CRD Flashcards
EO 1 - Purpose of CRD system
Control Rx power
Reactivity Control based on CRDM and soluble boron
EO 2 - List functions of each control rod group.
CRDM Groups 1-4: Safety Groups, fully withdrawn during s/u
CRDM Groups 5-7: Regulating Rods, withdrawn in sequence
CRDM Group 8: Axial Power Shaping Rods, shape the flux
EO 3 - Differentiate normal power supplies for the rod groups.
A train from B631
B train from breaker A501 and X8 xfrmr
6 phase xfrmr steps down 480 VAC (3 phase) to 120VAC (6 phase) THEN diode or SCR into 120VDC (6 phase)
EO 3 cont’d - Breakdown how each group is moved.
6 phases od DC through diodes give RIPPLE DC
Safety Groups 1-4: Diodes
Reg groups 5-7, APSRs, Aux power supply: SCR
EO 4 - Reason for sequential operation of rod groups.
Safety (1-4) and APSRs are pulled 1 group at a time.
Reg Rods (5-7) are moved in sequence. top and bottom 20% of groups are overlapped. more even reactivity addition.
EO 4 cont’d - Specify rod group configurations that satisfy the reason for sequential operation of rod groups.
Which CRDM component is considered the RCS pressure boudnary?
motor tube
EO 6 - Interpret the operation of the CRDM motor, mainly how the DC input signal is translated into linear movement of the control rod.
3 phase 480VAC stepped down to 6 phase 120VAC, then rectified via SCRs to a ripple DC
Programmer has 6 banks of SCRs for DC magnetic fields (A, B, C, AA, BB, CC)
EO 8 - Describe power dist. system as it pertains to the CRDMs: connecting the major components from source of power to CRDM stator.
‘A’ AC breaker receives 480VAC from B631.
‘B’ AC breaker receives 480VAC from A501 and X8.
EO 10 -How programmer control circuits control SCR gating to provide power to the CRDMs.
Uses solid state microcomputer to generate commands.
15VDC for programmer controls
24 VDC for gating power to the SCRs
Gates SCRs in 3-2-3-2 to move rods.
List DC hold buses
A and CC phase
EO 11 - Analyze how an automatic or manual reactor trip
removes power from the CRDM’s, including the CRD and
RPS trip logic/interface.
All brkr trips use RPS actuation Undervoltage trip relay to de-energize the trip relays and OPEN the the breaker
“A” RPS to “A” CRD Breaker
“B” RPS to “B” CRD Breaker
“C” RPS to “CC” Breakers and “E” Relays
“D” RPS to “DD” Breakers and “F” Relays
Describe Trip Confirm Lamp
When lighted, indicates that power to the CRDM’s has
been interrupted allowing rods to drop into the core.
Describe asymmetric rods lamp.
any control rod 6.5% out of alignment from its group average
Sends signal to OUT INHIBIT
What are the ball check valves needed for?
They allow fluid movement through motor tube to prevent vacuum binding and slow drop times during control rod movements.
How many phases need to be energized to keep rod from dropping?
1 phase
What method of sequencing is used to move rods in or out?
3-2-3 movement
Max stator temp, requiring de-energizing the CRDM, is ____
180F
Max temp of cooling water entering the CRDs is _____
120F
Min allowable cooling water temp is _____
60F
Min allowable RC temp for ICW to be aligned to de-energized
CRD stators is _____.
200F
During stator replacement, max stator temp w/o ICW flow is
_____
160F
Max CRD travel is ____ inches per hour
420in/hr
Max CRD run time is ___ min per hour.
30 min per hour
CRDM Stator High Temp Computer Alarm is set at ____F.
113F
IF more than one CRD stator in Groups 1-7 exceeds _____,
THEN:
TRIP the Reactor
180F
list both rod speeds:
RUN = 30”/min
JOG = 3”/minute
Fail Safe Commands
IN commands override OUT commands
Both sides (P & S) OUT commands required
If both speed commands are present, then it is a HOLD command.
DROPS actuation will only trip the ______ rods, however that requires an RPS failure.
Regulating rods
What is a SHUNT trip?
An energized trip
Undervoltage acutates a contact to supply ____ to the SHUNT trip relay to energize.
125 VDC
Undervoltage is ____________ to trip.
de-energized
Transformer over-voltage of ____ VAC has an alarm.
____ VAC for 10 seconds trips the respective ‘A’ or ‘B’ brkr.
130
140
Source Interruption Device (SIR) provides additional system protection, how?
AC overvoltage on the output of the xfrmr
DC undervoltage on the DC hold busses
DC undervoltage must occur on which side to trip its respective breaker?
both sides
describe absolute position indication (API)
2 ind reed switch strings that actuate a 5 volt divider circuit
closing the reed switches as the permanent magnet attached to the torque taker passes the reed switches
Describe function of Relative Position Indication (RPI).
Uses the “A” “C” and “BB” “PHASES” to drive a stepping motor
direction of the phases being energized and de-energized
determine the indication “IN or “OUT”
RPI only works when the rod is being moved, if the RX trips RPI
indicates full out
RPI is reset by running a stepping motor on the PI panel and selecting the specific group once the RX is shutdown and prior to
startup
distances for asymmetrical rod fault
Hi fault >9’ (6.5%)
Lo rod fault 7” (5%)
RPI provides:
- Individual indication
- Group average in the CRD room
- Sequence fault
- Computer indication
Describe Out Inhibit Lamp
control rods will not respond to any out command.
<10% power AND >2DPM SR OR >3 DPM IR OR >40% power AND EITHER Asymm Rod Fault 6.5% OR Loss of any safety group out limit
Describe Sequence Inhibit Lamp
indicates excessive overlap between regulating groups (>25%).
Describe Auto Inhibit Lamp
IF Diamond in manual: -Loss of any safety group OUT limit - >+-1% neutron error -Loss of ICS power IF Diamond in AUTO: -only loss of ICS power will bring in lamp and shift diamond to manual
Describe APSR Overlap Fault Lamp
bottom of group 6 within 2% of the top of the poison section of group 8
Describe Out limit lamps
Groups 1 - 8 (red): Indicates that at least one rod out of its respective
group is at the out limit.
This will stop rod withdrawal for all rods within that group.
What feeds sequence inhibit lamp
RPI
Describe Control On lamps
White lights that indicate a particular group has been selected for transfer OR
they have aux power
Describe In Limit Lamps
Group 1 - 8 (green): Indicates that at least one rod in that group is at the “in limit”.
This will stop rod movement in the “In” direction for that group.
Asymmetric Runback Req’s
–>40% power and in AUTO
- Loss of any Safety group OUT limit
- Group 5 in limit and asymmetric fault
- Group 6 in limit with Group 5 > 80% and asymmetric fault
- Group 7 in limit with Group 6 > 80% and asymmetric fault
TS 3.1.4 Control Rod Group Alignment
Each CONTROL ROD shall be OPERABLE and
aligned to within 6.5% of its group average height.
Modes 1 & 2
TS 3.1.5 Safety Rod Insertion Limits
Each safety rod shall be fully withdrawn.
Modes 1 & 2
TS 3.1.6 APSR Alignment Limits
Each APSR shall be OPERABLE and aligned
within 6.5% of the group average height.
Modes 1 & 2
TS 3.1.7 Position Indicator Channels
The API channel and RPI channel for each
CONTROL ROD and APSR shall be OPERABLE.
Modes 1 & 2
3.2.1 Regulating Rod Insertion Limits
Regulating rod groups shall be within the physical
insertion, sequence, and overlap limits specified in
the COLR.
Modes 1 & 2
3.2.2 APSR Insertion Limits
APSRs shall be positioned within the limits
specified in the COLR.
Modes 1 & 2
TS 3.3.4 CRD Trip Devices
The following CRD trip devices shall be OPERABLE:
a. Two AC CRD trip breakers;
b. Two DC CRD trip breaker pairs; and
c. Eight electronic trip assembly (ETA) relays.
Modes 1 & 2
Modes 3, 4, 5 with any CRD trip brkr in closed position & the CRD system capable of rod withdrawal.
