Fuel Assembly Bundle Retention Clip for Tie Plate Stability
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Solution Overview
Problem
In boiling water reactors, the vertical hydraulic forces during transient conditions can cause the lower tie plate of conventional fuel bundles to lift from its seated position, leading to potential instability and misalignment of the fuel bundle.
Innovation Solution
The introduction of a bundle retention clip with angled spring members and a base region, which is designed to be inserted into a slot on the lower tie plate and channel nosepiece, providing additional upward force resistance to prevent lift by exerting a downward force when the tie plate is subjected to upward motion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional fuel bundle structure is used, then the structure is simple, but the lower tie plate can lift from its seated position during transient conditions
Solution Approach 1:
The fuel assembly is divided into distinct components: the lower tie plate, the bundle retention clip, and the channel nosepiece. The retention clip acts as a separate segment that connects the tie plate to the nosepiece, providing independent functionality for preventing lift while maintaining the overall structural integrity of the fuel assembly.
Solution Approach 2:
The bundle retention clip is pre-installed on the channel nosepiece before the lower tie plate is positioned. This preliminary action ensures that the retention mechanism is already in place to counteract upward forces, preventing the tie plate from lifting during transient conditions rather than reacting after the problem occurs.
2Reliability
If the bundle retention clip is added to prevent lift, then the stability is improved, but the assembly complexity increases
Solution Approach 1:
The bundle retention clip combines multiple functions into a single component: it attaches to the channel nosepiece, engages with the lower tie plate, and provides upward force resistance through its spring members. This merging of functions reduces the need for multiple separate components while maintaining improved stability.
Solution Approach 2:
The spring members of the bundle retention clip are designed to be flexible and responsive to dynamic conditions. They can compress and expand to accommodate thermal expansion and contraction, as well as dynamic loads during operation, providing adaptive stability rather than rigid constraint.
3Force
If spring members with angled edges are used, then the force resistance is increased, but the manufacturing precision requirements increase
Solution Approach 1:
The spring members are designed with specific geometric parameters, including angled edges at defined angles (e.g., 45 degrees). By optimizing these parameters, the spring members achieve maximum force resistance while remaining manufacturable with standard tolerances. The angled geometry transforms vertical forces into lateral components that enhance the retention mechanism's effectiveness.
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 bundle retention clip effectively increases the force required to displace the lower tie plate, ensuring it remains seated and maintaining the desired position of the fuel bundle, thereby enhancing stability and preventing unintended movement.
Implementation Method 1
The at least one spring member includes a first protrusion extending outward from a central axis of the retention clip... causes the spring member to contract... configured to respond to the inward rotation by exerting an outward, lateral force
Data Source
Figure 1
Figure 2A
Figure 2B
AI summary
A fuel assembly (100) may include a channel nosepiece (190'); a lower tie plate (120') positioned above the channel nosepiece (190'); and at least one bundle retention clip (200A) connected to the channel nosepiece (190') and the lower tie plate (120') and configured to resist movement of the lower tie plate (120') away from the channel nosepiece (190').