BWR Fuel Assembly Snap-In Sleeve Spring Clamp
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Solution Overview
Problem
In nuclear fuel assemblies for boiling water reactors, the longitudinal holding force applied by spacer grids to partial length fuel rods may not be sufficient to prevent significant displacement or lift-off during reactor operation, necessitating additional attachment methods to ensure stability while maintaining cost-effectiveness.
Innovation Solution
A clamp system is introduced, where the clamp is an additional part fitted to the base, assembled via mechanical engagement, featuring support tabs and elastic retaining tabs to securely hold the lower end of partial length fuel rods, preventing upward or downward displacement and disengagement, and is designed for easy manufacturing and assembly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If clamps are made integral with the base, then the holding force and reliability are improved, but the manufacturing complexity and cost increase due to specific machining requirements
Solution Approach 1:
The clamp is separated from the base as an independent component. The base contains a housing that receives the clamp, allowing the clamp to be manufactured separately with simpler machining requirements while still providing the necessary holding force through its engagement with the housing.
Solution Approach 2:
The housing acts as an intermediary between the base and the clamp. It provides the mechanical engagement interface that connects the separately manufactured clamp to the base, enabling assembly without requiring complex integral machining of the base itself.
2Ease of manufacture
If clamps are made as additional separate parts, then the manufacturing cost and complexity are reduced, but the risk of lift-off during operation increases due to potential insufficient holding force
Solution Approach 1:
The clamp incorporates elastic assembly tabs that can deform elastically during assembly and operation. This dynamic capability allows the clamp to maintain continuous contact and adaptive holding force against the fuel rod, ensuring reliable retention while accommodating thermal expansion and operational movements.
Solution Approach 2:
The elastic properties of the assembly tabs change the mechanical parameters of the clamp-base connection. The elastic deformation capability allows the system to maintain optimal contact pressure and holding force under varying operational conditions, ensuring reliable fuel rod retention.
3Manufacturing precision
If integral clamps with adequate tolerances are used, then the longitudinal retention is sufficient, but the machining time and production cost increase
Solution Approach 1:
By segmenting the clamp from the base, each component can be manufactured with more relaxed tolerances using simpler, faster machining processes. The assembly tolerances are distributed between the housing and clamp interfaces rather than requiring high precision throughout the entire integral structure.
Solution Approach 2:
The clamp is designed as a simpler, more economical component that can be manufactured with standard machining tolerances. While individual clamps may be replaced, their simplified design and manufacturing process significantly reduce production costs compared to integral clamps requiring precision machining.
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 clamp system effectively reduces the risk of partial length fuel rod lift-off during reactor operation, simplifies the design and manufacturing process, and lowers costs by providing a secure and reliable attachment method without complex machining requirements.
Implementation Method 1
the first assembly comprise an abutting surface provided in the housing, and elastic assembly tabs, provided on the clamp and comprising free ends extending upwards, the abutting surface being adapted to engage with the free ends of the elastic assembly tabs
Implementation Method 2
the second assembly comprise a lower support surface provided in the housing, the support tabs being supported longitudinally on the lower support surface
Implementation Method 3
the clamp comprises elastic retaining tabs, spaced angularly about the longitudinal direction of the clamp and adapted to engage with a shoulder provided on the lower plug of the partial length fuel rod to prevent a disengagement of the partial length fuel rod from the base
Data Source
AI summary
A nuclear fuel assembly is provided for a boiling water reactor. The nuclear fuel assembly includes a base, a head, and a bundle of full length fuel rods and partial length fuel rods, said bundle extending upwardly and longitudinally from the base to the head. The nuclear fuel assembly includes at least one clamp for longitudinally retaining a lower plug of a partial length fuel rod with respect to the base. The clamp is an additional part fitted to the base, the clamp is at least partially received in a housing provided in the base, and the clamp is assembled to the base by mechanical engagement of complementary assemblies.