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LOIT 2020 exam prep > Exam 6 prep > Flashcards

Exam 6 prep Flashcards

Seismic, in plant, service gases, AFW, MT/MSR, ED, MFW/FPT

1
Q

How many communications systems are required for FD to CR communication?

A

2.

  • Plant two-way radio system, which establishes communication between the fixed and portable radios carried by plant personnel and fire department members outside the control room

Sound powered phones

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2
Q

What will happen if the MX system is lost to the CT fan controls?

A
  • MX system (NH/NG) is lost the Cooling Tower Fans will have to be operated manually at the breakers
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3
Q

Define a safe shutdown earthquake.

A
  • Maximum earthquake potential considering the regional and local geology and seismology
  • 0.20g! or 6.0 Richters (.25g design basis)
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4
Q

Define Operating basis Earthquake.

A
  • Operating Basis Earthquake
    • Vibratory ground motion for which those features of the nuclear power plant necessary for continued operation without undue risk to the health and safety of the public will remain functional
    • 0.10g! (.13g OBE design basis)
    • Shutdown to Mode 3
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5
Q

What provides DC power to the seismic recorder during a loss of local AC power and for how long?

A
  • Internal battery provides DC power to the recorder during a loss of local AC power for up to 30 hours.
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6
Q

What is the function of the STA with regards to seismic concerns?

A
  • STA determines:
    • OBE (Operating Basis Earthquake) exceedance threshold 0.10g means that the Unit is in an Unusual Event Notification
    • OBE w/ Safety systems being effecting (structures or equipment) ALERT classification.
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7
Q

How soon must the following be completed:

  • EAL classifications when indications of an EAL are met or exceeded.
  • Civil Engineering analysis of effects on facility features.
A

15 minutes from the first indication.

7 days.

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8
Q

How is a seismic alarm validated for false or real conditions?

A

An alarm without ground motion felt in the CR is considered a false alarm. This is validated by observing for waves in the FP.

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9
Q

State the requirements found in TLCO 3.3.103

A
  • 3.3.103 Requires all 6 accelerometers and all 6 digital recorders (at all times)
  • Seismic event > 0.02g – channel calibration within 5 days
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10
Q

What will cause the seismic digital recorders to begin recording?

A

Any accelerometer of the 6 forced balanced accelerometers will start all digital recorders.

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11
Q

State the power supplies and what signals will close GAA-UV-1/2.

A
  • GAA-UV-1/2 are PKA powered CIAS valves and fail closed on loss of power
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12
Q

State the high and low pressure N2 header operating pressures and how each are maintained.

A
  • Low pressure header is maintained @ 115 psig using pressure control valves from Liquid Nitrogen Tank. Secondary valve opens during high demand
  • High pressure header maintained @ 650 psig
    • High alarm: 690 psig
    • Backup pressure control valve opens: 630 psig
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13
Q

State the HP nitrogen pumps operating characteristics.

How long is the cooldown cycle?

What will block pump start?

A
  • High pressure liquid nitrogen pumps (positive displacement) starts when active bank @ 1400 psig and stops @ 2100 psig
  • Start cycle:
    • 15 min cooldown prior to start (nitrogen flows around the pump)
    • Pump will not start:
      • 2400 psig discharge pressure
      • 25” in the Nitrogen Storage Tank
      • HP Vaporizer temp is -20F and lowering
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14
Q

State the HP N2 loads.

A
  • Downcomer control and isolation valves
  • ADVs
  • SITs
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15
Q

What is a level 1 evaluation and when is it required to be performed?

A

Determination of whether an OBE or SSE has occurred and it must be done by the STA within 1 hr.

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16
Q

What is a level 2 evaluation, who performs it and how long do they have to complete it?

A

Determination of whether an SSE has occurred, done by Civil Engineering and must be completed within 7 days.

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17
Q

What action is required if an OBE has occurred?

What action is required if the seismic event is between 0.01g and OBE?

A

All units must be shutdown to M.3 and a plant cooldown is required to inspect the SG’s.

System and site walkdowns must be performed on SFP, AFW pumps and piping, RCS leakage evaluated,

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18
Q

State the design basis of the AFW system.

A
  • Provides the same design as CST 8 hrs HTBY then C/D @ 75f/hr to RCS @ 350F
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19
Q

What cools the AFW room coolers and how are they operated?

A
  • Cooled by EC start upon pump start and run for 5 min after pump shutdown
    • FOR AFA THIS MEANS WHEN 138 OR 134 go open.
  • Sized to maintain room temp < 104F
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20
Q

What is the limit placed on the AFN use

A
  • AFN should not be used when < 27% NR level UNLESS a minimum of 250 GPM per S/G to minimize water hammer due to steam voiding in the downcomer piping. This flowrate will quickly collapse the void and minimize water hammer effects
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21
Q

What range of operation is the AF system set to maintain?

A
  • AF valves cycle FULL OPEN to FULL CLOSED between 25.8% WR – 40.3% WR
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22
Q

What is the D/P lockout associated with the AFAS signals, and which SG is essentially isolated from feed?

A
  • @ 185 psid (D/P lockout) between SG-1 & SG-2 AFAS will not FEED the S/G with the lower pressure.
  • If D/P lockout occurs before AFAS initiation, AFAS will not initiate for S/G with lower pressure.
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23
Q

What is DAFAS and what setpoints actuate it?

A

DAFAS or Diverse Automatic Feedwater Actuation System is an independent and redundant backup to the AFAS signals designed to start AFW to any intact SG not receiving feed.

  • SPS actuated (2409#)
  • S/G level of 20.3% WR on 2 of 4 class level instruments
  • NO AFAS
  • NO MSIS
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24
Q

State what will start the class AFW pumps.

A
  • Both CLASS pumps start on AFAS-1 or AFAS-2
  • “B” AFP
    • SIAS
    • LOP
    • CSAS
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25
Q

State the operating characteristics of the AFB-P01 to include power supplies.

A
  • AFB-P01
    • 8 stage double volute motor driven feedwater pump
    • Max amps for “B” AFP is 151 AMPS (Bacardi 151)
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26
Q

State the operating characteristics of the AFA-P01 and include its motive force.

A
  • AFA-P01
    • 8 stage double volute turbine driven feedwater pump
  • Turbine operates @ ~3600 rpm
  • Minimum pump speed of 1000 rpm required for oil lube
    • Op < 1000 rpm not permitted for > than 5 min
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27
Q

How is AFA-P01 prevented from overspeed on a pump start?

A
  • 138A and 134A bypass valves open first to prevent turbine overspeed
    • 30 seconds later 138 and 134 open
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28
Q

How does the D/P lockout protection affect the operation of the AFA-P01 steam supply valves?

A
  • D/P LOCKOUT WILL NOT IMPACT OPERATION OF THE STEAM SUPPLY VALVES
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29
Q

How is overspeed indicated on the AFA-P01 handswitch and what is required to reset the pump?

A
  • Overspeed REQUIRES local reset of the trip tappet and latch lever
  • AFA-HS-54
    • On overspeed trip HS-54 initially will show red (for the motor “lower”) and green (for the valve “upper”)
    • After the motor drives closed BOTH lights indicate green
    • Also get a white overspeed light
      • But its blue @ RSP and local panel
    • When tripped (electrical trip) from the control room, RSP, or locally
      • The red light for the motor stays on until the operator manually drives in the motor by holding the switch to closed
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30
Q

What does a loss of PKA mean for AFA-P01?

How is it affected by a loss of PKC?

A
  • Loss of PKA means loss of governor control
    • If running the pump will trip on overspeed!
    • Steam supply valves fails as is
  • Loss of PKA or PKC
    • Steam generator feed valves for AFA-P01 will fail as is which means if not already open then the feed path will need to be manually operated
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31
Q

What is the control pwr for the AFN-P01?

What is its normal supply?

A
  • Receives control power from PKA bus (norm) or directly off the “A” Battery charger (alt)
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32
Q

How is the AFN-P01 path isolated from the SGs?

A
  • Uses normal downcomer feed path
    • Isolation valves close on MSIS but can be overridden!
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33
Q

State the permissives that must be met to start AFN-P01.

A
  • Start permissives
    • No SIAS (can override)
    • HV-1/4 are > 80% open
    • No lockouts on the breaker
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34
Q

Why are there relief valves installed on the bonnets of MOV feedwater valves?

Where do they relieve to?

A
  • Relief Valves on bonnets of motor operated feed valves relieve to the CST via the miniflow paths. (Prevents valve from pressure locking closed)
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35
Q

What is the consequence of leaving the AFAS handswitches in INITIATE following a manual AFAS initiation.

A
  • Hand switches for manually initiating AFAS will stay in the “Initiate” position
    • If left in the initiate position then there will be no automatic action of the feed reg and block valves. (THEY WILL STAY OPEN at >40.3% and continue to feed the SG).
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36
Q

What is the difference between a trip from the CR and a mechanical overspeed trip?

A

The mechanical overspeed trip is required to be reset locally at the pump.

Operator must ensure 134/138/54 closed, locally align latch lever and trip hook, then open 54

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37
Q

How is the following indicated in the CR:

Mechanical O/S trip?

Electrical/manual trip?

A
  • Mechanical trip = Green/Green & White
  • Electrical trip/manual PB (linkage remains reset) = Green/Red
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38
Q

How is the electrical trip of the AFA-P01 reset from the CR?

A

Ensure 134/138 closed, close 54 until 2 green lights, open 54 until 2 red lights (full open)

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39
Q

State the signals that will initiate an AFAS and what actions occur.

A

AFAS initiates on <25.8% WR level(2/4 in same SG).

  • Both AFA and AFB pumps start.
  • EDG, SP, EW and EC start for both trains.
  • All SG b/d and sampling is isolated.
  • Isolation and FCVs for AFA AND AFB are opened.
  • The affected SG will receive full AFW flow until SG lvl is restored to 40.3% WR and will be maintained between 25.8 and 40.3%.
  • These actions only occur if there is NOT a d/p of > 185psid between the SGs.
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40
Q

At what level will the SG be maintained if DAFAS has actuated?

A

20.3% - 40.3%

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41
Q

How is steam binding prevented in the AFW system and why is it so important?

A

Steam binding prevention – 5 isolation sources per path and temp strips (black to blue green) on pump discharges

Inboard CNMT check, AFW isolation/reg valves, and 2 pump discharge check valves

The prevention of any steam binding in the AFW system ensure that voids do not form that could lead to severe water hammer and that the AFW pumps are not vapor bound in the event of an AFAS/DAFAS actuation signal.

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42
Q

State the backup source of water for AFW system and how much volume is accounted for AF system.

A
  • RMWT – backup for essential AFW pps (manual alignment – 1 valve in pp room, 1 at RMWT); 300,000 for AF
    • Recirc will still go to CST = contamination in CST
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43
Q

State the TS requirements associated with LCO 3.7.5 Auxiliary Feedwater system.

A
  • Three AFW trains in Modes 1 - 3.
  • One MDAFW train in Mode 4 when SG is relied upon for DHR.
    • LCO 3.0.4.b is not applicable.
  • One TDAFW steam supply inoperable OR TDAFW inoperable in M3 (pre-startup) – 7 day LCO
  • One train inoperable – 72 hour LCO
  • Two trains inoperable – M3 in 6 hours
  • All trains inoperable – Restore immediately. LCO 3.0.3 does not apply.
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44
Q

When is AFA-P01 testing required to be performed according to LCO 3.7.5?

A
  • TDAFW pump testing not required to be performed until 72 hours after reaching 532°F in the RCS (SGs at 900 psia).
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45
Q

State the design basis for LCO 3.7.5 and include the limiting DBA’s and whether the AFN-P01 is credited.

A
  • Delivering at least the minimum required flow rate (650 gpm) to the SGs at pressures corresponding to 1270 psia.
  • Limiting DBAs: MSLB / FWLB
  • DHR during SBLOCAs

Non-essential MDAFW pump is important from a risk perspective, but NOT credited in accident analyses

46
Q

What protects the AFW pump rooms from beign affected by a flooding event?

A

Dampers that are interlocked to close on a high water level of 3’ 6” in either AFW room.

47
Q

State the operational characteristics of the Main Stop Valves.

A
  • Main stop valves (MSV)
    • Open when a speed request is selected at EHC, remain fully open until the turbine is tripped
    • MSV-2 has internal bypass used to warmup the turbine prior to startup
48
Q

State the operational characteristics of the Main Turbine Control Valves.

A
  • Control valves (CV)
    • Regulate steam to the high pressure turbine as directed by EHC
49
Q

State the operational characteristics of the Combined Intermediate Valves.

A
  • Combined Intermediate Valves (CIV)
    • Consists of two valves:
      • Intercept Valve (IV)
      • Stop Valve (ISV)
    • Contained within one valve body both sharing a combined seat
    • Work together (IV’s first) to shut off steam to the low pressure turbine from the cross-around steam piping to prevent over speeding the turbine and damaging it in the event of a turbine trip
50
Q

What is the purpose of the Control PAC for CIVs and how are they configured?

A
  • Control PAC for the valves
    • CIV’s #1-3 are the controlling (master) valves CIV’s #4-6 are the non-controlling (slave) valves
      • When the master valves reach 50% closed the slave valve will go closed
      • When the master valve goes 90% open the slave valve goes open
      • This does not happen when performing testing
51
Q

State the operational characteristics of the Moisture Separator Reheaters (MSRs).

A
  • Moisture Separator Reheater (MSR)
    • “D” MSR provides hot reheat to the Main Feedwater Pump Turbine
    • 2nd Stage re-heat (Main Steam)
      • 5% of total steam flow (should be less than 95% when placing it in service)
    • MSRs should be in service when power is greater than 15% (for 12 hours or more) to prevent damage to the last stage buckets of the turbine
52
Q

When is reheat steam admitted to the MSRs?

A

Isolated when < 10% power. Reheat Steam Source Valves (RSSVs) are prevented from opening by sensing x-around piping.

Can be opened > 10% power and when the Reheat Stop Check Vavle(RSCV) is open. Ensures 1st stage in service prior to 2nd stage.

53
Q

How is reheat steam regulation maintained between 15-65% power?

A
  • From 15-65% regulation is provided automatically using the pneumatically operated Low Load Valve which regulates based on D/P between Main Steam and cross around piping
54
Q

How is reheat steam controlled when >65% power?

A
  • > 65% (by cross around pressure) electrically operated High Load valve opens to bypass the RSLLV
55
Q

What occurs at -3” level in the MSR?

A

A Turbine Trip(2/3 logic)

56
Q

What is the purpose of steam blanketing in the MSR and what is the source of steam?

A
  • Reheater tube bundles are pressurized using auxiliary steam to keep air out and condensation off the tubes reduces corrosion
  • Drain tank vent valves closed, normal level control
  • RSSV & RSCV close when the switch is placed in Steam Blanketing
57
Q

What happens on a Purge of the MSRs?

A
  • The high level dump valves for the 1st Stage and 2nd Stage drain tanks are failed open to the condenser
    • Evacuates air from the tube bundles prior to the admission of any steam to the bundle
58
Q

What happens to the MSR when in Auto as power is lowered < 20 and < 10?

A
  • High level dump valves on MSR and 1st stage drain tanks are failed open to the condenser until > 10%
  • High level dump valves for 2nd stage drain tanks are failed open until >20 %
59
Q

How is the turning gear engaged?

A
  • Placing the switch in the START position starts the piggyback motor IF:
    • Main generator circuit breakers are open OR MOD is open
    • Bearing lift pumps are running
    • Bearing lube oil pressure is good
    • TG is dis-engaged
  • Once piggy back motor is energized the TG will engage the rotor IF:
    • Rotor speed < 2 RPM
  • Once Turning Gear is engaged:
    • Piggyback motor stops
    • Slow speed motor will start
      • When > 2 rpm rotor speed bearing lift oil pumps for bearings #7 & #10 stop automatically (pumps 5 & 8)
60
Q

When can the local control pushbutton be used for TG joggin?

A
  • Local control pushbutton allows the slow speed motor to be jogged only if the control room switch is in STOP or PULL-to- LOCK
61
Q

State when the following pumps start.

  • Motor Suction pump
  • TG oil pump
  • Emergency bearing oil pump
A
  • Motor Suction Pump
    • Starts:
      • Main shaft oil pump SUCTION pressure low
  • Turning Gear Oil Pump
    • Starts:
      • Main shaft oil pump low discharge pressure or bearing oil pressure low
  • Emergency bearing oil pump
    • Starts:
      • Main shaft oil pump low discharge pressure WITH turning gear pump discharge pressure low (only if turning gear handswitch is in auto after stop)
62
Q

State the Main turbine trips.

A
  • Overspeed: 110%
  • B/U Overspeed: 110.5%
  • Low Vacuum: 7.5” HgA
  • Reactor Trip
  • Generator Trip
  • Manual (Front standard & Control Room)
  • High Vibe: 12 Mils
  • High exhaust hood temp: 225F
  • MSR high level: -3”
  • Low EHC pressure: 1100 psig
  • Low bearing oil pressure: 12 psig
  • Loss of Stator Cooling Water: 549 gpm
  • Low discharge pressure on Shaft Lube Oil Pump: 100psig
  • Loss of 125 VDC control power (both)
63
Q

State the Extraction points and what each stage provides steam for.

A
  • HPT 3rd stage: FWH 7 and MSR 1st stage RH.
  • HPT 5th stage: FWH 6
  • HPT exhaust(cold reheat): FWH 5
  • LPT 8th: FWH 4
  • LPT 9th: FWH 3 and GS
  • LPT 11th: FWH 2
  • LPT 12th: FWH 1
64
Q

What provides 2nd stage MSR reheat steam?

A

Main steam. steam pressure is varied with load.

65
Q

How do the Bearing Oil Lift pumps operate and why do they exist?

A
  • 8 Brg Lift pumps – reduces torque on TG motor and stress on gear teeth
  • Usually manually operated (except 7,10 – auto stop when turbine on TG); Start/Auto/Stop
  • Auto starts on high TG pump Pdis; Auto stops on low suction pressure
  • Brg 7&10 pumps will stop when TG motor running and < 2 rpm – prevents disengaging TG
66
Q

How is thermal cycling of the MSRs prevented?

A

No reheat to MSRs unless 15% for 12 hrs to avoid thermal cycling

67
Q

Why is MSR steam not valved in if > 95% power and previously isolated?

A

5% of total steam flow will exceed power limits

68
Q

Describe when each stage is isolated on MSR tube leaks.

A

MSR tube leaks: 1st stage – isolate both stages, 2nd stage – isolate 2nd stage only

69
Q

Define differential expansioin.

A

Differential Expansion = clearance between stationary and rotating parts of turbine

70
Q

Where does the FW pumps receive their motive force from?

A

LP steam from D MSR which is hot reheat and MS for plant startup and low load conditions ~35% turbine power.

Aux steam for testing.

71
Q

Where do the FWPT exhausts go?

A

A and B condenser shells at the reheat trays to lower cond depression and improve efficiency of the secondary.

72
Q

State the configuration of the HP and LP stop valves and when the control valves reposition and why.

A
  • HP and LP STOP valves are fully open when FWPT is reset.
    • HP control valve (main steam) goes closed first so that when MSR “D” Re-heat has enough pressure to supply FWPT by itself the HP control valve is closed
      • This illuminates a green light on the valve (when the HP control valve is closed)
73
Q

State the purpose of the mini flows for the MFWPs and how they fail.

A

Ensures there is at least 5000 gpm of flow through the pump.

  • Mini-flow fails open on a loss of air
    • (Regardless of what you see below)
  • Mini-flow fails open on a loss of 120 VAC (due to a controller output of zero)
74
Q

What happens to the miniflow valves on a FWPT trip?

A
  • : It will close
    • Power to close on a trip comes from 125 VDC
75
Q

What happens to miniflow if a loss of 125vDC occurs while the FWP is operating?

What happens if that pump were to subsequently trip?

A
  • Loss of 125 VDC has no effect on miniflow operation during normal ops
    • Unless the turbine trips: if this happens then the valves will fail open…….Confusing right?
    • Think of it this way:
      • Air for normal operation is controlled by 120 VAC from the mini-flow controller however, when the turbine trip this overrides the air the mini-flow controller is sending and ports full closing air utilizing DC powered solenoids
      • When 125 VDC goes away and the turbine trips then the mini-flow controller senses flow going less than 5000 gpm and thereby opens the mini-flow valve since “DC trip air” isn’t there to override it closed.
76
Q

State how the SG is delivered feedwater at < 15%, 15-50% and > 50% power.

A
  • Feed flows
    • < 15% power all feed flow is through the downcomer to maximize SG preheat
    • 15%-50% power all feed flow is through the economizer
    • >50% power the downcomer control valve is opened to a preset value which supplies 10% of calculated 100% flow. Economizer actually modulates to control level
77
Q

How do the D/C and Econ control valves fail on loss of air and power?

A
  • Downcomer and Economizer Control Valves
    • FAIL AS IS on a loss of power or air
78
Q

What is controlling FWP speed when the A/M handswitch is in manual?

A

FTN-HS-99/100 potentiometer.

79
Q

When does the Emergency Lube oil pump auto start?

A
  • Auto start on LOW BEARING OIL SUPPLY PRESSURE
    • Must be manually stopped after condition clears
80
Q

Describe how the turning gear operates on the FWPT.

A
  • Turning gear
    • START/AUTO switch
      • When in START the motor runs continuously and turning gear engages based on rotor RPM (< 2RPM)
      • When in AUTO motor cycles ON when rotor goes < 2 RPM and engages. When > 2 RPM motor STOPS and disengages the turning gear.
81
Q

What are the FWPT trips?

A

LOHBALL

  • Low Suction Pressure (255 psig) (2 out of 3)
    • > 10 secs then “B” trips
    • > 15 secs then “A” trips
  • Overspeed
  • High discharge pressure (overspeed backup trip)
  • Bearing Low Pressure (4 psig) (1 out of 2)
  • Active & Inactive Thrust Bearing Wear High Pressure (40 psig
  • Low vacuum (13.5”) (2 out of 3)
  • Low Control Oil Pressure (75 psig)
82
Q

How is the FWPT reset following a trip or prior to start during startup?

A
  • FWPT Turbine reset
    • Reset with a blue pushbutton on B06
      • MUST ensure the speed potentiometer is fully counter clockwise (minimum) to ensure control valves are closed prior to the Stop valves opening on reset.
83
Q

How will a loss of NNN-D15 and D16 affect the FWPTs?

A
  • Loss of NNN-D15 “A” FWPT control valves fail closed and FWP coasts down w/o a RPCB. MUST trip the FWPT
  • Loss of NNN-D16 same thing but for the “B” FWPT
84
Q

How will a loss of NKN-D41 and D43 affect the FWPTs?

A
  • Loss NKN-D41
    • A Feed pump will need to be tripped locally, if necessary
    • A HDP discharge valve fails closed and both recirc valves fail open
  • Loss NKN-D43
    • B Feed pump will need to be tripped locally, if necessary
    • B HDP discharge valve fails closed
85
Q

how is an uncontrolled start of the FWPT prevented?

A

HP an dLP stop valves will not open until the CVs are closed.

86
Q

How is speed of the FWPT sensed?

A

Speed Detectors (4) – 2 for governor control, 1 for indication or TG interlock, 1 for TSI (detect CV position)

CR FT speed control pots with Auto/Manual switch (green light = manual); 10 rpm-single, 50 rpm-double

87
Q

Describes how the FWPT is affected on a loss of IA.

A
  • 80 PSIG
    • HDT pump discharge valves will start to fail close. Cond pump mini- flow valves will start to fail open.
    • MFP suction pressure will lower.
  • 75 - 65 PSIG:
    • MFP Mini-flow Recirc Valves will begin to open (lower suction pressure, lower SGWL)
    • ED drain valves open (change heater temp)
  • 60 - 50 PSIG:
    • SG Economizer Feedwater FCVs fail AS-IS.
    • Automatic SGWLC is lost. Manual operation is available.
  • 37 – 27 PSIG
    • TCW TCV to MFP Lube Oil Coolers fails open, manual control is required
  • ≤15 PSIG
    • MFP Mini-flow valves are fully failed open. (detrimental to condenser)
    • MFP Seal Return Backpressure PCVs fail open.
88
Q

What happens to the FWPTs on a loss of NNN-D11?

A

Loss of NNN-D11

  • MFP suction pressure drops (B Cond Pump mini-flow opens)
  • Loss of NNN-D12
  • MFP suction pressure drops (A/C Cond Pump mini-flow opens)
  • MFP Suction Pressure indication lost
89
Q

How do the MSR drain tank and RHDT normal control valves fail on loss of air or loss of power?

The high level control valves?

A
  • MSR Drain Tank and RHDT normal control valves fail closed on loss of power or air
    • High level control valves fail open on loss of power or air
90
Q

Where does the vents for the RHDT vent for each stage vent to?

A
  • The vents for 1st stage RHDT go to the #6 HPFW, vents for 2nd stage RHDT go to the #7 HPFW as well as the normal level control valves
91
Q

State how the FW heater drains are routed on their way to the condenser.

A
  • # 7 HPFW drains to #6 HPFW which drains to the HDT. (Normal)
  • # 5 HPFW gravity drains to the HDT with no control valves
  • LPFW heaters drain path 4 to 3 to 2 to 1 to the condenser (Normal)
  • High level control valves go to the condenser. (Exception #5 HPFW has no high level control
92
Q

What occurs on a HI HI heater level?

A
  • High-High Level signal:
    • Closes the associated extraction steam supply isolation (this automatically re-opens when the signal is clear if the switch is in AUTO)
    • Opens the extraction drain line valve (must be manually re-closed)
    • Depressurizes the BTV(s) (re-opens when signal clears)
    • CLOSES the normal level control valve of the PRECEDING heater. (when signal clears will be re-permitted to modulate)
93
Q

What happens to the RHDT vents on a HPFW heater HI HI level?

A
  • HPFW heater HI-HI Level redirects the associated reheater drain tank vents to the condenser and close its normal level control valves
94
Q

What happens to the LPFW heater on a HI HI level?

A
  • LPFW heater HI-HI level isolates the condensate side of the entire string and closes BTV on #3 and #4 LPFW Htrs (No block vlvs)
    • (NO BTV on #2 or #1 they have flow baffles instead)
95
Q

Where do the HPFW heaters vent to?

A

The condenser.

96
Q

Which LPFW heaters have 4 extraction steam inlets and why?

A
  • LPFW #1 & #2 have four extraction steam inlets due to lower steam pressures
97
Q

What is DCA and why is it important?

A

DCA= drain cooler approach.

Drain temp - condensate temp.

It is used to measure heater performance.

~10F DCA is target.

If DCA is too low, HTR level is too HIGH, reducing the heat transfer and affecting TTD.

If DCA is too hi, HTR level is too LOW allowing higher fluid velocities and could lead to tube fretting.

98
Q

What is TTD and why is it important?

A

TTD = terminal temperature difference.

Tsat-steam - Temp of condensate outlet

Used to determine the amount of subcooling after condensate has passed through the heater. If there is not enough cond depression, the cond. may not remove enough heat to prevent 2 phase flow in the ED piping. Consequently, if there is not enough heater level to submerge the drain cooler region, steam will enter. Both of these could lead to pipe wall thinning and drain cooler damage.

99
Q

State the operating characteristics of the HDPs to include trips, and cooling water/sealing water.

A
  • Heater Drain Pumps
    • OPPOSITE POWER SUPPLIES.
      • NBN-S01 = “B” Pump NBN-S02 = “A” Pump
    • Heater drain pumps auto stop:
      • HDT Lo-Lo level (4ft)
      • HDP Lo-Lo flow (<711 gpm) for 15 sec
      • Electrical Protection
    • Stuffing box seal water-condensate
    • Stuffing box cooling water-condensate service water
100
Q

How does the HDP discharge valve oeprate to control HD tank level?

What position does it fail on a loss of air or power?

A
  • HDP discharge valve
    • Throttles to maintain HDT level
    • Fails closed on a loss of power or air
    • Automatically opens 2 minutes after breaker closes.
    • Closes whenever the pump breaker is opened
101
Q

What flow range does the HDP recirc valve close and open?

A
  • HDP recirc valve
    • Auto opens after 5 secs after the HDP breaker closes
    • Auto closes whenever pump breaker is open
    • Closes @ 3200 gpm flow, Opens @ 1600 gpm
102
Q

Which HPFW heater vents to the HDT?

A

5 HPFW heater.

103
Q

What will auto isolate all inputs into the HDT?

A
  • @ 9ft in the HDT it auto isolates all inputs into the tank
104
Q

How does the HDT hi level dump operate and what position does it fail on loss of power and air?

A
  • HDT high level dump is air operator to the condenser & fails open on loss of air or power
105
Q

What is the purpose of the BTVs or bleeder trip valves?

How do they operate?

A
  • Prevents steam from reverse flowing back to the LP turbine on a trip, which would continue to power the turbine.
  • 2 installed in the #4 LPFW heater line because too much energy
  • 7A & 7B HPFW BTV’s installed upstream of motor operated block valve to allow 1st stage reheat in event the BTV go closed
  • Air is removed to closed a BTV
    • Happens on a turbine trip (OR)
    • High-high level in associated FW heater
106
Q

Why does the #5 HPFW heater not have a level control valve?

A

It is connected directly to the HDT which does have a level control program.

107
Q

State what happens if a HP FW heater experiences a HI HI level condition.

A
  • Steam Block MOV, associated BTV, and upstream FWH normal drain close
  • Extr Steam line upstream drain opens; drain tanks normal drains to FWH closes
  • 1st and 2nd stage drain tank vents to FWHs close and vents to condenser open
108
Q

State what happens on a HI HI level condition in a LPFW heater.

A
  • LP FWH train isolations and BTVs (for 3&4) close
  • Extr Steam line drains open
109
Q

Describe the positions of the 1 stage scavenging mode selector switch.

A
  • 1st Stage Scavenging Mode Selector Switch (controls 1st stage drain tank vents to FWH 6 and cond)
  • AUTO – vent to FWH 6 open and vent to cond closed if associated steam block valve is full open
  • PURGE – vent to FWH 6 closed and vent to cond open
  • STM BLKT – closes both valves (does not vent)
110
Q

Describe the 2nd stage scavenging mode selector switch positions.

A
  • 2nd Stage Scavenging Mode Selector Switch (controls 2nd stage drain tank vents to FWH 7 and cond)
  • AUTO – vent to FWH 7 open and vent to cond closed if associated steam block valve is full open
  • PURGE – vent to FWH 7 closed and vent to cond open
  • STM BLKT – closes both valves (does not vent)
111
Q

What does the subcooling region of the FWHs do?

A

Subcooling region of FWHs prevents steam in drain lines which would cause wall thinning

Subcooling region designed for liquid to liquid heat transfer = low velocity (if steam – vibration/tube failure)

112
Q

What happens to the ED system on a turbine trip?

A

Turbine Trip – BTVs close (will reopen once trip clear), drain valves open (don’t auto close when trip clears)

on a turbine trip and loss of power to the MSR isolation valve, the 2nd stage drain tank vents to FWH 7 and the condenser will close to prevent an ESD.

LOIT 2020 exam prep (12 decks)

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