Iron Source in Mercury-Catalyzed Acid Bath for Aluminum Dissolution
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Solution Overview
Problem
Conventional nuclear fuel dissolution processes face challenges in controlling off-gas generation rates, particularly hydrogen gas concentration, which can exceed safety levels and reduce process efficiency.
Innovation Solution
Incorporating an iron source into the acid bath with a metal catalyst, such as mercury, to control the dissolution rate and off-gas production, ensuring the hydrogen gas concentration remains below 4% by volume, thereby improving process efficiency and safety.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional acid dissolution processes are used to recover nuclear fuel, then the dissolution rate is acceptable, but hydrogen gas production increases to unsafe levels
Solution Approach 1:
A metal catalyst (such as mercury, copper, or zinc) is introduced as an intermediary substance that mediates the dissolution reaction. This catalyst selectively catalyzes the formation of nitrogen oxides from nitric acid, thereby redirecting the reaction pathway to produce less harmful gases while maintaining acceptable dissolution rates
Solution Approach 2:
The chemical parameters of the dissolution system are changed by adjusting the concentration and type of acid, the amount of metal catalyst added, and the temperature. These parameter modifications optimize the reaction to reduce hydrogen gas production while maintaining effective aluminum dissolution
2Productivity
If the dissolution rate is increased to improve throughput, then productivity increases, but off-gas generation rate increases beyond safety levels
Solution Approach 1:
The metal catalyst acts as a mediator that enables faster dissolution through selective catalysis of nitrogen oxide formation, allowing increased throughput while the catalyst simultaneously controls the gas production pathway to remain within safety limits
Solution Approach 2:
The system incorporates monitoring of off-gas composition and dissolution rate, with feedback control adjusting the metal catalyst addition rate and acid concentration to maintain optimal conditions that balance productivity with safety constraints
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 iron source effectively reduces hydrogen gas production rates and concentrations, allowing for more controlled and efficient dissolution of aluminum and separation of nuclear fuels, enhancing the overall throughput and safety of the nuclear fuel recycling process.
Implementation Method 1
Fuel elements containing an aluminum-uranium alloy contained in aluminum cladding, for instance, may be dissolved in a mercury-catalyzed, nitric acid flowsheet
Implementation Method 2
the aluminum material is dissolved. In one embodiment, the process for recovering fissionable materials is an aqueous process during which the fuel elements are dissolved in an acidic solution
Data Source
AI summary
A process for controlling the dissolution of a metal in an acid bath is described. The metal may comprise aluminum and the acid bath may contain a metal catalyst that causes the metal to dissolve. In order to control the rate of dissolution and/or the amount of gas evolved during the process, an iron source is added to the bath. In one embodiment, the process can be used to dissolve aluminum contained in spent fuel assemblies for recovering a nuclear fuel, such as uranium.