High-level radioactive waste geological disposal container and design method thereof

Abstract

The invention discloses a high-level radioactive waste geological disposal container and a design method thereof. The design method comprises the following steps that the service life of the high-level radioactive waste geological disposal container is determined; under the geological disposal environment condition, the corrosion characteristic and the borne mechanical load of the high-level radioactive waste geological disposal container material are determined; determining a reference structure design of the high-level radioactive waste geological disposal container; the manufacturing and welding requirements and technologies of the high-level radioactive waste geological disposal container are determined; according to the steps, a high-level radioactive waste geological disposal container is designed; performing welding structure long-term performance evaluation on the high-level radioactive waste geological disposal container; performing structural long-term integrity evaluation on the high-level radioactive waste geological disposal container; and if all the evaluations are qualified, determining that the designed high-level radioactive waste geological disposal container is qualified. The design method provides technical support for design, manufacturing and evaluation of the disposal container, fills the blank in related fields, and lays a foundation for ensuring that underground laboratories smoothly carry out disposal container related experimental researches.

Description

Technical Field

[0001] The present invention belongs to the technical field of geological disposal of high-level radioactive waste, and in particular relates to a geological disposal container for high-level radioactive waste and a design method thereof. Background Art

[0002] Geological disposal is a globally recognized and reliable method for the long-term safe disposal of high-level radioactive waste. This involves sealing the primary container of vitrified waste within a disposal container and disposing of it in a stable deep stratum, achieving long-term containment and isolation of radionuclides to reduce adverse impacts on the human environment. According to the design requirements of the high-level waste disposal concept, the geological disposal barrier system includes an engineered barrier 6 and a natural barrier. The engineered barrier 6 includes: vitrified waste 1, waste container 2, disposal container 3, buffer backfill material 4, and natural barrier surrounding rock 5. Figure 1 、 2 shown.

[0003] On June 17, 2021, construction began on a high-level radioactive waste underground laboratory. The first laboratory is scheduled to be completed in 2027, enabling experimental research on deep geological disposal of high-level radioactive waste. Disposal containers have long containment periods (thousands of years) and demand high safety standards. Currently, research on disposal containers is in its infancy, with a significant lag in research on their design, manufacture, inspection, and evaluation. There is an urgent need to expedite research on disposal container design. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a high-level radioactive waste geological disposal container and a design method thereof in view of the above-mentioned deficiencies in the prior art, and to provide technical support for the design, manufacture and evaluation of the disposal container.

[0005] The technical solution adopted to solve the technical problem of the present invention is to provide a design method for a high-level radioactive waste geological disposal container, comprising the following steps:

[0006] S1 Determine the life of the geological disposal container for high-level radioactive waste;

[0007] Under S2 geological disposal environmental conditions, determine the corrosion characteristics and mechanical loads of high-level radioactive waste geological disposal container materials;

[0008] S3 Determine the reference structural design of the high-level radioactive waste geological disposal container;

[0009] S4 Determine the requirements and techniques for the fabrication and welding of containers for geological disposal of high-level radioactive waste;

[0010] S5: Design a geological disposal container for high-level radioactive waste based on S1 to S4;

[0011] S6 evaluates the performance of welded structures for high-level radioactive waste geological disposal containers;

[0012] S7 Conduct operability and safety evaluation of high-level radioactive waste geological disposal containers during operation;

[0013] S8 Conduct structural integrity assessment of high-level radioactive waste geological disposal containers;

[0014] S9 If the evaluations in S6 to S8 are all qualified, the designed high-level radioactive waste geological disposal container is determined to be qualified.

[0015] Preferably, S1 determining the lifespan of the high-level radioactive waste geological disposal container specifically comprises the following steps:

[0016] The life of a high-level radioactive waste geological disposal container is determined based on the activity concentration, decay characteristics and heat release laws of the high-level radioactive waste nuclides, combined with the safety requirements, properties and design of the barrier system, where the barrier system includes engineered barrier systems and natural barrier systems.

[0017] Preferably, determining the corrosion characteristics of the high-level radioactive waste geological disposal container material in S2 specifically includes the following steps:

[0018] The corrosion behavior of high-level radioactive waste geological disposal containers is analyzed. Based on the research content, a corrosion resistance life prediction model for high-level radioactive waste geological disposal containers is established. The corrosion resistance life prediction model for high-level radioactive waste geological disposal containers is used to carry out corrosion evolution and life prediction of high-level radioactive waste geological disposal container materials in geological disposal environments.

[0019] Preferably, the analysis of the corrosion behavior of the high-level radioactive waste geological disposal container in S2 includes: the corrosion rate caused by the interaction between the high-level radioactive waste geological disposal container material and the barrier system in the geological disposal environment, the influence of the corrosion products of the high-level radioactive waste geological disposal container and the degradation of the barrier system performance on the corrosion rate of the high-level radioactive waste geological disposal container, and the corrosion rate of the high-level radioactive waste geological disposal container under different dissolved oxygen and pH conditions.

[0020] Preferably, determining the external mechanical load borne by the high-level radioactive waste geological disposal container in S2 specifically comprises the following steps:

[0021] It is determined that the high-level radioactive waste geological disposal container can withstand the external mechanical loads in the geological disposal environment and meet the following conditions:

[0022] High-level radioactive waste geological disposal containers have preset mechanical properties;

[0023] Under the preset time action of the external mechanical load of the geological disposal environment, the deformation generated will not cause the failure of the high-level radioactive waste geological disposal container, thus realizing the containment function.

[0024] Preferably, the mechanical loads under the geological disposal environmental conditions in S2 include: ground stress of surrounding rocks and loads of other engineering barriers.

[0025] Preferably, S3 determining the reference structural design of the high-level radioactive waste geological disposal container specifically includes the following steps:

[0026] Determine the corrosion reduction thickness of high-level radioactive waste geological disposal containers under geological disposal environmental conditions;

[0027] Determine the thickness of high-level radioactive waste geological disposal container to resist external mechanical load under geological disposal environment conditions;

[0028] The reference structural design of the high-level radioactive waste geological disposal container is determined based on the corrosion-thinning thickness of the high-level radioactive waste geological disposal container and the thickness of the high-level radioactive waste geological disposal container that can resist external mechanical loads.

[0029] Preferably, determining the corrosion reduction thickness of the high-level radioactive waste geological disposal container under the geological disposal environmental conditions in S3 specifically includes the following steps:

[0030] According to the functional requirements of high-level radioactive waste geological disposal containers, high-level radioactive waste geological disposal containers are subject to corrosion in the geological disposal environment. The corrosion has a preset corrosion rate, so that the high-level radioactive waste geological disposal container maintains structural integrity during its service life. According to the properties and design of the barrier system, the corrosion rate of the high-level radioactive waste geological disposal container in the geological disposal environment and the corrosion thinning thickness of the high-level radioactive waste geological disposal container during the disposal life are determined.

[0031] Preferably, under the geological disposal environmental conditions in S3, determining the thickness of the high-level radioactive waste geological disposal container to resist external mechanical loads specifically includes the following steps:

[0032] According to the properties and design of the barrier system, the external mechanical load conditions in the geological disposal environment are obtained, and the thickness of the high-level radioactive waste geological disposal container to resist the external mechanical load is determined on the premise of meeting the performance and deformation requirements of the high-level radioactive waste geological disposal container.

[0033] Preferably, determining the reference structural design of the high-level radioactive waste geological disposal container in S3 based on the corrosion-thinned thickness of the high-level radioactive waste geological disposal container and the thickness of the high-level radioactive waste geological disposal container capable of resisting external mechanical loads specifically includes the following steps:

[0034] On the basis of the conceptual design of the high-level radioactive waste geological disposal container, in accordance with the functional requirements of the high-level radioactive waste geological disposal container and the decay characteristics of the waste body, combined with the corrosion thinning thickness and the thickness of the high-level radioactive waste geological disposal container to resist external mechanical loads, as well as the requirements for inversion, operation, placement and retrieval during operation, and the preset safety margin, the process parameters of the form, size and thickness of the cylinder, top cover and bottom cover of the high-level radioactive waste geological disposal container are determined, and the reference structural design of the high-level radioactive waste geological disposal container is determined.

[0035] Preferably, determining the requirements and techniques for manufacturing a high-level radioactive waste geological disposal container in S4 specifically includes the following steps:

[0036] The geological disposal container for high-level radioactive waste includes: a base, a cylinder arranged on the base, and a top cover arranged on the cylinder. The manufacturing process of the cylinder is forging or punching. The manufacturing method and inspection method of the cylinder are determined based on the manufacturing process, heat treatment process, as well as residual stress, critical defects, fracture toughness, weld inspection and testing, and radiation protection requirements.

[0037] Preferably, determining the welding requirements and techniques for the high-level radioactive waste geological disposal container in S4 specifically includes the following steps:

[0038] The welding is sealed welding. According to the requirements that sealed welding must meet the maximum temperature limit of the waste body and the weldability requirements of the high-level radioactive waste geological disposal container material, weldability is the influence of welding thermal cycle on the material structure, mechanical properties and corrosion resistance. Combined with the parent material properties and design requirements, special welding materials and their welding material manufacturing process are proposed; sealed welding design is carried out according to the design requirements of the high-level radioactive waste geological disposal container, and welding methods and welding process parameters are proposed.

[0039] Preferably, S6 evaluating the welding structure performance of the high-level radioactive waste geological disposal container specifically includes the following steps:

[0040] Based on the metallurgical, casting, forging, welding and heat treatment processing technologies, as well as the test results, the segregation, micro-defects and microstructural characteristics were analyzed. Combined with the design requirements of the high-level radioactive waste geological disposal container, the fracture toughness, mechanical properties and corrosion resistance of the welded structure of the high-level radioactive waste geological disposal container were evaluated.

[0041] Preferably, S7 conducts an operability and safety evaluation of the high-level radioactive waste geological disposal container during operation, specifically comprising the following steps:

[0042] Based on the radiation protection requirements of high-level radioactive waste geological disposal containers, taking into account the inversion, operation and placement processes and requirements of high-level radioactive waste geological disposal containers, as well as the accident scenario analysis during operation, an operability and safety evaluation of high-level radioactive waste geological disposal containers during operation is carried out.

[0043] Preferably, S8 performing structural integrity assessment on the high-level radioactive waste geological disposal container specifically comprises the following steps:

[0044] Based on the input requirements and safety requirements for the design of high-level radioactive waste geological disposal containers, combined with the characteristics of the waste source, geological disposal environmental conditions and disposal plans, an integrity safety assessment of the high-level radioactive waste geological disposal container is carried out under time conditions of the order of thousands to tens of thousands of years under the coupled effects of temperature, crustal stress, hydraulic action, chemical action and radiation in the geological disposal repository.

[0045] The present invention also provides a high-level radioactive waste geological disposal container, which is designed by the above method.

[0046] The high-level radioactive waste geological disposal container and its design method, described in this patent, are based on the functional requirements for the long-term safety of high-level radioactive waste geological disposal. They address aspects such as material selection, structural design, manufacturing, inspection, and safety evaluation. This patent provides technical support for the design, manufacturing, and evaluation of disposal containers, filling a gap in related fields and laying the foundation for the smooth conduct of experimental research related to disposal containers in underground laboratories. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] Figure 1 It is a schematic diagram of the structure of the geological disposal multiple barrier system in the prior art;

[0048] Figure 2 It is a schematic diagram of the structure of the geological disposal multiple barrier system in the prior art;

[0049] Figure 3 This is the technical roadmap of the design method in Example 2 of the present invention;

[0050] Figure 4 This is a graph showing the heat release rate of a single glass solidified body product decaying from 1 to 1000 years in Example 2 of the present invention;

[0051] Figure 5 This is a design drawing of the buffer material in Example 2 of the present invention;

[0052] Figure 6 This is the preliminary structural design of the disposal container in Example 2 of the present invention;

[0053] Figure 7 This is a failure assessment diagram in Example 2 of the present invention.

[0054] In the figure: 1-glass solidification body; 2-waste container; 3-disposal container; 4-buffer backfill material; 5-surrounding rock; 6-engineering barrier. DETAILED DESCRIPTION

[0055] In order to enable those skilled in the art to better understand the technical solution of the present invention, the present invention is further described in detail below with reference to the accompanying drawings and specific implementation methods.

[0056] Example 1

[0057] This embodiment provides a design method for a high-level radioactive waste geological disposal container, comprising:

[0058] Follow these steps:

[0059] S1 Determine the life of the geological disposal container for high-level radioactive waste;

[0060] Under S2 geological disposal environmental conditions, determine the corrosion characteristics of high-level radioactive waste geological disposal container materials and determine the mechanical loads that high-level radioactive waste geological disposal containers can withstand;

[0061] S3 Determine the reference structural design of the high-level radioactive waste geological disposal container;

[0062] S4 Determine the requirements and techniques for the fabrication and welding of containers for geological disposal of high-level radioactive waste;

[0063] S5: Design a geological disposal container for high-level radioactive waste based on S1 to S4;

[0064] S6 evaluates the performance of welded structures for high-level radioactive waste geological disposal containers;

[0065] S7 Conduct operability and safety evaluation of high-level radioactive waste geological disposal containers during operation;

[0066] S8 Conduct structural integrity assessment of high-level radioactive waste geological disposal containers;

[0067] S9 If the evaluations in S6 to S8 are all qualified, the designed high-level radioactive waste geological disposal container is determined to be qualified.

[0068] This embodiment also provides a high-level radioactive waste geological disposal container, which is designed using the above method.

[0069] The high-level radioactive waste geological disposal container and its design method in this embodiment are based on the functional requirements of the disposal container for the long-term safety of high-level radioactive waste geological disposal. They address aspects such as material selection, structural design, manufacturing, inspection, and safety evaluation. This patent provides technical support for the design, manufacturing, and evaluation of disposal containers, filling a gap in related fields and laying the foundation for the smooth conduct of experimental research related to disposal containers in underground laboratories.

[0070] Example 2

[0071] This embodiment provides a method for designing a high-level radioactive waste geological disposal container, comprising the following steps:

[0072] S1 Determine the life of the geological disposal container for high-level radioactive waste;

[0073] Under S2 geological disposal environmental conditions, determine the corrosion characteristics of high-level radioactive waste geological disposal container materials and determine the mechanical loads that high-level radioactive waste geological disposal containers can withstand;

[0074] S3 Determine the reference structural design of the high-level radioactive waste geological disposal container;

[0075] S4 Determine the requirements and techniques for the fabrication and welding of containers for geological disposal of high-level radioactive waste;

[0076] S5: Design a geological disposal container for high-level radioactive waste based on S1 to S4;

[0077] S6 conducts long-term performance evaluation of welded structures for high-level radioactive waste geological disposal containers;

[0078] S7 Conduct operability and safety evaluation of high-level radioactive waste geological disposal containers during operation;

[0079] S8 conducts long-term structural integrity evaluation of high-level radioactive waste geological disposal containers;

[0080] S9 If the evaluations in S6 to S8 are all qualified, the designed high-level radioactive waste geological disposal container is determined to be qualified.

[0081] The design method of the high-level radioactive waste geological disposal container in this embodiment is a design method for the disposal container of the key engineering barrier for the geological disposal of high-level radioactive waste, which mainly includes the structural design, manufacturing, welding, inspection, performance evaluation and long-term integrity evaluation of the disposal container.

[0082] Preferably, S1 determining the lifespan of the high-level radioactive waste geological disposal container specifically comprises the following steps:

[0083] The life of high-level radioactive waste geological disposal containers is determined based on the activity concentration, decay characteristics and heat release laws of high-level radioactive waste nuclides, combined with the safety requirements, properties and design of the barrier system, to ensure that the long-term impact of high-level radioactive waste nuclides released into the environment through the geological disposal route on humans is less than the limit requirements. The barrier system includes engineered barrier systems and natural barrier systems.

[0084] Preferably, determining the corrosion characteristics of the high-level radioactive waste geological disposal container material in S2 specifically includes the following steps:

[0085] The corrosion behavior of high-level radioactive waste geological disposal containers was studied. Based on the research content, a corrosion resistance life prediction model for high-level radioactive waste geological disposal containers was established. The corrosion resistance life prediction model for high-level radioactive waste geological disposal containers is used to carry out corrosion evolution and life prediction of high-level radioactive waste geological disposal container materials in geological disposal environments.

[0086] Preferably, the study on the corrosion behavior of high-level radioactive waste geological disposal containers in S2 includes: the corrosion rate caused by the interaction between the high-level radioactive waste geological disposal container material and the barrier system in the geological disposal environment, the influence of the corrosion products of the high-level radioactive waste geological disposal container and the degradation of the barrier system performance on the corrosion rate of the high-level radioactive waste geological disposal container, and the corrosion rate of the high-level radioactive waste geological disposal container under different dissolved oxygen and pH conditions.

[0087] Preferably, determining the mechanical load borne by the high-level radioactive waste geological disposal container in S2 specifically comprises the following steps:

[0088] It is determined that the high-level radioactive waste geological disposal container can withstand the external mechanical loads in the geological disposal environment and meet the following conditions:

[0089] High-level radioactive waste geological disposal containers have preset mechanical properties;

[0090] Under the preset time action of the external mechanical load of the geological disposal environment, the deformation generated will not cause the failure of the high-level radioactive waste geological disposal container, thus realizing the containment function.

[0091] Specifically, the high-level radioactive waste geological disposal container should be able to withstand the external loads in the geological disposal environment. It is required that the high-level radioactive waste geological disposal container has good mechanical properties. Under the long-term action of the external loads in the disposal environment, the deformation produced will not cause the high-level radioactive waste geological disposal container to fail, and it can achieve long-term containment function.

[0092] Preferably, the mechanical loads under the geological disposal environmental conditions in S2 include: ground stress of surrounding rocks and loads of other engineering barriers.

[0093] Preferably, S3 determining the reference structural design of the high-level radioactive waste geological disposal container specifically includes the following steps:

[0094] Determine the corrosion reduction thickness of high-level radioactive waste geological disposal containers under geological disposal environmental conditions;

[0095] Determine the thickness of high-level radioactive waste geological disposal container to resist external mechanical load under geological disposal environment conditions;

[0096] The reference structural design of the high-level radioactive waste geological disposal container is determined based on the corrosion-thinning thickness of the high-level radioactive waste geological disposal container and the thickness of the high-level radioactive waste geological disposal container that can resist external mechanical loads.

[0097] Preferably, determining the corrosion reduction thickness of the high-level radioactive waste geological disposal container under the geological disposal environmental conditions in S3 specifically includes the following steps:

[0098] According to the functional requirements of high-level radioactive waste geological disposal containers, high-level radioactive waste geological disposal containers are subject to corrosion in the geological disposal environment. The corrosion has a preset corrosion rate, so that the high-level radioactive waste geological disposal container maintains structural integrity during its service life. According to the properties and design of the barrier system, the corrosion rate of the high-level radioactive waste geological disposal container in the geological disposal environment and the corrosion thinning thickness of the high-level radioactive waste geological disposal container during the disposal life are determined.

[0099] Specifically, in this embodiment, according to the functional requirements of the high-level radioactive waste geological disposal container, it should be able to withstand corrosion in the geological disposal environment and is required to have a low corrosion rate so that the high-level radioactive waste geological disposal container can maintain long-term structural integrity during its service life.

[0100] Preferably, under the geological disposal environmental conditions in S3, determining the thickness of the high-level radioactive waste geological disposal container to resist external mechanical loads specifically includes the following steps:

[0101] According to the properties and design of the barrier system, the external mechanical load conditions in the geological disposal environment are obtained, and the thickness of the high-level radioactive waste geological disposal container to resist the external mechanical load is determined on the premise of meeting the performance and deformation requirements of the high-level radioactive waste geological disposal container.

[0102] Preferably, determining the reference structural design of the high-level radioactive waste geological disposal container in S3 based on the corrosion-thinned thickness of the high-level radioactive waste geological disposal container and the thickness of the high-level radioactive waste geological disposal container capable of resisting external mechanical loads specifically includes the following steps:

[0103] Based on the conceptual design of the high-level radioactive waste geological disposal container, the process parameters for the form, size, and thickness of the cylinder, top cover, and bottom cover of the high-level radioactive waste geological disposal container are determined according to the functional requirements of the high-level radioactive waste geological disposal container and the decay characteristics of the waste material, in combination with the corrosion-reduced thickness and thickness required to withstand external mechanical loads, the requirements for inversion, operation, placement, and retrieval during operation, and a preset safety margin. This results in a reference structural design for the high-level radioactive waste geological disposal container. Specifically, the preset safety margin in this embodiment is a certain safety margin.

[0104] Preferably, determining the requirements and techniques for manufacturing a high-level radioactive waste geological disposal container in S4 specifically includes the following steps:

[0105] The geological disposal container for high-level radioactive waste includes: a base, a cylinder arranged on the base, and a top cover arranged on the cylinder. The manufacturing process of the cylinder is forging or punching. The manufacturing process is a reasonable manufacturing process. The manufacturing method and inspection method of the cylinder are determined based on the manufacturing process, heat treatment process, as well as residual stress, critical defects, fracture toughness, weld inspection and testing, and radiation protection requirements.

[0106] Preferably, determining the welding requirements and techniques for the high-level radioactive waste geological disposal container in S4 specifically includes the following steps:

[0107] The welding is sealed. Based on the requirement that sealed welding meet the maximum temperature limit for the waste body and the weldability requirements of the high-level radioactive waste geological disposal container material, which is the influence of welding thermal cycles on the material structure, mechanical properties, and corrosion resistance, and combined with the parent material properties and design requirements, special welding materials and their manufacturing processes are proposed. Based on the design requirements of the high-level radioactive waste geological disposal container, a sealed welding design is carried out, and the welding method and welding process parameters are proposed. The welding method is appropriate, and the welding process parameters are reasonable.

[0108] Preferably, S6 performs a long-term performance evaluation of the welded structure of the high-level radioactive waste geological disposal container, specifically comprising the following steps:

[0109] Based on the metallurgical, casting, forging, welding and heat treatment processing technologies, as well as the test results, the segregation, micro-defects and microstructural characteristics were analyzed. Combined with the design requirements of the high-level radioactive waste geological disposal container, the fracture toughness, mechanical properties and corrosion resistance of the welded structure of the high-level radioactive waste geological disposal container were evaluated.

[0110] Preferably, S7, conducting an operability and safety evaluation on the high-level radioactive waste geological disposal container during operation, specifically comprises the following steps:

[0111] Based on the radiation protection requirements of high-level radioactive waste geological disposal containers, taking into account the inversion, operation and placement processes and requirements of high-level radioactive waste geological disposal containers, as well as the accident scenario analysis during operation, an operability and safety evaluation of high-level radioactive waste geological disposal containers during operation is carried out.

[0112] Preferably, S8 performs a long-term structural integrity assessment on the high-level radioactive waste geological disposal container, specifically comprising the following steps:

[0113] Based on the input and safety requirements for the design of high-level radioactive waste geological disposal containers, combined with waste source characteristics, geological disposal environmental conditions, and disposal plans, a long-term integrity safety assessment of the high-level radioactive waste geological disposal container is conducted under conditions of timescales ranging from thousands to tens of thousands of years, under the coupled effects of temperature, crustal stress, hydraulic forces, chemical reactions, and radiation within the geological repository. Specifically, in this embodiment, a safety assessment of the high-level radioactive waste geological disposal container is conducted under conditions of large timescales of thousands to tens of thousands of years.

[0114] Specifically, the design method of the geological disposal container for high-level radioactive waste in this embodiment is applicable to a low-carbon steel disposal container for high-level radioactive waste vitrified bodies.

[0115] According to the design of the high-level waste disposal concept, the barrier system is shown in Figure 1 、2 , including engineering barriers 6 and natural barriers, the engineering barriers 6 include: glass solidification body 1, waste container 2, disposal container 3, buffer backfill material 4, natural barrier surrounding rock 5. Figure 3 As shown, the preselected site is located in Beishan, Gansu Province. The surrounding rock is granite and the buffer material is Gaomiaozi bentonite. The preselected material is a low-carbon steel disposal container for high-level radioactive waste vitrified bodies. The design method for the low-carbon steel disposal container for high-level radioactive waste vitrified bodies is analyzed, including the following steps:

[0116] S1. Determine the life of the disposal container

[0117] According to the heat release decay law of the solidified waste (see Figure 4 For single glass solid product (decay) 1 to 1000 years heat release rate change), pre-selected site conditions and engineering barrier concept design (see Figure 5 Table 1 is the design drawing of bentonite cushioning material and Table 2 is the design requirements of cushioning material). Combined with the relevant requirements of the International Atomic Energy Agency (IAEA) and taking into account a certain safety margin, it is proposed that the containment period of the disposal container should be greater than 2000 years.

[0118] Table 1 Design requirements for bentonite cushioning materials

[0119]

[0120]

[0121] S2. Determine the load on the disposal container under the disposal environment conditions

[0122] (1) Determine corrosion characteristics

[0123] To determine the corrosion rate of mild steel in a disposal environment, the interaction of containment materials with other barriers in groundwater conditions was analyzed, considering the following factors:

[0124] 1) During the formation of bentonite buffering properties, the influence of bentonite interstitial water chemical composition, bentonite water absorption and swelling force, cation exchange capacity, permeability and other properties on the double layer structure and corrosion kinetic parameters of mild steel surface.

[0125] 2) The influence of changes in dissolved oxygen concentration and the chemical composition of bentonite interstitial water on the interaction mechanism of corrosion product film formation and dissolution process of mild steel and the evolution law of corrosion rate.

[0126] 3) During the degradation of bentonite's buffering performance, the effects of the evolution of bentonite's water swelling capacity, cation exchange capacity, water permeability and other properties on the corrosion mode, cathodic depolarization mechanism of corrosion products and corrosion rate of mild steel.

[0127] 4) On this basis, a corrosion resistance life prediction model for candidate materials of disposal containers under deep geological disposal conditions is established, and the corrosion evolution and life prediction of container materials under the disposal environment are analyzed.

[0128] (2) Determine external mechanical load

[0129] According to the geostress structural characteristics of the granite in Beishan, Gansu, there is a relatively high horizontal stress area at a burial depth of 450 to 600 m, with an average stress of 16 MPa and a maximum horizontal stress of approximately 25 MPa. Taking into account the hydrostatic pressure of 5 MPa, it is determined that the external load pressure that the disposal container should withstand during its service life should be greater than 30 MPa.

[0130] S3. Reference structural design of disposal container

[0131] (1) Determine the corrosion reduction thickness of the disposal container

[0132] According to research and analysis, the corrosion of low-carbon steel disposal containers is divided into an aerobic phase (approximately 100 years) and an anaerobic phase (100 to 10,000 years). The corrosion rate in the aerobic phase is approximately 10 to 20 μm / yr, with a corrosion thickness of approximately 1 to 2 mm. The corrosion rate in the anaerobic phase is approximately 1 to 5 μm / yr, with a corrosion thickness of approximately 10 to 50 mm. Therefore, the estimated maximum reduction in the container thickness over its lifetime is approximately 50 mm.

[0133] (2) Determine the thickness of the disposal container to resist external mechanical loads

[0134] According to the maximum external load pressure of the disposal container of 30MPa, it is determined through calculation that the thickness of the disposal container to resist the external load is 100mm to meet the requirements.

[0135] (3) Determine the reference structural design of the disposal container

[0136] After comprehensive research on the functional requirements of the disposal container, the decay characteristics of the waste body, the corrosion reduction thickness of the disposal environment and the thickness of the container to resist external loads, combined with the requirements during operation, the outer and inner diameters of the disposal container are determined to be 740mm and 440mm respectively, and the wall thickness is 150mm. The main process parameters are shown in Figure 4 As shown in Table 2, Table 2 shows the parameters of the disposal container.

[0137] Table 2 Parameters of disposal containers

[0138] Geometric dimensions HLW container Total length [mm] 1778 Internal length [mm] 1348 Inner diameter [mm] 440 Outer diameter [mm] 740 Length gap in container [mm] 10 Side wall clearance [mm] 10 Depth of top cover embedded in container [mm] 30 Container wall thickness [mm] 150 Nominal thickness of base [mm] 200 Nominal thickness of top cover [mm] 200 Unladen weight of container [kg] 4531 Total weight of container contents [kg] 500 Loading weight of container [kg] 5031

[0139] S4. Determine the manufacturing and welding requirements and techniques for disposal containers

[0140] (1) Determine the manufacturing requirements and technology of disposal containers

[0141] The manufacture of disposal containers includes the manufacture of cylinder, top cover and base, and the manufacture of disposal containers should ensure the long-term integrity of the structure.

[0142] The factors that should be considered in manufacturing mainly include: manufacturing process, heat treatment process and manufacturing method (cylinder, base, top cover); hot chamber welding; base welding; relevant quality control standards; productivity (1-2 pieces / day); reasonable cost; technical maturity, experience and practical requirements, etc.

[0143] Initial consideration is to manufacture the disposal vessel using a process that forges the cylinder and welds the base. Alternatively, a process that forges the cylinder and base as a whole is possible. To reduce residual stress, heat treatment should be performed during the manufacture of the disposal vessel.

[0144] (2) Determine the sealing welding requirements and techniques of disposal containers

[0145] Sealing welding of disposal containers includes welding machine methods, joint design, control and elimination of post-weld residual stress, critical defects, and weld inspection and testing, etc. Sealing welding of disposal containers should ensure the long-term integrity of the weld.

[0146] 1) Based on the requirements, narrow gap welding or electron beam welding methods are initially considered.

[0147] 2) Connector design

[0148] Joint design mainly includes: groove form and size, allowable tolerance and weld thickness.

[0149] The factors that should be considered in the design mainly include: container material, geometric dimensions and form; groove preparation method; welding process; welding method and welding position; reducing the possibility of stress corrosion cracking (from the external surface) or hydrogen-induced cracking (inside); quality control requirements of welds; welding efficiency.

[0150] 3) Sealing welding

[0151] Sealing welding mainly includes: residual stress, critical defect requirements on weld surface and inside.

[0152] Factors to be considered in the design include: the maximum temperature limit of the waste body is initially set at 450°C; the magnitude, range and distribution of residual stress; local post-weld heat treatment (PWHT); remote operation in the hot chamber and the convenience of operation; and welding efficiency.

[0153] 4) Control and eliminate post-weld residual stress, and control the depth and level of residual stress.

[0154] Factors that should be considered in the design include: heat treatment method (considering temperature and high temperature duration, etc.); maximum temperature limit of the waste body; risk of stress corrosion cracking or hydrogen-induced cracking; fracture toughness requirements of the material; post-weld surface treatment method; repair requirements, etc.

[0155] S5. Design a geological disposal container for high-level radioactive waste based on S1 to S4;

[0156] S6. Conduct long-term performance evaluation of the welded structure of the disposal container

[0157] (1) Based on the test results, analyze the properties such as segregation, micro defects, and microstructure, and evaluate the mechanical properties and corrosion resistance of the disposal container.

[0158] (2) Fracture mechanics evaluation of disposal container design

[0159] The effects of residual stress and fracture toughness of disposal containers after welding on defects are analyzed, and critical defects are evaluated in combination with factors such as corrosion thickness and external load of ground stress.

[0160] The fracture toughness can be evaluated using the Failure Assessment Diagram (FAD). Figure 6 As shown in , FAD consists of two axes, Lr is the ratio of applied load divided by failure (or ultimate) load (P / PL), and Kr is the stress intensity factor divided by the fracture toughness value of the material (K / KIC). Lr indicates approaching failure due to plastic failure, while Kr indicates approaching failure due to structural fracture. Figure 7 As shown in Figure 1, if the evaluation point is within the area bounded by the axis and the failure evaluation line, the defect is considered acceptable. However, if the evaluation point falls outside the failure evaluation line, it is considered unacceptable and may lead to failure.

[0161] S7. Operability and safety evaluation of disposal containers during operation

[0162] Analyze the operability of the disposal container based on its structural form. Calculate the internal stresses generated during the lifting and placement of the disposal container during operation to analyze its structural safety. Study the impact of a drop accident during operation. Assuming the disposal container falls from a height of 5 meters to the ground, analyze the integrity of the disposal container after the drop, assuming the container already has defects and residual stresses.

[0163] S8. Evaluation of the structural integrity of disposal containers

[0164] The evaluation of the structural integrity of disposal containers mainly considers the impact of short-term loads and long-term loads.

[0165] (1) Influence of short-term load

[0166] The evaluation period spans several decades to a century during the initial stages of disposal. The waste releases significant heat, and the maximum disposal ambient temperature is approximately 130-140°C. Because the surrounding rock is granite, which is strong and stable, the initial external pressure applied during disposal is not considered due to the influence of the surrounding rock's in-situ stress, but only the expansion pressure of the buffer material (8 MPa). Corrosion of the disposal container is avoided. The container material strength is based on the yield strength corresponding to a temperature of 130-140°C.

[0167] (2) Impact of long-term load

[0168] The evaluation period is several thousand to ten thousand years, during which time the waste will have essentially released heat and the disposal environment temperature will be close to the initial temperature of the surrounding rock, approximately 25°C. Due to the long disposal period, geostress and water pressure will have already acted on the disposal container. The buffer material and the disposal container will work together in harmony, with external pressure primarily consisting of geostress and water pressure. Corrosion of the disposal container will occur (assuming a total corrosion thickness of 20 to 50 mm). The strength of the disposal container material should be based on the yield strength corresponding to a temperature of approximately 25°C.

[0169] If the evaluations in S9, S6 to S8 are all qualified, the designed high-level radioactive waste geological disposal container is determined to be qualified.

[0170] This embodiment also provides a high-level radioactive waste geological disposal container, which is designed using the above method.

[0171] The high-level radioactive waste geological disposal container and its design method in this embodiment are based on the functional requirements of the disposal container for the long-term safety of high-level radioactive waste geological disposal. They address aspects such as material selection, structural design, manufacturing, inspection, and safety evaluation. This patent provides technical support for the design, manufacturing, and evaluation of disposal containers, filling a gap in related fields and laying the foundation for the smooth conduct of experimental research related to disposal containers in underground laboratories.

[0172] It will be understood that the above embodiments are merely exemplary embodiments for illustrating the principles of the present invention, and the present invention is not limited thereto. Those skilled in the art will appreciate that various modifications and improvements can be made without departing from the spirit and substance of the present invention, and such modifications and improvements are also considered to be within the scope of protection of the present invention.

Claims

1. A method for designing a high-level radioactive waste geological disposal container, characterized in that: The following steps are involved: S1 Determine the life of the geological disposal container for high-level radioactive waste; Under S2 geological disposal environmental conditions, determine the corrosion characteristics of high-level radioactive waste geological disposal container materials and determine the mechanical loads that high-level radioactive waste geological disposal containers can withstand; S3 Determine the reference structural design of the high-level radioactive waste geological disposal container; S4 Determine the requirements and techniques for the fabrication and welding of containers for geological disposal of high-level radioactive waste; S5: Design a geological disposal container for high-level radioactive waste based on S1 to S4; S6 evaluates the performance of welded structures for high-level radioactive waste geological disposal containers; S7 Conduct operability and safety evaluation of high-level radioactive waste geological disposal containers during operation; S8 Conduct structural integrity assessment of high-level radioactive waste geological disposal containers; S9 If the evaluations in S6 to S8 are all qualified, the designed high-level radioactive waste geological disposal container is determined to be qualified.

2. The design method of a high-level radioactive waste geological disposal container according to claim 1, characterized in that: S1 Determining the life of a high-level radioactive waste geological disposal container specifically includes the following steps: The life of the high-level radioactive waste geological disposal container is determined based on the activity concentration, decay characteristics and heat release laws of the high-level radioactive waste nuclides, combined with the safety requirements, properties and design of the barrier system.

3. The design method of a high-level radioactive waste geological disposal container according to claim 1, characterized in that: Determining the corrosion characteristics of high-level radioactive waste geological disposal container materials in S2 specifically includes the following steps: The corrosion behavior of high-level radioactive waste geological disposal containers is analyzed. Based on the research content, a corrosion resistance life prediction model for high-level radioactive waste geological disposal containers is established. The corrosion resistance life prediction model for high-level radioactive waste geological disposal containers is used to carry out corrosion evolution and life prediction of high-level radioactive waste geological disposal container materials in geological disposal environments.

4. The design method of a high-level radioactive waste geological disposal container according to claim 3, characterized in that: The analysis of the corrosion behavior of high-level radioactive waste geological disposal containers in S2 includes: the corrosion rate caused by the interaction between the high-level radioactive waste geological disposal container material and the barrier system in the geological disposal environment, the influence of the corrosion products of the high-level radioactive waste geological disposal container and the degradation of the barrier system performance on the corrosion rate of the high-level radioactive waste geological disposal container, and the corrosion rate of the high-level radioactive waste geological disposal container under different dissolved oxygen and pH conditions.

5. The design method of a high-level radioactive waste geological disposal container according to claim 1, characterized in that: The determination of the mechanical load on the high-level radioactive waste geological disposal container in S2 specifically includes the following steps: It is determined that the high-level radioactive waste geological disposal container can withstand the external mechanical loads in the geological disposal environment and meet the following conditions: High-level radioactive waste geological disposal containers have preset mechanical properties; Under the preset time action of the external mechanical load of the geological disposal environment, the deformation generated will not cause the failure of the high-level radioactive waste geological disposal container, thus realizing the containment function.

6. The method for designing a high-level radioactive waste geological disposal container according to claim 1, characterized in that: The mechanical loads under the geological disposal environment conditions in S2 include: ground stress of surrounding rock and loads of other engineering barriers.

7. The design method of a high-level radioactive waste geological disposal container according to claim 1, characterized in that: S3 determines the reference structural design of the high-level radioactive waste geological disposal container, which specifically includes the following steps: Determine the corrosion reduction thickness of high-level radioactive waste geological disposal containers under geological disposal environmental conditions; Determine the thickness of high-level radioactive waste geological disposal container to resist external mechanical load under geological disposal environment conditions; The reference structural design of the high-level radioactive waste geological disposal container is determined based on the corrosion-thinning thickness of the high-level radioactive waste geological disposal container and the thickness of the high-level radioactive waste geological disposal container that can resist external mechanical loads.

8. The method for designing a high-level radioactive waste geological disposal container according to claim 7, characterized in that: Under the geological disposal environment conditions in S3, the corrosion reduction thickness of the high-level radioactive waste geological disposal container is determined, which specifically includes the following steps: According to the functional requirements of high-level radioactive waste geological disposal containers, high-level radioactive waste geological disposal containers are subject to corrosion in the geological disposal environment. The corrosion has a preset corrosion rate, so that the high-level radioactive waste geological disposal container maintains structural integrity during its service life. According to the properties and design of the barrier system, the corrosion rate of the high-level radioactive waste geological disposal container in the geological disposal environment and the corrosion thinning thickness of the high-level radioactive waste geological disposal container during the disposal life are determined.

9. The method for designing a high-level radioactive waste geological disposal container according to claim 7, characterized in that: Under the geological disposal environmental conditions in S3, the thickness of the high-level radioactive waste geological disposal container to resist external mechanical loads is determined, which specifically includes the following steps: According to the properties and design of the barrier system, the external mechanical load conditions in the geological disposal environment are obtained, and the thickness of the high-level radioactive waste geological disposal container to resist the external mechanical load is determined on the premise of meeting the performance and deformation requirements of the high-level radioactive waste geological disposal container.

10. The method for designing a high-level radioactive waste geological disposal container according to claim 7, characterized in that: In S3, the reference structural design of the high-level radioactive waste geological disposal container is determined based on the corrosion-thinning thickness of the high-level radioactive waste geological disposal container and the thickness of the high-level radioactive waste geological disposal container to resist external mechanical loads. The specific steps include: On the basis of the conceptual design of the high-level radioactive waste geological disposal container, in accordance with the functional requirements of the high-level radioactive waste geological disposal container and the decay characteristics of the waste body, combined with the corrosion thinning thickness and the thickness of the high-level radioactive waste geological disposal container to resist external mechanical loads, as well as the requirements for inversion, operation, placement and retrieval during operation, and the preset safety margin, the process parameters of the form, size and thickness of the cylinder, top cover and bottom cover of the high-level radioactive waste geological disposal container are determined, and the reference structural design of the high-level radioactive waste geological disposal container is determined.

11. The method for designing a high-level radioactive waste geological disposal container according to claim 1, characterized in that: S4 determines the requirements and technology for the manufacture of high-level radioactive waste geological disposal containers, including the following steps: The geological disposal container for high-level radioactive waste includes: a base, a cylinder arranged on the base, and a top cover arranged on the cylinder. The manufacturing process of the cylinder is forging or punching. The manufacturing method and inspection method of the cylinder are determined based on the manufacturing process, heat treatment process, as well as residual stress, critical defects, fracture toughness, weld inspection and testing, and radiation protection requirements.

12. The method for designing a high-level radioactive waste geological disposal container according to claim 1, characterized in that: The requirements and techniques for welding of high-level radioactive waste geological disposal containers in S4 specifically include the following steps: The welding is sealed welding. According to the requirements that sealed welding must meet the maximum temperature limit of the waste body and the weldability requirements of the high-level radioactive waste geological disposal container material, weldability is the influence of welding thermal cycle on the material structure, mechanical properties and corrosion resistance. Combined with the parent material properties and design requirements, special welding materials and their welding material manufacturing process are proposed; sealed welding design is carried out according to the design requirements of the high-level radioactive waste geological disposal container, and welding methods and welding process parameters are proposed.

13. The method for designing a high-level radioactive waste geological disposal container according to claim 1, characterized in that: S6 The evaluation of the welded structure performance of the high-level radioactive waste geological disposal container specifically includes the following steps: Based on the metallurgical, casting, forging, welding and heat treatment processing technologies, as well as the test results, the segregation, micro-defects and microstructural characteristics were analyzed. Combined with the design requirements of the high-level radioactive waste geological disposal container, the fracture toughness, mechanical properties and corrosion resistance of the welded structure of the high-level radioactive waste geological disposal container were evaluated.

14. The method for designing a high-level radioactive waste geological disposal container according to claim 1, characterized in that: S7 The operability and safety evaluation of the high-level radioactive waste geological disposal container during operation specifically includes the following steps: Based on the radiation protection requirements of high-level radioactive waste geological disposal containers, taking into account the inversion, operation and placement processes and requirements of high-level radioactive waste geological disposal containers, as well as the accident scenario analysis during operation, an operability and safety evaluation of high-level radioactive waste geological disposal containers during operation is carried out.

15. The method for designing a high-level radioactive waste geological disposal container according to claim 1, characterized in that: S8 Structural integrity assessment of high-level radioactive waste geological disposal containers specifically includes the following steps: Based on the input requirements and safety requirements for the design of high-level radioactive waste geological disposal containers, combined with the characteristics of the waste source, geological disposal environmental conditions and disposal plans, an integrity safety assessment of the high-level radioactive waste geological disposal container is carried out under time conditions of the order of thousands to tens of thousands of years under the coupled effects of temperature, crustal stress, hydraulic action, chemical action and radiation in the geological disposal repository.

16. A high-level radioactive waste geological disposal container, characterized in that: The method is designed by the method described in any one of claims 1 to 15.

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