CN114875882A - Multilayer radon-reducing covering material, application thereof and method for reducing radon exhalation rate of uranium mine waste stone heap - Google Patents
Multilayer radon-reducing covering material, application thereof and method for reducing radon exhalation rate of uranium mine waste stone heap Download PDFInfo
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- 229910052704 radon Inorganic materials 0.000 title claims abstract description 121
- SYUHGPGVQRZVTB-UHFFFAOYSA-N radon atom Chemical compound [Rn] SYUHGPGVQRZVTB-UHFFFAOYSA-N 0.000 title claims abstract description 121
- 239000000463 material Substances 0.000 title claims abstract description 43
- 229910052770 Uranium Inorganic materials 0.000 title claims abstract description 42
- JFALSRSLKYAFGM-UHFFFAOYSA-N uranium(0) Chemical compound [U] JFALSRSLKYAFGM-UHFFFAOYSA-N 0.000 title claims abstract description 42
- 230000001603 reducing effect Effects 0.000 title claims abstract description 25
- 238000000034 method Methods 0.000 title claims abstract description 22
- 239000002699 waste material Substances 0.000 title claims abstract description 19
- 239000004575 stone Substances 0.000 title claims abstract description 18
- 229910000278 bentonite Inorganic materials 0.000 claims abstract description 77
- 239000000440 bentonite Substances 0.000 claims abstract description 77
- SVPXDRXYRYOSEX-UHFFFAOYSA-N bentoquatam Chemical compound O.O=[Si]=O.O=[Al]O[Al]=O SVPXDRXYRYOSEX-UHFFFAOYSA-N 0.000 claims abstract description 77
- 239000010878 waste rock Substances 0.000 claims abstract description 30
- 238000005056 compaction Methods 0.000 claims abstract description 29
- 230000009467 reduction Effects 0.000 claims description 31
- 230000005855 radiation Effects 0.000 abstract description 24
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- 230000000052 comparative effect Effects 0.000 description 9
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- ONCZQWJXONKSMM-UHFFFAOYSA-N dialuminum;disodium;oxygen(2-);silicon(4+);hydrate Chemical compound O.[O-2].[O-2].[O-2].[O-2].[O-2].[O-2].[O-2].[O-2].[O-2].[O-2].[O-2].[O-2].[Na+].[Na+].[Al+3].[Al+3].[Si+4].[Si+4].[Si+4].[Si+4] ONCZQWJXONKSMM-UHFFFAOYSA-N 0.000 description 1
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Classifications
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- E—FIXED CONSTRUCTIONS
- E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
- E02D—FOUNDATIONS; EXCAVATIONS; EMBANKMENTS; UNDERGROUND OR UNDERWATER STRUCTURES
- E02D3/00—Improving or preserving soil or rock, e.g. preserving permafrost soil
- E02D3/02—Improving by compacting
- E02D3/046—Improving by compacting by tamping or vibrating, e.g. with auxiliary watering of the soil
-
- G—PHYSICS
- G21—NUCLEAR PHYSICS; NUCLEAR ENGINEERING
- G21F—PROTECTION AGAINST X-RADIATION, GAMMA RADIATION, CORPUSCULAR RADIATION OR PARTICLE BOMBARDMENT; TREATING RADIOACTIVELY CONTAMINATED MATERIAL; DECONTAMINATION ARRANGEMENTS THEREFOR
- G21F1/00—Shielding characterised by the composition of the materials
- G21F1/02—Selection of uniform shielding materials
-
- G—PHYSICS
- G21—NUCLEAR PHYSICS; NUCLEAR ENGINEERING
- G21F—PROTECTION AGAINST X-RADIATION, GAMMA RADIATION, CORPUSCULAR RADIATION OR PARTICLE BOMBARDMENT; TREATING RADIOACTIVELY CONTAMINATED MATERIAL; DECONTAMINATION ARRANGEMENTS THEREFOR
- G21F1/00—Shielding characterised by the composition of the materials
- G21F1/12—Laminated shielding materials
Abstract
The invention relates to the technical field of retirement treatment of nuclear facilities, in particular to a multilayer radon-reducing covering material, application thereof and a method for reducing radon exhalation rate of uranium mine waste stone heap. The multilayer radon-reducing covering material provided by the invention comprises a bentonite layer, a first loess layer positioned on the surface of the bentonite layer and a second loess layer positioned on the surface of the first loess layer. According to the invention, bentonite is used as a bottom layer covering soil material, so that the bentonite has strong adsorption capacity on radon, effectively prevents radon nuclide migration, can reduce the thickness and compaction degree of covering soil, can be applied to waste rock piles which are difficult to reach by mechanical equipment and construction areas where the compaction degree of common soil cannot meet the design requirement, and has a good retirement treatment effect on uranium mine waste rock piles; the invention adopts loess as the middle layer covering material and the top layer covering material, can further improve the effect of reducing the radon exhalation rate and the effect of reducing gamma radiation, has low treatment cost and is beneficial to the vegetation recovery in the later period.
Description
Technical Field
The invention relates to the technical field of retirement treatment of nuclear facilities, in particular to a multilayer radon-reducing covering material, application thereof and a method for reducing radon exhalation rate of uranium mine waste stone heap.
Background
With the rapid development of the current nuclear industry and nuclear power, environmental problems caused by the decommissioning of many nuclear facilities and the like have attracted great attention. The decommissioning of the uranium mining and metallurgy facility is an important component of decommissioning of nuclear facilities, and the uranium mining and metallurgy facility has the advantages of multiple natural radioactive substances, high toxicity, long service life, large amount of waste and close contact with residents, so that the task of the uranium mining and metallurgy facility is more complex and difficult. Up to now, more than 400 hundred million tons of uranium waste stones and more than 200 hundred million tons of uranium tailings are accumulated in the world, and the uranium waste stone tailings cause serious pollution to the ecological environment.
Radon is the most harmful to human body in the harm of uranium waste stone tailings. Radon is an inert radioactive gas with a half-life of 3.8 days, classified by the international cancer agency as a class a carcinogen with definitive carcinogenic effects. The reduction of the radon exhalation rate of the uranium waste stone tailings is a key link of retirement treatment.
At present, the most effective method for reducing the radon precipitation in uranium waste stone tailings is covering, namely, according to the characteristics of a radon migration mode, covering and other methods are adopted to reduce the precipitation rate of radon in waste stone piles and tailings, wherein soil covering is the most effective solving method. For example, Vigore, et al (see: Vigore, Huangqiang, research on reducing radon exhalation rate by covering a waste rock heap with loess [ J ]. Industrial safety and dust prevention, 1991, (10):9-10.) use loess as a covering material, wherein the radon exhalation reducing effect of loess of a sub-clay texture is the best; however, the radon reduction rate after covering loess having a sub-clay texture with a thickness of 50cm is only 18.7%, and the radon reduction rate is low.
Disclosure of Invention
In view of the above, the invention aims to provide a multilayer radon reduction covering material, application thereof and a method for reducing the radon exhalation rate of uranium mine waste rock heap. The radon reduction rate of the multilayer radon reduction covering material provided by the invention is as high as 99.77%.
In order to achieve the above object, the present invention provides the following technical solutions:
the invention provides a multilayer radon-reducing covering material which is characterized by comprising a bentonite layer, a first loess layer positioned on the surface of the bentonite layer and a second loess layer positioned on the surface of the first loess layer.
Preferably, the degree of compaction of the bentonite layer, the first loess layer and the second loess layer is independently 10 to 90%.
Preferably, the thickness of the bentonite layer is 4-12 cm.
Preferably, the thickness of the first loess layer is 7-15 cm.
Preferably, the thickness of the second loess layer is 15-20 cm.
The invention provides application of the multilayer radon reduction covering material in the technical scheme in uranium mine waste rock heap decommissioning treatment.
The invention provides a method for reducing the radon exhalation rate of uranium mine waste stone heap, which comprises the following steps:
covering bentonite on the surface of the uranium mine waste rock heap, and tamping to obtain a bentonite layer;
covering loess on the surface of the bentonite layer and tamping to obtain a first loess layer;
and covering loess on the surface of the first loess layer and tamping to obtain a second loess layer.
The invention provides a multilayer radon-reducing covering material which comprises a bentonite layer, a first loess layer positioned on the surface of the bentonite layer and a second loess layer positioned on the surface of the first loess layer. The bentonite adopted by the method has an expansion characteristic, and the bentonite expands in volume after absorbing water, so that the pores of the uranium mine waste rock heap can be blocked, the porosity of the uranium mine waste rock heap is reduced, and the bentonite has good tightness; the low permeability can effectively prevent groundwater pollution caused by surface water infiltration, and simultaneously has strong adsorption capacity on radon and effectively prevents radon nuclide migration. In the invention, the loess has wide distribution, can generally realize local materials, and can greatly reduce the cost of the retirement treatment of the uranium mine waste rock heap; in addition, the loess adopted by the invention is used as the middle layer covering material and the top layer covering material, so that the effects of reducing the radon exhalation rate and reducing the gamma radiation can be further improved, and the method is favorable for and easy for vegetation recovery in the late stage of the uranium mine waste rock heap.
The invention provides a method for reducing the radon exhalation rate of uranium mine waste stone heap, which comprises the following steps: in uranium mine spoil heapsCovering bentonite on the surface of the soil, and tamping to obtain a bentonite layer; covering loess on the surface of the bentonite layer and tamping to obtain a first loess layer; and covering loess on the surface of the first loess layer and tamping to obtain a second loess layer. The method provided by the invention can obviously reduce the radon exhalation rate and the gamma radiation dose, and the uranium mine waste rock heap retirement treatment cost is low, so that the later vegetation recovery is easy. Moreover, the method provided by the invention can meet the requirements of the uranium mining and metallurgy radiation protection and environmental protection regulations (GB23727-2009), and after the decommissioning treatment and the environmental remediation of facilities such as waste rock piles, open stopes and the like are carried out by the method provided by the invention, the surfaces of all sites can be subjected to the decommissioning treatment 222 The precipitation rate of Rn is not more than 0.74 Bq/(m) 2 S) limit requirements; simultaneously, the gamma ray can be effectively shielded, so that the gamma dose is lower than the local background plus 20 multiplied by 10 -8 Gy/h。
Drawings
FIG. 1 is a schematic diagram of radon exhalation rate and gamma radiation dose rate distribution points monitored in a test site;
FIG. 2 is a fitting curve of the thickness of a bentonite layer with the compaction degree of 10% and the ratio of radon exhalation rate before and after earthing;
FIG. 3 is a fitting curve of the thickness of a bentonite layer with 50% compactness and the ratio of radon exhalation rate before and after earthing;
FIG. 4 is a fitting curve of the thickness of a bentonite layer with 90% compactness and the ratio of radon exhalation rate before and after earthing;
FIG. 5 is a fitting curve of the thickness of a second loess layer with the compactness of 10% and the ratio of radon exhalation rate before and after earthing;
FIG. 6 is a fitting curve of the thickness of a second loess layer with the compactness of 50% and the ratio of radon exhalation rate before and after earthing;
FIG. 7 is a fitting curve of the thickness of a second loess layer with the compaction degree of 90% and the ratio of the radon exhalation rate before and after earthing.
Detailed Description
The invention provides a multilayer radon-reducing covering material which comprises a bentonite layer, a first loess layer positioned on the surface of the bentonite layer and a second loess layer positioned on the surface of the first loess layer.
In the present invention, all the raw material components are commercially available products well known to those skilled in the art unless otherwise specified.
In the present invention, the degree of compaction of the bentonite layer is preferably 10 to 90%, more specifically 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, or 90%. In the invention, the thickness of the bentonite layer is preferably 4-10 cm, and more specifically preferably 4cm, 5cm, 6cm, 7cm, 8cm, 9cm or 10 cm. In the present invention, the bentonite in the bentonite layer preferably includes sodium bentonite and/or calcium bentonite, and more preferably calcium bentonite. In the invention, the radon exhalation rate of the bentonite is preferably 0.02-0.12 Bq/(m) 2 S), the gamma radiation dose rate is preferably (24.6-29.3) multiplied by 10 -8 Gy/h. The bentonite adopted by the invention has the expansion characteristic, and the bentonite expands in volume after absorbing water, can block all pores in surrounding media, reduces the porosity of the media and has better tightness; the low permeability can effectively prevent groundwater pollution caused by surface water infiltration, and simultaneously has strong adsorption capacity on radon and effectively prevents radon nuclide migration.
In the present invention, the compaction degree of the first loess layer is preferably 10 to 90%, and more specifically, is preferably 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, or 90%. In the invention, the thickness of the first loess layer is preferably 7-13 cm, and more specifically preferably 7cm, 8cm, 9cm, 10cm, 11cm, 12cm or 13 cm. In the present invention, the texture of the loess in the first loess layer is preferably loam; in an embodiment of the present invention, the loess is collected from the Jiangxi province Jiangxi city south Yunnan Chang Zhen lake bridge soil source. In the invention, the radon exhalation rate of the loess is 0.01-0.29 Bq/(m) 2 S) and the gamma radiation dose rate is (21.7-25.4) x 10 -8 Gy/h. In the invention, the loess has wide distribution, can generally realize local materials, and can greatly reduce uranium oresCost of ex-service treatment of mountain waste rock piles; in addition, the loess adopted by the invention as the middle layer covering material can further improve the effect of reducing the radon exhalation rate and the effect of reducing gamma radiation.
In the present invention, the degree of compaction of the second loess layer is preferably 10 to 90%, and more specifically, is preferably 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, or 90%. In the invention, the thickness of the second loess layer is preferably 15-20 cm, and more preferably 18 cm. In the present invention, the texture of the loess in the second loess layer is preferably loam; in a specific embodiment of the present invention, the loess is collected from the southern Conn Congjiang province of Jiangxi Ganzhou city, Conn province of Shahu bridge soil source. In the invention, the radon exhalation rate of the loess is 0.01-0.29 Bq/(m) 2 S) and the gamma radiation dose rate is (21.7-25.4) x 10 -8 Gy/h. In the invention, the loess has wide distribution, can generally realize local materials, and can greatly reduce the cost of the retirement treatment of the uranium mine waste rock heap; in addition, the top layer covering material is loess, so that the effect of reducing the radon exhalation rate and the effect of reducing gamma radiation can be further improved, and meanwhile, the top layer covering material is beneficial to and easy for vegetation recovery in the later stage of the uranium mine waste rock heap.
The invention provides application of the multilayer radon reduction covering material in the technical scheme in uranium mine waste rock heap decommissioning treatment.
The invention provides a method for reducing the radon exhalation rate of uranium mine waste stone heap, which comprises the following steps:
covering bentonite on the surface of the uranium mine waste rock heap, and tamping to obtain a bentonite layer;
covering loess on the surface of the bentonite layer and tamping to obtain a first loess layer;
and covering loess on the surface of the first loess layer and tamping to obtain a second loess layer.
According to the method, the bentonite layer is obtained by covering bentonite on the surface of the uranium mine waste rock pile and then tamping. In the present invention, the thickness of the bentonite layer is the same as that of the bentonite layer, and thus, the description thereof is omitted. The tamping mode is not particularly limited, so that the compaction degree of the bentonite layer is 10-90%.
After the bentonite layer is obtained, the surface of the bentonite layer is covered with loess and then tamped to obtain a first loess layer. In the present invention, the thickness of the first loess layer is the same as that of the first loess layer, and is not described herein again. The tamping mode is not particularly limited, so that the compaction degree of the first loess layer is 10-90%.
After the first loess layer is obtained, the invention covers loess on the surface of the first loess layer and tamps the loess layer to obtain a second loess layer. In the present invention, the thickness of the second loess layer is the same as that of the second loess layer, and thus, the description thereof is omitted. The tamping mode is not particularly limited, and the degree of compaction of the second loess layer is 10-90%.
The technical solution of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. It is to be understood that the described embodiments are merely exemplary of the invention, and not restrictive of the full scope of the invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
Example 1
Sequentially covering bentonite on the surface of a uranium mine waste rock pile, and tamping to obtain a bentonite layer with the thickness of 4cm and the compaction degree of 10%;
covering loess on the surface of the bentonite layer and tamping to obtain a first loess layer with the thickness of 13cm and the compaction degree of 10%;
covering loess on the surface of the first loess layer, and tamping to obtain a second loess layer with a thickness of 18cm and a compaction degree of 10%;
wherein the loess is collected from the south Conus lake bridge soil source land of Jiangxi city of Jiangxi province, and the radon exhalation rate of the loess is 0.01-0.29 Bq/(m) 2 S) and the gamma radiation dose rate is (21.7-25.4) x 10 -8 Gy/h; the radon exhalation rate of the bentonite is 0.02-0.12 Bq/(m) 2 S) and the gamma radiation dose rate is (24.6-29.3) x 10 -8 Gy/h。
Examples 2 to 10
The surface of the uranium mine waste rock heap was covered with a casing material in accordance with the method of example 1, and the compositions of the casing materials of examples 2 to 9 are shown in table 1.
Comparative examples 1 to 6
The surface of the uranium mine waste rock heap was covered with casing material according to the method of example 1, and the compositions of the casing materials of comparative examples 1 to 6 are shown in table 1.
TABLE 1 casing material composition of examples 1-9
Test example 1
Gamma radiation dose rate and radon exhalation rate test
Reference standard: GB/T14583-93 environmental earth surface gamma radiation dose rate measuring specification, GB/T14582-93 standard measuring method of radon in environmental air and HJ/T61-2001 radiation environment monitoring technical specification.
Monitoring requirements: covering according to the designed covering thickness, tamping according to the requirement in layers, standing for one week, measuring until the radioactivity balance and the diffusion stabilization time of the radon are stable, monitoring the exhalation rate of the radon on the surface, and recording according to the specification.
Monitoring indexes are as follows: radon exhalation rate and gamma radiation dose rate, and simultaneously recording air temperature, ground temperature, relative humidity and meteorological parameters.
Using an instrument: FD216 environment radon measuring instrument, HD-2005 portable gamma radiation dose rate instrument, and hand-held weather station.
The monitoring instrument and the monitoring items are shown as the following table:
TABLE 2 monitoring instruments and monitoring items
The test method comprises the following steps: when the gamma radiation dose rate is measured, at a measuring point, the height of the probe from the ground is 1m, the reading is carried out for 1 time every 10s, the reading is carried out for 10 times in total, and the average value is the gamma radiation dose rate measuring value of the point; when the radon exhalation rate is measured, a flat field is selected at a measuring point, the instrument is connected, and the measurement is carried out after the gas is collected by the gas collecting hood for 1 hour.
Monitoring and stationing: 3-5 monitoring points are taken from each test site, and distribution points of gamma radiation dose rate and radon exhalation rate are shown in figure 1, wherein 1# to 5# are distribution points of gamma radiation dose rate, and 1# is distribution points of radon exhalation rate.
Monitoring frequency: the test results are shown in tables 3-4, which are monitored 1 time each at 09 hours and 15 hours per day.
TABLE 3 Radon exhalation Rate (Bq. m) -2 ·s -1 ) Test results
TABLE 4 Gamma radiation dose Rate (10) -8 Gy/h) test results
The following results are obtained from tables 3 to 4:
(1) earthing scheme with optimal radon reducing effect
The radon reduction rate of the soil covering material provided by the invention is 96.19-99.77%, and the shielding rate of the soil covering material to gamma radiation is 50.29-70.17%, wherein the effect of the embodiment 10 is the best. The invention shows that the multilayer soil covering material system provided by the invention achieves good treatment effect after treating the waste rock heap, and can meet the radon exhalation rate lower than 0.74 Bq.m -2 ·s -1 The treatment requirements of (1).
It is worth noting that after covering the second loess layer, the radon reduction rate is reduced (such as example 6, example 9, example 13, comparative example 1 and comparative example 2), although the radon reduction rate is reduced to a certain extent, the radon reduction rate still can meet the governing requirements of uranium mining and metallurgy radiation protection and environmental protection regulations (GB 23727-2009); probably due to the fact that the loess used for covering has certain radioactivity, namely a certain radon exhalation rate. The method provided by the invention is easy for vegetation growth after covering the second loess layer, and can realize vegetation recovery.
The radon reduction effect and the gamma ray shielding effect of comparative example 1 and comparative example 2 are higher than those of most examples, particularly the good effect of comparative example 2, which is determined by the strong adsorption and self-sealing property of bentonite itself, and in the engineering practice, if bentonite is used for covering soil, there are three disadvantages: firstly, the plants can not grow, and the vegetation is not easy to recover in the later period; the uranium mine waste rock heap is easy to be washed by rainwater, and the actual uranium mine waste rock heap is always large in gradient; and thirdly, the cost is higher, and the cost of the bentonite is higher than that of the loess. This comparative example 2 actually demonstrates the excellent radon-reducing effect of bentonite, but cannot be used for engineering applications for the reasons of the above three aspects. Similarly, the comparative example 1 is loess with 90% compactness, and the loess is basically used for covering soil in the current engineering practice, so that the radon reducing effect is good. However, the compaction and transportation construction difficulty of some waste stone piles is high, the loess consumption is large, and the cost is high.
The radon reducing effect of the bentonite under the conditions of the same thickness and the same compaction degree is higher than that of the loess.
(2) Relation between thickness of bentonite layer and radon exhalation rate
In order to analyze the influence of the thickness of the bentonite layer on the radon exhalation rate conveniently, the average exhalation rate of the radon with the same thickness is taken as the exhalation rate of the radon with the same thickness, and the relationship between different coverage thicknesses of the bentonite and the radon exhalation rate is obtained, and the result is shown in table 5:
TABLE 5 relationship between the precipitation rate of radon and the bentonite layer of different thickness
As can be seen from Table 5, after covering the bentonite layer, the radon exhalation rate decreases with the increase of the thickness of the bentonite layer, and when the thickness of the bentonite layer increases to 10cm, the radon exhalation rate is substantially equivalent to the background value of the bentonite.
The fitting function of the bentonite under different compactnesses can be obtained by linear fitting by using a coverage calculation formula of a single-layer coverage system, and the fitting function is as follows:
when the degree of compaction is 10%, the fitting function is as shown in equation (1) and FIG. 2:
in the formula (1), R 2 0.9790, the confidence interval is above 95%, the parameter a is 0.5926 and the parameter E is 3.0929 according to the fitting function, and the linear relationship is 3.0929x + 0.5926.
At a compaction of 50%, the fitting function is shown in equation (2) and FIG. 3:
in the formula (2), R 2 0.9932 confidence intervalAt 95% or more, the parameter a-0.2715 and the parameter E-2.8885 are obtained from the fitting function, and the linear relationship y-2.8885 x-0.2715 is obtained.
At 90% compactness, the fitting function is shown in equation (3) and FIG. 4:
in the formula (3), R 2 The confidence interval is above 95%, the parameter a is 0, the parameter E is 4.1885, and the linear relationship is y 41885 x.
The effect of the covering material to reduce the radon exhalation rate can be expressed by a radon reduction coefficient (k) as shown in formula (4).
In the formula (1), J t The exhalation rate of radon before covering soil is expressed as Bq.m -2 ·s -1 ；J c The unit of the precipitation rate of radon after covering soil is Bq.m -2 ·s -1 。
In order to analyze the influence of the thickness and the compaction degree of the bentonite layer on the radon exhalation rate, the average exhalation rate of the radon under the same thickness is taken as the exhalation rate of the radon with the thickness. The radon reduction coefficient results for bentonite layers of different thicknesses and different compactibility are shown in table 6.
TABLE 6 Radon reduction coefficient of different thickness and different compaction degree bentonite layer
As can be seen from Table 6, the radon reduction coefficient is different under different compactibility of the bentonite layer under the same thickness; under the condition of the same compactness, the larger the thickness of the bentonite layer is, the larger the radon reduction coefficient is, and the better the radon reduction effect is; the radon reduction effect is best when the compaction degree of the bentonite layer with the same thickness is 50 percent.
(3) Radon reduction coefficient of loess layers (first loess layer and second loess layer) under different thicknesses and compactibility
In order to analyze the influence of the total thickness of the first loess layer and the second loess layer on the radon exhalation rate, the average exhalation rate of radon under the same thickness is taken as the exhalation rate of radon with the thickness, so as to obtain the relationship between the total thickness of the loess layers and the radon exhalation rate, and the result is shown in table 7:
TABLE 7 relationship between loess layers of different thicknesses and radon exhalation rate
As can be seen from table 7, the radon exhalation rate after covering the loess layer decreased with the increase in the thickness of the loess because the radon exhalation rate on the surface of the waste rock heap was greatly decreased by the covering of the bentonite layer, and further decreased after covering the loess layer.
The fitting function of the bentonite under different compactnesses can be obtained by linear fitting by using a coverage calculation formula of a single-layer coverage system, and the fitting function is as follows:
when the degree of compaction is 10%, the fitting function is as shown in equation (5) and fig. 5:
in the formula (5), R 2 The confidence interval is above 95%, the parameter a is 1.0895, the parameter E is 12.325 and the linear relationship is 12.325x + 1.0895.
At a compaction of 50%, the fitting function is shown in equation (6) and FIG. 6:
in the formula (2), R 2 0.9755, the confidence interval is above 95%, the parameter A is 0.9217, the parameter E is 9.3456 and the linear relationship is 9.3456x +0.9217 according to the fitting function.
At a compaction of 90%, the fitting function is shown in equation (7) and FIG. 7:
in the formula (3), R 2 0.9878, the confidence interval is more than 95%, the parameter A is 0.2235 and the parameter E is 7.5739 according to the fitting function, and the linear relation is obtained as y 7.5739x + 0.2235;
in formulae (5) to (7), J t The exhalation rate of radon before covering soil is expressed as Bq.m -2 ·s -1 ；J c The exhalation rate of radon after covering soil is represented by Bq.m -2 ·s -1 。
In order to analyze the influence of the total thickness of the first loess layer and the second loess layer on the radon exhalation rate, the average exhalation rate of radon under the same thickness is taken as the exhalation rate of radon with the thickness. Similarly, the radon exhalation rate reducing effect of the covering material can be expressed by the radon reduction coefficient (k), which is shown in formula (1), and the radon reduction coefficient results for loess layers of different thicknesses and different compactities are shown in table 8.
TABLE 8 Radon reduction factor for loess layers of different thicknesses and different compactnesses
As can be seen from Table 8, the radon reduction coefficient is different for different compactnesses of the second loess layer at the same thickness; under the condition of the same compactness, the larger the total thickness of the loess layer is, the larger the radon reduction coefficient is, and the better the radon reduction effect is; the loess layer with the same thickness has the best radon reduction effect when the compaction degree is 90 percent.
(4) Optimal earthing scheme for inhibiting radon exhalation rate on waste stone pile surface
Through analysis of field test results, the covering material for inhibiting the radon exhalation rate on the surface of the waste stone heap in the research area (741 bamboo-mountain uranium mining area) is finally obtained: the covering material has the best effects of inhibiting radon exhalation rate and shielding gamma rays in a bentonite layer (with the thickness of 10cm and the degree of compaction of 50%), a first loess layer (with the thickness of 7cm and the degree of compaction of 50%) and a second loess layer (with the thickness of 18cm and the degree of compaction of 90%). The covering model of the covering material is shown in formulas (8) to (10):
in the formulas (8) to (10), Jt is the radon exhalation rate of the surface of the waste stone heap, and the unit is Bq cm -2 ·s -1 ；
J C1 The radon exhalation rate of the surface of the waste rock heap after covering the bentonite layer is represented by Bq cm -2 ·s -1 ；
X C1 -the thickness of the bentonite layer in cm;
J C2 the radon exhalation rate of the surface of the waste rock heap after covering the first loess layer is expressed in Bq cm -2 ·s -1 ；
X C2 -the thickness of the first loess layer in cm;
J C3 the radon exhalation rate of the surface of the waste rock heap after covering the second loess layer is expressed in Bq cm -2 ·s -1 ；
X C3 -the thickness of the second loess layer in cm.
The foregoing is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, various modifications and decorations can be made without departing from the principle of the present invention, and these modifications and decorations should also be regarded as the protection scope of the present invention.
Claims (7)
1. The utility model provides a radon cover material falls in multilayer which characterized in that, includes the bentonite layer, is located the first loess layer on bentonite layer surface and being located the second loess layer on first loess layer surface.
2. The multilayer radon reducing cover material in accordance with claim 1, wherein said bentonite layer, first loess layer and second loess layer independently have a degree of compaction of 10 to 90%.
3. The multilayer radon reduction covering material as claimed in claim 1 or 2, wherein said bentonite layer has a thickness of 4 to 12 cm.
4. The multilayer radon reduction covering material in accordance with claim 1 or 2, wherein said first loess layer has a thickness of 7 to 15 cm.
5. The multilayer radon reduction covering material in accordance with claim 1 or 2, wherein said second loess layer has a thickness of 15 to 20 cm.
6. The use of the multilayer radon-reducing covering material of claim 1 in decommissioning treatment of uranium mine waste rock piles.
7. A method for reducing the radon exhalation rate of uranium mine waste stone heap comprises the following steps:
covering bentonite on the surface of the uranium mine waste rock heap, and tamping to obtain a bentonite layer;
covering loess on the surface of the bentonite layer and tamping to obtain a first loess layer;
and covering loess on the surface of the first loess layer and tamping to obtain a second loess layer.
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| CN115722513A (en) * | 2022-10-14 | 2023-03-03 | 中核第四研究设计工程有限公司 | Uranium tailing slag warehouse covering structure and method for shielding radon gas and improving water seepage quality |
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