Fuel Assembly Shock-Absorbing Device for Drop Impact Protection
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Solution Overview
Problem
Fuel assemblies in nuclear reactors face deformation risks during transportation due to impact forces, particularly when the transporting cask drops vertically, leading to potential damage of the fuel rods.
Innovation Solution
A shock-absorbing device is implemented, comprising a nozzle support fitted to the depression of the nozzle and a buffer with stiffness equal to or less than the nozzle support, which absorbs and distributes impact forces, preventing deformation of the nozzles and subsequently the fuel rods.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the fuel assembly is transported without shock-absorbing protection, then the device complexity is reduced, but the fuel assembly deforms due to impact forces during dropping
Solution Approach 1:
The patent applies beforehand cushioning by installing shock-absorbing buffers between the fuel assembly and the cask bottom/lid before transportation. These buffers are positioned in advance to absorb impact forces during potential dropping events, preventing deformation of the fuel assembly while maintaining relatively simple device complexity
Solution Approach 2:
The patent uses shock-absorbing buffers as intermediary elements between the fuel assembly and the cask structure. These buffers act as mediators that absorb and distribute impact forces, protecting the fuel assembly from direct contact with hard surfaces during dropping events
2Reliability
If a rigid support structure is used to prevent fuel assembly deformation, then the fuel assembly integrity is improved, but the impact force is transmitted directly causing nozzle bending
Solution Approach 1:
The patent applies parameter changes by selecting buffer materials and designs with specific stiffness parameters that allow them to deform under impact loads. The buffers have controlled mechanical properties that enable them to absorb impact energy through elastic or plastic deformation, changing the force transmission characteristics from rigid to compliant
Solution Approach 2:
The patent may use composite material structures for the buffers that combine different materials with complementary properties. These composite structures provide both the necessary strength to support the fuel assembly and the compliance to absorb impact forces, preventing both direct force transmission and assembly deformation
3Shape
If the nozzle support stiffness is high, then the nozzle deformation is reduced, but the impact force absorption capability is decreased
Solution Approach 1:
The patent applies segmentation by dividing the shock-absorbing function into multiple separate buffer elements rather than using a single rigid support structure. These segmented buffers are distributed around the fuel assembly, with each element absorbing portion of the impact energy while collectively maintaining nozzle shape stability
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
The shock-absorbing device effectively suppresses deformation of the fuel assembly during drops by absorbing impact forces, ensuring the integrity and safety of the fuel rods and the assembly.
Implementation Method 1
a buffer (11) combined with the nozzle support (12), with stiffness in a longitudinal direction of the fuel rods being equal to or less than that of the nozzle support (12)
Data Source
Figure 1
Figure 2
Figure 3A~3C
AI summary
A fuel assembly 20 is constituted by combining a plurality of fuel rods 21, holding the fuel rods 21 by a plurality of support grids 22, and arranging a lower nozzle 24 and an upper nozzle 23 at opposite ends of the fuel rods 21. A shock-absorbing device 10 for a fuel assembly is fitted to the lower nozzle 24 and the upper nozzle 23. The shock-absorbing device 10 for a fuel assembly is constituted a nozzle support 12 fitted to a depression 24U of the lower nozzle 24 and a depression 23U of the upper nozzle 23, and a buffer 11 combined with the nozzle support 12, with stiffness thereof in a longitudinal direction of the fuel rods 21 being equal to or lower than that of the nozzle support 12.