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 –2 nd 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

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 12 Fuel Bundle / Assembly is the entire unit

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

Squaw Creek Reservoir Primary SystemsSecondary Systems Comanche Peak Overview 15

16 Unit 2Unit 1 345kV yard 138kV Yard Safe Shutdown Impoundment

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 19 Fuel Assembly Reactor

Spent Fuel Pool 20 Fuel Assembly

Containment Building 21 Unit 1 Unit 2 Fuel Building Equipment Hatch

REACTOR COOLANT SYSTEM - LOSS OF COOLANT ACCIDENT (LOCA) SECONDARY SYSTEM STEAMLINE BREAK NUCLEAR FUEL HANDLING ACCIDENT IN THE REACTOR CONTAINMENT OR FUEL HANDLING BUILDING NUCLEAR ACCIDENT CATEGORIES 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 safety- related 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

For back feed ops, ground at Generator flex link elephant foot and Upper PT fuses 26

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Operability Pairs for OPT kV Decordova 345 kV Johnson Sw. 345 kV Comanche Sw. 345 kV Parker #1 345 kV Parker #2 345 kV Everman 345 kV Wolf Hollow 138 kV Decordova and any 345kV ckt. 138 kV Stephenville and either Parker 345kV ckt. 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: KV Minimum and Maximum voltages for 138 KV are 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 safety- related 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 Under- frequency 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

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 Questions

1.A minimum of _________ transmission lines should be in service at all times at Comanche Peak. a)two b)three c)four d)five 46

2.The preferred source of offsite power considered by Comanche Peak in the event of a blackout is? a)Decordova 345kV b)Decordova 138kV c)Parker Switch 345kV d)Everman Switch 345kV 47

3.The CPNPP 345kV minimum and maximum switchyard voltage requirements for Operability are _______________. a)340kV and 361kV b)339kV and 362kV c)338kV and 363kV d)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)two b)four c)six d)eight 49

5.Comanche Peak’s main generator turbine controls are not configured to respond to ______________fluctuations. a)Grid frequency b)Regulation up c)Regulation down d)AGC signal 50