Digital Control Rod Drive Positioning With Redundant Sensor Channels
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Solution Overview
Problem
Existing control rod drives in nuclear reactors lack precision, with analog sensors reducing accuracy and single-channel analog controls posing a reliability risk, especially in high-precision applications like ESBWRs where finer increments are required for reactivity control.
Innovation Solution
An all-digital control rod drive system with redundant channels and digital position sensors, eliminating the need for analog-to-digital converters, and using fine motion motor controllers with precise digital transducers to achieve positioning in increments as small as 3 millimeters, along with a digital rod control and information system for reliable operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If analog sensors and single-channel analog controls are used in control rod drives, then device complexity is reduced, but measurement precision and reliability deteriorate
Solution Approach 1:
The patent replaces analog sensors and analog-to-digital converters with digital sensors that directly output digital signals. This substitution eliminates the analog measurement chain while maintaining device simplicity, thereby improving measurement precision without significantly increasing complexity.
Solution Approach 2:
The patent divides the control system into multiple independent channels, each with its own digital sensor and processing path. This segmentation allows redundant measurement paths that improve reliability and precision through cross-validation while keeping each channel relatively simple.
2Ease of manufacture
If analog sensors and single-channel controls are used, then ease of manufacture is improved, but reliability deteriorates due to lack of redundancy
Solution Approach 1:
The control system is segmented into multiple independent channels with separate digital sensors and processing paths. This modular segmentation enables easier manufacturing and testing of individual channels while providing inherent redundancy that improves overall reliability.
Solution Approach 2:
The patent implements redundant digital measurement channels that can compensate for sensor failures before they affect operation. This beforehand cushioning through redundancy protects against reliability issues while maintaining manufacturing simplicity through standardized modular components.
3Adaptability or versatility
If analog-to-digital converters are used in the control system, then compatibility with digital processors is achieved, but measurement precision and system reliability deteriorate due to conversion errors
Solution Approach 1:
The patent substitutes analog-to-digital conversion with direct digital sensing. Digital sensors output digital signals natively, eliminating the conversion step entirely. This maintains full compatibility with digital processors while preserving measurement precision by avoiding conversion errors.
4Manufacturing precision
If finer position control increments are implemented, then reactivity control precision is improved, but device complexity increases
Solution Approach 1:
The patent uses digital sensors and digital control signals to achieve fine position control increments. The digital domain naturally supports precise incremental control through software algorithms without requiring complex mechanical positioning mechanisms, thereby improving precision while limiting complexity growth.
Solution Approach 2:
The control system uses dynamic digital processing to achieve fine position control. By implementing control logic in the digital domain with flexible software algorithms, the system can adapt control increments dynamically without fixed mechanical constraints, improving precision while maintaining 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
The system achieves high-precision control rod positioning with reduced failure risk, enabling precise control and redundancy, thus enhancing the reliability and accuracy of control rod operations in nuclear reactors.
Implementation Method 1
A magnetic coupling 17 pairs internal and external magnets to rotate ball screw 11 across a pressure barrier
Data Source
AI summary
Control rod drives include all-digital monitoring, powering, and controlling systems for operating the drives. Each controlling system includes distinct microprocessor-driven channels that independently monitor and handle control rod drive position information reported from multiple position sensors per drive. Controlling systems function as rod control and information systems with top-level hardware interfaced with nuclear plant operators other plant systems. The top-level hardware can receive operator instructions and report control rod position, as well as report errors detected using redundant data from the multiple sensors. Positional data received from each drive is multiplexed across plural, redundant channels to allow verification of the system using independent position data as well as operation of the system should a single channel or detector fail. Control rod drives are capable of positioning and detecting position of control elements in fine increments, such as 3-millimeter increments, with plural position sensors that digitally report drive status and position.