High-level radioactive waste deep geological treatment and heat energy recovery collaborative method

Abstract

The invention discloses a high-level radioactive waste deep geological disposal and heat energy recovery collaborative method, which belongs to the field of high-level radioactive waste geological disposal, and comprises the following steps: S1, tunneling a disposal roadway in a complete bedrock of a disposal repository, excavating a disposal hole in a bottom plate of the disposal roadway, and tunneling the disposal roadway in a relatively complete crystal bedrock; s2, a heat insulation film is laid around the hole wall and the bottom of the treatment hole, and the thickness of the heat insulation film is 0.5 cm; s3, constructing a water injection station, a heat exchange pipe and a centralized heat exchange station; s4, filling a gap between the heat exchange pipe and the treatment tank with a bentonite buffer material; and S5, high-level radioactive waste is treated. The heat energy recovery pipe surrounding the high-level radioactive waste disposal hole is constructed on the basis of a traditional crystallized rock vertical hole high-level radioactive waste disposal method, the heat energy recovery pipe can effectively absorb decay heat of the high-level radioactive waste, the situation that the temperature of bed rock of crystallized rock rises and thermal stress is generated is avoided, meanwhile, decay heat recovery of the high-level radioactive waste is achieved, energy is fully utilized, and the energy utilization rate is increased. The carbon neutralization target is met, and wide application and popularization prospects are achieved.

Description

TECHNICAL FIELD

[0001] The present application relates to a high-level waste disposal method, in particular to a high-level waste deep geological disposal and heat energy recovery method. BACKGROUND

[0002] The disposal method of directly placing high-level waste in a deep crystalline rock disposal repository will generate a large amount of decay heat, causing the temperature of the disposal repository bedrock to increase significantly, and generating high thermal stress. The high thermal stress in the enclosed area is easy to cause the disposal hole to break, causing the disposal can to be damaged, inducing the nearby fault to slip, and ultimately leading to the leakage of radioactive nuclides, causing great harm to the surrounding animals and environment. SUMMARY

[0003] The purpose of the present application is to provide a high-level waste deep geological disposal and heat energy recovery method to solve the problem that the existing high-level waste disposal method will cause high thermal stress near the disposal can, and further cause the leakage of radioactive nuclides.

[0004] To achieve the above purpose, the specific scheme is as follows:

[0005] A high-level waste deep geological disposal and heat energy recovery method, comprising the steps of:

[0006] S1: excavating a disposal roadway in the intact bedrock of the disposal repository, and excavating a disposal hole in the floor of the disposal roadway, wherein the disposal roadway is excavated in the relatively intact crystalline rock bedrock;

[0007] S2: laying a heat insulation film around the hole wall and the bottom of the disposal hole to block the conduction of high-level waste decay heat to the bedrock, wherein the thickness of the heat insulation film is 0.5 cm;

[0008] S3: constructing a water injection station, heat exchange pipes, and a centralized heat exchange station;

[0009] S4: filling the gap between the heat exchange pipes and the disposal can with bentonite buffer material;

[0010] S5: disposing high-level waste.

[0011] Further, in step S1, the nuclear waste disposal roadway is a straight wall hole, and the disposal hole is cylindrical and is excavated in the middle of the floor of the disposal roadway.

[0012] Further, in step S2, the heat insulation film is a modified polyimide PI composite heat insulation film.

[0013] Further, in step S3, the heat exchange pipes include water injection pipes, surrounding pipes, and water outlet pipes.

[0014] Further, the disposal roadway is horizontally arranged at the water injection station, and the heat exchange surrounding pipes are arranged along the hole wall of the disposal hole.

[0015] Further, the heat exchange pipe is made of high-strength and high-thermal-conductivity material.

[0016] Further, the high-strength and high-thermal-conductivity material includes copper, aluminum, ceramic, graphite or carbon nanotube.

[0017] Further, the heat exchange pipe has a diameter of 5 cm, and a surface thereof is wrapped with a heat insulation film to reduce heat dissipation.

[0018] In summary, the present application has the following beneficial effects over the prior art:

[0019] The present application provides a heat exchange pipe arranged around a high-level waste disposal hole to realize decay heat recovery while avoiding thermal stress of bedrock caused by temperature rise, and the spacing of the heat exchange pipe and the flow rate of liquid in the pipe are designed according to the decay heat of the high-level waste, that is, the higher the decay heat of the high-level waste, the smaller the spacing of the heat exchange pipe and the flow rate of liquid in the pipe, so as to realize sufficient recovery of the decay heat.

[0020] The present application changes the previous method of realizing safe and effective heat management of a high-level waste deep geological disposal repository by controlling the amount of high-level waste, recycles and utilizes the decay heat of the high-level waste, avoids the generation of thermal stress that is harmful to the long-term safety of the disposal repository, and is conducive to the efficient use of the underground space of the disposal repository, which has important engineering significance and promotional value. BRIEF DESCRIPTION OF DRAWINGS

[0021] The accompanying drawings, which are included to provide a further understanding of the application and constitute a part of this application, illustrate certain illustrative embodiments of the application and together with the description serve to explain the application. In the drawings:

[0022] Figure 1 A schematic diagram of construction arrangement obtained by using the high-level waste deep geological disposal and heat energy recovery collaborative method provided by the present application;

[0023] Figure 2 A local enlarged view of the disposal hole.

[0024] In the above drawings, the following reference signs are used:

[0025] 1, disposal roadway; 2, disposal hole; 3, disposal hole spacing; 4, heat insulation film; 5, water injection station; 6, heat exchange water injection pipe; 7, heat exchange surrounding pipe; 8, heat exchange water outlet pipe; 9, centralized heat exchange station; 10, bentonite buffer; 11, disposal tank. DETAILED DESCRIPTION

[0026] It should be noted that the embodiments in the present application and the features in the embodiments can be combined with each other without conflict. The present application will be described in detail below with reference to the drawings and in combination with embodiments.

[0027] It is to be understood that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of example embodiments in accordance with the present application. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms "comprises" and / or "comprising," when used in this specification, specify the presence of stated features, steps, operations, elements, components, and / or groups thereof, but do not preclude the presence or addition of one or more other features, steps, operations, elements, components, and / or groups thereof.

[0028] The relative arrangement of parts and steps, numerical expressions, and numerical values set forth in the examples are not intended to limit the scope of the application unless otherwise specifically stated. It is to be understood that the drawings are not necessarily to scale as the dimensions of the parts shown are for the purpose of illustration and description only and not to limit the scope of the application. Techniques, methods, and apparatus known to those of ordinary skill in the relevant art can not be discussed in detail, but should be considered as if the techniques, methods, and apparatus were discussed in detail herein. In all examples shown and discussed herein, any specific values are to be interpreted as merely illustrative and not limiting. Other examples of the example embodiments can have different values. It is noted that like numbers and letters refer to like elements throughout the several views of the drawings and, as such, no further discussion with regard thereto is needed.

[0029] Referring to Figure 1 and Figure 2 The present application provides a high-level waste deep geological disposal and heat energy recovery collaborative method, comprising the steps of:

[0030] S1: excavating a disposal roadway 1 in the intact bedrock of the disposal repository, and excavating a disposal hole 2 in the floor of the disposal roadway 1, wherein the disposal roadway 1 is excavated in the relatively intact crystalline rock bedrock.

[0031] As a preferred, the nuclear waste disposal roadway 1 is a straight wall hole with a width of 4.9 m and a height of 5.4 m; the disposal hole 2 is excavated in the middle of the floor of the disposal roadway 1, and the disposal hole 2 is a cylinder with a height of 8 m and a diameter of 1.85 m, and the spacing between adjacent disposal holes 2 is 6 m;

[0032] Roadway excavation process: combined construction of "drilling and blasting + shield finishing", first forming a preliminary roadway profile through medium-depth hole blasting, and then using a small shield machine with a diameter of 5.5 m to finish the roadway wall surface to ensure the dimensional accuracy of the roadway cross section. The finally excavated straight wall arch-shaped disposal roadway 1 has a width of 4.9 m (error ± 0.05 m) and a height of 5.4 m (error ± 0.05 m), and the flatness of the roadway floor is controlled to be ≤3 mm / m, providing a stable working surface for subsequent disposal hole excavation.

[0033] Disposal hole excavation parameters: in the middle of the roadway floor, a cylindrical disposal hole 2 is vertically excavated by a hydraulic core drill, the borehole diameter is 1.85 m (matching the outer diameter of the disposal tank 11, leaving a 150 mm installation gap), the hole depth is 8.0 m (0.5 m longer than the disposal tank length, for laying the bottom heat insulation film and filling the buffer material). The spacing between adjacent disposal holes 2 is set to 6.0 m, which is verified by numerical simulation to avoid local high temperature caused by thermal superposition between adjacent holes, while ensuring the utilization rate of roadway space.

[0034] Quality detection standards: after construction is completed, an ultrasonic flaw detector is used to detect the integrity of the hole wall, requiring no cracks with a depth > 50 mm; a laser range finder is used to detect the hole perpendicularity, with a deviation ≤ 0.5° / 10 m, to ensure the installation accuracy of the subsequent heat exchange pipe.

[0035] As a preferred, a modified polyimide (PI) composite heat insulation film is selected, which has stable performance in the temperature range of -50℃ to 250℃, a thermal conductivity coefficient of only 0.023 W / (m·K), and radiation resistance (γ-ray dose resistance ≥ 10 6 Gy), anti-aging (service life ≥ 100 years) characteristics, meeting the requirements of high-level waste disposal environment.

[0036] I. Laying process:

[0037] (1) Pretreatment: first clean the debris and dust on the hole wall and bottom of the disposal hole 2 with high-pressure airflow (0.8 MPa), then wipe the hole wall with alcohol to ensure that the surface is clean and free of impurities;

[0038] (2) Bottom laying: lay the cut circular heat insulation film (diameter 1.85 m, thickness 0.5 cm) on the bottom of the disposal hole, with the film edge fitted to the hole wall, and seal the edge gap with high-temperature resistant silicone (temperature resistance 300℃);

[0039] (3) Hole wall laying: cut the heat insulation film into a rectangle with a width of 1.2 m and a length of 5.8 m (length = hole wall circumference + 10 cm overlap), lay it along the hole wall in a spiral using a special adhesive robot, with a 10 cm overlap, and fix it every 30 cm with titanium rivets (rivet diameter 3 mm, length 10 mm) to prevent the film from shifting during subsequent construction.

[0040] II. Laying quality acceptance:

[0041] After laying, the sealing property of the heat insulation film is detected by using a heat flow meter, and the film body is required to have no damage and no air bubbles, and the heat loss rate is ≤5%; meanwhile, the adhesion of the film body to the hole wall is detected, and the gap is ≤2 mm. S3: construction of the water injection station 5, the heat exchange pipe and the centralized heat exchange station 9; as an optimization, the heat exchange pipe includes a water injection pipe, a surrounding pipe and a water outlet pipe.

[0042] As an optimization, the water injection station 5 is arranged horizontally at the position of the disposal roadway 1, and the water injection station 5 sends normal temperature water into the high-level radioactive waste disposal roadway 1 through the heat exchange water inlet pipe, and the water flows through the heat exchange surrounding pipe 7; the heat exchange surrounding pipe 7 is arranged along the hole wall of the disposal hole 2, and the normal temperature water in the pipe absorbs the decay heat of the high-level radioactive waste, and the high-temperature water absorbing the decay heat is transported to the centralized heat exchange station 9 through the heat exchange water outlet pipe 8.

[0043] In use, the water injection station 5 injects normal temperature water into the heat exchange surrounding pipe 7 through the heat exchange water injection pipe 6, the heat exchange water outlet pipe 8 outputs the high-temperature water transported by the heat exchange surrounding pipe 7, and the centralized heat exchange station 9 receives the heat transported by the heat exchange water outlet pipe 8.

[0044] As an optimization, the heat exchange pipe is made of metal (such as copper and aluminum), ceramic or carbon material (such as graphite and carbon nanotube), has high strength and high thermal conductivity, and has a diameter of 5 cm. The heat exchange water outlet pipe 8 is wrapped by the heat insulation film 4 to reduce heat dissipation; the construction process is as follows:

[0045] (1) Pipe precasting: according to the depth of the disposal hole and the length of the roadway, the heat exchange water injection pipe 6, the heat exchange surrounding pipe 7 and the heat exchange water outlet pipe 8 are precast on the ground, and the precast length is controlled to be within 6 m to facilitate underground transportation and splicing; the pipe interface is welded by argon arc welding, and after the welding is completed, a water pressure test is performed (test pressure 2.0 MPa, pressure maintaining time 30 min, no leakage).

[0046] (2) Surrounding pipe installation: the precast heat exchange surrounding pipe 7 is vertically sent into the disposal hole 2 by using a special hoisting equipment, the position of the surrounding pipe is adjusted by a hole opening positioning device to ensure that the surrounding pipe closely adheres to the heat insulation film, and the deviation of the interval between the surrounding pipes is ≤2 cm; a 10 cm gap is reserved between the bottom of the surrounding pipe and the bottom of the hole to avoid the pipe being squeezed when the bottom buffer material is filled.

[0047] (3) Pipe connection: in the disposal roadway 1, the heat exchange water injection pipe 6, the heat exchange surrounding pipe 7 and the heat exchange surrounding pipe 7 are connected by copper flanges (the flange gasket is made of temperature-resistant asbestos rubber gasket), and after the connection is completed, a local water pressure test is performed again (test pressure 1.5 MPa, pressure maintaining time 20 min, no leakage).

[0048] (4) System debugging: normal temperature water is injected into the heat exchange system, and the water injection station frequency conversion water pump is started to adjust the flow rate from 2 m 3 / h to 8 m 3h, monitor the pressure and temperature of each pipe (normal working pressure 0.3-0.5 MPa) to ensure the system runs stably without blockage or leakage.

[0049] S4: Use bentonite to buffer the gap between the heat exchange pipe and the disposal tank 11;

[0050] (1) Buffer material ratio and performance: Select bentonite (montmorillonite content ≥ 85%), mixed with 10% quartz sand (particle size 0.1-0.3 mm) as modifier, after compaction, the dry density of the buffer material ≥ 1.6 g / cm 3 , compression modulus 15 MPa, permeability coefficient <1×10 -11 m / s, while having good expansibility (free expansion rate ≥ 300%), which can automatically expand and seal the gap when groundwater intrusion.

[0051] (2) Filling process:

[0052] Pre-treatment: Slowly hoist the disposal tank 11 (diameter 1.7 m, length 7.5 m) into the disposal hole 2, ensure the uniform spacing (about 5 cm) between the tank wall and the surrounding pipe; Install temporary positioning device on the top of the disposal tank to fix the tank position to avoid displacement during filling.

[0053] Layered filling: Use air pressure filling machine to fill the buffer material from the bottom of the disposal hole upwards, each layer filling thickness is 30 cm, immediately after filling, use hydraulic rammer (pressure 5 MPa) to compact until all the gaps between the disposal tank and the surrounding pipe, hole wall are filled; During the filling process, sample and test the dry density of the buffer material every 1.5 m to ensure that it meets the design requirements.

[0054] Top sealing: Lay a layer of 20 cm thick bentonite waterproof blanket on the top of the buffer material, then use concrete cover plate (strength grade C30, thickness 10 cm) to seal the disposal hole, use expansion cement to seal between the cover plate and the hole wall to form a multi-sealing structure.

[0055] In use, normal temperature water is injected into the heat exchange inlet pipe through the water injection station 5, flows through the heat exchange surrounding pipe 7, and hot water flows to the centralized heat exchange station 9 through the heat exchange outlet pipe 8, realizing the recovery of high-level waste decay heat.

[0056] In this process, the heat exchange pipe surrounding the high-level waste disposal hole 2 absorbs and recovers the high-level waste decay heat, reduces the heat conduction to the bedrock, avoids the significant increase of bedrock temperature, generates high thermal stress, effectively reduces the engineering disaster problems of the disposal hole 2 rupture and radionuclide rapid leakage described in the background engineering, while ensuring the safety of high-level waste deep geological disposal and realizing heat recovery.

[0057] Example:

[0058] In the bedrock surrounding treatment hole 2, holes (50mm diameter, 2.0m depth) were drilled at radial distances of 0.5m, 1.0m, 2.0m, and 3.0m, respectively, and fiber optic grating thermal stress sensors (measurement range 0-50MPa, accuracy ±0.1MPa) were implanted. At the same time, platinum resistance temperature sensors (measurement range -20℃~200℃, accuracy ±0.2℃) were attached to the surface of heat exchange surrounding pipe 7 to monitor the bedrock thermal stress and pipe temperature in real time.

[0059] The formula for calculating thermal stress in rock mass is:

[0060] σ T =αEΔT

[0061] Where: σ T α represents thermal stress; α is the coefficient of thermal expansion of granite, which is α = 9.8 × 10⁻⁶. -6 / ℃; E is the elastic modulus, the elastic modulus of granite E 岩 =60GPa; ΔT is the temperature increment.

[0062] Without a heat exchange system (simulating traditional treatment methods): In the initial stage of treatment (year 1), the bedrock temperature 0.5m around the treatment hole reached 102℃, and the calculated thermal stress value σ T =αEΔT=9.8×10 -6 / ℃×58×10 3 MPa×102℃≈58.7MPa, which is close to 40% of the compressive strength of granite, indicating a risk of bedrock cracking.

[0063] After the heat exchange system was put into operation: In the initial stage of treatment (year 1), the water temperature inside the heat exchange pipes stabilized at 55-60℃, the temperature at 0.5m depth in the bedrock dropped to 12.5℃, and the thermal stress σ T =9.8×10 -6 / ℃×58×10 3 MPa × 12.5℃ ≈ 7.0MPa, which is only 5% of the compressive strength of granite, completely avoiding the risk of bedrock fracture caused by thermal stress.

[0064] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for high-level waste disposal and heat energy recovery in deep geological disposal, characterized in that, The method comprises the steps of: S1: excavating a disposal roadway (1) in a disposal repository complete bedrock, excavating a disposal hole (2) in the floor of the disposal roadway (1), and excavating the disposal roadway (1) in a relatively complete crystalline rock bedrock; S2: laying a heat insulation film (4) around the hole wall and the bottom of the disposal hole (2), and the thickness of the heat insulation film (4) is 0.5 cm; S3: constructing a water injection station (5), a heat exchange pipe, and a centralized heat exchange station (9); S4: using bentonite buffer (10) to fill the gap between the heat exchange pipe and a disposal tank (11); S5: disposing high-level radioactive waste.

2. A high-level waste deep geological disposal and heat energy recovery collaborative method according to claim 1 characterised in that, In step S1, the disposal roadway (1) is a straight wall hole, and the disposal hole (2) is a cylindrical shape, which is excavated in the middle of the floor of the disposal roadway (1).

3. A high-level waste deep geological disposal and heat energy recovery collaborative method according to claim 1 characterised in that, In step S3, the heat exchange pipe comprises a water injection pipe, a surrounding pipe, and a water outlet pipe.

4. A high-level waste deep geological disposal and heat energy recovery collaborative method according to claim 3, characterised in that, The disposal roadway (1) is horizontally arranged at the water injection station (5), and the heat exchange surrounding pipe (7) is arranged along the hole wall of the disposal hole (2).

5. A high-level waste deep geological disposal and heat energy recovery collaborative method according to claim 3, characterised in that, The heat exchange pipe is made of high-strength and high-thermal-conductivity material.

6. A high-level waste deep geological disposal and heat energy recovery collaborative method according to claim 5, characterised in that, The high-strength and high-thermal-conductivity material comprises copper, aluminum, ceramic, graphite, or carbon nanotube.

7. A high-level waste deep geological disposal and heat energy recovery collaborative method according to claim 3 characterised in that, The diameter of the heat exchange pipe is 5 cm, and the surface of the heat exchange pipe is wrapped with a heat insulation film (4) to reduce heat dissipation.

8. A high-level waste deep geological disposal and heat energy recovery collaborative method according to claim 1 characterised in that, In step S2, the heat insulation film is a modified polyimide PI composite heat insulation film.

Images