A dry storage repository for spent nuclear fuel

Abstract

The present application relates to the technical field of spent fuel storage, and discloses a spent fuel dry storage vault, which comprises a top air inlet vertical shaft for introducing natural ventilation, a bottom air chamber in communication with the air inlet vertical shaft, a storage chamber above the bottom air chamber, a plurality of shafts arranged in the storage chamber in a vertical direction, a heat generating body sleeved in the shafts in a spaced manner, an annular gap formed between the shafts and the heat generating body, the heat generating body containing spent fuel, the bottom air chamber in communication with a top air chamber through the annular gap, and an air outlet vertical shaft in communication with the top air chamber. Air for natural ventilation enters the air inlet vertical shaft through an air inlet, then enters the bottom air chamber, and then flows into the annular gap and the top air chamber, and is discharged from an air outlet through the air outlet vertical shaft, so that the flow path of the internal air is optimized, the storage chamber enhances the ventilation efficiency and heat exchange performance in a combined manner of heat conduction, convection and radiation heat exchange, the decay heat of the spent fuel in the heat generating body is discharged, and the safety and stability of the spent fuel dry storage vault are ensured.

Description

Technical Field

[0001] This invention relates to the field of spent fuel storage technology, and more specifically to a dry storage facility for spent fuel. Background Technology

[0002] Existing dry storage facilities for spent fuel mainly rely on mechanical ventilation, resulting in high operation and maintenance costs. Utilizing natural ventilation can effectively reduce these operating costs.

[0003] However, existing technologies lack dry storage facilities for spent fuel that utilize natural ventilation. Summary of the Invention

[0004] In view of this, the present invention provides a dry storage facility for spent fuel to solve the problem of the lack of dry storage facilities for spent fuel that utilize natural ventilation in the prior art.

[0005] This invention provides a dry storage facility for spent fuel, comprising:

[0006] The air intake shaft has an air inlet at the top suitable for introducing natural ventilation; The bottom air chamber is connected to the bottom end of the air intake shaft; The storage chamber is located above the bottom air chamber; Multiple well shafts are arranged vertically within the storage chamber; A heating element is spaced out and sleeved inside the wellbore, forming an annular gap between the wellbore and the heating element; the heating element contains spent fuel. The top air chamber is located above the storage chamber; the bottom air chamber communicates with the top air chamber through the annular gap; The exhaust shaft is connected at its bottom to the top air chamber, and its top is equipped with an air outlet suitable for discharging natural ventilation. Beneficial effects: This application adopts the above technical solution, where air for natural ventilation enters the intake shaft through the air inlet, then enters the bottom air chamber, and then flows into the annular gap between the shaft and the heating element. It flows upward along each annular gap, into the top air chamber, and then exits through the exhaust shaft and air outlet. This optimizes the internal airflow path. The storage chamber enhances ventilation efficiency and heat exchange performance through a combination of heat conduction, convection, and radiation heat transfer, removing the decay heat of spent fuel from the heating element and ensuring the safety and stability of the dry-process spent fuel storage facility.

[0007] Optionally, multiple staggered baffles are provided on the upper part of the inner circumference of the air intake shaft to form a labyrinth structure for natural ventilation. Beneficial effects: This application adopts the above technical solution to realistically reflect the fluid movement inside the air intake shaft, thereby providing a more reliable basis for thermal calculations and enabling a more detailed study of the airflow path.

[0008] Optionally, the exhaust shaft has a structure that gradually narrows from bottom to top. Beneficial effects: This application adopts the above technical solution, which accelerates airflow; the high-speed airflow carries away more heat, improving heat transfer efficiency and resulting in better cooling.

[0009] Optionally, multiple heating elements can be vertically stacked within each well casing. Beneficial effect: This application utilizes the above technical solution to optimize space utilization.

[0010] Optionally, the inclination angle of the baffle ranges from 30° to 90°; the annular gap ranges from 59 mm to 184 mm. Beneficial effects: By adopting the above technical solution, the annular gap increases the airflow velocity through this area, generating higher turbulence and effectively removing heat from the surface of the heating element.

[0011] Optionally, the baffle has an inclination angle of 45°; the annular gap is 59 mm. Beneficial effects: This application employs the above technical solution to achieve the fastest airflow speed and the best cooling effect.

[0012] Optionally, the height of the exhaust shaft is not less than 50 meters; the number of exhaust shafts ranges from 2 to 5.

[0013] Optionally, the height of the air intake shaft is 11.8 meters, the height of the exhaust shaft is not less than 70 meters, and the number of exhaust shafts is 4. Beneficial effects: This application adopts the above technical solution to ensure smooth airflow, enhance the suction force of the airflow and the driving force of natural convection, thereby strengthening the air cooling effect; at the same time, it makes the air more evenly distributed, reduces local temperature differences, and improves the overall cooling effect.

[0014] Optionally, the heating element is a glass body.

[0015] Optionally, the exterior of the spent fuel dry storage facility is constructed of concrete. Beneficial effects: By adopting the above-mentioned technical solution, the spent fuel dry storage facility possesses excellent radiation protection performance. Attached Figure Description

[0016] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0017] Figure 1 This is a schematic cross-sectional view of the dry storage tank for spent fuel provided in an embodiment of the present invention. Figure 1 ; Figure 2 This is a schematic cross-sectional view of the dry storage tank for spent fuel provided in an embodiment of the present invention. Figure 2 .

[0018] Explanation of reference numerals in the attached figures: 1. Air inlet; 2. Baffle; 3. Air inlet shaft; 4. Bottom air chamber; 5. First steel plate; 6. Storage chamber; 7. Shaft; 8. Heating element; 9. Second steel plate; 10. Top air chamber; 11. Exhaust shaft; 12. Air outlet. Detailed Implementation

[0019] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0020] like Figures 1 to 2 A specific embodiment of the dry-process spent fuel storage facility shown includes: an intake shaft 3, a bottom air chamber 4, a storage chamber 6, multiple shafts 7, a heating element 8, a top air chamber 10, and an exhaust shaft 11. The dry-process spent fuel storage facility described in this application is located in a nuclear power plant and is used for the temporary storage of spent fuel and for ventilation and heat exchange. The exhaust shaft 11 is also known as an exhaust chimney.

[0021] like Figure 1 As shown, the top of the air intake shaft 3 is provided with an air inlet 1 suitable for introducing natural ventilation. There can be five air intake shafts 3 arranged side-by-side at intervals. The bottom air chamber 4 is connected to the bottom end of the air intake shaft 3. The storage chamber 6 is located above the bottom air chamber 4. Figure 1 and Figure 2As shown, multiple shafts 7 are vertically distributed within the storage chamber 6. A first steel plate 5 is located at the lower end of the storage chamber 6, and a second steel plate 9 is located at the upper end of the storage chamber 6; both the first steel plate 5 and the second steel plate 9 are horizontally arranged. Multiple corresponding circular holes are provided on the first steel plate 5 and the second steel plate 9, and the shafts 7 are installed into these circular holes. The shafts 7 can be arranged in a seven-row, eighteen-column configuration. Heating elements 8 are spaced within the shafts 7, forming an annular gap between the shafts 7 and the heating elements 8; specifically, the annular gap ranges from 59 mm to 184 mm. Preferably, the annular gap is 59 mm. The heating elements 8 contain spent fuel. The top ventilation chamber 10 is located above the storage chamber 6; the bottom ventilation chamber 4 communicates with the top ventilation chamber 10 through the annular gap. The bottom of the exhaust shaft 11 communicates with the top ventilation chamber 10, and the top of the exhaust shaft 11 is provided with an air outlet 12 suitable for discharging natural ventilation. Specifically, the outer diameter of the heating element 8 is 430 mm; the outer diameter of the shaft 7 is 658 mm and the wall thickness is 5 mm; the height of the exhaust shaft 11 is 60 meters.

[0022] The size of the annular gap affects airflow velocity and turbulence. Reducing the annular gap increases airflow velocity, induces higher turbulence, and more effectively removes heat from the surface of the heating element 8, thus significantly improving the overall cooling effect. The annular gap was changed from 109 mm to 59 mm, 84 mm, 159 mm, or 184 mm. The results show that when the annular gap is reduced from 109 mm to 59 mm, the maximum temperature of the concrete outer surface decreases by 8℃, and the average airflow velocity at the air inlet decreases by 0.06 m / s; when the annular gap is reduced to 84 mm, the maximum temperature of the concrete outer surface decreases by 4.4℃, and the average airflow velocity at the air inlet decreases by 0.02 m / s; when the annular gap is increased to 159 mm, the maximum temperature of the concrete outer surface increases by 2.7℃, and the average airflow velocity at the air inlet decreases by 0.03 m / s; when the annular gap is increased to 184 mm, the maximum temperature of the concrete outer surface increases by 4.9℃, and the average airflow velocity at the air inlet decreases by 0.01 m / s. Therefore, reducing the annular gap enhances the cooling effect of the air. Because a smaller annular gap leads to an increase in airflow velocity through the area, and a narrow annular gap is more likely to cause increased airflow turbulence, it can more effectively remove heat from the surface of the heat source 8 and improve the overall cooling effect.

[0023] Different ventilation methods affect the efficiency of heat transfer. Compared to external ventilation of shaft 7, internal ventilation of shaft 7, where air enters through the intake shaft 3, flows through the bottom air chamber 4, passes through the annular gap between shaft 7 and the heating element 8 to reach the top air chamber 10, and finally exits through the exhaust shaft 11, allows for more direct heat exchange with the heating element 8, providing a better cooling effect. When the ventilation method is changed from external ventilation of shaft 7 to internal ventilation of shaft 7, the maximum temperature of the concrete outer surface decreases by 33.1℃, and the average inlet velocity of the intake shaft 3 increases from 0.92m / s to 0.94m / s.

[0024] To optimize the ventilation method, the effects of ventilation inside and outside the shaft 7 on temperature distribution were compared. In external ventilation, air enters through the intake shaft 3, directly exchanges heat with the shaft 7, and is finally discharged through the exhaust shaft 11 to remove residual heat. The results show that the cooling effect of internal ventilation is significantly better than external ventilation. When the ventilation method is changed from external to internal, the maximum temperature of the concrete outer surface decreases by 33.1℃, and the average air inlet velocity increases by 0.02 m / s. Under external ventilation, the heat exchange between the heating element 8 and the shaft 7 wall is poor due to conduction and radiation; the airflow also undergoes convective heat exchange with the shaft 7 wall, resulting in poor heat removal capacity.

[0025] Furthermore, such as Figure 1 As shown, multiple staggered baffles 2 are provided on the upper part of the inner circumference of the air intake shaft 3 to form a labyrinth structure for natural ventilation. Specifically, the inclination angle of the baffles 2 ranges from 30° to 90°; preferably, the inclination angle of the baffles 2 is 45°. Setting the inclination angle of the baffles 2 in the air intake shaft 3 to 45° achieves the fastest airflow speed and the best cooling effect.

[0026] Different inclination angles of baffle 2 result in different pressure drops and resistance losses, affecting the cooling performance of the entire spent fuel dry storage facility. When the inclination angle of baffle 2 is adjusted from 90° to 45°, the maximum temperature of the concrete outer surface decreases by 6.4°C, and the average flow velocity at the inlet of the air intake shaft 3 increases from 0.94 m / s to 1.04 m / s.

[0027] To investigate the effect of the tilt angle of baffle 2 on ventilation and heat transfer, the tilt angle of baffle 2 was changed from 90° to 30°, 45°, or 60°. The results show that when the tilt angle of baffle 2 is changed from 90° to 30°, the maximum temperature of the concrete outer surface decreases by 4.3°C, and the average air velocity at the air inlet increases by 0.04 m / s; when the tilt angle of baffle 2 is changed from 90° to 45°, the maximum temperature of the concrete outer surface decreases by 6.4°C, and the average air velocity at the air inlet increases by 0.1 m / s; when the tilt angle of baffle 2 is changed from 90° to 60°, the maximum temperature of the concrete outer surface decreases by 6.2°C, and the average air velocity at the air inlet increases by 0.09 m / s. Therefore, it can be concluded that when the tilt angle of baffle 2 is 45°, the air velocity is the fastest, and the cooling effect of the airflow is the best. Different tilt angles lead to different pressure drops and resistance losses, affecting the overall cooling effect.

[0028] Furthermore, the exhaust shaft 11 has a structure that gradually narrows from bottom to top.

[0029] Different shapes of exhaust shafts 11 affect airflow velocity and turbulence characteristics. Using exhaust shafts 11 that taper from bottom to top, compared to square or circular shafts, can accelerate airflow, remove more heat, and improve heat transfer efficiency and cooling effect. When the exhaust shaft 11 is changed from a circular shaft to a structure that tapers from bottom to top, the maximum temperature of the concrete outer surface decreases by 0.9℃, and the average inlet velocity of the intake shaft 3 increases from 0.93m / s to 0.95m / s.

[0030] To investigate the influence of the shape of the exhaust shaft 11 on ventilation and heat exchange, the shape of the exhaust shaft 11 was changed from square to circular or a gradually tapering structure from bottom to top. When the exhaust shaft 11 was changed from square to circular, the inner diameter of the circular shaft was calculated while keeping the cross-sectional area of ​​the exhaust shaft 11 outlet constant. When the exhaust shaft 11 was changed from square to a gradually tapering structure from bottom to top, the cross-sectional area of ​​the bottom of the exhaust shaft 11 was kept constant. The results show that when the shape of the exhaust shaft 11 changed from square to circular, the highest temperature of the concrete outer surface decreased by 1.7℃, and the average air velocity at the air inlet decreased by 0.04 m / s. When the shape of the exhaust shaft 11 changed to a gradually tapering structure from bottom to top, the highest temperature of the concrete outer surface decreased by 2℃, and the average air velocity at the air inlet increased by 0.01 m / s. Therefore, the exhaust shaft 11 with a gradually tapering structure from bottom to top has better ventilation performance. When the exhaust shaft 11 has a structure that gradually narrows from bottom to top, the airflow through the narrowed channel accelerates the airflow, and the high-speed airflow carries away more heat, improving heat transfer efficiency and resulting in better cooling.

[0031] Furthermore, multiple heating elements 8 are vertically stacked within each well shaft 7. Specifically, seven heating elements 8 can be vertically stacked within each well shaft 7.

[0032] Specifically, the height of the exhaust shaft 11 is not less than 50 meters; the number of exhaust shafts 11 ranges from 2 to 5.

[0033] The height of the exhaust shaft 11 directly affects the suction force of the airflow and the driving force of natural convection. Increasing the height of the exhaust shaft 11 can significantly enhance the cooling effect of the airflow. Studies have shown that when the height of the exhaust shaft 11 increases from 50 meters to 90 meters, the maximum temperature of the concrete outer surface decreases by 8.5℃, and the average inlet velocity of the intake shaft 3 increases from 0.88 m / s to 1.06 m / s.

[0034] To investigate the effect of the height of the exhaust shaft 11 on ventilation and heat exchange, the height of the exhaust shaft 11 was changed from 60 meters to 50 meters, 70 meters, or 90 meters. The results show that when the height of the exhaust shaft 11 decreases by 10 meters, the maximum temperature of the concrete outer surface increases by 0.4℃, and the average air inlet velocity decreases by 0.06 m / s; when the height of the exhaust shaft 11 increases by 10 meters, the maximum temperature of the concrete outer surface decreases by 3.9℃, and the average air inlet velocity increases by 0.07 m / s; when the height of the exhaust shaft 11 increases by 30 meters, the maximum temperature of the concrete outer surface decreases by up to 8.1℃, and the average air inlet velocity increases by 1.02 m / s. Therefore, the higher the height of the exhaust shaft 11, the better the airflow cooling effect. This is because as the height of the exhaust shaft 11 increases, the draft increases, the driving force of natural convection increases, and the cooling effect of the air is enhanced.

[0035] The number of exhaust shafts 11 affects the airflow flux and uniformity. Appropriately increasing the number of exhaust shafts 11 can make the air more evenly distributed in the spent fuel dry storage tank, reduce local temperature differences, and thus improve the overall cooling effect. When the number of exhaust shafts 11 is increased from 2 to 4, the highest temperature of the concrete outer surface decreases by 7.8℃, and the average inlet velocity of the air intake shaft 3 increases from 0.84m / s to 0.9m / s.

[0036] Based on the heat load and space constraints, the size of the air intake shaft 3 is appropriately increased to reduce airflow resistance, create a more uniform flow pattern, and improve air intake velocity and volume. Keeping the inlet cross-sectional area and wall thickness of the air intake shaft 3 constant, when the width of the air intake shaft 3 is increased by 1000 mm, the study results show that the maximum temperature of the concrete outer surface decreases by 7.8℃, and the average inlet velocity of the air intake shaft 3 increases from 0.94 m / s to 1.06 m / s. Increasing the size of the air intake shaft 3 reduces airflow resistance, creates a more uniform flow pattern, improves air intake velocity and volume, thereby accelerating the supply of cold air and enhancing the cooling effect.

[0037] To investigate the effect of the dimensions of the air intake shaft 3 on temperature distribution, the shaft was reduced by 500 mm, increased by 500 mm, or increased by 1000 mm along its width. The results show that when the width of the air intake shaft 3 is reduced by 500 mm, the highest temperature on the outer surface of the concrete increases by 0.8℃, and the average air velocity at the inlet decreases by 0.03 m / s. When the width of the air intake shaft 3 is increased by 500 mm, the highest temperature on the outer surface of the concrete decreases by 5.8℃, and the average air velocity at the inlet increases by 0.06 m / s. When the width of the air intake shaft 3 is increased by 1000 mm, the highest temperature on the outer surface of the concrete decreases by 7.8℃, and the average air velocity at the inlet increases by 0.12 m / s. Therefore, as the size of the air intake shaft 3 increases, the inlet air velocity increases, and the air cooling effect gradually strengthens. This is because increasing the size of the air intake shaft 3 reduces airflow resistance, and the same pressure difference can drive more airflow, thereby increasing the intake velocity and air volume, and accelerating the supply of cold air.

[0038] Preferably, the height of the air intake shaft 3 is 11.8 meters, the height of the exhaust shaft 11 is not less than 70 meters, and the number of exhaust shafts 11 is 4.

[0039] To investigate the effect of the number of exhaust shafts 11 on ventilation and heat exchange, the number of exhaust shafts 11 was changed from 3 to 2, 4, or 5. The results show that when the number of exhaust shafts 11 decreases by 1, the maximum temperature of the concrete outer surface increases by 0.9℃, and the average air inlet velocity decreases by 0.1 m / s; when the number of exhaust shafts 11 increases by 1, the maximum temperature of the concrete outer surface decreases by 6.9℃, and the average air inlet velocity decreases by 0.04 m / s; when the number of exhaust shafts 11 increases by 2, the maximum temperature of the concrete outer surface decreases by 4℃, and the average air inlet velocity increases by 0.04 m / s. Therefore, increasing the number of exhaust shafts 11 enhances the cooling effect of the air. With an increase in the number of exhaust shafts 11, the airflow flux increases, the air distribution becomes more uniform, and local temperature differences are reduced, thus enhancing the overall cooling effect. However, when the number of exhaust shafts 11 increases to 5, the air cooling effect is not significantly enhanced compared to 4 exhaust shafts 11. Therefore, 4 exhaust shafts 11 is the optimal number.

[0040] Specifically, the heating element 8 is a glass body.

[0041] Specifically, the exterior of the spent fuel dry storage facility is constructed of concrete. The walls surrounding the air intake shaft 3, bottom air chamber 4, storage chamber 6, and top air chamber 10 are all concrete structures. The concrete structure is made of high-strength concrete.

[0042] Although embodiments of the invention have been described in conjunction with the accompanying drawings, those skilled in the art can make various modifications and variations without departing from the spirit and scope of the invention, and such modifications and variations all fall within the scope defined by this application.

Claims

1. A dry storage facility for spent fuel, characterized in that, include: The air intake shaft (3) has an air inlet (1) at the top suitable for introducing natural ventilation. The bottom air chamber (4) is connected to the bottom end of the air intake shaft (3); The storage chamber (6) is located above the bottom air chamber (4); Multiple well shafts (7) are arranged vertically within the storage chamber (6); A heating element (8) is spaced inside the well casing (7), forming an annular gap between the well casing (7) and the heating element (8); the heating element (8) contains spent fuel. The top air chamber (10) is located above the storage chamber (6); the bottom air chamber (4) is connected to the top air chamber (10) through the annular gap; The exhaust shaft (11) is connected at the bottom to the top ventilation chamber (10), and the top of the exhaust shaft (11) is provided with an air outlet (12) suitable for discharging natural ventilation.

2. The spent fuel dry storage facility according to claim 1, characterized in that, Multiple baffles (2) are provided at intervals on the upper part of the inner circumference of the air intake shaft (3) to form a labyrinth structure for natural ventilation.

3. The spent fuel dry storage facility according to claim 1, characterized in that, The exhaust shaft (11) has a structure that gradually narrows from bottom to top.

4. The spent fuel dry storage facility according to claim 1, characterized in that, Multiple heating elements (8) are stacked vertically inside each well shaft (7).

5. The spent fuel dry storage facility according to claim 2, characterized in that, The inclination angle of the baffle (2) ranges from 30° to 90°; the range of the annular gap is from 59 mm to 184 mm.

6. The spent fuel dry storage facility according to claim 5, characterized in that, The baffle (2) has an inclination angle of 45°; the annular gap is 59 mm.

7. The spent fuel dry storage facility according to any one of claims 1-6, characterized in that, The height of the exhaust shaft (11) is not less than 50 meters; the number of exhaust shafts (11) ranges from 2 to 5.

8. The spent fuel dry storage facility according to claim 7, characterized in that, The height of the air intake shaft (3) is 11.8 meters, the height of the exhaust shaft (11) is not less than 70 meters, and the number of exhaust shafts (11) is 4.

9. The spent fuel dry storage facility according to any one of claims 1-6, characterized in that, The heating element (8) is a glass body.

10. The spent fuel dry storage facility according to any one of claims 1-6, characterized in that, The exterior of the spent fuel dry storage facility is constructed of concrete.

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