Comanche Peak Nuclear
Power Plant
1
TERMINAL OBJECTIVES
• Describe Comanche Peak Design Basics
• Describe Nuclear Fuel used at Comanche Peak
• Describe the Basics of Nuclear Fission and
identify how Comanche Peak produces power
2
TRAINING OBJECTIVES
• Identify the configuration of the Comanche Peak
Electrical Distribution System
• Identify the Electrical Distribution System offsite power
requirements
• Identify Comanche Peak’s Minimum Switchyard Voltage
Requirements
• Identify Comanche Peak’s Station Blackout
Requirements
• Identify how Grid Frequency Disturbances affect
Comanche Peak
3
Comanche Peak Design Basics
• Two Nuclear Power Plant Units:
o Unit 1: Winter Maximum HSL of 1235 NMW
o Unit 2: Winter Maximum HSL of 1225 NMW
• 4 Loop Pressurized Water Reactors (PWR)
• Commercial Operation Dates:
o August 1990 CPNPP Unit 1
o August 1993 CPNPP Unit 2
• 2 Independent Trains of Safety Equipment for
the safe shutdown of each unit
4
Comanche Peak Information
• Located in Somervell County
– 2nd Smallest county in State of Texas
• 7,350,000 hours since last Lost Time Injury
• Payed $34 million in local taxes this year
• 706 Luminant employees
• 199 Contract employees
• 479 Teammates
• 19,896,924 Net MWH generated in 2012
5
Comanche Peak Information
• Institute Of Nuclear Power Operations (INPO) 1 rating
last 3 bi-annual assessments.
• Last 5 years achieved 98% capacity factor making
CPNPP best operating nuclear plant in USA
• Community projects include
– United Way of Hood County
– United Fund of Somervell County
– Healthy Habitat Wildlife Restoration Project Squaw
Creek Park
– Project Lead the Way, Science and Math career
curriculum with Granbury ISD
6
Fission
• Occurs when the nucleus of a relatively large atom (such
as U-235) absorbs a slow moving neutron.
• Upon neutron absorption, U-235 becomes the unstable
isotope U-236 and splits into two fission fragments.
• As part of the fission process, additional neutrons and
gamma radiation is released.
• The kinetic energy released produces heat which is
ultimately converted to steam and electrical energy.
7
Nuclear Fuel Properties
• Most common fuel used in commercial reactors
is Uranium-235.
• Under 1% of the uranium found in nature is the
easily fissionable U-235 isotope and as a result
most reactor designs require enriched fuel.
• Most commercial reactors use uranium enriched
to about 4% U-235.
• Uranium Oxide fuel is manufactured into ceramic
pellets.
8
Uranium Oxide Fuel Pellet
9
Fuel Assemblies
• Pellets are inserted into Zirconium Alloy
tubes and sealed.
• These tubes are called fuel rods.
• Fuel rods are joined together to form
assemblies, also called fuel bundles.
10
Control Rods
• Control rods are made of material that readily
absorbs neutrons but will not fission.
• Common materials are Silver, Indium, and
Cadmium.
• Control rods are inserted vertically into guide
tubes within the fuel bundle and can be
withdrawn as needed to control reactivity within
the core.
11
Control Rod
Assembly
Fuel Bundle /
Assembly is
the entire unit
12
Fuel Assembly Inspection
Engineering and Quality Control personnel inspect each
fuel assembly for defects, flaws or blemishes prior to
accepting for use.
13
Energy Output
• A kilogram of Uranium-235 (U-235)
converted via nuclear processes releases
approximately three million times more
energy than a kilogram of coal burned
conventionally.
* * * 3,000,000 times * * *
14
Comanche Peak Overview
Squaw
Creek
Reservoir
Primary Systems
Secondary Systems
15
138kV
Yard
345kV
yard
Unit 1
Unit 2
Safe Shutdown
Impoundment
16
NUCLEAR FISSION PRODUCT
BARRIERS OF PROTECTION
• NUCLEAR FUEL CLADDING
• REACTOR COOLANT SYSTEM
• CONTAINMENT STRUCTURE
17
NUCLEAR FISSION PRODUCT
BARRIERS OF PROTECTION
18
Reactor Cavity Fuel Load
Fuel
Assembly
Reactor
19
Spent Fuel Pool
Fuel Assembly
20
Containment Building
Unit 1
Unit 2
Fuel Building
Equipment Hatch
21
NUCLEAR ACCIDENT
CATEGORIES
• REACTOR COOLANT SYSTEM - LOSS
OF COOLANT ACCIDENT (LOCA)
• SECONDARY SYSTEM STEAMLINE
BREAK
• NUCLEAR FUEL HANDLING ACCIDENT
IN THE REACTOR CONTAINMENT OR
FUEL HANDLING BUILDING
22
NUCLEAR DESIGN
BASIS ACCIDENTS (DBA)
• A DBA represents the worst case possible
accident within an accident category.
• The initial conditions of a DBA assumes a
complete loss of ALL normal offsite and onsite
AC electrical power and failure of one
emergency diesel generator.
• One safety-related train can effectively mitigate
all DBAs. Comanche Peak has two safetyrelated trains for each nuclear unit.
23
ESF PROTECTION SYSTEMS
Engineered Safety Features (ESF)
Protection Systems provide the
necessary systems to ensure that
CPNPP can mitigate a Design Basis
Accident (DBA) by protecting the
nuclear fission product barriers and
preventing public exposure to
radiation.
24
Comanche
Peak
Electrical
Distribution
System
25
OP51.SYS.YD1.FIG2
West Bus
Placed In
service after
2RF14
East Bus
W11
8080
E11
8075
W10
8030
E10
8020
Unit 2
Main Transformers
2MT1 & 2MT2
W9
8645
Parker 2
8041
Parker 1
E8
8040
ONCOR
CONTROL
HOUSE
8039
W7
8090
Comanche
Switch
Stephenville
138 Kv
345 KV
Relay
House
W6
7980
2UT
2ST
2
MOAS 8012 M
E6
7970
W5
8050
MOAS 8032
Venus 2
M
MOAS
M
8052
1
1ST
E4
8650
Everman
XST2
XST2A
W3
8010
E3
8000
W2
8070
Wolf Hollow
1UT
E1
8060
Decordova 1
XST1
Unit 1
Main Transformers
1MT1 & 1MT2
345 Kv Switchyard
SDG
Relay
House
CAPACITOR
BANK
Stephenville
138 Kv
M
High Speed
Ground Switch
MOAS 8085
SDG
8435
XST1A
7050
7022
Available for
service in
December
25Kv Loop
7030
7040
7020
Decordova
138 Kv
25Kv Loop
West Bus
7052
East Bus
138 Kv Switchyard
345Kv and 138Kv Switchyards
Figure 2
07/30/2013
27
OP51.SYS.YD1.FIG13
Placed In
service after
East Bus
2RF14
West Bus
W11
8080
E11
8075
W10
8030
E10
8020
W9
8645
Parker 2
8041
Parker 1
Comanche
Switch
W7
8090
8039
Relay
House
MOAS
8032 M
MOAS
8052
M
E4
8650
W3
8010
M
E6
7970
W5
8050
Everman
2ST
ONCOR
Control
House
MOAS 8012
W6
7980
Venus 2
Johnson Switch
E8
8040
2UT
Unit 2
Main Transformers
2MT1 & 2MT2
E3
8000
XST2
1ST
XST2A
W2
8070
Wolf Hollow
E1
8060
Decordova 1
1UT
Unit 1
Main Transformers
1MT1 & 1MT2
Security Fence
345 Kv Switchyard
Figure 13
07/30/2013
28
Operability Pairs
for OPT-215
345 kV Decordova
345 kV Johnson Sw.
138 kV Decordova
and any 345kV ckt.
345 kV Comanche Sw.
345 kV Parker #1
345 kV Parker #2
345 kV Everman
138 kV Stephenville
and either Parker
345kV ckt.
345 kV Wolf Hollow
30
Nuclear Plant Interface
Requirements (NPIRs)
NERC Reliability Standard NUC-001
requires that a nuclear power plant
and applicable Transmission
Entities have an agreement in place
to ensure that all parties understand
the nuclear power plant’s Nuclear
Plant Interface Requirements
(NPIRs).
31
Nuclear Plant Interface Requirements (NPIRs)
CPNPP’s NPIRs include the following:
 minimum and maximum Comanche Peak
switchyard voltage (post-contingency
following both units being offline, post-trip)
 maximum available short circuit current at the
Comanche Peak switchyard
 Minimum of 2 required transmission lines
being in service at the Comanche Peak
switchyard
 maximum and minimum grid frequency that
Comanche Peak safety-related equipment
can support
32
CPNPP Minimum Switchyard
Voltage Requirements
CPNPP switchyard voltage is normally around 348 kV.
The CPNPP switchyard Voltage Requirements for
Operability are:
• Minimum and Maximum voltages for 345 KV are:
340 - 361 KV
• Minimum and Maximum voltages for 138 KV are
135 - 144 KV
33
CPNPP Minimum Switchyard
Voltage Requirements
• These minimum switchyard voltage values ensure that
safety-related equipment stay connected to offsite power
(preferred source of power) in the event of a nuclear
accident, as opposed to connecting safety-related
equipment to the station’s Emergency Diesel Generators.
• If the minimum switchyard voltage requirement for the given
CPNPP electrical bus alignment cannot be met, then
CPNPP is required to enter a Limiting Condition for
Operation (LCO). This initiates a requirement to shutdown
the plants at 24 hours (both offsite sources affected) or 72
hours (one offsite source affected) .
34
Loss of Offsite Power (LOOP)
• Offsite power is needed to prevent degradation of the
fission product barriers and to provide electrical support
for systems and subsystems needed for cooling.
• As a nuclear power plant, Comanche Peak is a priority
load, and offsite power should be restored to the plant
within 4 hours.
• Also, each Comanche Peak unit has two independent
emergency diesel generators (one per safety-related
train) that provides emergency AC power to safetyrelated equipment during a LOOP.
• Comanche Peak cannot restart the Units without offsite
power support.
35
Station Blackout (SBO)
• If both offsite power and onsite AC power
Emergency Diesel Generators (EDG) are lost,
then Comanche Peak will experience a station
blackout.
• Comanche Peak has safety-related station
batteries that can support a 4-hour SBO event.
• The safety-related station batteries are used to
perform the generator field flash required to start
an Emergency Diesel Generator and power
inverters for protection and instrumentation.
36
Comanche Peak
Blackstart Plan
• Comanche Peak has developed a Blackstart
Plan that focuses on power restoration from near
by Decordova SES.
• The combustion Turbines at Decordova will be
started and aligned to the 138 KV switchyard to
provide Comanche Peak offsite power.
• Special procedures have been developed and
are routinely practiced by Comanche Peak
Operations personnel.
37
Grid Disturbances
• On large plant trips (i.e. South Texas), or grid
disturbances, Comanche Peak safety-related
equipment is designed to operate during grid
frequency deviations.
• Comanche Peak safety-related equipment can
operate under minor grid frequency fluctuations.
• The Reactor Coolant Pumps will trip on Underfrequency Protection at 57.2 Hz.
• The Reactor Coolant Pumps also trip on
Undervoltage at 4850 volts. (70% of 6900 volts)
• If the Reactor Coolant Pumps trip, the reactor will
also trip and the unit automatically shuts down.
38
Grid Disturbances
The Main Generator Turbine Control System is
not configured to respond to grid frequency
fluctuations and will cause reactor power
fluctuations.

The main generator is operated in a
manner to maintain constant loading.

Per its Operating License with the
Nuclear Regulatory Commission (NRC),
Comanche Peak is not permitted to exceed
the thermal limit of the nuclear reactor.
Nuclear power control is ONLY ALLOWED
under the control of NRC licensed operators.
39
CPNPP Reactor Operator
Reactor Operators train for 1 year and then must pass Nuclear
Regulatory Commission written and performance examinations
prior to being awarded their license.
40
Dry Cask for Spent Fuel Storage
Dry Casks are stored outside in a fenced,
guarded slab.
41
New Steam Generator
Unit 1 steam generators were replaced
in 2007
42
Control Room Simulator
Reactor Operators and Senior Reactor Operators
train once every five weeks on normal and accident
scenarios in the control room simulator.
43
Artist conception of CPNPP Units 3 and 4
Project Engineering with Mitsubishi is currently on hold as they
assist in the Fuskishima Diachi recovery effort. CPNPP is still
pursuing the combined construction and operating license from
NRC
44
Questions
45
1. A minimum of _________ transmission lines should be
in service at all times at Comanche Peak.
a)
b)
c)
d)
two
three
four
five
46
2. The preferred source of offsite power considered by
Comanche Peak in the event of a blackout is?
a)
b)
c)
d)
Decordova 345kV
Decordova 138kV
Parker Switch 345kV
Everman Switch 345kV
47
3. The CPNPP 345kV minimum and maximum switchyard
voltage requirements for Operability are
_______________.
a)
b)
c)
d)
340kV and 361kV
339kV and 362kV
338kV and 363kV
337kV and 364kV
48
4. As a nuclear power plant, Comanche Peak is a priority
load, and offsite power should be restored to the plant
within __________ hours.
a)
b)
c)
d)
two
four
six
eight
49
5. Comanche Peak’s main generator turbine controls are
not configured to respond to
______________fluctuations.
a)
b)
c)
d)
Grid frequency
Regulation up
Regulation down
AGC signal
50