Fuel Rod Diameter Measurement Apparatus

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Solution Overview

Problem

Conventional apparatuses for measuring the outer diameters of fuel rods in nuclear fuel assemblies cannot measure the diameter over the length of the rods, leading to incomplete measurements and reduced fuel rod lifespan due to inability to accurately check for abnormalities.

Innovation Solution

An apparatus with a support unit fixed to the floor, a moving measuring unit equipped with pneumatic motors, and a transducer using a linear variable differential transformer (LVDT) to measure the outer diameters of fuel rods without disassembling the nuclear fuel assembly, allowing for up-and-down movement and contact with multiple rods simultaneously.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If conventional measurement apparatuses are used, then the measurement process is simple, but the measurement is incomplete (cannot measure outer diameter over the length of fuel rods)

Engineering Contradiction:

Improveouter diameter measurement completenessVSAvoidapparatus structure

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The measuring unit is designed to move vertically along the fuel rods, transforming a static measurement device into a dynamic one. This allows the contact arms to scan the outer diameter at multiple positions along the length of the fuel rods, achieving complete measurement coverage while maintaining relatively simple device structure

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The invention adds the vertical dimension to the measurement process. Instead of only measuring at a single horizontal position, the measuring unit travels along the vertical length of the fuel rods, converting a point measurement into a multi-point linear measurement across the rod's length

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

2Reliability

If conventional measurement apparatuses are used, then the apparatus structure is simple, but abnormalities cannot be accurately detected

Engineering Contradiction:

Improveabnormality detection accuracyVSAvoidapparatus structure

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The vertical movement capability of the measuring unit enables continuous monitoring of outer diameter variations along the fuel rod length, significantly improving the reliability of abnormality detection by capturing defects that may occur at any position along the rod

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The invention replaces conventional mechanical measurement systems with a transducer-based measurement system. The transducer converts mechanical displacement of the contact arms into electrical signals, providing more accurate and reliable measurement data for detecting subtle abnormalities in fuel rod outer diameter

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Reliability

If complete measurement of outer diameters over length is implemented, then fuel rod lifespan can be protected, but measurement time increases

Engineering Contradiction:

Improvefuel rod lifespan protectionVSAvoidmeasurement time

Core Design Contradiction:

ReliabilityVSLoss of time

Solution Approach 1:

The vertical movement mechanism enables continuous measurement along the entire length of the fuel rods in a single scanning operation. This continuous measurement process protects fuel rod lifespan by detecting abnormalities anywhere along the rod, while the automated scanning reduces total measurement time compared to multiple discrete measurements

Inventive Principle:

Principle #20Continuity of useful 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 accurate and efficient measurement of fuel rod outer diameters, preventing reduced lifespan by allowing comprehensive checks without disassembly, ensuring precise detection of abnormalities and extending the operational life of the fuel rods.

Implementation Method 1

a transducer configured to cooperate with the measuring unit, configured to convert the measured outer diameters of the fuel rods into electrical signals

Methodology Applied

Scientific EffectLinear variable differential transformer (LVDT): Electromagnetic Induction

Implementation Method 2

a base mounted on the support unit and configured to move up and down by a pneumatic motor installed on the support unit

Methodology Applied

Scientific EffectPneumatic motor:

Data Source

PatentUS8832952B2Apparatus for measuring outer diameters of fuel rods of nuclear fuel assembly

Publication Date: 2014.09.16 KEPCO NUCLEAR

AI summary

Provided is an apparatus for measuring outer diameters of fuel rods of a nuclear fuel assembly, in which the fuel rods are standing upright and are used in a light water reactor. The apparatus includes a support unit fixed to a floor at a lower portion thereof so as to be kept insulated from vibrations caused by external forces, a measuring unit mounted on the support unit and moving up and down to measure the outer diameters of the fuel rods, and a transducer cooperating with the measuring unit, converting the measured outer diameters of the fuel rods into electrical signals, and sending the converted signals to the outside. Thus, the apparatus moves up and down to measure the outer diameters of the fuel rods, so that it can accurately check abnormalities in the outer diameters of the fuel rods.