DFWCS (Digital Feed Water Contrl Signal)

Question 1

Which one of the following describes the level transmitter signal(s) used for SG level control on SG 1 DFWCS when it is in a normal configuration?

A. The higher output of LT-1111 and LT-1112.
B. The output of LT-1111 only.
C. The lower output of LT-1111 and LT-1112.
D. The average output of LT-1111 and LT-1112.

Answer 1

A. The higher output of LT-1111 and LT-1112.

Question 2

Unit is at 16% power.
All control systems are operating normally, in automatic.
MFP ‘A’ is operating at 4150 rpm with 0 bias.
An Operator adds MINUS 100 rpm bias to the ‘A’ main feed pump controller.
MFP ‘A’ is now operating at…

A. 4050 rpm, and will increase speed based on master controller output.
B. 4050 rpm, and will be unaffected by small master controller output changes.
C. 4150 rpm, and will slow to 4050 rpm if the master controller goes into single element control.
D. 4150 rpm, and will be unaffected if the master controller goes to single element control.

Answer 2

D. 4150 rpm, and will be unaffected if the master controller goes to single element control.

Question 3

Assume that all digital feedwater control system control input transmitters are in service and selected to AVERAGE.
The plant is at 15.5% power.
Power is slowly increasing.
Steam Generator #1 downcomer valve position 80% and is opening slowly.
Steam Generator #2 downcomer valve position is 70% and is opening slowly.
Concerning the digital feedwater control system, which (if any) of the following automatic actions will occur?

A. No DFWCS automatic action will occur until 16.5% power is reached.
B. No DFWCS automatic action will occur until both SG downcomer valves are 80% open.
C. Only SG #1 will go through swap over.
D. Both SG #1 and SG #2 will go through swap over.

Answer 3

D. Both SG #1 and SG #2 will go through swap over.

Question 4

At rated power.
FWCS #1 Master in manual with 50% output.
FWCS #2 Master in automatic with 50% output.
A Reactor Trip occurs.
Which one of the following is true?

A. FWCS #2 will enter RTO, FWCS #1 will not.
B. Both FWCS will enter RTO and feed based on Tavg ONLY.
C. Both FWCS will enter RTO and remain in RTO if SG levels are <51.9% NR.
D. Bot FWCS will enter RTO, but FWCS #1 will continue to feed past 51.9% NR level.

Answer 4

C. Both FWCS will enter RTO and remain in RTO if SG levels are <51.9% NR.

Question 5

Unit 1 is operating at rated power.
Both Feed water control systems are in auto.
SGN-LT-1111, SG-1 Level fails High
Based on these conditions, the operator can expect:

A. Feed pump speed to lower.
B. DFWCS (both) enter high level override.
C. SG-1 downcomer and economizer control valves to throttle closed.
D. No effect on DFWCS, alarm only

Answer 5

D. No effect on DFWCS, alarm only

Question 6

Which of the following inputs to the Digital Feedwater Control System is used for indication only?

A. Downcomer flow transmitters
B. Tavg
C. Turbine Load Index
D. Steam Bypass Master Controller Output

Answer 6

A. Downcomer flow transmitters

Question 7

Unit 1 is operating at rated power.
DFWCS is in normal line up (No transmitters in maintenance).
RRS has Tavg selected to ‘Average’.
If Tavg fails HIGH during a reactor trip, both DFWCS would…

A. Feed at the maximum rate as permitted by RTO.
B. Be prevented from entering RTO.
C. Prevent feeding of the Steam Generators.
D. Feed at the minimum rate as permitted by RTO.

Answer 7

A. Feed at the maximum rate as permitted by RTO.

Question 8

Unit 1 is operating at rated power.
DFWCS is in a normal line up.
A feedwater temperature transmitter fails low.
With no operator action, which of the following represents the response of DFWCS?

A. DFWCS shifts to 1E control.
B. Adaptive Tuning (ATUN) Lockout and the temperature transmitter will shift to maintenance mode.
C. DFWCS uses a canned value of 425 degrees for feedwater temperature.
D. DFWCS feeds to the High Level Override setpoint.

Answer 8

C. DFWCS uses a canned value of 425 degrees for feedwater temperature.

Question 9

How will a momentary loss (10 seconds) of NNN-D11 affect DFWCS at 100% power?

A. DFWCS will be de-energized and return in Manual on the Master Controller.
B. DFWCS will be de-energized and return in single element control.
C. DFWCS will be unaffected; power will transfer to NNN-D12 and remain there until an operator shifts power supplies back to NNN-D11
D. DFWCS will be unaffected; power will transfer to NNN-D12 and then automatically shift back to NNN-D11

Answer 9

D. DFWCS will be unaffected; power will transfer to NNN-D12 and then automatically shift back to NNN-D11.

Question 10

Rx power is 100%.
All the control input transmitters to the Digital Feedwater Control system are in service and selected to AVERAGE.
If a SG feed flow transmitter fails low which of the following describes the automatic action that would take place in the DFWCS if a 6% deviation between the feed flow transmitters developed?
The affected master controller would:

A. Stay in automatic but in single-element control.
B. Shift to manual with the output signal that was present at the 4% deviation point.
C. Stay in automatic, 3-element control, using the average feedwater flow transmitter signal.
D. Stay in automatic, 3-element control, using the highest feedwater flow transmitter signal only.

Answer 10

C. Stay in automatic, 3-element control, using the average feedwater flow transmitters signal.

(Note: 8% is the deviation to go to single-element)

Question 11

Unit 1 is at 100% power.
All control input transmitters to the Digital Feedwater Control system (DFWCS) are in service and functioning normally.
A #1 SG level transmitter fails low.
SG #1 DFWCS Master Controller will ____.

A. Remain in automatic 3-element control using the higher indicating level transmitter.
B. Shift to manual single element control.
C. Remain in automatic 3-element control, using the lower indicating level transmitter.
D. Shift to single element automatic control, using the higher indicating level transmitter.

Answer 11

A. Remain in automatic 3-element control using the higher indicating level transmitter.

Question 12

The plant is at 100% power.
DFWCS is selected to Excore Nuclear Instrumentation Control Channel 1.
The Excore Nuclear Control Channel 1 fails low.
Which ONE of the following describes appropriate operator actions as a result of this failure?

A. No operator action is necessary, ATUN lockout prevents DFWCS response.
B. Take manual control of S/G 1 economizer, downcomer and associated FWPT and restore S/G 1 level; All S/G 2 components are left in automatic.
C. Take the manual control of the S/G 1 and S/G 2 Economizer, Downcomer and FWPT speed and restore S/G levels.
D. Trip the Reactor

Answer 12

D. Trip the reactor

Note: DFWCS is selected to Control Channel 1, answer as assuming its the only operable channel

Question 13

Unit 1 is operating at rated power.
FWCS #1 Master in manual.
FWCS #2 Master in automatic.
A Reactor Trip occurs.
With no post trip operator action both SG levels are now 55% Narrow Range.
Which of the following is true of the Master Controllers?

A. FWCS #1 is in Auto in 1E control, FWCS #2 is in Auto in 1E control.
B. FWCS #1 is in Auto in 1E control, FWCS #2 is in manual.
C. Both Master Controllers are in RTO tracking.
D. FWCS #1 is in Auto in 1E control, FWCS #2 is RTO tracking.

Answer 13

A. FWCS #1 is in Auto in 1E control, FWCS #2 is in Auto in 1E control.

Question 14

Unit 1 tripped from 100% power due to a trip of Reactor Coolant Pump 1B and has the following conditions:
DFWCS is in a normal line up (no transmitters in maintenance)
The Reactor Regulating System (RRS) T-avg has failed high.
SG 1 level is recovering and currently 54% NR.
SG 2 level is recovering and currently 45% NR.
Which one of the following describes the status of the Digital Feedwater Control System (DFWCS)?

A. SG 1 and SG 2 are each feeding in single element control.
B. SG 1 and SG 2 are each feeding at the maximum rate as allowed by Reactor Trip Override (RTO)
C. SG 1 is feeding in single element control, SG 2 is feeding at the minimum rate as allowed by Reactor Trip Override (RTO).
D. SG 1 is feeding in single element control, SG 2 is feeding at the maximum rate as allowed by Reactor Trip Override (RTO).

Answer 14

D. SG 1 is feeding in single element control, SG 2 is feeding at the maximum rate as allowed by Reactor Trip Override (RTO).

Question 15

Assume that all Digital Feedwater Control System (DFWCS) input transmitters are in service and selected to AVERAGE.
An increase to 20% power is in progress.
The plant is currently at 14.5% power by control channel indication.
SG #1 downcomer valve position is 80% and is opening slowly.
SG #2 downcomer valve position is 70% and is opening slowly.
Under these conditions which one of the following is the expected response of the DFWCS system?

A. Only SG 1 should now go through swapover.
B. Both SGs 1 and 2 should n ow go through swapover.
C. Neither SG will go through swapover until >15% power is reached.
D. Neither SG will go through swapover until both SG downcomer valves are >80% open.

Answer 15

C. Neither SG will go through swapover until >15% power is reached.

Question 16

Unit 1 is operating at a rated power, while monitoring DFWCS you observe the following:
SG 1 LT-1111 indicates 50% NR level and stable.
SG 1 LT-1112 has failed to 54% NR and stabilized.
SG 2 LT-1121 indicates 51% NR level and stable.
SG 2 LT-1122 indicates 50% NR level and stable.
1. What effect will the failure of LT-1112 have on SG 1 level?
2. Which of the following automatic OR manual actions are found in 40AL-9RK6A, ARP that must occur to control SG 1 level?

A. 1. Actual SG 1A level will lower.
2. When SG 1 level deviation exceeds 8%, then a canned value will be inserted into the SG 1 DFWCS to restore level.
B. 1. Actual SG 1 level will rise.
2. Place LT-1112 in the maintenance mode, SG 1 level will lower to the level setpoint.
C. 1. Actual SG 1 level will rise.
2. SG 1 DFWCS will then use SG 2 LT-1121 signal and lower SG 1 level.
D. 1. Actual SG 1 level will lower
2. Place LT-1112 in the maintenance mode and then slowly raise SG 1 level to the level setpoint.

Answer 16

D. 1. Actual SG 1 level will lower

2. Place LT-1112 in the maintenance mode and then slowly raise SG 1 level to the level setpoint.

Question 17

Unit 1 is operating at 100% power.
Main Turbine Control and Stop valve testing is about to commence.
Which ONE of the following is a set of plant perturbations and an associated mitigating actin identified in 40OP-9MT02, Main Turbine?

A. 1. Due to swings in RCS temperature, ensure CEDMCS IS in Auto Sequential.
2. Due to deviations between steam flow transmitters, place DFWCS in single element control.
B. 1. Due to swings in RCS temperature, ensure CEDMCS IS NOT in Auto Sequential.
2. Due to deviations between steam flow transmitters, place DFWCS in single element control.
C. 1. Due to swings in RCS temperature, ensure CEDMCS IS in Auto Sequential.
2. Due to oscillations in RCS pressure, place the Pressurizer in Boron Equalization.
D. 1. Due to swings in RCS temperature, ensure CEDMCS IS NOT in Auto Sequential.
2. Due to oscillations in RCS pressure, place the Pressurizer in Boron Equalization.

Answer 17

D. 1. Due to swings in RCS temperature, ensure CEDMCS IS NOT in Auto Sequential.
2. Due to oscillations in RCS pressure, place the Pressurizer in Boron Equalization.

Question 18

Unit 1 is operating at 100% power.
An RCS Overcooling event is in progress.
PZR pressure is 2150 psia and lowering.
Loop 1 and 2 Tcold is 552 F and lowering.
The CRS directs a manual reactor trip.
How will this event affect the plant post trip?
The DFWCS will…

A. Overfeed in RTO and the SBCS will not generate a quick open block signal.
B. Not feed in RTO and the SBCS will generate a quick open block signal.
C. Overfeed in RTO and the SBCS will generate a quick open block signal.
D. Not feed in RTO and the SBCS will not generate a quick open block signal.

Answer 18

B. Not feed in RTO and the SBCS will generate a quick open block signal.

Question 19

Unit 1 is operating at 50% power.
RCN-TT-111Y, Loop 1A Tcold, has failed high.
Which one of the following identifies ____ the impact on the Main Feedwater system and ____ the procedure and actions to mitigate these consequences?

A. 1. No refill demand in Reactor Trip Override.
2. Select the Loop 2 temperature instrument at the RRS Test Panel per 40AO-9ZZ16, RRS Malfunctions.
B. 1. Maximum refill demand in Reactor Trip Override.
2. Select the Loop 2 temperature instrument at the RRS Test Panel per 40AO-9ZZ16, RRS Malfunctions.
C. 1. No refill demand in Reactor Trip Override.
2. Place the faulty transmitter in maintenance mode per 40AL-9RK6A, B06 Alarm Response procedure.
D. 1. Maximum refill demand in Reactor Trip Override.
2. Place the faulty transmitter in maintenance mode per 40AL-9RK6A, B06 Alarm Response Procedure

Answer 19

B. 1. Maximum refill demand in Reactor Trip Override.

2. Select the Loop 2 temperature instrument at the RRS Test Panel per 40AO-9ZZ16, RRS

Question 20

Instrument failure on feedwater control system #1.
Steam generator #1 level is 45% narrow range and dropping slowly.
Secondary operator believes MANUAL on the master or economizer controllers will stabilize the plant.
Which ONE of the following describes the action the secondary operator is to take for the observed indications?

A. Inform the Control Room Staff; obtain control room supervisor concurrence; manual trip the reactor.
B. Immediately take MANUAL control of the master controller and raise the output; inform the Control Room Staff of results.
C. Inform the Control Room Staff; obtain control room supervisor concurrence; take MANUAL control of the master controller.
D. Immediately take MANUAL control of the economizer controller and raise the output; inform the Control Room Staff of results.

Answer 20

C. Inform the Control Room Staff; obtain control room supervisor concurrence; take MANUAL control of the master controller.