Control Element Drive System

Question 1

Describe the number of CEAs.

Answer 1

• {73} [87] CEA’s, {24} [0] Dual CEA’s, 2 S/D & {7} [5] Reg Groups

Question 2

Which Unit 1 CEA groups have the dual CEAs?

Answer 2

A & B Shutdown groups are the dual CEA’s
24 CEA’s driven by 12 drive units

Question 3

Discuss the Reed switch & Ovation Tech Spec accuracy requirement.

Answer 3

Within {2.25”} [2.50”], ARO at 129”

Question 4

What constitutes a Dropped CEA?

Answer 4

15” or more from other rods in the same group

Question 5

What constitutes a Misaligned CEA?

Answer 5

> {7.5”} [7”] but < 15” misaligned from other CEA’s in same group

Question 6

Describe LTSSIL.

Answer 6

Need Rods withdrawn > 103” on {Group 7 at Unit 1} and [Group 5 on Unit 2] before >20% power

Question 7

Describe CEDMs.

Answer 7

The Coil Power Management Drawers control the sequencing of the CEDM coils by providing sequential pulses to the coils. These pulses control the direction of movement of the CEA’s.
The CEDM’s contain a series of coils to hold, withdraw, or insert the CEA’s. In the absence of MG Set power, all coils de-energize, CEA’s fall into the core due to gravity. TCBs interrupt MG Set power

Question 8

Describe CEDM MG sets.

Answer 8

• Motor, 480 VAC powered from A2/B2 Load Centers, Generates 240 VAC (515 amps) for CEDS
• Placed in service in Parallel Mode; Flywheel for 1 second power interruption
• Interlocked such that Output Contactor must be closed before Output Breaker is closed
• Interlocked so that Output Breaker will open if Input Breaker opens
• Diverse Scram System (DSS) / ATWS – Trips Output (Load) Contactor @ Ppzr of 2437 psia
• Input breaker trips on UV and Overcurrent
• [MG Set Load Center Feeder Breaker opens on SIAS - train specific]

Question 9

Describe DSS Interface with Control Element Drive system (CEDS).

Answer 9

Diverse Scram System senses an Anticipated Transient without Scram (ATWS) as:
2/4 Pressurizer pressures > 2437 psia,
* DSS opens the MG set output contactors
* Thus, this scram is diverse from RPS since DSS uses a different method of tripping the reactor
(MG set output contactors vs. 8 TCB’s)

Question 10

What powers RPI and Ovation?

Answer 10

SAS SUPS/Vital SUPS, auctioneered

Question 11

Describe CEA Gripper Coils.

Answer 11

• Upper Gripper is normally engaged when rods are stationary.
• Lift Coil (LC) – Energizes to lift the Upper Gripper Coil (UG), Moves CEA shaft up
• Pulldown Coil (PD) – energizes to lower the upper gripper coil. Moves CEA shaft down
• Load Transfer Coil (LT) – Ensure the lower grip coil (LG) has the weight
• Lower Gripper Coil (LG) – Holds CEA shaft while Upper Gripper is relocating.
• {Anti-Ejection Gripper} – Operates with the Lift coil. Spring operated, no DC power.

Question 12

Describe CEA speed.

Answer 12

Unit 1
20”/min Shutdown Groups
30”/min Regulating Groups

Unit 2
30”/min Shutdown Groups
30”/min Regulating Groups

Question 13

Describe Withdraw Gripper Sequence.

Answer 13

Withdraw –
* Lift Coil on first AEG out, UG raise = CEA goes up 3/4”
 LG coil on LG in
 LT coil on LG raises 1/16” = load is shifted to LG
 UG coil off UG out
 PD coil on, LC coil off UG pulled down and AEG in
 UG coil on, PD coil off UG in
 LT coil off Shaft drops 1/16” = load is shifted to UG
 LG coil off LG out
 UG coil to ½ power Hold

Question 14

Describe Insert Gripper Sequence.

Answer 14

Insert –
* LG on first LG in
 LT coil on LG raises 1/16” = load is shifted to LG
 UG coil off UG out
 LC coil on AEG out, UG raised 3/4”
 UG coil on UG in
 LT coil off, LG coil off Drop shaft 1/16”, LG out = load is shifted to UG
 LC coil off, PD coil on UG pulled down, AEG in
 PD coil off, UG-½ power Hold

Question 15

Discuss the two types of CEA position indication.

Answer 15

1) Pulse counting – Ovation: Tracks the Up & down pulses for alarms, display & the following control functions:
a) Upper Group Stop (UGS) - 132”– stops group withdrawal at 132” using the lagging CEA in the group
b) Lower Group Stop (LGS) - 4.5” – stops group insertion at 4.5” using the using the lagging CEA in the group
c) Sequential Permissive (SP) - Allows Manual Sequential motion when < {55”} [54”] overlap

2) Reed Switches – Analog & Digital
a) Analog – Analog section contains 100 switches spaced 1.5” apart and wired in a voltage divider network such that output voltage is proportional to CEA position (0-136”). Analog System feeds all CEA position info to RPI, which sends position to Ovation.
b) Digital – Sends information to Ovation. Uses Reed Switches to detect rod position and provides digital contact info to drive Upper Electrical Limit (UEL); Lower Electrical Limit (LEL) and Dropped Rod Contact (DRC) color indicators.
* Extra switches at:
DRC (0”)
Lower Electrical Limit (LEL) (~1”)
Upper Electrical Limit (UEL) (136.5”) (2 switches – one is a backup switch)

Question 16

Discuss RSPT (Reed Switch Position Transmitters) Interface with RPI/Ovation.

Answer 16

• 100 switches at 1.5” intervals.
• Reed switches are actuated by a Permanent Magnet affixed to the top of the CEA Extension Shaft
• Reed Switches remain powered if there is a LOOP/SBO

Question 17

Discuss Upper CEA Limit (UEL).

Answer 17

136”
* Stops CEA Withdrawal in all modes
* 2 UEL contacts, one slightly higher than the other that acts as backup if other fails
* Causes a Red Color indication on Core Mimic

Question 18

Discuss Lower CEA Limit (LEL).

Answer 18

1”
* Stops CEA Insertion in all modes
* Causes a Green Color indication on Core Mimic

Question 19

Discuss Dropped Rod Contact (DRC).

Answer 19

0”
* Resets Pulse Counter to 0,
* Causes a “CEA Drop Alarm”
* Causes an Amber Color indication on Core Mimic

Question 20

Discuss Ovation CEA Mode Select Positions.

Answer 20

MANUAL INDIVIDUAL MODE (MI):
* When selected, any CEA in any group can be withdrawn or inserted individually by selecting the CEA and the group containing it and then operating the manual arrow or inputting the target.

MANUAL GROUP MODE (MG):
* When selected, any group of CEAs can be withdrawn or inserted by selecting the desired group and then operating the manual arrow or inputting the target.

MANUAL SEQUENTIAL MODE (MS):
* When selected, only the regulating groups of CEAs can be withdrawn or inserted by operating the manual arrow or inputting the target. The particular groups that are withdrawn or inserted are determined automatically by group permissive signals from the pulse counting. In this mode, the GROUP SELECTION have no effect on CEA operation.

Question 21

What happens when an Urgent Failure Alarm is generated?

Answer 21

Energizes UG and LG coils to prevent dropping the CEA.

Question 22

Discuss Motion Interlocks.

Answer 22

Can be bypassed CEA Motion Inhibit Bypass
1) ISH (Inhibit Shutdown Group) Interlock- Blocks Shutdown Group motion if any Reg Group CEA is more than 10” withdrawn (by RSPT). No annunciation, however the info tile is highlighted on the core mimic display.
2) IRG (Inhibit Regulating Group) Interlock – Blocks Reg Group motion if any Shutdown Group CEA is less than 129” withdrawn (by RSPT). No annunciation, however the info tile is highlighted on the core mimic display.

Question 23

Discuss Motion Inhibits (CMI).

Answer 23

All of following causes a CMI that Inhibits ALL CEA Motion-either direction
CMI can be bypassed CEA Motion Inhibit Bypass
1. CMISH (CEA Motion Inhibit on Shutdown Groups) - Caused by a deviation of any Shutdown group CEA of greater than 6” (by RSPT). Causes CMI annunciator and blocks all CEA motions.
2. CMIRG (CEA Motion Inhibit of Regulating Groups) - Deviation of any Reg group CEA of greater than 6” (by RSPT), OR Out of Sequence Alarm (by RSPT), OR PDIL Alarm (by RSPT).
3. Group Out of Sequence/Overlap –
GrN<87” and GrN+1>10.5” (withdrawal); GrN<129” and GrN+1>50” (insert) – OOS GrN <129” and GrN+1>10.5” and delta<87” - Overlap
N=highest, N+1=lowest
* During withdrawal of rods, if Regulating Group N+1 is greater than 10” while Regulating Group N is less than 94.5”.
* During insertion of rods, if Regulating Group N is less than 129” while Regulating Group N+1 is greater than 41.3”.
4. Group Deviation > 6.0” – highest to lowest rod in group, Motion block (one alarm for Pulse Count and one for RSPT)

Question 24

Discuss CWP (CEA Withdrawal Prohibit) Motion Inhibits.

Answer 24

• Prevents CEA Withdrawal in ANY Mode
• 2/4 Pretrips from VHP, TM/LP, LPD, SUR
• [CWP bypasses: TMLP by ZPM bypass & switch; SUR < 10-4% by Log Bistable]
• Can be bypassed in Ovation Rod Control

Question 25

Discuss Power Dependent Insertion Limit (PDIL).

Answer 25

Maintaining CEA’s above the PDIL ensures:
* Adequate SDM on Rx trip
* Ensures acceptable power distribution limits are maintained
* Limits the reactivity excursion due to an ejected CEA

Question 26

Discuss CEA withdrawal/insertion on startup/shutdown.

Answer 26

Startup
* SDG-A to UGS in MS, then individually to UEL, repeat for SDG-B
* RG-1 to UGS in MS checking overlap, then individually to UEL
* Repeat for RG-2-6 [2-4], RG-7 [5] to criticality, and PDIL arrow markers enforcing begin at 10-4%
Shutdown
* RG-7-1 to LGS in MS checking overlap, then to LEL in MI
* SDG-A then SDG-B in MS to LGS, then to LEL in MI
* Open TCB’s, verify DRC’s on, verify Ovation = 0” for all rods

Question 27

Discuss Reactor Trip Criteria Due to CEA Problems.

Answer 27

• If CEA has any motion after OFF is selected on Ovation Rod Control Panel
• If 2 or more CEA’s are Dropped or Misaligned >15” in Modes 1 or 2

Question 28

Discuss Recovering Dropped Rod.

Answer 28

• Have limited amount of time to try and recover the dropped CEA based on time allotted by the COLR using the value of FrT. Currently set at {1.65 = 60 min}; [1.65= 63 min].
• If ∆T power is greater than 70% and:
  1) It is expected that the CEA cannot be realigned within {7.5”} [7”] of all the other CEA’s in the group.
  2) Allowable time elapses before CEA can be realigned with it’s group,
  STOP the recovery and reduce power to less than or equal to 70% and then resume recovery actions.

Question 29

Discuss RPI Tech Spec Timer Alarms.

Answer 29

Red (background) - exceeded time limit
Yellow (background) - 90% of Tech Spec Limit time has elapsed
White (background) - Major CEA Deviation or LTSSIL reached

Deviation Tech Spec Timer:

Tracks: 1) Time that any CEA deviation exceeds 7.5” [7.0”].
2) % Column tracks percent of time incremented vs Tech Spec limits.

	Tech Spec Limits:	*7 days per occurrence
				*14 days per calendar year

LTSSIL Tech Spec Timer:

Tracks: 1) Time that Reg Group CEAs have been inserted below the LTSSIL.
2) Timer will not increment while Low Power Cutoff is enabled.
3) % Column tracks percent of time incremented vs Tech Spec limits.

Tech Spec Limits:
*4 hours per 24 hour interval
*5 effective full power days (EFPD) per 30 EFPD interval
*14 EFPD per 365 EFPD

Question 30

Discuss CEA Position Setpoints.

Answer 30

• 136.5” UEL from RSPT, RED COLOR
• 132” UGS from Ovation
• 129” IRG Interlock from RPI
• 94.5” NORMAL OVERLAP BEGINS WHEN WITHDRAWING RODS
• 82” EARLIEST ALLOWABLE RG OVERLAP WITHDRAWING, Ovation
• 54” EARLIEST ALLOWABLE RG OVERLAP INSERTING, Ovation
• 41” NORMAL OVERLAP BEGINS WHEN INSERTING RODS
• 10” ISH Interlock from RPI
• 4.5” LGS from Ovation
• 1” LEL from RSPT, GREEN COLOR
• 0” DRC FROM RSPT, AMBER COLOR

Question 31

What are the CEA MG Breaker Trips?

Answer 31

Output
Input UV; Output Overvoltage; Overcurrent; Under frequency; Hi/Low Field Current; Output Contactor open

Input
UV, Overcurrent

Load Center
[SIAS on Unit 2]

Question 32

How is a Rx Trip communicated to trip the turbine?

Answer 32

{Trip Circuit Breaker Switchgear} [CEDMCS Cabinet 1 and 2] UV Coils send Rx Trip signal to DEH (4/4 logic) to trip the Turbine

Question 33

How is a Rx Trip communicated to SBCS?

Answer 33

{Trip Circuit Breaker Switchgear} [CEDMCS Cabinet 1 and 2] UV Coils send Rx Trip signal to SBCS (4/4 logic)