CEDMCS Flashcards
Where does CEDMCS send signals on a Reactor Trip?
Main Turbine for tripping
DFWCS for RTO
SBCS for QOB
ERFDADS for indications
SRP Downtown
How long does it take to drop rods?
4 seconds
How far is one step for a Control Element Assembly (CEA)?
0.75 inches
At how many steps does the Upper Electrical Limit occur?
200 steps
At how many steps does the Lower Electrical Limit occur?
1 step
What functions does the Dropped Rod Contact serve in CEDMCS?
The rod bottom light on B04
Tells the Plant Computer to zero the pulse counters.
Which rod inhibition can be bypassed?
CWP
(CEA Withdrawl Prohibit)
When is an (Automatic Motion Inhibit) AMI enacted?
- > 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.
When is an Automatic Withdrawl Prohibit (AWP) enacted?
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
What are the power supplies to the CEDMCS MGs?
NGN-L03
NGN-L10
Is one CEDMCS MG enough for control rod operation in Manual Group?
No. But it is enough for Manual Individual operation
When does Supplementary Protection System (SPS) open the CEDMCS MG output contactors and open the Trip Circuit Breakers?
2409 psia
From where can you open the Trip Circuit Breakers?
- B05
- Locally
- PPS Cabinets (testing)
- SPLA Cabinets (testing)
From where can you close the Reactor Trip Switchgear Circuit Breakers?
- PPS Cabinets (normal)
- Locally (testing)
- SPLA Cabinets (not OPS)
What is the purpose in the CEDMCS MG flywheels?
- Flywheels maintain > 58 Hz on a 1 second power interruption.
What results from any CEA subgroup being placed on the Hold Bus?
- CEDMCS Trouble Alarm
- Rods on Hold Bus won’t move in Manual or Auto
When rods move, what speed do they move?
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
- Auto Sequential: Auto RRS control of sequential Regulating Groups (requires Plant Computer)
What happens to CEDMCS on a loss of PNA or PNB?
The associated RTCBs open (A and C or B and D) but power is maintained to the CEAs
What happens to CEDMCS on a loss of PNC?
- 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
What happens to CEDMCS on a loss of PND?
- 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
What happens to CEDMCS on a loss of NNN-D11 or NNN-D12?
Nothing
What happens to CEDMCS on a loss of NNN-D11 AND NNN-D12?
- 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)
What happens to CEDMCS on a loss of the Plant Computer?
- 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)
What are the requirements and actions for LCO 3.1.5 CEA Alignment?
- 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
What causes a CEA Withdrawl Prohibit (CWP)in CPC’s?
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)
What is the spacing for the Reed Switches?
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
What kind of power do the MG sets provide the CEDMCS Control Cabinets?
MG Sets produce a reliable and constant power at 240 VAC to rectifiers in the CEDMCS Control Cabinets via the RTSG.
What happens if a CEDMCS logic power supply loses power?
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)
What does an AMBER light on the Subgroup Logic Housing Assemblies (SCR Drive Logic Modules) in CEDMCS mean?
- Amber lights: Lit if circuit board is not fully seated or incorrect type card
Where do the Upper Group Stop and Lower Group Stops come from?
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”
How does a Pulse Counter get reset?
- Re-zeroed by 0” Reed Switch Position Transmitter (RSPT) rod dropped contact
What does “Selected CEA Group Position” display?
Displays on a digital display (shows average CEA position of the group, except highest and lowest) from the Pulse Counters.
What happens on loss of CEDM cooling?
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)
