SBOGS (GT) Flashcards
What does 10CFR50.63 require for SBOGS ?
Section 50.2:
1.)Each light water cooled nuclear plant must be withstand and recover from a station blackout
2.) Reactor core and associated coolant,control,protection,station batteries must provide sufficient power for containment integrity during blackout
How does 10CFR50.2 define a station blackout?
-Defined as a complete loss of AC power to essential & nonessential switchgear buses
What does a PVNGS blackout look like ?
-Loss of offsite power to class buses,and coincidentally loss of both Class Diesel Generators
What is the PVNGS coping time for station blackout ?
Has a 16hr coping time based on voluntary license conditions
What is the Main Purpose for the SBOGS ?
-To provide AC power within 1 hour of station blackout
-Provides sufficient capacity and reliability to operate systems required for the 16 hour station blackout coping time
What is the minimum continuous output rating for each SBOG ?
-3,400kW
-13.8kV
When do the SBOGS normally operate ?
-Station Blackout
-Operators discretion during a LOOP
-A loss of normal power to the MCC supplying power to SBOG control system
-System testing
What’re the goals for the Loss Of Offsite Power/ Loss of Forced Circulation procedure ?
-Mitigate effects of LOOP or LOFC
and
-Maintain plant in hot standby or hot shutdown
or
-Establish shutdown cooling system entry conditions
while
-Minimizing radiological release to environment and maintaining adequate core cooling
How is ,standard appendix 57,performed during a Loss of Off-Site Power and Failure of a Single Diesel generator?
-Align SBOG to a vital bus either,PBA-S03 or PBB-S04, to provide power to class battery chargers
What are the goals for the Station Blackout procedure ?
-Restore availability of vital components
and
-Safety establish entry conditions of the LOOP/LOFC emergency operating procedure or procedure provided by TSC
while
-Minimizing any radiological release to the environment adequate core cooling
What Standard appendices does the station blackout procedure direct you towards to supply power to coping loads?
-Standard appendix 80- Align SBOG to PBA-S03
One SBOG is analyzed to supply station blackout loads on A Train
-Standard appendix 81- Align SBOG to PBB-S0
B-Train non-design basis SBO scenario
What is the Station Blackout procedures strategy ?
-Bring plant to stable conditions and restore vital auxiliaries
What is the first major action of the Blackout procedure ?
-Ensure safety equipment that don’t rely on AC power to function
-Aux. FW pump to maintain SG level and use of ADVs for heat removal
-Next steps would be to restore electrical power
What is the second major action of the Blackout Procedure Strategy?
-Ensure the plant is coping with the loss of power
-This includes maintaining RCS cooling by a limited controlled cooldown
If offsite power or diesel generator are not expected to restore power within 4 hours, where will the Blackout Coping strategy direct you ?
-Will be directed to do a Controlled cooldown to Shutdown Cooling Entry conditions to be started
If power isn’t restored from offsite or diesel generators within 8 hours, what will the Blackout Coping Strategy direct you to do ?
-Will direct Spent Fuel Pool Cooling to be restored
Operators will restore enough electrical capacity to allow for what ?
-Allow for transition from Blackout Coping Strategy to either the Loss of Offsite Power procedure or another procedure directed by TSC
During a license basis SBO, what’re the two objectives that operator actions are expected to achieve ?
-Establish power to 1 of the Class 4.16kv trains.
-Maintain natural circulation of NSSS until power is restored
There are circumstances in Both LOOP procedure & Blackout procedure that have you perform Standard Appendix 54,what does the appendix 54 have you perform ?
-Align SBOG to NAN-S05 to supply switchyard loads (unit1 only)
-Align SBOG power to NAN-S01, then to NGN-L13 to supply ‘EF’ battery charger to power NKN-M45 for control power to trip NAN-S05 breakers to protect SBOG from switchyard faults
What is the theory of a Gas Turbine engine ?
-Engine that converts chemical energy into mechanical energy using air a medium of conversion
-Mechanical energy created is used to drive rotor of an electrical generator
What’re the 4 processes that comprise Brayton Cycle ?
-Compression:Atmospheric air drawn into compressor
-Combustion: Fuel injected into compressed air creating fuel/air mixture,which is then ignited creating rapid expanding gases
-Expansion: Expanding hot gases are directed into turbine to turn shaft
-Exhaust :Gases discharge to atmosphere
What’re the major package components attached to the skid base frame?
-Gas Turbine Engine
-Speed-reducing Gearbox
-AC generator
-Interconnect shaft that connects the turbine to the AC generator
-Package enclosure
-On skid Gage panel
-Auxiliary equipment:
Start system
Fuel system
Lube oil system
What are the features built into the Skid Base frame ?
-Lube oil reservoir & support for smaller components of auxiliary support system
-Connections are around perimeter of the frame for Fuel,Oil,Instrument air, communications,& other services
What’re the features of the SBOG package enclosure ?
-Steel enclosure rests on skid base frame
-Reduces noise levels
-Protects equipment from harmful weather
-Provides enclosed space for fire protection
-Isolate heat generated form human work environments
Describe the doors on the SBOG enclosure.
-Sealed removable panels
-Hinged doors for easy access
-doors incorporate external locking safety handle & may be operated inside enclosure as well
How does ventilation work on the enclosure?
-Louvered shutters at inlet/outlet
-inlet draws air through filter and silencer
-Exhaust is discharged through exhaust silencer
When does the ventilation system start/stop?
-Starts when the engine is started
-Stops when the engine is shutdown when the enclosure temp. Reaches set point
Why must the enclosure doors be closed while the SBOG is running ?
-Maintain proper ventilation & cooling
Why should you be careful when you open doors when engine is running ?
-Enclosure Ventilation Fans maintains positive pressure inside closure
-Be cautious when opening enclosure doors while running for doors being opened rapidly
What happens if fire happens in enclosure ?
-Contains protective equipment for Fire Detection and suppression system
-Enclosure ventilation dampers will close to contain discharged CO2
What are the Enclosures two space heaters for ?
-Prevent buildup of moisture in the enclosure
-Protects generator insulation windings from moisture
What indications do the Enclosure Gauge Panel have ?
-Engine LO temperature
-Engine LO pressure
-Engine LO filter D/P
-Engine compressor discharge pressure
-Air accumulator pressure
-Engine Fuel Oil pressure
What switches does the panel have ? What’re the switches used for ?
-Two position switch(Starter load& bypass/auto)
-Two push buttons (Crank on & Crank Off )
-They’re used to manually start Diesel Starting Engine to run associated air compressor to pressurize Air Accumulator
What major components does the Turbine Engine consist of ?
-Air inlet assembly
-Air Compressor Assembly
-Compressor Diffuser Assembly
-Combustion Assembly
-Turbine assembly
-Exhaust assembly
Explain the Air Inlet Assembly ?
Atmospheric air drawn into 3 stage filtration system Screen,filter,silencer:
Screen-Protects from leave,insects,moisture
Filter-20pre-filters & 20high efficiency filters protect from dirt, dust, and debris
Silencer-Uses baffles to dissipate sound
Where Air Compressor Assembly located ?
-Bolted to the aft face of the air inlet assembly
-Contains 12 stage axial flow compressor
How does the compressor work ?
The stages in the compressor correct the deflection in the air and straighten the flow of air going towards the diffuser
What is compressor surge ?
-Pressure ratio across compressor becomes greater than the compressor is able to support at given rotor speed
-Compressor forward stages will produce more compressed air that the aft can handle
When is compressor surge most likely to happen ? What happens during compressor surge ?
-Happens at lower compressor speeds during starting & stopping
-Build up of compressed air happens at final compression stages and if severe enough may flow backward through compressor
What’re the two ways to avoid compressor surge ?
-Variable Guide vanes
-Bleed Air Valve
What are the Variable Guide Vanes used for ?
-installed first stages of compressor used to match low pressure forwards stage to the high pressure rear stages
-Changing of vane position changes volume of air entering compressor
What is a Variable Stator Vane used for ?
Is an electro-mechanical system consisting of inlet Guide Vanes and the first 3 rows of stator vanes
What’re the two positions the Variable Stator Vane system works in ?
-At startup & low rpm’s they’re at minimum open position restricting incoming air
-Vanes begin to open at 90% speed and are fully open in 2seconds allowing full air flow into turbine
What is the Bleed Air Valve used for ?
-During low engine speeds,helps reduce excess volume of air in the engine to prevent engine compressor surge
-Maintains T5 average temp.(3rd stage turbine rotor temp) within 5degrees
How does the Bleed Air Valve work ?
Diverts excess air from discharge of compressor and bypasses combustion and turbine section, straight to the exhaust
Where is the Compressor Diffuser located at ? What is the diffuser used for ?
-Stationary casing located at the aft of the compressor section
-used for larger flow path for air exiting compressor,reducing its velocity& giving final pressure increase
What is the first 25% primary air used for ?
-It is mixed with fuel for combustion
What is the other 75% of secondary air used for ?
-Used to cool combustion gases and inner heat shield
-keeps flame come from touching liner
-Ensure complete combustion and reduces gas temp PRIOR to entering turbine section
What does the external combustion assembly support ?
-Fuel injectors
-Fuel Manifold
-Igniter torch
-Bleed Air Valve
-Thermocouples that measure 3rd stage turbine inlet temp
What does the internal combustion assembly support ?
-Supports combustion chamber
-Turbine Nozzle housing
How many fuel injectors protrude around the combustion chamber ?
12 fuel injectors
What is each injector supplied with ?
Supplied with air assist connection to atomize fuel for better ignition
What is the Igniter torch used for ? When does the ignitor torch turn off ?
-It is used to ignite the fuel/air mixture during startup
-Igniter is turned off when engine becomes self-sustaining (66% engine speed)
What is 2/3 of the power generated used for ? What is the remainder of the power used for
-Used to drive engine compressor & accessories
-Remainder of power is to drive Gearbox & Generator
What’re the nozzles used for in the turbine section ?
-Nozzles funnel accelerate the expanding combustion gas to enter next turbine rotor blades at increase velocity
What is the air that is tapped off the 11th stage of the compressor for ?
It gets sent to the turbine rotor blades of the 1st & 2nd stage
What is the Exhaust Diffuser for on the exhaust assembly ?
-Helps reduce the velocity of the gases from the turbine section by have an expanding volume flow path
What is a Exhaust Collector used for in the Exhaust assembly ?
-Provides expanding path which collects and redirects exhaust gas flow & also further reduced velocity
What is an exhaust bellows for on the exhaust assembly ?
-installed between exhaust collector and downstream exhaust ducting to allow thermal expansion
What inside the Exhaust Stack is used for on the exhaust assembly ?
-An exhaust silencer to reduce noise
-Rain stack is used to prevent rain water from collecting whole engine isn’t running
What is the T5 temperature ? How is it measured ?
-Temperature of gases entering the 3rd stage Turbine rotors
-Measured by multiple thermocouples installed at 3rd stage nozzles
What’re the signals for T5 averaged for ?
They’re averaged for Engine Temperature control
What T5 the primary indicator of ?
-Engine loading
-Control limit to which the engine will normally be controlled
What happens to T5 if generator loading goes up ?
T5 will go up with the engine loading
What happens if T5 limit is reached ?
Control system will restrict fuel flow to prevent engine from exceeding limit
What happens if T5 temperature is greater than 1340degrees Fahrenheit for 10 seconds ? What happens after 20 seconds ?
-An alarm will be generated on 10 seconds
-SBOG will trip after 20 seconds
Where is T5 Average displayed ?
Displayed on HMI screen, along with each individual thermocouple value
What is P2 mean ?
-P2 is the pressure of the air exiting the engine compressor in the diffuser section
-Also known as Pcd(compressor discharge pressure )
What does Pcd represent ?
-Represents mass flow of air entering combustor
-Primary indicator of engine power
What does a high Pcd mean ?
-Means more fuel can be mixed and combusted to provide an increase in releases energy, and thus output power
How does the control system use the Pcd signal ?
Control system used Pcd signal to help schedule fuel flow during certain phases of operation
What is Pcd a good indication for besides compressor discharge pressure ?
-Good indication of cleanliness and condition of engine compressor,should be monitored by operator to help predict routine maintenance
Where is Pcd displayed at ?
HMI screens
What is the SBOG reduction gear used for ?
Reduction Gear Unit is used to REDUCE turbine output shaft speed to the lower input speed required by generator
What kind of gear arrangement is the reduction gear ?
It’s an epicyclic high-speed star gear arrangement
What is the output speed of the reduction gear ?
-Output speed is 1800rpm and 60HZ
What is reduction ratio of the Reduction Gear ?
~8.3/1
Turbine speed=14,951rpm,
Generator speed=1800rpm
What commoners does the Reduction Gear provide mounting for ?
-Engine Lube Oil Pump
-Starter Motor
What is the main purpose for the SBOG generator ?
Convert mechanical energy produced by turbine into electrical energy
What is the three phase AC generator output rated for ?
kV output :14.2kV
kW output:4270kW
@.8 Lagging power factor
What’re the design basis loads ?
-Using a HPSI pump on a single SBOG is 3364.3kW
-Using two charging pumps on a single SBOG 2699.4kW
What’re the main components of the generator ?
-Stator
-Rotor
-Exciter
-Permanent Magnet Generator
What is the stator used for ?
Has theee stator windings in generator casing and as magnetic field from rotor passed over it induces voltage into stator windings
Where does the output leads from the three stator windings go to ?
Connected to power distribution system in the Generator terminal box
What is rotor used for in the generator ?
-Need a rotating magnetic field to induce voltage onto stator
-Magnetic field on rotor controls the output voltage of the generator
What does the Exciter do for the generator ?
Provides DC current to induce voltage onto the rotor which controls output voltage of generator
What does the Permanent Magnet Generator do for the generator ?
-Produces a voltage to provide power for the voltage regulation system
When does the Permanent Magnet Generator start producing power ?
-As soon as generator begins to rotate
-Generator does NOT need external initial excitation or field flashing
How is the PMG and Exciter all put together ?
Generator rotation rotates PMG on exciter end of the shaft and induces single phase output into PMG stator winding, this AC output is then rectified into DC by Voltage Regulation system, which is then fed to exciter, then gets induced into rotor
PMG power is supplied through relay contacts which are open during early stages of start sequence, when will the relay contacts close ?
They will close on 80% engine speed
Why do the relay contacts close when engine speed reaches 80% ?
To prevent voltage build up in generator causing drag on engine acceleration during early start sequence
How is the generator stator winding and rotor windings cooled ?
Achieved by circulating air from fans on both end of generator drawing in air & exhausted out through top of generator
What is the SBOG Hydraulic Start system main purpose for ?
Provides engine rotation from standstill to self sustaining engine speed (66%Ngp)
What’re the major components of Hydraulic Start system ?
-Diesel Engine
-Hydraulic pump
-Hydraulic Starting Motor
-Hydraulic Oil Filters
-Hydraulic Oil Reservoir
-Hydraulic Accumulator
-Starter Engage Solenoid Valve
-Starter Adapter Housing
-Sprag Clutch Assembly
What kind of diesel engine is on the SBOG ?
Turbo charged, fuel injected that is started by a 24VDC Diesel Starter Motor
When will the Diesel Starter Motor be actuated ? What is the Motor powered from ?
-Actuated by a start signal from control system
-Motor is power by a 24VDC Start Batteries located in SBOG control room
What’re the diesel engines two functions upon SBOG startup ?
-Drives an attached air compressor to pressurize Turbine Engines Air Assist Accumulator up to 120psig at Engine startup
-Also supplies rotational power to drive hydraulic pump which is used to start rotation of Engine
Where does the diesel engine receive it fuel from ?
Supplied from Diesel Start Engine Fuel Oil Day Tank mounted outside of enclosure
What level is the Start Diesel Engine Fuel Oil Day Tank required to be maintained at ?
Tank is required to be filled >70% at all times
Where does the Diesel Start Engine Fuel Oil Day Tank receive its fuel from ?
Diesel Start Engine Fuel Oil Day Tank fill line taps off of Fuel Oil tanks for the SBOGS
What does the hydraulic pump do for the Hydraulic Start system?
-Supplies pressure needed to drive hydraulic motor
-Incorporates a integral low pressure gear type charge pump to prime servo system and transmission lines during startup. Ensures positive pressure at pump and motor when flow is demanded
What is piston stroke length of the high pressure pump determined by ?
Determined by the angle of the variable swash plate
What is the Hydraulic Starting Motor used for on the Hydraulic starting system ?
-Hydraulic Motor cranks turbine engine through overrunning sprag Clutch and Reduction Accessory Gear Unit
Where is the Hydraulic Motor mounted on ?
Mounted on Reduction Gearbox/accessory drive which rotates the engine by means of overrunning sprag clutch
What is the Hydraulic Oil Filters used for on the Hydraulic Start system ?
Prevents containments from damaging Hydraulic Pump,Hydraulic Motor, and other components of Hydraulic Start system
Where are the Two Oil filters installed at ?
-One filter is downstream of Supply Oil Start Transmission Pump and maintained cleanliness of servo system
-Second filters is on return line to reservoir
What happens if Hydraulic Filters become clogged ?
There is a bypass in each filter that will open on high D/P and actuate alarm
What features does the Hydraulic Oil Reservoir have ?
-Level gauge
-Level switch
-Fill point with integral filter
-Temperature monitor
-Heater to maintain >50F
Where is the Hydraulic Start System Oil Reservoir located at ?
Located below the Generator
What is Hydraulic Accumulator used for on the Hydraulic Start system ?
Located downstream of hydraulic pump to maintain pressure during pressurization and depressurization transients
What is the Starter Engine Solenoid Valve used for on the Hydraulic Start system ?
Is energized by 24VDC from control system to control the transmission of hydraulic pressure to the Starter Motor during start sequence
What is Starter Adapter Housing used for ?
Attached to reduction gear box/accessory drive gearing to provide connecting and mounting of hydraulic motor to engine
What is Sprag Clutch Assembly used for on the Hydraulic Start System ?
Interconnected with shaft within Starter Adapting Housing to transfer Starter Motor torque to Reduction Gearbox/accessory drive gearing