Nuclear Fuel Sheath Deformation for Efficient Emptying
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Solution Overview
Problem
Existing methods for emptying nuclear fuel cladding are inefficient, particularly when fuel pellets have little clearance with the sheath, are fragile, non-homogeneous, or flaking, leading to jamming and irregularities that hinder the grinding process and fuel extraction.
Innovation Solution
A method involving repeated cycles of progressive and degressive ovalization of the cladding using rollers with a conical attack and exit portion, gradually crushing the fuel and restoring the original roundness of the sheath, facilitated by a machine with inclined rollers and a sheath guide for effective emptying.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If plastic deformation is applied to the sheath using rollers to reduce thickness and increase diameter, then clearance with fuel is increased facilitating emptying, but the process fails when pellets are fragile, non-homogeneous, or flaking causing alterations and interruptions in reduction
Solution Approach 1:
The sheath is opened in advance before the rolling operation, ensuring that the opening is positioned flush with or slightly beyond the first fuel pellet. This preliminary action prevents the rolling pressure from creating a constriction at the opening location, thereby maintaining continuous process operation even with fragile or non-homogeneous pellets
Solution Approach 2:
The rolling process parameters are optimized by controlling the reduction percentage (typically 5-15% of original diameter) and the number of rolling passes. This parameter control ensures sufficient fuel grinding while maintaining sheath integrity and preventing process interruptions with fragile pellets
2Ease of operation
If the sheath opening is made flush with the first fuel pellet to prevent constriction, then fuel outlet is maintained, but the cutting tool may be damaged if it contacts the fuel
Solution Approach 1:
A positioning device or guide is introduced as an intermediary element between the cutting tool and the fuel pellets. This intermediary ensures the opening is positioned flush with the first pellet while preventing direct contact between the cutting tool and fuel, eliminating the damage risk while maintaining fuel outlet
Solution Approach 2:
The sheath opening position is predetermined and prepared in advance with precise positioning, ensuring it aligns flush with the first fuel pellet before the rolling operation begins. This preliminary positioning prevents constriction while avoiding cutting tool contact with fuel
3Productivity
If repeated ovalization cycles are applied to crush fuel and improve emptying, then grinding effectiveness increases, but the sheath shape becomes irregular affecting fuel extraction
Solution Approach 1:
The rolling operation is applied in repeated periodic cycles, where the sheath passes between rollers multiple times with each pass creating incremental ovalization. This periodic action gradually crushes the fuel while the cumulative effect maintains overall sheath roundness, preventing irregularities that would hinder fuel extraction
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 approach ensures better emptying of nuclear fuel cladding by achieving fine grinding of fuel pellets while maintaining the original shape of the sheath, reducing diameter by at least 3%, and ensuring efficient fuel extraction even with long duct lengths.
Implementation Method 1
applying a deformation to the cladding by repeated ovalization for a plurality of cycles involving plastic deformations of the cladding
Implementation Method 2
a sheath guide for effective emptying
Data Source
Figure 1~2
Figure 3~5
AI summary
The invention relates to a machine that includes two rollers (3) for imparting an oval shape to a nuclear fuel sheath (16) in order to crush the content thereof so that said content can easily be removed even when the pellets have been arranged within the sheath with little clearance. The opposite inclinations of the rollers (3) promote the automatic advance of the sheaths (16). The opening and the inclination of the sheaths result in the discharge of the crushed fuel. The rollers are biconical with an inlet portion having an increasing diameter and an outlet portion having a decreasing diameter in order to apply a sufficiently oval shape for crushing the fuel while restoring the circular symmetry of the sheath at the machine outlet for facilitating the flow of debris.