Method for identifying the evolution of the presence or absence of oxygen corrosion of materials in a high-level waste geological disposal environment

Abstract

The present application relates to the field of metal corrosion behavior monitoring and characterization, in particular to a method for identifying oxygen corrosion evolution of materials in high-level waste geological disposal environment. The method includes two indicators, one is the oxidation-reduction potential reflecting the overall oxidation-reduction characteristics of the corrosion system, that is, the Eh value; the other is the time constant reflecting the kinetics characteristics of the dissolved oxygen reduction reaction (ORR) in the corrosion system, that is, the ORR-log(τ / s) value; the Eh value is measured by Eh electrode, and the ORR-log(τ / s) value is obtained by measuring the electrochemical impedance spectroscopy (EIS) of the working electrode of the metal material, and then analyzing the EIS data by relaxation time distribution function. The present application is suitable for identifying the oxygen corrosion evolution of candidate materials of disposal containers in high-level waste geological disposal environment, and has the characteristics of simple method, easy to obtain parameters, strong operability, high accuracy, good long-term stability and real-time measurement.

Description

Technical Field

[0001] This invention relates to the field of metal corrosion behavior monitoring and characterization, and in particular to a method for identifying the evolution of material corrosion in both anaerobic and non-anaerobic environments in geological disposal environments for high-level radioactive waste. Background Technology

[0002] High-level radioactive waste (HRF) mainly refers to high-level radioactive liquids and their solidified forms generated from spent fuel reprocessing. HRF is a special type of waste that poses a potentially enormous threat to the environment. The radionuclides contained in HRF are characterized by high radioactivity, high toxicity, long half-lives, and pyrophoric activity. Once they enter the human environment, they cause immense harm and are difficult to eliminate. Therefore, the safe disposal of HRF has become a major issue affecting the sustainable development of nuclear energy, environmental protection, and the well-being of future generations, and it is also a significant scientific, technological, and engineering challenge.

[0003] Currently, the internationally recognized method for the safe disposal of high-level radioactive waste is deep geological disposal, which involves burying the waste in stable geological formations at a depth of approximately 400–1000 meters below the surface, effectively isolating it from the biosphere. Disposal containers are generally constructed of metal, and their primary safety function is to contain the high-level waste, prevent groundwater intrusion, and maintain this containment for at least 1000 years. Therefore, research on the corrosion evolution behavior of disposal container materials in geological disposal reservoir environments is essential.

[0004] Since a certain amount of oxygen will inevitably remain in the disposal facility for a considerable period after its closure, the consumption and evolution of dissolved oxygen will directly affect the corrosion rate of the disposal container materials. Therefore, it is essential to develop and design methods for identifying the anaerobic / anaerobic corrosion evolution of packaging container materials in geological disposal environments to better study their evolutionary behavior and characteristics. Summary of the Invention

[0005] In response to the needs of high-level radioactive waste geological disposal engineering, the purpose of this invention is to provide a method for identifying the anaerobic / anaerobic corrosion evolution of materials in high-level radioactive waste geological disposal environments. This identification method has a clear principle, simple steps, and readily available parameters. Furthermore, the method is highly accurate, easy to operate, and has good long-term stability, making it suitable for the identification and research of anaerobic / anaerobic corrosion evolution of materials in high-level radioactive waste geological disposal environments.

[0006] A method for identifying the evolution of materials in anaerobic and anaerobic corrosion in geological disposal environments for high-level radioactive waste includes two indicators: one is the redox potential (Eh value), reflecting the overall redox characteristics of the corrosion system; the other is the time constant (ORR-log(Eh value), reflecting the kinetic characteristics of the oxygen reduction reaction (ORR) in the corrosion system. t / s) value.

[0007] The materials used in the geological disposal environment of high-level radioactive waste, which are used to simulate the materials of geological disposal containers for high-level radioactive waste, are low-carbon steel, copper, cast iron, nickel-based alloys, and titanium alloys.

[0008] The geological environment for the disposal of high-level radioactive waste includes the groundwater environment of the rock strata surrounding the disposal reservoir and the backfill material environment around the disposal container, including bentonite with different moisture contents.

[0009] The corrosion system is used to simulate the closed environment characteristics of a high-level radioactive waste geological disposal site. Depending on the environment of the disposal site and the characteristics of the surrounding rock strata and groundwater, the environmental parameters of the closed system vary, including SO42- concentration, Cl- concentration, HCO3- / CO32- concentration, pH value, pressure, and moisture content of the backfill material.

[0010] The Eh value is used to reflect the overall oxidizing power of the corrosion system, and is related to the dissolved oxygen content and the overall oxidizing power of all oxidizing substances containing Fe(III) in the corrosion system; by measuring with an Eh electrode, the evolution characteristics of the Eh value with corrosion time can be obtained.

[0011] The ORR-log ( t The ORR-log( / s) value is used to reflect the ease with which dissolved oxygen undergoes ORR in the corrosion system and is related to the dissolved oxygen content; the ORR-log( / s) value is obtained by analyzing the relaxation time distribution (DRT) of the measured electrochemical impedance spectroscopy (EIS). t Evolution characteristics of / s value with corrosion time.

[0012] The Eh electrode is used to measure the overall oxidizing property of the corrosion system. The Eh electrode can be obtained in-house or commercially. However, during use, the Eh electrode needs to be periodically subjected to small-amplitude cathodic polarization to ensure the surface of the Eh electrode is clean, thereby ensuring the accuracy of the Eh electrode measurement.

[0013] Taking dissolved oxygen as an example, its redox potential and the corrosion rate of the treatment container material have the following relationship: Based on the measured Eh value, which reflects the overall chemical properties of the corrosion system, plot the evolution curve of the Eh value with corrosion time.

[0014] Candidate materials are processed into working electrodes for corrosion electrochemical testing, and EIS data are acquired using a traditional three-electrode system or a two-electrode system; based on The relationship is analyzed by performing DRT on the EIS data to obtain the number of time constants contained in the EIS spectrum and their corresponding log( t Plot the log( / s) value. t The evolution spectrum of ORR ( / s) value with corrosion time was obtained, and thus the ORR-log( t The evolution of the / s value with corrosion time.

[0015] When Eh > -640 mV (vs. SSC); the ORR-log( t When the / s) value is less than 1.2, the material of the disposal container is in the aerobic corrosion stage.

[0016] When Eh < -640 mV (vs. SSC); the ORR-log( t When the / s value is greater than 1.2~1.5, the material of the disposal container enters the oxygen-free corrosion stage.

[0017] This invention utilizes the sensitivity of Eh electrodes to oxidizing substances in a corrosion system, especially to the dissolved oxygen content. By measuring with commercially purchased or self-made Eh electrodes, an Eh value that reflects the overall oxidizing properties of the corrosion system can be obtained. By plotting the evolution curve of the Eh value with corrosion time, the evolution behavior of the content of oxidizing substances in the entire corrosion system with corrosion time can be identified.

[0018] Because DRT analysis can identify the time constants contained in the EIS spectrum and correlate them with the electrochemical reactions involved in the corrosion process, DRT analysis can identify the time constant corresponding to ORR; since the time constant corresponding to ORR is log( t The oxygen concentration (ORR / s) is closely related to the oxygen concentration; therefore, it can be obtained by ORR-log( t The evolution of the / s value further determines the dissolved oxygen concentration in the corrosion system.

[0019] The evolution behavior of Eh value measured during material corrosion in high-level radioactive waste geological disposal environments and ORR-log( t By comprehensively considering the evolution behavior of the / s value, this invention can identify the evolution behavior of aerobic / anaerobic corrosion of materials in high-level radioactive waste geological disposal environments. Therefore, this invention is applicable to the identification and research of aerobic / anaerobic corrosion evolution of materials in high-level radioactive waste geological disposal environments, and features simple method, readily available parameters, strong operability, high accuracy, good long-term stability, and real-time measurement.

[0020] The advantages and beneficial effects of this invention are:

[0021] The Eh electrode structure used in this invention is simple, commercially available, or can be fabricated. Furthermore, the Eh testing method is straightforward. EIS measurements based on three-electrode and two-electrode systems are commonly used methods in corrosion electrochemistry. Additionally, the DRT analysis method for EIS data is simple, highly accurate, and can accurately identify the time constant log(ORR) corresponding to the ORR during aerobic / anaerobic corrosion processes. t The evolution is / s). Therefore, only the Eh value and ORR-log( tThe two parameters ( / s) can accurately identify the evolution of aerobic / anaerobic corrosion of materials in the geological disposal environment of high-level radioactive waste, effectively avoiding the disadvantages of low accuracy and complexity of traditional identification methods.

[0022] The method for identifying the aerobic / anaerobic corrosion evolution of materials in geological disposal environments of high-level radioactive waste provided by this invention is simple in steps, clear in principle, and highly accurate in identification. Furthermore, the method is simple, the parameters are readily available, and it is highly operable, making it suitable for the identification and research of the aerobic / anaerobic corrosion evolution of materials in geological disposal environments of high-level radioactive waste. Attached Figure Description

[0023] Figure 1 The Eh value and ORR-log(Eh- ... t The evolution of the two parameters ( / s) over corrosion time;

[0024] Figure 2 The initial oxygen concentration is 10 -4 Eh value and ORR-log( ) during the aerobic / anaerobic corrosion evolution of Q345R low carbon steel in the groundwater environment of the sealed Beishan treatment reservoir. t The evolution of the two parameters ( / s) over corrosion time. Detailed Implementation

[0025] The present invention will be further described in detail below through embodiments.

[0026] To facilitate understanding of the present invention, a more complete description will be given below with reference to the accompanying drawings. Typical embodiments of the invention are shown in the drawings. However, the present invention is applicable to many different scenarios and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a thorough and complete understanding of the disclosure of the present invention.

[0027] It should be noted that all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the specification of this invention is for the purpose of describing particular embodiments only and is not intended to limit the invention.

[0028] Example 1

[0029] In this embodiment, the corrosion simulation solution uses groundwater from Beishan Reservoir BS-01, which is boiled and cooled under normal room temperature and pressure conditions before use. At this time, the oxygen content in the water is about 8 ppm.

[0030] Two electrodes, an Eh electrode, and an Ag / AgCl reference electrode made of Q345R low-carbon steel were exposed together in 400 mL of groundwater. The corrosion system was then sealed at room temperature and atmospheric pressure to isolate it from the surrounding air environment. At this time, the initial oxygen content in the corrosion solution was about 8 ppm.

[0031] During the corrosion process, the evolution of the Eh value of the entire corrosion system with corrosion time was measured using an Eh electrode and an Ag / AgCl reference electrode, and the evolution curve of Eh value versus corrosion time t was recorded. Two electrodes made of Q345R low-carbon steel were used as the working electrode and the counter electrode, with Ag / AgCl as the reference electrode. The evolution of the EIS spectrum of the working electrode with corrosion time was measured, and the EIS spectrum was analyzed using DRT to obtain the distribution of log(τ / s) in the entire frequency domain. The value of log(τ / s) versus corrosion time was also recorded. t The evolution curve.

[0032] Depend on Figure 1 The data shows that during the entire 40-day corrosion process, the monitored Eh value reached -680 mV (vs. SSC) at day 20, and remained stable thereafter; correspondingly, the ORR-log( t The ORR (or ORR / s) value reaches 1.2 at 20 days, after which it transforms into a time constant related to water reduction. Note: When Eh > -640 mV (vs. SSC), ORR-log( t When the ORR / s value is less than 1.2, the candidate material for the disposal container, Q345R low-carbon steel, is in the oxygen corrosion stage; when Eh < -640 mV (vs. SSC), ORR-log( t When the / s) value is greater than 1.2, the candidate material for the disposal container, Q345R low carbon steel, enters the oxygen-free corrosion stage.

[0033] As can be seen, the results of this embodiment show that the method for identifying the evolution of anaerobic / anaerobic corrosion of materials in geological disposal environments of high-level radioactive waste can effectively identify the evolution behavior of anaerobic / anaerobic corrosion of materials in geological disposal environments of high-level radioactive waste.

[0034] Example 2

[0035] In this embodiment, the corrosion simulation solution uses groundwater from Beishan Reservoir BS-01, which is boiled and cooled under normal room temperature and pressure conditions before use. At this time, the oxygen content in the water is about 8 ppm.

[0036] The corrosion system was prepared in a low-oxygen glove box (gas phase oxygen content less than 0.1 ppm). The materials for the corrosion simulation solution, two electrodes made of Q345R low-carbon steel, the Eh electrode, and the Ag / AgCl reference electrode were placed in the glove box. The corrosion system was then prepared and sealed; at this point, the initial oxygen content in the corrosion solution was approximately 10 ppm.-4 ppb.

[0037] During the corrosion process, the evolution of the Eh value of the entire corrosion system with corrosion time was measured using an Eh electrode and an Ag / AgCl reference electrode, and the Eh value-corrosion time ratio was recorded. t The evolution curves were obtained; two electrodes made of Q345R low-carbon steel were used as the working electrode and the counter electrode, and Ag / AgCl was used as the reference electrode to measure the evolution of the EIS spectrum of the working electrode with corrosion time. The EIS spectrum was analyzed by DRT to obtain the distribution of log(τ / s) in the full frequency domain, and the value of log(τ / s) minus corrosion time was recorded. t The evolution curve.

[0038] Depend on Figure 2 The data shows that during the entire 40-day corrosion process, the monitored Eh value reached -680 mV (vs. SSC) at day 15, and remained stable thereafter; correspondingly, the ORR-log( t The ORR (or ORR / s) value reaches 1.2 at 15 days, after which it transforms into a time constant related to water reduction. Note: When Eh > -640 mV (vs. SSC), ORR-log( t When the ORR / s value is less than 1.2, the candidate material for the disposal container, Q345R low-carbon steel, is in the oxygen corrosion stage; when Eh < -640 mV (vs. SSC), ORR-log( t When the / s) value is greater than 1.2, the candidate material for the disposal container, Q345R low carbon steel, enters the oxygen-free corrosion stage.

[0039] As can be seen, the results of this embodiment show that the method for identifying the anaerobic / anaerobic corrosion evolution of materials in high-level radioactive waste geological disposal environments can effectively identify the anaerobic / anaerobic corrosion evolution behavior of materials in high-level radioactive waste geological disposal environments.

[0040] The results of the embodiments show that the method for identifying the anaerobic / aerobic corrosion evolution of materials in high-level radioactive waste geological disposal environments provided by the present invention is applicable to the identification and research of anaerobic / aerobic corrosion evolution of materials in high-level radioactive waste geological disposal environments. It is evident that the method for identifying the anaerobic / aerobic corrosion evolution of materials in high-level radioactive waste geological disposal environments of the present invention has the characteristics of simple steps, clear principles, high identification accuracy, and is also simple in method, readily available parameters, and strong operability.

[0041] The above-described embodiments are merely one implementation of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention. Any modifications, substitutions, or improvements made within the spirit and principles of the present invention are within the scope of protection of the present invention. Therefore, the scope of protection of this patent should be determined by the appended claims.

Claims

1. A method for identifying the anaerobic and anaerobic corrosion evolution of materials in a high-level radioactive waste geological disposal environment, characterized in that, It includes two indicators: one is the redox potential, Eh value, which reflects the overall redox characteristics of the corrosion system; the other is the time constant, ORR-log(Eh value), which reflects the ORR kinetics of dissolved oxygen reduction in the corrosion system. τ / s) value; The materials used in the geological disposal environment of high-level radioactive waste are candidate materials for simulating geological disposal containers for high-level radioactive waste, including low-carbon steel, copper, cast iron, nickel-based alloys, and titanium alloys. The geological environment for the disposal of high-level radioactive waste includes the rock strata and groundwater environment surrounding the disposal reservoir and the backfill material environment surrounding the disposal container; The corrosion system described herein is used to simulate the closed environment characteristics of a high-level radioactive waste geological disposal repository. Depending on the environment of the repository and the characteristics of the surrounding rock strata and groundwater, the environmental parameters of the closed environment system vary, including SO4. 2- Concentration, Cl - Concentration, HCO3 - / CO3 2- Concentration, pH value, pressure, and moisture content of backfill material; The Eh value is used to reflect the overall oxidizing power of the corrosion system, and is related to the dissolved oxygen content and the overall oxidizing power of all oxidizing substances containing Fe(III) in the corrosion system; by measuring with an Eh electrode, the evolution characteristics of the Eh value with corrosion time can be obtained. The ORR-log ( τ The ORR-log( / s) value is used to reflect the ease with which dissolved oxygen undergoes ORR in the corrosion system and is related to the dissolved oxygen content; the ORR-log( / s) value is obtained by performing relaxation time distribution (DRT) analysis on the measured electrochemical impedance spectroscopy (EIS). τ The evolution characteristics of the / s value with corrosion time; When Eh > -640 mV (vs. SSC) and ORR-log( τ When the / s) value is less than 1.2, the material of the disposal container is in the aerobic corrosion stage; When Eh < -640 mV (vs. SSC) and ORR-log( τ When the / s) value is greater than 1.2, the material of the disposal container enters the oxygen-free corrosion stage.

2. The method for identifying the anaerobic and anaerobic corrosion evolution of materials in a high-level radioactive waste geological disposal environment according to claim 1, characterized in that, The Eh electrode is used to measure the overall oxidizing property of the corrosion system. During use, the Eh electrode needs to be periodically subjected to small-amplitude cathodic polarization with an external potential to ensure the surface of the Eh electrode is clean, thereby ensuring the accuracy of the Eh electrode measurement.

3. The method for identifying the anaerobic and anaerobic corrosion evolution of materials in a high-level radioactive waste geological disposal environment according to claim 1, characterized in that, Candidate materials are processed into working electrodes for corrosion electrochemical testing, and EIS data are acquired using a traditional three-electrode system or a two-electrode system; based on The relationship is analyzed by performing DRT on the EIS data to obtain the number of time constants contained in the EIS spectrum and their corresponding log( τ Plot the log( / s) value. τ The evolution spectrum of ORR ( / s) value with corrosion time was obtained, and thus the ORR-log( τ The evolution of the / s value with corrosion time.

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