Nuclear Fuel Lower Nozzle Debris Filter Retention
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Solution Overview
Problem
Conventional lower nozzles for nuclear fuel assemblies are costly to manufacture and inefficient in filtering debris, leading to potential damage to fuel rods and reactor shutdowns, which are expensive and disruptive.
Innovation Solution
A lower nozzle design featuring a transverse lower tie plate, a tubular skirt with snap-fit springs that retain and center a debris filter, ensuring efficient coolant flow while preventing debris from reaching the fuel rods, with the springs configured to seal gaps and create a secure axial retention mechanism.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a debris filter is snap-fitted in the housing of the lower nozzle, then debris filtration is achieved, but the filter can be easily dislodged by coolant flow and is difficult to replace
Solution Approach 1:
The debris filter is designed as a separate, removable component that can be independently replaced without disassembling the entire lower nozzle assembly. The filter element is segmented from the housing structure, allowing for easy removal and replacement while maintaining reliable filtration function during operation.
Solution Approach 2:
The debris filter is designed with dynamic retention features including protrusions that engage with recesses in the housing and elastic retaining elements that provide continuous axial retention force. This dynamic engagement prevents dislodgement by coolant flow while allowing controlled removal for replacement.
2Stability of the object's composition
If the debris filter is retained axially in the housing, then filtration stability is improved, but the filter cannot be easily removed for replacement
Solution Approach 1:
The debris filter is designed as a separable component with distinct engagement features (protrusions and recesses) that allow stable axial retention during operation but enable easy removal when needed for replacement or maintenance.
Solution Approach 2:
The retaining mechanism uses elastic elements and geometric engagement features that provide dynamic axial stability during operation while allowing controlled release for removal. The protrusions engage with recesses to maintain stability, but the same features guide removal when required.
3Reliability
If the lower nozzle is designed with a debris filter, then fuel rod protection is achieved, but manufacturing cost and complexity increase
Solution Approach 1:
The debris filter is designed as a separate, modular component that can be manufactured independently and assembled into the lower nozzle. This segmentation allows for simplified manufacturing of individual components and easier assembly, reducing overall manufacturing complexity and cost while maintaining fuel rod protection.
Solution Approach 2:
The lower nozzle design integrates multiple functions (coolant flow channeling, debris filtration, and filter retention) into a unified structure with standardized features. The housing and retaining mechanisms are designed to accommodate filter elements while maintaining structural integrity, reducing overall design complexity.
4Reliability
If the debris filter is securely retained in the housing, then filtration reliability is improved, but the filter cannot be easily replaced causing reactor shutdown
Solution Approach 1:
The debris filter is designed as a modular, separable component that can be quickly removed and replaced without disassembling the entire lower nozzle assembly. This segmentation enables rapid filter replacement while maintaining secure retention during operation, minimizing reactor downtime.
Solution Approach 2:
The retaining mechanism uses elastic elements and geometric features that provide secure axial retention during operation but enable quick release for replacement. The dynamic engagement features allow the filter to be held firmly during coolant flow while enabling rapid removal when needed, reducing reactor downtime.
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 design enhances debris filtration efficiency, reduces manufacturing costs, and allows for easy replacement of the debris filter, minimizing reactor downtime and operational expenses.
Implementation Method 1
snap-fit springs for retaining the debris filter in the housing after insertion, wherein the springs are configured to shift the debris filter axially towards the lower tie plate
Implementation Method 2
a debris filter configured for axial insertion in the housing and snap-fit springs for retaining the debris filter in the housing after insertion
Implementation Method 3
the springs are configured to seal gaps between side faces of the debris filter and inner faces of the housing
Data Source
AI summary
A lower nozzle for use in a nuclear fuel assembly provided. The lower nozzle is of the type having an axis and comprising a transverse lower tie plate for channeling the coolant through the lower tie plate and a tubular skirt extending axially from the periphery of the lower tie plate, the skirt delimiting an axial housing closed at one end by the lower tie plate and open at the opposite end, a debris filter configured for axial insertion in the housing and snap-fit springs for retaining the debris filter in the housing after insertion. The springs are configured to shift the debris filter axially towards the lower tie plate.