Week 2: Rod Control System & DRPI

Question 1

What is the design basis of the Rod Control System?

Answer 1

10% full power step change in load
5% per minute ramp change in demand without an Rx trip, steam dumps, or pressure relief
50% step load decrease in demand with 40% from steam dumps

Question 2

What are the different types of coils on the Control Rod Drive Mechanism, and in what order?

Answer 2

Lift
Moveable
Stationary

Question 3

What are the different types of grippers in the Control Rod Drive Mechanism, and in what order?

Answer 3

Moveable
Stationary

Question 4

What is the function of the CRDM power cabinets?

Answer 4

To contain the power control circuits that switch and regulate the current to the connected rod drive mechanism. They receive their orders from the logic cabinet, and there are 5 power cabinets in total.

Question 5

What is the function of the CRDM logic cabinet?

Answer 5

To generate the timing and sequencing signals necessary for rod motion.

Question 6

What is the function of the CRDM reactor control unit?

Answer 6

To provide speed and direction signals to the logic cabinet based on a total error signal.

Question 7

Describe the inputs to the total error signal and the resulting rod movement resulting from the error sign change.

Answer 7

(Tref - Tavg) + (P_imp - P_NI) = Total Error Signal
0 = no change
+ = outward rod motion
- = inward rod motion

Question 8

How quickly do the control banks move in auto mode? In manual?

Answer 8

Auto: 8-72 spm
Manual: 48 spm

Question 9

How quickly do the shutdown banks move?

Answer 9

Cannot be moved in automatic mode
Manual: 64 spm

Question 10

Describe the control banks.

Answer 10

The control banks are available for reactor temperature control in automatic mode, and may be inserted into the core when at power. Bank D is inserted first, with a 113 step overlap.
Bank A: 4 RCCAs
Bank B: 8 RCCAs
Bank C: 8 RCCAs
Bank D: 5 RCCAs

Question 11

Describe the shutdown banks.

Answer 11

The shutdown banks are not available for reactor temperature control in automatic mode, and may not be inserted into the core when at power. They are for ensuring adequate SDM only.
Bank SA: 8 RCCAs
Bank SB: 8 RCCAs
Bank SC: 4 RCCAs
Bank SD: 4 RCCAs
Bank SE: 4 RCCAs

Question 12

Describe the sequence of CRDM actions to perform a 1 step rod withdrawal.

Answer 12

Stationary coil is holding rod in placed at reduced current
Movable Coil is energized (Both Stationary and Movable are holding rod)
Stationary coil deenergized (Moveable holding rod)
Lift Coil energized (Moveable holding rod, moves up 1 step)
Stationary Coil energized (Moveable and Stationary holding rod)
Movable deenergized (Stationary holding rod)
Lift Coil deenergizes (Stationary holding rod, moveable grippers move back down one step)
Stationary coil placed at reduced current

Question 13

Describe the sequence of CRDM actions to perform a 1 step rod insertion.

Answer 13

Stationary coil is holding rod in placed at reduced current
Lift coil is energized (Stationary holding rod, movable grippers move up 1 step)
Moveable coils energized (Stationary and Moveable holding rod)
Stationary coil deenergized (moveable holding rod)
Lift coils deenergized (moveable holding rod, drops one step)
Stationary coils energized (Stationary and Moveable holding rod)
Moveable coils deenergized (stationary holding rod)
Stationary coils placed at reduced current

Question 14

What control interlocks affect the Rod Control System?

Answer 14

C-1
C-2
C-3
C-4
C-5
C-11

Question 15

Describe the Digital Rod Position Indication System.

Answer 15

To provide a highly reliable indication of actual control rod position, but at a lower accuracy than the bank position step counters.

Question 16

Describe the Bank Position Step Counters.

Answer 16

To supply a highly accurate indication of bank demand position, but with limited reliability insofar as the actual position of the rods.

Question 17

What is the source of electricity for the Rod Control System?

Answer 17

2 Non-Safety Motor Generator Sets