Mandrel-Wound Splined Monolithic Fuel Assembly Core
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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, which allow hot propellant gas to penetrate and cause casing failure.
Innovation Solution
The development of an insulated fuel assembly core with a plurality of fuel monoliths, an exhaust support plate, an exhaust shield assembly, and an insulation layer, where the fuel monoliths are stacked axially and have a shape of an eccentric cylinder or a right circular cylinder, and splining features are used to align and prevent rotation of the structures.
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 and cause failure
Solution Approach 1:
The fuel assembly is divided into discrete monolithic fuel elements rather than continuous ribbon fuel. Each monolith is a self-contained unit with integrated insulation, eliminating the layered tube structure that is prone to cracking and separation. The segmentation into individual monoliths allows each unit to maintain structural integrity independently.
Solution Approach 2:
The fuel and insulation are merged into a single monolithic structure rather than separate layers. The monolithic fuel element integrates the fuel core and insulation layer into one unified component, eliminating the interface between layers where cracking and separation occur in conventional designs.
2Manufacturing precision
If fuel monoliths are stacked axially to form an insulated fuel assembly core, then manufacturing precision and alignment are improved, but device complexity increases due to splining features and multiple components
Solution Approach 1:
Splining features are incorporated into the fuel monoliths to prevent rotation and ensure precise alignment. The asymmetric splines provide a mechanical keying system that eliminates the need for complex external alignment mechanisms while maintaining manufacturing precision during assembly.
Solution Approach 2:
Alignment features and splining elements are pre-integrated into the fuel monoliths during manufacturing. This preliminary incorporation of alignment mechanisms ensures precise stacking and positioning occurs automatically during assembly, reducing the need for post-assembly adjustments and complex alignment procedures.
Data Source
AI summary
Insulated fuel assembly core with axially arranged fuel monoliths including channels and having a composition including a fissionable fuel component, exhaust support plate, exhaust shield assembly, and insulation layer. Fuel monoliths have an eccentric cylinder shape or a right circular cylinder shape with side surface keyway. The eccentric shape and/or a keyway (with associated alignment rod) provide alignment. Channels in the exhaust support plate are oriented so propellant gas flowing from the fuel monoliths through the exhaust support plate does not impinge the exhaust shield assembly. Insulated fuel assembly cores are manufactured by forming a tensioned fuel monolith stack mandrel assembly using mandrel spacers and internal tensioning components and mandrel winding an insulation layer on an outer surface of the tensioned fuel monolith stack mandrel assembly. Insulated fuel assembly cores can be incorporated into fuel assemblies of nuclear propulsion fission reactor structures, for example, a nuclear thermal propulsion engine.