Electrolytic Cleaning Solution Conditioning for Nuclear Steam Generators
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Solution Overview
Problem
The disposal of cleaning solutions from nuclear steam generators contaminated with radioactive metallic nuclides above the permitted limit poses significant challenges due to the need for complex and costly conditioning and special disposal, leading to large volumes of radioactively contaminated waste.
Innovation Solution
Electrolytic treatment using diamond electrodes for the cleaning solution, where radioactive metallic nuclides are deposited on a cathode, and organic components are denatured, reducing contamination to levels below the exemption limit, allowing for simplified disposal of the cathode as radioactive waste, with optional two-stage electrolysis for high Co60 concentrations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If ion exchange resins are used to load cleaning solution ingredients, then radioactive metallic nuclides are removed from the cleaning solution, but enormous volumes of radioactively contaminated waste are generated
Solution Approach 1:
The patent changes the physical-chemical parameters of the cleaning solution through controlled electrolysis, adjusting pH levels and applying electrical potential to precipitate radioactive metals as solid deposits on electrode surfaces. This transforms dissolved radioactive contaminants into concentrated solid forms that can be easily separated, reducing waste volume while achieving decontamination goals
Solution Approach 2:
The patent replaces the chemical adsorption mechanism of ion exchange resins with an electrochemical precipitation process. Instead of relying on resin binding sites to capture radioactive ions, the system uses electrical current to directly deposit metals onto electrode surfaces, eliminating the need for large volumes of resin waste
2Ease of operation
If cleaning solutions are incinerated as hazardous waste, then disposal is simplified, but complex and expensive conditioning is required when radioactive nuclides are present above exemption limits
Solution Approach 1:
The patent extracts radioactive metallic nuclides from the cleaning solution through electrolytic deposition on cathode surfaces. By selectively removing radioactive contaminants as solid deposits, the remaining liquid solution falls below exemption limits and can be disposed of through simpler incineration processes, while only the concentrated radioactive deposits require specialized waste handling
Solution Approach 2:
The patent separates radioactive metals from the cleaning solution for targeted disposal, while the treated solution can be neutralized and disposed of through standard hazardous waste incineration. This selective separation allows different disposal pathways based on contamination levels, simplifying overall waste management
3Object-affected harmful factors
If diamond electrodes are used for electrolytic treatment, then radioactive metallic nuclides are effectively deposited on the cathode, but the treatment process requires extended electrolysis time
Solution Approach 1:
The patent employs periodic electrolysis cycles with alternating current directions and varying intensity levels. By applying electrical potential in periodic bursts rather than continuous operation, the system achieves effective metal deposition while allowing intervals for precipitate formation and separation, reducing overall treatment time
Solution Approach 2:
The diamond electrodes serve multiple functions simultaneously: they act as sites for radioactive metal deposition, facilitate organic component denaturation through electrochemical reactions, and provide large surface area for precipitate adsorption. This multi-functionality accelerates the overall decontamination process by addressing multiple contamination types in parallel
4Object-affected harmful factors
If organic components are denatured during electrolysis, then COD and TOC values are significantly reduced, but the treatment complexity increases
Solution Approach 1:
The patent combines radioactive metal removal and organic component denaturation into a single integrated electrolysis process. By applying electrical current to the cleaning solution, both inorganic radioactive metals deposit on cathodes while organic compounds undergo electrochemical oxidation and breakdown at anodes, achieving dual decontamination objectives through one unified treatment system
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 volume and effort required for disposing of contaminated waste by concentrating radioactive and organic contaminants, enabling the cathode's reuse after metal removal and neutralization, with over 99% reduction in EDTA and COD values.
Implementation Method 1
the cleaning solution is electrolytically treated and radioactive metallic nuclides contained in the cleaning solution are deposited on a cathode
Implementation Method 2
Since the cathode is a diamond electrode and consequently consists of a material which has a hydrogen overvoltage and whose potential is set above the potential for hydrogen evolution, a particularly effective separation of radioactive metallic nuclides is achieved
Implementation Method 3
If, in addition, the anode also consists of a material that exhibits an oxygen overvoltage, preferably also a diamond electrode, the potential of which is set below the potential for oxygen development, the organic components in the cleaning solution, e.g. a complexing agent, can be denatured during the electrolysis at the same time, so that almost all Fe precipitates as oxide or hydroxide
Implementation Method 4
Due to the large surface area of the precipitated iron oxide or iron hydroxide, any radioactive metallic nuclides still present in the solution, for example Co60, are adsorbed on it and also removed from the cleaning solution in this way
Data Source
Figure 1~2
AI summary
In a method for conditioning a cleaning solution resulting from the wet chemical cleaning of a nuclear steam generator, the cleaning solution is electrolytically treated and radioactive metal nuclides contained in the cleaning solution are precipitated at a cathode.