Oxide Nuclear Fuel Redox Buffer for Oxygen Potential Control
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Solution Overview
Problem
Current nuclear fuel technologies face challenges in controlling the oxygen potential during operation, leading to uncontrolled thermomechanical properties, gas speciation, and corrosion of the cladding, which affects the retention of fission products and the overall performance and safety of nuclear fuels.
Innovation Solution
Incorporating a redox system with a pair of species having different oxidation states into the nuclear fuel to buffer the oxygen potential, stabilizing it within a range that minimizes the formation of corrosive species like Tel2 and maximizes the presence of non-corrosive forms of volatile gases, thereby controlling the oxygen potential and improving fuel performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional oxide nuclear fuel is used without redox additives, then the fuel structure is simple and manufacturing is easier, but the oxygen potential becomes uncontrolled during operation leading to corrosion of cladding and formation of harmful volatile species
Solution Approach 1:
The redox buffer system (e.g., MoO2-Mo couple) is incorporated into the fuel itself, allowing it to autonomously regulate oxygen potential during operation without requiring external control mechanisms. The buffer system self-adjusts to maintain optimal oxygen potential ranges, preventing corrosion and controlling volatile species formation through its inherent redox chemistry.
Solution Approach 2:
The invention changes the chemical composition parameter by adding redox buffer materials (such as MoO2, Mo, or other redox-active compounds) to the fuel matrix. This compositional change enables dynamic control of oxygen potential through redox reactions, transforming the fuel from a passive material to an actively regulating system that maintains optimal oxygen chemical potential during irradiation.
2Productivity
If the oxygen potential is allowed to increase with combustion rate, then fission reactions proceed normally, but corrosive species like Tel2 form and attack the cladding
Solution Approach 1:
The invention converts the harmful effect of oxygen release during fission into a beneficial control mechanism. The redox buffer system utilizes the oxygen released during combustion to drive redox reactions that maintain optimal oxygen potential. Instead of allowing oxygen accumulation to create corrosive conditions, the buffer system consumes excess oxygen through reduction reactions, transforming a harmful byproduct into a self-regulating control mechanism.
Solution Approach 2:
The redox buffer system acts as an intermediary between the fission reactions and the cladding. It mediates the oxygen potential by providing a chemical buffer that absorbs excess oxygen through reduction reactions (e.g., MoO2 + Mo → 2MoO3) while preventing oxygen from reaching levels that would form corrosive volatile species and attack the cladding.
3Reliability
If redox buffer system is added to control oxygen potential, then corrosive species formation is reduced, but the fuel composition becomes more complex requiring precise manufacturing control
Solution Approach 1:
The invention employs partial action by adding redox buffer materials at relatively low concentrations (typically 0.1-5 wt%) rather than requiring large quantities. This partial addition is sufficient to provide effective oxygen potential control through the buffer capacity of the redox couple, avoiding the need for precise control of large additive amounts while still achieving reliable corrosion protection and volatile species control.
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
The redox system effectively maintains the oxygen potential within an optimal range, reducing corrosive species formation and enhancing the fuel's thermal conductivity, creep behavior, and microstructural stability, while minimizing gas release and corrosion risks.
Implementation Method 1
additivated with at least one oxidation-reduction system comprising a first and a second species having a common element with a different degree of oxidation in each of the two species
Data Source
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AI summary
Oxide nuclear fuel which is a regulator of corrosive fission products, additivated with at least one oxidation-reduction system. The subject matter of the invention is an additivated nuclear fuel, comprising an oxide nuclear fuel generating fission products such as tellurium, caesium or iodine, which generate potentially corrosive species by chemical interaction, characterized in that it is additivated with at least one oxidation-reduction system comprising a first species and a second species comprising a common element having a different oxidation state in each of the two species, wherein said system exhibits a curve of oxygen potential as a function of temperature located in an interval delimited by: • - an upper limit: the curve of coexistence of the chemical species I2, Te(g) and Csl(g) under the same partial pressure imposed by the equilibrium between Csl(l) and Csl(g), estimated at between 1000°C and 2000°C by a right segment of which the ends P02/11 and P02/12 have the coordinates: P02/11 (T = 1000°C) ≈ -370 kJ/molO2 and P02/12 (T = 2000°C) ≈ -230 kJ/molO2; • - a lower limit: the curve of oxygen potential of the system (Cs2MoO4/Cs +Mo) estimated at between 1000°C and 2000°C by a right segment of which the ends P02/21 and P02/22 have the coordinates: P02/21 (T = 1000°C) ≈ -530 kJ/molO2 and P02/22 (T = 2000°C) ≈ -390 kJ/molO2.