Covering layer structure of near-surface disposal site, covering method of covering layer structure and radioactive waste disposal system

Abstract

The invention discloses a covering layer structure of a near-surface disposal site, a covering method of the covering layer structure and a radioactive waste disposal system, and the covering layer structure can cover the near-surface disposal site and can reduce the damage of a drought wind and sand climate environment to the covering layer structure, so that nuclide leakage can be avoided. The covering layer structure comprises a supporting layer, a nuclide blocking layer, an impermeable layer, a biological invasion prevention layer, a stable layer and a wind erosion prevention layer. The supporting layer covers a near-surface disposal site; the nuclide blocking layer, the anti-seepage layer and the wind erosion prevention layer sequentially cover the supporting layer from bottom to top, the nuclide blocking layer is used for effectively blocking nuclide from being released outwards, the anti-seepage layer is used for preventing water located above the anti-seepage layer from leaking downwards, and the biological invasion prevention layer is used for preventing external organisms from invading and damaging the structure below the anti-seepage layer. The stabilizing layer is used for stably supporting the structure above the stabilizing layer, and the wind erosion preventing layer is used for preventing the structure below the wind erosion preventing layer from being damaged by the wind erosion effect.

Description

Technical Field

[0001] The invention belongs to the technical field of radioactive waste disposal, and particularly relates to a cover layer structure of a near-surface disposal site, a covering method thereof, and a radioactive waste disposal system. Background Art

[0002] The extensive application of nuclear energy is accompanied by the generation of a large amount of radioactive waste. Among them, the safe disposal of low- and intermediate-level radioactive waste has become an increasingly concerned focus issue due to its huge proportion.

[0003] Radioactive waste disposal refers to the activity of finally placing radioactive waste in specially constructed facilities, which is an indispensable part of the complete nuclear industry industrial chain. The near-surface disposal site has advantages such as reasonable engineering cost, convenient construction, and good safety.

[0004] At present, the disposal sites for low- and intermediate-level radioactive waste generated from the operation and decommissioning of nuclear facilities are all near-surface disposal sites.

[0005] The cover layer is one of the most important engineering barriers in the closure stage of the near-surface radioactive waste disposal site. As an important engineering barrier of the near-surface disposal site, it can protect humans and the environment from the harm of ionizing radiation of leaked radionuclides.

[0006] Due to the large climate differences in different regions, taking arid regions as an example, the climate in this region is dry, with strong evaporation, large day-night temperature differences, and serious wind erosion. It is necessary to properly design its cover layer scheme based on the characteristics of this region to ensure the containment and isolation capabilities of multiple near-surface disposal facilities in this region. Summary of the Invention

[0007] The technical problem to be solved by the present invention is to provide a cover layer structure of a near-surface disposal site, a covering method thereof, and a radioactive waste disposal system in view of the above deficiencies existing in the prior art. This cover layer structure can cover the near-surface disposal site and can reduce the damage of the arid sandy climate environment to the cover layer structure, thereby avoiding radionuclide leakage.

[0008] In a first aspect, an embodiment of the present invention provides a cover layer structure for a near-surface disposal site. The cover layer structure includes a support layer, a radionuclide retardation layer, a waterproof layer, an anti-biological invasion layer, a stabilizing layer, and a wind erosion prevention layer. The support layer covers the near-surface disposal site; the radionuclide retardation layer, the waterproof layer, the anti-biological invasion layer, the stabilizing layer, and the wind erosion prevention layer are successively covered on the support layer from bottom to top. The radionuclide retardation layer is used to retard the outward release of radionuclides, the waterproof layer is used to prevent the moisture above it from leaking downward, the anti-biological invasion layer is used to prevent external organisms from damaging the structure below after invasion, the stabilizing layer is used to stably support the structure above it, and the wind erosion prevention layer is used to prevent the wind erosion effect from damaging the structure below the wind erosion prevention layer.

[0009] In some embodiments, the surface profile of the cover layer structure of the near-surface disposal site is divided into a slope and a crest. The slope surrounds the bottom of the crest. The slope has a gradient of p1, where 20% ≤ p1 ≤ 33%, and the crest has a gradient of p2, where 1% ≤ p2 ≤ 5%.

[0010] In some embodiments, the surface shape of the radionuclide retardation layer is the same as the surface shape of the wind erosion prevention layer.

[0011] In some embodiments, the support layer is formed of gravel, and geogrids are provided in the middle and on the upper surface of the support layer to reinforce the structure of the support layer; and / or, a first geotextile is laid between the support layer and the radionuclide retardation layer, and the first geotextile is used to prevent the material of the radionuclide retardation layer from entering the support layer under the action of water flow; and / or, the radionuclide retardation layer is formed of compacted soil mixed with bentonite, and the permeability coefficient of the radionuclide retardation layer is less than 1e-5 cm / s; and / or, the waterproof layer includes a compacted clay layer, a bentonite waterproof blanket, a geomembrane, and a second geotextile from bottom to top; the geomembrane is a double-rough surface geomembrane, and the thickness of the geomembrane is greater than or equal to 2 mm, and the permeability coefficient is less than 1e-12 cm / s; the permeability coefficient of the compacted clay layer is less than 1e-6 cm / s; and / or, the anti-biological invasion layer is formed of cobblestones; and / or, the stabilizing layer is a stable structure formed of compacted soil mixed with bentonite, and the permeability coefficient of the stabilizing layer is less than 1e-5 cm / s; and / or, the wind erosion prevention layer is formed of gravel; the thickness of the wind erosion prevention layer at the slope part is greater than the thickness of the wind erosion prevention layer at the crest part.

[0012] In some embodiments, a third geotextile is provided between the stabilizing layer and the anti-biological invasion layer, and between the stabilizing layer and the wind erosion prevention layer. The third geotextile is used to prevent the material of the stabilizing layer from being mixed in the anti-biological invasion layer and the wind erosion prevention layer.

[0013] In some embodiments, a plurality of marker blocks are evenly distributed on the joint surface between the stabilizing layer and the wind erosion prevention layer. The marker blocks can be exposed after the wind erosion prevention layer is damaged, and are used to remind the staff to repair the wind erosion prevention layer.

[0014] In some embodiments, a water collection gallery or a sump is provided at the bottom of the support layer. The water collection gallery or the sump is used to collect the water infiltrating into the support layer and discharge it to the outside of the cover layer structure of the near-surface disposal site.

[0015] In some embodiments, the height of the water collection gallery or the sump is lower than the elevation of the horizontal bottom slab of the disposal unit in the near-surface disposal site. The cover layer structure further includes a drain pipe; the drain pipe is arranged in the water collection gallery or the sump and is communicated with the water collection gallery or the sump of the disposal unit, and is used to discharge the water in the water collection gallery or the sump to the outside of the cover layer structure of the near-surface disposal site.

[0016] Therefore, for the cover layer structure of the near-surface disposal site provided by the embodiments of the present invention, by providing a support layer and covering the near-surface disposal site with the support layer, the support layer can support the multi-layer structures arranged thereon; by sequentially arranging a nuclide retardation layer, an anti-seepage layer and a wind erosion prevention layer on the support layer, the nuclide retardation layer can prevent the leakage of nuclides from the near-surface disposal site, the anti-seepage layer can prevent water from seeping downward into the disposal unit of the near-surface disposal site, the anti-biological invasion layer can prevent the damage to the underlying structures after biological invasion, the stabilizing layer can stably support the structures above it, and the wind erosion prevention layer can prevent the damage to the entire cover layer structure caused by the wind erosion effect of sand and wind, so that the cover layer structure can reduce the damage to the cover layer structure in the arid sandstorm climate environment on the basis of covering the near-surface disposal site and isolating nuclides, and maintain the long-term integrity of the cover layer structure.

[0017] In a second aspect, an embodiment of the present invention further provides a radioactive waste disposal system. The radioactive waste disposal system includes a near-surface disposal site and the cover layer structure of the near-surface disposal site in the first aspect. In the near-surface disposal site, a plurality of disposal units are arranged, and the disposal units are used to dispose of radioactive waste.

[0018] In a third aspect, an embodiment of the present invention further provides a method for covering a near-surface disposal site. The covering method includes: covering a support layer on the area of the disposal unit of the near-surface disposal site; and sequentially completing the construction of a nuclide retardation layer, an anti-seepage layer, an anti-biological invasion layer, a stabilizing layer and a wind erosion prevention layer above the support layer, so as to form a cover layer structure.

[0019] The radioactive waste disposal system and the covering method of the near-surface disposal site provided by the embodiments of the present invention have the same beneficial effects as the covering layer structure of the above-mentioned near-surface disposal site, which will not be elaborated here. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 : is a schematic diagram of a covering layer structure of a near-surface disposal site provided by an embodiment of the present invention;

[0021] Figure 2 : is a schematic diagram of the relative position between the covering layer structure of a near-surface disposal site and a disposal unit provided by an embodiment of the present invention;

[0022] Figure 3 : is a top view of a covering layer structure of a near-surface disposal site provided by an embodiment of the present invention;

[0023] Figure 4 : is a partial cross-sectional view of a covering layer structure of a near-surface disposal site provided by an embodiment of the present invention.

[0024] Wherein, 1 - support layer; 2 - nuclide retardation layer; 3 - anti-seepage layer; 4 - anti-biological invasion layer; 5 - stabilizing layer; 6 - wind erosion prevention layer; 7 - disposal unit; 8 - drain pipe. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0025] To enable those skilled in the art to better understand the technical solutions of the present invention, the present invention will be further described in detail below with reference to the drawings and embodiments.

[0026] Embodiment 1:

[0027] As Figure 1 , Figure 2 , Figure 3 shown, an embodiment of the present invention provides a covering layer structure for a near-surface disposal site. The covering layer structure is applied to the disposal of a near-surface disposal site and is used to cover the near-surface disposal site to prevent the leakage of nuclides from the near-surface disposal site.

[0028] As Figure 4 shown, the covering layer structure of the near-surface disposal site includes a support layer 1, a nuclide retardation layer 2, an anti-seepage layer 3, an anti-biological invasion layer 4, a stabilizing layer 5, and a wind erosion prevention layer 6. The support layer 1 covers the near-surface disposal site. The nuclide retardation layer 2, the anti-seepage layer 3, and the wind erosion prevention layer 6 are successively covered on the support layer 1 from bottom to top. The nuclide retardation layer 2 is used to retard the release of nuclides outward, the anti-seepage layer 3 is used to prevent the moisture above it from leaking downward, the anti-biological invasion layer 4 is used to prevent external organisms from damaging the structure below it, the stabilizing layer 5 is used to stably support the structure above it, and the wind erosion prevention layer 6 is used to prevent the wind erosion effect from damaging the structure below the wind erosion prevention layer 6.

[0029] Exemplarily, the near-surface disposal site in this embodiment refers to a disposal site for low- and medium-level radioactive waste, especially a near-surface disposal site set in arid sandy areas. A plurality of disposal units 7 are provided in the near-surface disposal site, and the disposal units 7 are used to dispose of radioactive waste.

[0030] As Figure 1 shown, the support layer 1 is mainly used to support the multi-layer structure disposed thereon.

[0031] Exemplarily, the material of the support layer 1 is a high-strength material such as gravel, so that the support layer 1 has high support strength and stability.

[0032] Exemplarily, the material of the nuclide retardation layer 2 is the local soil that has been compacted to prevent the nuclides in the near-surface disposal site from leaking through the nuclide retardation layer 2.

[0033] Exemplarily, waterproof materials and compacted clay materials are provided in the anti-seepage layer 3 to prevent the moisture above it from seeping downward through the anti-seepage layer 3.

[0034] Exemplarily, the anti-biological invasion layer 4 is a thick gravel structure, so as to prevent organisms from burrowing and damaging the underlying stable layer 3, nuclide retardation layer 2, etc. after entering, which is beneficial to maintaining the integrity of the cover layer structure of the near-surface disposal site, thereby ensuring the functions of each layer structure in the cover layer structure of the near-surface disposal site.

[0035] The stable layer 5 is formed by compacting a material with higher strength, such as formed by compacted soil, so it can stably support the structure above it.

[0036] Exemplarily, the wind erosion prevention layer 6 is formed of pebble materials with high hardness, good roundness, high density, and strong wear resistance, so as to increase the service life of the wind erosion prevention layer 6, and further reduce the damage caused by the wind erosion effect of external wind and sand to the structure below the wind erosion prevention layer 6 to the greatest extent.

[0037] Therefore, through the above settings, the cover layer structure can achieve the long-term containment and isolation ability of the waste nuclides in the disposal units in the near-surface disposal site, and the cover layer structure has good waterproof and wind erosion prevention capabilities, so that the cover layer structure can be applicable to the arid sandy climate environment.

[0038] Accordingly, for the cover layer structure of the near-surface disposal site provided by the embodiments of the present invention, by providing the support layer 1 and covering the near-surface disposal site with the support layer 1, the support layer 1 can support the multi-layer structure disposed thereon; by sequentially providing the nuclide retardation layer 2, the anti-seepage layer 3, the anti-biological invasion layer 4, the stabilization layer 5, and the wind erosion prevention layer 6 on the support layer 1, the nuclide retardation layer 2 can prevent the leakage of nuclides from the near-surface disposal site, the anti-seepage layer 3 can prevent water from seeping downward into the disposal unit of the near-surface disposal site, the anti-biological invasion layer 4 can prevent the damage to the structure below after biological invasion, the stabilization layer 5 can stably support the structure above it, and the wind erosion prevention layer 6 can prevent the damage to the entire cover layer structure caused by the wind erosion effect of sand and dust, so that the cover layer structure can, on the basis of covering the near-surface disposal site and isolating nuclides, reduce the damage to the cover layer structure in the arid sandstorm climate environment and maintain the long-term integrity of the cover layer structure.

[0039] In some embodiments, as Figure 1 、 Figure 2 and Figure 3 shown, the surface profile of the cover layer structure of the near-surface disposal site is divided into a slope A and a slope top B, and the slope A surrounds the bottom of the slope top B. The slope of the slope A is p1, 20% ≤ p1 ≤ 33%, and the slope of the slope top B is p2, 1% ≤ p2 ≤ 5%.

[0040] Exemplarily, as Figure 2 and Figure 3 shown, the shape of the near-surface disposal site is strip-shaped, and the top view of the surface profile of the cover layer structure of the near-surface disposal site can be rectangular.

[0041] Exemplarily, the slope p1 of the slope A can be 20%, 25% or 33%, etc. The slope p2 of the slope top B can be 1%, 3% or 5%, etc.

[0042] The design of the surface profile of the cover layer structure of the near-surface disposal site not only considers the rationality of the slope, but also takes into account the stability and functionality of the overall structure. The slope p1 of the slope A is between 20% and 33%, and the design within this range can effectively reduce the erosion effect of sand and dust on the wind erosion prevention layer 6, while ensuring the stability of the surface structure of the wind erosion prevention layer 6. The slope p2 of the slope top B is between 1% and 5%, and this design can not only further reduce the impact of sand and dust on the wind erosion prevention layer 6, but also provide good drainage conditions for the discharge of rainwater, avoiding water accumulation on the slope top B.

[0043] In practical applications, the structural design of the wind erosion prevention layer 6 usually needs to be optimized in combination with specific topographic conditions and environmental factors. For example, in areas with strong winds, the slope p1 of the slope A can be appropriately reduced to enhance the wind erosion prevention effect; while in areas with large rainfall, the slope p2 of the slope top B can be appropriately increased to improve the drainage efficiency.

[0044] Through reasonable structural design, the erosion of the wind erosion prevention layer 6 by the high wind and sand environment can be effectively reduced, the service life of the wind erosion prevention layer 6 can be extended, and then the service life of the covering layer structure can be extended. At the same time, the maintenance cost of the wind erosion prevention layer 6 can be reduced.

[0045] In some embodiments, the surface shape of the nuclide blocking layer 2 is the same as that of the wind erosion prevention layer.

[0046] Exemplarily, when covering the layers above the nuclide blocking layer 2, the shapes of the support layer 1 and the nuclide blocking layer 2 need to be adjusted.

[0047] Through the above settings, the basic outline of the covering layer structure can be formed after the nuclide blocking layer 2 is covered. The subsequent layers do not need to make excessive shape adjustments and can be directly covered on the nuclide blocking layer 2, which is beneficial to reducing the construction difficulty of the layers on the nuclide blocking layer 2.

[0048] In some embodiments, the support layer 1 is formed by gravel, and geogrids are arranged in the middle and upper surfaces of the support layer 1 to reinforce the structure of the support layer 1 through the geogrids.

[0049] Exemplarily, the gravel of the support layer 1 is magmatic rock gravel with a particle size of about 20 mm to 50 mm (uniform particle size distribution) and distinct edges and corners (which can increase the bite force).

[0050] The geogrid material is a two-dimensional grid or a three-dimensional three-dimensional grid screen with a certain height formed by thermoplastic or molding of high molecular polymers such as polypropylene and polyvinyl chloride. When the geogrid material is used in civil engineering, it is called a geogrid.

[0051] The geogrid has the characteristics of high strength, small creep, and adaptability to various environmental soils, and is commonly used as the reinforcement material of reinforced soil structures or the reinforcement material of composite materials, etc.

[0052] By setting the geogrid, the structural strength of the support layer 1 can be improved to maintain the shape and structural stability of the support layer 1.

[0053] A first geotextile is laid between the support layer 1 and the nuclide blocking layer 2, and the first geotextile is used to prevent the material of the nuclide blocking layer 2 from entering the support layer 1 under the action of water flow.

[0054] Exemplarily, the first geotextile is a water-permeable geosynthetic material formed by needling or weaving synthetic fibers, mainly playing roles such as isolation, reverse filtration, drainage, reinforcement, and protection.

[0055] Through the above settings, the waterproof isolation effect between the support layer 1 and the nuclide blocking layer 2 can be improved.

[0056] In some embodiments, the nuclide retardation layer 2 is formed of compacted soil admixed with bentonite, and the permeability coefficient of the nuclide retardation layer 2 is less than 1e-5 cm / s.

[0057] Exemplarily, the compacted soil can be formed by compacting local soil.

[0058] Exemplarily, the average thickness of the nuclide retardation layer 2 is about 1000 mm, and the thickness difference at various locations of the nuclide retardation layer 2 is less than 100 mm.

[0059] Exemplarily, the permeability coefficient of the nuclide retardation layer 2 can be 0.8e-5 cm / s, 0.9e-5 cm / s, 0.95e-5 cm / s, etc.

[0060] The compacted soil admixed with bentonite has a good adsorption effect on nuclides. When nuclides are released, the nuclide retardation layer 2 can play an effective role in retarding nuclides. The compacted soil admixed with bentonite can also achieve a good backfilling effect.

[0061] In some embodiments, the anti-seepage layer 3 includes a compacted clay layer, a bentonite waterproof blanket, a geomembrane, and a second geotextile from bottom to top. The geomembrane uses a double-rough surface geomembrane, and the thickness of the geomembrane is greater than or equal to 2 mm, and the permeability coefficient is less than 1e-12 cm / s. The permeability coefficient of the compacted clay layer is less than 1e-6 cm / s.

[0062] Exemplarily, the compacted clay layer is formed by compacting local clay. The permeability coefficient of the compacted clay layer can be 0.8e-6 cm / s, 0.9e-6 cm / s, 0.99e-6 cm / s, etc. The average thickness of the compacted clay layer is about 1000 mm, and the thickness difference at various locations of the compacted clay layer is less than 100 mm.

[0063] The bentonite waterproof blanket, also known as the GCL bentonite waterproof blanket, is a bentonite anti-seepage pad made by filling highly swellable sodium-based bentonite between a special composite geotextile and a non-woven fabric through a needle punching method. This material can form many small fiber spaces, preventing the bentonite particles from flowing in one direction, and forming a uniform and high-density colloidal waterproof layer in the pad when encountering water, thus effectively preventing water leakage.

[0064] The geomembrane is a waterproof barrier material made of high molecular polymers as the basic raw material, and is widely used in various civil engineering, environmental protection engineering and other fields. The double-rough surface geomembrane is a special type of geomembrane with rough surfaces on both sides. Compared with ordinary smooth surface geomembranes, it has higher stability and better drainage performance in slope engineering.

[0065] Exemplarily, the geomembrane in this embodiment can be a high-density polyethylene geomembrane (HDPE) or a linear low-density polyethylene geomembrane (LLDPE).

[0066] Exemplarily, the thickness of the geomembrane can be 2 mm, 2.5 mm, 3 mm, etc., and the permeability coefficient can be 0.8e-12 cm / s, 0.9e-12 cm / s, 0.99e-12 cm / s, etc.

[0067] Exemplarily, the material of the second geotextile can be the same as that of the first geotextile.

[0068] Through the above settings, the impermeable layer 3 can have better waterproof and impermeable properties.

[0069] In some embodiments, the anti-biological invasion layer 4 is formed by cobblestones. The stabilizing layer 5 is a stabilizing structure formed by compacted soil mixed with bentonite, and the permeability coefficient of the stabilizing layer 5 is less than 1e-5 cm / s.

[0070] Exemplarily, the average thickness of the anti-biological invasion layer 4 is about 800 mm, and the thickness difference at each part of the anti-biological invasion layer 4 is less than 100 mm.

[0071] Exemplarily, the permeability coefficient of the stabilizing layer 5 can be 0.8e-5 cm / s, 0.9e-5 cm / s, 0.99e-5 cm / s, etc. The average thickness of the stabilizing layer 5 is about 800 mm, and the thickness difference at each part of the stabilizing layer 5 is less than 100 mm.

[0072] Through the above settings, it is possible to prevent external organisms from damaging the covering layer structure and enable the stabilizing layer 5 to stably support the upper wind erosion prevention layer 6.

[0073] In some embodiments, the wind erosion prevention layer 6 is formed by gravel; the thickness of the wind erosion prevention layer 6 at the A part of the slope is greater than the thickness of the wind erosion prevention layer 6 at the B part of the slope top.

[0074] Exemplarily, the thickness at each part of the wind erosion prevention layer 6 is between 300 mm and 500 mm. For example, the thickness of the wind erosion prevention layer 6 at the A part of the slope is 500 mm, and the thickness of the wind erosion prevention layer 6 at the B part of the slope top is 300 mm.

[0075] Exemplarily, the gravel particle size of the wind erosion prevention layer 6 at the B of the slope top is between 1 cm and 15 cm.

[0076] Exemplarily, the part of the wind erosion prevention layer 6 at the A of the slope is formed by gravel with a roundness greater than 0.85 and a particle size between 5 cm and 15 cm to achieve a better wind erosion prevention effect.

[0077] The gravel of the wind erosion prevention layer 6 is preferably magmatic rock gravel with a relatively large density, a dense structure, and a low breakage rate. Among them, large-sized gravel (particle size reference range: 5 cm to 15 cm) is placed in the upper layer of the wind erosion prevention layer 6, and medium and small-sized gravel (particle size reference range: 2 cm to 5 cm) is placed in the lower layer of the wind erosion prevention layer 6, with a natural transition from top to bottom. The gaps between the gravel are filled with small-sized gravel (particle size reference range: 1 cm to 2 cm).

[0078] Through the above settings, the wind erosion prevention layer 6 has better wind erosion prevention performance.

[0079] In some embodiments, as Figure 4 shown, a third geotextile is provided between the stabilization layer 5 and the anti-biological invasion layer 4, and between the stabilization layer 5 and the wind erosion prevention layer 6. The third geotextile is used to prevent the materials of the stabilization layer 5 from being mixed in the anti-biological invasion layer 4 and the wind erosion prevention layer 6.

[0080] Exemplarily, the material of the third geotextile is the same as that of the first geotextile.

[0081] Through the above settings, it is possible to prevent the stabilization layer 5 from being mixed with the anti-biological invasion layer 4 and the wind erosion prevention layer 6.

[0082] In some embodiments, a plurality of marking blocks are evenly distributed on the joint surface between the stabilization layer 5 and the wind erosion prevention layer 6. The marking blocks can be exposed after the wind erosion prevention layer 6 is damaged, so as to remind the staff to repair the wind erosion prevention layer 6.

[0083] Exemplarily, the material of the marking blocks is a stable and strong material. For example, the marking blocks are concrete round cakes made of concrete.

[0084] Through the above settings, it is convenient for the staff to repair the wind erosion prevention layer 6 in time to maintain the integrity of the cover layer structure.

[0085] In some embodiments, as Figure 4 shown, a water collection gallery or a sump is provided at the bottom of the support layer 1. The water collection gallery or the sump is used to collect the water infiltrating into the support layer 1 and discharge it to the outside of the cover layer structure of the near-surface disposal site.

[0086] Exemplarily, the water collection gallery or the sump can be arranged around the near-surface disposal site.

[0087] Through the above settings, the water at the bottom of the cover layer structure can be discharged in time, avoiding the accumulation of water at the bottom of the cover layer structure and infiltrating into the near-surface disposal site. This not only helps to maintain a dry environment for the cover layer structure, prevent the release of radionuclides in the disposal unit 7 to the external environment due to water accumulation, but also helps to maintain the long-term stability and safety of the near-surface disposal site.

[0088] In some embodiments, as Figure 4 shown, the height of the collection pipe gallery or sump is lower than the elevation of the horizontal bottom plate of the disposal unit 7 in the near-surface disposal site. The cover layer structure further includes a drain pipe 8; the drain pipe 8 is arranged in the collection pipe gallery or sump and is communicated with the collection pipe gallery or sump of the disposal unit 7 for discharging the moisture in the collection pipe gallery or sump to the outside of the cover layer structure of the near-surface disposal site.

[0089] Through the above settings, it is convenient for the moisture in the disposal unit 7 to flow out into the drain pipe 8, avoiding the accumulation of moisture in the near-surface disposal site, and also contributing to maintaining the long-term stability and safety of the near-surface disposal site.

[0090] In summary, the beneficial effects of the cover layer structure of the near-surface disposal site provided by the embodiments of the present invention are as follows:

[0091] (1) The cover layer structure adopts an anti-wind erosion layer 6 formed by gravel, which can reduce the damage of the wind erosion effect to the cover layer structure to the greatest extent in the environment of strong wind and high wind speed in arid areas, and protect the long-term integrity of the cover layer structure.

[0092] (2) The single-layer anti-seepage structure (i.e., the anti-seepage layer 3) adopted in the cover layer structure is suitable for the climatic conditions of less rainfall and large evaporation in the northwest region; because the construction difficulty of the anti-seepage structure in the cover layer structure is relatively low, the damage of the anti-seepage structure caused by construction mistakes can be reduced, so as to better ensure the integrity of the anti-seepage structure and make the anti-seepage structure play a good long-term anti-seepage effect in the arid northwest region.

[0093] (3) A stabilizing layer 5 and an anti-biological invasion layer 4 are arranged under the anti-wind erosion layer 6 and above the anti-seepage layer 3 in the cover layer structure. The stabilizing layer 5 has a certain anti-seepage effect, and it can form a capillary blocking effect with the lower anti-biological invasion layer 4, which can further reduce the leaching effect of the contact between the moisture and the geomembrane of the anti-seepage layer 3 on the geomembrane and increase the service life of the anti-seepage layer 3.

[0094] (4) The support layer 1 under the nuclide retardation layer 2 of the present invention can play a role in guiding and draining seepage water after the structures above the support layer 1 finally fail, so as to avoid the infiltration of moisture into the disposal unit 7 of the near-surface disposal site as much as possible.

[0095] Embodiment 2:

[0096] The embodiments of the present invention further provide a radioactive waste disposal system for disposing radioactive waste. The radioactive waste disposal system includes a near-surface disposal site and the cover layer structure of the near-surface disposal site in Embodiment 1. A plurality of disposal units 7 are arranged in the near-surface disposal site, and the disposal units 7 are used to accommodate radioactive waste.

[0097] Exemplarily, multiple disposal units 7 are distributed in a grid pattern within the near-surface disposal site, with an appropriate interval left between each disposal unit 7. The disposal unit 7 is made of high-strength concrete or a steel container, filled with radioactive waste inside, and undergoes strict sealing treatment to ensure that radioactive substances do not leak.

[0098] Through the above settings, the disposal of radioactive waste can be achieved through the near-surface disposal site, and the containment and isolation of the near-surface disposal site can be realized through the cover layer structure, avoiding the leakage of radionuclides to protect humans and the environment from the harm of ionizing radiation from potentially leaking radionuclides. Moreover, this cover layer structure can improve the adaptability of the radioactive waste disposal system to the arid sandy environment.

[0099] Example 3:

[0100] The embodiment of the present invention also provides a covering method for a near-surface disposal site for containing and isolating the near-surface disposal site. This covering method includes: covering a support layer 1 on the disposal unit area of the near-surface disposal site; successively completing the construction of a radionuclide retardation layer 2, an anti-seepage layer 3, an anti-biological invasion layer 4, a stabilizing layer 5, and a wind erosion prevention layer 6 above the support layer 1, thereby forming a cover layer structure.

[0101] Exemplarily, the material of the support layer 1 is a high-strength material such as gravel, so that the support layer 1 has a high support strength and stability, and can provide good support for the radionuclide retardation layer 2, the anti-seepage layer 3, and the wind erosion prevention layer 6 above it.

[0102] Exemplarily, the construction method of successively completing the radionuclide retardation layer 2, the anti-seepage layer 3, the anti-biological invasion layer 4, the stabilizing layer 5, and the wind erosion prevention layer 6 above the support layer 1 is: covering the support layer 1 with the radionuclide retardation layer 2, covering the radionuclide retardation layer 2 with the anti-seepage layer 3, covering the anti-seepage layer 3 with the anti-biological invasion layer 4, covering the anti-biological invasion layer 4 with the stabilizing layer 5, and covering the stabilizing layer 5 with the wind erosion prevention layer 6.

[0103] Exemplarily, the material of the radionuclide retardation layer 2 is a material with a relatively high density, such as compacted local soil, to prevent the radionuclides in the near-surface disposal site from leaking through the radionuclide retardation layer 2.

[0104] Exemplarily, waterproof materials are provided in the anti-seepage layer 3 to prevent the moisture above it from seeping downward through the anti-seepage layer 3.

[0105] Exemplarily, the anti-biological invasion layer 4 is a gravel structure with a relatively thick thickness, so as to prevent organisms from entering and digging holes to damage the stabilizing layer 3, the radionuclide retardation layer 2, etc. below it, which is beneficial to maintaining the integrity of the cover layer structure of the near-surface disposal site, thereby ensuring the functions of each layer structure in the cover layer structure of the near-surface disposal site.

[0106] The stable layer 5 is formed by compacting a material with relatively high strength, such as compacted soil, and can thus stably support the structure above it.

[0107] Exemplarily, the wind erosion prevention layer 6 is made of a material with relatively high hardness that can reduce the wind erosion phenomenon caused by high-speed wind and sand, so as to increase the service life of the wind erosion prevention layer 6 and further prevent the external air flow from damaging the structure below the wind erosion prevention layer 6.

[0108] Thus, in an arid wind and sand climate environment, the long-term containment and isolation ability of radionuclides in the near-surface disposal site can be achieved through the support layer 1, the radionuclide retardation layer 2, the anti-seepage layer 3, the anti-biological invasion layer 4, the stable layer 5, and the wind erosion prevention layer 6, avoiding radionuclide leakage and protecting humans and the environment from the harm of ionizing radiation of leaked radionuclides.

[0109] It can be understood that the above embodiments are merely exemplary embodiments adopted to illustrate the principle of the present invention, but the present invention is not limited thereto. For those of ordinary skill in the art, various modifications and improvements can be made without departing from the spirit and essence of the present invention, and these modifications and improvements are also regarded as the protection scope of the present invention.

Claims

1. A cover layer structure for a near-surface disposal site, characterized in that It includes a support layer (1), a nuclide retardation layer (2), an anti-seepage layer (3), an anti-biological invasion layer (4), a stabilizing layer (5) and a wind erosion prevention layer (6); The support layer (1) covers the near-surface disposal site; the nuclide retardation layer (2), the anti-seepage layer (3), the anti-biological invasion layer (4), the stabilizing layer (5) and the wind erosion prevention layer (6) are sequentially covered on the support layer (1) from bottom to top. The nuclide retardation layer (2) is used to retard the outward release of nuclides, the anti-seepage layer (3) is used to prevent the moisture above it from leaking downward, the anti-biological invasion layer (4) is used to prevent the structures below from being damaged after external biological invasion, the stabilizing layer (5) is used to stably support the structures above it, and the wind erosion prevention layer (6) is used to prevent the structures below the wind erosion prevention layer (6) from being damaged by wind erosion.

2. The cover layer structure of the near-surface disposal site according to claim 1, characterized in that, The surface profile of the cover layer structure of the near-surface disposal site is divided into a slope and a slope top, and the slope surrounds the bottom of the slope top; The slope has a slope of p1, where 20% ≤ p1 ≤ 33%, and the slope top has a slope of p2, where 1% ≤ p2 ≤ 5%.

3. The cover layer structure of the near-surface disposal site according to claim 2, characterized in that, The surface shape of the nuclide retardation layer (2) is the same as the surface shape of the wind erosion prevention layer.

4. The cover layer structure of the near-surface disposal site according to claim 2, characterized in that The support layer (1) is formed by gravel, and geogrids are arranged in the middle and upper surface of the support layer (1) to reinforce the structure of the support layer (1); and / or, A first geotextile is laid between the support layer (1) and the nuclide retardation layer (2), and the first geotextile is used to prevent the material of the nuclide retardation layer (2) from entering the support layer (1) under the action of water flow; and / or, The nuclide retardation layer (2) is formed by compacted soil mixed with bentonite, and the permeability coefficient of the nuclide retardation layer (2) is less than 1e-5 cm / s; and / or, The anti-seepage layer (3) includes a compacted clay layer, a bentonite waterproof blanket, a geomembrane and a second geotextile from bottom to top; the geomembrane is a double-rough surface geomembrane, and the thickness of the geomembrane is greater than or equal to 2 mm, and the permeability coefficient is less than 1e-12 cm / s; the permeability coefficient of the compacted clay layer is less than 1e-6 cm / s; and / or, The anti-biological invasion layer (4) is formed by cobblestones; and / or, The stabilizing layer (5) is a stable structure formed by compacted soil mixed with bentonite, and the permeability coefficient of the stabilizing layer (5) is less than 1e-5 cm / s; and / or, The wind erosion prevention layer (6) is formed by gravel; the thickness of the wind erosion prevention layer (6) at the slope part is greater than the thickness of the wind erosion prevention layer (6) at the slope top part.

5. The cover layer structure of the near-surface disposal site according to claim 4, characterized in that, Third geotextiles are arranged between the stabilizing layer (5) and the anti-biological invasion layer (4), and between the stabilizing layer (5) and the wind erosion prevention layer (6), and the third geotextiles are used to prevent the material of the stabilizing layer (5) from being mixed in the anti-biological invasion layer (4) and the wind erosion prevention layer (6).

6. The cover layer structure of the near-surface disposal site according to claim 4, characterized in that, A plurality of marker blocks are evenly distributed on the joint surface between the stable layer (5) and the wind erosion prevention layer (6). The marker blocks can be exposed after the wind erosion prevention layer (6) is damaged, and are used to remind the staff to repair the wind erosion prevention layer (6).

7. The covering layer structure of the near-surface disposal site according to claim 1, characterized in that, A water collection pipe gallery or a sump is arranged at the bottom of the support layer (1). The water collection pipe gallery or the sump is used to collect the water infiltrating into the support layer (1) and discharge it to the outside of the cover layer structure of the near-surface disposal site.

8. The cover layer structure of the near-surface disposal site according to claim 7, characterized in that, The height of the water collection pipe gallery or the sump is lower than the elevation of the horizontal bottom plate of the disposal unit (7) in the near-surface disposal site; The cover layer structure further includes a drain pipe (8); the drain pipe (8) is arranged in the water collection pipe gallery or the sump and is communicated with the water collection pipe gallery or the sump of the disposal unit (7), and is used to discharge the water in the water collection pipe gallery or the sump to the outside of the cover layer structure of the near-surface disposal site.

9. A radioactive waste disposal system, characterized in that, Comprising: A near-surface disposal site, in which a plurality of disposal units (7) are arranged, and the disposal units (7) are used to dispose of radioactive waste; And, The cover layer structure of the near-surface disposal site according to any one of claims 1-8.

10. A covering method for a near-surface disposal site, characterized in that, Comprising: Cover the support layer (1) on the disposal unit area of the near-surface disposal site; Construct the nuclide retardation layer (2), the anti-seepage layer (3), the anti-biological invasion layer (4), the stable layer (5) and the wind erosion prevention layer (6) in sequence above the support layer (1) to form a cover layer structure.

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