Segmented Rod Assembly with Adaptor Subassemblies for Fretting Wear Reduction
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Solution Overview
Problem
Nuclear reactors face issues with debris, such as small fasteners and metal clips, getting wedged between fuel rods and causing fretting wear, leading to potential fuel rod failure and premature withdrawal from service, despite the use of debris filters which do not completely obviate the problem.
Innovation Solution
A rod assembly for nuclear reactors comprising multiple segments connected via adaptor subassemblies at spacer locations, shifting the fretting wear from the rod segments to the adaptor subassemblies, and including irradiation targets within the segments for producing desired isotopes when irradiated.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If debris filters are employed to filter debris from reactor coolant, then debris removal is improved, but fretting wear on fuel rods still occurs
Solution Approach 1:
The fuel rod is divided into multiple rod segments connected by adaptor subassemblies. The adaptors are positioned at spacer locations where debris tends to accumulate, allowing the adaptors to absorb fretting wear while protecting the rod segments. This segmentation enables targeted protection at critical locations without compromising the overall structural integrity of the fuel rod.
2Reliability
If rod assembly uses multiple segments connected via adaptor subassemblies, then fretting wear on rod segments is reduced, but device complexity increases
Solution Approach 1:
Adaptor subassemblies serve as intermediary components between rod segments. These adaptors are strategically positioned at spacer locations where debris accumulation is most problematic. The adaptors act as sacrificial elements that protect the rod segments from fretting wear, reducing the need for complex protective coatings or designs on the rod segments themselves.
3Device complexity
If rod segments are made longer to reduce number of connections, then device complexity is reduced, but fretting wear resistance decreases
Solution Approach 1:
The rod assembly employs local quality by concentrating protective adaptor subassemblies at specific spacer locations where fretting wear is most likely to occur, rather than uniformly protecting the entire rod length. This allows for effective wear protection at critical points while maintaining simpler rod segment designs with fewer connections.
Data Source
AI summary
A rod assembly for a fuel bundle of a nuclear reactor may include an upper end piece, lower end piece and a plurality of rod segments attached between the upper and lower end pieces and to each other so as to form an axial length of the rod assembly. The rod assembly may include an adaptor subassembly provided at given connection points for connecting adjacent rod segments or a given rod segment with one of the upper and lower end pieces. The connection points along the axial length of the rod assembly may be located where the rod assembly contacts a spacer in the fuel bundle. One (or more) of the rod segments may include an irradiation target therein for producing a desired isotope when a fuel bundle containing one (or more) rod assemblies is irradiated in a core of the reactor.