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 leading to decreased accuracy and single-channel controls posing a failure risk, especially in high-precision applications like ESBWRs.
Innovation Solution
Implementing an all-digital control rod drive system with redundant channels and digital transducers, eliminating the need for analog-to-digital converters, and utilizing redundant position sensors for precise control and verification, ensuring high reliability and precision.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If analog sensors and mixed analog-digital control systems are used, then device complexity is reduced, but measurement precision and control accuracy deteriorate
Solution Approach 1:
The patent replaces analog sensors and analog-to-digital converters with all-digital position sensors and digital signal processing. This substitution eliminates the precision losses inherent in analog systems while maintaining manageable device complexity through integrated digital control architecture.
Solution Approach 2:
The system changes the parameter domain from analog continuous signals to digital discrete signals. By operating entirely in the digital domain, the system achieves higher measurement precision without the degradation that occurs in analog systems, while the parameter change enables more robust error handling and verification.
2Device complexity
If single-channel control systems are used, then device complexity is reduced, but reliability deteriorates due to failure risk
Solution Approach 1:
The control system is segmented into multiple independent channels, each capable of autonomous operation. This segmentation allows the system to maintain reliability through redundancy while managing complexity by dividing the control function into separable, testable units with defined interfaces.
Solution Approach 2:
The system implements beforehand cushioning through redundant control channels and cross-verification mechanisms. Before a failure can compromise system reliability, the redundant channels are already in place to detect and compensate for failures, providing a safety buffer that maintains operational reliability.
3Reliability
If all-digital control systems with redundant channels are implemented, then reliability and measurement precision are improved, but device complexity increases
Solution Approach 1:
The patent merges the control functions of multiple channels into a unified digital control architecture. By combining the redundant channels at the digital logic level with shared processing and communication resources, the system achieves high reliability without proportionally increasing overall device complexity.
Solution Approach 2:
The control channels are designed with universality, where each channel can perform multiple functions including primary control, backup control, and diagnostic monitoring. This multi-functionality reduces the need for dedicated specialized components, thereby controlling device complexity while maintaining reliability through redundancy.
4Manufacturing precision
If fine motion control with 3-millimeter increments is implemented, then manufacturing precision is improved, but device complexity increases
Solution Approach 1:
The patent replaces complex mechanical fine-motion adjustment mechanisms with digital control and sensing systems. The 3-millimeter positioning precision is achieved through digital signal processing and controlled motion algorithms rather than through complex mechanical linkages, reducing device complexity while maintaining manufacturing precision.
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
Achieves precise control with 3-millimeter increments and rapid, large strokes, reducing failure risks through redundancy and digital communication, enhancing reliability and resistance to nuclear reactor environments.
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.