Digital Rod Position Indication System Using XOR Logic
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Solution Overview
Problem
Existing digital rod position indication systems in nuclear reactors have limitations in accurately determining the position of control rods, typically achieving only 6-step accuracy due to the mechanical constraints and sensing methods used.
Innovation Solution
The proposed digital rod position indication system improves accuracy by utilizing a processing circuit that performs an exclusive OR (XOR) logic operation on signals from A and B coils, allowing for 3-step accuracy in determining the position of the drive rod tip, and by extension, the control rod.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional coil-based sensing methods are used, then the system structure is simple, but the measurement precision is limited to 6-step accuracy
Solution Approach 1:
The system divides the rod position measurement into two separate measurement systems (A-coils and B-coils), each providing 6-step accuracy. By segmenting the measurement process and combining results through XOR logic, the system achieves 3-step accuracy while maintaining relatively simple individual coil structures.
Solution Approach 2:
The patent introduces a logical dimension by performing XOR operations on the measurement results from A-coils and B-coils. This logical processing layer adds a new dimension to the measurement system, transforming two 6-step measurements into a 3-step measurement without requiring physical refinement of the coil structures.
2Measurement precision
If mechanical penetrations are used for control rod position sensing, then direct measurement is possible, but the pressure vessel integrity is compromised
Solution Approach 1:
The patent uses the drive rod as an intermediary object. Instead of penetrating the pressure vessel to measure control rod position directly, the system measures drive rod position through external coils and relies on the known mechanical coupling between drive rod and control rod to infer control rod position, thus maintaining pressure vessel integrity.
Solution Approach 2:
The system creates a positional copy by measuring the drive rod position (which is mechanically coupled to the control rod) and using this information to determine control rod position. This indirect measurement approach avoids direct penetration while providing sufficient positional information.
3Manufacturing precision
If 6-step accuracy is accepted, then the system is easier to operate, but the control rod placement precision is insufficient
Solution Approach 1:
The system implements feedback through logical processing of coil signals. By continuously monitoring the states of A-coils and B-coils and applying XOR logic, the system generates precise 3-step position feedback without requiring complex mechanical feedback mechanisms, thus improving precision while maintaining operational simplicity.
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
The system achieves enhanced accuracy of 3-step positioning for control rods, improving the precision of control rod placement and operation within nuclear reactors.
Implementation Method 1
An alternating current (AC) of a sufficiently low frequency is established within the individual coils 28 so that the resulting AC flux will penetrate the rod travel housing 22
Implementation Method 2
With a sufficiently low frequency, the skin depth of the resulting magnetic flux will be larger than the thickness of the rod travel housing 22, and the AC flux will penetrate all the way through the thickness of the rod travel housing 22
Implementation Method 3
When the drive rod 16 is moved longitudinally through the rod travel housing and passes through the central opening of a given coil 28, the impedance of the coil 28 will change
Data Source
AI summary
A rod position indication system is disclosed. The rod position indication system includes first coils and second coils disposed around a drive rod travel housing in an alternating arrangement, a first data encoder unit connected to each of the first coils and configured to generate a first reference signal, a second data encoder unit connected to the each of the second coils and configured to generate a second reference signal, and a processing circuit in signal communication with the first and second data encoder units. The processing circuit is configured to generate a logic comparison of the first and second reference signals, generate a logic signal based on first position data and second position data, and perform a logic operation on the logic signal and a result of the logic comparison.