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LOIT 2020 exam prep > Exam 7 prep > Flashcards

Exam 7 prep Flashcards

1
Q

What are the power supplies to DFWCS?

A
  • Power Supply:
    • Supplied normally by NNN-D11 alternately by NNN-D12
      • Has a normal seeking transfer switch
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2
Q

What indications does 1E use to control SGWL?

A
  • Looks at 2 S/G Level Indicators
    • Chooses the highest of the 2 indicators for a value
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3
Q

How is SGWL controlled in 1E control?

A
  • Looks at the setpoint that is entered into the master controller and compares it to SGWL.
  • The deviation from setpoint then causes the system to open or close the downcomer control valve to maintain SGWL (also has the ability to adjust feed pump speed……or open the economizer [will not happen if <15% because swapover would not have happened])
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4
Q

Describe the anticipatory signal for 1E control of SGWL.

A
  • Anticipatory signal for 1E control:
    • SBCS Master Control & TLI (Turbine First Stage Pressure)
      • They send a demand signal to DFWCS so it can see an increase or decrease in steam demand
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5
Q

What is ATUN for 1E control?

A
  • ATUN or Adaptive tuning.
    • FW Temp provides adaptive tuning for 1E control
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6
Q

What 3 indications are used for 3E control of SGWL?

A
  • Three Element Control
    • Looks at 3 things (YOU CANNOT BE IN 3E WITHOUT THESE INSTRUMENTS WORKING PROPERLY):
      • SGWL
      • Feed Water Flow
      • Steam Flow
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7
Q

How is SGWL used in 3E control to adjust SGWL?

A
  • Looks at 2 S/G Level Indicators
    • Chooses the highest of the 2 indicators for a value
  • Then looks at the setpoint that is entered into the master controller
  • The deviation from setpoint then causes the system to open or close the downcomer control valve to maintain SGWL (also has the ability to adjust feed pump speed……or open the economizer [will not happen if <15% because swapover would not have happened])
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8
Q

How is Steam Flow used in 3E control to adjust SGWL?

A
  • Steam Flow
    • Adds a BIAS to the deviation of level output
      • This will increase responsiveness of the controller for level deviations
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9
Q

How is Feedwater flow used in 3E control to adjust SGWL?

A
  • Feedwater flow
    • Compares to the deviation that is output from the SGWL & Steam Flow and what current Flow is and makes an adjustment to the output to the valves or feed pump speed
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10
Q

What is HLO and how is it used in DFWCS?

A
  • HLO (High Level Override)
    • 88% NR!
      • Sends a zero signal to both control valves and MFP speed controller
        • However since MFP controller also receives the other side of DFWCS demand it auto chooses the higher so it will be unaffected if the other side is not also in HLO
      • Signal is upstream of the individual controllers therefore if a controller is in MANUAL IT IS NOT AFFECTED
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11
Q

What is RTO and how is it used in DFWCS?

A
  • RTO (Reactor Trip Override)
    • IMPORTANT TEMP: 564F Tavg from RRS (Same output as PLCS)
  • How RTO works:
    • Prevents an overcooling transient on a reactor trip
    • Receives signal from CEDMCS that there has been a Reactor trip
    • Immediately sends
      • -5% demand for Economizer (valve goes closed)
      • 0% demand to MFWP speed controller (pump goes to min speed)
    • It then feeds using the downcomer controller based on temperature.
    • It is trying to feed to maintain 564F.
    • ≥ 564F the downcomer controller will modulate based on the deviation from 564F
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12
Q

What is the signal that shifts DFWCS to RTO?

A
  • Important Concept:
    • To shift to RTO you must have EITHER UV-1 & UV-2 or UV-3 & UV-4 (I.E. UV-1 & UV-3 will not give you a reactor trip signal)
    • This comes from CEDMCS we will learn more about that later
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13
Q

How will the master controller in DFWCS respond to RTO?

A
  • Think of it this way:
    • The RTO controller receives Tavg from RRS and comes up with a deviation from 564F and sends an output signal through the master controller to the downcomer control valve.
    • While this is happening the Master controller will “track” the output that the RTO controller is sending through it.
    • This output on the RTO controller is limited to 9%
    • IF SGWL gets to 51.9% NR the master controller takes over and shifts to 1E control at whatever the last output of RTO was (bumpless). This occurs even if the master controller was in manual prior to the trip. It will now be in Auto 1E
    • 1E control will then regulate SGWL to its setpoint however, if level lowers to 26% NR RTO will take back over
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14
Q

How does DFWCS respond to natural circulation conditions when in RTO?

A
  • Natural Circulation in RTO
    • WHEN IN NATURAL CIRC RTO WILL OVERFEED!!!!!!!!
      • This is due to the large delta T generated and with longer loop transit times
      • THIS WILL OVERCOOL THE PRIMARY
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15
Q

State the total feedwater flow deviation alarm and actions associated with the DFWCS system.

A
  • Total Feedwater flow
    • 4% alarm
    • 8% Selects 1E and generates 3E lockout
    • Select maintenance mode for BROKEN INDICATOR
      • Then uses just the unaffected indicator and you can return the system to 3E control
    • Uses only downcomer flow when ≤ 13% reactor power
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16
Q

State the Steam Flow deviation alarms and what actions occur in the DFWCS system.

A
  • Steam Flow
    • 40% alarm
    • 50% Selects 1E and generates 3E lockout
    • Select maintenance mode for BROKEN INDICATOR
      • Then uses just the unaffected indicator doubles it and you can return the system to 3E control
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17
Q

State the FW temperature deviation alarms and what actions occur in the DFWCS system.

A
  • FW temp
    • 4% alarm
    • 8% Generates ATUN lockout and inserts canned value 425F
    • Select maintenance mode for BROKEN INDICATOR
      • Then uses just the unaffected indicator and you can clear the ATUN lockout
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18
Q

State the Rx power deviation alarm and actions that would occur assiociated with DFWCS.

A
  • Reactor Power (ONLY CAN BE SELECTED ON FWCS #1)
    • 4% alarm
    • 8% Generates ATUN lockout (3E only) and inserts canned value
      • 5% < 16.5%
      • 60% >16.5%
    • Select maintenance mode for BROKEN INDICATOR
      • Then uses just the unaffected indicator and you can clear the ATUN lockout (3E only)
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19
Q

State the SG level deviation alarm and actions that would occur assiociated with DFWCS.

A
  • SG Level
    • 10% alarm (This is only between same S/G level transmitters)
    • 15% (this is between opposite S/G’s)

It will control affected S/G level (higher indicated level) with the lower SG lvl indicator

  • To select MAINTENANCE MODE YOU MUST:
    • Make sure the setpoint matches actual level to avoid a feedwater transient.
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20
Q
  • S/G #1 has 2 level indicators each reading 51% NR
  • S/G#2 has 2 level indicators one reading 50% NR and one reading 66% NR
  • How is SG level being controlled in each SG?
A
  • SG 1 is in normal 3E control.
  • The deviation of 15% will be seen and the affected SG (#2 in this case) will automatically select and control to the 50% NR indicated level for #2 SG
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21
Q

What happens at the following Rx powers during a startup?

13, 14, 15-16.5 and 50%

A
  • Power increasing (going up)
    • 13% Swap to total feedwater flow indication
    • 14% Shift to 3E control
    • 15% to 16.5% Swapover
      • For 15% 1 S/G downcomer MUST be at least 80% open
      • For 16.5% Swapover happens regardless of valve position
      • Downcomer goes closed over 15 minutes
    • 50% Downcomer Control Valves go to 10% position in relation to 100% flow
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22
Q

What happens at the following Rx powers on a shutdown?

A
  • Power decreasing (going down)
    • < 50% Downcomers go closed over a 10 minute period
    • <15% Economizer control valves immediately go closed and Downcomers go to between 20 and 80% open
    • <13.5% power 1E control
    • <13% Swap to downcomer flow indicators ONLY
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23
Q

State the power supplies associated with the EHC system.

A
  • When turbine is not rotating power is supplied from NNN-D15
  • When turbine is > 1500 RPM power switches to the PMG (Permanent Magnet Generator
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24
Q

How does the Permanent Magnet Generator operate to ensure it is the controlling power supply when the turbine is at rated speed?

A

The voltage output from the PMG is set higher than house power so that the PMG is in control when the turbine is at rated speed.

If the PMG is lost for any reason then the house power (NNN-D15) will automatically supply

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25
Q

What speed is the only one allowed by the speed control unit when the generator breakers are closed?

A

1800 RPM

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26
Q

What are the following valve positions when the turbine trip is reset?

MTSV

MTCV

CIV stop valves

CIV control valves

A
  • Stop and Control valves are closed
  • CIV stop valves are open
  • CIV control valves are closed
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27
Q

What happens to the stop valves when a speed is first selected?

A

MTSVs will open on a speed demand.

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28
Q

How are the speed signals used in the EHC system?

A
  • 2 speed signals input into the speed control unit
    • These speed signals go to 3 “comparators”
      • Speed Errors x2 (Utilizes each speed sensor to generate an error)
      • Acceleration Error (Utilizes both speeds sensors to generate an acceleration and then an acceleration error)
      • Backup speed signal has an additional BIAS applied so that the primary is normally in control
      • Loss of 1 speed signal will double the acceleration error
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29
Q

Which error gets passed as actual demand from the comparators?

A
  • The SMALLEST ERROR is always the one that gets passed thru as the actual demand
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30
Q

How is the reference for speed error selected?

A

the control operator with speed pushbuttons.

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31
Q

When shell warming is in progress, what is inserted into the speed error circuit?

A

a zero error signal is inserted to keep the control valves throttled closed during shell warming and preventing the turbine from rolling off the TG.

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32
Q

What conditions will cause a turbine trip on loss of both speed signals?

A
  • Loss of BOTH speeds signals trips the turbine IF either:
    • Not in standby
    • > 100 RPM (5.5%)
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33
Q

Describe the aux speed control unit.

A
  • Auxiliary Speed Control Section
    • 3 separate speed sensing circuits
      • 2 out of 3 logic needed for enabling the following:
        • B/U Overspeed Trip (111.5%)
        • Main Shaft Lube Oil Pressure Low Trip Permissive (75%)
        • Permissive for Loss of Both Speed Signals (100 rpm/5.5%)
34
Q

What positions the load set drive motor?

A
  • Load set drive motor is controlled by using the Increase/Decrease pushbuttons
    • Decrease is pressed: Lowers at ~ 130%/min
    • Increase is pressed: Raises at selected Loading Rate
      • Automatically selected to 10%/min when the First Main Generator Output breaker is closed
35
Q

What happens to the LSDM when reducing turbine load with the load limit pot?

Why?

A
  • When Lowering Load with the Load Limit Potentiometer the Load Set Drive Motor will automatically follow down 3.5-4% above the potentiometer set point
  • Ensures that a large secondary transient does not occur if the load limit pot is rapidly raised inadvertently.
36
Q

what will happen when load is raised past the LSDM with the load limit pot in a controlled manner?

A
  • When Raising Load with the Load Limit Potentiometer load will go up until it surpasses the Load Set Drive Motor Setpoint.
    • At that point the load limit light will go out
37
Q

Describe what will happen to the RCS if Decrease load pushbutton is continuously held down.

A
  • If you hold down the Decrease Load Push Button or Continuously Lower on the Load Limit Potentiometer, load will continue to go down
    • Doing this will cause a big transient Temp going Up, Pressure going Up, PZR level going Up
38
Q

What will inhibit the INCREASE pushbutton on the LSDM?

A
  • INCREASE pushbutton is inhibited when the following:
    • PLUB (Power Load Unbalance)
    • RPCB (Reactor Power Cutback)
    • When the Load Set Motor is > 2% above the Load Limit Potentiometer
39
Q

What is the normal position of the CIVs and what will cause them to throttle closed?

A
  • CIV’s NORMALLY OPEN throttle closed to control speed @ 105-107%
40
Q

Describe the PLUB, power load unbalance.

A
  • PLUB
    • Rapid lowering of generator output compared to sensed cross-over pressure a PLUB generated resulting in turbine trip. Prevents overspeed after a large load reject.
41
Q

What happens to the LCU signal on a RPCB?

A
  • RPCB
    • Concurrently receives a Load Setback and Runback signal from RPCS circuitry to rapidly reduce Control Valve Position to 60%
42
Q

Describe the difference between a setback signal and a runback signal.

A
  • Setback:
    • Immediately:
      • 480%/min (5secs to 60%)
      • Comes from the Load Limit Pot LVG
      • That’s all it does…….straight to 60%
  • Runback
    • Lowers the Load Set Motor @ 130% min (LAGS SETBACK)
    • Continues to lower load in an attempt to match primary and secondary power
      • Looks @ Tavg vs Main Steam Header Pressure
43
Q

Which signal, setback or runback, takes turbine load to 60% and which signal will continue to lower below 60% to match pri and sec power?

A
  • Setback will take you to 60% load position…..then if needed runback will take you even lower to match primary and secondary power
44
Q

How does Standby affect the LCU and SCU sections?

A
  • Standby
    • NO SETBACK OR RUNBACK
    • Backup Overspeed trip goes to 105%
    • Mechanical Overspeed is now the backup @ 110%
    • Loss of Both Speed Signals Deactivated
45
Q

How is chest and shell warming performed when starting up the turbine?

A
  • Chest and Shell Warming
    • Shell Warming First because the chest would rapidly cool when the control valves were opened for shell warming
    • Shell:
      • Control Valves Partially open with CIV’s closed allowing bypass steam through MSV-2 bypass to warm the shell of the turbine
    • Chest:
      • **Everything closed except MSV-2 bypass valve**
46
Q

Describe Stage presure feedback.

When is it used?

A
  • Stage Pressure Feedback (SPF)
    • Used to compensate perturbations during control valve testing
      • Takes first stage pressure and when the test button for the CV is depressed it will send a signal for the other control valves to compensate.
47
Q

Concerning control valves or Stop valves, which set opens simultaneously?

Which valve has a servo to allow for chest and shell warming?

A

Control valves open simultaneously.

Stop valve #2 has a servo, All CVs.

48
Q

Which set of CIVs have servo valves?

Describe how the CIV master and slave valves operate in concert with each other.

How are all CIVs closed(what is the motive force)?

A
  • IV #1-3
    • Have SERVO valves
    • Master valves when they reach 90% open the slave will open
    • When they reach 50% closed the slave valve closes
      • NO SLAVE/MASTER when in Test
      • ALL VALVES CLOSED BY SPRING PRESSURE
49
Q

Describe how the Mechanical trip solenoid valve operates to trip the turbine.

A
  • Mechanical Trip Solenoid Valve
    • Energizes to trip utilizes 125 VDC to shut off oil to the piston allows spring pressure to close the valve
50
Q

Describe how the Electrical trip solenoid valve operates to trip the turbine.

A
  • Electrical Trip Solenoid Valve
    • De-energizes to trip utilizes 24 VDC power
51
Q

Describe the electrical trips associated with the turbine.

A
  • Electrical Trips
    • Generator Trip
    • Reactor Trip
    • Loss of Both Speed Signals
    • B/U Overspeed Trips (Aux Speed)
52
Q

What kind of trip is initiated with the Master Trip P/B?

A
  • Master Trip Pushbutton
    • Will cause an electrical and mechanical trip
53
Q

When will the loss of 125VDC trip arm?

Does a mechanical trip affect the electrical trips?

A
  • Mechanical Trip Signal will Cross trip the Electrical Trip
  • Loss of 125 VDC does not arm until >75%
54
Q

What cools the CO fluid coolers?

A

TC.

TCVs fail open to the full cooler position.

55
Q

State the operating characteristics associated with the CO/EHC system.

When does the turbine trip on a loss of EHC pressure?

A
  • Pressures:
    • Normal pressure: 1600 psig
    • Standby pump start pressure: 1300 psig (Header pressure)
      • Amber annunciator in the control room
    • Pumps(powered from NG) will vary their stroke based on flow demand to maintain constant pressure.
    • Turbine trip pressure: 1100 psig (Header pressure 2 out of 3)
56
Q

What makes up the filtering agent associated with the EHC system?

How is flow through the filters controlled and maintained?

A
  • Fullers Earth Filters
    • Maintain neutral pH
      • Absorbs acid and water also, maintains chlorine content within spec
    • FCV-27 is maintained in a manually locked throttled position to control flow
57
Q

State the operating characteristics associated with the EHC accumulators.

A
  • Accumulators
    • 4 accumulators are available to help supply the system in times of high demand
    • Precharged with 1000# of Nitrogen pressure
58
Q

What is the purpose of the SO system?

A

Prevents escape of H2 and air inleakage along MG rotor shaft; put in service before H2 to MG

Seal Oil supplied from TLO to vacuum tank thru level float valve

59
Q

If vacuum is not present in the SO tank, how is H2 affected over time?

A
  • With no vacuum in the tank hydrogen purity goes down 2% every 8 hours
60
Q

What is the result on the SO system if the ESOP is running?

A
  • Vaccum tank DOES NOT remove entrained gasses when using ESOP because ESOP draws off the return header to fill the tank
    • Results in lower hydrogen purity
61
Q

What causes the ESOP to start?

Does it trip on electrical protection?

A
  • ESOP auto starts at 110# MSOP discharge pressure
    • WILL NOT trip on electrical protection only annunciate an alarm
62
Q

What is the relationship between SO pressure and H2 pressure in the generator?

A
  • Main Seal Oil Pressure is normally 83# with hydrogen pressure normally 75#
    • 8# D/P
63
Q

Regarding SO that has gone thru the detraining sections, what is its flowpath if MLO is operating?

What is its flowpath if MLO is not operating?

A
  • Oil that enters the detraining sections get directed back to the MLO system
    • Due to MLO system pressure holding closed the SO return line check valve
  • On a loss of MLO the detraining oil goes back to the vacuum tank
    • This will result in a closed loop SO system and cause the SO temperature to increase.
64
Q

What is the major action(s) required for a complete loss of SO?

A

The turbine must be tripped and the MG purged of H2.

65
Q

What effect does a loss of ESOP and Main SO pump have on the SO system?

A

MLO will supply seal oil at a reduced pressure ~ 25#. Vacuum detraining is not available. H2 pressure drops to just below MLO pressure. This is below the minimum H2 pressure for operation, and requires a MG shutdown.

66
Q

What is the signifigance of the SO/H2 DP LO alarm?

A

H2 may be escaping to atmosphere out of the MG seals.

67
Q

State the purpose of the Vacuum tank and its normal vacuum.

A

Vacuum Tank maintained at 1” HgA via Vacuum Pump (solenoid suction valve opens when pump starts)

Purpose of vacuum tank = H2 purity

68
Q

Which Subgroups are used in the RPCB system?

A

4, 5 and 22 of reg groups 4 and 5.

69
Q

What initiates a RPCB?

A
  • Initiates:
    • Loss of MFP
      • Caused by 2 out of 3 75# trip oil pressure
    • Large Load Reject
      • Sent from SBCS
      • Compares steam flow & TLI to Pressurizer Pressure
      • Rapid lowering of steam concurrent with rapid rise in PZR pressure identifies the large load reject
      • Both Channels must indicate condition
70
Q

What is the consequences of losing NNN-D12 with regards to RPCB?

A
  • Loss of NNN-D12
    • Setback with NO RUNBACK
    • Go to 60% and sit there
71
Q

What is the consequence of NNN-D11 with regards to RPCB?

A

RPCB system is lost.

72
Q

What signals from SBCS will block a RPCB?

A
  • Runback is BLOCKED when SBCS is in TEST or DISCONNECTED
73
Q

Will a runback occur if EHC is in standby mode of operation?

A

NO runback will occur.

74
Q

What does the Test/Reset pushbutton do in RPCB?

A
  • TEST/RESET
    • 1st push
      • Removes RPCS from service
      • De-selects CEAs
    • 2nd push
      • Resets RPCB however no rods will be selected!
75
Q

What does the Auto Actuate OOS pushbutton do?

A
  • Auto Actuate Out-of-Service
    • Disables automatic initiation of a RPCB
    • Still have the ability to manual initiate RPCB
      • Must press both the event and drop groups button simultaneously
76
Q

Which pushbutton on the RPCB panel actually drops the subgroups?

A. Drop Subgroups

B. Large Load Reject or Loss of Feed Pump

C. Lamp test

D. Turbine Runback

A

A. Drop Subgroups will drop the groups designated by either Large Load Reject or Loss of Feed Pump.

77
Q

What inputs does RPCB have to the CPC system?

A
  • Generate a flag based on seeing subgroups 4, 5, and 22 insert concurrently
    • This prevents a Reactor Trip
78
Q

If either 4, 5 or 22 are on the hold bus, what will happen on a RPCB from the CPC system?

A
  • IF on subgroup is on the hold bus it won’t generate this flag and then a reactor trip will happen
  • IF a CEA doesn’t fully insert then it will generate a reactor trip
79
Q

State what occurs on a MFP runback.

A

LOFP – MFP trip oil pressure < 75 psig from pressure switches (2/3 logic)

  • LOFP = Logic met and > 74%; Signal sent to SBCS for a QO Block (QOB)
  • Signals (ARM and DROP) sent to CEDMCS to drop selected subgroups (10 sec signal)
    • 10 sec ARM signal is to prevent CEA relatch before hitting bottom
  • MT Setback – moves MT at 480%/min to 60%
  • MT Runback – lowers load reference 130%/min
  • RRS matches Tave to Tref after 10 sec signal gone
80
Q
A

LOIT 2020 exam prep (12 decks)

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