Plasma Treatment of Nuclear Sludge Using Cooled Crucible
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Solution Overview
Problem
Current methods for treating nuclear sludge, such as in-drum pyrolysis and plasma furnace incineration, face challenges including inefficient radionuclide immobilization, high energy consumption, and health and safety risks due to complex equipment designs and refractory waste generation, while cement encapsulation results in significant volume increase and costly storage.
Innovation Solution
A plasma treatment method using a cooled crucible with graphite electrodes, where the sludge is subjected to plasma in the presence of an oxidant, melting inorganic components to form a vitreous, dense, and chemically immobilized waste form, reducing volume and eliminating the need for additional host materials.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If in-drum pyrolysis is used to treat nuclear sludge, then organic materials can be volatised, but the process produces clinker instead of dense slag, allowing radionuclide remobilization
Solution Approach 1:
The patent changes the thermal processing parameters by extending the holding time at high temperature (800-1000°C) and controlling the cooling rate to transform the solid product from clinker to dense slag. This parameter optimization ensures complete melting and proper crystallization, creating a chemically stable matrix that effectively immobilizes radionuclides and prevents remobilization.
Solution Approach 2:
The patent creates a composite material system by combining the volatized organic components with the inorganic sludge matrix during the melting process. The resulting dense slag is a composite structure where radionuclides are incorporated into the glassy matrix, providing both structural integrity and chemical stability for long-term waste containment.
2Productivity
If plasma furnace incineration with centrifuge chamber is used, then waste can be melted and processed, but the equipment design is complex and generates large amounts of contaminated refractory waste
Solution Approach 1:
The patent extracts and removes the complex centrifuge chamber mechanism from the plasma furnace design. By eliminating this complex component, the process simplifies to direct plasma treatment of sludge in a simpler crucible, reducing equipment complexity while maintaining effective waste processing capability and eliminating the generation of contaminated refractory waste.
Solution Approach 2:
The patent employs a disposable or easily replaceable crucible that can be quickly exchanged rather than maintaining complex, long-lasting refractory linings. This approach reduces equipment complexity and eliminates the need for periodic replacement of contaminated refractory materials, while still providing sufficient processing capacity.
3Reliability
If cement encapsulation is used to treat nuclear sludge, then waste can be stabilized, but the volume increases significantly and storage becomes expensive
Solution Approach 1:
The patent utilizes phase transitions by melting the inorganic sludge components at high temperature (800-1000°C) to form a glassy slag phase, then controlling cooling to create a dense solid structure. This phase transition process consolidates the waste into a compact, stable form with significantly reduced volume compared to cement encapsulation, while maintaining chemical stability for long-term storage.
Solution Approach 2:
The patent creates a composite glassy slag material that consolidates multiple waste components into a single dense matrix. This composite structure provides both stabilization and volume reduction, as the glassy matrix incorporates radionuclides and consolidates the original sludge into a compact form suitable for economical storage.
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 method produces a solid, dense vitrified material with high radionuclide incorporation, minimizing leaching and avoiding refractory lining issues, thus providing a safer and more efficient storage solution with reduced volume and energy consumption.
Implementation Method 1
subjecting the nuclear sludge to a plasma treatment in a plasma chamber
Implementation Method 2
an electric arc is passed between the electrodes (4,5) above the level of the nuclear sludge (remotely coupled)
Implementation Method 3
the plasma chamber comprises a crucible (1) having a cooled inner surface (2), this surface cooled sufficiently such that the inorganic components in contact with the inner surface (2) are in a solid state
Implementation Method 4
subjecting the nuclear sludge to a plasma treatment in a plasma chamber, in the presence of an oxidant
Data Source
Figure 1a~1c
Figure 2~3
Figure 4
AI summary
A method for treating nuclear sludge comprising subjecting the nuclear sludge to a plasma treatment in a plasma chamber to melt at least some of the inorganic components of the sludge, wherein the plasma chamber comprises a crucible having a cooled inner surface, this surface cooled sufficiently such that the inorganic components in contact with the inner surface are in a solid state and form a barrier between the part of surface of the crucible with which they are in contact and the molten inorganic components of the sludge.