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loit 2020 exam prep > Exam 4 prep > Flashcards

Exam 4 prep Flashcards

Sec chem b/d, PW, CW, TC, NC, EC, WC

1
Q

State when SG BD valves will close automatically?

A

All containment isolation valves close on SAM
o SIAS
o AFAS
o MSIS

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2
Q

What will happen to the SG BD system on CSAS?

A

CSAS or Loss of PKA
IA to containment has isolated
▪ 500R & P fail close and blowdown isolates
▪ To restore:
• Must take both valves to override and closed position
• Then override and open IA-UV-2 to restore IA to containment.
• This prevents re-initiating blowdown uncontrollably

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3
Q

Where are the BD sample line points?

What cools the sample lines and at what point in the system?

A

Blowdown sample line points
o Hot leg blowdown
o Downcomer blowdown line
o Directly from downcomer blowdown
▪ NC cools field coolers and WC cools the cold lab sample lines
▪ Sample lines are upstream of blowdown isolation valves to allow sample even if blowdown flow isn’t from that path

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4
Q

Why is the D/C line the normally and preferred aligned flowpath?

A

Promotes efficiency of blowdown process

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5
Q

What component cannot accomodate any Hi Rate B/D, or both SG’s @ abnormal rate?

A

the BFT.

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6
Q

How is BFT pressure maintained normally?

Alternately?

WHy is 4A isolated on power changes => 5%?

A

Pressure maintained by 2 valves:
▪ Normally: 4A which directs flow to the HDT equalizing line
• Must keep pressure > 150 psig to maintain D/P to prevent back flow from the equalizing line to the condenser
▪ Alternately: 4B which opens to maintain pressure to the condenser
• 4B opens when 4A is unable to maintain setpoint pressure
▪ When changing power by 5% 4A is isolated to prevent a chemistry excursion

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7
Q

How is BFT level maintained by the following?

DEMIN/RETIN LV 3B/3C

BYP DEMIN

A

Level is maintained by HS-3
▪ DEMIN/RETIN LV 3B/3C
• Controls BFT level by sending flow to the blowdown demin package.

▪ BYP DEMIN
• Controls BFT level by sending flow to the #3 LPFW shells

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8
Q

What must occur on a high temperature at the B/D demins?

A

the system isolates flow to the B/D Demin package.

The operator MUST take the handswitch to BYP DEMIN to allow level in the BFT to be controlled and prevent relief valve lifting

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9
Q

Where do the B/D Low TDS sump pumps discharge to?

Where can they also discharge to?

A

Discharge to CW return line
o Can also discharge to the CWNTs and LRS TDS system

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10
Q

What is the heat sink for the BD HX?

A

Condensate cooled.

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11
Q

When is blowdown routed directly to the condenser?

A

BFT Not available.

HI Rate BD

< 25% pwr with long path recirc secured.

when it is desired to use condensate demins instead of BD demins.

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12
Q

Unit is operating normally with blowdown aligned to the BFT, when a SIAS occurs. Chemistry has requested the ability to sample 1 SG. What actions are required to get this sample?

A

SGBD sample lines will close on SIAS. Must take the sample isolations to override.

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13
Q

What are the starting interlocks associated with the CW pump discharge valves?

A

CW pump discharge valves:

  • 1st pump start IN A LOOP
    • Pump starts and its associated pump discharge goes to 44% open
  • 2nd pump start IN A LOOP
    • pump starts and disch valve goes to 44%.
    • waits for 3 min and then goes to 100%, after 2nd pump discharge goes 100% then the 1st pump valve goes to 100%
  • 1st pump stopped IN A LOOP (with 2 pumps running)
    • Pump switch to stop, associated discharge valve goes to 8% open, the associated pump will trip, and discharge valve full closes. Discharge valve is interlocked closed for 2 min
    • Discharge valve of the 2nd pump auto closes to 44% if the cross-tie valve is full open AND only 1 CW Pump is running in the other loop or cross-tie is not FULL open.
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14
Q

How will UV-11 respond to a loss of all running CW pumps in a loop?

A

UV-11 will auto close when there are no running pumps in a CW loop.

If taken to open then UV-11 will open regardless.

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15
Q

What will block a CW pump start? How is this bypassed?

A

The associated loop condenser outlet valve closed will block CW pump start in that loop.

Can bypass with pushbutton on B07.

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16
Q

what must be met to open the CW Condenser outlet valves?

A

Pressure switches must indicate that the waterboxes are full.

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17
Q

What cools the CW pump bearing and motor lube oil coolers?

A

TC

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18
Q

What are the limits on CW pump operations with respect to the number of towers in operation?

A

With 1 tower in operation, only 1 CW pump can be run. WIth 2 towers, up to 2 CW pumps can be operated.

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19
Q

What happens to the HI vibration trip of the CW tower fans on fan start?

A

It is bypassed for 30 seconds.

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20
Q

Describe what makes up the A train and B train with respect to the CW system and the hotwells

A

“A” Train (NAN-S01) = A&B CW pumps, 2A/2B/2C hotwells, A cond pump, HV-10

“B” Train (NAN-S02 = C&D CW pumps, 1A/1B/1C hotwells, C cond pump, HV-9

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21
Q

What is the design dT across the condenser?

A

32F dT

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22
Q

What is the position of the CW pump discharge valves and cross-tie valve(HV-11) with >=3 pumps operating?

A

100% open.

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23
Q

State the normal and alternate PW return points.

A

Normal is the Main CW return line.

Alternate is to Tower 2.

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24
Q

How is canal level contrlled? Why is proper canal level important?

A

A controller provides makeup as necessary to maintain level. This prevents short circuit of the cooling tower and adequate pump suction.

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25
Q

What is the purpose of the circulating water system?

A. acts as the ultimate heat sink for safe reactor shutdown and long term core decay heat removal.

B. receives the heat rejected by the turbine cycle and plant cooling water system and dissipates it to the cooling towers for removal by evaporation.

C. acts as both the ultimate heat sink for safe reactor shutdown and long term core decay heat removal AND receives the heat rejected by the turbine cycle, plant cooling water and dissipates it to the cooling towers.

D. removes heat from the plant cooling water system ONLY and dissipates it to the cooling towers.

A

B. receives the heat rejected by the turbine cycle and plant cooling water system and dissipates it to the cooling towers for removal by evaporation.

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26
Q

How is CW system piping initially filled on startup?

A

Using the PW system. It can withstand drawing initial vacuum in the condenser.

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27
Q

Concerning the CW Condenser inlet and outlet valves, what is prevented from operating if these valves are closed? How long of a stroke time do they have?

A

CW pumps won’t start if Condenser outlet valves are closed. They have a 60 sec. stroke time.

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28
Q

What will automatically close Cross tie valve(HV-11)?

A

If both CW pumps in a loop are stopped, HV-11 will auto close. This causes CW SYS TRBL in the cr.

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29
Q

Describe what happens to pump disch valves as each pump is started on system startup.

A
  • 1st CW pump start in Loop - pump starts and discharge valve opens to 44%
  • 2nd CW pump start in Loop – pump starts and discharge valve opens to 44%,
  • 3 min TD, 2nd discharge valve to 100%, 1st discharge valve to 100%.
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30
Q

State the CW pump start permissive interlock that must be met prior to pump start; this interlock exists for ___________.

A. Cooling tower return valve closed; prevent lifting waterbox relief.

B. associated train Condenser outlet valve open; prevent lifting waterbox relief.

C. Cooling tower return valve closed; water hammer concerns

D. associated train Condenser outlet valve open; water hammer concerns

A

D. associated train Condenser outlet valve open; Water hammer concerns.

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31
Q

State what happens when the first CW pump in a loop is stopped.

What does this prevent?

A

On pump stop:

  • that pump disch valve starts to close.
    • At 8% open, the associated pump trips and the valve finishes closing.
    • This disch valve is interlocked closed for 2 min.
  • Following pump stop, the running pump discharge valve in the SAME loop will auto close to 44% if:
    • The cross tie valve is not full open OR
    • The cross tie valve is full open AND only 1 pump is running in the other loop.
  • Prevents runout of the running CW pump in the loop.
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32
Q

How is an operator alerted to a CT fan HI VIbration trip?

A

a blue light at the loadcenter, computer input and alarms in the CR.

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33
Q

What is the start sequence for CT fans?

A

Fans started/stopped in sequence

Sequence found in 40OP-9CW03 see attached picture.

Outer ring fans started before inner ones.

Started or stopped one at a time.

Alternate between in-service cooling towers for each fan start or stop.

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34
Q

What systems or components does PW cool?

What cools PW?

A

Cools NC HX, TC HX, and Air Removal vacuum pump seal coolers

Fills CW, screen wash for CW

Heat removed by CW/cooling towers.

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35
Q

State the operating characteristics of the PW pumps.

A
  • 50 psig
  • 75°F
  • 29,000 gpm
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36
Q

State the minimum canal level needed to operate PW pumps. What is prevented by maintaining this level.

A

19’ minimum canal level prevents air binding of the PW pump.

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37
Q

What auto starts are associated with the PW pumps?

What trips exist?

A

Low hdr pressure of 40psig. amber light will be lit.

Will trip on electrical protection and Load Shed.

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38
Q

When will the PW pumps restart following a restoration of power?

A

the pump that is GREEN FLAGGED will auto start after 20 seconds.

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39
Q

State what will give a PCW SYS TRBL and PCW DSCH PRESS HI-LO

A

PCW SYS TRBL - Pump A/B Electrical Protection Trip OR Not In Auto/ Not Running

PCW DSCH PRESS HI-LO - 58 psig / 40 psig

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40
Q

Where does the PW system return to CW?

A

Normally, it is returned to directly to CW header

Alternate return is CT # 2.

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41
Q

Unit is at 100% power and experiences a loss of PW. What major plant action is directed by Loss of CW AOP?

A

The reactor/turbine must be tripped immediately.

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42
Q

A 86 lockout has occurred on the A PW pump. Can this lockout be reset from the CR?

A

NO.

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43
Q

State the Auto starts associated with the TC pumps.

A

TC pumps will auto start on low pressure < 55psig.

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44
Q

What will happen to the TC pumps during a loss of power to the non class buses?

A

They will be load shed and the TC pump that is green flagged will restart 15 seconds after power is restored if TC pressure is < 55psig.

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45
Q

How are the TC pump discharge valves positioned for pump start and pump stop evolutions.

A

Disch valve is closed on initial pump start to prevent water hammer.

During pump swapping, the disch valve is open when the stby pump is started.

Disch valve is closed on pump stop to prevent check valve slamming.

46
Q

State the minimum NPSH required for TC pump operations.

A

11psig.

47
Q

How many TC heat exchangers are normally kept in service?

How is TC temperature controlled?

A
  • Normally one in-service.
  • Temperature controlled by adjusted outlet and/or bypass valve.
  • One HX stays isolated (outlet valve closed)
48
Q

State the operating characteristics associated with the TC surge tank.

A

Normally 20-30 psig maintained by N2 overpressure.

Normal lvl is 48”, with an auto makeup from DI water at 45”-51”

49
Q

How is the TC system normally operated?

A
  • 1 pump / 1 HX
  • 105 psig (pump discharge pressure)
  • 85-100°F
    • Max Temp 105°F
    • Min Temp 85°F (Ensures temperature oscillations in supported systems does not occur)
  • Vent valves on top of the H2 coolers cracked open (keep air out of the system high point)
50
Q

How can IA compressor cooling continue if TC is out of service?

A
  • Whenever TC is out of service, temporary alternate cooling can be provided to the IA compressors using the Domestic Water System (DS).
51
Q

State the loads of the TC system?

A

Generator H2 Coolers (TCV)

Stator Coolers

FWPT Oil Coolers (TCVs)

EHC Coolers

Main Turb Oil Coolers (TCV)

Isophase Bus Coolers

Service Air

Condensate Pump Oil Coolers

Instrument Air

Heater Drain Pump Oil Coolers

SG/FW Sample Coolers

Gland Steam Exhauster

52
Q

State what will cause a TC SYS TRBL?

A
  • Surge Tank Level or Pressure Hi-Lo
  • Header Temperature HI
  • Pump Electrical Protection or Not in Auto/Not Running
53
Q

When does the TCW HDR PRESS HI-LO alarm come in?

A

120psig/60 psig

54
Q

What actions are required if TC is lost?

A
  • must trip MFPs to prevent wiping a bearing = Rx trip = turbine trip
  • must also trip turbine (wiping bearings)
  • IA backup N2 may concentrate in low areas in TB – personnel safety
55
Q

State the priority and non priority loads associated with NC.

A

Priority Loads (can be supplied by EW)

  • Normal Chillers (WC)
  • HC CEDM Normal ACUs.
  • Nuclear Sampling System (SS)
  • RCPs (Seal Coolers (HP, Seal 1 and Seal 2), Thrust Bearing Lube Oil coolers, Motor Air Coolers, and Motor Lube Oil Coolers.)

Non-Priority Load (can be supplied by EW)

  • Spent Fuel Pool Cooling HX (PC)

Non-Priority Loads (Cannot be supplied by EW)

  • Gas stripper & boric acid concentrator (BAC)
  • Letdown heat exchanger.
  • Radwaste evaporator.
  • Waste Gas Compressors
  • Non-nuclear sample coolers.
  • AS vent condenser and AS Radiation Monitoring
56
Q

State the operating characteristics of the NC system.

A

Normal parameters

  • Discharge header pressure ~ 90-100 psig.
  • Temperature 75 – 105°F
  • Surge tank 20 – 40 inches
57
Q

State the operating characteristics of the NC pumps.

A

NC Pumps (NCN-P01A and NCN-P01B):

  • ~ 17,500 gpm
  • Power supply: 4160 VAC non-class NBN-S01 and NBN-S02.
  • Mechanical seals should not have any leakage
  • Full load current rating is 135 amps
58
Q

What will happen to the NC system on low discharge pressure of 79psig?

A

The standby NC pump will start. and an amber light will be lit above the HS on b07

59
Q

State the motor start limits associated with the NC pumps.

A
  • Motor start limits:
    • At ambient / off > 2 hour: 2 consecutive starts
    • Above ambient / off < 2 hour: 1 start

After the above are met, cool for 15 min (running) or 45 min (shutdown) prior to starting

60
Q

How are the NC heat exchangers normally operated?

A
  • Cooled by Plant Cooling Water (PW) System
  • Normally one is in-service
61
Q

How is NC temperature controlled?

A
  • NCW Temperature control
    • Manual flow control of NCW HX flow (outlet valve) and bypass flow.
    • Either the HX outlet valve or the bypass will remain FULL OPEN.
    • PCW outlet valve normally kept at 33% open (can be adjusted, normally not done)
62
Q

How will the NC system respond to a loss of and return to power?

A

Any running NC pumps are load shed.

When power is returned, any green flagged(normally just the stby) NC pumps will start after a 10 sec time delay.

This start occurs due to the AUTO low disch press start.

63
Q

State the NC containment isolation valves, power supplies and on what signal they will close.

A

NCW Containment Isolations

  • Supply line – one MOV and a check valve.
  • Return line – two MOVs
  • Isolate on CSAS (can be overridden with MCR HS)
  • Power supply: PHA-M37 (NCA-UV-402) and PHB-M34 (NCB-UV-401 & 403).
64
Q

How is the NC system monitored for a primary leak condition?

A
  • SQN-RU-006 (RU-6) – located near the NCW pumps
  • Sample flow provided by NCW Pump ∆P
  • Monitors for gross gamma activity
65
Q

Unit is operating at 100% power with a loss of NC in progress. The operators have successfully supplied priority NC loads with the A train of EW per the Loss of Cooling Water AOP. What will be the first indication of a potential seal injection cooler leak on the 1A RCP?

A. The NC system RM, RU-6 will alarm when gross gamma activity is above the high setpoint.

B. The EW system RM, RU-2 will alarm when gross gamma activity is above the high setpoint.

C. There is no monitoring capability when EW is supplying NC priority loads.

D. The EW sysem RM, RU-3, will alarm when gross gamma activity is above the high setpoint.

A

B. The EW system RM, RU-2 will alarm when gross gamma activity is above the high setpoint.

66
Q

State the operating characteristics of the NC system Surge Tank.

A

NCW Surge Tank

  • 1000 gallon tank
  • Location: Auxiliary Building roof
  • Auto level control (NCN-LV-75) from Demineralized Water (DW)
  • Manual make-up available from Cooling Water Holdup Tank pumps
  • N2 blanket from the Service Gases System (GA)
  • Relief valve and vacuum breaker
    • Relief valve overflows to an open drain on the roof. Directed to the Cooling Water Holdup Tank.
67
Q

What setpoint do the NC return line containment reliefs lift at and why do they exist?

A
  • Two 6” safety relief valves (PSV-614 & 615) installed on the return line inside containment.
    • Lift at 135 psig
    • Ensure closure capability of the CIVs during an RCP High Pressure Seal Cooler tube rupture by preventing header pressure from precluding proper operation of the valves. PRA requirement to prevent exceeding 10CFR100 limits from surge tank.
    • Correct sequence must be followed when restoring NC flow to containment to prevent lifting the reliefs. Open return valves prior to the supply valve.
68
Q

Why does PSV-617 exist on the return line penetration?

A
  • One 1” relief valve (PSV-617) on the return line penetration.
    • Protect the penetration from thermal expansion.

Lifts at 150 psig

69
Q

What isolates non priority loads from the EW system when supplying NC with EW?

A
  • NCW Containment header return valve (NCN-UV-99) is closed to isolate the “non-priority” loads.
    • Valve is located on the NC return header and receives non-class 1E power from NHN-M19.
  • Check valve on the supply header (NCN-V020) isolates that portion of the NC system during crosstie operations.
70
Q

State the parameters that will cause the CR to NUC CLG WTR SYS TRBL.

A
  • NUC CLG WTR SYS TRBL
    • Surge Tank pressure HI/LO
    • Surge Tank Level HI/LO
    • NCW Discharge Temperature HI
    • CEDM Outlet Temperature HI
    • NCW Pump Electrical Trip
    • NCW Pump not-in-auto or pump not running
71
Q

What is the NC flow limitation to the LDHX and why does it exist?

A

Vibration damage to the letdown HX may result if NCW flow is > 1800 gpm.

72
Q

What plant actions are required if NC is lost to the CEDM cooling and not restored?

A

Lose CEDM cooling – Rx trip in 40 minutes and cooldown to 300F

73
Q

Why are the HPSC isolation valves open and downpowered?

A

HPSC isolation valves open and down powered to ensure operability in a CR fire

74
Q

Which of the following activites will NOT render that associated EW train inoperable?

A. Lining up EW to supply cooling to the Fuel Pool cooling heat exchangers and performing an EW flow balance.

B. Lining up EW to supply NC priority loads with the A train of EW supplying NC.

C. Lining up EW to supply NC priority loads with the B train of EW supplying NC.

D. Lining up EW to supply cooling to the Fuel Pool cooling heat exchangers and priority NC loads with the A train of EW supplying NC.

A

A. Lining up EW to supply cooling to the Fuel Pool cooling heat exchangers and performing an EW flow balance.

75
Q

What is the sequence used to restore NC system from a CSAS isolation?

A

Must open the return line isolation valves PRIOR to supply line valves to prevent lifting the relief valves due to system pressure perturbations.

76
Q

Why is N2 overpressure maintained on the NC Surge Tank?

A. NPSH of the NC pumps.

B. prevents O2 instrusion into the NC system.

C. NPSH of the NC pumps AND prevents O2 instrusion into the NC system.

D. N2 overpressure is not maintained on the NC surge tank.

A

B. prevents O2 instrusion into the NC system.

77
Q

State why simultaneous operation of the NC pumps should be minimized.

A

Undue stresses to NC piping.

78
Q

State the number, power supplies and relative capacity of the chillers.

How are the chillers operated during the cooler and warmer months?

A
  • Three large capacity chiller packages (Chillers A, B, C)
    • A Chiller: PBA-S03 (4.16 kV)
    • B Chiller: NBN-S01
    • C Chiller: NBN-S02
  • One small capacity chiller package (Chiller 2)
    • Power: NBN-S02
    • Operates as needed in conjunction with one or two of the larger units.
  • Cooler months: one large chiller fully loaded, small chiller ran to supplement cooling.
  • Summer months: two large chillers, and possibly the small chiller will be run.
79
Q

Which of the following signals will trip the A normal chiller?

  1. SIAS 2. CSAS 3. MSIS 4. DGSS

A. 1, 2, 3, 4

B. 2, 3, 4

C. 1 ONLY

D. 4 ONLY

A

C. SIAS, and it can be overridden.

80
Q

State the compressor start cycle for the A chiller.

A
  • Compressor start:
    • Circ pump starts and NCW valves open
    • 23 (±10) seconds later – lube oil pump starts
    • 28 (±10) seconds after LO pump starts, compressor starts
81
Q

What is the Auto Load recycle and why does it exist?

A
  • Auto Load Recycle (Cooler Low Chilled Water Temp 38°F):
    • Compressor will stop
    • ≥ 45°F (Chilled Water) - white Load Recycle light energizes
    • Indicates Auto Load Recycle Circuit reset

Compressor will restart in ~ 15 minutes

82
Q

State the Chiller trips associated with the normal chillers.

A

ROOMNARC

  • Ref pressure hi
  • Oil Pressure low
  • Overload
  • Motor temp hi
  • NC flow low
  • Auto load recycle
  • Ref temp low
  • Circ water flow low
83
Q

How are the Normal Chilled water pumps controlled and what are their power supplies?

A

They are automatically started and stopped with the chiller package.

A: NHN-M19

B,C E02: NH.

84
Q

State the 3 most limiting concerns associated with a loss of the normal chillwater system.

A
  • Containment temperature (Tech Specs limits)
  • Main generator collector housing (potential generator shutdown)
  • CEDMC cabinet room (can lead to possible rod slippage)
85
Q

State the auto makeup and overpressure features associated with the WC surge tank.

A

Auto makeup from DW and overpressure with N2 to prevent corrosion in the WC system and to provide NPSH to the WC circ pumps.

86
Q

What are the containment isolation valve associated with the WC system? What signal will give them a close signal?

A

CIVs are MOV.

UV-63/CNMT/Check vlv UV-61/CNMT/UV-62

CIAS signal.

87
Q

How will a loss of IA affect the WC system?

A
  • WCN-70/71(supply valves to Radwaste, Control, and Auxiliary building headers) fail closed.
    • This DOES NOT include the CCP room coolers
  • Temperature control valves on various different building ACUs will fail to through cooler position
    • This DOES include the CCP room coolers
88
Q

State the purpose of the EC system.

A
  • Supply chilled water to selected safety related air handling systems during a Design Basis Accident (DBA) or transient.
  • Two 100% capacity, redundant, safety-related trains that cannot be cross-connected.
  • Normally in standby
  • Two “subsystems”:
    • Chiller Package
    • Circulating (pump, valves, and piping)
89
Q

Concerning the EC circ pumps, what are the power supplies, how are the pumps operated.

A
  • Power supplies: PHA / PHB (480V)
  • Auto start when the chiller gets a start signal
  • Can be operated independently of the chiller using local start switch on the MCC (stopped using chiller MCR HS)
90
Q

If the disconnect switch on the Aux power panel is used to start the EC circ pump, what consequence exists using this method?

How is this method used to start the EC circ pump?

A

the associated EC chiller is considered INOPERABLE when the disc switch is open.

The disconnect would be opened, then the MCR handswitch for the CHILLER to start. the compressor will not start but the circ pump will start. The HS is used again to stop the circ pump.

91
Q

State the operating characteristics associated with the EC surge tank.

A
  • 80 gallon capacity
  • Pressurized with N2 to 28 psig
  • Auto make-up on low level.
  • Make-up stops on high level OR low-low level.
92
Q

What are the makeup sources associated with the EC surge tank?

A
  • Make-up sources (automatic SOVs)
    • Demineralized Water System (normal source)
    • Condensate Storage System provides a backup
    • Fire Protection System(manual only)
93
Q

How is EC flow controlled to the CR Essential AHUs?

What about all other EC cooled AHUs?

A
  • Control Room Essential AHUs have 3-way valves to control flow.
    • When running, flow is controlled by MCR air temperature.
    • When AHU is not running, the valves goes to bypass (prevents condensate buildup on coils)

All other coolers have manual valves

94
Q

State the power supplies and auto starts associated with the EC chillers.

A

Power supplies: PBAS03 and PBBS04 (4.16 kV)

Auto start signal (BOP ESFAS – 30 seconds): CCALCS

  • CREFAS
  • CRVIAS
  • AFAS
  • LOP
  • CSAS
  • SIAS
95
Q

What is the starting sequence associated with the EC chillers?

Does this change if the chiller is started from BOP ESFAS or not?

A

Starting Sequence (Manual or automatic)

  • (T + 0) - Circ Pump starts immediately
  • (T + 23 sec) – Lube oil pump starts
  • (T + 51 sec) – Chiller starts
  • Once the chiller starts, a timer is energized that will block a restart attempt.
    • 20 minutes – normal start
    • 190 seconds – ESFAS start
96
Q

State the AUTO trips associated with the EC chillers.

A
  • Taking the MCR HS to STOP will clear the red lights.

FORDEMCOPSB

  • Flow low: prevents icing
  • Oil pressure low: motor brg damage
  • Refrigerant temp Low: prevents icing
  • Disch temp Hi: actuates on loss of EW
  • Excessive impeller displacement: protects against surging
  • Motor Temp Hi: loss of cooling to motor
  • Chillwater temp low: initiates auto load recycle @ 38F, resets @ 45F
  • Overload: protects motor.
  • Press. refrig High: actuates on loss of EW
  • Safety indicator reset:
  • Bearing oil temp Hi: protects motor bearings
97
Q

Describe the Stop sequence of the EC chillers.

A
  • Chiller compressor and circ pump immediately stop and the compressor’s inlet guide vanes go closed.
  • 40 seconds later, the lube oil pump stops.
98
Q

Describe the Auto Load Recycle feature with the EC chillers.

A

Auto Load Recycle

  • < 38°F chill water temp (e.g. due to reduced heat load), the chiller enters the “Auto Load Recycle” condition and shuts off.
  • Automatically restart in ~20 minutes if chill water temperature > 45°F.
    • Continuously operating in this manner should be avoided in order to limit wear on the compressor.
    • RHPCV will limit the times the chiller cycles, but does not prevent all recycle conditions.
99
Q

State the TS requirements of LCO 3.7.10 EC system

A
  • Two EC trains shall be operable in Modes 1-4.
  • 72 hour LCO
  • Bases:
    • Remove the post-accident heat load from ESF spaces following a DBA coincident with a loss of offsite power.
    • Maximum heat load in the ESF pump room area occurs during the recirculation phase of a LOCA.
    • Isolation of one cooler on a train is allowed.
    • Isolation of more than one cooler on a train will make the EC train inoperable unless an Engineering evaluation is performed.
100
Q

State what will cause a ESS CHD WTR SYS TRBL in the CR.

A
  • ESS CHLD WTR SYS TRBL
    • Chiller Electrical Protection Pre-Trip
    • Supply Header Temperature Hi
    • Expansion Tank Level Hi/Lo
    • Expansion Tank Pressure Hi/Lo
101
Q

State the purpose of the following chiller components:

Cooler(evaporator)

A
  • Removes heat from the chilled water. Low pressure liquid refrigerant comes in contact with the tubes and boils (flashes).
102
Q

State the purpose of the following chiller components:

Compressor

A
  • Suction: low pressure gas in the cooler shell. Discharges to the condenser.
  • Variable inlet vanes control the flow rate of the refrigerant which controls the rate at which the liquid refrigerant flashes to vapor in the cooler.
  • Maintains refrigerant temperature in the cooler in order to keep chill water outlet temperature at ~ 44°F.
  • Compressor cooled by the refrigerant.
103
Q

State the purpose of the following chiller components:

Lubrication

A
  • Lubricating oil pump supplies the compressor. Reservoir, pump, filter and HX.
  • Chiller start: oil pump starts ~28 seconds prior to the compressor.
  • Chiller stop: oil pump runs for 41 seconds after the chiller is stopped.
  • Oil heater maintains oil 130-150°F when shutdown. Forces the refrigerant out of the oil. Prevent foaming / bearing damage.
  • Oil is cooled by the chill water. Normally 140-150°F
104
Q

State the purpose of the following chiller components:

Hot Gas Bypass

A
  • Prevent surging during low load conditions. (Compressor can’t pump the gas well). Hot gas bypass re-directs some of the flow.
105
Q

State the purpose of the following chiller components:

Condenser

A
  • Heat exchanger which receives the high pressure, high temperature gas from the compressor and condenses it back into a liquid. Cooling by Essential Cooling Water (EW) System.
106
Q

State the purpose of the following chiller components:

Thermal Economizer

A
  • In the bottom part of the condenser. This area is exposed to the coldest EW flow; in order to increase refrigeration cycle efficiency.
107
Q

State the purpose of the following chiller components:

Refrigerant Head Pressure Control Valve

A
  • Located on the EW outlet from the condenser.
  • This valve regulates the flow of water through the condenser based on condenser pressure.
    • > 23 psig valve is fully OPEN.
    • < 14 psig valve is fully CLOSED
  • Prevents “stacking” which occurs during cold or low load conditions.
108
Q

Flash Economizer

A
  • Provides an intermediate pressure reservoir for liquid refrigerant before it is directed to the cooler. Provides additional subcooling of the liquid refrigerant (improving efficiency).
109
Q

Describe the refrigerant cycle as it pertains to the EC chillers. Include what the hot gas bypass does and how the motor is cooled and lubricated.

A
  • Cooler (HX) has warm EC thru tubes and low pressure refrigerant in shell which vaporizes (latent heat of vap)
  • Compressor takes suction on cooler shell and raises refrigerant temp and pressure
  • Variable inlet vanes controls refrigerant flow which controls EC outlet temp to 44F
    • Lube oil pump for compressor starts 28 sec before compressor and stops 41 sec after compressor stops
    • Oil heater maintains 130-150F when shutdown to force refrigerant out of oil (temp switch)
  • EC from condenser thru cooler cools oil cooler - maintains oil 140-150F when running (V321)
  • Hot gas bypass sends refrigerant from compressor back to cooler = recirc valve, opens on low EC temp
  • Eliminates surging effect by compressor during low load conditions
110
Q

How is refrigerant kept out of the oil?

What is a consequence of refrigerant in oil?

What can occur if Oil Cooler outlet valve EC-V321 is adjusted when the chiller is not running?

A

By heating the oil when shutdown to 130-150F and 140-150F when running.

foaming in the oil which will lead to bearing damage.

Renders the Chiller INOPERABLE.

loit 2020 exam prep (12 decks)

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