A personnel-accessible fuel transfer tunnel shield structure

Abstract

The application discloses a shielding structure of a fuel transfer channel which can be accessed by personnel. The shielding structure is arranged around the fuel transfer channel. The shielding structure comprises a first shielding body and a second shielding body. The first shielding body and the second shielding body make the shielding structure comprise a first space and a second space. The fuel transfer channel is located in the first space. Two or more personnel channels are arranged on the shielding structure. At least one personnel channel connects the first space and the second space. At least one personnel channel connects the second space and the outside of the shielding structure. The personnel channels are staggered. The shielding structure is provided with multiple shielding bodies around the fuel transfer channel. The high-energy and high-intensity rays emitted by the spent fuel can be reduced to reach the acceptable range of the radiation protection design. Meanwhile, multiple personnel channels are provided. The engineering personnel can enter the fuel transfer channel to perform operation, maintenance and repair tasks under normal operation and specific abnormal working conditions, so that the operation efficiency of the nuclear power plant is improved.

Description

Technical Field

[0001] This invention belongs to the field of nuclear power plant radiation shielding technology, specifically relating to a shielding structure for a fuel transfer channel that is accessible to personnel. Background Technology

[0002] The fuel transfer channel is a passageway structure connecting the reactor refueling pool and the spent fuel storage pool in the fuel building. It mainly consists of a fuel transfer pipe and a shielded fuel transfer channel. The two ends of the fuel transfer pipe are connected to the reactor refueling pool and the spent fuel storage pool, respectively. It is mainly used for the equipment layout and operation of the fuel loading, unloading, transportation, and storage system.

[0003] Spent fuel assemblies are the most powerful source of radiation after a nuclear power plant is shut down (their surface dose rate can reach 10). 3 -10 4 Compared to second-generation nuclear power plants, the radioactivity levels of spent fuel assemblies in third-generation reactors (Gy / h), modular small modular reactors, and advanced reactor types increase significantly with burnup. The structures used for their transport and storage are key areas of concern for nuclear radiation safety. To improve overall nuclear safety, all reactor types have incorporated enhanced seismic resistance requirements into their engineering designs, which greatly increases the engineering challenges of fuel transport routes.

[0004] Because third-generation light water reactors and advanced reactor nuclear power plants have improved the ultimate earthquake safety (the peak earthquake acceleration is not less than 0.3g), a certain distance of seismic expansion joints is required between the shielding bodies of fuel transfer channels in different buildings. At the same time, in order to ensure the safety of fuel transfer channels throughout their service life, professional technicians need to enter the fuel transfer channels to carry out maintenance and repair tasks under normal operating conditions and specific abnormal conditions.

[0005] An investigation revealed that the shielding design of fuel transfer channels in domestically operating Generation II and Generation II Plus nuclear power plants has failed to provide effective radiation protection, resulting in excessive radiation doses to personnel operating nearby during reactor shutdowns and refueling. Furthermore, the lead brick shielding support structure installed outside the seismic expansion joints of these fuel transfer channels hinders personnel access for maintenance and operations.

[0006] Currently, the shielding design for fuel transfer channels in third-generation nuclear power units under construction internationally employs a method of filling seismic expansion joints with 2-inch-thick, approximately 5-cm-thick air bladders. These air bladders are made of high-molecular-weight polyethylene fiber material, filled with demineralized water to form a "water bladder," and positioned on the upper and left / right sides of the transfer channel. This design, however, is costly due to the special material "water bladder," has complex fixing and installation methods, is inconvenient for maintenance and replacement, and poses certain potential risks during earthquakes. Furthermore, this design has not yet been tested in engineering practice, and its maturity and reliability remain to be verified.

[0007] The EPR nuclear power plant's third-generation nuclear power unit, designed by France, employs a shielding design for the fuel transfer passage using walls and additional lead shielding outside the seismic expansion joint between the outer containment structure and the fuel building. This design places the walls on the ground, making them susceptible to natural and man-made damage. The additional lead shielding is expensive, complex to fix and install, inconvenient for inspection and maintenance, and may compromise the seismic performance of the fuel transfer passage shielding, potentially threatening its integrity during earthquakes.

[0008] Existing patent CN108417285A discloses a multi-maze-type fuel transfer channel shielding structure, which includes several shielding bodies installed on the outer walls of the containment vessel and fuel plant and surrounding the fuel transfer pipe. The shielding bodies are nested together to form a seismic expansion joint in the maze structure. This shielding device can be used to provide radiation shielding for the fuel transfer pipe that passes through the gap between the containment vessel and the outer wall of the fuel plant, and the shielding structure is relatively simple.

[0009] Existing patent CN106531266A discloses a shielding device for a spent fuel transfer channel, which is installed on a fuel transfer channel between two adjacent buildings. The shielding device includes a shielding body with a U-shaped structure. An expansion joint is provided on the shielding body, and both the inner and outer sides of the expansion joint are sealed with baffles, forming a cavity between the expansion joint and the shielding body. This cavity is filled with granular shielding material. This shielding device has low inspection and maintenance costs, simplifies the design of the expansion joint, and simultaneously accommodates relative movement between adjacent buildings.

[0010] The two patents mentioned above mainly improved the shielding effect and seismic performance of the shielding body, but did not solve the problems of low maintenance requirements and low personnel accessibility of equipment in the area near the fuel transfer channel during spent fuel transfer.

[0011] In view of the above technical problems, this invention is proposed. Summary of the Invention

[0012] The main purpose of this application is to propose a solution to the problem of low maintenance requirements and low personnel accessibility of equipment in the vicinity of fuel transfer channels during spent fuel transfer. At the same time, it proposes a new shielding structure to effectively reduce the high-energy and high-intensity radiation emitted by spent fuel and improve seismic performance.

[0013] To achieve the above objectives, this application proposes a personnel-accessible fuel transfer channel shielding structure. The shielding structure is arranged around the fuel transfer channel and includes a first-level shield and a second-level shield. The first-level shield and the second-level shield make the shielding structure include a first space and a second space. The fuel transfer channel is located in the first space. Two or more personnel channels are provided on the shielding structure. At least one personnel channel connects the first space and the second space, and at least one personnel channel connects the second space and the outside of the shielding structure. The personnel channels are arranged alternately.

[0014] Optionally, the personnel passage includes a first personnel passage and a second personnel passage. The first personnel passage is located within the first-level shield and connects the first space and the second space. The second personnel passage is located within the second-level shield and connects the second space and the outside of the shielding structure. The first personnel passage and the second personnel passage satisfy the following relationship:

[0015] D 12 ≥Max(L1,L2)

[0016] Where L1 is the diameter of the first personnel passage or the diameter of its inscribed circle, L2 is the diameter of the second personnel passage or the diameter of its inscribed circle, and D 12 This is the distance between the axes of the first and second personnel passages.

[0017] Optionally, the first personnel passage and the second personnel passage satisfy the following relationship:

[0018] D 12 ≥2×Max(L1,L2)

[0019] Optionally, the axes of the first and second personnel passages are parallel to each other.

[0020] Optionally, the personnel passage includes a third personnel passage and a fourth personnel passage. The third personnel passage connects the first space and the second space, and the fourth personnel passage connects the second space and the outside of the shielding structure. The axes of the third personnel passage and the fourth personnel passage are perpendicular to each other.

[0021] Optionally, the first and second personnel passages are manholes.

[0022] Optionally, the third personnel passage is a manhole, and the fourth personnel passage is a doorway.

[0023] Optionally, the diameter of the manhole or the diameter of the inscribed circle of the manhole shall not be less than 500 mm.

[0024] Optionally, the width of the doorway shall not be less than 500mm and the height of the doorway shall not be less than 1500mm.

[0025] Optionally, the personnel passage has a covering structure, the overlap gap between the covering structure and the first-level shield or the second-level shield is less than 10mm, and the overlap width between the covering structure and the first-level shield or the second-level shield is not less than 50mm.

[0026] Optionally, the manhole cover structure is a cover plate. The cover plate installed on the first-level shield has a thickness of 3mm-200mm and a load-bearing capacity of not less than 100kg; the cover plate installed on the second-level shield has a thickness of 10mm-500mm and a load-bearing capacity of not less than 1000kg.

[0027] Optionally, the doorway can be covered by a shielded door.

[0028] Optionally, the first-level shielding includes an upper shielding, a lower shielding, a left shielding, and a right shielding. The interior formed by the upper shielding, lower shielding, left shielding, and right shielding forms at least a part of the first space. The interior formed by the upper shielding, left shielding, right shielding, and second-level shielding forms at least a part of the second space. The width of the first space and the second space are not less than 1m, the length is not less than 1m, and the height is not less than 1.5m.

[0029] Optionally, the first-level shield and the second-level shield are located between the building structure and on both sides of the containment. Seismic expansion joints are provided between the first-level shield and the containment, and between the second-level shield and the containment. The width of the seismic expansion joints is 10mm-500mm.

[0030] Optionally, at least some of the seismic expansion joints are provided with shielding blocks. The shielding blocks are located at one end of the seismic expansion joint on the first-level shield near the transfer channel. The shielding blocks are installed on the containment structure and have a length of 50mm-300mm in the direction perpendicular to the containment structure.

[0031] Based on the above technical solution, the present invention has at least the following beneficial effects:

[0032] 1. This invention proposes to set up multi-level shielding in the material transfer channel. Through the combined effect of multiple shielding mechanisms, the high-energy and high-intensity radiation emitted by spent fuel is reduced to meet the radiation protection design requirements of third-generation and advanced nuclear power plants, and to provide effective radiation safety protection for personnel and equipment.

[0033] 2. This invention proposes setting up multiple personnel passages on the shielding structure, enabling engineering personnel to enter the fuel transfer passage for operation, maintenance and repair tasks during normal operation and specific abnormal conditions. This solves the problem of low operation and maintenance needs and low personnel accessibility of equipment near the fuel transfer passage during spent fuel transfer, and improves the operating efficiency of nuclear power plants.

[0034] 3. The shielding structure proposed in this invention does not require the addition of other high-cost shielding devices and materials, such as lead brick shielding and supporting steel frames. The project cost is low, it is easy to implement, can shorten the construction time, reduce the construction burden, and has a relatively certain maturity. At the same time, it can avoid the safety risks caused by the failure, malfunction and damage of such devices.

[0035] 4. The shielding structure proposed in this invention uses a relatively simple seismic expansion joint without adding other installation components and fixing structures, thereby avoiding interference from such factors, making full use of its seismic mechanism, giving full play to its seismic effect, and making its seismic resistance stronger. Attached Figure Description

[0036] The accompanying drawings, which form part of this specification, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings:

[0037] Figure 1 This is a schematic diagram of a personnel-accessible fuel transfer channel shielding structure according to a specific embodiment of this application;

[0038] Figure 2 yes Figure 1 Sectional view along axis AA;

[0039] Figure 3 yes Figure 1 BB-direction sectional view;

[0040] The above figures include the following reference numerals:

[0041] 1. First-level shielding; 12. Upper shielding; 13. Lower shielding;

[0042] 14. Left-side shielding; 15. Right-side shielding; 2. Second-level shielding; 3. First-level space;

[0043] 4. Second space; 5. Fuel transfer channel; 61. First personnel channel;

[0044] 62. Second personnel passage; 63. Third personnel passage; 64. Fourth personnel passage;

[0045] 71. First personnel passage cover; 72. Second personnel passage cover;

[0046] 73. Third personnel access cover plate; 8. Shielding door; 91. Internal structure walls of reactor building;

[0047] 92. Containment building; 93. Outer containment building or fuel building and its structural walls;

[0048] 10. Seismic expansion joints; 11. Shielding blocks. Detailed Implementation

[0049] It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other. The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0050] The present invention will be further described in detail below with reference to specific embodiments, which should not be construed as limiting the scope of protection claimed by the present invention.

[0051] In this description, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of these terms in this invention based on the specific circumstances. Furthermore, in the description of this invention, unless otherwise stated, "a plurality of" means two or more.

[0052] Example

[0053] Due to the extremely high radioactivity of spent fuel assemblies, the transfer process significantly impacts the area near the transfer corridor, restricting equipment inspection, maintenance, replacement, and the flow of personnel and materials. Workers also suffer substantial radiation doses. Furthermore, considering the insufficient radiation protection and shielding capabilities of existing second-generation nuclear power plant fuel transfer corridor shielding designs and the high engineering costs of third-generation nuclear power plant fuel transfer corridor shielding designs, a redesign of the fuel transfer corridor's radiation shielding is necessary. This redesign must meet the operational and maintenance needs of personnel entering the corridor for necessary operation, maintenance, and inspection under normal operating conditions and specific abnormal conditions, while simultaneously saving investment under high seismic resistance requirements, thereby improving the economic efficiency and safety of the nuclear power plant.

[0054] To achieve the above objectives, the present invention proposes a shielded structure for a fuel transfer channel that is accessible to personnel.

[0055] Figure 1The figure illustrates a fuel transfer channel shielding structure according to an embodiment of this application. As shown, the shielding structure surrounds the fuel transfer channel and is used to provide radiation shielding for fuel assemblies that penetrate the fuel transfer channel from the containment building to the outer wall of the fuel building. The shielding structure includes a reactor building interior wall 91, a containment building 92, an outer containment building or fuel building and its interior wall 93, and a first-level shield 1 and a second-level shield 2 surrounding the fuel transfer channel. The first-level shield 1 and the second-level shield 2 enable the shielding structure to include a first space 3 and a second space 4, with the fuel transfer channel 5 located in the first space 3. Based on the building layout and personnel / material flow requirements, this embodiment includes four personnel passages, combined with… Figures 1 to 3 As can be seen, the first personnel passage 61 and the third personnel passage 63 connect the first space 3 and the second space 4, and the second personnel passage 62 and the fourth personnel passage 64 connect the second space 4 and the outside of the shielding structure. This personnel passage design makes it convenient for engineers to enter the second space 4 from the outside of the shielding structure and enter the first space 3 from the second space 4 for maintenance and other work. At the same time, the personnel passages on the shielding structure are staggered, and the axes of the passages are offset from each other to increase the penetration distance of the rays and reduce the radiation intensity.

[0056] like Figure 2 The AA cross-sectional view shown indicates that the first-level shield 1 includes an upper shield 12, a lower shield 13, a left shield 14, and a right shield 15. The internal space formed by the upper shield 12, lower shield 13, left shield 14, and right shield 15 constitutes at least a portion of the first space 3. The internal space formed by the upper shield 12, left shield 14, right shield 15, and second-level shield 2 constitutes at least a portion of the second space 4. The width of the first space 3 and the second space 4 are not less than 1m, the length is not less than 1m, and the height is not less than 1.5m.

[0057] Based on the above description, it can be seen that the reactor building interior walls 91, containment vessel 92, outer containment vessel or fuel building and its interior walls 93, upper first-level shield 12, lower first-level shield 13, left first-level shield 14, right first-level shield 15, and second-level shield 2 together constitute a three-dimensional labyrinthine fuel transfer channel shielding structure. By utilizing the labyrinth formed to increase the spatial volume, the radiation intensity per unit volume can be reduced, and the radiation penetration distance can be increased to reduce the radiation level, ensuring that the radiation level at all points outside the fuel transfer channel meets the radiation protection requirements.

[0058] The shielding body is made of one or more of the following materials, including but not limited to ordinary concrete, biological shielding heavy concrete, radiation-proof concrete, hematite concrete, limonite concrete, barite concrete, serpentine concrete, carbon steel, stainless steel, alloy steel, other alloys, or other metals. The ordinary concrete used has a mass density of 1500 kg / m³. 3 -2500kg / m 3 The biological shielding heavy concrete, radiation-proof concrete, hematite concrete, limonite concrete, barite concrete, and serpentine concrete used have a mass density of 2500 kg / m³. 3 -6500kg / m 3 .

[0059] Meanwhile, in order to achieve better shielding effect and reduce radiation intensity, this application provides a reference range for the thickness of the shielding structure.

[0060] Combination Figure 1 Based on the shielding structure shown, the thickness of the reactor building interior wall 91 between the upper shield 12 and the lower shield 13 of the first-level shield is approximately 500mm-1500mm; the thickness of the reactor building interior wall 91 between the upper shield 12 and the second shield 2 is approximately 300mm-1300mm.

[0061] Furthermore, this application provides corresponding thickness reference values ​​for the containment vessel 92 made of different materials. Specifically, when the containment vessel 92 is made of one or more of the following metal materials: carbon steel, stainless steel, alloy steel, etc., its thickness reference range is 5mm-150mm; when the containment vessel 92 is made of one or more of the following materials: concrete, biological shielding heavy concrete, radiation shielding concrete, hematite concrete, limonite concrete, barite concrete, serpentine concrete, etc., its thickness reference range is 100mm-1500mm.

[0062] The thickness of the outer containment or fuel building and its structure wall 93 between the upper shield 12 and the lower shield 13 of the first-level shield is 500mm-2000mm; the thickness of the outer containment or fuel building and its structure wall 93 between the upper shield 12 and the second shield 2 is 300mm-2000mm.

[0063] The thickness of the upper shield 12 of the first-level shield has a reference range of 500mm-2000mm, and the thickness of the lower shield 13 of the first-level shield has a reference range of 800mm-2000mm.

[0064] Combination Figure 2From the shielding structure shown, the thickness of the left shield 14 of the first-level shield between the lower shield 13 and the upper shield 12 of the first-level shield is in the range of 800mm-2000mm. The thickness of the left shield 14 of the first-level shield on the left side of the second space 4 between the upper shield 12 and the second shield 2 is in the range of 500mm-1500mm.

[0065] The thickness of the first-level shielding right side shielding body 15 on the right side of the first space 3 between the lower shielding body 13 and the upper shielding body 12 of the first-level shielding has a reference range of 800mm-2000mm, and the thickness of the first-level shielding right side shielding body 15 between the upper shielding body 12 and the second-level shielding body 2 has a reference range of 500mm-1200mm.

[0066] The thickness of the second-level shield 2 is within the reference range of 300mm-1500mm.

[0067] Without considering the penetration of seismic expansion joints, manholes, entrances and exits, etc., the thickness range of the shielding body mentioned above can reduce the radiation rays to the control value range of radiation protection requirements. That is, the dose rate outside the outermost shielding body of fuel transfer channel 5 is 0.0001mSv / h-100mSv / h or 0.0001mGy / h-100mGy / h.

[0068] At the same time, pipes, fixing components, or other devices that could weaken the shielding effect are avoided on each shielding body of the shielding structure.

[0069] To measure the shielding effect of the shielding structure, in this embodiment, various calculation and analysis methods and tools were used to compare and verify the shielding effect of the fuel transfer channel shielding structure proposed in this invention.

[0070] The theoretical estimate of the shielding effect of the fuel transfer channel can be derived using the following empirical formula.

[0071] The empirical formula for the differential albedo of incident gamma rays is given in formula (1):

[0072]

[0073] Where, α i2 C is the gamma-ray albedo. i and C' i These are constants related to the γ energy and the scatterer;

[0074] E0 is the incident energy of the gamma rays; θ0 is the initial incident angle of the gamma rays; φ is the gamma ray fluence rate.

[0075] K(θ s) is the Compton scattering differential section.

[0076] The gamma-ray reflected dose rate can be derived from formula (2):

[0077]

[0078] R1 is the incident dose rate; R1 is the distance from the scattering surface to the measuring point; ΔA is the scattering area.

[0079] Verification has shown that the shielding structure meets the radiation protection design requirements for third-generation nuclear power plants and advanced reactors, and compared with the design scheme of second-generation nuclear power plants, the radiation shielding effect is improved by an order of magnitude. Specifically, the dose rate outside the fuel transfer channel of a second-generation nuclear power plant is 10-1. -1 -10 0 At the mSv / h level, the external dose rate of the fuel transfer channel in this shielding structure is 10. -4 -10 -2 mSv / h level.

[0080] Furthermore, in this embodiment, the first-level shield 1 and the second-level shield 2 are disposed between the building structures and located on both sides of the containment 92, for radiation shielding of the fuel assemblies penetrating the fuel transfer pipe from the containment 92 to the corresponding building structure. Specifically, seismic expansion joints 10 are provided between the first-level shield 1 and the containment 92, and between the second-level shield 2 and the containment 92. The width range of the seismic expansion joints 10 given in this application is 10mm-500mm, which can meet the expansion distance between the reactor building's internal structure walls 91 and the containment 92 under earthquake conditions with a peak seismic acceleration of 0.3g, as well as the expansion distance between the containment 92 and the outer containment or the fuel building and its structural walls 93, achieving good seismic resistance.

[0081] The seismic expansion joint 10 can be filled with lead fiber, iron fiber, steel fiber, flexible shielding material, water bladder, or other liquid medium bladder. The filling rate of the filling material is matched with the width of the seismic expansion joint, and the filling rate is between 10% and 100%. The cross-sectional diameter of the fibrous filling material is between 0.001 mm and 10 mm.

[0082] After the seismic expansion joint 10 is filled with shielding material, to prevent the filling shielding material from falling into the internal space of the fuel transfer channel, shielding blocks 11 are installed on some of the seismic expansion joints 10, such as... Figure 1 As shown, the shielding block 11 is located at one end of the seismic expansion joint 10 on the first-level shield 1, near the transfer channel, and has a length of 50mm-300mm in the direction perpendicular to the containment 92. The material of the shielding block 11 is concrete, carbon steel, stainless steel or other metals.

[0083] exist Figure 2 The cross-sectional view shown reveals two personnel passages in this embodiment: a first personnel passage 61 and a second personnel passage 62. The first personnel passage 61 is located in the first-level shield 1 and connects the first space 3 and the second space 4. The second personnel passage 62 is located in the second-level shield 2 and connects the second space 4 and the outside of the shielding structure. This personnel passage structure facilitates engineering personnel to enter the second space 4 from the outside of the shielding structure through the second personnel passage 62, and enter the first space 3 from the second space 4 through the first personnel passage 61 to complete maintenance and other tasks.

[0084] Specifically, the first personnel passage 61 and the second personnel passage 62 satisfy the following relationship:

[0085] D 12 ≥Max(L1,L2)

[0086] Wherein, L1 is the diameter of the first personnel passage 61 or the diameter of the inscribed circle of the first personnel passage 61, L2 is the diameter of the second personnel passage 62 or the diameter of the inscribed circle of the second personnel passage 62, and D 12 The distance between the axes of the first personnel passage 61 and the second personnel passage 62.

[0087] This can be understood as the relationship between the first personnel passage 61 and the second personnel passage 62 needing to satisfy the following condition: the distance D between the axes of the first personnel passage 61 and the second personnel passage 62. 12 The value must be greater than or equal to the maximum of L1 and L2. In this embodiment, the diameter or inscribed circle diameter of both the first personnel passage 61 and the second personnel passage 62 is not less than 500mm, and the distance D between the axes of the two passages is... 12 Not less than 500mm.

[0088] Furthermore, to increase the radiation penetration distance and reduce the radiation level, the distance between the axes of the first personnel passage 61 and the second personnel passage 62 can be increased. This application also proposes that the first personnel passage 61 and the second personnel passage 62 can satisfy the following relationship:

[0089] D 12 ≥2×Max(L1,L2)

[0090] In this relation, L1, L2, and D 12 The meaning is the same as the above relationship, which can be understood as follows: the relationship between the first personnel passage 61 and the second personnel passage 62 needs to satisfy: the distance D between the axes of the first personnel passage 61 and the second personnel passage 62 12 The distance D between the axes of the two passages must be greater than or equal to twice the maximum value of L1 and L2. If the diameter or inscribed circle diameter of both the first personnel passage 61 and the second personnel passage 62 is not less than 500 mm, then... 12Not less than 1m.

[0091] The axial distances between the first personnel passage 61 and the second personnel passage 62 satisfy the above-mentioned relationship and are also parallel to each other.

[0092] In addition, in this embodiment, the first personnel passage 61 and the second personnel passage 62 are manholes. Specifically, the cross-sectional shape of the manhole can be circular, square, rectangular, regular polygon or regular polygon. To facilitate the entry of engineering personnel, the diameter of the circular manhole is not less than 500mm, and the diameter of the inscribed circle of the square, rectangular, regular polygon or regular polygon manhole is not less than 500mm.

[0093] exist Figure 3 The cross-sectional view shown reveals two additional personnel passages in this embodiment: a third personnel passage 63 and a fourth personnel passage 64. The third personnel passage 63 connects the first space 3 and the second space 4, while the fourth personnel passage 64 connects the second space 4 to the outside of the shielding structure. Engineering personnel can enter the second space 4 from the outside of the shielding structure via the fourth personnel passage 64, and then enter the first space 3 from the second space 4 via the third personnel passage 63 to complete maintenance and other tasks. Furthermore, the axes of the third personnel passage 63 and the fourth personnel passage 64 are perpendicular to each other; this design increases the radiation's travel distance within the space and reduces the radiation level.

[0094] Among them, the third personnel passage 63 is a manhole, and the fourth personnel passage 64 is a doorway.

[0095] Specifically, the requirements for the cross-sectional shape, manhole diameter, or inscribed circle diameter of the third personnel passage 63 are the same as those for the first and second personnel passages, and will not be repeated here. To facilitate the entry and exit of engineering personnel, this application stipulates that the width of the fourth personnel passage 64 is not less than 500mm and the height of the doorway is not less than 1500mm.

[0096] It should be noted that in other embodiments, only the first and second personnel passages may be included, or only the third and fourth personnel passages may be included.

[0097] In addition, to further reduce radiation levels, the personnel passage also has a covering structure. The overlap width between the covering structure and the first-level shield 1 or the second-level shield 2 is less than 10 mm, and the overlap width between the covering structure and the first-level shield 1 or the second-level shield 2 is not less than 50 mm.

[0098] The manhole is covered by a cover plate, which is installed on the first-level shield 1, such as... Figure 2 , Figure 3The overlap gap between the first personnel passage cover plate 71, the third personnel passage cover plate 73 and the first-level shielding body 1 around the passage is less than 10mm, and the overlap width is not less than 50mm.

[0099] The cover plate installed on the second-level shield 2, such as Figure 2 The overlap gap between the cover plate 72 of the second personnel passage and the second-level shield 2 around the passage is less than 10mm, and the overlap width is not less than 50mm.

[0100] The doorway is covered by a shielding door 8. The overlap gap between the shielding door 8 and the left side shielding body 14 of the first level of shielding is less than 10mm and the overlap width is not less than 50mm.

[0101] Specifically, the covering structure is made of lead, carbon steel, stainless steel, other metals, or a combination of materials.

[0102] In addition, to prevent personnel from accidentally falling through manholes, this application proposes a reference range for the thickness of the shielding cover plates and their load-bearing capacity. Specifically, the cover plates installed on the first-level shielding body 1, namely the first personnel passage cover plate 71 and the third personnel passage cover plate 73, have a thickness of 3mm-200mm and a load-bearing capacity of not less than 100kg. The cover plates installed on the second-level shielding body 2, namely the second personnel passage cover plate 72, have a thickness of 10mm-500mm and a load-bearing capacity of not less than 1000kg.

[0103] Meanwhile, to prevent people from accidentally entering or entering the space without permission, the manhole covers and shielding doors are locked under normal circumstances.

[0104] In summary, it can be seen from the above description that the embodiments of the present invention achieve the following technical effects:

[0105] 1. This invention proposes to set up multi-level shielding in the fuel transfer channel, and reduce the high-energy and high-intensity radiation emitted by spent fuel through the combined effect of multiple shielding mechanisms, so as to meet the radiation protection design requirements of third-generation and advanced nuclear power plants. This shielding structure has advanced radiation protection and shielding levels, providing effective radiation safety protection for personnel and equipment.

[0106] 2. This invention proposes to set up multiple personnel passages on the shielding structure, so that engineering personnel can enter the fuel transfer passage to carry out operation, maintenance and repair tasks during normal operation and specific abnormal conditions. This solves the problem of low operation and maintenance needs and low personnel accessibility of equipment in the vicinity of the fuel transfer passage during spent fuel transfer, thereby improving the operating efficiency of nuclear power plants.

[0107] 3. The shielding structure proposed in this invention does not require the addition of other high-cost shielding devices and materials, such as lead brick shielding and supporting steel frames. The project cost is low, it is easy to implement, can shorten the construction time, reduce the construction burden, and has a relatively certain maturity. At the same time, it can avoid the safety risks caused by the failure, malfunction and damage of such devices.

[0108] 4. The shielding structure proposed in this invention uses a relatively simple seismic expansion joint without adding other installation components and fixing structures, thereby avoiding interference from such factors, making full use of its seismic mechanism, giving full play to its seismic effect, and making its seismic resistance stronger.

[0109] The above description is merely a preferred embodiment of the present invention and is not intended to limit the 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 personnel accessible fuel transfer tunnel shield structure, said shield structure disposed about said fuel transfer tunnel, characterized in that, The shielding structure comprises a first shielding body (1) and a second shielding body (2), the first shielding body (1) and the second shielding body (2) make the shielding structure comprise a first space (3) and a second space (4), a fuel transfer channel (5) is located in the first space (3), two or more personnel channels are arranged on the shielding structure, at least one of the personnel channels connects the first space (3) and the second space (4), at least one of the personnel channels connects the second space (4) and the outside of the shielding structure, and the personnel channels are staggered; the personnel channels comprise a first personnel channel (61) and a second personnel channel (62), the first personnel channel (61) is arranged on the first shielding body (1) and connects the first space (3) and the second space (4), the second personnel channel (62) is arranged on the second shielding body (2) and connects the second space (4) and the outside of the shielding structure, and the first personnel channel (61) and the second personnel channel (62) satisfy the following relationship: D 12 ≥Max(L1,L2) wherein L1 is the diameter of the first personnel passage (61) or the diameter of the incircle of the first personnel passage (61), L2 is the diameter of the second personnel passage (62) or the diameter of the incircle of the second personnel passage (62), D 12 is the distance between the axes of the first personnel passage (61) and the second personnel passage (62).

2. The shielding structure of claim 1, wherein The first personnel channel (61) and the second personnel channel (62) satisfy the following relationship: D 12 ≥ 2 x Max(L1, L2).

3. The shielding structure according to any one of claims 1-2, characterized in that, The axes of the first personnel channel (61) and the second personnel channel (62) are parallel to each other.

4. The shielding structure of claim 3, wherein, The personnel channels comprise a third personnel channel (63) and a fourth personnel channel (64), the third personnel channel (63) connects the first space (3) and the second space (4), the fourth personnel channel (64) connects the second space (4) and the outside of the shielding structure, and the axes of the third personnel channel (63) and the fourth personnel channel (64) are perpendicular to each other.

5. The shielding structure of claim 4, wherein, The first personnel channel (61) and the second personnel channel (62) are manholes.

6. The shielding structure of claim 5, wherein, The third personnel channel (63) is a manhole, and the fourth personnel channel (64) is a door opening.

7. The shielding structure according to any of claims 5-6, characterized in that, The diameter of the manhole or the diameter of an inscribed circle of the manhole is not less than 500 mm.

8. The shielding structure of claim 6, wherein, The width of the door opening is not less than 500 mm, and the height of the door opening is not less than 1500 mm.

9. The shielding structure according to any one of claims 5-6, wherein, The personnel channels have a covering structure, the covering structure has a lap joint gap width of less than 10 mm with the first shielding body (1) or the second shielding body (2), and the covering structure has a lap joint width of not less than 50 mm with the first shielding body (1) or the second shielding body (2).

10. The shielding structure according to any one of claims 5-6, wherein, The covering structure of the manhole is a cover plate, the cover plate arranged on the first shielding body (1) has a thickness of 3 mm-200 mm and a bearing weight of not less than 100 kg, and the cover plate arranged on the second shielding body (2) has a thickness of 10 mm-500 mm and a bearing weight of not less than 1000 kg.

11. The shielding structure of claim 6, wherein, The covering structure of the door opening is a shielding door (8).

12. The shielding structure according to any one of claims 5-6, wherein, The first level shielding body (1) comprises an upper shielding body (12), a lower shielding body (13), a left shielding body (14) and a right shielding body (15), the upper shielding body (12), the lower shielding body (13), the left shielding body (14) and the right shielding body (15) surround an interior to form at least a part of the first space (3), the upper shielding body (12), the left shielding body (14), the right shielding body (15) and the second level shielding body (2) surround an interior to form at least a part of the second space (4), the first space (3) and the second space (4) have a width of not less than 1m, a length of not less than 1m and a height of not less than 1.5m.

13. The shielding structure according to any one of claims 1-2, wherein, The first level shielding body (1) and the second level shielding body (2) are arranged between building structures and on both sides of a safety shell (92), an anti-seismic expansion joint (10) is arranged between the first level shielding body (1) and the safety shell (92) and between the second level shielding body (2) and the safety shell (92), the width of the anti-seismic expansion joint (10) is 10mm-500mm.

14. The shielding structure of claim 10, wherein, A shielding block (11) is arranged on at least part of the anti-seismic expansion joint (10), the shielding block (11) is located at one end of the anti-seismic expansion joint (10) on the first level shielding body (1) close to the transfer channel, the shielding block (11) is mounted on the safety shell (92) and has a length of 50mm-300mm in a direction perpendicular to the safety shell (92).

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