Nuclear Fuel Assembly Segmentation for MOX UOX Energy Equivalence
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current nuclear fuel assemblies face challenges in achieving energy equivalence when using multi-recycled MOX fuel, particularly in mixed cores containing both MOX and UOX assemblies, due to neutron spectrum differences and plutonium isotopic degradation, which complicates reactor operation and manufacturing processes.
Innovation Solution
A nuclear fuel assembly design with a central zone of MOX fuel and a peripheral zone of UOX fuel, allowing for the use of multi-recycled MOX fuel in cores with UOX fuel, without requiring enrichment of uranium, thus maintaining energy equivalence and simplifying the manufacturing process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of substance
If multi-recycled MOX fuel is used in conventional MOX assemblies, then plutonium recycling is achieved, but energy equivalence with UOX assemblies deteriorates due to plutonium isotopic degradation
Solution Approach 1:
The fuel assembly is segmented into a central zone containing MOX fuel rods and a peripheral zone containing UOX fuel rods. This segmentation allows the MOX fuel to utilize multi-recycled plutonium while the UOX fuel in the periphery compensates for the degraded energy output, collectively achieving energy equivalence with conventional UOX assemblies.
Solution Approach 2:
Different zones of the fuel assembly are assigned different fuel types with specific local qualities: the central zone uses MOX fuel with multi-recycled plutonium for maximum recycling utilization, while the peripheral zone uses UOX fuel to ensure adequate energy output. This local differentiation resolves the contradiction between recycling and energy equivalence.
2Reliability
If uranium support material is enriched to restore energy equivalence, then energy equivalence is achieved, but manufacturing complexity increases due to managing multiple enrichment levels
Solution Approach 1:
Rather than enriching uranium to a higher level throughout the entire fuel assembly, the solution segments the assembly into MOX and UOX zones. This avoids the need to manage multiple uranium enrichment levels at the fabrication plant, as the UOX rods use standard enrichment while the MOX rods use recycled plutonium.
Solution Approach 2:
The UOX fuel rods in the peripheral zone act as an intermediary that compensates for the lower energy output of multi-recycled MOX fuel. This intermediary approach achieves energy equivalence without requiring complex enrichment management, as the UOX rods provide the necessary energy buffer.
3Loss of substance
If 100% MOX core is operated, then plutonium recycling is maximized, but absorber effectiveness is reduced due to neutron spectrum differences
Solution Approach 1:
The fuel assembly creates local quality differences between the central MOX zone and peripheral UOX zone. The UOX rods in the periphery produce a more thermal neutron spectrum that enhances absorber effectiveness, while the central MOX zone maintains high plutonium recycling. This local differentiation preserves control effectiveness while enabling recycling.
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
This design enables energy equivalence with UOX assemblies, allows for multi-recycling of MOX fuel, and maintains acceptable radial power distribution, reducing the complexity of reactor operation and manufacturing costs.
Implementation Method 1
a central zone (41), all the rods (24) in the central zone (41) being rods (24) whose fuel, before irradiation, is exclusively based on mixed oxide of uranium and plutonium, i.e. MOX fuel; and a peripheral zone (42) extending along the outer faces of the assembly (16), all the rods (24) in the peripheral zone (42) containing, before irradiation, uranium oxide but not plutonium oxide, i.e. UOX fuel
Data Source
Figure 1
Figure 2
Figure 3
AI summary
Said nuclear fuel assembly (16) for a pressurised water nuclear reactor comprises nuclear fuel rods (24), guide tubes (31) for receiving absorbent rods from a control cluster and, optionally, an instrumentation tube, the rods (24) being distributed into two areas (41, 42): - a central area (41), all the rods (24) of the central area (41) being rods (24) whose fuel, before irradiation, is exclusively composed of a mixture of uranium and plutonium oxide; and - a peripheral area (42) extending along outer surfaces of the assembly (16), all the rods of the peripheral area (42) being rods (24) containing, before irradiation, uranium oxide but no plutonium oxide.