Plasma Sputtering of Reactor Components for Radioactive Surface Removal
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Solution Overview
Problem
Existing methods for decontaminating irradiated reactor graphite and nuclear reactor components suffer from inefficiencies in removing surface radioactivity, require dismantling and grinding of high-level radioactive materials, increase waste volume, and lack mechanisms for selective pollutant removal, compromising safety and efficiency.
Innovation Solution
A method involving low-temperature plasma sputtering using a reactionless gas to sputter radioactive isotopes from the surface of nuclear reactor components, condensing them on a cooled electrode for collection and potential reuse, while minimizing waste generation and maintaining safety.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If thermal treatment or plasma methods are used to release radioactive isotopes from graphite, then the radioactivity can be removed from the material, but gaseous radioactive waste is released into the atmosphere
Solution Approach 1:
The patent employs an inert gas atmosphere (argon or nitrogen) in the plasma-chemical reactor to prevent oxidation of graphite and control the chemical environment during treatment. This inert environment allows for selective sputtering and chemical reactions without unwanted side reactions, enabling removal of radioactive carbon-14 while preventing formation of additional gaseous radioactive compounds.
Solution Approach 2:
The patent utilizes phase transitions by converting radioactive carbon-14 from solid graphite form to gaseous phase through plasma treatment, then capturing and condensing it back to solid form on cooled surfaces. The process involves heating graphite to release carbon-14 as gas, followed by cooling to condense the gas into collectible solid deposits, thereby preventing atmospheric release.
2Object-generated harmful factors
If graphite is ground and mixed with reactive chemicals for high-temperature synthesis, then gaseous waste release is prevented, but the process complexity and waste volume increase
Solution Approach 1:
The patent extracts and separates radioactive carbon-14 from the graphite matrix using plasma treatment and selective chemical reactions. By targeting and removing only the radioactive portion rather than processing the entire graphite volume, the method reduces waste volume and simplifies the overall process compared to complete grinding and reprocessing approaches.
Solution Approach 2:
The patent introduces intermediate substances such as titanium, aluminum, silicon, or their oxides that facilitate the conversion and capture of radioactive carbon-14. These intermediaries react with carbon-14 to form stable solid compounds that can be easily separated and disposed of, simplifying the process compared to direct high-temperature synthesis without additives.
3Object-affected harmful factors
If plasma torch is used to ignite and melt graphite layers, then surface treatment is achieved, but radioactive isotopes are released and metal structures are contaminated
Solution Approach 1:
The patent replaces the mechanical plasma torch ignition system with a more controlled plasma-chemical reaction approach. Instead of using high-energy plasma torches that cause uncontrolled melting and release, the method uses controlled plasma environments with specific gas compositions to achieve selective removal of radioactive materials through chemical reactions, preventing both isotope release and metal structure contamination.
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
Significantly reduces the radioactivity of treated components, reduces waste volume, and allows for selective recovery of valuable isotopes, enhancing safety and efficiency in decontamination processes.
Implementation Method 1
plasma sputtering the surfaces of irradiated design components of nuclear power plants and graphite stack
Implementation Method 2
the electrode and gas pipeline, diverting inert gas from the discharge zone are cooled to the temperature sufficient for the precipitation of the sputtered atoms on the surface of the electrode and lines
Data Source
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AI summary
The present invention is referred to the nuclear engineering field and can be applied for effective decontamination of the design components of the nuclear power plants (NPP) - pipelines, pumps and other metal structures of the primary coolant circuit, as well as irradiated graphite stack of reactors that contain active isotopes 14C, 60Co, 134Cs, 137Cs and others, which concentrate during operation mainly on the surface of these design components. The method allows to conduct controlled plasma sputtering of the selected surface sites of radioactive reactor designs in the atmosphere of reactionless gas with the transfer and condensation of active isotope atoms on a replaceable platform. The technical result achieved by the invention lies in the fact that at plasma sputtering the surface of design components of the nuclear power plants and graphite stack, as the most contaminated with radioactive isotopes, a significant reduction of radioactivity of the treated designs of the nuclear power plants, as well as concentration and the corresponding a contraction of the volume of the radioactive waste is achieved. The indicated technical result is achieved by the fact that in the decontamination method for the nuclear reactor design component, comprising the nuclear reactor design component treating with a low-temperature plasma under the flow of reactionless gas according to the claimed decision to the selected site on the surface of the design component is supplied to the electrode, ignite plasma discharge between the surface of the design component is chosen as the cathode, and the electrode is chosen as the anode, the operating parameters of the discharge effective to sputtering of the cathode are chosen, the cathode is sputtered, the electrode and gas pipeline, diverting inert gas from the discharge zone are cooled to the temperature sufficient for the precipitation of the sputtered atoms on the surface of the electrode and lines, after sputtering the cathode to the specified depth, the electrode is moved to a new area of treatment and the process steps are repeated until the complete treatment of the entire surface decontaminated design component.