Week 1: Excore Instrumentation Flashcards
What range of power must the excore dectector system cover?
0-200% RTP
Neutron Flux from 10^-1 to 10^11
12 Decades
What is the range of the source range dectectors?
1 to 10^6 counts/s or 6 decades
Describe the operational principle of the source range detectors.
BF3-filled proportional detectors.
Operating in the proportional region allows for separate pulses for gamma rays and neutrons, allowing for the gammas to be discriminated out.
What is the range of the intermediate range detectors?
10^-11 to 10^-3 amps, or 8 decades
What is the operational principle of the intermediate detectors?
Compensated Ion Chamber.
Consists of 2 concentric detectors with different operating principles:
The outer detector is lined with boron and operated in the ion chamber region. This allows for a gamma + neutron signal.
The inner detector is not lined and is operated in the recombination region. This results in a gamma only signal.
These two signals are subtracted to obtain a neutron-only signal.
What impact does improper immediate range detector compensation have on plant indication?
If undercompensated, a higher than actual indication at a lower decay rate can be seen. Overcompensation has the opposite effect.
This could potentially impact the release of P-6.
What is the range of the power detectors?
0-200% RTP
~2 decades
What is the operational principle of the power range detectors?
Uncompensated B-10 ion chamber.
In this range, gamma production is small relative to neutron flux and proportional to power. Therefore, no compensation is needed.
Describe the axial locations of the excore detectors.
The source ranges are in a tunnel with the intermediate detectors near the bottom of the core.
The intermediate ranges are near the midplane of the core.
The power ranges are in a separate tunnel, one detector high, one low.
Describe the radial locations of the excore detectors.
The 4 power range tunnels are positioned at the 4 corners of the core.
The 2 source/intermediate tunnels are positioned at the north and south of the core.
Describe how QPTR is measured and what limit it is compared against.
Measurement of radial power distributions utilizing the PR detector signals.
Max_top/Average_top vs Max_bottom/Average_bottom, highest is compared to limit of 1.02.
What is the definition of AFD?
The difference in normalized flux signals between the top and bottom PR detectors.
