Subcritical Reactivity Measurement via Background Noise Isolation
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Solution Overview
Problem
Current methods for measuring neutron radiation levels in nuclear reactors lack accuracy due to background signal components, which affect the determination of core reactivity changes, especially in subcritical conditions, and require no changes to existing equipment or practices.
Innovation Solution
A method that involves monitoring source range detector signals at different coolant moderator temperatures to determine and remove the background non-neutron signal component, using the relationship N = Keff H - Keff H - Keff C + R T H + R T C + F H C - 1, allowing for more accurate inverse count rate ratio calculations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If source range detectors are used to measure neutron flux in the source range, then the power level can be monitored, but the background signal component reduces measurement accuracy
Solution Approach 1:
The patent extracts and removes the background signal component from the detector output signal through mathematical processing. The background signal is separated from the neutron signal using the inverse count rate ratio method, allowing accurate measurement of subcritical reactivity by eliminating the harmful background component that would otherwise contaminate the measurement.
Solution Approach 2:
The patent introduces an intermediary mathematical relationship (inverse count rate ratio) that mediates between the raw detector signal and the desired neutron population measurement. This intermediary approach allows the background signal to be accounted for and removed, enabling accurate reactivity measurements without directly modifying the detector hardware.
2Measurement precision
If conventional measurement methods are used without background correction, then the measurement process is simple, but the determination of core reactivity changes is inaccurate
Solution Approach 1:
The patent replaces complex hardware modifications with a mathematical/ computational approach. Instead of modifying detector hardware or introducing complex physical systems to eliminate background signals, the invention uses mathematical processing of the detector output signal to achieve accurate reactivity measurements, substituting mechanical complexity with computational simplicity.
3Reliability
If the background signal is not removed, then the measurement process is straightforward, but the uncertainty in criticality determinations increases
Solution Approach 1:
The patent uses feedback by continuously monitoring the detector signal and applying corrections based on the calculated background component. The inverse count rate ratio method provides a feedback mechanism that adjusts the measurement by accounting for background signals, thereby improving reliability without requiring complex additional hardware.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach enhances the accuracy of neutron population measurements and reactivity changes, reducing uncertainty in criticality determinations and improving the reliability of reactor operation by isolating background noise from neutron signals.
Implementation Method 1
Fission and ionization chambers have been used to measure flux in the source, intermediate and power range of a reactor
Implementation Method 2
Hydrogen within the coolant water moderates the neutrons emitted from enriched uranium within the fuel to increase the number of nuclear reactions
Implementation Method 3
When inserted, the control rods absorb neutrons and thus reduce the number of nuclear reactions and the amount of heat generated within the core
Implementation Method 4
heat is generated within the core of a pressure vessel by a fission chain reaction occurring in a plurality of fuel rods
Data Source
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AI summary
A method of determining the spatially corrected inverse count ratio (SCICR) used to determine reactor criticality, which subtracts a background noise signal from the source range detector output. The method monitors the source range detector signal at two different core temperature levels during a transient portion of the detector output as the power output of the reactor is increased in the source range. This information is employed to analytically determine the background noise signal, which is then subtracted from the detector outputs to obtain the SCICR reactivity measurement.