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Flashcards in CRD Deck (61):
1

What is the purpose of the CRD system?

  • To provide short-term reactivity control by positioning neutron absorbing control rods within the core.
  • To furnish a quick reactor shutdown mechanism through rapid control rod insertion
  • To provide position indication of the control rods within the core

2

Housing pressure and temperature design?

Internal conditions:

  • 2485 psig
  • 650°F

Ambient conditions:

  • 250°F
  • 9.7 to 14.7 psia
  • 0 to 100% humidity,
  • 50 REM/Hr gamma radiation

3

What is weight capcity, stroke length and stroke speed?

  • Control weight of 215 pounds
  • Stroke of 132”.
  • Rod speed is 46” per minute.

4

What is the drop time?

  • From receiving a trip signal to 90% of the full-in position of the rod is less than 2½ seconds.
  • Accelerates to about 11 ft/s

5

Describe the seal package.

  • PCS pressure boundary prevents PCS from leaking into upper housing.
  • Seal leakage cup, located above seal, collects any leakage past the seal and contains a thermocouple to monitor for cooling water (CCW) or seal failure.
  • CRDM leak off is directed to the containment sump,
  • Cooling jacket surrounds seal area to maintain temperature of seal and O-rings below 250°F. Cooled by CCW.

6

Describe the drive motor and brake?

  • Motivating force for withdrawal of a control rod and also insures that a control rod is inserted on a reactor trip if the magnetic clutch fails
  • Brake functions to hold the control rod in the desired position. Energized (90V DC) it releases. De-energized, the brake engages
    • Mechanical failure of the brake, results in rod "coasting" into core.

    • Brakes tend to grab somewhat differently, seen as control rod "drift" when the joystick is released.

    • Mechanical or electrical failure of the brake, that prevents the brake from disengaging, the motor will probably burn up.

  • The joystick control switch, located on C-02, energizes the motor and brake causing control rod movements.

 

7

What are the motor power supplies?

  • Breaker 52-125 powers CRDM transformer #2, EX-46 (120 VAC)
  • Breaker 52-226 powers CRDM transformer #1, EX-45 (120 VAC)
  • Transformer #1 or 2 is selected by selector switch behind C-15 panel (in Cable Spreading room). 
  • Loss of power to the CRDM motor will not affect the control rod position. The CRDM will not move unless it is tripped. The brake engages when de-energized.

8

Describe the funtion of the magnetic clutch?

  • When energized, connects the motor to the vertical drive shaft to allow raising and lowering of:
    • Shutdown rods (Groups A and B)
    • Regulating rods (Groups 1, 2, 3 and 4)
  • De-energized, the drive shaft is disconnected from the motor and brake,

    Gravity pulls shutdown and regulating rods into the core.

  • Anti-reverse feature functions when the clutch is de-energized. Ensures a control rod is forced down into the core by the motor if necessary, 

  • Limit switch at full insertion de-energizes the motor and the brake

    • Anti- reverse and brake prevent any outward motion of the control rod.

9

What are the clutch power supplies?

  • Y-30 and Y-40
    • Transformers located in the Cable Spreading Room, reduce the voltage to 28 VAC.
      • Rectifier changes to 24 V DC for magnetic clutch
      • Individual rod clutches (except part length) can be de-energized with toggle switches

  • Either Y-30 or Y-40 can supply all the Clutches. A loss of one will not cause a loss of power to any clutches.

10

What decelerates rod on trip?

Buffer Piston: PCS water level is required inside the guide tube so that hydraulic action of the buffer piston, traveling through the guide tube, will prevent mechanism damage on a CRDM trip.

  • Permanent magnet on top of Buffer Piston activates the reed switches, located along the CRDM housing for secondary position indication.

11

How are control rods grouped?

  • Shutdown Rods (2 Groups)
    • 20 rods total
  • Regulating Rods (4 Groups)
    • 21 rods total
  • Part-Length Rods
    • 4 rods total
    • Do not trip

12

Describe the shutdown rods.

Shutdown Rods (2 Groups)

  • Group A has a total of 12 rods
  • Group B has a total of 8 rods

First to be withdrawn on start-ups

  • Remain withdrawn in MODE 1 & 2: Definite shutdown margin at all times.

Reactivity worth approximately 4% DK

  • BOL = ~3.23 % ΔK;
  • EOL ~3.86 % ΔK

Operated Manual Individual (MI) or Manual Group (MG)

13

Describe the regulating rods.

Regulating Rods (4 Groups) ;

  • Group 1 - has a total of 8 rods
  • Group 2 - has a total of 4 rods
  • Group 3 - has a total of 5 rods
  • Group 4 - has a total of 4 rods

Operated Manual Individual (MI), Manual Group (MG) or Manual Sequential (MS)

Provide short-term reactivity control to maintain/adjust power/Tave.

Total reactivity worth of all four groups approximately 3% DK

  • BOL = ~3.16 % ΔK
  • EOL ~3.61 % ΔK

14

Describe the Part Length Rods.

One group with 4 rods

  • Original purpose was to be used for axial flux shaping, but they are not used at all.
  • Withdrawn completely after shutdown rods are withdrawn and kept withdrawn at all times since inserting the part-lengths at power may have an adverse effect on flux distribution.

Inserted after the Reactor has been tripped in GOP-8,

  • Power Reduction and Plant Shutdown to Mode 2 or Mode 3 ≥ 525°F

Operated Manual Individual (MI) or Manual Group (MG)

15

Discuss Manual Individual mode of operation for control rods.

Rod Mode Selector Switch - Manual Individual (MI)

  • Allows an individual rod to be selected for movement.

NOTE: When moving the Part Length Rods and the "Individual Rod Selector Switch" for the Part Length Rod Group is in "GR" position, then all Part Length Rods will still move as a group even if the Rod Mode Selector Switch is in Manual Individual.

16

Discuss Manual Group mode of operation for control rods.

Rod Mode Selector Switch - Manual Group (MG)

  • Allows an entire group to be selected for movement

17

Discuss Manual Sequential mode of operation for control rods.

Rod Mode Selector Switch - Manual Sequential (MS)

  • Allows sequential movement of the regulating rods according to the Rod Sequence Program.

18

Discuss Emergency Off mode of operation for control rods.

Rod Mode Selector Switch - Emergency Off (OFF)

  • De-energizes all CRDM motors and brakes

19

Describe the function of the Rod Control Group Selector Switch.

Selects a single group (e.g., A, B, 1, 2, 3, 4 or Part) for group movement or individual rod movement within the selected group

  • OFF - No banks are selected for operation.
  • A, B - Shutdown rods
  • 1, 2, 3, 4 - Regulating rods
  • P - Part-length rods

20

Describe the function of the Individual Rod Selector Switches for each group.

Selects an individual rod for movement if the Mode Select switch is in Manual Individual (MI) and its group is selected.

  • Selects which rod in the particular group will have its position displayed on the LED display.
  • Selects which rod in the particular group (group target rod) that will be used for sequencing purposes by PIP.
  • Part-length rods have a "GR" position, which is the same position indication as rod "42". However, when moving the part-length rods and the "Individual Rod Selector Switch" for the Part Length Rod Group is in "GR" position, then all part-length rods will still move as a group even if the Rod Mode Selector Switch is in Manual Individual.

21

Describe the Primary Position Indication; power supply, method of function, accuracy and outputs to.

Power Supply:

  • Y-20

Primary indicator is a synchrotransmitter geared to the clutch output shaft.

  • Shaft has a rotor coil attached to it surrounded by three stationary coils located 120 degrees apart. When it rotates it produces a voltage in the stationary coils that is related to the position of the control rod.

    • Full rod travel corresponds to 264 degrees of synchro rotation.

Transmitted to PPC to PIP Node, which scans and converts synchro outputs into inches of control rod withdrawal.

  • Accuracy ± 0.5"

The primary position indication via the PIP node provides contact inputs for the LRS (lower rod stop) and URS (upper rod stop) for the C-12 rod matrix lights

 

 

22

Describe the Secondary Position Indication.

Secondary Position Indication (SPI)

An assembly containing a number of series resistors to form a voltage divider network with reed switches (approximately 2 inches apart) connected at each junction. Voltage is applied to the network; output voltage depends on which reed switches are closed in the voltage divider. Overlap between adjacent reed switches is provided. The output is a voltage directly proportional to control rod position.

  • Power Supply - Y-40
  • Accuracy is ± 1.5 inches 
  • Transmit rod height signals to the secondary position indication and rod matrix light display.

23

Describe the function of the limit switches.

Six switches controlled by cams on the control rod synchro shaft.

Independent of the Primary or Secondary Control Rod Position Systems, these limit switches provide:

  • Shutdown/regulating control rod insertion/withdrawal interlocks
  • Control Rod upper and lower electrical cutoff
  • Rod matrix light display
  • Various alarms (shutdown rod position abnormal, dropped rod)

24

Describe the Upper Electrical Limit.

Upper Electrical Limit (UEL)

  • Synonymous with upper limit switch
  • Highest point of rod withdrawal for Shutdown rods in Manual Group
  • Highest point of rod withdrawal for Shutdown, Regulating, and Part-Length rods in Manual Individual
  • apprx 131 inches for all rods

25

Describe the Upper Rod Stop.

Upper Rod Stop (URS)

  • Furthest a rod group can be withdrawn in Manual Group or Manual Sequential Mode for the Regulating and Part-Length rods
  • Rod position input comes from the PIP Node (fed from drive package synchros)

26

Describe the Lower Rod Stop.

Lower Rod Stop (LRS)

  • Lowest point rods can be inserted in Manual Group or Manual Sequential Mode for the Regulating and Part-Length rods
  • Rod position input comes from the PIP Node (fed from drive package synchros)

27

Describe the Lower Electrical Limit.

Lower Electrical Limit (LEL)

Synonymous with lower limit switch

  • Lowest point of insertion in either Manual Individual or Manual Group
    • ~ 3 inches withdrawn for Shutdown and Regulating rods

    • ~ 0.5 inches withdrawn for Part-Length rods

  • Controlled by limit switches within the drive package

 

28

What is the control rod Matrix Lights power supply.

Matrix Lights

Power Supply: Y-01

 

 

29

Describe the function and methodology of the Shutdown Matrix Lights.

Shutdown Matrix Lights

PIP 'b' Contact Closed at <122 inches withdrawn

  • Green On = LEL = <3 inch withdrawn = lower limit switch (LS-4) open
  • White On = >3 inches withdrawn < 122" = lower limit switch (LS-4) closed (Green Off)

PIP 'b' Contact OPEN, PIP 'a' contact CLOSED at >122 inches withdrawn

  • White Off/Blue On:
    • Rods move up to approximately 122" to the Shutdown/Regulating Rod Interlock.
    • Blue light signifies that the shutdown rods are above the exercise limit and it will stay On no matter what the rod positions are as long as they are above 122 inches.

  • Blue On/Red On:
    • At 131" reach the Upper Limit reed switch. - SPI

30

Describe the function and methodology of the Regulating Rod Matrix Lights.

Regulating Rod Matrix Lights

  • Green Light On: 
    • Rods on bottom (<3 inches w/d) will result in limit switch LS-4 to be open.
  • Green Off/White On:
    • Rods move up to approximately 3" w/d, LS-4 will close.
  • White Off/Amber On:
    • Rods move up to approximately 130" to the Upper Rod Stop.
    • PIP cam and Aux Relay
  • Amber Off/Red On:
    • At 131" reach LS-5

31

Describe the function and methodology of the Part Length Rod Matrix Lights.

Part Length Rod Matrix Lights

  • Green Light On: 
    • Rods on bottom will result in limit switch LS-4 to be open. <3 inches w/d
  • Green Off/White Intermitent:
    • Rods move up to approximately 3" w/d, LS-4 will close.
    • White light  will only be on during rod movement.

  • Amber On:
    • Rods move up to approximately 130" 
  • Amber Off/Red On:
    • At 131" reach LS-5

32

Describe the control rod LED displays.

LED Displays

  • Digital read-out of the selected rod position from the PIP
    • Indicated position by the LED Display is the rod that is that of the selected via Rod Control Selector Switches.
  • Regulating rods selected are the target rods used by PIP for sequencing.
  • Deviation light next to each display indicates a 4” deviation exists within that group. Should accompany an annunciator. This light is independent of selector switch positions.

33

What could cause TRA-0150, CRDM Seal Leak Off Temperature Alarm Recorder, to alarm?

TRA-0150, CRDM Seal Leak Off Temperature Alarm Recorder

On the back of C-12, provides indication of CRDM seal leak off temperature

EK‑0954, “ROD DRIVE SEAL LEAK OFF HI TEMP.

  • Could be a bad thermocouple
  • Excessive CRDM leakage
  • Loss of CCW
  • Loss of CRDM cooling fans

34

How does the group selector switch function as an interlock?

Group selector switch as Interlock

It prevents simultaneous withdrawal of groups of rods when in manual group mode

  • (e.g., only one group can be selected at a time).

35

What are the regulating and shutdown rod Interlocks?

Regulating and Shutdown Rod Interlocks

Shutdown/regulating rod interlock is bypassed while in Manual Individual (MI).

Regulating rods cannot be withdrawn any amount in group until each shutdown rod is withdrawn above its regulator rod withdrawal interlock (limit switch LS-3 at 122" on each Shutdown Rod)

  • Shutdown rods must be above 122" in order to withdraw regulating rods in group.

Shutdown rods cannot be inserted below 122" whenever regulating rod is withdrawn ≥ 6 inches. (Limit Switches LS-3 closed below 6" on each Regulating Rod)

  • Regulating rod withdrawn ≥ 6 inches, then shutdown rods can only be inserted to 122"

36

What is the lower rod stop (LRS) interlock?

Lower Rod Stop

Applies to the regulating group in Manual Sequential (MS), Manual Group (MG) and part-length rods in Manual Group (MG).

  • Stops inward group rod motion at 4".

37

What is the Lower Electrical Limit Interlock?

Lower Electrical Limit

Stops all inward rod motion at approximately 3 inches

  • Part-length rods can be inserted to bottom limit switch (apprx .5 inch) if in manual individual.

38

What is the Upper rod stop (URS) Interlock?

Upper rod stop Interlock

For regulating group and the part-length rods.

  • Stops all outward group rod motion at approximately 130".
  • Must be manual individual driven up 131 inches. (UEL)

 

39

Rod Withdrawel Prohibit

Rod Withdrawel Prohibit

  1. 1 out of 4 for High Power Rate Pre-Trip (1.5 dpm) between 10-4% and 15% power
  2. 2 out of 4 for Variable High Power Pre-Trip.  Minimum of 28.5%, Variable setpoint of 13.5% above reset power, or a maximum of 105%.
  3. 1 of 4 for Removal/Failure of RPS Bistable High Power Rate Pre-Trip/Trip < 15% power
  4. Rod Mode Select Switch in “EM OFF”.

40

What feeds information to the Reg Rod Seq scheme?

Reg Rod Sequence

Automatic sequencing is provided by outputs from the PIP based on the position of the Group Target Rod, which is the rod displayed on the LED.

41

What permissive is required for Group 1 regulating rods to be sequenced in or out?

How do they withdraw?

Group 1 control rods to be sequenced either in or out

  • The selected Group 2 rod must be less than 52 inches.

Group '1' moves alone from 3 to 83 inches withdrawal

42

What permissive is required to move the Group 2 Regulating rods?

How do they withdraw?

For Group 2 control rods to be sequenced either in or out, two conditions must be true

  • The selected Group 1 control rod must be greater than 80 inches
  • The selected Group 3 control rod must be less than 52 inches

Group '2' moves from 3 to 51 inches withdrawal as Group '1' moves from
83 inches to fully withdrawn.

Group '2' moves alone from 51 to 83 inches withdrawal

43

What is the permissive for Group 3 Rod Sequencing?

How do they withdraw?

In order for Group 3 control rods to be sequenced either in or out, the following two conditions must be true.

  • The selected Group 2 control rod must be greater than 80 inches.
  • The selected Group 4 control rod must be less than 52 inches.

Group '3' moves from 3 to 51 inches withdrawal as Group '2' moves from
83 inches to fully withdrawn.

Group '3' moves alone from 51 to 83 inches withdrawal.

44

What is the permissive for Group 4 Rod Sequencing?

How do they withdraw?

In order for Group 4 control rods to sequence either in or out, the selected Group 3 control rod must be greater than 80 inches

Group '4' moves from 3 to 51 inches withdrawal as Group '3' moves from
83 inches to fully withdrawn.

Group '4' moves alone from 51 inches to fully withdrawn

45

How far apart are regulating rod groups required to be during manual sequencing of rods?

In manual sequencing, the Regulating Rods are maintained 80 inches to 92 inches apart (80 plus 12 inches minus 0 inches).

Must follow normal group sequencing unless an approved, written procedure for another sequence is provided to the operator.

46

What are the PIP Inputs?

PIP Inputs

Analog Inputs:

  • 45 synchro positions
  • Loop 2 delta temp
    • For PDIL determination

Digital Inputs:

  • 45 rotary switch positions
  • Rod drop timing start

47

What are the PIP Outputs?

PIP Outputs

Analog Outputs:

  • 45 rod position (in inches) to host
  • Loop 2 delta temperature "core power"
  • Rod drop timing data

Digital Outputs:

  • Rod Control Relays
  • Annunciators
  • Digital Rod displays

48

What happens to the selected rod position display if  the PIP Synchro is bad?

GTR - Bad Synchro

Display = -199.9

  • Signal from synchro not good
  • Switch contacts not made up or more than one made up

49

How does PIP process to develop a 4-inch deviation alarm?

PIP processing 4-inch deviation

PIP software controls the state of the 7 four inch group deviation contacts

If the highest rod in a group is more than 4 inches from the lowest rod in the group, the four-inch deviation contact for that group is opened.

50

How is the PIP 8-inch deviation alarm developed?

PIP 8-inch deviation alarm

The PIP software controls the state of the 7 eight inch group deviation contacts

  • If the highest rod in a group is more than 8 inches from the lowest rod in the group, the eight-inch deviation contact for that group is opened
  • If the deviation is less than 8 inches minus the deadband, the contact is closed

51

How does PIP assist with the Sequential Processing Permissives?

PIP Controls the Contacts for Rod Sequencing Permissives

USP and LSP are used in the Manual Sequential Raise/Lower logic.

  • PIP sets the state of the 3 upper sequential permissive (USP) contacts based on the position of the GTR for regulating groups 1, 2, and 3
  • PIP sets the state of the 3 lower sequential permissive (LSP) contacts based on the position of the GTR for regulating groups 2, 3, and 4

52

PIP Out of Sequencing Processing functions how?

PIP Out of Sequencing Processing

PIP sets the state of the out of sequence (OOS) contact based on the positions of the GTR for the four regulating groups.

If any of the regulating group target rods have bad synchrotransmitters, no OOS processing is completed between adjacent rod groups

53

What is the Power Dependent Insertion Limit?

PDIL

PIP uses Loop 2 DT via TDY_0200 to determin core power

PIP then sets the Power Dependent Insertion limits and the status of the four PDIL contacts based on the GTR position.

IF TYT-200 input is bad, Group 1 PDIL alarm is initiated.

PIP also sets a pre-PDIL alarm.

54

What is SPI?

Secondary Position Indication

SPI along with the host computer provides redundent control rod indication to the PIP.

SPI Node does this through RODMON program.

55

What is RODMON and its inputs?

RODMON - PPC Program

  • Uses PIP synchro information to perform all the same calculations as PIP.
  • Does NOT interface with rod control, annunciators or the LEDs.

Only PPC alarms.

INPUTS

  • Uses synchro rod positions and the Loop 2 ΔT (from PIP) as long as they are valid. 
  • Otherwise
  • Uses the reed switch rod positions (SPI inputs) and/or Loop 1 ΔT (SPI input).

56

What does RODMON output?

RODMON Outputs

45 validated rod positions

7 validated Group Target Rod (GTR)

Upper Rod Stop (URS)

Lower Rod Stop (LRS).

Shutdown Rod Insertion (SRI)*

Upper Sequential Permissive (USP)

Lower Sequential Permissive (LSP)

Four Inch Deviation

Eight Inch Deviation - w/ PPC Alarm

Out of Sequence (OOS) - w/ PPC Alarm

Power Dependent Insertion Limit - w/ PPC Alarm

Pre-power Dependent Insertion Limit

57

When is a CR considered fully withdrawn?

Fully withdrawn

128 inches

Should be withdrawn to UEL - approx 131 inches

58

What is the procedurally driven sustained SUR Limit?

SUR Limit

0.5 dpm

59

What return to service testing requirements are there for Rod Replacement/repair?

Rod Replacement/Repair RTC Testing

If a Control Rod Drive is replaced or repaired at any time, it shall be drop timed per
Technical Specification Surveillance Procedure RO-22, "Control Rod Drop Times."

60

What is the length of control Rod manipulations?

Rod Manipulations

Control Rod manipulations are recommended to be made in increments of
approximately 33 inches and should not exceed 35 inches. Control Rod
manipulations in smaller increments are allowed.

61

What is the Regulating Rod Insertion Sequence?

Regulating Rod Insertion Sequence

  • Group '4' moves from fully withdrawn to 51 inches withdrawal alone.
  • Group '3' moves from fully withdrawn to 83 inches as Group '4' moves from 51 inches to fully inserted.
  • Group '3' moves from 83 to 51 inches withdrawal alone.
  • Group '2' moves from fully withdrawn to 83 inches as Group '3' moves from 51 inches to fully inserted.
  • Group '2' moves alone from 83 to 51 inches withdrawal.
  • Group '1' moves from fully withdrawn to 83 inches as Group '2' moves from 51 inches to fully inserted.
  • Group '1' moves from 83 inches to fully inserted alone