Incore NIs

Question 1

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

Answer 1

• Maps radial / axial flux distribution to confirm core design parameters
• Determines magnitude / location of fuel burnup
• Identify misaligned rod***
• 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• 72 ft/min from withdrawn to bottom of core ***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

• Stops automatic MIDS withdrawal
  and
• prevents operation of the 5 or 10 path rotary device unless the detector is in the withdrawn position
• Deenergizes drive motor

Question 5

What does the Safety Limit Switch do?

Answer 5

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

Question 6

What is the purpose of the guide tubes?

Answer 6

• Provide support and structure for the guide thimbles and are an integral part of the RCS Pressure Boundary

Question 7

What is the purpose of the Guide Thimbles?

Answer 7

• Guide thimbles are located inside guide tubes

- 58 stainless steel incore flux thimbles that insert into fuel assemblies and are retracted during refueling

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

• All 10 path devices have a common drain and if there is a leak, it alarms in CR ***
• 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 align to?

Answer 10

• C 10-Path transfer device

Question 11

What do the CETCs do?

Answer 11

• Measures, processes, and displays reactor core outlet temperatures.
• Provides fuel assembly outlet temperatures at selected core locations to monitor core performance during operational and emergency conditions and during half-loop operations.

Question 12

How many CETCs are rated at 200°F - 2300°F?

Answer 12

• 63 CETCs

Question 13

How many CETCs are rated at 200°F - 500°F for mid loop monitoring?

Answer 13

• 2 CETCs

Question 14

What powers the Train A CETCs?

Answer 14

• CRID 1

Question 15

What powers the Train B CETCs?

Answer 15

• CRID 4

Question 16

How many core locations are available for MIDs?

Answer 16

• 58

Question 17

CETC wiring pass thru RV Head penetrations, how many do they use?

Answer 17

• 5

Question 18

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

Answer 18

• Next 10 Path

Question 19

What two dissimilar metals do the CETCs use?

Answer 19

• Chromel and Alumel

Question 20

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

Answer 20

• AFD, QPTR, Rod Insertion Limit

Question 21

CETCs have an input to which CR indications?

Answer 21

• SMM, PPC, MLM, and Recorders