Magnetite Oxide Layer Formation for Nickel Contamination Control
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Solution Overview
Problem
The existing processes for reducing corrosion-related contamination in nuclear reactor primary circuits, particularly from nickel and cobalt, are inefficient over time due to purification actions in auxiliary circuits, leading to increased radioactivity and operational downtime.
Innovation Solution
A process that calculates and introduces a quantity of magnetite into the primary circuit water to form a protective oxide layer on metallic parts, combined with continuous injection of aqueous iron downstream of purification means to compensate for iron losses, effectively reducing nickel and cobalt contamination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If magnetite is introduced into the primary circuit water to form a protective oxide layer on metal parts, then nickel and cobalt corrosion products are reduced, but iron is continuously removed by purification means in auxiliary circuits
Solution Approach 1:
The patent recovers iron that would otherwise be lost through purification means by reintroducing it into the primary circuit. The purification system removes iron-containing corrosion products, but the invention captures and returns this iron to maintain the protective oxide layer on metal surfaces, transforming a loss into a recovered resource.
Solution Approach 2:
The invention implements a feedback mechanism where the effect of purification (iron removal) is detected and compensated for by reintroducing iron into the primary circuit. This closed-loop approach ensures that the protective oxide layer is maintained despite continuous purification operations that would otherwise deplete iron.
2Reliability
If the primary circuit water is continuously purified to remove corrosion products, then water quality is improved, but the protective oxide layer degrades and nickel/cobalt release increases
Solution Approach 1:
The invention recovers iron removed during purification and returns it to the primary circuit to replenish the protective oxide layer. This allows continuous purification to maintain water quality while preventing degradation of the protective layer that would otherwise increase metal release.
Solution Approach 2:
The invention performs preliminary action by reintroducing iron into the primary circuit before significant degradation of the protective oxide layer occurs. This proactive approach prevents nickel and cobalt release rather than reacting to it after the fact.
3Object-affected harmful factors
If iron is reintroduced into the primary circuit to maintain the protective oxide layer, then nickel and cobalt corrosion is reduced, but the complexity of the treatment system increases
Solution Approach 1:
The invention makes the purification system multi-functional by having it both remove unwanted corrosion products and recover iron for reuse. This universal approach allows a single system to perform multiple functions (purification plus iron recovery) without adding separate dedicated equipment, thereby limiting complexity increase.
Solution Approach 2:
The invention merges the iron recovery function with the existing purification system. Rather than adding a completely separate iron reintroduction system, the invention integrates iron recovery and reintroduction into the flow path of the purification process, combining multiple functions into a unified system.
Data Source
Figure 1
AI summary
The invention relates to a method of treating an internal surface of a metallic part in a nickel-based or cobalt-based alloy of a primary circuit (1) during an operating cycle of a PWR reactor (2).It includes: - an estimate of the amount of nickel likely to be released into the primary circuit by all the metallic parts of the primary circuit in contact with the water of the primary circuit, during a reactor operating cycle; - a calculation of the amount of magnetite needed to fix the entire estimated amount of nickel; - the formation of treated water obtained by dissolving the calculated amount of magnetite in the water of the primary circuit when the water has a temperature between 80°C and 180°C; and - the circulation of this treated water in the primary circuit so as to form, on the internal surface of at least one metallic part, a layer of a protective oxide capable of fixing all or part of the estimated amount of nickel.A portion of the treated water circulating in the primary circuit is continuously purified during the operating cycle by being diverted into an auxiliary circuit (5) comprising purification means (6) and then reinjected into the primary circuit. The process further includes an injection (7) into this auxiliary circuit and downstream of the purification means of an aqueous iron (Fe(II)) solution to compensate for the amount of iron removed from the treated water purified by the purification means.