Device and method for measuring diffusion coefficient of nuclide in rock matrix based on electric field acceleration

Abstract

The invention provides a device and method for measuring the diffusion coefficient of nuclide in a rock matrix based on electric field acceleration, and relates to the technical field of nuclear waste geological disposal safety evaluation.The device comprises a sample chamber used for containing a rock sample to be measured; the electric field generating unit is connected to the sample chamber and is used for generating a uniform electric field in the sample chamber, and the concentration monitoring unit is used for collecting experimental data; and the data acquisition and processing unit is connected with the concentration monitoring unit and is used for acquiring the experimental data acquired by the concentration monitoring unit, processing and analyzing the experimental data and calculating the diffusion coefficient of the nuclide in the rock matrix. According to the device and the method, an electric field driving mechanism is introduced on the basis of a penetration diffusion experiment, so that the diffusion coefficient of nuclide in a rock matrix is rapidly determined. The invention aims to greatly shorten the experimental period, improve the efficiency and accuracy of nuclide migration behavior research, and provide important technical support for safety assessment of high-level radioactive waste geological disposal.

Description

Technical Field

[0001] The present application relates to the technical field of safety assessment of geological disposal of nuclear waste, and in particular to a device and method for determining the diffusion coefficient of nuclides in a rock matrix based on electric field acceleration. Background Art

[0002] In the process of nuclear energy utilization, the safe disposal of high-level radioactive waste is a global challenge. Deep geological disposal is a geological disposal method for high-level radioactive waste recognized by all countries in the world. It is to bury high-level radioactive waste deep in the rock mass hundreds of meters underground. In order to ensure the safety performance of geological disposal repositories, it is necessary to simulate the migration behavior of nuclides in the disposal repository, among which the diffusion coefficient of nuclides in the rock matrix is ​​a key parameter. At present, almost all available diffusion data are obtained through laboratory experiments. However, there are some problems with traditional experimental methods. For example, traditional static batch adsorption experiments will break rock samples into fine particles, thereby increasing the specific surface area and porosity of the samples, resulting in a large diffusion coefficient obtained in the experiment. Although traditional through-diffusion experiments can accurately determine the diffusion coefficient of nuclides, due to the low permeability and small porosity of the rock matrix, the experiment is time-consuming, often taking months or even years, which seriously restricts the progress of related research. Therefore, how to achieve rapid and efficient determination of the diffusion coefficient of nuclides in rock matrices is a technical problem that needs to be solved urgently. Summary of the invention

[0003] The present application provides a device and method for determining the diffusion coefficient of nuclides in rock matrix based on electric field acceleration, which greatly shortens the experimental time and can also be used to conduct experiments on large intact rock samples. The present application applies an electric field to the intact rock sample to increase the flux of charged substances, thereby accelerating the diffusion process of nuclides, so that the diffusion coefficient of nuclides in rock matrix can be determined quickly and accurately, providing an important scientific basis for the safety assessment of geological disposal repository for high-level radioactive waste.

[0004] In a first aspect, the present application provides a device for determining the diffusion coefficient of nuclides in a rock matrix based on electric field acceleration, comprising:

[0005] A sample chamber, used for placing the rock sample to be tested, wherein the sample chamber is a structure to which an electric field can be applied;

[0006] An electric field generating unit, connected to the sample chamber, for generating a uniform electric field in the sample chamber; wherein the direction of the electric field is perpendicular to the diffusion direction of the rock sample to be tested;

[0007] A concentration monitoring unit, disposed in the sample chamber, for collecting experimental data;

[0008] The data acquisition and processing unit is connected to the concentration monitoring unit and is used to obtain the experimental data collected by the concentration monitoring unit and perform processing and analysis to calculate the diffusion coefficient of the nuclide in the rock matrix.

[0009] Further, the sample chamber comprises:

[0010] A nuclide solution tank, used for containing a solution containing nuclides of set concentration;

[0011] An ultrapure water tank, used to hold ultrapure water to receive the nuclides diffused from the nuclide solution tank through the rock matrix;

[0012] The rock slice holder is used to fix the rock sample to be tested between the nuclide solution tank and the ultrapure water tank.

[0013] Furthermore, it also includes a first agitator and a second agitator; wherein the first agitator and the second agitator are respectively arranged in the nuclide solution tank and the ultrapure water tank.

[0014] Furthermore, the electric field generating unit includes a power supply, a first electrode and a second electrode, the first electrode and the second electrode are electrically connected to the positive electrode and the negative electrode of the power supply respectively, and the first electrode and the second electrode are respectively arranged in the nuclide solution tank and the ultrapure water tank.

[0015] Furthermore, the electric field generating unit includes a voltmeter and an ammeter; wherein the voltmeter is connected in parallel between the power supply and the first electrode and the second electrode, and the ammeter is connected in series with the first electrode and the second electrode.

[0016] Furthermore, the data acquisition processing unit is used to calculate the effective diffusion coefficient of the nuclide in the rock matrix according to the effective diffusion coefficient expression (5) of the tracer ion:

[0017]

[0018] Among them, D e is the effective diffusion coefficient, V is the volume of the solution in the ultrapure water tank, k is the Boltzmann constant, T is the temperature, is the slope of the penetration curve, c t is the concentration of the nuclide in the ultrapure water tank at time t, A is the cross-sectional area of ​​the rock sample, z is the charge number of the nuclide ion, e is the elementary charge, is the potential gradient, c is the concentration of the nuclide in the ultrapure water tank, t is the time, φ is the potential on the rock surface, and x is the migration distance of the nuclide ions.

[0019] In a second aspect, the present application provides an experimental method based on the device for determining the diffusion coefficient of nuclides in rock matrix based on electric field acceleration described in the first aspect, comprising:

[0020] Preparation stage: selecting a rock sample, exhausting the air in the pores of the rock matrix of the rock sample, and setting an initial nuclide concentration gradient;

[0021] Applying an electric field: placing the rock sample in an electric field, applying a predetermined electric field in the sample chamber through an electric field generating unit, so that the cations are accelerated to migrate toward the cathode under the action of the electric field force, and after the current is stable, injecting a tracer to track the migration path of the nuclide;

[0022] Monitoring and recording: Use the concentration monitoring unit to monitor and record the changes in nuclide concentration in real time;

[0023] Data processing: Input the monitoring data into the data acquisition and processing unit for data analysis and processing, and calculate the diffusion coefficient of the nuclide in the rock matrix.

[0024] Furthermore, in the preparation stage, the air in the pores of the rock matrix of the rock sample is exhausted, including:

[0025] immersing the rock sample in a sodium chloride solution to saturate all pores within the rock matrix;

[0026] The pore-saturated rock sample is placed in a desiccator and suspended over a sodium chloride solution;

[0027] The desiccator is vacuumed to create an environment consisting of water vapor, which diffuses into the voids of the rock sample and expels the air.

[0028] Furthermore, the tracer is a nuclide ion.

[0029] Furthermore, the monitoring data is input into the data acquisition and processing unit for data analysis and processing, and the diffusion coefficient of the nuclide in the rock matrix is ​​calculated, including:

[0030] When the nuclide ions in the rock matrix of the rock sample to be tested are forced to move toward the electrode with opposite charge under the action of the electric field, the migration velocity of the nuclide ions in the rock sample is calculated according to formula (1):

[0031]

[0032] Where v is the migration velocity of the nuclide ion, μ is the mobility of the nuclide ion, is the potential gradient, φ is the potential of the rock surface, and x is the migration distance of the nuclide ion;

[0033] The nuclide ion flux in the rock sample exposed to the electric field is calculated using the ion migration velocity according to formula (2):

[0034]

[0035] Where j is the nuclide ion flux in the rock sample, c t is the concentration of the nuclide in the ultrapure water tank at time t;

[0036] The effective diffusion coefficient is calculated according to formula (3):

[0037]

[0038] Where D e is the effective diffusion coefficient, k is the Boltzmann constant, T is the temperature, z is the charge number of the nuclide ion, and e is the elementary charge;

[0039] The nuclide ion flux in the rock sample exposed to the electric field is calculated using the slope of the penetration curve according to formula (4):

[0040]

[0041] Where V is the volume of the solution in the ultrapure water tank, is the slope of the breakthrough curve, c is the concentration of the nuclide in the ultrapure water tank, t is the time, and A is the cross-sectional area of ​​the rock sample;

[0042] According to equations (2)-(4), the expression for determining the effective diffusion coefficient of nuclide ions in rock matrix is ​​as follows:

[0043]

[0044] Based on the effective diffusion coefficient expression of nuclide ions, the effective diffusion coefficient of nuclides in rock matrix is ​​calculated according to the concentration data monitored by the concentration monitoring unit.

[0045] The device and method for determining the diffusion coefficient of nuclides in rock matrix based on electric field acceleration provided in this application significantly shorten the experimental cycle from the traditional several months or even several years to less than one day by introducing an electric field driving mechanism, greatly improving the research efficiency. At the same time, the migration of nuclides driven by the electric field is more uniform and controllable, which helps to improve the accuracy of the diffusion coefficient determination. In addition, the device and method provided in this application are not only suitable for the determination of the diffusion coefficient of nuclides in granite, but can also be extended to other similar fields, such as groundwater pollution monitoring, soil remediation effect evaluation, etc., and have wide applicability. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the present application and, together with the description, serve to explain the principles of the present application.

[0047] Figure 1 A schematic diagram of the structure of a device for measuring the diffusion coefficient of nuclides in a rock matrix based on electric field acceleration provided in an embodiment of the present application;

[0048] Figure 2 A flow chart of an experimental method for a device for determining the diffusion coefficient of nuclides in a rock matrix based on electric field acceleration provided in an embodiment of the present application;

[0049] Figure 3 This is a curve showing the change of iodide concentration over time provided in the examples of the present application; wherein the points represent experimental data and the lines represent the linear regression fitting results of the data.

[0050] Description of reference numerals:

[0051] 100. Sample chamber; 101. Nuclide solution tank; 102. Ultrapure water tank; 103. Rock slice holder;

[0052] 200. Rock samples to be tested;

[0053] 300, electric field generating unit; 301, power supply; 302, first electrode; 303, second electrode; 304, voltmeter; 305, ammeter;

[0054] 400. concentration monitoring unit;

[0055] 500. Data acquisition and processing unit;

[0056] 600, a first agitator;

[0057] 700. A second agitator.

[0058] The above drawings have shown clear embodiments of the present application, which will be described in more detail later. These drawings and text descriptions are not intended to limit the scope of the present application in any way, but to illustrate the concept of the present application to those skilled in the art by referring to specific embodiments. DETAILED DESCRIPTION

[0059] Exemplary embodiments will be described in detail herein, examples of which are shown in the accompanying drawings. When the following description refers to the drawings, the same numbers in different drawings represent the same or similar elements unless otherwise indicated. The implementations described in the following exemplary embodiments do not represent all implementations consistent with the present application. Instead, they are merely examples of devices and methods consistent with some aspects of the present application as detailed in the appended claims.

[0060] At present, in view of the problems of inaccurate results of static batch adsorption experiments and long time consumption of diffusion experiments in the prior art, the embodiment of the present application provides a device and method for determining the diffusion coefficient of nuclides in rock matrix based on electric field acceleration, which introduces an electric field driving mechanism on the basis of traditional laboratory experiments to accelerate the migration of nuclides in rock matrix, thereby greatly shortening the experimental cycle. Specifically, the present application solves the following technical problems:

[0061] The problem of slow migration of nuclides in the rock matrix: By introducing an electric field driving mechanism, the migration speed of nuclides in the rock matrix can be accelerated, thereby shortening the experimental period.

[0062] The problem of inaccurate results in static batch adsorption experiments: The electric field driven mechanism can avoid the rock samples from being broken into fine particles, reduce the specific surface area and porosity of the samples, and improve the accuracy of the experimental results.

[0063] The problem of long time consumption in diffusion experiments: the electric field driven mechanism can significantly shorten the experimental cycle and improve experimental efficiency.

[0064] The problem of inaccurate determination of nuclide diffusion coefficients in rock matrix: The electric field driven mechanism can provide more accurate nuclide diffusion coefficient determination results and improve the reliability of experimental results.

[0065] Problems with complex experimental equipment and operations: The electric field driving mechanism proposed in this application can be combined with traditional experimental equipment and operating procedures to simplify experimental operations and equipment configuration.

[0066] The technical solution of the present application and how the technical solution of the present application solves the above-mentioned technical problems are described in detail below with specific embodiments. The following specific embodiments can be combined with each other, and the same or similar concepts or processes may not be repeated in some embodiments. The embodiments of the present application will be described below in conjunction with the accompanying drawings.

[0067] Embodiment 1:

[0068] Figure 1 A schematic diagram of the structure of a device for measuring the diffusion coefficient of nuclides in rock matrix based on electric field acceleration provided in an embodiment of the present application. Figure 1 As shown, the device for determining the diffusion coefficient of nuclides in rock matrix based on electric field acceleration includes a sample chamber 100, an electric field generating unit 300, a concentration monitoring unit 400 and a data acquisition and processing unit 500.

[0069] Among them, the sample chamber 100 is used to place the rock sample 200 to be tested, and the sample chamber 100 is a structure to which an electric field can be applied; the electric field generating unit 300 is connected to the sample chamber 100, and is used to generate a uniform electric field in the sample chamber 100; wherein the direction of the electric field is perpendicular to the diffusion direction of the rock sample to be tested; the concentration monitoring unit 400 is arranged in the sample chamber 100, and is used to collect experimental data; the data acquisition and processing unit 500 is connected to the concentration monitoring unit 400, and is used to obtain the experimental data collected by the concentration monitoring unit and perform processing and analysis, and calculate the diffusion coefficient of the nuclide in the rock matrix.

[0070] In this embodiment, the electric field generating unit 300 is used to apply an electric field, and the concentration monitoring unit 400 is arranged on both sides or at a specific position of the sample chamber 100, and is used to detect the change of the tracer over time, that is, the rate of change of the tracer concentration, by sampling, and then transmit it to the concentration monitoring unit 400, and the concentration monitoring unit 400 calculates the diffusion coefficient of the nuclide in the rock matrix.

[0071] In some embodiments, the sample chamber 100 includes a nuclide solution tank 101, an ultrapure water tank 102, and a rock slice holder 103. The nuclide solution tank 101 is used to hold a solution containing a set concentration of nuclides; the ultrapure water tank 102 is used to hold ultrapure water to receive nuclides diffused from the nuclide solution tank through the rock matrix; and the rock slice holder 103 is used to fix the rock sample to be tested between the nuclide solution tank 101 and the ultrapure water tank 103.

[0072] Specifically, the nuclide solution tank 101 and the ultrapure water tank 102 contain different solutions respectively, and the nuclide solution tank 101 is connected to the ultrapure water tank 102, and the connection is separated by the rock sample to be tested clamped by the rock slice holder 103. The nuclide solution tank 101 is located on the left side of the rock sample, and is used to hold a solution containing a certain concentration of nuclides as a diffusion source in the experiment. The ultrapure water tank 102 is located on the right side of the rock sample, and is used to receive nuclides diffused from the nuclide solution tank through the rock matrix.

[0073] The rock sample to be tested can be a rock slice, and the thickness, size, density and porosity of the rock slice should meet the experimental requirements.

[0074] In some embodiments, Figure 1 As shown, the device further includes a first stirrer 600 and a second stirrer 700, wherein the first stirrer 600 and the second stirrer 700 are respectively arranged in the nuclide solution tank 101 and the ultrapure water tank 102. The first stirrer 600 and the second stirrer 700 are used to stir the water samples in the nuclide solution tank and the ultrapure water tank during the experiment to make the concentration of the nuclide solution evenly distributed.

[0075] In some embodiments, Figure 1 As shown, the electric field generating unit 300 includes a power supply 301, a first electrode 302 and a second electrode 303, the first electrode 302 and the second electrode 303 are electrically connected to the positive electrode and the negative electrode of the power supply respectively, and the first electrode 302 and the second electrode 303 are respectively arranged in the nuclide solution tank 101 and the ultrapure water tank 102. The electric field generating unit 300 also includes a voltmeter 304 and an ammeter 305; wherein the voltmeter 304 is connected in parallel between the power supply and the first electrode 302 and the second electrode 303, and the ammeter 305 is connected in series with the first electrode 302 and the second electrode 303.

[0076] In this embodiment, the first electrode 302 is a positive electrode, the second electrode 303 is a negative electrode, and the voltmeter 401 and the ammeter 402 can be connected to an electric field control module to monitor and record the voltage and current values ​​during the experiment to ensure the stability of the electric field. The power supply 301 can be selected as a DC regulated power supply.

[0077] In some embodiments, the data acquisition processing unit 500 is used to calculate the effective diffusion coefficient of the nuclide in the rock matrix according to the effective diffusion coefficient expression (5) of the tracer ion:

[0078]

[0079] Among them, D e is the effective diffusion coefficient of the nuclide, V is the volume of the solution in the ultrapure water tank, k is the Boltzmann constant, T is the temperature, is the slope of the penetration curve, c t is the concentration of the nuclide in the ultrapure water tank at time t, A is the cross-sectional area of ​​the rock sample, z is the charge number of the nuclide ion, e is the elementary charge, is the potential gradient, c is the concentration of the nuclide in the ultrapure water tank, t is the time, φ is the potential on the rock surface, and x is the migration distance of the nuclide ions.

[0080] Embodiment 2:

[0081] The present application embodiment provides an experimental method for determining the diffusion coefficient of a nuclide in a rock matrix based on electric field acceleration as provided in Example 1, such as Figure 2 As shown, the experimental method includes the following steps:

[0082] S1. Preparation stage: Select rock samples, exhaust the air in the pores of the rock matrix of the rock samples, and set the initial nuclide concentration gradient.

[0083] In this embodiment, a representative study area is selected in the preparation stage to ensure the typicality and representativeness of the sample. Multiple different locations are selected in the study area to drill cores at different depths to obtain vertical profile information of the rock. Then, the core is sliced ​​and the slice is mounted in a slice holder to fix the position and angle of the slice. Finally, a nuclide solution tank and an ultrapure water tank are placed on both sides of the slice holder to facilitate relevant experiments and tests.

[0084] S2. Applying an electric field: placing the rock sample in an electric field, applying a predetermined electric field in the sample chamber through an electric field generating unit, so that the cations are accelerated to migrate toward the cathode under the action of the electric field force, and after the current stabilizes, injecting a tracer to track the migration path of the nuclide.

[0085] In this embodiment, a predetermined electric field is applied to both sides of the rock slice through an electric field generating unit and a control system, thereby starting the accelerated migration process of the nuclides under the action of the electric field force. At the same time, a voltmeter is used to measure the potential and current on the sample in real time. After the current stabilizes, the tracer is injected to track the migration path of the nuclides. To ensure the reliability and accuracy of the experimental results, this step will be performed immediately after the current stabilizes.

[0086] S3. Monitoring and recording: Use the concentration monitoring unit to monitor and record the changes in nuclide concentration in real time.

[0087] In this embodiment, samples are taken regularly at preset time intervals in the ultrapure water tank on the right side of the rock slice to obtain dynamic information about the migration process of nuclides in the rock matrix. The concentration of nuclides in the samples is measured using appropriate analytical methods, such as a gamma spectrometer, a mass spectrometer or other related technologies, and the data is recorded.

[0088] S4. Data processing: Input the monitoring data into the data acquisition and processing unit, perform data analysis and processing, and calculate the diffusion coefficient of the nuclide in the rock matrix.

[0089] In this embodiment, in the data processing step, a control equation for the diffusion of nuclide ions in a rock matrix under the action of an electric field is established to determine an effective diffusion coefficient expression of the nuclide ions. The specific calculation principle is as follows:

[0090] The main consideration is the diffusion of charged species in the rock matrix under the action of ion exchange. Charged species are forced to move to the electrode with the opposite charge under the action of the electric field. The migration speed of charged species depends on the strength of the electric field and the ionic mobility of the species:

[0091]

[0092] Where v is the migration velocity of the nuclide ion, μ is the mobility of the nuclide ion, is the potential gradient, φ is the potential of the rock surface, and x is the migration distance of the nuclide ions.

[0093] The ion migration velocity is used to calculate the nuclide ion flux in the rock sample exposed to the electric field as shown in formula (2):

[0094]

[0095] Where j is the nuclide ion flux in the rock sample, c t is the concentration of the nuclide in the ultrapure water tank at time t;

[0096] The ion mobility can be converted to the effective diffusion coefficient using the Einstein relationship as shown in equation (3):

[0097]

[0098] Where D e is the effective diffusion coefficient, k is the Boltzmann constant, T is the temperature, z is the charge number of the nuclide ion, and e is the elementary charge.

[0099] The nuclide ion flux in a rock sample exposed to an electric field can be calculated using the slope of the penetration curve as shown in formula (4):

[0100]

[0101] Where V is the volume of the solution in the ultrapure water tank, is the slope of the penetration curve, a is the cross-sectional area of ​​the rock sample, c is the concentration of the nuclide in the ultrapure water tank, and t is the time.

[0102] Formula (4) can be used in combination with formula (2) and formula (3) to give the expression (5) of the effective diffusion coefficient of nuclide ions in rock matrix:

[0103]

[0104] The following embodiments of the present application will be combined with specific experimental cases to further illustrate the feasibility and progress of the present application.

[0105] A representative cylindrical rock sample was cut into slices with a length of 47 mm and a width of 15 mm. The sample was then pretreated by immersing the slice in a sodium chloride solution to saturate all pores within the rock matrix. After pretreatment, the slice was placed in a desiccator and suspended above the sodium chloride solution. To expel the residual air in the sample pores, the desiccator was vacuumed to create an environment composed mainly of water vapor. The slice was then placed under low pressure to allow water vapor to diffuse into the sample pores while air was expelled. The sample was then placed in the solution and the ambient pressure was restored to atmospheric pressure, using the pressure difference to further diffuse the solution into the rock matrix. Typically, the sample was immersed in the solution for 12 hours or more to ensure that the pores were fully saturated. Electrodiffusion experiments using iodide as a tracer were performed on slices with a length of 47 mm and a width of 15 mm. After the voltage was applied and stabilized, the tracer injection began. During the experiment, 5 mL of sample was extracted from the ultrapure water tank on the right twice a day, and the potential above the sample and the current through the rock slice were recorded. After each sampling, 5 mL of the initial solution was immediately added to keep the volume in the ultrapure water tank constant. It is worth noting that the electromigration experiment was not significantly affected by the Joule heating effect. The chemical reagents NaCl and NaI used in the experiment were analytically pure, and the experimental solution was prepared with distilled water. The concentration of iodide was measured by an ion electrode (RIO3001). During the experiment, the potential gradient was set to 200 V / m, and the concentration of sodium iodide in the solution was 10 mM.

[0106] See also Figure 3 , Figure 3 The results show that breakthrough occurs after about 1.5 h, which is several hundred times faster than the breakthrough time obtained by the penetration diffusion method using similar sample sizes. At the same time, the slope of the linear regression line can also be used to determine the rate of change of tracer concentration in the ultrapure water tank during the steady state period, and the effective diffusion coefficient of iodide is calculated according to formula (5). The calculation results show that the effective diffusion coefficient of iodide is 4.0×10 -13 m 2 / s, which is consistent with the results reported in the literature and provides an important scientific basis for the safety performance assessment of deep-site disposal repositories for high-level radioactive waste.

[0107] The various embodiments or implementation methods in this specification are described in a progressive manner. Each embodiment focuses on the differences from other embodiments, and the same or similar parts between the various embodiments can be referenced to each other.

[0108] It should be noted that the phrases "one embodiment", "an embodiment", "an exemplary embodiment", "some embodiments", etc. mentioned in the specification indicate that the described embodiments may include certain features, structures or characteristics, but not every embodiment may include the certain features, structures or characteristics. In addition, such phrases do not necessarily refer to the same embodiment. In addition, when describing certain features, structures or characteristics in conjunction with an embodiment, it is within the knowledge of those skilled in the art to implement such features, structures or characteristics in conjunction with other embodiments, whether explicitly or not explicitly described.

[0109] In general, terms should be understood, at least in part, by the context in which they are used. For example, the term "one or more" as used herein may be used to describe any feature, structure, or characteristic in a singular sense, or may be used to describe a combination of features, structures, or characteristics in a plural sense, depending, at least in part, on the context. Similarly, terms such as "a," "an," or "the" may also be understood to convey singular usage or to convey plural usage, depending, at least in part, on the context.

[0110] It should be easily understood that “on,” “above,” and “over” in the present disclosure should be interpreted in the broadest manner, so that “on” not only means “directly on something,” but also includes the meaning of “on something” with intervening features or layers therebetween, and “above” or “over” not only includes the meaning of “above” or “over,” but also may include the meaning of “above” or “over something” with no intervening features or layers therebetween (i.e., directly on something).

[0111] In addition, spatially relative terms, such as "below," "below," "beneath," "above," "above," etc., may be used herein for ease of description to describe the relationship of one element or feature relative to other elements or features as shown in the figures. Spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation shown in the figures. The device may have other orientations (rotated 90 degrees or at other orientations), and the spatially relative descriptors used herein may likewise be interpreted accordingly.

[0112] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit it. Although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A device for measuring the diffusion coefficient of nuclides in rock matrix based on electric field acceleration, characterized in that: include: A sample chamber, used for placing the rock sample to be tested, wherein the sample chamber is a structure to which an electric field can be applied; An electric field generating unit, connected to the sample chamber, for generating a uniform electric field in the sample chamber; wherein the direction of the electric field is perpendicular to the diffusion direction of the rock sample to be tested; Concentration monitoring unit, used to collect experimental data; The data acquisition and processing unit is connected to the concentration monitoring unit and is used to obtain the experimental data collected by the concentration monitoring unit and perform processing and analysis to calculate the diffusion coefficient of the nuclide in the rock matrix.

2. The device for determining the diffusion coefficient of nuclides in rock matrix based on electric field acceleration according to claim 1 is characterized in that: The sample chamber comprises: A nuclide solution tank, used for containing a solution containing nuclides of set concentration; An ultrapure water tank, used to hold ultrapure water to receive the nuclides diffused from the nuclide solution tank through the rock matrix; The rock slice holder is used to fix the rock sample to be tested between the nuclide solution tank and the ultrapure water tank.

3. The device for determining the diffusion coefficient of nuclides in rock matrix based on electric field acceleration according to claim 2, characterized in that: It also includes a first agitator and a second agitator; wherein the first agitator and the second agitator are respectively arranged in the nuclide solution tank and the ultrapure water tank.

4. The device for determining the diffusion coefficient of nuclides in rock matrix based on electric field acceleration according to claim 1, characterized in that: The electric field generating unit comprises a power supply, a first electrode and a second electrode. The first electrode and the second electrode are electrically connected to the positive electrode and the negative electrode of the power supply respectively. The first electrode and the second electrode are respectively arranged in the nuclide solution tank and the ultrapure water tank.

5. The device for determining the diffusion coefficient of nuclides in rock matrix based on electric field acceleration according to claim 1, characterized in that: The electric field generating unit further comprises a voltmeter and an ammeter; wherein the voltmeter is connected in parallel between the power supply and the first electrode and the second electrode, and the ammeter is connected in series with the first electrode and the second electrode.

6. The device for determining the diffusion coefficient of nuclides in rock matrix based on electric field acceleration according to claim 1, characterized in that: The data acquisition processing unit is used to calculate the effective diffusion coefficient of the nuclide in the rock matrix according to the effective diffusion coefficient expression (5) of the nuclide ion: Among them, D e is the effective diffusion coefficient of the nuclide, V is the volume of the solution in the ultrapure water tank, k is the Boltzmann constant, T is the temperature, is the slope of the penetration curve, c t is the concentration of the nuclide in the ultrapure water tank at time t, A is the cross-sectional area of ​​the rock sample, z is the charge number of the nuclide ion, e is the elementary charge, is the potential gradient, c is the concentration of the nuclide in the ultrapure water tank, t is the time, φ is the potential on the rock surface, and x is the migration distance of the nuclide ions.

7. An experimental method for determining the diffusion coefficient of nuclides in rock matrix based on electric field acceleration according to any one of claims 1 to 5, characterized in that: include: Preparation stage: selecting a rock sample, exhausting the air in the pores of the rock matrix of the rock sample, and setting an initial nuclide concentration gradient; Applying an electric field: placing the rock sample in an electric field, applying a predetermined electric field in the sample chamber through an electric field generating unit, so that the cations are accelerated to migrate toward the cathode under the action of the electric field force, and after the current is stable, injecting a tracer to track the migration path of the nuclide; Monitoring and recording: Use the concentration monitoring unit to monitor and record the changes in nuclide concentration in real time; Data processing: Input the monitoring data into the data acquisition and processing unit for data analysis and processing, and calculate the diffusion coefficient of the nuclide in the rock matrix.

8. The experimental method according to claim 7, characterized in that: In the preparation stage, the air in the pores of the rock matrix of the rock sample is exhausted, including: immersing the rock sample in a sodium chloride solution to saturate all pores within the rock matrix; The pore-saturated rock sample is placed in a desiccator and suspended over a sodium chloride solution; The desiccator is vacuumed to create an environment consisting of water vapor, which diffuses into the voids of the rock sample and expels the air.

9. The experimental method according to claim 7, characterized in that: The tracer is a nuclide ion.

10. The experimental method according to claim 7, characterized in that: The monitoring data is input into the data acquisition and processing unit for data analysis and processing, and the effective diffusion coefficient of nuclides in the rock matrix is ​​calculated, including: When the nuclide ions in the rock matrix of the rock sample to be tested are forced to move toward the electrode with opposite charge under the action of the electric field, the migration velocity of the nuclide ions in the rock sample is calculated according to formula (1): Where v is the migration velocity of the nuclide ion, μ is the mobility of the nuclide ion, is the potential gradient, φ is the potential of the rock surface, and x is the migration distance of the nuclide ion; The nuclide ion flux in the rock sample exposed to the electric field is calculated using the ion migration velocity according to formula (2): Where j is the nuclide ion flux in the rock sample, c t is the concentration of the nuclide in the ultrapure water tank at time t; The effective diffusion coefficient is calculated according to formula (3): Where D e is the effective diffusion coefficient of the nuclide, k is the Boltzmann constant, T is the temperature, z is the charge number of the nuclide ion, and e is the elementary charge; The nuclide ion flux in the rock sample exposed to the electric field is calculated using the slope of the penetration curve according to formula (4): Where V is the volume of the solution in the ultrapure water tank, is the slope of the breakthrough curve, c is the concentration of the nuclide in the ultrapure water tank, t is the time, and A is the cross-sectional area of ​​the rock sample; According to equations (2)-(4), the expression for determining the effective diffusion coefficient of nuclide ions in rock matrix is ​​as follows: Based on the effective diffusion coefficient expression of nuclide ions, the effective diffusion coefficient of nuclides in rock matrix is ​​calculated according to the concentration data monitored by the concentration monitoring unit.

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