.AR RI-Incore Instrumentation (Welch's Highlighted Notes)

Question 1

Purpose / Design Bases:

• Incores measure flux where? They provide an input to what system?
• Monitors CETs for…?

Answer 1

Purpose / Design Bases:

• Measure flux at localized areas in the core (provides input to COLSS)
  
  • Operating characteristics (power distribution, flux tilt, and peaking factors).
  • Gross power distribution (20 - 100%)
  • Estimate fuel burn-up in each F/A
  • Thermal margins in the core.
• Monitors CETs for indication / trending of core uncovering and recovering. (inputs to QSPDS)

Question 2

How many fixed incore instrumentation detector assemblies?…They consist of what?:

• How many # have flux probes
  
  • How many # self-powered rhodium detectors does each have?
  • Located at what % active core height?
• How many # background detector(s)?
• How many # CET (chromel-alumel thermocouple)?
• CETs and HJTCs (inputs/monitor…)…

Answer 2

61 fixed incore instrumentation detector assemblies, each consists of:

• 53 have flux probes
  
  • Each has 5 self-powered rhodium detectors
  • Located at 10, 30, 50, 70, and 90% active core height
• 1 background detector
  
  • Confirmation of correction coefficients to the plant computer
  • Compensates for signal errors induced in the signal wire. Signal wire without a rhodium detector. Also sensitive to neutrons and radiation (noise or background). Signal is subtracted from the detector signal to determine true signal level.
• 1 CET (chromel-alumel thermocouple)
• Core exit thermocouples (CETs) and heated junction thermocouples (HJTCs)
  
  • Input to QSPDS
  • Monitor for ICC
  • Monitor natural circ conditions (uses CET subcooling and ∆T (max quadrant CET vs. Th)).
  • Level indication determined using HJTCs.
• 1 dry movable detector calibration tube.

Question 3

Incore Neutron Detectors

Rhodium is depleted over time, resulting in a decreased signal for a given flux.

• • Correction factor is applied where?…

Answer 3

Incore Neutron Detectors

• Neutron sensitive rhodium element fitted over the signal wire.
• Emitted beta particle goes to the signal cable sheath where it undergoes an electron capture reaction.
• Creates difference in potential, therefore current flow to the amplifier.
• Rhodium is depleted over time, resulting in a decreased signal for a given flux.
  
  • Correction factor is applied in the plant computer
• Failed detector’s signals are automatically ignored by the computer if the failure is bad enough.
• Detector signals can also be manually turned off if it is determined that they have failed.

Question 4

Incore Amplifiers (Not highlighted in Welch’s Notes):

• Location?
• Alarms in MCR?
• Power supply: ?

Answer 4

Incore Amplifiers (Not highlighted in Welch’s Notes):

• Located in the auxiliary protection cabinets above the CPC modules (one amplifier chassis in each of the four bays). Each chassis processes up to 16 incore assemblies and up to 96 individual incore signals. Converts the micro-amp signal to a suitable voltage signal for the computer.
• System trouble alarm in the MCR
• Power supply: Class 120 Vac (PN)

Question 5

TRM TLCO 3.3.102 Incore Detectors (Not highlighted in Welch’s Notes):

• Functional when?…
• ?…

Answer 5

TRM TLCO 3.3.102 Incore Detectors (Not highlighted in Welch’s Notes):

• Functional when used for monitoring Azimuthal Power Tilt, Radial Peaking Factors, LPD, and DNB Margin.
• ≥ 75% of incore locations
• ≥ 75% of all incore detectors with at least one incore detector in each quadrant at each level
• Sufficient incore detectors to perform at least six tilt estimates with at least one tilt estimate at each of three levels
• All 4x4 arrays of F/As that contain 16 F/As must contain at least one incore location.
  
  • Incore Detection System contains 53 incore locations with 5 detectors in each fixed detector string.
  • A functional incore location consists of a fixed detector string with ≥ 3 detectors.

Question 6

Core Exit Thermocouples (CETs)

• Temp Range in °F?(QSPDS and ERFDADS)
  
  • Accuracy reduced > ? °F
• Located where? This allows for what?
• LCO 3.3.10 PAM Instrumentation (Modes 1-3)
  
  • How many channels required per quadrant?

Answer 6

Core Exit Thermocouples (CETs)

• 200 – 2300°F (QSPDS and ERFDADS)
  
  • Accuracy reduced > 1800°F
• Located in the bullet nose assembly of the incore instrument (ICI) assembly. Above the fuel alignment plate in the reactor coolant outlet plenum allowing for an accurate measure of the coolant as it exits the fuel.
• LCO 3.3.10 PAM Instrumentation (Modes 1-3)
  
  • 2 Channels (≥ 2 CETs each) required per core quadrant (long term monitoring of core cooling)