ML13308A317

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DAEC-SDP-2013-001 - PRA Risk Assessment, 'A' EDG Lube Oil Cooler Leak
ML13308A317
Person / Time
Site: Duane Arnold NextEra Energy icon.png
Issue date: 10/29/2013
From: Kulczycky T
NextEra Energy Duane Arnold
To:
Office of Nuclear Reactor Regulation
Shared Package
ML13308A274 List:
References
DAEC-SDP-2013-001, EA-13-182
Download: ML13308A317 (21)
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Text

DAEC-SDP-2013-001 PRA Risk Assessment

'A' EDG Lube Oil Cooler Leak

[March 8, 2013 event]

Revision 1 Prepared by /O-Z.9- 1.,

Ted Kulczyck Reviewed by 1& o6,*--*A÷/

Brad Hopkinl Reviewed b~6~/ ~ (-z'/

Russ Severson Approved byC. Lic--[( ---2.----

Anil Julka(j 10/29/2013 03:52 PM

1. PURPOSE &SCOPE This evaluation provides a Significance Determination Process (SDP) estimate of the risk associated with the 'A' EDG lube oil cooler failure that occurred on March 8, 2013. This event is a consequence of a leak from the lube oil cooler stationary tubesheet gasket installed during the fall 2012 outage on October 10, 2012. CR Number 01855032 responses and attachments provide a detailed discussion of the event and the root cause evaluation.

Page 1 of 20

2. METHODOLOGY & ACCEPTANCE CRITERIA RISK CALCULATION ACDF and ALERF are the metrics used to evaluate SDP risk. The following SDP thresholds apply:

NRC SDP Color Thresholds ACDF ALERF Color

> 1E-06 to 1E-05 > 1E-07 to 1E-06 WHITE

> 1E-05 to 1E-04 > 1E-06 to 1E-05 YELLOW ACDF and ALERF are calculated as follows':

Internal Events ACDF

1. Evaluate core damage frequency associated with the degraded condition by setting the A EDG "fail to run" basic event probability to 1.0 and re-quantifying the DAEC internal events model, DAEC Rev 6B.
2. Subtract the baseline CDF (Rev 6 B internal events CDF) from step 1 results.
3. Calculate ACDF by multiplying step 2 results by the exposure time (in days) divided by 365 days.

This calculation accounts for normal (average) maintenance during the time the degraded condition existed.

Methodology reference: SignificanceDeterminationProcessBasis Document, NRC Inspection Manual 0308, Attachment 3 Page2 of 20

Internal Events ALERF Internal Events ALERF is evaluated using the internal events LERF model and calculated in the same way as the internal events ACDF. In addition, ACUBE was applied to the generated cutsets to improve the accuracy of the minimal cutset calculation. ACUBE applies the Binary Decision Diagram method to a set of cutsets to address the loss of precision due to high probability basic events and dependence between cutsets for highly redundant systems as is the case for the internal events LERF model. Therefore the ACUBE LERF results more closely represent the true risk for this configuration.

External Events ACDF:

External events ACDF is evaluated using the IPEEE CDF model and calculated in the same way as internal events ACDF. The DAEX-5b external events model was used for the quantification.

External events ALERF External events ALERF is 10% of the external events ACDF. The external events LERF model is outdated. It does not include information gained from NFPA 805 project.

EXPOSURE TIME Exposure time is calculated using the method in RASP Handbook Vol. 1 section 2.2:

T= t + repairtime. For afailure that was determined to have occurred when the component was last functionally operated in a test or unplanned demand (e.g., failure occurred when the component was being secured), the exposure time (T) is equal to the total time from the last successful operation to the unsuccessful operation (t) plus repairtime.

This exposure time determination approach is appropriatefor standby or periodically operated components thatfail due to a degradationmechanism that is not graduallyaffecting the component during the standby time period.

The t period should be consideredfor the following cases:

- Known inception of failure. The failure was determined to have occurred when the component was lastfunctionally operatedin a test or unplanned demand.

- Unknown inception of failure or no root cause assessment. The failure mechanism was unknown and the root cause assessment was not sufficient or not complete to identify the cause of the failure.

Page3 of 20

3. INPUTS and ASSUMPTIONS:
a. EXPOSURE TIME. Two exposure times are evaluated:

3.69 Days. AR 01855032 Past Operability Review (POR) established the point in time when the A EDG was no longer capable of performing its function as occurring on 3/6/2013 at 8:12. At this time the lube oil keep warm system was removed from service which affected the condition of the lube oil heater gasket that caused a small lube oil leak when the A EDG was started (maintenance run) on 3/8/2013 at 2:15.

The diesel lube oil gasket was repaired and A EDG returned to service as available on 3/10/2013 at 0:49. The total exposure time for this degraded condition was 3.69 days.

ACTION DATE & TIME Start 'A' EDG conduit inspections, unit INOP but Available 3/6/2013 8:12 Stopped 'A' EDG conduit inspections for day - 'A' EDG Operable 3/6/2013 2"1:31 Start 'A' EDG conduit inspections, unit INOP 3/7/2013 7:30 Took 'A' EDG to Unavailble to support conduit inspections 3/7/2013 7:57 Returned 'A' EDG to Available following conduit inspections 3/8/2013 2:49 Maintenance Run per W040209288-01/02 3/8/2013 2:15 Maintenance Run Complete with identified 60dpm LO leak 3/8/2013 4:01 Maintenance Run to investigate leak - shutdown due to gross leak at 3/8/2013 12:08 start. 'A' EDG declared Unavailable.

POR End Time - 'A' EDG returned to Available status 3/10/2013 0:49 ii. 22 Days. NRC evaluation assumes a 22 day exposure time. The time period is the 'A' EDG start on February 16, 2013 (with no leakage) through to its return to available status on March 10, 2013; 22 days.

b. FAILURE MODE. The 'A' EDG ran for more than 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br /> on 3/8/2013 before it was shutdown to repair the gasket leak; the recorded run time noted in AR 01855032 is 2hour and 46 minutes. As such the evaluation is based on setting the "Fail to Run > 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br />" EDG 2D031 basic event probability to 1.0. This assumption is used to calculate conditional core damage and large early release using the DAEC 6B internal events model.
c. RUN DURATION. The assessment is based on assuming the nominal run duration associated with an EDG failure to run for more than 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br />. This assumption is conservative based on the following:
1. The run was NOT ended due to the leakage rate.
2. The initial leakage rate was 5 dpm and was 30-40 dpm as the EDG approached rated power. At the end of the maintenance run of 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br /> and 46 minutes the leak rate was 60 dpm. This leak rate was not consequential; 'A' EDG could have continued to run if required.
3. After the run, maintenance was performed on the gasket and significant gasket leakage occurred during the post maintenance run. The second restart of the EDG on 3/18/2013 showed significantly increased leakage, beginning within 1 minute of EDG startup. The observed increased leakage rate is consistent with the root cause analysis that concluded the gasket failure was due to the pressure Page 4 of 20

transient in the lube oil system experienced only during startup. As such, the time when the A EDG was no longer capable of performing its function is conservatively assumed as occurring on 3/6/2013 at 8:12.

4. Over the 1.5 hour5.787037e-5 days <br />0.00139 hours <br />8.267196e-6 weeks <br />1.9025e-6 months <br /> maintenance run on 3/6/2013 the leak grew from 5 dpm up to 60 dpm at the end of the maintenance run. If an exponential leakage growth rate was conservatively assumed EDG shutdown and repair would have been required at 5.85 hours9.837963e-4 days <br />0.0236 hours <br />1.405423e-4 weeks <br />3.23425e-5 months <br />. More likely, the postulated leak rate growth would have not required shutting down the diesel within the 24 hour2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> mission time.
d. RECOVERY. EDG recovery would have been straightforward and could have been completed within the 24 hour2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> mission time. Once the low lube oil alarm was received there would have been sufficient time to diagnose the problem and to take compensatory actions. Given a condition where EDG A was needed, the leakage would likely have been tolerable and a decision made to continue running the EDG and stage personnel at the leak to monitor the leakage and to prepare for a repair. If the leakage rate increased to a point where failure was likely, the EDG would have been shutdown and the repair likely completed within 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br />. Since this failure mode and recovery time is consistent with the assumptions of the baseline PRA, no changes are required to the recovery or convolution assumptions. The baseline probability for recovery of this diesel over a 24 hour2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> period was not changed given the straightforward repair and diagnosis associated with this failure mode.

Time required to repair lube oil cooler fixed end joint upon discovery of leak [reference, D Westendorf email, 9/11/13]. Times are estimated based on response following initial leakage identification on March 8th, 2013 (CR 1854872):

Summary of Recovery Actions Recovery Action Time to Recover Repair lube oil cooler fixed end joint 6 .5 hours5.787037e-5 days <br />0.00139 hours <br />8.267196e-6 weeks <br />1.9025e-6 months <br /> Install clamp over flange to slow down leakage rate 3 hours3.472222e-5 days <br />8.333333e-4 hours <br />4.960317e-6 weeks <br />1.1415e-6 months <br /> Let lube oil bleed - install catch basket to assure all leakage directed to drain Immediate Page5 of 20

. t...S . .. . ... REPAIR LUBE OIL COOLER FIXED ,. END

.. " .JOINT  : ." ." : i .: : ii ED G ,.

Step Task Hours D Powering Bus Plan work order: Collect in-stock gaskets from warehouse for fixed end and packing rings 2.5 YES 1 forfloating end.

2 Stop EDG. Tagout system, drain, de-energize: 1 NO 3 Remove stationary end and floating end heads: 1.5 NO Install strongback and pull rod. Remove tube bundle several inches to replace lube oil side 1 NO gasket. 1 _NO 5 Replace fixed end channel head to shell water side gasket and reinstall channel head. 1 NO 6 Replace packing rings and install floating end head. 1 NO 8 Clear tags, re-energize lube oil. 1 NO Start Diesel.

9 Based on March 6t history, the lube oil temperaturewill reach the minimum oil sump temp ".'

for startingdiesels approx. 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> after de-energizing heaters. (Oil temp not requiredfor the start,engine may not meet a 10 second start,but not requiredfor Availability) .... ...... _... _

INSTALL CLAMP TO SLOW DOWN LEAKAGE RATE

.. .. " EDG Step Task Hours Powering. Bus Assume once leak rate hits 0.5 gpm, the leak rate is too high to successfully install clamp. Based on exponential growth curve, 0.5 gpm would occur six hours after 0 ..

leak initiation. So repair would need to occur within 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> of the initial leak E based on the worst case estimate.

Fashion sheet metal clamp, approx. 4" wide (combined width of shell flange, tube sheet, and head flange) by circumference of joint plus overlap (70"). Install 2 YES adhesive weather-stripping foam to edges of clamp for entire circumference.

2 1 Install sheet metal clamp over joint and fasten with pop rivets or straps. 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br /> [ 1  : YES The worst case total time to repair diesel is 9 hours1.041667e-4 days <br />0.0025 hours <br />1.488095e-5 weeks <br />3.4245e-6 months <br /> but diesel would have continued running while work was planned and parts were collected, i.e. the first 2.5 hours5.787037e-5 days <br />0.00139 hours <br />8.267196e-6 weeks <br />1.9025e-6 months <br />. The total time the EDG would not powering the bus is 6.5 hours5.787037e-5 days <br />0.00139 hours <br />8.267196e-6 weeks <br />1.9025e-6 months <br />.

e. COMMON CAUSE. The common cause treatment for the other diesel generator was not adjusted since the failure mode for the A EDG was not present in the B EDG. The common cause calculation applies a shape factor for both EDGs failing based on industry data. That probability of the other EDG failing due to a common cause was not considered to change with the one EDG failed, since the underlying industry information does not change.
f. CONSERVATISMS. The following modeling conservatisms affect the top cutsets and sequences relevant to this failure:
i. RCIC/HPCI. No credit is given in the convolution analysis for availability of RCIC and HPCI after failing to recover the failed EDG.

ii. M01942. The action to manually open M01942 uses a screening value of 0.1. At the time of the model update the procedure was in development. An HRA evaluation of this action would result in a much lower value. Manual opening of M01942 allows RHRSW crosstie to provide for late alternate injection in the event of losing Division I AC. This action was only applied to situations where the Page 6 of 20

containment cooling has failed and where operations would have more than 20 hours2.314815e-4 days <br />0.00556 hours <br />3.306878e-5 weeks <br />7.61e-6 months <br /> to determine the valve has no power and should be manually opened. In this case the loss of Division IAC would be noted much earlier and M01942 would be opened early; if credited in the PRA this action would lead to more successful sequences.

iii. Leakage rate. If an exponential leakage growth rate was conservatively assumed EDG shutdown and repair would have been required at 5.85 hours9.837963e-4 days <br />0.0236 hours <br />1.405423e-4 weeks <br />3.23425e-5 months <br />. More likely, the leak rate growth, if any, would have not required shutting down the diesel within the 24 hour2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> mission time.

iv. LERF. The internal events LERF model has significant conservatisms due to classifying many long term sequences greater than 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> as large early releases - ~30% or more contribution to LERF.

v. Convolution does not separate the two EDGs; i.e. cannot treat one independent from the other.

vi. Limited credit is given for alternate injection during an SBO using the portable diesel fire pump. An HEP of 0.5 is assumed. Given the need for alternate injection would be required late in the event, a screening HEP value of 0.01 could be applied.

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4. RESULTS 2 Base Case For the exposure time, ACDF 3 is less than 1E-06 (GREEN SDP) and ALERF is slightly higher than 1E-07 (WHITE SDP). As noted in the assumptions section, LERF is affected by the conservatism of classifying many long term sequences greater than 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> as large early releases. Correction of this conservatism would reduce ALERF below the WHITE threshold. Also other qualitative factors such as the fact that the oil leak was fixed the same day, a few hours after it was discovered, was not included in the model.

CDF [truncation= E-1I1 Internal Events External Events ACDF (exposure time)

EXP CDF CDF =ACDFyear*EXpOSUre Days/365 Description TIME -A CDF A CDF Days BASE Config (year) BASE Config (year)

(days) PRA Specific PRA IE EE Total Specific 4

Base Case Model 3.69 3.5E-06 8.9E-06 5.4E-06 3.OE-06 3.9E-06 8.6E-07 Sensitivity - 22 days 22 3.5E-06 8.9E-06 5.4E-06 3.OE-06 3.9E-06 8.6E-07

5. CONCLUSION Based on the results this issue is not a "substantial safety significance" finding.

2 DAEC 6B internalevents model and the DAEX-Sb external events model were used to perform the quantification.

The SDP is evaluating a CDP, an integral undera CDF spike, and translatingit to an increasein CDF (ACDF) for the year in which the finding occurred.

Some applies to ALERF [reference:NRC Inspection Manual 0308, attachment3 section 8.]

Model updated to correct an inaccuracyidentified in the process of reviewing the convolution equationsfor this SDP. PRA task tracking # IPL 637 Page8 of 20

APPENDIX A Importance Weather centered loss of offsite power is the dominant initiator; recovery of offsite power is least likely for this LOOP initiator category. The top operator action is manually opening M01942 to allow RHRSW crosstie to provide for late alternate injection in the event of losing Division I AC.

Event Probability FV RAW Description DEDG--ESDGIG31-FR-- 1.00E+00 0.6145 1 DIESELGENERATOR 1G31 FTRUN FOR24 HR DSWYRDENOPWNRC3ORX- 7.73E-01 0.55668 1.2 FAIL TO RECOVER OFFSITE POWER IN 30 MIN - WEATHER CENTERED

%TE-W 1.12E-02 0.55448 50.0 WEATHER CENTERED LOSS OF OFFSITE POWER ADJ FACTOR FOR 1 EDG FTR CONVOLUTION WITH NO EDG RECOVERY - 30 MIN SEQ -

DSWYRDENOPH06NDWRX- 3.07E-01 0.36487 1.8 WEATHER DRHR--CNOPRECVRVRX-- 3.50E-01 0.33414 1.6 OP FAILS TO RECOVER TORUS COOLING (W/I 20 HRS) - VENT SUCCESS SCENARIOS DRHRSWOPMOO1942-HE- 1.O0E-01 0.18569 2.7 OPERATIONS FAILS TO REMOTE MANUALLY OPEN M01942 DSWYRDENOPGNRC30RX-- 8.25E-01 0.14989 1.0 FAIL TO RECOVER OFFSITE POWER IN 30 MIN - GRID DRHRSWDNOPLTINJ-HE-- 1.OOE+00 0.12055 1 OP FAILS TO ALIGN ALT LP INJECTION (TRAN, SLOCA, MLOCA, IORV)

DHPCI-CFMO2238OPCE-- 1.O0E-O1 0.11197 2.0 COND. PROB. THAT M02238 IS INITIALLY CLOSED DRHRSWDNOPLTINJ-HERX 5.70E-02 0.11006 2.8 OP FAILS TO ALIGN ALT LP INJECTION (TRAN, SLOCA, MLOCA, IORV)

%TE-S 8.69E-03 0.10797 13.3 SWITCHYARD CENTERED LOSS OF OFFSITE POWER TOP SEQUENCES Sequence 18 events:

1. LOOP and unavailability of one EDG.
2. Loss of Suppression pool cooling. Loss of EDG A fails RHRSW LOOP AC and RHRSW BD is in maintenance and recovery of this train is not credited.
3. Operator action to open M01942 is not credited at this point (early) in the event tree, this precludes aligning ESW or GSW as an alternate means of injection. Early is defined as before reach heat capacity limit.
4. RCIC, HPCI and CRD are available. RCIC is available for injection since the Division II battery is continuously charged by the 'B' diesel generator.
5. Control of reactor pressure is successful.
6. CRD Injection fails due to loss of CRD A pump - two pumps are required for success. - HVAC is lost due to cooling water unavailable due to loss of Well Water pumps that are powered by offsite and onsite power (Wet Well pumps A and C are powered by A EDG). Opening the CRD room doors is not credited in the PRA, which likely would be sufficient to cool these rooms, a conservatism. A room heat up calculation has not been performed to assess whether loss of CRD HVAC results in adverse temperatures being reached during the mission time.
7. Core Spray and LPCI are available for low pressure injection.

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8. As the suppression pool temperature rises the heat capacity limit (HCL) is reached and the vessel must be depressurized to allow injection by low pressure systems. Primary low pressure injection systems fail once NPSH limits are reached. Without injection, core damage results. Alternate low pressure injection systems are required to prevent core damage.
9. Alternate injection systems are unavailable because the operator fails to open M01942 and this precludes aligning ESW or GSW as an alternate means of injection. Manually opening MO 1942 is required when Div 1 power is not available, as is the case in this cutset. However, as noted earlier, opening M01942 is not credited early in this sequence before containment impacts can defeat HPCI and RCIC and is assumed to fail after containment venting. This operator action currently uses a 0.1 screening value for this action. However, given the time available and the obvious indication that opening this valve is necessary, a much smaller value can be justified.
10. Without injection core damage results.

This sequence also applies to cutsets 2, 15, and 19. Cutsets 6 and 9 are similar but instead of operator failing to open M01942 the operator fails to align alternate injection.

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APPENDIX B TREATMENT OF CONVOLUTION The first cutset contains a basic event (DSWYRDENOPWNRC3ORX--) representing the probability that offsite power is not recovered within 30 minutes from the time of plant shutdown due to loss-of-offsite power. If offsite power is recovered, the remainder of the event is evaluated using the 'General Transient' event tree. If offsite power is not recovered within this early time frame, the remainder of the event is evaluated in event trees designed for assessment of longer term LOOP events. Since this is the case for the cutset of interest, a second non-recovery term is present (DSWYRDENOPH06RDWRX--.)

The value of basic event DSWYRDENOPHO6RDWRX-- is derived using convolution methodology. It considers the possibility that offsite power is not yet recovered at the time the 'A' standby diesel generator fails to run. It also includes the possibility that the 'A' diesel generator is not recovered before core damage occurs upon its failure.

The time available for recovering the diesel generator is conservatively assumed to be only one-half hour.

The calculated value of DSWYRDENOPHO6RDWRX-- is adjusted such that the multiplication of the early non-recovery term, DSWYRDENOPWNRC30RX--, and late non-recovery term DSWYRDENOPHO6RDWRX-- provides the correct AC power non-recovery probability over the entire mission time.

Reference appendix G.5 in the Component Notebook for more details on the basis for the Convolution method applied at DAEC.

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APPENDIX C TOP 50 CDF CUTSETS Cutset Report I I DAEC-L1-CDF = 8.926E-06 ( Probability)

  1. Cutset Prob. BE Prob Inputs I 3.08E-07 1.12E-02 %TE-W WEATHER CENTERED LOSS OF OFFSITE POWER 1.00E+O0 DEDG--ESDGIG31-FR-- DIESEL GENERATOR 1G31 FT RUN FOR 24 HR 3.SOE-O1 DRHR--CNOPRECVRVRX-- OP FAILS TO RECOVER TORUS COOLING (W/I 20 HRS) - VENT SUCCESS SCENARIOS 3.31E-03 DRHRSWDN--TBD--MU-- RHRSW LOOP BD in Maintenance 1.OOE-01 DRHRSWOPMOO1942-HE-- OPERATIONS FAILS TO REMOTE MANUALLY OPEN M01942 7.73E-O1 DSWYRDENOPWNRC30RX-- FAIL TO RECOVER OFFSITE POWER IN 30 MIN -WEATHER CENTERED 3.07E-01 DSWYRDENOPH06NDWRX- ADJ FACTOR FOR 1 EDG FTR CONVOLUTION WITH NO EDG RECOVERY - 30 MIN SEQ- WEATHER 2 2.83E-07 1.12E-02 %TE-W WEATHER CENTERED LOSS OF OFFSITE POWER 1.00E+O0 DEDG--ESDGIG31--FR-- DIESEL GENERATOR 1G31 FT RUN FOR 24 HR 3.5OE-O1 DRHR--CNOPRECVRVRX-- OP FAILS TO RECOVER TORUS COOLING (W/I 20 HRS) - VENT SUCCESS SCENARIOS 3.04E-03 DRHR--CN-SUPCLBMU-- Suppr. Pool Cooling Loop B Maintenance 1.OOE-01 DRHRSWOPMOO1942-HE- OPERATIONS FAILS TO REMOTE MANUALLY OPEN M01942 7.73E-01 DSWYRDENOPWNRC30RX- FAIL TO RECOVER OFFSITE POWER IN 30 MIN - WEATHER CENTERED 3.07E-01 DSWYRDENOPH06NDWRX-- ADJ FACTOR FOR 1 EDG FTR CONVOLUTION WITH NO EDG RECOVERY - 30 MIN SEQ - WEATHER 3 1.76E-07 1.12E-02 %TE-W WEATHER CENTERED LOSS OF OFFSITE POWER 1.00E+O0 DEDG--ESDG1G31--FR-- DIESEL GENERATOR 1G31 FT RUN FOR 24 HR 3.50E-01 DRHR--CNOPRECVRVRX-- OP FAILS TO RECOVER TORUS COOLING (W/I 20 HRS) - VENT SUCCESS SCENARIOS 1.OOE+00 DRHRSWDNOPLTINJ-HE-- OP FAILS TO ALIGN ALT LP INJECTION (TRAN, SLOCA, MLOCA, IORV) 5.70E-02 DRHRSWDNOPLTINJ-HERX OP FAILS TO ALIGN ALT LP INJECTION (TRAN, SLOCA, MLOCA, IORV) 3.31E-03 DRHRSWDN--TBD--MU- RHRSW LOOP BD in Maintenance 7.73E-O1 DSWYRDENOPWNRC30RX-L FAIL TO RECOVER OFFSITE POWER IN 30 MIN - WEATHER CENTERED 3.07E-01 DSWYRDENOPH06NDWRX- ADJ FACTOR FOR 1 EDG FTR CONVOLUTION WITH NO EDG RECOVERY - 30 MIN SEQO-WEATHER 4 1.61E-07 1.12E-02 %TE-W WEATHER CENTERED LOSS OF OFFSITE POWER 1.OOE+00 DEDG--ESDGIG31--FR-- DIESEL GENERATOR 1G31 FT RUN FOR 24 HR 3.5OE-O1 DRHR--CNOPRECVRVRX-- OP FAILS TO RECOVER TORUS COOLING (W/I 20 HRS) - VENT SUCCESS SCENARIOS 3.04E-03 DRHR--CN--SUPCLBMU-- Suppr. Pool Cooling Loop B Maintenance 1.00E+0O DRHRSWDNOPLTINJ-HE-- OP FAILS TO ALIGN ALT LP INJECTION (TRAN, SLOCA, MLOCA, IORV) 5.70E-02 DRHRSWDNOPLTiNJ-HERX OP FAILS TO ALIGN ALT LP INJECTION (TRAN, SLOCA, MLOCA, IORV) 7.73E-01 DSWYRDENOPWNRC30RX-- FAIL TO RECOVER OFFSITE POWER IN 30 MIN - WEATHER CENTERED 3.07E-01 DSWYRDENOPHO6NDWRX- ADJ FACTOR FOR 1 EDG FTR CONVOLUTION WITH NO EDG RECOVERY - 30 MIN SEQ- WEATHER S 1.15E-07 2.03E-02 %TI IORV 2.05E-02 DEDG--ENDGMTIG21MU-- DIESEL GENERATOR 1G21 IN MAINTENANCE 1.OOE+OO DEDG--ESDGIG31--FR-- DIESEL GENERATOR 1G31 FT RUN FOR 24 HR 1.50E-01 DLLSRVNFRVOWPRESCE-- RELIEF VALVE FAILS TO RESEAT AS RPV PRESSURE DROPS 2.40E-02 DSWYRDEN--CLOOPLCE- CONDITIONAL LOOP PROB GIVEN LOCA SIGNAL INITIATOR 8.25E-01 DSWYRDENOPGNRC3ORX- FAIL TO RECOVER OFFSITE POWER IN 30 MIN - GRID 9.32E-02 DSWYRDENOPHO6NDGRX-- ADJ FACTOR FOR 1 EDG FTR CONVOLUTION WITH NO EDG RECOVERY - 30 MIN SEQ - GRID 6 1.09E-07 1.12E-02 %TE-W WEATHER CENTERED LOSS OF OFFSITE POWER 7.50E-01 D125DCENCB102CLICE-- CONDITIONAL PROBABILITY THAT BREAKER 1D102 IS CLOSED 1.00E+00 D125DCENOPALNCHGHE- OPERATOR FAILS TO ALIGN STANDBY 125VDC BATTERY CHARGER 5.OOE-01 D250DCENCB403CLICE- CONDITIONAL PROBABILITY THAT BREAKER 1D403 IS CLOSED 1.00E+O0 D25ODCENOPCB4023HE-- OPERATOR FAILS TO CLOSE ALTERNATE 250V BREAKER W/I 2 HOURS 9.90E-01 DADS--ANOPINH BSCHE-- OPERATOR SUCCESSFULLY INITIATES ADS INHIBIT 1.OOE+00 DADS--ANOPTRANS-HE-- OP FAILS TO INITIATE RPV EMERGENCY DEPRESS (TRANSIENTS) 1.OOE+00 DEDG--ESDGIG31--FR-- DIESEL GENERATOR 1G31 FT RUN FOR 24 HR Page 12 of 20

7.73E-01 DSWYRDENOPWNRC30RX- FAIL TO RECOVER OFFSITE POWER IN 30 MIN - WEATHER CENTERED 1.10E-04 HRACOMB3 HRA combination recovery term.

3.07E-O1 DSWYRDENOPH06NDWRX- ADJ FACTOR FOR 1 EDG FTR CONVOLUTION WITH NO EDG RECOVERY - 30 MIN SEQ- WEATHER 7 1.0SE-07 1.12E-02 %TE-W WEATHER CENTERED LOSS OF OFFSITE POWER 1.OOE+O0 DEDG--ESDGIG31-FR-- DIESEL GENERATOR IG31 FT RUN FOR 24 HR 1.13E-03 DRHR--CN-LOOPBDMU- RHR LOOP BD IN MAINTENANCE 3.50E-O1 DRHR--CNOPRECVRVRX-- OP FAILS TO RECOVER TORUS COOLING (W/I 20 HRS) - VENT SUCCESS SCENARIOS 1.O0E-01 DRHRSWOPMOO1942-HE-- OPERATIONS FAILS TO REMOTE MANUALLY OPEN M01942 7.73E-01 DSWYRDENOPWNRC30RX-- FAIL TO RECOVER OFFSITE POWER IN 30 MIN - WEATHER CENTERED 3.07E-01 DSWYRDENOPH06NDWRX- ADJ FACTOR FOR 1 EDG FTR CONVOLUTION WITH NO EDG RECOVERY - 30 MIN SEQ- WEATHER 8 9.02E-08 1.12E-02 %TE-W WEATHER CENTERED LOSS OF OFFSITE POWER 1.00E+00 DEDG--ESDG1G31-FR-- DIESEL GENERATOR 1G31 FT RUN FOR 24 HR 3.50E-01 DRHR--CNOPRECVRVRX-- OP FAILS TO RECOVER TORUS COOLING (W/I 20 HRS) - VENT SUCCESS SCENARIOS 9.70E-04 DRHRSWDNOPLOOPB-HU-- PRE-INITIATOR HEP: FAILURE TO RESTORE RHRSW LOOP B POST T/M 1.O0E-01 DRHRSWOPMOO1942-HE-- OPERATIONS FAILS TO REMOTE MANUALLY OPEN M01942 7.73E-01 DSWYRDENOPWNRC30RX- FAIL TO RECOVER OFFSITE POWER IN 30 MIN - WEATHER CENTERED 3.07E-01 DSWYRDENOPH06NDWRX-- ADJ FACTOR FOR 1 EDG FTR CONVOLUTION WITH NO EDG RECOVERY - 30 MIN SEQ- WEATHER 9 7.48E-08 7.74E-01 %TT TURBINE TRIP WITH BYPASS 1.00E+00 DFEED-CNOPSTRTLAHE-- OPERATOR FAILS TO INITIATE FEEDWATER (LARGE LOCA OR ATWS) 1.0OE+00 DFEED-CNOPVEL-I-HE-- OP FAILS TO CONTROL FEEDWATER FOLLOWING SCRAM 1.00E+00 DRPS--NNOPLWLVL1HE-- OP FAILS TO CONTROL RPV LEVEL LOW (MC UNAVAIL - SLC EARLY W/HP INJ) 2.10E-06 DRPS--NN--RPSMCHTF-- MECHANICAL FAILURE OF SCRAM 4.60E-02 HRACOMB276 HRA combination recovery term.

10 6.83E-08 7.74E-01 %TT TURBINE TRIP WITH BYPASS 1.00E+00 DRPS-NNOPLWLVL6HE-- OP FAILS TO CONTROL RPV LEVEL LOW (MC AVAIL - SLC LATE W/HP INJ) 2.1OE-06 DRPS--NN--RPSMCHTF- MECHANICAL FAILURE OF SCRAM 1.OOE+00 DSBLC-CNOP-EARLYHE-- OPERATOR FAILS TO INJECT SLC EARLY 4.20E-02 HRACOMB455 HRA combination recovery term.

11 6.71E-08 1.12E-02 %TE-W WEATHER CENTERED LOSS OF OFFSITE POWER 7.50E-01 D125DCENCB102CLICE- CONDITIONAL PROBABILITY THAT BREAKER 1D102 IS CLOSED 1.00E+00 D125DCENOPALNCHGHE- OPERATOR FAILS TO ALIGN STANDBY 125VDC BATTERY CHARGER 9.90E-01 DADS--ANOPINHBSCHE- OPERATOR SUCCESSFULLY INITIATES ADS INHIBIT 1.00E+00 DADS-ANOPTRANS-HE-- OP FAILS TO INITIATE RPV EMERGENCY DEPRESS (TRANSIENTS) 3.40E-04 DADS--ANOPTRANS-HERX OP FAILS TO INITIATE RPV EMERGENCY DEPRESS (TRANSIENTS) 1.OOE+00 DEDG--ESDG1G31--FR-- DIESEL GENERATOR 1G31 FT RUN FOR 24 HR 1.00E-01 DHPCI-CFMO2238OPCE-- COND. PROB. THAT M02238 IS INITIALLY CLOSED 7.73E-01 DSWYRDENOPWNRC3ORX-- FAIL TO RECOVER OFFSITE POWER IN 30 MIN - WEATHER CENTERED 3.O7E-01 DSWYRDENOPH06NDWRX-- ADJ FACTOR FOR 1 EDG FTR CONVOLUTION WITH NO EDG RECOVERY - 30 MIN SEQ - WEATHER 12 6.34E-08 7.74E-01 %TT TURBINE TRIP WITH BYPASS 1.00E+00 DADS-ANOPINHBHPHE-- FAILURE OF OPERATOR INHIBIT ADS (HPI AVAIL) 3.90E-02 DADS--ANOPINHBHPHERX FAILURE OF OPERATOR INHIBIT ADS (HPI AVAIL) 2.10E-06 DRPS--NN--RPSMCHTF-- MECHANICAL FAILURE OF SCRAM 13 6.05E-08 1.78E+00 %MSD MANUAL SHUTDOWN 1.OOE+00 DCNDSTCNOPTINJ-HE-- OP FAILS TO INIT. COND. FOR ALT. INJ. (TRANSIENT EVENTS) 1.00E+00 DFEED-CNOPSTRT-HE- OPERATOR FAILS TO INITIATE FEEDWATER 1.00E+O0 DFEED-CNOPVEL-TTHE-- OP FAILS TO CONTROL FEEDWATER FOLLOWING SCRAM 2.OOE-01 DPCONTNNCTDWZN4-RP-- TORUS AIRSPACE RUPTURE (QUASI-STATIC, LOW TEMP CHALLENGE) 1.00E+0O DRHR--CNOPSPCELYHE-- OPERATOR FAILS TO INITIATE TORUS COOLING (EARLY TIMEFRAME) 1.00E+00 DRHR--CNOPSPCLT-HE-- CONDITIONAL HEP FOR LATE SPC INITIATION GIVEN FAILURE IN EARLY TIME FRAME 1.OOE+00 DSBGT-CNOP-VENT-H E-- OP FAILS TO VENT PRIMARY CONTAINMENT (EOP-2 Step PC/P-iO) 1.70E-07 HRACOMB185 HRA combination recovery term.

14 5.99E-08 1.12E-02 %TE-W WEATHER CENTERED LOSS OF OFFSITE POWER 1.00E+00 DEDG--ESDG1G31-FR-- DIESEL GENERATOR 1G31 FT RUN FOR 24 HR 1.13E-03 DRHR--CN-LOOPBDMU- RHR LOOP BD IN MAINTENANCE 3.50E-01 DRHR--CNOPRECVRVRX-- OP FAILS TO RECOVER TORUS COOLING (W/I 20 HRS) - VENT SUCCESS SCENARIOS 1.00E+00 DRHRSWDNOPLTINJ-HE-- OP FAILS TO ALIGN ALT LP INJECTION (TRAN, SLOCA, MLOCA, IORV) 5.70E-02 DRHRSWDNOPLTINJ-HERX OP FAILS TO ALIGN ALT LP INJECTION (TRAN, SLOCA, MLOCA, IORV)

Page 13 of 20

7.73E-01 DSWYRDENOPWNRC30RX- FAIL TO RECOVER OFFSITE POWER IN 30 MIN - WEATHER CENTERED 3.07E-01 DSWYRDENOPHO6NDWRX- ADJ FACTOR FOR 1 EDG FTR CONVOLUTION WITH NO EDG RECOVERY -30 MIN SEQ- WEATHER 15 5.61E-08 1.12E-02 %TE-W WEATHER CENTERED LOSS OF OFFSITE POWER 1.00E+00 DEDG--ESDG1G31-FR-- DIESEL GENERATOR 1G31 FT RUN FOR 24 HR 2.11E-05 DLPCSRHRCSB-RHRBMA- LPCS B, RHR LOOP B CONCURRENTLY OUR FOR MAINTENANCE 7.73E-01 DSWYRDENOPWNRC30RX- FAIL TO RECOVER OFFSITE POWER IN 30 MIN - WEATHER CENTERED 3.07E-01 DSWYRDENOPHO6NDWRX- ADJ FACTOR FOR I EDG FTR CONVOLUTION WITH NO EDG RECOVERY - 30 MIN SEQ - WEATHER 16 5.45E-08 1.12E-02 %TE-W WEATHER CENTERED LOSS OF OFFSITE POWER 2.05E-02 DEDG--ENDGMTIG21MU-- DIESEL GENERATOR 1G21 IN MAINTENANCE 1.00E+O0 DEDG--ESDGIG31-FR-- DIESEL GENERATOR 1G31 FT RUN FOR 24 HR l.O0E-01 DHPCI-CFMO223BOPCE-- COND. PROB. THAT M02238 IS INITIALLY CLOSED 1.00E-02 DRCIC-CSPHINLTPTCE-- COND. PROB. THAT INLET DRN POT OVERFILL CAUSES WTR HAMMER 7.73E-01 DSWYRDENOPWNRC3ORX- FAIL TO RECOVER OFFSITE POWER IN 30 MIN - WEATHER CENTERED 3.07E-01 DSWYRDENOPHO6NDWRX- ADJ FACTOR FOR 1 EDG FTR CONVOLUTION WITH NO EDG RECOVERY - 30 MIN SEQ - WEATHER 17 5.20E-08 7.74E-01 %TT TURBINE TRIP WITH BYPASS 1.00E+0O DFEED-CNOPSTRTLAHE-- OPERATOR FAILS TO INITIATE FEEDWATER (LARGE LOCA OR ATWS) 1.00E+00 DFEED-CNOPVEL-1THE-- OP FAILS TO CONTROL FEEDWATER FOLLOWING SCRAM 1.DOE+00 DHPCI-CNOPLPTRP-HE-- OPERATOR FAILS TO BYPASS HPCI LOW RPV PRESS TRIP 1.00E+00 DRCIC-CNOPLPTRPAHE-- OPERATOR FAILS TO BYPASS RCIC LOW RPV PRESS TRIP (ATWS) 1.00E+00 DRPS--NNOPLWLVL2HE-- OP FAILS TO CONTROL RPV LEVEL LOW (MC UNAVAIL - SLC EARLY W/LP INJ) 2.10E-06 DRPS--NN--RPSMCHTF-- MECHANICAL FAILURE OF SCRAM 3.20E-02 HRACOMB272 HRA combination recovery term 18 5.20E-08 7.74E-01 %TT TURBINE TRIP WITH BYPASS 1.00E+00 DFEED-CNOPSTRTLAHE-- OPERATOR FAILS TO INITIATE FEEDWATER (LARGE LOCA OR ATWS) 1.00E+00 DFEED-CNOPVEL-T-HE-- OP FAILS TO CONTROL FEEDWATER FOLLOWING SCRAM 1.00E+00 DHPCI-CNOPLPTRP-HE-- OPERATOR FAILS TO BYPASS HPCI LOW RPV PRESS TRIP 2.10E-06 DRPS--NN-RPSMCHTF-- MECHANICAL FAILURE OF SCRAM 1.0DE+00 DSBLC-CNOP-EARLYHE- OPERATOR FAILS TO INJECT SLC EARLY 1.00E+00 DSBLC-CNOPLTWOMCHE-- OPERATOR FAILS TO INJECT SLC LATE GIVEN FAILURE EARLY (MC UNAVAILABLE) 3.20E-02 HRACOMB275 HRA combination recovery term 19 5.14E-08 1.12E-02 %TE-W WEATHER CENTERED LOSS OF OFFSITE POWER 1.0OE+OO DEDG--ESDGIG31-FR-- DIESEL GENERATOR 1G31 FT RUN FOR 24 HR 3.sOE-O1 DRHR--CNOPRECVRVRX-- OP FAILS TO RECOVER TORUS COOLING (W/I 20 HRS) - VENT SUCCESS SCENARIOS 9.70E-04 DRHRSWDNOPLOOPB-HU-- PRE-INITIATOR HEP: FAILURE TO RESTORE RHRSW LOOP B POST T/M 1.00E+00 DRHRSWDNOPLTINJ-HE-- OP FAILS TO ALIGN ALT LP INJECTION (TRAN, SLOCA, MLOCA, IORV) 5.70E-02 DRHRSWDNOPLTINJ-HERX OP FAILS TO ALIGN ALT LP INJECTION (TRAN, SLOCA, MLOCA, IORV) 7.73E-01 DSWYRDENOPWNRC3ORX-- FAIL TO RECOVER OFFSITE POWER IN 30 MIN - WEATHER CENTERED 3.07E-01 DSWYRDENOPHO6NDWRX-- ADJ FACTOR FOR 1 EDG FTR CONVOLUTION WITH NO EDG RECOVERY - 30 MIN SEQ - WEATHER 20 4.71E-08 7.74E-01 %TT TURBINE TRIP WITH BYPASS 1.DOE+00 DFEED-CNOPSTRTLAHE-- OPERATOR FAILS TO INITIATE FEEDWATER (LARGE LOCA OR ATWS) 1.OOE+00 DFEED-CNOPVEL-TTHE- OP FAILS TO CONTROL FEEDWATER FOLLOWING SCRAM 1.0OE+00 DHPCI-CNOPLPTRP-HE-- OPERATOR FAILS TO BYPASS HPCI LOW RPV PRESS TRIP 1.OOE+O0 DRPS--NNOPLWLVL4HE-- OP FAILS TO CONTROL RPV LEVEL LOW (MC UNAVAIL - SLC LATE W/LP INJ) 2.10E-06 DRPS-NN-RPSMCHTF-- MECHANICAL FAILURE OF SCRAM 1.O0E+00 DSBLC-CNOP-EARLYHE-- OPERATOR FAILS TO INJECT SLC EARLY 2.90E-02 HRACOMB274 HRA combination recovery term 21 4.54E-08 1.12E-02 %TE-W WEATHER CENTERED LOSS OF OFFSITE POWER 1.41E-03 D125DCENBAID2---MU-- BATFERY 1D2 UNAVAIL. DUE TO MAINTENANCE 1.00E+00 DEDG--ESDGIG31--FR-- DIESEL GENERATOR IG31 FT RUN FOR 24 HR 1.21E-02 DRCIC-CN-MAINT-MU-- RCIC IN MAINTENANCE 7.73E-01 DSWYRDENOPWNRC3ORX- FAIL TO RECOVER OFFSITE POWER IN 30 MIN - WEATHER CENTERED 3.07E-01 DSWYRDENOPHD6NDWRX- ADJ FACTOR FOR I EDG FTR CONVOLUTION WITH NO EDG RECOVERY - 30 MIN SEQ- WEATHER 22 4.39E-08 1.12E-02 %TE-W WEATHER CENTERED LOSS OF OFFSITE POWER 9.88E-01 D125DCENOPSHDSUCHE-- OP SUCCESSFULLY SHEDS BATTERIES PER AOP 301 DURING SBO 2.0SE-02 DEDG--ENDGMTIG21MU-- DIESEL GENERATOR 1G21 IN MAINTENANCE 1.00E+00 DEDG--ESDG1G31-FR-- DIESEL GENERATOR 1G31 FT RUN FOR 24 HR 7.73E-O1 DSWYRDENOPWNRC3ORX-- FAIL TO RECOVER OFFSITE POWER IN 30 MIN -WEATHER CENTERED Page 14 of 20

3.09E-01 DSWYRDENOPWNRC9-RX-- FAIL TO RECOVER OFFSITE POWER IN 9 HRS - WEATHER 1.79E-02 DTSC--ESDGTSCDG-FR-- TSC Diesel Generator Fails To Continue Running 4.53E-02 DSWYRDENOP902RDWRX- ADJ FACTOR FOR 1 EDG FTR CONVOLUTION AND EDG RECOVERY - 9 HOUR SEQ - WEATHER 23 4.37E-08 8.69E-03 %TE-S SWITCHYARD CENTERED LOSS OF OFFSITE POWER 1.OOE+00 DEDG--ESDGIG31--FR-- DIESEL GENERATOR 1G31 FT RUN FOR 24 HR 3.50E-01 DRHR--CNOPRECVRVRX-- OP FAILS TO RECOVER TORUS COOLING (W/I 20 HRS) - VENT SUCCESS SCENARIOS 3.31E-03 DRHRSWDN--TBD--MU-- RHRSW LOOP BD in Maintenance l.O0E-0D DRHRSWOPMOO1942-HE-- OPERATIONS FAILS TO REMOTE MANUALLY OPEN M01942 5.95E-01 DSWYRDENOPSNRC3ORX-- FAIL TO RECOVER OFFSITE POWER IN 30 MIN - SWYRD 7.29E-02 DSWYRDENOPH06NDSRX-- ADJ FACTOR FOR 1 EDG FTR CONVOLUTION WITH NO EDG RECOVERY - 30 MIN SEQ - SWYRD 24 4.02E-08 1.12E-02 %TE-W WEATHER CENTERED LOSS OF OFFSITE POWER 1.00E+O0 DEDG--ESDG1G31--FR-- DIESEL GENERATOR 1G31 FT RUN FOR 24 HR 4.32E-04 DRHR--CFMO1940--FC-- MOTOR OPERATED VALVE M01940 FAILS TO CLOSE ON DEMAND 3.50E-01 DRHR--CNOPRECVRVRX-- OP FAILS TO RECOVER TORUS COOLING (W/I 20 HRS) - VENT SUCCESS SCENARIOS 1.00E-01 DRHRSWOPMOO1942-HE-- OPERATIONS FAILS TO REMOTE MANUALLY OPEN M01942 7.73E-01 DSWYRDENOPWNRC30RX- FAIL TO RECOVER OFFSITE POWER IN 30 MIN - WEATHER CENTERED 3.07E-01 DSWYRDENOPH06NDWRX-- ADJ FACTOR FOR 1 EDG FTR CONVOLUTION WITH NO EDG RECOVERY - 30 MIN SEQ - WEATHER 25 4.02E-08 1.12E-02 %TE-W WEATHER CENTERED LOSS OF OFFSITE POWER 1.00E+0D DEDG--ESDG1G31--FR-- DIESEL GENERATOR 1G31 FT RUN FOR 24 HR 4.32E-04 DRHR--CFMO1932--FO-- Motor Operated Valve M01932 Fails TO Open on Demand 3.50E-01 DRHR--CNOPRECVRVRX-- OP FAILS TO RECOVER TORUS COOLING (W/I 20 HRS) - VENT SUCCESS SCENARIOS 1.00E-01 DRHRSWOPMOO1942-HE- OPERATIONS FAILS TO REMOTE MANUALLY OPEN M01942 7.73E-01 DSWYRDENOPWNRC3ORX- FAIL TO RECOVER OFFSITE POWER IN 30 MIN - WEATHER CENTERED 3.07E-01 DSWYRDENOPHO6NDWRX- ADJ FACTOR FOR 1 EDG FTR CONVOLUTION WITH NO EDG RECOVERY - 30 MIN SEQ - WEATHER 26 4.02E-08 1.12E-02 %TE-W WEATHER CENTERED LOSS OF OFFSITE POWER 1.OOE+O0 DEDG--ESDG1G31--FR-- DIESEL GENERATOR 1G31 FT RUN FOR 24 HR 4.32E-04 DRHR--CFMO1934--FO-- Motor Operated Valve M01934 Fails TO Open on Demand 3.50E-01 DRHR--CNOPRECVRVRX-- OP FAILS TO RECOVER TORUS COOLING (W/I 20 HRS) - VENT SUCCESS SCENARIOS 1.00E-01 DRHRSWOPMOO1942-HE-- OPERATIONS FAILS TO REMOTE MANUALLY OPEN M01942 7.73E-01 DSWYRDENOPWNRC3ORX- FAIL TO RECOVER OFFSITE POWER IN 30 MIN - WEATHER CENTERED 3.07E-01 DSWYRDENOPHO6NDWRX-- ADJ FACTOR FOR 1 EDG FTR CONVOLUTION WITH NO EDG RECOVERY - 30 MIN SEQ- WEATHER 27 4.01E-08 8.69E-03 %TE-S SWITCHYARD CENTERED LOSS OF OFFSITE POWER 1.OOE+O0 DEDG--ESDGlG31--FR-- DIESEL GENERATOR 1G31 FT RUN FOR 24 HR 3.50E-01 DRHR--CNOPRECVRVRX-- OP FAILS TO RECOVER TORUS COOLING (W/I 20 HRS) - VENT SUCCESS SCENARIOS 3.04E-03 DRHR--CN--SUPCLBMU-- Suppr. Pool Cooling Loop B Maintenance 1.00E-01 DRHRSWOPMOO1942-HE-- OPERATIONS FAILS TO REMOTE MANUALLY OPEN M01942 5.95E-01 DSWYRDENOPSNRC3ORX-- FAIL TO RECOVER OFFSITE POWER IN 30 MIN - SWYRD 7.29E-02 DSWYRDENOPHO6NDSRX-- ADJ FACTOR FOR 1 EDG FTR CONVOLUTION WITH NO EDG RECOVERY - 30 MIN SEQ - SWYRD 28 3.80E-08 1.12E-02 %TE-W WEATHER CENTERED LOSS OF OFFSITE POWER 1.00E+O0 DEDG--ESDGiG31-FR-- DIESEL GENERATOR 1G31 FT RUN FOR 24 HR 3.50E-01 DRHR--CNOPRECVRVRX-- OP FAILS TO RECOVER TORUS COOLING (W/I 20 HRS) - VENT SUCCESS SCENARIOS 4.08E-04 DRHRRHSWRHRBRSWBMA-- RHR LOOP B, RHRSW LOOP B CONCURRENTLY OUR FOR MAINTENANCE i.00E-0D DRHRSWOPMOO1942-HE-- OPERATIONS FAILS TO REMOTE MANUALLY OPEN M01942 7.73E-01 DSWYRDENOPWNRC3ORX-- FAIL TO RECOVER OFFSITE POWER IN 30 MIN - WEATHER CENTERED 3.07E-01 DSWYRDENOPHO6NDWRX- ADJ FACTOR FOR 1 EDG FTR CONVOLUTION WITH NO EDG RECOVERY - 30 MIN SEQ- WEATHER 29 3.77E-08 1.12E-02 %TE-W WEATHER CENTERED LOSS OF OFFSITE POWER 2.05E-02 DEDG--ENDGMT1G21MU-- DIESEL GENERATOR 1G21 IN MAINTENANCE 1.DOE+O0 DEDG--ESDGIG31-FR-- DIESEL GENERATOR 1G31 FT RUN FOR 24 HR 1.54E-01 DSWYRDENOPWNRC23RX-- FAIL TO RECOVER OFFSITE POWER IN 23 HOURS - WEATHER 7.73E-01 DSWYRDENOPWNRC3ORX-- FAIL TO RECOVER OFFSITE POWER IN 30 MIN - WEATHER CENTERED ADJ FACTOR FOR 1 FO PUMP FTR CONVOLUTION WITH NO EDG RECOVERY - 23 HOUR SEQ-1.38E-03 DSWYRDENOPLO2RDWRX-- WE 30 3.75E-08 1.12E-02 %TE-W WEATHER CENTERED LOSS OF OFFSITE POWER 1.41E-03 D125DCENBAID2---MU-- BATTERY 1D2 UNAVAIL. DUE TO MAINTENANCE 1.DOE+O0 DEDG--ESD1G3I1-FR-- DIESEL GENERATOR 1G31 FT RUN FOR 24 HR 1.00E-02 DRCIC-CSPHINLTPTCE-- COND. PROB. THAT INLET DRN POT OVERFILL CAUSES WTR HAMMER 7.73E-01 DSWYRDENOPWNRC3ORX- FAIL TO RECOVER OFFSITE POWER IN 30 MIN - WEATHER CENTERED Page 15 of 20

3.07E-01 DSWYRDENOPH06NDWRX- ADJ FACTOR FOR 1 EDG FTR CONVOLUTION WITH NO EDG RECOVERY -30 MIN SEQ- WEATHER 31 3.52E-08 1.78E+00 %MSD MANUAL SHUTDOWN 9.90E-O1 DADS-ANOPINHBSCHE-- OPERATOR SUCCESSFULLY INITIATES ADS INHIBIT 1.D0E+00 DADS-ANOPTRANS-HE-- OP FAILS TO INITIATE RPV EMERGENCY DEPRESS (TRANSIENTS) 1.DDE+00 DFEED-CNOPSTRT--HE-- OPERATOR FAILS TO INITIATE FEEDWATER 1.OOE+00 DFEED-CNOPVEL-TTHE-- OP FAILS TO CONTROL FEEDWATER FOLLOWING SCRAM 2.OOE-01 DPCONTNNCTDWZN4-RP- TORUS AIRSPACE RUPTURE (QUASI-STATIC, LOW TEMP CHALLENGE) 1.OOE+O0 DRHR-CNOPSPCELYHE-- OPERATOR FAILS TO INITIATE TORUS COOLING (EARLY TIMEFRAME) 1.00E+00 DRHR--CNOPSPCLT-HE-- CONDITIONAL HEP FOR LATE SPC INITIATION GIVEN FAILURE IN EARLY TIME FRAME 1.OOE+00 DSBGT-CNOP-VENT-HE-- OP FAILS TO VENT PRIMARY CONTAINMENT (EOP-2 Step PC/P-10) 1.0OE-07 HRACOMB172 HRA combination recovery term.

32 3.30E-08 2.03E-02 %TI IORV 1.00E+O0 DEDG--ESDG1G31--FR-- DIESEL GENERATOR 1G31 FT RUN FOR 24 HR 1.50E-01 DLLSRVNFRVOWPRESCE-- RELIEF VALVE FAILS TO RESEAT AS RPV PRESSURE DROPS 5.87E-03 DRVRW-DN--TRWSLBMU-- River Water Supply Loop B OOS due to Maintenance 2.40E-02 DSWYRDEN--CLOOPLCE-- CONDITIONAL LOOP PROB GIVEN LOCA SIGNAL INITIATOR 8.25E-O1 DSWYRDENOPGNRC30RX-- FAIL TO RECOVER OFFSITE POWER IN 30 MIN - GRID 9.32E-02 DSWYRDENOPH06NDGRX-- ADJ FACTOR FOR 1 EDG FTR CONVOLUTION WITH NO EDG RECOVERY - 30 MIN SEQ - GRID 33 3.30E-08 1.12E-02 %TE-W WEATHER CENTERED LOSS OF OFFSITE POWER 9.38E-03 D4160-ENCB22FC--AFC- CCF FACTOR FOR 2/2 4160V CIRCUIT BREAKERS TO CLOSE 3.32E-03 D416OVENCB224311FCL- INDEP FAIL PROB PORTION OF CBs 1A311/1A411 CCFTC 1.54E-01 DSWYRDENOPWNRC23RX-- FAIL TO RECOVER OFFSITE POWER IN 23 HOURS - WEATHER 7.73E-01 DSWYRDENOPWNRC30RX-- FAIL TO RECOVER OFFSITE POWER IN 30 MIN - WEATHER CENTERED 7.94E-O1 DSWYRDENOPLOINNWRX-- ADJ FACTOR FOR 1 EDG FTS CONVOLUTION AND EDG RECOVERY - 23 HOUR SEQ - WEATHER 34 3.09E-08 3.47E-03 %TE-G GRID CENTERED LOSS OF OFFSITE POWER 1.OOE+00 DEDG--ESDGIG31--FR-- DIESEL GENERATOR 1G31 FT RUN FOR 24 HR 3.50E-O1 DRHR--CNOPRECVRVRX-- OP FAILS TO RECOVER TORUS COOLING (W/I 20 HRS) - VENT SUCCESS SCENARIOS 3.31E-03 DRHRSWDN--TBD---MU- RHRSW LOOP BD in Maintenance 1.OOE-01 DRHRSWOPMOO1942-HE-- OPERATIONS FAILS TO REMOTE MANUALLY OPEN M01942 8.25E-01 DSWYRDENOPGNRC3ORX-- FAIL TO RECOVER OFFSITE POWER IN 30 MIN - GRID 9.32E-02 DSWYRDENOPH06NDGRX-- ADJ FACTOR FOR 1 EDG FTR CONVOLUTION WITH NO EDG RECOVERY - 30 MIN SEQ - GRID 35 2.96E-08 1.12E-02 %TE-W WEATHER CENTERED LOSS OF OFFSITE POWER 1.00E+00 DEDG--ESDGIG31--FR-- DIESEL GENERATOR 1G31 FT RUN FOR 24 HR 3.18E-04 DLPCSRHRSWCSBSWBMA-- LPCS B AND RHRSW B CONCURRENTLY OUT FOR MAINTENANCE 3.50E-01 DRHR--CNOPRECVRVRX-- OP FAILS TO RECOVER TORUS COOLING (W/I 20 HRS) - VENT SUCCESS SCENARIOS 1.O0E-O1 DRHRSWOPMOO1942-HE-- OPERATIONS FAILS TO REMOTE MANUALLY OPEN M01942 7.73E-01 DSWYRDENOPWNRC30RX-- FAIL TO RECOVER OFFSITE POWER IN 30 MIN - WEATHER CENTERED 3.07E-01 DSWYRDENOPHO6NDWRX-- ADJ FACTOR FOR 1 EDG FTR CONVOLUTION WITH NO EDG RECOVERY - 30 MIN SEQ - WEATHER 36 2.84E-08 3.47E-03 %TE-G GRID CENTERED LOSS OF OFFSITE POWER 1.OOE+00 DEDG--ESDGIG31--FR-- DIESEL GENERATOR 1G31 FT RUN FOR 24 HR 3.50E-01 DRHR--CNOPRECVRVRX-- OP FAILS TO RECOVER TORUS COOLING (W/I 20 HRS) - VENT SUCCESS SCENARIOS 3.04E-03 DRHR--CN-SUPCLBMU-- Suppr. Pool Cooling Loop B Maintenance 1.00E-O1 DRHRSWOPMOO1942-HE-- OPERATIONS FAILS TO REMOTE MANUALLY OPEN M01942 8.25E-01 DSWYRDENOPGNRC3ORX-- FAIL TO RECOVER OFFSITE POWER IN 30 MIN - GRID 9.32E-02 DSWYRDENOPHO6NDGRX-- ADJ FACTOR FOR 1 EDG FTR CONVOLUTION WITH NO EDG RECOVERY - 30 MIN SEQ - GRID 37 2.63E-08 7.74E-01 %TT TURBINE TRIP WITH BYPASS 1.OOE+O0 DCNDSTCNOPTINJ--HE-- OP FAILS TO [NIT. COND. FOR ALT. INJ. (TRANSIENT EVENTS) 1.00E+00 DFEED-CNOPSTRT--HE-- OPERATOR FAILS TO INITIATE FEEDWATER 1.00E+00 DFEED-CNOPVEL-TTHE-- OP FAILS TO CONTROL FEEDWATER FOLLOWING SCRAM 2.OOE-01 DPCONTNNCTDWZN4-RP- TORUS AIRSPACE RUPTURE (QUASI-STATIC, LOW TEMP CHALLENGE) 1.OOE+O0 DRHR--CNOPSPCELYHE-- OPERATOR FAILS TO INITIATE TORUS COOLING (EARLY TIMEFRAME) 1.00E+00 DRHR--CNOPSPCLT-HE-- CONDITIONAL HEP FOR LATE SPC INITIATION GIVEN FAILURE IN EARLY TIME FRAME 1.DOE+00 DSBGT-CNOP-VENT-HE-- OP FAILS TO VENT PRIMARY CONTAINMENT (EOP-2 Step PC/P-10) 1.70E-07 HRACOMB185 HRA combination recovery term.

38 2.60E-08 1.12E-02 %TE-W WEATHER CENTERED LOSS OF OFFSITE POWER 1.00E+00 DEDG--ESDGIG31-FR-- DIESEL GENERATOR 1G31 FT RUN FOR 24 HR 3.50E-01 DRHR--CNOPRECVRVRX-- OP FAILS TO RECOVER TORUS COOLING (W/I 20 HRS) - VENT SUCCESS SCENARIOS Page 16 of 20

2.79E-04 DRHRSWDFMOO1947-FO- Motor Operated Valve M01947 Fails To Open on Demand 1.00E-01 DRHRSWOPMOO1942-HE-- OPERATIONS FAILS TO REMOTE MANUALLY OPEN M01942 7.73E-01 DSWYRDENOPWNRC30RX- FAIL TO RECOVER OFFSITE POWER IN 30 MIN - WEATHER CENTERED 3.07E-01 DSWYRDENOPH06NDWRX- ADJ FACTOR FOR 1 EDG FTR CONVOLUTION WITH NO EDG RECOVERY - 30 MIN SEQ - WEATHER 39 2.58E-08 1.12E-02 %TE-W WEATHER CENTERED LOSS OF OFFSITE POWER 4.11E-04 D125DCENBA2212--FDL- INDEP FAIL PROB PORTION OF BATTERIES 1D1/1D2 CCF WITH NO OUTPUT 1.06E-02 D---DCENBA22NO--AFC- CCF FACTOR FOR 2/2 BATTERIES TO FAIL 8.49E-01 DSWYRDENOPWNRC1-RX-- FAIL TO RECOVER OFFSITE POWER IN 1 HR - WEATHER 7.73E-01 DSWYRDENOPWNRC30RX- FAIL TO RECOVER OFFSITE POWER IN 30 MIN - WEATHER CENTERED 8.07E-01 DSWYRDENOP1OSNNWRX-- ADJ FACTOR FOR 1 EDG FTS CONVOLUTION WITH NO EDG RECOVERY - 1 HOUR SEQ - WEATHER 40 2.57E-08 1.12E-02 %TE-W WEATHER CENTERED LOSS OF OFFSITE POWER 2.05E-02 DEDG--ENDGMTIG21MU-- DIESEL GENERATOR 1G21 IN MAINTENANCE 1.OOE+00 DEDG--ESDG1G31--FR-- DIESEL GENERATOR 1G31 FT RUN FOR 24 HR 1.00E-01 DHPCI-CFMO2238OPCE-- COND. PROB. THAT M02238 IS INITIALLY CLOSED 4.72E-03 DRCIC-C5TP226---FR- TURBINE DRIVEN PP 1P226 FT RUN FOR 24 H 7.73E-01 DSWYRDENOPWNRC30RX-- FAIL TO RECOVER OFFSITE POWER IN 30 MIN - WEATHER CENTERED 3.D7E-01 DSWYRDENOPHO6NDWRX-- ADJ FACTOR FOR 1 EDG FTR CONVOLUTION WITH NO EDG RECOVERY - 30 MIN SEQ - WEATHER 41 2.57E-08 1.12E-02 %TE-W WEATHER CENTERED LOSS OF OFFSITE POWER 1.71E-02 D4160-ENCB22FO--AFC- CCF FACTOR FOR 2/2 4160V CIRCUIT BREAKERS TO OPEN 1.42E-03 D416OVENCB224322FO-- Independent Event Circuit Breaker Normally Closed, Fails To Open on Demand 1.54E-01 DSWYRDENOPWNRC23RX- FAIL TO RECOVER OFFSITE POWER IN 23 HOURS - WEATHER 7.73E-01 DSWYRDENOPWNRC3ORX-- FAIL TO RECOVER OFFSITE POWER IN 30 MIN - WEATHER CENTERED 7.94E-01 DSWYRDENOPLO1NNWRX-- ADJ FACTOR FOR 1 EDG FTS CONVOLUTION AND EDG RECOVERY - 23 HOUR SEQ - WEATHER 42 2.52E-08 2.03E-02 %TI IORV 1.00E+O0 DEDG--ESDG1G31-FR-- DIESEL GENERATOR 1G31 FT RUN FOR 24 HR 4.49E-03 DESW-DN-BMAINTMU- EMERGENCY SERVICE WATER TRAIN B IN MAINTENANCE 1.50E-01 DLLSRVNFRVOWPRESCE-- RELIEF VALVE FAILS TO RESEAT AS RPV PRESSURE DROPS 2.40E-02 DSWYRDEN--CLOOPLCE-- CONDITIONAL LOOP PROB GIVEN LOCA SIGNAL INITIATOR 8.25E-01 DSWYRDENOPGNRC3ORX-- FAIL TO RECOVER OFFSITE POWER IN 30 MIN - GRID 9.32E-02 DSWYRDENOPHD6NDGRX-- ADJ FACTOR FOR 1 EDG FTR CONVOLUTION WITH NO EDG RECOVERY - 30 MIN SEQ - GRID 43 2.49E-08 8.69E-03 %TE-S SWITCHYARD CENTERED LOSS OF OFFSITE POWER 1.00E+00 DEDG--ESDGIG31--FR-- DIESEL GENERATOR 1G31 FT RUN FOR 24 HR 3.50E-01 DRHR--CNOPRECVRVRX-- OP FAILS TO RECOVER TORUS COOLING (W/I 20 HRS) - VENT SUCCESS SCENARIOS 1.00E+00 DRHRSWDNOPLTINJ-HE-- OP FAILS TO ALIGN ALT LP INJECTION (TRAN, SLOCA, MLOCA, IORV) 5.70E-02 DRHRSWDNOPLTINJ-HERX OP FAILS TO ALIGN ALT LP INJECTION (TRAN, SLOCA, MLOCA, IORV) 3.31E-03 DRHRSWDN--TBD---MU-- RHRSW LOOP BD in Maintenance 5.95E-01 DSWYRDENOPSNRC30RX-- FAIL TO RECOVER OFFSITE POWER IN 30 MIN - SWYRD 7.29E-02 DSWYRDENOPH06NDSRX- ADJ FACTOR FOR 1 EDG FTR CONVOLUTION WITH NO EDG RECOVERY - 30 MIN SEQ - SWYRD 44 2.46E-08 1.12E-02 %TE-W WEATHER CENTERED LOSS OF OFFSITE POWER 9.88E-01 D125DCENOPSHDSUCHE-- OP SUCCESSFULLY SHEDS BATTERIES PER AOP 301 DURING SBO 2.05E-02 DEDG--ENDGMTIG21MU-- DIESEL GENERATOR 1G21 IN MAINTENANCE 1.D0E+00 DEDG--ESDGIG31--FR-- DIESEL GENERATOR 1G31 FT RUN FOR 24 HR 7,73E-01 DSWYRDENOPWNRC3ORX- FAIL TO RECOVER OFFSITE POWER IN 30 MIN - WEATHER CENTERED 3.09E-01 DSWYRDENOPWNRC9-RX-- FAIL TO RECOVER OFFSITE POWER IN 9 HRS - WEATHER 1.00E-02 DTSC--ESDGTSCDG-MU-- TSC DIESEL IN MAINTENANCE 4.53E-02 DSWYRDENOP902RDWRX-- ADJ FACTOR FOR 1 EDG FTR CONVOLUTION AND EDG RECOVERY - 9 HOUR SEQ - WEATHER 45 2.44E-08 2.03E-02 %TI IORV 4.34E-03 DEDG--DSMP1P44B-FS-- FUEL OIL TRANSFER PUMP 1B44B FAILS TO START ON DEMAND 1.00E+00 DEDG--ESDG1G31-FR-- DIESEL GENERATOR 1G31 FT RUN FOR 24 HR 1.50E-01 DLLSRVNFRVOWPRESCE-- RELIEF VALVE FAILS TO RESEAT AS RPV PRESSURE DROPS 2.40E-02 DSWYRDEN-CLOOPLCE-- CONDITIONAL LOOP PROB GIVEN LOCA SIGNAL INITIATOR 8.25E-01 DSWYRDENOPGNRC30RX- FAIL TO RECOVER OFFSITE POWER IN 30 MIN - GRID 9.32E-02 DSWYRDENOPH06NDGRX-- ADJ FACTOR FOR 1 EDG FTR CONVOLUTION WITH NO EDG RECOVERY - 30 MIN SEQ- GRID 46 2.42E-08 1.78E+00 %MSD MANUAL SHUTDOWN 1.00E+O0 DCNDSTCNOPTINJ--HE- OP FAILS TO INIT. COND. FOR ALT. INJ. (TRANSIENT EVENTS) 1.00E+00 DFEED-CNOPSTRT--HE-- OPERATOR FAILS TO INITIATE FEEDWATER 1.ODE+00 DFEED-CNOPVEL-TTHE- OP FAILS TO CONTROL FEEDWATER FOLLOWING SCRAM Page 17 of 20

8.O0E-02 DPCONTNNCTDWZN5-RP- TORUS WATERSPACE RUPTURE (QUASI-STATIC, LOW TEMP CHALLENGE) 1.00E+00 DRHR--CNOPSPCELYHE-- OPERATOR FAILS TO INITIATE TORUS COOLING (EARLY TIMEFRAME) 1.00E+00 DRHR--CNOPSPCLT-HE-- CONDITIONAL HEP FOR LATE SPC INITIATION GIVEN FAILURE IN EARLY TIME FRAME 1.00E+00 DSBGT-CNOP-VENT-HE-- OP FAILS TO VENT PRIMARY CONTAINMENT (EOP-2 Step PC/P-10) 1.70E-07 HRACOMB185 HRA combination recovery term.

47 2.29E-08 1.12E-02 %TE-W WEATHER CENTERED LOSS OF OFFSITE POWER 1.O0E+00 DEDG--ESDGIG31--FR-- DIESEL GENERATOR 1G31 FT RUN FOR 24 HR 4.32E-04 DRHR--CFMO1932--FO-- Motor Operated Valve M01932 Fails TO Open on Demand 3.50E-01 DRHR--CNOPRECVRVRX-- OP FAILS TO RECOVER TORUS COOLING (W/I 20 HRS) - VENT SUCCESS SCENARIOS 1.00E+00 DRHRSWDNOPLTINJ-HE-- OP FAILS TO ALIGN ALT LP INJECTION (TRAN, SLOCA, MLOCA, IORV) 5.70E-02 DRHRSWDNOPLTINJ-HERX OP FAILS TO ALIGN ALT LP INJECTION (TRAN, SLOCA, MLOCA, IORV) 7.73E-01 DSWYRDENOPWNRC3ORX- FAIL TO RECOVER OFFSITE POWER IN 30 MIN.- WEATHER CENTERED 3.07E-01 DSWYRDENOPH06NDWRX- ADJ FACTOR FOR 1 EDG FTR CONVOLUTION WITH NO EDG RECOVERY - 30 MIN SEQ - WEATHER 48 2.29E-08 1.12E-02 %TE-W WEATHER CENTERED LOSS OF OFFSITE POWER 1.OOE+00 DEDG--ESDGIG31-FR-- DIESEL GENERATOR 1G31 FT RUN FOR 24 HR 4.32E-04 DRHR--CFMO1934--FO-- Motor Operated Valve M01934 Fails TO Open on Demand 3.50E-01 DRHR--CNOPRECVRVRX-- OP FAILS TO RECOVER TORUS COOLING (W/I 20 HRS) - VENT SUCCESS SCENARIOS 1.00E+00 DRHRSWDNOPLTINJ-HE-- OP FAILS TO ALIGN ALT LP INJECTION (TRAN, SLOCA, MLOCA, IORV) 5.70E-02 DRHRSWDNOPLTINJ-HERX OP FAILS TO ALIGN ALT LP INJECTION (TRAN, SLOCA, MLOCA, IORV) 7.73E-01 DSWYRDENOPWNRC3ORX- FAIL TO RECOVER OFFSITE POWER IN 30 MIN - WEATHER CENTERED 3.07E-01 DSWYRDENOPHO6NDWRX-- ADJ FACTOR FOR 1 EDG FTR CONVOLUTION WITH NO EDG RECOVERY - 30 MIN SEQ- WEATHER 49 2.29E-08 1.12E-02 %TE-W WEATHER CENTERED LOSS OF OFFSITE POWER 1.00E+00 DEDG-ESDG1G31-FR-- DIESEL GENERATOR 1G31 FT RUN FOR 24 HR 4.32E-04 DRHR--CFMO1940-FC-- MOTOR OPERATED VALVE M01940 FAILS TO CLOSE ON DEMAND 3.50E-01 DRHR--CNOPRECVRVRX-- OP FAILS TO RECOVER TORUS COOLING (W/I 20 HRS) - VENT SUCCESS SCENARIOS 1.00E+O0 DRHRSWDNOPLTINJ-HE-- OP FAILS TO ALIGN ALT LP INJECTION (TRAN, SLOCA, MLOCA, IORV) 5.70E-02 DRHRSWDNOPLTINJ-HERX OP FAILS TO ALIGN ALT LP INJECTION (TRAN, SLOCA, MLOCA, IORV) 7.73E-01 DSWYRDENOPWNRC3ORX-- FAIL TO RECOVER OFFSITE POWER IN 30 MIN - WEATHER CENTERED 3.07E-01 DSWYRDENOPH06NDWRX- ADJ FACTOR FOR 1 EDG FTR CONVOLUTION WITH NO EDG RECOVERY - 30 MIN SEQ- WEATHER 50 2.29E-08 8.69E-03 %TE-S SWITCHYARD CENTERED LOSS OF OFFSITE POWER 1.00E+00 DEDG--ESDGIG31--FR-- DIESEL GENERATOR 1G31 FT RUN FOR 24 HR 3.50E-01 DRHR--CNOPRECVRVRX-- OP FAILS TO RECOVER TORUS COOLING (W/I 20 HRS) - VENT SUCCESS SCENARIOS 3.04E-03 DRHR--CN--SUPCLBMU-- Suppr. Pool Cooling Loop B Maintenance 1.00E+00 DRHRSWDNOPLTINJ-HE-- OP FAILS TO ALIGN ALT LP INJECTION (TRAN, SLOCA, MLOCA, IORV) 5.70E-02 DRHRSWDNOPLTINJ-HERX OP FAILS TO ALIGN ALT LP INJECTION (TRAN, SLOCA, MLOCA, IORV) 5.95E-01 DSWYRDENOPSNRC30RX-- FAIL TO RECOVER OFFSITE POWER IN 30 MIN - SWYRD 7.29E-02 DSWYRDENOPH06NDSRX-- ADJ FACTOR FOR 1 EDG FTR CONVOLUTION WITH NO EDG RECOVERY - 30 MIN SEQ- SWYRD Page 18 of120

APPENDIX D TOP CDF SEQUENCES ToppSequences A.EDG Fails to Run Set toa1.0 Sequence Initiator Class Sequence.Cutset Characteristics LOOPDG-018 LOOP-EDG IV These cutsets lead to core damage events that occur with loss of containment heat removal but with successful containment vent (Class IIV).

  • Any loss of offsite power event
  • Onsite AC power is available from at least one EDG
  • Suppression pool cooling initiation early (i.e., before reaching the EOP Heat Capacity Temperature Limit, HCTL) does not occur
  • Feedwater and Condensate are not available due to the LOOP condition
  • RCIC and HPCI are initially available and providing core cooling
  • RPV emergency depressurization is initiated upon reaching the EOP HCTL curve given failure of torus cooling early, resulting in inadequate steam pressure for HPCI and RCIC operation.

CRD fails as an alternative core cooling method

  • Core Spray or LPCI is available and used for low pressure injection following RPV ED Torus cooling remains unavailable throughout the scenario
  • Emergency containment venting is pursued as the alternative containment heat removal method and is successful Injection post containment venting is unsuccessful, resulting in loss of adequate core cooling and core damage.

These cutsets are core damage events that occur due to a Station Blackout event and no AC power recovery (Class 1130).

  • Any loss of offsite power event

- SRVs open and then close SBO-025 SBO-XFR IB30 - Onsite emergency AC power is unavailable

  • HPCI and RCIC both are initially unavailable to provide core cooling
  • RPV emergency depressurization is pursued per the EOPs and is successful
  • Recovery of offsite and onsite AC power is unsuccessful before the onset of core damage.

Time to align fire protection for alternate core cooling is not available before core damage ensues at approximately t=~0.5 hrs.

Page 19 of 20

" Top Sequences A EDG Fails to Run Set to 1.0.

Sequence Initiator.. Class:. Sequence Cutset Characteristics....

These cutsets are core damage events that occur due to a Station Blackout event and no AC power recovery (Class 11B9).

  • Any loss of offsite power event
  • SRVs open and then close
  • Onsite emergency AC power is unavailable
  • HPCI or RCIC is available and being used for core cooling SBO-009 SBOXFR 1139 The TSC diesel generator is not aligned to the battery chargers

" Operators successfully perform DC load shedding (extending DC battery life to an estimated 7 hrs)

" RPV emergency depressurization is performed upon reaching the EOP Heat Capacity Temperature Limit (HCTL). Operators follow the caution to maintain RPV pressure at 150 PSI and thus RCIC continues to operate.

  • Recovery of offsite and onsite AC power is unsuccessful before the batteries deplete at approximately t=7 hrs, failing RCIC. Time to align fire protection for alternate core cooling is not available before core damage ensues at approximately t=-9 hrs.

These cutsets lead to core damage events that occur with a steam LOCA condition for which the RPV pressure is low and no effective injection is available (Class IIIC).

IORV initiator, or any of the general transients or special initiators

  • with a stuck-open relief valve
  • Open relief valve does not re-close and remains open throughout the scenario
  • Successful scram IORV-014 IORV-SORV IIC Offsite AC power is available

" The primary containment vapor suppression function is successful

" Feedwater is unavailable

  • HPCI and RCIC are available for high pressure injection
  • The RPV ultimately depressurizes due to the open relief valve, defeating HPCI and RCIC due to inadequate steam pressure
  • CRD and low pressure ECCS injection are unavailable
  • Alternate low pressure injection options are not aligned or are unavailable These cutsets lead to core damage events that occur with loss of inventory makeup and the RPV pressure remains high (Class IA).
  • Any loss of offsite power event
  • SRVs open and then close LOOPDG-006 LOOP-EDG IA Onsite AC power is available from at least one EDG

" Suppression pool cooling is initiated early (i.e., before reaching the EOP Heat Capacity Temperature Limit, HCTL)

" Feedwater and Condensate are not available due to the LOOP condition

  • RPV emergency depressurization per the EOPs is not performed.
  • Core damage ensues due to inadequate core cooling and the RPV at high pressure.

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