Twisted Ribbon Fuel Bundle Casing for Radial Compression Stability
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Solution Overview
Problem
Existing twisted ribbon fuel rodlets in nuclear fission reactors face failure modes due to high temperature plasticity and axial force-induced twisting, as well as hot hydrogen ablation of insulation and casing materials, necessitating improvements in radial restraint and manufacturing processes.
Innovation Solution
The implementation of geometric-specific end fixtures, fiber architectures, and advanced manufacturing methods for twisted ribbon fuel rodlets, including extrusion, twisting, and defect detection, to enhance radial compression and uniformity, along with a multilayer casing design that includes compliant insulating layers and directional fibers to mitigate failure modes and improve performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If twisted ribbon fuel rodlets are used in nuclear thermal propulsion reactors, then fuel performance and power density are improved, but radial restraint and structural stability deteriorate due to high temperature plasticity and axial force-induced twisting
Solution Approach 1:
The patent implements a nested structure where twisted ribbon fuel rodlets are placed inside a tube restraint system, which is further enclosed within a fuel bundle casing. This nested arrangement provides multiple levels of structural support and radial restraint, preventing the fuel rodlets from deforming under axial forces while maintaining their high power density characteristics
Solution Approach 2:
The patent employs a tube restraint system with specific wall thickness and material properties that provide flexible yet sufficient radial support to the twisted ribbon fuel rodlets. The tube structure accommodates thermal expansion and deformation while maintaining structural integrity under high temperature and pressure conditions
2Device complexity
If simple tube restraint system is used for twisted ribbon fuel rodlets, then device complexity is reduced, but reliability deteriorates due to fuel element plasticity and twisting failure modes
Solution Approach 1:
The patent uses composite material structures for the tube restraint system and fuel bundle casing, combining materials with different mechanical properties to achieve both simplicity and high reliability. The composite structure provides enhanced strength-to-weight ratio and resistance to high temperature plasticity without significantly increasing system complexity
3Power
If twisted ribbon fuel rodlets operate at high temperatures, then power output is improved, but durability deteriorates due to hot hydrogen ablation of insulation and casing materials
Solution Approach 1:
The patent employs an inert or controlled atmosphere environment within the fuel bundle to protect insulation and casing materials from hot hydrogen ablation. This creates a protective environment that extends component durability while allowing the fuel rodlets to operate at high temperatures for optimal power output
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 solution strengthens the fuel bundle by maintaining radial compression, reducing fracture risk, and improving manufacturability, leading to enhanced performance and reduced failures in high-temperature regions of the fuel assembly.
Implementation Method 1
strengthen the twisted ribbon fuel rodlets (and materials of the fuel bundle casing) against fracture by keeping the entire fuel bundle in radial compression
Implementation Method 2
methods of manufacture including extrusion of ribbon fuel rodlets and twisting of ribbon fuel rodlets
Implementation Method 3
twisting of ribbon fuel rodlets to form twisted ribbon fuel rodlets that have uniform characteristics
Data Source
AI summary
Fuel bundle has plurality of twisted ribbon fuel rodlets arranged hexagonal packing or circle packing arrangement in a reactor core encased in a multilayer casing. Arrangement of twisted ribbon fuel rodlets is facilitated by rodlet seating fixture with seating surface having a plurality of protrusions that form a receiving space for ends of the twisted ribbon fuel rodlets. Manufacture of the fuel bundle incorporates fiber manufacturing technologies and, optionally, infiltration of spaces in the reactor core by infiltrant. Twisted ribbon fuel rodlet manufacturing system has sub-systems that impart twist periodicity to extruded ribbons, inspect twisted extruded ribbons, and cut twisted extruded ribbons to length. Inspection sorts twisted ribbon fuel rodlets as well as provides feedback to adjust operation of sub-systems. The fuel bundle (and optional fuel bundle support) can be incorporated into a fuel assembly of nuclear propulsion fission reactor structure of, for example, a nuclear thermal propulsion engine.