Post-irradiation fuel cladding tube circumferential tensile test device and method

Abstract

The invention discloses a post-irradiation fuel cladding tube circumferential tensile test device and method, and relates to the field of radioactive nuclear material mechanical property tests.The post-irradiation fuel cladding tube circumferential tensile test device comprises two loading tools connected to a testing machine, each loading tool is provided with a clamping end, and the two clamping ends can be controlled by the testing machine to be close to or away from each other in the opposite direction; the two clamping ends are respectively used for clamping the two semicircular pins; the two semicircular pins are locally provided with semicircular sections with semicircular outer walls, the two semicircular sections can be mutually spliced to form a cylinder, and the cylinder is matched with the inner diameter of the cladding tube sample; and the cylinder can be inserted into the cladding tube sample. By adopting the scheme, the two semicircular pins with the diameter slightly smaller than the inner diameter of the cladding tube move in opposite directions to load the cladding tube, so that the circumferential stress of the irradiated fuel cladding tube can be effectively obtained; the device is easy to operate and can be applied to a small-diameter thin-wall fuel cladding pipe with high radioactivity.

Description

Technical Field

[0001] The invention relates to the field of mechanical property testing of radioactive nuclear materials, and in particular to a circumferential tensile testing device and method for a fuel cladding tube after irradiation. Background Art

[0002] The fuel cladding is a sealed shell that holds the fuel pellets. Its function is to prevent the escape of fission products and avoid the corrosion of fuel by coolant. It is called the first safety barrier of the reactor core. During the operation of the reactor, the working conditions of the fuel cladding are the most demanding. It is subjected to high temperature, high pressure and strong neutron irradiation. At the same time, the inner wall of the cladding is subject to the hazards of fission gas pressure, corrosion, fuel swelling and hydrogen absorption embrittlement, and the outer wall of the cladding is subject to the corrosion and temperature and pressure of coolant pressure, scouring, vibration and corrosion, hydrogen embrittlement and other threats. In particular, the mechanical interaction between the fuel pellets and the cladding and the release of fission gas products in the later stage of the operation of the fuel assembly cause the internal pressure of the cladding to continue to increase. Therefore, the mechanical properties of the cladding are crucial to prevent the cladding from rupturing when it is subjected to excessive internal pressure, causing the fission products to overflow.

[0003] Internal pressure burst test and mandrel expansion test can produce hoop stress in cladding tube, which is used to determine the failure hoop stress of circular uniform thin-walled annular specimen, and is an effective method to detect the mechanical properties of cladding tube. The internal pressure burst test is to place high pressure fluid inside the cladding tube until it bursts, but this test technology is very expensive, it is difficult to completely seal both ends of the specimen, and the burst test is dangerous. At the same time, the cladding tube sample uses more materials and is generally 160mm in length. If the available irradiated cladding tube size is limited, it is not suitable. The mandrel expansion test is composed of a multi-piece (3-6 pieces) mandrel. The cladding tube to be tested surrounds the mandrel. There are two cones on the mandrel, which move the mandrel in opposite directions to cause radial deformation of the cladding tube. However, the mandrel is small in size and has a large number of pieces. It is difficult for the manipulator in the hot chamber to install the mandrel in a thin-diameter thin-walled fuel cladding tube (the inner diameter of the cladding tube is generally 5mm or 8.36mm).

[0004] Therefore, there is an urgent need for an effective mechanical experimental method that is suitable for thin-diameter and thin-walled fuel cladding tubes and has high safety performance. Summary of the invention

[0005] The present invention aims to solve the deficiencies of the prior art and to provide a device and method for the hoop tensile test of a fuel cladding tube after irradiation. By adopting the scheme, the hoop stress of the fuel cladding tube after irradiation can be effectively obtained by only moving two semicircular pins with diameters slightly smaller than the inner diameter of the cladding tube in opposite directions to load the cladding tube. The device is simple to operate and can be applied to thin-diameter, thin-walled fuel cladding tubes with strong radioactivity.

[0006] The present invention is achieved through the following technical solutions:

[0007] A circumferential tensile test device for irradiated fuel cladding tubes, comprising:

[0008] Two loading fixtures connected to the testing machine, the loading fixtures having clamping ends, and the two clamping ends can be controlled by the testing machine to move closer to or farther away from each other;

[0009] Two semicircular pins, two clamping ends are used to clamp one semicircular pin respectively;

[0010] The two semicircular pins partially have semicircular segments with semicircular outer walls. The two semicircular segments can be spliced ​​together to form a cylinder, and the inner diameter of the cylinder and the cladding tube sample are adapted; the cylinder can be inserted into the interior of the cladding tube sample.

[0011] Compared with the existing technology, the internal pressure burst test is to place a high-pressure fluid inside the cladding tube until it bursts, but this test technology is very expensive, it is difficult to completely seal both ends of the sample, and the burst test is dangerous. At the same time, the cladding tube sample uses more material. The length is generally 160mm. If the available irradiated cladding tube size is limited, it is not suitable. The mandrel expansion test is composed of a multi-piece (3-6 pieces) mandrel. The cladding tube to be tested surrounds the mandrel. There are two cones on the mandrel, which move the mandrel in opposite directions to cause radial deformation of the cladding tube. However, the mandrel is small in size and has a large number of pieces. It is difficult for the manipulator in the hot chamber to install the mandrel in the thin-diameter, thin-walled fuel cladding tube (the inner diameter of the cladding tube is generally 5mm or 8.36mm). The present invention provides a device and method for the circumferential tensile test of irradiated fuel cladding tubes. Compared with the internal pressure explosion test and the mandrel expansion test, the circumferential tensile test only uses two semicircular pins with a diameter slightly smaller than the inner diameter of the cladding tube to load the cladding tube in opposite directions until it breaks. The sample size used in the circumferential tensile test is small, and more test samples can be cut from the irradiated cladding tube. At the same time, the test device can slightly improve the existing test equipment to save costs, and the test tooling is relatively simple and convenient for the manipulator to operate, and the circumferential stress of the irradiated fuel cladding tube can be effectively obtained. Especially for the thin-diameter, thin-walled fuel cladding tube with strong radioactivity, the designed test tooling is easy for the manipulator to remotely complete the installation and removal of the sample in the shielded hot chamber, and the mechanical properties such as the circumferential strength and plasticity of the irradiated fuel cladding tube can be obtained through data processing.

[0012] In the specific scheme, the diameter of the thin-walled fuel cladding tube is generally 6mm-12mm, and the wall thickness is relatively thin, about 0.35mm-1.0mm. The entire cladding tube is relatively long and needs to be cut for sampling. First, a CNC slow-feed wire cutting machine is used to cut a sample with a length of 3mm to 10mm along the length direction of the cladding tube. The shape and position tolerance is not less than 0.02, the cut end surface is smooth and flat, and there are no burrs inside and outside; the outer diameter and wall thickness of the sample are consistent with the initial state of the fuel cladding tube. The circumferential tensile test device includes two loading fixtures and two semicircular pins. The two loading fixtures are used to load the cladding tube sample and are connected to the testing machine. The testing machine drives the two loading fixtures to move closer or farther away from each other. The loading fixture clamps and limits the semicircular pins through the corresponding clamping ends. The semicircular pins are provided with semicircular segments with semicircular outer walls at local positions. The two semicircular pins can be inserted into the cladding tube sample towards each other. At this time, the cladding tube sample is sleeved on the outside of the cylinder, and the cladding tube sample is located between the two ends of the spliced ​​cylinder. In this way, through the cylinder and cladding tube sample with matching sizes, when the two semicircular pins are driven away from each other through the clamping end, the cladding tube sample is uniformly stressed as a whole. The two loading fixtures are separated under the tensile force of the testing machine, and the two semicircular pins move relatively with the loading fixtures. The semicircular segments are close to the inner wall of the cladding tube, and load is applied to the cladding tube sample. The cladding tube sample undergoes circumferential strain until it breaks. The circumferential tensile test can be completed, and the loading fixture is removed from the testing machine. After completing the circumferential tensile test, the mechanical properties such as circumferential strength and plasticity of the irradiated fuel cladding tube can be obtained through data processing.

[0013] In order to reserve a hole for the semicircular pin to pass through so that the semicircular section of the semicircular pin can be quickly inserted into the cladding tube sample, the clamping end includes a step structure, the step structure includes a first step extending outward, a circular hole is opened on the first step, the semicircular pin also includes a cylindrical section connected to the semicircular section, and the diameter of the circular hole is adapted to the diameter of the cylindrical section;

[0014] The step structures of the two clamping ends are rotationally symmetrical, and the two semicircular segments are used to be spliced ​​with each other between the two first steps. In this scheme, during a specific experiment, the clamping ends of the loading fixture can be placed on both sides of the cladding tube sample and placed rotationally symmetrically with each other, and the two circular holes are coaxial with the cladding tube sample. In this way, semicircular pins can be inserted into the circular holes on both sides respectively, and the semicircular segments of the semicircular pins are inserted into the interior of the cladding tube sample, and the two semicircular segments can be spliced ​​in the cladding tube sample to form a cylinder.

[0015] In order to locate the splicing position of the semicircular segment, the step structure also includes a third step extending outward, and a notch is opened at the end of the third step, and the size of the notch is adapted to the size of the semicircular segment;

[0016] The third step is located on one side of the first step, and its end face is flush with the end face of the semicircular segment. In this solution, the third step is used to locate the insertion end of the semicircular pin and position it at the notch of the third step; the end face of the third step is flush with the end face of the semicircular segment, so that the two clamping ends can be seamlessly spliced ​​through rotational symmetry, and the two semicircular segments can be seamlessly spliced.

[0017] In order to clamp and position the two ends of the semicircular pin, so that the cladding tube sample is evenly stressed through uniform tension, and to prevent the semicircular pin from rotating, and reduce the friction of the inner wall of the cladding tube sample, the notch is a triangular arc hole, the triangular arc hole is triangular, and the bottom of the triangular arc hole is an arc segment that matches the arc surface of the semicircular pin; the arc segment and the circular hole are coaxially arranged;

[0018] The end of the semicircular segment away from the cylindrical segment is also connected to an arc triangular segment, and the size of the arc triangular segment is adapted to the size of the slot. In this solution, the slot adopts a triangular arc hole, and a matching arc triangular segment is adopted at the end of the semicircular pin, so that the semicircular pin passes through the circular hole and the cladding tube sample in turn, and finally inserts into the triangular arc hole, and the two ends of the semicircular pin are limited and clamped by the triangular arc hole and the circular hole, so that the force is evenly applied during the tension process; in addition, polygonal arc holes other than triangular arc holes can also be used, as long as the semicircular pin can be prevented from rotating during the tension process, so as to reduce the friction of the inner wall of the cladding tube sample.

[0019] In order to provide sufficient splicing positions for the semicircular segments and facilitate quick splicing between the clamping ends, the step structure also includes a second step extending outward, the second step is located between the first step and the third step; the end face of the second step is flush with the end face of the third step, and a semicircular hole is opened at the end of the second step, the size of the semicircular hole is adapted to the size of the semicircular segment; the semicircular hole and the circular hole are coaxially arranged. In this solution, the second step is connected to the side wall of the first step, so that the semicircular hole extends outward from the circular hole, leaving enough length to provide sufficient splicing positions for the semicircular segments; in addition, the two clamping ends can be quickly aligned and spliced ​​through rotational symmetry and the flush first and second steps.

[0020] In order to reserve a place for the cladding tube sample and ensure that the cladding tube sample has sufficient deformation space, a rectangular groove is left between the second step and the third step, the width of the rectangular groove is greater than the length of the cladding tube sample, and the depth of the rectangular groove is greater than the radius of the cladding tube sample. In this solution, the rectangular groove is opened between the second step and the third step. When the two clamping ends are spliced ​​together, the two rectangular grooves are spliced ​​together to form a rectangular frame. The rectangular frame is used to place the cladding tube sample. The width of the rectangular frame is slightly greater than the length of the cladding tube sample, and the depth of the rectangular frame is slightly greater than 2 times the diameter of the cladding tube sample, ensuring that the cladding tube sample has sufficient deformation space.

[0021] In order to facilitate the installation and placement of the cladding tube sample and provide an installation operation surface, an assembly base is also included. A support block is provided on the operation surface of the assembly base. The top of the support block has an arc-shaped groove for placing the cladding tube sample. The diameter of the arc-shaped groove is adapted to the outer diameter of the cladding tube sample. In this solution, the diameter of the arc-shaped groove is equivalent to the outer diameter of the cladding tube sample, and is concentric with the cladding tube sample, the circular hole of the loading tooling, and the semicircular pin. The manipulator takes the cylindrical section of the semicircular pin and passes it through the circular hole, semicircular hole, cladding tube and triangular arc hole of the fixture body in turn. The two fixture bodies are connected and fixed together with the cladding tube sample through the semicircular pin.

[0022] In order to prevent the loading tool and the clamping end from moving during the operation of the manipulator, a groove is also provided on the operating surface of the assembly base, the support block is located in the middle of the bottom surface of the groove, and the surrounding sides of the groove are provided with baffles for limiting the clamping end. In this solution, the loading tool can be placed in the groove, and after the two clamping ends are spliced, the baffle can be used to limit it, thereby preventing it from moving.

[0023] A further solution, an experimental method of a circumferential tensile test apparatus for a fuel cladding tube after irradiation, comprises the following steps:

[0024] S1: Cut a number of cladding tube samples evenly along the length direction of the cladding tube, and place the cladding tube samples on the operating surface of the assembly base;

[0025] S2: Control the manipulator to place the two loading fixtures on the assembly base respectively, so that the two clamping ends are located on both sides of the cladding tube sample respectively and are placed in rotational symmetry; at this time, the circular hole and the cladding tube sample are coaxial;

[0026] S3: Control the manipulator to take the semicircular pins, and make the two semicircular pins pass through the two circular holes respectively, and pass through the cladding tube sample in opposite directions, so that the semicircular segments can be spliced ​​together to form a cylinder. At this time, the cladding tube sample is sleeved on the outside of the cylinder and is located between the two ends of the cylinder;

[0027] S4: Connect the loading fixture and the testing machine, and control the clamping ends of the two loading fixtures to gradually separate towards each other under the action of tension, until the cladding tube sample is stressed and circumferential strain occurs until it breaks, completing the circumferential tensile test.

[0028] A further solution also includes the following steps:

[0029] After completing the hoop tensile test, according to the tensile curve collected by the testing machine software system, the formula R m =F m / 2wt and R p0.2 =F s / 2wt respectively calculates the tensile strength and yield strength; where w and t represent the length and wall thickness of the cladding tube sample respectively;

[0030] Take photos using a video microscope in a thermal chamber and use image analysis software to measure the circumference of the outer wall of the cladding tube sample after fracture;

[0031] According to the formula A=(l u -l0) / l0 to calculate the elongation after fracture; where l0 and l u They represent the circumference of the outer wall of the cladding tube sample before and after fracture.

[0032] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0033] 1. The present invention provides a circumferential tensile test method for irradiated fuel cladding tubes. For the circumferential tensile test of thin-walled and thin-diameter cladding tubes, the required test sample size is small (the sample length is only 3-10 mm), and the circumferential stress and plasticity of the material can be obtained, which saves precious irradiated fuel cladding tubes and can obtain more test data. At the same time, compared with other types of radioactive samples, the circumferential tensile sample size is smaller, which also greatly reduces the radioactive dose of a single sample.

[0034] 2. The circumferential tensile test device and method for irradiated fuel cladding tubes provided by the present invention only require machining of a set of special test fixtures, and can be operated using existing test equipment, thereby improving equipment utilization. For cladding tubes of different diameters and wall thicknesses, only the matching semicircular pins need to be replaced, thereby reducing the generation of radioactive contaminated solid waste.

[0035] 3. The present invention provides a device and method for the circumferential tensile test of irradiated fuel cladding tubes. The loading fixture adopts a rotationally symmetrical step structure. After the sample is fixed, a rectangular structure is formed. When two loading fixtures are separated under the action of tension, the two semicircular pins move relative to each other to apply load to the cladding tube sample. The symmetrical structure ensures that the cladding tube sample is evenly stressed.

[0036] 4. The present invention provides a device and method for the circumferential tensile test of a fuel cladding tube after irradiation. The two semicircular pins supporting the cladding tube pass through the circular hole and the cladding tube sample in sequence and are finally inserted into the triangular arc hole. The two ends of the semicircular pin are limited and clamped by the triangular arc hole and the circular hole, so that the force is evenly applied during the tension process. In addition, the triangular arc hole can also prevent the semicircular pin from rotating during the tension process to reduce the friction of the inner wall of the cladding tube sample.

[0037] 5. The present invention provides a circumferential tensile test device and method for irradiated fuel cladding tubes. Baffles are arranged around the assembly base to prevent the movement of the fixture body during the operation of the manipulator. At the same time, there is an arc-shaped groove on the assembly base for placing the cladding tube sample. The diameter of the arc-shaped groove is equivalent to the outer diameter of the cladding tube sample, and is concentric with the cladding tube sample, the circular hole of the loading tool, and the semicircular pin. The manipulator takes the cylindrical section of the semicircular pin and passes it through the circular hole, semicircular hole, cladding tube and triangular arc hole of the fixture body in sequence, so that the two fixture bodies are connected and fixed together with the cladding tube sample through the semicircular pin.

[0038] 6. The present invention provides a device and method for the circumferential tensile test of irradiated fuel cladding tubes, which are remotely operated by a manipulator or other tools in a radioactive environment. The entire process only requires the placement of two clamps and cladding tube samples, and the insertion of two pins. The operation is simple, fast, and easy to implement, which reduces the exposure time of the staff.

[0039] 7. The present invention provides a device and method for the circumferential tensile test of fuel cladding tubes after irradiation. The device and method are simple mechanical structures formed by the combination of a clamp body and pins of special shapes. It only requires placing each component at a specified position and inserting the pins toward each other. Finally, the corresponding experimental data can be obtained by pulling them against each other. The device and method are simple to operate and can be applied to repetitive experiments, greatly improving the experimental efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] In order to more clearly illustrate the technical solutions of the exemplary embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments. It should be understood that the following drawings only illustrate certain embodiments of the present invention and should not be regarded as limiting the scope. For those of ordinary skill in the art, other relevant drawings can be obtained based on these drawings without creative work. In the drawings:

[0041] Figure 1 A schematic diagram of the structure of the loading tooling provided by the present invention;

[0042] Figure 2 A schematic diagram of the structure of the semicircular pin provided by the present invention;

[0043] Figure 3 This is a structural schematic diagram of the assembly base provided by the present invention.

[0044] Marks and corresponding parts names in the attached drawings:

[0045] 1-cladding tube sample, 2-loading tool, 3-semicircular pin, 4-assembly base, 5-step structure, 6-first step, 7-circular hole, 8-second step, 9-semicircular hole, 10-third step, 11-notch, 12-rectangular groove, 13-arc triangle segment, 14-semicircle segment, 15-cylindrical segment, 16-baffle, 17-arc groove, 18-pin hole. DETAILED DESCRIPTION

[0046] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with embodiments and drawings. The exemplary embodiments of the present invention and their description are only used to explain the present invention and are not intended to limit the present invention.

[0047] Embodiment 1:

[0048] This embodiment 1 provides a circumferential tensile test device for irradiated fuel cladding tubes, such as Figure 1-Figure 3 As shown, including:

[0049] Two loading fixtures 2 connected to the testing machine, the loading fixtures 2 having clamping ends, and the two clamping ends can be controlled by the testing machine to move closer to or farther from each other;

[0050] Two semicircular pins 3, and two clamping ends are respectively used to clamp one semicircular pin 3;

[0051] The two semicircular pins 3 partially have a semicircular segment 14 with a semicircular outer wall. The two semicircular segments 14 can be spliced ​​together to form a cylinder, and the inner diameter of the cylinder and the cladding tube sample 1 are adapted; the cylinder can be inserted into the cladding tube sample 1.

[0052] Compared with the prior art, the internal pressure burst test is to place a high-pressure fluid inside the cladding tube until it bursts, but this test technology is very expensive, it is difficult to completely seal both ends of the sample, and the burst test is dangerous. At the same time, the cladding tube sample 1 uses more materials. The length is generally 160mm. If the available irradiated cladding tube size is limited, it is not suitable. The mandrel expansion test is composed of a multi-piece (3-6 pieces) mandrel. The cladding tube to be tested surrounds the mandrel. There are two cones on the mandrel, which move the mandrel in opposite directions to cause radial deformation of the cladding tube. However, the mandrel is small in size and has a large number of pieces. It is difficult for the manipulator in the hot chamber to install the mandrel in the thin-diameter, thin-walled fuel cladding tube (the inner diameter of the cladding tube is generally 5mm or 8.36mm). The present invention provides a device and method for the circumferential tensile test of irradiated fuel cladding tubes. Compared with the internal pressure explosion test and the mandrel expansion test, the circumferential tensile test only uses two semicircular pins 3 with a diameter slightly smaller than the inner diameter of the cladding tube to load the cladding tube in opposite directions until it breaks. The sample size used in the circumferential tensile test is small, and more test samples can be cut from the irradiated cladding tube. At the same time, the test device can slightly improve the existing test equipment to save costs, and the test tooling is relatively simple and convenient for the manipulator to operate, and the circumferential stress of the irradiated fuel cladding tube can be effectively obtained. Especially for the thin-diameter, thin-walled fuel cladding tube with strong radioactivity, the designed test tooling is easy for the manipulator to remotely complete the installation and removal of the sample in the shielded hot chamber, and the mechanical properties such as the circumferential strength and plasticity of the irradiated fuel cladding tube can be obtained through data processing.

[0053] In the specific scheme, the diameter of the thin-walled fuel cladding tube is generally 6mm-12mm, and the wall thickness is relatively thin, about 0.35mm-1.0mm. The entire cladding tube is relatively long and needs to be cut for sampling. First, a CNC slow-feed wire cutting machine is used to cut a sample with a length of 3mm to 10mm along the length direction of the cladding tube. The shape and position tolerance is not less than 0.02, the cut end surface is smooth and flat, and there are no burrs inside and outside; the outer diameter and wall thickness of the sample are consistent with the initial state of the fuel cladding tube. The circumferential tensile test device includes two loading fixtures 2 and two semicircular pins 3. The two loading fixtures 2 are used to load the cladding tube sample 1 and are connected to the testing machine, and the two loading fixtures 2 are driven to move toward or away from each other through the testing machine; the loading fixtures 2 clamp and limit the semicircular pins 3 through the corresponding clamping ends; the semicircular pins 3 are provided with semicircular segments 14 with semicircular outer walls at local positions, and the two semicircular pins 3 can be inserted into the cladding tube sample 1 toward each other. At this time, the cladding tube sample 1 is sleeved on the outside of the cylinder, and the cladding tube sample 1 is located between the two ends of the spliced ​​cylinder. In this way, through the cylinder and the cladding tube sample 1 with matching sizes, when the two semicircular pins 3 are driven away from each other through the clamping end, the cladding tube sample 1 is subjected to uniform force as a whole. The two loading fixtures 2 are separated under the tensile force of the testing machine, and the two semicircular pins 3 move relatively with the loading fixtures 2. The semicircular segment 14 is close to the inner wall of the cladding tube, and a load is applied to the cladding tube sample 1. The cladding tube sample 1 undergoes circumferential strain until it breaks, and the circumferential tensile test is completed, and the loading fixture 2 is removed from the testing machine. After the circumferential tensile test is completed, the mechanical properties such as the circumferential strength and plasticity of the irradiated fuel cladding tube can be obtained through data processing.

[0054] In order to reserve a hole for the semicircular pin 3 to pass through so that the semicircular segment 14 of the semicircular pin 3 can be quickly inserted into the cladding tube sample 1, the clamping end includes a step structure 5, the step structure 5 includes a first step 6 extending outward, and a circular hole 7 is opened on the first step 6. The semicircular pin 3 also includes a cylindrical segment 15 connected to the semicircular segment 14, and the diameter of the circular hole 7 is adapted to the diameter of the cylindrical segment 15;

[0055] The step structures 5 of the two clamping ends are rotationally symmetrical, and the two semicircular segments 14 are used to be spliced ​​between the two first steps 6. In this scheme, in a specific experiment, the clamping ends of the loading tool 2 can be placed on both sides of the cladding tube sample 1, and are placed rotationally symmetrically with each other, and the two circular holes 7 are coaxial with the cladding tube sample 1. In this way, the semicircular pins 3 can be inserted into the circular holes 7 on both sides respectively, and the semicircular segments 14 of the semicircular pins 3 are inserted into the inside of the cladding tube sample 1, and the two semicircular segments 14 can be spliced ​​in the cladding tube sample 1 to form a cylinder.

[0056] In order to locate the splicing position of the semicircular segment 14, the step structure 5 further includes a third step 10 extending outward, and a notch 11 is opened at the end of the third step 10, and the size of the notch 11 is adapted to the size of the semicircular segment 14;

[0057] The third step 10 is located on one side of the first step 6, and its end face is flush with the end face of the semicircular segment 14. In this solution, the third step 10 is used to locate the insertion end of the semicircular pin 3 and locate it at the notch 11 of the third step; the end face of the third step 10 is flush with the end face of the semicircular segment 14, so that the two clamping ends can be seamlessly spliced ​​through rotational symmetry, and the two semicircular segments 14 are seamlessly spliced.

[0058] In order to clamp and position the two ends of the semicircular pin 3, so that the cladding tube sample 1 is subjected to uniform force through uniform tension, and to prevent the semicircular pin 3 from rotating, and to reduce the friction of the inner wall of the cladding tube sample 1, the notch 11 is a triangular arc hole, the triangular arc hole is triangular, and the bottom of the triangular arc hole is an arc segment that matches the arc surface of the semicircular pin 3; the arc segment and the circular hole 7 are coaxially arranged;

[0059] The end of the semicircular segment 14 away from the cylindrical segment 15 is also connected to an arc triangular segment 13, and the size of the arc triangular segment 13 is adapted to the size of the slot 11. In this solution, the slot 11 adopts a triangular arc hole, and a matching arc triangular segment 13 is adopted at the end of the semicircular pin 3, so that the semicircular pin 3 passes through the circular hole 7 and the cladding tube sample 1 in turn, and finally inserts into the triangular arc hole, and the two ends of the semicircular pin 3 are limited and clamped by the triangular arc hole and the circular hole 7, so that the force is evenly applied during the tension process; in addition, polygonal arc holes other than triangular arc holes can also be used, as long as the semicircular pin 3 can be prevented from rotating during the tension process, so as to reduce the friction of the inner wall of the cladding tube sample 1.

[0060] In order to provide sufficient splicing positions for the semicircular segment 14 and facilitate quick splicing between the clamping ends, the step structure 5 also includes a second step 8 extending outwards, and the second step 8 is located between the first step 6 and the third step 10; the end face of the second step 8 is flush with the end face of the third step 10, and a semicircular hole 9 is opened at the end of the second step 8, and the size of the semicircular hole 9 is adapted to the size of the semicircular segment 14; the semicircular hole 9 and the circular hole 7 are coaxially arranged. In this solution, the second step 8 is connected to the side wall of the first step 6, so that the semicircular hole 9 extends outwards from the circular hole 7, leaving enough length to provide sufficient splicing positions for the semicircular segment 14; in addition, the two clamping ends can be quickly aligned and spliced ​​through rotational symmetry and the flush first step 6 and second step 8.

[0061] In order to reserve a placement position for the cladding tube sample 1 and ensure that the cladding tube sample 1 has sufficient deformation space, a rectangular groove 12 is left between the second step 8 and the third step 10, and the width of the rectangular groove 12 is greater than the length of the cladding tube sample 1, and the depth of the rectangular groove 12 is greater than the radius of the cladding tube sample 1. In this solution, the rectangular groove 12 is opened between the second step 8 and the third step 10. When the two clamping ends are spliced ​​together, the two rectangular grooves 12 are spliced ​​together to form a rectangular frame. The rectangular frame is used to place the cladding tube sample 1. The width of the rectangular frame is slightly greater than the length of the cladding tube sample 1, and the depth of the rectangular frame is slightly greater than 2 times the diameter of the cladding tube sample 1, ensuring that the cladding tube sample 1 has sufficient deformation space.

[0062] In order to facilitate the installation and placement of the cladding tube sample 1 and provide an installation operation surface, an assembly base 4 is also included. A support block is provided on the operation surface of the assembly base 4. The top of the support block has an arc-shaped groove 17 for placing the cladding tube sample 1. The diameter of the arc-shaped groove 17 is adapted to the outer diameter of the cladding tube sample 1. In this solution, the diameter of the arc-shaped groove 17 is equivalent to the outer diameter of the cladding tube sample 1, and is concentric with the cladding tube sample 1, the circular hole 7 of the loading tool 2, and the semicircular pin 3. The manipulator takes the cylindrical section 15 of the semicircular pin 3, and passes through the circular hole 7, the semicircular hole 9, the cladding tube and the triangular arc hole of the fixture body in turn. The two fixture bodies are connected and fixed together with the cladding tube sample 1 through the semicircular pin 3.

[0063] In order to prevent the loading tool 2 and the clamping end from moving during the operation of the manipulator, a groove is further provided on the operating surface of the assembly base 4, the support block is located in the middle of the bottom surface of the groove, and the surrounding sides of the groove are provided with baffles 16 for limiting the clamping end. In this solution, the loading tool 2 can be placed in the groove, and after the two clamping ends are spliced, they can be limited by the baffles 16 to prevent them from moving.

[0064] Embodiment 2:

[0065] This embodiment 2 is further limited on the basis of embodiment 1, and provides a specific implementation case and a specific operation method of the experimental operation.

[0066] In this embodiment, a radioactive fuel cladding tube with a diameter of 9.5 mm and a wall thickness of 0.57 mm is used as an example to complete a hoop tensile test in a hot chamber by a special test fixture operated by a manipulator. The specific steps are as follows:

[0067] 1. Processing of fuel cladding tube samples: Using the CNC wire cutting machine in the hot chamber, 5 samples 1 with a length of 5 mm are cut along the length direction of the cladding tube. The form and position tolerance is 0.02. The cut end surface of the sample is smooth and flat, and the inner and outer walls are smooth and free of burrs. The outer diameter and wall thickness of the sample are consistent with the initial state of the fuel cladding tube.

[0068] 2. Special test fixture: It consists of two loading fixtures 2 of the same shape and structure, two semicircular pins 3 and an assembly base 4. The specific process is as follows:

[0069] The two loading fixtures 2 are used to load the cladding tube sample 1 and connect it to the testing machine. The main body of the clamping end of the loading fixture is a step structure 5, which is rotationally symmetrical. The two loading fixtures 2 are combined to form a regular rectangular parallelepiped structure, which ensures the symmetry of the overall structure of the loading fixture, so that the cladding tube sample 1 is evenly stressed. The first step 6 of the step structure 5 has a circular hole 7, the second step 8 is a semicircular hole 9, and the third step 10 is a notch 11, that is, a triangular arc hole. The circular hole 7, the semicircular hole 9 and the triangular arc hole are concentric and have the same diameter. The middle part of the step structure 5 is a through rectangular groove 12 for placing the cladding tube sample 1. The width of the rectangular frame formed by the two rectangular grooves 12 is 6mm, which is slightly larger than the length of the cladding tube sample 1. The depth of the rectangular frame formed by the two rectangular grooves 12 is 20mm, which is slightly larger than twice the diameter of the cladding tube sample 1, ensuring that the cladding tube sample 1 has sufficient deformation space.

[0070] The two semicircular pins 3 are composed of three sections of concentric and same diameter arc triangular section 13, semicircular arc section 14, and cylindrical section 15. The top of the semicircular pin 3 is the arc triangular section 13. After being inserted into the triangular arc hole on the loading tooling 2, the semicircular pin 3 can be prevented from rotating, and the friction of the inner wall of the cladding tube sample 1 can be reduced; the middle section of the semicircular pin 3 is the semicircular section 14, which is the position that bears the force of the cladding tube sample 1. The arc diameter of its outer surface is 8.15mm, which is slightly smaller than the inner diameter 8.36 of the cladding tube sample 1. The roughness of the arc surface is 1.6, and the hardness of the material used is HRC43; the rear end of the semicircular pin 3 is the cylindrical section 15, which is used for robot grasping.

[0071] The assembly base 4 is provided with baffles 16 around it to prevent the loading tool 2 from moving axially along the cladding tube sample 1 during the operation of the manipulator. There is an arc groove 17 in the center of the assembly base 4 for placing the cladding tube sample 1. The diameter of the arc groove 17 is 9.55 mm, which is equivalent to the outer diameter of the cladding tube sample 1, and is concentric with the cladding tube sample 1, the circular hole 7 of the loading tool 2, and the semicircular pin 3. The manipulator takes the cylindrical section of the semicircular pin and passes it through the circular hole, semicircular hole, cladding tube and triangular arc hole of the fixture body in turn. The two fixture bodies are connected and fixed together with the cladding tube sample through the semicircular pin.

[0072] 3. Assembling the special test fixture: The manipulator takes two loading fixtures 2 and places them on the assembly base 4. The two loading fixtures 2 are respectively located on both sides of the cladding tube sample 1. The cladding tube sample 1 is placed in the arc groove 17. The manipulator takes the cylindrical section 15 of one of the semicircular pins 3 and passes through the circular hole 7, semicircular hole 9, cladding tube sample 1 and triangular arc hole of a loading fixture 2 in sequence. Repeat the above operation with another semicircular pin 3 and another loading fixture 2. The two loading fixtures 2 are connected and fixed to the cladding tube sample 1 through two semicircular pins 3.

[0073] 4. Circumferential tensile test process: The combined loading fixture 2 and cladding tube sample 1 are taken out from the assembly base 4 as a whole by a manipulator. There is a pin hole 18 on the other end of the loading fixture 2, which is connected to the testing machine through a pin. The two loading fixtures 2 are separated under the action of tension, and the two semicircular pins 3 move relatively with the loading fixture 2. The two semicircular pins 3 apply load to the inner wall of the cladding tube sample 1. The cladding tube sample 1 is stressed and circumferential strain occurs until it breaks, completing the circumferential tensile test. Use a manipulator to remove the cladding tube sample 1, the loading fixture 2 and the semicircular pins 3 from the testing machine.

[0074] 5. Circumferential tensile test result processing: After completing the circumferential tensile test, according to the tensile curve collected by the testing machine software system, the formula R m =F m / 2wt and R p0.2 =F s / 2wt respectively calculate the tensile strength and yield strength; where w and t represent the length and wall thickness of the cladding tube sample respectively; take pictures with a video microscope in the hot room and use image analysis software to measure the circumference of the outer wall of the cladding tube sample after fracture; according to the formula A=(l u -l0) / l0 to calculate the elongation after fracture; where l0 and l u They represent the circumference of the outer wall of the cladding tube sample before and after fracture. Finally, the strength and plasticity of the radioactive fuel cladding tube are obtained.

[0075] The above scheme, that is, for the thin-diameter and thin-walled fuel cladding tubes with strong radioactivity, the designed test tooling is easy for the manipulator to remotely complete the installation and removal of samples in the shielded hot chamber, and uses a special test fixture that is easy for the hot chamber manipulator to remotely operate. The circumferential tensile test is loaded on the existing testing machine, and the mechanical properties such as the circumferential strength and plasticity of the fuel cladding tubes are obtained through data processing.

[0076] The specific implementation methods described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific implementation method of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A circumferential tensile test device for irradiated fuel cladding tubes, characterized in that: include: Two loading fixtures (2) connected to the testing machine, the loading fixtures (2) having clamping ends, and the two clamping ends can be moved toward or away from each other through the control of the testing machine; Two semicircular pins (3), and two clamping ends are respectively used to clamp one semicircular pin (3); The two semicircular pins (3) are partially provided with a semicircular segment (14) with a semicircular outer wall. The two semicircular segments (14) can be connected to each other to form a cylinder, and the inner diameter of the cylinder and the cladding tube sample (1) are adapted; the cylinder can be inserted into the cladding tube sample (1).

2. The circumferential tensile test device for irradiated fuel cladding tubes according to claim 1, characterized in that: The clamping end comprises a step structure (5), the step structure (5) comprises a first step (6) extending outward, a circular hole (7) is formed on the first step (6), the semicircular pin (3) further comprises a cylindrical section (15) connected to the semicircular section (14), and the diameter of the circular hole (7) is adapted to the diameter of the cylindrical section (15); The step structures (5) of the two clamping ends are rotationally symmetrical, and the two semicircular segments (14) are used to be spliced ​​with each other between the two first steps (6).

3. The circumferential tensile test device for irradiated fuel cladding tubes according to claim 2, characterized in that: The step structure (5) further comprises a third step (10) extending outwards, a notch (11) being formed at the end of the third step (10), and the size of the notch (11) being adapted to the size of the semicircular segment (14); The third step (10) is located on one side of the first step (6), and its end surface is flush with the end surface of the semicircular segment (14).

4. The circumferential tensile test device for irradiated fuel cladding tubes according to claim 3, characterized in that: The notch (11) is a triangular arc hole, the triangular arc hole is triangular in shape, and the bottom of the triangular arc hole is an arc segment that matches the arc surface of the semicircular pin (3); the arc segment and the circular hole (7) are coaxially arranged; One end of the semicircular segment (14) away from the cylindrical segment (15) is also connected to a circular arc triangular segment (13), and the size of the circular arc triangular segment (13) is adapted to the size of the notch (11).

5. The circumferential tensile test device for irradiated fuel cladding tubes according to claim 3, characterized in that: The step structure (5) further comprises a second step (8) extending outwards, wherein the second step (8) is located between the first step (6) and the third step (10); the end face of the second step (8) is flush with the end face of the third step (10), and a semicircular hole (9) is formed at the end of the second step (8), and the size of the semicircular hole (9) is matched with the size of the semicircular segment (14); the semicircular hole (9) and the circular hole (7) are coaxially arranged.

6. The circumferential tensile test device for irradiated fuel cladding tubes according to claim 5, characterized in that: A rectangular groove (12) is left between the second step (8) and the third step (10), the width of the rectangular groove (12) is greater than the length of the cladding tube sample (1), and the depth of the rectangular groove (12) is greater than the radius of the cladding tube sample (1).

7. The circumferential tensile test device for irradiated fuel cladding tubes according to claim 1, characterized in that: It also includes an assembly base (4), the operating surface of which is provided with a support block, the top of which is provided with an arc-shaped groove (17) for placing the cladding tube sample (1), and the diameter of the arc-shaped groove (17) is adapted to the outer diameter of the cladding tube sample (1).

8. The circumferential tensile test device for irradiated fuel cladding tubes according to claim 7, characterized in that: The operating surface of the assembly base (4) is also provided with a groove, the support block is located in the middle of the bottom surface of the groove, and the surrounding sides of the groove are provided with baffles (16) for limiting the clamping end.

9. The experimental method of the circumferential tensile test device for irradiated fuel cladding tubes according to any one of claims 2 to 8, characterized in that: The following steps are involved: S1: uniformly cutting a number of cladding tube samples (1) along the length direction of the cladding tube, and placing the cladding tube samples (1) on the operating surface of the assembly base (4); S2: Control the manipulator to place the two loading fixtures (2) on the assembly base respectively, so that the two clamping ends are respectively located on both sides of the cladding tube sample (1) and are placed in a rotationally symmetrical manner; at this time, the circular hole (7) and the cladding tube sample (1) are coaxial; S3: Control the manipulator to take the semicircular pins (3), and make the two semicircular pins pass through the two circular holes (7) respectively, and pass through the cladding tube sample (1) in opposite directions, so that the semicircular segments (14) can be spliced ​​together to form a cylinder. At this time, the cladding tube sample (1) is sleeved on the outside of the cylinder and is located between the two ends of the cylinder; S4: Connect the loading fixture (2) and the testing machine, and control the clamping ends of the two loading fixtures (2) to gradually separate towards each other under the action of tension, until the cladding tube sample (1) is stressed and undergoes circumferential strain until it breaks, thereby completing the circumferential tensile test.

10. The experimental method of the circumferential tensile test device for irradiated fuel cladding tubes according to claim 9, characterized in that: The following steps are also included: After completing the hoop tensile test, according to the tensile curve collected by the testing machine software system, the formula R m =F m / 2wt and R p0.2 =F s / 2wt respectively calculates the tensile strength and yield strength; where w and t represent the length and wall thickness of the cladding tube sample respectively; Take photos using a video microscope in a thermal chamber and use image analysis software to measure the circumference of the outer wall of the cladding tube sample after fracture; According to the formula A=(l u -l0) / l0 to calculate the elongation after fracture; where l0 and l u They represent the circumference of the outer wall of the cladding tube sample before and after fracture.

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