Incore NIs Flashcards
What is the purpose of Incore NIs (Movable Incore Detection System (MIDS))?
- Maps radial / axial flux distribution to confirm core design parameters
- Determines magnitude / location of fuel burnup
- Identify misaligned rod***
- Perform flux profiles / QPTRs
What is the speed of the MIDS Drive Units in SLOW speed?
- 12ft/min while scanning core ***
What is the speed of the MIDS Drive Units in FAST speed?
- 72 ft/min from withdrawn to bottom of core ***
What does the Withdraw Limit Switch do?
- Stops automatic MIDS withdrawal
and - prevents operation of the rotary device unless the detector is in the withdrawn position
- Deenergizes drive motor
What does the Safety Limit Switch do?
- Stops automatic MIDS withdrawal if the withdraw limit switch fails ***
- Deenergizes drive motor
What provides power to MIDS?
- CRP-3
What is the purpose of the guide tubes?
- Provide support and structure for the guide thimbles and are an integral part of the RCS Pressure Boundary
What is the purpose of the Guide Thimbles?
- Guide thimbles are located inside guide tubes
- 58 stainless steel incore flux thimbles that insert into fuel assemblies and are retracted during refueling
Why do we hang a clearance on the Moveable Incore Detection System when not in use?
- 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
What type of detector are the Incore NIs?
- Fission Chamber (6 of them)
- consist of a miniature canister containing an anode, cathode, detector gas, and fissionable material coating on the inner surface
- Detector gas is Argon (Ar) and the fissionable material is 93% enriched U235 (U3O8 – triuranium octoxide)
What are the seal table valves for?
- 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
What does the leak detection system for the Incore NIs do?
- 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
Where does the Five Path common group align to?
- C 10-Path transfer device
What do the CETCs do?
- 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.
How many CETCs are rated at 200°F - 2300°F?
- 63 CETCs
