Reliability Analysis of the Electrical Power Distribution System to Selected Portions of the Nuclear HVAC System Rev 00A, ICN 00

100-PSA-EE00-00100-000-00A

December 2004

1. PURPOSE 
A design requirement probability of 0.01 or less in a 4-hour period ensures that the nuclear 
heating, ventilation, and air-conditioning (HVAC) system in the primary confinement areas of 
the Dry Transfer Facilities (DTFs) and Fuel Handling Facility (FHF) is working during a 
Category 1 drop event involving commercial spent nuclear fuel (CSNF) assemblies (BSC 2004a , 
Section 5.1.1.48). This corresponds to an hourly HVAC failure rate of 2.5E-3 per hour or less, 
which is contributed to by two dominant causes: equipment failure and loss of electrical power. 
Meeting this minimum threshold ensures that a Category 1 initiating event followed by the 
failure of HVAC is a Category 2 event sequence. 
The two causes for the loss of electrical power include the loss of offsite power and the loss of 
onsite power distribution. Thus, in order to meet the threshold requirement aforementioned, the 
failure rate of mechanical equipment, loss of offsite power, and loss of onsite power distribution 
must be less than or equal to 2.5E-3 per hour for the nuclear HVAC system in the primary 
confinement areas of the DTFs and FHF. The loss of offsite power occurs at a frequency of 
1.1E-5 per hour (BSC 2004a, Section 5.1.1.48). 
The purpose of this analysis is to determine the probability of occurrence of the unavailability of 
the nuclear HVAC system in the primary confinement areas of the DTFs and FHF due to loss of 
electrical power. In addition, this analysis provides insights on the contribution to the 
unavailability of the HVAC system due to equipment failure. The scope of this analysis is 
limited to finding the frequency of loss of electrical power to the nuclear HVAC system in the 
primary confinement areas of the DTFs and FHF. 
2. QUALITY ASSURANCE 
The development of this analysis is subject to requirements of the Quality Assurance 
Requirements and Description (DOE 2004). This analysis is developed in accordance with 
procedure AP-3.12Q, Design Calculations and Analyses. Technical product inputs and 
references are identified and tracked in accordance with AP-3.15Q, Managing Technical Product 
Inputs. 
3. USE OF COMPUTER SOFTWARE 
3.1 SOFTWARE APPROVED FOR QUALITY ASSURANCE WORK 
.. Title: SAPHIRE (Systems Analysis Programs for Hands-on Integrated Reliability 
Evaluations) 
.. Version/Revision Number: 7.18 
.. Software Tracking Number: 10325-7.18-00 
.. Status/Operating System: Microsoft Windows 2000 Professional 
.. Computer Type: DELL GX240 Desktop PC 
.. Computer Number: CRWMS M&O Tag Number 501141

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The software code SAPHIRE V7.18 (BSC 2002) is used to develop and quantify fault trees in 
this analysis. SAPHIRE V7.18 (BSC 2002) is a state-of-the-art probabilistic risk analysis 
software program that utilizes integrated event tree and fault tree methodology to develop and 
analyze the logical interactions that may occur between systems and components to determine 
the probability of an events occurrence. 
SAPHIRE V7.18 (BSC 2002) is qualified software that was obtained from Software 
Configuration Management. Independent software testing and verification using test cases of 
physical problems are documented in Independent Verification and Validation Report for Legacy 
Code SAPHIRE V7.18 (BSC 2003, Section 3.5). This software is appropriate for use in the 
present analysis, and is used only within its range of validation in accordance with 
LP-SI.11Q-BSC, Software Management. 
3.2 OTHER SOFTWARE 
The Microsoft Excel 97 spreadsheet program is used to perform simple calculations as 
documented in Section 6.3.3. User-defined formulas, inputs, and results are documented in 
sufficient detail in Sections 6.1 through 6.4 to allow for the independent duplication of various 
computations without recourse to the originator. This software is exempt from the requirements 
of LP-SI.11Q-BSC, Software Management. 
4. INPUTS 
4.1 Electrical power system description is established by the Electrical Power System 
Description Document (BSC 2004b). This input contains the latest design information 
available for this report. 
4.2 Electrical power system architecture is established by the Electrical Power System 
Description Document (BSC 2004b, Figure 4-1 and 4-3), and Switchyard Switchgear 
Bldg Single Line Diagram 125 V DC System (BSC 2004c). These inputs contain the 
latest design information available for this report. 
4.3 Sources used for failure rate data are the Generic Component Failure Data Base (Eide 
and Calley 1993, Tables 1 and 2) and IEEE Guide to the Collection and Presentation of 
Electrical, Electronic, Sensing Component, and Mechanical Equipment Reliability Data 
for Nuclear-Powered Generating Stations (IEEE Std 500-1984 (Reaffirmed 1991)). 
These sources have compiled failure rate data for use in probabilistic risk assessment. 
4.4 Categorization of Event Sequences for License Application (BSC 2004a, Sections 
5.1.1.48 and 6.3.1.3) establishes the threshold failure probability that ensures that a 
Category 1 initiating event followed by the failure of HVAC is a Category 2 event 
sequence. This input also provides the failure rate for the loss of offsite power. 
4.5 Reliability Analysis of the Mechanical System in Selected Portions of the Nuclear HVAC 
System (BSC 2004d , Section 6.3) establishes the success requirement for the nuclear 
HVAC system in the primary confinement areas of the DTFs and FHF.

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5. ASSUMPTIONS 
5.1 Assumption: Electrical power to at least one important motor control center (MCC I) is 
sufficient to prevent the failure of the nuclear HVAC system in the primary confinement 
areas of the DTFs and FHF. 
Basis: The basis comes from the success requirement in the Reliability Analysis of the 
Mechanical System in Selected Portions of the Nuclear HVAC System (BSC 2004d, 
Section 6.3), which identifies the threshold for success of the HVAC system as being two 
supply fans and two exhaust fans for the DTFs and one supply fan and one exhaust fan 
for the FHF. An MCC I powers two supply and two exhaust fans at a time for the DTFs, 
while an MCC I powers one supply and one exhaust fan at a time for the FHF. 
Used in: Sections 6.2.1, 6.2.3, 6.3, 7.2, 7.3, 7.5 and Figure A-2. 
5.2 Assumption: Failures on loads not used for the distribution of power to the fans of 
interest are not analyzed in detail, but are compared to other loads of their kind that are 
fully analyzed. 
Basis: Most loads that feed from the same power bus have the same components and 
distribute power similarly. Thus, by analyzing the failure of one load, an educated 
estimate can be done for the other loads. 
Used in: Sections 6.3.2.1, 6.3.2.2, 6.3.2.3.2, and 6.3.3. 
5.3 Assumption: If the emergency diesel generator (EDG) is successfully started and 
connected to the emergency SWGR of interest, all appropriate loads will be sequentially 
connected and powered. 
Basis: The EDG is actuated automatically by an electronic control system, which when 
successful, will also work to sequentially connect the loads to the emergency SWGR bus. 
Automatic connection of EDGs and automatic sequencing of breakers to the emergency 
SWGR buses is described in Electrical Power System Description Document (BSC 
2004b, Section 4.1.1.4). 
Used in: Section 7. 
5.4 Assumption: The basic mission time (t) used for calculating the failure probabilities of 
components is equal to 4 hours, which is the time required for the HVAC in the primary 
confinement areas of the DTFs and FHF to be in operation after a Category 1 drop 
involving CSNF assemblies. 
Basis: This is a design requirement that ensures that a Category 1 initiating event 
followed by the failure of HVAC is a Category 2 event sequence (BSC 2004a, Section 
5.1.1.48). 
Used in: Sections 6.2.4, 6.3.3, 6.4, and 7.

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5.5 Assumption: No credit is given for human operator interaction with the electrical power 
distribution system and thus, no human failure is analyzed in the Fault Tree Analysis 
(FTA). 
Basis: The Electrical Power System Description Document (BSC 2004b, Section 3.2.6) 
does not specify human operator interaction within the system other than the manual 
connection of Substation B to the switchyard. It does describe most functions within the 
electrical power distribution system as being automated. When more operator interaction 
information is available, human error will be considered as a failure mode for this system. 
Used in: Throughout document. 
5.6 Assumption: Maintenance on redundant subsystems and components will be performed 
with a staggered schedule. 
Basis: This is a recommended practice for highly reliable systems as a means of reducing 
the probability of common-cause failure (CCF). This permits use of the staggered 
maintenance Alpha Factor Model for CCF. 
Used in: Sections 6.2.5, and 6.3.4. 
5.7 Assumption: Power distribution from LC A and LC B to the supply and exhaust fans on 
the MCC Is will be as shown in Figure A-2. 
Basis: This is standard design as described in the Electrical Power System Description 
Document (BSC 2004b ). 
Used in: Throughout document. 
5.8 Assumption: Normal cooling of all electrical components is always present. 
Basis: There is not enough information to indicate that loss of cooling to electrical 
components located in the equipment room is a potential cause of power failure in the 
required 4-hr mission time. When this information is available, loss of cooling to 
electrical equipment will be considered as a failure mode for this system. Currently, the 
failure rates of some of the electrical components include generic overheating. 
Used in: Throughout document.

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6. ANALYSIS 
6.1 OBJECTIVE 
The objective of this analysis is to perform an FTA on the portion of the onsite electrical power 
distribution system that provides power from the offsite power source to the Nuclear HVAC 
supply and exhaust fans in the primary confinement areas of the DTFs and FHF to determine its 
reliability. Because the loss of power distribution to the nuclear HVAC system in the primary 
confinement areas of the DTFs (DTF 1 and DTF 2) and FHF occurs the same way, only one FTA 
is performed. The text in the FTA refers to the DTF 1, but the results apply to the DTF 1, 
DTF 2, and FHF. 
6.2 METHODOLOGY 
FTA is a deductive failure analysis that focuses on one particular undesired event, called a top 
event, and provides a logic model for determining causes and quantifying the probability of 
occurrence for that event. FTA is performed to determine the safety and reliability of a system 
with the use of Boolean logic and probability theory. It also helps to improve the understanding 
of the system in question, identify components that may need further testing or redundancy, and 
identify root causes of equipment failure. This analysis is performed using the methods of the 
Fault Tree Handbook (Vesely et al. 1981). Steps in the analysis process are described in 
Sections 6.2.1 through 6.2.6. 
6.2.1 Step One: Identify Top Event to be Analyzed 
The undesirable event for the system in question is termed top event. The top event is then 
logically broken down into all credible ways it can occur. Because the lower level break down 
of the top event includes only those faults that contribute to this top event, it is important to 
identify the specific top event, which corresponds to a particular system failure mode. The top 
event for this analysis is Failure of the electrical power distribution system to provide power to 
the nuclear HVAC system in the DTF 1 primary confinement. 
Once the top event has been established, success criteria must be identified. Identifying the 
success criteria helps break down the top event by defining the specific threshold that must be 
met in order to maintain the system in working order. For example, the nuclear HVAC system in 
the primary confinement areas of the DTFs is successful as long as one MCC I, which contains 
one set of two supply fans and one set of two exhaust fans, is powered (Assumption 5.1). This 
means that anything less than one MCC I powered designates failure and results in the top event. 
6.2.2 Step Two: Understand the System 
In order to identify the events that directly contribute to the top event, it is necessary to have a 
good understanding of the system being analyzed. Research must be done to understand how the 
system works as a whole, the direct interface between its subsystems, and the function performed 
by all components in each subsystem to accomplish the overall system function. This will help 
depict the interrelationships of basic events that lead to the top event. A basic event is found at 
the lowest level of break down of an FT and can represent the failure of an individual 
component, a particular human action, a CCF event, or an undeveloped event. A circle is used in

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an FT to represent basic events, except for undeveloped events, which are represented with a 
diamond shape. Undeveloped events are those events that have not enough available 
information, but are modeled for completeness of the FT and can be developed at a later time. 
In the study of the Electric Power Distribution system, it is important to understand how the 
overall system works (i.e., substations, switchyards, switchgears, and DC power), identify the 
specific path of power distribution from the outside source to the DTFs and FHF supply and 
exhaust fans, and know in detail the duty of each component along that path in order to conduct 
this power. 
6.2.3 Step Three: Make a Logic Model 
The FT model is done by breaking down the top event into combinations of basic events that 
lead to it. This is done with the use of Boolean logic gates. Logic gates show the relationships 
of events needed for the occurrence of a higher event. The higher event is the output of the gate; 
the lower events are the inputs to the gate. The gate symbol denotes the type of relationship of 
the input events required for the output event (Vesely et al. 1981, p. IV-1). 
Boolean logic analysis consists of binary inputs and outputs to a gate such as 1s or 0s, and TRUE 
or FALSE. The two basic types of logic gates are AND and OR. The output of an OR-gate is 
TRUE if one or more of the input events is TRUE; otherwise, it is FALSE. This gate is used for 
components in series, only when each component is essential for the successful operation of a 
system. For example, in order to have successful power distributed to a load, it is necessary that 
safety devices placed in series such as circuit breakers and interrupter switches, remain closed to 
connect the load. Because the spurious opening of any of these devices will cause loss of power 
distribution to the load, they should be input to an OR-gate. 
The output of an AND-gate is TRUE only if all the input events are TRUE; otherwise, it is 
FALSE. This gate is used for components in parallel only when not all components are essential 
for the operation of a system, meaning they are redundant. For example, a successful HVAC 
system requires only one MCC I to be successful (Assumption 5.1), yet the electrical power 
distribution system provides power to two MCC Is. Because only one MCC I is needed for the 
success of the HVAC, the second MCC I is redundant and the failure of the two MCC Is is 
represented by an AND-gate. Systems with components in series, when they are essential for the 
successful operation of a system, are less reliable than those with components in parallel that are 
also redundant. To quantify an OR-gate, inputs to it are added; to quantify an AND-gate, inputs 
to it are multiplied together. 
It is important to note that components in series may be redundant to a system, and components 
in parallel may all be essential for the successful operation of a system. 
With the use of logic gates, one is able to work backward to determine the intermediate events 
that lead to the top event and continue the process until arriving at the basic events 
(Section 6.2.2). The final FT can be constructed and analyzed with the use of computer program 
software such as SAPHIRE.

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6.2.4 Step Four: Assess the Probability of Basic Events 
Once the FT model has been made, the basic events are quantified using reliability data resources 
and probability calculations. A process of gathering and assembling component failure rate data 
from reliability databases for basic events is first done. Such databases include the Generic 
Component Failure Data Base (Eide and Calley 1993, Tables 1 and 2) and IEEE Guide to the 
Collection and Presentation of Electrical, Electronic, Sensing Component, and Mechanical 
Equipment Reliability Data for Nuclear-Powered Generating Stations (IEEE Std 500-1984 
(Reaffirmed 1991) ). Component reliability is expressed as a failure rate, symbolized as ., and 
having units of per hour, or as a failure probability, symbolized as q, and having units of per 
demand. 
The probability calculation of basic event failure is done with the use of the Poisson equation 
from NUREG/CR-2300 (NRC 1983, Section 5.5.2.4.1) and the mission time. The Poisson 
equation for predicting the probability of a specific number of failures (r) in mission time (t) is: 
! 
) t ( ) ( 
) t ( 
r
e r P 
r . . - 
= (Eq. 1) 
where: 
r = number of failures in time (t) 
. = failure rate per hour 
t = mission time in hours 
P(r) = probability of getting r failures in time t 
The probability of having one or more failures (r) in the mission time (t) is given as: 
) t ( 1 ) 0 ( 1 ) 1 ( . - - = = - = = e r P r P (Eq. 2) 
For small values of ., Equation 2 can be approximated as: 
q = .t (Eq. 3) 
where q is the probability of failure in time t. 
Note that per demand failure probabilities are already in the form q and do not need to be 
multiplied by the mission time. 
The mission time is the time required for the system to be successfully in operation. For 
example, if there was a drop of a CSNF assembly in the DTFs, the time required for the HVAC 
to be in operation to clean up the concentration of a radiological release in the air is the mission 
time. The mission time is set by the design requirement to be 4 hours (Assumption 5.4). 
After all basic events are assessed and probability values are calculated, they are input into 
SAPHIRE.

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6.2.5 Step Five: Perform Common-Cause Failure Analysis 
CCFs occur simultaneously in two or more identical and redundant components with the same 
manufacturer due to a single cause. The root cause may be operation, maintenance errors, 
design, or location (Mosleh 1998). 
The assessment of CCF events (Section 6.2.2) is done by multiplying the redundant components 
failure probability by a special factor that considers how many are in the redundant group and 
how many are needed for success. There are many methods of CCF modeling such as the Beta 
Factor, the Multiple Greek Letter, and the Alpha Factor. The method recommended by the U.S. 
Nuclear Regulatory Commission (NRC) is the Alpha Factor in NUREG/CR-5497 
(Marshall 1998) and NUREG/CR-5485 (Mosleh 1998). A table shown in Section 6.3.4 is a 
guideline for using the alpha factor method in CCF analyses (BSC 2004e, Table II-2) assuming 
staggered maintenance on redundant components (Assumption 5.6). 
Figure 1 shows the basic way of modeling CCF in OR-gates. Logic analysis shows that 
whenever redundant events are inputs to an OR-gate, the success criteria for the CCF basic event 
is n-of-n, where n is the number of redundant events in the system. The CCF basic event is then 
quantified by multiplying the failure probability of the redundant basic event by the alpha factor 
of n-of-n in Section 6.3.4 
OR-GATE 
1.0E-3 
A 
1.0E-3 
B 
1.0E-3 
C 
6.2E-5 
CCF 
If any input to this 
gate is TRUE, the 
output is TRUE 
Fan A fails Fan B fails Fan C fails A, B, C fail 
(Success 3/3) 
Figure 1. CCF Input to an OR-Gate 
It is important to note from Figure 1 that a CCF input to an OR-gate is only qualitatively 
important because quantitatively it does not contribute significantly to the output of the FT. In

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this case, the output without CCF is 3.0E-3, whereas with CCF, it is 3.1E-3. Note that the CCF 
failure probability of 6.2E-5 is equal to the component failure probability of 1.0E-3 times the 
alpha factor of 0.062 for a 3-out-of 3 success from Section 6.3.4. 
Figure 2 shows the basic way of modeling CCF in AND-gates. Logic analysis shows that 
whenever redundant events are inputs to an AND-gate, the success criteria for the CCF basic 
event is always 1-of-n, where n is the number of redundant events in the system. The CCF basic 
event is then quantified by multiplying the failure probability of the redundant basic event by the 
alpha factor of 1-of-n in Section 6.3.4. 
AND-GATE 
1.0E-3 
A 
1.0E-3 
B 
1.0E-3 
C 
OR-GATE 
2.6E-5 
CCF 
If any input to this 
gate is TRUE, the 
output is TRUE 
If and only if all inputs 
to this gate are TRUE, 
the output is TRUE 
Fan Afails Fan B fails Fan C fails 
A, B, C fail 
(Success 1/3) 
Figure 2. CCF Input to an AND-Gate 
A CCF event to an AND-gate is modeled with the use of an OR-gate as shown in Figure 2. This 
CCF event is qualitatively and quantitatively important to the output of the FT. In this case, the 
output without CCF is 1.0E-9 whereas with CCF, it is 2.6E-5, which is the value of the CCF and 
dominates the total output. Note that the CCF failure probability of 2.6E-5 is equal to the 
component failure probability of 1.0E-3 times the alpha factor of 0.026 for a 1-out-of 3 success 
from Section 6.3.4. 
CCF is not applied to human action events or to undeveloped events.

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6.2.6 Step Six: Interpret Qualified and Quantified Results 
Once the FT has been modeled and failure probabilities have been input into all the basic events, 
it is ready to be evaluated. With the aid of SAPHIRE, the appropriate Boolean algebra is 
performed and the result is output in a cut set report that contains the minimal cut sets. A 
minimal cut set is the smallest combination of component failures, which, if they all occur, will 
cause the top event to occur. If one of the failures in the cut set does not occur, then the top event 
will not occur by this combination (Vesely et al. 1981, VII-15). A cut set report can be either 
qualitative, quantitative, or both. 
A qualitative cut set report shows all the different combinations of basic events that make the top 
event TRUE. Each combination is a minimal cut set that can range from one event to six or 
more, depending on the complexity of the tree. The report arranges minimal cut sets in 
increasing order, which shows how sensitive the system is to each cut set. The most critical 
events in an FT are those at the top of the report because it takes fewer components to make the 
top event occur, whereas the higher the number of events in a cut set, the more components it 
takes to make the top event occur. 
A quantitative cut set report shows the same arrangement of minimal cut sets as the qualitative 
report, but contains the probability of each cut set to occur and the percentage contribution of the 
cut set to the total system failure. This report provides insight in the major contributors to the 
top event. 
A cut set report analysis can improve the systems reliability by identifying the main contributing 
events and either adding redundancy to these components or using more reliable ones. 
6.3 FAULT TREE ANALYSIS 
The FTA discussed in Sections 6.3 through 6.4 analyzes the entire portion of the onsite electrical 
power distribution system that provides power from the offsite power source to the Nuclear 
HVAC supply and exhaust fans in the primary confinement areas of the DTFs and FHF. The 
FTA discussed in Sections 6.3 through 6.4 does not take credit for any backup power such as 
standby or emergency. Sensitivity analyses discussed in Sections 7.1 through 7.4 consider 
options where emergency power is credited. The drawings used for this analysis are 
Figures A-1, A-2, A-3, and A-4. 
Because the loss of power distribution to the nuclear HVAC system in the primary confinement 
areas of the DTFs (DTF 1 and DTF 2) and FHF occurs the same way, only one FTA is 
performed. The text in the FTA refers to the DTF 1, but the results apply to the DTF 1, DTF 2, 
and FHF. 
Top Event 
The top event of the FT in Figure A-5 is described as Failure of the Electrical Power 
Distribution system to provide power to the Nuclear HVAC system in the DTF 1 Primary 
Confinement. It is represented by an AND-gate called LOSP_ONSITE.

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Success Criteria 
The success criteria determine what the top logic gate should be. In this case, the nuclear HVAC 
system in the primary confinement areas of the DTF 1 is successful as long as one MCC I, which 
contains one set of two supply fans and one set of two exhaust fans, is powered (Assumption 
5.1). One MCC I is on side A and another on side B. No credit is given for partial success, 
meaning that no credit is given for the success of each individual fan. It is apparent from Figure 
A-2 that if an MCC I fails, then the fans attached to it (one set of two supply fans and one set of 
2 exhaust fans) will fail to be powered. Because of the success criterion aforementioned, losing 
power to one MCC I does not mean failure. In order to lose power to the HVAC, both MCC Is 
would have to be lost. This is represented with an AND-gate that has inputs FANS_SIDEA and 
FANS_SIDEB. 
6.3.1 Electrical Power Distribution System Description 
Figure A-1 depicts the power distribution path from an offsite source at Substations A and B to 
the DTF 1, DTF 2, and FHF. The electrical power distribution system starts with two 
substations, A and B, that receive the power transmitted from the electrical power utility 
company, and then step down the voltages for distribution to the monitored geologic repository. 
Substation A receives 230 kiloVolts (kV) of electricity, and with the use of its main transformer 
A, steps down the power to 12.47kV of electricity to be distributed to the entire repository 
through the switchyard, which is a bus that can split the distribution off in multiple directions. 
The switchyard bus has medium voltage circuit breakers so that the substation can be 
disconnected from the transmission grid, or separate distribution lines can be disconnected from 
the substations when necessary. Substation B works the same as Substation A, but receives only 
138kV, which is used only if and when Substation A fails (BSC 2004b, Section 4.1.1.1). Other 
components in each substation include a coupling capacitor voltage transformer, which is used 
for metering, protection, and control of high voltages; a power circuit breaker that isolates the 
transmission power from the distribution power when necessary; a normally closed 4,000 Amp 
medium voltage circuit breaker; and protection devices such as surge and lightning arrestors. 
Note that the power circuit breaker consists of two motor operated disc switches and one 
medium voltage circuit breaker. 
As shown in Figure A-1, the switchyard bus is composed of two main SWGR buses (A and B) 
that are connected by a 4,000 Amp medium voltage circuit breaker that is normally closed. The 
switchyard provides power to South Portal and North Portal facilities through a number of 
distribution lines. Each distribution line is called a load to the switchyard bus. When the 
switchyard bus fails to be powered, all medium voltage circuit breakers that connect the 
distribution lines to the repository facilities will automatically open and shed all the loads until 
they are sequentially reconnected when another source of power is acknowledged. Other sources 
of power, which are not initially connected to the switchyard unless the preferred (Substation A) 
supply fails, are Substation B and standby diesel generators, respectively. These sources are 
started and connected manually upon loss of power to the switchyard. All medium voltage 
circuit breakers along the 12.47kV switchyard also open or trip when a current fault on its load is 
detected. This is to prevent damage to the supplying switchyard bus.

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Following the distribution along the bolded lines to the emergency SWGR loads A and B, there 
is another step down transformer reducing the power from 12.47kV to 4.16kV that is to be used 
by the loads of each emergency SWGR bus. The line that connects each emergency SWGR load 
to the switchyard has a medium voltage fused interrupter switch downstream of the 12.47kV to 
4.16kV transformer and a medium voltage circuit breaker upstream of the transformer for 
protection of the switchyard in case of a current fault in the emergency SWGR load. 
Emergency SWGRs A and B provide power through five distribution lines to different parts of 
the DTF 1, DTF 2, FHF, Canister Handling Facility (CHF), and Central Control Center Facility 
(CCCF) (Figure A-1). Each distribution line going to each building is called a load to the 
particular emergency SWGR. When the 4.16kV emergency SWGR bus fails to be powered, all 
medium voltage circuit breakers that connect the distribution lines to the facilities will 
automatically open until they are sequentially reconnected when another source of power is 
acknowledged. There is one EDG on each emergency SWGR and it is the other source of power 
that is to be used if normal power is lost. The EDG is initially disconnected from the emergency 
SWGR until it is started, and then connected automatically upon loss of power to it. Medium 
voltage circuit breakers along the 4.16kV Emergency SWGRs A and B also open or trip when a 
current fault on its load is detected. This is to prevent damage to the particular emergency 
SWGR bus. 
Each load line connected to an emergency SWGR bus has a step down transformer that reduces 
the power from the 4.16kV to 480V, which is used by the load center (LC) bus in each building 
(Figure A-1). Each load line has a medium voltage circuit breaker and a medium voltage fused 
interrupter switch that disconnect the load in case of a current fault for protection of the 
emergency SWGR bus, as explained earlier. 
Figure A-2 shows the continuing distribution of power from the 480V LC A bus and the 480V 
LC B bus, shown in Figure A-1, to the MCCs that feed motor loads. The LC A has four lines of 
distribution loads: MCC I, MCC A, MCC B, and MCC C. The LC B has four lines of 
distribution loads: MCC I(B), MCC X, MCC Y, and MCC Z. Each line has a molded case 
circuit breaker that trips and sheds its load in case of a current fault in the particular MCC load. 
The MCC I in the LC A has one set of two supply fan motors and one set of two exhaust fan 
motors of the primary confinement areas of the DTF 1, while the same is true for the MCC I in 
the LC B. The DTF 2 has the same arrangement as the DTF 1. The FHF has the same 
arrangement as the DTF 1 and the DTF 2, except the MCC I on each side has only one supply 
fan and one exhaust fan. 
All medium voltage circuit breakers are DC powered and therefore, it is also important to 
understand the normal and emergency 125V DC distribution systems shown in Figures A-3 and 
A-4. The normal 125V DC system (Figure A-3) consists of a 125V DC panelboard powered by 
480V AC from MCC through a rectifier unit and a battery system (BSC 2004b, Section 4.1.1.3). 
There are two 125V DC distribution buses, A and B. Each has a 125V battery cell and a battery 
charger unit that delivers DC power by rectifying the 480V AC from an MCC. There is also a 
backup battery charger that can provide power to DC buses A and B in the event their charger 
fails. The function of the battery charger is to provide the transformed 125V DC power as well 
as keeping the set of battery cells fully charged (BSC 2004b, Section 4.1.1.3). The 125V DC

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distribution bus A is the primary DC power distributor to the 12.47kV Main SWGR A and the 
backup DC supply to the 12.47kV Main SWGR B circuit breakers. The 125V DC distribution 
bus B is the primary DC power distributor to the 12.47kV Main SWGR B and the backup DC 
supply for the 12.47kV Main SWGR A circuit breakers. The emergency 125V DC systems 
(Figure A-4) located in the Emergency SWGR Building (ESB) provide control power for the 
4.16kV emergency SWGR circuit breakers. Each emergency 125V DC system consists of a 
125V DC distribution panelboard, a 125V DC battery bank and a battery charger (BSC 2004b, 
Section 4.1.1.4). Power to the emergency 125V DC distribution panelboard can be provided by 
the battery cell or battery charger. Each emergency battery charger is fed from the 480V AC on 
the MCC, which is fed from the emergency SWGR (Figure A-4). 
6.3.2 Fault Tree Logic Model 
Once the top event and its success criteria have been defined (Section 6.3), the rest of the FT can 
be developed. Figure A-5 shows that in order for the top event (represented by AND-gate 
LOSP_ONSITE) to occur, MCC Is on both sides of the distribution grid must fail. As explained 
in Section 6.3.1, one set of two supply fan motors and one set of two exhaust fan motors are 
powered by the same MCC I. To model the loss of power to more than two supply fans and two 
exhaust fans, only two inputs to AND-gate LOSP_ONSITE are necessary. Each input 
FANS_SIDEA and FANS_SIDEB represents the loss of power to MCC I and MCC I (B), 
respectively. 
This analysis is approached by using the emergency SWGR bus as a pivot point, since it is the 
nearest source of power to each MCC I (Figure A-2). The following three events can cause the 
loss of power distribution to an MCC I and thus, can make OR-gates FANS_SIDEA and 
FANS_SIDEB occur: 
.. A disconnect of the DTF 1 load carrying the MCC I from the emergency SWGR bus. This is 
represented with TRANSFER-gate inputs, DISCONNECT_SWGREA and 
DISCONNECT_SWGREB. 
.. The unavailability of the emergency SWGR bus. This is represented with TRANSFER-gate 
inputs, BUS_SWGREA and BUS_SWGREB. 
.. The loss of power to the emergency SWGR bus. This is represented with TRANSFER-gate 
inputs, SWYDA_SWGREA and SWYDA_SWGREB. 
Note that each TRANSFER-gate (i.e. triangular shaped event) is the top event of a subtree 
developed on a different page. 
Because the logic break down of FANS_SIDEA and FANS_SIDEB is the same, only side A is 
explained in this analysis. Figures A-6 through A-13 represent the logic break down of 
FAN_SIDEA and are explained in Sections 6.3.2.1 through 6.3.2.5. Different types of bullets are 
used throughout this report to emphasize the hierarchy of events in the FT. CCF events are 
explained in Section 6.3.4. 
The FT model for FANS_SIDEB is shown in Attachment B.

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6.3.2.1 Disconnect from Emergency Switchgear A 
Figure A-6 shows subtree DISCONNECT_SWGREA, which is a sub-top event defined as 
Failure of MCC I to remain connected to the Emergency Switchgear A. The distribution path 
from the emergency SWGR to the MCC I is made up of components in series (Section 6.3.1). 
Therefore, the sub-top event is represented by an OR-gate (Section 6.2.3), which means that if 
any of the inputs to it are TRUE, the top event occurs. This is one major cause for the loss of 
power distribution to one set of two supply fans and one set of two exhaust fans (Section 6.3.2), 
and is the expansion of TRANSFER-gate DISCONNECT_SWGREA in Figure A-5. The 
following events are inputs to DISCONNECT_SWGREA based on Figure A-1: 
.. TRANSFER-gate 125VDC_SWGREA: 125V DC System fails to supply power to SWGR 
EA Medium Voltage Circuit Breakers (Section 6.3.2.5). 
.. Basic Event MCKTBRKR_O_DTF1: Medium Voltage Circuit Breaker fails to remain 
closed to connect DTF 1 load. 
.. Basic Event FUSE_O_DTF1: Fused interrupter switch fails to remain closed to connect 
DTF 1 load. 
.. Basic Event XFMR_DTF1: 4160-480V Transformer fails to operate. 
.. Basic Event LINE_DTF1: Power line fails to remain intact to connect DTF 1 load. 
.. OR-gate DISCONNECT_LCA: Failure of MCC I to remain connected to Load Center A. 
.. OR-gate BUS_LCA: Load Center A Bus failure. 
Input 125VDC_SWGREA is explained in Section 6.3.2.5 and CCF inputs are explained in 
Section 6.3.4. 
The DTF 1 load refers to the entire load as seen by SWGR EA (Figure A-1), and LC A refers to 
the bus that powers the MCCs on the DTF 1 load (Figure A-2). DISCONNECT_LCA continues 
the series of break down from the LC A down to the MCC I that powers one set of two supply 
fans and one set of two exhaust fans in the DTF 1 primary confinement area (Figure A-2). The 
following three events are inputs to DISCONNECT_LCA that can cause a disconnect of the 
MCC I from the LC A: 
. Basic Event IBUS_MCCI: MCC I bus fails short circuited. Notice that this is not a direct 
disconnect, but an indirect one that will cause the circuit breaker to disconnect MCC I from 
LC A when this event occurs. 
. Basic Event LINE_MCCI: Power line fails to remain intact to connect MCC I load. 
. Basic Event LCKTBRKR_O_MCCI: Low Voltage Circuit Breaker fails to remain closed to 
connect MCC I load. 
Note that CCF inputs are explained in Section 6.3.4.

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BUS_LCA is another subtree input to DISCONNECT_SWGREA that shows the failure of the 
LC A bus that will cause an indirect disconnect from the SWGR EA by the protective medium 
voltage fused interrupter switch or the medium voltage circuit breaker (Figure A-1). Failures in 
electric current such as shorts and overloads are what cause protective devices to trip. The 
following two events are inputs to OR-gate BUS_LCA that describe faults in electric current on 
the LC A bus: 
. Basic Event IBUS_LCA: LC A Bus fails short circuited. 
. OR-gate CBUS_LCA: LC A Bus fails overloaded. 
CBUS_LCA is a subtree that describes the failure of the LC A bus due to all MCC loads 
connected to it causing an overload. Due to the protective devices in each load, this is a rare 
failure, but nonetheless, must be modeled. 
There are three other MCC loads besides the MCC I feeding from LC A: MCC A, MCC B, and 
MCC C (Figure A-2). If one of these loads has an unknown electrical current fault, and if the 
circuit breaker fails to isolate this fault, the LC A bus will suffer an overload, which means it is 
unavailable to the remaining loads connected to it. The time period of the unavailability of LC A 
may be short and thus, may not completely cease power to the loads, but will cause a disconnect 
from SWGR EA by the protective devices. The following four events are inputs to OR-gate 
CBUS_LCA that describe a possible overload to LC A by any of its MCC loads: 
.. AND-gate OLOAD_MCCI: MCC I fault fails to be shed from LC A bus. 
.. AND-gate OLOAD_MCCA: MCC A fault fails to be shed from LC A bus. 
.. AND-gate OLOAD_MCCB: MCC B fault fails to be shed from LC A bus. 
.. AND-gate OLOAD_MCCC: MCC C fault fails to be shed from LC A bus. 
OLOAD_MCCI will occur if MCC I bus fails short circuited, represented by basic event 
IBUS_MCCI, and the low voltage circuit breaker fails to shed it upon demand, represented by 
basic event LCKTBRKR_S_MCCI. It is important to note that basic event IBUS_MCCI will 
cause a disconnect from the LC A bus (as seen in subtree DISCONNECT_LCA), given that the 
low voltage circuit breaker works. Otherwise, if the low voltage circuit breaker fails, 
IBUS_MCCI will cause an overload on the LC A bus as seen in OLOAD_MCCI. In turn, 
OLOAD_MCCI will cause a disconnect from the SWGR EA (as seen in subtree BUS_LCA), 
given that the medium voltage circuit breaker or medium voltage fused interrupter switch works. 
The rest of the above mentioned gates are TRUE only if there is an unknown fault in the load, 
represented by undeveloped event FAULT_MCCX, and the low voltage circuit breaker fails to 
shed it upon demand, represented by basic event LCKTBRKR_S_MCCX. Each undeveloped 
fault is assumed to be comparable to the fault in the MCC I (Assumption 5.2), IBUS_MCCI.

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6.3.2.2 Emergency Switchgear A Bus Unavailable 
Figure A-7 shows subtree BUS_SWGREA, which is a sub-top event defined as Emergency 
Switchgear A Bus Unavailable. The SWGR EA bus will be unavailable to power the MCC I if 
it has an electrical current failure due to a short or an overload. This is another major cause 
for the loss of power distribution to one set of two supply fans and one set of two exhaust fans 
(Section 6.3.2), and is the expansion of TRANSFER-gate BUS_SWGREA in Figure A-5. 
BUS_SWGREA is represented by an OR-gate with the following inputs based on Figure A-1: 
.. Basic Event IBUS_SWGREA: SWGR EA bus fails short circuited. 
.. OR-gate CBUS_SWGREA: SWGR EA bus fails overloaded. 
CBUS_SWGREA is a subtree that describes the failure of the SWGR EA bus due to all loads 
connected to it causing an overload. Due to the protective devices in each load, this is a rare 
failure, but nonetheless, must be modeled. 
There are four other loads besides LC A feeding from SWGR EA: LC C, MCC S, LC G, and 
MCC K (Figure A-1). If one of these loads has an unknown electrical current fault and if the 
circuit breaker fails to isolate this fault, the SWGR EA bus will suffer an overload, which means 
it is unavailable to the remaining loads connected to it. The time period of the unavailability of 
SWGR EA may be short and thus, may not completely cease power to the loads, but for 
conservatism, it is modeled in this analysis. Notice that the EDG is not one of the contributing 
loads to the overload of the SWGR EA because it is not connected to it. A current fault on the 
SWGR EA bus can also cause a disconnect from Main SWGR A by the protective devices as 
will be seen in Section 6.3.2.3.1. The following five events are inputs to OR-gate 
CBUS_SWGREA that describe a possible overload to SWGR EA by any of its loads: 
. AND-gate OLOAD_LCC: LC C fault fails to be shed from SWGR EA bus. 
. AND-gate OLOAD_MCCS: MCC S fault fails to be shed from SWGR EA bus. 
. AND-gate OLOAD_LCG: LC G fault fails to be shed from SWGR EA bus. 
. AND-gate OLOAD_MCCK: MCC K fault fails to be shed from SWGR EA bus. 
. AND-gate OLOAD_LCA: LC A fault fails to be shed from SWGR EA bus. 
OLOAD_LCA will occur if LC A bus fails due to a current fault, represented by FAULT_LCA, 
and the medium voltage circuit breaker or the fused interrupter switch fails to shed it upon 
demand, represented by basic events MCKTBRKR_S_LCA and FUSE_S_LCA, respectively. 
FAULT_LCA represents the current fault that was developed in subtree 
DISCONNECT_SWGREA (Figure A-6), BUS_LCA, and a failure in the 4160-480V 
transformer of the DTF 1 load, represented by XFMR_DTF1. The DTF 1 load refers to the 
entire load as seen by SWGR EA (Figure A-1), and LC A refers to the bus that powers the 
MCCs on the DTF 1 load (Figure A-2). It is important to note that BUS_LCA and 
XFMR_DTF1 will cause a disconnect from the SWGR EA bus (as seen in subtree 
DISCONNECT_SWGREA), given the medium voltage circuit breaker or medium voltage fused

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interrupter switch works (Section 6.3.2.1). Otherwise, if the medium voltage circuit breaker and 
medium voltage fused interrupter switch fail, BUS_LCA and XFMR_DTF1 will cause an 
overload on the SWGR EA bus as seen in OLOAD_LCA. 
Note that CCF inputs are explained in Section 6.3.4. 
The rest of the above mentioned gates are TRUE only if there is an unknown fault in the load, 
represented by undeveloped event FAULT_XXX; the medium voltage circuit breaker fails to 
shed it upon demand, represented by basic event MCKTBRKR_S_XXX; and the fused 
interrupter switch fails to open after a fault in the load, represented by FUSE_S_XXX. Each 
undeveloped fault is assumed to be comparable to the fault on the LC A bus (Assumption 5.2), 
FAULT_LCA. 
6.3.2.3 Loss of Power to the Emergency Switchgear A 
The power distributed to SWGR EA is supplied by Main SWGR A (Figure A-1). Therefore, any 
failures along the path of distribution from the Main SWGR A to SWGR EA will cause loss of 
power to SWGR EA. This is one last major cause for the loss of power distribution to one set of 
two supply fans and one set of two exhaust fans (Section 6.3.2), and it is the expansion of 
TRANSFER-gate SWYDA_SWGREA in Figure A-5. 
Figure A-8 shows subtree SWYDA_SWGREA, which is a sub-top event defined as Failure of 
Main Switchgear A to power Emergency Switchgear A. The following three overall events can 
make OR-gate SWYDA_SWGREA occur based on Figure A-1: 
.. A disconnect of the SWGR EA load carrying the MCC I from its nearest source of power, the 
Main SWGR A bus. This is represented with subtree DISCONNECT_SWYDA. 
.. The unavailability of the Main SWGR A bus. This is represented with subtree 
BUS_SWYDA. 
.. The loss of power to the Main SWGR A bus. This is represented with TRANSFER-gate 
input LOSP_SWYDA. 
Sections 6.3.2.3.1 through 6.3.2.3.3 describe in detail each subtree mentioned above that is an 
input to OR-gate SWYDA_SWGREA. 
6.3.2.3.1 Disconnect from Main SWGR A 
Figure A-8 shows subtree DISCONNECT_SWYDA, which is defined as Failure of SWGR EA 
to remain connected to Main SWGR A. The distribution path from Main SWGR A to SWGR 
EA is made up of components in series (Section 6.3.1) and therefore, DISCONNECT_SWYDA 
is represented by an OR-gate. The following events are inputs to DISCONNECT_SWYDA 
based on Figure A-1: 
.. TRANSFER-gate 125VDC_SIDEA: 125V DC System fails to supply power to Side A 
Medium Voltage Circuit Breakers (Section 6.3.2.4).

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.. Basic Event MCKTBRKR1_O_SWGREA: Medium Voltage Circuit Breaker 1 fails to 
remain closed to connect the SWGR EA load. 
.. Basic Event FUSE_O_SWGREA: Fused interrupter switch fails to remain closed to connect 
the SWGR EA load. 
.. Basic Event XFMR_SWGREA: 12.47-4.16kV Transformer fails to operate. 
.. Basic Event LINE_SWGREA: Power line fails to remain intact to connect the SWGR EA 
load. 
.. Basic Event MCKTBRKR2_O_SWGREA: Medium Voltage Circuit Breaker 2 fails to 
remain closed to connect the SWGR EA load. 
.. TRANSFER-gate BUS_SWGREA: Emergency Switchgear A bus unavailable 
(Section 6.3.2.2). 
Input 125VDC_SIDEA is explained in Section 6.3.2.4 and CCF inputs are explained in 
Section 6.3.4. 
It is important to note that while subtree BUS_SWGREA (Section 6.3.2.2) represents the 
unavailability of power to the DTF 1, it also causes a disconnect from the Main SWGR A bus, 
given the medium voltage circuit breaker or medium voltage fused interrupter switch works. 
Otherwise, if the medium voltage circuit breaker and medium voltage fused interrupter switch 
fail, BUS_SWGREA will cause an overload on the Main SWGR A bus. This possibility is 
discussed in the next section. 
6.3.2.3.2 Main SWGR A Bus Unavailable 
Figure A-8 shows subtree BUS_SWYDA, which is defined as Main SWGR A Bus 
Unavailable. The Main SWGR A bus will be unavailable to power the SWGR EA load if it has 
an electrical current failure due to a short or an overload. Due to the interconnect circuit 
breaker that connects Main SWGR A to Main SWGR B, the unavailability of Main SWGR B 
must also be considered for the case in which the interconnect circuit breaker fails to isolate the 
failure. The following three inputs can make OR-gate BUS_SWYDA occur based on 
Figure A-1: 
.. Basic Event IBUS_SWYDA: Main SWGR A Bus fails short circuited. 
.. TRANSFER-gate CBUS_SWYDA: Main SWGR A Bus fails overloaded. 
.. AND-gate BUSINT_SWYDB: Interconnect Medium Voltage Circuit Breaker fails to isolate 
failure in Main SWGR B. 
Note that CCF inputs are explained in Section 6.3.4.

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Figure A-9 shows subtree CBUS_SWYDA, which is defined as Main SWGR A Bus fails 
overloaded. This figure is the expansion of TRANSFER-gate CBUS_SWYDA in Figure A-8 
that if TRUE, can make the Main SWGR A bus unavailable. This subtree describes the failure 
of the Main SWGR A bus due to all loads connected to it causing an overload. 
There are seven other loads in addition to SWGR EA, feeding from Main SWGR A: LC 12, 
SWGR 01A, SWGR 08, SWGR 06, 2MVA, 11.7MVA, and SWGR C (Figure A-1). If one of 
these loads has an unknown electrical current fault, and if the circuit breaker or fused interrupter 
switch fails to isolate this fault, the Main SWGR A bus will suffer an overload, which means it is 
unavailable to remaining loads connected to it. The time period of the unavailability of Main 
SWGR A may be short and thus, may not completely cease power to the loads, but for 
conservatism, it is modeled in this analysis. A current fault on the Main SWGR A bus can also 
cause load disconnects from Main SWGR A by the protective devices. Notice that the two 
standby diesel generators are not contributing loads to the overload of Main SWGR A because 
they are not connected to it. The following eight events are inputs to OR-gate CBUS_SWYDA 
that describe a possible overload to Main SWGR A by any of its loads: 
. AND-gate OLOAD_LC12: LC 12 fault fails to be shed from Main SWGR A bus. 
. AND-gate OLOAD_SWGR01A: SWGR 01A fault fails to be shed from Main SWGR A 
bus. 
. AND-gate OLOAD_SWGR08: SWGR 08 fault fails to be shed from Main SWGR A bus. 
. AND-gate OLOAD_SWGR06: SWGR 06 fault fails to be shed from Main SWGR A bus. 
. AND-gate OLOAD_2MVA: 2MVA fault fails to be shed from Main SWGR A bus. 
. AND-gate OLOAD_11.7MVA: 11.7MVA fault fails to be shed from Main SWGR A bus. 
. AND-gate OLOAD_SWGRC: SWGR C fault fails to be shed from Main SWGR A bus. 
. AND-gate OLOAD_SWGREA: SWGR EA fault fails to be shed from Main SWGR A bus. 
OLOAD_SWGREA will occur if the SWGR EA bus fails due to a current fault, represented by 
FAULT_SWGREA, and the medium voltage circuit breaker or the medium voltage fused 
interrupter switch fails to shed it upon demand, represented by basic events 
MCKTBRKR_S_SWGREA and FUSE_S_SWGREA, respectively. FAULT_SWGREA 
represents the current fault that was developed in subtree BUS_SWGREA, and a failure in the 
12.47-4.16kV transformer of the SWGR EA load, represented by XFMR_SWGREA. It is 
important to note that event BUS_SWGREA will cause a disconnect from the Main SWGR A 
bus (as seen in subtree DISCONNECT_SWYDA), given the medium voltage circuit breaker or 
medium voltage fused interrupter switch works (Section 6.3.2.3.1). Otherwise, if the medium 
voltage circuit breaker and medium voltage fused interrupter switch fail, BUS_SWGREA will 
cause an overload on the Main SWGR A bus, as seen in OLOAD_SWGREA. 
Note that CCF inputs are explained in Section 6.3.4.

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With the exception of OLOAD_2MVA, OLOAD_11.7MVA, and OLOAD_SWGRC, the rest of 
the above mentioned gates are TRUE only if there is an unknown fault in the load, represented 
by undeveloped event FAULT_XXX; the medium voltage circuit breaker fails to shed it upon 
demand, represented by basic event MCKTBRKR_S_XXX; and the fused interrupter switch fails 
to open after a fault in the load, represented by FUSE_S_XXX. 
OLOAD_2MVA or OLOAD_11.7MVA can occur if there is an unknown fault in the load, 
represented by undeveloped event FAULT_XXX, and the medium voltage circuit breaker fails to 
shed it upon demand, represented by basic event MCKTBRKR_S_XXX. 
OLOAD_SWGRC can occur if there is an unknown fault in the load, represented by 
undeveloped event FAULT_SWGRC; medium voltage circuit breaker 1 fails to shed it upon 
demand, represented by basic event MCKTBRKR_S1_SWGRC; and medium voltage circuit 
breaker 2 fails to shed it upon demand, represented by basic event MCKTBRKR_S2_SWGRC. 
Each undeveloped fault is assumed to be comparable to the fault on the SWGR EA bus 
(Assumption 5.2), FAULT_SWGREA. 
Figure A-8 shows subtree BUSINT_SWYDB, which is a third input to OR-gate BUS_SWYDA 
that if TRUE, can make the Main SWGR A bus unavailable and successively FANS_SIDEA will 
occur. BUSINT_SWYDB is defined as Interconnect Medium Voltage Circuit Breaker fails to 
isolate failure in Main SWGR B. Also, note that when BUSINT_SWYDB is TRUE, Main 
SWGR B bus has failed to provide power to SWGR EB, which carries an MCC I and 
successively FANS_SIDEB occurs. Because BUSINT_SWYDB makes FANS_SIDEA and 
FANS_SIDEB occur simultaneously, AND-gate LOSP_ONSITE in Figure A-5 is TRUE and the 
top event occurs. The following two inputs must both be TRUE in order for AND-gate 
BUSINT_SWYDB to occur: 
. Basic event ICKTBRKR_S: Interconnect Medium Voltage Circuit Breaker fails to open 
after a failure on Main SWGR B. 
. OR-gate BUS_SWYDBB: Main SWGR B bus failure. 
Subtree BUS_SWYDBB in Figure A-8 describes the failure of the Main SWGR B bus. This 
subtree is similar to OR-gate BUS_SWYDA, which describes the failure of the Main SWGR A 
bus, except for BUS_SWYDBB describes the failure of Main SWGR B and has only two inputs: 
.. Basic event IBUS_SWYDB: Main SWGR B bus fails short circuited. 
.. TRANSFER-gate CBUS_SWYDB: Main SWGR B bus fails overloaded. 
Figure A-10 shows subtree CBUS_SWYDB, which is defined as Main SWGR B Bus fails 
overloaded. This figure is the expansion of TRANSFER-gate CBUS_SWYDB in Figure A-8 
that if TRUE, can cause the failure of the Main SWGR B bus. This subtree describes the failure 
of the Main SWGR B bus due to all loads connected to it causing an overload. 
There are eight other loads in addition to SWGR EB, feeding from Main SWGR B: SWGR 01B, 
LC 13, SWGR 09, SOLAR POWER, SWGR 07, 3.8MVA, 11.8MVA, and SWGR D

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(Figure A-1). If one of these loads has an unknown electrical current fault and if the circuit 
breaker or fused interrupter switch fails to isolate this fault, the Main SWGR B bus will suffer an 
overload, which means it is unavailable to remaining loads connected to it. Notice that the two 
standby diesel generators are not contributing loads to the overload of Main SWGR B because 
they are not connected to it. The following nine events are inputs to OR-gate CBUS_SWYDB 
that describe a possible overload to Main SWGR B by any of its loads: 
.. AND-gate OLOAD_SWGR01B: SWGR 01B fault fails to be shed from Main SWGR B bus. 
.. AND-gate OLOAD_LC13: LC 13 fault fails to be shed from Main SWGR B bus. 
.. AND-gate OLOAD_SWGR09: SWGR 09 fault fails to be shed from Main SWGR B bus. 
.. AND-gate OLOAD_SOLAR: SOLAR POWER fault fails to be shed from the Main 
SWGR B bus. 
.. AND-gate OLOAD_SWGR07: SWGR 07 fault fails to be shed from Main SWGR B bus. 
.. AND-gate OLOAD_3.8MVA: 3.8MVA fault fails to be shed from Main SWGR B bus. 
.. AND-gate OLOAD_11.8MVA: 11.8MVA fault fails to be shed from Main SWGR B bus. 
.. AND-gate OLOAD_SWGRD: SWGR D fault fails to be shed from Main SWGR B bus. 
.. AND-gate OLOAD_SWGREB: SWGR EB fault fails to be shed from Main SWGR B bus. 
OLOAD_SWGREB will occur if SWGR EB bus fails due to a current fault, represented by 
FAULT_SWGREB, and the medium voltage circuit breaker or the medium voltage fused 
interrupter switch fails to shed it upon demand, represented by basic events 
MCKTBRKR_S_SWGREB and FUSE_S_SWGREB, respectively. 
Note that CCF inputs are explained in Section 6.3.4. 
With the exception of OLOAD_3.8MVA, OLOAD_11.8MVA, and OLOAD_SWGRD, the rest 
of the above mentioned gates are TRUE only if there is an unknown fault in the load, represented 
by undeveloped event FAULT_XXX; the medium voltage circuit breaker fails to shed it upon 
demand, represented by basic event MCKTBRKR_S_XXX; and the fused interrupter switch fails 
to open after a fault in the load, represented by FUSE_S_XXX. 
OLOAD_3.8MVA or OLOAD_11.8MVA can occur if there is an unknown fault in the load, 
represented by undeveloped event FAULT_XXX, and the medium voltage circuit breaker fails to 
shed it upon demand, represented by basic event MCKTBRKR_S_XXX. 
OLOAD_SWGRD can occur if there is an unknown fault in the load, represented by 
undeveloped event FAULT_SWGRD; medium voltage circuit breaker 1 fails to shed it upon 
demand, represented by basic event MCKTBRKR1_S_SWGRD; and medium voltage circuit 
breaker 2 fails to shed it upon demand, represented by basic event MCKTBRKR2_S_SWGRD.

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Each undeveloped fault is assumed to be comparable to the fault on the SWGR EB bus 
(Assumption 5.2), FAULT_SWGREB. 
6.3.2.3.3 Loss of Power to the Main SWGR A 
Figure A-11 shows subtree LOSP_SWYDA, which is defined as Failure of 230kV system to 
supply power to Main SWGR A. This is another cause for the loss of power distribution from 
Main SWGR A to SWGR EA (Section 6.3.2.3) and is the expansion of TRANSFER-gate 
LOSP_SWYDA in Figure A-8. Loss of power distribution to Main SWGR A will occur if 
Substation A fails to deliver power to it. As explained in Section 6.3.1, Main SWGRs A and B 
are normally connected by an interconnect medium voltage circuit breaker and powered by the 
preferred source of power, Substation A. If this source fails, Substation B will act as a backup to 
power Main SWGRs A and B. For the event that a shift in power source is necessary (i.e. from 
Substation A to Substation B), power to the Main SWGRs A and B will be interrupted for a 
period of time during which Substation B is connected and loads sequenced back on to the Main 
SWGRs A and B. This event is considered loss of power and thus no credit is given for 
Substation B as a source of power. This subtree, based on Figure A-1, describes the way 
Substation A can fail to supply power to Main SWGR A since it is directly connected to it. 
Because all the components in Substation A are in series, LOSP_SWYDA is described by an 
OR-gate. Any of the following six inputs, if TRUE, can make subtree LOSP_SWYDA occur: 
.. Basic Event SOURCE_230KV: Loss of 230kV source. 
.. Basic Event CCVTA_230KV: Coupling Capacitor Voltage Transformer A fails to operate. 
.. Basic Event PWRCKTBRKRA_230KV: Power Circuit Breaker A fails to remain closed to 
connect 230kV power. Note that the power circuit breaker consists of two motor operated 
disc switches and one medium voltage circuit breaker (Section 6.3.1). 
.. Basic Event XFMRA_230KV: 230-12.47kV Main Transformer A fails to operate. 
.. Basic Event 4KCKTBRKR_O_230KV: 4kA Medium Voltage Circuit Breaker fails to 
remain closed to connect 230kV power. 
.. Basic Event LINE_230KV: Power line fails to remain intact to connect 230kV power. 
Note that CCF inputs are explained in Section 6.3.4. 
6.3.2.4 Normal 125V DC System Failure - Side A 
Figure A-12 shows subtree 125VDC_SIDEA, which is defined as 125V DC System fails to 
supply power to Side A medium voltage circuit breakers. This causes the disconnection of 
SWGR EA from the Main SWGR A. Thus, it is the expansion of TRANSFER-gate 
125VDC_SIDEA in subtree DISCONNECT_SWYDA (Figure A-8).

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100-PSA-EE00-00100-000-00A 31 December 2004 
In Figure A-3 and Section 6.3.1, it is shown that all normal medium voltage circuit breakers on 
Side A of the power grid are powered by the 125V DC distribution bus A and can be powered 
from 125V DC distribution bus B when bus A is unavailable. Thus, in order for AND-gate 
125VDC_SIDEA to occur, the following two events must occur: 
.. OR-gate DCBUSA_SIDEA: Failure of 125V DC Distribution Bus A to supply power to 
Side A Circuit Breakers. 
.. OR-gate DCBUSB_SIDEA: Failure of 125V DC Distribution Bus B to supply backup 
power to Side A Circuit Breakers. 
Subtree DCBUSA_SIDEA describes the failure of the 125V DC distribution bus A to power all 
normal medium voltage circuit breakers on side A of the power grid. The following four events 
are inputs that can make OR-gate DCBUSA_SIDEA occur: 
. Basic Event LCKTBRKR_O_SIDEA: Low voltage circuit breaker fails to remain closed to 
connect Side A load. 
. Basic Event LINE_SIDEA: Power line fails to remain intact to connect Side A load. 
. Basic Event DCBUSA: 125V DC Distribution Bus A fails short circuited. 
. AND-gate POWER_DCBUSA: Loss of DC power to Distribution Bus A. 
Note that CCF inputs are explained in Section 6.3.4. 
Subtree POWER_DCBUSA describes the loss of power to the distribution bus A from the 
battery chargers and the 125V DC battery cell shown in Figure A-3. In order for AND-gate 
POWER_DCBUSA to occur, the following two events must occur: 
.. Basic Event BATTERY_DCBUSA: 125V DC Distribution Bus A battery fails to operate. 
.. AND-gate CHARGR_DCBUSA: 125V DC Distribution Bus A Battery Chargers fail to 
operate. 
CHARGR_DCBUSA occurs if battery charger D11 and backup battery charger D13 fail to 
operate simultaneously, represented by basic events CHARGRD11_DCBUSA and 
CHARGRD13_BACKUP, respectively. 
Subtree DCBUSB_SIDEA describes the failure of the 125V DC distribution bus B to supply 
backup power to all normal medium voltage circuit breakers on side A of the power grid. The 
following four events are inputs that can make OR-gate DCBUSB_SIDEA occur: 
. Basic Event LCKTBRKRB_C_SIDEA: Low voltage circuit breaker fails to close upon 
demand to connect Side A load. 
. Basic Event LINEB_SIDEA: Power line fails to remain intact to connect Side A load.

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. Basic Event DCBUSB: 125V DC Distribution Bus B fails short circuited. 
. AND-gate POWER_DCBUSB: Loss of DC power to Distribution Bus B. 
Note that CCF inputs are explained in Section 6.3.4. 
Subtree POWER_DCBUSB describes the loss of power to the distribution bus B from the battery 
chargers and the 125V DC battery cell shown in Figure A-3. In order for AND-gate 
POWER_DCBUSB to occur, the following two events must occur: 
.. Basic Event BATTERY_DCBUSB: 125V DC Distribution Bus B battery fails to operate. 
.. AND-gate CHARGR_DCBUSB: 125V DC Distribution Bus B Battery Chargers fail to 
operate. 
CHARGR_DCBUSB occurs if battery charger D12 and backup battery charger D13 fail to 
operate simultaneously, represented by basic events CHARGRD12_DCBUSB and 
CHARGRD13_BACKUP, respectively. 
It is important to note that the 480V AC power that supplies the chargers is not modeled in this 
FT because the loss of AC power is modeled by the entire FTA and would make the top event 
occur much faster than modeling it in this FT. 
6.3.2.5 Emergency 125V DC System Failure  SWGR EA 
Figure A-13 shows subtree 125VDC_SWGREA, which is defined as 125V DC System fails to 
supply power to SWGR EA medium voltage circuit breakers. This causes the disconnection of 
the DTF 1 load from SWGR EA. Thus, it is the expansion of TRANSFER-gate 
125VDC_SWGREA in subtree DISCONNECT_SWGREA (Figure A-6). 
In Figure A-4 and Section 6.3.1, it is shown that all emergency medium voltage circuit breakers 
on SWGR EA are powered by an independent emergency 125V DC system that is fed by SWGR 
EA. The emergency 125V DC system can fail if it fails to remain connected SWGR EA or the 
125V DC system components fail. Thus, in order for OR-gate 125VDC_SWGREA to occur, the 
following two events must occur: 
.. OR-gate DISCONN_SWGREA: Failure of MCC to remain connected to Emergency 
SWGR A. 
.. OR-gate 125VDC: 125V DC system fails to supply power to SWGR EA Medium Voltage 
Circuit Breakers. 
Subtree DISCONN_SWGREA describes the failure of the emergency 125V DC system located 
in the ESB, to remain connected to SWGR EA. The following seven events are inputs that can 
make OR-gate DISCONN_SWGREA occur: 
. OR-gate DISCONN_MCC: Failure of 125V DC system to remain connected to MCC.

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. Basic Event MCKTBRKR_O_ESB: Medium Voltage Circuit Breaker fails to remain closed 
to connect ESB load. 
. Basic Event FUSE_O_ESB: Fused Interrupter Switch fails to remain closed to connect 
ESB load. 
. Basic Event XFMR_ESB: 4160-480V Transformer fails to operate. 
. Basic Event LINE_ESB: Power line fails to remain intact to connect ESB load. 
. Basic Event LCKTBRKR_O_ESB: Low Voltage Circuit Breaker fails to remain closed to 
connect ESB load. 
. Basic Event IBUS_MCC: MCC bus fails short circuited. 
Note that CCF inputs are explained in Section 6.3.4. 
Subtree DISCONN_MCC describes the failure of the emergency 125V DC system to remain 
connected to the MCC located in the ESB as shown in Figure A-4. In order for OR-gate 
DISCONN_MCC to occur, any of the following two events must occur: 
.. Basic Event LINE_125VDC: Power line fails to remain intact to connect 125V DC load. 
.. Basic Event LCKTBRKR_O_125VDC: Low Voltage Circuit Breaker fails to remain closed 
to connect 125V DC. 
Subtree 125VDC describes the failure of the emergency 125V DC system components. The 
following four events are inputs that can make OR-gate 125VDC occur: 
. Basic Event LCKTBRKR_O_SWGREA: Low Voltage Circuit Breaker fails to remain 
closed to connect SWGR EA load. 
. Basic Event LINE_SWGEA: Power line fails to remain intact to connect SWGR EA load. 
. Basic Event DCBUS_SWGREA: 125V DC distribution bus for SWGR EA fails short 
circuited. 
. AND-gate DCPOWER_SWGREA: Loss of DC power to 125VDC distribution bus to 
SWGR EA. 
Note that CCF inputs are explained in Section 6.3.4. 
Subtree DCPOWER_SWGREA describes the loss of power to the 125V DC distribution bus 
from the battery charger and the 125V DC battery cell shown in Figure A-4. In order for 
AND-gate DCPOWER_SWGREA to occur, the following two events must occur:

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.. OR-gate SWGREA_CHARGR: SWGR EA 125V DC battery charger fails to operate. 
.. OR-gate SWGREA_BATTERY: SWGR EA 125V DC battery fails to operate. 
SWGREA_CHARGR occurs if the battery charger fails to operate or if the low voltage circuit 
breaker fails to remain closed to connect the battery charger to the 125V DC distribution bus, 
represented by basic events CHARGR_SWGREA and LCKTBRKR_O_CHARGRA, 
respectively. 
SWGREA_BATTERY occurs if the battery fails to operate or if the low voltage circuit breaker 
fails to remain closed to connect the battery to the 125V DC distribution bus, represented by 
basic events BATTERY_SWGREA and LCKTBRKR_O_BATTA. 
Note that CCF inputs are explained in Section 6.3.4. 
6.3.3 Basic Events Quantification 
Once the FT logic model is completed as seen in Figures A-5 through A-13, probabilities of all 
basic events are assessed (Section 6.2.4). Component failure rate data for this FTA were 
gathered from two main component reliability information sources: Generic Component Failure 
Data Base (Eide and Calley 1993, Tables 1 and 2) and IEEE Guide to the Collection and 
Presentation of Electrical, Electronic, Sensing Component, and Mechanical Equipment 
Reliability Data for Nuclear-Powered Generating Stations (IEEE Std 500-1984 (Reaffirmed 
1991)). These sources have compiled failure rate data for use in probabilistic risk assessment 
from nuclear facilities, fossil-fired generating stations, chemical industries, transmission grids 
and industrial plants. However, data in Generic Component Failure Data Base (Eide and Calley 
1993, Tables 1 and 2) is mostly based on nuclear power plant standards. 
The collected data represents the failure rate of generic components in failure per million 
hours (.) or per demand (q). The Generic Component Failure Data Base (Eide and Calley 1993, 
Tables 1 and 2) shows two modes per component, failure to start and failure to continue 
operation. The IEEE Guide (IEEE Std 500-1984 (Reaffirmed 1991)) has failure rates for 
specific failure modes of components as well as failure rates that represent the summation of all 
failure modes. 
All component reliability numbers must be converted to probabilities before they are input into 
SAPHIRE. Equation 3 is used to turn failure rates (.) into probabilities, while per demand 
probabilities (q) are already in this form. All generic components used for basic events are 
compiled in Table 1, which was developed with the use of Microsoft Excel 97. 
The first column in Table 1 contains the generic component name as listed in the database. The 
second column describes the failure mode(s) used in the FT for each component. The failure 
rates and failure probabilities for each components failure mode and their units are found in 
columns three and four, respectively. For components whose specific failure modes were not 
listed, the number used for the failure rate or probability was conservatively taken as the all 
failure mode, which is the summation of all failure modes, including the needed failure mode. 
The data source and reference columns identify the source where the data were taken from for 
each component. The basis for probability column gives the basis for obtaining a probability,

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100-PSA-EE00-00100-000-00A 35 December 2004 
which is given in the next column, for each component to be input for basic events into 
SAPHIRE. Lastly, the comment column in Table 1 indicates which components in the FT model 
are represented by those probabilities. It is important to note that SAPHIRE displays only two 
significant digits. 
All basic events in the FT can be found on this table except for CCFs; all undeveloped events 
termed FAULT_XXX that describe unknown faults in loads connected to the SWGR EA, Main 
SWGR A, Main SWGR B; and basic event termed PWRCKTBRKRA_230KV that describe the 
failure of the power circuit breaker configuration in substation A. 
The offsite power loss failure rate was gathered from BSC (2004a, Section 5.1.1.48). 
The power circuit breakers shown in Figure A-1 as part of Substations A and B, and described in 
subtree LOSP_SWYDA, are not listed on Table 1. The power circuit breakers are configured by 
two motor operated disc switches and a medium voltage circuit breaker and thus, is not found as 
a single component on any database source. Therefore, the failure probability used to represent 
the failure of the power circuit breaker, as shown on basic event PWRCKTBRKRA_230KV on 
subtree LOSP_SWYDA, is a combination of two motor operated switches and one medium 
voltage circuit breaker. This failure probability is 9.2E-6. 
All undeveloped events termed FAULT_XXX that describe unknown faults in loads connected 
to SWGR EA, Main SWGR A, and Main SWGR B are not listed on Table 1. 
All undeveloped events in subtree DISCONNECT_SWGREA are quantified based on the 
similarities between all MCCs (Assumption 5.2) connected to LC A. Therefore, 
FAULT_MCCA, FAULT_MCCB, and FAULT_MCCC are given the same failure probability of 
1.92E-6 as IBUS_MCCI, which is the fault of the MCC I load. 
All undeveloped events in subtree BUS_SWGREA are quantified based on the similarities 
between all loads connected to SWGR EA. Therefore, FAULT_LCC, FAULT_MCCS, 
FAULT_LCG, and FAULT_MCCK are given a failure probability of 3.88E-6, which is obtained 
by adding BUS_LCA and XFMR_DTF1, described in subtree DISCONNECT_SWGREA.

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Reliability Analysis of the Electrical Power Distribution System to Selected Portions of the Nuclear HVAC System 
Table 1. Basic Event Failure Rates and Probability Calculations 
Component/ 
Subsystem Type Failure Mode 
Failure 
Rate 
Unit 
Data Source Reference 
Basis for 
Probability 
Probability 
of Basic 
Event in FT 
Model 
Comment 
Substation Transformer 
Liquid Filled, 3 phase 
146-242kV 
Fails to operate 2.2310-06 h IEEE 
Std 500-1991 
p. 392 .t 8.9210-06 Used for 230kV-12.47kV Main 
Transformer A 
Substation Transformer 
Liquid Filled, 3 phase 
73-145kV 
Fails to operate 1.2410-06 h IEEE 
Std 500-1991 
p. 391 .t 4.9610-06 Used for 138kV-12.47kV Main 
Transformer B 
Transmission Tie 
Transformer - Liquid Filled, 3 
phase 2-30kV 
Fails to operate 0.4910-06 h IEEE 
Std 500-1991 
p. 372 .t 1.9610-06 Used for 12.47kV-4.16kV 
Transformer and 4.16kV-480V 
Transformer 
Power Cables Fails to conduct 
power 
4.8410-06 h IEEE 
Std 500-1991 
p. 747 .t 1.9410-05 Used for all Internal Power Lines 
Bus Duct 480V, 3phase 
100-1600 Amps 
Fails short circuited 0.4810-06 h IEEE 
Std 500-1991 
p. 797 .t 1.9210-06 Used for LCA, LCB, and all MCC 
Buses 
Bare Buses, Outdoor 
Switchgear 
Fails short circuited 0.2610-06 h IEEE 
Std 500-1991 
p. 804 .t 1.0410-06 Used for Main SWGR A and B, 
Emergency Switchgear A and B, and 
125V DC Distribution Bus A and B 
Fails to close 
Fails to shed 
Metal Clad Drawout Circuit 
Breaker 
Above 600 Amps 
Fails to connect 
0.3010-06 h IEEE 
Std 500-1991 
p. 146 .t 1.2010-06 Used for Medium Voltage Circuit 
Breakers 
Fails to close 
Fails to shed 
Molded Case 
Circuit Breaker 
Fails to connect 
1.1310-06 h IEEE 
Std 500-1991 
p. 124 .t 4.5210-06 Used for Low Voltage Circuit Breaker 
Fails to start 1.0010-02 d Eide and 
Calley 1993 
p. 1177 q 1.0010-02 Diesel Generator 
Fails to operate 5.0010-03 h Eide and 
Calley 1993 
p. 1177 .t 2.0010-02 
Used for Emergency Diesels A and B

Table 1. Basic Event Failure Rates and Probability Calculations (Continued) 
100-PSA-EE00-00100-000-00A 37 December 2004 
Reliability Analysis of the Electrical Power Distribution System to Selected Portions of the Nuclear HVAC System 
Component/ 
Subsystem Type Failure Mode 
Failure 
Rate 
Unit 
Data Source Reference 
Basis for 
Probability 
Probability 
of Basic 
Event in FT 
Model 
Comment 
Wet Cell Battery Fails to operate 0.1010-06 h IEEE 
Std 500-1991 
p. 76 .t 0.4010-06 Used for 125V DC Batteries 
Battery Charging Unit Fails to operate 1.6910-06 h IEEE 
Std 500-1991 
p. 63 .t 6.7610-06 Used for 125V DC Battery Chargers 
Relay, General Fails to open 3.0010-04 d Eide and 
Calley 1993 
p. 1179 q 3.0010-04 Used for all Fused Interrupter 
Switches 
Spurious opening 5.0010-07 h Eide and 
Calley 1993 
p. 1179 .t 2.0010-06 Used for all Fused Interrupter 
Switches 
Offsite Power Loss 1.1010-05 h BSC 2004a Section 
5.1.1.48 
.t 4.4010-05 Used for 230kV Source and 138kV 
Source 
General Switch Spurious operation 1.0010-06 h Eide and 
Calley 1993 
p. 1179 .t 4.0010-06 Used for Motor Operated Disc 
Switches on 230kV and 138kV Lines 
Transmission Tie 
Transformer - Liquid Filled, 
3 phase 
146-242kV 
Fails to operate 1.3210-06 h IEEE 
Std 500-1991 
p. 375 .t 5.2810-06 Used for CCVT on Side A 
Transmission Tie 
Transformer - Liquid Filled, 3 
phase 
73-145kV 
Fails to operate 1.0210-06 h IEEE 
Std 500-1991 
p. 374 .t 4.0810-06 Used for CCVT on Side B 
NOTES: Mission Time = 4 hr (Assumption 5.4) 
q Failure on demand of in-service component 
.t Unavailability of in-service components during mission time = 1 - exp(-Failure rate  Mission Time) . Failure rate  Mission Time 
(NRC 1983, Section 5.3.1.1, Eq. 5.1)

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100-PSA-EE00-00100-000-00A 38 December 2004 
All undeveloped events in subtree CBUS_SWYDA are quantified based on the similarities 
between all loads connected to Main SWGR A. Therefore, FAULT_LC12, 
FAULT_SWGR01A, FAULT_SWGR08, FAULT_SWGR06, FAULT_2MVA, 
FAULT_11.7MVA, and FAULT_SWGRC are given a failure probability of 3.00E-6, which is 
obtained by adding BUS_SWGREA and XFMR_SWGREA, as described in subtree 
BUS_SWGREA and SWYDA_SWGREA, respectively. 
All undeveloped events in subtree CBUS_SWYDB are quantified based on the similarities 
between all loads connected to Main SWGR B. Therefore, FAULT_SWGR01B, FAULT_LC13, 
FAULT_SOLAR, FAULT_SWGR09, FAULT_SWGR07, FAULT_3.8MVA, 
FAULT_11.8MVA, and FAULT_SWGRD are given a failure probability of 3.00E-6, which is 
obtained by adding BUS_SWGREB and XFMR_SWGREB, as described in subtree 
BUS_SWGREB and SWYDB_SWGREB, respectively. 
The quantification of all CCF events is discussed in the following section. 
6.3.4 Common-Cause Failure Analysis 
CCF analysis is omitted from the discussion of the fault tree logic model in Section 6.3.2 and 
basic event quantification in Section 6.3.3 because it cannot be performed until the FT model is 
built and quantified. 
The first step in CCF analysis is identifying which components are identical and redundant in a 
subsystem and subject to a root cause failure (Section 6.2.5). Figures A-6 through A-13 show 
subtrees that represent subsystems of the electrical power distribution system. Each subtree is 
scoped for common events, starting with subtree DISCONNECT_SWGREA in Figure A-6. 
Common events are determined by type of component and failure mode. If two components are 
alike and redundant, but have different failure modes, they do not share a root cause failure. 
Next, the probability of the identified CCF events is derived by multiplying the failure 
probability of the independent event by the alpha factor found in column four of Table 2. 
The first column of Table 2 identifies the number of redundant components subject to CCF in a 
system. The second column defines how many out of the group are needed for success. The 
third column contains the formulas used to derive the alpha factor values, which are in column 
four. These factors are based on a staggered maintenance schedule for the components 
(Assumption 5.6) 
For example, subtree DISCONNECT_SWGREA has three CCF events, 
CCF_LINE_SWGREAB, CCF_480VBUS_LCAB, and CCF_LCKTBRKR_S_LCA. 
CCF_LINE_SWGREAB describes the failure of the power lines to remain intact to connect the 
DTF 1 loads to SWGR EA and SWGR EB. To obtain success, it is necessary that one power 
line remain intact. This is represented by a basic event termed CCF_LINE_SWGREA, 
described as CCF Power Line (1/2)  DTF 1 load Side A and Side B. This event is then 
quantified by multiplying the event failure probability of 1.94E-5 from Table 1 by a factor of 
0.047 from Table 2 that represents a 1-out-of-2 success configuration. This results in a failure 
probability of 9.12E-7 for CCF_LINE_SWGREA.

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Table 2. Alpha Factor Expressions for Common Cause Failure (Staggered Maintenance) 
Common Cause 
Component Group 
CCCG Size 
Success 
Configuration CCF Probability: Staggered Testing 
Value CCF 
Probability/qT - 
Staggered Testing 
2 1 of 2 
2 of 2 
a2qT 0.047 
3 1 of 3 a3qT 0.026 
2 of 3 
3 of 3 
(3a2/2+a3)qT 0.062 
4 1 of 4 a4qT 0.019 
2 of 4 (4a3/3+a4)qT 0.032 
3 of 4 
4 of 4 
(4a2/2+4a3/3+a4)qT 0.075 
5 1 of 5 a5qT 0.015 
2 of 5 (5a4/4+a5)/qT 0.022 
3 of 5 (5a3/3+5a4/4+a5)qT 0.039 
4 of 5 
5 of 5 
(5a2/2+5a3/3+5a4/4+a5)qT 0.085 
6 1 of 6 a6qT 0.012 
2 of 6 (6a5/5+a6)qT 0.018 
3 of 6 (6a4/4+6a5/5+a6) qT 0.027 
4 of 6 (6a3/3+ 6a4/4+6a5/5+a6) qT 0.047 
5 of 6 
6 of 6 
(6a2/2+6a3/3+6a4/4+6a5/5+a6) qT 0.091 
7 1 of 7 a7qT 0.010 
2 of 7 (7a6/6+a7)qT 0.013 
3 of 7 (7a5/5+7a6/6+a7) qT 0.019 
4 of 7 (7a4/4+ 7a5/5+7a6/6+a7) qT 0.030 
5 of 7 (7a3/3+7a4/4+7a5/5+7a6/6+a7) qT 0.050 
6 of 7 
7 of 7 
(7a2/2+7a3/3+7a4/4+7a5/5+7a6/6+a7) qT 0.094 
8 1 of 8 a8qT 0.009 
2 of 8 (8a7/7+a8)qT 0.011 
3 of 8 (8a6/6+8a7/7+a8)qT 0.015 
4 of 8 (8a5/5+8a6/6+8a7/7+a8)qT 0.022 
5 of 8 (8a4/4+8a5/5+8a6/6+8a7/7+a8)qT 0.034 
6 of 8 (8a3/3+8a4/4+8a5/5+8a6/6+8a7/7+a8)qT 0.055 
7 of 8 
8 of 8 
(8a2/2+8a3/3+8a4/4+8a5/5+8a6/6+8a7/7+a8)qT 0.098 
Source: BSC 2004e, Table II-2.

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CCF_480VBUS_LCAB describes the failure of the LC A bus and LC B bus. To obtain success, 
it is necessary that one bus be operating properly. This is represented by a basic event termed 
CCF_480VBUS_LCAB, described as CCF 480V Bus (1/2)  LC A Bus & LC B. This event 
is then quantified by multiplying the event failure probability of 1.92E-6 from Table 1 by a 
factor of 0.047 from Table 2 that represents a 1-out-of-2 success configuration. This results in a 
failure probability of 9.02E-8 for CCF_480VBUS_LCAB. 
CCF_LCKTBRKR_S_LCA describes the failure of the low voltage circuit breakers to shed 
MCC I, MCC A, MCC B, and MCC C upon demand. To obtain success, it is necessary that all 
four low voltage circuit breakers be operating properly. This is represented by a basic event 
termed CCF_LCKTBRKR_S_LCA, described as CCF Low Voltage Circuit Breaker Shed 
(4/4)  LC A Bus. This event is then quantified by multiplying the event failure probability 
of 4.52E-6 from Table 1 by a factor of 0.075 from Table 2 that represents a 4-out-of-4 success 
configuration. This results in a failure probability of 3.39E-7 for CCF_LCKTBRKR_S_LCA. 
The OR-gates termed MCCI_LCKTBRKR_S, MCCA_LCKTBRKR_S, 
MCCB_LCKTBRKR_S, and MCCC_LCKTBRKR_S are a result of including the CCF as a 
possibility of failure of all low voltage circuit breakers. 
The remaining CCF events in Figures A-7 through A-13 are derived in the same fashion as that 
explained above. 
6.4 FAULT TREE ANALYSIS RESULTS 
Once the FT has been modeled and failure probabilities have been input into all basic events, the 
FT is solved with the aid of SAPHIRE to identify and quantify the minimal cut sets 
(Section 6.2.6). The result is output in a quantitative cut set report. 
The summary of the cut set report, shows that the top event can occur from any one of 26 
singles that combine to give a probability of 9.456E-5, any one of 763 doubles that combine 
to give a probability of 2.610E-8, and any one of 44 triples that combine to give a probability 
of 1.412E-13. All cut sets are added together and result in a final probability of 9.458E-5 
(Table 3) for the occurrence of the top event in a 4-hour mission time (Assumption 5.4) 
or 2.365E-5 failures per hour. This result applies to the DTF 1, DTF 2, and FHF. 
A detailed quantitative cut set list of the top 37 cut sets is shown on Table 3, providing the exact 
event name(s), event description(s), and failure probability for each cut set, including its 
percentage contribution to the total probability. Table 3 shows that the dominant contributors to 
the top event making 76.7 percent of the total probability are three singles, which are 
independent events. The top three singles are independent events that involve the loss of 
offsite power, a power line failure, and a power circuit breaker failure at Substation A, 
respectively, and are found in subtree LOSP_SWYDA.

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Reliability Analysis of the Electrical Power Distribution System to Selected Portions of the Nuclear HVAC System 
Table 3. SAHPIRE Cut Sets Report for the entire Electrical Power Distribution System with no Emergency Power

Reliability Analysis of the Electrical Power Distribution System to Selected Portions of the Nuclear HVAC System 
100-PSA-EE00-00100-000-00A 42 December 2004 
7. SENSITIVITY ANALYSIS 
As indicated in Section 6.4, the failure of the electrical power distribution system to distribute 
power to the nuclear HVAC system in the primary confinement areas of the DTF 1, DTF 2, and 
FHF is 2.365E-5/hr. Note that this number takes credit for the entire power grid from the offsite 
source at Substation A to the supply and exhaust fans at each building powered by Emergency 
SWGRs A and B (Section 6.3), but not for backup or emergency power. This number is 
approximately four orders of magnitude below the required failure rate of 2.5E-3/hr mentioned in 
Section 1, which confirms that the power grid is very reliable. Sections 7.1 through 7.5 discuss 
other options to meet the required reliability goal, including taking credit for emergency power. 
FTA of Emergency Diesel Generators 
As mentioned in Section 6.3.1, each emergency SWGR bus has an EDG as a source of 
emergency power. The EDG is started and connected automatically upon loss of power to the 
emergency SWGR. Loads on the emergency SWGR are then sequentially reconnected to the 
bus. Figure A-14 shows subtree EDGA_SWGREA, which represents the failure of the EDG to 
power the SWGR EA bus. Both EDGs are identical and for practical purposes only, one is 
explained in this section. Based on the success criterion explained in Section 6.3, only one 
successful EDG is necessary to keep the top event from occurring. This subtree assumes that if 
the EDG is successfully started and connected, all appropriate loads to the emergency SWGR 
bus will be sequentially connected and powered (Assumption 5.3). 
There are eight events that are inputs to OR-gate EDGA_SWGREA that if TRUE, can make it 
occur: 
.. Basic Event START_EDGA: EDG A fails to start operation. 
.. Basic Event RUN_EDGA: EDG A fails to continue operation. 
.. Basic Event MCKTBRKR_O_EDGA: Medium Voltage Circuit Breaker fails to remain 
closed to connect EDG A. 
.. Basic Event LINE_EDGA: Power line fails to remain intact to connect EDGA. 
.. Basic Event CCF_START_EDGAB: CCF Diesel Start (1/2)  EDG A & EDG B. 
.. Basic Event CCF_RUN_EDGAB: CCF Diesel Run (1/2)  EDG A & EDG B. 
.. Basic Event CCF_MCKTBRKR_O_EDGAB: CCF Medium Voltage Circuit Breaker 
Connect (1/2)  EDG A & EDG B. 
.. Basic Event CCF_LINE_EDGAB: CCF Power Line (1/2)  EDG A & EDG B. 
Except for CCFs, the quantification of each basic event was done with the use of Table 1 
(Section 6.3.3). CCF events were identified and quantified for redundant components between 
both EDGs based on Section 6.3.4. The resulting failure probability of EDGA_SWGREA 
is 3.119E-2 in a 4-hour mission time (Assumption 5.4) or 7.798E-3 failures per hour.

Reliability Analysis of the Electrical Power Distribution System to Selected Portions of the Nuclear HVAC System 
100-PSA-EE00-00100-000-00A 43 December 2004 
7.1 FTA OF ENTIRE POWER GRID WITH EMERGENCY POWER 
Figure A-15 shows the FT model that credits the entire power grid as well as all emergency 
power to prevent the occurrence of the top event. The entire power grid with emergency power 
is the path of power distribution from the offsite power received at Substation A down to the 
Emergency SWGRs A and B (Figure A-1), which are powered by EDGs A and B, to two MCC 
Is of the nuclear HVAC system in the primary confinement areas of the DTF 1 (Figure A-2), 
DTF 2, and FHF. 
This FT is the same as that explained in Section 6.3.2 with the only difference that the third 
overall event, which is the loss of power to the emergency SWGR bus, requires two events for 
failure: failure of the EDG and switchyard to power the emergency SWGR bus. This is 
represented with AND-gates LOSP_SWGREA and LOSP_SWGREB. 
The summary of the cut set report, shows that the top event can occur from 13 singles that give 
a probability of 4.756E-6, any one of 456 doubles that combine to give a probability of 
1.445E-7, any one of 2454 triples that combine to give a probability of 8.189E-8, and 
60 quadruples that combine to give a probability of 6.561E-13. All cut sets are added together 
and result in a final probability of 4.982E-6 (Table 4) for the occurrence of the top event in a 
4-hour mission time, or 1.246E-6 failures per hour. This result applies to the DTF 1, DTF 2, and 
FHF. 
A detailed quantitative cut set list of the top 27 cut sets is shown in Table 4, providing the exact 
event name(s), event description(s), and failure probability for each cut set, including its 
percentage contribution to the total probability. Table 4 shows that the dominant contributors to 
the top event making 73.2 percent of the total probability are four singles, which are CCF 
events that involve power line failure events that occur on both emergency SWGR buses and are 
found in subtrees 125VDC_SWGREA and DISCONNECT_SWGREA.

100-PSA-EE00-00100-000-00A 44 December 2004 
Reliability Analysis of the Electrical Power Distribution System to Selected Portions of the Nuclear HVAC System 
Table 4. SAPHIRE Cut Sets Report for the Entire Power Grid with Emergency Power

Reliability Analysis of the Electrical Power Distribution System to Selected Portions of the Nuclear HVAC System 
100-PSA-EE00-00100-000-00A 45 December 2004 
7.2 FTA OF ONE SIDE OF GRID WITH EMERGENCY POWER 
From Assumption 5.1, it is known that electrical power to at least one MCC I is sufficient to 
prevent the failure of the nuclear HVAC system in the primary confinement areas of the DTFs 
and FHF. Thus, it is not necessary to take credit for the entire grid as evidenced in Sections 6.3.2 
through 6.4 and Section 7.1. 
Figure A-16 shows the FT model that credits one side of the power grid (Side A) as well as its 
emergency power (EDG A) to prevent the occurrence of the top event. One side of the power 
grid with emergency power involves the path of power distribution from the offsite power 
received at Substation A to Main SWGRs A and B to SWGR EA (Figure A-1), which is powered 
by EDG A, to an MCC I of the nuclear HVAC system in the primary confinement areas of 
DTF 1 (Figure A-2), DTF 2, and FHF. 
This FT is the same as that explained in Section 7.1 with the exception that only one input, 
FANS_SIDEA, to the AND-gate LOSP_ONSITE is analyzed. 
The summary of the cut set report, shows that the top event can occur from any one of 
33 singles that give a probability of 1.380E-4, any one of 182 doubles that combine to give a 
probability of 3.694E-6, and any one of 59 triples that combine to give a probability of 
1.988E-11. All cut sets are added together and result in a final probability of 1.417E-4 (Table 5) 
for the occurrence of the top event in a 4-hour mission time, or 3.543E-5 failures per hour. This 
result applies to the DTF 1, DTF 2, and FHF. 
A detailed quantitative cut set list of the top 38 cut sets is shown in Table 5, providing the exact 
event name(s), event description(s), and failure probability for each cut set, including its 
percentage contribution to the total probability. Table 5 shows that the dominant contributors to 
the top event making 68.5 percent of the total probability are five singles, which are 
independent events that involve power line failure events that occur upstream of SWGR EA and 
are found in subtrees 125VDC_SWGREA and DISCONNECT_SWGREA.

100-PSA-EE00-00100-000-00A 46 December 2004 
Reliability Analysis of the Electrical Power Distribution System to Selected Portions of the Nuclear HVAC System 
Table 5. SAPHIRE Cut Sets Report for One Side of Power Grid with Emergency Power

Reliability Analysis of the Electrical Power Distribution System to Selected Portions of the Nuclear HVAC System 
100-PSA-EE00-00100-000-00A 47 December 2004 
7.3 FTA OF ONE SIDE OF GRID WITH NO EMERGENCY POWER 
From Assumption 5.1, it is known that electrical power to at least one MCC I is sufficient to 
prevent the failure of the nuclear HVAC system in the primary confinement areas of the DTFs 
and FHF. Thus, it is not necessary to take credit for the entire grid as evidenced in Sections 6.3.2 
through 6.4 and Section 7.1. 
Figure A-17 shows the FT model that credits one side of the power grid with no emergency 
power to prevent the occurrence of the top event. One side of the power grid without emergency 
power involves the path of power distribution from the offsite power received at Substation A to 
Main SWGRs A and B to SWGR EA (Figure A-1), then to an MCC I of the nuclear HVAC 
system in the primary confinement areas of DTF 1 (Figure A-2), DTF 2, and FHF. 
This FT is the same as that explained in Section 7.2 with the exception that the third input, ANDgate 
LOSP_SWGREA, is replaced with TRANSFER-gate SWYDA_SWGREA. 
The summary of the cut set report, shows that the top event can occur from any one of 
53 singles that give a probability of 2.555E-4, any one of 38 doubles that combine to give a 
probability of 7.211E-10, and eight triples that combine to give a probability of 1.021E-14. 
All cut sets are added together and result in a final probability of 2.555E-4 (Table 6) for the 
occurrence of the top event in a 4-hour mission time, or 6.388E-5 failures per hour. This result 
applies to the DTF 1, DTF 2, and FHF. 
A detailed quantitative cut set list of the top 47 cut sets is shown in Table 6, providing the exact 
event name(s), event description(s) and failure probability for each cut set, including its 
percentage contribution to the total probability. Table 6 shows that the dominant contributors to 
the top event making 70.4 percent of the total probability are eight singles, which are 
independent events that involve loss of offsite power at Substation A, and power line failure 
events that occur at Substation A, the 125VDC emergency distribution system, and that cause the 
disconnection of the MCC I load, DTF 1 load, and SWGR EA load. These events are found in 
subtrees DISCONNECT_SWGREA, SWYDA_SWGREA, 125VDC_SWGREA and 
LOSP_SWYDA.

100-PSA-EE00-00100-000-00A 48 December 2004 
Reliability Analysis of the Electrical Power Distribution System to Selected Portions of the Nuclear HVAC System 
Table 6. SAPHIRE Cut Sets Report for One Side of Grid with No Emergency Power

Reliability Analysis of the Electrical Power Distribution System to Selected Portions of the Nuclear HVAC System 
100-PSA-EE00-00100-000-00A 49 December 2004 
7.4 FTA OF EMERGENCY POWER ONLYTWO SIDES 
Another option to meet the required reliability goal includes taking credit for emergency power 
only on side A and B to power the MCC Is. 
Figure A-18 shows the FT model that credits two sides of the power grid with only emergency 
power to prevent the occurrence of the top event. Emergency power on both sides of the power 
grid involves the path of power distribution from emergency SWGRs A and B, which are 
powered by EDG A and EDG B (Figure A-1), to two MCC Is of the nuclear HVAC system in 
the primary confinement areas of the DTF 1 (Figure A-2), DTF 2, and FHF. 
This FT is the same as that explained in Section 6.3.2 with the only difference that the third 
overall event, which is the loss of power to the emergency SWGR bus, depends solely on the 
failure of the EDG to power the emergency SWGR bus. This is represented with 
TRANSFER-gates EDGA_SWGREA and EDGB_SWGREB. 
The summary of the cut set report, shows that the top event can occur from any one of 17 
singles that give a probability of 1.415E-3, any one of 580 doubles that combine to give a 
probability of 9.090E-4, and any one of 68 triples that combine to give a probability of 
5.309E-12. All cut sets are added together and result in a final probability of 2.323E-3 (Table 7) 
for the occurrence of the top event in a 4-hour mission time, or 5.808E-4 failures per hour. It is 
important to note that this number does not reflect the failure rate of offsite power, which is 
1.1E-5/hr (BSC 2004a, Section 5.1.1.48). This result applies to the DTF 1, DTF 2 and FHF. 
A detailed quantitative cut set list of the top 27 cut sets is shown on Table 7, providing the exact 
event name(s), event description(s), and failure probability for each cut set, including its 
percentage contribution to the total probability. Table 7 shows that the dominant contributors to 
the top event making 60.7 percent of the total probability are two singles, which are CCF 
events that involve the start and continuing operation of both EDGs and are found in subtrees 
EDGA_SWGREA and EDGB_SWGREB.

100-PSA-EE00-00100-000-00A 50 December 2004 
Reliability Analysis of the Electrical Power Distribution System to Selected Portions of the Nuclear HVAC System 
Table 7. SAPHIRE Cut Sets Report of the Emergency Power Only  Two Sides

Reliability Analysis of the Electrical Power Distribution System to Selected Portions of the Nuclear HVAC System 
100-PSA-EE00-00100-000-00A 51 December 2004 
7.5 FTA OF EMERGENCY POWER ONLY  ONE SIDE 
From Assumption 5.1, it is known that electrical power to at least one MCC I is sufficient to 
prevent the failure of the nuclear HVAC system in the primary confinement areas of the DTFs 
and FHF. Thus, it is not necessary to take credit for emergency power on sides A and B of the 
power grid as was done in Section 7.4. 
Figure A-19 shows the FT model that credits one side of the power grid with only emergency 
power to prevent the occurrence of the top event. Emergency power on one side of the power 
grid involves the path of power distribution from SWGR EA, which is powered by EDG A 
(Figure A-1), to one MCC I of the nuclear HVAC system in the primary confinement areas of the 
DTF 1 (Figure A-2), DTF 2, and FHF. 
This FT is the same as that explained in Section 7.4 with the exception that only one input, 
FANS_SIDEA, to the AND-gate LOSP_ONSITE is analyzed. 
The summary of the cut set report, shows that the top event can occur from any one of 
41 singles that give a probability of 3.132E-2, any one of 22 doubles that combine to give a 
probability of 8.853E-11, and any one of four triples that combine to give a probability of 
5.773E-15. All cut sets are added together and result in a final probability of 3.132E-2 (Table 8) 
for the occurrence of the top event in a 4-hour mission time, or 7.830E-3 failures per hour. It is 
important to note that this number does not reflect the failure rate of offsite power, which is 
1.1E-5/hr (BSC 2004a, Section 5.1.1.48). This result applies to the DTF 1, DTF 2, and FHF. 
A detailed quantitative cut set list of the top 44 cut sets is shown in Table 8, providing the exact 
event name(s), event description(s), and failure probability for each cut set, including its 
percentage contribution to the total probability. Table 8 shows that the dominant contributors to 
the top event making 95.8 percent of the total probability are two singles, which are 
independent events that involve the start and continuing operation of EDG A and are found in 
subtree EDGA_SWGREA.

100-PSA-EE00-00100-000-00A 52 December 2004 
Reliability Analysis of the Electrical Power Distribution System to Selected Portions of the Nuclear HVAC System 
Table 8. SAPHIRE Cut Sets Report of the Emergency Power Only  One Side.

Reliability Analysis of the Electrical Power Distribution System to Selected Portions of the Nuclear HVAC System 
100-PSA-EE00-00100-000-00A 53 December 2004 
8. CONCLUSIONS AND RECOMMENDATIONS 
The FTA for the electrical power distribution system presented in Sections 6.3 through 6.4 and 
the sensitivity analyses presented in Sections 7.1, 7.2, 7.3, 7.4, and 7.5 demonstrate that the 
probability of loss of power to the nuclear HVAC system in the primary confinement areas of the 
DTF 1, DTF 2, and FHF, due to a loss of offsite and onsite electrical power distribution, is less 
than the design requirement failure rate of 2.5E-3 per hour (BSC 2004a, Section 5.1.1.48). A 
summary of the FTAs presented in this report is shown in Table 9. 
The first FTA presented in Sections 6.3 through 6.4 credits the entire power grid, without 
emergency power, to prevent the occurrence of the top event. The entire power grid is the path 
of power distribution from the offsite power received at Substation A down to emergency 
SWGRs A and B (Figure A-1) to two MCC Is of the nuclear HVAC system in the primary 
confinement areas of the DTF 1 (Figure A-2), DTF 2, and FHF . This also includes the normal 
and emergency 125V DC system, which are support systems to the power grid (Figure A-3 and 
A-4). The FTA results give a failure rate of 2.365E-5 per hour, which is only 0.95 percent of the 
reliability requirement and leaves 99.05 percent for HVAC mechanical failure. 
The FTA presented in Section 7.1 credits the entire power grid, with emergency power, to 
prevent the occurrence of the top event. The entire power grid with emergency power is the path 
of power distribution from the offsite power received at Substation A down to the emergency 
SWGRs A and B (Figure A-1), including EDG A and EDG B, to two MCC Is of the nuclear 
HVAC system in the primary confinement areas of the DTF 1 (Figure A-2), DTF 2, and FHF. 
This FTA results in a failure rate of 1.246E-6 per hour, which is 0.05 percent of the reliability 
requirement and leaves 99.95 percent for HVAC mechanical failure. 
The FTA presented in Section 7.2 credits one side of the power grid, with emergency power, to 
prevent the occurrence of the top event. One side of the power grid with emergency power 
involves the path of power distribution from the offsite power received at Substation A down to 
Main SWGR A and Main SWGR B down to SWGR EA (Figure A-1), including EDG A, to one 
MCC I of the nuclear HVAC system in the primary confinement areas of the DTF 1 (Figure A- 
2), DTF 2, and FHF. This FTA results in a failure rate of 3.543E-5 per hour, which is only 1.42 
percent of the reliability requirement and leaves 98.58 percent for HVAC mechanical failure. 
The FTA presented in Section 7.3 credits one side of the power grid, without emergency power, 
to prevent the occurrence of the top event. One side of the power grid without emergency power 
involves the path of power distribution from the offsite power received at Substation A down to 
the Main SWGR A and Main SWGR B down to SWGR EA (Figure A-1), to one MCC I of the 
nuclear HVAC system in the primary confinement areas of the DTF 1 (Figure A-2), DTF 2, and 
FHF. This FTA results in a failure rate of 6.388E-5 per hour, which is only 2.56 percent of the 
reliability requirement and leaves 97.44 percent for HVAC mechanical failure. 
The FTA presented in Section 7.4 credits only emergency power on both sides of the power grid 
to prevent the occurrence of the top event. Emergency power on both sides of the power grid 
involves the path of power distribution from the emergency SWGRs A and B, powered by EDGs 
A and B (Figure A-1), to two MCC Is of the nuclear HVAC system in the primary confinement 
areas of the DTF 1 (Figure A-2), DTF 2, and FHF. Including loss of offsite power, this results in

Reliability Analysis of the Electrical Power Distribution System to Selected Portions of the Nuclear HVAC System 
100-PSA-EE00-00100-000-00A 54 December 2004 
a failure rate of 5.918E-4 per hour, which is 23.67 percent of the reliability requirement and 
leaves 76.33 percent for HVAC mechanical failure. 
The last FTA presented in Section 7.5 credits only emergency power on one side of the power 
grid to prevent the occurrence of the top event. Emergency power on one side of the power grid 
involves the path of power distribution from SWGR EA, powered by EDG A (Figure A-1), to 
one MCC I of the nuclear HVAC system in the primary confinement areas of the DTF 1 
(Figure A-2), DTF 2, and FHF. Including the loss of offsite power, this results in a failure rate of 
7.841E-3 per hour, which is over 2.5E-3 per hour and thus, does not satisfy the reliability 
requirement. 
In order to limit the amount of components credited to prevent the top event and still meet the 
reliability requirement of 2.5E-3 per hour, while leaving room for mechanical failure, it is 
recommended that credit be taken for either one side of the power grid with no emergency power 
(Section 7.3) or emergency power only on both sides of the power grid (Section 7.4). 
The results presented in this analysis indicate that the outputs are reasonable compared to the 
identified inputs and that the results are suitable for their intended use. 
Table 9. Summary of Fault Tree Analyses 
Fault Tree Analysis 
Failure Ratea 
(h-1) 
No Emergency Power 2.365E-5 Entire Power Grid 
Emergency Power 1.246E-6 
No Emergency Power 6.388E-5 One Side of Power Grid 
Emergency Power 3.543E-5 
Both Sides of Power Grid 5.918E-4 Emergency Power Only 
One Side of Power Grid 7.841E-3 
NOTE: a Failure rates reflect loss of offsite power 1.1E-5 per hour (BSC 2004a , Section 
5.1.1.48).

Reliability Analysis of the Electrical Power Distribution System to Selected Portions of the Nuclear HVAC System 
100-PSA-EE00-00100-000-00A 55 December 2004 
9. REFERENCES 
9.1 DOCUMENTS CITED 
160873 BSC (Bechtel SAIC Company) 2002. Software Code: SAPHIRE. V7.18. PC - 
Windows 2000/NT 4.0. 10325-7.18-00. 
169234 BSC (Bechtel SAIC Company) 2003. Independent Verification and Validation Report 
for Legacy Code SAPHIRE V7.18. STN: 10325-7.18-00. Las Vegas, Nevada: Bechtel 
SAIC Company. ACC: MOL.20040112.0070. 
171429 BSC (Bechtel SAIC Company) 2004a. Categorization of Event Sequences for License 
Application. 000-00C-MGR0-00800-000-00B. Las Vegas, Nevada: Bechtel SAIC 
Company. TBV#7102. 
171342 BSC (Bechtel SAIC Company) 2004b. Electrical Power System Description 
Document. 000-3YD-EE00-00200-000-003. Las Vegas, Nevada: Bechtel 
SAIC Company. TBV#7022. 
171210 BSC (Bechtel SAIC Company) 2004c. Switchyard Switchgear Bldg Single Line 
Diagram 125 V DC System. 27A-E10-EEC0-00201-000-00B. Las Vegas, Nevada: 
Bechtel SAIC Company. ACC: ENG.20040518.0005. 
171491 BSC (Bechtel SAIC Company) 2004d. Reliability Analysis of the Mechanical System 
in Selected Portions of the Nuclear HVAC System. 100-PSA-MGR0-00100-000-00A. 
Las Vegas, Nevada: Bechtel SAIC Company. TBV#7109. 
169554 BSC (Bechtel SAIC Company) 2004e. Waste Package Transporter Preclosure Safety 
Analysis. 800-MQC-HET0-00200-000-00A. Las Vegas, Nevada: Bechtel 
SAIC Company. ACC: ENG.20040623.0002. 
171539 DOE (U.S. Department of Energy) 2004. Quality Assurance Requirements and 
Description. DOE/RW-0333P, Rev. 16. Washington, D.C.: U.S. Department of 
Energy, Office of Civilian Radioactive Waste Management. ACC: 
DOC.20040907.0002. 
146564 Eide, S.A. and Calley, M.B. 1993. "Generic Component Failure Data Base." PSA '93, 
Proceedings of the International Topical Meeting on Probabilistic Safety Assessment, 
Clearwater Beach, Florida, January 26-29, 1993. 2, 1175-1182. 
La Grange Park, Illinois: American Nuclear Society. TIC: 247455. 
171825 IEEE Std 500-1984 (Reaffirmed 1991). 1991 IEEE Guide to the Collection and 
Presentation of Electrical, Electronic, Sensing Component, and Mechanical 
Equipment Reliability Data for Nuclear-Power Generating Stations. New York, 
New York: Institute of Electrical and Electronics Engineers. TIC: 256281.

Reliability Analysis of the Electrical Power Distribution System to Selected Portions of the Nuclear HVAC System 
100-PSA-EE00-00100-000-00A 56 December 2004 
167710 Marshall, F.M.; Rasmuson, D.M.; and Mosleh, A. 1998. Common-Cause Failure 
Parameter Estimations. NUREG/CR-5497. Washington, D.C.: U.S. Nuclear 
Regulatory Commission. ACC: MOL.20040220.0105. 
167711 Mosleh, A.; Rasmuson, D.M.; and Marshall, F.M. 1998. Guidelines on Modeling 
Common-Cause Failures in Probabilistic Risk Assessment. NUREG/CR-5485. 
Washington, D.C.: U.S. Nuclear Regulatory Commission. 
ACC: MOL.20040220.0106. 
106591 NRC (U.S. Nuclear Regulatory Commission) 1983. PRA Procedures Guide, A Guide 
to the Performance of Probabilistic Risk Assessments for Nuclear Power Plants. 
NUREG/CR-2300. Two volumes. Washington, D.C.: U.S. Nuclear Regulatory 
Commission. TIC: 205084. 
128494 Vesely, W.E.; Goldberg, F.F.; Roberts, N.H.; and Haasl, D.F. 1981. Fault Tree 
Handbook. NUREG - 0492. Washington, D.C.: U.S. Nuclear Regulatory 
Commission. TIC: 208328. 
9.2 CODES, STANDARDS, REGULATIONS AND PROCEDURES 
AP-3.12Q. Design Calculations and Analyses. 
AP-3.15Q. Managing Technical Product Inputs. 
LP-SI.11Q-BSC. Software Management.

Reliability Analysis of the Electrical Power Distribution System to Selected Portions of the Nuclear HVAC System 
100-PSA-EE00-00100-000-00A A-1 December 2004 
ATTACHMENT A 
ELECTRICAL POWER DISTRIBUTION SYSTEM ARCHITECTURE AND FAULT 
TREE MODEL - SIDE A

Reliability Analysis of the Electrical Power Distribution System to Selected Portions of the Nuclear HVAC System 
100-PSA-EE00-00100-000-00A A-2 December 2004 
INTENTIONALLY LEFT BLANK

Reliability Analysis of the Electrical Power Distribution System to Selected Portions of the Nuclear HVAC System 
100-PSA-EE00-00100-000-00A A-3 December 2004 
Source: BSC 2004b, Figure 4-3 
Figure A-1. Electrical Power Distribution System 
for the Monitored Geologic 
Repository

Reliability Analysis of the Electrical Power Distribution System to Selected Portions of the Nuclear HVAC System 
100-PSA-EE00-00100-000-00A A-4 December 2004 
INTENTIONALLY LEFT BLANK

Reliability Analysis of the Electrical Power Distribution System to Selected Portions of the Nuclear HVAC System 
100-PSA-EE00-00100-000-00A A-5 December 2004 
Figure A-2. Electrical Power Distribution from 
LC A and LC B to Supply and 
Exhaust Fan Motors 
(Assumption 5.7)

Reliability Analysis of the Electrical Power Distribution System to Selected Portions of the Nuclear HVAC System 
100-PSA-EE00-00100-000-00A A-6 December 2004 
INTENTIONALLY LEFT BLANK

Reliability Analysis of the Electrical Power Distribution System to Selected Portions of the Nuclear HVAC System 
100-PSA-EE00-00100-000-00A A-7 December 2004 
Source: BSC 2004c 
Figure A-3. Normal 125V DC Power Distribution 
System

Reliability Analysis of the Electrical Power Distribution System to Selected Portions of the Nuclear HVAC System 
100-PSA-EE00-00100-000-00A A-8 December 2004 
INTENTIONALLY LEFT BLANK

Reliability Analysis of the Electrical Power Distribution System to Selected Portions of the Nuclear HVAC System 
100-PSA-EE00-00100-000-00A A-9 December 2004 
Source: BSC 2004b, Figure 4-1 
Figure A-4. Emergency 125V DC Power 
Distribution Systems

Reliability Analysis of the Electrical Power Distribution System to Selected Portions of the Nuclear HVAC System 
100-PSA-EE00-00100-000-00A A-10 December 2004 
INTENTIONALLY LEFT BLANK

100-PSA-EE00-00100-000-00A A-11 December 2004 
Reliability Analysis of the Electrical Power Distribution System to Selected Portions of the Nuclear HVAC System 
LOSP_ONSITE 
FANS_SIDEA FANS_SIDEB 
DISCONNECT_SWGREA DISCONNECT_SWGREB SWYDB_SWGREB BUS_SWGREA BUS_SWGREB SWYDA_SWGREA
Failure of the Electrical Power 
Distribution System to provide 
power to the Nuclear HVAC 
System in the DTF1 Primary Conf. 
Loss of Power Distribution to 2 
Supply and 2 Exhaust Fan 
Motors on MCC I - 
DTF1 Side A 
Loss of Power Distribution to 2 
Supply and 2 Exhaust Fan 
Motors on MCC I (B) - 
DTF1 Side B 
Failure of MCC I to 
remain connected to 
Emergency Switchgear A 
Failure of MCC I (B) to 
remain connected to 
Emergency Switchgear B 
Failure of Switchyard 
Switchgear B to power 
Emergency Switchgear B 
Emergency 
Switchgear A 
Bus Unavailable 
Emergency 
Switchgear B 
Bus Unavailable 
Failure of Switchyard 
Switchgear A to power 
Emergency Switchgear A 
Figure A-5. FT Model of the Electrical Power Distribution System with no Emergency Power

Reliability Analysis of the Electrical Power Distribution System to Selected Portions of the Nuclear HVAC System 
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INTENTIONALLY LEFT BLANK

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100-PSA-EE00-00100-000-00A A-13 December 2004 
DISCONNECT_SWGREA 
1.2E-6 
MCKTBRKR_O_DTF1 
1.9E-5 
LINE_DTF1 
2.0E-6 
FUSE_O_DTF1 
2.0E-6 
XFRM_DTF1 DISCONNECT_LCA 
1.9E-6 
IBUS_MCCI 
9.1E-7 
CCF_LINE_SWGREAB 
3.4E-7 
CCF_LCKTBRKR_S_LCA 
MCCC_LCKTBRKR_S 
3.4E-7 
CCF_LCKTBRKR_S_LCA 
MCCB_LCKTBRKR_S MCCA_LCKTBRKR_S 
9.0E-8 
CCF_480VBUS_LCAB 
3.4E-7 
CCF_LCKTBRKR_S_LCA 
4.5E-6 
LCKTBRKR_S_MCCC 
1.9E-6 
FAULT_MCCC 
4.5E-6 
LCKTBRKR_S_MCCB 
1.9E-6 
FAULT_MCCB 
4.5E-6 
LCKTBRKR_S_MCCA 
1.9E-6 
FAULT_MCCA 
OLOAD_MCCC OLOAD_MCCB OLOAD_MCCA 
CBUS_LCA 
1.9E-6 
IBUS_LCA 
BUS_LCA 
4.5E-6 
LCKTBRKR_O_MCCI 
1.9E-5 
LINE_MCCI 
MCCI_LCKTBRKR_S 
3.4E-7 
CCF_LCKTBRKR_S_LCA 
4.5E-6 
LCKTBRKR_S_MCCI 
OLOAD_MCCI 
1.9E-6 
IBUS_MCCI 
125VDC_SWGREA 
Failure of MCC I to 
remain connected to 
Emergency Switchgear A 
Med Volt Ckt Brkr fails 
to remain closed to 
connect DTF1 load 
Power line fails to 
remain intact to 
connect DTF1 load 
4160-480V 
Transformer fails 
to operate 
Fused Interrupter 
Switch fails to remain 
closed to connect DTF1 
Failure of MCC I 
to remain connected 
to Load Center A 
MCCI Bus fails 
short circuited 
CCF Power Line 
(1/2) - DTF1 Load 
Side A and Side B 
Low Volt Ckt Brkr 
fails to shed MCC C 
load upon demand 
Low Volt Ckt Brkr 
fails to shed MCC B 
load upon demand 
Low Volt Ckt Brkr 
fails to shed MCC A 
load upon demand 
CCF Low Voltage 
Circuit Breaker Shed 
(4/4) - LC A Bus 
CCF Low Voltage 
Circuit Breaker Shed 
(4/4) - LC A Bus 
CCF 480V Bus 
(1/2) - LC A Bus 
& LC B Bus 
CCF Low Voltage 
Circuit Breaker Shed 
(4/4) - LC A Bus 
Low Volt Ckt Brkr 
fails to shed MCC C 
load upon demand 
Low Volt Ckt Brkr 
fails to shed MCC B 
load upon demand 
Low Volt Ckt Brkr 
fails to shed MCC A 
load upon demand 
MCC C Load 
failure 
MCC B Load 
failure 
MCC A Load 
failure 
MCC C fault fails 
to be shed from 
LCA Bus 
MCC B fault fails 
to be shed from 
LCA Bus 
MCC A fault fails 
to be shed from 
LCA Bus 
LC A Bus fails 
overloaded 
LC A Bus fails 
short circuited 
Load Center A 
Bus failure 
Low Volt Ckt Brkr fails 
to remain closed to 
connect MCCI 
Power line fails to 
remain intact to 
connect MCCI load 
Low Volt Ckt Brkr 
fails to shed MCC I 
load upon demand 
CCF Low Voltage 
Circuit Breaker Shed 
(4/4) - LC A Bus 
Low Volt Ckt Brkr 
fails to shed MCC I 
load upon demand 
MCC I fault fails 
to be shed from 
LCA Bus 
MCCI Bus fails 
short circuited 
125VDC system fails to 
supply power to SWGREA 
Med Voltage Ckt Brkrs 
Figure A-6. Subtree DISCONNECT_SWGREA

Reliability Analysis of the Electrical Power Distribution System to Selected Portions of the Nuclear HVAC System 
100-PSA-EE00-00100-000-00A A-14 December 2004 
INTENTIONALLY LEFT BLANK

Reliability Analysis of the Electrical Power Distribution System to Selected Portions of the Nuclear HVAC System 
100-PSA-EE00-00100-000-00A A-15 December 2004 
BUS_SWGREA 
1.0E-6 
IBUS_SWGREA CBUS_SWGREA 
OLOAD_LCC OLOAD_MCCS 
OLOAD_LCG 
1.2E-6 
MCKTBRKR_S_LCC 
3.0E-4 
FUSE_S_LCC 
1.2E-6 
MCKTBRKR_S_MCCS 
3.0E-4 
FUSE_S_MCCS 
1.2E-6 
MCKTBRKR_S_LCG 
3.9E-6 
FAULT_LCG 
3.0E-4 
FUSE_S_LCG 
1.0E-7 
CCF_MCKTBRKR_S_SWGREA 
2.5E-5 
CCF_FUSE_S_SWGREA 
LCC_FUSE_S LCC_MCKTBRKR_S 
1.0E-7 
CCF_MCKTBRKR_S_SWGREA 
2.5E-5 
CCF_FUSE_S_SWGREA 
MCCS_MCKTBRKR_S MCCS_FUSE_S 
LCG_MCKTBRKR_S 
1.0E-7 
CCF_MCKTBRKR_S_SWGREA 
2.5E-5 
CCF_FUSE_S_SWGREA 
LCG_FUSE_S MCCK_FUSE_S MCCK_MCKTBRKR_S 
2.5E-5 
CCF_FUSE_S_SWGREA 
1.0E-7 
CCF_MCKTBRKR_S_SWGREA 
3.0E-4 
FUSE_S_MCCK 
1.2E-6 
MCKTBRKR_S_MCCK 
3.9E-6 
FAULT_MCCK 
OLOAD_MCCK OLOAD_LCA 
1.9E-6 
BUS_LCA 
LCA_MCKTBRKR_S LCA_FUSE_S 
1.2E-6 
MCKTBRKR_S_LCA 
1.0E-7 
CCF_MCKTBRKR_S_SWGREA 
3.0E-4 
FUSE_S_LCA 
2.5E-5 
CCF_FUSE_S_SWGREA 
3.9E-6 
FAULT_MCCS 
3.9E-6 
FAULT_LCC 
2.0E-6 
XFRM_DTF1 
FAULT_LCA 
Emergency 
Switchgear A 
Bus Unavailable 
SWGR EA Bus 
fails short circuited 
LC C fault fails to 
be shed from 
SWGR EA Bus 
MCC S fault fails 
to be shed from 
SWGR EA Bus 
LC G fault fails 
to be shed from 
SWGR EA Bus 
LC G Load 
failure 
Med Volt Ckt Brkr 
fails to shed LC C 
Load upon demand 
Med Volt Ckt Brkr 
fails to shed MCC S 
Load upon demand 
Med Volt Ckt Brkr 
fails to shed LC G 
Load upon demand 
Fused Interrupter 
Switch fails to open 
after a LC C overload 
Fused Interrupter 
Switch fails to open 
after a MCC S overload 
Fused Interrupter 
Switch fails to open 
after a LC G overload 
CCF Medium Voltage 
Circuit Breaker Shed 
(5/5) - SWGR EA Bus 
CCF Fused Int 
Switch Open (5/5) - 
SWGR EA Bus 
SWGR EA Bus 
fails overloaded 
CCF Medium Voltage 
Circuit Breaker Shed 
(5/5) - SWGR EA Bus 
CCF Fused Int 
Switch Open (5/5) - 
SWGR EA Bus 
CCF Medium Voltage 
Circuit Breaker Shed 
(5/5) - SWGR EA Bus 
CCF Fused Int 
Switch Open (5/5) - 
SWGR EA Bus 
CCF Fused Int 
Switch Open (5/5) - 
SWGR EA Bus 
CCF Medium Voltage 
Circuit Breaker Shed 
(5/5) - SWGR EA Bus 
Fused Interrupter 
Switch fails to open 
after a MCCK overload 
Med Volt Ckt Brkr 
fails to shed MCC K 
Load upon demand 
MCC K Load 
failure 
MCC K fault fails 
to be shed from 
SWGR EA Bus 
Med Volt Ckt Brkr 
fails to shed LC C 
Load upon demand 
Fused Interrupter 
Switch fails to open 
after a LCC overload 
Med Volt Ckt Brkr 
fails to shed LC G 
Load upon demand 
Fused Interrupter 
Switch fails to open 
after a LC G overload 
Med Volt Ckt Brkr 
fails to shed MCC S 
Load upon demand 
Fused Interrupter 
Switch fails to open 
after a MCC S overload 
Med Volt Ckt Brkr 
fails to shed MCC K 
Load upon demand 
Fused Interrupter 
Switch fails to open 
after a MCC K overload 
LC A fault fails 
to be shed from 
SWGR EA Bus 
Load Center A 
Bus failure 
Med Volt Ckt Brkr 
fails to shed LCA 
load upon demand 
Med Volt Ckt Brkr 
fails to shed LCA 
load upon demand 
CCF Medium Voltage 
Circuit Breaker Shed 
(5/5) - SWGR EA Bus 
Fused Interrupter 
Switch fails to open 
after a LCA overload 
Fused Interrupter 
Switch fails to open 
after a LCA overload 
CCF Fused Int 
Switch Open (5/5) - 
SWGR EA Bus 
MCC S Load 
failure 
LC C Load 
failure 
4160-480V 
Transformer fails 
to operate 
LC A load failure 
Figure A-7. Subtree BUS_SWGREA

Reliability Analysis of the Electrical Power Distribution System to Selected Portions of the Nuclear HVAC System 
100-PSA-EE00-00100-000-00A A-16 December 2004 
INTENTIONALLY LEFT BLANK

Reliability Analysis of the Electrical Power Distribution System to Selected Portions of the Nuclear HVAC System 
100-PSA-EE00-00100-000-00A A-17 December 2004 
SWYDA_SWGREA 
DISCONNECT_SWYDA LOSP_SWYDA 
1.2E-6 
MCKTBRKR1_O_SWGREA 
1.2E-6 
MCKTBRKR2_O_SWGREA 
2.0E-6 
XFMR_SWGREA 
1.9E-5 
LINE_SWGREA 
2.0E-6 
FUSE_O_SWGREA 125VDC_SIDEA 
5.6E-8 
CCF_MCKTBRKR_O_SWYDAB 
BUS_SWYDA 
BUS_SWYDBB 
BUSINT_SWYDB 
1.0E-6 
IBUS_SWYDA CBUS_SWYDA 
4.9E-8 
CCF_BUS_SWYDAB 
1.2E-6 
ICKTBRKR_S 
1.0E-6 
IBUS_SWYDB CBUS_SWYDB 
BUS_SWGREA 
Failure of Main 
Switchgear A to power 
Emergency Switchgear A 
Failure of SWGR EA to 
remain connected to 
Main SWGR A 
125V DC System fails 
to supply power to Side A 
Med Voltage Ckt Brkrs 
Med Volt Ckt Brkr 1 
fails to remain closed to 
connect SWGR EA load 
Med Volt Ckt Brkr 2 
fails to remain closed to 
connect SWGR EA load 
Fused Interrupter Switch 
fails to remain closed to 
connect SWGR EA load 
12.47-4.16kV 
Transformer fails 
to operate 
Power line fails to 
remain intact to connect 
SWGR EA load 
CCF Medium Voltage 
Circuit Breaker Connect 
(1/2) - Switchyards A & B 
Main SWGR A 
Bus Unavailable 
Main SWGR A 
Bus fails short 
circuited 
Main SWGR A Bus 
fails overloaded 
Interconnect Med Volt 
Ckt Brkr fails to isolate 
failure in Main SWGR B 
CCF Bus (1/2) - 
Main SWGRs A & B 
Interconnect Med Volt Ckt 
Brkr fails to open after a 
failure on Main SWGR B 
Main SWGR B 
Bus failure 
Main SWGR B 
Bus fails short 
circuited 
Main SWGR B 
Bus fails 
overloaded 
Emergency 
Switchgear A 
Bus Unavailable 
Failure of 230kV 
system to supply power 
to Main SWGR A 
Figure A-8. Subtree SWYDA_SWGREA

Reliability Analysis of the Electrical Power Distribution System to Selected Portions of the Nuclear HVAC System 
100-PSA-EE00-00100-000-00A A-18 December 2004 
INTENTIONALLY LEFT BLANK

Reliability Analysis of the Electrical Power Distribution System to Selected Portions of the Nuclear HVAC System 
100-PSA-EE00-00100-000-00A A-19 December 2004 
CBUS_SWYDA 
OLOAD_LC12 OLOAD_SWGR01A 
OLOAD_11.7MVA 
OLOAD_SWGR08 
OLOAD_SWGR06 OLOAD_2MVA 
3.0E-6 
FAULT_LC12 
1.2E-6 
MCKTBRKR_S_LC12 
3.0E-4 
FUSE_S_LC12 
3.0E-6 
FAULT_SWGR01A 
1.2E-6 
MCKTBRKR_S_SWGR01A 
3.0E-4 
FUSE_S_SWGR01A 
3.0E-6 
FAULT_SWGR08 
1.2E-6 
MCKTBRKR_S_SWGR08 
3.0E-4 
FUSE_S_SWGR08 
3.0E-6 
FAULT_SWGR06 
1.2E-6 
MCKTBRKR_S_SWGR06 
3.0E-4 
FUSE_S_SWGR06 
3.0E-6 
FAULT_2MVA 
1.2E-6 
MCKTBRKR_S_2MVA 
3.0E-6 
FAULT_11.7MVA 
1.2E-6 
MCKTBRKR_S_11.7MVA 
3.0E-6 
FAULT_SWGRC 
1.2E-6 
MCKTBRKR_S1_SWGRC 
LC12_MCKTBRKR_S LC12_FUSE_S 
1.2E-7 
CCF_MCKTBRKR_S_SWYDA 
2.5E-5 
CCF_FUSE_S_SWYDA 
SWGR01A_MCKTBRKR_S SWGR01A_FUSE_S 
1.2E-7 
CCF_MCKTBRKR_S_SWYDA 
2.5E-5 
CCF_FUSE_S_SWYDA 
1.2E-7 
CCF_MCKTBRKR_S_SWYDA 
2.5E-5 
CCF_FUSE_S_SWYDA 
SWGR08_MCKTBRKR_S SWGR08_FUSE_S 
OLOAD_SWGRC 
1.2E-7 
CCF_MCKTBRKR_S_SWYDA 
2.5E-5 
CCF_FUSE_S_SWYDA 
SWGR06_MCKTBRKR_S SWGR06_FUSE_S 
1.2E-7 
CCF_MCKTBRKR_S_SWYDA 
2MVA_MCKTBRKR_S 
1.2E-7 
CCF_MCKTBRKR_S_SWYDA 
11.7MVA_MCKTBRKR_S 
1.2E-7 
CCF_MCKTBRKR_S_SWYDA 
SWGRC_MCKTBRKR_S1 SWGRC_MCKTBRKR_S2 
1.2E-7 
CCF_MCKTBRKR_S_SWYDA 
1.2E-6 
MCKTBRKR_S2_SWGRC 
OLOAD_SWGREA 
SWGREA_MCKTBRKR_S 
BUS_SWGREA 
SWGREA_FUSE_S 
1.2E-6 
MCKTBRKR_S_SWGREA 
1.2E-7 
CCF_MCKTBRKR_S_SWYDA 
3.0E-4 
FUSE_S_SWGREA 
2.5E-5 
CCF_FUSE_S_SWYDA 
2.0E-6 
XFMR_SWGREA 
FAULT_SWGREA 
LC 12 fault fails to be 
shed from Main 
SWGR A Bus 
SWGR 01A fault fails to 
be shed from 
Main SWGR A Bus 
SWGR 08 fault fails 
to be shed from 
Main SWGR A Bus 
SWGR 06 fault fails 
to be shed from 
Main SWGR A Bus 
2MVA fault fails to 
be shed from Main 
SWGR A Bus 
11.7MVA fault fails 
to be shed from 
Main SWGR A Bus 
LC 12 Load 
failure 
SWGR 01A 
Load failure 
SWGR 08 Load 
failure 
SWGR 06 Load 
failure 
Med Volt Ckt Brkr fails 
to shed SWGR 01A 
Load upon demand 
Med Volt Ckt Brkr fails 
to shed SWGR 08 Load 
upon demand 
Med Volt Ckt Brkr fails 
to shed SWGR 06 Load 
upon demand 
2MVA Load 
failure
Med Volt Ckt Brkr 
fails to shed 2MVA 
Load upon demand 
11.7MVA Load 
failure 
Med Volt Ckt Brkr fails 
to shed 11.7MVA Load 
upon demand 
Fused Interrupter Switc 
fails to open after a LC12 
overload 
Fused Interrupter 
Switch fails to open after 
a SWGR 01A overload 
Fused Interrupter 
Switch fails to open after 
a SWGR 08 overload 
Fused Interrupter 
Switch fails to open 
after a SWGR 06 overload 
CCF Medium Voltage 
Circuit Breaker Shed 
(9/9) - Main SWGR A Bus 
CCF Fuse Int Switch 
Open (5/5) - Main 
SWGR A Bus 
CCF Medium Voltage 
Circuit Breaker Shed 
(9/9) - Main SWGR A Bus 
CCF Fuse Int Switch 
Open (5/5) - Main 
SWGR A Bus 
Med Volt Ckt Brkr fails 
to shed SWGR 01A 
Load upon demand 
Fused Interrupter 
Switch fails to open after 
a SWGR 01A overload 
CCF Medium Voltage 
Circuit Breaker Shed 
(9/9) - Main SWGR A Bus 
CCF Fuse Int Switch 
Open (5/5) - Main 
SWGR A Bus 
Med Volt Ckt Brkr fails 
to shed SWGR 08 Load 
upon demand 
Fused Interrupter 
Switch fails to open after 
a SWGR 08 overload 
Med Volt Ckt Brkr 1 
fails to shed SWGR C 
Load upon demand 
SWGR C Load 
failure 
SWGR C fault fails 
to be shed from 
Main SWGR A Bus 
CCF Medium Voltage 
Circuit Breaker Shed 
(9/9) - Main SWGR A Bus 
CCF Fuse Int Switch 
Open (5/5) - Main 
SWGR A Bus 
Med Volt Ckt Brkr fails 
to shed SWGR 06 Load 
upon demand 
Fuse Int Switch fails 
to open after a 
SWGR 06 overload 
CCF Medium Voltage 
Circuit Breaker Shed 
(9/9) - Main SWGR A Bus 
Med Volt Ckt Brkr 
fails to shed 2MVA 
Load upon demand 
CCF Medium Voltage 
Circuit Breaker Shed 
(9/9) - Main SWGR A Bus 
Med Volt Ckt Brkr fails 
to shed 11.7MVA Load 
upon demand 
CCF Medium Voltage 
Circuit Breaker Shed 
(9/9) - Main SWGR A Bus 
Med Volt ckt Brkr 1 fails 
to shed SWGR C Load 
upon demand 
CCF Medium Voltage 
Circuit Breaker Shed 
(9/9) - Main SWGR A Bus 
Med Volt Ckt Brkr 2 
fails to shed SWGR C 
Load upon demand 
Med Volt Ckt Brkr 2 
fails to shed SWGR C 
Load upon demand 
Main SWGR A 
Bus fails 
overloaded 
Med Volt Ckt Brkr 
fails to shed LC 12 
Load upon demand 
Fused Interrupter 
Switch fails to open 
after a LC 12 overload 
Med Volt Ckt Brkr 
fails to shed LC 12 
Load upon demand 
SWGR EA fault fails to 
be shed from Main 
SWGR A Bus 
Med Volt Ckt Brkr fails 
to shed SWGR EA Load 
upon demand 
Med Volt Ckt Brkr fails 
to shed SWGR EA Load 
upon demand 
CCF Medium Voltage 
Circuit Breaker Shed 
(9/9) - Main SWGR A Bus 
Emergency 
Switchgear A Bus 
Unavailable 
Fused Interrupter 
Switch fails to open 
after a SWGREA overload 
Fused Interrupter 
Switch fails to open 
after a SWGR EA overload 
CCF Fuse Int Switch 
Open (5/5) - Main 
SWGR A Bus 
SWGR EA Load 
failure 
12.47-4.16kV 
Transformer fails 
to operate 
Figure A-9. Subtree CBUS_SWYDA

Reliability Analysis of the Electrical Power Distribution System to Selected Portions of the Nuclear HVAC System 
100-PSA-EE00-00100-000-00A A-20 December 2004 
INTENTIONALLY LEFT BLANK

Reliability Analysis of the Electrical Power Distribution System to Selected Portions of the Nuclear HVAC System 
100-PSA-EE00-00100-000-00A A-21 December 2004 
CBUS_SWYDB 
OLOAD_SWGR01B OLOAD_LC13 
OLOAD_11.8MVA 
OLOAD_SWGR09 
OLOAD_SWGRD OLOAD_SWGR07 OLOAD_3.8MVA 
3.0E-6 
FAULT_SWGR01B 
1.2E-6 
MCKTBRKR_S_SWGR01B 
3.0E-4 
FUSE_S_SWGR01B 
3.0E-6 
FAULT_LC13 
1.2E-6 
MCKTBRKR_S_LC13 
3.0E-4 
FUSE_S_LC13 
3.0E-6 
FAULT_SWGR09 
1.2E-6 
MCKTBRKR_S_SWGR09 
3.0E-4 
FUSE_S_SWGR09 
3.0E-6 
FAULT_SWGR07 
1.2E-6 
MCKTBRKR_S_SWGR07 
3.0E-4 
FUSE_S_SWGR07 
3.0E-6 
FAULT_3.8MVA 
1.2E-6 
MCKTBRKR_S_3.8MVA 
3.0E-6 
FAULT_11.8MVA 
1.2E-6 
MCKTBRKR_S_11.8MVA 
3.0E-6 
FAULT_SWGRD 
1.2E-6 
MCKTBRKR1_S_SWGRD 
1.2E-6 
MCKTBRKR2_S_SWGRD 
SWGR01B_FUSE_S SWGR01B_MCKTBRKR_S 
1.2E-7 
CCF_MCKTBRKR_S_SWYDB 
2.7E-5 
CCF_FUSE_S_SWYDB 
LC13_MCKTBRKR_S LC13_FUSE_S 
1.2E-7 
CCF_MCKTBRKR_S_SWYDB 
2.7E-5 
CCF_FUSE_S_SWYDB 
SWGR09_MCKTBRKR_S SWGR09_FUSE_S 
1.2E-7 
CCF_MCKTBRKR_S_SWYDB 
2.7E-5 
CCF_FUSE_S_SWYDB 
SWGR07_FUSE_S SWGR07_MCKTBRKR_S 
1.2E-7 
CCF_MCKTBRKR_S_SWYDB 
2.7E-5 
CCF_FUSE_S_SWYDB 
3.8MVA_MCKTBRKR_S 
1.2E-7 
CCF_MCKTBRKR_S_SWYDB 
11.8MVA_MCKTBRKR_S 
1.2E-7 
CCF_MCKTBRKR_S_SWYDB 
SWGRD_MCKTBRKR1_S SWGRD_MCKTBRKR2_S 
1.2E-7 
CCF_MCKTBRKR_S_SWYDB 
1.2E-7 
CCF_MCKTBRKR_S_SWYDB 
OLOAD_SWGREB 
SWGREB_MCKTBRKR_S SWGREB_FUSE_S 
BUS_SWGREB 
1.2E-6 
MCKTBRKR_S_SWGREB 
1.2E-7 
CCF_MCKTBRKR_S_SWYDB 
3.0E-4 
FUSE_S_SWGREB 
2.7E-5 
CCF_FUSE_S_SWYDB 
FAULT_SWGREB 
2.0E-6 
XFMR_SWGREB 
OLOAD_SOLAR 
SOLAR_MCKTBRKR_S SOLAR_FUSE_S 
3.0E-6 
FAULT_SOLAR 
1.2E-6 
MCKTBRKR_S_SOLAR 
1.2E-7 
CCF_MCKTBRKR_S_SWYDB 
3.0E-4 
FUSE_S_SOLAR 
2.7E-5 
CCF_FUSE_S_SWYDB 
SWGR 01B fault fails to 
be shed from Main 
SWGR B Bus 
LC 13 fault fails to be 
shed from Main 
SWGR B Bus 
SWGR 09 fault fails 
to be shed from 
Main SWGR B Bus 
SWGR 07 fault fails 
to be shed from 
Main SWGR B Bus 
3.8MVA fault fails 
to be shed from 
Main SWGR B Bus 
11.8MVA fault fails 
to be shed from 
Main SWGR B Bus 
SWGR D fault fails 
to be shed from 
Main SWGR B Bus 
SWGR 01B Load 
failure 
LC 13 Load 
failure 
SWGR 09 Load 
failure 
SWGR 07 Load 
failure 
SWGR D Load 
failure 
Med Volt Ckt Brkr fails 
to shed SWGR 01B 
Load upon demand 
Med Volt Ckt Brkr 
fails to shed LC 13 
Load upon demand 
Med Volt Ckt Brkr fails 
to shed SWGR 09 Load 
upon demand 
Med Volt Ckt Brkr fails 
to shed SWGR 07 Load 
upon demand 
3.8MVA Load 
failure 
Med Volt Ckt Brkr fails 
to shed 3.8MVA Load 
upon demand 
11.8MVA Load 
failure 
Med Volt Ckt Brkr fails 
to shed 11.8MVA Load 
upon demand 
Med Volt Ckt Brkr 1 
fails to shed SWGR D 
Load upon demand 
Fused Interrupter 
Switch fails to open after 
a SWGR 01B overload 
Fused Interrupter 
Switch fails to open 
after a LC 13 overload 
Fused Interrupter 
Switch fails to open after 
a SWGR 09 overload 
Fused Interrupter 
Switch fails to open 
after a SWGR 07 overload 
Med Volt Ckt Brkr 2 
fails to shed SWGR D 
Load upon demand 
Main SWGR B 
Bus fails 
overloaded 
CCF Medium Voltage 
Circuit Breaker Shed 
(9/9) - Main SWGR B Bus 
CCF Fused Int 
Switch (6/6) - Main 
SWGR B Bus 
Med Volt Ckt Brkr fails 
to shed SWGR 01B 
Load upon demand 
Fused Interrupter 
Switch fails to open after 
a SWGR 01B overload 
CCF Medium Voltage 
Circuit Breaker Shed 
(9/9) - Main SWGR B Bus 
CCF Fused Int Switch 
(6/6) - Main 
SWGR B Bus 
Med Volt Ckt Brkr 
fails to shed LC 13 
Load upon demand 
Fused Interrupter 
Switch fails to open 
after a LC 13 overload 
CCF Fused Int 
Switch (6/6) - Main 
SWGR B Bus 
CCF Medium Voltage 
Circuit Breaker Shed 
(9/9) - Main SWGR B Bus 
Med Volt Ckt Brkr fails 
to shed SWGR 09 Load 
upon demand 
Fused Interrupter 
Switch fails to open after 
a SWGR 09 overload 
CCF Medium Voltage 
Circuit Breaker Shed 
(9/9) - Main SWGR B Bus 
CCF Fused Int 
Switch (6/6) - Main 
SWGR B Bus 
Med Volt Ckt Brkr fails 
to shed SWGR 07 Load 
upon demand 
Fused Interrupter 
Switch fails to open after 
a SWGR 07 overload 
CCF Medium Voltage 
Circuit Breaker Shed 
(9/9) - Main SWGR B Bus 
Med Volt Ckt Brkr fails 
to shed 3.8 MVA Load 
upon demand 
CCF Medium Voltage 
Circuit Breaker Shed 
(9/9) - Main SWGR B Bus 
Med Volt Ckt Brkr fails 
to shed 11.8MVA Load 
upon demand 
CCF Medium Voltage 
Circuit Breaker Shed 
(9/9) - Main SWGR B Bus 
CCF Medium Voltage 
Circuit Breaker Shed 
(9/9) - Main SWGR B Bus 
Med Volt Ckt Brkr 1 
fails to shed SWGR D 
Load upon demand 
Med Volt Ckt Brkr 2 
fails to shed SWGR D 
Load upon demand 
SWGR EB fault fails to 
be shed from Main 
SWGR B Bus 
Emergency 
Switchgear B 
Bus Unavailable 
Me Volt Ckt Brkr fails to 
shed SWGR EB Load 
upon demand 
Med Volt Ckt Brkr fails 
to shed SWGREB Load 
upon demand 
CCF Medium Voltage 
Circuit Breaker Shed 
(9/9) - Main SWGR B Bus 
Fused Interrupter 
Switch fails to open 
after a SWGR EB overload 
Fused Interrupter 
Switch fails to open 
after a SWGR EB overload 
CCF Fused Int 
Switch (6/6) - Main 
SWGR B Bus 
SWGR EB Load 
failure 
12.47-4.16kV 
Transformer fails 
to operate 
SOLAR POWER fault 
fails to be shed from 
Main SWGR B Bus 
SOLAR POWER 
Load failure 
Med Volt Ckt Brkr fails 
to shed SOLAR POWER 
Load upon demand 
Fused Interrupter Switch 
fails to open after a SOLAR 
POWER overload 
Med Volt Ckt Brkr fails 
to shed SOLAR POWER 
Load upon demand 
CCF Medium Voltage 
Circuit Breaker Shed 
(9/9) - Main SWGR B Bus 
Fused Interrupter Switch 
fails to open after a 
SOLAR POWER overload 
CCF Fused Int 
Switch (6/6) - Main 
SWGR B Bus 
Figure A-10. Subtree CBUS_SWYDB

Reliability Analysis of the Electrical Power Distribution System to Selected Portions of the Nuclear HVAC System 
100-PSA-EE00-00100-000-00A A-22 December 2004 
INTENTIONALLY LEFT BLANK

Reliability Analysis of the Electrical Power Distribution System to Selected Portions of the Nuclear HVAC System 
100-PSA-EE00-00100-000-00A A-23 December 2004 
LOSP_SWYDA 
8.9E-6 
XFMRA_230KV 
1.9E-5 
LINE_230KV 
5.3E-6 
CCVTA_230KV 
9.2E-6 
PWRCKTBRKRA_230KV 
1.2E-6 
4KCKTBRKR_O_230KV 
4.4E-5 
SOURCE_230KV 
5.6E-8 
CCF_4KCKTBRKR_O_AB 
9.1E-7 
CCF_LINE_SUBAB 
2.5E-7 
CCF_CCVT_SUBAB 
4.3E-7 
CCF_PWRCKTBRKR_SUBAB 
Failure of 230kV 
system to supply power 
to Main SWGR A 
Power line fails to 
remain intact to connect 
230kV power 
230-12.47kV 
Main Transfomer 
A fails to operate 
Coupling Capacitor 
Voltage Transformer A 
fails to operate 
Power Ckt Brkr A fails 
to remain closed to 
connect 230kV power 
4kA Med Volt Ckt Brkr 
fails to remain closed to 
connect 230kV power 
Loss of 230kV 
source 
CCF Power Line (1/2) - 
Substations A & B 
CCF Coupling Capacitor 
Voltage Trasformer (1/2) - 
Substations A & B 
CCF Power Circuit 
Breaker (1/2) - 
Substations A & B 
CCF 4kA Med Volt Ckt 
Brkr Connect (1/2) - 
Substations A & B 
Figure A-11. Subtree LOSP_SWYDA

Reliability Analysis of the Electrical Power Distribution System to Selected Portions of the Nuclear HVAC System 
100-PSA-EE00-00100-000-00A A-24 December 2004 
INTENTIONALLY LEFT BLANK

Reliability Analysis of the Electrical Power Distribution System to Selected Portions of the Nuclear HVAC System 
100-PSA-EE00-00100-000-00A A-25 December 2004 
125VDC_SIDEA 
DCBUSA_SIDEA 
4.5E-6 
LCKTBRKR_O_SIDEA 
1.9E-5 
LINE_SIDEA 
1.0E-6 
DCBUSA 
CHARGR_DCBUSA 
4.0E-7 
BATTERY_DCBUSA 
1.9E-5 
LINEB_SIDEA 
1.0E-6 
DCBUSB 
4.0E-7 
BATTERY_DCBUSB CHARGR_DCBUSB 
6.8E-6 
CHARGRD13_BACKUP 
6.8E-6 
CHARGRD11_DCBUSA 
6.8E-6 
CHARGRD12_DCBUSB 
6.8E-6 
CHARGRD13_BACKUP 
DCBUSB_SIDEA 
4.5E-6 
LCKTBRKRB_C_SIDEA POWER_DCBUSA POWER_DCBUSB 
DCBUSA_BATTERY 
1.9E-8 
CCF_BATTERY_DCBUSAB 
DCBUSA_CHARGR 
4.2E-7 
CCF_CHARGRS_DCBUSAB 
9.1E-7 
CCF_LINE_DCBUSAB 
4.9E-8 
CCF_BUS_DCBUSAB 
DCBUSB_BATTERY 
1.9E-8 
CCF_BATTERY_DCBUSAB 
DCBUSB_CHARGR 
4.2E-7 
CCF_CHARGRS_DCBUSAB 
9.1E-7 
CCF_LINE_DCBUSAB 
4.9E-8 
CCF_BUS_DCBUSAB 
125V DC System fails 
to supply power to Side A 
Med Voltage Ckt Brkrs 
Failure of 125V DC Dist 
Bus A to supply power 
to Side A Ckt Brkrs 
Low Volt Ckt Brkr fails 
to remain closed to 
connect Side A load 
Power line fails to 
remain intact to 
connect Side A load 
125V DC Distribution 
Bus A Bus fails short 
circuited 
125V DC Distribution 
Bus A Battery fails to 
operate 
125V DC Dist Bus 
A Battery Chargers 
fail to operate 
Battery Charger 
D11 fails to 
operate 
Backup Battery 
Charger D13 fails 
to operate 
Power line fails to 
remain intact to 
connect Side A load 
125V DC 
Distribution Bus B 
fails short circuited 
125V DC Dist 
Bus B Battery 
fails to operate 
125V DC Dist Bus B 
Battery Chargers fail 
to operate 
Battery Charger 
D12 fails to 
operate 
Backup Battery 
Charger D13 fails 
to operate 
Failure of 125V DC Dist 
Bus B to supply backup 
power to Side A Ckt Brkrs 
Low Voltage Ckt Brkr 
fails to close upon demand 
to connect Side A load 
Loss of DC power to 
Distribution Bus A 
Loss of DC power to 
Distribution Bus B 
CCF Power Line 
(1/2) - 125V DC 
Dist Bus A & B 
CCF Switchgear Bus 
(1/2) - 125V DC 
Dist Bus A & B 
125V DC Dist 
Bus A Battery 
fails to operate 
125V DC Dist Bus 
A Battery Chargers 
fail to operate 
CCF Battery Charger 
(2/3) - 125V DC 
Dist Bus A & B 
CCF Battery 
(1/2) - 125V DC 
Dist Bus A & B 
CCF Battery 
(1/2) - 125V DC 
Dist Bus A & B 
CCF Battery Charger 
(2/3) - 125V DC 
Dist Bus A & B 
125V DC Dist 
Bus B Battery 
fails to operate 
125V DC Dist Bus B 
Battery Chargers fail 
to operate 
CCF Power Line 
(1/2) - 125V DC 
Dist Bus A & B 
CCF Switchgear Bus 
(1/2) - 125V DC 
Dist Bus A & B 
Figure A-12. FT Model of the Normal 125V DC 
Distribution System

Reliability Analysis of the Electrical Power Distribution System to Selected Portions of the Nuclear HVAC System 
100-PSA-EE00-00100-000-00A A-26 December 2004 
INTENTIONALLY LEFT BLANK

Reliability Analysis of the Electrical Power Distribution System to Selected Portions of the Nuclear HVAC System 
100-PSA-EE00-00100-000-00A A-27 December 2004 
125VDC_SWGREA 
DISCONN_SWGREA 
2.0E-6 
XFMR_ESB 
2.0E-6 
FUSE_O_ESB 
1.9E-5 
LINE_ESB 
1.2E-6 
MCKTBRKR_O_ESB 
4.5E-6 
LCKTBRKR_O_ESB 
1.9E-6 
IBUS_MCC DISCONN_MCC 
1.9E-5 
LINE_125VDC 
4.5E-6 
LCKTBRKR_O_125VDC 
125VDC 
SWGREA_CHARGR SWGREA_BATTERY 
DCPOWER_SWGREA 
1.9E-5 
LINE_SWGEA 
4.5E-6 
LCKTBRKR_O_SWGREA 
1.0E-6 
DCBUS_SWGREA 
6.8E-6 
CHARGR_SWGREA 
4.5E-6 
LCKTBRKR_O_CHARGRA 
4.0E-7 
BATTERY_SWGREA 
4.5E-6 
LCKTBRKR_O_BATTA 
5.6E-8 
CCF_MCKTBRKR_ESB 
9.4E-8 
CCF_FUSE_ESB 
9.2E-8 
CCF_XFMR_ESB 
9.1E-7 
CCF_LINE_ESB 
2.1E-7 
CCF_LCKTBRKR_ESB 
9.0E-8 
CCF_MCC_ESB 
9.1E-7 
CCF_LINE_125VDC 
2.1E-7 
CCF_LCKTBRKR_125VDC 
2.1E-7 
CCF_LCKTBRKR_SWGRAB 
9.1E-7 
CCF_LINE_SWGRAB 
4.9E-8 
CCF_DCBUS_SWGRAB 
3.2E-7 
CCF_CHARGR_SWGRAB 
2.1E-7 
CCF_LCKTBRKR_CHARGAB 
1.9E-8 
CCF_BATTERY_SWGRAB 
2.1E-7 
CCF_LCKTBRKR_BATTAB 
Failure of 125VDC 
system to remain 
connected to MCC 
125VDC system fails to 
supply power to SWGREA 
Med Voltage Ckt Brkrs 
Failure of MCC to 
remain connected to 
Emergency SWGR A 
4160-480V 
Transformer fails 
to operate 
Fused Interrupter 
Switch fails to remain 
closed to connect ESB load 
Powe line fails to 
remain intact to 
connect ESB load 
Low Volt Ckt Brkr 
fails to remain closed 
to connect ESB load 
MCC bus fails 
short circuited 
Power line fails to 
remain intact to connect 
125VDC load 
Low Volt Ckt Brkr fails 
to remain closed to 
connect 125VDC 
125VDC system fails to 
supply power to SWGREA 
Med Volt Ckt Brkrs 
Low Volt Ckt Brkr fails 
to remain closed to 
connect SWGREA load 
Power line fails to 
remain intact to connect 
SWGREA load 
125VDC distribution 
bus for SWGREA 
fails short circuited 
Loss of DC power to 
125VDC distribution bus 
to SWGREA 
SWGREA 125VDC 
battery charger fails 
to operate 
SWGREA 
125VDC battery 
fails to operate 
SWGREA 125VDC 
battery charger fails 
to operate 
SWGREA 
125VDC battery 
fails to operate 
Low Volt Ckt Brkr fails 
to remain closed to connect 
SWGREA DC charger 
Low Volt Ckt Brkr fails 
to remain closed to connect 
SWGREA DC battery 
CCF Med Volt Ckt Brkr 
(1/2) - 125VDC 
SWGREA & SWGREB 
CCF Fused Interrupter 
Switch (1/2) - 125VDC 
SWGREA & SWGREB 
CCF 4160-480V 
Transformer (1/2) - 125VDC 
SWGREA & SWGREB 
CCF Power line (1/2) - 
125VDC SWGREA & 
SWGREB 
CCF Low Volt Ckt Brkr 
(1/2) - 125VDC 
SWGREA & SWGREB 
CCF MCC bus (1/2) - 
125VDC SWGREA & 
SWGREB 
CCF Power line (1/2) - 
125VDC SWGREA & 
SWGREB 
CCF Low Volt Ckt Brkr 
(1/2) - 125VDC 
SWGREA & SWGREB 
CCF Low Volt Ckt Brkr 
(1/2) - 125VDC 
SWGREA & SWGREB 
CCF Power line (1/2) - 
125VDC SWGREA & 
SWGREB 
CCF DC Bus (1/2) - 
125VDC SWGREA 
& SWGREB 
CCF Battery Charger 
(1/2) - 125VDC 
SWGREA & SWGREB 
CCF Low Volt Ckt Brkr 
(1/2) - 125VDC 
SWGREA & SWGREB 
CCF Battery (1/2) - 
125VDC SWGREA 
& SWGREB 
CCF Low Volt Ckt Brkr 
(1/2) - 125VDC 
SWGREA & SWGREB 
Med Volt Ckt Brkr 
fails to remain closed 
to connect ESB load 
Figure A-13. FT Model of the Emergency 
125V DC Distribution System

Reliability Analysis of the Electrical Power Distribution System to Selected Portions of the Nuclear HVAC System 
100-PSA-EE00-00100-000-00A A-28 December 2004 
INTENTIONALLY LEFT BLANK

100-PSA-EE00-00100-000-00A A-29 December 2004 
Reliability Analysis of the Electrical Power Distribution System to Selected Portions of the Nuclear HVAC System 
EDGA_SWGREA 
1.0E-2 
START_EDGA 
2.0E-2 
RUN_EDGA 
1.2E-6 
MCKTBRKR_O_EDGA 
1.9E-5 
LINE_EDGA 
4.7E-4 
CCF_START_EDGAB 
9.4E-4 
CCF_RUN_EDGAB 
5.6E-8 
CCF_MCKTBRKR_O_EDGAB 
9.1E-7 
CCF_LINE_EDGAB 
Failure of Emergency 
Diesel Gen A to power 
Emergency Switchgear A 
Emergency Diesel 
Generator A fails to 
start operation 
Emergency Diesel 
Generator A fails to 
continue operation 
Med Volt Ckt Brkr 
fails to operate to 
connnect EDG A 
Power line fails to 
remain intact to 
connect EDG A 
CCF Diesel Start 
(1/2) - Emergency 
Diesel Gens A & B 
CCF Diesel Run 
(1/2) - Emergency 
Diesel Gens A & B 
CCF Med Volt Ckt Brkr 
Connect (1/2) -Emergency 
Diesel Gens A & B 
CCF Power Line 
(1/2) - Emergency 
Diesel Gens A & B 
Figure A-14. FT Model of the Emergency Diesel Generator A

100-PSA-EE00-00100-000-00A A-30 December 2004 
Reliability Analysis of the Electrical Power Distribution System to Selected Portions of the Nuclear HVAC System 
LOSP_ONSITE 
FANS_SIDEA FANS_SIDEB 
DISCONNECT_SWGREA DISCONNECT_SWGREB 
SWYDB_SWGREB 
BUS_SWGREA BUS_SWGREB 
SWYDA_SWGREA 
LOSP_SWGREA 
EDGA_SWGREA 
LOSP_SWGREB 
EDGB_SWGREB 
Failure of the Electrical Power 
Distribution System to provide 
power to the Nuclear HVAC 
System in the DTF1 Primary Conf. 
Loss of Power Distribution to 2 
Supply and 2 Exhaust Fan 
Motors on MCC I - 
DTF1 Side A 
Loss of Power Distribution to 2 
Supply and 2 Exhaust Fan 
Motors on MCC I (B) - 
DTF1 Side B 
Failure of MCC I to 
remain connected to 
Emergency Switchgear A 
Failure of MCC I (B) to 
remain connected to 
Emergency Switchgear B 
Failure of Switchyard 
Switchgear B to power 
Emergency Switchgear B 
Emergency 
Switchgear A 
Bus Unavailable 
Emergency 
Switchgear B 
Bus Unavailable 
Failure of Switchyard 
Switchgear A to power 
Emergency Switchgear A 
Loss of Power to the 
Emergency 
Switchgear A 
Failure of Emergency 
Diesel Gen A to power 
Emergency Switchgear A 
Loss of Power to the 
Emergency 
Switchgear B 
Failure of Emergency 
Diesel Gen B to power 
Emergency Switchgear B 
Figure A-15. FT Model of Entire Power Grid with Emergency Power

100-PSA-EE00-00100-000-00A A-31 December 2004 
Reliability Analysis of the Electrical Power Distribution System to Selected Portions of the Nuclear HVAC System 
FANS_SIDEA 
DISCONNECT_SWGREA BUS_SWGREA 
SWYDA_SWGREA 
LOSP_SWGREA 
EDGA_SWGREA 
Loss of Power Distribution to 2 
Supply and 2 Exhaust Fan 
Motors on MCC I - 
DTF1 Side A 
Failure of MCC I to 
remain connected to 
Emergency Switchgear A 
Emergency 
Switchgear A 
Bus Unavailable 
Failure of Switchyard 
Switchgear A to power 
Emergency Switchgear A 
Loss of Power to the 
Emergency 
Switchgear A 
Failure of Emergency 
Diesel Gen A to power 
Emergency Switchgear A 
Figure A-16. FT Model of One Side of Power Grid with Emergency Power

100-PSA-EE00-00100-000-00A A-32 December 2004 
Reliability Analysis of the Electrical Power Distribution System to Selected Portions of the Nuclear HVAC System 
FANS_SIDEA 
DISCONNECT_SWGREA BUS_SWGREA SWYDA_SWGREA 
Loss of Power Distribution to 2 
Supply and 2 Exhaust Fan 
Motors on MCC I - 
DTF1 Side A 
Failure of MCC I to 
remain connected to 
Emergency Switchgear A 
Emergency 
Switchgear A 
Bus Unavailable 
Failure of Switchyard 
Switchgear A to power 
Emergency Switchgear A 
Figure A-17. FT Model of One Side of Power Grid with No Emergency Power

100-PSA-EE00-00100-000-00A A-33 December 2004 
Reliability Analysis of the Electrical Power Distribution System to Selected Portions of the Nuclear HVAC System 
LOSP_ONSITE 
FANS_SIDEA FANS_SIDEB 
DISCONNECT_SWGREA DISCONNECT_SWGREB BUS_SWGREA BUS_SWGREB EDGA_SWGREA EDGB_SWGREB 
Failure of the Electrical Power 
Distribution System to provide 
power to the Nuclear HVAC 
System in the DTF1 Primary Conf. 
Loss of Power Distribution to 2 
Supply and 2 Exhaust Fan 
Motors on MCC I - 
DTF1 Side A 
Loss of Power Distribution to 2 
Supply and 2 Exhaust Fan 
Motors on MCC I (B) - 
DTF1 Side B 
Failure of MCC I to 
remain connected to 
Emergency Switchgear A 
Failure of MCC I (B) to 
remain connected to 
Emergency Switchgear B 
Emergency 
Switchgear A 
Bus Unavailable 
Emergency 
Switchgear B 
Bus Unavailable 
Failure of Emergency 
Diesel Gen A to power 
Emergency Switchgear A 
Failure of Emergency 
Diesel Gen B to power 
Emergency Switchgear B 
Figure A-18. FT Model of the Emergency Power Only  Two Sides

100-PSA-EE00-00100-000-00A A-34 December 2004 
Reliability Analysis of the Electrical Power Distribution System to Selected Portions of the Nuclear HVAC System 
FANS_SIDEA 
DISCONNECT_SWGREA BUS_SWGREA EDGA_SWGREA 
Loss of Power Distribution to 2 
Supply and 2 Exhaust Fan 
Motors on MCC I - 
DTF1 Side A 
Failure of MCC I to 
remain connected to 
Emergency Switchgear A 
Emergency 
Switchgear A 
Bus Unavailable 
Failure of Emergency 
Diesel Gen A to power 
Emergency Switchgear A 
Figure A-19. FT Model of Emergency Power Only - One Side

Reliability Analysis of the Electrical Power Distribution System to Selected Portions of the Nuclear HVAC System 
100-PSA-EE00-00100-000-00A B-1 December 2004 
ATTACHMENT B 
FAULT TREE MODEL - SIDE B

Reliability Analysis of the Electrical Power Distribution System to Selected Portions of the Nuclear HVAC System 
100-PSA-EE00-00100-000-00A B-2 December 2004 
INTENTIONALLY LEFT BLANK

Reliability Analysis of the Electrical Power Distribution System to Selected Portions of the Nuclear HVAC System 
100-PSA-EE00-00100-000-00A B-3 December 2004 
DISCONNECT_SWGREB 
1.2E-6 
MCKTBRKR_O_DTF1B 
1.9E-5 
LINE_DTF1B 
2.0E-6 
FUSE_O_DTF1B 
2.0E-6 
XFRM_DTF1B DISCONNECT_LCB 
1.9E-6 
IBUS_MCCIB 
9.1E-7 
CCF_LINE_SWGREAB 
MCCZ_LCKTBRKR_S 
3.4E-7 
CCF_LCKTBRKR_S_LCB 
MCCY_LCKTBRKR_S 
3.4E-7 
CCF_LCKTBRKR_S_LCB 
MCCX_LCKTBRKR_S 
9.0E-8 
CCF_480VBUS_LCAB 
3.4E-7 
CCF_LCKTBRKR_S_LCB 
4.5E-6 
LCKTBRKR_S_MCCZ 
1.9E-6 
FAULT_MCCZ 
4.5E-6 
LCKTBRKR_S_MCCY 
1.9E-6 
FAULT_MCCY 
4.5E-6 
LCKTBRKR_S_MCCX 
1.9E-6 
FAULT_MCCX 
OLOAD_MCCZ OLOAD_MCCY OLOAD_MCCX 
CBUS_LCB 
1.9E-6 
IBUS_LCB 
BUS_LCB 
4.5E-6 
LCKTBRKR_O_MCCIB 
1.9E-5 
LINE_MCCIB 
MCCIB_LCKTBRKR_S 
3.4E-7 
CCF_LCKTBRKR_S_LCB 
4.5E-6 
LCKTBRKR_S_MCCIB 
OLOAD_MCCIB 
1.9E-6 
IBUS_MCCIB 
125VDC_SWGREB 
Failure of MCC I (B) to 
remain connected to 
Emergency Switchgear B 
Med Volt Ckt Brkr fails 
to remain closed to 
connect DTF1 load 
Power line fails to 
remain intact to 
connect DTF1 load 
4160-480V 
Transformer fails 
to operate 
Fused Interrupter 
Switch fails to remain 
closed to connect 
Failure of MCC I (B) 
to remain connected 
to Load Center B 
MCCIB Bus fails 
short circuited 
CCF Power Line 
(1/2) - DTF1 Load 
Side A and Side B 
Low Volt Ckt Brkr 
fails to shed MCC Z 
load upon demand 
Low Volt Ckt Brkr 
fails to shed MCC Y 
load upon demand 
Low Volt Ckt Brkr 
fails to shed MCC X 
load upon demand 
CCF Low Voltage 
Circuit Breaker Shed 
(4/4) - LC B Bus 
CCF Low Voltage 
Circuit Breaker Shed 
(4/4) - LC B Bus 
CCF 480V Bus (1/2) 
- LC A Bus & LC B 
Bus 
CCF Low Voltage 
Circuit Breaker Shed 
(4/4) - LC B Bus 
Low Volt Ckt Brkr 
fails to shed MCC Z 
load upon demand 
Low Volt Ckt Brkr 
fails to shed MCC Y 
load upon demand 
Low Volt Ckt Brkr 
fails to shed MCC X 
load upon demand 
MCC Z Load 
failure 
MCC Y Load 
failure 
MCC X Load 
failure 
MCC Z fault fails 
to be shed from 
LC B Bus 
MCC Y fault fails 
to be shed from 
LC B Bus 
MCC X fault fails 
to be shed from 
LC B Bus 
LC B Bus fails 
overloaded 
LC B Bus fails 
short circuited 
Load Center B 
Bus failure 
Low Volt Ckt Brkr fails 
to remain closed to 
connect MCCIB 
Power line fails to 
remain intact to connect 
MCCIB load 
Low Volt Ckt Brkr 
fails to shed MCC IB 
load upon demand 
CCF Low Voltage 
Circuit Breaker Shed 
(4/4) - LC B Bus 
Low Volt Ckt Brkr 
fails to shed MCC IB 
load upon demand 
MCC IB fault 
fails to be shed 
from LC B Bus 
MCCIB Bus fails 
short circuited 
125VDC system fails to 
supply power to SWGREB 
Med Voltage Ckt Brkrs 
Figure B-1. Subtree DISCONNECT_SWGREB

Reliability Analysis of the Electrical Power Distribution System to Selected Portions of the Nuclear HVAC System 
100-PSA-EE00-00100-000-00A B-4 December 2004 
INTENTIONALLY LEFT BLANK

Reliability Analysis of the Electrical Power Distribution System to Selected Portions of the Nuclear HVAC System 
100-PSA-EE00-00100-000-00A B-5 December 2004 
BUS_SWGREB 
1.0E-6 
IBUS_SWGREB CBUS_SWGREB 
OLOAD_MCCN 
OLOAD_MCCT OLOAD_LCD 
3.9E-6 
FAULT_MCCN 
1.2E-6 
MCKTBRKR_S_MCCN 
3.0E-4 
FUSE_S_MCCN 
3.9E-6 
FAULT_LCH 
3.9E-6 
FAULT_LCD 
1.2E-6 
MCKTBRKR_S_LCD 
3.0E-4 
FUSE_S_LCD 
1.2E-6 
MCKTBRKR_S_MCCT 
3.9E-6 
FAULT_MCCT 
3.0E-4 
FUSE_S_MCCT 
1.0E-7 
CCF_MCKTBRKR_S_SWGREB 
2.5E-5 
CCF_FUSE_S_SWGREB 
MCCN_MCKTBRKR_S MCCN_FUSE_S 
MCCT_MCKTBRKR_S MCCT_FUSE_S 
1.0E-7 
CCF_MCKTBRKR_S_SWGREB 
2.5E-5 
CCF_FUSE_S_SWGREB 
LCH_FUSE_S LCH_MCKTBRKR_S 
1.0E-7 
CCF_MCKTBRKR_S_SWGREB 
2.5E-5 
CCF_FUSE_S_SWGREB 
3.0E-4 
FUSE_S_LCH 
1.2E-6 
MCKTBRKR_S_LCH
OLOAD_LCH 
LCD_MCKTBRKR_S LCD_FUSE_S 
1.0E-7 
CCF_MCKTBRKR_S_SWGREB 
2.5E-5 
CCF_FUSE_S_SWGREB 
OLOAD_LCB 
1.9E-6 
BUS_LCB 
LCB_MCKTBRKR_S LCB_FUSE_S 
1.2E-6 
MCKTBRKR_S_LCB 
1.0E-7 
CCF_MCKTBRKR_S_SWGREB 
3.0E-4 
FUSE_S_LCB 
2.5E-5 
CCF_FUSE_S_SWGREB 
2.0E-6 
XFRM_DTF1B 
FAULT_LCB 
Emergency 
Switchgear B 
Bus Unavailable 
SWGR EB Bus 
fails short circuited 
MCC N fault fails 
to be shed from 
SWGR EB Bus 
MCC T fault fails 
to be shed from 
SWGR EB Bus 
LC D fault fails 
to be shed from 
SWGR EB Bus 
MCC N Load 
failure 
LC H Load 
failure 
MCC T Load 
failure 
LCD Load failure 
Med Volt Ckt Brkr 
fails to shed MCC N 
Load upon demand 
Med Volt Ckt Brkr 
fails to shed MCC T 
Load upon demand 
Med Volt Ckt Brkr 
fails to shed LCD 
Load upon demand 
Fused Interrupter 
Switch fails to open 
after a MCC N overload 
Fused Interrupter 
Switch fails to open 
after a MCC T overload 
Fused Interrupter 
Switch fails to open 
after a LCD overload 
CCF Medium Voltage 
Circuit Breaker Shed 
(5/5) - SWGR EB Bus 
CCF Fused Int 
Swicth (5/5) - 
SWGR EB Bus 
SWGR EB Bus 
fails overloaded 
CCF Medium Voltage 
Circuit Breaker Shed 
(5/5) - SWGR EB Bus 
CCF Fused Int 
Swicth (5/5) - 
SWGR EB Bus 
CCF Medium Voltage 
Circuit Breaker Shed 
(5/5) - SWGR EB Bus 
CCF Fused Int 
Swicth (5/5) - 
SWGR EB Bus 
Fused Interrupter 
Switch fails to open 
after a LC H overload 
Med Volt Ckt Brkr 
fails to shed LC H 
Load upon demand 
LC H fault fails 
to be shed from 
SWGR EB Bus 
CCF Medium Voltage 
Circuit Breaker Shed 
(5/5) - SWGR EB Bus 
CCF Fused Int 
Swicth (5/5) - 
SWGR EB Bus 
Med Volt Ckt Brkr 
fails to shed MCC N 
Load upon demand 
Fused Interrupter 
Switch fails to open 
after a MCC N overload 
Med Volt Ckt Brkr 
fails to shed MCC T 
Load upon demand 
Fused Interrupter 
Swicth fails to open 
after a MCC T overload 
Med Volt Ckt Brkr 
fails to shed LC H 
Load upon demand 
Fused Interrupter 
Switch fails to open 
after LC H overload 
Med Volt Ckt Brkr 
fails to shed LC D 
Load upon demand 
Fused Interrupter 
Switch fails to open 
after a LC D overload 
LC B fault fails to 
be shed from 
SWGR EB Bus 
Med Volt Ckt Brkr 
fails to shed LC B 
load upon demand 
Med Volt Ckt Brkr 
fails to shed LCB 
load upon demand 
Fused Interrupter 
Switch fails to open 
after a LCB overload 
CCF Medium Voltage 
Circuit Breaker Shed 
(5/5) - SWGR EB Bus 
CCF Fused Int 
Swicth (5/5) - 
SWGR EB Bus 
Fused Interrupter 
Switch fails to open 
after a LCB overload 
LC B load failure 
Load Center B 
Bus failure 
4160-480V 
Transformer fails 
to operate 
Figure B-2. Subtree BUS_SWGREB

Reliability Analysis of the Electrical Power Distribution System to Selected Portions of the Nuclear HVAC System 
100-PSA-EE00-00100-000-00A B-6 December 2004 
INTENTIONALLY LEFT BLANK

Reliability Analysis of the Electrical Power Distribution System to Selected Portions of the Nuclear HVAC System 
100-PSA-EE00-00100-000-00A B-7 December 2004 
SWYDB_SWGREB 
DISCONNECT_SWYDB 
1.2E-6 
MCKTBRKR1_O_SWGREB 
1.2E-6 
MCKTBRKR2_O_SWGREB 
2.0E-6 
XFMR_SWGREB 
1.9E-5 
LINE_SWGREB 
2.0E-6 
FUSE_O_SWGREB 125VDC_SIDEB 
5.6E-8 
CCF_MCKTBRKR_O_SWYDAB 
BUS_SWYDB 
1.0E-6 
IBUS_SWYDB CBUS_SWYDB BUSINT_SWYDA 
1.2E-6 
ICKTBRKR_S BUS_SWYDAA 
4.9E-8 
CCF_BUS_SWYDAB 
1.0E-6 
IBUS_SWYDA CBUS_SWYDA 
BUS_SWGREB 
LOSP_SWYDB 
1.2E-6 
ICKTBRKR_O LOSP_SWYDA 
Failure of Main 
Switchgear B to power 
Emergency Switchgear B 
Failure of SWGR EB to 
remain connected to 
Main SWGR B 
125V DC System fails 
to supply power to Side B 
Med Voltage Ckt Brkrs 
Med Volt Ckt Brkr 1 
fails to remain closed to 
connect SWGR EB load 
Med Volt Ckt Brkr 2 
fails to remain closed to 
connect SWGR EB load 
Fused Interrupter Switch 
fails to remain closed to 
connect SWGR EB load 
12.47-4.16kV 
Transformer fails 
to operate 
Power line fails to 
remain intact to connect 
SWGR EB load 
CCF Medium Voltage 
Circuit Breaker Connect 
(1/2) - Switchyard A & B 
Main SWGR B 
Bus Unavailable 
Main SWGR B Bus 
fails short circuited 
Main SWGR B Bus 
fails overloaded 
Interconnect Med Volt 
Ckt Brkr fails to isolate 
failure in Main SWGR A 
Interconnect Med Volt 
Ckt Brkr fails to open after 
a failure in Main SWGR A 
CCF Bus (1/2) - 
Main SWGRs A & B 
Main SWGR A 
Bus failure 
Main SWGR A 
Bus fails short 
circuited 
Main SWGR A 
Bus fails 
overloaded 
Emergency 
Switchgear B 
Bus Unavailable 
Failure of Main SWGR 
A to supply power to 
Main SWGR B 
Interconnect Med Volt 
Ckt Brkr fails to remain 
closed to connect Main 
SWGR A 
Failure of 230kV 
system to supply power 
to Main SWGR A 
Figure B-3. Subtree SWYDB_SWGREB

Reliability Analysis of the Electrical Power Distribution System to Selected Portions of the Nuclear HVAC System 
100-PSA-EE00-00100-000-00A B-8 December 2004 
INTENTIONALLY LEFT BLANK

Reliability Analysis of the Electrical Power Distribution System to Selected Portions of the Nuclear HVAC System 
100-PSA-EE00-00100-000-00A B-9 December 2004 
125VDC_SIDEB 
DCBUSA_SIDEB 
4.5E-6 
LCKTBRKRA_C_SIDEB 
1.9E-5 
LINEA_SIDEB 
1.0E-6 
DCBUSA 
CHARGR_DCBUSA 
4.0E-7 
BATTERY_DCBUSA 
6.8E-6 
CHARGRD13_BACKUP 
6.8E-6 
CHARGRD11_DCBUSA 
POWER_DCBUSA 
DCBUSA_BATTERY 
1.9E-8 
CCF_BATTERY_DCBUSAB 
DCBUSA_CHARGR 
4.2E-7 
CCF_CHARGRS_DCBUSAB 
DCBUSB_SIDEB 
4.5E-6 
LCKTBRKR_O_SIDEB 
1.9E-5 
LINE_SIDEB 
1.0E-6 
DCBUSB 
4.0E-7 
BATTERY_DCBUSB CHARGR_DCBUSB 
6.8E-6 
CHARGRD12_DCBUSB 
6.8E-6 
CHARGRD13_BACKUP 
POWER_DCBUSB 
DCBUSB_BATTERY 
1.9E-8 
CCF_BATTERY_DCBUSAB 
DCBUSB_CHARGR 
4.2E-7 
CCF_CHARGRS_DCBUSAB 
9.1E-7 
CCF_LINEB_DCBUSAB 
4.9E-8 
CCF_BUS_DCBUSAB 
9.1E-7 
CCF_LINEB_DCBUSAB 
4.9E-8 
CCF_BUS_DCBUSAB 
125V DC System fails 
to supply power to Side B 
Med Voltage Ckt Brkrs 
Failure of 125V DC Dist 
Bus A to supply backup 
power to Side B Ckt Brkr 
Low Voltage Ckt Brkr 
fails to close upon demand 
to connect Side B load 
Power line fails to 
remain intact to 
connect Side B load 
125V DC Distribution 
Bus A Bus fails short 
circuited 
125V DC Distribution 
Bus A Battery fails to 
operate 
125V DC Dist Bus 
A Battery Chargers 
fail to operate 
Battery Charger 
D11 fails to 
operate 
Backup Battery 
Charger D13 fails 
to operate 
Loss of DC power to 
Distribution Bus A 
125V DC Dist 
Bus A Battery 
fails to operate 
125V DC Dist Bus 
A Battery Chargers 
fail to operate 
CCF Battery Charger 
(2/3) - 125V DC 
Dist Bus A & B 
CCF Battery 
(1/2) - 125V DC 
Dist Bus A & B 
Failure of 125VDC 
Dist bus B to supply 
power to Side B Ckt Brkrs 
Power line fails to 
remain intact to 
connect Side B load 
125V DC 
Distribution Bus B 
fails short circuited 
125V DC Dist 
Bus B Battery 
fails to operate 
125V DC Dist Bus B 
Battery Chargers fail 
to operate 
Battery Charger 
D12 fails to 
operate 
Backup Battery 
Charger D13 fails 
to operate 
Loss of DC power to 
Distribution Bus B 
CCF Battery 
(1/2) - 125V DC 
Dist Bus A & B 
CCF Battery Charger 
(2/3) - 125V DC 
Dist Bus A & B 
CCF Power Line 
(1/2) - 125V DC 
Dist Bus A & B 
CCF Switchgear Bus 
(1/2) - 125V DC 
Dist Bus A & B 
CCF Power Line 
(1/2) - 125V DC 
Dist Bus A & B 
CCF Switchgear Bus 
(1/2) - 125V DC 
Dist Bus A & B 
Low Volt Ckt Brkr fails 
to remain closed to 
connect Side B load 
125V DC Dist 
Bus B Battery 
fails to operate 
125V DC Dist Bus B 
Battery Chargers fail 
to operate 
Figure B-4. Subtree 12VDC_SIDEB

Reliability Analysis of the Electrical Power Distribution System to Selected Portions of the Nuclear HVAC System 
100-PSA-EE00-00100-000-00A B-10 December 2004 
INTENTIONALLY LEFT BLANK

Reliability Analysis of the Electrical Power Distribution System to Selected Portions of the Nuclear HVAC System 
100-PSA-EE00-00100-000-00A B-11 December 2004 
125VDC_SWGREB 
DISCONN_SWGREB 
2.0E-6 
XFMR_ESBB 
2.0E-6 
FUSE_O_ESBB 
1.9E-5 
LINE_ESBB 
1.2E-6 
MCKTBRKR_O_ESBB 
4.5E-6 
LCKTBRKR_O_ESBB 
1.9E-6 
IBUS_MCCB DISCONN_MCCB 
1.9E-5 
LINE_125VDCB 
4.5E-6 
LCKTBRKR_O_125VDCB 
125VDCB 
SWGREB_CHARGR SWGREB_BATTERY 
DCPOWER_SWGREB 
1.9E-5 
LINE_SWGEB 
4.5E-6 
LCKTBRKR_O_SWGREB 
1.0E-6 
DCBUS_SWGREB 
6.8E-6 
CHARGR_SWGREB 
4.5E-6 
LCKTBRKR_O_CHARGRB 
4.0E-7 
BATTERY_SWGREB 
5.6E-8 
CCF_MCKTBRKR_ESB 
9.4E-8 
CCF_FUSE_ESB 
9.2E-8 
CCF_XFMR_ESB 
9.1E-7 
CCF_LINE_ESB 
2.1E-7 
CCF_LCKTBRKR_ESB 
9.0E-8 
CCF_MCC_ESB 
9.1E-7 
CCF_LINE_125VDC 
2.1E-7 
CCF_LCKTBRKR_125VDC 
2.1E-7 
CCF_LCKTBRKR_SWGRAB 
9.1E-7 
CCF_LINE_SWGRAB 
4.9E-8 
CCF_DCBUS_SWGRAB 
3.2E-7 
CCF_CHARGR_SWGRAB 
2.1E-7 
CCF_LCKTBRKR_CHARGAB 
1.9E-8 
CCF_BATTERY_SWGRAB 
2.1E-7 
CCF_LCKTBRKR_BATTAB 
4.5E-6 
LCKTBRKR_O_BATTB 
Failure of 125VDC 
system to remain 
connected to MCC 
125VDC system fails to 
supply power to SWGREB 
Med Voltage Ckt Brkrs 
Failure of MCC to 
remain connected to 
Emergency SWGR B 
4160-480V 
Transformer fails 
to operate 
Fused Interrupter 
Switch fails to remain closed 
to connect ESB load 
Powe line fails to 
remain intact to 
connect ESB load 
Med Volt Ckt Brkr 
fails to remain closed 
to connect ESB load 
Low Volt Ckt Brkr 
fails to remain closed 
to connect ESB load 
MCC bus fails 
short circuited 
Power line fails to 
remain intact to connect 
125VDC load 
Low Volt Ckt Brkr fails 
to remain closed to 
connect 125VDC load 
125VDC system fails to 
supply power to SWGREB 
Med Volt Ckt Brkrs 
Low Volt Ckt Brkr fails 
to remain closed to 
connect SWGREB 
Power line fails to 
remain intact to connect 
SWGREB load 
125VDC distribution 
bus for SWGREB 
fails short circuited 
Loss of DC power to 
125VDC distribution bus 
to SWGREB 
SWGREB 125VDC 
battery charger fails 
to operate 
SWGREB 
125VDC battery 
fails to operate 
SWGREB 125VDC 
battery charger fails 
to operate 
SWGREB 
125VDC battery 
fails to operate 
Low Volt Ckt Brkr fails 
to remain closed to 
connect SWGREB charger 
CCF Med Volt Ckt Brkr 
(1/2) - 125VDC 
SWGREA & SWGREB 
CCF Fused Interrupter 
Switch (1/2) - 125VDC 
SWGREA & SWGREB 
CCF 4160-480V 
Transformer (1/2) - 125VDC 
SWGREA & SWGREB 
CCF Power line (1/2) - 
125VDC SWGREA & 
SWGREB 
CCF Low Volt Ckt Brkr 
(1/2) - 125VDC 
SWGREA & SWGREB 
CCF MCC bus (1/2) - 
125VDC SWGREA & 
SWGREB 
CCF Power line (1/2) - 
125VDC SWGREA & 
SWGREB 
CCF Low Volt Ckt Brkr 
(1/2) - 125VDC 
SWGREA & SWGREB 
CCF Low Volt Ckt Brkr 
(1/2) - 125VDC 
SWGREA & SWGREB 
CCF Power line (1/2) - 
125VDC SWGREA & 
SWGREB 
CCF DC Bus (1/2) - 
125VDC SWGREA 
& SWGREB 
CCF Battery Charger 
(1/2) - 125VDC 
SWGREA & SWGREB 
CCF Low Volt Ckt Brkr 
(1/2) - 125VDC 
SWGREA & SWGREB 
CCF Battery (1/2) - 
125VDC SWGREA 
& SWGREB 
CCF Low Volt Ckt Brkr 
(1/2) - 125VDC 
SWGREA & SWGREB 
Low Volt Ckt Brkr fails 
to remain closed to 
connect SWGREB battery 
Figure B-5. Subtree 125VDC_SWGREB

Reliability Analysis of the Electrical Power Distribution System to Selected Portions of the Nuclear HVAC System 
100-PSA-EE00-00100-000-00A B-12 December 2004 
INTENTIONALLY LEFT BLANK

Reliability Analysis of the Electrical Power Distribution System to Selected Portions of the Nuclear HVAC System 
100-PSA-EE00-00100-000-00A B-13 December 2004 
EDGB_SWGREB 
1.0E-2 
START_EDGB 
2.0E-2 
RUN_EDGB 
1.2E-6 
MCKTBRKR_O_EDGB 
1.9E-5 
LINE_EDGB 
4.7E-4 
CCF_START_EDGAB 
9.4E-4 
CCF_RUN_EDGAB 
5.6E-8 
CCF_MCKTBRKR_O_EDGAB 
9.1E-7 
CCF_LINE_EDGAB 
Failure of Emergency 
Diesel Gen B to power 
Emergency Switchgear B 
Emergency Diesel 
Generator B fails to 
start operation 
Emergency Diesel 
Generator B fails to 
continue operation 
Med Volt Ckt Brkr 
fails to operate to 
connnect EDG B 
Power line fails to 
remain intact to 
connect EDG B 
CCF Diesel Start 
(1/2) - Emergency 
Diesel Gens A & B 
CCF Diesel Run 
(1/2) - Emergency 
Diesel Gens A & B 
CCF Med Volt Ckt Brkr 
Connect (1/2) -Emergency 
Diesel Gens A & B 
CCF Power Line 
(1/2) - Emergency 
Diesel Gens A & B 
Figure B-6. Subtree EDGB_SWGREB

Reliability Analysis of the Electrical Power Distribution System to Selected Portions of the Nuclear HVAC System 
100-PSA-EE00-00100-000-00A B-14 December 2004 
INTENTIONALLY LEFT BLANK