ML20107K828

County Station PRA Summary Document

ML20107K828
Person / Time
Site:	LaSalle
Issue date:	03/31/1996
From:	Janecek R, Kalache M, Momsen B COMMONWEALTH EDISON CO.
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References
GL-88-20, NUDOCS 9604290051
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i P  !

! LASALLE COUNTY STATION f

s PROBABILISTIC RISK ASSESSMENT P

(PRA)

SUMMARY

f DOCUMENT O

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MARCH 1996 PREPARED BY NES PRA GROUP is4%88!!o!8$$!7a p PDR

b LaSalle COUNTY STATION D

Probabilistic Risk Assessment '

l l l h Summary Document 1

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Abstract t

The purpose of this document is to provide an overview of the technology of probabilistic risk assessment

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(PRA), and to summarize the details, results and potential applications of the LaSalle County Station PRA model. The report addresses the level one (core damage end state) portion of the LSCS PRA, which was based on the configuration of Unit 2 as of May 31,1994. The Individual Plant Examination (IPE) report, which was submitted to the NRC in April,1994 in response to Generic Letter 88-20 is voluminous, addressing details which are likely to be of interest only to analysts and reviewers. This document provides a concise summary of the important features and conclusion of the LSCS PRA analysis, and gives those who may wish to use the PRA a general understanding of the process and how it may be applied.

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l March 1996 Bruce F. Momsen (708)663 7438 Milad R. Kalache (708)663 7477 p Robert F. Janecek (815) 357-6761 (ext. 2421)

PRA Group Analysis & Design Support Services Nuclear Engineering Services D

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ACKNOWLEDGMENTS D

The LaSalle County Station Probabilistic Risk Assessment (PRA) documented in this report was developed with internal Comed engineering resources. The following Comed individuals are recognized for their significant efforts on this project:

Milad Kalache (the technical team leader),

Bob Janecek, D Jim Ahlman, Lee Raney, Jim Hawiey, Rich Johnson, Bob Herbert, and Manu Sharma.

I We also wish to acknowledge the timely assistance provided by numerous LaSalle County Station personnel during the various phases of this project.

The SAIC.

Comed team also received important technical assistance from Jeff Reily and Chris Cragg from D

Finally, special thanks and a deep feeling of gratitude are extended to Dr. Anhur Payne of Sandia National Laboratory for his invaluable guidance and advice.

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l, Table of Contents m# I. Background .. ... . . . . . . . . . . . . . . . ... . . . . . .. . . . .

.. LSCS-1

11. Model Structure.. . .. ... . . . .

!!I. Data

. .. . . . . . . . . .LSCS5 IV.

.. .. . . . . . . . . LSCS-7 Model Maintenance.. . . . . . .. . . . . . . ..

. LSCS-10 V. Quantification . .. . .

VI.

. LSCS-10 General Results . .. ..

, Vll.

. . LSCS 11

1. Accident Sequence Analysis . .. ..

VIII.

. .. . LSCS 22 Applications. .. ...

. . . LSCS-27 XI. Insights . . . . .. . .. . .. . . . . . . ... .. . . LSCS-29 List of Tables Table 1 PRA Model Levels..

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.. .. . .. . . . . . LSCS 2 Table 2 LSCS Initiating Events and Frequencies.. . .

. LSCS-3 Table 3 List of Systems Modeled in LaSalle PRA...

Table 4 Plant-Specific Failure Data.. . .

. LSCS-4

. LSCS-9 Table Sa Component Failure Mode Importance to CDF - RAW 2 2.. .. .

. LSCS-15 Table 5b Cornponent Failure Mode Importance to CDF - Fussell-Vesely . . LSCS-18

.) Table 6 Operator Action importances to CDF... .

. . . .. . . LSCS-22 List of Figures Figure 1 LaSalle Station PRA Data Collection and Analysis: Information Flow .

. LSCS 8 I Figure 2 CDF Contributions by Initiating Event. . .

. LSCS-13  !

N, Figure 3 Importance of Plant Systems to Core Damage Risk.. . . . .. .

. . LSCS-14 )

Figure 4 Contribution of Accident Sequence Types to Core Damage Risk.. . .

. LSCS-26 l Appendices Appendix A Event Trees. . . . . .

. . . . A-1 Appendix B Low Pressure Core Spray Fault Tree..

Appendix C Core Damage Cutsets

..B-1 Table 1 Top 100 Core Damage Cutsets.. ..

.. ..C-1 Table 2 Top Cutsets for LOSP Sequences . . .

. . . . . ...C-12 Table 3 Top Cutsett for Transient Sequences .. .. .. . . .. ... ..C-15 Table 4 Top Cutsets for IORV Sequences . ... . .

..C 18 J Table 5 Top Cutsets for ATWS Sequences . . ... .. ...C-20 Table 6 Top Cutsets for LOCA Sequences . .. .

..C-23 Table 7 Top Cutsets for SBO Sequences . . .

..C-26 O

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LaSalle County Station

) Probabilistic Risk Assessment Summary Document

)

I. Background A probabilistic risk assessment (PRA) is a useful tool for quantitative and qualitative evaluations of the

) likelihood and consequences of core damage that could conceivably result from events occurring during power plant operation. There are three levels of PRAs (Table 1), each corresponding to a different end state, and each utilizing a different set of plant models. A level 1 PRA analysis is performed to determine the frequency of core damage. The core damage for this PRA is defined as initiation of reactor fuel melting. It consists of models of the systems needed for reactor shutdown and core cooling, as well as necessary support systems. A level 2 PRA analysis has an end state of radioactive release following core

) damage. It begins with damage states from the level 1 model and combines them with a containment failure model and Radionuclide source term estimates. A level 3 PRA analysis has an end state that quantifies the impact of a radioactive release upcn public health and safety, and accounts for site specific topography, meteorology, demographics and emergency planning actions. Typically, each level of a PRA analysis addresses the risk associated with reactor power operation, as contrasted with the risk associated I with shutdown operations and outages. An effort is underway to develop a shutdown model to provide

') quantitative insights into the risk of various outage-related configurations. Sandia National Laboratory, under contract to the NRC, completed a level 1 and 2 PRA for LaSalle Unit 2. A summary of the Sandia PRA was submitted as the LaSalle Station Individual Plant Examination (IPE) to the NRC in April,1994.

Approximately four person-years of effort were expended over a one and one-half year time frame to update the level 1 analysis of the Sandia LaSalle PRA done for the NRC. A level 2 analysis is in progress

} a6d expected to be complete in the second quarter of 1996. There are no plans to complete a level 3 analysis at this time.

The following equations represent the concept of PRA analyses:

1 Level 1:

J I(Initiating Event Frequency x Mitigating Systems Failure Probability) = Core Damage Frequency Level 2:

I(Core Damage Frequency x Containment Failure Probability) = Radioactive Release Frequency and 3 Source Term Magnitude Level 3:

I(Radioactive Release Frequency x Site Characteristics) = Public Health Impact

} In a very simplistic manner, these equations are the basis for the calculations perfonned for each of the three levels of a PRA, Level II is build upon the level 1 analyses by including additional data. The introduced data are related to the progression of core damage. The level 3 analysis addresses the fission LSCS-1 D

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products release and propagation, and their biologicalimpact on the populadon . This document will address the level 1 equation only.

) An inidating event is the starting point of a level 1 PRA analysis. An initiating event is defined as an event which causes a reactor trip (either directly or indirectly) or wh'ch requires an immediate plant shutdown due to technical specification or operationallimits. A list of the initiating events used in the LSCS PRA is provided in Table 2.

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Table 1 l PRA ModelLevels

} PRA LEVEL END STATE MODEL 1 CORE DAMAGE REAC'lVR SHUTDOWN, CORE COOLING AND SUPPORT SYSTEMS 2 RADIOACTIVE RELEASE \

ABOVE + CONTAINMENT l

3 3 PUBLIC HEALTH IMPACT ABOVE + SITE CHARACTERISTICS 1

Re LSCS level 1 PRA addresses internal events and loss of offsite power. It does not address external events such as fires, earthquakes, hurricanes and external flooding. These events were analyzed in the Sandia PRA for LaSalle and no additional effort in this area is contemplated.

3 The mitigating systems referred to in the level 1 equation are those which shut down the reactor and provide core cooling to prevent overheating and ultimately melting of the fuel. Any support systems that are necessary for the front-line systems are also included within the level I scope. A list of the systems modeled in the level 1 analysis is provided in Table 3.

) The level 1 equation uses the initiating event frequencies and, the failure probabilities of the systems required to mitigate these initiating events to estimate the overall core damage frequency per year. The basic concept of a level 1 PRA is simple. However, the large number of initiating events, systems, components, and human interactions associated with a nuclear plant operation and maintenance, make the performance of a PRA analysis complex.

] The LSCS PRA model is maintained on personal computers, it will be updated periodically to reflect plant modifications, procedure changes, and the plant-specific failure data for major plant components.

He current PRA model represents the core damage frequency for LSCS unit 2. The model reflects the plant configuration for Unit 2, as of May 31,1994, and its dependencies on unit 1.

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D LSCS-2 h

O Table 2 O

LSCS Initiating Events and Frequeneles DESCRIPTION FREQUENCY (per reactor-year)

Transients D Turbine Trip With Main Condenser Available 2.4 (see Note 1)

} Ttubine Trip With Main Condenser Unavailable 8.lE-01 Total Loss of Feedwater 2.8E-01 i

Single Unit Loss of Offsite Power (LOOP) 5.3E-02 Dual Unit LOOP 1.6E-02

O inadvenentiy Open Reiief vaive 5.3E-02 Total MSIV Closure 4.7E-01 4

Loss ofInstrument Air 5.3E-02 SpecialInitiators loss of125 VDC(single bus)

,0 2.63E-04 (see Note 2)

> loss of125 VDC(double bus) 2.63E-05 (see Note 2)

Loss of 4160 VAC(single bus) 2.63E-04 (see Note 2)

Flooding Scenario - Service Water Piping Rupture, Ground Floor 2.0E-04 (see Note 3)

(El. 711') or Main Floor (El. 761') of Reactor Building i LOCA's p

/. Large Break LOCA 3.0E-04 (see Note 1)

Medium Break LOCA 8.0E-04

Small Break LOCA 3.0E-03 NOTES

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D The Transent and LOCA ininatmg event frequencies are documected in the following report:

Comed Nuclear Engineenng Servuss, PRA Group, "LaSalle County Stanon Ininaung Event Frequency Analysis,"

Revision 0, dated June 6.1995.

'Ihe values chosen are based on site-specific and gesteric data. For consistency, two digits are given for allininanas event J frequencies, although the second digit is significant only for the first transient listed. 'the Dual Unit LOOP frequency has units o "per site-year" rather than "per reaaor. year."

2.

The ininanns event frequency fcr loss of a single AC bus a a single DC bus is based on the quantificauon of a fauk tr single bus failure modes. For a double DC bus failure, the value is the single bus frequency mukiplied by 0.1 (Beta factcr).

3.

Flooding report: scenano ininating event frequencies ice the two different Reactor Building locanons are documented in the Comed Nuclear Engineenns Services, PRA Group. "LaSalle County Station Internal Flooding Review," Revision 0, dated August 28,1995.

The flooding scenario ininating event frequency given in the table above is the sum of the inidating event frequencies for the tw locanons times a factor of 0.76, the average fraaion of time that the LaSalle units were critical dunng the PRA Baseline pe

,C factcr converts the internal flooding frequency to a "per reactor-year" basis, and is documented in the following memorandum:

R.H. Johnson memcrandum to M. Kalache, "Addanonal Data for LaSalle PRA," dated 9n/95.

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LSCS 3

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Table 3 List of Systems Modeled in LaSalle PRA.

DESCRIPTION SYSTEM High Pressure Core Spray HPCS Reactor Core Isolation Cooling

) Main Feedwater(Motor Driven Pump)

RCIC MFW ControlRod Drive CRD Automatic Depressurization System ADS IAw Pressure Core Spray LPCS law Pressure Core Injection Mode of RHR LPCI(RHR)

Condensate / Condensate Booster /Hotwell Makeup CDS Shutdown Cooling Mode of RHR SDC(RHR)

] Suppression Pool Cooling Mode of RHR SPC(RHR)

Containment Spray System Mode of RHR CSS (RHR)

Containment Vent VQ AC Power Distribution / Diesel Generators AC POWER 125/250Vdc Power Dist/ Batteries / Chargers DC POWER Diesel Generator Ventilation DG HVAC Turbine Building Closed Cooling Water TBCCW

) Reactor Building Closed Cooling Water RBCCW Plant Service Water PSW Service Air / Instrument Air SA/IA Drywell Pneumatic Systent DPS 3

RHR Service Water /DG Cooling Water / Equipment Room Cooling CSCS Standby Liquid Control SBLC Reactor Protection /Altemate Rod Insertion RPS/ARI

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D LSCS-4

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H. Model Structure

] Re LSCS PRA level 1 model consists of three basic components: event trees, fault trees and failure data.

The actual logical structure of the PRA model is created in the event trees and fault trees.

l Event Trees  !

i Event trees are used to create the sequence of events which must occur to result in a core damage event.

) They are roughly equivalent to the training scenario sequences that are used to train the operators on the plant simulator. He event tree is structured to describe all of the critical safety functions which must be satisfied to protect the core. De safety functions for LSCS are: )

1. Reactor subcriticality

2. Containment pressure suppression

3. Reactor coolant boundary integrity D 4. Core inventory makeup

5. Core heat removal

6. l Containment heat removal Before each event tree in the PRA model could be used as the basis for processing the probabilistic and frequency information " success" and " failure" definitions were defined for each event. He definitions of D these " success criteria

• were determined from the past safety analyses or from the results of specific analyses performed to support the PRA. Timing studies using thermal bydraulic computer models were performed to determine estimated accident response times and to confirm success criteria. In addition, discussions were held with operations personnel to verify the validity of the proposed events. When event tree construction was complete, the end point for each possible event tree sequence was defined as a core damage, or non-core damage plant state.

D The event trees are shown in Appendix A.

1 The following brief discussion of the Large LOCA event tree is expected to help the reviewers to I understand the logical structure of all event trees shown in Appendix A.

D First, the initiating event, large LDCA (LLOCA) is defined as any rupture of the prunary coolant system boundary large enough to cause the reactor vessel to depressurize to the point that the low pressure injection systems will be able to provide makeup shortly after break initiation and in time to prevent core damage.

LLOCA, and necessary mitigating functions are displayed across the top of the event tree diagram O (Appendix A). An upward branch on the event tree means success of the particular function, while a downward branch indicates a failure.

Dunng a LIDCA, core damage can oaur when vapor suppression (VSP), reactisity control (RC), or all large volume injection souras fail (HPCS and LPCI-ISCS).

He LSCS event trees are briefly described in the following paragraphs:

0 Transient Event Trees The general transient event trees are developed to evaluate the plant response to a given transient initiator group. The LSCS-specific transient event trees are:

g 1.

General transient tree for sequences in which there is a successful scram, primary system pressure boundary remains intact, off-site power remains available, but with the condenser unavailable ;

LSCS-5 4

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Transient tree for sequences in which there is a successful scram, primary system pressure boundary remains intact, condenser available, and off-site power available; 3.

Event tree for sequences initiated by (or resulting in) a stuck-open safety relief valve with successful scram and off-site power available; i

4. i Event tree for single unit loss of off-site power (LOOP) and dual unit loss of off-site power (DLOOP) with successful scram. l 5.

Three ATWS event trees for transient or small LOCA sequences in which there is a failure of RPS and ARI to complete an automatic scram.

By using sequence transfers between trees, and evaluating each initiator individually, these event tree structures can be used to represent all postulated transient sequences.

LOCA Event Trees l

The LOCA event trees are developed to examine the plant response to each LOCA initiating event category:

B 6. Event tree for Large LOCA (LLOCA).

7.

Event tree for Medium LOCA (MLOCA).

8.

Event tree for Small LOCA (SLOCA).

) Flooding Event Tree One event tree was also developed for intemal flooding events. This event tree was derived from a modified transient event tree to include the effects of flood specific source / location. He flood initiator is derived from some pipe ruptures that have impact on safety systems. Those ruptures are postulated in one

$ of.the following areas: The ground and the main floors of the Reactor Building, the Cable Spreading Room in the Auxiliary Building, and the Service Water Intake Structure.

Fault Trees

$ Fault trees are used to model functions specified in the event trees, and typically represent the logic associated with failure of a system or combinations of systems (such as HPCS and RCIC for loss of high pressure injection). An example of a portion of the fault tree associated with the Low Pressure Core Spray (LPCS) function is provided in Appendix B.

His fault tree represents the combination of events causing a failure of the Low Pressure Core Spray p system. Fault trees are made up of gates and basic events. A gate represents the logical combination of component and operator failures that will prevent successful operation of the system. Two types of gates are used for the LSCS PRA model: 1) OR gates, which are used when Atly of the inputs to the gate cause the defined failure; and 2) AND gates, which are used when all the inputs to the gate are required to cause the defined failure. As shown in Appendix B, gates are linked together to form the logic that m def' es the failure combinations that will result in occurrence of the " top event". A basic event is represented on the g fault tree as a box with a circle beneath it. A basic event can represent a component failure probability, a component test and maintenance unavailability, an initiating event frequency or a human error LSCS-6

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probability. De basic events represent the lowest level of detail in the model. Once the fault tree is developed down to the level of a basic event, probability data must be input to the model.

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IH. Data Bere are four basic data types used in the LaSalle Station PRA model:

e Component failure data,

) e Initiating event data, Component test and maintenance unavailability data, and e Human reliability data.

Dese data can be acquired from plant specific information, or from generic industry data. Generic data can be obtained from various industry publications, such as other PRAs, NUREGs and IEEE-500, or from

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a combination of the sources. Generic data may be based on expert opinions for rare events, such as large LOCA's. Plant-specific data is preferred over generic data because it will reflect the plant's current design and operating and maintenance history.

Component Failure /UnavaHability Data

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Component performance is modeled in the fault trees as a total failure probability. This total failure probability is computed using the following equation:

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(Run q Run Time Failures (Missionm Time) ,a g + ,

Start

= Total Failures' Failure Probability Figure 1 provides a diagram showing data sources and indicates how the data has been used to give the failure and unavailability data.

Failure information: ne number of failures was determined from a review of equipment failure

) recorth (LER/DVR and PIP Records), and work history records (TJM).

Componem Operating Hours: For most components the operating hours were estimated from component breaker hour meter logs kept by System Engineering. For the Diesel Generators the operating hours were obtained from the EDG computerized start log on the IBM Mainframe. l

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• Component Demands: Estimated using surveillance and preventive maintenance testing requirements.

• l Component Unavailability Hours: Estimates of unavailability time were made using TJM records.

The components with plant-specific failure data are listed in Table 4. All other component failure data is

) based on generic estimates.

De component failure data is also used to determine the probability of common cause failures, that is, failures of multiple similar components due to a single fault. An example might be a common cause failure of all three RHR pumps to start due to a faulty maintenance activity that was performed on each pump. Although such failures are much less likely, they are very important because of their ability to

) disable redundant trains of mitigating or support systems. To determine the probability of multiple failures due to a common cause, a term called a Beta Factor is calculated and then multiplied by the s component failure probability to arrive at the desired result.

LSCS 7

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J Plant Records  ! ......................

Raw Data

'O  : Parameter Estimates DVRs/LERs  ! . Failures PIFs j { ,

/ .

. Failure to Start

w .

Operating

-- . Demands  :

O  : surveillances - .

Failure to Run Equipment Operation Records i

Wng he f[: i i

0  :

1

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i Maintenance  !

p.# Frequency N '

/ '

0 -

Work Requests N Maintenance N s unavailabilities

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N Maintenence /

r Duration l Monthly O -

pasg i

Transie.it laitiating Event Reports Initiators "

Frequencies O

Figure 1 LaSalleStation PRA

• O Data Collection and Analysis:

Information Flow O

'O tscs4 lO

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l Table 4 O

l Plant Specifle Failure Data Component Failure l Unavailability Probability Probability Condensate / Condensate Booster Pumps 2.63E-03 7.93E-03 Diesel Generators (0, I A, and 2A) 2.53E-02 5.23E-02 Diesel Generator Cooling Water Pumps (0,1 A, and 2A) 3.97E-03 3.61E-04 Feed Water Regulating Valves 1.52E-02 7.88E-04 Motor Driven Reactor Feed Water Pumps 3.40E-03 9.22E -03 High Pressure Low Pressure Core Sprav Pumps 5.89E-02 3.44E N DieselGenerators (IB and 2B) 1.29E-02 1.89E-02 Diesel Generator Cooling Water Pumps (IB and 2B) 1.13E-02 2.22E-05 C low Pressure Low Pressure Core Spray Pump 2.67E-02 2.83E-04 ControlRod Drive Pump 1.67E-03 2.30E-03 Residual Heat Removal Heat Exchangers 3.13E-03 4.44E-04 Residual Heat Removal Pumps 2.48E-03 3.14E-03 Residual Heat Removal Service Water Pumps 2.67E-03 1.64E-03 g Reactor Core Isolation Cooling 2.97E-01 2.32E-03 i Station AirCompressors 5.30E-03 7.44E-03 Standby Liquid Control Pumps 2.97E-02 3.69E-M 1

Reactor Building Closed Cooling Water Heat Exchangers 3.63E-03

! 8.33E-03 Reactor Building Closed Cooling Water Pumps 3.63E-03 g Station Service Water Pumps 1.46E-03 2.53E-03 7.68E-03

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Turbine Building Closed Cooling Water Heat Exchangers 4.56E-03 4.58E-04 Turbine Building Closed Cooling Water Pumps 9.03E-03 ---

% Initiating Event Data

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< Initiating event frequency data are either generic or plant-specific. The frequency ofinitiating events which are relatively common, such as unplanned reactor trips, or losses of main feedwater can be readil calculated for LSCS based on the plant's operatmg history. For less frequent events, such as loss of offsite power, generic industry data can be used, supplemented with plant-specific information if available. For y

M rare events, such as large LOCA's, expert opinion found in various publications is used. For those initiating events which are dependent upon plant component configurations and failure data, such as loss of service water, fault tree analysis techniques are used to evaluate the likelihood of the event using generic component data and plant-specific data, when available.

Human Reliability Data O

Human error probabilities are the least certain of all PRA data. Quantification of human error is accomplished by performing a human reliability analysis (HRA) for each operator action identified in the event trees and fault trees. For each action, the HRA analyst documents the conditions under which the action may have to be performed, including the operator stress at the time of the action, the environment in which the action is performed (for local actions only), the complexity of the action, the procedural v guidance available, the cues which inform the opta at that the action is required, whether there is conflict experienced in performing the action and the time available to perform the action. 'Ihis LSCS-9 Q

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3' information is factort>d into the methodology for calculating a failure probability.- Interviews and simulator observations are conducted, when possible, to verify the results of this analysis.

O In addition to operats actions, the probabilities of maintenance, calibration, and restoration errors, occurring prior to tre event, are similarly estimated.

IV. ModelMaintenance

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ne LSCS PRA model is maintained on a personal computer using an EPRI-developed software package called CAFTA, or Computer Assisted faultIree Analysis. De model can be readily manipulated to evaluate risk impact or individual system reliability due to modifications, procedure changes, or equipment status. The model will be penodically updated to reflect the cur .mt plant configuration and the accumulation of additional plant operating history and component failuie data.

A second software package called RMQS, or Risk Management Query System is used to display and O evaluate the results of the LSCS PRA. Various report features of RMQS are used to document the LSCS PRA.

A third software package called EOOSPRA (Equipment Out Of Service flant Bisk Analyzer) is an on-line Risk Monitor used to evaluate changing plant configurations. This tool will be used to evaluate past, day-to-day, and future (planned) plant configuration changes (failures, maintenance, modifications) with Q respect to their impact on risk (core damage frequency). It is capable of performing instantaneous as well as integrated risk calculations for specific configurations or for trending purposes.

V. Quantification Quantification is the process of evaluating the event trees and fault trees using the component and human Q reliability data to determine the various sequeaces of events which can lead to core damage, and to j

' calculate the frequency at which they are expected to occur. The event trees and fault trees are linked together to represent each accident sequence to be evaluated and, using basic event data, the model is t

quantified. De CAFTA computer code is used to quantify the several thousand gates and basic events of the LSCS PRA model.

i Q Re output of the quantification process consists of the combinations of all sets of basic events relating to the event sequences which will cause a core damage accident. These combinations of the minimum numbers of failures leading to core damage are called cutsets. De numerical value of a cutset consists of the product of an initiating event frequency and the failure probabilities of the basic events which define the sequence. Because of the number ofinitiating events and the numerous combinations of event tree branches that are represented by fault trees, the total number of cutsets that could cause a core dunage O event could con ceivably be in the millions, given the level of detail to which system failures are codeled.

For this reason, a truncation frequency, or cutoff point, of 1 x 10~" per year is chosen, and only cutets with a frequeru:y of occurrence above this value are calculated as part of the core damage frequency and are loaded into the RMQS and EOOSPRA software.

Any operator action which is considered to be part of the planned response to emergency conditions is Q incorporated into the model. Credit is only taken if an action is addressed in appropriate abnormal or emergency operating procedures.

i LSCS-10 0

O VL GeneralResults Core Damage Frequency The total core damage frequency (CDF) at LSCS is calculated to be 1.0 x 10 per year. This is below the NRC's published safety goal of I x 10" per year. Typical BWR CDFs are in the range of 10 4 10-5 per year, with a few outlier plants on either end of this range. The CDF for LSCS is neither exceptionally low nor high. The CDP value must be understood within a specific context. The many assumptions made to facilitate the analysis, the various sources of data, choices made as to what failure modes to model, as well O as the subjective nature of HRA and the uncertainties associated with the data for each pan of the model, all affect to varying degrees the CDF value. The overall CDF should be viewed as an " order of {

magnitude" estimate. CDF's from other plants, in reality, cannot be directly compared to LSCS, since different data and analysis techniques may have been applied. Thus a plant with a CDF 4 of 5 x 10 per )

l year or 2 x10 per year cannot be said to be significantly more or less safe, respectively, than LSCS.

Further, the level 1 analysis does not evaluate the performance of containment systems in preventing the O release of radioactive fission products to the environment after a postuinted core damaging event occurs.

This is considered in the level 2 evaluation.

i Although much attention is given to the overall CDF, the most valuable information of a PRA is found in the relative imnorman of systems, components, human interactions and initiating events to the risk of l

core damage. These relative importance values provide a basis for prioritization of resources applied to O the operation, maintenance and design of a nuclear power plant.

Core Damage Sequences:

A list of the 100 top core riamage sequence cutsets is provided in Table 1 in the Appendix C. These cutsets are presented in order of descending frequency per year and their percent contribution to the O overali core damage frequency. The sequence names reflect the order or those sequences in the appropriate event trees.

Initiating Event importance:

The pie chart shown in Figure 2 shows the relative contributions of the individual initiating events to

.O LSCS core damage frequency.

Transiests with loss of instrument air, (T11) , are the largest initiating event category, contributing 32%

of the CDF. These transients are significant because venting containment cannot be performed without instrument air. Failure to vent results in the loss of the ADS function (and subsequent loss of the low pressure injection systems) and eventual containment failure, causing potential loss ofinjection systems in

.g the reactor building due to severe environments.

less of offsite power, LOSP, events are the second highest contributor to CDP. Single unit LOSP events contribute 6.5% of CDF and dual unit LOSP even" contribute 22.9%. If AC power can be restored to the emergency buses by the diese! generaters or crosstics, the,n the plant response is similar to transient events. If both diesel generators or the crosstieuxome unavailable, the unit is considered to be in a Q'

station blackout sequence. The core damage concibution of those SBO sequences (subset of LOSP) is 17.2%.

The SBO sequences involve:

Successful scram following a loss of offsite power.

Q

• Failure of the emergency diesel generators to function.

Failure to recover offsite power to unit 2 or use the unit I cross-ties to restore . .. ..... .

power to unit 2 emergency busses.

LSCS-11 4

ind - - w:-,r

. _ .- - ..--- - . - . . - - . . - - ..- - - -. -.- - .. - _ - . . _ . ~ _ -

4 Safe shutdown of unit (1)is assumed.

i

..0 To prevent battery depletaan, at least one emergency bus must be recovered tMthin 3 hours3.472222e-5 days <br />8.333333e-4 hours <br />4.960317e-6 weeks <br />1.1415e-6 months <br /> (without operator action to shed loads),

i i Iasses (failures) of AC or DC emergency buses contribute 11% of the CDF. 'IhfAe events are signi5 cant because of the unavailsality dthose systems powered by the failed bus (es).

I Turbine / generator trips, w A or without bypass valves, and MSIV cicours et eatxontribute 8%, 7%, and

_O I 4% of the CDF, respectively. 'Ibese events are agni8 cant because of their relatively high frequency of occurream or the loss of the main enndannar as a heat sink, which resular in a larger reliance on the

! avaitahility of the RHR system to remove decay best.

i Studc open (or inadvertently open) safetyhelief valve events cont:1tnra 4% of the CDF, 'Ibene events are i

nifnsficent because of the nanti==== loss ofvesselinventory and the accelerated bestup of the

O suppression pool.

?

IDCA's and other transients each contnhte anallar =====ta to the CDF.

l> Systema Imapertance:

I O The bar chart shown in Figure 3 gives the relative importance of the vanous systems to core damage risk l This chart canbe used in ?

5 where resources cAn be ebu.4 apphed to improve plant safety.

The chart shows the relatrve raniang of the systems aardeled in the PRA based on the increase in CDF

}

which occur if the system were unavadable (i.e., it always fails), which is refened to as its Risk i

i Actuevement Worth (RAW). 'Ibe chart denwwunates the importance of the dicael geacrator coohng water pumps, which nwntmin the operabahty of not only the diesels, but also vanous igection and decay heat 10 removal systems via room coohng. High pressure igoction from HPCS or RCIC is important fbr i  !

j mair taining core coverage after plant tranments The PRA resuhs illustrate that support systems such as AC and DC power and instrument air are important to core damage risk because they are required for the

! l sureessful operation of several mitigating functions The diesel- driven Brewster pumps (PPS) are  !

tmportant because they could be the only low pressure law source avadabic dunng a station blackout i event. RHR pumps are used for nnneminmant cooling, reflecting the importance ofdecay heat removal 3

Consponent Importance:

Table 5a lists the LSCS components in order of their importance to core damage risk based on their RAW j

value. On a system level, component importana is used to prioritize design, maintenance, surveillance, and training activities. Table 5b lists the LSCS components in order of their importance to core damage b risk based on their Fussell-Vesely importance, that is, the reduction in CDF which would occur if the j component neverfaded.

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Table 52 Component Failure Mode Importances to CDF RAW;t2 Event Name RAW Dwiption RPS-ARI-F 2.93E+03 RPS and ARI FAILURE ( RMIEP, NMPC, WNP-2) 125DC-CM 1.16E+03 CS-COOL-PMP-CM 6.32E+02 125 DC BUS COMMON MODE FAILURE (B US FAULT

• BETA =.1)

COMMON MODE CS COOL. WTR PMPS LPCI-CM 3.35E+02 lEB235A-BCO 2.24E+02 COMMON MODE FAILURE OF ALL 3 LPCI PUMPS (BETA = .05) 1E42YB-FAULTS 1.66E+02 CB 2AP04E-4 FEED FROM 4KV BUS 241Y TO 480 BUSES 235X & 235Y 4KV 242Y FAULTS 1E41YA FAULTS 1.62E+02 4KV 241Y FAULTS DGS FAIL CM 8.66E+01 ADS DGs DIV 1,2 common mode failure (DG2A FAIL *(BETA =.012))

7.48E+01 VSP 6 OF 7 ADS VLVS FAIL TO FUNLTION ON DEMAND 3.18E+01 VAPOR SUPPRESSION POOL SRV DIDNOT--OPEN 2.58E+01 SRV FAILURE TO OPEN (Reset prob to 6.64E-04 aft quant)

C0DG01P-FAULTS 2.57E+01 1E35YA-480-LPW MOTOR-DRIVEN PUMP CODG0lP SS FAULTS 2.33E+01 LOSS OF POWER AT480 BUS 1E35YA 2E22C002-FAULTS 2.30E+01 SWVYO2AX-INHTR 2.27E+01 2E22C002 DG2B COOL WTR PUMP PLANT SPECIFIC FLT DATA (

IEB35Y2X BCO 2.11E+01 INADEQUATE HEAT REMOVAL VIA AIR COOLING SWVY02AX l C2DG032 XOC-LP ELECTRIC POWER CIRCUlT BREAKER lEB35Y2X CO 2.09E+01 2E22C001-PMS-SS 2.07E+01 2DG032: CSCS DIVI COOLING FLOW ISOLATION M ANUAL VALVE HP-MOV-FAULTS 2.0$E+01 2E22C001 HPCS PUMP PLANT SPECIFIC FAULT DATA (GEN)

HPCS MOV VALVES FAULTS HP-CHK-MAN-FLT 1.89E+01 HPCS MANUAL OR CHECK VALVES FAULTS SEVYO3CB-FMS-SS 1.86E+01 SEVYO3AX-ACX-LFI MO'IDR-DRIVEN FAN SEVY03CB SS FAULTS 1.83E+01 LOCAL FAULT CAUSING INADEQUATE HEAT REMOVAL IN ACX SEVYO3AX i' SEVB001X-BCO-LF 1.82E+01 1EB236B-BCO LOCAL FAULT OF CIRCUIT BREAKER SEVB001X 1.8M+01 l TBCCW-PSW U1-FLT 1.81E+01 FDR BRKR 2AP06E-5:4KV BUS 242Y TO 480V BUSES 236X/236Y FAILi (U1 )TBCCW/PSW SYSTEMS FAILURES IE36YB 480-LPW 1.81E+01 l

LOSS OF POWER AT480 BUS 1E36YB 1E211YA 125-LF 1.76E+01 LOCAL FAULTOF 125 BUS 1E211YA FLT-CSCINT-005 1.71E+01 1E36XB-480-LPW 1.70E+01 COMPONENT FAULT OCCURS IN INTERFACE CSCS SEGMENT 005 LOSS OF POWER AT480 BUS 1E36XB 2DG0lP-FAULTS 1.64E+0!

1E243-1-480-LPW 1.58E+01 DG2A COOL WTR PUMP 2DG01P PLANT SPECIFIC FAULTS (PSD)

LOSS OF POWER AT480 BUS 1E2431 1EB36YIX BCO 1.57E+01 IAS TROUBLE ELECTRIC POWER CIRCUIT BREAKER 1EB36YlX CO 1.52E+01 INSTR AIRTROUBLES 2E12C002B FLT 1.35E+01 RHRB01BB-BOO 1.34E+01 2E12C002B RHR TRAIN B MOTOR-DRIVEN PUMP FAULTS (PSD) 2E12B001B HTX-LF ELECTRIC POWER CIRCUlT BREAKER RHRB01BB 00 1.33E+01 SAT LOCAL-FAULT 1.32E+01 2E12B001B HX TRAIN B PLANT SPECIFIC FAULT DATA (PSD)

SAT LOCAL FAULT RHRSWB lfrX-ISO-V 1.31E+01 CSCD300B STR-PLG RHRSW B HTX ISOLATION VALVE FAULTS 1.31E+01 RHRF48BB VOO 2E12D300B STRAINER RHR SW TRAIN B PLUG 1.31E+01 MOTOR-OPERATED VALVE RHRF48BB 00 RHRF03BB VOC 1.24E+01 RHRF47BB VOC MOTOR-OPERATED VALVE RHRF03BB OC 1.24E+01 MOTOR-OPERATED VALVE RHRF47BB OC 2E12C002B-OUT V 1.22E+01 2E12C002A-FLT RHR TRAIN B PUMP DISCHARGE ISOLATION VALVES 1.20E+01 IE12D301B-STR-F 1.20E+01 2E12C002A RHR TRAIN A MOTOR-DRIVEN PUMP FAULTS (PSD) 1E12D301B SUPP POOL SUCTION STRNR FOR RHR PUMP B (GE

! RHRB01AA-BOO 1.19E+01 2E12B001A HTX-LF ELECTRIC POWER CIRCUIT BREAKER RHRB01 AA 00 1.19E+01 i NWVY0lCA-FMS-SS 1.18E+01 2E12B001 A HX 1 RAIN A PLANT SPECIFIC FAULT DATA (PSD)

! RHRF48AA-VOO MOTOR-DRIVEN FAN NWVY01CA SS FAULTS 1.18E+01

' MOTOR-OPERATED VALVE RHRF48AA 00 RHRSWA-HTX ISO-V 1.18E+01 RHRSW A HTSISOLATION VALVE FAULTS LSCS-15

)

Table 52 Component Failure Mode Importances to CDF - RAW22 i Event Name RAW Dwiption

)

NWVY01AX-ACX-LF1 1.16E+01 LOCAL FAULT CAUSING INADEQUATE HEAT REMOVAL IN ACX NWVY01AX NWVB001X BCO 1.16E+01 ELECTRIC POWER CIRCUIT BREAKER NWVB001X CO LPCI-INJ.VLV-CM 1.15E+01 CSCD300A-STR PLG 1.15E+01 LPCI INJECTION VALVE COMON MODE FAILURE TO OPEN(BETA = .0

) RHRF03AA-VOC 1.10E+01 2E12D300A STRAINER RHR SW TRAIN A PLUG MOTOR-OPERATED VALVE RHRF03AA OC RHRF47AA-VOC 1.10E+01 MOTOR-OPERATED VALVE RHRF47AA OC 1E35Y2A-480-LPW 1.08E+01 LOSS OF POWER AT480 BUS 1E35Y2A 2E12C002A-OUT-V 1.08E+01 RHR TRAIN A PUMP DISCHARGE ISOLATION VALVES FLT-CSCINT-018 1.07E+01 1E12D301A-STR-F COMPONENT FAULT OCCURS IN INTERFACE CSCS SEGMENT 018 1.06E+01

) 1EB2Y22X-BCO 9.80E+00 1E12D301 A SUPP POOL SUCTION STRNR FOR RHR PUMP A (GEN)

NOS-PIP-LAK3BB 9.19E+00 4KV BRKRS:DIV2125VDC CNTRL PWR CKT BRKR 1EB2Y22X XFER OPN I IEB1Y22X-BCO FAULT OCCURS PRIOR TO INPUT OF 3 OF 3 LOGIC UNIT LAK3BB 7.93E+00 NEVYO4CA-FMS-SS 7.08E+00 4KV BRKRS: DIV1 125VDC CNTRL PWR CKT BRKR lEB1Y22 XFER OPN MOTOR-DRIVENFAN NEVYO4CA SS FAULTS NEVYO4AX-ACX-LFI 6.83E+00

- FAULT-SLC-C03 LOCAL FAULT CAUSING INADEQUATE HEAT REMOVAL IN ACX 6.81E+00

)- NEVB001X BCO 6.80E+00 COMPONENT FAULT OCCURS IN STDB Y LIQUID CTRL SEGMENT C03 ELECTRIC POWER CIRCUIT BREAKER NEVB001X CO SLC-XPLOSV-CM 6.72E+00 NOS-PIP-SAV1B1X 6.72E+00 SLC EXPLOSIVE VALVE FAILURE TO EXPLODE CM (BETA = .03) 1E36Y1B-480-LPW FAULT OCCURS PRIOR TO INPUT OF 2 OF 2 LOGIC UNIT SAV1B1X 6.63E+00 LOSS OF POWER AT480 BUS lE36YlB SLC-XPLOSV-AB-F 6 54E+00 Both SLC explosive valves fail to explode SRV-DIDNOT-CLOSE 6N E+n0 SRV FAILURE TO CLOSE (Reset quant to 6.64E-04 aft quant)

) LAK10BB-ROO-LFO 5.99ti+00 FAULTIN RELAY COIL LAK10BB OO IN LCI SIGNAL PATH V2N LOSP-AT Ul-ONLY 5.67E+00 RC1/LCS-COOL-V LOSS OF OFFSITE POWER (UNIT 1) ONLY GIVEN OSP AVAIL AT U2 5.64E+00 RCIC/LPCS RM COOLING VALVE FAULTS PIP-SAP 1AAC2 5.53E+00 RHR-CNTRL-FUSES 4.81E+00 FAULT OCCURS PRIOR TO INPUT OF 1 OF 2 LOGIC UNIT SAP 1 AAC2 RHR CONTROL POWER BRKR AND FUSES FAULTS DW-HP-RHR-SGNB-F 4.70E+00 ,

) 2FWOOS-PATH-FLT 4.45E+00 DW HI-PRESS RHR TRAIN B SGNL FAIL 2FW005 MDRFPREG VALVE P A TH FAULTS l

DW-HP-RHR-SGNA-F 4.32E+00 DW HI-PRESS RHR 1 RAIN A FN F.UL RHR RECOVERY 4.31E+00 PSW-TBCCW-PATH 4.24E+00 FAILURE TO RECOVER l OF-2 Mi?. TRAINS WITHIN 33 Hrs (ERIN)

PSW TO TBCCW HTX A PATH FAULTS CST-HOTWELL-LF 4.22E+00 CST TO HOTWELL MAKEUPLOCAL FAULTS CD-POLISHER-OUT 4.16E+00 3 DG2B-AUX-SYS 3.96E+00 FAULT OCCURS PRIOR TO THE OUTPUT OF CONDENS ATE POLISHER ,

HPCS DIESEL AUXILIARY SYTEMS FAILURE l 2E225001-FAULTS 3.95E+00 DG2B PLANTSPECIFIC FAULTS (PSD)

FOP-OUT-CDS-J1 3.91E+00 1EB433C-BOO 3.91E+00 FAULT OCCURS PRIOR TO THE OUTPUT OF CONDENS ATEJl DG 2B OUTPUT BRKR FAILURE TO CLOSE 1E212YB 125-LF 3.75E+00 LOCAL FAULT OF 125 BUS 1E212YB DG2B-LOGIC-FTS 3.67E+00 dg2b start logic failure (auto)** calculated value.

) 1EB432C-BCC TBCCW-HTXA-FLT 3.64E+00 B US 243 NORMAL FEEDER BRKR FAILS 10 OPEN GIVEN LOSP 3.64E+00 FAULT-TCW-T13 TBCCW HTX A OR INLET / OUTLET VALVES FAILURE 3.49E+00 PSWO25DX-VOC COMPONENT FAULT OCCURS IN TBCCW SEGMENT TI3 3.42E+00 RCIF063C-VOC 2WS025 MOV: TBCCW HTXs PLANT SW INLET VALVE 3.25E+00 MOTOR-OPERATED VALVE RCIF063C OC RCIC001X TDP SS 3.24E+00 TURBINE-DRIVEN PUMP RCIC001 SS FAULTS RCIF013C FAULTS

') RCIF045C-VCC 3.21E+00 3.20E+00 MOV RCIC F013 VALVEFAULTS l MOTOR-OPERATED VALVE RCIF045C CC RCIF046C-FAULTS 3.20E+00 i MOTOR-OPERATED VALVE RCIF046C CC CD-HO1WLL-TNK-LF 3.15E+00 LOCAL FAULT OF CONDENSER HOTWELL TANK LSCS 16

)

- 1

I 9 Tcble 52 Component Failure Mode Importances to CDF - RAW22 l

Event Name RAW Description O

CST-TNK 3.15E+00 CSTTANK FAILURE i

RCIF008C-VOC  !

3.14E+00 MOTOR-OPERATED VALVE RCIF008C OC RCIC.EXHST-VLYS 3.09E+00 RCIC EXHAUSTVALVES MODULE '

VALVECL-RCI-011 2.94E+00 VALVEIN SEGMENT FAULTS RCI TTT-GVRNR-F 2.90E+00 C 1EB413A-BOO 2.67E+00 MOV/HOV THROTTLE /GVRNR VALVES FAULTS SY VNF-HVDG2A ELECTRIC POWER CIRCUIT BREAKER lEB413 A 00 2.60E+00 l RCIC-RPV-CHKVLV 2.54E+00 ROOM HVDG2A COOLING OR VENTILATION SYSTEM FAULTS ,

VALVE IN SEGMENTFAULTS  !

DG2A-FAULTS 2.53E+00 DG2A PLANT SPECIFIC FAULTS

.1EB412A-BCC 2.50E+00 ELECTRIC POWER CB IEB412A CC '

CCB2G1P-BCO 2.49E+00 O NOS-PIP-LAK10BB 2.47E+00 ELECIRIC POWER CIRUIT BREAKER CCB2G1P 00 RCIC-ISOL-VLVS 2.46E+00 FAULT OCCURS PRIOR TO INPUT OF 1 OF 2 LOGIC UNIT LAK10BB 1E243C-FAULTS 2.44E+00 EITHER RCIC PUMP L.O. ISOLATION VALVES TRANSFERS CLOSED 4KV BUS 234 FAULTS lE213C 125-LP 2.44E+00 LOCAL FAULT OF 125 BUS IE213C IEB423B BOO 2.35E+00 RCIRD001 ELECIRIC POWER CIRCUIT BREAKER IEB423B 00 2.33E+00 RUI*TURE DISC RCIRD001 FAILS O FLT-CSC1NT-004 2.29E+00 1E35XA-480-LPW 2.28E+00 COMPONENT FAULT OCCURS IN INTERFACE CSCS SEGMENT 001 LOSS OF POWER AT 480 BUS 1E35XA LEE-GOB-CTP 2.28E+00 2DG01P-CP-BRKR 2.27E+00 LOSS OF CONTROL POWER TO COMPONENTS IN LEE SIGNAL PATH 1EB422B-BCC 2DG01P CONTROL POWER BREAKER / FUSE FAULTS 2.22E+00 ELECTRIC POWER CB 1EB422B CC 1EB234X.BCC 2.22E+00 l O 1EB425B BCC ELECTRIC POWER CIRCUIT BREAKER 1EB234B CC  !

2.22E+00 ELECTRIC POWER CB 1EB425B CC RX-LO PR SGNL-F 2.19E+00 RCIC RESPONSETO RX 14 PRES SGNL FAIL 1EB2Y14X-BCO 2.14E+00 DGO. FAULTS 2.13E+00 DG2A LOCAL CONTROL PNL CNTRL CIRCUIT BREAKER lEB2Y14X CO DGO PLANT SPECIFIC FAULTS (PSD)

DG0V01YA-FAULTS 2.12E+00 OVD01YA MOD FAULTS 1E36X3B-FAULTS ' 2.11E+00 1E36X3B CB FAULTS

'O DGOV01CA FMS-SS 2.10E+00 DGOV02YA-FAULTS OVD01C MOTOR-DRIVEN FAN DG0V01CA SS FAULTS 2.09E+00 OVD02YA FAULTS DGOV03YA-FAULTS 2.09E+00 OVD03YA MOD FAULTS NEB 2522-BCO-LF 2.04E+00 LOCAL FAULT OF CIRCUIT BREAKER NEB 2522

. DIVI-BRKR-SGNL 2.02E+00 DG0 BREAKER CONTROL SIGNALS FAULT 2FWO1PC-FAULTS 2.01E+00 O COMPONENT FAULT OCCURS IN MAIN FEEDWATER SEGMENT L3 O

l P

ISCS-17

'O

Teble 5b i

Component Failure Mode Importances to CDF - Fussell-Vesely Fussell-Event Name Vesely Description RHR-RECOVERY DG2A FAULTS 2.34E-01 FAILURE TO RECOVER 1-OF-2 RHR TRAINS WITHIN 33 Hrs (ERIN 1.34E-01 DG2A PLANT SPECIFIC FAULTS DOO-FAULTS 1.33E-01 DG0 PLANT SPECIFIC FAULTS (PSD) 2E22C002-FAULTS 2E22S001-FAULTS 1.32E-01 2E22C002 DG2B COOL WTR PUMP PLANT SPECIFIC FLT DATA (PS 1.21E-01 DG2B PLANT SPECIFIC FAULTS (PSD) 2E22C001-PMS-SS CODG01P-FAULTS 1.06E-01 2E22C001 HPCS PUMP PLANT SPECIFIC FAULT DATA (GEN) 1.05E-01 MOTOR-DRIVEN PUMP C0DG01P SS FAULTS ROP 3 HP-MOV-FAULTS 9.70E-02 failure to recover OSP within 3 HRS ( NO LOAD SHED) 9.01E-02 HPCS MOV VALVES FAULTS 2DG01P FAULTS RPS-ARI F 8.28E-02 DG2A COOL W1R PUMP 2DG01P PLANT SPECIFIC FAULTS (PSD) 8.19E-02 RPS and ARI FAILURE ( RMIEP, NMPC, WNP-2)

! SWVY02AX-INifI'R 2FWOOS-PATH-FLT 7.72E-02 INADEQUATE HEAT REMOVAL VIA AIR COOLING SWVYO2AX i 7.54E-02 2FW005 MDRFP REG VALVE PATH FAULTS  !

2E12C002B-FLT i 2E12C002A-FLT 7.39E-02 2E12C002B RHR TRAIN B MOTOR DRIVEN PUMP FAULTS (PSD)

SEVYO3CB-FMS-SS 7.11E-02 2E12C002A RHR TRAIN A MOTOR-DRIVEN PUMP FAULTS (PSD) 6.67E-02 MOTOR-DRIVEN FAN SEVYO3CB SS FAULTS RC1C001X-TDP-SS 5.64E-02 TURBINE-DRIVEN PUMP RCIC001 SS FAULTS NWVY01CA-FMS-SS 5.35E-02 MOTOR-DRIVEN FAN NWVY01CA SS FAULTS HPCS-TOTAL--UUM 5.25E-02 HPCS total unavailability due to mech and elec maintenance l

RHRF48BB-VOO 5.01E-02 MOTOR-OPERATED VALVE RHRF48BB 00 RHRSWB-HTX ISO-V 5.01E-02 RHRSW B HTX ISOLATION VALVE FAULTS RHRSWA-HTX ISO-V l 4.82E-02 RHRSW A HTS ISOLATION VALVE FAULTS

RHRF48AA.VOO 4.82E-02 MOTOR OPERATED VALVE RHRF48AA 00

) CSCD300B-STR-PLG 4.62E-02 2E12D300B STRAINER RHR SW TRAIN B PLUG CSCD300A-STR-PLG LPCI-CM 4.45E-02 2E12D300A STRAINER RHR SW TRAIN A PLUG RCIF063C-VOC 4.43E-02 COMMON MODE FAILURE OF ALL 3 LPCI PUMPS (BETA = .05) 4.36E-02 MOTOR-OPERATED VALVE RCIF063C OC 2E12B001B HTX-LF 2E12B001A-HTX-LF 4.09E-02 2E12B001B HX TRAIN B PLANT SPECIFIC FAULT DATA (PSD)

ROP 24 3.94E-02 2E12B001 A HX TRAIN A PLANT SPECIFIC FAULT DATA (PSD) 3.50E-02 failure to recover OSP within 24 hrs RCIF013C-FAULTS 2.70E-02 MOV RCIC F013 VALVE FAULTS DG2B-AUX-SYS 2.67E-02 HPCS DIESEL AUXILIARY SYTEMS FAILURE RCIF046C-FAULTS 2.52E-02 MOTOR-OPERATED VALVE RCIF046C CC DGS-FAIL-CM 2.50E-02 DGs DIV 1,2 common mode failure (DG2A FAIL *(BETA =.012))

RCIF045C-VCC 2.50E-02 MOTOR-OPERATED VALVE RCIF045C CC i

CS-COOL-PMP-CM 2.42E-02 COMMON MODE CS COOL. WTR PMPS TBCCW-PSW-U1-FLT 2FWO1PC-FAULTS 2.40E-02 (U1 ) TBCCW/PSW SYSTEMS FAILURES (FROM: TBCCW-OR l ADS 2.20E-02 COMPONENT FAULT OCCURS IN MAIN FEEDWATER SEGMENT L3 l SY-VNF-HVDG2A 1.67E-02 6 OF 7 ADS VLVS FAIL TO FUNCTION ON DEMAND (ADS QUANTIF CST HOTWEL1 LP 1.67E-02 ROOM HVDG2A COOLING OR VENTILATION SYSTEM FAULTS 1.12E-02 CST TO HOTWELL MAKEUP LOCAL FAULTS DW-HP-RHR-SGNB-F LCSC001A-PMS-SS 1.01E-02 DW Hi-PRESS RHR TRAIN B SGNL FAIL (QUANT:NOS-POP-RHR-9.64E-03 MOTOR-DRIVEN PUMP LCSC001 A SS FAULTS 1E12D301B-STR-F 1 DW-HP-RHR-SGNA-F 9.16E-03 1E12D301B SUPP POOL SULTION STRNR FOR RHR PUMP B (GE I

1E12D301 A-STR-F 8.97E-03 DW H1-PRESS RHR 'IRAIN A SGNL FAIL (QUANT:NOS-POP-RH RX-LO-PR-SGNL-F 8.82E-03 1E12D301 A SUPP POOL SUCTION STRNR FOR RHR PUMP A (G OSA01C-PATH-FLT 8.70E-03 RCIC RESPONSE TO RX LO PRES SGNL FAIL (FROM:RCIACT-X ISA01C-PATH-FLT 8.27E-03 OSA01C COMMON UNIT STATION AIR COMRESSOR PATH FAULTS 1EB235A-BCO 8.27E-03 ISA01 CIA UNIT 1 STATION AIR COMPRESSOR PATH FAULTS LPCS-LOGIC-FLT 8.06E-03 CD 2APO4E-4 FEED FROM 4KV BUS 241Y TO 480 BUSES 235X & 23 7.40E-03 LPCS PUMP LOGIC FAULTS LSCS-18

O Tabl35b Component Failure Mode Importances to CDF - Fussell-Vesely Fussell-Event Name Vesely 1 Description

'O l LCSF005A-FLT 7.10E-03 LCSF005A CB OR OTHER LOCAL FAILURES NEVYO4CA-FMS-SS 6.85E-03 MOTOR-DRIVEN FAN NEVYMCA SS FAULTS DGOV01YA-FAULTS 6.57E-03 OVD01YA MOD FAULTS RCIC-EXHST VLVS - 6.57E-03 RCIC EXHAUSTVALVES MODULE DGOV03YA FAULTS 6.52E-03 OVD03YA MOD FAULTS

'O HP-CHK MAN-FLT i 3.90E-03 HPCS MANUAL OR CHECK VALVES FAULTS l DG0V01CA-FMS-SS 3.81E-03 OVD01C MOTOR-DRIVEN FAN DG0V01CA SS FAULTS VALVECL-RCI-011 3.22E-03 VALVEINSEGMENTFAULTS l

l RHRB01BB BOO 3.01E-03 ELECTRIC POWER CIRCUIT BREAKER RHRB01BB 00 l RCIF008C-VOC 2.91E-03 MOTOR-OPERATED VALVE RCIF008C OC l RHRB01AA BOO

O 2.90E-03 ELECTRIC POWER CIRCUIT BREAKER RHRB01 AA 00 RHR-CNTRL-FUSES 2.35E-03 RHR CONTROL POWER BRKR AND FUSES FAULTS SRV-DIDNOT-CLOSE 2.06E-03 SRV FAILURE TO RECLOSE (RMIEP) 1EE-GOB-CTP C0DG035-VOC 1.65E-03 LOSS OF CONTROL POWER TO COMPONENTS IN 1EE SIGNAL PATH t 1.39E-03 MOTOR-OPERATED VALVE CODG035 OC DG0V02YA-FAULTS 1.36E-03 OVD02YA FAULTS l FAULT SLC-C03 10 D0VMODCOM CC-UUM 1.32E-03 COMPONENT FAULT OCCURS IN STDBY LIQUID CTRL SEGMENT C0 LCSD302X-STR 1.31E-03 UNAVAILABLE FOR PERIOD OF UNSCHD MAINT ONCONTROL SYSTE 2E12C002B-OUT-V 1.25E-03 SUPPRESSION POOL SUCTION STRAINER LCSD302X FAULTS j 1.12E-03 RHR TRAIN B PUMP DISCHARGE ISOLATION VALVES '

2E12C002A-OUT-V 1.08E-03 RHR TRAIN A PUMP DISCHARGE ISOLATION VALVES FOP-OUT-CDS-J1 i NOS-PIP-SAV1B1X 8.92E-N FAULT OCCURS PRIOR TO THE OUTPUT OF CONDENSATEJ1 '

'O 1E35YA-480-LPW 7.80E-04 FAULT OCCURS PRIOR TO INPUT OF 2 OF 2 LOGIC UNIT SAV1B1X 6.80E-04 LOSS OF POWER AT480 BUS 1E35YA RCIC-RPV-CHKVLV 6.06E-04 VALVE IN SEGMENT FAULTS ]

1E36YB-480-LPW 5.76E-04 LOSS OF POWER AT 480 BUS 1E36YB LPCI-INJ VLV-CM 1E243-1-480-LPW 5.58E-04 LPCI INJECTION VALVE COMON MODE FAILURE TO OPEN(BETA 5.41E-04 LOSS OF POWER AT 480 BUS 1E243-1 1E36XB-480-LPW ,

5.26E-04 LOSS OF POWER AT480 BUS 1E36XB C SLC-XPLOSV-CM l

LCSB002A BOO 4.87E-04 SLC EXPLOSIVE VALVE FAILURE TO EXPLODE CM (BETA = .03) l 4.16E-04 ELECTRIC POWER CIRCUIT BREAKER LCSB002A 00 1E41YA-FAULTS 3.77E-N 4KV241YFAULTS 1EB35Y2X-BCO 3.67E-04 ELECTRIC POWER CIRCUIT BREAKER 1EB35Y2X CO 1E42YB FAULTS - 3.56E-04 4KV 242Y FAULTS 1EB236B BCO

'O lEB36YlX-BCO 3.24E-04 FDR BRKR 2AP06E-5:4KV BUS 242Y TO 480V BUSES 236X/236Y FAILS 3.04E-04 ELECTRIC POWER CIRCUIT BREAKER 1EB36YlX CO SEVB001X-BCO VSP 3.04E-04 ELECTRIC POWER CIRCUIT BREAKER SEVB001X CO 2.99E-04 VAPOR SUPPRESSION POOL 1EB1Y22X BCO 1EB432C-BCC 2.89E-N 4KV BRKRS: DIV1 125VDC CNTRL PWR CKT BRKR 1EB1Y22 XFER OPN 1EB2Y22X-BCO 2.87E-04 BUS 243 NORMAL FEEDER BRKR FAILS TO OPEN GIVEN LOSP

.O LPS FUSES 2.77E-04 4KV BRKRS:DIV2125VDC CNTRL PWR CKT BRKR 1EB2Y22X XFER O 2.75E-04 LPS CONTROL FUSES NWVB001X-BCO 2.70E-04 ELECTRIC POWER CIRCUIT BREAKER NWVB001X CO 2DG01P-CP-BRKR 1EB433C-BOO 2.28E-04 '2DG01P CONTROL POWER BREAKER / FUSE FAULTS 2.20E-04 DG 2B OUTPUT BRKR FAILURE TO CLOSE TBCCW-HTXA-FLT 1.88E-04 TBCCW HTX A OR INLET / OUTLET VALVES FAILURE VALVECL-LCS-S1 1.56E-N VALVE IN SEGMENT FAULTS Q FLT-CSC1NT-028 1.54E-04 COMPONENT FAULT OCCURS IN INTERFACE CSCS SEGMENT 028 i

SAT LOCAL-FAULT 1.44E-04 SATLOCALFAULT LPCS-SGNL-FLT 8.53E-05 LPCS PERMISSIVE SIGNAL FAULTS DAMPERCL-D0V B 7.47E-05 DAMPER IN SEGMENTFAULTS l

LSCS-19 0

Tchl25b Component Failure Mode Importances to CDF - Fussell-Vesely Fussen.

Event Name Vesely Description 125DC-CM IEBlY13X-BCO 7.08E-05 125 DC BUS COMMON MODE FAILURE (BUS FAULT

• BETA =.1)

NEVB001X BCO 5.36E-05 CONTROL POWER CIRCUIT BREAKER lEB lY13X CO 1E35XA-480-LPW 5.10E-05 ELECTRIC POWER CIRCUlT BREAKER NEVB00lX CO 5.05E-05 LOSS OF POWER AT480 BUS 1E35XA SLC-XPLOSV-AB-F 4.78E-05 Both SLC explosive valves fail to explode LOSP-AT-Ul-ONLY RHRIV3BB-VOC-LF 2.64E-05 LOSS OF OFFSITE POWER (UNIT 1) ONLY GIVEN OSP AVAIL AT U2 RHRF47AA-VOC-LF 9.15E-06 LOCAL FAULT OF MOTOR-OPERATED VALVE RHRF03BB RHRF47BB VOC-LF 9.15E-06 LOCAL FAULT OF MOTOR-OPERATED VALVE RHRF47AA RHRF03AA-VOC-LF 9.15E-06 LOCAL FAULT OF MOTOR-OPERATED VALVE RHRF47BB 1E21IXA-125-LF 9.15E-06 LOCAL FAULT OF MOTOR-OPERATED VALVE RHRF03AA 6.36E-06 LOCAL FAULT OF 125 BUS lE21IXA RHRB&C-COOL-FLT 3.19E-06 RHR PMPS B&C ROOM COOLING FAULTS 1E35Y2A-480-LPW 2.20E-06 LOSS OF POWER AT480 BUS lE35Y2A l

i LSCS-20

O Important Operator Actions:

.O The dominating operator actions are shown in Table 6. The actions are ranked in decreasing order o importance based on the reduction in CDF which would occur if the action never failed, referred to as its Fussen-Vesely (F V) value. The failure to depressurize after a loss of high pressure injection is the mos important because the vessel must be depressurized to allow for low pressure injection, or core dam will occur. If AC power is not restored, the diesel driven firewater pump may be the only injection source.

HPCS, RCIC and ADS (manual depressurization) are dependent upon DC power.

O The otner operator actions are related to coping with the dominant accident sequences. As a rule of 2

thumb, operator action failure probabilities fall in the range of 10 to 10" while component failure probabilities tend to fall in the range of 102 to 10'8. Therefore, operator errors can be dominant contributors to system failures and CDF.

'O O

O

.o 1

-O

'O O'

tsCs-21 O

O l

Table 6

O Operator Action Importances Fussell-Event Nanu Vesely Dw4een O

OADS 9.92E-02 INITIA'IE ADS OP-VENT-CNTNMNT 3.88E-02 VENTCONTAINMENT ODPS 3.05E-02 DEPRESSURIZE USING ONLY BYPASS VALVES OFWLC-A 2.04E-02 FW CNTRL TO LOWER PWR < BYPASS CAPACITY (AMS)

OADS-A 1.83E-02 O ADS AND RESTARTPUMPS GIVEN OFWLC A FAILS (A7wS) i ORPVLC-A  !

1.61E-02 '

OP-SBLC-A RESTORE RPV LEVEL TO MIX BORON (ATWS) 1.58E-02 INITIATE SBLC(ATWS)

ODFP I 1.37E-02 LINE START AND ALIGN FIRE PROTECTION SYSTEM TO FW OSW 1.20E-02 O OADS-B SECURE SW PUMPS FROM THE CN"IRL ROOM 1.08E-02 (A1WS) ADS AND RESTART PUMPS GIVEN FW UNAVAILABLE OPTL-A 7.06E-03 FTL LPCS, HPCS, LPCI PMPS (ATWS)

OP-STRT-MDFP-CE 6.29E-03 ORHR 1 RIP BOTH TDRFPS OR M ANUALLY START MDFWP 4.96E-03 INITIATE SCS, SPC OR CSS MODE (LWR / PARRY / ERIN)

O s

VH. Accident Sequence Analysis in Figure 2, the Core Damage Frequency was displayed as a pie chart according to the contributions from '

.O the various initiating events. In order to be more useful for plant applications, the results can be presented ,

according to contributions to CDF by accident sequence. The dominant accident sequences for LSCS are represented in Figure 4 below. j 4

The distinction between initiating event and accident sequence depends on how the accident progresses, j For example, a LOOP initiating event could result in a station blackout event if the EDGs fail, or, if the

.O EDGs are successful, it could result in a transient event with other postulated failures. Among these failures are failure to scram, which would be categorized as an ATWS event, or successful scram, but failure of an SRV to reclose, which would be categorized as an IORV due to the accident behavior. The following discussion describes the details of the important accident sequences in the LSCS PRA.

Station Blackout (17% of CDF) i

.O Even though the functional requirements for a LOOP are similar to those for other transients, loss of off-site power can lead to unit blackout (UBO, total loss of AC power within an individual unit) or to station blackout (SBO, no AC power available to either unit). A UBO/SBO is a particularly important event because station blackout conditions mean that many normally used safety systems are unavailable.

]

O less of off-site power can be caused either by a complete grid loss or switchyard faults which isolate duses from the grid. Both of these events are included within the definition of the event, which is LSCS-22 0

. - - ... - - - - - ~ ~~ . . .- - . . .

designated as a LOSP or DLOSP in the PRA. A review ofindustry experience led to the following conclusions:

A switchyard fault is more likely than grid loss and more often results los af power to a single unit (LOSP), rather than a station (DLOSP). These events can usually be recovered within one half hour, a

less of power to the station (DLOSP) because of a transmission grid failure is less likely than a switchyard failure, but, frequently requires more time to restore.

A LOSP can result in an immediate loss of power to all station AC buses, except 120 VAC instrumentation buses which are fed from the batteries through the inverters, and result in MSIV closure, initiation of a reactor scram, cycling of the SRVs as the primary system pressure increases, and coast-down of the recirculation pumps.

I l

'Ibe ability of the plant to successfully respond to a LOSP event depends upon how widespread the loss of power actually is. For a station DLOSP, at least one emergency diesel generator must start and the emergency 4KV bus unit cross-tie must be hrplemented to maintain power to both units' battery chargers to provide DC power to keep the SRVs opmable on each unit, to keep an RHR pump operable on each  ;

unit, and to keep an RHRSW system pump operable for each unit. The availability of this minimum set of equipment maintains the low-pressure injection and decay heat removal capabilities in both units Transients at High Pressure (77% of CDF) l i

Transient initiated sequences with core damage at high reactor vessel pressure involve the loss of high  !

pressure injection and failure to depressurize. HPCS, RCIC, and the SRVs depend on DC power to function. Common cause battery failures either due to component faults or due to battery depletion can  !

disable all three DC power divisions and thus disable HPCS, RCIC and the SRVs so that the reactor remains at high pressure without any injection. Other types of failures include independent failures of HPCS and RCIC (e.g. failure to start, tagged out of service for maintenance), coupled with an operator failure to successfully depressurize. With decay heat levels still fairly high, steam is being discharged into the suppression pool, reducing vessel water level and after about one hour, ausing the core to be uncovered and fuel damage will ensue unless recovery actions can be taken.

The following sequences are included in this category: T104; GTR03,06,09,10, and 11; LOOP 03,07, 12,15,16,17, and 18.

Transients with Loss of Decay Heat Removal (62% of CDF)

Transient initiated sequences which result in the loss of decay heat removal involve a transient initiating event, such as closure of the MSIVs, successful scram, successful injection of cooling water to the core; and loss of the following long term decay heat removal options:

1, Failure of the Residual Heat Removal (RHR) system (or failure of the operator to initiate RHR) in the shutdown cooling, suppression pool cooling, and containment spray modes.

2.

Losa of the condenser a heat sink so that the Condensate /Feedwater pumps cannot supply core cooling water.

3. Inability to vent the containment to remove decay heat.

The following sequences are included in this category: GTR03 and 11;IORV03 and 10; and LOOP 03, 16,17, and 18.

LOCA's (0.7% of CDF)

LSCS-23 1

s

. c m

)

ne small LOCA (SLOCA) initiating event category represents all breaks inside the drywell which are 2

less than 5.0E-3 ft* for liquids and less than 0.1 ft for steam. However, it was assumed the break

)-

discharge would always be large enough to pressurize the drywell to 2 psig and initiate a reactor scram. A small break would not necessarily result in low reactor water level. Breaks which are too small to pressurize the containment would be detected by the drywell floor drain system, and cause a manual reactor shutdown to be initiated. No specific break location was assumed during the development of the SLOCA event tree.

)

An SLOCA is expected to increase drywell pressure by 2 psig and initiate a reactor trip. The HPCS system will be actuated by high drywell pressure. Depending upon the rate of decrease in feedwater flow and the speed at which the HPCS system flow inacases, the reactor vessel water level may, or may not, drop to Low level 2. If HPCS does not start successfully, reactor vessel level will decrease to low level 2 and initiate a start of the RCIC system. Both HPCS and RCIC have sufficient capability to maintain adequate coolant make-up to the primary system for this range of break sizes.

Because the small break is relatively small and incapable of removing large amounts of energy from the primary system, the pressure will remain high enough to continue to challenge the SRVS, which will cycle between open and closed. He combined energy from the break and from the SRVS will be transferred to the suppression pool which will then heat-up unless containment cooling is successfully implemented.

)

The medium LOCA (MLOCA) initiating event category includes breaks inside the drywell in the ranges of:

5.0E-3 to 0.3 ft2 forliquid 0.1 to 0.3 ft2 for steam No specific break locations were assumed during event tree development.

Following the occurrence of a medium LOCA, the following core protection functions are critical:

a reactormust be made subcritical

+

reactor coolant inventory must be replenished and maintained.

)

For MLOCA, operation of both high and low-pressure systems is required. The energy removed through the break will maintain an adequate level of reactor energy removal. This function is passive and will assure core protection so long as adequate vessel inventory is maintained.

All LOCA' sequences are included in this category.

) Anticipated Transients Without Scram (8% of CDF)

When a transient occurs and the reactor fails to scram, the event is known as an ATWS. To prevent serious core damage from occurring in a relatively short period of time, the operating staff must:

Initiate negative reactivity insertion with SBLC.

+

Reduce core power by lowering the vessel water level.

Limit the effects of the ATWS event by maintaining primary system injection rates which can remove adequate amounts energy from the core.

)

• Maintain, or establish, effective overpressure protection for the primary system and containment conditions.

LSCS-24

)

When a transient is followed by RPS/ARI failure, several other systems are normally available to provide the alternate success paths for the subcriticality function. These systems are:

)

• Manual scram Actuation of SLC Manual insertion of individual control rods.

To successfully limit the effects of an ATWS, an equilibrium between coolant injection rates and power ,

) level is required. The equilibrium power level is the one where injection capacity is sufficient to maintain  !

acceptable core temperatures yet not lead to excessive heat-up rates in the suppression pool.

For isolation transients, in which the MSIVs close, recirculation pump trip (RPT) is necessary to decrease i

power to the level which can be matched by non-balance of plant systems. If the MSIVs remain open, the feedwater and turbine bypass systems will remain available as sources ofinjection and core energy removal.

For this reason, the energy discharged to the suppression pool will be lower than that for an isolated

) ATWS. However, to limit suppression pool heatup so that short term containment protection is not j

required, successful initiation of RPT and SLC is still required.

All ATWS sequences are included in this category.

)

l l

)

1

)

)

)

)

LSCS-25

)

O O O O ~4 U U U U #

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Figure 4 -

2s.os Contribution of Accident Sequence Types to Core Damage Risk e

~

15.0% -

10.0% -- -

j t

sus -- - -

GTR11 GTR03

--111mu....I LOOP 14 LOOP 17 LOOP 16 LOOP 07 T104 seguence Name LSCS-26 GTR06 DRV06 LOOP 18 ATW12 ATWO3 RB-FLD Otw

A

~O VHL Applications

O sy applying the knowledge and insights gained from the LSCS PRA to the various activities supporting plant operation, Comed may be able to realize cost savings by redirecting regulatory attention on margit al safety issues, prioritizing work, and making resource expenditure decisions within a common framework of overall plant safety.

A criticism of the use of PRA in decision making is the presence of uncertainties in the model. There are 0

two important poims relevant to this criticism. First, while uncertainties may Mde the exact meaning of the absolute CDF calculated, the relative risks calculated for different accident equences, or for different plant systems and components, represent the true worth of the PRA, and these are less impacted by the existing uncertainties. Secondly, the alternative to the use of PRA is to base decisions on each individual's assessment of the situation, which can vary considerably depending upon the person's background and biases. PRA is a tool for prioritization and relative worth comparisons. It provides a logical structural

O basis for decisions, and provides conunon ground for discussions relevant to piant safety.

It is important to note that PRA analysis must be used in conjunction with other methods to assure plant safety. If a design basis condition is not being met, the necessary actions must be taken to bring the plant back into the proper design bounds. Even if a PRA analysis concludes that the increase in core damage

,O risk due to a particular design basis problem is negligible, the problem must still be fixed. The PRA analysis can provide an insight on how critical the problem is and what priority it should receive, but a PRA analysis by itself does not provide sufficientjustification to allow a design basis problem to remain unfixed.

He most important lesson teamed from the creation of the LSCS PRA is what is important to safety and what, in a relative sense, is not. This applies to systems, components, initiating events and operator

-O actions. A nuclear power plant is a complex system composed of many subsystems with many inter-dependent relationships, including the human interfaces. The PRA model allows us to group these relationships together and quantify their effects on a relative basis.

The LSCS plant staff should be familiar with the PRA results and apply the information to its full advantage. The results of the PRA should be used to prioritize the allocation of resources to maximize the O impact on plant safety and system reliability. The identification of the important accident sequences and operator actions should be used as an input to operator training programs.

In the licensing area, the LSCS PRA can be used to evaluate the risk significance of regulatory concerns, and limit or eliminate proposed requirements of plant-initiated activities which provide no appreciable improvement in plant safety. The PRA can be used for plant-specific cost-benefit analyses to evaluate O generic requirements which may not provide any real benefit to LSCS.  !

I ne tools used to build the PRA models can be useful in other applications, such as evaluating non-safety systems which impact plant performance in order to focus resources on those components which are most likely to cause an upset condition.

l O As PRA becomes a more integral part of routine plant operations, it will be necessary to better integrate data collection requirements needed to maintain the model up-to-date. Performance trending of major safety-related equipment is required to evaluate the plant-specific failure probability of these items. This data collection should become part of other, ongoing efforts to me:9or and trend major equipment, rather than a separate, manpower intensive function of the risk ass::ssment groop.

-O in view of the NRC's emphasis on the Severe Accident Policy Statement programs such as the Individual Plant Examination they might expect to see the use of PRA by licensees in many areas of plant operation.

The LSCS PRA is a valuable tool for licensing, engineering, maintenance, training and operations LSCS-27 iO

~. __ . ._ . _, ._ _ __. __

activities, and should be used to its full extent. It is hoped that this document will help non-PRA personn to understand and appreciate this value, and better see how PRA can be applied to their areas of responsibilities.

To help illustrate the various uses of the PRA, some past applications are described below.

Outage Risk V--- nt .

4 System fault trees similar to those used in the PRA have been incorporated into a software tool named l Outage Risk Assessment Management (ORAM). ORAM has been developed at LSCS to assist with ou) l planning and execution. De fault tree input will allow plant personnel to examine proposed outage

i. schedules to determine if the requirements of station risk management procedures are satisfied down to the component level. The benefit of the PRA and ORAM for outage planning should result in higher j

confidence levels of outage planning and conseq1ently shorter outages.

l Although the PRA models power operations, application of reliability techniques can also be applied to '

shutdown conditions.

l 1

l On line Maintenance l

Moving maintenance from outages to power operation is an important initiative to reduce outage length.

The PRA is an excellent tool to determine if voluntary on-line maintenance is acceptable from a risk perspective. Out of service times are modeled in the PRA for major plant systems and can be adjusted to check the impact on the CDP. Information about the importance of systems, given a system is taken out of service, is used to manage the overall risk.

Ongoing and Future Applications

! Maintenance Rule l l The results of the PRA are being used to help establish the basis for including system and components into  !

the Maintenance Rule program, and in developing the required performance criteria and goals against which system and component performance will be monitored.

i

! Severe Accident Management The Severe Accident Management program will require development and implementation of severe accident (beyond corp melt) guidehnes. Much of this work will be based on PRA results and insights. It has been proposed that the PRA be used to screen severe accident guidelines based on their plant applicability and importance and to assist with subsequent training prioritization.

Graded QA i

The graded QA program will re-examine the plant Q-list and base in part the pedigree of plant components

' on their relative contribution to the overall core damage rick. EPRI estimates saving based on the Grand Gulf plant to be as much as $10 million dollars per year for the life of the plant.

Risk Based Regulation

' As the NRC and utilities become more familiar and comfortable with PRA, it is likely that the application of PRA techniques will increase in many facets of plant operation. Ongoing initiatives such as reliability-centered maintenance and risk-based regulation strategies will become more common.

LSCS-28 c

D in addition to programs which may arise as regulatory requirements, Comed could use the PRA as a means to reduce operating costs. Some examples which may prove viable include prioritization of preventive maintenance and testing activities (such as the MOV testing program), and surveillance test interval and D

allowed out of service time (LCO) relaxation. Other initiatives which may help improve plant safety include using the PRA to prioritize operator training programs, emergency drill scenarios, and developin analyses to evaluate shutdown risk and apply the results to outage planning.

IL Insights insights are those observations regarding station configuration or practices suggested by the PRA which may affect the risk profile of the plant. Insights can suggest changes to enhance the capability of the plant and its operators to respond to an initiating event to either prevent core damage or to mitigate the consequences of core damage. Allinsights that are developed during the PRA development will be evaluated for significance. The beneficial insights will be submitted to the plant for disposition.

The generic procedure enhancements that were identified during the Dresden and Quad Cities IPE analys are also applicable to the LaSalle County Station and have been forwarded to the BWR Owners Group (BWROG) and to LaSalle County Station for their consideration.

[J Containment venting is an essential EOP step needed to maintain availability of ADS under emergency conditions. The Instrument (IA)and Service Air (SA) systems are required to ensure availability of the containment venting function. Therefore, the loss ofIA/SA initiating event is the top contributor to core damage. This important insight should be addressed.

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Appendix C - Table 1 Top 100 Core Damage Cutsets

~

Total CDF Frequency: 1.0E-05/yr l Seq. C: p Percent of  !

No. Name CDF Total CDF Event Prob. Event Name Accident-Sequence Event F C 1. '

3 1 LOOP 18 2.30E-07 2.31 % 1.60E-02 %DLOSP i DUAL LOSS OF OFFSITE POWER lE 7.63E-02 DG2A-FAULTS DG2A PLANT SPECIFIC FAULTS 7.63E-02 DGO-FAULTS DGO PLANT SPECIFIC FAULTS (PSD) 2.47E-03 ROP 24 failure to recover OSP within 24 hrs ,

2 LOOP 17 1.72E-07 1.73 % 1.60E-02 %DLOSP DUAL LOSS OF OFFSITE POWER lE [

4.33E-02 2E22S001-FAULTS  ;

7.63E-02 DG2A-FAULTS DG2B PLANT SPECIFIC FAULTS (PSD) t DG2A PLANT SPECIFIC FAULTS

' 7.63E-02 DGO-FAULTS 4.27E-02 ROP 3 DGO PLANT SPECIFIC FAULTS (PSD) 3 ATWO3 1.65E-07 1.65 % failure to recover OSP within 3 HRS ( NO LOAD SHED)  ;

2.40E+00 %T1-IE TURBINE TRIPWITH BYPASS lE 1.00E+00 ATWS ATWS FLAG TO IDENTIFY ATWS CUTSETS }

5.20E-02 OADS-A j 4.40E-02 OFWLC-A OP ACT: ADS AND RESTART PUMPS GIVEN OFWLC-A FAILS (ATWS) 3.00E-05 RPS-ARI-F OP ACT: FW CNTRL TO LOWER PWR < BYPASS CAPACITY (ATWS) t 4 GTR03 1.52E-07 1.52 %

RPS and ARI FAILURE ( RMIEP, NMPC, WNP-2) 5.30E-02 %T11-lE 6

i- LOSS OF INSTRUMENT AIR IE OR LOSP AT UNIT 1 1.24E-04 LPCI-CM i 7.00E-02 RHR-RECOVERY COMMON MODE FAILURE OF ALL 3 LPCI PUMPS (BETA = .05) i 3.30E-01 SURVIVABILITY FAILURE TO RECOVER 1-OF-2 RHR TRAINS WITHIN 33 Hrs (ERIN) {

i 5 LOOP 17 1.05E-07 1.05 % INJECTION FAILS TO SURVIVE AFTER CONTAINMENT FAILS (ERIN)!

1.60E-02 %DLOSP DUAL LOSS OF OFFSITE POWER lE  !

!- 1.54E-04 DGS-FAIL-CM DGs DIV 1,2 common mode failure (DG2A FAIL *(BETA =.012))

4.27E-02 ROP 3  ;

6 RB-FLD e.68E-08 0.97% failure to recover OSP within 3 HRS ( NO LOAD SHED) '

2.00E-04 %FS FLOOD lE'S GROUND OR MAIN RB FLOOR (x capacity factor.7 2.20E-02 ODFP i 2.20E-02 OSW OP ACT: START AND ALIGN FIRE PROTECTION SYSTEM TO FW LINE i l 7 ATWO8 9.36E-00 0.94 % OP ACT: SECURE SW PUMPS FROM THE CNTRL ROOM

2.40E+00 %T1-lE TURBINE TRIP WITH BYPASS lE l

1.00E+00 ATWS  !

l ATWS FLAG TO IDENTIFY ATWS CUTSETS  !

i 1.30E-03 OP-SBLC-A 3.00E-05 RPS-ARI-F OP ACT: INITIATE SBLC(ATWS) r 8 ATW12 7.78E-08 0.78 % RPS and ARI FAILURE ( RMIEP. NMPC, WNP-2)  !

8.10E-01 %T2T4-lE 1.00E+00 ATWS TURBlNE TRIP WITH CONDENSER UNAVAILABLE OR LOSS OF VACUUM

' ATWS FLAG TO IDENTIFY ATWS CUTSETS '

3.20E-03 ORPVLC-A 3.00E-05 RPS-ARI-F OP ACT: RESTORE RPV LEVEL TO MIX BORON (ATWS) i 9 LOOP 14 6.15E-08 0.62 % RPS and ARI FAILURE ( RMlEP, NMPC, WNP-2) 1.60E-02 %DLOSP DUAL LOSS OF OFFSITE POWERIE 4.33E-02 2E22S001-FAULTS 7.63E-02 DGO-FAULTS DG23 PLANT SPECIFIC FAULTS (PSD)

DG0 PLANT SPECIFIC FAULTS (PSD) 1.53E-02 RCIC001X-TDP-SS TURalNE-DRIVEN PUMP RCIC001 SS FAULTS 10 7.63E-02. DG2A-FAULTS DG"_A PLANT SPECIFIC FAULTS ATW12 5.59E-08 0.56 %

8.10E-01 %T2T4-lE i 1.00E+00 ATWS TURBINE TRIP WITH CONDENSER UNAVAILABLE OR LOSS OF VACUUM ATWS FLAG TO IDENTIFY ATWS CUTSETS 2.30E-03 OADS-B 3.00E-05 RPS-ARI-F OP ACT: ADS AND RESTART PUMPS GIVEN FW UNAVAILABLE (AT

• RPS and ARI FAILURE ( RMIEP. NMPC, WNP-2) l C-1 '

t f

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Appendix C - Tcble 1 Top 100 Core Damage Cutsets Seq. Sequence Total CDF Frequency: 1.0E-05/yr Percent of No. Name CDF Total CDF Event Prob. Event Name Accident-Sequence Event Descrir"r.

11 LOOP 07 4.90E-08 0.49% 5.30E-02 %LOSP LOSS OF OFFSITE POWER INIT EVENT 4.33E-02 2E22S001-FAULTS DG2B PLANT SPECIFIC FAULTS (PSD) 1.53E-02 RCIC001X-TDP-SS TURBINE DRIVEN PUMP RCIC001 SS FAULTS 1.40E-03 OADS OP ACT: INITIATE ADS 12 GTR11 4.77E-08 0.48 % 5.30E-02 %T11-lE LOSS OF INSTRUMENT AIR IE OR LOSP AT UNIT 1 7.26E-03 2E22C002-FAULTS 1.24E-04 LPCI-CM 2E22C002 DG2B COOL WTR PUMP PLANT SPECIFIC FLT DATA (PSD) 13 LOOP 14 4.76E-08 0.48 % COMMON MODE FAILURE OF ALL 3 LPCI PUMPS (BETA = .05) 1.60E-02 %DLOSP DUAL LOSS OF OFFSITE POWER lE 4.33E-02 2E22S001-FAULTS DG2B PLANT SPECIFIC FAULTS (PSD) 7.63E-02 DGO-FAULTS DGO PLANT SPECIFIC FAULTS (PSD) 7.63E-02 DG2A-FAULTS DG2A PLANT SPECIFIC FAULTS 1.18E-02 RCIF063C-VOC MOTOR-OPERATED VALVE RCIF063C OC 14 GTR11 . 04E-08 0.47 % 5.30E-02 %T11-lE LOSS OF INSTRUMENT AIR IE OR LOSP AT UNIT 1 7.06E-03 2E22C001-PMS-SS 1.24E-04 LPCI-CM 2E22C001 HPCS PUMP PLANT SPECIFIC FAULT DATA (GEN) 15 ATW12 4.51E-08 0.45% 4.70E-01 COMMON MODE FAILURE OF ALL 3 LPCI PUMPS (BETA = .05)

%MSIV MSIV CLOSURE lE(includeg loss of 100 psi pneumatic IE) 1.00E+00 ATWS ATWS FLAG TO IDENTIFY ATWS CUTSETS 3.20E-03 ORPVLC-A 3.00E-05 RPS-ARl-F OP ACT: RESTORE RPV LEVEL TO MIX BORON (ATWS) 16 GTR03 4.41E-08 RPS and ARI FAILURE ( RMIEP, NMPC, WNP-2) 0.44 % 5.30E-02 %T11-!E LOSS OF INSTRUMENT AIR IE OR LOSP AT UNIT 1 3.60E-05 CS-COOL-FMP-CM COMMON MODE CS COOL WTR PMPS 7.00E-02 MHR-RECOVERY.

3.30E-01 SURVIVABILITY FAILURE TO RECOVER 1-OF-2 RHR TRAINS WITHIN 33 Hrs (ERIN) 17 ATWO7 4.18E-08 0.42 % INJECTION FAILS TO SURVIVE AFTER CONTAINMENT FAILS (ERIN) 2.40E+00 %T1-lE TURBINE TRIP WITH BYPASS IE 1.00E+00 ATWS ATWS FLAG TO IDENTIFY ATWS CUTSETS 5.80E-04 OPTL-A OP ACT: PTL LPCS, HPCS, LPCI PMPS (ATWS) 3.00E-05 RPS-ARI-F RPS and ARI FAILURE ( RMIEP, NMPC, WNP-2) 18 IORV06 4.11E-08 0.41 % 5.30E-02 %T7-lE IORV IE 7.26E-03 2E22C002-FAULTS 1.98E-02 2FWOO5-PATH-FLT 2E22C002 DG2B COOL WTR PUMP PLANT SPECIFIC FLT DATA (PSD) 2FW005 MDRFP REG VALVE PATH FAULTS 19 5.39E-03 LCSC001 A-PMS-SS MOTOR-DRIVEN PUMP LCSC001 A SS FAULTS IORV06 4.01E-08 0.40% 5.30E-02 %T7-lE lORV IE 7.26E-03 2E22C002-FAULTS 1.98E-02 2FWOOS-PATH-FLT 2E22C002 DG2B COOL WI R PUMP PLANT SPECIFIC FLT DATA (PSD) 2FW005 MDRFP REG VALVE PATH FAULTS 20 5.26E-03 CODG01P-FAULTS MOTOR-DRIVEN PUMP CODG01P SS FAULTS GTR11 3.97E-08 0.40 % 5.30E-02 %T11-lE LOSS OF INSTRUMENT AIR lE OR LOSP AT UNIT 1 6.04E-03 HP-MOV-FAULTS HPCS MOV VALVES FAULTS 1.24E-04 LPCI-CM COMMON MODE FAILUPE OF ALL 3 LPCI PUMPS (BETA = .05)

C-2

7 i i

' Appendix C -Table 1 i

. Top 100 Core Damage Cutsets - '

Total CDF Frequency: 1.0E-05/yr

, No. Name CDF Total CDF Event Prob. Event Name 21 GTR03 3.86E-08 0.39% Accident-N-z - Event E W^

5.30E-02 %T11-lE LOSS OF INSTRUMENT AIR lE OR LOSP AT UNIT 1  ;

5.61E-03 2E12C0028-FLT 5.61 E-03 2E12C002A-FLT 2E12C0028 RHR TRAIN B MOTORCRIVEN PUMP FAULTS (PSD) ,

7.00E-02 RHR-RECOVERY 2E12C002A RHR TRAIN A MOTORDRIVEN PUMP FAULTS (PSD) 3.30E-01 SURVIVABILITY FAILURE TO RECOVER 1-OF-2 RHR TRAINS WITHIN 33 Hrs (ERIN) t 22 LOOP 17 3.85E-08 0.39% INJECTION FAILS TO SURVIVE AFTER CONTAINMENT FAILS (ERIN) 1.60E-02 %DLOSP DUAL LOSS OF OFFSITE POWER IE '  ;

i 9.69E-03 DG28-AUX-SYS HPCS DIESEL AUXILIARY SYTEMS FAILURE  !

7.63E-02 DG2A-FAULTS DG2A PLANT SPECIFIC FAULTS

' 7.63E-02 DGO-FAULTS t DGO PLANT SPECIFIC FAULTS (PSD) 4.27E-02 ROP 3 l 23 LOOP 07 ' 3.80E-08 0.38 % failure to recover OSP within 3 HRS ( NO LOAD SHED)

5.30E-02 %LOSP LOSS OF OFFSITE POWER INIT EVENT 4.33E-02 2E22S001-FAULTS DG2B PLANT SPECIFIC FAULTS (PSD) 1.18E-02 RCIF063C-VOC MOTOR-OPERATED VALVE RCIF063C OC .(

1.40E-03 OADS OP ACT: INITIATE ADS i 24 LOOP 14 3.76E-08 0.38 %

1.60E-02 %DLOSP DUAL LOSS OF OFFSITE POWER lE

• 1.53E-02 RCIC001X-TDP-SS TURBNEORIVEN PUMP RCIC001 SS FAULTS 25 1.54E-04 DGS-FAIL-CM DGs DIV 1,2 common mode failure (DG2A FAIL *(BETA =.012))

GTR03 3.61 E-08 0.36 % 5.30E-02 %T11-iE LOSS OF INSTRUMENT AIR IE OR LOSP AT UNIT 1  :

5.26E-03 2DG01P-FAULTS 5.61E-03 2E12C002A-FLT DG2A COOL WTR PUMP 2DG01P PLANT SPECIFIC FAULTS (PSD) l 7.00E-02 RHR-RECOVERY 2E12C002A RHR TRAIN A MOTOR-DRIVEN PUMP FAULTS (PSD)  ;

l

' 3.30E-01 SURVIVABILITY . FAILURE TO RECOVER 1-OF-2 RHR TRAINS WITHIN 33 Hrs (ERIN) 26 GTR03 3.61 E-08 0.36 % INJECTION FAILS TO SURVIVE AFTER CONTAINMENT FAILS (ERIN) 5.30E-02 %T11-lE LOSS OF INSTRUMENT AIR IE OR LOSP AT UNIT 1 5.26E-03 CODG01P-FAULTS MOTOR-DRIVEN PUMP CODG01P SS FAULTS l 5.61E-03 2E12C002B-FLT

' 7.00E RHR-RECOVERY 2E12C0028 RHR TRAIN B MOTORCRIVEN PUMP FAULTS (PSD)  !

3.30E-01 SURVIVABILITY ALLURE TO RECOVER 1-OF-2 RHR TRAINS WITHIN 33 Hrs (ERIN)  :

27 GTR03 3.41 E-08 0.34 % INJECTION FAILS TO SURVIVE AFTER CONTAINMENT FAILS (ERIN) 2.63E-04 %T101-lE 5.61 E-03 2E12C0028-FLT LOSS OF 4160V AC BUS 241Y IE(OUANT SWGR241YA)  !

7.00E-02 ' RHR-RECOVERY 2E12C0028 RHR TRAIN B MOTORORIVEN PUMP FAULTS (PSD) 3.30E-01 SURVIVABILITY ALLURE TO RECOVER 1-OF-2 RHR TRAINS WITHIN 33 Hrs (ERIN) 1 28 GTR03 3.41 E-08 0.34 % INJECTION FAILS TO SURVIVE AFTER CONTAINMENT FAILS (ERIN) '

2.63E-04 %T102-lE 5.61E-03 2E12C002A-FLT LOSS OF 4160V AC BUS 242Y IE(OUANT SWGR242YA) i 7.00E-02 RHR-RECOVERY 2E12C002A RHR TRAIN A MOTORDRIVEN PUMP FAULTS (PSD) {

3.30E-01 SURVIVABILITY ALLURE TO RECOVER 1-OF-2 RHR TRAINS WITHIN 33 Hrs (ERIN) 29 GTR03 3.39E-08 0.34 % INJECTION FAILS TO SURVIVE AFTER CONTAINMENT FAILS (ERIN) 5.30E-02 %T11-lE

! LOSS OF INSTRUMENT AIR IE OR LOSP AT UNIT 1 i

5.26E-03 CODG01P-FAULTS MOTORORIVEN PUMP CODG01P SS FAULTS 5.26E-03 2DG01P-FAULTS  :

j

' 7.00E-02 RHR-RECOVERY DG2A COOL WTR PUMP 2DG01P PLANT SPECIFIC FAULTS (PSD) 3.30E-01 SURVIVABILITY ALLURE TO RECOVER 1-OF-2 RHR TRAINS WITHIN 33 Hrs (ERIN)  ;

INJECTION FAILS TO SURVIVE AFTER CONTAINMENT FAILS (ERIN)

• i C-3 t

g _

g v W W

' ~ - ~

Appendix C - Tcble 1 Top 100 Core Damage Cutsets Seq. Sequence Total CDF Frequency: 1.0E-05/yr Percent of No. Name CDF Total CDF Event Prob. Event Name 30 ATW12 3.24E-08 Accident-Sequence Event Description 0.32 % 4.70E-01 %MSIV 1.00E+00 ATWS MSIV CLOSURE IE(including loss of 100 psi pneumatic IE) 2.30E-03 OADS-B ATWS FLAG TO IDENTIFY ATWS CUTSETS 31 GTR03 3.20E-08 3.00E-05 RPS-ARI-F OP ACT: ADS AND RESTART PUMPS GIVEN FW UNAVAILABLE (AT RPS and ARI FAILURE ( RMIEP NMPC, WNP-2) 0.32 % 2.63E-04 %T101-lE 5.26E-03 2DG01P-FAULTS LOSS OF 4160V AC BUS 241Y IE(OUANT SWGR241YA) 7.00E-02 RHR-RECOVERY DG2A COOL WTR PUMP 2DG01P PLANT SPECIFIC FAULTS (PSD) 32 .GTR03 3.20E-08 3.30E-01 SURVIVABILITY FAILURE TO RECOVER 1-OF-2 RHR TRAINS WITHIN 33 Hrs (ERIN) 0.32 % 2.63E-04 %T102-IE INJECTION FAILS TO SURVIVE AFTER CONTAINMENT FAILS (ERIN) 5.26E-03 CODG01P-FAULTS LOSS OF 4160V AC BUS 242Y IE(QUANT SWGR242YA) 7.00E-02 RHR-RECOVERY MOTOR-DRIVEN PUMP CODG01P SS FAULTS 33 IORV06 3.16E-08 3.30E-01 SURVIVABILITY FAILURE TO RECOVER 1-OF-2 RHR TRAINS WITHIN 33 Hrs (ERIN) 0.32 % 5.30E-02 %T7-lE INJECTION FAILS TO SURVIVE AFTER CONTAINMENT FAILS (ERIN lORV IE 7.26E-03 2E22C002-FAULTS 1.98E-02 2FWOO5-PATH-FLT 2E22C002 DG2B COOL WTR PUMP PLANT SPECIFIC FLT DATA (

2FWOO5 MDRFP REG VALVE PATH FAULTS 34 ATW15 4.15E-03 LPCS-LOGIC-FLT LPCS PUMP LOGIC FAULTS 3.16E-08 0.32 % 8.10E-01 %T2T4-lE 1.00E+00 ATWS TURB1NE TR:P WITH CONDENSER UNAVAILABLE OR LOSS OF VACUUM 1.30E-03 OP-SBLC-A ATWS FLAG TO IDENTIFY ATWS CUTSETS 3.00E-05 RPS-ARI-F OP ACT: INITIATE SBLC (ATWS) 35 IORV06 3.04E-08 0.30 % RPS and ARI FAILURE ( RMIEP. NMPC, WNP-2) 5.30E-02 %T7-lE IORV IE 7.26E-03 2E22C002-FAULTS 1.98E-02 2FWOOS-PATH-FLT 2E22C002 DG2B COOL WTR PUMP PLANT SPECIFIC FLT DATA (PS 2FWOO5 MORFP REG VALVE PATH FA'JLTS 36 LOOP 14 3.98E-03 LCSF005A-FLT 2.96E-08 0.30 % 1.60E-02 %DLOSP LCSF005A CB OR OTHER LOCAL FAILURES DUAL LOSS OF OFFSITE POWER IE 4.33E-02 2E22S001-FAULTS 7.63E-02 DGO-FAULTS DG2B PLANT SPECIFIC FAULTS (PSD) 7.63E-02 DG2A-FAULTS DGO PLANT SPECIFIC FAULTS (PSD)

DG2A PLANT SPECIFIC FAULTS 37 LOOP 14 7.34E-03 RCIF013C-FAULTS MOV RCIC F013 VALVE FAULTS 2.91E-08 0.29% 1.60E-02 %DLOSP DUAL LOSS OF OFFSITE POWER IE 1.18E-02 RCIF063C-VOC MOTOR-OPERATED VALVE RCIF063C OC 38 GTR03 1.54E-04 DGS-Fall-CM 2.91E-08 0.29% 5.30E-02 %T11-IE DGs DIV 1,2 common mode failure (DG2A FAIL *(BETA =.012))

5.61E-03 2E12C0028-FLT LOSS OF INSTRUMENT AIR IE OR LOSP AT UNIT 1 4.23E-03 NWVYO1CA-FMS-SS 2E12C002B RHR TRAIN B MOTOR-DRIVEN PUMP FAULTS (PSD) 7.00E-02 RHR-RECOVERY MOTOR-DRIVEN FAN NWVYO1CA SS FAULTS 3

39 GTR03 2.91 E-08 3.30E-01 SURVIVABILITY FAILURE TO RECOVER 1-OF-2 RHR TRAINS WITHIN 33 Hrs (ERIN) l 0.29% 5.30E-02 %T11-IE INJECTION FAILS TO SURVIVE AFTER CONTAINMENT FAILS (ERIN) 4.23E-03 SEVYO3CB-FMS-SS LOSS OF INSTRUMENT AIR lE OR LOSP AT UNIT 1 MOTOR-DRIVEN FAN SEVYO3CB SS FAULTS 5.61 E-03 2E12C002A-FLT 7.00E-02 RHR-RECOVERY 2E12C002A RHR TRAIN A MOTOR-DRIVEN PUMP FAULTS (PSD) 40 LOOP 18 2.90E-08 3.30E-01 SURVIVABILITY FAILURE TO RECOVER 1-OF-2 RHR TRAINS WITHIN 33 Hrs (ERIN) 0.29% 1.60E-02 %DLOSP INJECTION FAILS TO SURVIVE AFTER CONTAINMENT FAILS (ERIN)

DUAL LOSS OF OFFSITE POWER IE C-4

O O O O O O O O O O O i

Appendix C - Tchle 1 Top 100 Core Damage Cutsets Seq. Sequence Total CDF Frequency: 1.0E-05/yr Percent of No. Narne CDF Total CDF Event Prob. Event Name Accident-Sequence Event Description 9.62E-03 SY-VNF-HVDG2A 7.63E-02 DGO-FAULTS ROOM HVDG2A COOLING OR VENTILATION SYSTEM FAULTS DGO PLANT SPECIFIC FAULTS (PSD) '

2.47E-03 ROP 24 failure to recover OSP within 24 hrs 41 LOOP 17 2.89E-08 0.29% 1.60E-02 %DLOSP DUAL LOSS OF OFFSITE POWER IE 7.26E-03 2E22C002-FAULTS  ;

7.63E-02 DG2A-FAULTS 2E22C002 DG2B COOL WTR PUMP PLANT SPECIFIC FLT DATA (PS DG2A PLANT SPECIFIC FAULTS 7.63E-02 DGO-FAULTS 4.27E-02 ROP 3 DGO PLANT SPECIFIC FAULTS (PSD) 42 LOOP 17 2.81 E-08 0.28 % failure to recover OSP within 3 HRS ( NO LOAD SHED) 1.60E-02 %DLOSP DUAL LOSS OF OFFSITE POWER IE 7.06E-03 2E22C001-PMS-SS 7.63E-02 DG2A-FAULTS 2E22C001 HPCS PUMP PLANT SPECIFIC FAULT DATA (GEN)

DG2A PLANT SPECIFIC FAULTS 7.63E-02 DGO-FAULTS 4.27E-02 ROP 3 DGO PLANT SPECIFIC FAULTS (PSD) 43 GTR11 2.80E-08 0.28% failure to recover OSP within 3 HRS ( NO LOAD SHED) 5.30E-02 %T11-lE LOSS OF INSTRUMENT AIR lE OR LOSP AT UNIT 1 4.26E-03 SWVYO2AX-INHTR 1.24E-04 LPCI-CM INADEQUATE HEAT REMOVAL VIA AIR COOLING SWVYO2AX 44 LOOP 14 2.77E-08 0.28% COMMON MODE FAIL *JRE OF ALL 3 LPCI PUMPS (BETA = .05) 1.60E-02 %DLOSP DUAL LOSS OF OFFSITE POWER lE 4.33E-02 2E22S001-FAULTS 7.63E-02 DGO-FAULTS DG2B PLANT SPECIFIC FAULTS (PSD)

DGO PLANT SPECIFIC FAULTS (PSD) 6.85E-03 RCIF046C-FAULTS MOTOR-OPERATED VALVE fiCIF046C CC 45 7.63E-02 DG2A-FAULTS DG2A PLANT SPECIFIC FAULTS LOOP 14 2.75E-08 0.28 % 1.60E-02 %DLOSP DUAL LOSS OF OFFSITE POWER lE 4.33E-02 2E22S001-FAULTS 7.63E-02 DGO-FAULTS DG2B PLANT SPECIFIC FAULTS (PSD) 7.63E-02 DG2A-FAULTS DGO PLANT SPECIFIC FAULTS (PSD)

DG2A PLANT SPECIFIC FAULTS 6.81 E-03 RCIF045C-VCC MOTOR-OPERATED VALVE RCIF045C CC 46 GTR03 2.73E-08 0.27% 5.30E-02 %T11-lE LOSS OF INSTRUMENT AIR IE OR LOSP AT UNIT 1 5.26E-03 2DG01P-FAULTS 4.23E-03 NWVYO1CA-FMS-SS DG2A COOL WTR PUMP 2DG01P PLANT SPECIFIC FAULTS (PSD)

MOTOR-DRIVEN FAN NWVYO1CA SS FAULTS 7.00E-02 RHR-RECOVERY 3.30E-01 SURVIVABILITY FAILURE TO RECOVER 1-OF-2 RHR TRAINS WITHIN 33 Hrs (ERIN) 47 GTR03 2.73E-08 0.27% INJECTION FAILS TO SURVlVE AFTER CONTAINMENT FAILS (ERIN) 5.30E-02 %T11-lE LOSS OF INSTRUMENT AIR IE OR LOSP AT UNIT 1 5.26E-03 CODG01P-FAULTS MOTOR-DRIVEN PUMP CODG01P SS FAULTS 4.23E-03 SEVYO3CB-FMS-SS MOTOR-DRIVEN FAN SEVYO3C8 SS FAULTS 7.00E-02 RHR-RECOVERY 3.30E-01 SURVlVABILITY FAILURE TO RECOVER 1-OF-2 RHR TRAINS WITHIN 33 Hrs (ERIN) 48 GTR03 2.63E-08 0.26 % INJECTION FAILS TO SURVIVE AFTER CONTAINMENT FAILS (ERIN) 5.30E-02 %T11-lE  ;

LOSS OF INSTRUMENT AtR IE OR LOSP AT UNIT 1 3.82E-03 RHRSWB-HTX-ISO-V RHRSW B HTX ISOLATION VALVE ' AULTS 5.61 E-03 2E12C002A-FLT 7.00E-02 RHR-RECOVERY 2E12C002A RHR TRAIN A MOTOR-DRIVEN PUMP FAULTS (PSD) 3.30E-01 SURVIVABILITY FAILURE TO RECOVER 1-OF-2 RHR TRAINS WITHIN 33 Hrs (ERIN) 49 GTR03 2.63E-08 0.26 % INJECTION FAILS TO SURVIVE AFTER CONTAINMENT FAILS (ERIN) 5.30E-02 %T11-lE LOSS OF INSTRUMENT AIR lE OR LOSP AT UNIT 1 5.61 E-03 2E1200028-FLT 2E12C002B RHR TRAIN B MOTOR-DRIVEN PUMP FAULTS (PSD) c-5 t

_ -_y_ __ ___ __ __ _ _ _

g__ __

__V_

i 3

Appendix C - Table 1 I Top 100 Core Damage Cutsets i Smi. Segance Total CDF Frequency: 1.0E-05/yr Percent of No. Name CDF TotsiCDF Event Prob. Event Name Accident ~. quence Event r' __ - _ _

3.82E-03 RHRSWA-HTX-ISO-V RHRSW A HTS ISOLATION VALVE FAULTS 7.00E-02 RHR-RECOVERY .

3.30E-01 SURVIVABILITY FAILURE TO RECOVER 1-OF-2 RHR TRANS WITHW 33 Hrs (ERIN) 50 GTR03 2.63E-08 ' O.26 % INJECTION FAILS TO SURVIVE AFTER CONTAINMENT FAILS (ERI '

' 5.30E-02 %T11-lE

, LOSS OF INSTRUMENT AIR lE OR LOSP AT UNIT 1  ;

3.82E-03 RHRF48BB-VOO MOTOR-OPERATED VALVE RHRF48BB OO 5.61 E-03 2E12C002A-FLT i 7.00E-02 RHR-RECOVERY 2E12C002A RHR TRAIN A MOTOR-DRIVEN PUMP FAULTS (PSD) 3.30E-01 SURVIVABILITY FAILURE TO RECOVER 1-OF-2 RHR TRAINS WITHIN 33 Hrs (ERIN) 51 GTR03 2.63E-08 0.26 % INJECTION FAILS TO SURVIVE AFTER CONTAINMENT FAILS (ERIN 5.30E-02 %T11-lE LOSS OF INSTRUMENT AIR IE OR LOSP AT UNIT 1 3.82E-03 RHRF48AA-VOO MOTOR-OPERATED VALVE RHRF48AA OO 5.61E-03 2E12C0028-FLT 7.00E-02 RHR-RECOVERY 2E12C0028 RHR TRAIN B MOTOR-DRIVEN PUMP FAULTS (PSD) 3.30E-01 SURVIVABILITY FAILURE TO RECOVER 1-OF-2 RHR TRANS WITHN 33 Hrs (ERIN)

• 52 GTR03 2.57E-08 0.26 % INJECTION FAILS TO SURVIVE AFTER CONTAINMENT FAILS (ERI 2.63E-04 %T101-lE n

4.23E-03 SEVYO3CB-FMS-SS LOSS OF 4160V AC BUS 241Y lE(OUANT SWGR241YA) i MOTOR-DRIVEN FAN SEVYO3CB SS FAULTS 7.00E-02 RHR-RECOVERY i 3.30E-01 SURVIVABILITY FAILURE TO RECOVER 1-OF-2 RHR TRAINS WITHIN 33 Hrs (ERIN) 53 GTR03 2.57E-08 0.26 % INJECTION FAILS TO SURVIVE AFTER CONTAINMENT FAILS (ERI 2.63E-04 %T102-lE

' 4.23E-03 NWVYO1CA-FMS-SS LOSS OF 4160V AC BUS 242Y IE(OUANT SWGR242YA) '

MOTOR-DRIVEN FAN NWVYO1CA SS FAULTS 7.00E-02 RHR-RECOVERY

' 3.30E-01 SURVIVABILITY FAILURE TO RECOVER 1-OF-2 RHR TRAINS WITHIN 33 Hrs (ERIN) 54 GTR03 2.46E-08 0.25 % 5.30E-02 %T11-lE INJECTION FAILS TO SURVIVE AFTER CONTAINMENT FAILS (E LOSS OF INSTRUMENT AIR lE OR LOSP AT UNIT 1 5.26E-03 2DG01P-FAULTS 3.82E-03 RHRSWA-HTX-ISO-V DG2A COOL WTR PUMP 2DG01P PLANT SPECIFIC FAULTS (PSD RHRSW A HTS ISOLATION VALVE FAULTS 7.00E-02 RHR-RECOVERY 3.30E-01 SURVIVABILITY FAILURE TO RECOVER 1-OF-2 RHR TRAINS WITHIN 33 Hrs (ERN) '

55 GTR03 2.46E-08 0.25 % 5.30E-02 %T11-lE INJECTION FAILS TO SURVIVE AFTER CONTAINMENT FAILS (ERI LOSS OF INSTRUMENT AIR IE OR LOSP AT UNIT 1 i 5.26E-03 CODG01P-FAULTS MOTOR-DRIVEN PUMP CODG01P SS FAULTS 3.82E-03 RHRSWB-HTX-ISO-V RHRSW B HTX ISOLATION VALVE FAULTS 7.00E-02 RHR-RECOVERY ,

3.30E-01 SURVIVABILITY FAILURE TO RECOVER 1-OF 2 RHR TRAINS WITHIN 33 Hrs (ERIN) 56 GTR03 2.46E-08 0.25% 5.30E-02 %T11-lE INJECTION FAILS TO SUPVIVE AFTER CONTAINMENT FAILS (E LOSS OF INSTRUMENT AIR IE OR LOSP AT UNIT 1 5.26E-03 CODG01P-FAULTS MOTOR-DRIVEN PUMP CODG01P SS FAULTS i 3.82E-03 RHRF48BB-VOO MOTOR-OPERATED VALVE RHRF48BB OO 7.00E-02 RHR-RECOVERY 3.30E-01 SURVIVABILITY FAILURE TO RECOVER 1-OF-2 RHR TRANS WITHIN 33 Hrs (ERIN) 57 GTR03 2.46E-08 ' O.25 % 5.30E-02 %T11-lE INJECTION FAILS TO SURVIVE AFTER CONTAINMENT FAILS (ERI LOSS OF INSTRUMENT AIR 18 OR LOSP AT UNIT 1 3.82E-03 RHRF48AA-VOO MOTOR-OPERATED VALVF. RHRF4eM 00 5.26E-03 2DG01P-FAULTS 7.00E-02 RHR-RECOVERY DG2A COOL WTR PUMP 2 )G01 P PLANT SPECIFIC FAULTS (PSD) 3.30E-01 SURVIVABILITY FAILURE TO RECOVER 1-OF-2 RHR TRAINS WITHIN 33 Hrs (ERIN) 58 GTR03 2.42E-08 0.24 % 5.30E-02 %T11-lE INJECTION FAILS TO SURVIVE AFTER CONTAINMENT FAILS (ER t LOSS OF INSTRUMENT AIP IE OR LOSP AT UNIT 1 5.61E-03 2E12C0028-FLT i

C-6 2E12C0028 RHR TRAIN B MOTOR-DRIVEN PUMP FAULTS (PSD) t

O O' O -

O O O O O O O '

O Appendix C - Table 1 l Top 100 Core Damage Cutsets Seq. *=^ r.; Total CDF Frequency: 1.0E-05/yr Percent of No. Name CDF Total CDF Event Prob. Event Name AccMent *- ; .c Event E .',_~_ -

1 3.53E-03 CSCD300A-STR-PLG 2E12D300A STRAINER RHR SW TRAIN A PLUG

{ 7.00E-02 RHR-RECOVERY

3.30E-01 SURVIVABILITY FAILURE TO RECOVER 1-OF-2 RHR TRAfNS WITHW 33 Hrs (ERIN) 59 GTR03 2.42E-08 0.24 % 5.30E-02 %T11-lE ' INJECTION FAILS TO SURVIVE AFTER CONTAWMENT FAILS (ERN)

LOSS OF INSTRUMENT AIR lE OR LOSP AT UNIT 1 3.53E-03 CSCD3000-STR-PLG 2E12D3000 STRAINER RHR SW TRAW B PLUG 5.61E-03 2E12C002A-FLT 7.00E-02 RHR-RECOVERY 2E12C002A RHR TRAIN A MOTOR-DRIVEN PUMP FAULTS (PSD)

{

i 60 3.30E-01 SURVIVABILITY ' FAILURE TO RECOVER 1-OF-2 RHR TRAINS WITHW 33 Hrs (ERIN IORV06 2.41E-08 0.24 % INJECTION FAILS TO SURVIVE AFTER CONTAINMENT FAILS (ER 5.30E-02 %T7-IE . IORV IE 1.98E-02 2FWOOS-PATH-FLT 2FWOO5 MDRFP REG VALVE PATH FAULTS l 4.26E-03 SWVYO2AX-INHTR 5.39E-03 LCSC001A-PMS-SS INADEOUATE HEAT REMOVAL VIA AIR COOLNG SWVYO2AX

, 61 LOCP17 2.40E-08 0.24% MOTOR-DRIVEN PUMP LCSC001 A SS FAULTS 1.60E-02 %DLOSP DUAL LOSS OF OFFSITE POWER lE 7.63E-02 DG2A-FAULTS DG2A PLANT SPECIFIC FAULTS 6.04E-03 HP-MOV-FAULTS HPCS MOV VALVES FAULTS 7.63E-02 DGO-FAULTS 4.27E-02 ROP 3 DG0 PLANT SPECIFIC FAULTS (PSD) 62 MLOO9 2.40E-08 0.24 % failure to recover OSP within 3 HRS ( NO LOAD SHED) 8.00E-04 %MLOCA MEDIUM LOCA IE 1.00E+00 ATWS ATWS FLAG TO IDENTIFY ATWS CUTSETS 63 3.00E-05 RPS-ARl-F RPS and ARI FAILURE ( RMIEP, NMPC, WNP-2)

LOOP 07 2.36E-08 0.24 %

' 5.30E-02 %LOSP LOSS OF OFFSITE POWER INIT EVENT 4.33E-02 2E22S001-FAULTS -

7.34E-03 RCIF013C-FAULTS DG2B PLANT SPECIFIC FAULTS (PSD)

MOV RCIC F013 VALVE FAULTS 64 1.40E-03 OADS OP ACT: INITIATE ADS

' IORV06 2.35E-08 0.24 % 5.30E-02 %T7-IE lORVIE 1.98E-02 2FWOOS-PATH-FLT 2FW005 MDRFP REG VALVE PATH FAULTS 5.26E-03 CODG01P-FAULTS MOTOR-DRIVEN PUMP CODG01P SS FAULTS 65 GTR11 4.26E-03 SWVYO2AX-INHTR 2.33E-08 0.23% 5.30E-02 %T11-lE INADEQUATE HEAT REMOVAL VIA AIR COOLING SWVYO2AX 1

' LOSS OF INSTRUMENT AIR IE OR LOSP AT UNIT 1 3.55E-03 HPCS-TOTAL-UUM HPCS total unavailainlity due to mech and elec mamtenance 66 1.24E-04 LPCI-CM GTR03 2.32E-08 0.23% COMMON MODE FAILURE OF ALL 3 LPCI PUMPS (BETA = .05) 2.63E-04 %T102-lE 3.82E-03 RHRSWA-HTX-ISO-V LOSS OF 4160V AC BUS 242Y IE(OVANT SWGR242YA)

RHRSW A HTS ISOLATION VALVE FAULTS 7.00E-02 RHR-RECOVERY 67 3.30E-01 SURVIVABILITY FAILURE TO RECOVER 1-OF-2 RHR TRAINS WITHIN 33 Hrs (ERIN)

GTR03 2.32E-08 0.23 % INJECTION FAILS TO SURVIVE AFTER CONTAINMENT FAILS (ERIN) 2.63E-04 %T101-lE 3.82E-03 RHRSWB-HTX-ISO-V LOSS OF 4160V AC BUS 241Y lE(OUANT SWGR241YA)

RHRSW B HTX ISOLATION VALVE FAULTS 7.00E-02 RHR-RECOVERY 3.30E-01 SURVIVABILITY FAILURE TO RECOVER 1-OF-2 RHR TRAINS WITHIN 33 Hrs (ERIN) 68 GTR03 2.32E-08 0.23% 2.63E-04 %T101-lE INJECTION FAILS TO SURVIVE AFTER CONTAINMENT FAILS (ERfN) 3.82E-03 RHRF48BB-VOO ' LOSS OF 4160V AC BUS 241Y IE(OUANT SWGR241YA)

MOTOR-OPERATED VALVE RHRF48BB OO 7.00E-02 RHR-RECOVERY 3.30E-01 SURVlVABILITY FAILURE TO RECOVER 1-OF-2 RHR TRAINS WITHIN 33 Hrs (ERIN)

C-7 INJECTION FAILS TO SURVIVE AFTER CONTAINMENT FAILS (ERIN)

. _ _ - . . _ - - - _ _ _ _ - _ _ = _ - _ - _ _ - _ - _ _ _ _ _ _ _ _ - - . . _ - _ ..- -- .-_ - - . , _ . ~

O O O O O O O O O O O Appendix C - Ttble 1 Top 100 Core Damage Cutsets Seq. Sequence Total CDF Frequency: 1.0E-05/yr Percent of No. Name CDF Total CDF Event Prob. Event Name Accident-Sequence Event Description 69 GTR03 2.32E-08 0.23% 2.63E-04 %T102-lE 3.82E-03 RHRF48AA-VOO LOSS OF 4160V AC BUS 242Y IE(OUANT SWGR242YA)

MOTOR-OPERATED VALVE RHRF48AA OO 7.00E-02 RHR-RECOVERY 3.30E-01 SURVIVABILITY FAILURE TO RECOVER 1-OF-2 RHR TRAINS WITHIN 33 Hrs (ERIN) 70 RB-FLD 2.29E-08 0.23% INJECTION FAILS TO CURVIVE AFTER CONTAINMENT FAILS (ERIN) 2.00E-04 %FS 5.42E-02 FLOOD lE'S GROUND OR MAIN RB FLOOR (x capacity factor .7 INTR-JOCKY-P-LF INTERMEDIATE JOCKY PMP FAILURE 3.10E-01 DFPA DIESEL FIRE PUMP TRAIN A 3.10E-01 DFPB DIESEL FIRE PUMP TRAIN 8 2.20E-02 OSW 71 GTR03 2.27E-08 0.23% 5.30E-02 %T11-lE OP ACT: SECURE SW PUMPS FROM THE CNTRL ROOM LOSS OF INSTRUMENT AIR IE OR LOSP AT UNIT 1 5.26E-03 CODG01 P-FAULTS MOTOR-DRIVEN PUMP CODG01P SS FAULTS 3.53E-03 CSCD300B-STR-PLG 2E12D3008 STRAINER RHR SW TRAIN 8 PLUG 7.00E-02 RHR-RECOVERY 3.30E-01 SURVlVABILITY FAILURE TO RECOVER 1-OF-2 RHR TRAINS WITHIN 33 Hrs (ERIN) 72 GTR03 2.27E-08 0.23 % INJECTION FAILS TO SURVIVE AFTER CONTAINMENT FA!LS(ERIN) 5.30E-02 %T11-lE LOSS OF INSTRUMENT AIR IE OR LOSP AT UNIT 1 5.26E-03 2DG01P-FAULTS 3.53E-03 CSCD300A-STR-PLG DG2A COOL WTR PUMP 2DG01P PLANT SPECIFIC FAULTS (PSD) 2E12D300A STRAINER RHR SW TRAIN A PLUG 7.00E-02 RHR-RECOVERY 3.30E-01 SURVIVABILITY FAILURE TO RECOVER 1-OF-2 RHR TRAINS WITHIN 33 Hrs (ERIN) 73 LOOP 07 2.20E-08 0.22 % INJECTION FAILS TO SURVIVE AFTER CONTAINMENT FAILS (ERIN) 5.30E-02 %LOSP LOSS OF OFFSITE POWER INIT EVENT 4.33E-02 2E22S001-FAULTS DG2B PLANT SPECIFIC FAULTS (PSD) 6.85E-03 RCIF046C-FAULTS MOTOR-OPERATED VALVE RClF046C CC 1.40E-03 OADS OP ACT: INITIATE ADS 74 ATW14 2.20E-08 0.22 % 8.10E-01 %T2T4-lE 3.01 E-02 2C41C0018-PMP-F TURBINE TRIP WITH CONDENSER UNAVAILABLE OR LOSS OF VACUUM 2C41C001B SLC PUMP B LOCAL FAULTS 3.01 E-02 2C41C001 A-PMP-F 1.00E+00 ATWS 2C41C001 A SLC PUMP A LOCAL FAULTS (PSD)

ATWS FLAG TO IDENTIFY ATWS CUTSETS 3.00E-05 RPS-ARI-F RPS and ARI FAILURE ( RMIEP, NMPC, WNF-2) 75 GTR03 2.20E-08 0.22 % 2.63E-04 %T101-lE 3.62E-03 DW-HP-RHR-SGNB-F LOSS OF 4160V AC BUS 241Y IE(OUANT SWGR241YA) 7.00E-02 RHR-RECOVERY DW Hi-PRESS RHR TRAIN B SGNL Fall (OVANT:NOS-POP-RHR-T24A) 3.30E-01 SURVlVABILITY FAILURE TO RECOVER 1-OF-2 RHR TRAINS WITHIN 33 Hrs (ERIN) 76 GTR03 2.20E-08 0.22 % INJECTION FAILS TO SURVIVE AFTER CONTAINMENT FAILS (ERIN) 2.63E-04 %T102-iE 3.62E-03 DW-HP-RHR-SGNA-F LOSS OF 4160V AC BUS 242Y IE(OUANT SWGR242YA) 7.00E-02 RHR-RECOVERY DW Hi-PRESS RHR TRAIN A SGNL Fall (OUANT:NOS-POP-RHR-T24B) 3.30E-01 SURVIVABILITY FAILURE TO RECOVER 1-OF-2 RHR TRAINS WITHIN 33 Hrs (ERIN) 77 GTR03 2.20E-08 0.22 % INJECTION FAILS TO SURVIVE AFTER CONTAINMENT FAILS (ERIN) 5.30E-02 %T11-lE LOSS OF INSTRUMENT AIR IE OR LOSP AT UNIT 1 4.23E-03 SEVYO3CB-FMS-SS MOTOR-DRIVEN FAN SEVYO3CB SS FAULTS 4.23E-03 NWVYOICA-FMS-SS MOTOR-DRIVEN FAN NWVYO1CA SS FAULTS 7.00E-02 RHR-RECOVERY 3.30E-01 SURVIVABILITY FAILURE TO RECOVER 1-OF-2 RHR TRAINS WITHIN 33 Hrs (ERIN) 78 LOOP 07 2.19E-08 0.22 % INJECTION FAILS TO SURVIVE AFTER CONTAINMENT FAILS (ERIN) 5.30E-02 %LOSP LOSS OF OFFSITE POWER INIT EVENT 4.33E-02 2E22S001-FAULTS DG2B PLANT SPECIFIC FAULTS (PSD)

C-8

, .O O O O O O O O O O- O'  ;

i Appendix C - Tcble I Top 100 Core Damage Cutsets j

seg.  !+;m Total CDF Frequency: 1.0E-05/yr  !

Percent of No. Narne CDF Total CDF j Event Prob. - Event Name Accident-?: ra Event r" - f_^ -

j 6.81 E-03 RCIF045C-VCC MOTOR-OPERATED VALVE RCIF045C CC -  !

1.40E-03 OADS OP ACT: INITIATE ADS 79 LOOP 17 2.17E-08 0.22 % t 1.60E-02 %DLOSP DUAL LOSS OF OFFSITE POWER IE 4.33E-02 2E22S001-FAULTS l DG2B PLANT SPECIFIC FAULTS (PSD)  ;

9.62E-03 SY-VNF-HVDG2A 7.63E-02 DGO-FAULTS ROOM HVDG2A COOLING OR VENTILATION SYSTEM FAULTS  !

DGO PLANT SPECIFIC FAULTS (PSD) 4.27E-02 ROP 3 i

80 GTR03 215E-08 failure to recover OSP within 3 HRS ( NO LOAD SHED) .

0.22 % 5.30E-02 %T11-lE LOSS OF INSTRUMENT AIR IE OR LOSP AT UNIT 1

'}'

5.61E-03. 2E12C002A-FLT 3.13E-03 2E128001B-HTX-LF 2E12C002A RHR TRAIN A MOTOR-DRfVEN PUMP FAULTS (PSD) ,

7.00E-02 RHR-RECOVERY 2E128001B HX TRAIN B PLANT SPECIFIC FAULT DATA (PSD) l 3.30E-01 SURVIVABILITY FAILURE TO RECOVER 1-OF-2 RHR TRANS WITHW 33 Hrs (ERIN) 81 GTR03 2.15E-08 0.22 % INJECTION FAILS TO SURVIVE AFTER CONTAINMENT FAILS (ERN) 5.30E %T11-lE LOSS OF INSTRUMENT AIR IE OR LOSP AT UNIT 1 5.61 E-03 2E12C0028-FLT 3.13E-03 2E128001A-HTX-LF 2E12C0028 RHR TRAIN B MOTOR-DRIVEN PUMP FAULTS (PSD) 7.00E-02 RHR-RECOVERY 2E128001 A HX TRAIN A PLANT SPECIFIC FAULT DATA (PSD) 3.30E-01 SURVIVABILITY FAILURE TO RECOVER 1-OF-2 RHR TRANS WITHN 33 Hrs (ERW) 82

~

GTR03 2.14E-08 0.21 % 2.63E-04 %T101-lE INJECTION FAILS TO SURVIVE AFTER CONTANMENT FAILS (ERIN) 3.53E-03 CSCD300B-STR-PLG LOSS OF 4160V AC BUS 241Y lE(QUANT SWGR241YA) 2E12D3008 STRAINER RHR SW TRAIN B PLUG 7.00E-02 RHR-RECOVERY 3.30E-01 SURVIVABILITY FAILURE TO RECOVER 1-OF-2 RHR TRANS WITHIN 33 Hrs (ERIN) 83 GTR03 2.14E-08 0.21 % INJECTION FAILS TO SURVIVE AFTER CONTAWMENT FAILS (ERIN) 2.63E-04 %T102-lE 3.53E-03 CSCD300A-STR-PLG LOSS OF 4160V AC BUS 242Y lE(QUANT SWGR242YA) 2E12D300A STRAINER RHR SW TRAIN A PLUG 7.00E-02 RHR-RECOVERY 3.30E-01 SURVIVABILITY FAILURE TO RECOVER 1-OF-2 RHR TRAINS WITHIN 33 Hrs (ERIN) 84 GTR03 2.09E-08 0.21 % 8.10E-01 INJECTION FAILS TO SURVIVE AFTER CONTAINMENT FAILS (ERIN)

%T2T4-lE 1.24E-04 LPCI-CM TURBINE TRIP WITH CONDENSER UNAVAILABLE OR LOSS OF VACUUM 9.00E-03 OP-VENT-CNTNMNT COMMON MODE FAILURE OF ALL 3 LPCI PUMPS (BETA = .05) .

OP ACT: VENT CONTAINMENT 7.00E-02 RHR-RECOVERY 3.30E-01 . SURVIVABILITY FAILURE TO RECOVER 1-OF-2 RHR TRANS WITHIN 33 Hrs (ERIN) i 85 GTR03 2.02E-08 0.20 % INJECTION FAILS TO SURVIVE AFTER CONTAINMENT FAILS (ERIN) 5.30E-02 %T11-lE LOSS OF INSTRUMENT AIR IE OR LOSP AT UNIT 1 '

5.26E-03 CODG01P-FAULTS MOTOR-DRIVEN PUMP CODG01P SS FAULTS 3.13E-03 2E1290018-HTX-LF 7.00E-02 RHR-RECOVERY 2E128001B HX TRAIN B PLANT SPECIFIC FAULT DATA (PSD) 3.30E-01 SURVIVABILITY FAILURE TO RECOVER 1-OF-2 RHk TRAINS WITHIN 33 Hrs (ERIN) 86 GTR03 '

2.02E-08 0.20% 5.30E-02 %T11-lE INJECTION FAILS TO SURVIVE AFTER CONTAINMENT FAILS (ERIN)

LOSS OF INSTRUMENT AIR IE OR LOSP AT UNIT 1 5.26E-03 2DG01P-FAULTS 3.13E-03 2E12B001 A-HTX-LF DG2A COOL WTR PUMP 2DG01P PLANT SPECIFIC FAULTS (PSD) 7.00E-02 RHR-RECOVERY 2E12B001 A HX TRAIN A PLANT SPECIFIC FAULT DATA (PSD) 3.30E-01 SURVIVABILITY FAILURE TO RECOVER 1-OF-2 RHR TRAINS WITHIN 33 Hrs (ERIN)

I 87 GTR03 1.98E-08 0.20 % 5.30E-02 %T11-lE INJECTION FAILS TO SURVIVE AFTER CONTAINMENT FAILS (ERIN)

LOSS OF INSTRUMENT AIR IE OR LOSP AT UNIT 1 3.82E-03 RHRSWB-HTX-ISO-V RHRSW B HTX ISOLATION VALVE FAULTS 4.23E-03 NWVYO1CA-FMS-SS MOTOR-DRIVEN FAN NWVYO1CA SS FAULTS i

C-9

y- - m m u m m m _ _

Appendix C - Tchl21 Top 100 Core Damage Cutsets Seq. Sequence Percent of Total CDF Frequency: 1.0E-05/yr No. Name CDF Total CDF Event Prob. Event Name Accident': ;z Evens P 4 J^_..

7.00E-02 RHR-RECOVERY 88 GTR03 1.98E-08 3.30E-01 SURVIVABILITY FAILURE TO RECOVER 1-OF-2 RHR TRANS WITHIN 33 Hrs (ERIN) 0.20% 5.30E-02 %T11-IE INJECTION FAILS TO SURVIVE AFTER CONTAINMENT FAILS (ERW 4.23E-03 SEVYO3CB-FMS-SS LOSS OF INSTRUMENT AIR IE OR LOSP AT UNIT 1 MOTOR-DRIVEN FAN SEVYO3CB SS FAULTS 3.82E-03 RHRSWA-HTX-ISO-V RHRSW A HTS ISOLATION VALVE FAULTS 7.00E-02 RHR-RECOVERY 89 GTR03 1.98E-08 3.30E-01 SURVIVABILITY FAILURE TO RECOVER 1-OF-2 RHR TRAINS WITHIN 33 Hrs (ERIN 0.20% 5.30E-02 %T11-IE INJECTION FAILS TO SURVIVE AFTER CONTAINMENT FAILS (E 3.82E-03 RHRF48BB-VOO LOSS OF INSTRUMENT AIR IE OR LOSP AT UNIT 1 MOTOR-OPERATED VALVE RHRF48BB OO 4.23E-03 NWVYO1CA-FMS-SS 7.00E-02 RHR-RECOVERY MOTOR-DRIVEN FAN NWVYO1CA SS FAULTS 90 GTR03 1.98E-08 3.30E-01 SURVIVABILITY FAILURE TO RECOVER 1-OF-2 RHR TRAINS WITHIN 33 Hrs (ERIN 0.20% 5.30E-02 %T11-lE INJECTION FAILS TO SURVIVE A;'TER CONTAINMENT FAILS (ERIN) 3.82E-03 RHRF48AA-VOO LOSS OF INSTRUMENT AIR IE OR LOSP AT UNIT 1 MOTOR-OPERATED VALVE RHRF48AA OO 4.23E-03 SEVYO3CB-FMS-SS 7.00E-02 RHR-RECOVERY MOTOR-DRIVEN FAN SEVYO3C8 SS FAULTS 91 GTR03 1.90E-08 0.19%

3.30E-01 SURVIVABILITY FAILURE TO RECOVER 1-OF-2 RHR TRAINS WITHIN 33 Hrs (ERIN 2.63E-04 %T101-lE INJECTION FAILS TO SURVIVE AFTER CONTAINMENT FAILS (E 3.13E-03 2E1280018-HTX-LF LOSS OF 4160V AC BUS 241Y IE(OUANT SWGR241YA) 7.00E-02 RHR-RECOVERY 2E128001B HX TRAIN B PLANT SPECIFIC FAULT DATA (PSD) 92 GTR03 1.90E-08 3.30E-01 SURVIVABILITY FAILURE TO RECOVER 1-OF-2 RHR TRAINS WITHIN 33 Hrs (ERI 0.19% 2.63E-04 %T102-lE INJECTION FAILS TO SURVIVE AFTER CONTAINMENT FAILS (E 3.13E-03 2E128001A-HTX-LF LOSS OF 4160V AC BUS 242Y lE(OUANT SWGR242YA) 7.00E-02 RHR-RECOVERY 2E128001 A HX TRAIN A PLANT SPECIFIC FAULT DATA (PSD) 93 IORV06 1.86E-08 3.30E-01 SURVIVABILITY FAILURE TO RECOVER 1-OF-2 RHR TRAINS WITHIN 33 Hrs (ERI 0.19% 5.30E-02 %T7-lE INJECTION FAILS TO SURVIVE AFTER CONTAINMENT FAILS (E lORVIE 1.98E-02 2FWOOS-PATH-FLT 4.26E-03 SWVYO2AX-INHTR 2FW005 MDRFP REG VALVE PATH FAULTS 94 ATW15 4.15E-03 LPCS-LOGIC-FLT INADEQUATE HEAT REMOVAL VIA AIR COOLING SWVYO2AX 1.83E-08 0.18% 4.70E-01 LPCS PUMP LOGIC FAULTS

%MSIV 1.00E+00 ATWS MSIV CLOSURE IE(including loss of 100 psi pneumatic IE) 1.30E 03 OP-SBLC-A ATWS FLAG TO IDENTIFY ATWS CUTSETS 3.00E-05 RPS-ARI-F OP ACT: INITIATE SBLC (ATWS) 95 GTR03 1.83E-08 0.18% 5.30E-02 %T11-lE RPS and ARI FAILURE ( RMIEP NMPC WNP-2) 3.53E-03 CSCD300B-STR-PLG LOSS OF INSTRUMENT AIR IE OR LOSP AT UNIT 1 2E12D3008 STRAINER RHR SW TRAIN B PLUG 4.23E-03 NWVYO1CA-FMS-SS 7.00E-02 RHR-RECOVERY MOTOR-DRIVEN FAN NWVYO1CA SS FAULTS 96 GTR03 1.83E-08 3.30E-01 SURVIVABILITY FAILURE TO RECOVER 1-OF-2 RHR TRAINS WITHIN 33 Hrs (ERIN 0.18% 5.30E-02 %T11-lE INJECTION FAILS TO SURVIVE AFTER CONTAINMENT FAILS (ERI 4.23E-03 SEVYO3CB-FMS-SS LOSS OF INSTRUMENT AIR IE OR LOSP AT UNIT 1 MOTOR-DRIVEN FAN SEVYO3CB SS FAULTS 3.53E-03 CSCD300A-STR-PLG 7.00E-02 RHR-RECOVERY 2E12D300A STRAINER RHR SW TRAIN A PLUG 3.30E-01 SURVIVABILITY FAILURE TO RECOVER 1-OF-2 RHR TRAINS WITHIN 33 Hrs (ERIN)

C-10 INJECTION FAILS TO SURVIVE AFTER CONTAINMENT FAILS (ER

O O O O O O O O O O O Appendix C - Tc.ble 1 Top 100 Core Damage Cutsets Seq. Sequence Total CDF Frequency: 1.0E-05/yr Percent of No. Name CDF Total CDF Event Prob. Event Name 97 LOOP 14 Accident-Sequence Event Description 1.81 E-08 0.18% 1.60E-02 %DLOSP DUAL LOSS OF OFFSITE POWER lE 7.34E-03 RCIF013C-FAULTS MOV RCIC F013 VALVE FAULTS 98 1.54E-04 DGS-FAIL-CM GTR03 1.79E-08 0.18% DGs DIV 1,2 common mode failure (DG2A FAIL *(BETA =.012))

5.30E-02 %T11-lE LOSS OFINSTRUMENT AIR IE OR LOSP AT UNIT 1 3.82E-03 RHRSWB-HTX-ISO-V RHRSW B HTX ISOLATION VALVE FAULTS 3.82E-03 RHRSWA-HTX-ISO-V RHRSW A HTS ISOLATION VALVE FAULTS 7.00E-02 RHR-RECOVERY 3.30E-01 SURVIVABILITY FAILURE TO RECOVER 1.OF-2 RHR TRAINS WITHIN 33 Hrs (ERIN) 99 GTR03 1.79E-08 0.18% INJECTION FAILS TO SURVIVE AFTER CONTAINMENT FAILS (ERI 5.30E-02 %T11-lE ,

LOSS OF INSTRUMENT AIR IE OR LOSP AT UNIT 1 3.82E43 RHRF48AA-VOO MOTOR-OPERATED VALVE RHRF48AA OO 3.82E-03 FiHRSWB-HTX-ISO-V RHRSW B HTX ISOLATION VALVE FAULTS 7.00E-02 RMR-RECOVERY 3.30E-01 EURVIVABILITY FAILURE TO RECOVER 1-OF-2 RHR TRAINS WITHIN 33 Hrs (ERIN) 100 GTR03 1.79E-08 0.18 % 5.30E-02

• LT11-lE INJECTION FAILS TO SURVIVE AFTER CONTAINMENT FAILS (ERIN LOSS OF INSTRUMENT AIR lE OR LOSP AT UNIT 1 3.82E-03 HHRF48BB-VOO MCTOR-OPERATED VALVE RHRF48BB OO 3.82E-03 RHRSWA-HTX-ISO-V RHRSW A HTS ISOLATION VALVE FAULTS 7.00E-02 RHR-RECOVERY 3.30E-01 SURVIVABILITY FAILURE TO RECOVER 1-OF-2 RHR TRAINS WITHIN 33 Hrs (ERIN)

INJECTION FAILS TO SURVIVE AFTER CONTAINMENT FAILS (ERI Totah: 3.68E-06 36.91 % Of Total CDFFrequency: 1.0E-85 C-11

Appendix C - Tcble 2 L

Top Cutsets for LOSP Sequences Seq. Sequence Total CDF Frequency: 1.0E-05/yr Percent of No. Name CDF Total CDF Event Prob.  !

Event Name Accident-t f- ~ s Event r -- _ , _ :

LOOP 18 1 2.30E-07 2.31 % 1.60E-02 %DLOSP DUAL LOSS OF OFFSITE POWER IE 7.63E-02 DG2A-FAULTS DG2A PLANT SPECIFIC FAULTS i

7.63E-02 DGO-FAULTS 2.47E-03 ROP 24 DGO PLANT SPECIFIC FAULTS {PSD) 2 LOOP 17 1.72E-07 failure to recover OSP within 24 hrs 1.73% 1.60E-02 %DLOSP 1 DUAL LOSS OF OFFSITE POWER IE 4.33E-02 2E22S001-FAULTS 7.63E-02 DG2A-FAULTS DG2B PLANT SPECIFIC FAULTS (PSD)

DG2A PLANT SPECIFIC FAULTS t

7.63E-02 DGO-FAULTS i 4.27E-02 ROP 3 DGO PLANT SPECIFIC FAULTS (PSD) '

3 LOOP 17 1.05E-07 failure to recover OSP within 3 HRS ( NO LOAD SHED) 1.05 % 1.60E-02 %DLOSP DUAL LOSS OF OFFSITE POWER lE

, 1.54E-04 DGS-FAIL-CM DGs DIV 1,2 common mode failure (DG2A FAIL *(PETA =.012))

1

' 4.27E-02 ROP 3  !

4 LOOP 14 6.15E-08 0.62% failure to recover OSP within 3 HRS ( NO LOAD GHED) 1.60E-02 %DLOSP DUAL LOSS OF OFFSITE POWER lE 4.33E-02 2E22S001-FAULTS i 7.63E-02 DGO-FAULTS DG2B PLANT SPECIFIC FAULTS (PSD)  !

DGO PLANT SPECIFIC FAULTS (PSD) 1.53E-02 RCIC001X-TDP-SS TURBINE-DRIVEN PUMP RCIC001 SS FAULTS 5

7.63E-02 DG2A-FAULTS DG2A PLANT SPECIFIC FAULTS LOOP 07 4.90E-08 0.49% 5.30E-02 %LOSP LOSS OF OFFSITE POWER INIT EVENT 4.33E-02 2E22S001-FAULTS DG2B PLANT SPECIFIC FAULTS (PSD)-

4 1.53E-02 RCIC001X-TDP-SS TURBINE-DRIVEN PUMP RCIC001 SS FAULTS 1.40E-03 OADS OP ACT: INITIATE ADS i 6 LOOP 14 4.76E-08 0.48 % 1.60E-02 %DLOSP DUAL LOSS OF OFFSITE POWER lE j 4.33E-02 2E22S001-FAULTS +

7.63E-02 DGO-FAULTS DG2B PLANT SPECIFIC FAULTS (PSD)

DG0 PLANT SPECIFIC FAULTS (PSD) 7.63E-02 DG2A-FAULTS DG2A PLANT SPECIFIC FAULTS 7 1.18E-02 RCIF063C-VOC MOTOR-OPERATED VALVE RClF063C OC '

LOOP 17 3.85E-08 0.39 % 1.60E-02 %DLOSP DUAL LOSS OF OFFSITE POWER IE

• i 9.69E-03 DG28-AUX-SYS HPCS DIESEL AUXILIARY SYTEMS FAILURE 7.63E-02 DG2A-FAULTS DG2A PLANT SPECIFIC FAULTS 7.63E-02 DGO-FAULTS 4.27E-02 ROP 3 DGO PLANT SPECIFIC FAULTS (PSD) 8 LOOP 07 3.80E-06 0.38 % failure to recover OSP within 3 HRS ( NO LOAD SHED) 5.30E-02 %LOSP  !

LOSS OF OFFSITE POWER INIT EVENT '

4.33E-02 2E22S001-FAULTS i 1.18E-02 RCIF063C-VOC DG2B PLANT SPECIFIC FAULTS (PSD)  !

MOTOR-OPERATED VALVE RCIF063C OC  ;

1.40E-03 OADS OP ACT: INITIATE ADS 9 LOOP 14 3.76E-08 0.38 % 1.60E-02 %DLOSP f DUAL LOSS OF OFFSITE POWER IE t 1.53E-02 RCIC001X-TDP-SS TURBINE-DRIVEN PUMP RCIC001 SS FAULTS  !

1.54E-04 DGS-Fall-CM DGs DIV 1,2 common mode failure (DG2A FAIL *(BETA =.012))

l i

C-12 i i

_ . _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ . _ _ _ _ _____ _c _ - _ _ _ . _ _ _ _ _ _ _ _ , _ _ _ _ _ _ _ _ _ _ _ _ _ . . _ _ _ _ _ _ _ . _ _ _ _

p,v - v v. v - m - - -

Appendix C- Tcble 2

' Top Cutsets for LOSP Sequences Seq. 0 -_r Total CDF Frequency: 1.0E-05/yr Percent of No. Name _CDF Total CDF Event Prob. Event Name Accident-Trp a Event & - ,1.

10 LOOP 14 2.96E-08 0.30 %

1.60E-02 %DLOSP DUAL LOSS OF OFFSITE POWER IE 4.33E-02 2E22S001-FAULTS 7.63E-02 DGO-FAULTS DG2B PLANT SPECIFIC FAULTS (PSD) t DGO PLANT SPECIFIC FAULTS (PSD) 7.63E-02 DG2A-FAULTS DC2A PLANT SPECIFIC FAULTS 7.34E-03 RCIF013C-FAULTS MOV RCIC F013 VALVE FAULTS 11 LOOP 14 2.91E-08 0.29% 1.60E-02 %DLOSP DUAL LOSS OFOFFSITE POWER IE 1.18E-02 RCIF063C-VOC MOTOR-OPERATED VALVE RClF063C OC 12 LOOP 18 1.54E-04 DGS-Fall-CM . DGs DIV 1,2 common mode failure (DG2A FAIL *(BETA =.012))

2.90E-08 0.29% 1.60E-02 %DLOSP DUAL LOSS OF OFFSITE POWERIE 9.62E-03 SY-VNF-HVDG2A 7.63E-02 DGO-FAULTS ROOM HVDG2A COOLING OR VENTILATION SYSTEM FAULTS -

2.47E-03 ROP 24 DGO PLANT SPECIFIC FAULTS (PSD) 13 LOOP 17 2.89E-08 failure to recover OSP within 24 hrs 0.29% 1.60E-02 %DLOSP DUAL LOSS OF OFFSITE POWER lE 7.26E-03 2E22C002-FAULTS 7.63E-02 DG2A-FAULTS 2E22C002 DG2B COOL WTR PUMP PLANT SPECIFIC FLT DATA (PSD DG2A PLANT SPECIFIC FAULTS 7.63E-02 DGO-FAULTS DGO PLANT SPECIFIC FAULTS (PSD) 4.27E-02 ROP 3 14 LOOP 17 2.81 E-08 0.28% failure to recover OSP within 3 HRS ( NO LOAD SHED) 1.60E-02 %DLOSP DUAL LOSS OF OFFSITE POWER IE i

7.06E-03 2E22C001-PMS-SS 7.63E-02 DG2A-FAULTS 2E22C001 HPCS PUMP PLANT SPECIFIC FAULT DATA (GEN) i DG2A PLANT SPECIFIC FAULTS 7.63E-02 DGO-FAULTS 4.27E-02 ROP 3 DG0 PLANT SPECIFIC FAULTS (PSD) 15 LOOP 14 2.77E-08 0.28 % failure to recover OSP within 3 HRS ( NO LOAD SHED) 1.60E-02 %DLOSP DUAL LOSS OF OFFSITE POWER IE 4.33E-02 2E22S001-FAULTS 7.63E-02 DGO-FAULTS DG2B PLANT SPECIFIC FAULTS (PSD)

DGO PLANT SPECIFIC FAULTS (PSD) 6.85E-03 RCIF046C-FAULTS MOTOR 4PERATED VALVE RCIF046C CC 7.63E-02 DG2A-FAULTS DG2A PLANT SPECIFIC FAULTS 16 LOOP 14 2.75E-08 0.28% 1.60E-02 %DLOSP DUAL LOSS OF OFFSITE POWER lE 4.33E-02 2E22S001-FAULTS DG2B PLANT SPECIFIC FAULTS (PSD) 7.63E-02 DGO-FAULTS DGO PLANT SPECIFIC FAULTS (PSD)

' 7.63E-02 DG2A-FAULTS DG2A PLANT SPECIFIC FAULTS 6.81E-03 RCIF045C-VCC MOTOR-OPERATED VALVE RCIF045C CC 17 LOOP 17 2.40E-08 0.24 % 1.60E-02 %DLOSP DUAL LOSS OF OFFSITE POWER lE 7.63E-02 DG2A-FAULTS DG2A PLANT SPECIFIC FAULTS 6.04E-03 HP-MOV-FAULTS HPCS MOV VALVES FAULTS 7.63E-02 DGO-FAULTS 4.27E-02 ROP 3 DGO PLANT SPECIFIC FAULTS (PSD) 18 LOOP 07 2.36E-08 0.24% failure to recover OSP within 3 HRS ( NO LOAD SHED) 5.30E-02 %LOSP LOSS OF OFFSITE POWER INIT EVENT 4.33E-02 2E22S001-FAULTS DG2B PLANT SPECIFIC FAULTS (PSD) 7.34E-03 RCIF013C-FAULTS MOV RCIC F013 VALVE FAULTS -

1.40E-03 OADS OP ACT: INITIATE ADS C-13

O O O O. O O O O O O O i i

Appendix C - Table 2 Top Cutsets for LOSP Sequences i Total CDF Frequency: 1.0E-05/yr

= Se , - ot No. Nome CDF Total CDF Event Prob. - Event Name Accident-Sequence Event CT:

19 LOOP 07 2.20E-08

, _ _ . j 0.22 % 5.30E-02 %LOSP LOSS OF OFFSITE POWER INIT EVENT 4.33E-02 2E22S001-FAULTS [

DG2B PLANT SPECIFIC FAULTS (PSD)-

6.85E-03 RCIF0460-FAULTS MOTOR 4PERATED VALVE RCIF046C CC 1.40E-03 OADS OP ACT: INITIATE ADS i

20 LOOP 07 2.19E-08 0.22% 5.30E-02 %LOSP LOSS OF OFFSITE POWER INIT EVENT 4.33E-02 2E22S001-FAULTS DG2B PLANT SPECIFIC FAULTS (PSD) 6.81 E-03 RCIF045C-VCC MOTOR-OPERATED VALVE RCIF045C CC 1.40E-03 OADS i OP ACT: NTIATE ADS '

Totals: 1.07E-06 10.74 % Of Total CDF Frequency- 1.9E-05  !

t t

(o!v i

t i

I C-14 i

s Appendix C - Tcb!: 3 Top Cutsets for Transient Sequences Seq. Sequence Percent of Total CDF Frequency: 1.0E-05/yr No. Name CDF Total CDF Event Prob- - Event Name Accident-Sequence Event Description 1 GTR03 1.52E-07 1.52 % 5.30E-02 %T11-lE 1.24E-04 LPCI-CM LOSS OFINSTRUMENT AIR IE OR LOSP AT UNIT 1 7.00E-02 RHR-RECOVERY COMMON MODE FAILURE OF ALL 3 LPCI PUMPS (BETA = .05) 2 GTR11 4.77E-08 3.30E-01 SURVIVABILITY FAILURE TO RECOVER 1-OF-2 RHR TRAINS WITHIN 33 Hrs (ERIN 0.48 % 5.30E-02 %T11-lE INJECTION FAILS TO SURVIVE AFTER CONTAINMENT FA!LS(E LOSS OF INSTRUMENT AIR IE OR LOSP AT UNIT 1 7.26E-03 2E22C002-FAULTS 3 GTR11 4.64E-08 0.47%

1.24E-04 LPCI-CM 2E22C002 DG2B COOL WTR PUMP PLANT SPECIFIC FLT DATA 5.30E-02 %T11-lE COMMON MODE FAILURE OF ALL 3 LPCI PUMPS (BETA =.05) 7.06E-03 2E22C001-PMS-SS LOSS OF INSTRUMENT AIR IE OR LOSP AT UNIT 1 4 GTR03 4.41 E-08 1.24E-04 LPCI-CM 2E22C001 HPCS PUMP PLANT SPECIFIC FAULT DATA (GEN) 0.44 % 5.30E-02 %T11-lE COMMON MODE FAILURE OF ALL 3 LPCI PUMPS (BETA = .05) 3.60E-05 CS-COOL-FMP-CM LOSS OF INSTRUMENT AIR lE OR LOSP AT UNIT 1 COMMON MODE CS COOL WTR PMPS 7.00E-02 RHR-RECOVERY 5 GTR11 3.97E-08 3.30E-01 SURVIVABILITY FAILURE TO RECOVER 1-OF-2 RHR TRAINS WITHIN 33 Hrs (ERIN 0.40% 5.30E-02 %T11-lE INJECTION FAILS TO SURVIVE AFTER CONTAINMENT FAILS (ER 6.04E-03 HP-MOV-FAULTS LOSS OF INSTRUMENT AIR lE OR LOSP AT UNIT 1 HPCS MOV VALVES FAULTS 6 GTR03 1.24E-04 LPCI-CM 3.86E-08 0.39% 5.30E-02 %T11-lE COMMON MODE FAILURE OF ALL 3 LPCI PUMPS (BETA = .05) 5.61E-03 2E12C0028-FLT LOSS OF INSTRUMENT AIR IE OR LOSP AT UNIT 1 5.61E-03 2E12C002A-FLT 2E12C0028 RHR TRA!N B MOTOR-DRIVEN PUMP FAULTS (PSD) 7.00E-02 RHR-RECOVERY 2E12C002A RHR TRAIN A MOTOR-DRIVEN PUMP FAULTS (PSD) 7 GTR03 3.61E-08 0.36 %

3.30E-01 SURVIVABILITY FAILURE TO RECOVER 1-OF-2 RHR TRAINS WITHIN 33 Hrs (ERI 5.30E-02 %T11-lE INJECTION FAILS TO SURVIVE AFTER CONTAINMENT FAILS (ER LOSS OF INSTRUMENT AIR IE OR LOSP AT UNIT 1 5.26E-03 2DG01P-FAULTS 5.61 E-03 2E12C002A-FLT DG2A COOL WTR PUMP 2DG01P PLANT SPECIFIC FAULTS (PS 7.00E-02 RHR-RECOVERY 2E12C002A RHR TRAIN A MOTOR-DRIVEN PUMP FAULTS (PSD) 8 GTR03 3.61 E-08 0.36 %

3.30E-01 SURVIVABILITY FAILURE TO RECOVER 1-OF-2 RHR TRAINS WITHIN 33 Hrs (ERIN 5.30E-02 %T11-lE INJECTION FAILS TO SURVIVE AFTER CONTAINMENT FAILS (ER LOSS OF INSTRUMENT AIR IE OR LOSP AT UNIT 1 5.26E-03 CODG01P-FAULTS 5.61E-03 2E12C0028-FLT MOTOR-DRIVEN PUMP CODG01P SS FAULTS 7.00E-02 RHR-RECOVERY 2E12C002B RHR TRAIN B MOTOR-DRIVEN PUMP FAULTS (PSD) 9 GTR03 3.41 E-08 3.30E-01 SURVIVABILITY FAILURE TO RECOVER 1-OF-2 RHR TRAINS WITHIN 33 Hrs (ERIN 0.34 % 2.63E-04 %T101-lE INJECTION FAILS TO SURVIVE AFTER CONTAINMENT FA!LS(ERI 5.61 E-03 2E12C0028-FLT LOSS OF 4130V AC BUS 241Y IE(OUANT SWGR241YA) 7.00E-02 RHR-RECOVERY 2E12C0028 RHR TRAIN B MOTOR-DRIVEN PUMP FAULTS (PSD) 10 GTR03 3.41E-08 3.30E-01 SURVIVABILITY FAILURE TO he. COVER 1-OF-2 RHR TRAINS WITHIN 33 Hrs (ERIN 0.34 % 2.63E-04 %T102-lE INJECTION FAILO TO SURVIVE AFTER CONTAINMENT FAILS (ER 5.61E-03 2E12C002A-FLT LOSS OF 4160V AC BUS 242Y lE(OUANT SWGR242YA) 7.00E-02 RHR-RECOVERY 12C002A RHR TRAIN A MOTOR-DRIVEN PUMP FAULTS (PSD) 3.30E-01 SURVIVABILITY FAILURE TO RECOVER 1-OF-2 RHR TRAINS WITHIN 338.-= (ERIN)

INJECTION FAILS TO SURVIVE AFTER CONTAINMENT FAILS (ERIN)

C-15

e e u u u u Q u 'U U U Appendix C - Tchie 3 Top Cutsets for Transient Sequences Seq. Sequence Total CDF Frequency: 1.0E-05/yr Percent of No- Name CDF Total CDF Event Prob. Event Name Accident-Sequence Event Description 11 GTR03 3.39E-08 0.34 % 5.30E-02 %T11-lE LOSS OF INSTRUMENT AIR IE OR LOSP AT UNIT 1 5.26E-03 CODG01P-FAULTS MOTOR-DRIVEN PUMP CODG01P SS FAULTS 5.26E-03 2DG01P-FAULTS 7.00E-02 RHR-RECOVERY DG2A COOL WTR PUMP 2DG01P PLANT SPECIFIC FAULTS (PSD) 3.30E-01 SURVIVABILITY FAILURE TO RECOVER 1-OF-2 RHR TRAINS WITHIN 33 Hrs (ERIN) 12 GTR03 3.20E-08 0.32 % 2.63E-04 %T101-lE INJECTION FAILS TO SURVIVE AFTER CONTAINMENT FAILS (ERIN) 5.26E-03 2DG01P-FAULTS LOSS OF 4160V AC BUS 241Y IE(OUANT SWGR241YA) 7.00E-02 RHR-RECOVERY DG2A COOL WTR PUMP 2DG01P PLANT SPECIFIC FAULTS (PSD) 3.30E-01 SURVIVABILITY FAILURE TO RECOVER 1-OF-2 RHR TRAINS WITHIN 33 Hrs (ERIN) 13 GTR03 3.20E-08 0.32 % INJECTION FAILS TO SURVIVE AFTER CONTAINMENT FAILS (ERIN) 2.63E-04 %T102-lE 5.26E-03 CODG01P-FAULTS LOSS OF 4160V AC BUS 242Y IE(QUANT SWGR242YA)

MOTOR-DRIVEN PUMP CODG01P SS FAULTS 7.00E-02 RHR-RECOVERY 3.30E-01 SURVlVABILITY FAILURE TO RECOVER 1-OF-2 RHR TRAINS WITHIN 33 Hrs (ERIN) 14 GTR03 2.91 E-08 0.29% INJECTION FAILS TO SURVIVE AFTER CONTAINMENT FAILS (ERIN) 5.30E-02 %T11-lE LOSS OF INSTRUMENT AIR IE OR LOSP AT UNIT 1 5.61 E-03 2E120002B-FLT 4.23E-03 NWVYO1CA-FMS-SS 2E12C002B RHR TRAIN B MOTOR-DRIVEN PUMP FAULTS (PSD)

MOTOR-DRIVEN FAN NWVYO1CA SS FAULTS 7.00E-02 RHR-RECOVERY 3.30E-01 SURVIVABILITY FAILURE TO RECOVER 1-OF-2 RHR TRAINS WITHIN 33 Hrs (ERIN) 15 GTR03 2.91 E-08 0.29% INJECTION FAILS TO SURVIVE AFTER CONTAINMENT FAILS (ERIN) 5.30E-02 %T11-lE LOSS OF INSTRUMENT AIR IE OR LOSP AT UNIT 1 4.23E-03 SEVYO3CB-FMS-SS MOTOR-DRIVEN FAN SEVYO3CB SS FAULTS 5.61 E-03 2E12C002A-FLT 7.00E-02 RHR-RECOVERY 2E12C002A EHR TRAIN A MOTOR-DRfVEN PUMP FAULTS (PSD) 3.30E-01 SURVIVABILITY FAILURE TO RECOVER 1-OF-2 RHR TRAINS WITH!N 33 Hrs (ERIN) 16 GTR11 2.00E-08 0.28 % INJECTION FAILS TO SURVIVE AFTER CONTAINMENT FAILS (ERIN) 5.30E-02 %T11-lE LOSS OFINSTRUMENT AIR IE OR LOSP AT UNIT 1 4.26E-03 SWVYO2AX-INHTR 1.24E-04 LPCI-CM INADEQUATE HEAT REMOVAL VIA AIR COOLING SWVYO2AX 17 GTR03 2.73E-08 0.27% COMMON MODE FAILURE OF ALL 3 LPCI PUMPS (BETA = .05) 5.30E-02 %T11-lE LOSS OF INSTRUMENT AIR IE OR LOSP AT UNIT 1 5.26E-03 2DG01P-FAULTS 4.23E-03 NWVYO1CA-FMS-SS DG2A COOL WTR PUMP 2DG01P PLANT SPECIFIC FAULTS (PSD)

MOTOR-DRIVEN FAN NWVYO1CA SS FAULTS 7.00E-02 RHR-RECOVERY 3.30E-01 SURVIVABILITY FAILURE TO RECOVER 1-OF-2 RHR TRAINS WITHIN 33 Hrs (ERIN) 18 GTR03 2.73E-08 07~- INJECTION FAILS TO SURVIVE AFTER CONTAINMENT FAILS (ERIN) 5.30E-02 %T11-lE LOSS OF INSTRUMENT AIR IE OR LOSP AT UNIT 1 5.26E-03 CODG01P-FAULTS MOTOR-DRIVEN PUMP CODG01P SS FAULTS 4.23E-03 SEVYO3CB-FMS-SS MOTOR-DRIVEN FAN SEVYO3CB SS FAULTS 7.00E-02 RHR-RECOVERY 3.30E-01 SURVIVABILITY FAILURE TO RECOVER 1-OF-2 RHR TRAINS WITHIN 33 Hrs (ERIN) 19 GTR03 2.63E-08 0.26% INJECTION FAILS TO SURVIVE AFTER CONTAINMENT FAILS (ERIN) 5.30E-02 %T11-lE LOSS OF INSTRUMENT AIR lE OR LOSP AT UNIT 1 3.82E-03 RHRSWB-HTX-ISO-V RHRSW B HTX ISOLATION VALVE FAULTS 5.61 E-03 2E12C002A-FLT 7.00E-02 RHR-RECOVERY 2E12C002A RHR TRAIN A MOTOR-DRIVEN PUMP FAULTS (PSD) 3.30E-01 SURVIVABILITY FAILURE TO RECOVER 1-OF-2 RHR TRAINS WITH!N 33 Hrs (ERIN)

INJECTION FAILS TO SURVIVE AFTER CONTAINMENT FAILS (ERIN)

C-16

O O O O O O O O O O O '

Appendix C - Tcble 3 ,

Top Cutsets for Transient Sequences  :

Seq. Sequence Total CDF Frequency: 1.0E-05/yr  !

Percent of No. Name CDF Total CDF Event Prob. r Event Name Accident-Sequence Event C:: --fixi i 20 GTR03 2.63E-08 0.26% 5.30E-02 %T11-IE  !

LOSS OF INSTRUMENT AIR lE OR LOSP AT UNIT 1 5.61 E-03 2E12C002B-FLT [

3.82E-03 RHRSWA-HTX-ISO-V 2E12C0028 RHR TRAIN 8 MOTOR-DRIVEN PUMP FAULTS (PSD) [

RHRSW A HTS ISOLATION VALVE FAULTS  !

7.00E-02 RHR-RECOVERY 3.30E-01 SURVIVABILITY FAILURE TO RECOVER 1-OF-2 RHR TRAINS WITHIN 33 Hrs (ERIN)  !

INJECTION FAILS TO SURVIVE AFTER CONTAINMENT FAILS (ERIN)

Totals: 8.00E-07 8.03 % Of Total CDFFrequency: 1.eE-05 f

t t

t c

I f

t C-17

Appendix C - Tcbl2 4 Top Cutsets for IORY Sequences ,

Seq. Seqtmace Total CDF Frequency: 1.0E-05/yr Percent of No. Name CDF Total CDF Event Prob. Event Name IORV06 Accident-Sequence Event Description 1

4.11E-08 0.41 % 5.30E-02 %T7-lE lORV IE 7.26E-03 2E22C002-FAULTS 1.98E-02 2FWOOS-PATH-FLT 2E22C002 DG2B COOL WTR PUMP PLANT SPECIFIC FLT DATA (PS 2FWOO5 MDRFP REG VALVE PATH FAULTS 2 5.39E-03 LCSC001A-PMS-SS MOTOR-DRIVEN PUMP LCSC001 A SS FAULTS IORV06 4.01 E-08 0.40 % 5.30E-02 %T7-lE IORV IE 7.26E-03 2E22C002-FAULTS 1.98E-02 2FWOOS-PATH-FLT 2E22C002 DG2B COOL WTR PUMP PLANT SPECIFIC FLT DATA (Pi 2FWOO5 MDRFP REG VALVE PATH FAULTS 3 5.26E-03 CODG01P-FAULTS MOTOR-DRIVEN PUMP CODG01P SS FAULTS IORV06 3.16E-08 0.32 % 5.30E-02 %T7-IE l lORVIE 7.26E-03 2E22C002-FAULTS 1.98E-02 2FWOOS-PATH-FLT 2E22C002 DG2B COOL WTR PUMP PLANT SPECIFIC FLT DATA (P 2FW005 MDRFP REG VALVE PATH FAULTS 4 4.15E-03 LPCS-LOGIC-FLT LPCS PUMP LOGIC FAULTS IORV06 3.04E-08 0.30 % 5.30E-02 %T7-lE ,

IORV IE '

7.26E-03 2E22C002-FAULTS 1.98E-02 2FWOOS-PATH-FLT 2E22C002 DG2B COOL WTR PUMP PLANT SPECIFIC FLT DATA (PSD 2FWOO5 MDRFP REG VALVE PATH FAULTS 5

3.98E-03 LCSF005A-FLT LCSF005A C8 OR OTHER LOCAL FAILURES IORV06 2.41E-08 0.24 % 5.30E-02 %T7-lE IORV IE 1.98E-02 2FWOO5-PATH-FLT 2FWOO5 MDRFP REG VALVE PATH FAULTS 4.26E-03 SWVYO2AX-INHTR 5.39E-03 LCSC001A-PMS-SS INADEQUATE HEAT REMOVAL VIA AIR COOLING SWVYO2AX 6 IORV06 2.35E-08 0.24 % MOTOR-DRIVEN PUMP LCSC001 A SS FAULTS 5.30E-02 %T7-lE lORV IE 1.98E-02 2FWOOS-PATH-FLT 2FW005 MDRFP REG VALVE PATH FAULTS 5.26E-03 CODG01P-FAULTS MOTOR-DRIVEN PUMP CODG01P SS FAULTS 7 IORV06 4.26E-03 SWVYO2AX-INHTR 1.86E-08 0.19% 5.30E-02 %T7-IE INADEQUATE HEAT REMOVAL VIA AIR COOLING SWVYO2AX IORV IE 1.98E-02 2FWOOS-PATH-FLT 2FWOO5 MDRFP REG VALVE PATH FAULTS 4.26E-03 SWVYO2AX-INHTR 4.15E-03 LPCS-LOGIC-FLT INADEQUATE HEAT REMOVAL VIA AIR COOLING SWVYO2AX 8 IORV06 1.78E-08 0.18% LPCS PUMP LOGIC FAULTS ,.

5.30E-02 %T7-lE lORV IE 1.98E-02 2FWOO5-PATH-FLT 2FW005 MDRFP REG VALVE PATH FAULTS 4.26E-03 SWVYO2AX-INHTR 3.98E-03 LCSF005A-FLT INADEQUATE HEAT REMOVAL VIA AIR COOLING SWVYO2AX 9 IORV06 1.71 E-08 0.17% LCSF005A CB OR OTHER LOCAL FAILURES 5.30E-02 %T7-IE IORV IE 7.26E-03 2E22C002-FAULTS 1.98E-02 2FWOOS-PATH-FLT 2E22C002 DG2B COOL WTR PUMP PLANT SPECIFIC FLT DATA (PS i 2FWOO5 MDRFP REG VALVE PATH FAULTS 10 IORV06 2.24E-03 NEVYO4CA-FMS-SS MOTOR-DRIVEN FAN NEVYO4CA SS FAULTS 1.00E-08 0.10% 5.30E-02 %T7-lE lORV IE 1.98E-02 2FWOO5-PATH-FLT 2FW005 MDRFP REG VALVE PATH FAULTS 4.26E-03 SWVYO2AX-INHTR INADEQUATE HEAT REMOVAL VIA AIR COOLING SWVYO2AX 2.24E-03 NEVYO4CA-FMS-SS MOTOR-DRlVEN FAN NEVYO4CA SS FAULTS C-18

O O O '

O O O O O O O O i

Appendix C- Table 4 j

Top Cutsets for IORV Sequences

{

Seq. Sequence Total CDF Frequency: 1.0E-05/yr Percent of 1 No. Narne CDF Total CDF Event Prob. Event Narne A 11 IORV06 6.25E-09 0.06 %

^ J "n_m Event P - ^ '

i 5.30E-02 %T7-lE lORV IE 7.26E-03 2E22C002-FAULTS i

3.01E-03 CST-HOTWELL-LF 2E22C002 DG2B COOL WTR PUMP PLANT SPECIFIC FLT DATA (PSD

, CST TO HOTWELL MAKEUP LOCAL FAULTS 12-5.39E-03 LCSC001A-PMS-SS MOTORDRIVEN PUMP LCSC001A SS FAULTS lORV06 6.12E-09 0.06 % 5.30E-02 %T7-lE lORV IE 7.26E-03 2E22C002-FAULTS 1.98E-02 2FWOOS-PATH-FLT 2E22C002 DG2B COOL WTR PUMP PLANT SPECIFIC FLT DATA (PSD

! 2FW005 MDRFP REG VALVE PATH FAULTS 8.02E-04 CODG035-VOC MOTOR 4PERATED VALVE CODG035 OC 13 IORV06 6.10E-09 0.06 %

i 5.30E-02 %T7-lE lORV IE 7.26E-03 2E22C002-FAULTS 3.01E-03 CST-HOTWELL-LF 2E220002 DG2B COOL WTR PUMP PLANT SPECIFIC FLT DATA (PSD CST TO HOTWELL MAKEUP LOCAL FAULTS 14 5.26E-03 CODG01P-FAULTS MOTORORIVEN PUMP CODG01P SS FAULTS IORV06 5.49E-09 0.06 % 5.30E-02 %T7-lE LORY lE 7.26E-03 2E22C002-FAULTS 1.90E-02 2FWOOS-PATH-FLT 2E22C002 DG2B COOL WTR PUMP PLANT SPECIFIC FLT DATA (PSD

2FWOO5 MDRFP REG VALVE PATH FAULTS 7.20E-04 LCSD302X-STR 15 IORV06 4.81E-09 0.05 % SUPPRESSION POOL SUCTION STRAINER LCSD302X FAULTS 5.30E-02 %T7-lE LORY lE 7.26E-03 2E22C002-FAULTS 3.01E-03 CST-HOTWELL-LF 2E22C002 DG2B COOL WTR PUMP PLANT SPECIFIC FLT DATA (PSD CST TO HOTWELL MAKEUP LOCAL FAULTS 16 4.15E-03 LPCS-LOGIC-FLT LPCS PUMP LOGIC FAULTS IORV06 4.62E-09 0.05 % 5.30E-02 %T7-lE lORV IE 7.26E-03 2E22C002-FAULTS 3.01E-03 CST-HOTWELL-LF 2E22C002 DG2B COOL WTR PUMP PLANT SPECIFIC FLT DATA (PSD

! CST TO HOTWELL MAKEUP LOCAL FAULTS 17 3.98E-03 LCSF005A-FLT LCSF005A CB OR OTHER LOCAL FAILURES IORV06 4.23E-09 0.04 % 5.30E-02 %T7-lE lORV BE 7.26E-03 2E22C002-FAULTS 5.39E-03 LCSC001A-PMS-SS 2E22C002 DG2B COOL WTR PUMP PLANT SPECIFIC FLT DATA (PSD i MOTORORIVEN PUMP LCSC001A SS FAULTS 18 2.04E-03 TBCCW-PSW-U1-FLT IORV06 4.13E-09 0.04 % 5.30E-02 %T7-lE (U1 )IETBCCW/PSW SYSTEMS FAILURES (FROM: TBCCW-OR-PSW-FL lORV t 7.26E-03 2E22C002-FAULTS 5.26E-03 CODG01P-FAULTS 2E22C002 DG2B COOL WTR PUMP PLANT SPECIFIC FLT DATA (PSD MOTORORIVEN PUMP CODG01P SS FAULTS 19 2.04E-03 TBCCW-PSW-U1-FLT IORV06 3.67E-09 0.04% 5.30E-02 %T7-lE (U1 )IETBCCW/PSW SYSTEMS FAILURES (FROM: TBCCWOR-PSW-F IORV 3.01 E-03 CST-HOTWELL-LF CST TO HOTWELL MAKEUP LOCAL FAULTS 4.26E-03 SWVYO2AX-INHTR 5.39E-03 LCSC001 A-PMS-SS INADEQUATE HEAT REMOVAL VIA AIR COOLING SWVYO2AX j 20 IORV06 3.59E-09 0.04 % MOTORDRIVEN PUMP LCSC001A SS FAULTS 5.30E-02 %T7-lE LORY IE 1.98E-02 2FWOOS-PATH-FLT 2FWOO5 MDRFP REG VALVE PATH FAULTS 4.26E-03 SWVYO2AX-INHTR i 8.02E-04 CODG035-VOC INADEOUATE HEAT REMOVAL VIA AIR COOLING SWVYO2AX MOTOR-OPERATED VALVE CODG035 OC

Totah

3.03E-07 3.04 % Cf Total CDF TKqasy. I.eE-45 C-19

'~

O O O O O O O O O O O 6

Appendix C - Tchte 5 Top Cutsets for ATWS Sequences Seq. Sequence Total CDF Frequency: 1.0E-05/yr Percent of No. Name CDF Total CDF Event Prob. - Event Name Accident-Sequence Event Description 1 ATWO3 1.65E-07 1.65% 2.40E+00 %T1-lE TURBINE TRIP WITH BYPASS IE 1.00E+00 ATWS ATWS FLAG TO IDENTIFY ATWS CUTSETS 5.20E-02 OADS-A 4.40E-02 OFWLC-A OP ACT: ADS AND RESTART PUMPS GIVEN OFWLC-A FAILS (ATWS) 3.00E-05 RPS-ARI-F OP ACT: FW CNTRL TO LOWER PWR < BYPASS CAPACITY (ATWS) 2 ATWO8 9.36E-08 RPS and ARI FAILURE ( RMIEP, NMPC, WNP-2) 0.94% 2.40E+00 %T1-lE TURBINE TRIP WITH BYPASS IE 1.00E+00 ATWS ATWS FLAG TO IDENTIFY ATWS CUTSETS 1.30E-03 OP-SBLC-A OP ACT: INITIATE SBLC (ATWS) 3.00E-05 RPS-ARI-F RPS and ARI FAILURE ( RMIEP, NMPC, WNP-2) 3 ATW12 7.78E-08 0.78 % 8.10E-01 %T2T4-lE 1.00E+00 ATWS TURBINE TRIP WITH CONDENSER UNAVAILABLE OR LOSS OF VACUUM ATWS FLAG TO IDENTIFY ATWS CUTSETS '

3.20E-03 ORPVLC-A 3.00E-05 RPS-ARI-F OP ACT: RESTORE RPV LEVEL TO MIX BORON (ATWS) 4 ATW12 5.59E-08 0.56 %

RPS and ARI FAILURE ( RMIEP, NMPC, WNP-2) 8.10E-01 %T2T4-lE 1.00E+00 ATWS TURBINE TRIP WITH CONDENSER UNAVAILABLE OR LOSS OF VACUUM ATWS FLAG TO IDENTIFY ATWS CUTSETS 2.30E-03 OADS-B 3.00E-05 RPS-ARI-F OP ACT: ADS AND RESTART PUMPS GIVEN FW UNAVAILABLE (ATW 5 ATW12 4.51 E-08 0.45 %

RPS and ARI FAILURE ( RMIEP, NMPC, WNP-2) 4.70E-01 %MSIV MSlV CLOSURE IE(including loss of 100 psi pneumatic IE) 1.00E+00 ATWS ATWS FLAG TO IDENTIFY ATWS CUTSETS 3.20E-03 ORPVLC-A 3.00E-05 RPS-ARI-F OP ACT: RESTORE RPV LEVEL TO MIX BORON (ATWS) 6 ATWO7 4.18E-08 RPS and ARI FAILURE ( RMIEP, NMPC, WNP-2) 0.42% 2.40E+00 %T1-lE TURBINE TRIP WITH BYPASS IE 1.00E+00 ATWS ATWS FLAG TO IDENTIFY ATWS CUTSETS  ;

5.80E-04 OPTL-A OP ACT: PTL LPCS, HPCS, LPCI PMPS (ATWS) 3.00E-05 RPS-ARI-F RPS and ARI FAILURE ( RMIEP, NMPC, WNP-2) i 7 ATW12 3.24E-08 0.32 % 4.70E-01 %MSIV MSIV CLOSURE lE(including loss of 100 psi pneumatic IE) 1.00E+00 ATWS ATWS FLAG TO IDENTIFY ATWS CUTSETS 2.30E-03 OADS-B 3.00E-05 RPS-ARI-F OP ACT: ADS AND RESTART PUMPS GIVEN FW UNAVAILABLE (ATW 8 ATW15 3.16E-08 RPS and ARI FAILURE ( RMIEP, NMPC, WNP-2) 0.32 % 8.10E-01 %T2T4-lE 1.00E+00 ATWS TURBINE TRIP WITH CONDENSER UNAVAILABLE OR LOSS OF VACUUM [

ATWS FLAG TO IDENTIFY ATWS CUTSETS 1.30E-03 OP-SBLC-A i OP ACT: INITIATE SBLC (ATWS) '

3.00E-05 RPS-ARI-F RPS and ARI FAILURE ( RMIEP, NMPC, WNP-2) 9 ATW14 2.20E-08 0.22 % 8.10E-01 %T2T4-lE  !

3.01 E-02 2C41C0018-PMP-F TURBlNE TRIP WITH CONDENSER UNAVAILABLE OR LOSS OF VACUUM 2C41C001B SLC PUMP B LOCAL FAULTS 3.01E-02 2C41C001 A-PMP-F 1.00E+00 ATWS 2C41C001 A SLC PUMP A LOCAL FAULTS (PSD)

ATWS FLAG TO IDENTIFY ATWS CUTSETS 3.00E-05 RPS-ARI-F RPS and ARI FAILURE ( RMIEP, NMPC, WNP-2) i 10 ATW15 1.83E-08 0.18 % 4.70E-01 %MSIV ,

MSIV CLOSURE IE(including loss of 100 psi pneumatic IE)  !

1.00E+00 ATWS ATWS FLAG TO IDENTIFY ATWS CUTSETS "

1.30E-03 OP-SBLC-A OP ACT: INITIATE SBLC (ATWS) 3.00E-05 RPS-ARI-F RPS and ARI FAILURE ( RMIEP, NMPC, WNP-2) ,

C-20

O O O O O O O O O O O Appendix C -Table 5 Top Cutsets for ATWS Sequences Seq. Sequence Total CDF Frequency: 1.0E-05/yr Percent of No. Name CDF Total CDF Event Prob. - Event Name Accident-Sequence Event 6 f_1.

11 ATW13 1.41 E-08 0.14 % 8.10E-01 %T2T4-iE 1.00E+00 ATWS TURBINE TRIP WITH CONDENSER UNAVAILABLE OR LOSS OF VACUU ATWS FLAG TO IDENTIFY ATWS CUTSETS 5.80E-04 OPTL-A OP ACT: PTL LPCS, HPCS, LPCI PMPS (ATWS) 12 ATW14 3.00E-05 RPS-ARI-F RPS and ARI FAILURE ( RMIEP, NMPC, WNP-2) 1.28E-08 0.13% 4.70E-01 %MSIV MSIV CLOSURE lE(including loss of 100 psi pneumatic IE) 3.01 E-02 2C41C0018-PMP-F 2C41C001B SLC PUMP B LOCAL FAULTS 3.01E-02 2C41C001 A-PMP-F 1.00E+00 ATWS 2C41C001 A SLC PUMP A LOCAL FAULTS (PSD)

ATWS FLAG TO IDENTIFY ATWS CUTSETS '

13 3.00E-05 RPS-ARI-F RPS and ARI FAILURE ( RMIEP, NMPC, WNP-2)

ATWO3 1.01E-08 0.10 % 2.40E+00 %T1-lE TURBINE TP.lP WITH BYPASS lE 1.00E+00 ATWS ATWS FLAG TO IDENTIFY ATWS CUTSETS 4.40E-02 OFWLC-A 3.20E-03 ORPVLC-A OP ACT: FW CNTRL TO LOWER PWR < BYPASS CAPACITY (ATWS 3.00E-05 RPS-ARI-F OP ACT: RESTORE RPV LEVEL TO MIX BORON (ATWS) 14 ATW13 8.18E-09 0.08 % RPS and ARI FAILURE ( RMIEP, NMPC, WNP-2) 4.70E-01 %MS!V MS;V CLOSURE lE(including loss of 100 psi pneumatic IE) 1.00E+00 ATWS ATWS FLAG TO IDENTIFY ATWS CUTSETS 5.80E-04 OPTL-A OP ACT: PTL LPCS, HPCS, LPCI PMPS (ATWS) 15 3.00E-05 RPS-ARI-F RPS and ARI FAILURE ( RMIEP, NMPC, WNP-2)

ATWO5 6.53E-09 0.07% 2.40E+00 %T1-lE TURBlNE TRIP WITH BYPASS IE

? 3.01E-02 2C41C0018-PMP-F 2C41C001B SLC PUMP B LOCAL FAULTS 3.01 E-02 2C41C001 A-PMP-F 1.00E+00 ATWS 2C41C001 A SLC PUMP A LOCAL FAULTS (PSD)

ATWS FLAG TO IDENTIFY ATWS CUTSETS 3.00E-05 RPS-ARI-F RPS and ARI FAILURE ( RMIEP, NMPC, WNP-2) 1.00E-01 SBLC2 16 ATW12 6.34E-09 0.06 % BORON INJECTION USING RWCU GIVEN SBLC FAILURE B.10E-01 %T2T4-lE 2.61E-04 ADS TURBINE TRIP WITH CONDENSER UNAVAILABLE OR LOSS OF VACU 1.00E+00 ATWS 6 OF 7 ADS VLVS Fall TO FUNCTION ON DEMAND (ADS OUANTIFIED M ATWS FLAG TO IDENTIFY ATWS CUTSETS 17 3.00E-05 RPS-ARI-F RPS and ARI FAILURE ( RMIEP, NMPC, WNP-2)

ATW14 5.90E-09 0.06 % 8.10E-01 %T2T4-lE 2.43E-04 FAULT-SLC-CO3 TURBINE TRIP WITH CONDENSER UNAVA!LABLE OR LOSS OF VACUU 1.00E+00 ATWS COMPONENT FAULT OCCURS IN STDBY LIQUlO CTRL SEGMENT C03 ATWS FLAG TO IDENTIFY ATWS CUTSETS 18 ATW17 3.00E-05 RPS-ARI-F RPS and ARI FAILURE ( RMIEP, NMPC, WNP-2) 5.09E-09 0.05 % 5.30E-02 %LOSP LOSS OF OFFSITE POWER INIT EVENT 3.20E-03 ORPVLC-A 3.00E-05 RPS-ARI-F OP ACT: RESTORE RPV LEVEL TO MIX BORON (ATWS) 19 ATW12 4.56E-09 0.05 % RPS and ARI FAILURE ( RMIEP NMPC, WNP-2) 2.40E+00 %T1-IE TURBINE TRIP WITH BYPASS lE

> 1.98E-02 2FWOO5-PATH-FLT 2FW005 MDRFP REG VALVE PATH FAULTS 1.00E+00 ATWS ATWS FLAG TO IDENTIFY ATWS CUTSETS 3.20E-03 ORPVLC-A 3.00E-05 RPS-ARI-F OP ACT: RESTORE RPV LEVEL TO MIX BORON (ATWS)

RPS and ARI FAILURE ( RMIEP, NMPC, WNP-2)

C-21

O O O O O O O O O O O Appendix C - Tcble 5 Top Cutsets for ATWS Sequences Seq. Sequence Total CDF Frequency: 1.0E-05/yr Percent of No. Name CDF Total CDF Event Prob. Event Name 20 ATW12 Accident-Sequence Event Description 4.40E-09 0.04 % 2.40E+00 %T1-lE TURBINE TRIP WITH BYPASS IE 1.91E-02 2FWO1PC-FAULTS 1.00E+00 ATWS COMPONENT FAULT OCCURS IN MAIN FEEDWATER SEGMENT L3 ATWS FLAG TO IDENTIFY ATWS CUTSETS 3.20E-03 ORPVLC-A 3.00E-05 RPS-ARI-F OP ACT: RESTORE RPV LEVEL TO MIX BORON (ATWS)

RPS and ARI FAILURE ( RMIEP, NMPC, WNP-2)

Totals: 6.62E-07 6.63 % Of Total CDF Frequency: 1.eE-95 c-22

y v v v v v v "

6 Appendix C - Table 6 Top Cutsets for LOCA Sequences Seq. 0:- - w Percent of Total CDF Frequency: 1.0E-05/yr ~

No. Name CDF- Total CDF Event Prob. Event Name 1 MLOO9 2.40E-08 0.24 %

Accident ?:;rw Event E ", _^ _

8.00E-04 %MLOCA MEDIUM LOCA IE 1.00E+00 ATWS 3.00E-05 RPS-ARI-F ATWS FLAG TO IDENTIFY ATWS CUTSETS 2 LLOO5 9.00E-09 0.09% RPS and ARI FAILURE ( RMIEP, NMPC, WNP-2) 3.00E-04 %LLOCA LARGE LOCA IE 1.00E+00 ATWS 3.00E-05 RPS-ARI-F ATWS FLAG TO IDENTIFY ATWS CUTSETS 3 MLOO5 8.13E-09 RPS and ARI FAILURE ( RMIEP, NMPC, WNP-2) 0.08 % 8.00E-04 %MLOCA MEDIUM LOCALE 7.26E-03 2E22C002 rAULTS 4 MLOO5 7.91 E-09 1.40E-03 OADS 2E22C002 OP DG2B ACT: INITIATE ADS COOL WTR PUMP PLANT SPECIFIC FLT DATA (P 0.08 % 8.00E-04 %MLOCA MEDIUM LOCALE 7.06E-03 2E22C001-PMS-SS 5 ML005 6.76E-09 1.40E-03 OADS 2E22C001 OP HPCS ACT: INITIATE ADSPUMP PLANT SPECIFIC FAULT DATA (GEN) 0.07% 8.00E-04 %MLOCA MEDIUM LOCAIE 6.04E-03 HP-MOV-FAULTS HPCS MOV VALVES FAULTS 6 MLOO5 t.40E-03 OADS OP ACT: INITIATE ADS 4.77E-09 0.05 % 8.00E-04 %MLOCA MEDIUM LOCALE 4.26E-03 SWVYO2AX-INHTR 7 1.40E-03 OADS INADEQUATE HEAT REMOVAL VIA AIR COOLING SWVYO2AX ML005 3.98E-09 0.04 % OP ACT: INITIATE ADS 8.00E-04 %MLOCA MEDIUM LOCALE 3.55E-03 HPCS-TOTAL-UUM HPCS total unavailability due to tr.ach and else maintenance 8 LLOO4 1.40E-03 OADS OP ACT: INITIATE ADS 3.00E-09 0.03% 3.00E-04 %LLOCA LARGE LOCA lE 9 MLOO5 1.00E-05 VSP 1.52E-09 0.02% VAPOR SUPPRESSION POOL 8.00E-04 %MLOCA MEDIUM LOCAIE 7.26E-03 2E22C002-FAULTS .

10 MLOO5 1.47E-09 2.61 E-04 ADS 2E22C002 DG2B COOL WTR PUMP PLANT SPECIFIC FLT DATA (PS 0.01 % 8.00E-04 %MLOCA 6 OF 7 ADS VLVS Fall TO FUNCTION ON DEMAND (ADS QUANTIFIED M MEDIUM LOCA IE 7.06E-03 2E22C001-PMS-SS 11 MLOOS 2.61E-04 ADS 2E22C001 HPCS PUMP PLANT SPECIFIC FAULT DATA (GEN) 1.26E-09 0.01 % 8.00E-04 %MLOCA 6 OF 7 ADS VLVS Fall TO FUNCTION ON DEMAND (ADS QUANTIFIED M MEDIUM LOCALE 6.04E-03 HP-MOV-FAULTS HPCS MOV VALVES FAULTS 12 MLOO5 2.61E-04 ADS 8.90E-10 0.01 % 8.00E-04 %MLOCA 6 OF 7 ADS VLVS FAllTO FUNCTION ON DEMAND (ADS QUANTIFIED M MEDIUM LOCA IE 4.26E-03 SWVYO2AX-INHTR 13 2.61E-04 ADS INADEOUATE HEAT REMOVAL VIA AIR COOLING SWVYO2AX MLOOS 7.41E-10 0.01 % 8.00E-04 %MLOCA 6 OF 7 ADS VLVS Fall TO FUNCTION ON DEMAND (ADS QUANTIFIED M MEDIUM LOCAIE 3.55E-03 HPCS-TOTAL-UUM HPCS total unavailability due to mech and elec maintenance 14 MLOOS 2.61E-04 ADS 3.23E-10 0.00% 8.00E-04 %MLOCA 6 OF 7 ADS VLVS Fall TO FUNCTION ON DEMAND (ADS OUANTIFIED M

, MEDIUM LOCA IE I 2.89E-04 HP-CHK-MAN-FLT 1.40E-03 OADS HPCS MANUAL OR CHECK VALVES FAULTS OP ACT: INITIATE ADS C-23

Appendix C - Table 6 '

Top Cutsets for LOCA Sequences seg. Sequence Total CDF Frequency: 1.0E-05/yr Percent of t No. Nome CDF Total CDF Event Prob-  ;

Event Name Accident-Sequence Event Description 15 LLOO3 7.84E-11 0.00 % 3.00E*4 %LLOCA ,

LARGE LOCA IE 7.26E-03 2E22C002-FAULTS  !

3.60E-05 CS-COOL-PMP-CM 2E22C002 DG2B COOL WTR PUMP PLANT SPECIFIC FLT DATA (PS 16 SL903 7.73E-11 0.00 % COMMON MODE CS COOL WTR PMPS 3.00E-03 %SLOCA SMALL LOCALE 1.24E-04 LPCI-CM  :

9.00E-03 OP-VENT-CNTNMNT COMMON MODE FAILURE OF ALL 3 LPCI PUMPS (BETA = .05)  !

OP ACT: VENT CONTAINMENT i 7.00E-02 RHR-RECOVERY 3.30E-01 SURVIVABILITY FAILURE TO RECOVER 1-OF-2 RHR TRAINS WITHIN 33 Hrs (ERIN) 17 LLOO3 7.63E-11 0.00 % INJECTION FAILS TO SURVIVE AFTER CONTAINMENT FAILS (ERIN) l 3.00E-04 %LLOCA LARGE LOCALE 7.06E-03 2E22C001-PMS-SS

' 3.60E-05 CS-COOL-FMP-CM 2E22C001 HPCS PUMP PLANT SPECIFIC FAULT DATA (GEN) 18 LLOO3 6.52E-11 0.00 % COMMON MODE CS COOL W(R PMPS 3.00E-04 %LLOCA LARGE LOCA IF 6.04E-03 HP-MOV-FAULTS HPCS MOV VALVES FAULTS 19 3.60F 05 CS-COOL-PMP-CM COMMON MODE CS COOL WTR PMPS ML005 6.02E-t 1 0.00 %  % 0E-04 %MLOCA  ;

MEDIUM LOCA lE '

2.89E-04 HP-CHK-MAN-FLT HPCS MANUAL OR CHECK VALVES FAULTS 2.61 E-04 ADS 20 LLOO3 6.02E-11 0.00 % 6 OF 7 ADS VLVS Fall TO FUNCTION ON DEMAND (ADS QUANTIFIED M 3.00E-04 %LLOCA LARGE LOCA lE i

7.26E-03 2E22CC92-FAULTS 5.26E-03 CODG01P-FAULTS 2E22C002 DG2B COOL WTR PUMP PLANT SPECIFIC FLT DATA (PSD MOTOR-DRIVEN PUMP CODG01P SS FAULTS i

21 5.26E-03 2DG01P-FAULTS LLOO3 5.86E-11 0.00 % DG2A LOCALE COOL WTR PUMP 2DG01P PLANT SPECIFIC FAULTS (PSD) 3.00E-04 %LLOCA LARGE 5.26E-03 CODG01P-FAULTS MOTOR-DRIVEN PUMP CODG01P SS FAULTS 5.26E-03 2DG01P-FAULTS 7.06E-03 2E22C001-PMS-SS DG2A COOL WTR PUMP 2DG01P PLANT SPECIFIC FAULTS (PSD) 22 LLOO3 5.01 E-11 0.00 % 2E22C001 HPCS PUMP PLANT SPECIFIC FAULT DATA (GEN) 3.00E-04 %LLOCA LARGE LOCAIE 5.26E-03 CODG01P-FAULTS MOTOR-DRIVEN PUMP C0DG01P SS FAULTS 5.26E-03 2DG01P-FAULTS 6.04E-03 HP-MOV-FAULTS DG2A COOL WTR PUMP 2DG01P PLANT SPECIFIC FAULTS (PSD)

HPCS MOV VALVES FAULTS

! 23 LLOO3 4.85E-11 0.00 %

3.00E-04 %LLOCA LARGE LOCALE

' 7.26E-03 2E22C002-FAULTS 5.26E-03 CODG01P-FAULTS 2E22C002 DG28 COOL WTR PUMP PLANT SPECIFIC FLT DATA (P MOTOR-DRIVEN PUMP CODG01P SS FAULTS 24 LLOO3 4.23E-03 SEVYO3CB-FMS-SS MOTOR-DRIVEN FAN SEVYO3CB SS FAULTS 4.72E-11 0.00 % 3.00E-04 %LLOCA LARGE LOCALE i

5.26E-03 CODG01P-FAULTS MOTOR-DRIVEN PUMP CODG01P SS FAULTS 4.23E-03 SEVYO3CB-FMS-SS MOTOR-DR!VEN FAN SEVYO3CB SS FAULTS 25 LLOO3 7.06E-03 2E22C001-PMS-SS 4.60E-11 0.00 % 3.00E-04 %LLOCA 2E22C001 HPCS PUMP PLANT SPECIFIC FAULT DATA (GEN)

LARGE LOCALE 4.26E-03 SWVYO2AX-INHTR 3.60E-05 CS-COOL-PMP-CM INADEOUATE HEAT REMOVAL VIA AIR COOLING SWVYO2AX

' COMMON MODE CS COOL WTR PMPS C-24

m , v v v " ~

6 " - " "

Appendix C - Tchle 6 Top Cutsets for LOCA Sequences Seq. Sequence Totat CDF Frequency: 1.0E-05/yr Percent of No. Name CDF Total CDF Event Prob. Event Name 26 MLOO5 4.38E-11 Accident-Sequen.w Event DescrlWc+.

0.00 % 8.00E-04 %MLOCA MEDIUM LOCA IE ~

3.91 E-05 1E243-1-480-LPW 1.40E-03 OADS LOSS OF POWER AT 480 BUS 1E243-1 27 LLOO3 4.03E-11 0.00 % OP ACT: INITIATE ADS 3.00E-04 %LLOCA LARGE LOCA IE 5.26E-03 CODG01P-FAULTS 4.23E-03 SEVYO3CB-FMS-SS MOTORORIVEN PUMP CODG01P SS FAULTS 6.04E-03 HP-MOV-FAULTS MOTOR-DRIVEN FAN SEVYO3CB SS FAULTS HPCS MOV VALVES FAULTS Totsh: 7.45E-08 0.75 % O'TotalCDFFrequency 1.9E-05 C-25 f Of _ _ _ _ _ - _ _ _ _ _ _ _ -

]O O O O O O O O O O O Appendix C - Ttble 7 Top Cutsets for SBO Sequences Seq. Sequence Total CDF Frequency: 1.0E-05dr Percent of No. Name CDF Total CDF Event Prob. Event Name 1 SBO14 9.18E-11 Accident-Sequence Event Description 0.00 % 1.60E-02 %DLOSP t DUAL LOSS OF OFFSITE POWER lE 9.62E-03 SY-VNF-HVDG2A 3.82E-03 DGOV01YA-FAULTS ROOM HVDG2A COOLING OR VENTILATON SYSTEM FAULTS OVD01YA MOD FAULTS 4.33E-02 2E22S001-FAULTS 3.60E-03 RX-LO-PR-SGNL-F DG2B PLANT SPECIFIC FAULTS (PSD) 2 SBO14 9.t2E-11 0.00 % 1.60E-02 %DLOSP RCIC RESPONSE TO RX LO PRES SGNL Fall (FROM RCIACT-X DUAL LOSS OF OFFSITE POWER IE 9.62E-03 SY-VNF-HVDG2A 4.33E 02 2E22S001-FAULTS ROOM HVDG2A COOLING OR VENTILATON SYSTEM FAULTS 3.80E-02 DGOV03YA-FAULTS DG2B PLANT SPECIFIC FAULTS (PSD)

OVD03YA MOD FAULTS 3 SBO14 3.60E-03 RX-LO-PR-SGNL-F 8.69E-11 0.00 % 1.60E-02 %DLO9P RCIC RESPONSE TO RX LO PRES SGNL FAIL (FROM RCIACT DUAL LOSS OF OFFSITE POWER IE 9.62E-03 SY-VNF-HVDG2A 3.82E-03 DGOV01YA-FAULTS ROOM HVDG2A COOLING OR VENTILATION SYSTEM FAULTS OVD01YA MOD FAULTS 1.53E-02 RCIC001X-TDP-SS TURBINE-DRIVEN PUMP RCIC001 SS FAULTS 4 S8014 9.69E-03 DG28-AUX-SYS 8.64E-11 0.00 % 1.60E-02 %DLOSP HPCS DIESEL AUXILIARY SYTEMS FAILURE DUAL LOSS OF OFFSITE POWER IE 9.62E-03 SY-VNF-HVDG2A 1.53E-02 RCIC001X-TDP-SS ROOM HVDG2A COOLING OR VENTILATION SYSTEM FAULTS 1 TURBINE-DRIVEN PUMP RCIC001 SS FAULTS 9.69E-03 DG28-AUX-SYS HPCS DIESEL AUXILIARY SYTEMS FAILURE S S8014 3.80E-03 DGOV03YA-FAULTS OVD03YA MOD FAULTS 8.21E-11 0.00% 1.60E-02 %DLOSP DUAL LOSS OF OFFSITE POWER lE 7.63E-02 DG2A-FAULTS DG2A PLANT SPECIFIC FAULTS 1.82E-03 HCIC-EXHST-VLVS RCIC EXHAUST VALVES MODULE 3.82E-03 DGOV01YA-FAULTS OVD01YA MOD FAULTS 9.69E-03 DG28-AUX-SYS  ;

6 SBO14 8.15E-t 1 0.00 % HPCS DIESEL AUXlLIARY SYTEMS FAILURE 1.60E-02 %DLOSP DUAL LOSS OF OFFSITE POWER IE 7.63E-02 DG2A-FAULTS DG2A PLANT SPECIFIC FAULTS 1.82E-03 RCIC-EXHST-VLVS RCIC EXHAUST VALVES MODULE 9.69E-03 DG28-AUX-SYS HPCS DIESEL AUXILIARY SYTEMS FAILURE I 7 SBO14 3.80E-03 DGOV03YA-FAULTS OVD03YA MOD FAULTS 6.73E-11 0.00 % 1.60E-02 %DLOSP DUAL LOSS OF OFFSITE POWER IE 9.62E-03 SY-VNF-HVDG2A 3.62E-03 DGOV01YA-FAULTS ROOM HVDG2A COOLING OR VENTILATON SYSTEM FAULTS OVD01YA MOD FAULTS 9.69E-03 DG2B-AUX-SYS HPCS DIESEL AUXILIARY SYTEMS FAILURE 8

1.18E-02 RCIF063G-VOC MOTOR-OPERATED VALVE RCIF063C OC SBO14 6.69E-11 0.00 % 1.60E-02 %DLOSP DUAL LOSS OF OFFSITE POWER IE 9.62E-03 SY-VNF-HVDG2A 9.69E-03 DG2B-AUX-SYS ROOM HVDG2A COOLING OR VENTILATON SYSTEM FAULTS HPCS DIESEL AUXILIARY SYTEMS FAILURE 1.18E-02 RCIF063C-VOC MOTOR-OPERATED VALVE RCIF063C OC 3.80E-03 DGOV03YA-FAULTS OVD03YA MOD FAULTS C-26 s

.........., g Appendix C - Ttble 7 Top Cutsets for SBO Sequences Seq. Sequence Total CDF Frequency: 1.0E-05/yr Percent of No. Name CDF Total CDF Event Prob. Event Name Accident-Sequence Event Description 9 SBO14 6.51 E-11 0.00% 1.60E-02 % DL O Fr' DUAL LOSS OF OFFSITE POWER IE 9.62E-03 SY-VNF-HVDG2A ROOM HVDG2A COOLING OR VENTILATION SYSTEM FAULTS 3.82E-03 DGOV01YA-FAULTS OVD01YA MOD FAULTS 1.53E-02 RCIC001X-TDP-SS TURBINE-DRIVEN PUMP RCIC001 SS FAULTS 7.26E-03 2E22C002-FAULTS 10 SBO14 6.47E-11 0.00% 2E22C002 DG2B COOL WTR PUMP PLANT SPECIFIC FLT DATA (PSD 1.60E-02 %DLOSP DUAL LOSS OF OFFSITE POWER lE 9.62E-03 SY-VNF-HVDG2A ROOM HVDG2A COOLING OR VENTIL ATION SYSTEM FAULTS 1.53E-02 RCIC001X-TDP-SS TURBINE-DRIVEN PUMP RCIC001 SS FAULTS 7.26E-03 2E22C002-FAULTS 3.80E-03 DGOV03YA-FAULTS 2E22C002 DG2B COOL WTR PUMP PLANT SFECIFIC FLT DATA (PSD OVD03YA MOD FAULTS 11 SBO14 6.34E-11 0.00% 1.60E-02 %DLOSP DUAL LOSS OF OFFSITE POWER IE 7.06E-03 2E22C001-PMS-SS 9.62E-03 SY-VNF-HVDG2A 2E22C001 HPCS PUMP PLANT SPECIFIC FAULT DATA (GEN)

ROOM HVDG2A COOLING OR VENTILATION SYSTEM FAULTS 3.82E-03 DGOV01YA-FAULTS OVD01YA MOD FAULTS 1.53E-02 RCIC001X-TDP-SS TURB!NE-DRIVEN PUMP RCIC001 SS FAULTS 12 SBO14 6.30E-11 0.00% 1.60E-02 %DLOSP DUAL LOSS OF OFFSITE POWER lE 7.06E-03 2E22C001-PMS-SS 9.62E-03 SY-VNF-HVDG2A 2E22C001 HPCS PUMP PLANT SPECIFIC FAULT DATA (GEN)

ROOM HVDG2A COOLING OR VENTILATION SYSTEM FAULTS 1.53E-02 RCIC001X-TDP-SS TURBINE-DRIVEN PUMP RCIC001 SS FAULTS 13 3.80E-03 DGOV03YA-FAULTS OVD03YA MOD FAULTS SBO14 5.76E-11 0.00 % 1.60E-02 %DLOSP DUAL LOSS OF OFFSITE POWER lE 9.62E-03 SY-VNF-HVDG2A ROOM HVDG2A COOLING OR VENTILATION SYSTEM FAULTS 5.26E-03 CODG01P-FAULTS MOTOR-DRIVEN PUMP CODG01P SS FAULTS 9.69E-03 DG28-AUX-SYS HPCS DIESEL AUXILIARY SYTEMS FAILURE 14 7.34E-03 RCIF013C-FAULTS MOV RCIC F013 VALVE FAULTS SBO14 5.42E-11 0.00% 1.60E-02 %DLOSP DUAL LOSS OF OFFSITE POWER IE 9.62E-03 SY-VNF-HVDG2A 3.82E-03 DGOV01YA-FAULTS ROOM HVDG2A COOLING OR VENTILATION SYSTEM FAULTS OVD01YA MOD FAULTS 1.53E-02 RCIC001X-TDP-SS TURBINE-DRIVEN PUMP RCIC001 SS FAULTS 6.04E-03 HP-MOV-FAULTS HPCS MOV VALVES FAULTS 15 S9014 5.38E-11 0.00% 1.60E-02 %DLOSP DUAL LOSS OF OFFSITE POWER IE 9.62E-03 SY-VNF-HVDG2A ROOM HVDG2A COOLING OR VENTUTION SYSTEM FAULTS 1.53E-02 RCIC001X-TDP-SS TURBINE-DRIVEN PUMP RCIC001 SS FAULTS 6.04E-03 HP-MOV-FAULTS HPCS MOV VALVES FAULTS 3.80E-03 DGOV03YA-FAULTS OVD03YA MOD FAULTS 16 SBO14 5.38E-11 0.00 % 1.60E-02 %DLOSP DUAL LOSS OF OFFSITE POWER IE 9.62E-03 SY-VNF-HVDG2A 5.26E-03 CODG01P-FAULTS ROOM HVDG2/' COOLING OR VENTILATION SYSTEM FAULTS MOTOR-DRIVEi, PUMP CODG01P SS FAULTS 6.85E-03 RCIF046C-FAULTS MOTOR-OPERATED VALVE RCIF046C CC 9.69E-03 DG28-AUX-SYS HPCS DIESEL AUXILIARY SYTEMS FAILURE C-27

I Appendix C - Tchle 7 Top Cutsets for SBO Sequences Seq. Sequence Total CDF Frequency: 1.0E-05/yr Percent of No. Name CDF Total CDF Event Prob. Event Name Accident-Sequence Event Description 17 SB014 5.34E-11 0.00 % 1.60E-02 %DLOSP ' DUAL LOSS OF OFFSITE POWER IE 9.62E-03 SY-VNF-HVDG2A 5.26E-03 CODG01P-FAULTS ROOM HVDG2A COOLING OR VENTILATION SYSTEM FAULTS MOTOR-DRIVEN PUMP CODG01P SS FAULTS 9.69E-03 DG28-AUX-SYS HPCS DIESEL AUXILIARY SYTEMS FAILURE 6.81E-03 RCIF045C-VCC MOTOR-OPERATED VALVE RCIF045C CC 18 SBOt4 5.10E-11 0.00 % 1.60E-02 %DLOSP DUAL LOSS OF OFFSITE POWER IE '

2.24E-03 DGOVOICA-FMS-SS OVD01C MOTOR-DRIVEN FAN DGOVOICA SS FAULTS 9.62E-03 SY-VNF-HVDG2A 1.53E-02 RCIC001X-TDP-SS ROOM HVDG2A COOLING OR VENTILATION SYSTEM FAULTS TURBINE-DRIVEN PUMP RCIC001 SS FAULTS 19 9.69E-03 DG28-AUX-SYS HPCS DIESEL AU>0LIARY SYTEMS FAILURE SBO14 5.05E-11 0.00 % 1.60E-02 %DLOSP DUAL LOSS OF 0FFSITE POWER IE 9.62E-03 SY-VNF-HVDG2A 3.82E-03 DGOV01YA-FAULTS ROOM HVDG2A COOLING OR VENTILATION SYSTEM FAULTS OVD01YA MOD FAULTS 7.26E-03 2E22C002-FAULTS 1.18E-02 RCIF063C-VOC 2E22C002 DG2B COOL WTR PUMP PLANT SPECIFIC FLT DATA (P 20 SBO14 5.01 E-11 0.00 % MOTOR-OPERATED VALVE RCIF063C OC 1.60E-02 %DLOSP DUAL LOSS OF OFFSITE POWER IE 9.62E-03 SY-VNF-HVDG2A 7.26E-03 2E22C002-FAULTS ROOM HVDG2A COOLING OR VENTILATION SYSTEM FAULTS l 1.18E-02 RCIF063C-VOC 2E22C002 DG2B COOL WTR PUMP PLANT SPECIFIC FLT DATA (P MOTOR-OPERATED VALVE RCIF063C OC 21 3.80E-03 DGOV03YA-FAULTS OVD03YA MOD FAULTS SBO14 4.91 E-11 Q.00% 1.60E-02 %DLOSP DUAL LOSS OF OFFSITE POWER lE

'.06 E-03 2E22C001-PMS.SS 9.62E-03 SY-VNF-HVDG2A 2E22C001 HPCS PUMP PLANT SPECIFIC FAULT DATA (GEN) 3.82E-03 DGOV01YA-FAULTS ROOM HVDG2A COOLING OR VENTILATION SYSTEM FAULTS OVD01YA MOD FAULTS 22 1.18E-02 RCIF063C-VOC MOTOR-OPERATED VALVE RCIF063C OC SBO14 4.88E-t 1 0.00 % 1.60E-02 %DLOSP ,

DUAL LOSS OF OFFSITE POWER IE i 7.06E-03 2E22C001-PMS-SS 9.62E-03 SY-VNF-HVDG2A 2E220001 HPCS PUMP PLANT SPECIFIC FAULT DATA (GEN) 1.18E-02 RCIF063C-VOC ROOM HVDG2A COOLING OR VENTILATION SYSTEM FAULTS MOTOR-OPERATED VALVE RCIF063C OC 23 SBO14 3.80E-03 DGOV03YA-FAULTS OVD03YA MOD FAULTS 4./dC 11 0.00 % 1.60E-02 %DLOSP DUAL LOSS OF OFFSITE POWER IE 3.82E-03 DGOV01YA-FAULTS OVD01YA MOD FAULTS 1.53E-02 RCIC001X-TDP-SS TURBINE-DRIVEN PUMP RCIC001 SS FAULTS 9.69E-03 DG28-AUX-SYS HPCS DIESEL AUXILIARY SYTEMS FAILURE 24 SBO14 5.26E-03 2DG01P-FAULTS  !

4.72E-11 0.00 % 1.60E-02 %DLOSP DG2A COOL WTR PUMP 2DG01P PLANT SPECIFIC FAULTS (PSD) t DUAL LOSS OF OFFSITE POWER IE l 1.53E-02 RCIC001X-TDP-SS TURBINE-DRIVEN PUMP RCIC001 SS FAUu d 9.69E-03 DG28-AUX-SYS HPCS DIESEL AUXlLIARY SYTEMS FAILURE t

5.26E-03 2DG01P-FAULTS 3.80E-03 DGOV03YA-FAULTS DG2A COOL WTR PUMP 2DG01 P PLANT SPECIFIC FAULTS (PSD OVD03YA MOD FAULTS t C-28

Appendix C - Tcble 7 Top Cutsets for SBO Sequences Seq. Sequence Total CDF Frequency: 1.0E-05/yr Percent of No. Name CDF Total CDF Event Prob. Event Name Accident-Sequence Event Description E5 SBO14 4.63E-11 0.00 % 1.60E-02 %DLOSP DUAL LOSS OF OFFSITE POWER lE 1.82E-03 RCIC-EXHST-VLVS RCIC EXHAUST VALVES MODULE 9.62E-03 SY-VNF-HVDG2A ROOM HVDG2A COOLING OR VENTILATION SYSTEM FAULTS 3.82E-03 DG0V01YA-FAULTS OVD01YA MOD FAULTS 4.33E-02 2E22S001-FAULTS 26 SBO14 4.60E-11 0.00 % DG2B PLANT SPECIFIC FAULTS (PSD) 1.60E-02 %DLOSP DUAL LOSS OF OFFSITE POWER IE 1.82E-03 RCIC-EXHST-VLVS RCIC EXHAUST VALVES MODULE 9.62E-03 SY-VNF-HVDG2A 4.33E-02 2E22S001-FAULTS ROOM HVDG2A COOLING OR VENTILATION SYSTEM FAULTS DG2B PLANT SPECIFIC FAULTS (PSD) 27 3.80E-03 DGOV03YA-FAULTS OV%DLOSP SBO14 4.20E-11 0.00% 1.60E-02 %DLOSP DUAL LOSS OF OFFSITE POWER lE 9.62E-03 SY-VNF-HVDG2A 3.82E-03 DGOV01YA-FAULTS ROOM HVDG2A COOLING OR VENTILATION SYSTEM FAULTS OVD01YA MOD FAULTS 6.04E-03 HP-MOV-FAULTS HPCS MOV VALVES FAULTS 28 1.18E-02 RCIF063C-VOC MOTOR-OPERATED VALVE RCIF060C OC SB014 4.18E-11 0.00 % 1.60E-02 %DLOSP DUAL LOSS OF OFFSITE POWER IE 9.62E-03 SY-VNF-HVDG2A 3.82E-03 DGOV01YA-FAULTS ROOM H\DG2A COOLING OR VENTIL/ TION SYSTEM FAULTS t OVD01YA MOD FAULTS 9.69E-03 DG2B-AUX-SYS HPCS DIESEL AUXILIARY SYTEMS FAILURE 29 7.34E-03 RCIF013C-FAULTS MOV RCIC F013 VALVE FAULTS SBO14 4.17E-11 0.00 % 1.60E-C2 %DLOSP DUAL LOSS OF OFFSITE POWER IE 9.62E-03 SY-VNF-HVDG2A 6.04E-03 HP-MOV-FAULTS ROOM HVDG2A COOLING OR VENTILATION SYSTEM FAULTS HPCS MOV VALVES FAULTS 1.18E-02 RClF063C-VOC MOTOR-OPERATED VALVE RCIF063C OC 30 3.80E-03 DGOV03YA-FAULTS OVD03YA MOD FAULTS SBO14 4.16E-11 0.00 % 1.60E-02 %DLOSP DUAL LOSS OF OFFSITE POWER IE 9.62E-03 SY-VNF-HVDG2A 9.69E-03 DG2B-AUX-SYS ROOM HVDG2A COOLING OR VENTILATION SYSTEM FAULTS HPCS DIESEL AUXILIARY SYTEMS FAILURE 7.34E-03 RCIF013C-FAULTS MOV RCIC F013 VALVE FAULTS 3.80E-03 DGOV03YA-FAULTS OVD03YA MOD FAULTS Totah: 1.79E-09 0.02 % Of Total CDF Frequency: 1.0E-05 C-29

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