Systems Exam 3 - Rod Control Flashcards
(40 cards)
Lift Coil Disconnect Switch - Location and Purpose
Lift coil disconnect switch provided for each rod and contained in a single cabinet in the back on the MCB CB07. These switches allow disconnecting the lift coil to prevent a rod from moving. Provides ability to withdraw a single rod for dropped or misaligned rod.
Toggle switch UP to disconnect.
CBO (Control Bank Offset) - Definition and Purpose
CBO: Process of moving all control banks in or out over core life to minimize wear to the rodlets. Also done to minimize fretting of the rods. The total span used is 9 steps.
- Offset of 1 raises rod height by 1, 2 raises 2, etc.
- 222+0, 223+1, 224+2, 225+3, 226+4….231+9
Metal Impact Monitoring Systems function
The Metal Impact Monitoring Systems function is to prevent the Loose Parts Monitoring System (LPMS) from inadvertently generating an alarm when the rods are stepped.
How does uPC1 failure affect rod control?
→uPC1 failure will cause T-ref to drop due to loss of PT-505
→rods drive inward in auto
Rod Speeds in Manual? In Auto? For SB-C, D and E?
In Manual:
→control banks move at 48 steps/min
→shutdown banks move at 64 steps/min (only when that individual bank is selected on switch)
→Reactor Control System provides input to Rod Control to tell rods what to do based upon plant conditions (Rod Bank Selector Switch must be in auto)
→rod speed indication for SB-C, D and E reads 0, but they actually move at 64 steps/min
Non-Linear Gain Function
Non-Linear Gain looks at error signal and changes rod speed based upon amount of error.
Variable Gain Function
→Variable Gain compares turbine power to error signal and for higher power levels it decreases the rod speed to minimize potential overshoot
→at lower power levels it may increase the rod speed →compares Auctioneered Hi NIS and Turbine 1st Stage Impulse Pressure (PT-505 or PT-506, selectable), then goes through rate comparator to develop power mismatch function (may cause rods to change speed based on rate mismatch)
List Rod Stops
→C1: stops any outward rod motion, IR Rod Stop IR Amps ~ 20% (1/2)
→C2: stops any outward rod motion, PR Hi Flux 103% (1/4)
→C3: stops any outward rod motion, OT N16 (2/4) 3% below trip setpoint
→C4: stops any outward rod motion, OP N16 (2/4) 3% below trip setpoint (109% normal)
→C5: stops only automatic outward rod motion, Turb Pwr < 15% (1/1) (PT-505 or 506, selected via switch on CB-07)
→C11: stops only automatic outward rod motion, CB-D > 223 steps
Rod Control Block Diagram
Inputs to Rod Control
→auctioneered Hi N-16 goes to Rod Insertion Limit monitor (graph available in COLR)
→supports Tech Specs
→compares rod position to power to determine if rods are too far in and provides alarm
→auctioneered Hi NIS used to compare to Turbine 1st stage impulse pressure to generate power mismatch
→Average T-ave compared to T-ref to develop error signal
→Reference T-ave (a.k.a. T-ref) supplied from 1st Stage Turbine Impulse Pressure (PT-505 or PT-506, Selectable)
Rx Trip and Bypass Breakers Auto and Manual Trips
→RTBs are the only safety related components of Rod Control
→bypass breakers DO NOT get shunt trip on automatic trip signals
→bypass breakers get a shunt trip AND UV trip on manual only
→main breakers have both shunt and UV trip on automatic as well as manual
→SSPS A Train goes to RTA and BYB, B Train goes to RTB and BYA
→with an SSPS train in test, its associated RT breaker can be tested without causing a reactor trip (auto trip signals will open the breaker) while Bypass breaker is connected
→BUT… all breakers will open on a manual trip
Note: loss of uED1 or uED2 will prevent shunt trip, but UV trip will still be available.
How do Shunt Trip and UV Trips Work?
Shunt Trip: once energized, uses mechanical force to force breaker open
UV Trip: once de-energized, releases spring to force breaker open
How Does DC Hold Cabinet Work? How does it work on a Rx Trip if in use?
→DC Hold power applies DC hold voltage to the stationary gripper coil to hold the rods such that when normal power to the stationary gripper is removed, the rods stay in position
→Group Hold Switch positions: OFF, LATCH, and HOLD
→Latch is 125 VDC; Hold is 70 VDC
→Latch position applies greater voltage to ensure stationary gripper is properly latched
→only one group can be held at a time, only one not in OFF at a time
Bank Overlap. How many steps, and why?
→107 steps of bank overlap, done to control flux shape and even out rod worth
→107 steps of overlap means 2 banks are moving together for 107 steps
→individual thumbwheels provided (total of 6) are set to tell when to start and stop rods from moving based upon total number of steps counted
→115 step overlap means when CB-A at 115 steps, CB-B starts to step (0 with all control banks in, 452 control bank C all the way out, adjusted in + direction only if required to adjust manually)
- S1: 115 steps on CB-A, start CB-B
- S2: 222 steps Stop CB-A, CB-B at 107 steps
- S3: 230 steps start CB-C, CB-B at 115 steps
- S4: 337 steps stop CB-B, CB-C at 107 steps, CB-B at 222 steps
- S5: 345 steps start CB-D, CB-C at 115 steps
- S6: 452 steps stop CB-C, CB-D at 107 steps, CB-C at 222 steps
- With CB-D all the way out counter should read 560 steps (no CBO)
- If reset then it sees that CB-A needs to be first moved (not good at power)
- Bank overlap and step overlap only affects control banks
Pulse to Analog Converter (P/A) Purpose, Inputs, Outputs
→provides input along with Auctioneered Hi N-16 to RIL monitor
→individual slave cyclers send signals to P/A Converter in order for it to track bank position
→since it only tracks signals, indication could be incorrect if signal is sent and rods do not actually move
→toggle switches on front of converter allow for manual adjustment of bank rod position
→located in back of DC Hold cabinet, only tracks control banks
Control Rod Control S/U Reset Pushbutton Resets What?
→located on CB-07
→should never be used with rods pulled - resets the entire system, which will require manually resetting each individual counter, Master cycler, Bank overlap, etc.
→does not cause a reactor trip, just a headache; rods will stay in place
→no effect on DRPI
→used to reset the rod control system prior to startup
→if not reset prior to startup, Bank Overlap unit will not work as designed
Resets the following (POSSUM):
P- P/A converter,
O- Bank Overlap,
S- Slave Cycler,
S- Step Counters,
U- Urgent Alarms,
M- Master Cycler
Urgent Failure In Logic Cabinet
If failure is in logic cabinet, it stops rods in all power cabinets except SCDE
Power Cabinet Urgent Failures:
LLRPM
→Logic failure: simultaneous zero current order to stationary and movable grippers
→Loose or removed circuit card
→Regulation failure: coil current does not match the current order within a preset time or a full current order is on too long. This protects against dropping rods or overheating the coils
→Phase failure: voltage to coils has excess ripple. This would mean that one of the three phases of AC was being processed differently than the others, perhaps due to a blown fuse, a thyristor that has lost gate control, etc.
→Multiplexer error: wrong rods trying to move- locks up rods in that cabinet
Logic Cabinet Urgent Failures:
SLO
Stops all rods except SCDE from moving
→Slave cycler Failure: slave cycler receives a “GO” pulse before completing the previous step, initiates a step without receiving a “GO” pulse, or receives a “GO” pulse without initiating a step
→Loose or Removed circuit card
→Oscillator Failure: fails to generate pulses when signaled
Non-Urgent Failure caused by…
Loss of a power supply (Logic or Power Cabinet).
Amber light (PS) provided on locally on each cabinet; alarm provided on CB-07
During a Reactor startup, when will 1-ALB-6D/3.7, “ANY ROD AT BOT” clear?
When CB A rods clear 12 steps withdrawn
What are the inputs to the Rod Insertion Limit Monitor?
→Bank position from P/A converter
→Auctioneered High N-16
→Ave T-ave (set to zero)
The rod control system looks at what to determine rod speed and direction?
→the magnitude of the difference between turbine load (T-ref) and Ave T-ave
AND
→the RATE OF CHANGE between turbine load (1st stage impulse pressure) and Auctioneered Hi NIs.
Power cabinet 1BD supplies power to which banks?
Control Bank B group 1
Control Bank D group 1
Shutdown Bank B group 1
