A device and method for measuring uranium migration in small column simulated soil

Abstract

The present invention belongs to the technical field of experimental devices, and discloses a small column simulated soil uranium migration determination device and method, wherein the small column simulated soil uranium migration determination device is provided with a simulated soil gas heating unit, a gas circulation pump and one or more simulated soil medium units; the simulated soil gas heating unit is provided with a PVC pipe, a disturbance fan is installed inside the PVC pipe, an upper pipe cover is buckled and installed at the upper end, a lower pipe cover is buckled and installed at the lower end, and a heating wire is installed inside the lower pipe cover; the simulated soil medium unit is provided with a PVC pipe, the interior of the PVC pipe is filled with uniform rock and soil medium, the bottom end of the rock and soil medium is filled with a uranium-containing substrate, an upper pipe cover is buckled and installed at the upper end, and a lower pipe cover is buckled and installed at the lower end. When the present invention is used, the uranium element can penetrate the rock and soil medium in the model to form an observable uranium content in the sampled gas in the PVC pipe at the upper end of the rock and soil medium, which greatly shortens the original observation time.

Description

Technical Field

[0001] The invention belongs to the technical field of experimental devices, and in particular relates to a device and a method for determining uranium migration in a small column simulated soil. Background Art

[0002] Uranium is a natural radioactive element and is currently the most important nuclear raw material. In the application of nuclear energy and nuclear technology, it may diffuse into the environment, and after migration and deposition, it will cause soil pollution, which will then endanger human health. Due to the complexity of the medium environment and fluid environment in the actual soil, there are certain difficulties in studying the migration law of uranium in the soil, and it is impossible to accurately understand the influencing conditions of uranium nuclide migration. At the same time, the migration of uranium in the soil is a long and slow process. It is difficult to observe the distribution changes of uranium in a large range of soil media in a short period of time.

[0003] At present, most of the research on uranium migration is carried out by numerical simulation methods. Only a few researchers place uranium ore in the air in a wide-mouth glass bottle or place uranium-containing media in river sand to study the migration behavior of uranium in the air or in pores.

[0004] In summary, the problems existing in the prior art are:

[0005] The migration of uranium in soil is a slow and complex process. There are certain difficulties in studying the environmental impact of the migration process. The research methods or devices currently proposed by scholars in the field cannot meet the controllable and short-term experimental requirements of soil uranium migration. Summary of the invention

[0006] In view of the problems existing in the prior art, the present invention provides a device and method for determining uranium migration in a small column simulated soil.

[0007] The present invention is implemented in this way: a small column simulated soil uranium migration measuring device, wherein the small column simulated soil uranium migration measuring device is provided with a simulated soil gas heating unit, a gas circulation pump and one or more simulated soil medium units;

[0008] The simulated soil gas heating unit is provided with a PVC pipe, a disturbance fan is installed inside the PVC pipe, an upper pipe cover is buckled and installed at the upper end, a lower pipe cover is buckled and installed at the lower end, and an electric heating wire is installed inside the lower pipe cover;

[0009] The simulated soil medium unit is provided with a PVC pipe, the interior of the PVC pipe is filled with uniform rock and soil medium, the bottom of the rock and soil medium is filled with a uranium-containing matrix, the upper end is buckled with an upper pipe cover, and the lower end is buckled with a lower pipe cover.

[0010] Furthermore, a temperature sensor is installed in the PVC pipe at the lower end of the disturbance fan of the simulated soil gas heating unit, and the fan and the temperature sensor are respectively connected to an external DC+12V power supply and a thermostat through wires.

[0011] Furthermore, the rock and soil medium and the uranium-containing substrate are placed on a porous bearing plate in the PVC tube of the simulated soil medium unit, and the porous bearing plate is horizontally fixed in the PVC tube of the simulated soil medium unit by bolts.

[0012] Furthermore, a group of pagoda joints are installed on the pipe wall at the lower end of the PVC pipe of the simulated soil gas heating unit.

[0013] Furthermore, a group of pagoda joints are respectively installed on the pipe wall of the upper end and the lower end of the PVC pipe of the simulated soil medium unit.

[0014] Furthermore, two sets of pagoda joints at the upper and lower ends of the PVC pipe of the simulated soil gas heating unit and the simulated soil medium unit PVC pipe are respectively installed on the same horizontal line.

[0015] Another object of the present invention is to provide a method for measuring uranium migration in a small column simulated soil of the device for measuring uranium migration in a small column simulated soil, wherein the method comprises:

[0016] (1) preparing uranium-containing substrate and rock and soil medium;

[0017] (2) Combined model unit;

[0018] (3) Experimental measurement;

[0019] (4) Analysis of experimental results

[0020] Furthermore, the steps of preparing the uranium-containing substrate and rock and soil medium include:

[0021] 1) Use a precision electronic balance to weigh 150g of 60-mesh dry mud powder and put it in a container, inject 20g of distilled water, and stir the mud powder and water evenly;

[0022] 2) Put the evenly stirred yellow mud into a mold, and place the mold in a hydraulic press;

[0023] 3) Apply pressure to the mold through a hydraulic press, and maintain it for 5 minutes after the hydraulic press reaches the target pressure;

[0024] 4) Release the pressure of the hydraulic press and remove the mold, and put the mold and the rock and soil medium into a constant temperature box for baking until the rock and soil medium are separated from the mold;

[0025] 5) Remove the rock medium and continue to bake it to dry weight.

[0026] Further, the experimental measurement step includes:

[0027] 1) Turn on the thermostat to heat the gas in the simulated soil gas heating unit to a target constant temperature;

[0028] 2) Turn on the circulating air pump to allow the heated gas in the simulated soil gas heating unit to circulate in the bottom chamber of each simulated soil medium unit for a period of time;

[0029] 3) Record the time when the air pump starts circulating as the start time of the experiment;

[0030] 4) Samples are collected from the upper chamber of the simulated soil medium unit using a nitric acid solution and a micro air pump at regular intervals. The nitric acid solution is prepared using ultrapure water and commercially available high-grade pure nitric acid. A buffer bottle is connected between the air pump and the sampling bottle;

[0031] 5) Draw the standard curve for uranium content analysis by spectrophotometry;

[0032] 6) Analyze the uranium content in each nitric acid solution sample, measure each sample twice to obtain the average value, and conduct a third measurement when the difference between the two contents exceeds ±15% of the first measurement value;

[0033] 7) Record the data and make a graph.

[0034] Furthermore, samples were collected from the upper chamber of the simulated soil medium unit using a nitric acid solution and a micro air pump at regular intervals. The nitric acid solution was prepared using ultrapure water and commercially available high-purity nitric acid. The nitric acid concentration of the solution was 2.0 mol / L. The amount of nitric acid solution used each time was 5 ml. The air pump flow rate was set to 1 L / min during vacuuming, and the vacuuming time was 15 min. A buffer bottle was connected between the air pump and the sampling bottle.

[0035] The advantages and positive effects of the present invention are as follows: the device for measuring uranium migration in simulated soil with a small column can prove that the temperature of simulated soil gas circulating in the device can be stably controlled during the experimental observation process;

[0036] Uranium can migrate in the rock medium along with the simulated soil air flow. The porosity of the rock medium has an important influence on the migration of uranium in the rock medium. The greater the porosity of the rock medium, the more conducive it is to the migration of uranium.

[0037] According to the experimental results, after about 18 days, the uranium element was able to penetrate the rock and soil media in the model, thereby forming an observable uranium content in the sampling gas in the PVC tube at the upper end of the rock and soil media, greatly shortening the original observation time. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 It is a schematic structural diagram of a simulated soil gas heating unit of a small column simulated soil uranium migration determination device provided in an embodiment of the present invention;

[0039] Figure 2 It is a schematic structural diagram of a simulated soil medium unit of a small column simulated soil uranium migration determination device provided in an embodiment of the present invention;

[0040] Figure 3 It is a schematic diagram of the appearance structure of a simulated soil gas heating unit and a simulated soil medium unit of a small column simulated soil uranium migration determination device provided by an embodiment of the present invention;

[0041] Figure 4 It is a schematic diagram of pipeline connections for a uranium element migration simulation experiment of a uranium migration determination device in a small column simulated soil provided by an embodiment of the present invention;

[0042] Figure 5 It is a schematic diagram of the connection of the uranium-containing gas sampling pipeline of the small column simulated soil uranium migration determination device provided by an embodiment of the present invention;

[0043] Figure 6 It is a uranium standard curve used for measuring the uranium content in the sampled gas of the uranium migration determination device in the small column simulated soil provided by the embodiment of the present invention;

[0044] Figure 7 It is a graph showing the detection results of uranium content in the sample gas in the upper chamber of each model unit of the small column simulated soil uranium migration determination device provided by an embodiment of the present invention;

[0045] Figure 1 Middle: 1. Upper pipe cover of simulated soil gas heating unit; 2. PVC pipe of simulated soil gas heating unit; 3. Disturbance fan; 4. Lower pipe cover of simulated soil gas heating unit; 5. Heating wire; 6. Air inlet pagoda connector; 7. Air outlet pagoda connector; 8. Temperature sensor;

[0046] Figure 2 Middle: 9. Upper pipe cover of simulated soil medium unit; 10. PVC pipe of simulated soil medium unit; 11. Geotechnical medium; 12. Lower pipe cover of simulated soil medium unit; 13. Pagoda joint of circulating air outlet; 14. Pagoda joint of circulating air inlet; 15. Porous supporting plate; 16. Pagoda joint of sampling air inlet; 17. Pagoda joint of sampling air outlet; 18. Uranium-containing substrate. DETAILED DESCRIPTION

[0047] In order to further understand the content, features and effects of the present invention, the following embodiments are given as examples and described in detail with reference to the accompanying drawings.

[0048] The structure of the present invention is described in detail below in conjunction with the accompanying drawings.

[0049] Depend on Figures 1 to 7 As shown, the uranium migration determination device in the small column simulated soil comprises a simulated soil gas heating unit and one or more simulated soil medium units;

[0050] The simulated soil gas heating unit is provided with a simulated soil gas heating unit PVC pipe 2, a disturbance fan 3 is mounted inside the simulated soil gas heating unit PVC pipe 2, a temperature sensor 8 is installed inside the simulated soil gas heating unit PVC pipe 2 at the lower end of the disturbance fan 3, the disturbance fan 3 is connected to an external DC+12V power supply through a wire, and the temperature sensor 8 is connected to an external temperature controller through a signal line;

[0051] The upper end of the simulated soil gas heating unit PVC pipe 2 is buckled with a simulated soil gas heating unit upper pipe cover 1, and the lower end of the simulated soil gas heating unit PVC pipe 2 is installed with a simulated soil gas heating unit lower pipe cover 4, and the lower pipe cover 4 of the simulated soil gas heating unit is installed with an electric heating wire 5 inside, and the electric heating wire 5 is connected to an external temperature controller through a wire;

[0052] An air inlet pagoda joint 6 and an air outlet pagoda joint 7 are installed on the lower end of the simulated soil gas heating unit PVC pipe 2;

[0053] The simulated soil medium unit is provided with a simulated soil medium unit PVC pipe 10, the interior of the simulated soil medium unit PVC pipe 10 is filled with a uniform rock and soil medium 11, the bottom end of the rock and soil medium 11 is filled with a uranium-containing substrate 18, the rock and soil medium 11 and the uranium-containing substrate 18 are placed on a porous supporting plate 15 in the simulated soil medium unit PVC pipe 10, and the porous supporting plate 15 is horizontally fixed in the simulated soil medium unit PVC pipe 10 by bolts.

[0054] As a preferred embodiment of the present invention, the air inlet pagoda joint 6 and the air outlet pagoda joint 7 on the lower end tube wall of the simulated soil gas heating unit PVC tube 2 should be installed on the same horizontal line about 3.5 cm high from the bottom of the lower tube cover 4 of the simulated soil gas heating unit; the sampling air inlet pagoda joint 16 and the sampling air outlet pagoda joint 17 on the upper end tube wall of the simulated soil medium unit PVC tube 10 should be installed on the same horizontal line about 3.5 cm high from the bottom of the upper tube cover 9 of the simulated soil medium unit, and the circulation air outlet pagoda joint 13 and the circulation air inlet pagoda joint 14 on the lower end tube wall should be installed on the same horizontal line about 3.5 cm high from the bottom of the lower tube cover 4 of the simulated soil gas heating unit;

[0055] A certain amount of insulation material should be wrapped outside the simulated soil gas heating unit PVC pipe 2, and the electric heating wire 5 is used to heat the air in the simulated soil gas heating unit PVC pipe 2. The heated air is transported by the air circulation pump to the lower end chamber of the rock and soil medium 11 in the simulated soil medium unit PVC pipe 10 to form simulated soil gas; the temperature sensor 8 and the electric heating wire 5 are connected to the external temperature controller through a wire to accurately control the gas temperature in the simulated soil gas heating unit PVC pipe 2;

[0056] The rock and soil medium 11 in the simulated soil medium unit PVC tube 10 and the inner wall of the simulated soil medium unit PVC tube 10 are fully sealed;

[0057] When conducting the experiment, the air inlet pagoda joint 6 and the air outlet pagoda joint 7 of the simulated soil gas heating unit of the small column simulated soil uranium migration determination device and one or more of the circulating air outlet pagoda joints 13 and the circulating air inlet pagoda joints 14 at the bottom of the simulated soil medium unit of the small column simulated soil uranium migration determination device are connected end to end through a silicone hose to form a closed loop.

[0058] The working principle of the present invention is:

[0059] 1. Preparation of uranium-containing substrate and rock and soil medium

[0060] 1) Use a precision electronic balance to weigh 150g of 60-mesh dry mud powder and put it in a container, inject 20g of distilled water, and stir the mud powder and water evenly;

[0061] 2) Put the evenly stirred yellow mud into a mold, and place the mold in a hydraulic press;

[0062] 3) Apply pressure to the mold through a hydraulic press, and maintain it for 5 minutes after the hydraulic press reaches the target pressure;

[0063] 4) Release the pressure of the hydraulic press and remove the mold, and put the mold and the rock and soil medium into a constant temperature box for baking until the rock and soil medium are separated from the mold;

[0064] 5) removing the rock and soil medium and continuing to bake it to dry weight;

[0065] In the process of preparing rock and soil media, the purpose of making different rock and soil media porosity sizes is achieved by controlling the pressing pressure of the hydraulic press;

[0066] The preparation process of the uranium-containing substrate is the same as that of the rock and soil medium. The difference is that when the evenly stirred yellow mud is put into the mold, a circular groove with a diameter of 4 cm is reserved in the center of the yellow mud, and 50 g of 200-mesh uranium ore powder is placed in the circular groove.

[0067] 2. Combined model unit

[0068] The uranium-containing substrate and the rock and soil medium are placed on a porous support plate in the PVC tube of the simulated soil medium unit, the rock and soil medium and the inner wall of the PVC tube are sealed with silicone grease, and the upper and lower bottom covers are respectively bonded to the upper and lower ends of the PVC tube by glue for sealing;

[0069] Install the various components of the simulated soil gas heating unit according to the structure shown in the figure, connect the temperature sensor, the heating wire and the external thermostat through the wires, seal the wire holes on the PVC pipe wall of the simulated soil gas heating unit, and wrap the outer wall of the PVC pipe of the simulated soil gas heating unit with insulation cotton and other materials;

[0070] The air inlet pagoda joint and the air outlet pagoda joint of the simulated soil gas heating unit and the air inlet pagoda joint and the air outlet pagoda joint at the bottom of one or more simulated soil medium units as well as the air inlet and the air outlet of an air circulation pump are connected end to end through a silicone hose to form a closed loop.

[0071] A pressure gauge and a pressure regulating valve are installed on the pipe wall above the rock medium of each simulated soil medium unit to adjust the pressure difference between the upper and lower chambers of each simulated soil medium unit during the experiment;

[0072] The connected small column simulates the uranium migration determination device in soil. Figure 4 shown.

[0073] 3. Experimental measurement steps

[0074] 1) Turn on the thermostat to heat the gas in the simulated soil gas heating unit to a target constant temperature;

[0075] 2) Turn on the air circulation pump to allow the heated gas in the simulated soil gas heating unit to circulate in the bottom chamber of each simulated soil medium unit for a period of time;

[0076] 3) Record the time when the air circulation pump starts circulating as the start time of the experiment;

[0077] 4) Use nitric acid solution and air pump to collect gas samples from the upper chamber of the simulated soil medium unit at regular intervals (e.g. Figure 5 ), the nitric acid solution is prepared with ultrapure water and commercially available high-grade pure nitric acid, the nitric acid concentration of the solution is 2.0 mol / L, the amount of nitric acid solution used each time is 5 ml, the air pump flow rate is set to 1 L / min during air extraction, the air extraction time is 15 min, and a buffer bottle is connected between the air pump and the sampling bottle to prevent nitric acid from being sucked into the air pump;

[0078] 5) Draw the standard curve for uranium content analysis by spectrophotometry;

[0079] 6) Analyze the uranium content in each nitric acid solution sample, measure each sample twice to obtain the average value, and conduct a third measurement when the difference between the two contents exceeds ±15% of the first measurement value;

[0080] 7) Record the data and make a graph.

[0081] 4. Experimental analysis results

[0082] Four simulated soil medium units were set up in this experiment. Unit #1, unit #2, and unit #3 were used for comparative experiments. The porosity of the soil medium in each unit was #1 < #2 < #3 from small to large. RTM1688-2 radon detector was used in unit #4 for long-term radon concentration measurement. The standard curve of uranium content analysis by spectrophotometry used this time is as follows: Figure 6 As shown, the standard curve fitting goodness R 2 It is 0.997, indicating that there is a good linear relationship between the relative absorbance values ​​measured in the uranium concentration range of 0 to 4 μg / ml.

[0083] use Figure 6 The uranium standard curve in the uranium standard curve was used to analyze the uranium content of the nitric acid solution samples collected from the air in the upper chamber of the simulated soil medium units #1, #2, and #3. The uranium content changes of the nitric acid solution samples collected from the air in the upper chamber of each unit are shown in the following figure: Figure 7 shown.

[0084] Depend on Figure 7 It can be seen that the uranium content of the samples collected in the upper chamber of the three simulated soil medium units shows a consistent change relationship. After a period of diffusion, the content of uranium in the air of the upper sampling chamber gradually begins to increase. Since the last sampling operation destroyed the airtightness of the upper chamber, the uranium content in the sampling chambers of Models 2 and 3 has decreased. Compared with Model #1, the uranium content values ​​of the samples detected in Units #2 and #3 at the same time are larger than those in Unit #1. The reason is that the greater the porosity of the caprock, the more conducive it is to the migration of uranium in the voids of the rock and soil medium.

[0085] The results of the time-dependent changes in the uranium elements in the samples collected in the upper chambers of each unit prove that uranium can be carried through the porous covering layer medium under the action of weak geogas flow, and the diffusion behavior of geogas flow is significantly affected by the porosity of the covering layer medium. Furthermore, since the fluid medium in this experiment only exists in the gas phase and there is no liquid phase carrier that may dissolve uranium and related elements, the experimental results can also prove that the migration form of uranium and other metal elements is nanoparticles or other clustered particles.

[0086] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any form. Any simple modification, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention are within the scope of the technical solution of the present invention.

Claims

1. A device for measuring uranium migration in a small column simulated soil, characterized in that: The uranium migration determination device in the small column simulated soil is provided with a simulated soil gas heating unit, a gas circulation pump and one or more simulated soil medium units; The simulated soil gas heating unit is provided with a PVC pipe, a disturbance fan is installed inside the PVC pipe, an upper pipe cover is buckled and installed at the upper end, a lower pipe cover is buckled and installed at the lower end, and an electric heating wire is installed inside the lower pipe cover; The simulated soil medium unit is provided with a PVC pipe, the interior of the PVC pipe is filled with uniform rock and soil medium, the bottom of the rock and soil medium is filled with a uranium-containing substrate, the upper end is buckled with an upper pipe cover, and the lower end is buckled with a lower pipe cover; A temperature sensor is installed in the PVC pipe at the lower end of the disturbance fan of the simulated soil gas heating unit. The fan and the temperature sensor are connected to an external power supply and a thermostat through wires respectively. The rock and soil medium and the uranium-containing substrate are placed on a porous bearing plate in the PVC tube of the simulated soil medium unit, and the porous bearing plate is horizontally fixed in the PVC tube by bolts.

2. The device for measuring uranium migration in a small column simulated soil as claimed in claim 1, characterized in that: A group of pagoda joints are installed on the pipe wall at the lower end of the PVC pipe of the simulated soil gas heating unit.

3. The device for measuring uranium migration in a small column simulated soil as claimed in claim 1, characterized in that: A set of pagoda joints are respectively installed on the pipe walls at the upper and lower ends of the PVC pipe of the simulated soil medium unit.

4. The device for measuring uranium migration in a small column simulated soil as claimed in claim 3, characterized in that: The two sets of pagoda joints at the upper and lower ends of the PVC pipe of the simulated soil medium unit are installed on the same horizontal line.

5. A method for measuring uranium migration in a small column simulated soil of the device for measuring uranium migration in a small column simulated soil as claimed in claim 1, characterized in that: The method for determining uranium migration in a small column simulated soil comprises: (1) preparing uranium-containing substrate and rock and soil medium; (2) Combined model unit; (3) Experimental measurement; (4) Analysis of experimental results 6. The method for determining uranium migration in a small column simulated soil according to claim 5, characterized in that: The steps of preparing the uranium-containing substrate and rock and soil medium include: 1) Use a precision electronic balance to weigh 150g of 60-mesh dry mud powder and put it in a container, inject 20g of distilled water, and stir the mud powder and water evenly; 2) Put the evenly stirred yellow mud into the mold, and place the mold on the hydraulic press bearing platform; 3) Apply pressure to the mold through a hydraulic press, and maintain it for 5 minutes after the hydraulic press reaches the target pressure; 4) Release the pressure of the hydraulic press and remove the mold, and put the mold and the rock and soil medium into a constant temperature box for baking until the rock and soil medium are separated from the mold; 5) Remove the rock medium and continue to bake it to dry weight.

7. The method for determining uranium migration in a small column simulated soil according to claim 5, characterized in that: The experimental measurement steps include: 1) Turn on the thermostat to heat the gas in the simulated soil gas heating unit to a target constant temperature; 2) Turn on the circulating air pump to allow the heated gas in the simulated soil gas heating unit to circulate in the bottom chamber of each simulated soil medium unit for a period of time; 3) Record the time when the air pump starts circulating as the start time of the experiment; 4) At regular intervals, a nitric acid solution and a micro air pump are used to collect gas samples from the upper chamber of the simulated soil medium unit. The nitric acid solution is prepared using ultrapure water and commercially available high-grade pure nitric acid. A buffer bottle is connected between the air pump and the sampling bottle; 5) Draw the standard curve for uranium content analysis by spectrophotometry; 6) Analyze the uranium content in each nitric acid solution sample, measure each sample twice to obtain the average value, and conduct a third measurement when the difference between the two contents exceeds ±15% of the first measurement value; 7) Record the data and make a graph.

8. The method for determining uranium migration in a small column simulated soil according to claim 7, characterized in that: Samples were collected from the upper chamber of the simulated soil medium unit using nitric acid solution and a micro air pump at regular intervals. The nitric acid solution was prepared using ultrapure water and commercially available high-purity nitric acid. The nitric acid concentration of the solution was 2.0 mol / L. The amount of nitric acid solution used each time was 5 ml. The air pump flow rate was set to 1 L / min during vacuuming, and the vacuuming time was 15 min. A buffer bottle was connected between the air pump and the sampling bottle.

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