Variable Gain Amplifier for Ex-Core Neutron Detection
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Solution Overview
Problem
The existing ex-core nuclear instrumentation systems face challenges in accurately measuring and amplifying minute neutron detector currents, particularly in advanced PWRs, where the reduced neutron leakage requires a high-gain circuit to achieve the necessary output voltage levels for reactor power monitoring, while maintaining measurement accuracy.
Innovation Solution
A detector signal processing circuit with a variable gain amplification unit, incorporating an operational amplifier and D/A converters, allows for adjustable gain selection and amplification, ensuring accurate conversion of neutron detector currents into output voltage levels corresponding to reactor power, using a resistance circuit and D/A converters to finely adjust the gain.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a conventional detector signal processing circuit is used, then the circuit structure is simple, but the output voltage level cannot be obtained when neutron detector current is minute
Solution Approach 1:
The patent implements a variable gain amplifier with dynamically adjustable gain through D/A converters, allowing the circuit to adapt its amplification factor based on the input signal level. This dynamic adjustment enables the circuit to handle both minute currents from advanced PWRs and larger currents from conventional PWRs, resolving the contradiction between measurement precision and device complexity.
Solution Approach 2:
The patent changes the electrical parameters (gain, resistance values) of the signal processing circuit to match different operational requirements. By adjusting the gain parameter through D/A converters and using switchable resistance circuits, the system can optimize its response for different neutron current levels, achieving accurate measurement across varying conditions without requiring completely different circuit designs.
2Power
If the gain is increased to amplify minute neutron detector currents, then the output voltage level can be achieved, but the measurement accuracy may be compromised
Solution Approach 1:
The variable gain amplifier allows the system to dynamically adjust the amplification factor based on the actual input signal level. For minute currents, high gain is applied to achieve sufficient output voltage, while for larger currents, the gain is reduced to prevent saturation and maintain accuracy. This dynamic adaptation resolves the contradiction between achieving adequate output power and maintaining measurement precision.
Solution Approach 2:
The system incorporates feedback mechanisms that monitor the input signal level and automatically adjust the gain setting. This feedback control ensures that the amplification is optimized for each specific measurement condition, preventing both insufficient output voltage and measurement distortion, thereby resolving the trade-off between power output and accuracy.
3Adaptability or versatility
If a fixed gain amplifier is used, then the circuit is simple, but it cannot satisfy both conventional PWR and advanced PWR measurement ranges
Solution Approach 1:
The patent employs a variable gain amplifier with programmable gain control through D/A converters, enabling the circuit to adapt its characteristics based on the operational mode. The system can switch between different gain settings to accommodate both conventional PWR (100 μA to 3 mA) and advanced PWR (1 μA to 30 μA) measurement ranges, achieving versatility without requiring multiple separate circuits.
Solution Approach 2:
The detector signal processing circuit is designed as a universal system that can handle multiple measurement ranges and reactor types through programmable gain control and switchable resistance circuits. This multi-functional design allows a single circuit to replace what would traditionally require multiple specialized circuits, balancing adaptability with manageable complexity.
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 solution enables accurate measurement and output of voltage levels corresponding to reactor power, even with minute neutron detector currents, ensuring correct neutron flux monitoring and highly accurate measured values, capable of handling both conventional and advanced PWRs.
Implementation Method 1
a variable gain amplification unit which has an operational amplifier having a resistance circuit for corresponding to current levels, the resistance circuit being capable of selecting a gain
Implementation Method 2
a D/A converter that adjusts the gain
Implementation Method 3
a current/voltage conversion unit which converts the current value converted by the neutron detector into a voltage value corresponding to the current value
Data Source
AI summary
An ex-core nuclear instrumentation system in which the width of measurable neutron detector current can be accurately widened is obtained. In order to output the condition of neutron flux in operation by performing arithmetic processing of a current value measured by a neutron detector by using a detector signal processing circuit, the detector signal processing circuit includes a current/voltage conversion unit which converts the current value converted by the neutron detector into a voltage value corresponding to the current value; and a variable gain amplification unit which has an operational amplifier having a resistance circuit for corresponding to current levels, the resistance circuit being capable of selecting a gain, and a D/A converter that adjusts the gain, and amplifies the voltage value converted by the current/voltage conversion unit.