Swaged Lock Nut for Nuclear Fuel Assembly Visual Engagement
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Solution Overview
Problem
Existing end fitting fastening arrangements in nuclear fuel assemblies lack visual feedback for complete engagement, leading to potential errors, and often require additional components and complexity for locking mechanisms.
Innovation Solution
A connection system using a male threaded shaft from an end plug passing through the lower end fitting, secured by a female lock nut with a deformable locking mechanism, allowing visual verification of engagement and locking without welding or separate locking elements, utilizing a designated tool for installation and swaging.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a threaded fastener is used to connect the lower end fitting to the guide tube, then the connection can be assembled and disassembled, but visual feedback for complete engagement is lacking leading to potential errors
Solution Approach 1:
The patent applies feedback by providing visual indicators that allow operators to verify complete engagement of the threaded connection. The locking element incorporates features such as visible alignment marks or position indicators that provide immediate visual confirmation when the nut is properly tightened and engaged with the threaded shaft, eliminating uncertainty about connection completeness.
2Stability of the object's composition
If additional locking elements are added to prevent the threaded connection from working loose, then connection stability is improved, but device complexity increases
Solution Approach 1:
The patent merges the locking function directly into the nut structure itself. The locking element is integrated as part of the nut assembly, combining the fastening and locking functions into a single component rather than requiring separate locking elements. This integration reduces the number of parts while maintaining connection stability.
Solution Approach 2:
The locking element is designed to automatically engage and lock the threaded connection without requiring additional operations or separate components. The self-locking mechanism activates during the normal tightening process, providing automatic stabilization of the connection as the nut is threaded onto the shaft, eliminating the need for separate locking steps or elements.
3Device complexity
If a deformable locking mechanism is used in the lock nut, then welding and separate locking elements are eliminated, but the manufacturing process becomes more complex
Solution Approach 1:
The patent employs parameter changes by utilizing material deformability in the locking element. The locking mechanism relies on controlled plastic deformation of the nut material during assembly, where the deformable portion is shaped to engage with corresponding features on the shaft. This approach replaces welding and separate locking elements with a deformation-based locking mechanism that achieves equivalent or superior stability.
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 verified engagement of fuel assembly components, reducing errors and complexity while maintaining structural integrity and ease of assembly/disassembly.
Implementation Method 1
deforming a locking portion of the female lock nut into a recess of the nuclear reactor fuel assembly lower end fitting to lock the female lock nut with the nuclear reactor fuel assembly 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.