Nuclear Bottom End-Piece Baffle Design for Debris Retention
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Solution Overview
Problem
Conventional bottom end-pieces for nuclear fuel assemblies in light water reactors face challenges in balancing debris retention capacity with pressure drop, leading to potential fretting and damage to fuel rods due to lateral water flows and vibrations.
Innovation Solution
The design incorporates nozzles arranged at nodes of a regular network within the bottom end-piece, combined with an anti-debris device that forms offset water flow channels and baffles to direct and retain debris, reducing pressure drop while enhancing debris retention capacity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If complex anti-debris devices are integrated in the bottom end-piece, then debris retention capacity is improved, but pressure drop increases
Solution Approach 1:
The anti-debris device is segmented into multiple independent baffles (first baffle, second baffle, third baffle) arranged at different positions and orientations. Each baffle captures debris in different flow zones, distributing the retention function across multiple simple elements rather than one complex structure, thereby maintaining low pressure drop while achieving high debris retention capacity.
Solution Approach 2:
The invention introduces baffles that extend in the radial direction (perpendicular to the main axial flow) to create multi-dimensional flow paths. The first baffle extends radially outward, the second baffle extends radially inward, and the third baffle extends axially, creating a three-dimensional debris capture network that intercepts debris from multiple directions without significantly increasing pressure drop.
2Reliability
If bottom end-pieces with higher pressure drop are used to increase debris retention, then debris retention capacity is improved, but cooling efficiency decreases and fretting damage increases
Solution Approach 1:
The anti-debris function is segmented into multiple oriented baffles that work together to capture debris without creating a single high-resistance flow path. The segmented baffle structure allows cooling water to flow through multiple alternative paths, maintaining high cooling efficiency while achieving effective debris retention through the combined action of all baffles.
Solution Approach 2:
The baffles act as intermediary elements that intercept debris particles from the cooling water flow without significantly obstructing the overall water flow. The baffles are positioned and oriented to capture debris while allowing water to flow around them, serving as mediators between the debris retention requirement and the cooling efficiency requirement.
3Reliability
If lateral flows are increased to improve debris retention, then debris retention capacity is improved, but fretting damage to fuel rods increases
Solution Approach 1:
The baffles are strategically positioned and oriented to create localized flow disturbances only in regions where debris is likely to accumulate, while maintaining smooth vertical flow in the regions adjacent to fuel rods. The first baffle is positioned to capture debris in the upper region, the second baffle in the lower region, and the third baffle in the intermediate region, with each baffle oriented to minimize lateral flow impact on fuel rods while maximizing local debris capture 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
This configuration effectively reduces pressure drop, increases debris retention, and minimizes fretting damage to fuel rods by orienting water flow vertically and laterally retaining the lower ends of fuel rods, thus improving the overall performance and safety of the nuclear fuel assembly.
Implementation Method 1
at least one water passage comprises a first section and a second section which are mutually offset radially relative to the corresponding node of the network in order to form a baffle
Implementation Method 2
an anti-debris device which delimits water flow channels... effectively increases the capacity for retaining debris
Data Source
AI summary
This bottom end-piece includes nozzles for directing the flow of water of the reactor along the lower ends of the fuel rods, the nozzles being arranged at nodes of the substantially regular network of the fuel rods, and an anti-debris device which delimits water flow channels. At least some of the water flow channels are arranged at nodes of the substantially regular network. Direction nozzles are arranged at least partially in the channels in order to delimit water passages therewith, and at least one water passage includes a first section and a second section which are mutually offset radially relative to the corresponding node of the network in order to form a baffle.