WEEK 6 REMEDIAL Flashcards
Ovation (SJ) EO: 1.5 Describe the use of Points in the Ovation system
Digital Points are used to identify or define discrete digital states such as an On/Off switch, High/Low switch, relay activation, etc.
Analogue Points are used to identify or define a value over some variable range such as a tank level or pressure, flow rate, etc.
EO: 1.4 Describe the flow paths of the Safety Injection subsystem.
Active Injection - SIAS Each High Pressure Safety Injection (HPSI) Pump injects borated water from the Refueling Water Tank (RWT) to all four RCS Cold Legs.
Each Low Pressure Safety Injection (LPSI) Pump injects borated water from the Refueling Water Tank (RWT) to two RCS Cold Legs.
Both Pumps recirculate water back to the RWT.
Passive Injection - SIAS All four Safety Injection Tanks (SIT) inject borated water into their associated RCS Cold Leg when RCS pressure drops below SIT pressure.
Active Injection – SIAS & RAS The water that was injected into the RCS from the RWT spills out of the break and collects in the Containment Recirculation Sump. When the water level in the RWT reaches 9.4% a Recirculation Actuation Signal (RAS) is initiated. The Containment Recirculation Sump isolation valves automatically open to supply water to both Trains of High Pressure Safety Injection (HPSI) Pumps for injection into all four RCS Cold Legs. The RAS also closes all the Safety Injection Pump recirculation valves. The RWT outlet valves must be closed manually by the Control Room Operators following a RAS.
Active Injection – Long Term Cooling Long Term Core Cooling is established 2-3 hours post LOCA initiation. The Containment Recirculation Sump supplies water to both Trains of High Pressure Safety Injection (HPSI) Pumps. The HPSI Pump discharge is manually realigned by the Control Room via motor operated valves for simultaneous Cold Leg injection into all four Cold Legs, and Hot Leg injection into the associated Train Hot Leg. The flow rate is split such that 50% of the total flow is directed to the Hot Leg while the remaining 50% is directed to all four Cold Legs. This maintains subcooling and insures flushing to prevent boiling induced boron precipitation in the Reactor Core, which could cause core heat removal to be diminished or stopped, particularly for a large Cold Leg break. All the Safety Injection Pump recirculation valves are closed.
EO: 1.5 Describe the purpose, operation, and location of the LPSI Pumps.
Purpose
The Low Pressure Safety Injection (LPSI) Pumps (SIA-P01 & SIB-P01) serve two functions:*Inject large quantities of borated water into the Reactor Coolant System in the event of a large break Loss of Coolant Accident (LOCA) too Prevent significant fuel cladding failure during injection mode of operation following the large break LOCA. Provide continuous flow during a LOCA after the Safety Injection Tanks (SITs) have emptied. Provide Shutdown Cooling flow through the Reactor Core and Shutdown Cooling Heat Exchangers for normal plant Shutdown Cooling operation or as required for long term core cooling.
Operation
The Low-Pressure Safety Injection Pumps are vertical, single stage centrifugal units with mechanical seals. The Pump motors are have the capability of starting and accelerating the Pump, under load, to design running speed within 5 seconds. They are rated for 4300 gpm, with runout flow of 5500 gpm, and a shutoff head at ~210 psig. Sizing of the Low-Pressure Safety Injection Pump is governed by the Shutdown Cooling function. The flow available with a single LPSI Pump is sufficient to maintain a core ΔT at an acceptable level at the initiation of shutdown cooling.
Normal Operation
The LPSI Pumps Are maintained in a standby condition Have locked open Motor operated suction valves. Manually operated discharge valves. Are isolated from the RCS by motor operated loop injection valves.
Automatic Actuation
The LPSI Pump will auto start upon receipt of either Safety Injection Actuation Signal (SIAS)Containment Spray Actuation Signal (CSAS)
When a Recirculation Actuation Signal (RAS) occurs (9.4% RWT level) then The LPSI Pump shuts off Both the LPSI Pump motor operated recirculation valve and the Safety Injection Train common recirculation header solenoid operated valve to the Refueling Water Tank (RWT) close.
Power Supplies
The LPSI Pumps receive power from the Class 1E 4.16 kV buses, PBA-S03 & PBB-S04.
Rumble Region
The LPSI Pumps operation in the “rumble region” of 2500 to 3500 gpm should be avoided.
EO: 1.7 Describe the purpose, operation, and location of the Safety Injection Tanks.
Purpose
Safety Injection Tanks, SIE-X01A-D, provide a passive means of rapidly reflooding the Reactor Core with borated water following a large break Loss of Coolant Accident (LOCA), and keeping it covered until flow from SI Pumps is available.
Operation
Each Safety Injection Tank (SIT) contains ~14,000 gallons of borates water and is pressurized with high pressure nitrogen at ~600 psig. SIT water and gas volumes and gas pressure are based on three of the four Tanks operating to partially recover the core before significant clad melting or zirconium water reaction can occur following a LOCA. In cold leg breaks, the entire contents of one SIT are assumed to be completely lost.
Normal Operation
Each Safety Injection Tank is has a motor operated valve and two check valves for isolation from the RCS. During normal operation, the motor operated valve is open with its power removed (breaker locked open) to prevent inadvertent closure.
Injection
When Reactor Coolant System (RCS) pressure drops below SIT pressure then each SIT automatically discharges into its associated Cold Leg. In the early stages of a LOCA, coincident with a Loss Of Offsite Power (LOOP), the SITs provide the sole source of makeup water to the RCS. This is because the LPSI pumps and HPSI pumps cannot deliver flow until the Diesel Generators (DGs) start, come to rated speed, and go through their timed loading sequence.
Controlled cooldown and depressurization
During a controlled cooldown and depressurization of the RCS, when RCS pressure reaches 750 psia then SIT pressure is lowered to 300 psig by venting off the nitrogen cover gas to Containment atmosphere. When RCS pressure is < 430 psia then the SIT Motor Operated Valves (MOVs) may be closed to isolate them from the RCS to allow cooldown and depressurization without discharging the SITs into the RCS.
Controlled heat up and pressurization
When RCS pressure is raised above 430 psia then the SIT motor operated valves are opened, power is removed and the breakers are locked open.
Interlocks
The SIT motor operated isolation valves are interlocked with Pressurizer pressure to ensure that the valves will automatically open as RCS pressure increases above SIT pressure, and prevent closure
EO: 1.20 Describe the Mission Times associated with the Safety Injection system.
Mission Time is the time from the start of an initiating event that a System, Structure, or Component (SSC), and its supporting SSCs, are required to perform specific safety function(s), in the assessment of OPERABILITY, to mitigate any event or accident.
All SSCs shall function for the duration of their Mission Time without the need to stop, repair, or restart the SSC. Reasonable Operator actions are allowed after 30 minutes into the Design Basis Accident (DBA), if the area is accessible and habitable, to maintain the SSC for Degraded or Nonconforming conditions that occur during a DBA. Examples of Operator action include the addition of consumables such as oil, fuel, and water.
The safety Injection system has a Mission Time of 30 days for the following components
High Pressure Safety Injection Pumps
Containment Spray Pumps
Shutdown Cooling Heat Exchangers
The Low Pressure Safety Injection Pumps have an administrative Mission Time of 30 days because Emergency Operating Procedures (EOPs) allow the use of LPSI Pumps for extended Emergency Core Cooling functions.
Anything that challenges the 30-day OPERABILITY of these components, such as an oil leak, challenges the required Mission Time of the component. Auxiliary Operators must identify anything that challenges the Mission Time of these components and promptly raise the issue to the Control Room Supervisor.
EO: 1.1 Describe the purpose of the Control Element Drive Mechanism Control System (CEDMCS).
Purpose
The Control Element Drive Mechanism Control System (CEDMCS)develops the control voltage to withdraw, hold, or insert Control Element Assemblies (CEA’s).
Control Element Assemblies (CEAs), also known as Control Rods, are used to control the fission rate of the Reactor(Reactor power).
CEDMCS allows the movement of CEAs to achieve power control, and power distribution control, so that the Reactor power may be operated from full-rated power to cold shutdown, and that the power distribution at any given power level is controlled within acceptable limits.
CEDMCS allows CEA groups to be used to compensate for reactivity changes.
CEA movement controls the location of power in the Core, compensates for minor variations in moderator temperature and boron concentrations, and dampens axial xenon oscillations.
*CEDMCS allows the CEAs to drop into the Core upon an interruption of power to the Control Element Drive Mechanism (CEDM) Coil Stacks(a.k.a., Reactor trip).
CEAs are used to maintain reactivity control with a positive means of inserting negative reactivity.
CEDMCS provides signals upon a Reactor trip too the plant systems
Main Turbine
Feedwater Control system
Steam Bypass Control System
Emergency Response Facility Digital Acquisition Display system (ERFDADs)
SRP Plant Multiplexer
CEDMCS provides signals for CEA positioning.
CEA position is used as an indication to assure the reactivity control system has maintained the plant within safety limits.
EO: 1.19 Identify the equipment in the CEDMCS system that has a Technical Specifications Limiting Condition for Operation, a the basis for it.
The LCO requires four Reactor Trip Circuit Breakers (RTCB)channels to be OPERABLE in MODES 1 and 2,as well as in MODES3, 4, and 5 when the RTCBs are closed and any CEA is capable of being withdrawn.
Bases
The RPS initiates a Reactor trip to protect against violating the Core fuel design limits and Reactor Coolant pressure boundary integrity during anticipated operational occurrences (AOOs). By tripping the Reactor, the RPS also assists the Engineered Safety Features (ESF)systems in mitigating accidents.
The Reactor Trip Circuit Breakers are considered to be OPERABLE when their associated support circuitry is OPERABLE.
EO: 1.6 Describe the purpose and operation of the Liquid Nitrogen Pumps.
Pump Cooldown and Operation
When a Liquid Nitrogen Pump receives a start signal, either automatic or manual, then its solenoid operated inlet valve, GAN-UV-105 or GAN-UV-106,opens to admit from the Liquid Nitrogen Storage Tank to the Pump. As it enters the relatively warm piping of the Pump suction, and the Pump itself, much of it will initially flash to a vapor. A solenoid operated valve in a common vapor return line also opens upon a Pump start signal to direct this vapor back to the Liquid Nitrogen Storage Tank.
The system will remain in this static state for 15 minutes for the Pump suction line, and the Pump, to cooldown. After 15 minutes, the Liquid Nitrogen Pump “Cooldown” light will turn off and the Pump will start. 15seconds after the Pump starts the vapor return solenoid valve shuts.
The Pump transfers Liquid nitrogen through the High Pressure Vaporizer to both Storage Banks until the Active bank reaches 2100 psig, at which point the Pump will secure and it’s inlet solenoid valve will shut.
EO: 1.6 Describe the purpose and operation of the Liquid Nitrogen Pumps.
Pump Cooldown and Operation
When a Liquid Nitrogen Pump receives a start signal, either automatic or manual, then its solenoid operated inlet valve, GAN-UV-105 or GAN-UV-106, opens to admit from the Liquid Nitrogen Storage Tank to the Pump. As it enters the relatively warm piping of the Pump suction, and the Pump itself, much of it will initially flash to a vapor. A solenoid operated valve in a common vapor return line also opens upon a Pump start signal to direct this vapor back to the Liquid Nitrogen Storage Tank.
The system will remain in this static state for 15 minutes for the Pump suction line, and the Pump, to cooldown. After 15 minutes, the Liquid Nitrogen Pump “Cooldown” light will turn off and the Pump will start. 15seconds after the Pump starts the vapor return solenoid valve shuts.
The Pump transfers Liquid nitrogen through the High-Pressure Vaporizer to both Storage Banks until the Active bank reaches 2100 psig, at which point the Pump will secure and it’s inlet solenoid valve will shut.
1.6 Describe the purpose and operation of Load Center’s circuit breakers.
Purpose
A circuit breaker is an automatically operated electrical switch designed to protect an electrical circuit from damage caused by excess current from an overload or short circuit. Its basic function is to interrupt current flow after a fault is detected.
Operation
Each Class 1E 480 VAC Load Center bus is provided with three types of circuit breakers
480 VAC Main Feeder Breaker
Motor supply breakers
MCC supply breakers
The Non-Class 480 VAC LC circuit breakers are designed with front panel mounted control switches for manually closing and tripping the circuit breakers. Each circuit breaker switch has two positions, TRIP, which opens it; and CLOSE, which shuts it.
The breakers are stored energy type, three pole, single throw, electrically and mechanically trip free breaker which operates automatically on faults or continued overloads. All lockout relays are reset locally at the switchgear and shall not be reset without the permission of the Control Room Supervisor/Shift Manager.
Main Feeder Breakers
The 480 VAC Main Feeder Breaker (‘B2’ input breaker) controls the supply of power to the Load Center bus. Upon a breaker trip due to a fault, both the 480V main feeder breaker and the 13.8 kV supply breaker are tripped by the actuation of the 86 lockout relay to prevent re-closing of the breakers.
Motor Feeder Breakers
Motor breakers are equipped with a 600A frame. They are equipped with a solid state overcurrent trip with long time and instantaneous elements for automatic tripping. They are also provided with solid state ground fault protective relays for ground fault protection. Lockout relays are provided to prevent the breaker from re-closing after tripping on a fault condition. Resetting of the Lockout relay must be done locally at the Load Center.
MCC Supply Breakers
These breakers are equipped with a 600A frame. They are equipped with solid state overcurrent trip devices with long time and short time elements and a separate inverse time ground relay to facilitate selective automatic tripping (tripping of breakers closest to the fault and sequentially closer to main supply as necessary to isolate fault). Lockout relays are provided to prevent the breaker from re-closing after tripping on a fault condition. Resetting of the Lockout Relay must be done locally at the Load Center.
Controls
Each breaker is normally operated remotely. They are, however, equipped with “Close” and “Trip” buttons mounted on the breaker for local manual operation. Some breakers have “Close” and “Trip” push buttons on the breaker itself that are used for testing while the breaker is racked to the “Test” position.
Control Power
Each breaker is electrically operated with Non-Class 125 VDC Control Power (NK). If the breaker control power is lost, the LC breaker will remain as-is, regardless of external signals generated to close or trip the breaker, and its indicating lights will de-energize.
Breaker Racking Positions
All breakers are provided with an interlock to prevent insertion or withdrawal from the operating position with the breaker closed. The breakers are equipped with three racking positions
Connected(Racked In)
Main, Auxiliary, and Control contacts are connected for breaker operation
Test(Racked out 14 turns)
Main contacts are disconnected, but the Auxiliary and Control contacts are closed for breaker and control circuit testing.
Disconnected (Racked out 21 turns)
All contacts are disconnected
Breaker Indicating Lights
Lamps located at each circuit breaker control switch provide indication of breaker status.
Red
Indicates that the breaker is CLOSED and that there is continuity of power through the trip coil. If the red light is not lit then the trip circuit may not function.
The current through the red light is limited by a resistor. The resistor keeps the current to a value that will illuminate the light but not generate enough of a magnetic field to activate the breakers trip coil.
Green
Indicates that the breaker is OPEN. This light becomes bright green when the breaker has tripped on a fault (lockout relay actuation) or the breaker is racked to the test position.
Either of these conditions will close a contact that bypasses some of the resistor that is in series with the green light. This causes the intensity of the light to increase.
Blue
Cooling Tower Load Center Breakers supplying the Cooling Tower Fans have a blue light which will light when the breaker trips due to a high vibration condition of the fan.
Clearance and Tagging
When establishing a clearance on a 480V Load Center breaker the breaker must first be in the Disconnected(Racked Out) position. Then the breakers Locking Hasp is pulled out, which locks the breaker in the ‘Tripped’ position and the Clearance Tag is hung on it.
Tags Plus is established by the Tag hanger by installing a metal lock on the Locking Hasp, separate from the Tag itself.
EO: 1.2 Draw and label a simplified diagram of the Non-Class 125 VDC Control Power system.
NK 125 VDC CONTROL POWER
EO: 1.3 Describe the flow path of the Non-Class 125 VDC Non-Class Power system.
480VAC is supplied to each Battery Charger from a Non-Class Motor Control Center. The Battery Chargers convert the 480VAC to 135VDC and supply it to the Battery Bus, Non-Class Batteries, and Non-Class DC loads (e.g. ,DC motors, control power for breakers, solenoids).
The ‘E’ Battery Charger normally supplies 135VDC power to NKN-M45(Control Center ‘E’). The spare Battery Charger “E1”may be manually connected to NKN-M45 when the ‘E’ Battery Charger is not available. ‘E’ Battery
NQN Inverter supplying power to Distribution Panel NQN-D01 which supplies power to the Plant Computer
Distribution Panels NKN-D41, NKN-D42, NKN-D43
Main Generator primary and backup Tripping Circuits
The ‘F’ Battery Charger normally supplies 135VDC power to Control Center NKN-M46(Control Center ‘F’).
‘F’ Battery Distribution Panels NKN-D44, NKN-D45Main Feedwater Pump Turbines Emergency Lube Oil Pumps
Main Turbine Emergency Bearing Oil Pump (EBOP)Main Turbine Emergency Seal Oil Pump (ESOP)The common backup Battery Charger “EF”(Swing Charger) may be manually connected to a single Control Center, NKN-M45 or NKN-M46, to carry the loads during maintenance of the normal Battery Charger or periodic testing of the 135 VDC system. The ‘G’ Battery Charger supplies135 VDC power to Distribution Panel NKN-D19.
‘G’ Battery
Control Power for Cooling Tower Load Centers
Chlorine Injection Panels (operated by Water Resources)
Startup Switchyard Control Power
NKN-M45 and NKN-M46 each supply power to cabinets NKN-U45 and NKN-U46,respectively, which supply Control Power to the Switchgear out at the Startup Switchyard (each Units NAN-S05 & NAN-S06). These cabinets each contain two breakers which align the incoming power source (either NKN-M45 or NKN-M46) to the Switchyard.
There are no interconnections among the three Non-Class 125 VDC Control Center buses within each Unit.
EO: 1.6 State the purpose, operation, and location of the Non-Class 120 VAC Instrument Power Distribution Panels.
Purpose
NNN-D11 & NNN-D12 provide power for Reactor Control Instrumentation and other station service loads.
Feedwater Control System
Steam Bypass Control System
Control Element Drive Mechanism Control System (CEDMCS)
Fuel Pool Instrumentation
RCS & CVCS Process Instrumentation
NNN-D15 & NNN-D16 provide power for Balance of Plant (BOP) and miscellaneous station service loads.
Control Oil Cabinet for Turbine Trip
Generator Hydrogen and Stator Cooling Cabinet
Billing and Metering Instrumentation
Plant Annunciator Cabinets
Ground Detection circuitry
Operation.
Breakers
The main breakers and the individual feeder circuit breakers are manually operated at the local distribution panels. A trip of any of these breakers will be enunciated in the control room. When the breaker trips, it will be in the “TRIP FREE” position, half way between OFF and ON. The breaker must be taken to OFF before it can be shut again.
Grounding
NNN-D11 & NNN-D12 are ungrounded and are equipped with a ground detection system. This system includes a ground detection relay, a RED ground light, and a RESET pushbutton. Upon a receipt of a ground, ground isolation should be commenced as soon as possible. This procedure includes opening circuit breakers and seeing if the ground condition clears by pressing the RESET pushbutton and seeing if the ground light clears.
NNN-D15 & NNN-D16 are grounded and thus are not equipped with a ground detection system.
EO: 1.3 Describe the purpose, operation, and location of the PMS UPS Inverter.
Purpose
The Static Inverter is designed to be used as a continuous AC power supply providing single phase 120 VAC power to PMS System I/O cabinets and accessories.
Operation
The Inverter uses the Non-Class 125 VDC bus NKN-M45 as its input power source. DC to AC conversion is accomplished by four main single-phase inverter assemblies. The outputs of the power running-transformers (secondaries) are added to form a multi-stepped, notched sine-wave which approximates to a sine wave at 60Hz and 120 VAC. A constant voltage transformer CVT-1 maintains the output voltage regulated at 120 VAC (+2%) for input DC voltages of 105-140 VDC.
Inverter AC frequency is maintained constant at 60 Hz (+0.5 Hz) by a low level precision oscillator or is varied to enable synchronization of the inverter output voltage with the alternate AC power source.
The static transfer switch has a Voltmeter and an Ammeter indicating the output parameters.
EO: 1.10 Describe the purpose and operation of the SBOG Generator.
Purpose
The purpose of the Generator is to convert the mechanical energy produced by the Turbine engine into useful electrical energy.
Operation
The mechanical to electrical energy conversion is accomplished via electromagnetic Induction. The three-phase AC Generator output is rated at 14.2 kV and 4270 kW @ 0.8 Lagging power factor.
The design basis load using a HPSI Pump on a single SBOG is 3364.3 kW.*The design basis load using two Charging Pumps on a single SBOG is 2699.4 kW.
The main components of the Generator
Stator (Armature).
The Main Stator Windings are three sets of conductor coils mounted in the Main Generator Casing. As the rotating magnetic field passes each set of coils, a voltage will be induced in each coil. The output leads from each of these three coils (or phases) are connected to the power distribution system in the Generator terminal box.
Rotor
In order to induce the voltage in the Generator Stator, a rotating magnetic field is required. This is achieved by generating an electromagnet in the laminated Main Field Windings located on the Generator Rotor. Controlling the strength of this magnetic field will in turn control the main output voltage from the generator.
Exciter
The Exciter provides a Direct Current (DC) from the Voltage Regulation system that is required to produce the magnetic field in the Main Field Windings on the Generator Rotor. By controlling this DC current (or “Excitation Current”) the exciter field strength is controlled and thereby the voltage induced in the Stator (Armature) will be controlled.
It is installed at the Non-Drive End (or Exciter End) of the Generator.
Permanent Magnet Generator (PMG)
The PMG produces a voltage to provide power for the Voltage Regulation system. Since a permanent magnet is used, this power will be available as soon as the generator begins to rotate, thus, no external initial “excitation” or “field flashing” is required, as is the case with generators not equipped with a PMG.
Putting it all together
As soon as the generator begins rotation, the permanent magnet field of the PMG rotates on the exciter end of the generator shaft, and induces a single-phase output into the PMG stator winding. This AC output is then fed to the Voltage Regulation System where it is rectified to DC and regulated. The regulated DC output is now fed to the Exciter, which causes a magnetic field to be built up in the Rotor with the strength proportional to the DC output (or “Excitation Current”). As the Rotor rotates its corresponding magnetic field rotates inside the Stator Windings, and a 3-phase voltage will be induced proportional to the strength of the Rotor’s magnetic field. In this way, the output voltage of the Generator is controlled by regulating the excitation current from the Voltage Regulation system.
The system is “self-starting” in the sense that the PMG will provide power for the voltage regulation system on initial rotation of the generator. In practice, the PMG power is supplied through relay contacts, which are open until the engine speed reaches a typical value of 80%. This prevents the voltage build up in the generator causing a drag on the engine acceleration during the early stages of the start sequence.
Generator Cooling
Operating temperature is the factor that imposes the greatest limit on the performance of a generator. This is because the insulating materials will break down if their design temperatures are exceeded. Therefore, if the stator winding temperature can be kept below a value that provides a safe margin for the insulation, the generator will be able to accept load to the point where the turbine is unable to deliver any more input power.
Generator cooling is achieved by circulating air through the stator and across the rotor windings by means of a cooling fan installed at both ends of the rotor. These fans draw air from both ends of the generator, which is then exhausted through the top of the generator body.
