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ZZ LOIT CWS Systems 2018 > SBCS: Steam Bypass Control System > Flashcards

SBCS: Steam Bypass Control System Flashcards

1
Q

What is SBCS designed to do?

A

Prevent unnecessary reactor trips and opening of Pressurizer and SG Safeties.

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2
Q

How much of a load rejection can SBCS handle without a RPCB?

A

57%

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3
Q

What valves make up Group X in SBCS?

A

1001, 1004, 1003, 1006

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4
Q

When does Group X Quick Open?

A

On a Reactor Trip if Tc > 575F

A step change of 15%-20%

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5
Q

What valves make up Group Y in SBCS?

A

1002, 1005, 1007, 1008

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6
Q

When does Group Y Quick Open?

A

A step change of 45%-50%

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7
Q

How many SBCS valves does each condenser shell have?

A

A - 3
B - 2
C - 1
Atmosphere - 2

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8
Q

Why the uneven number of SBCS valves to the condenser shells?

A

To ensure equal shell loading

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9
Q

What is the only position the System Mode Selector Switch can be in where SBCS will work?

A

OPERATE

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10
Q

What must be done prior to changing the TLI Selection in the SBCS?

A

You have to be in EMERGENCY OFF or you have to be in MANUAL on the Master Controller.

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11
Q

When changing the position of the System Mode Selector Switch on the SBCS, what must be done?

A

You have to be in EMERGENCY OFF or a QO may be generated.

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12
Q

What is the black needle on the SBCS Master Controller?

A

The local setpoint generated with the thumbwheel

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13
Q

What is the black and white needle on the SBCS Master Controller?

A

The remote setpoint

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14
Q

What is the Modulation signal based on when in AUTO on the SBCS Master Controller?

A

error between steam header pressure and the pressure setpoint

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15
Q

When in MANUAL on the SBCS Master Controller, how is the output controlled?

A

Via the slide switch

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16
Q

What must be done before going to LOCAL on the SBCS Master Controller?

A

You have to go to Manual or you’ll get a QO.

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17
Q

If power is lost to the SBCS Master Controller for < 2 seconds, in what mode will it return?

A

Manual

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18
Q

If power is lost to the SBCS Master Controller for > 2 seconds, in what mode will it return?

A

SBCS shifts to EMERGENCY OFF

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19
Q

What SBCS function is not available while in REMOTE/AUTO on the Master Controller?

A

Quick Open

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20
Q

To what does the output on the SBCS Master Controller go when a Quick Open occurs? Why?

A

83.3%

So that transfer to modulation occurs smoothly

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21
Q

What do you want to do before going to LOCAL/AUTO on the SBCS Master Controller?

A

Input manual permissives to prevent popping SBC valves.

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22
Q

When in AUTO, from where do the Individual Controllers get their demand signal?

A

From the SBCS Master Controller

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23
Q

What are the implications of going to MANUAL on an Individual Controller in the SBCS?

A

It reduces your availability

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24
Q

What indicates actual valve position on an Individual Controller in the SBCS?

A

The red needle

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25
Q

When an Individual Valve in the SBCS is placed in OFF on the switch, what happens?

A

The valve will not open under any circumstances

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26
Q

When an Individual Valve in the SBCS is placed in AUTO on the switch, what happens?

A

The valve will get its permissive signal from the permissive circuit

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27
Q

When an Individual Valve in the SBCS is placed in MANUAL on the switch, what happens?

A

The permissive signal is manually input and energizes the permissive solenoid. White light comes in.

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28
Q

How many Individual Valves in SBCS can be given a manual permissive at a time?

A

one

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29
Q

What provides the inputs to the Modulation Circuit for SBCS?

A 
Steam Pressure (PT-1024)
Steam Flow (FT-1011/1012)
Pzr Pressure (PT-100X)
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30
Q

What provides the inputs to the Permissive Circuit for SBCS?

A 
Steam Pressure (PT-1027)
Steam Flow (FT-1021/1022)
Pzr Pessure (PT-100Y)
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31
Q

How is the Modulation Setpoint generated in SBCS?

A

Steam flow from #1 SG biased by “X” Pressurizer Pressure

32
Q

How does Pressurizer Pressure bias the Modulation Setpoint for SBCS?

A

-0.2 psia for every 1 psia above 2250 psia.

1170 psia from 0%-50% and ramps down to 1090 psia at 100%

33
Q

What is compared to the setpoint in the Modulation circuitry?

A

PT-1024

34
Q

What are the Auto Modulation Interlocks for SBCS?

A

Connected 1 and 2
SBCS not in TEST
Individual switch not in OFF

35
Q

How is the Permissive Setpoint generated in SBCS?

A

Steam flow from #2 SG biased by “Y” Pressurizer Pressure

36
Q

How does Pressurizer Pressure bias the Permissive Setpoint for SBCS?

A

-0.2 psia for every 1 psia above 2250 psia.

The Permissive Setpoint is biased a second time to be 20 psia lower than the Modulate Setpoint

1150 psia from 0%-50% and ramps down to 1070 psia at 100%

37
Q

What is compared to the setpoint in the Permissive circuitry?

A

PT-1027

38
Q

How long is the time delay after the permissive signal is lost before valves can be opened again?

A

15 seconds

39
Q

When the permissive signal is present, what indications exist in the Control Room?

A

The small white light above the EMERGENCY OFF switch for SBCS.

40
Q

What solenoids are energized when the permissive signal is present?

A

The “P” solenoids

41
Q

When the permissive signal is present, what is the minimum time the associated solenoids will be energized?

A

15 seconds

42
Q

For SBCS Groups X and Y, when is a QOB generated for a Reactor Trip?

A

X: Trip + <573F Tave
Y: On the Trip

43
Q

For SBCS Groups X and Y, when is a QOB generated for a LOFP?

A

X: On the LOFP
Y: On the LOFP

44
Q

If a QO is generated in SBCS, to what is the output of the Master Controller set? Why?

A

83.3%
That output will open all the SBCS valves that go to the condenser.
Defeated if QOB is present

45
Q

What happens if the Emergency Off/Reset Switch is taken to Emergency Off?

A

SBCS will not open any valves.

46
Q

How can you reset a condenser interlock?

A

Taking the Emergency Off/Reset Switch to Reset. Also, depressing the Emergency Off Condenser Interlock Reset button on the SBCS Test Panel would work.

47
Q

When the Emergency Off/Reset Switch for SBCS is taken to Emergency Off, what physically is happening to the SBCS valves?

A

The air is vented off the bottom of the valve actuator and IA is ported to the top of the valve actuator. The valve is held closed by spring pressure and IA.

48
Q

When is a Condenser Interlock generated in the SBCS?

A

5.5” HgA with a 2/3 logic across the shells.

49
Q

How many pressure switches does each condenser shell have?

A

2
1 for Interlock #1 for Modulation and QO
1 for Interlock #2 Permissive

50
Q

Which valves are effected by the Condenser Interlocks in SBCS?

A

1001-1006

51
Q

When is an AMI sent to CEDMCS from SBCS?

A
  1. When Reactor Power from RRS is < 15%
  2. When TLI from RRS < 15%(permissive for AMI) + Reactor Power < the lesser of either the AMI Threshold or SBCS Availability.
52
Q

What happens to SBCS on a loss of IA?

A

All valves fail closed at ~80 psig

53
Q

What happens to SBCS on a loss of NKN-D42?

A

NKN-D42 powers the P and Q solenoids. These fail closed.

54
Q

What happens to SBCS on a loss of NNN-D11?

A

All SBCS valves fail closed because SBCS loses logic power. If power comes back in < 2 seconds SBCS comes back in Manual with 0 output. If > 2 seconds SBCS comes back in Emergency Off

55
Q

What happens to SBCS on a loss of NNN-D12?

A

All SBCS valves fail closedbecause SBCS loses logic power. If power comes back in < 2 seconds SBCS comes back in Manual with 0 output. If > 2 seconds SBCS comes back in Emergency Off

56
Q

What is the effect to SBCS if SGN-PT-1024 fails HIGH?

A
  • SBCS will generate a 100% Modulate Signal

- If a Runback were to occur, it would stop at 60%

57
Q

What is the effect to SBCS if SGN-PT-1024 fails LOW?

A
  • SBCS will not generate a Modulate Signal

- If a Runback were to occur, it would not stop.

58
Q

What is the effect to SBCS if SGN-PT-1027 fails HIGH?

A

This would generate a permanent Permissive Signal to SBCS

59
Q

What is the effect to SBCS if SGN-PT-1027 fails LOW?

A

This would prevent SBCS from generating a Permissive Signal = no SBCS

60
Q

What is the effect to SBCS if Tave fails LOW?

A
  • This would prevent any valves from Quick Opening after a Reactor Trip
  • If a Runback were to occur, it would not stop.
61
Q

What is the effect to SBCS if Tave fails HIGH?

A
  • This would prevent a Quick Open Block from being generated for the X valves on a Reactor Trip allowing them to open.
  • If a Runback were to occur, it would stop at 60%
62
Q

What is the effect to SBCS if Reactor Power fails HIGH?

A
  • Reactor power will never drop < 15% therefore no low power AMI
  • Reactor power will never reach the AMI Threshold should TLI drop <15%.
63
Q

What is the effect to SBCS if Reactor Power fails LOW?

A
  • Reactor power will drop below <15% therefore Low Power AMI generated
  • Reactor power will always read < AMI Threshold. If TLI drops < 15%, an AMI will be generated.
64
Q

What is the effect to SBCS if PT-100X for Pressurizer Pressure fails HIGH?

A
  • Results in the Modulate setpoint being biased downward its maximum value of 50 psia which places the Modulate setpoint below the Permissive setpoint. This results in slamming open and closed SBCS Valves if actual steam header pressure reaches the now higher Permissive setpoint.
  • Results in the X1 and Y1 QO bistables and RPCB 1 bistable being actuated.
  • Prevents the “rate” of Pressurizer pressure change from inputting into the QO circuitry (rate=0) which could delay actual QO on a real Load Rejection.
65
Q

What is the effect to SBCS if PT-100X for Pressurizer Pressure fails LOW?

A
  • Results in the Modulate setpoint not being biased.
  • Prevents the X1 and Y1 QO bistables and RPCB 1 bistable from being actuated.
  • Prevents the “rate” of Pressurizer pressure change from inputting into the QO circuitry (rate=0) which could delay actual QO on a real Load Rejection.
66
Q

What is the effect to SBCS if PT-100Y for Pressurizer Pressure fails HIGH?

A

Results in the Permissive setpoint being biased down its maximum value of 50 psia which would place the Permissive setpoint further below the Modulate setpoint. This results in SBCS Valves receiving a permissive earlier than they normally would.

67
Q

What is the effect to SBCS if PT-100Y for Pressurizer Pressure fails LOW?

A
  • Results in the Permissive setpoint not being biased.
  • Prevents the X2 and Y2 QO bistables and RPCB 2 bistable from being actuated.
  • Prevents the “rate” of Pressurizer pressure change from inputting into the QO circuitry (rate=0) which could delay actual QO on a real Load Rejection.
68
Q

What is the effect to SBCS if SGN-FT-1021 or SGN-FT-1022 fail HIGH?

A
  • SBCS will see max steam flow. Therefore it will decrease the Modulate setpoint.
69
Q

What is the effect to SBCS if SGN-FT-1021 or SGN-FT-1022 fail LOW?

A
  • SBCS will see minimum steam flow. Therefore it will increase the Modulate setpoint to 1170 psia.
70
Q

What is the effect to SBCS if RRS TLI (HP First Stage Pressure) fails HIGH?

A
  • If a Runback were to occur, it would not stop.
  • SBCS will misread secondary plant load capability as higher than actual. This effect is minimal as the AMI Threshold takes the lower input.
  • Prevents the X2 and Y2 QO bistables and RPCB 2 bistable from being actuated as SBCS thinks the Main Turbine is at 100%.
  • Will prevent SBCS from seeing an actual LLR because it sees the Main Turbine constantly at a higher power than it is.
71
Q

What is the effect to SBCS (Runback, AMI, bistables) if RRS TLI (HP First Stage Pressure) fails LOW?

A
  • If a Runback were to occur, it would stop at 60%.
  • SBCS will provide a false low input to the AMI circuitry possibly resulting in a lower AMI Threshold.
  • Will actuate the X2 and Y2 QO bistables and RPCB 2 bistable as SBCS thinks the Main Turbine in at 0%
  • Will prevent SBCS from seeing an actual LLR because it sees the Main Turbine at a lower power than it is.
72
Q

What is the effect to SBCS if SGN-FT-1011 or SGN-FT-1012 fail HIGH?

A
  • Will prevent the X1 and Y1 QO bistables and RPCB 1 bistable from being actuated as SBCS sees max steam flow.
  • Will prevent SBCS from seeing an actual LLR because it sees the Main Turbine at a higher power than it is.
  • SBCS will lower the Auto Modulation Setpoint because it sees higher steam flow
73
Q

What is the effect to SBCS if SGN-FT-1011 or SGN-FT-1012 fail LOW?

A
  • Will actuate the X1 and Y1 QO bistables and RPCB 1 bistable as SBCS thinks the Main Turbine operating at a lower power than it is.
  • Will prevent SBCS from seeing an actual LLR because it sees the Main Turbine at a lower power than it is.
  • SBCS will raise the Auto Modulation Setpoint because it sees lower steam flow
74
Q

What are the Auto Permissive Interlocks for SBCS?

A
  • Connected #1 and #2
  • Individual Valve switch in AUTO
  • No Condenser Interlock #2 (Permissive)
  • No Emergency Off
75
Q

What are the Manual Permissive Interlocks for SBCS?

A
  • No Condenser Interlock #2 (Permissive)(Only 1001-1006)

- No Emergency Off

76
Q

What are the Manual Modulation Interlocks for SBCS?

A
  • No Condenser Interlock #1 (Manual)(Only 1001-1006)

- No Emergency Off

77
Q

What are the Quick Open Interlocks for SBCS?

A
  • Connected #1 and #2
  • Individual Valve Switch in MAN or AUTO
  • Individual Controller in AUTO
  • No Condenser Interlock #1
  • No Emergency Off
  • SBCS Master Controller in Remote/Auto

ZZ LOIT CWS Systems 2018 (35 decks)

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