Guide Thimble Plug Screw Coupling Thermal Deformation
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Solution Overview
Problem
Conventional guide thimble plugs used in nuclear fuel assemblies often result in deformed welded portions when coupling a double tube structure of guide thimbles and shock absorption tubes to the bottom nozzle, leading to compromised assembly quality and reduced productivity due to thermal deformation and difficulty in maintaining the straightness of the guide thimble and shock absorption tube.
Innovation Solution
A guide thimble plug with an internal threaded hole for screw coupling to the bottom nozzle, an upper insert part for secure engagement with the shock absorption tube, and a thermal deformation prevention part that creates a gap to minimize thermal strain, along with a protruding part for support and caulking features for reliable assembly, ensuring stable coupling without excessive thermal expansion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If welding method is used to couple the guide thimble plug to the guide thimble and shock absorption tube, then strong joining strength is achieved, but thermal deformation occurs causing distorted welded portions and assembly difficulty
Solution Approach 1:
The coupling structure is divided into multiple functional parts: the guide thimble plug body, the guide thimble insertion portion, and the shock absorption tube insertion portion. Each part can be independently positioned and secured, allowing the welding process to be segmented into smaller, more controllable operations that reduce thermal deformation while maintaining overall joining strength.
Solution Approach 2:
Positioning protrusions and positioning grooves are provided beforehand to pre-align the guide thimble and shock absorption tube with the guide thimble plug before welding. This preliminary positioning ensures correct assembly precision is achieved before the welding process begins, preventing thermal deformation from causing misalignment.
2Stability of the object's composition
If the guide thimble and shock absorption tube are tightly coupled, then assembly stability is improved, but thermal strain during welding increases causing deformation
Solution Approach 1:
The guide thimble plug has different structural characteristics in different regions: the guide thimble insertion portion has positioning protrusions for tight coupling and stability, while the shock absorption tube insertion portion has a recessed structure that creates thermal strain relief zones. This local differentiation allows stable assembly in critical areas while reducing thermal strain in welding-prone areas.
Solution Approach 2:
The recessed structure in the shock absorption tube insertion portion acts as a beforehand cushioning feature that anticipates and accommodates thermal expansion during welding. This pre-designed space prevents thermal strain from causing deformation while maintaining assembly stability through the overall coupling structure.
3Device complexity
If a single guide thimble plug is used to couple both guide thimble and shock absorption tube, then device complexity is reduced, but assembly difficulty increases due to thermal deformation
Solution Approach 1:
The guide thimble plug is designed as a universal coupling component that simultaneously accommodates both the guide thimble and shock absorption tube through its dual insertion portions. This multi-functional design reduces the number of separate coupling devices needed while the built-in positioning and thermal strain relief features maintain assembly ease despite the combined coupling function.
Solution Approach 2:
The guide thimble plug serves as an intermediary component that mediates between the guide thimble and shock absorption tube, providing a standardized interface for both. This intermediary structure simplifies the overall assembly process by consolidating multiple coupling functions into a single mediating component with built-in alignment and positioning features.
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 solution enables reliable coupling of the guide thimble and shock absorption tube to the bottom nozzle, minimizing thermal deformation and enhancing the efficiency and quality of nuclear fuel assembly manufacturing by reducing thermal strain and assembly difficulties.
Implementation Method 1
an internal threaded hole formed therethrough so that the main body is coupled to the bottom nozzle by screw coupling
Implementation Method 2
a thermal deformation prevention part formed on the main body below the upper insert part, the thermal deformation prevention part being recessed inwards from an outer surface of the main body such that, when the main body is coupled to the guide thimble, a gap is defined between the thermal deformation prevention part and the guide thimble
Data Source
AI summary
A guide thimble plug for a nuclear fuel assembly is provided, in which an internal threaded hole is formed through a main body so that the main body is coupled to a bottom nozzle by a screw coupling. An upper insert part is formed in the upper end of the main body. The upper insert part is inserted into a shock absorption tube. A thermal deformation prevention part is formed on the main body below the upper insert part and is recessed inward from the outer surface of the main body such that, when the main body is coupled to the guide thimble, a gap is defined between the thermal deformation prevention part and the guide thimble. The guide thimble and the shock absorption tube can be reliably fastened to the bottom nozzle, and thermal deformation of the guide thimble can be minimized.