Nuclear Decontamination via Controlled Oxidant Dosing
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Solution Overview
Problem
Current decontamination methods for nuclear power plant coolant systems require long treatment periods and additional external ion exchangers, leading to premature ion exchanger exhaustion and potential corrosion of metal surfaces, with 'hot spots' of radioactivity forming due to oxygen depletion and metal ion concentration increases.
Innovation Solution
A method involving an oxidation step with an oxidant, followed by a decontamination step using an organic acid to dissolve the metal oxide layer, with controlled oxidant addition to manage oxygen depletion and selectively remove nickel ions, ensuring the decontamination solution's ion load remains within safe limits, utilizing the power plant's own ion exchangers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If decontamination is performed using conventional methods with organic acid to dissolve oxide layer, then the oxide layer is removed and radioactivity is reduced, but the treatment period becomes excessively long and ion exchangers become exhausted prematurely
Solution Approach 1:
The patent changes the chemical parameters of the decontamination solution by adding specific oxidants (hydrogen peroxide, ozone, or air) to create a synergistic effect with the organic acid. This parameter change accelerates the dissolution of the oxide layer while controlling metal ion release, thereby reducing treatment time without compromising decontamination effectiveness
Solution Approach 2:
The patent implements periodic dosing of oxidants during the decontamination process to maintain optimal oxidation conditions. This periodic action ensures continuous effectiveness of the decontamination solution throughout the treatment period, preventing ion exchanger exhaustion and reducing overall treatment time
2Reliability
If decontamination solution is used to dissolve oxide layer, then radioactive substances are removed, but metal ion concentration increases causing ion exchanger exhaustion and potential corrosion
Solution Approach 1:
The patent introduces oxidants as intermediary substances that facilitate the decontamination process by oxidizing metal ions in the oxide layer, making them more soluble and easier to remove. This intermediary action reduces direct contact between the organic acid and the metal surface, thereby minimizing corrosion risk while maintaining effective radioactivity reduction
Solution Approach 2:
The patent employs strong oxidants (hydrogen peroxide, ozone, or air) to accelerate the oxidation of metal ions in the oxide layer. This accelerated oxidation enhances the dissolution of radioactive substances while controlling the release of metal ions, preventing ion exchanger exhaustion and reducing corrosion risk to the metal surface
3Quantity of substance
If external ion exchangers are used to handle high ion load, then ion removal capacity is increased, but device complexity and cost increase
Solution Approach 1:
The patent enables the existing ion exchangers within the power plant to serve themselves by optimizing the decontamination process to match their capacity. Through controlled oxidant addition and pH management, the system ensures that metal ion release rates do not exceed the ion exchangers' removal capacity, eliminating the need for additional external ion exchanger systems
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 approach allows for reliable, controlled decontamination of large-scale nuclear power plant systems without external ion exchangers, preventing corrosion and radioactivity accumulation, while maintaining process stability and reducing waste production.
Implementation Method 1
an oxidation step in which the metal oxide layer is contacted with an aqueous oxidation solution comprising an oxidant
Implementation Method 2
a decontamination step wherein the metal oxide layer treated in the oxidation step is contacted with an aqueous solution of an organic acid having up to six carbon atoms to dissolve the metal oxide layer
Implementation Method 3
the decontamination solution is passed over an ion exchanger to immobilize the metal ions and the radioactive substances
Implementation Method 4
in step b) an oxidant of the group consisting of oxygen, air, hydrogen peroxide and ozone is dosed into the decontamination solution
Data Source
Figure 1
Figure 2~3
Figure 4
AI summary
The invention relates to a method of decontaminating a metal surface, wherein the metal surface is located on a component within a nuclear plant, in particular within the cooling system of a nuclear power plant, and is covered with a metal oxide layer containing radioactive substances, and wherein the method comprises a decontamination step in which a metal oxide layer pretreated in an oxidation step is contacted with an aqueous solution of an organic acid to dissolve the metal oxide layer, forming a decontamination solution containing the organic acid as well as metal ions and the radioactive substances, and wherein the decontamination solution is passed over an ion exchanger to immobilize the metal ions and the radioactive substances. An oxidant selected from the group consisting of oxygen, air, hydrogen peroxide and ozone is dosed into the decontamination solution to control the dissolution rate of the metal oxide layer. The method is particularly suitable for large-scale system decontamination and ensures high process stability.