Nuclear Fuel Assembly Body Composite Structure for Neutron Balance
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current nuclear fuel assembly bodies for sodium-cooled fast neutron reactors face challenges with mechanical integrity and neutron compatibility at high temperatures, as stainless steels used degrade beyond the operating temperature range, and refractory materials are incompatible from a neutron perspective.
Innovation Solution
A composite assembly body is designed with metal end sleeves and a central ceramic structure, optimizing material choice to improve neutron balance and mechanical properties, featuring a perforated metallic frame and internal ceramic channels to control fluid flow and minimize neutron-inhibiting material volume.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If stainless steel is used for the assembly body, then mechanical strength and structural integrity are ensured, but neutron compatibility deteriorates at high temperatures due to material degradation
Solution Approach 1:
The patent employs a composite structure combining stainless steel end sleeves with a ceramic internal structure. The stainless steel provides mechanical strength and structural integrity, while the ceramic material (such as SiC or Si3N4) offers superior neutron compatibility and high-temperature stability. This composite approach resolves the contradiction by allowing each material to perform its optimal function without the limitations of using a single material for both mechanical and neutron requirements.
2Temperature
If refractory materials are used to withstand high temperatures, then temperature resistance is improved, but neutron compatibility worsens due to incompatible neutron properties
Solution Approach 1:
The patent selects specific ceramic materials such as silicon carbide (SiC) or silicon nitride (Si3N4) that provide both high-temperature resistance and acceptable neutron compatibility. These ceramics can withstand temperatures up to 1400-1600°C while having lower neutron absorption cross-sections compared to traditional refractory materials, thus resolving the contradiction between temperature resistance and neutron compatibility.
Solution Approach 2:
The ceramic material is specifically placed in the internal structure where it directly contacts the cooling fluid and fuel elements, providing localized high-temperature resistance where most needed, while the stainless steel end sleeves handle the mechanical loading. This local differentiation optimizes both temperature and neutron properties in their respective zones.
3Strength
If a monolithic metallic tube is used for the body, then mechanical connection and structural rigidity are ensured, but the volume fraction of neutron-inhibiting materials increases
Solution Approach 1:
The patent divides the assembly body into separate functional components: stainless steel end sleeves for mechanical connection and structural rigidity, and a ceramic internal structure for fluid guidance and fuel containment. This segmentation reduces the overall volume of neutron-inhibiting stainless steel while maintaining necessary mechanical properties through the steel-ceramic composite architecture.
Solution Approach 2:
The patent extracts the function of guiding cooling fluid and containing fuel elements from the metallic tube and assigns it to a separate ceramic internal structure. This extraction removes the unnecessary metallic material from the central flow path, reducing the volume fraction of neutron-inhibiting materials while preserving all essential functions.
Data Source
Figure 1
Figure 2
Figure 3
AI summary
The invention relates to a body for a nuclear fuel assembly having a longitudinal axis (X) and comprising: first (4) and second (6) tubular segments made of a metal material and forming the longitudinal ends of the assembly body; a frame (8) made of a metal material and connecting the first (4) and second (6) segments, wherein the frame (8) is perforated; and an inner tubular ceramic structure (10) arranged between the first (4) and second (6) segments inside the frame (8).