Removable Debris Shield for Nuclear Fuel Rod Protection
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Solution Overview
Problem
Conventional methods fail to effectively prevent debris from entering nuclear fuel assemblies during refueling, inspections, and when coolant flow is reversed, leading to potential fuel rod fretting and premature failure.
Innovation Solution
A method involving a removable or permanently integrated debris shield within the upper tie plate of a nuclear fuel bundle assembly that deflects, captures, and retains debris, allowing for the removal of fuel rods while maintaining structural support and minimizing coolant flow resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional upper tie plate is used without a removable debris shield, then the fuel bundle structure is simple and easy to manufacture, but debris can fall through and cause fuel rod fretting during reactor operation
Solution Approach 1:
The upper tie plate assembly is segmented into two main components: the upper tie plate itself and a separate debris shield. The debris shield can be further divided into a support structure and a debris trapping mechanism. This segmentation allows the debris shield to be removed independently for fuel rod replacement while maintaining the upper tie plate structure, thus protecting fuel rods from debris without requiring complete disassembly of the upper tie plate.
Solution Approach 2:
The debris shield acts as an intermediary component between the upper tie plate and the fuel rods. It provides a debris collection zone that intercepts falling debris before it can reach the fuel rods, while still allowing coolant flow and rod access. This intermediary structure resolves the contradiction by adding protection functionality without requiring fundamental changes to the upper tie plate design.
2Reliability
If the debris shield is permanently integrated into the upper tie plate, then debris protection is maximized, but fuel rod removal becomes difficult and time-consuming
Solution Approach 1:
The debris shield is designed with dynamic characteristics that allow it to transition between a fixed protective position during operation and a removable state during maintenance. The support structure includes features such as removable fasteners, snap-fit connections, or tool-less release mechanisms that enable quick deployment and removal of the debris shield when fuel rods need to be accessed, thus reducing maintenance time while maintaining protection during operation.
3Productivity
If the debris shield is designed to be removable for fuel rod access, then maintenance efficiency improves, but the structural integrity and debris blocking capability may be compromised
Solution Approach 1:
The debris shield is pre-configured with support structures and attachment mechanisms that ensure proper positioning and secure debris trapping before fuel rod removal begins. The design includes pre-positioned support elements that maintain the shield's structural integrity during the removal process, and pre-designed attachment points that allow rapid reinstallation after maintenance, thus preserving debris blocking capability while enabling efficient fuel rod access.
4Device complexity
If administrative controls are used to prevent debris entry, then no additional hardware is needed, but debris can still fall into fuel assemblies during refueling and inspection operations
Solution Approach 1:
The debris shield is designed to be self-contained and self-activating, requiring no external power source or complex control systems. The support structure automatically positions the debris trapping elements in the correct location, and the design leverages the natural flow of coolant and gravity to enhance debris collection. This self-service approach provides reliable debris prevention without adding complex hardware or control systems, making it suitable for use during refueling and inspection operations where administrative controls alone are insufficient.
Data Source
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AI summary
A method to clean or replace a debris shield in a nuclear reactor fuel bundle assembly (10), wherein the fuel bundle assembly includes a bundle of fuel rods (11, 12) in which the fuel enriched portions of the rods are below an upper tie plate (13, 100, 130, 150) and housed in a channel (20), the method comprising: inserting a debris shield (102, 136, 152, 168) in the upper tie plate; maintaining the shield in the upper tie plate and above the fuel enriched portions of the fuel rods, while the fuel assembly is in an operating nuclear reactor core (21); flowing coolant through the bundle and the debris shield during operation of the nuclear reactor core; capturing or deflecting debris flowing through the fuel bundle assembly with the debris shield; removing the fuel bundle assembly from the nuclear reactor core, and removing the debris shield from the upper tie plate.