CEDMCS

Question 1

Where does CEDMCS send signals on a Reactor Trip?

Answer 1

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

Question 2

How long does it take to drop rods?

Answer 2

4 seconds

Question 3

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

Answer 3

0.75 inches

Question 4

At how many steps does the Upper Electrical Limit occur?

Answer 4

200 steps

Question 5

At how many steps does the Lower Electrical Limit occur?

Answer 5

1 step

Question 6

What functions does the Dropped Rod Contact serve in CEDMCS?

Answer 6

The rod bottom light on B04

Tells the Plant Computer to zero the pulse counters.

Question 7

Which rod inhibition can be bypassed?

Answer 7

CWP
(CEA Withdrawl Prohibit)

Question 8

When is an (Automatic Motion Inhibit) AMI enacted?

Answer 8

• > 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.

Question 9

When is an Automatic Withdrawl Prohibit (AWP) enacted?

Answer 9

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

Question 10

What are the power supplies to the CEDMCS MGs?

Answer 10

NGN-L03
NGN-L10

Question 11

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

Answer 11

No. But it is enough for Manual Individual operation

Question 12

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

Answer 12

2409 psia

Question 13

From where can you open the Trip Circuit Breakers?

Answer 13

• B05
• Locally
• PPS Cabinets (testing)
• SPLA Cabinets (testing)

Question 14

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

Answer 14

• PPS Cabinets (normal)
• Locally (testing)
• SPLA Cabinets (not OPS)

Question 15

What is the purpose in the CEDMCS MG flywheels?

Answer 15

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

Question 16

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

Answer 16

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

Question 17

When rods move, what speed do they move?

Answer 17

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

Question 18

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

Answer 18

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

Question 19

What happens to CEDMCS on a loss of PNC?

Answer 19

• 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

Question 20

What happens to CEDMCS on a loss of PND?

Answer 20

• 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

Question 21

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

Answer 21

Nothing

Question 22

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

Answer 22

• 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)

Question 23

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

Answer 23

• 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)

Question 24

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

Answer 24

• 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

Question 25

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

Answer 25

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)

Question 26

What is the spacing for the Reed Switches?

Answer 26

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

Question 27

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

Answer 27

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

Question 28

What happens if a CEDMCS logic power supply loses power?

Answer 28

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)

Question 29

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

Answer 29

* Amber lights: Lit if circuit **board is not fully seated** or incorrect type card

Question 30

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

Answer 30

**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”

Question 31

How does a Pulse Counter get reset?

Answer 31

* Re-zeroed by 0” Reed Switch Position Transmitter (**RSPT**) rod dropped contact

Question 32

What does “Selected CEA Group Position” display?

Answer 32

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

Question 33

What happens on loss of CEDM cooling?

Answer 33

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)