Mandrel-Wound Eccentric Fuel Cores to Reduce Insulation Cracking
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Solution Overview
Problem
Conventional nuclear thermal propulsion reactors face failure modes such as cracking of insulation layers, layer separation, and ablation, allowing hot propellant gas to penetrate and cause casing failure, necessitating improvements in fuel assembly geometry, structure, and manufacturing.
Innovation Solution
The development of an insulated fuel assembly core comprising eccentric cylinder-shaped fuel monoliths, an exhaust support plate, and an exhaust shield assembly, manufactured through mandrel winding with tensioned fuel monolith stacks and insulation layers to enhance alignment and protection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional ribbon fuel forms are assembled into a tube with insulation layers, then the fuel assembly can be constructed, but cracking of the insulation layer, layer separation, and ablation occur allowing hot propellant gas to penetrate
Solution Approach 1:
The fuel assembly is divided into discrete monolithic fuel bodies stacked in series, each with its own insulation layer and flow channels. This segmentation allows each component to be independently optimized and reduces stress concentration points that would lead to cracking in continuous structures.
Solution Approach 2:
The patent uses composite construction with monolithic fuel bodies made of fissionable material combined with insulation layers, creating a multi-material structure that provides both nuclear fuel functionality and thermal protection, preventing gas penetration while maintaining structural integrity.
2Manufacturing precision
If stacked monolithic fuel bodies are used with mandrel winding insulation, then alignment is improved and defects are reduced, but the manufacturing process becomes more complex
Solution Approach 1:
A mandrel assembly with tensioning cables and alignment features serves as an intermediary tool during manufacturing. The mandrel provides a temporary structural framework that holds fuel monoliths in precise alignment while insulation layers are wound around them, ensuring manufacturing precision without requiring complex permanent fixtures.
Solution Approach 2:
The mandrel assembly with pre-installed tensioning cables and alignment features is prepared before fuel monolith stacking. This preliminary configuration establishes the geometric framework that guides precise alignment of fuel monoliths and ensures proper positioning before the insulation winding process begins.
3Ease of manufacture
If tensioned fuel monolith stack mandrel assembly with mandrel winding is used, then insulation layer application is improved, but manufacturing time and process steps increase
Solution Approach 1:
The mandrel winding process applies insulation layers continuously around the tensioned fuel monolith stack in a single operational sequence. The tensioning cables maintain constant pressure during the winding process, ensuring uniform insulation application without interruption, which improves ease of manufacture despite the complex setup.
Data Source
AI summary
Insulated fuel assembly core with plurality of fuel monoliths, exhaust support plate, exhaust shield assembly, and insulation layer in which the plurality of fuel monoliths are located axially along a longitudinal axis and each of the plurality of fuel monoliths has a shape of an eccentric cylinder and a composition including a fissionable fuel component. Channels in the exhaust support plate are oriented so that propellant gas flow through the exhaust support plate does not impinge the exhaust shield assembly. The insulated fuel assembly core is manufactured by forming a tensioned fuel monolith stack mandrel assembly using mandrels spacers and internal tensioning components and forming an insulation layer on an outer surface of the tensioned fuel monolith stack mandrel assembly by mandrel winding. The insulated fuel assembly core can be incorporated into a fuel assembly of nuclear propulsion fission reactor structure of, for example, a nuclear thermal propulsion engine.