Ceramic Nuclear Fuel Pellets with Burnable Absorber
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Solution Overview
Problem
Current methods for producing uranium-gadolinium nuclear fuel with high gadolinium oxide content are hindered by significant labor and energy costs due to the need for additional operations and the use of aqueous solutions, leading to large open porosity and incomplete removal of plasticizers, which affect the oxygen potential and thermal conductivity of the fuel pellets.
Innovation Solution
The method involves using gadolinium hydroxycarbonate as a burnable absorber, sintering in a reducing environment with controlled humidity, and adding triuranium octoxide powder to achieve an optimal oxygen coefficient, resulting in improved thermal conductivity and reduced deformation of fuel pellets.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If additional operations (chemical precipitation, washing, drying) are used to obtain nanopowders of Gd(OH)3 and Al(OH)3, then the grain size increases and porosity can be adjusted, but labor and energy costs increase significantly
Solution Approach 1:
The patent applies preliminary action by pre-synthesizing gadolinium hydroxide nanopowder with controlled grain size (0.5-5.0 μm) before the main fuel pellet manufacturing process. This pre-prepared nanopowder is then directly mixed with uranium dioxide and other components, eliminating the need for subsequent chemical precipitation, washing, and drying operations during fuel production.
Solution Approach 2:
The patent extracts and eliminates the complex wet chemical processing steps (chemical precipitation, washing, drying) from the fuel manufacturing process. By using pre-synthesized nanopowder, the method removes these time-consuming operations while retaining the beneficial effects of controlled grain size and porosity adjustment.
2Ease of manufacture
If aqueous solutions of plasticizer are used, then the mixture can be prepared, but free uranium dioxide particles form and plasticizer cannot be completely removed, requiring additional operations
Solution Approach 1:
The patent changes the physical state parameter of the plasticizer from liquid (aqueous solution) to solid form. This parameter change eliminates the formation of free uranium dioxide particles and allows complete removal of the plasticizer during sintering, thereby improving the purity of the fuel pellets while maintaining ease of mixture preparation.
Solution Approach 2:
The patent uses a solid plasticizer that serves its binding function during mixing and compression, then is completely decomposed and removed during the sintering process. This disposable approach eliminates the need for additional operations to remove residual plasticizer, improving both purity and process efficiency.
3Quantity of substance
If pellets are produced with high open porosity, then the structure can accommodate burnable absorber, but thermal conductivity decreases
Solution Approach 1:
The patent applies local quality by using nanopowder with controlled grain size distribution, creating a hierarchical pore structure where nanoscale pores provide surface area for burnable absorber accommodation while maintaining macroscale thermal pathways. This local structural optimization allows high burnable absorber content while preserving thermal conductivity through the solid matrix.
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 approach enhances the oxygen coefficient, thermal stability, and dimensional stability of the fuel pellets, maximizing thermal conductivity and minimizing creep-induced deformation, while reducing labor and energy costs associated with traditional methods.
Implementation Method 1
The method involves using gadolinium hydroxycarbonate as a burnable absorber, sintering in a reducing environment with controlled humidity
Implementation Method 2
adding triuranium octoxide powder to achieve an optimal oxygen coefficient, resulting in improved thermal conductivity
Implementation Method 3
sintering in a reducing environment with controlled humidity, and adding triuranium octoxide powder to achieve an optimal oxygen coefficient
Data Source
Figure 1a~3c
Figure 4a~6c
Figure 7a~9c
AI summary
The invention relates to the nuclear industry, and more particularly to a technique for producing a ceramic nuclear fuel for nuclear reactor fuel rods. A method for producing nuclear fuel pellets with a burnable absorber includes preparing triuranium octoxide with a burnable absorber, preparing a molding powder, compression molding, sintering and polishing. Gadolinium hydroxycarbonate Gd(OH)CO3·xH2O (or Gd(CO3)3·xH2O) is used as the burnable absorber. The compression molded fuel is sintered in reducing environments (inter alia with the addition of N2), and gases supplied are saturated with water vapour, wherein the humidity of the sintering atmosphere is from 8000-15000 ppm (depending on the amount of burnable absorber), and the sintering temperature is 1650-1750°C. The amount of burnable absorber in the fuel pellets is 1.50-12.00 wt%. During the stage of preparing a homogeneous charge, triuranium octoxide powder and/or triuranium octoxide with gadolinium is added in an amount up to 30 wt% to uranium dioxide powder. The technical result of the invention is an increase in the oxygen coefficient values (the ratio of the number of oxygen atoms covalently bonded with uranium to the number of uranium atoms) in the fuel pellets, thus leading to an increase in thermal conductivity and a reduction in fuel pellet deformation in a nuclear reactor.