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LOIT 2024 > CEDMCS > Flashcards

CEDMCS Flashcards

1
Q

Where does CEDMCS send signals on a Reactor Trip?

A

Main Turbine for tripping
DFWCS for RTO
SBCS for QOB
ERFDADS for indications
SRP Downtown

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2
Q

How long does it take to drop rods?

A

4 seconds

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3
Q

How far is one step for a Control Element Assembly (CEA)?

A

0.75 inches

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4
Q

At how many steps does the Upper Electrical Limit occur?

A

200 steps

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5
Q

At how many steps does the Lower Electrical Limit occur?

A

1 step

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6
Q

What functions does the Dropped Rod Contact serve in CEDMCS?

A

The rod bottom light on B04

Tells the Plant Computer to zero the pulse counters.

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7
Q

Which rod inhibition can be bypassed?

A

CWP
(CEA Withdrawl Prohibit)

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8
Q

When is an (Automatic Motion Inhibit) AMI enacted?

A
  • > 5% deviation between redundant indicators for TLI, Reactor Power, and Tave when AVERAGE is selected on RRS
  • Whenever Reactor Power < 15%
  • When TLI < 15% and Reactor Power is below the lesser of
  • SBCS availability + TLI or…
  • AMI threshold setpoint.
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9
Q

When is an Automatic Withdrawl Prohibit (AWP) enacted?

A

From Reactor Regulating System
* Tave > Tref by 6F
* Tcold > 575F*

From SBCS
* Actual Steam bypass demand signal present
o TURB BYP DEMAND alarm will be in

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10
Q

What are the power supplies to the CEDMCS MGs?

A

NGN-L03
NGN-L10

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11
Q

Is one CEDMCS MG enough for control rod operation in Manual Group?

A

No. But it is enough for Manual Individual operation

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12
Q

When does Supplementary Protection System (SPS) open the CEDMCS MG output contactors and open the Trip Circuit Breakers?

A

2409 psia

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13
Q

From where can you open the Trip Circuit Breakers?

A
  • B05
  • Locally
  • PPS Cabinets (testing)
  • SPLA Cabinets (testing)
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14
Q

From where can you close the Reactor Trip Switchgear Circuit Breakers?

A
  • PPS Cabinets (normal)
  • Locally (testing)
  • SPLA Cabinets (not OPS)
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15
Q

What is the purpose in the CEDMCS MG flywheels?

A
  • Flywheels maintain > 58 Hz on a 1 second power interruption.
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16
Q

What results from any CEA subgroup being placed on the Hold Bus?

A
  • CEDMCS Trouble Alarm
  • Rods on Hold Bus won’t move in Manual or Auto
17
Q

When rods move, what speed do they move?

A

30”/min or 3”/min in manual

    • Auto Sequential: Auto RRS control of sequential Regulating Groups (requires Plant Computer)
      o Insert at 30”/min or 3”/min
      o Withdraw at 3”/min
18
Q

What happens to CEDMCS on a loss of PNA or PNB?

A

The associated RTCBs open (A and C or B and D) but power is maintained to the CEAs

19
Q

What happens to CEDMCS on a loss of PNC?

A
  • RTCBs A and C open
  • Pac-Man on Core Mimic
  • Pulse Counters for the lit Rod Bottom Lights will zero
  • Manual Individual only method available for moving the remaining 1/4 of the rods
20
Q

What happens to CEDMCS on a loss of PND?

A
  • RTCBs B and D open
  • Reverse Pac-Man on Core Mimic
  • Pulse Counters for the lit Rod Bottom Lights will zero
  • Manual Individual only method available for moving the remaining 3/4 of the rods
21
Q

What happens to CEDMCS on a loss of NNN-D11 or NNN-D12?

A

Nothing

22
Q

What happens to CEDMCS on a loss of NNN-D11 AND NNN-D12?

A
  • All CEAs will drop into the core.
  • No Core Mimic, UEL, or LEL lights (during a Station Blackout, there is no easy way to verify that the rods are on the bottom)
23
Q

What happens to CEDMCS on a loss of the Plant Computer?

A
  • Only methods available for moving rods are MI and MG.
  • Rods will not automatically stop at UGS and LGS
  • Pulse counters are lost
  • PDIL alarms are lost (out-of-sequenc, deviation, and exercise limit)
24
Q

What are the requirements and actions for LCO 3.1.5 CEA Alignment?

A
  • All full strength rods have to be operable
  • All full and part strength rods aligned within 6.6” in their group - of not, then reduce power and restore alignment
  • if 2 or more CEAs are > 9.9” = Trip immediately
  • if 1 or more CEAs are untrippable = M3 in 6 hrs
25
Q

What causes a CEA Withdrawl Prohibit (CWP)in CPC’s?

A

CWP (CEA Withdrawal Prohibit)
* Stops ALL rod withdrawals to prevent a reactor trip
* High PPZR Pre-Trip (2/4 logic) (generated in PPS)
* Low DNBR Pre-Trip (2/4 logic) (generated in CPCs)
* High LPD Pre-Trip (2/4 logic) (generated in CPCs)
* RPCB flag (clears ~ 10 seconds post cutback)
* CEA misalignment from CPC’s/CEAC’s
* Can be bypassed (dropped / misaligned CEA recovery)
o Push / hold bypass button on CEDMCS module (B04)

26
Q

What is the spacing for the Reed Switches?

A

Reed Switch Position Transmitters (RSPTs)
* Provide position indication of all 89 CEAs.
* Magnetic assembly closes dual reed switch contacts. (2 assemblies and voltage ladders per CEA)
* Located on CEA extension shaft.
o **Two position reed switches every 1.5”. **
o 0” reed switches – Drop Rod Contact
o 1 step – LEL
o 200 steps – UEL
o 203 steps – UEL backup

27
Q

What kind of power do the MG sets provide the CEDMCS Control Cabinets?

A

MG Sets produce a reliable and constant power at 240 VAC to rectifiers in the CEDMCS Control Cabinets via the RTSG.

28
Q

What happens if a CEDMCS logic power supply loses power?

A

Logic Power Supply (DC):
* Loss of power to logic assembly causes PSA to apply a high voltage to the CEDM upper gripper coil.
* Upper gripper high voltage (CGHV) condition > 10 minutes: coil may burn out and cause the CEA to drop.
* If one CEDM has a CGHV condition, the subgroup can be placed on the Hold bus
* If CGHV occurs on > 1 CEDM subgroups, manual reactor trip is required. (Only one hold bus)

29
Q

What does an AMBER light on the Subgroup Logic Housing Assemblies (SCR Drive Logic Modules) in CEDMCS mean?

A
  • Amber lights: Lit if circuit board is not fully seated or incorrect type card
30
Q

Where do the Upper Group Stop and Lower Group Stops come from?

A

Pulse Counters tell the plant computers.
UGS (Upper Group Stop)
* From plant computer based on counting “up” pulses.
* Stops outward Group motion at 146.5”
LGS (Lower Group Stop)
* From plant computer based on counting “down” pulses.
* Stops inward Group motion at 4.5”

31
Q

How does a Pulse Counter get reset?

A
  • Re-zeroed by 0” Reed Switch Position Transmitter (RSPT) rod dropped contact
32
Q

What does “Selected CEA Group Position” display?

A

Displays on a digital display (shows average CEA position of the group, except highest and lowest) from the Pulse Counters.

33
Q

What happens on loss of CEDM cooling?

A

CEDM Cooling (40AO-9ZZ20)
* If RCS ≥ 300°F, CEDM coils may be damaged within 40 minutes.
* Restore in 10 minutes or start rapid shutdown (Secure from shutdown if restored in 40 minutes).
* Cooldown RCS to < 300°F in the next 4 hours if not restored (Use SNOW GOP)

LOIT 2024 (69 decks)

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