Self-aligning neutron absorber insert for nuclear fuel storage
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Solution Overview
Problem
Conventional neutron absorber materials in nuclear fuel storage racks, such as Boraflex and Tetrabor, degrade over time, leading to reduced reactivity and the need to reduce fuel storage density, causing operational hardships in nuclear generation plants.
Innovation Solution
A neutron absorber insert system is developed, comprising a plurality of absorber inserts that can be directly inserted into existing storage cells, utilizing a locking feature to secure the inserts without modifying the fuel rack, allowing for remote deployment underwater, thus maintaining storage capacity and reactivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional polymeric neutron absorber materials (Boraflex, Tetrabor) are used in storage cells, then reactivity control is achieved, but the materials degrade over time causing splitting and erosion, forcing reduction of storage density
Solution Approach 1:
The patent replaces the conventional polymeric neutron absorber materials (Boraflex, Tetrabor) with a metal-based neutron absorber insert that has superior long-term durability. The metal insert is designed to last the entire operational life of the storage cell without the splitting and erosion problems of polymeric materials, eliminating the need to reduce storage density due to material degradation.
Solution Approach 2:
The patent employs a composite structure combining a metal neutron absorber insert with a fuel storage cell. The metal insert provides enhanced neutron absorption capability and durability compared to conventional polymeric materials, while the composite design allows the insert to be easily installed and removed without modifying the existing cell structure.
2Reliability
If neutron absorber material is installed in existing storage cells, then reactivity reduction capacity is restored, but the fuel rack must be modified to accommodate the insert
Solution Approach 1:
The patent divides the neutron absorber system into a separate, self-contained insert that can be independently installed in existing storage cells. This segmentation allows the insert to be added without modifying the overall fuel rack structure, maintaining simplicity while restoring reactivity control capability.
Solution Approach 2:
The metal neutron absorber insert is designed to fit within the existing storage cell structure, effectively nesting the new component inside the old one. The insert utilizes the available space within the cell without requiring external modifications to the fuel rack, thereby restoring reactivity reduction capacity while maintaining structural simplicity.
3Adaptability or versatility
If storage density is reduced to compensate for degraded neutron absorbers, then operational flexibility is maintained, but fuel storage capacity decreases causing operational hardship
Solution Approach 1:
The patent introduces a durable metal neutron absorber insert that eliminates the need to reduce storage density due to material degradation. By using a long-lasting metal-based absorber instead of polymeric materials, the system maintains full storage capacity throughout its operational life without requiring density reductions that would cause operational hardships.
4Reliability
If existing fuel rack is modified to accommodate new neutron absorber, then reactivity control is improved, but installation time and expense increase
Solution Approach 1:
The patent segments the neutron absorber into a separate insert that can be independently installed in existing cells without modifying the fuel rack. This segmentation enables quick installation using remote handling equipment, significantly reducing installation time and cost while maintaining effective reactivity control.
Solution Approach 2:
The metal neutron absorber insert is designed to be self-contained with all necessary features (neutron absorption material, structural integrity, and compatibility with existing cells) integrated into a single component. This self-service design allows for rapid installation without requiring complex modifications to the fuel rack, thereby reducing installation time and expense while improving reactivity control.
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 neutron absorber insert system effectively restores reactivity reduction capacity in degraded storage cells, eliminating the need for rack modifications and reducing operational disruptions, while maintaining storage capacity and allowing for remote underwater installation.
Implementation Method 1
an elastically deformable locking protrusion disposed on one of the absorber plates, the locking protrusion resiliently movable between an outward extended position and an inward retracted position
Implementation Method 2
a plurality of neutron absorber apparatuses which may be in the form of absorber inserts configured for direct insertion into and securement to the fuel storage cells
Data Source
AI summary
A neutron absorber apparatus for use in restoring reactivity control to a nuclear fuel rack. The apparatus comprises an elongated tubular insert assembly configured for insertion in a storage cell of the rack. First and second absorber plates, each formed of a boron-containing material, are coupled together by upper and lower stiffening bands at the insert extremities and form a longitudinally-extending cavity configured for receiving a fuel assembly. The absorber plates and stiffening bands may have a rectilinear cross sectional configuration in one embodiment. At least one elastically deformable locking protrusion mounted proximate to the lower end of the absorber plates lockingly engages an available lower edge disposed in the cell sidewall above its bottom end. This fixes the tubular insert axially in the cell, thereby preventing its withdrawal after installing the insert. In one embodiment, the edge may be the bottom of existing absorber sheathing in the cell.