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LCO 3.1.6: Regulating Rod Group Position Limits
LCO 3.1.6: PDIL alarm circuit and the control rod out of sequence (CROOS) alarm circuit shall be operable and the regulating rod groups shall be limited to the withdrawal sequence, overlap, and insertion limits specified in the COLR
APP: Modes 1&2
- Actions: PDIL or CROOS alarm circuit inoperable
- -perform SR 188.8.131.52 (group position verification)
- --once within 15 minutes following any rod motion
Control rod limit switches
- 6 switches controlled by cams on the synchro shaft
- Independent of PIP and SPI
- -shutdown/regulating control rod insertion/withdrawal interlocks
- -control rod upper and lower electrical cutoff
- -rod matrix light supply
- -various alarms (shutdown rod position abnormal, dropped rod)
LCO 3.1.4: Control Rod Alignment
LCO 3.1.4: all rods, including their position indication channels, shall be operable and aligned to with in 8 inches of all other rods in their group, and the control rod position deviation alarm shall be operable
APP: Modes 1 and 2
- Actions: 1 channel of rod position indication inoperable
- -perform rod position verification with in 15 minutes of rod motion
- Rod position deviation alarm inoperable
- -perform rod position verification with in 15 minutes of rod motion
Lower rod stop processing
- PIP determines the state of the 25 lower rod stop (LRS) contacts for the rods in the regulating and power shaping rod groups
- Suspended for rods with a bad synchro
- LRS contacts are used in:
- -manual sequential (MS) lower logic
- -manual group (MG) lower logic
Shutdown rod indication on the rod matrix
- Lower limit switch at approximately 3"
- -turns on limit switch when inserting
- -turns off green light, turns on white light when pulling rods
- Upper limit switch at approximately 131.5" (reed switch)
- -stops rod movement at 131"
- -red light from SPI via a reed switch
- Blue light comes on when rods are >122"
Secondary position indication (SPI) inputs/outputs
- SPI node inputs
- -reed switches
- -loop 1 differential temperature
- SPI node outputs
- -45 rod positions (inches)
- -loop 1 differential temperature core power
What is RODMON?
- Determines and displays the following and provides an audible PPC alarm for those with an asterick:
- -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)
- -4 inch deviation
- -8 inch deviation *
- -out of sequence (OOS)*
- -power dependent insertion limit (PDIL)*
- -pre-power dependent insertion limit (PPDIL)
RO-22 control rod drop times prerequisites
- Mode 3 with greater than 525F with 4 PCPs running
- -what rods would see when required to drop
- RPS reset-allows rods to trip
- LCO 3.3.9 neutron flux monitoring channels met
- If both groups of SD rods are being withdrawn during the test, PCS boron concentration shall be >/= all rods out critical boron +50 ppm
- -ensures adequate SDM exists
- If only 1 rod is being tested at a time, SDM is maintained >/= 2%
- If at any time during performance of this test, a sustained count rate of twice the base count rate is observed, trip the RX
8 inch deviation processing
- PIP determines the state of the 7, 8 inch group deviation contacts
- Initiates "rod position 8 inches deviation" alarm
Why can no more than 1 control rod be withdrawn until after a bubble is established in the PZR?
Establishes a steam bubble and normal water level to protect from PCS overpressure while the plant is in a solid state with a multiple rod withdrawal
What happens when the magnetic clutch is deenergized?
- The drive shaft is disconnected from the motor and brake, allowing the shutdown and regulating rods to fall into the core by gravity
- Part length rods do not have magnetic clutches, they do not trip
Purpose of the control rod clutch toggle switches?
- Individual rod clutches can be deenergized with toggle switches for each rod
- Located inside the RPS cabinets
Inputs to PIP?
- Analog inputs
- -45 synchro positions
- -loop 2 differential temperature
- Digital inputs
- -45 rotary switch positions
- -rod drop timing start
Why are control rod manipulations recommended to be made in 33 inch increments and not to exceed 35 inches?
Prevents getting the 4 inch deviation alarm
PIP node power supply?
How many inches withdrawn is considered fully withdrawn?
- Withdrawn >/= 128 inches
- Should be withdrawn to the upper electrical limit
- -this ensures an even burnout of all fuel assemblies
Watch dog timer processing
- PIP must maintain the watchdog timer, which is implemented using a programmable delay timer card.
- If the software for any reason fails to update this watchdog timer or power is lost, you will get a PIP trouble alarm
Control rod drive magnetic clutch power supplies?
Y-30 and Y-40
Purpose of the control rod drive system?
- Provides short term reactivity control by positioning neutron absorbing control rods within the core
- Furnishes a quick RX shutdown mechanism through rapid control rod insertion
- Provides position indication of the control rods within the core
Why do we align control rods when any 2 control rods within a group are >/= 2 inches apart?
- Prevents getting the 4" deviation alarm
- Prevents wearing out the contacts due to more frequent alignments
When is PIP system for shutdown and regulating rods considered operable?
- If digital position readout or the PPC display provides valid rod position OR
- If the cam operated matrix light (reg rods) gives positive (on) indication of rod position
EK-0947 "Emergency rod drive power interrupt"
- Indicates rod mode selector switch is in emergency off "EM off"
- No redundant indications
SPI node power supply?
Function of the anti-reverse feature of the CRDM magnetic clutches?
- Functions when the clutch is deenergized
- Ensures a control rod is forced down into the core by the motor if necessary in the event of a reactor trip
- Prevents upward forces from forcing the rod out of the core
- Has a pawl system
What is required if more than 1 control rod drive is electrically disconnected at the same time? Why?
- A local physical verification shall be made of the individual control rods involved
- -ensures the correct motor has been connected to the proper rod
Magnetic CRDM clutch power supplies
- Y-30 and Y-40
- Either Y-30 or Y-40 can supply all the clutches. A loss of one will not cause a loss of power to any of the clutches.
Rod drop timing
- Allows operators to acquire a drop time profile of a rod under test.
- All normal PIP activities suspended except the watchdog timer
- PIP system is used exclusively for acquiring the profile of the rod drop
Primary position indication (PIP)
- Uses synchro transmitter
- 264 degrees of synchro rotation for full rod travel
- Accuracy to =/- 0.5%
- Powered from Y-20
- Input to PIP node of the PPC
When is the SPI considered operable for shutdown and regulating rods?
- When the magnetically operated reed switches are providing valid indication either via the PPC or by direct readings of the output of the reed switches OR
- If the reed switch operated red matrix light (shutdown rods) gives positive indication of rod position
Upper sequential permissive processing
- PIP software determines state of the 3 USP contacts based on position of the group target rods in reg groups 1,2,3
- The USP contacts are used in manual sequential (MS) raise logic
Out of sequence processing
- PIP determines the state of the OOS contact based on the positions of the target rods in the regulating groups
- If you have a bad target rod, then no OOS processing is completed
- If an OOS condition is detected, annunciator "Control rods out-of-sequence" is recieved
- -78.5" to 81.5"
Upper rod stop processing
- PIP determines the state of the 45 sets of upper rod stop contacts
- Processing suspended for any rod with a bad synchro
- Upper rod stop contacts stay "as is" if either the PIP loses power or if the synchrotransmitter fails
- URS contacts used in
- -core matrix logic
- -manual sequential (MS) raise logic
- -manual group (MG) regulating and power shaping rod logic
EK-0971 "SPI trouble"
- A failure of the SPI node will cause watchdog timer to not be reset bringing in the alarm.
- SPI is lost
- Alarms on the PPC are lost for:
- -control rod out of sequence
- -PPDIL and PDIL
- -4 inch and 8 inch deviation
- Validated with the PPC status page and control rod page
- Analog outputs
- -45 rod positions (in inches) to host
- -Loop 2 differential temperature "core power"
- -Rod drop timing data
- Digital outputs
- -Rod control relays
- -Digital rod displays
Rod matrix C-12
- Lights powered from Y-01
- Shutdown rods reach an upper limit reed switch at 131 inches which turns on the red light
4 inch deviation processing
- PIP software determines state of the 7 four inch deviation contacts
- Contacts used to initiate "Rod position 4 inches deviation" alarm
What happens if the CRD break fails?
Brake won't disengage and could burn up the motor
Control rod drive seal packages
- PCS pressure boundary prevents PCS from leaking into upper housing where it could reach indication components
- CRDM leakoff is directed to the containment sump, preventing pressure buildup above the seal
- Cooling jacket surrounds seal area to maintain temperature of the seal and o-rings below 250F. Cooled by CCW.
Lower sequential permissive processing
- PIP software determines state of the 3 lower sequential permissives (LSP) contacts based on the position of group target rods for regulating groups 2,3,4
- The LSP contacts are used in manual sequential (MS) lower logic
When is the primary rod position indication system for part length rods considered operable?
- Digital position readout or PPC display provides valid rod position indication OR
- The cam operated red matrix light (for part length) gives positive (on) indication of rod position
When CRDM motor loses power what happens?
- Will not affect control rod position
- CRDM will not move unless tripped
- Brake engages when de-energized
Power dependent insertion limit (PDIL) processing
- PIP calculates PDIL for each regulating group and determines the state of the 4 PDIL contacts based on target rod position
- If core power signal is invalid, get a PDIL alarm
- If a PDIL condition is detected, you get an alarm for the group
EK-0954 "Rod drive seal leak off hi temp"
- Seal leakoff temp >200F
- -Take seal leakage measurement ASAP
- -Check status of CCW to/from containment
- -Check containment sump
Control rod interlocks
- Group selector switch prevents simultaneous withdrawal of groups of rods when in manual group (only 1 group selected at a time)
- Regulating rods cannot be withdrawn any amount in group until each S/D rod withdrawn above its regulating rod withdrawal interlock (LS-3 @ 122" on each S/D)
- S/D rods can't be inserted below 122" when regulating rods is > 6 inches
- Lower rod stop at 4". LEL stops rods @ 3 inches
- Upper rod stop @ 130"
- Upper electrical limit stops rods @ 131"
- Rod withdrawal prohibit
What are the regulating rod indications on the rod matrix?
- Lower limit switch (3 inches)
- -turns on the green light when inserting
- -turns off the green light, turns on the white light when pulling rods
- Upper limit switch (131.5 inches) cam operated
- -turns off the amber light, turns on the red light
- At 130 inches the amber light on and the white light is off (upper rod stop reed switch)
What is the regulating rod sequencing/overlap?
- In order for group 1 control rods to be sequenced in or out, the selected group 2 rod must be <52 inches
- In order for group 2 control rods to be sequenced either in or out, 2 conditions must be true:
- -the selected group 1 control rod must be >80 inches
- -the selected group 3 control rod must be <52 inches
- In order for group 3 rods to be sequenced the following 2 must be true:
- -the selected group 2 rod must be > 80 inches
- -the selected group 4 rod must be <52 inches
- In order for group 4 rods to sequence either in or out, the selected group 3 rod must be >80 inches
Pre power dependent insertion limit (PPDIL) processing
- PIP calculates the 4 PPDIL and determines the state of the 4 PPDIL contacts based on group target rods
- PPDIL=PDIL + 10"
- If a PPDIL condition is detected, you get an alarm for that group.
LCO 3.1.5: Shutdown and part-length control rod insertion limits
LCO 3.1.5: All S/D and part length rod groups shall be withdrawn to >/= 128 inches.
- APP: Mode 1, Mode 2 with any regulating rod withdrawn above 5 inches
- -this is not applicable when doing the rod exercise test.
- -1 or more S/D or part length rods not within limits
- --declare the affected control rods inoperable and enter applicable conditions and required actions of LCO 3.1.4-IMMEDIATELY
What indications do you have on the rod matrix for part length rods?
- Lower limit
- -turns on the green light when inserting
- -turns off the green light when pulling
- -the white light is only on when the rod is moving
- Upper limit switch (131.5 inches) cam driven
- -turns off the amber light, turns on the red light when you are pulling rods
- 130 inches (upper rod stop reed switch)
- -turns on the amber light
How many rods are in each group?
- Shutdown rods
- -group A
- --12 rods
- -group B
- -8 rods
- Regulating rods
- -group 1
- --8 rods
- -group 2
- --4 rods
- -group 3
- --5 rods
- -group 4
- --4 rods
- Part length rods
- --4 rods
What does rod withdrawal prohibit (RWP) do, and what brings it in?
- Prevents rod withdrawal in Manual Sequential (MS), Manual Group (MG), or Manual Individual(MI)
- Brought in by:
- -1 out of 4 for high power rate pre-trip (1.5 dpm) between 10-4% and 15% power
- -2/4 for variable high power pre-trip, minimum of 28.5%, variable setpoint of 13.5% above reset power, or a maximum of 105%
- -1/4 for removal/failure of the RPS bistable high power rate pre-trip/trip <15% power
- -Rod mode select switch in "EM OFF"
Secondary position indication (SPI)
- Uses the reed switches and a magnet
- Powered from Y-40
- Accuracy +/- 1.5 inches
- SPI node on the PPC
Group target rod processing
- PIP software determines the 7 group target rod selections based on the rod control selector switches
- Target rod positions are provided to the PPC for use in manual sequencing and in determining the PDIL and the PPDIL
- If target rod position is bad, PPC processing is suspended for the programs using the "bad" group target rod.
- -no contacts or more than one contact closed on a switch
CRDM motor power supplies
- CRD transformers 45 and 46
- Powered from MCC-1 and 2
- 120 VAC
- Transformer 1 is off of MCC-2
- Transformer 2 is off of MCC-1
Per Techspec 3.1.4. Control Rod Alignment What do you do if:
If one or more shutdown rods are inserted beyond the insertion limit,
- Condition 3.1.5 A is entered;
- the rods are declared inoperable and Condition 3.1.4 D (when one rod is immovable but trippable) or Condition 3.1.4 E (when a movable rod is inserted beyond its insertion limit, or when more than one rod is inoperable for any reason) must be entered.
- If the rods can be moved, they should be withdrawn and all Conditions exited.
- If one rod cannot be moved (but is still considered trippable), operation may continue in accordance with Condition 3.1.4 D (and 3.1.4 C if it is misaligned).
- If more than one rod cannot be moved, Condition 3.1.4 E must also be entered. The plant must be in MODE 3 in 6 hours in accordance with ACTION 3.1.4 E.1.
- If one or more part length rods are inserted beyond the limit, Condition 3.1.5 A is entered; the rods are declared inoperable and Condition 3.1.4 E is entered (and 3.1.4 C if it is misaligned). Condition 3.1.4 D is not applicable to part-length rods since it only addresses full-length rods.