Irradiated fuel pellet thickness measurement method, thermal conductivity measurement method, and system

Abstract

This application discloses a method and system for measuring the thickness of irradiated fuel cores, as well as a method and system for measuring thermal conductivity. The thickness measurement method includes: calibrating the levelness of a laser thickness measurement platform using a calibrated standard thickness gauge; measuring the height of the laser thickness measurement platform without a thermal conductivity sample after calibration; placing the thermal conductivity sample on the laser thickness measurement platform and measuring the height of the platform with the sample placed, repeating this measurement multiple times; and subtracting the height measurement value without the thermal conductivity sample from the average height measurement value to obtain the thickness measurement value of the thermal conductivity sample. This application employs a hot-room laser thickness measurement method, which meets the requirements for hot-room operation of irradiated thermal conductivity samples, significantly reducing the adverse effects of highly radioactive samples on personnel; while ensuring the accuracy of thickness measurement of irradiated thermal conductivity samples.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of irradiated fuel material performance measurement, and particularly relates to an irradiated fuel pellet thickness measurement method, a thermal conductivity measurement method and a system. BACKGROUND

[0002] During the service of the fuel assembly, the heat generated in the irradiation process needs to be continuously removed from the fuel assembly by cooling water, so the thermal conductivity of the fuel pellet will inevitably affect the heat removal of the fuel pellet during the irradiation process. The physical quantity for measuring the thermal conductivity of the fuel is the thermal conductivity, and it is of great significance to master the change rule of the thermal conductivity of the fuel pellet in the reactor for the use of the fuel assembly and the safe operation of the reactor.

[0003] During the irradiation in the reactor, the nuclear fuel will appear phenomena such as grain refinement, fission gas redistribution and defect generation, which will all lead to the decrease of the thermal conductivity of the fuel. With the increase of burnup, the thermal conductivity of the fuel pellet decreases, and the heat transfer performance of the fuel pellet will be poor, and the overall temperature rise of the fuel element will lead to abnormal swelling and mechanical instability of the fuel assembly, affecting the safe operation of the reactor. Therefore, the thermal conductivity measurement research of the irradiated nuclear fuel has important scientific and engineering values.

[0004] The thermal conductivity test method of the irradiated fuel pellet is usually the laser flash method, which principle is that under a certain set temperature T (constant temperature condition), a light pulse is emitted by a laser source in an instant, uniformly irradiates the lower surface of the sample, and the lower surface layer absorbs the light energy, and the temperature rises instantaneously, and the energy is propagated to the cold end (the upper surface) in one-dimensional heat conduction mode as the hot end. The corresponding temperature rise process of the center part of the upper surface is continuously measured by using an infrared detector, and the relationship curve of temperature (detector signal) rise versus time is obtained, and then the thermal diffusivity of the material at temperature T is obtained through the following equation.

[0005]

[0006] Wherein, d is the thickness of the sample, the thickness is accurate to 0.01 mm; t 50 is the half heating time, also known as t 1 / 2 is the time required for the temperature (detector signal) of the upper surface of the sample to rise to half of the maximum value after receiving the light pulse irradiation.

[0007] Then, the thermal conductivity at the temperature can be calculated according to the thermal diffusivity, specific heat capacity and density at the known temperature.

[0008] From the above, the accuracy of the thickness of the sample is closely related to the thermal conductivity measurement result of the sample, the radioactivity of the irradiated fuel core body is very strong, the non-irradiated sample commonly used can be measured by a contact micrometer screw, the accuracy is better than 10μm, but the personnel need to contact the measured object during the measurement process, and the operation process is complex, which cannot meet the requirements of the in-cell operation of the thermal conductivity sample of the irradiated fuel core body. SUMMARY

[0009] In order to realize the accuracy and safety of the thickness measurement of the irradiated fuel core body thermal conductivity sample, the present application provides an irradiated fuel core body thickness measurement method, a thermal conductivity measurement method and a system, the present application adopts a non-contact measurement method, realizes the in-cell measurement requirement of the thermal conductivity sample of the irradiated fuel core body, and ensures that the measurement accuracy meets the experimental requirements of the thermal conductivity measurement of the irradiated fuel core body.

[0010] The present application realizes the following technical solutions:

[0011] An irradiated fuel core body thickness measurement method, the thickness measurement method comprises:

[0012] A standard thickness gauge block qualified by detection is used to correct the levelness of the laser thickness measuring platform;

[0013] After the correction, the height of the laser thickness measuring platform without placing the thermal conductivity sample is measured;

[0014] The thermal conductivity sample is placed on the laser thickness measuring platform, the height of the laser thickness measuring platform with the thermal conductivity sample is measured, and each thermal conductivity sample is repeatedly measured multiple times;

[0015] The height measurement average value of the laser thickness measuring platform with the thermal conductivity sample is obtained according to the multiple measurement results, the height measurement average value is subtracted from the height measurement value without placing the thermal conductivity sample, and the thickness measurement value of the thermal conductivity sample is obtained.

[0016] In some embodiments, the standard thickness gauge block qualified by detection is used to correct the levelness of the laser thickness measuring platform, specifically comprising:

[0017] The height of the laser thickness measuring platform without placing the standard thickness gauge block is measured;

[0018] The standard thickness gauge block qualified by detection is placed on the laser thickness measuring platform, the height of the laser thickness measuring platform with the standard thickness gauge block is measured, and the average value obtained by multiple measurements is taken as the height measurement result of the standard thickness gauge block;

[0019] Subtracting the height measurement result of the standard thickness gauge without placing the standard thickness gauge from the height measurement result of the standard thickness gauge with placing the standard thickness gauge, the thickness measurement result of the standard thickness gauge is obtained;

[0020] Comparing the thickness measurement result of the standard thickness gauge with the calibration result of the standard thickness gauge, if the difference between the two does not meet the experimental precision requirement, the laser thickness measuring platform is adjusted, and the next correction is returned until the measurement result meets the experimental precision requirement.

[0021] In some embodiments, the thickness measurement method further comprises:

[0022] The thickness measurement process of the irradiated fuel pellet thermal conductivity sample is completed by the mechanical hand operating the related equipment in the hot cell.

[0023] In a second aspect, the present application provides a method for measuring the thermal conductivity of an irradiated fuel pellet, the method comprising:

[0024] Measuring the surface zero-distance radiation level of the irradiated thermal conductivity sample, if the measured radiation level does not exceed the threshold value, the subsequent thermal conductivity measurement process is continued, otherwise it is exited;

[0025] Transporting the thermal conductivity sample to the thermal conductivity measurement hot cell, and measuring the thickness of the thermal conductivity sample by the above thickness measurement method;

[0026] Judging whether the reflectivity of the surface of the thermal conductivity sample after thickness measurement meets the requirements, if the reflectivity does not meet the requirements, the surface of the thermal conductivity sample is treated to make the surface light energy absorption ratio meet the requirements, and then the thermal conductivity sample is transported to the thermal conductivity measurement device, otherwise the thermal conductivity sample is directly transported to the thermal conductivity measurement device;

[0027] According to the measured thickness of the thermal conductivity sample, performing thermal conductivity measurement test on the thermal conductivity measurement device to obtain the thermal diffusivity coefficient of the thermal conductivity sample;

[0028] According to the thermal diffusivity coefficient of the thermal conductivity sample, the thermal conductivity coefficient of the irradiated fuel pellet is calculated.

[0029] In some embodiments, the treatment of the surface of the thermal conductivity sample specifically comprises:

[0030] Spraying a layer of graphite powder or other high-emissivity coating on the surface of the thermal conductivity sample.

[0031] In some embodiments, the thermal conductivity coefficient calculation formula is:

[0032] λ(T)=α(T)*C p(T)*ρ(T)

[0033] Where λ(T) is the thermal conductivity at temperature T, α(T) is the thermal diffusivity at temperature T, and C p ρ(T) is the specific heat at temperature T, and ρ(T) is the density at temperature T.

[0034] In some embodiments, prior to the step of measuring the surface zero-distance radiation level of the irradiated thermal conductivity sample, the method further includes:

[0035] Preparation of thermal conductivity samples of fuel cores;

[0036] After sample preparation, irradiation experiments were conducted.

[0037] After the irradiation experiment was completed, the thermal conductivity sample after irradiation was obtained.

[0038] Thirdly, this application proposes a post-irradiation fuel core thickness measurement system, the thickness measurement system comprising:

[0039] The calibration module is configured to perform levelness calibration on the laser thickness measurement platform using a calibrated standard thickness gauge block.

[0040] Measurement module A is configured to measure the height of the laser measurement platform without a thermal conductivity sample after calibration.

[0041] Measurement module B is configured to: place the thermal conductivity sample on the laser thickness measuring platform, measure the height of the laser thickness measuring platform on which the thermal conductivity sample is placed, and repeat the measurement multiple times for each sample.

[0042] And, calculation module A, which is configured to: obtain the average height measurement value based on the height of the laser thickness measuring platform on which the thermal conductivity sample is placed, obtained from multiple measurements, and subtract the height measurement value of the thermal conductivity sample without placing the thermal conductivity sample from the average height measurement value to obtain the thickness measurement value of the thermal conductivity sample.

[0043] Fourthly, this application proposes a system for measuring the thermal conductivity of irradiated fuel cores, the system comprising:

[0044] The radiation determination module is configured to measure the zero-distance radiation level of the surface of the thermal conductivity sample after irradiation, and if the radiation level does not exceed the threshold, drive the thickness measurement module to perform thickness measurement.

[0045] A thickness measurement module is configured to: transfer the thermal conductivity sample to the thermal conductivity measurement hot chamber and measure the thickness using the above-described thickness measurement method;

[0046] The state determination module is configured to: determine whether the reflectivity of the surface of the thermal conductivity sample after the thickness measurement is completed meets the requirements; if the reflectivity does not meet the requirements, the surface of the thermal conductivity sample is processed to make its surface light energy absorption ratio meet the requirements, and then the irradiated thermal conductivity sample is transferred to the thermal conductivity measuring device; otherwise, the thermal conductivity sample is directly transferred to the thermal conductivity measuring device.

[0047] A thermal diffusivity measurement module is configured to: perform a thermal conductivity measurement test based on the thickness of the thermal conductivity sample obtained by measurement, and obtain the thermal diffusivity of the thermal conductivity sample;

[0048] And, calculation module B, which is configured to calculate the thermal conductivity of the irradiated fuel core based on the thermal diffusivity of the thermal conductivity sample.

[0049] In some embodiments, the thermal conductivity measurement system further includes:

[0050] A sample preparation module, configured to prepare thermal conductivity samples of fuel cores;

[0051] An irradiation module configured to perform an irradiation experiment on the thermal conductivity sample;

[0052] The disassembly module is configured to: remove the irradiated thermal conductivity sample from the irradiation device and transfer it to the sample preparation hot chamber;

[0053] A cleaning and drying module is configured to clean and dry the irradiated thermal conductivity sample in the sample preparation chamber.

[0054] This application proposes a method and system for measuring the thickness and thermal conductivity of irradiated fuel cores. For highly radioactive samples after irradiation, a laser thickness measurement method is used within a hot chamber, fulfilling the requirements for hot chamber operation of irradiated thermal conductivity samples and significantly reducing the adverse effects of highly radioactive samples on personnel. Simultaneously, the laser thickness measurement platform is checked using a calibrated standard thickness brightness before actual measurement to ensure its measurement accuracy meets experimental requirements, thereby guaranteeing the accuracy of thickness measurement for irradiated thermal conductivity samples.

[0055] This application proposes a method and system for measuring the thickness and thermal conductivity of irradiated fuel core samples. The thickness of the irradiated fuel core thermal conductivity sample is measured. The accuracy of the operation and measurement results in the hot chamber can meet the experimental requirements for measuring the thermal conductivity of the fuel core sample, thus providing data support for the measurement of the thermal conductivity of the fuel core and realizing the measurement of the thermal conductivity of the irradiated fuel core.

[0056] This application proposes a method and system for measuring the thickness and thermal conductivity of fuel cores after irradiation. This method enables the measurement of the thermal conductivity of fuel cores after irradiation, thereby obtaining the variation law of the thermal conductivity of fuel cores before and after irradiation, and providing a technical reference for the improvement and development of new fuel cores. Attached Figure Description

[0057] The accompanying drawings, which are included to provide a further understanding of the embodiments of this application and form part of this application, do not constitute a limitation on the embodiments of this application. In the drawings:

[0058] Figure 1 This is a flowchart of the thickness measurement method according to an embodiment of this application;

[0059] Figure 2 This is a flowchart of the thermal conductivity measurement method according to an embodiment of this application;

[0060] Figure 3 This is a block diagram illustrating the principle of the thickness measurement system according to an embodiment of this application.

[0061] Figure 4 This is a block diagram illustrating the principle of the thermal conductivity measurement system according to an embodiment of this application. Detailed Implementation

[0062] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with the embodiments and accompanying drawings. The illustrative embodiments and descriptions of this application are only for explaining this application and are not intended to limit this application.

[0063] Example:

[0064] To meet the requirements of hot chamber operation for thermal conductivity samples of irradiated fuel cores, and to ensure that the thickness measurement accuracy meets the experimental requirements for thermal conductivity measurement of irradiated fuel cores, this embodiment proposes a method for measuring the thickness of irradiated fuel cores. This method utilizes a robotic arm to perform hot chamber operation, assisting in the thickness measurement of irradiated fuel cores, and employs non-destructive measurement technology to achieve high-precision measurement, thereby meeting the experimental requirements for thermal conductivity measurement of irradiated fuel cores.

[0065] like Figure 1 As shown, the thickness measurement method proposed in this embodiment specifically includes the following steps:

[0066] Step 100: Use a calibrated standard thickness gauge block to perform levelness correction on the laser thickness measurement platform.

[0067] This step first involves calibrating the levelness of the laser thickness measurement platform using a certified standard thickness gauge block to ensure the accuracy of subsequent thickness measurements. The specific calibration process is as follows:

[0068] Step 101: Measure the height of the laser thickness measuring platform without placing the standard thickness gauge block.

[0069] Step 102: Place the qualified standard thickness gauge block on the laser thickness measuring platform, measure the height of the laser thickness measuring platform where the standard thickness gauge block is placed, and calculate the average value of the multiple measurements (at least three) as the height measurement result of the standard thickness gauge block.

[0070] Step 103: Subtract the height measurement result of the gauge block without a standard thickness gauge block from the height measurement result of the gauge block with the standard thickness gauge block in place, and obtain the thickness measurement result of the gauge block.

[0071] Step 104: Compare the thickness measurement result of the gauge block with the calibration result of the gauge block. If the difference between the two does not meet the experimental accuracy requirements, adjust the laser thickness measurement platform and return to step 101 for the next calibration until the measurement result meets the experimental accuracy requirements.

[0072] Step 200: After calibration, the height of the laser thickness measurement platform without a thermal conductivity sample is measured.

[0073] Step 300: Place the thermal conductivity sample on the laser thickness measuring platform and measure the height of the laser thickness measuring platform where the thermal conductivity sample is placed. Repeat the measurement multiple times (at least three times) for each sample.

[0074] Step 400: Obtain the average height measurement value based on the height of the laser thickness measurement platform where the thermal conductivity sample is placed, obtained from multiple measurements. Subtract the height measurement value of the thermal conductivity sample without placing the thermal conductivity sample from the average height measurement value to obtain the thickness measurement value of the thermal conductivity sample.

[0075] The thickness measurement method proposed in this embodiment uses a calibrated standard thickness gauge block to check the platform before actual measurement. After the check meets the experimental requirements, a thermal conductivity sample can be placed for thickness measurement. The thickness of a single sample is measured at least three times and the average value is taken. This average value is the thickness measurement result of the thermal conductivity sample of the fuel core, thereby achieving accurate measurement of the thickness of the thermal conductivity sample of the fuel core after irradiation.

[0076] During the thickness measurement of the thermal conductivity sample of the fuel core, the operator outside the hot chamber can use a robotic arm to manipulate the relevant equipment inside the hot chamber to complete the thickness measurement process of the thermal conductivity sample of the irradiated fuel core, which greatly reduces the adverse effects of highly radioactive samples on personnel.

[0077] The thickness measurement method proposed in this embodiment can realize the thickness measurement of the thermal conductivity sample of the fuel core after irradiation. The accuracy of the operation in the hot chamber and the measurement results can meet the experimental requirements of the thermal conductivity measurement of the fuel core sample, thus providing data support for the measurement of the thermal conductivity of the fuel core.

[0078] Based on the same technical concept described above, this embodiment also proposes a method for measuring the thermal conductivity of irradiated fuel cores, such as... Figure 2 As shown, the thermal conductivity measurement method proposed in this embodiment specifically includes the following steps:

[0079] Step S1: Measure the zero-distance radiation level on the surface of the irradiated thermal conductivity sample. If the radiation level does not exceed the threshold, continue the subsequent thermal conductivity measurement process; otherwise, exit. To avoid damage to the thermal conductivity measurement equipment in the thermal chamber from the gamma rays emitted by the sample, it is necessary to monitor the radiation level on the surface of the irradiated thermal conductivity sample. If the radiation level is too high, the thermal conductivity measurement process cannot be performed; if the radiation level meets the requirements, the thermal conductivity measurement process continues.

[0080] Optionally, before step S1, the process may include: preparation of the thermal conductivity sample, irradiation, and disassembly / cutting. The thermal conductivity sample is prepared before irradiation, and the sample size is preferably 12.7 mm in diameter and 2 mm in thickness. The surface should be flat with a parallelism error within 0.5% of the thickness, and no surface defects (such as pinholes, scratches, streaks, etc.) are allowed, as these defects will severely affect the experimental results.

[0081] The prepared thermal conductivity sample is placed in the corresponding irradiation device. In order to ensure the surface condition of the thermal conductivity sample after irradiation, a special irradiation device is customized for the thermal conductivity sample. That is, the size and structure of the irradiation container are matched with the size and structure of the thermal conductivity sample. At the same time, these irradiation devices must be easy to disassemble and sample in the hot chamber.

[0082] The irradiation device containing the thermal conductivity sample is placed in the reactor for irradiation. After the target burn-up is reached, the irradiation device is removed and transferred to the disassembly and cutting hot chamber. In the disassembly and cutting hot chamber, the thermal conductivity sample is removed from the irradiation device and transferred to the sample preparation hot chamber for cleaning (using alcohol or acetone, etc.) and drying.

[0083] Step S2: The thermal conductivity sample is transferred to the thermal conductivity measurement chamber, and the thickness of the irradiated thermal conductivity sample is measured using the thickness measurement method described above.

[0084] Step S3 involves determining whether the reflectivity of the irradiated thermal conductivity sample surface after thickness measurement meets the requirements. If the reflectivity is severe (i.e., does not meet the requirements), the surface of the thermal conductivity sample needs to be treated to ensure its surface light energy absorption ratio meets the requirements before transferring the irradiated thermal conductivity sample to the thermal conductivity measuring device. Otherwise, the irradiated thermal conductivity sample is directly transferred to the thermal conductivity measuring device. Severe reflectivity, meaning the surface light energy absorption ratio is less than the threshold, will reduce the accuracy and reliability of subsequent thermal conductivity measurement results. Therefore, step S3 requires surface treatment of the thermal conductivity sample based on its reflectivity to ensure measurement accuracy. Specifically, a robotic arm can be used to hold a graphite canister and spray a layer of graphite powder or other high-emissivity coating onto the sample surface to ensure the surface light energy absorption ratio meets the requirements.

[0085] Step S4: Based on the measured thickness of the thermal conductivity sample, a thermal conductivity measurement test is performed on the thermal conductivity measuring device to obtain the thermal diffusivity of the sample. Specifically, step S4 can involve using a robotic arm to place the thermal conductivity sample onto the sample holder of the thermal conductivity measuring device, lowering the heating furnace, and starting the thermal conductivity measurement test. During the test, the temperature stability should be manually or automatically verified, and a safety monitoring device should be used to monitor the operating status of the thermal conductivity measuring device within the heating chamber.

[0086] Step S5: Based on the thermal diffusivity of the thermal conductivity sample, the thermal conductivity of the irradiated fuel core is calculated. This step S5 calculates the thermal conductivity of the irradiated fuel core using the relationship between thermal conductivity and thermal diffusivity, i.e., the following formula:

[0087] λ(T)=α(T)*C p (T)*ρ(T)

[0088] Where λ(T) is the thermal conductivity at temperature T, α(T) is the thermal diffusivity at temperature T, and C p ρ(T) represents the specific heat at temperature T, and ρ(T) represents the density at temperature T. From the above formula, it can be seen that the thermal conductivity at temperature T can be calculated given the thermal diffusivity, specific heat, and density. The thermal conductivity can be measured using the aforementioned thermal conductivity measuring device. The density used is the apparent density (also known as bulk density, i.e., mass / apparent volume), which is generally tested at room temperature. Its variation with temperature can be corrected using a table of the material's thermal expansion coefficients. It can also be approximated as constant when the measurement temperature is not too high and the density change is not too large. The specific heat can be obtained using empirical values ​​or by differential scanning calorimetry (DSC).

[0089] The thermal conductivity measurement method proposed in this embodiment can realize the measurement of thermal conductivity of fuel core samples after irradiation, thereby further obtaining the change law of thermal conductivity of fuel cores before and after irradiation, providing technical support and technical reference for the improvement and development of new fuel cores.

[0090] The thermal conductivity measurement method proposed in this embodiment allows operators outside the hot chamber to manipulate relevant equipment inside the hot chamber via a robotic arm to complete the preparation, transfer, and thermal conductivity measurement of the irradiated thermal conductivity sample, significantly reducing the adverse effects of highly radioactive samples on personnel.

[0091] Based on the same technical concept described above, this embodiment also proposes a post-irradiation fuel core thickness measurement system, such as... Figure 3 As shown, the thickness measurement system proposed in this embodiment specifically includes:

[0092] The calibration module is configured to perform levelness calibration on the laser thickness measurement platform using calibrated standard thickness gauge blocks.

[0093] Measurement module A is configured to measure the height of the laser measurement platform without a thermal conductivity sample after calibration.

[0094] Measurement module B is configured to place the thermal conductivity sample on a laser thickness measuring platform, measure the height at which the thermal conductivity sample is placed, and repeat the measurement multiple times for each sample.

[0095] And, calculation module A, which is configured to: obtain the average height measurement value based on the height of the placed thermal conductivity sample obtained from multiple measurements, and subtract the height measurement value of the unplaced thermal conductivity sample from the average height measurement value to obtain the thickness measurement value of the thermal conductivity sample.

[0096] It should be noted that the specific implementation process of each functional module in the thickness measurement system described above is as described in steps 100-400, and will not be repeated here.

[0097] This embodiment also proposes a system for measuring the thermal conductivity of irradiated fuel cores, such as... Figure 4 As shown, the thermal conductivity measurement system proposed in this embodiment specifically includes:

[0098] The radiation determination module is configured to measure the zero-distance radiation level of the surface of the thermal conductivity sample after irradiation, and if the radiation level does not exceed the threshold, drive the thickness measurement module to perform thickness measurement.

[0099] A thickness measurement module is configured to transfer the thermal conductivity sample to the thermal conductivity measurement hot chamber and measure the thickness of the irradiated thermal conductivity sample using the thickness measurement method described above.

[0100] The status determination module is configured to: determine whether the reflectivity of the surface of the irradiated thermal conductivity sample after thickness measurement meets the requirements; if the reflectivity of the sample is severe (i.e. does not meet the requirements), the surface of the thermal conductivity sample needs to be treated to make its surface light energy absorption ratio meet the requirements before the irradiated thermal conductivity sample is transferred to the thermal conductivity measuring device; otherwise, the thermal conductivity sample is directly transferred to the thermal conductivity measuring device.

[0101] The thermal diffusivity measurement module is configured to perform a thermal conductivity measurement experiment based on the thickness of the measured thermal conductivity sample to obtain the thermal diffusivity of the thermal conductivity sample.

[0102] And, calculation module B, which is configured to calculate the thermal conductivity of the irradiated fuel core based on the thermal diffusivity of the thermal conductivity sample.

[0103] It should be noted that the specific implementation process of each functional module of the thermal conductivity measurement system is as described in steps S1-S5 above, and will not be repeated here.

[0104] In an optional embodiment, the thermal conductivity measurement system further includes:

[0105] The sample preparation module is configured to prepare thermal conductivity samples of the fuel core. The prepared thermal conductivity samples are preferably 12.7 mm in diameter and 2 mm thick. The surface should be flat with a parallelism error within 0.5% of the thickness. No surface defects (such as pinholes, scratches, streaks, etc.) are allowed, as these defects will seriously affect the experimental results.

[0106] In an optional embodiment, the thermal conductivity measurement system further includes:

[0107] The irradiation module is configured to place the prepared thermal conductivity sample into a corresponding irradiation device. To ensure the surface condition of the irradiated sample, a dedicated irradiation device is custom-designed for the sample; that is, the size and structure of the irradiation container match the size and structure of the sample. These irradiation devices must also facilitate disassembly and sampling within the hot chamber. The irradiation device containing the thermal conductivity sample is placed in the reactor for irradiation. After the target burn-up is achieved, the irradiation device is removed and transported to the disassembly and cutting hot chamber.

[0108] In an optional embodiment, the thermal conductivity measurement system further includes:

[0109] The disassembly module is configured to remove the thermal conductivity sample from the irradiation device and transfer it to the sample preparation hot chamber in the disassembly and cutting hot chamber.

[0110] In an optional embodiment, the thermal conductivity measurement system further includes:

[0111] The cleaning and drying module is configured to clean (using alcohol or acetone, etc.) and dry the irradiated thermal conductivity sample in the sample preparation hot chamber.

[0112] Those skilled in the art will understand that embodiments of this application can be provided as methods, systems, or computer program products. Therefore, this application can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, this application can take the form of a computer program product embodied on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0113] This application is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of this application. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, generate instructions for implementing the flowchart... Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0114] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1 One or more processes and / or boxes Figure 1 The function specified in one or more boxes.

[0115] These computer program instructions may also be loaded onto a computer or other programmable data processing equipment to cause a series of operational steps to be performed on the computer or other programmable equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable equipment for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.

[0116] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of this application. It should be understood that the above description is only a specific embodiment of this application and is not intended to limit the scope of protection of this application. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the scope of protection of this application.

Claims

1. A method for measuring the thermal conductivity of irradiated fuel cores, characterized in that, The thermal conductivity measurement method includes: Measure the zero-distance radiation level on the surface of the thermal conductivity sample after irradiation. If the measured radiation level does not exceed the threshold, continue the subsequent thermal conductivity measurement process; otherwise, exit. The thermal conductivity sample is transferred to the thermal conductivity measurement chamber, and its thickness is measured using a thickness measurement method. The thickness measurement method includes: calibrating the laser thickness measuring platform for levelness using a calibrated standard thickness gauge block; measuring the height of the laser thickness measuring platform without the thermal conductivity sample; placing the thermal conductivity sample on the laser thickness measuring platform and measuring the height of the platform with the sample placed; repeating this measurement multiple times for each thermal conductivity sample; obtaining an average height measurement value based on the multiple measurements of the platform height with the sample placed; and subtracting the height measurement value without the sample from the average height measurement value to obtain the thickness measurement value of the thermal conductivity sample. After the thickness measurement is completed, determine whether the reflectivity of the thermal conductivity sample surface meets the requirements. If the reflectivity does not meet the requirements, process the surface of the thermal conductivity sample to make its surface light energy absorption ratio meet the requirements before transferring the thermal conductivity sample to the thermal conductivity measuring device. Otherwise, transfer the thermal conductivity sample directly to the thermal conductivity measuring device. Based on the thickness of the thermal conductivity sample obtained by measurement, a thermal conductivity measurement test is performed on the thermal conductivity measuring device to obtain the thermal diffusivity of the thermal conductivity sample. The thermal conductivity of the fuel core after irradiation was calculated based on the thermal diffusivity of the thermal conductivity sample.

2. The method for measuring the thermal conductivity of irradiated fuel cores according to claim 1, characterized in that, The surface treatment of the thermal conductivity sample specifically includes: A layer of graphite powder or other high emissivity coating is sprayed onto the surface of the thermal conductivity sample.

3. The method for measuring the thermal conductivity of irradiated fuel cores according to claim 2, characterized in that, The formula for calculating the thermal conductivity is as follows: ； in, Let T be the thermal conductivity at temperature T. Let be the thermal diffusivity at temperature T. Specific heat at temperature T Let T be the density at temperature T.

4. A method for measuring the thermal conductivity of irradiated fuel cores according to any one of claims 1-3, characterized in that, Prior to the step of measuring the surface zero-distance radiation level of the irradiated thermal conductivity sample, the method further includes: Preparation of thermal conductivity samples of fuel cores; Irradiation experiments were conducted after sample preparation. After the irradiation experiment was completed, the thermal conductivity sample after irradiation was obtained.

5. A method for measuring the thermal conductivity of irradiated fuel cores according to any one of claims 1-3, characterized in that, The aforementioned method of using calibrated standard thickness gauges to perform levelness correction on the laser thickness measurement platform specifically includes: The height of the laser thickness measuring platform without a standard thickness gauge block was measured. The qualified standard thickness gauge block is placed on the laser thickness measuring platform, and the height of the laser thickness measuring platform where the standard thickness gauge block is placed is measured. The average value of the multiple measurements is used as the height measurement result of the standard thickness gauge block. The thickness measurement result of the standard thickness gauge block is obtained by subtracting the height measurement result of the standard thickness gauge block without placing it from the height measurement result of the standard thickness gauge block. The thickness measurement result of the standard thickness gauge block is compared with the calibration result of the standard thickness gauge block. If the difference between the two does not meet the experimental accuracy requirements, the laser thickness measurement platform is adjusted and returned for the next calibration until the measurement result meets the experimental accuracy requirements.

6. A method for measuring the thermal conductivity of irradiated fuel cores according to any one of claims 1-3, characterized in that, The thickness measurement method further includes: The thickness measurement process of the irradiated fuel core thermal conductivity sample is completed by manipulating the relevant equipment in the hot chamber using a robotic arm.

7. A system for measuring the thermal conductivity of irradiated fuel cores, characterized in that, The thermal conductivity measurement system includes: The radiation determination module is configured to measure the zero-distance radiation level of the surface of the thermal conductivity sample after irradiation, and if the radiation level does not exceed the threshold, drive the thickness measurement module to perform thickness measurement. A thickness measurement module is configured to: transfer a thermal conductivity sample to a thermal conductivity measurement chamber and measure the thickness using a thickness measurement method; the thickness measurement method includes: using a calibrated standard thickness gauge block to perform leveling correction on a laser thickness measurement platform; after correction, measuring the height of the laser thickness measurement platform without the thermal conductivity sample; placing the thermal conductivity sample on the laser thickness measurement platform and measuring the height of the laser thickness measurement platform with the thermal conductivity sample placed, repeating the measurement multiple times for each thermal conductivity sample; obtaining an average height measurement value based on the multiple measurements of the laser thickness measurement platform height with the thermal conductivity sample placed; subtracting the height measurement value without the thermal conductivity sample from the average height measurement value to obtain the thickness measurement value of the thermal conductivity sample. The state determination module is configured to: determine whether the reflectivity of the surface of the thermal conductivity sample after the thickness measurement is completed meets the requirements; if the reflectivity does not meet the requirements, the surface of the thermal conductivity sample is processed to make its surface light energy absorption ratio meet the requirements, and then the irradiated thermal conductivity sample is transferred to the thermal conductivity measuring device; otherwise, the thermal conductivity sample is directly transferred to the thermal conductivity measuring device. A thermal diffusivity measurement module is configured to: perform a thermal conductivity measurement test based on the thickness of the thermal conductivity sample obtained by measurement, and obtain the thermal diffusivity of the thermal conductivity sample; And, calculation module B, which is configured to calculate the thermal conductivity of the irradiated fuel core based on the thermal diffusivity of the thermal conductivity sample.

8. A post-irradiation fuel core thermal conductivity measurement system according to claim 7, characterized in that, The thermal conductivity measurement system also includes: A sample preparation module, configured to prepare thermal conductivity samples of fuel cores; An irradiation module configured to perform an irradiation experiment on the thermal conductivity sample; The disassembly module is configured to: remove the irradiated thermal conductivity sample from the irradiation device and transfer it to the sample preparation hot chamber; A cleaning and drying module is configured to clean and dry the irradiated thermal conductivity sample in the sample preparation chamber.

9. A post-irradiation fuel core thermal conductivity measurement system according to claim 7, characterized in that, The aforementioned method of using calibrated standard thickness gauges to perform levelness correction on the laser thickness measurement platform specifically includes: The height of the laser thickness measuring platform without a standard thickness gauge block was measured. The qualified standard thickness gauge block is placed on the laser thickness measuring platform, and the height of the laser thickness measuring platform where the standard thickness gauge block is placed is measured. The average value of the multiple measurements is used as the height measurement result of the standard thickness gauge block. The thickness measurement result of the standard thickness gauge block is obtained by subtracting the height measurement result of the standard thickness gauge block without placing it from the height measurement result of the standard thickness gauge block. The thickness measurement result of the standard thickness gauge block is compared with the calibration result of the standard thickness gauge block. If the difference between the two does not meet the experimental accuracy requirements, the laser thickness measurement platform is adjusted and returned for the next calibration until the measurement result meets the experimental accuracy requirements.

10. A system for measuring the thermal conductivity of irradiated fuel cores according to claim 7, characterized in that, The thickness measurement method further includes: The thickness measurement process of the irradiated fuel core thermal conductivity sample is completed by manipulating the relevant equipment in the hot chamber using a robotic arm.

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