Method for Disposing Mud Based on Measurement of Radioactivity of In-Situ Leaching Uranium Drilling Mud

Abstract

The present invention relates to a mud disposal method and system for calculating the radioactive activity of borehole mud in in-situ leaching uranium mining. The method includes: establishing a calculation model for the radioactive activity of borehole mud in in-situ leaching uranium mining based on the principle of material balance; for the mud that is not recycled, predicting the radioactive activity level of the mud according to the radioactive activity calculation model; for the recycled mud, predicting the radioactive activity level of the mud after recycling according to the radioactive activity calculation model and the mud recycling rate; determining the disposal method of the mud according to whether the radioactive activity level exceeds the radioactive activity exemption level. By using the method of the present invention, it is possible to pre-judge before the project implementation whether the radioactive activity level of the mixed waste drilling mud exceeds the radioactive activity exemption level that is exempt from radiation protection supervision, and accordingly determine the disposal method of the mud, so as to classify and dispose of the mud, improve the level of radiation protection and ecological environment protection, and enhance the effectiveness and pertinence of supervision.

Description

Technical Field

[0001] The present invention relates to the technical field of in-situ leaching uranium radiation environment management, and particularly to a mud disposal method based on the measurement of the radioactive activity of borehole mud in in-situ leaching uranium mining. Background Technique

[0002] In-situ leaching uranium technology, also known as in-situ leaching uranium mining technology, does not extract uranium ore to the surface for treatment. Instead, a leaching solution is used to inject into the sandstone-type uranium ore layer under natural burial conditions through an injection borehole, changing the geochemical environment during uranium deposition and mineralization. Oxygen is used to oxidize tetravalent uranium to hexavalent uranium, and bicarbonate is used to complex with hexavalent uranium to dissolve uranium, forming a uranium-containing leaching solution, which is then lifted to the surface through a pumping borehole and transported to the hydrometallurgy workshop, and processed into a product through processes such as adsorption, elution, and precipitation. This is an integrated uranium mining and metallurgy process. This process consists of two major parts: in-situ leaching and leaching solution treatment. The former is a cyclic process in which a leaching agent is used through an injection borehole to transfer uranium in the ore from the solid phase to the liquid phase to form a leaching solution, which is extracted to the surface through a pumping borehole; the latter is the process of treating the leaching solution to finally obtain a uranium concentrate product.

[0003] In in-situ leaching uranium drilling engineering, drilling fluid (or "mud") is an essential substance to ensure the smooth progress of drilling work. It plays roles such as balancing formation pressure, carrying suspended drill cuttings, preventing wellbore collapse, cooling and lubricating drill tools, etc. During the drilling process, waste drilling fluid (also known as used mud) is inevitably generated. It is a multiphase steady-state colloidal suspension system containing clay, various chemical treatment agents, sewage, waste oil, and drill cuttings.

[0004] The drilling construction process is generally a continuous construction process. The drill rig drills at a certain speed. First, it drills through the overlying rock layer of the ore-bearing layer. The mud generated in this part generally does not contain radioactivity or the radioactive activity level is equivalent to the environment. Then it drills into the ore-bearing layer and reaches the mudstone layer below the ore layer. The mud generated in this part usually contains a certain amount of radioactivity due to the presence of radioactive cuttings. However, the radioactivity will decrease after this part of the mud is mixed with the overlying layer mud. The drill bit is withdrawn to carry out logging work. At this time, the ore-bearing layer mud deposits at the bottom. After logging is completed, the drill bit is replaced to carry out reaming drilling work. This process is a continuous process. The recycled mud is pumped out and screened for solid components such as drill cuttings through a vibrating screen. The mud is temporarily stored in a temporary mud pit or mud tank, and the used mud is transported to the comprehensive mud pit of the entire factory area.

[0005] The main sources of waste mud are as follows: First, waste drilling mud sewage, mainly the waste drilling mud after well completion; second, waste mechanical sewage, mainly including the flushing water of the drilling pump rod after well completion, the discharged wastewater from well flushing, etc.; third, various flushing sewage, mainly including the water used for flushing the vibrating screen, the water used for flushing the drill floor and drill tools, the water used for cleaning equipment and other wastewater; fourth, various cuttings, mainly the large amount of fine-grained cuttings generated during drilling, and the cuttings adsorbed a large amount of waste drilling mud and were discharged into the waste mud pond; fifth, other waste liquids, mainly including some acidified well-flushing wastewater, the wastewater increased by natural rainfall intrusion, etc. Since the waste drilling mud contains pollutants that are difficult to naturally degrade and have different toxicities, especially the waste mud containing natural radioactivity inevitably generated in the in-situ leaching uranium mining process, if not properly treated, it will cause pollution of soil, surface and groundwater, and bring direct or indirect harm to the environment and humans. For example, due to the soda ash and plant gum added to the drilling mud configuration, under the action of the drilling rig, the components and states of different formation substances change violently, and the radioactive U, Ra, harmful elements Pb, Cr, Cd, etc. and high-concentration K, Ca, Mg elements carried by the mud migrate and accumulate on the surface through different channels, destroying the surface ecology and posing a radioactive hazard with uncertain dose. Secondly, the small-particle cuttings of the in-situ leaching uranium mine drilling mud are pumped into the hole, causing repeated crushing, and the bit wear increases rapidly; the solid content accumulates, reducing the drilling efficiency and causing downhole accidents.

[0006] Due to the large amount of drilling work, a large amount of waste drilling mud will be generated during the drilling construction process. If these waste drilling muds are not properly managed, they will surely pollute the local environment and cause incalculable losses, and environmental pollution will in turn restrict the development of the uranium mining and metallurgy industry.

[0007] At present, there are many problems in the utilization and disposal of drilling mud in the in-situ leaching process. The primary problem in the disposal of uranium mine drilling mud is that under the existing technical means, ordinary mud and radioactive ore-containing mud are mixed and recycled, but the nuclide concentration and the possible radioactive level of the radioactive nuclide-containing mud are not clear, lacking a data basis. Secondly, at present, the centralized collection and treatment method is mainly used to treat waste drilling mud. The component characteristics and radioactive nuclide concentration status of the drilling mud are unknown, which is likely to lead to insufficient supervision pertinence, resulting in mismanagement or overmanagement; the production unit stores the waste mud produced in the mixed mud pond, and after the mud dries, it is covered and restored as the final disposal method. The final radioactive activity level of the mud cannot be ensured to be lower than the exemption level, or the waste mud that should originally be disposed of by conventional disposal means is disposed of by radioactive waste disposal methods, increasing the disposal cost.

[0008] Therefore, there is an urgent need for a method that can predict the radioactive activity level of drilling mud during the production construction process in advance by understanding the basic properties of surface radioactivity and uranium ore, as well as the process information of the drilling construction process, etc., guide the classified disposal of radioactive mud in segments, improve the level of radiation protection and ecological environment protection, and enhance the effectiveness and pertinence of supervision. Summary of the Invention

[0009] To solve or at least alleviate the above problems, the present invention proposes a mud disposal method based on the measurement and calculation of the radioactive activity of in-situ leaching uranium drilling mud, which can predict whether the concentration of radionuclides in the mixed waste drilling mud generated during the construction of boreholes in the in-situ leaching uranium project site exceeds the exemption limit for radiation protection supervision before the project implementation, so as to classify and dispose of the mud, improve the level of radiation protection and ecological environment protection, and enhance the effectiveness and pertinence of supervision.

[0010] To achieve the above object, the present invention provides the following solutions:

[0011] A mud disposal method based on the measurement and calculation of the radioactive activity of in-situ leaching uranium drilling mud, comprising:

[0012] Establish a radioactive activity measurement and calculation model for in-situ leaching uranium drilling mud based on the principle of material balance;

[0013] For the mud that is not recycled, predict the radioactive activity level of the mud according to the radioactive activity measurement and calculation model;

[0014] For the recycled mud, predict the radioactive activity level of the mud after recycling according to the radioactive activity measurement and calculation model and the mud recycling rate;

[0015] Determine the disposal method of the mud according to whether the radioactive activity level exceeds the radioactive activity exemption level.

[0016] Optionally, the establishment of the radioactive activity measurement and calculation model based on the principle of material balance specifically includes:

[0017] Establish a radioactive activity measurement and calculation model based on the principle of material balance where a U is the radioactive activity level of the mud obtained from the construction of a single borehole; D is the borehole diameter; H C is the thickness of the overburden layer; ρ c is the density of the overlying rock layer of the ore deposit; F c is the average radioactive grade of the overlying rock layer of the ore deposit; H O is the thickness of the ore-bearing layer; F o is the radioactive grade of the ore-bearing layer; ρ o is the density of the ore-bearing layer; C is the conversion factor of the mass activity of the radionuclide; ρ m is the density of the mud; M mis the amount of mud used; η u is the sand content rate of waste mud; F m is the solid radioactive activity level of recycled mud; F w is the radioactive activity level of the mud supernatant; M n is the amount of fresh mud; η n is the sand content rate of fresh mud; F n is the solid radioactive activity level of fresh mud; η m is the recycling rate of waste mud.

[0018] Optionally, for the recycled mud, according to the radioactive activity measurement model and the mud recycling rate, predict the radioactive activity level of the mud after recycling, specifically including:

[0019] For the recycled mud, predict the initial radioactive activity level of the mud according to the radioactive activity measurement model;

[0020] Obtain the recycling rate R of the recycled mud, and use the formula I = 1.7013R 2 -0.1662R + 1.08 to determine the growth multiple I of the radioactive activity level of the mud;

[0021] Multiply the initial radioactive activity level by the growth multiple I of the radioactive activity level to obtain the radioactive activity level of the mud after recycling.

[0022] Optionally, the method for determining the disposal method of the mud according to whether the radioactive activity level exceeds the radioactive activity exemption level specifically includes:

[0023] Judge whether the radioactive activity level of the mud exceeds the radioactive exemption level. If it exceeds, dispose of the mud as radioactive waste; otherwise, dispose of the mud as general waste; the radioactive exemption level is 1000 Bq / kg.

[0024] Optionally, the method further includes:

[0025] Determine the corresponding relationship between the ore grade of the ore deposit and the ratio of the thickness of the overlying rock layer to the ore-bearing layer of the ore deposit according to the radioactive activity level;

[0026] Based on the corresponding relationship between the ore grade of the ore deposit and the ratio of the thickness of the overlying rock layer to the ore-bearing layer of the ore deposit, use the ratio of the thickness of the overlying rock layer to the ore-bearing layer of the ore deposit as the abscissa, the ore grade of the ore deposit as the ordinate, and the radioactive exemption demarcation line of the solid components of the waste mud as the diagonal line to construct an analysis chart of the radioactive exemption management range of the waste mud;

[0027] Determine the disposal method of the mud according to the analysis chart of the radioactive exemption management range of the waste mud.

[0028] A mud disposal system for calculating the radioactivity of borehole mud in the in-situ leaching uranium mining process, comprising:

[0029] A radioactivity calculation model establishment module, configured to establish a radioactivity calculation model for borehole mud in in-situ leaching uranium mining according to the principle of material balance;

[0030] A radioactivity level prediction module for non-recycled mud, configured to predict the radioactivity level of the mud according to the radioactivity calculation model for non-recycled mud;

[0031] A radioactivity level prediction module for recycled mud, configured to predict the radioactivity level of the recycled mud according to the radioactivity calculation model and the mud recycling rate;

[0032] A mud disposal module, configured to determine the mud disposal method according to whether the radioactivity level exceeds the radioactivity exemption level.

[0033] Optionally, the radioactivity calculation model establishment module specifically includes:

[0034] A radioactivity calculation model establishment unit, configured to establish a radioactivity calculation model according to the principle of material balance where a U is the radioactivity level of the mud obtained from a single borehole construction; D is the borehole diameter; H C is the thickness of the overburden layer; ρ c is the density of the overlying rock layer of the ore deposit; F c is the average radioactive grade of the overlying rock layer of the ore deposit; H O is the thickness of the ore-bearing layer; F o is the radioactive grade of the ore-bearing layer; ρ o is the density of the ore-bearing layer; C is the conversion factor of nuclide mass activity; ρ m is the density of the mud; M m is the amount of mud used; η u is the sand content rate of the waste mud; F m is the solid radioactivity level of the recycled mud; F w is the radioactivity level of the mud supernatant; M n is the amount of fresh mud; η n is the sand content rate of the fresh mud; F n is the solid radioactivity level of the fresh mud; η m is the recycling rate of the waste mud.

[0035] Optionally, the radioactivity level prediction module for recycled mud specifically includes:

[0036] Initial radioactivity level prediction is used to predict the initial radioactivity level of the slurry for recycling according to the radioactivity measurement model;

[0037] The radioactivity level growth multiple calculation unit is used to obtain the recycling rate R of the recycled slurry, and uses the formula I = 1.7013R 2 - 0.1662R + 1.08 to determine the radioactivity level growth multiple I of the slurry;

[0038] The radioactivity level calculation unit is used to multiply the initial radioactivity level by the radioactivity level growth multiple I to obtain the radioactivity level of the slurry after recycling.

[0039] Optionally, the slurry disposal module specifically includes:

[0040] The slurry disposal unit is used to judge whether the radioactivity level of the slurry exceeds the radioactive exemption level. If it exceeds, the slurry is disposed of as radioactive waste; otherwise, the slurry is disposed of as general waste. The radioactive exemption level is 1000 Bq / kg.

[0041] Optionally, the system further includes:

[0042] The corresponding relationship determination unit is used to determine the corresponding relationship between the ore grade of the ore deposit and the ratio of the thickness of the overlying rock stratum to the ore-bearing stratum according to the radioactivity level;

[0043] The radioactive exemption management range analysis chart construction unit is used to construct an analysis chart of the radioactive exemption management range of the waste slurry based on the corresponding relationship between the ore grade of the ore deposit and the ratio of the thickness of the overlying rock stratum to the ore-bearing stratum, with the ratio of the thickness of the overlying rock stratum to the ore-bearing stratum as the abscissa, the ore grade of the ore deposit as the ordinate, and the radioactive exemption demarcation line of the solid components of the waste slurry as the diagonal line;

[0044] The disposal method determination unit is used to determine the disposal method of the slurry according to the analysis chart of the radioactive exemption management range of the waste slurry.

[0045] According to the specific embodiments provided by the present invention, the following technical effects of the present invention are disclosed:

[0046] The present invention provides a mud disposal method and system for calculating the radioactive activity of borehole mud in in-situ leaching uranium mining. The method includes: establishing a calculation model for the radioactive activity of borehole mud in in-situ leaching uranium mining based on the principle of material balance; for the mud that is not recycled, predicting the radioactive activity level of the mud according to the radioactive activity calculation model; for the recycled mud, predicting the radioactive activity level of the mud after recycling according to the radioactive activity calculation model and the mud recycling rate; determining the disposal method of the mud according to whether the radioactive activity level exceeds the radioactive activity exemption level. By using the method of the present invention, it is possible to pre-judge before the project implementation whether the radioactive activity level of the mixed waste drilling mud generated during the construction of the boreholes in the in-situ leaching uranium mining project site exceeds the radioactive activity exemption level that is exempt from radiation protection supervision, and determine the disposal method of the mud accordingly, so as to classify and dispose of the mud, improve the level of radiation protection and ecological environment protection, and enhance the effectiveness and pertinence of supervision. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0048] Figure 1 It is a flowchart of a mud disposal method for calculating the radioactive activity of borehole mud in in-situ leaching uranium mining according to the present invention;

[0049] Figure 2 It is a schematic diagram of the drilling structure of the in-situ leaching uranium mining process provided by an embodiment of the present invention;

[0050] Figure 3 It is a schematic diagram of the curve of nuclide concentration change under different mud recycling rates provided by an embodiment of the present invention;

[0051] Figure 4 It is a schematic diagram of the analysis diagram of the radioactive exemption management range of waste mud provided by an embodiment of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0052] The following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the drawings in the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, rather than all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention.

[0053] The object of the present invention is to provide a method for disposing of drilling mud based on the measurement of the radioactivity of in-situ leaching uranium drilling mud, which can predict whether the radioactivity level of the mixed waste drilling mud generated during the construction of boreholes in the in-situ leaching uranium engineering site exceeds the radioactivity exemption level from radiation protection supervision before the project implementation, and determine the disposal method of the mud accordingly, so as to classify and dispose of the mud, improve the level of radiation protection and ecological environment protection, and enhance the effectiveness and pertinence of supervision.

[0054] In order to make the above objects, features and advantages of the present invention more obvious and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0055] Figure 1 It is a flow chart of a method for disposing of drilling mud based on the measurement of the radioactivity of in-situ leaching uranium drilling mud of the present invention. See Figure 1 , a method for disposing of drilling mud based on the measurement of the radioactivity of in-situ leaching uranium drilling mud of the present invention specifically includes:

[0056] Step 1: Establish a measurement model for the radioactivity of in-situ leaching uranium drilling mud based on the principle of material balance.

[0057] The research object of the present invention is the waste mud (referred to as mud for short) generated during the drilling of in-situ leaching uranium technology. The typical drilling structure of in-situ leaching uranium technology is as Figure 2 shown, where D in the figure is the diameter of the drill hole (also called borehole); H C is the thickness of the overburden layer (overlying rock formation); H O is the thickness of the ore-bearing layer. The process of drilling a well includes drilling through the overlying rock formation without radioactive ore or with a relatively low radioactive level; then the drill bit drills into the ore-bearing layer, and the mud will mix with radioactive nuclides. After reaching the bottom of the ore-bearing layer, the mud precipitates and well logging work is carried out; after the well logging is completed, a larger drill bit is used for reaming and subsequent well completion processes; the mud is mixed and recycled throughout the process.

[0058] The drilling construction process is generally a continuous construction process. The drill rig drills at a certain speed. First, it drills through the overlying rock formation of the ore-bearing layer. The mud generated in this part generally does not contain radioactivity or the radioactivity level is equivalent to the environment; then it drills into the ore-bearing layer and reaches the mudstone layer below the ore layer. The mud generated in this part usually contains a certain amount of radioactivity due to the inclusion of radioactive cuttings, but the radioactivity will decrease after this part of the mud is mixed with the overlying layer mud. The drill bit is withdrawn to carry out well logging work, and at this time, the ore-bearing layer mud deposits at the bottom. After the well logging is completed, the drill bit is replaced to carry out reaming drilling work. This process is a continuous process. The recycled mud is pumped out and screened for solid components such as cuttings through a vibrating screen. The mud is temporarily stored in a temporary mud pit or mud tank, and the waste mud is transported to the comprehensive mud pit of the entire plant area.

[0059] Based on the drilling engineering characteristics and drilling physical model of the in-situ leaching uranium mining process, an estimation model for the radioactive activity level of waste drilling mud in in-situ leaching uranium mining is established according to the principle of material balance. The model assumes that the waste mud is recycled, and the radioactive substances in the waste mud are fully mixed during the construction process, and the radioactive activities of each aquifer above the ore-bearing layer are the same. The natural radioactive nuclides of uranium ore 238 U and 226 Ra are in equilibrium. Therefore, the model takes 238 U as the simulation object, and through the model, the activity A 238 of U U in the solid sample of the waste mud is simulated. The theoretical expression of the estimation model is as follows:

[0060]

[0061] The denominator part of the estimation model includes: the mass of the overlying rock layer soil sandstone, etc. in the borehole, the mass of the ore in the ore-bearing layer, the mass of the sand-containing part of the fresh mud, the sand-containing part of the circulating mud, etc. The numerator part of the estimation model is the radioactive nuclide activity, including the background radioactive activities of the overlying rock layer soil rock, etc. in the borehole, the radioactive activity contribution of the ore in the ore-bearing layer, the radioactive activities contributed by the fresh mud and the mud and sand carried by the waste mud, etc.

[0062] The parameters of this estimation model are shown in Table 1.

[0063] Table 1 Parameter Table of the Estimation Model

[0064]

[0065]

[0066] The superscript i of each parameter in Table 1 indicates that this parameter is the corresponding parameter of the i-th drilling.

[0067] Substituting each parameter into the estimation model (1), we can get:

[0068]

[0069] Formula (2) is the measurement model of the radioactive activity A U of the mud for a total of x boreholes. Based on this, the radioactive activity of the mud obtained from the construction of a single borehole can be obtained as:

[0070]

[0071] Formula (3) is the radioactive activity measurement model established by the present invention according to the principle of material balance. Among them, a U is the radioactive activity level of the mud obtained from the construction of a single borehole (also simply referred to as radioactive activity); D is the borehole diameter (usually during the construction process, the borehole diameters D i are the same, all being D); HC is the thickness of the overburden (overlying strata); ρ c is the density of the overlying strata of the ore deposit; F c is the average radioactive grade of the overlying strata of the ore deposit; H O is the thickness of the ore-bearing layer; F o is the radioactive grade of the ore-bearing layer; ρ o is the density of the ore-bearing layer; C is the conversion factor of the mass activity of the radionuclide; ρ m is the density of the mud; M m is the amount of mud used; η u is the sand content rate of the waste mud; F m is the solid radioactive activity level of the circulating mud; F w is the radioactive activity level of the supernatant of the mud; M n is the amount of fresh mud; η n is the sand content rate of the fresh mud; F n is the solid radioactive activity level of the fresh mud; η m is the recycling rate of the waste mud.

[0072] Step 2: For the mud that is not recycled, predict the radioactive activity level of the mud according to the radioactive activity measurement model.

[0073] For the mud that is not recycled, directly predict the radioactive activity level a of the mud according to the radioactive activity measurement model (3) U , and then judge whether the radioactive activity level a of the mud U exceeds the radioactive exemption level. That is to say, calculate the radioactive activity a of the mud according to the depth, thickness, and activity (grade) of the mineral deposit U , so as to judge whether a U exceeds the radioactive activity exemption level of 1 Bq / g (1000 Bq / kg). If it exceeds, it shall be disposed of as radioactive waste. The waste mud shall be completely dug out from the mud pit, transported to a special disposal site for burial, and then the soil shall be replaced and the vegetation shall be restored. If it does not exceed, it shall be disposed of as general waste and can be directly buried.

[0074] Before construction in the prior art, it was not known whether the formed mud was radioactive mud or conventional waste, so it was impossible to arrange engineering measures and related costs. Usually, it could only be disposed of as general waste according to experience. However, if these waste drilling muds are not properly managed, they will surely pollute the local environment and cause incalculable losses. Moreover, environmental pollution will in turn restrict the development of the uranium mining and metallurgy industry. By establishing the radioactive activity measurement model (3) of the present invention, only based on the known depth, thickness, and grade of the overburden and ore, the radioactive activity level a of the mud can be predicted through the radioactive activity measurement model (3) of the present invention U, so as to arrange supervision measures, engineering measures and corresponding funds in advance, improving the effectiveness and pertinence of supervision. And the radioactive level a of drilling mud during the production and construction process is predicted in advance. U , and it can also guide the classified disposal of radioactive mud in sections, improving the level of radiation protection and ecological environment protection.

[0075] Step 3: For the recycled mud, predict the radioactive activity level of the mud after recycling according to the radioactive activity measurement model and the mud recycling rate.

[0076] During the development and construction of the in-situ leaching well field, the recycling of waste mud is an important cost-saving and efficiency-increasing technical means. However, with the recycling of waste mud, the concentration of radionuclides in the waste mud will gradually accumulate, resulting in a rapid increase in the radionuclides in the waste mud, thus increasing the risk that the activity level of the natural radionuclides in the mud exceeds the radioactive exemption level. The present invention also conducts estimation and simulation analysis on this phenomenon.

[0077] For any recycled mud, the solid radioactive level of the recycled mud is equivalent to the radioactive level of the waste mud calculated by the model in the previous cycle. That is, the radioactive activity level a U value obtained from the previous cycle is used as the parameter F m value in the current cycle and substituted into formula (3) to estimate the radioactive activity level of the recycled mud.

[0078] Under certain circumstances, model calculation is adopted to obtain the nuclide concentration change curves under the conditions of mud recycling rates R of 60%, 70% and 80%, as Figure 3 shown. From Figure 3 , it can be seen that generally, when the number of times of recycling waste mud reaches more than 6 times, the growth trend of the radioactive level of radionuclides becomes gentle. Under the conditions of lower initial mud radioactive level and higher initial mud radioactive level, the final radioactive level of the waste mud accumulates and increases, but when it reaches a certain level, usually about 3 times, the concentration no longer increases significantly as the mud continues to recycle. The recycling of mud may change the original initial mud at the exemption level into low-level radioactive waste. Therefore, it is necessary to measure the radioactive activity level of the mud after recycling.

[0079] Different waste mud recycling rates will result in different multiples of the cumulative increase in the final radioactive level of the mud. Generally, the higher the recycling rate, the higher the cumulative multiple, the higher the initial radioactive level of the recycled mud, and the higher the cumulative radioactive activity level of the final mud. For a given mud recycling rate, the higher the initial radioactive activity of the mud, the lower the growth multiple of its final radioactive activity. Therefore, there is a critical level point at which the final mud breaks through the radioactive exemption management level. If the initial radioactive activity of the recycled mud is higher than this activity level, the radioactive level will increase due to recycling, resulting in the radioactive activity of the final mixed mud exceeding the radioactive solid waste exemption level. For each given mud recycling rate, this initial radioactive activity level is determined. For example, in the case of a 60% mud recycling rate, when the initial mud is 628 Bq / kg, the maximum cumulative multiple of the final mud's radioactivity is 1.59, and the final mud's radioactive level will exceed the radioactive waste exemption value. Similarly, in the case of a 70% mud recycling rate, when the initial mud is 556.1 Bq / kg, the maximum cumulative multiple of the final mud's radioactivity is 1.80; in the case of an 80% mud recycling rate, when the initial mud is 491 Bq / kg, the maximum cumulative multiple of the final mud's radioactivity is 2.04, and the final mud's radioactive level will exceed the radioactive waste exemption value.

[0080] Therefore, it is necessary not only to estimate the possibility of exceeding the radioactive exemption for the initial mud, but also to estimate the initial mud's radioactive level at different mud recycling rate levels to control the final mud's radioactive level.

[0081] Therefore, for the recycled mud of the present invention, first, according to the radioactive activity measurement model (3), predict the U value of a as the initial radioactive activity level of the mud.

[0082] Obtain the recycling rate R of the recycled mud, and use formula (4) to determine the growth multiple I of the radioactive activity level of the mud:

[0083] I = 1.7013R 2 - 0.1662R + 1.08 (4)

[0084] Multiply the initial radioactive activity level a U by the growth multiple I of the radioactive activity level to obtain the radioactive activity level of the mud after recycling.

[0085] During the in-situ leaching of uranium, the slurry is recycled. That is, when the first borehole is drilled and the slurry is used, the original initial slurry without radionuclides becomes the initial mixed slurry. At this time, the mixed slurry has some radioactivity, but the radioactivity level is relatively low. However, the slurry needs to be recycled. That is, in the next step, some of the slurry will be mixed and used in the new borehole, adding new radionuclides, and gradually increasing the radioactivity level of the recycled slurry. Step 3 of the present invention solves the problem of measuring the radioactivity level of the recycled slurry.

[0086] Step 4: Determine the disposal method of the slurry according to whether the radioactivity level exceeds the radioactivity exemption level.

[0087] For the radioactivity level a of the slurry predicted in Step 2 U , or the radioactivity level of the slurry after recycling predicted in Step 3, it is necessary to determine whether the radioactivity level exceeds the radioactivity exemption level (usually 1 Bq / g). If it exceeds, the slurry will be disposed of as radioactive waste; otherwise, the slurry will be disposed of as general waste.

[0088] Through the modeling method, the present invention calculates whether the radioactive waste slurry containing radionuclides generated during the borehole construction process of the in-situ leaching uranium well field exceeds the requirements of the national standards "Basic Standards for Ionizing Radiation Protection and Radiation Source Safety" (GB18871-2002) and "Activity Concentration of Radionuclides in Materials Exempt from Radiation Protection Supervision" (GB27742-2011) based on the basic situation of the uranium ore deposit. It provides a regulatory basis and regulatory method for the radiation protection supervision department, provides on-site management strategies and technical support for the construction and operation units of uranium mines, and provides high-transparency data judgment for the general public. Therefore, it has a wide range of application prospects.

[0089] In addition, since the ore grade directly affects the radioactivity of the waste slurry, and the ratio relationship between the thickness of the ore-bearing layer and the overlying layer determines the dilution multiple of the radioactive slurry in the ore-bearing layer. Therefore, through the estimation model, the minimum ratio relationship between the ore-bearing layer and the overlying layer can be proposed for ore deposits with different grades, so as to ensure that the radioactivity level of the waste slurry does not exceed 1 Bq / g.

[0090] Therefore, the method of the present invention further includes:

[0091] Determine the correspondence between the ore grade of the deposit and the ratio of the thickness of the overlying strata on the deposit to the ore-bearing strata based on the radioactivity level; construct an analysis chart of the scope of radioactivity exemption management for waste mud based on the correspondence between the ore grade of the deposit and the ratio of the thickness of the overlying strata on the deposit to the ore-bearing strata, take the ratio of the thickness of the overlying strata on the deposit to the ore-bearing strata as the horizontal coordinate, take the ore grade of the deposit as the vertical coordinate, take the radioactivity exemption boundary line of the solid components of the waste mud as the diagonal line; determine the disposal method of the mud based on the analysis chart of the scope of radioactivity exemption management for waste mud.

[0092] Figure 4 An example of the analysis diagram of the scope of radioactive exemption management of waste mud provided in the embodiment of the present invention is that if the uranium ore grade and burial conditions (given by Figure 4 The dotted line in the middle represents the part above the diagonal line (not recycled) in the figure. The final composition of the waste mud (non-recyclable mud) 238 U(or 226 If the radioactivity of the uranium ore is more than 1Bq / g, it should be managed as radioactive waste. If the characteristics of the uranium ore meet the characteristics below the slash, the concentration of natural radionuclides in the waste mud (non-recycled mud) will be lower than 1Bq / g, and it can be treated as general solid waste, strengthened management, and disposed of by conventional methods.

[0093] In the case of mud circulation, or when the regional radioactive background level is high, even if the uranium ore grade and burial conditions meet some of the conditions below the radioactive exemption boundary, there is still a risk that the radioactive level of waste mud nuclides exceeds the exemption level. For this reason, management should be strengthened according to the classification situation. Figure 3 When the medium mud recycling rate R is 60%, 70% and 80% respectively, the maximum radioactivity level increase multiple I of the initial mud after recycling is 1.59, 1.80 and 2.04 respectively. The reference initial waste mud management radioactivity level is 628Bq / kg, 556.1Bq / kg and 491Bq / kg.

[0094] For different mud recycling rates used in practice, the following empirical formula can be used to calculate the relationship between the mud recycling rate and the increase multiple of the final mixed mud radioactivity level compared to the initial circulating mud radioactivity level:

[0095] I=1.7013R 2 -0.1662R+1.08 (4)

[0096] Where R is the recycling rate of the mud, and I is the growth multiple of the radioactive level of the mud. In practice, it is also possible to divide 1000 Bq / kg by I, and the resulting value is used as the management level of the radioactive concentration of the initial mud corresponding to the recycled mud. When the radioactive level of the initial circulating mud exceeds this concentration, the mud at this well site should be managed and disposed of as low-level radioactive waste.

[0097] Using the radioactive activity measurement model (3) provided by the method of the present invention, after obtaining the uranium ore grade and the buried information of the ore-bearing layer, and combining the drilling construction technology information of the in-situ leaching stope, the radioactive level a of natural nuclides in the mixed mud can be estimated using the model. U Radioactive regulators can use the estimated activity level of radioactive nuclides in the mud to determine the key points of radioactive supervision and the management requirements for matters; uranium ore producers can use the estimated activity level of radioactive nuclides in the mud to assist in formulating on-site operation radiation protection measures and the final disposal plan for waste mud.

[0098] Two specific embodiments are provided below to verify the effectiveness of the method of the present invention.

[0099] (1) Comparison between the estimated radioactive level of waste mud during the construction process of an in-situ leaching uranium mine in a certain place in Inner Mongolia, China and the on-site monitoring data.

[0100] This uranium mine is a sandstone-type uranium mine with a uranium grade of 0.01%, a burial depth of 100 m, an average thickness of the ore-bearing layer of 3 m, and an average 238 U concentration of 18 Bq / kg in the overlying rock layer of the ore deposit.

[0101] The density of the overlying rock layer and the ore-bearing layer of the ore deposit is taken as 2500 kg / m 3 ; the density of the mud is taken as 1280 kg / m 3 ; the sand content rate of the fresh mud is taken as 0.05, the sand content rate of the waste mud is taken as 0.075, and the recycling rate of the waste mud is calculated at 60%; the borehole diameter is taken as 0.12 m; 238 The conversion factor of the mass activity of U is taken as 12328 Bq / g.

[0102] According to the method of the present invention, during the construction process of this mine, the estimated result of the radioactive level of the initial mixed mud is 287.34 Bq / kg. The final radioactive activity of the circulating mud is 466.93 Bq / kg.

[0103] During the construction period of the uranium mine, the radioactive level of the slurry was monitored on-site by means of segmented sampling. According to the formation structure of Mine A, samples were taken in a timely manner from the non-radioactive slurry in the overlying rock formation of the ore bed, the mixed slurry in the ore-bearing aquifer, the thick slurry before logging, the reaming and washing slurry, and the comprehensive slurry during the drilling construction process, including solid samples and supernatant samples. The same set of on-site samples should include different sample types. The solid samples include the coarse rock powder rapidly precipitated in the temporary slurry pond and the fine rock powder precipitated from the water slurry. The liquid sample is the filtered supernatant. The analysis items of the drilling mud samples include: radionuclides 238 U, 226 Ra, and non-radioactive nuclides such as Pb, Cr, Cd, and As. The monitoring results are shown in Table 2. In Table 2, LLD indicates below the detection limit or not detected. The concentration of 238 U in the samples before the disposal of the radioactive slurry at this site was 456.87 Bq / kg.

[0104] Table 2 Analysis results of the radioactive activity of segmented slurry in the in-situ leaching mine

[0105]

[0106]

[0107] Comparison with the on-site monitoring data: The simulated result of 287.34 Bq / kg obtained by using the method of the present invention is 7.22% higher than the on-site monitoring result of 268 Bq / kg. The difference between the simulated result of the final radioactive level of the slurry and the actual on-site data is 2.21%. It shows that the method of the present invention can effectively predict the radioactive level of the slurry.

[0108] (2) Estimation of the radioactive level of the waste slurry during the construction process of an in-situ leaching uranium mine in a certain place in Xinjiang, China, and comparison with the on-site monitoring data.

[0109] This uranium mine is a sandstone-type uranium mine with a uranium grade of 0.04%, a burial depth of 100 m, an average thickness of the ore-bearing layer of the ore body of 8 m, and an average 238 U concentration in the overlying rock formation of the ore bed of 25 Bq / kg.

[0110] The density of the overlying rock formation and the ore-bearing layer of the ore body is taken as 2500 kg / m 3 ; the density of the slurry is taken as 1280 kg / m 3 ; the sand content rate of the fresh slurry is taken as 0.05, the sand content rate of the waste slurry is taken as 0.075, and the recycling rate of the waste slurry is calculated according to 60%; the borehole diameter is taken as 0.12 m; 238 The conversion factor of the mass activity of

[0111] According to the method of the present invention for estimating the process of mine construction, the estimated result of the radioactive level of the initial mixed mud is 240.67 Bq / kg. The final radioactivity of the circulating mud is 389.67 Bq / kg.

[0112] During the construction period of the uranium mine, the radioactive level of the mud was monitored on-site by means of sectional sampling. According to the formation structure of Mine A, samples were taken in a timely manner from the non-radioactive mud in the overlying rock stratum of the ore bed, the mixed mud in the ore-bearing aquifer, the thickened mud before logging, the reaming and washing mud, and the comprehensive mud during the drilling construction process, including solid samples and supernatant samples. The same group of samples taken on-site should include different sample types. The solid samples include the coarse rock powder rapidly precipitated in the temporary mud pond and the fine rock powder precipitated from the water slurry; the liquid sample is the filtered supernatant. The analysis items of the drilling mud samples include: radionuclides 238 U, 226 Ra, and non-radionuclides such as Pb, Cr, Cd, and As. The monitoring results are shown in Table 3. The concentration of 238 U in the samples before the radioactive mud disposal at this site is 382.66 Bq / kg.

[0113] Table 3 Analysis results of the radioactive activity of sectional mud in the in-situ leaching mine

[0114]

[0115] Comparison with the on-site monitoring data: The simulated result of 240.67 Bq / kg predicted by the method of the present invention is 4.64% higher than the on-site monitoring result of 230 Bq / kg. The difference between the simulated result of the final radioactive level of the mud and the actual on-site data is 4.17%. It shows that the method of the present invention can effectively predict the radioactive level of the mud.

[0116] The present invention adopts the basic principle based on material balance to create an estimation method and an estimation model for the radioactive activity of in-situ leaching waste mud applicable to the process of in-situ leaching borehole construction; through the model method, on the basis of obtaining basic information such as the ore grade and the buried depth and thickness of the ore deposit in the uranium mine, the final radioactive level of the waste mud generated during the processes of the uranium mine construction, recycling, etc. can be effectively predicted; thus providing a judgment basis for the regulatory department and the construction unit on whether the mud is disposed of as radioactive exempt waste or as conventional waste.

[0117] Based on the method provided by the present invention, the present invention also provides a mud disposal system for calculating the radioactive activity of borehole mud in the in-situ leaching uranium mining process, including:

[0118] A radioactive activity calculation model establishment module, which is used to establish a radioactive activity calculation model for in-situ leaching uranium mining borehole mud according to the principle of material balance;

[0119] An uncirculated mud radioactivity level prediction module, which is used for uncirculated mud and predicts the radioactivity level of the mud according to the radioactivity measurement model;

[0120] A circulated mud radioactivity level prediction module, which is used for circulated mud and predicts the radioactivity level of the mud after circulation according to the radioactivity measurement model and the mud circulation utilization rate;

[0121] A mud disposal module, which is used to determine the mud disposal method according to whether the radioactivity level exceeds the radioactivity exemption level.

[0122] Among them, the radioactivity measurement model establishment module specifically includes:

[0123] A radioactivity measurement model establishment unit, which is used to establish a radioactivity measurement model based on the material balance principle where a U is the radioactivity level of the mud obtained from a single borehole construction; D is the borehole diameter; H C is the thickness of the overburden layer; ρ c is the density of the overlying rock layer of the ore deposit; F c is the average radioactive grade of the overlying rock layer of the ore deposit; H O is the thickness of the ore-bearing layer; F o is the radioactive grade of the ore-bearing layer; ρ o is the density of the ore-bearing layer; C is the conversion factor of the mass activity of the nuclide; ρ m is the density of the mud; M m is the amount of mud used; η u is the sand content rate of the waste mud; F m is the solid radioactivity level of the circulated mud; F w is the radioactivity level of the mud supernatant; M n is the amount of fresh mud; η n is the sand content rate of the fresh mud; F n is the solid radioactivity level of the fresh mud; η m is the recycling rate of the waste mud.

[0124] The circulated mud radioactivity level prediction module specifically includes:

[0125] An initial radioactivity level prediction unit, which is used for circulated mud and predicts the initial radioactivity level of the mud according to the radioactivity measurement model;

[0126] A radioactivity level growth multiple calculation unit, which is used to obtain the circulation utilization rate R of the circulated mud and uses the formula I = 1.7013R 2-0.1662R + 1.08 determines the growth multiple I of the radioactivity level of the mud;

[0127] The radioactivity level calculation unit is used to multiply the initial radioactivity level by the growth multiple I of the radioactivity level to obtain the radioactivity level of the mud after recycling.

[0128] The mud disposal module specifically includes:

[0129] The mud disposal unit is used to determine whether the radioactivity level of the mud exceeds the radioactive exemption level. If it exceeds, the mud is disposed of as radioactive waste; otherwise, the mud is disposed of as general waste. The radioactive exemption level is 1000 Bq / kg.

[0130] The system further includes:

[0131] The corresponding relationship determination unit is used to determine the corresponding relationship between the ore grade of the ore deposit and the ratio of the thickness of the overlying rock stratum to the ore-bearing layer based on the radioactivity level.

[0132] The radioactive exemption management range analysis chart construction unit is used to construct an analysis chart of the radioactive exemption management range of the waste mud by taking the ratio of the thickness of the overlying rock stratum to the ore-bearing layer as the abscissa, the ore grade of the ore deposit as the ordinate, and the radioactive exemption demarcation line of the solid components of the waste mud as the diagonal line, based on the corresponding relationship between the ore grade of the ore deposit and the ratio of the thickness of the overlying rock stratum to the ore-bearing layer.

[0133] The disposal method determination unit is used to determine the disposal method of the mud according to the analysis chart of the radioactive exemption management range of the waste mud.

[0134] In this specification, each embodiment is described in a progressive manner. Each embodiment focuses on the differences from other embodiments. The same or similar parts among the embodiments can be referred to each other. For the system disclosed in the embodiments, since it corresponds to the method disclosed in the embodiments, the description is relatively simple. For the relevant parts, refer to the description in the method part.

[0135] Specific examples are used in this article to elaborate on the principles and implementation manners of the present invention. The descriptions of the above embodiments are only used to help understand the method and its core idea of the present invention. At the same time, for those of ordinary skill in the art, according to the idea of the present invention, there will be changes in the specific implementation manners and application scopes. In summary, the content of this specification should not be construed as a limitation to the present invention.

Claims

1. A method for treating drilling mud based on calculating the radioactive activity of in-situ leaching uranium drilling mud, characterized in that, Including: Based on the principle of material balance, a radioactive activity measurement model for borehole mud in in-situ leaching uranium mining is established, specifically including: Establish a radioactive activity measurement model based on the principle of material balance where a U is the radioactive activity level of the mud obtained from the construction of a single borehole; D is the borehole diameter; H C is the thickness of the overburden layer; ρ c is the density of the overlying rock layer of the ore deposit; F c is the average radioactive grade of the overlying rock layer of the ore deposit; H O is the thickness of the ore-bearing layer; F o is the radioactive grade of the ore-bearing layer; ρ o is the density of the ore-bearing layer; C is the conversion factor of the mass activity of the nuclide; ρ m is the density of the mud; M m is the amount of mud used; η u is the sand content rate of the waste mud; F m is the radioactive activity level of the solid in the circulating mud; F w is the radioactive activity level of the mud supernatant; M n is the amount of fresh mud; η n is the sand content rate of the fresh mud; F n is the radioactive activity level of the solid in the fresh mud; η m is the recycling rate of the waste mud; For the non-recycled mud, predict the radioactive activity level of the mud according to the radioactive activity measurement model; For the recycled mud, predict the radioactive activity level of the mud after recycling according to the radioactive activity measurement model and the mud recycling rate; Determine the disposal method of the mud according to whether the radioactive activity level exceeds the radioactive activity exemption level.

2. The method according to claim 1, characterized in that, For the recycled mud, predicting the radioactive activity level of the mud after recycling according to the radioactive activity measurement model and the mud recycling rate specifically includes: For the recycled mud, predict the initial radioactive activity level of the mud according to the radioactive activity measurement model; Obtain the recycling rate R of the recycled mud, and use the formula I = 1.7013R 2 - 0.1662R + 1.08 to determine the growth multiple I of the radioactive activity level of the mud; Multiply the initial radioactive activity level by the radioactive activity level growth multiple I to obtain the radioactive activity level of the mud after recycling.

3. The method according to claim 1, wherein Determining the disposal method of the mud according to whether the radioactive activity level exceeds the radioactive activity exemption level specifically includes: Judge whether the radioactive activity level of the mud exceeds the radioactive exemption level. If it exceeds, dispose of the mud as radioactive waste; otherwise, dispose of the mud as general waste. The radioactive exemption level is 1000 Bq / kg.

4. The method according to claim 1, wherein The method further includes: Determine the corresponding relationship between the ore grade of the ore deposit and the ratio of the thickness of the overlying rock stratum to the ore-bearing stratum of the ore deposit according to the radioactive activity level; Based on the corresponding relationship between the ore grade of the ore deposit and the ratio of the thickness of the overlying rock stratum to the ore-bearing stratum of the ore deposit, take the ratio of the thickness of the overlying rock stratum to the ore-bearing stratum as the abscissa, the ore grade of the ore deposit as the ordinate, and the radioactive exemption demarcation line of the solid components of the waste mud as the diagonal line to construct an analysis chart of the radioactive exemption management range of the waste mud; Determine the disposal method of the mud according to the analysis chart of the radioactive exemption management range of the waste mud.

5. A mud disposal system for calculating the radioactive activity of borehole mud in the in-situ leaching uranium mining process, characterized in that, Including: A radioactive activity measurement model establishment module for establishing a radioactive activity measurement model for borehole mud in in-situ leaching uranium mining based on the principle of material balance; The radioactive activity measurement model establishment module specifically includes: A radioactive activity measurement model establishment unit for establishing a radioactive activity measurement model based on the principle of material balance where a U is the radioactive activity level of the mud obtained from the construction of a single borehole; D is the borehole diameter; H C is the thickness of the overburden layer; ρ c is the density of the overlying rock layer of the ore deposit; F c is the average radioactive grade of the overlying rock layer of the ore deposit; H O is the thickness of the ore-bearing layer; F o is the radioactive grade of the ore-bearing layer; ρ o is the density of the ore-bearing layer; C is the conversion factor of the mass activity of the nuclide; ρ m is the density of the mud; M m is the amount of mud used; η u is the sand content rate of the waste mud; F m is the solid radioactive activity level of the circulating mud; F w is the radioactive activity level of the mud supernatant; M n is the amount of fresh mud; η n is the sand content rate of the fresh mud; F n is the solid radioactive activity level of the fresh mud; η m is the recycling rate of the waste mud; A non-recycled mud radioactive activity level prediction module for predicting the radioactive activity level of the non-recycled mud according to the radioactive activity measurement model; A recycled mud radioactive activity level prediction module for predicting the radioactive activity level of the recycled mud after recycling according to the radioactive activity measurement model and the mud recycling rate; A mud disposal module for determining the disposal method of the mud according to whether the radioactive activity level exceeds the radioactive activity exemption level.

6. The system according to claim 5, wherein The recycled mud radioactive activity level prediction module specifically includes: An initial radioactive activity level prediction module for predicting the initial radioactive activity level of the recycled mud according to the radioactive activity measurement model; The radioactive activity level growth multiple calculation unit is used to obtain the recycling rate R of the recycled mud, and determines the radioactive activity level growth multiple I of the mud by using the formula I = 1.7013R 2 - 0.1662R + 1.08 A radioactive activity level calculation unit for multiplying the initial radioactive activity level by the radioactive activity level growth multiple I to obtain the radioactive activity level of the recycled mud.

7. The system according to claim 5, wherein The mud disposal module specifically includes: A mud disposal unit, which is used to determine whether the radioactivity level of the mud exceeds the radioactive exemption level. If it exceeds, the mud is disposed of as radioactive waste; otherwise, the mud is disposed of as general waste. The radioactive exemption level is 1000 Bq / kg.

8. The system according to claim 5, wherein The system further includes: A correspondence determination unit, which is used to determine the correspondence between the ore grade of the ore deposit and the ratio of the thickness of the overlying rock stratum to the ore-bearing layer according to the radioactivity level. A radioactive exemption management scope analysis chart construction unit, which is used to construct an analysis chart of the radioactive exemption management scope of the waste mud based on the correspondence between the ore grade of the ore deposit and the ratio of the thickness of the overlying rock stratum to the ore-bearing layer, with the ratio of the thickness of the overlying rock stratum to the ore-bearing layer as the abscissa, the ore grade of the ore deposit as the ordinate, and the radioactive exemption demarcation line of the solid components of the waste mud as the diagonal line. A disposal method determination unit, which is used to determine the disposal method of the mud according to the analysis chart of the radioactive exemption management scope of the waste mud.

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