Nuclear Fuel End Fitting Locknut With Visible Swage Locking
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Solution Overview
Problem
Existing end fitting fastening arrangements in nuclear fuel assemblies lack visual feedback for complete engagement and are complex, with additional components increasing costs and complexity.
Innovation Solution
A connection system using an end plug with a male threaded shaft and a female lock nut that can be visually verified for engagement, featuring a deformable locking mechanism for secure locking without welding or separate locking elements, facilitated by a designated tool for installation and swaging.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a threaded fastener with separate locking element is used to connect the lower end fitting to the guide tube, then the connection reliability is improved, but the device complexity and manufacturing cost increase
Solution Approach 1:
The locking element is integrated into the lower end fitting as a unitary structure, combining the fastening and locking functions into a single component. This eliminates the need for separate locking elements while maintaining connection reliability through the interlocked geometry of the integrated locking features.
2Reliability
If a threaded fastener with separate locking element is used to connect the lower end fitting to the guide tube, then the connection reliability is improved, but the manufacturing cost increases
Solution Approach 1:
The locking element is integrated into the lower end fitting as a unitary structure, combining the fastening and locking functions into a single component. This eliminates the need for separate locking elements while maintaining connection reliability through the interlocked geometry of the integrated locking features.
3Ease of operation
If a conventional threaded fastener is used without visual feedback features, then the assembly process is simpler, but the engagement completeness cannot be verified
Solution Approach 1:
The integrated locking element incorporates visual feedback features that allow operators to verify complete engagement and proper locking of the lower end fitting to the guide tube. This feedback mechanism provides immediate confirmation of correct assembly without complicating the fastening process.
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
Ensures reliable and visually confirmed engagement of fuel assembly components, reducing errors and complexity while eliminating the need for additional locking elements, thus simplifying the assembly process and reducing costs.
Implementation Method 1
female lock nuts may have locking portions that are outwardly deformed into recesses of the lower end fitting to lock the lock nuts with the lower end fitting
Data Source
AI summary
An apparatus including a lower end fitting having a top planar surface, a bottom planar surface, a counterbore defined therebetween, an opening extending from the counterbore to the top planar surface, and a lock recess that extends both radially outwardly from the counterbore and extends inwardly into the lower end fitting from the bottom planar surface. The apparatus includes a guide tube having a lower end and an end plug configured to connect with the lower end of the guide tube. The end plug has a threaded shaft sized to pass through the opening of the lower end fitting, and a female lock nut has a deformable side wall configured to be swaged into the recess of the lower end fitting. The lock recess remains visible as viewed from the bottom planar surface of the lower end fitting when the female lock nut is fully disposed in the counterbore.