Spent fuel post-processing facility through-ground valve structure evaluation method

Abstract

The invention discloses a spent fuel post-processing facility through-ground valve structure evaluation method, which is characterized in that through-ground valve modal analysis is carried out through a finite element analysis method, and an all-parametric modeling-multi-modal analysis-dynamic stress path evaluation integrated method is provided. According to the method, the dynamic coupling response of a plurality of key components is covered, the stress limit value is determined, accurate quantitative evaluation is achieved for high-risk areas such as reducing, welding seams and pressure-bearing interfaces, finally, the finite element calculation result is compared with the stress limit value according to the selected calculation evaluation path, and whether the valve structure meets the requirement or not can be judged. The method can effectively evaluate the structural characteristics of the through-ground valve, and compared with experimental research, numerical simulation greatly reduces the economic cost and shortens the structural evaluation period.

Description

Technical Field

[0001] The present invention relates to the field of nuclear power operation, and in particular to a method for evaluating the structure of a through-ground valve in a spent fuel reprocessing facility. Background Art

[0002] The through-the-ground valves used in spent fuel reprocessing facilities are special valves that operate in environments with certain levels of radioactivity and corrosive conditions. They are installed between two partitions, with a reinforced concrete shield separating the valve body from the actuator. The valve body is located in an area with higher radioactivity and can control the flow of process media. The manual control mechanism for opening the valve is located in an area with lower radioactivity and is used by the operator. The through-the-ground valve's primary function is to control the valve on the other side of the floor from the operating side of the maintenance hall, thereby opening or shutting off the flow of media. Due to its complex structure, limited research has been conducted on this type of valve, and its structural characteristics are still unclear, preventing widespread application. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to provide a method for evaluating the structure of through-ground valves in spent fuel reprocessing facilities.

[0004] The technical solution adopted by the present invention to solve the technical problem is to construct a method for evaluating the structure of a through-ground valve in a spent fuel reprocessing facility, which includes the following steps:

[0005] S1. Identify the key components of the through-ground valves in the spent fuel reprocessing facility and establish a three-dimensional model of the through-ground valves in the spent fuel reprocessing facility;

[0006] S2. Based on the three-dimensional model of the through-ground valve of the spent fuel reprocessing facility, a finite element model of the through-ground valve is established in finite element analysis software, and non-critical structural components and media are loaded into the finite element model of the through-ground valve at equivalent mass points;

[0007] S3. Adding material attributes to key components of the through-ground valve of the spent fuel reprocessing facility;

[0008] S4. Meshing the finite element model of the through-ground valve, performing mesh sensitivity analysis, and determining the model mesh size;

[0009] S5. Applying loads and boundary conditions to the finite element model of the through-ground valve;

[0010] S6. Perform a modal analysis on the ground-penetrating valve finite element model, calculate the first-order natural frequency of the ground-penetrating valve finite element model, and determine whether an equivalent static method can be used to perform stress analysis under seismic loads based on the first-order natural frequency of the ground-penetrating valve finite element model. If the first-order natural frequency of the ground-penetrating valve finite element model is greater than or equal to a preset natural frequency value, perform the stress analysis under seismic loads using the equivalent static method.

[0011] S7. Determine the stress limit of the finite element model of the ground-penetrating valve;

[0012] S8. Select multiple assessment paths for calculation and extract stress linearization results of each path;

[0013] S9. Compare the stress linearization results of each path obtained in step S8 with the stress limit obtained in step S7 to determine whether the stresses of different paths of the finite element model of the through-ground valve are all less than their corresponding stress limits. If the assessment results of all paths are qualified, it is determined that the through-ground valve of the spent fuel reprocessing facility meets the safety function; otherwise, the structure or material needs to be optimized.

[0014] In some embodiments, key components of a through-ground valve structure of a spent fuel reprocessing facility include a valve body, a valve disc, a valve core assembly, a sleeve assembly, a front compression sleeve, a front transmission rod, an intermediate compression sleeve, an intermediate transmission rod, a rear transmission rod, a rear compression sleeve assembly, a compression flange, a connecting rod, and a manual actuator.

[0015] In some embodiments, in step S3, the material of the valve body, valve disc and valve core assembly is defined as 022Cr19Ni10;

[0016] The material of the casing assembly, front compression sleeve, middle compression sleeve, rear compression sleeve assembly, compression flange and manual actuator is defined as 06Cr19Ni10;

[0017] The material of the front transmission rod, intermediate transmission rod, rear transmission rod and connecting rod is defined as 14Cr17Ni2.

[0018] In some embodiments, in step S4, SOLID187 volume elements are used to divide the mesh.

[0019] In some embodiments, in step S4, in the mesh sensitivity analysis, the mesh size of the variable diameter region is less than or equal to 3 mm, and the maximum stress deviation is controlled to be less than or equal to 5%.

[0020] In some embodiments, in step S5, the load types applied to the finite element model of the ground-penetrating valve include internal pressure, pipe load, deadweight, and earthquake acceleration;

[0021] The internal pressure is applied to the pressure-bearing boundary of the valve, the pipe load is applied to the valve body outlet, and different accelerations in three directions, including the safety shutdown earthquake load and the operating reference earthquake load, are selected according to different working conditions and applied to the finite element model of the ground-penetrating valve.

[0022] In some embodiments, in step S5, the boundary condition of the through-ground valve of the spent fuel reprocessing facility is the through-ground portion of the casing assembly.

[0023] In some embodiments, the preset natural frequency value is 33 Hz.

[0024] In some embodiments, in step S7 , the stress assessment only involves the overall primary membrane stress and the sum of the local membrane stress and the primary bending stress;

[0025] In the discontinuous area of the overall structure, the local membrane stress and bending stress are both evaluated as the local membrane stress plus the bending stress.

[0026] In some embodiments, in step S8, ten evaluation paths are selected in the finite element model of the through-ground valve, wherein the first to eighth paths are located in the valve body part, the ninth path is located in the valve disc part, and the tenth path is located in the valve cover part.

[0027] Implementing this invention has the following beneficial effects: This method for evaluating the structure of through-ground valves in spent fuel reprocessing facilities uses finite element analysis to conduct modal analysis of through-ground valves. This method proposes an integrated approach combining fully parametric modeling, multimodal analysis, and dynamic stress path assessment. This method covers the dynamic coupled responses of multiple key components, determines stress limits, and enables precise quantitative evaluation of high-risk areas such as variable diameters, welds, and pressure-bearing interfaces. Finally, based on the selected computational assessment path, the finite element calculation results are compared with the stress limits to determine whether the valve structure meets the requirements. This method can effectively evaluate the structural characteristics of through-ground valves. Compared to experimental research, numerical simulation significantly reduces economic costs and shortens the structural evaluation cycle. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In order to more clearly illustrate the technical solution of the present invention, the present invention will be further described below with reference to the accompanying drawings and embodiments. It should be understood that the following drawings only illustrate certain embodiments of the present invention and should not be considered as limiting the scope. A person of ordinary skill in the art can derive other relevant drawings based on these drawings without inventive effort. In the drawings:

[0029] Figure 1 is a flow chart of a method for evaluating the structure of a through-ground valve in a spent fuel reprocessing facility in some embodiments of the present invention;

[0030] Figure 2is an overall schematic diagram of a through-ground valve structure for a spent fuel reprocessing facility in some embodiments of the present invention;

[0031] Figure 3 is a schematic diagram of the first to eighth paths in the evaluation paths in some embodiments of the present invention;

[0032] Figure 4 is a schematic diagram of a ninth path in the evaluation path in some embodiments of the present invention;

[0033] Figure 5 is a schematic diagram of the tenth path in the evaluation path in some embodiments of the present invention. DETAILED DESCRIPTION

[0034] In order to have a clearer understanding of the technical features, purposes and effects of the present invention, the specific embodiments of the present invention are now described in detail with reference to the accompanying drawings. In the following description, it should be understood that the directions or positional relationships indicated by "front", "back", "up", "down", "left", "right", "longitudinal", "horizontal", "vertical", "horizontal", "top", "bottom", "inside", "outside", "head", "tail", etc. are based on the directions or positional relationships shown in the accompanying drawings and are constructed and operated in specific directions. They are only for the convenience of describing the technical solution and do not indicate that the devices or components referred to must have specific directions. Therefore, they should not be understood as limiting the present invention.

[0035] It should also be noted that, unless otherwise clearly specified and limited, terms such as "installed", "connected", "connected", "fixed", and "set" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integrated connection; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, and it can be the internal connection of two elements or the interaction relationship between two elements. When an element is referred to as being "on" or "under" another element, the element can be "directly" or "indirectly" located on the other element, or there may be one or more intervening elements. The terms "first", "second", "third", etc. are only for the convenience of describing the present technical solution, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first", "second", "third", etc. may explicitly or implicitly include one or more of such features. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to the specific circumstances.

[0036] See also Figure 1 , is a method for evaluating the structure of a through-ground valve in a spent fuel reprocessing facility in some embodiments of the present invention, comprising the steps of:

[0037] S1. Identify the key components of the through-ground valves in the spent fuel reprocessing facility and establish a three-dimensional model of the through-ground valves in the spent fuel reprocessing facility;

[0038] S2. Based on the three-dimensional model of the underground valve of the spent fuel reprocessing facility, a finite element model of the underground valve is established in the finite element analysis software. Non-critical structural components and media are loaded into the finite element model of the underground valve at equivalent mass points.

[0039] S3. Add material attributes to key components of the through-ground valves in the spent fuel reprocessing facility;

[0040] S4. Divide the mesh of the finite element model of the through-ground valve and conduct mesh sensitivity analysis to determine the model mesh size;

[0041] S5. Apply loads and boundary conditions to the finite element model of the through-ground valve;

[0042] S6. Perform a modal analysis on the ground-penetrating valve finite element model, calculate the first-order natural frequency of the ground-penetrating valve finite element model, and determine whether the equivalent static method can be used to perform stress analysis under seismic loads based on the first-order natural frequency of the ground-penetrating valve finite element model. If the first-order natural frequency of the ground-penetrating valve finite element model is greater than or equal to the preset natural frequency value, then use the equivalent static method to perform stress analysis under seismic loads.

[0043] S7. Determine the stress limit of the finite element model of the through-ground valve;

[0044] S8. Select multiple assessment paths for calculation and extract stress linearization results of each path;

[0045] S9. Compare the stress linearization results of each path obtained in step S8 with the stress limit values obtained in step S7 to determine whether the stresses of different paths of the finite element model of the through-ground valve are all less than their corresponding stress limits. If the assessment results of all paths are qualified, it is determined that the through-ground valve of the spent fuel reprocessing facility meets the safety function; otherwise, the structure or material needs to be optimized.

[0046] Specifically, in step S1, the overall structure of the through-ground valve of the spent fuel reprocessing facility is sorted out, such as Figure 2As shown, the structural components of the through-ground valve specifically include a valve body 1, a valve disc 2, a cotter pin 3, a valve core assembly 4, an M20 nut 5, an M20×80 bolt 6, a steel ball 7, a sleeve assembly 8, a front compression sleeve 9, a front transmission rod 10, an intermediate compression sleeve 11, an intermediate transmission rod 12, a rear transmission rod 13, a rear compression sleeve assembly 14, a compression flange 15, a connecting rod 16, an M20×50 stud 17, an M20×110 stud 18, a manual actuator 19, a φ8h10×60 cylindrical pin 20, a φ12h10×100 cylindrical pin 21 and a double-ear stop washer 22. The key components of the through-ground valve structure of the spent fuel reprocessing facility include the valve body 1, valve disc 2, valve core assembly 4, sleeve assembly 8, front compression sleeve 9, front transmission rod 10, intermediate compression sleeve 11, intermediate transmission rod 12, rear transmission rod 13, rear compression sleeve assembly 14, compression flange 15, connecting rod 16 and manual actuator 19.

[0047] In step S2, a finite element model is established using the finite element analysis software ANSYS. This model is based on the key components of the spent fuel reprocessing facility's through-the-ground valve structure. Non-critical structural components and the medium are loaded as equivalent mass points within the through-the-ground valve finite element model. In other words, the medium and other components within the spent fuel reprocessing facility's through-the-ground valve are uniformly distributed within the through-the-ground valve finite element model as added mass.

[0048] In step S3, the material of the valve body 1, valve disc 2, and valve core assembly 4 is defined as 022Cr19Ni10; the material of the sleeve assembly 8, front compression sleeve 9, intermediate compression sleeve 11, rear compression sleeve assembly 14, compression flange 15, and manual actuator 19 is defined as 06Cr19Ni10; and the material of the front transmission rod 10, intermediate transmission rod 12, rear transmission rod 13, and connecting rod 16 is defined as 14Cr17Ni2. In order to define the constitutive relationships of key components, the yield strength and elastic modulus of key components are also defined.

[0049] In step S4, the SOLID187 volume element is used to divide the mesh, which can achieve higher solution accuracy. In the high-order hexahedral mesh, more accurate stress results can be obtained at locations with larger stress gradients. It has strong adaptability to complex models and can perform adaptive mesh encryption based on volume elements, making it suitable for various complex geometric shapes. In addition, in step S4, in the mesh sensitivity analysis, the mesh size of the variable diameter area is less than or equal to 3mm, and the maximum stress deviation is controlled to be less than or equal to 5%. Mesh sensitivity analysis is a method for evaluating the changes in structural response characteristics with changes in design variables or parameters. Mesh sensitivity analysis is used to measure the redundancy of structural components and identify key components of the structure. This analysis uses the cross-sectional area of the unit as a structural parameter and defines the sensitivity of the structural parameter as the derivative of the structural response under load with respect to the cross-sectional area.

[0050] Furthermore, in step S5, the load types applied to the through-ground valve finite element model include internal pressure, pipe load, deadweight, and seismic acceleration. The internal pressure is applied to the valve's pressure-bearing boundary, and the pipe load is applied to the valve body's outlet. Based on different operating conditions, different accelerations in three directions, namely, the safety shutdown seismic load and the operating reference seismic load, are applied to the through-ground valve finite element model. Specifically, the internal pressure can be applied to the valve's pressure-bearing boundary with a safety factor of 1.5 times the design pressure, and the pipe load is calculated according to NB / T 20005. The safety shutdown seismic load is the SL2 safety shutdown seismic load, and the operating reference seismic load is the SL1 operating reference seismic load. The accelerations for the SL2 safety shutdown seismic load and the SL1 operating reference seismic load are selected based on a site seismic hazard analysis, combining the three-direction distribution ratios and the equipment's dynamic characteristics. Seismic compliance is ensured through finite element analysis and testing. Specific parameters should refer to the RG1.60 design response spectrum or the nuclear facility building floor response spectrum, the ASME III-1 code, and equipment installation requirements.

[0051] In step S5, the boundary condition of the through-ground valve of the spent fuel reprocessing facility is the through-ground portion of the casing assembly 8. It can be understood that in order to avoid rigid body displacement, the bottom flange surface of the through-ground portion of the casing assembly 8 needs to be fixed, such as by applying full constraints through bolt holes to ensure a rigid connection between the structure and the foundation under seismic loads.

[0052] In step S6, a cutoff frequency of 33 Hz is preset. During modal analysis, if the first-order natural frequency is ≥ 33 Hz (to avoid the frequency range of 5-25 Hz corresponding to the seismic spectrum acceleration peak), the equivalent static method is used to calculate seismic stresses. If the first-order natural frequency is less than the preset cutoff frequency, the structure of the spent fuel reprocessing facility's through-the-ground valve is optimized before further processing.

[0053] In step S7, the stress assessment only involves the overall primary membrane stress and the sum of the local membrane stress and the primary bending stress. In areas of structural discontinuity, both the local membrane stress and the bending stress are assessed as the sum of the local membrane stress and the primary bending stress. The bending stress also includes the secondary bending stress. Specifically, the sum of the overall primary membrane stress, the local membrane stress, and the bending stress is calculated according to the ASME III-1 specification, and the stress limit is dynamically adjusted based on the yield strength of the nuclear-grade material.

[0054] And in step S8, if Figures 3 to 5As shown, ten assessment paths are selected in the finite element model of the through-the-ground valve, of which the first to eighth paths are located in the valve body 1 part, the ninth path is located in the valve disc 2 part, and the tenth path is located in the valve cover part. It can be understood that, considering that the diameter-changing part of the through-the-ground valve will cause stress concentration, assessment paths are set in a total of 10 dangerous sections, including the valve body 1 part (8 paths), the valve disc 2 part (1 path) and the valve cover part (1 path), with a focus on the diameter-changing part and the weld joint area. The rule for selecting the assessment path is that the first to eighth paths are sampling in multiple layers along the wall thickness of the diameter-changing area, as shown in the figure. Figure 3 As shown; the ninth path is that the sealing surface of the valve disc 2 covers the contact stress gradient area, such as Figure 4 As shown; the tenth path is to evaluate the coupling effect of bolt preload and internal pressure on the bonnet flange, as shown Figure 5 As shown in Figure 1, ten evaluation paths were selected to achieve precise quantitative evaluation of the variable diameter area, disc 2 sealing surface, and bonnet flange.

[0055] In summary, this structural evaluation method for through-the-ground valves in spent fuel reprocessing facilities uses finite element analysis to conduct modal analysis of through-the-ground valves. This method proposes an integrated approach combining fully parametric modeling, multimodal analysis, and dynamic stress path assessment. This method covers the dynamic coupled responses of multiple key components, determines stress limits, and enables precise quantitative evaluation of high-risk areas such as variable diameters, welds, and pressure-bearing interfaces. Finally, based on the selected computational evaluation path, the finite element calculation results are compared with the stress limits to determine whether the valve structure meets the requirements. This method can effectively evaluate the structural characteristics of through-the-ground valves. Compared to experimental research, numerical simulation significantly reduces economic costs and shortens the structural evaluation cycle.

[0056] It can be understood that the above embodiments only express the preferred implementation methods of the present invention, and the description thereof is relatively specific and detailed, but it cannot be understood as limiting the patent scope of the present invention. It should be pointed out that for ordinary technicians in this field, without departing from the concept of the present invention, the above technical features can be freely combined, and several deformations and improvements can be made, all of which fall within the scope of protection of the present invention. Therefore, all equivalent changes and modifications made to the scope of the claims of the present invention should fall within the scope of coverage of the claims of the present invention.

Claims

1. A method for evaluating the structure of underground valves in spent fuel reprocessing facilities, characterized in that: Including steps: S1. Identify the key components of the through-ground valves in the spent fuel reprocessing facility and establish a three-dimensional model of the through-ground valves in the spent fuel reprocessing facility; S2. Based on the three-dimensional model of the through-ground valve of the spent fuel reprocessing facility, a finite element model of the through-ground valve is established in finite element analysis software, and non-critical structural components and media are loaded into the finite element model of the through-ground valve at equivalent mass points; S3. Adding material attributes to key components of the through-ground valve of the spent fuel reprocessing facility; S4. Meshing the finite element model of the through-ground valve, performing mesh sensitivity analysis, and determining the model mesh size; S5. Applying loads and boundary conditions to the finite element model of the through-ground valve; S6. Perform a modal analysis on the ground-penetrating valve finite element model, calculate the first-order natural frequency of the ground-penetrating valve finite element model, and determine whether an equivalent static method can be used to perform stress analysis under seismic loads based on the first-order natural frequency of the ground-penetrating valve finite element model. If the first-order natural frequency of the ground-penetrating valve finite element model is greater than or equal to a preset natural frequency value, perform the stress analysis under seismic loads using the equivalent static method. S7. Determine the stress limit of the finite element model of the ground-penetrating valve; S8. Select multiple assessment paths for calculation and extract stress linearization results of each path; S9. Compare the stress linearization results of each path obtained in step S8 with the stress limit obtained in step S7 to determine whether the stresses of different paths of the finite element model of the through-ground valve are all less than their corresponding stress limits. If the assessment results of all paths are qualified, it is determined that the through-ground valve of the spent fuel reprocessing facility meets the safety function; otherwise, the structure or material needs to be optimized.

2. The method for evaluating the structure of underground valves in spent fuel reprocessing facilities according to claim 1, characterized in that: The key components of the through-ground valve structure of a spent fuel reprocessing facility include a valve body (1), a valve disc (2), a valve core assembly (4), a sleeve assembly (8), a front compression sleeve (9), a front transmission rod (10), an intermediate compression sleeve (11), an intermediate transmission rod (12), a rear transmission rod (13), a rear compression sleeve assembly (14), a compression flange (15), a connecting rod (16) and a manual actuator (19).

3. The method for evaluating the structure of underground valves in spent fuel reprocessing facilities according to claim 2, characterized in that: In step S3, the material of the valve body (1), valve disc (2) and valve core assembly (4) is defined as 022Cr19Ni10; The material of the sleeve assembly (8), the front compression sleeve (9), the middle compression sleeve (11), the rear compression sleeve assembly (14), the compression flange (15) and the manual actuator (19) is defined as 06Cr19Ni10; The material of the front transmission rod (10), the intermediate transmission rod (12), the rear transmission rod (13) and the connecting rod (16) is defined as 14Cr17Ni2.

4. The method for evaluating the structure of underground valves in spent fuel reprocessing facilities according to claim 1, characterized in that: In step S4, the SOLID187 volume element is used to divide the mesh.

5. The method for evaluating the structure of underground valves in spent fuel reprocessing facilities according to claim 1, characterized in that: In step S4, in the mesh sensitivity analysis, the mesh size of the variable diameter area is less than or equal to 3 mm, and the maximum stress deviation is controlled to be less than or equal to 5%.

6. The method for evaluating the structure of underground valves in spent fuel reprocessing facilities according to claim 1, characterized in that: In step S5, the load types applied to the finite element model of the ground-penetrating valve include internal pressure, pipe load, deadweight, and earthquake acceleration; The internal pressure is applied to the pressure-bearing boundary of the valve, the pipe load is applied to the outlet of the valve body (1), and different accelerations in three directions, namely, a safety shutdown earthquake load and an operating reference earthquake load, are selected according to different working conditions and applied to the finite element model of the ground-penetrating valve.

7. The method for evaluating the structure of underground valves in spent fuel reprocessing facilities according to claim 1, characterized in that: In step S5, the boundary condition of the underground valve of the spent fuel reprocessing facility is the underground portion of the casing assembly (8).

8. The method for evaluating the structure of underground valves in spent fuel reprocessing facilities according to claim 1, characterized in that: The preset natural frequency value is 33 Hz.

9. The method for evaluating the structure of underground valves in spent fuel reprocessing facilities according to claim 1, characterized in that: In step S7, the stress assessment involves only the overall primary membrane stress and the sum of the local membrane stress and the primary bending stress; In the discontinuous area of the overall structure, the local membrane stress and bending stress are both evaluated as the local membrane stress plus the bending stress.

10. The method for evaluating the structure of underground valves in spent fuel reprocessing facilities according to claim 1, characterized in that: In step S8, ten evaluation paths are selected in the finite element model of the through-ground valve, wherein the first to eighth paths are located in the valve body (1) part, the ninth path is located in the valve disc (2) part, and the tenth path is located in the valve cover part.

Images