Nuclear Fuel Dissolution via Ultrasonic Cavitation
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Solution Overview
Problem
Current nuclear fuel dissolution processes, particularly for MOX fuels with high plutonium content, face inefficiencies in dissolving valuable compounds like plutonium and uranium, leading to high levels of insoluble fractions and requiring excessive nitric acid volumes or mechanical agitation, which is difficult to implement in rotating dissolvers.
Innovation Solution
A process involving simultaneous immersion and mechanical milling of nuclear fuel in a nitric acid solution, which increases the specific surface area and activation of reaction sites, optimizing dissolution without excessive nitric acid volumes or additional agitation systems, and can be applied to both batch and continuous operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If mechanical agitation is used to improve dissolution of MOX fuels with high plutonium content, then dissolution efficiency is improved, but device complexity increases due to difficulty of implementation in rotating dissolvers
Solution Approach 1:
The patent replaces complex mechanical agitation systems with ultrasonic vibration technology. Ultrasonic waves generate cavitation bubbles that collapse violently, creating localized high-pressure shock waves and micro-jets that mechanically disrupt the fuel matrix and enhance dissolution. This substitution eliminates the need for complex rotating agitation mechanisms while achieving superior dissolution efficiency, particularly for MOX fuels with high plutonium content.
Solution Approach 2:
The patent changes the physical state and energy parameters of the nitric acid solution by applying ultrasonic vibration at specific frequencies and intensities. This transforms the solution from a static chemical environment to an dynamically active medium with enhanced mass transfer, increased reaction sites, and improved penetration into the fuel matrix. The parameter changes enable efficient dissolution without requiring complex mechanical agitation devices.
2Productivity
If excessive nitric acid volumes are used to dissolve valuable compounds, then dissolution efficiency is improved, but loss of substance increases
Solution Approach 1:
By replacing chemical volume increase with ultrasonic mechanical energy input, the patent achieves enhanced dissolution through physical activation rather than chemical excess. The ultrasonic cavitation and shock waves increase the reactivity and penetration power of the nitric acid, allowing complete dissolution with optimized rather than excessive acid volumes, thereby reducing material loss and waste treatment requirements.
Solution Approach 2:
The ultrasonic field enables the nitric acid solution to self-penetrate and self-activate within the fuel matrix through cavitation-induced micro-stirring and localized heating. This self-service mechanism eliminates the need for external mechanical agitation or excessive acid volumes, as the solution automatically enhances its own dissolution capability through ultrasonic-induced cavitation and shock wave generation.
3Area of stationary object
If mechanical milling is performed dry before immersion, then specific surface area is increased, but contamination risks increase
Solution Approach 1:
The patent performs mechanical milling of the nuclear fuel in advance, before immersion in nitric acid, to increase the specific surface area and create more reaction sites. By completing the size-reduction operation beforehand, the fuel particles are ready for immediate chemical dissolution upon contact with the acid, eliminating the need for additional mechanical agitation during the dissolution process itself and reducing contamination risks.
Solution Approach 2:
The patent replaces the need for continuous mechanical agitation during dissolution with preliminary mechanical milling. The pre-milled fuel particles have sufficiently high surface area that ultrasonic cavitation alone can maintain effective dissolution without requiring additional mechanical contact or agitation, thereby reducing contamination risks from mechanical systems operating during the dissolution phase.
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 process significantly enhances the dissolution efficiency of nuclear fuels, including MOX fuels with high plutonium content, by increasing the surface area and reaction sites, allowing for higher recovery of valuable compounds and reducing contamination risks compared to dry milling methods.
Implementation Method 1
The use of ultrasonic vibrations, in other words of cavitation, makes it possible to obtain a double effect: on the one hand, the liquid is mechanically activated with formation of local high pressure zones and shock waves, and on the other hand, a significant heating effect is generated locally
Implementation Method 2
The use of ultrasonic vibrations, in other words of cavitation, makes it possible to obtain a double effect
Implementation Method 3
the liquid is mechanically activated with formation of local high pressure zones and shock waves
Implementation Method 4
on the other hand, a significant heating effect is generated locally
Implementation Method 5
the assemblies of irradiated nuclear fuel, composed of sealed claddings inside which the material forming the nuclear fuel is confined, are typically cut into segments having a length of about 3 cm to 5 cm. These segments are then immersed in a concentrated nitric acid solution to dissolve the nuclear material confined within the claddings
Data Source
AI summary
A process for dissolving nuclear fuel, in particular irradiated nuclear fuel, comprising immersion of the nuclear fuel in a nitric acid solution. This dissolution process further comprises mechanical milling of the nuclear fuel, this mechanical milling being performed in the nitric acid solution during the immersion. The disclosure also relates to the use of a mill equipped with mechanical milling structure to implement the dissolution process.