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CRDM Groups 1-4: Safety Groups, fully withdrawn during s/u
CRDM Groups 5-7: Regulating Rods, withdrawn in sequence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