Rod Ctrl Flashcards
What is the C-1 Conditional?
Intermediate Range Rod Stop
- Stops AUTO and MANUAL Rod Withdraw
- 1/2 - IRNI > 18% (16%)
- Manually blocked above P10 (≥ 10% PR)
- Unblocked below P10
What is the C-2 Conditional?
Power Range Rod Stop
- Stops AUTO and MANUAL Rod Withdraw
- 1/4 PR > 103%
- Blocked when ROD STOP BYPASS selected to alarming channel
What is the C-3 Conditional?
OTΔT Rod Stop
- 2/4 PRNI 3% < trip setpoint
- Stops AUTO and MANUAL rod withdraw
- No Block!
What is the C-4 Conditional?
OPΔT Rod Stop
- 2/4 PRNI 3% < trip setpoint
- Stops AUTO and MANUAL rod withdraw
- No Block!
What is the C-5 Conditional?
Turbine Power Interlock
- MPC-253 < 15%
- Stops AUTO ONLY rod withdraw
- No Block!
What is the C-11 Conditional?
Control Bankd D Rod Stop
- Ctrl Bank D at 229 steps
- Stops AUTO ONLY rod withdraw
- No Block!
What are the Rod Ctrl Inputs?
- Auctioneered High Tave
- Auctioneered High PR NI
- MPC-253, Turbine 1st Stage Impulse #
What is the Rod Control System designed to do?
Maintain Tavg within 5°F of program and restore Tavg within 1°F following:
- 10% step load change
- 5%/min ramped load change
- 50% step load change with steam dumps (40% dumps)
Where are the MG Sets powered from?
11/21A and 11/21D busses
What will trip the CRD MG Set Output Bkrs?
- Overvoltage
- Overcurrent
- Reverse Current
- Supply Bkr Open
What will trip the CRD MG Set Supply Bkrs?
- Load Con
- Overcurrent
If there is an urgent failure in the power cabinet, what is affected?
Rod Control
Rod groups for that cabinet
If there is an urgent failure in the logic cabinet, what is affected?
ALL RODS
What happens if you have an urgent failure on a Logic or Power Cabinet?
Stops all rod motion by de-energizing lift coil and energizing stationary and movable gripper
During a power escalation, Control Bank C – Group 1 Rod B-8 dropped. At the time the event occurred, reactor power was 48% and Rod B-8 was fully withdrawn.
While recovering the rod per 1-OHP-4022-012-005, Attachment B, “Recovery By Positioning Single Rod,” a Rod Control Urgent Failure alarm occurred.
Why was this alarm actuated?
All Control Bank C – Group 2 rod lift coil disconnect switches are open.
Given the following conditions:
* Unit 1 is at 100% power
* A loss of power to CRP-3 occurs
What is the effect on the Rod Position Indication (RPI) system and the procedural action necessary, if any?
RPI indications are lost. Dispatch an operator to manually align backup power supply (via ELSC) to energize the RPI Cabinets. Operation is allowed since RPI has been restored.
What does the Variable Gain Unit do?
Increases the output at low power because reactivity change at lower power has a smaller effect on power than at high power
At what speed do the shutdown banks move?
62 SPM
At what speed do the rod ctrl banks move in auto?
8-72 SPM
- Error of 1.5-3 degrees = 8 steps per minute
- Error of 3-5 degrees = 32 steps per Degree + 8
1.5-3 degrees - 8 steps
3.5 degrees - 24 steps
4 degrees - 40 steps
4.5 degrees - 56 steps
5 degrees - 72 steps
At what speed do the rod ctrl banks move in manual?
48 SPM
What is Differential Rod Worth?
The change in reactivity resulting from a unit change of rod position. (pcm/step)
What is Integral Rod Worth?
Reactivity inserted by moving a control rod from a reference position to any other rod height
When does the Rod dropped/Rod Bottom alarm clear for Control Bank A?
When all shutdown Banks are withdrawn AND Control Bank A gets to 20 Steps
If MPC-253 fails low, what happens with rods in automatic? Why?
Rods will step in due to PR rate change and temp error
When does the Rod Dropped alarm enabled for Control Banks B-C?
When demand is > 35 steps for that group
When does the Rod Dropped alarm annunciate for Control Banks B -C?
When IRPI is < 20 steps with a demand > 35 steps, AFTER the alarm has been enabled.
When do Rod Bottom lights clear for the control banks?
When the rods are withdrawn > 20 steps
If MPC-253 fails high, what happens with rods in automatic? Why?
Rods step OUT due to power rate of change and temperature error
If Tavg fails high, what happens with rods in automatic? Why?
Rods step in due to the temperature error
If Tavg fails low, what happens with rods in automatic? Why?
NOTHING! Rod control uses auctioneered high Tavg
If a Power Range NI fails low, what happens with rods in automatic? Why?
Nothing! Rod control uses auctioneered high
If a power range NI fails high, what happens with rods in automatic? Why?
Rods step in due to the power rate of change.
If you have a PR NI Failure high, will rods step back out due to the temperature error afterwards?
It depends. If C2 (103% on 1/4 PRNI) is met, NO. If the failure is less than that setpoint, yes, they will step back out
What is the purpose of bank overlap?
Provides a more uniform axial power distrubtion as well as a more uniform Differential Rod Worth
When moving which rods would you expect no indication on your rod speed indicator?
Shutdown Banks C and D
If a rod is dropped, is the effect on axial or radial power distribution more noticable?
Radial power distribution
Will dropping a peripheral or center control rod have more of an effect on the radial power distribution?
Center Rod
If a rod is inserted 20 steps, is the greater effect on radial or axial power distribution?
Axial
What is the purpose of maintaining QPTR within limits?
It keeps radial power distribution within limits
What is the purpose of maintaining raidal and axial core power distribution within limits?
It keeps power density (kw/ft) and DNBR within limits
What provides the Reactor Power input to the rod insertion limit comparator?
RCS Delta-T
What is the normal source of power to the Rod Control Logic Cabinets?
120 VAC stepped down from Rod Drive MG Set Output
Given the following conditions: Unit stable at 75% power w equilibrium Xe. Rod control is in auto. Rod height is 180 Steps on CB D. PR Channel N-44 fails High. Which one of the following describes the response of the Rod Control system? The control rods will….
Step in until the power mismatch circuit output decays away
