Incore NIs

Question 1

What is the purpose of Movable Incore Detection System (MIDS))

Answer 1

• Identify misaligned rod
• Maps radial / axial flux distribution to confirm core design parameters
• Determines magnitude / location of fuel burnup
• Perform flux profiles / QPTRs

Question 2

What is the speed of the MIDS Drive Units in SLOW speed?

Answer 2

12ft/min while scanning core

Question 3

What is the speed of the MIDS Drive Units in FAST speed?

Answer 3

72 ft/min from withdrawn to bottom of core

Question 4

What does the Withdraw Limit Switch do?

Answer 4

Withdrawn - Stops drive motor & detector withdrawal

Inserted- Prevents operation of associated 5 & 10 path

Question 5

What does the Safety Limit Switch do?

Answer 5

• Deenergizes drive motor
• Stops automatic MIDS withdrawal if the withdraw limit switch fails

Question 6

Why do we hang a clearance on the Moveable Incore Detection System when not in use?

Answer 6

• Personnel Safety
• The clearance ensures that the detectors are in a safe location to allow for personnel entry into containment.
• The radiation fields produced by the detectors can be thousands of R/hr

Question 7

What type of detector are the Incore NIs?

Answer 7

• Fission Chamber (6 of them)
• U308 coated, gas (argon) filled

Question 8

What are the seal table valves for?

Answer 8

• Designed to close without cable through but has the ability to cut cable for emergency isolation.
• Prevent RCS leakage in case of thimble tube rupture

Question 9

What does the leak detection system for the Incore NIs do?

Answer 9

• Monitors ten path transfer devices for thimble tube leaks
• Pressure switch provides an alarm to the control room for sufficiently sized leak in a thimble tube
• Pressure switch also opens drain solenoid valve and directs water to the sump
• When level decreases the alarm will extinguish and drain valve will close

Question 10

Where does the Five Path common group (position 4) align to?

Answer 10

C 10-Path transfer device

Question 11

What do the CETCs do?

Answer 11

Measures fuel assembly COOLANT and core outlet temperatures

Question 12

What temperatures are the CETCs rated for?

Answer 12

100°F - 2300°F

Question 13

What powers the Train A CETCs?

Answer 13

CRID 1

Question 14

What powers the Train B CETCs?

Answer 14

CRID 4

Question 15

On the 5 path device, where does the detector go when selected to Emergency?

Answer 15

• Next 10 Path

Question 16

Where is the MIDS storage (Position 5)?

Answer 16

On the containment wall

Question 17

Which guide tube do we use to calibrate (position 2) the MIDs?

Answer 17

J-10

Question 18

How do we frequently verify Hot Channel Factors during normal ops?

Answer 18

AFD, QPTR, Rod Insertion Limit

Question 19

What is the travel path of MIDs (Inst room to Core)?

Answer 19

Drives => Limit Switch => 5 Path => Wyes => 10 Path => Valves => Seals => Core

Question 20

CETCs have an input to which CR indications?

Answer 20

Subcooling Monitor Meter, PPC, Mid Loop Monitoring, and Recorders

Question 21

Where do the drains for the 10 path transfer devices go?

Answer 21

There is a common drain and if there is a leak, it alarms in CR

Question 22

How will a thermocouple fail if there is an open?

Answer 22

LOW

Question 23

How will a thermocouple fail if thre is a short?

Answer 23

LOW