Nuclear Reactor Fuel Assembly Removable Head Design
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Solution Overview
Problem
The existing nuclear reactor fuel assembly design limits uranium capacity due to increased axial dimensions, which restricts the height of the fuel column and requires precise positioning of collet tubes to avoid jamming, and does not allow for reduced head height without altering the assembly dimensions.
Innovation Solution
The design incorporates a removable head with a tubular upper shell and coaxially located collet tubes, featuring base platforms and bosses, allowing for reduced axial dimensions while maintaining the ability to absorb control rod energy through springs, thus enabling increased uranium capacity without altering the assembly's end-to-end dimensions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the removable head is designed with traditional collet tubes fixed to guide channels and upper shell plate, then the control rod can be supported, but the axial dimensions of the head increase and uranium capacity is limited
Solution Approach 1:
The collet tube is divided into two separate parts: a lower collet tube fixed to the guide channel and an upper collet tube fixed to the upper shell plate. These two parts work together to support the control rod, allowing the head height to be reduced while maintaining support functionality. The segmentation enables independent positioning of each collet tube part, optimizing space utilization.
Solution Approach 2:
The invention introduces a radial clearance dimension between the support element and the upper shell plate hole, allowing the support element to move radially within the hole. This radial movement capability provides an additional degree of freedom that compensates for reduced axial height, enabling the head to maintain control rod support functionality with smaller axial dimensions.
2Reliability
If the holes in the upper shell plate are accurately positioned for collet tube passage, then jamming is avoided, but manufacturing complexity increases
Solution Approach 1:
Instead of requiring precise positioning of holes for exact collet tube passage, the invention provides excessive radial clearance between the support element and the hole. This excessive clearance ensures that the collet tube can move radially within the hole, preventing jamming even with less precise hole positioning. The radial movement capability compensates for manufacturing tolerances.
3Reliability
If the upper shell height is increased to prevent collet interaction with control rod elements, then control rod support is improved, but head height increases and uranium capacity is reduced
Solution Approach 1:
The collet support system is segmented into lower and upper parts that can independently position themselves radially. This segmentation allows the upper shell plate hole to be positioned lower without causing collet-control rod element interaction, as the radial clearance prevents unwanted contact. The segmented design enables optimized height while maintaining reliable control rod support.
Solution Approach 2:
The radial clearance acts as an intermediary space between the support element and the upper shell plate hole, allowing controlled movement and preventing direct contact between the collet and control rod elements. This intermediary clearance zone enables the head height to be reduced while still preventing harmful interactions.
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 design effectively reduces the axial dimensions of the removable head, allowing for a higher fuel column height and increased uranium capacity while ensuring stable fixation and energy dissipation during emergency protection, without increasing the overall assembly dimensions.
Implementation Method 1
springs (8)
Implementation Method 2
falling control rod energy dissipation
Data Source
AI summary
Nuclear reactor fuel assembly comprising fuel elements installed in a frame having guide channels and spacer grids; a bottom nozzle; and a removable head. The head comprising collet tubes, an upper shell, a support element in the form of a tube, and springs. The collet tubes comprise two coaxially arranged tubes that are movable relative to each other and that each have stops on their side surfaces. The stops interact with each other to select the length of the collet tubes. The upper shell has a tube with a rigidly fixed plate interacting with the springs. The plate has plural holes having a shape corresponding to a shape of a respective boss of the support element. The clearance in plan view between a respective hole and a respective boss being at least the mounting clearance between the tube of the support element and the tube of the upper shell.