Digital Control Rod Drive Positioning With Redundant Sensing

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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 precise positioning and control, such as 3-millimeter increments, with redundant systems for reliability.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If analog sensors and single-channel analog controls are used, then device complexity is reduced, but measurement precision and reliability deteriorate

Engineering Contradiction:

Improveposition detection precisionVSAvoidcontrol system complexity

Core Design Contradiction:

Measurement precisionVSDevice complexity

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 signal chain while maintaining position detection functionality, thereby improving measurement precision without proportionally increasing device complexity.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The control system is divided 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 comparison and verification of multiple independent readings.

Inventive Principle:

Principle #1Segmentation

2Reliability

If single-channel analog controls are used, then device complexity is reduced, but reliability deteriorates

Engineering Contradiction:

Improvecontrol system reliabilityVSAvoidcontrol system complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The control system is divided into multiple independent channels with separate digital sensors and processing paths. This segmentation creates redundant measurement and control paths, improving reliability through diversity and enabling failure detection when channel readings diverge.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The system continuously compares readings from multiple independent channels and uses feedback mechanisms to detect discrepancies. When channel readings diverge beyond acceptable thresholds, the system can detect potential failures and switch to redundant channels, thereby improving overall reliability.

Inventive Principle:

Principle #23Feedback

3Adaptability or versatility

If analog-to-digital converters are used, then compatibility with digital systems is improved, but susceptibility to noise and vibration increases

Engineering Contradiction:

Improvedigital system compatibilityVSAvoidnoise and vibration susceptibility

Core Design Contradiction:

Adaptability or versatilityVSObject-affected harmful factors

Solution Approach 1:

The patent eliminates analog-to-digital converters by using digital sensors that natively output digital signals. This substitution removes the vulnerable analog signal chain entirely, providing direct digital output that is inherently more resistant to noise and vibration while maintaining full compatibility with digital control systems.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

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 all-digital system enhances precision and reliability by allowing precise control and monitoring of control rod positions, reducing the risk of failure and susceptibility to noise and vibration, enabling precise control element positioning and operation even in challenging nuclear environments.

Implementation Method 1

several position sensors that digitally report control rod drive status and insertion position in these fine increments

Methodology Applied

Scientific EffectDigital transduction:

Implementation Method 2

Control and information systems may be divided into distinct channels with switches and controls of each channel performing independent and redundant control rod drive monitoring and controlling

Methodology Applied

Scientific EffectRedundancy:

Data Source

PatentUS11276504B2Digital systems and methods for high precision control in nuclear reactors

Publication Date: 2022.03.15 GE HITACHI NUCLEAR ENERGY AMERICAS LLC

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.