Nuclear Fuel Top Nozzle Spring Insert Hole Machining
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Solution Overview
Problem
Conventional top nozzles for nuclear fuel assemblies experience structural instability and manufacturing challenges due to widened T-slots and difficulties in precise machining of spring insert holes, leading to inadequate vibration absorption and potential deformation or breakage.
Innovation Solution
The top nozzle features spring insert holes formed through electro-discharge machining without T-slots, allowing for precise coupling of hold-down spring units and enhanced structural stability, achieved by casting a main body with integral coupling plates and perimeter walls, and using elliptical pin head seats to facilitate precise machining.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If spring insert holes are formed by milling with T-slots, then the machining process is simplified, but the T-slots widen under uplift force causing structural instability and loosening of hold-down spring units
Solution Approach 1:
The invention removes the T-slot structure from the spring clamp design. Instead of having T-slots that can widen and cause instability, the patent uses conventional through-holes for spring insertions. This extraction of the problematic T-slot element eliminates the structural instability while maintaining the functionality of spring insertion and fastening.
Solution Approach 2:
The invention inverts the conventional approach by not using T-slots for spring insertion but rather using standard through-holes. This inversion changes the fundamental geometry of the spring clamp from having T-shaped slots to having circular through-holes, thereby eliminating the widening problem under uplift force while maintaining ease of manufacture through standard drilling operations.
2Ease of manufacture
If spring insert holes are formed by milling, then the manufacturing process is straightforward, but precise machining is difficult due to the presence of fastening parts and T-slots
Solution Approach 1:
The invention removes the T-slot features and fastening parts that interfere with precise machining. By using conventional through-holes instead of T-slots, the patent eliminates the geometric complexities that make precise machining difficult, allowing for accurate spring insert hole formation without interference from surrounding structural features.
Solution Approach 2:
The invention separates the spring clamp function from the fastening function by using distinct through-holes for spring insertion rather than integrated T-slots. This segmentation allows each feature to be machined independently with high precision, as the spring insert holes are simple circular openings that can be accurately positioned and sized without the geometric constraints imposed by T-slot configurations.
3Ease of operation
If T-slots are used in spring clamps, then spring insertion is facilitated, but the T-slots widen under uplift force leading to inadequate vibration absorption and potential breakage
Solution Approach 1:
The invention removes the T-slot structure that causes widening under uplift force. By replacing T-slots with conventional through-holes, the patent maintains easy spring insertion while eliminating the structural weakness that compromises vibration absorption reliability. The through-holes provide stable, fixed positioning that prevents the widening problem.
Solution Approach 2:
The invention inverts the conventional T-slot design by using standard through-holes for spring insertion. This inversion changes the geometric configuration from T-shaped slots that widen under load to circular holes that maintain stable dimensions, thereby ensuring reliable vibration absorption and preventing spring clamp breakage while still facilitating easy spring installation.
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
This approach enhances the structural stability and manufacturing efficiency of the top nozzle, ensuring reliable vibration absorption and preventing deformation or breakage, while allowing for precise machining and improved coupling of hold-down spring units.
Implementation Method 1
a spring insert hole is formed by electro-discharge machining in a insert direction of the hold-down spring
Data Source
AI summary
A top nozzle is provided. The top nozzle can include a coupling plate, a perimeter wall and a hold-down spring unit. The coupling plate can be coupled to a guide thimble of the nuclear fuel assembly. The perimeter wall can protrude upwards from the perimeter of the coupling plate. A spring clamp can be provided on the upper surface of the perimeter wall. The hold-down spring unit can be mounted to the upper surface of the perimeter wall in such a way to couple a corresponding end of the hold-down spring unit to the spring clamp. A fastening pin hole can be vertically formed through an upper surface of the spring clamp. A spring insert hole into which the hold-down spring unit can be inserted and formed by electro-discharge machining in an insert direction of the hold-down spring.