF-UVDAB CCF UV DRIVERS TRAINS A AND B (2 0F 2) 1.04E-5 RPS-XHE-XE-NSGNL OPERATOR FAILS TO RESPOND WITH NO RPS SIGNAL PRESENT 5.00E-1 RPS-XHE-XE-SIGNL OPERATOR FAILS TO RESPOND WITH RPS SIGNAL PRESENT 1.00E-2 UNIT-2-CVCS UNDEVELOPED EVENT FOR U2 CVCS HARDWARE 1.00E-3

LER 315-2014-003 A-5 CRA-1 Summary of Conditional Event Changes Event Description Cond Value Nominal Value AFW-PMP-FR-PP4 FAILURE OF AFW PUMP UNIT PP4 True 1.58E-3 Event Tree Dominant Results Only items contributing at least 1.0% to the total CCDP are displayed.

EVENT TREE CCDP CDP CDP DESCRIPTION SLB 1.19E-6 9.88E-7 1.98E-7 Cook 1 & 2 PWR B Steam Line Break TRANS 1.81E-7 8.14E-8 9.94E-8 Cook 1 & 2 PWR B Transient LODCA 4.94E-8 2.23E-9 4.71E-8 Cook 1 & 2 PWR B Loss of 250 VDC Unit 1 Train A LOMFW 4.52E-8 8.16E-9 3.71E-8 Cook 1 & 2 PWR B LOSS OF MFW Transient LOCHS 3.85E-8 6.93E-9 3.15E-8 Cook 1 & 2 PWR B Loss of Condenser Heat Sink LOOPGR 2.94E-8 5.79E-9 2.36E-8 Cook 1 & 2 PWR B Loss of Offsite Power (Grid Related)

LOOPSC 2.27E-8 4.24E-9 1.85E-8 Cook 1 & 2 PWR B Loss of Offsite Power (Switchyard Centered)

LOOPWR 1.22E-8 3.75E-9 8.49E-9 Cook 1 & 2 PWR B Loss of Offsite Power (Weather Related)

LOESW2 2.39E-7 2.33E-7 6.23E-9 Cook 1 & 2 PWR B Loss of Unit 1 Essential Service Water LOESW4 2.31E-6 2.30E-6 6.19E-9 Cook 1 & 2 PWR B Loss of All Essential Service Water LOCCW 1.49E-7 1.43E-7 6.17E-9 Cook 1 & 2 PWR B Loss of Component Cooling Water SLOCA 1.60E-7 1.55E-7 5.34E-9 Cook 1 & 2 PWR B Small Loss of Coolant Accident Total 4.73E-6 4.24E-6 4.94E-7 Dominant Sequence Results Only items contributing at least 1.0% to the total CCDP are displayed.

EVENT TREE SEQUENCE CCDP CDP CDP DESCRIPTION SLB 06 1.94E-7 6.35E-10 1.93E-7

/RPS, /ISGTR, AFW, /FAB, HPR TRANS 20 1.05E-7 7.11E-9 9.81E-8

/RPS, AFW, MFW, FAB LODCA 12 4.88E-8 1.64E-9 4.71E-8

/RPS, AFW, FAB LOMFW 20 3.73E-8 7.86E-10 3.65E-8

/RPS, AFW, MFW, FAB LOCHS 12 3.17E-8 6.65E-10 3.10E-8

/RPS, AFW, FAB LOOPGR 15 1.23E-8 2.76E-10 1.20E-8

/RPS, /EPS, AFW-L, FAB-L LOOPSC 15 1.05E-8 2.29E-10 1.02E-8

/RPS, /EPS, AFW-L, FAB-L LOESW2 16 6.20E-9 1.86E-11 6.18E-9 IEFT-LOESW2, /RPS, AFW-E2, REC-ESW LOESW4 15 6.20E-9 1.86E-11 6.18E-9 IEFT-LOESW4, /RPS, AFW-E, FAB LOCCW 16 6.19E-9 1.86E-11 6.17E-9 IEFT-LOCCW, /RPS, AFW, REC-CCW LOOPGR 12 6.02E-9 1.16E-10 5.90E-9

/RPS, /EPS, AFW-L, /FAB-L, /OPR-06H, HPR LOOPGR 16-45 5.61E-9 2.88E-10 5.32E-9

/RPS, EPS, AFW-B, OPR-01H, DGR-01H LOOPSC 12 5.27E-9 9.94E-11 5.17E-9

/RPS, /EPS, AFW-L, /FAB-L, /OPR-06H, HPR Total 4.73E-6 4.24E-6 4.94E-7 Referenced Fault Trees Fault Tree Description AFW AUXILIARY FEEDWATER AFW-B AUXILIARY FEEDWATER AFW-E AUXILIARY FEEDWATER AFW-E2 AUXILIARY FEEDWATER AFW-L COOK 1 & 2 PWR B AFW USING LOOP-FT FAULT TREE FLAGS

LER 315-2014-003 A-6 Fault Tree Description DGR-01H OPERATOR FAILS TO RECOVER EMERGENCY DIESEL IN 1 HOUR EPS EMERGENCY POWER FAB FEED AND BLEED FAB-L COOK 1 & 2 PWR B FEED AND BLEED USING LOOP-FTF FAULT TREE FL HPR HIGH PRESSURE RECIRCULATION IEFT-LOCCW LOCCW INITIATING EVENT FAULT TREE IEFT-LOESW2 LOESW UNIT 1 INITIATING EVENT FAULT TREE IEFT-LOESW4 LOESW (TOTAL) INITIATING EVENT FAULT TREE MFW MAIN FEEDWATER OPR-01H OPERATOR FAILS TO RECOVER OFFSITE POWER IN 1 HOUR REC-CCW CCW RECOVERY REC-ESW ESW RECOVERY Cut Set Report - SLB 06 Only items contributing at least 1% to the total are displayed.

CCDF TOTAL%

CUT SET 1.57E-6 100 Displaying 77 Cut Sets. (77 Original) 1 1.46E-6 92.84 IE-SLB,AFW-PMP-CF-FRALL,AFW-XHE-XM-XTIEUNIT 2

3.65E-8 2.32 IE-SLB,AFW-PMP-CF-FRALL,AFW-SYS-TM-U2TRNB 3

3.65E-8 2.32 IE-SLB,AFW-PMP-CF-FRALL,AFW-SYS-TM-U2TRNA Cut Set Report - TRANS 20 Only items contributing at least 1% to the total are displayed.

CCDF TOTAL%

CUT SET 8.53E-7 100 Displaying 270 Cut Sets. (270 Original) 1 4.45E-7 52.15 IE-TRANS,AFW-PMP-CF-FRALL,AFW-XHE-XM-XTIEUNIT,HPI-XHE-XM-FB,MFW-XHE-XM-STRT 2

2.67E-7 31.26 IE-TRANS,AFW-PMP-CF-FRALL,AFW-XHE-XM-XTIEUNIT,HPI-XHE-XM-FB1,MFW-XHE-XM-ERROR 3

5.54E-8 6.49 IE-TRANS,DCP-BAT-CF-ALL 4

1.11E-8 1.30 IE-TRANS,AFW-PMP-CF-FRALL,AFW-SYS-TM-U2TRNB,HPI-XHE-XM-FB,MFW-XHE-XM-STRT 5

1.11E-8 1.30 IE-TRANS,AFW-PMP-CF-FRALL,AFW-SYS-TM-U2TRNA,HPI-XHE-XM-FB,MFW-XHE-XM-STRT Cut Set Report - LODCA 12 Only items contributing at least 1% to the total are displayed.

CCDF TOTAL%

CUT SET 3.96E-7 100 Displaying 53 Cut Sets. (53 Original) 1 1.40E-7 35.35 IE-LODCA,AFW-PMP-CF-FRALL,AFW-XHE-XM-XTIEUNIT 2

1.17E-7 29.63 IE-LODCA,AFW-MDP-TM-PP3E,AFW-XHE-XM-XTIEUNIT 3

4.64E-8 11.74 IE-LODCA,AFW-PMP-FR-PP3E,AFW-XHE-XM-XTIEUNIT 4

2.80E-8 7.09 IE-LODCA,AFW-AOV-OO-257,AFW-XHE-XM-XTIEUNIT 5

2.79E-8 7.06 IE-LODCA,AFW-MDP-FS-PP3E,AFW-XHE-XM-XTIEUNIT 6

1.07E-8 2.70 IE-LODCA,AFW-MDP-FR-PP3E,AFW-XHE-XM-XTIEUNIT

LER 315-2014-003 A-7 Cut Set Report - LOMFW 20 Only items contributing at least 1% to the total are displayed.

CCDF TOTAL%

CUT SET 3.02E-7 100 Displaying 147 Cut Sets. (147 Original) 1 2.61E-7 86.46 IE-LOMFW,AFW-PMP-CF-FRALL,AFW-XHE-XM-XTIEUNIT,HPI-XHE-XM-FB 2

6.54E-9 2.16 IE-LOMFW,AFW-PMP-CF-FRALL,AFW-SYS-TM-U2TRNB,HPI-XHE-XM-FB 3

6.54E-9 2.16 IE-LOMFW,AFW-PMP-CF-FRALL,AFW-SYS-TM-U2TRNA,HPI-XHE-XM-FB 4

5.53E-9 1.83 IE-LOMFW,DCP-BAT-CF-ALL 5

3.11E-9 1.03 IE-LOMFW,AFW-PMP-CF-FRALL,AFW-XHE-XM-XTIEUNIT,HPI-CKV-OO-151W 6

3.11E-9 1.03 IE-LOMFW,AFW-PMP-CF-FRALL,AFW-XHE-XM-XTIEUNIT,HPI-CKV-OO-151E Cut Set Report - LOCHS 12 Only items contributing at least 1% to the total are displayed.

CCDF TOTAL%

CUT SET 2.57E-7 100 Displaying 135 Cut Sets. (135 Original) 1 2.22E-7 86.49 IE-LOCHS,AFW-PMP-CF-FRALL,AFW-XHE-XM-XTIEUNIT,HPI-XHE-XM-FB 2

5.56E-9 2.16 IE-LOCHS,AFW-PMP-CF-FRALL,AFW-SYS-TM-U2TRNB,HPI-XHE-XM-FB 3

5.56E-9 2.16 IE-LOCHS,AFW-PMP-CF-FRALL,AFW-SYS-TM-U2TRNA,HPI-XHE-XM-FB 4

4.71E-9 1.83 IE-LOCHS,DCP-BAT-CF-ALL 5

2.65E-9 1.03 IE-LOCHS,AFW-PMP-CF-FRALL,AFW-XHE-XM-XTIEUNIT,HPI-CKV-OO-151W 6

2.65E-9 1.03 IE-LOCHS,AFW-PMP-CF-FRALL,AFW-XHE-XM-XTIEUNIT,HPI-CKV-OO-151E Cut Set Report - LOOPGR 15 Only items contributing at least 1% to the total are displayed.

CCDF TOTAL%

CUT SET 9.98E-8 100 Displaying 298 Cut Sets. (298 Original) 1 4.63E-8 46.40 IE-LOOPGR,AFW-PMP-CF-FRALL,AFW-XHE-XM-XTIEUNIT,HPI-XHE-XM-FB 2

8.35E-9 8.37 IE-LOOPGR,ACP-XHE-XM-T11A12B2,AFW-PMP-CF-FRALL,AFW-XHE-XM-XTIEUNIT,EPS-DGN-FR-1AB 3

7.00E-9 7.02 IE-LOOPGR,ACP-XHE-XM-T11A12B2,AFW-MDP-TM-PP3E,AFW-XHE-XM-XTIEUNIT,EPS-DGN-FR-1AB 4

3.99E-9 4.00 IE-LOOPGR,ACP-XHE-XM-T11A12B2,AFW-PMP-CF-FRALL,AFW-XHE-XM-XTIEUNIT,EPS-DGN-TM-1AB 5

3.34E-9 3.35 IE-LOOPGR,ACP-XHE-XM-T11A12B2,AFW-MDP-TM-PP3E,AFW-XHE-XM-XTIEUNIT,EPS-DGN-TM-1AB 6

2.78E-9 2.78 IE-LOOPGR,ACP-XHE-XM-T11A12B2,AFW-PMP-FR-PP3E,AFW-XHE-XM-XTIEUNIT,EPS-DGN-FR-1AB 7

1.68E-9 1.68 IE-LOOPGR,ACP-XHE-XM-T11A12B2,AFW-AOV-OO-257,AFW-XHE-XM-XTIEUNIT,EPS-DGN-FR-1AB 8

1.67E-9 1.67 IE-LOOPGR,ACP-XHE-XM-T11A12B2,AFW-MDP-FS-PP3E,AFW-XHE-XM-XTIEUNIT,EPS-DGN-FR-1AB 9

1.32E-9 1.33 IE-LOOPGR,ACP-XHE-XM-T11A12B2,AFW-PMP-FR-PP3E,AFW-XHE-XM-XTIEUNIT,EPS-DGN-TM-1AB 10 1.16E-9 1.16 IE-LOOPGR,AFW-PMP-CF-FRALL,AFW-SYS-TM-U2TRNB,HPI-XHE-XM-FB 11 1.16E-9 1.16 IE-LOOPGR,AFW-PMP-CF-FRALL,AFW-SYS-TM-U2TRNA,HPI-XHE-XM-FB Cut Set Report - LOOPSC 15 Only items contributing at least 1% to the total are displayed.

CCDF TOTAL%

CUT SET 8.48E-8 100 Displaying 274 Cut Sets. (274 Original)

LER 315-2014-003 A-8 CCDF TOTAL%

CUT SET 1

3.95E-8 46.53 IE-LOOPSC,AFW-PMP-CF-FRALL,AFW-XHE-XM-XTIEUNIT,HPI-XHE-XM-FB 2

7.12E-9 8.40 IE-LOOPSC,ACP-XHE-XM-T11A12B2,AFW-PMP-CF-FRALL,AFW-XHE-XM-XTIEUNIT,EPS-DGN-FR-1AB 3

5.97E-9 7.04 IE-LOOPSC,ACP-XHE-XM-T11A12B2,AFW-MDP-TM-PP3E,AFW-XHE-XM-XTIEUNIT,EPS-DGN-FR-1AB 4

3.40E-9 4.01 IE-LOOPSC,ACP-XHE-XM-T11A12B2,AFW-PMP-CF-FRALL,AFW-XHE-XM-XTIEUNIT,EPS-DGN-TM-1AB 5

2.85E-9 3.36 IE-LOOPSC,ACP-XHE-XM-T11A12B2,AFW-MDP-TM-PP3E,AFW-XHE-XM-XTIEUNIT,EPS-DGN-TM-1AB 6

2.37E-9 2.79 IE-LOOPSC,ACP-XHE-XM-T11A12B2,AFW-PMP-FR-PP3E,AFW-XHE-XM-XTIEUNIT,EPS-DGN-FR-1AB 7

1.43E-9 1.68 IE-LOOPSC,ACP-XHE-XM-T11A12B2,AFW-AOV-OO-257,AFW-XHE-XM-XTIEUNIT,EPS-DGN-FR-1AB 8

1.42E-9 1.68 IE-LOOPSC,ACP-XHE-XM-T11A12B2,AFW-MDP-FS-PP3E,AFW-XHE-XM-XTIEUNIT,EPS-DGN-FR-1AB 9

1.13E-9 1.33 IE-LOOPSC,ACP-XHE-XM-T11A12B2,AFW-PMP-FR-PP3E,AFW-XHE-XM-XTIEUNIT,EPS-DGN-TM-1AB 10 9.87E-10 1.16 IE-LOOPSC,AFW-PMP-CF-FRALL,AFW-SYS-TM-U2TRNB,HPI-XHE-XM-FB 11 9.87E-10 1.16 IE-LOOPSC,AFW-PMP-CF-FRALL,AFW-SYS-TM-U2TRNA,HPI-XHE-XM-FB Cut Set Report - LOESW2 16 Only items contributing at least 1% to the total are displayed.

CCDF TOTAL%

CUT SET 5.03E-8 100 Displaying 26 Cut Sets. (26 Original) 1 4.67E-8 92.87 IE-LOESW2,AFW-PMP-CF-FRALL,AFW-XHE-XM-XTIEUNIT 2

1.17E-9 2.32 IE-LOESW2,AFW-PMP-CF-FRALL,AFW-SYS-TM-U2TRNA 3

1.17E-9 2.32 IE-LOESW2,AFW-PMP-CF-FRALL,AFW-SYS-TM-U2TRNB Cut Set Report - LOESW4 15 Only items contributing at least 1% to the total are displayed.

CCDF TOTAL%

CUT SET 5.03E-8 100 Displaying 26 Cut Sets. (26 Original) 1 4.67E-8 92.87 IE-LOESW,AFW-PMP-CF-FRALL,AFW-XHE-XM-XTIEUNIT 2

1.17E-9 2.32 IE-LOESW,AFW-PMP-CF-FRALL,AFW-SYS-TM-U2TRNA 3

1.17E-9 2.32 IE-LOESW,AFW-PMP-CF-FRALL,AFW-SYS-TM-U2TRNB Cut Set Report - LOCCW 16 Only items contributing at least 1% to the total are displayed.

CCDF TOTAL%

CUT SET 5.02E-8 100 Displaying 24 Cut Sets. (24 Original) 1 4.67E-8 92.97 IE-LOCCW,AFW-PMP-CF-FRALL,AFW-XHE-XM-XTIEUNIT 2

1.17E-9 2.32 IE-LOCCW,AFW-PMP-CF-FRALL,AFW-SYS-TM-U2TRNB 3

1.17E-9 2.32 IE-LOCCW,AFW-PMP-CF-FRALL,AFW-SYS-TM-U2TRNA Cut Set Report - LOOPGR 12 Only items contributing at least 1% to the total are displayed.

CCDF TOTAL%

CUT SET 4.88E-8 100 Displaying 212 Cut Sets. (212 Original)

LER 315-2014-003 A-9 CCDF TOTAL%

CUT SET 1

7.63E-9 15.63 IE-LOOPGR,ACP-XHE-XM-T11D12C2,AFW-PMP-CF-FRALL,AFW-XHE-XM-XTIEUNIT,EPS-DGN-FR-1CD,/OEP-XHE-XL-NR06HGR 2

6.40E-9 13.10 IE-LOOPGR,ACP-XHE-XM-T11D12C2,AFW-MDP-TM-PP3W,AFW-XHE-XM-XTIEUNIT,EPS-DGN-FR-1CD,/OEP-XHE-XL-NR06HGR 3

4.23E-9 8.66 IE-LOOPGR,AFW-PMP-CF-FRALL,AFW-XHE-XM-XTIEUNIT,HPI-XHE-XM-RECIRC,/OEP-XHE-XL-NR06HGR 4

3.64E-9 7.46 IE-LOOPGR,ACP-XHE-XM-T11D12C2,AFW-PMP-CF-FRALL,AFW-XHE-XM-XTIEUNIT,EPS-DGN-TM-1CD,/OEP-XHE-XL-NR06HGR 5

3.05E-9 6.25 IE-LOOPGR,ACP-XHE-XM-T11D12C2,AFW-MDP-TM-PP3W,AFW-XHE-XM-XTIEUNIT,EPS-DGN-TM-1CD,/OEP-XHE-XL-NR06HGR 6

2.53E-9 5.19 IE-LOOPGR,ACP-XHE-XM-T11D12C2,AFW-PMP-FR-PP3W,AFW-XHE-XM-XTIEUNIT,EPS-DGN-FR-1CD,/OEP-XHE-XL-NR06HGR 7

2.04E-9 4.17 IE-LOOPGR,AFW-PMP-CF-FRALL,AFW-XHE-XM-XTIEUNIT,/OEP-XHE-XL-NR06HGR,RHR-MOV-OO-390 8

1.53E-9 3.13 IE-LOOPGR,ACP-XHE-XM-T11D12C2,AFW-AOV-OO-247,AFW-XHE-XM-XTIEUNIT,EPS-DGN-FR-1CD,/OEP-XHE-XL-NR06HGR 9

1.52E-9 3.12 IE-LOOPGR,ACP-XHE-XM-T11D12C2,AFW-MDP-FS-PP3W,AFW-XHE-XM-XTIEUNIT,EPS-DGN-FR-1CD,/OEP-XHE-XL-NR06HGR 10 1.21E-9 2.48 IE-LOOPGR,ACP-XHE-XM-T11D12C2,AFW-PMP-FR-PP3W,AFW-XHE-XM-XTIEUNIT,EPS-DGN-TM-1CD,/OEP-XHE-XL-NR06HGR 11 7.33E-10 1.50 IE-LOOPGR,ACP-XHE-XM-T11D12C2,AFW-PMP-CF-FRALL,AFW-XHE-XM-XTIEUNIT,EPS-DGN-FS-1CD,/OEP-XHE-XL-NR06HGR 12 7.30E-10 1.50 IE-LOOPGR,ACP-XHE-XM-T11D12C2,AFW-AOV-OO-247,AFW-XHE-XM-XTIEUNIT,EPS-DGN-TM-1CD,/OEP-XHE-XL-NR06HGR 13 7.27E-10 1.49 IE-LOOPGR,ACP-XHE-XM-T11D12C2,AFW-MDP-FS-PP3W,AFW-XHE-XM-XTIEUNIT,EPS-DGN-TM-1CD,/OEP-XHE-XL-NR06HGR 14 6.15E-10 1.26 IE-LOOPGR,ACP-XHE-XM-T11D12C2,AFW-MDP-TM-PP3W,AFW-XHE-XM-XTIEUNIT,EPS-DGN-FS-1CD,/OEP-XHE-XL-NR06HGR 15 6.07E-10 1.24 IE-LOOPGR,ACP-CRB-CC-T11D12,ACP-XHE-XM-STRIP-T11D,ACP-XHE-XM-T11D12C2,AFW-PMP-CF-FRALL,AFW-XHE-XM-XTIEUNIT,/OEP-XHE-XL-NR06HGR 16 5.83E-10 1.19 IE-LOOPGR,ACP-XHE-XM-T11D12C2,AFW-MDP-FR-PP3W,AFW-XHE-XM-XTIEUNIT,EPS-DGN-FR-1CD,/OEP-XHE-XL-NR06HGR 17 5.09E-10 1.04 IE-LOOPGR,ACP-CRB-CC-T11D12,ACP-XHE-XM-STRIP-T11D,ACP-XHE-XM-T11D12C2,AFW-MDP-TM-PP3W,AFW-XHE-XM-XTIEUNIT,/OEP-XHE-XL-NR06HGR Cut Set Report - LOOPGR 16-45 Only items contributing at least 1% to the total are displayed.

CCDF TOTAL%

CUT SET 4.55E-8 100 Displaying 42 Cut Sets. (42 Original) 1 1.65E-8 36.25 IE-LOOPGR,EPS-DGN-CF-RUN4,EPS-DGN-SDG2,EPS-DUAL-UNIT-LOOP,EPS-XHE-XL-NR01H,OEP-XHE-XL-NR01HGR,OEP-XHE-XX-NR01HGR0 2

1.29E-8 28.25 IE-LOOPGR,EPS-DGN-CF-STRT4,EPS-DGN-SDG2,EPS-DUAL-UNIT-LOOP,EPS-XHE-XL-NR01H,OEP-XHE-XL-NR01HGR 3

5.71E-9 12.54 IE-LOOPGR,EPS-DGN-SDG2,EPS-DUAL-UNIT-LOOP,EPS-FAN-CF-U12EXFTS,EPS-XHE-XL-NR01H,OEP-XHE-XL-NR01HGR 4

5.25E-9 11.54 IE-LOOPGR,EPS-DGN-SDG2,EPS-DUAL-UNIT-LOOP,EPS-XHE-XL-NR01H,ESW-MDP-CF-RUN,OEP-XHE-XL-NR01HGR 5

4.00E-9 8.78 IE-LOOPGR,EPS-DGN-SDG2,EPS-DUAL-UNIT-LOOP,EPS-XHE-XL-NR01H,ESW-MDP-CF-STRT,OEP-XHE-XL-NR01HGR

LER 315-2014-003 A-10 Cut Set Report - LOOPSC 12 Only items contributing at least 1% to the total are displayed.

CCDF TOTAL%

CUT SET 4.28E-8 100 Displaying 198 Cut Sets. (198 Original) 1 6.70E-9 15.68 IE-LOOPSC,ACP-XHE-XM-T11D12C2,AFW-PMP-CF-FRALL,AFW-XHE-XM-XTIEUNIT,EPS-DGN-FR-1CD,/OEP-XHE-XL-NR06HSC 2

5.62E-9 13.14 IE-LOOPSC,ACP-XHE-XM-T11D12C2,AFW-MDP-TM-PP3W,AFW-XHE-XM-XTIEUNIT,EPS-DGN-FR-1CD,/OEP-XHE-XL-NR06HSC 3

3.71E-9 8.69 IE-LOOPSC,AFW-PMP-CF-FRALL,AFW-XHE-XM-XTIEUNIT,HPI-XHE-XM-RECIRC,/OEP-XHE-XL-NR06HSC 4

3.20E-9 7.48 IE-LOOPSC,ACP-XHE-XM-T11D12C2,AFW-PMP-CF-FRALL,AFW-XHE-XM-XTIEUNIT,EPS-DGN-TM-1CD,/OEP-XHE-XL-NR06HSC 5

2.68E-9 6.27 IE-LOOPSC,ACP-XHE-XM-T11D12C2,AFW-MDP-TM-PP3W,AFW-XHE-XM-XTIEUNIT,EPS-DGN-TM-1CD,/OEP-XHE-XL-NR06HSC 6

2.23E-9 5.21 IE-LOOPSC,ACP-XHE-XM-T11D12C2,AFW-PMP-FR-PP3W,AFW-XHE-XM-XTIEUNIT,EPS-DGN-FR-1CD,/OEP-XHE-XL-NR06HSC 7

1.79E-9 4.18 IE-LOOPSC,AFW-PMP-CF-FRALL,AFW-XHE-XM-XTIEUNIT,/OEP-XHE-XL-NR06HSC,RHR-MOV-OO-390 8

1.34E-9 3.14 IE-LOOPSC,ACP-XHE-XM-T11D12C2,AFW-AOV-OO-247,AFW-XHE-XM-XTIEUNIT,EPS-DGN-FR-1CD,/OEP-XHE-XL-NR06HSC 9

1.34E-9 3.13 IE-LOOPSC,ACP-XHE-XM-T11D12C2,AFW-MDP-FS-PP3W,AFW-XHE-XM-XTIEUNIT,EPS-DGN-FR-1CD,/OEP-XHE-XL-NR06HSC 10 1.06E-9 2.48 IE-LOOPSC,ACP-XHE-XM-T11D12C2,AFW-PMP-FR-PP3W,AFW-XHE-XM-XTIEUNIT,EPS-DGN-TM-1CD,/OEP-XHE-XL-NR06HSC 11 6.44E-10 1.51 IE-LOOPSC,ACP-XHE-XM-T11D12C2,AFW-PMP-CF-FRALL,AFW-XHE-XM-XTIEUNIT,EPS-DGN-FS-1CD,/OEP-XHE-XL-NR06HSC 12 6.41E-10 1.50 IE-LOOPSC,ACP-XHE-XM-T11D12C2,AFW-AOV-OO-247,AFW-XHE-XM-XTIEUNIT,EPS-DGN-TM-1CD,/OEP-XHE-XL-NR06HSC 13 6.39E-10 1.49 IE-LOOPSC,ACP-XHE-XM-T11D12C2,AFW-MDP-FS-PP3W,AFW-XHE-XM-XTIEUNIT,EPS-DGN-TM-1CD,/OEP-XHE-XL-NR06HSC 14 5.40E-10 1.26 IE-LOOPSC,ACP-XHE-XM-T11D12C2,AFW-MDP-TM-PP3W,AFW-XHE-XM-XTIEUNIT,EPS-DGN-FS-1CD,/OEP-XHE-XL-NR06HSC 15 5.33E-10 1.25 IE-LOOPSC,ACP-CRB-CC-T11D12,ACP-XHE-XM-STRIP-T11D,ACP-XHE-XM-T11D12C2,AFW-PMP-CF-FRALL,AFW-XHE-XM-XTIEUNIT,/OEP-XHE-XL-NR06HSC 16 5.12E-10 1.20 IE-LOOPSC,ACP-XHE-XM-T11D12C2,AFW-MDP-FR-PP3W,AFW-XHE-XM-XTIEUNIT,EPS-DGN-FR-1CD,/OEP-XHE-XL-NR06HSC 17 4.47E-10 1.05 IE-LOOPSC,ACP-CRB-CC-T11D12,ACP-XHE-XM-STRIP-T11D,ACP-XHE-XM-T11D12C2,AFW-MDP-TM-PP3W,AFW-XHE-XM-XTIEUNIT,/OEP-XHE-XL-NR06HSC Referenced Events Event Description Probability ACP-CRB-CC-T11D12 4KV BREAKER T11D12FAILS TO OPEN 2.39E-3 ACP-XHE-XM-STRIP-T11D HUMAN ERROR FAILS TO MANUALLY STRIP BUS T11D 1.00E+0 ACP-XHE-XM-T11A12B2 OPERATOR FAILS TO CLOSE BREAKERS T11A12 AND T11B2 1.20E-1 ACP-XHE-XM-T11D12C2 OPERATOR FAILS TO CLOSE BREAKERS T11D1 AND T11C2 1.20E-1 AFW-AOV-OO-247 EMERG. LEAK OFF FRV-247 FAILS TO CLOSE: FLOW DIVERSION 9.51E-4 AFW-AOV-OO-257 EMERG. LEAK OFF FRV-257 FAILS TO CLOSE: FLOW DIVERSION 9.51E-4 AFW-MDP-FR-PP3E AFW MDP PP3E FAILS TO RUN 3.62E-4 AFW-MDP-FR-PP3W AFW MDP PP3W FAILS TO RUN 3.62E-4 AFW-MDP-FS-PP3E AFW MDP PP3E FAILS TO START 9.47E-4 AFW-MDP-FS-PP3W AFW MDP PP3W FAILS TO START 9.47E-4 AFW-MDP-TM-PP3E AFW MDP PP3E UNAVAILABLE DUE TO TEST AND MAINTENANCE 3.98E-3

LER 315-2014-003 A-11 Event Description Probability AFW-MDP-TM-PP3W AFW MDP 3W UNAVAILABLE DUE TO TEST AND MAINTENANCE 3.98E-3 AFW-PMP-CF-FRALL COMMON CAUSE FAILURE OF AFW PUMPS 4.74E-3 AFW-PMP-FR-PP3E FAILURE OF AFW PUMP UNIT PP3E 1.58E-3 AFW-PMP-FR-PP3W FAILURE OF AFW PUMP UNIT PP3W 1.58E-3 AFW-SYS-TM-U2TRNA UNIT 2 TRAIN A OUT FOR MAINTENANCE 1.00E-3 AFW-SYS-TM-U2TRNB UNIT 2 AFW TRAIN B OUT FOR MAINTENANCE 1.00E-3 AFW-XHE-XM-XTIEUNIT OPERATOR FAILS TO XTIE OPPOSITE UNIT AFW SYSTEM 4.00E-2 DCP-BAT-CF-ALL FAILURE OF BATTERIES IN BOTH UNITS 8.03E-8 EPS-DGN-CF-RUN4 COMMON CAUSE FAILURE OF ALL 4 DIESEL GENERATORS TO RUN 4.82E-5 EPS-DGN-CF-STRT4 COMMON CAUSE FAILURE OF ALL 4 DIESEL GENERATORS TO START 6.31E-6 EPS-DGN-FR-1AB DIESEL GENERATOR 1AB FAILS TO RUN 3.01E-2 EPS-DGN-FR-1CD DIESEL GENERATOR 1CD FAILS TO RUN 3.01E-2 EPS-DGN-FS-1CD DIESEL GENERATOR 1CD FAILS TO START 2.89E-3 EPS-DGN-SDG2 SDGS ALIGNED TO OTHER UNIT IN DUAL UNIT SBO 5.00E-1 EPS-DGN-TM-1AB DIESEL GENERATOR 1AB UNAVAILABLE DUE TO TEST AND MAINTENANCE 1.43E-2 EPS-DGN-TM-1CD DIESEL GENERATOR 1CD UNAVAILABLE DUE TO TEST AND MAINTENANCE 1.43E-2 EPS-DUAL-UNIT-LOOP LOOP EVENT HAS AFFECTED BOTH UNITS 5.82E-1 EPS-FAN-CF-U12EXFTS CCF U1&2 EDG FANS FAIL TO START 2.80E-6 EPS-XHE-XL-NR01H OPERATOR FAILS TO RECOVER EMERGENCY DIESEL IN 1 HOUR 8.71E-1 ESW-MDP-CF-RUN CCF U1&2 ESW PUMPS FAIL TO RUN 2.58E-6 ESW-MDP-CF-STRT CCF U1&2 ESW PUMPS FAIL TO START 1.96E-6 HPI-CKV-OO-151E FAILURE OF RHR EAST TRAIN DISCHARGE CKV 151E (HPI FLOW DIVERSION) 2.38E-4 HPI-CKV-OO-151W FAILURE OF RHR WEST TRAIN DISCHARGE CKV 151W (HPI FLOW DIVERSION) 2.38E-4 HPI-XHE-XM-FB OPERATOR FAILS TO INITIATE FEED AND BLEED COOLING 2.00E-2 HPI-XHE-XM-FB1 OPERATOR FAILS TO INITIATE FEED AND BLEED COOLING (DEP) 5.09E-2 HPI-XHE-XM-RECIRC OPERATOR FAILS TO START HIGH PRESSURE RECIRC 2.00E-3 IE-LOCCW LOSS OF COMPONENT COOLING WATER 2.46E-4 IE-LOCHS LOSS OF CONDENSER HEAT SINK INITIATING EVENT 5.86E-2 IE-LODCA LOSS OF 250 VDC UNIT 1 TRAIN A INITIATING EVENT 7.37E-4 IE-LOESW LOSS OF ESSENTIAL SERVICE WATER 2.46E-4 IE-LOESW2 LOSS OF ESW TO UNIT 1 INITIATING EVENT 2.46E-4 IE-LOMFW LOSS OF MFW TRANSIENT 6.89E-2 IE-LOOPGR LOSS OF OFFSITE POWER INITIATOR (GRID-RELATED) 1.22E-2 IE-LOOPSC LOSS OF OFFSITE POWER INITIATOR (SWITCHYARD-CENTERED) 1.04E-2 IE-SLB STEAM LINE BREAK OUTSIDE CONTAINMENT 7.70E-3 IE-TRANS TRANSIENT INITIATING EVENT 6.90E-1 MFW-XHE-XM-ERROR OPERATOR FAILS TO RESTORE MFW FLOW - GENERAL TRANS 4.00E-2 MFW-XHE-XM-STRT OPERATOR FAILS TO START MAIN FEED PUMP (PSA) 1.70E-1 OEP-XHE-XL-NR01HGR OPERATOR FAILS TO RECOVER OFFSITE POWER IN 1 HOUR (GRID-RELATED) 6.59E-1 OEP-XHE-XX-NR01HGR0 CONVOLUTION FACTOR FOR CCF-OPR (1HR-GR Avail) 1.68E-1 RHR-MOV-OO-390 RWST DISCHARGE MOV SI-390 TO LPR TRAINS FAIL 9.63E-4

LER 315-2014-003 B-1 Appendix 2: Dominant Sequence Figure 2A: D. C. Cook, Unit 1 SLOCA Event Tree Figure 2B: D. C. Cook, Unit 1 SLB Event Tree