CRD

Question 1

What is the purpose of the CRD system?

Answer 1

• 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

Question 2

Housing pressure and temperature design?

Answer 2

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

Question 3

What is weight capcity, stroke length and stroke speed?

Answer 3

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

Question 4

What is the drop time?

Answer 4

• 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

Question 5

Describe the seal package.

Answer 5

• 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.

Question 6

Describe the drive motor and brake?

Answer 6

• 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.

Question 7

What are the motor power supplies?

Answer 7

• 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.

Question 8

Describe the funtion of the magnetic clutch?

Answer 8

• 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.

Question 9

What are the clutch power supplies?

Answer 9

• 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.

Question 10

What decelerates rod on trip?

Answer 10

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.

Question 11

How are control rods grouped?

Answer 11

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

Question 12

Describe the shutdown rods.

Answer 12

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)

Question 13

Describe the regulating rods.

Answer 13

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

Question 14

Describe the Part Length Rods.

Answer 14

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)

Question 15

Discuss Manual Individual mode of operation for control rods.

Answer 15

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.

Question 16

Discuss Manual Group mode of operation for control rods.

Answer 16

Rod Mode Selector Switch - Manual Group (MG)

• Allows an entire group to be selected for movement

Question 17

Discuss Manual Sequential mode of operation for control rods.

Answer 17

Rod Mode Selector Switch - Manual Sequential (MS)

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

Question 18

Discuss Emergency Off mode of operation for control rods.

Answer 18

Rod Mode Selector Switch - Emergency Off (OFF)

• De-energizes all CRDM motors and brakes

Question 19

Describe the function of the Rod Control Group Selector Switch.

Answer 19

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

Question 20

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

Answer 20

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.

Question 21

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

Answer 21

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

Question 22

Describe the Secondary Position Indication.

Answer 22

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.

Question 23

Describe the function of the limit switches.

Answer 23

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)

Question 24

Describe the Upper Electrical Limit.

Answer 24

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

Question 25

Describe the Upper Rod Stop.

Answer 25

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)

Question 26

Describe the Lower Rod Stop.

Answer 26

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)

Question 27

Describe the Lower Electrical Limit.

Answer 27

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

Question 28

What is the control rod Matrix Lights power supply.

Answer 28

Matrix Lights Power Supply: Y-01

Question 29

Describe the function and methodology of the Shutdown Matrix Lights.

Answer 29

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

Question 30

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

Answer 30

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

Question 31

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

Answer 31

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

Question 32

Describe the control rod LED displays.

Answer 32

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.

Question 33

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

Answer 33

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

Question 34

How does the group selector switch function as an interlock?

Answer 34

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).

Question 35

What are the regulating and shutdown rod Interlocks?

Answer 35

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"*

Question 36

What is the lower rod stop (LRS) interlock?

Answer 36

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".

Question 37

What is the Lower Electrical Limit Interlock?

Answer 37

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.

Question 38

What is the Upper rod stop (URS) Interlock?

Answer 38

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)

Question 39

Rod Withdrawel Prohibit

Answer 39

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”.

Question 40

What feeds information to the Reg Rod Seq scheme?

Answer 40

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.

Question 41

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

Answer 41

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

Question 42

What permissive is required to move the Group 2 Regulating rods? How do they withdraw?

Answer 42

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

Question 43

What is the permissive for Group 3 Rod Sequencing? How do they withdraw?

Answer 43

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.

Question 44

What is the permissive for Group 4 Rod Sequencing? How do they withdraw?

Answer 44

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

Question 45

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

Answer 45

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.

Question 46

What are the PIP Inputs?

Answer 46

PIP Inputs Analog Inputs: * 45 synchro positions * Loop 2 delta temp * For PDIL determination Digital Inputs: * 45 rotary switch positions * Rod drop timing start

Question 47

What are the PIP Outputs?

Answer 47

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

Question 48

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

Answer 48

GTR - Bad Synchro Display = -199.9 * Signal from synchro not good * Switch contacts not made up or more than one made up

Question 49

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

Answer 49

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.

Question 50

How is the PIP 8-inch deviation alarm developed?

Answer 50

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

Question 51

How does PIP assist with the Sequential Processing Permissives?

Answer 51

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

Question 52

PIP Out of Sequencing Processing functions how?

Answer 52

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

Question 53

What is the Power Dependent Insertion Limit?

Answer 53

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.

Question 54

What is SPI?

Answer 54

Secondary Position Indication SPI along with the host computer provides redundent control rod indication to the PIP. SPI Node does this through RODMON program.

Question 55

What is RODMON and its inputs?

Answer 55

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).

Question 56

What does RODMON output?

Answer 56

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

Question 57

When is a CR considered fully withdrawn?

Answer 57

Fully withdrawn 128 inches Should be withdrawn to UEL - approx 131 inches

Question 58

What is the procedurally driven sustained SUR Limit?

Answer 58

SUR Limit 0.5 dpm

Question 59

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

Answer 59

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."

Question 60

What is the length of control Rod manipulations?

Answer 60

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.

Question 61

What is the Regulating Rod Insertion Sequence?

Answer 61

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