CRD Flashcards by Spenser Mayden

EO 1 - Purpose of CRD system

Control Rx power

Reactivity Control based on CRDM and soluble boron

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CRDM Groups 1-4: Safety Groups, fully withdrawn during s/u
CRDM Groups 5-7: Regulating Rods, withdrawn in sequence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

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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)

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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

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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.

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EO 4 cont’d - Specify rod group configurations that satisfy the reason for sequential operation of rod groups.

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Which CRDM component is considered the RCS pressure boudnary?

motor tube

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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)

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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.

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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.

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List DC hold buses

A and CC phase

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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

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Describe Trip Confirm Lamp

When lighted, indicates that power to the CRDM’s has

been interrupted allowing rods to drop into the core.

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Describe asymmetric rods lamp.

any control rod 6.5% out of alignment from its group average

Sends signal to OUT INHIBIT

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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.

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How many phases need to be energized to keep rod from dropping?

1 phase

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What method of sequencing is used to move rods in or out?

3-2-3 movement

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Max stator temp, requiring de-energizing the CRDM, is ____

180F

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Max temp of cooling water entering the CRDs is _____

120F

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Min allowable cooling water temp is _____

60F

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Min allowable RC temp for ICW to be aligned to de-energized

CRD stators is _____.

200F

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During stator replacement, max stator temp w/o ICW flow is

_____

160F

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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.