Vibration-Based Annulus Spacer Detection in Nuclear Reactors

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Solution Overview

Problem

There is a need for a method and apparatus to detect and reposition tight-fitting annulus spacers in nuclear reactors, as existing electromagnetic techniques are ineffective due to the non-welded girdle wire design, which does not provide a continuous electrical path.

Innovation Solution

A method involving vibrationally isolating a section of the inner tube, vibrating the tube wall to detect the presence of annulus spacers by measuring vibration reductions, and using a tool head with piezo-actuators and accelerometers to axially reposition the spacers by overcoming their tension through controlled vibrations.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of operation

If electromagnetic techniques are used to detect and reposition annulus spacers, then detection and repositioning can be achieved, but the method is ineffective for snug-fitting spacers with non-welded girdle wire that do not provide a continuous electrical path

Engineering Contradiction:

Improvedetection and repositioning capabilityVSAvoideffectiveness with non-welded girdle wire

Core Design Contradiction:

Ease of operationVSReliability

Solution Approach 1:

The patent replaces electromagnetic detection and repositioning methods with a mechanical vibration-based system. A tool head generates mechanical vibrations that travel through the pressure tube, and changes in vibration characteristics detect the presence and position of annulus spacers. This mechanical approach works regardless of whether the girdle wire is welded or non-welded, solving the reliability issue with snug-fitting spacers.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent changes the detection parameter from electrical conductivity (electromagnetic method) to mechanical vibration transmission. By measuring changes in vibration frequency, amplitude, or phase as vibrations pass through the pressure tube, the system can detect spacers without requiring continuous electrical paths, thus working with both loose-fitting and snug-fitting spacer designs.

Inventive Principle:

Principle #35Parameter changes

2Adaptability or versatility

If spacers are held in position by spring tension and friction without rigid fixation, then the design allows for potential repositioning, but the spacers may move from their desired position during reactor operation

Engineering Contradiction:

Improverepositioning capabilityVSAvoidposition stability

Core Design Contradiction:

Adaptability or versatilityVSStability of the object's composition

Solution Approach 1:

The patent implements a feedback-based detection system that monitors the position of annulus spacers during reactor operation. By continuously measuring vibration characteristics, the system can detect when spacers have moved from their desired positions and provide information for corrective repositioning, thus maintaining position stability while preserving adaptability.

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The patent enables preliminary detection of spacer positions during installation and before reactor operation. This allows verification that spacers are correctly positioned before the reactor starts operating, preventing position-related issues before they occur while maintaining the ability to reposition if needed.

Inventive Principle:

Principle #10Preliminary action

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

Enables effective detection and repositioning of annulus spacers without damaging the reactor components, ensuring proper spacing and support to prevent tube contact and extend reactor life.

Implementation Method 1

A method involving vibrationally isolating a section of the inner tube, vibrating the tube wall to detect the presence of annulus spacers

Methodology Applied

Scientific EffectPiezoelectric effect: Piezoelectric Effect

Implementation Method 2

using a tool head with piezo-actuators and accelerometers to axially reposition the spacers

Methodology Applied

Scientific EffectInertial sensing: Accelerometer

Implementation Method 3

vibrating the annulus spacer by vibrating the isolated section of the wall at a desired frequency such that the annulus spacer is displaced longitudinally from an initial position to a required position, whereby the vibration of the annulus spacer produces accelerations sufficient to overcome the tension of the annulus spacer on the inner tube

Methodology Applied

Scientific EffectMechanical vibration: Vibration

Data Source

PatentUS10347384B2Method for annulus spacer detection in nuclear reactors

Publication Date: 2019.07.09 ATOMIC ENERGY OF CANADA LIMITED

AI summary

The present invention provides an apparatus for detecting and/or repositioning annulus spacers used to maintain the position of a pressure tube within a calandria tube of a nuclear reactor. The method comprises the steps of: vibrationally isolating a section of the pressure tube; vibrating the wall of said pressure tube within said isolated section; detecting vibration of the wall at a minimum of two axial positions within said isolated sections; and detecting the reduction in vibration level of the wall at one or more of said axial positions in comparison to the remaining axial positions. The apparatus comprises a tool head to be inserted into the pressure tube, the tool head comprising a first end and a second and a clamping block m each of said ends. The clamping blocks are used to vibrationally isolate a section of the pressure tube located between said ends. The apparatus also comprises piezo-actuators operable to vibrate said pressure tube; and accelerometers used for measuring vibration of said pressure tube.