A ceramic thin-wall tube strength testing system and method for nuclear fuel cladding

Abstract

The present invention relates to a ceramic thin-wall tube strength test system and method for nuclear fuel cladding, the system comprising: a sample clamping device (1) for dynamically sealing the outer surface of the cladding tube sample; a hydraulic medium filling device (2) for filling the cladding tube sample with hydraulic medium; a pressure increasing device (3) for increasing the pressure of the hydraulic medium filling device (2); a data acquisition device (4) for collecting test process data and a safety protection device (5) for safety protection; the cladding tube sample and the sample clamping device (1) are arranged in the safety protection device (5), the hydraulic medium filling device (2) is connected with the pressure increasing device (3) and the cladding tube sample, and the data acquisition device (4) comprises a flow sensor (41) and a pressure sensor (42). Compared with the prior art, the present invention can provide a more accurate and reliable evaluation and testing means for the research and production of small-sized and other various inner diameter, thin-walled, brittle ceramic pipe fittings.

Description

Technical Field

[0001] The invention relates to the technical field of ceramic matrix composite material pipe performance testing, and in particular to a ceramic thin-wall pipe strength testing system and method for nuclear fuel cladding. Background Art

[0002] The nuclear fuel cladding tube is one of the most important components in the nuclear reactor core structure with the most demanding service environment. It is not only in direct contact with the nuclear fuel, but also needs to have good high temperature resistance and radiation resistance. It also needs to be in direct contact with coolants such as supercritical water, molten fluoride salt, lead-bismuth coolant, etc. under high temperature and high pressure. The core of nuclear energy safety application is to prevent the radioactive fission products in the reactor from leaking into the surrounding environment. The component cladding material is a key component for installing nuclear fuel. Its function is to prevent the leakage of fission products, especially to prevent the escape of fission products when the nuclear reactor suffers an accident. Therefore, the mechanical property test of the cladding tube can be used to conduct a safety assessment of the cladding tube.

[0003] SiC f SiC composite materials are considered to be a potential nuclear power cladding material in the future due to their radiation resistance, low neutron absorption cross section, excellent high temperature performance and good chemical stability. f / SiC composite cladding will be subjected to large internal pressure during manufacturing, transportation and working conditions, and the cladding needs to have high circumferential strength. f / SiC composite ceramic cladding tubes are long, small in diameter, thin in wall thickness, and brittle in material. The standard strength test method currently widely used for zirconium alloy claddings uses solid-state compression elastomers to apply internal pressure to destroy them. This method is an approximate simulation method and cannot effectively ignore the effects of the elastomer's own strength, stiffness, and assembly on the test results, and cannot obtain accurate results. When using the external radial compression method, the circumferential strength of the ceramic cladding tube is converted by bending, which is affected by the sensitivity of brittle material defects and other factors, resulting in large errors. General hydraulic methods can only be applied through the inner diameter. For ceramic claddings, the diameter is too small to achieve sealing under high pressure. In addition, problems such as joint connection, installation positioning, and high-pressure sealing cannot respond dynamically with deformation, so testing cannot be achieved. Summary of the invention

[0004] The purpose of the present invention is to provide a ceramic thin-wall tube strength testing system and method for nuclear fuel cladding, which has higher method reliability and result accuracy.

[0005] The object of the present invention can be achieved by the following technical scheme: A ceramic thin-wall tube strength testing system for nuclear fuel cladding, comprising:

[0006] A sample clamping device for dynamically sealing the outer surface of the cladding tube sample;

[0007] A hydraulic medium filling device for filling the cladding tube sample with hydraulic medium;

[0008] A pressure boosting device for boosting the pressure of a device filled with a hydraulic medium;

[0009] Data acquisition devices for collecting test process data and safety protection devices for safety protection;

[0010] The cladding tube sample and the sample clamping device are arranged in the safety protection device, the hydraulic medium filling device is connected with the boosting device and the cladding tube sample, and the data acquisition device includes a flow sensor and a pressure sensor.

[0011] The invention provides a destructive strength testing system for a cladding pipe fitting by static pressure injection of hydraulic media such as water or oil, which realizes destructive strength measurement under safe conditions by applying internal liquid pressure.

[0012] In the present invention, the sample clamping device can clamp and seal the cladding tube sample, so that hydraulic media such as water or oil can only be input into the cladding tube sample through the hydraulic medium filling device. The present invention uses the basic principle of hydraulics to truly load the inner wall of the cladding tube sample, which is completely consistent with the load mechanism under the ceramic cladding working condition. At the same time, the outer surface dynamic seal is adopted to solve the sealing problem of small-sized pipe fittings, subverting the traditional understanding that only the loading surface can be sealed during static pressure testing, and realizing that static pressure destruction is suitable for small inner diameter samples.

[0013] In the present invention, the pressure sensor is used to monitor and record the pressure changes applied to the cladding tube in real time during the cladding tube test, thereby ensuring the accuracy and reliability of the test data. The flow sensor is used to monitor and record the flow rate of hydraulic media such as fluid water or oil flowing through the cladding tube during the test.

[0014] Preferably, the sample clamping device comprises a pressurizing seat and an outer surface dynamic sealing seat respectively arranged at both ends of the cladding tube sample;

[0015] The pressurizing seat is provided with a through hole for connecting the cladding tube sample with the hydraulic medium filling device.

[0016] Further preferably, one end of the cladding tube sample is inserted into a pressurizing seat, and the other end is inserted into an outer surface dynamic sealing plugging seat, and dynamic sealing rings are provided between the outer surface of the cladding tube sample and the pressurizing seat and the outer surface dynamic sealing plugging seat, and the pressurizing seat and the outer surface dynamic sealing plugging seat are provided with fixing steps and matching fastening bolts for squeezing and fixing the dynamic sealing ring.

[0017] More preferably, the fastening bolt is threadedly connected to the pressurizing seat and the outer surface dynamic sealing seat.

[0018] More preferably, the dynamic sealing ring is an elastic sealing ring sleeved on the cladding tube sample.

[0019] Preferably, the dynamic sealing ring is a rubber sealing ring.

[0020] Preferably, there are axial gaps between the two ends of the cladding tube sample and the pressurizing seat and the outer surface dynamic sealing seat.

[0021] In the static pressure water injection destruction experiment, the sealing of the cladding tube sample is crucial to the reliability of the experimental data. The commonly used method for sealing open pipe fittings is to insert a metal stepped shaft and seal it with adhesive. However, disassembling this seal requires a destructive method, which may cause damage to the pipe fittings, thereby affecting the analysis of the blasting damage characteristics of the sample. Another sealing method is to use a gland to connect multiple bolt columns on the base flange to fasten the sample. However, this method may cause the sample to deform due to uneven force during assembly, and easily damage the fibers and ceramic matrix on the end face of the composite pipe fitting, affecting the accuracy of the experimental results. The present invention can ensure the sealing of the cladding tube sample while being easy to disassemble and assemble through the coordinated arrangement of a pressurizing seat, a sealing seat, a sealing ring and a fastening bolt, and the sample is subjected to uniform force during assembly, and the sample is not easily deformed or damaged.

[0022] Compared with the traditional adhesive sealing method, the dynamic sealing ring in the present invention allows the sample to expand and contract. The seal of the present invention is a dynamic seal. As the loading progresses, the SiC f Cladding tube samples such as / SiC composite ceramic cladding will expand and contract due to the Poisson effect. The dynamic sealing ring of the present invention can follow the response, fundamentally solving the problems of poor coaxiality, poor authenticity, and large discreteness of test data in circumferential strength testing, and realizing high-precision detection of key circumferential strength of similar slender and small-diameter brittle cladding tubes.

[0023] Further preferably, the pressurizing seat and the outer surface dynamic sealing seat are fixed on the base using the same positioning reference;

[0024] The safety protection device is a safety protection cover, and the pressurizing seat, the outer surface dynamic sealing seat and the base are all arranged in the safety protection cover.

[0025] In the present invention, the safety shield is used to prevent the splashing of the broken sample fragments from causing harm to personnel, and reduce the impact of the destructive test on personnel, the environment, etc.

[0026] More preferably, the safety shield is a transparent shield.

[0027] SiC f / SiC composite cladding pipe static pressure water injection or oil and other hydraulic medium destruction experiments require the use of safety protection mechanisms to protect the safety of the experimenter during the experiment, and at the same time, the rupture of the cladding pipe under water pressure can be observed. The existing cladding pipe static pressure water injection destruction experiment lacks relevant safety protection mechanisms, and it is necessary to design an adaptive mechanism to ensure the safety of the experiment. In addition, the damage of composite cladding pipes during the blasting process is diverse and complex, and it is necessary to ensure that the damage behavior can be observed while protecting safety.

[0028] Preferably, the hydraulic medium filling device comprises a hydraulic medium tank and a hydraulic medium filling pipeline;

[0029] The hydraulic medium box is connected to the cladding tube sample through a hydraulic medium injection pipeline, the booster device is connected to the hydraulic medium injection pipeline, and a flow sensor and a pressure sensor are arranged on the hydraulic medium injection pipeline.

[0030] Further preferably, the flow sensor is used for measuring the flow of the hydraulic medium, is a liquid column metering type, and the accuracy of the sensor should not be lower than level 0.5.

[0031] Further preferably, the accuracy of the pressure sensor is not less than level 0.5.

[0032] In the present invention, the hydraulic medium box is used to perform static pressure injection of hydraulic medium such as water or oil into the cladding tube sample.

[0033] Further preferably, the hydraulic medium injection pipeline is provided with a hydraulic medium discharge branch pipe and a valve.

[0034] More preferably, the hydraulic medium injection pipeline comprises a first main pipeline, a branch pipeline and a second main pipeline in sequence, one end of the first main pipeline is connected to the hydraulic medium tank, and the other end is connected to the branch pipeline, one end of the second main pipeline is connected to the branch pipeline, and the other end is connected to the sample clamping device, the branch pipeline comprises two parallel branch pipes, one of which is provided with a hydraulic medium discharge branch pipe and a valve, and the other branch is provided with a booster device.

[0035] Preferably, the pressurizing device comprises a high-pressure pump connected to a pressure gauge. The high-pressure pump uses compressed air as a power source, and the hydraulic medium filling device injects the hydraulic medium into the cladding tube sample by driving the air source.

[0036] Further preferably, the pressure gauge is used for pressure monitoring, with an accuracy of not less than level 1.6, and a maximum range of the pressure gauge is 1.5 to 3 times the designed bursting pressure of the gas cylinder.

[0037] Further preferably, the high-pressure pump is connected to a compressed air delivery pipeline, and a valve is provided on the compressed air delivery pipeline.

[0038] More preferably, the compressed air delivery pipeline is connected in series with the hydraulic medium box, and a loading drive is applied from the source to drive the hydraulic medium to continuously flow to the cladding tube sample to achieve continuous pressurization.

[0039] Preferably, the pipeline used in the ceramic thin-walled tube strength testing system for nuclear fuel cladding is a pressure-bearing pipeline, which should undergo a pressure test, and the test pressure should be no less than twice the design failure pressure of the cladding tube sample.

[0040] Further preferably, the pipeline is a stainless steel pipe.

[0041] Preferably, the data acquisition device also includes a data collector.

[0042] Further preferably, the pressure sensor is connected to a data collector. The data collector sends out an electrical signal, the output current value increases, and the driving gas source pressure gradually increases until the pressure in the tube to be tested decreases, indicating that the tube sample to be tested is damaged and failed.

[0043] More preferably, the flow sensor is connected to a data collector.

[0044] In the present invention, the data collector automatically draws a pressure-inlet hydraulic medium flow curve of the tested cladding tube sample based on the collected data of the inlet hydraulic medium flow and pressure, and the data collection frequency of the pressure and inlet hydraulic medium flow is not less than 10 times / s.

[0045] In the present invention, the data acquisition device digitally displays the failure pressure of the tested cladding tube sample, such as 0-70MPa, according to the pressure-inlet hydraulic medium flow curve, and the theoretical failure pressure is 63MPa. For the tested cladding tube sample without obvious yield phenomenon, the pressure value when the curve deviates (or deviates to a very small specified value) from the proportional expansion line displays the failure pressure of the tested cladding tube sample. The maximum failure pressure of this system is 80MPa. The circumferential failure strength of the cladding tube can be obtained by recording the failure pressure and converting and processing the data.

[0046] A method for testing the strength of a ceramic thin-wall tube for nuclear fuel cladding is carried out using the above-mentioned testing system and comprises the following steps:

[0047] S1. Sample installation: Install the cladding tube sample to be tested on the sample clamping device, install the strain gauge on the surface of the cladding tube sample, and cover it with a safety cover;

[0048] S2. Sealing performance test: Turn on the booster device, and continuously and evenly inject the hydraulic medium of the hydraulic medium filling device into the cladding tube sample through the driving air source, then stop injecting the hydraulic medium, and perform sealing performance test on the cladding tube sample;

[0049] S3. Static pressure injection hydraulic medium destruction test: After the sealing performance test is qualified, continue to inject hydraulic medium into the cladding tube sample, and gradually increase the driving gas source pressure until the pressure in the cladding tube sample to be tested decreases, indicating that the cladding tube sample is destroyed and failed. The data acquisition device collects the pressure-time curve of the test process.

[0050] Preferably, during the static pressure injection hydraulic medium destruction test, observe whether there are cracks or damage on the surface of the cladding tube sample, and record relevant data in time. After the test, clean the cladding tube sample, observe and record the final destruction damage morphology of the cladding tube sample.

[0051] Preferably, after the test is completed, the strength value of the cladding tube sample is calculated based on the pressure-time curve.

[0052] Further preferably, the maximum failure pressure P is obtained based on the pressure-time curve, and the hoop strength σ of the cladding tube sample is obtained based on the following formula:

[0053] σ=P*D / 2t;

[0054] Where P is the maximum failure pressure of the cladding tube sample, D is the inner diameter of the cladding tube sample, and t is the thickness of the cladding tube sample.

[0055] Preferably, the rated working pressure of the booster device is not less than twice the designed bursting pressure of the cladding tube sample, and no other external force other than the test hydraulic medium pressure is applied to the tested cladding tube sample.

[0056] Preferably, the hydraulic medium comprises water or oil.

[0057] Preferably, the flow rate of the hydraulic medium is adjusted manually or automatically according to the test rate of the tested cladding tube sample.

[0058] Preferably, the testing method specifically comprises the following steps:

[0059] (1) Prepare samples. Prepare SiC of a certain size according to requirements. f / SiC composite cladding tube specimen.

[0060] (2) Sample installation. Install the cladding tube sample to be tested in the sample clamping device, install the strain gauge on the surface of the cladding tube sample, and cover it with a safety cover.

[0061] (3) Sealing performance test. Open the compressed air delivery pipeline valve and high-pressure pump, and continuously and evenly inject liquid water into the cladding tube sample by driving the air source. Then stop the water injection and close the pipeline valve to perform a sealing performance test on the cladding tube sample.

[0062] (4) Static pressure water injection failure test. After the sealing performance test is qualified, continue to pump liquid water into the cladding tube sample, and gradually increase the driving gas source pressure until the pressure in the tube to be tested decreases, indicating that the tube sample to be tested has failed. The data acquisition device automatically collects the pressure-time curve of the test process.

[0063] (5) Observation and recording. During the water injection process, observe whether there are cracks or damage on the surface of the sample, and record the relevant data in time. After the test, clean the sample to be tested, observe and record the final damage morphology of the test tube, such as the path of crack formation and propagation, the location of damage, etc.

[0064] (6) Data processing: Data processing is performed based on the test results to calculate the strength value of the cladding tube sample.

[0065] The burst pressure is an important parameter to measure the pressure resistance of cladding pipes during the design and manufacturing stages. The ratio of the burst pressure to its design pressure can characterize the safety margin of the cladding pipes to a certain extent, which is particularly important in engineering applications. Once the cladding pipes fail in strength and break during use, serious nuclear safety accidents will occur. Therefore, SiC f The hydrostatic pressure destructive test of SiC / SiC composite cladding pipes is very important for their application in the engineering field.

[0066] In the prior art, commonly used methods for strength testing of brittle ceramic materials include axial tension, circumferential tension, and radial crushing. However, due to the brittle nature of ceramic materials, these testing methods have problems such as unreliability, large discreteness, and difficulty in sample preparation to a certain extent. Compared with conventional testing methods, the static pressure destruction test of the nuclear cladding tube of the present invention can more comprehensively reflect the mechanical properties of the material. This method helps to evaluate the safety performance of nuclear reactors and predict the load limit and rupture mechanism of nuclear cladding tubes in unexpected situations.

[0067] The static pressure destruction method of the clad pipe fitting of the present invention is tested by applying pressure of a liquid water medium to the inner surface of the pipe fitting. During the experiment, the pressure is gradually increased until the pipe fitting fails, and the maximum pressure at this time, that is, the destruction pressure of the material, is measured to obtain the destruction strength of the material. This process can be converted through a theoretical formula to obtain a more specific destruction strength value. The static pressure destruction method can be used to evaluate the strength and pressure resistance of a material, and is suitable for situations where it is necessary to understand the performance of a material under high pressure. The destruction pressure obtained through experimental measurement can provide an important reference for engineering design and material selection, helping engineers and researchers to better understand the performance characteristics and ultimate bearing capacity of the material.

[0068] Compared with the prior art, the present invention has the following beneficial effects:

[0069] 1. The present invention provides a method for testing the strength of thin-walled ceramic tubes of nuclear fuel cladding by means of hydrostatic water injection or hydraulic medium destruction such as oil. Compared with conventional testing methods such as radial crushing and outer crushing of elastomers, the method of the present invention can solve the inherent mechanism problems of ceramic brittle material testing and has higher test reliability and data accuracy.

[0070] 2. The present invention adopts a hydraulic medium destruction method such as static pressure water injection or oil, which can accurately achieve the same load mode as the actual working condition, and improve the problems of principle deviation, approximate simulation, and difficulty in measuring small sizes during the test process. The strength test method of the present invention will provide a more accurate and reliable test evaluation method for the research and production of brittle ceramic pipe fittings.

[0071] 3. The test clamping and sealing device of the present invention is equipped with a pressurizing seat, a clamping device sealing seat for dynamic sealing of the outer surface of the sample, a sealing ring and a fastening bolt. The dynamic sealing of the outer surface of the sample is adopted to achieve internal loading and external sealing, which can solve the inherent problem that the inner surface of a small-sized thin-walled tube is difficult to seal and thus difficult to use static pressure loading. During the loading process, the sealing method allows the sample diameter to expand and axially expand and contract, realizing dynamic accompanying sealing, eliminating the additional impact that the sealing may have on the test, and achieving high reliability and high precision of the test.

[0072] 4. The ceramic cladding tube sample of the present invention uses a fixing seat, a plugging seat, etc. on the same positioning reference during assembly, eliminating the additional load that may be caused by the fixing device, so that the sample only bears a uniform internal radial pressure, the test data has a small discreteness, and more accurately reflects the actual mechanical properties of the sample. The implementation method is scientific and the test results are reliable.

[0073] 5. The cladding tube sample of the present invention is sealed on the outside and loaded on the inside, which can achieve uniform hydraulic loading and uniform internal pressure, avoid additional loads, and eliminate failures caused by additional factors such as different axes of installation and bending. The discreteness will be reduced, the data will be more stable, and the real working conditions will be simulated, and the test data will be more real and reliable.

[0074] 6. The present invention ensures the sealing of the cladding tube sample and does not require additional processing or sample preparation. The sample is easy to disassemble and assemble during testing, and the influence that may be caused by the testing method is systematically eliminated.

[0075] 7. The present invention can provide a more accurate and reliable evaluation and testing means for the research and production of small-sized and other various inner diameter, thin-walled, brittle ceramic pipe fittings. BRIEF DESCRIPTION OF THE DRAWINGS

[0076] Figure 1 It is a structural schematic diagram of the test system of the present invention;

[0077] Figure 2 It is a structural schematic diagram of the sample clamping device of the present invention;

[0078] Figure 3 This is a pressure-time curve diagram of the silicon carbide ceramic cladding tube in Example 3;

[0079] In the figure: 1-sample clamping device, 11-pressurizing seat, 12-outer surface dynamic sealing seat, 13-base, 14-dynamic sealing ring, 2-hydraulic medium filling device, 21-hydraulic medium box, 22-hydraulic medium filling pipeline, 3-boosting device, 31-high pressure pump, 32-pressure gauge, 4-data acquisition device, 41-flow sensor, 42-pressure sensor, 5-safety protection device, 6-cladding tube sample, a-valve. DETAILED DESCRIPTION

[0080] The present invention is described in detail below in conjunction with the accompanying drawings and specific embodiments. This embodiment is implemented based on the technical solution of the present invention, and provides a detailed implementation method and specific operation process, but the protection scope of the present invention is not limited to the following embodiments.

[0081] Example 1

[0082] A ceramic thin-wall tube strength test system for nuclear fuel cladding, such as Figure 1 As shown, it includes: a sample clamping device 1, a hydraulic medium filling device 2, a pressurizing device 3, a data acquisition device 4 and a safety protection device 5.

[0083] Specifically, the sample clamping device 1 is used to clamp the cladding tube sample to be tested and ensure that other parts are sealed under the premise that the cladding tube sample is connected to the hydraulic medium filling device 2. The hydraulic medium filling device 2 is connected to the boosting device 3 and is used to inject water into the cladding tube sample 6 under the pressure of the boosting device 3. The data acquisition device 4 includes a flow sensor 41 for detecting the flow rate of the injected hydraulic medium and a pressure sensor 42 for detecting the pressure of the injected hydraulic medium. The safety protection device 5 includes a safety protection cover. The cladding tube sample and the sample clamping device 1 are arranged in the safety protection device 5.

[0084] Example 2

[0085] A ceramic thin-wall tube strength test system for nuclear fuel cladding, such as Figure 2As shown, the sample clamping device 1 includes a pressurizing seat 11, an outer surface dynamic sealing seat 12 and a base 13. The pressurizing seat 11 and the outer surface dynamic sealing seat 12 are fixed on the base 13. The cladding tube sample 6 with openings at both ends is inserted into the pressurizing seat 11 at one end and inserted into the outer surface dynamic sealing seat 12 at the other end. A through hole for connecting the cladding tube sample 6 with the hydraulic medium filling device 2 is opened on the pressurizing seat 11, and the outer surface dynamic sealing seat 12 blocks the other end of the cladding tube sample 6. In addition, a dynamic sealing ring 14 is provided between the outer wall of the cladding tube sample 6 and the pressurizing seat 11 and the outer surface dynamic sealing seat 12. The pressurizing seat 11 and the outer surface dynamic sealing seat 12 are both threadedly connected with fastening bolts for squeezing and fixing the dynamic sealing ring 14.

[0086] Moreover, in this embodiment, the hydraulic medium filling device 2 includes a hydraulic medium box 21 and a hydraulic medium filling pipeline 22, the booster device 3 includes a high-pressure pump 31 and a pressure gauge 32, and the data acquisition device 4 also includes a data acquisition device 43. The hydraulic medium box 21 is connected to the cladding tube sample 6 through the hydraulic medium filling pipeline 22, the flow sensor 41 and the pressure sensor 42 are arranged on the hydraulic medium filling pipeline 22 and connected to the data acquisition device 43, the high-pressure pump 31 is connected to the pressure gauge 32 and is connected to the hydraulic medium filling pipeline 22, and the hydraulic medium of the hydraulic medium filling pipeline 22 is driven by compressed air to inject the hydraulic medium into the cladding tube sample 6. The rest is the same as that of Embodiment 1.

[0087] This embodiment uses compressed air as a power source and a high-pressure pump as a booster device, and injects the liquid medium into the cladding tube sample through the driving gas source. The output liquid pressure value is adjusted by adjusting the driving gas source pressure.

[0088] This embodiment integrates the test installation, static pressure destruction test, and data acquisition device on the same platform. This system can complete the static pressure water injection or oil and other hydraulic medium destruction test and mechanical performance evaluation. This embodiment uses the cladding tube sample, pressurization seat, outer surface dynamic sealing plugging seat, fastening bolts and dynamic sealing ring as the sample clamping device, and uses a high-pressure pump and a pressure sensor to perform a pressurized destruction test on the cladding tube sample placed in the safety protection cover. The data acquisition device completes the data recording of the cladding tube sample destruction process, and the data acquisition is convenient, high-precision, safe and reliable.

[0089] Example 3

[0090] A system and method for testing the strength of ceramic thin-walled tubes for nuclear fuel cladding, the system comprising a water tank (hydraulic medium tank 21), a flow sensor 41, a data acquisition unit 43, a pressure gauge 32, a high-pressure pump 31, a pressure sensor 42, a sample clamping device 1, a safety shield (safety shield 5), and a valve a. The water tank is connected to the flow sensor 41, the flow sensor 41 and the pressure sensor 42 are connected to the data acquisition unit 43, the high-pressure pump 31 is connected to the pressure gauge (pressure gauge 32), and the sample clamping device 1 is placed in the safety shield.

[0091] In this embodiment, the two ends of the cladding tube sample clamped by the sample clamping device have a pressurizing seat and a plugging seat, a sealing ring is sleeved on the pressurizing seat, the outer side of the pressurizing seat is connected to the water injection pipeline, and the sealing ring is squeezed by tightening the bolts inside the pressurizing seat to achieve a sealing effect. The plugging seat is the plugging end of the cladding tube sample, and a sealing ring is sleeved on it. The sealing ring is squeezed by tightening the bolts inside the pressurizing seat to achieve a sealing effect.

[0092] During the cladding tube test, the pressure sensor monitors and records the pressure changes applied to the cladding tube in real time, thereby ensuring the accuracy and reliability of the test data.

[0093] During the cladding tube test, the flow sensor monitors and records the liquid water flow through the cladding tube in real time during the test.

[0094] During the static pressure water injection destruction test, when the test pressure of the tested cladding tube sample does not reach the cladding tube sample destruction pressure and a failure occurs in the equipment or system so that the test cannot be continued, it is allowed to re-test after the failure is repaired.

[0095] During the static pressure water injection failure test, if the pressure of the tested cladding tube sample exceeds the failure pressure of the tested cladding tube sample, regardless of the reason for the test stop, the tested cladding tube sample cannot be tested again. Another sample should be drawn for retesting.

[0096] The above device, when conducting a static pressure water injection failure test, includes the following steps:

[0097] S1. Prepare samples. Prepare SiC of a certain size according to requirements. f / SiC composite cladding tube samples are tested for outer surface roughness and finish to determine the appearance eligibility of the samples. The qualified samples are tested for their inner diameter and tube thickness.

[0098] S2. Sample installation. Install the cladding tube sample to be tested in the sample clamping device, install strain gauges on the surface of the sample to record deformation, and cover the safety cover.

[0099] S3. Sealing test. Open the compressed air pipeline valve and high-pressure pump, and continuously and evenly inject liquid water or oil and other hydraulic media into the cladding tube sample through the driving air source, then stop the water injection and close the pipeline valve, and perform sealing performance test on the sample.

[0100] S4. Static pressure water injection destruction test. If there is no leakage of the medium and the pressure rises, it indicates that the sealing performance test is qualified. Continue to pump liquid water into the cladding tube sample, and gradually increase the pressure of the driving gas source until the pressure in the tube to be tested decreases instantly, indicating that the tube sample to be tested is destroyed and fails. The data acquisition device automatically collects the pressure-time curve of the test process.

[0101] S5. Observation and recording. During the water injection process, observe whether there are cracks or damage on the surface of the sample, and record the relevant data in time. After the test, clean the tube sample to be tested, observe and record the final damage morphology of the tube to be tested. In addition to recording the original data of the tested cladding tube sample, including the tested cladding tube sample number, water pressure test pressure, cladding tube sample size, and cladding tube sample weight, the test report also includes at least the following main contents:

[0102] a) Test water temperature and ambient temperature;

[0103] b) Pressure-water inlet curve chart;

[0104] c) Failure pressure of the tested cladding tube sample;

[0105] d) Yield pressure of the tested cladding tube sample;

[0106] e) Total water pressure;

[0107] f) rupture location and rupture shape;

[0108] h) Volumetric deformation rate.

[0109] S6. Data processing: Perform data processing based on the test results and calculate the strength value of the cladding tube sample.

[0110] The details are as follows:

[0111] On the silicon carbide ceramic cladding tube prepared by the normal process, a 300mm long silicon carbide ceramic cladding tube was cut and tested for the roughness and smoothness of the outer surface. The measured results were: in compliance with the requirements of this test system. The inner diameter and thickness were tested, and the inner diameter D was measured to be 8.1mm and the thickness t was 0.98mm. The "o"-shaped rubber sealing rings with an inner diameter of 8mm and a diameter of 1.2mm were installed on both ends of the measured cladding tube sample. After installation, they were tightened with fixed steps and fastening nuts, and installed in the safety protection device, and strain gauges were installed on the outer surface to record the deformation. Slowly inject 20℃ water and observe that no water seepage is found. Continue to pressurize, and the pressure continues to rise, indicating that the seal is good. Continue to pressurize, and when the maximum breaking pressure P is 57.6MPa, the sample breaks in the middle. The system also automatically records the yield pressure, strain and other information, and obtains the pressure-deformation curve and Figure 3 The pressure-time curve is shown.

[0112] The hoop strength σ is calculated according to the following formula:

[0113] σ=P*D / 2t

[0114] =57.6*8.1 / 2*0.98

[0115] =238(MPa)

[0116] Among them, P is the maximum breaking pressure, D is the inner diameter of the cladding tube, and t is the thickness of the cladding tube.

[0117] The theoretical strength value of the cladding tube of the above-mentioned size is 245 MPa. The circumferential strength test is realized by using the system of the present invention, and the result is close to the theoretical value and within the acceptable system error of the engineering.

[0118] In order to verify the effectiveness of the system test method, a sample of the same ceramic cladding tube was tested by elastic plug internal pressure method, and the result was 205MPa. The main reason is that the elastomer is solid, and the stiffness and strength cannot be ignored, which caused the actual test value to be low. The radial crushing method was used for testing, and the specimen was partially broken in the length direction. The converted strength was 148MPa. The paper sample was tested again, and the converted strength was 197MPa. The port morphology was observed, and it was found that the two sample failures were random sample damage caused by local cracks. This method did not achieve the expected effect and failed to effectively detect the strength of the ceramic cladding tube.

[0119] The present invention provides a system and method for high-precision testing of the circumferential strength of ceramic thin-walled tubes for nuclear fuel cladding, which has higher dimensional adaptability, working condition authenticity, method reliability and result accuracy.

[0120] The above description of the embodiments is to facilitate the understanding and use of the invention by those skilled in the art. It is obvious that those skilled in the art can easily make various modifications to these embodiments and apply the general principles described herein to other embodiments without creative work. Therefore, the present invention is not limited to the above embodiments, and improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the present invention should be within the scope of protection of the present invention.

Claims

1. A ceramic thin-wall tube strength testing system for nuclear fuel cladding, characterized in that: include: A sample clamping device (1) for dynamically sealing the outer surface of a cladding tube sample; A hydraulic medium filling device (2) for filling the cladding tube sample with a hydraulic medium; A pressure boosting device (3) for boosting the pressure of the hydraulic medium filling device (2); A data acquisition device (4) for collecting test process data and a safety protection device (5) for safety protection; The cladding tube sample and the sample clamping device (1) are arranged in a safety protection device (5), the hydraulic medium filling device (2) is connected to the pressure boosting device (3) and the cladding tube sample, and the data acquisition device (4) includes a pressure sensor (42).

2. The ceramic thin-wall tube strength testing system for nuclear fuel cladding according to claim 1 is characterized in that: The sample clamping device (1) comprises a pressurizing seat (11) and an outer surface dynamic sealing seat (12) respectively arranged at both ends of the cladding tube sample; The pressurizing seat (11) is provided with a through hole for connecting the cladding tube sample with the hydraulic medium filling device (2).

3. The ceramic thin-wall tube strength testing system for nuclear fuel cladding according to claim 2 is characterized in that: One end of the cladding tube sample is inserted into the pressurizing seat (11), and the other end is inserted into the outer surface dynamic sealing seat (12), and a dynamic sealing ring (14) is provided between the outer surface of the cladding tube sample and the pressurizing seat (11) and the outer surface dynamic sealing seat (12), and a fixing step and matching fastening bolts for squeezing and fixing the dynamic sealing ring (14) are provided on the pressurizing seat (11) and the outer surface dynamic sealing seat (12).

4. The ceramic thin-wall tube strength testing system for nuclear fuel cladding according to claim 2, characterized in that: The pressurizing seat (11) and the outer surface dynamic sealing seat (12) are fixed on the base (13) using the same positioning reference; The safety protection device (5) is a safety protection cover, and the pressurizing seat (11), the outer surface dynamic sealing seat (12) and the base (13) are all arranged inside the safety protection cover.

5. The ceramic thin-wall tube strength testing system for nuclear fuel cladding according to claim 1, characterized in that: The hydraulic medium filling device (2) comprises a hydraulic medium box (21) and a hydraulic medium filling pipeline (22); The hydraulic medium box (21) is connected to the cladding tube sample via a hydraulic medium injection pipeline (22), the booster device (3) is connected to the hydraulic medium injection pipeline (22), and a flow sensor (41) and a pressure sensor (42) are provided on the hydraulic medium injection pipeline (22).

6. The ceramic thin-wall tube strength testing system for nuclear fuel cladding according to claim 5, characterized in that: The hydraulic medium injection pipeline (22) is provided with a hydraulic medium discharge branch pipe and a valve.

7. The ceramic thin-wall tube strength testing system for nuclear fuel cladding according to claim 1, characterized in that: The pressurizing device (3) comprises a high-pressure pump (31), the high-pressure pump (31) is connected to a pressure gauge (32), and the high-pressure pump (31) uses compressed air as a power source, and drives the air source to realize the hydraulic medium filling device (2) to inject the hydraulic medium into the cladding tube sample.

8. The ceramic thin-wall tube strength testing system for nuclear fuel cladding according to claim 7, characterized in that: The high-pressure pump (31) is connected to a compressed air delivery pipeline, and a valve is provided on the compressed air delivery pipeline.

9. A method for testing the strength of ceramic thin-walled tubes for nuclear fuel cladding, characterized in that: The method is carried out using the test system according to any one of claims 1 to 8, comprising the following steps: S1. Sample installation: install the cladding tube sample to be tested on the sample clamping device (1), install the strain gauge on the surface of the cladding tube sample, and cover it with a safety cover; S2. Sealing performance test: Turn on the booster device (3), and continuously and evenly inject the hydraulic medium of the hydraulic medium filling device (2) into the cladding tube sample by driving the gas source, then stop injecting the hydraulic medium, and perform a sealing performance test on the cladding tube sample; S3. Static pressure injection hydraulic medium destruction test: After the sealing performance test is qualified, continue to inject hydraulic medium into the cladding tube sample, and gradually increase the driving gas source pressure until the pressure in the cladding tube sample to be tested decreases, indicating that the cladding tube sample is destroyed and failed. The data acquisition device (4) collects the pressure-time curve of the test process.

10. The method for testing the strength of ceramic thin-walled tubes for nuclear fuel cladding according to claim 9, characterized in that: During the hydrostatic pressure injection test, observe whether there are cracks or damage on the surface of the cladding tube sample, and record the relevant data in time. After the test, clean the cladding tube sample, observe and record the final damage morphology of the cladding tube sample; After the test, the strength value of the cladding tube sample was calculated based on the pressure-time curve.

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