In-reactor temperature measurement method based on SiC thermal diffusion coefficient change after neutron irradiation

Abstract

The invention discloses a method for measuring temperature in a reactor based on SiC thermal diffusion coefficient change after neutron irradiation. The method comprises the following steps: S1, processing a SiC crystal material into a flaky sample; s2, packaging the SiC crystal sample and the to-be-irradiated material sample into an irradiation sample box, and then putting the irradiation sample box into a reactor for a neutron irradiation experiment; s3, after the neutron irradiation experiment is completed, taking out the irradiation sample box from the reactor, cutting and disintegrating the irradiation sample box, and taking out the irradiated SiC crystal sample; s4, putting the SiC crystal sample into thermal conductivity meter equipment, and measuring thermal diffusion coefficients of the SiC crystal sample at different temperatures; and S5, drawing a curve chart of the thermal diffusion coefficient of the SiC crystal sample after irradiation along with temperature change, wherein the inflection point of the curve is the irradiation temperature of the position of the SiC crystal sample in the reactor. The method has the beneficial effects that the neutron irradiation temperature in the reactor at the position of the SiC crystal can be efficiently and quickly obtained.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of irradiation temperature measurement, in particular to a reactor in-situ temperature measurement method based on SiC thermal diffusion coefficient change after neutron irradiation. BACKGROUND

[0002] The irradiation temperature of materials in the reactor has always been one of the key indicators for nuclear energy materials to withstand neutron irradiation and then move towards engineering application. Due to the factors such as strong neutron irradiation, coolant corrosion and closed environment in the reactor, the traditional temperature measurement method is difficult to be applied to the reactor operation and material irradiation temperature measurement, which restricts the development and advancement of related engineering applications and affects the rapid optimization and selection of irradiation sample box design parameters.

[0003] The methods currently used for reactor in-situ temperature measurement mainly include thermocouples, crystal temperature measurement, temperature indicating paint and metal fuses. Among them, the radiation-resistant metal thermocouple can obtain the internal temperature of the reactor in real time during operation, but the external lead is complex and requires additional open circuit and other special engineering supporting devices, so it cannot be used for measuring the irradiation temperature of materials in a closed cavity, and the applicable scene is limited. The temperature indicating paint method is easily affected by the use conditions such as heating speed, heating time and environmental pollution, has large subjective error, limited temperature measurement range and poor precision. The metal fuse method can only obtain the discrete value of the highest temperature in the whole material irradiation cycle, and a series of metal fuses with different melting points need to be prepared, which has complex structure and process and large temperature measurement interval.

[0004] The SiC crystal passive temperature measurement technology can obtain the average highest temperature in the material irradiation cycle, has many advantages such as high upper limit of temperature measurement, good accuracy, no lead and small destructiveness, and is an effective measurement method suitable for strong irradiation, strong corrosion, high temperature and closed environment in the reactor. Compared with the reactor in-situ temperature measurement technologies such as thermocouples, fuses and temperature indicating paint, the SiC crystal temperature measurement technology has the advantages of small size, low gamma heating rate and low residual radioactivity. However, at present, the reactor in-situ irradiation temperature of SiC crystal is mainly obtained by measuring the physical property change curve of SiC crystal at room temperature after multiple isochronal annealing, which needs to transfer and process samples between different devices, and the process needs to be operated in series, which is extremely tedious and consumes a lot of time and labor cost. SUMMARY

[0005] Therefore, the present application provides a reactor in-situ temperature measurement method based on SiC thermal diffusion coefficient change after neutron irradiation, which can efficiently and quickly obtain the reactor in-situ neutron irradiation temperature of the position where the SiC crystal is located, and has the advantages of convenient operation and simple process.

[0006] To achieve the above-mentioned purpose, the technical scheme of the present application is as follows:

[0007] The application relates to a reactor in-situ temperature measuring method based on SiC thermal diffusion coefficient change after neutron irradiation.

[0008] Step S1: processing SiC crystal material into a sheet-shaped sample;

[0009] Step S2: packaging the SiC crystal sample into an irradiation sample box together with a sample of a material to be irradiated, and then placing the irradiation sample box into a reactor for neutron irradiation experiment;

[0010] Step S3: after the neutron irradiation experiment is completed, taking the irradiation sample box out of the reactor, cutting and disassembling the irradiation sample box, and taking out the SiC crystal sample after irradiation;

[0011] Step S4: placing the SiC crystal sample into a thermal conductivity instrument device to measure the thermal diffusion coefficient of the SiC crystal sample at different temperatures;

[0012] Step S5: drawing a curve of the thermal diffusion coefficient of the SiC crystal sample after irradiation changing with temperature, and the inflection point of the curve is the irradiation temperature of the position of the SiC crystal sample in the reactor.

[0013] As preferred: in step S4, the thermal diffusion coefficient test steps of the SiC crystal sample are as follows:

[0014] Step S4.1: measuring and recording the thickness of the SiC crystal sample to be measured;

[0015] Step S4.2: sequentially turning on the power switches of the main machine, the water bath box, the laser and the heating box of the laser thermal conductivity instrument, placing the SiC crystal sample to be measured into the sample bin, and confirming that the SiC crystal sample to be measured is kept centered and stable in the sample bin;

[0016] Step S4.3: placing the sample bin on the sample support of the thermal conductivity instrument, and then lowering the sample support to the bottom of the furnace body;

[0017] Step S4.4: setting the measurement parameters on the control computer of the thermal conductivity instrument, and inputting the thickness of the SiC crystal sample to be measured into the device;

[0018] Step S4.5: closing the sample chamber, and vacuumizing the sample chamber, and then inputting the temperature ladder and the temperature rising rate, the temperature holding time and the measurement times on the test software;

[0019] Step S4.6: recording the thermal diffusion coefficient data of the SiC crystal sample at different test temperatures.

[0020] As preferred: in step S1, the SiC crystal is processed into a round sheet-shaped sample with a diameter of 5-15 mm and a height of 1-5 mm.

[0021] As preferred: the irradiation sample box comprises a 6061 Al capsule, a Zr4 capsule is arranged in the 6061 Al capsule, a sleeve and an end plug are arranged in the Zr4 capsule, the sleeve is used for loading the SiC crystal sample to be irradiated, and a heating body is loaded in the sleeve.

[0022] As preferred: the sleeve is a ceramic sleeve, and the end plug is a ceramic end plug.

[0023] As preferred: a compression spring is arranged between the top of the ceramic end plug and the Zr4 capsule.

[0024] As preferred: a gasket is arranged between the heating body and the ceramic end plug.

[0025] As preferred: the sleeve is an alumina sleeve, and the end plug is a zirconia end plug.

[0026] As preferred: the height of the 6061 Al capsule is 185 mm, and the outer diameter is 39 mm; and the height of the Zr4 capsule is 168 mm, and the outer diameter is 35 mm.

[0027] As preferred: in step S4.5, the heating rate is set to 20 K / min, the holding time is set to 2 min, and the measurement times are 3-5 times.

[0028] Compared with the prior art, the present application has the following beneficial effects:

[0029] 1. The method for measuring the temperature in the reactor based on the change of the thermal diffusion coefficient of SiC after neutron irradiation provided by the present application can obtain the irradiation temperature of the SiC crystal in the reactor by measuring the change of the thermal diffusion coefficient of the SiC crystal at different temperatures after neutron irradiation. This method does not require multiple annealing processes, sample transfer and processing, etc., and can obtain the curve of the thermal diffusion coefficient of the required SiC crystal material with the test temperature in one device, and then determine the neutron irradiation temperature of the SiC crystal through the inflection point of the curve, which has the advantages of simple operation and simple steps, and greatly reduces the time and labor cost.

[0030] 2. The irradiation temperature of the material to be irradiated in the sample box is closely related to the design parameters of the sample box, such as material, shape, size, clearance between components, etc. The method can simply and effectively measure the actual irradiation temperature of the material to be irradiated in the sample box, and can provide accurate reference for verifying whether the irradiation design parameters of the sample box are qualified. BRIEF DESCRIPTION OF DRAWINGS

[0031] Figure 1 is a cross-sectional view of the irradiation sample box 1;

[0032] Figure 2Figure 7 is a schematic diagram of the disassembly of the irradiation sample box 1;

[0033] Figure 3 Figure 8 is a perspective view of the irradiation sample box 1;

[0034] Figure 4 Figure 9 is a graph of the thermal diffusivity of an unirradiated SiC crystal (sample 1) as a function of temperature;

[0035] Figure 5 Figure 10 is a graph of the thermal diffusivity of an unirradiated SiC crystal (sample 2) as a function of temperature;

[0036] Figure 6 Figure 11 is a graph of the thermal diffusivity of an unirradiated SiC crystal (sample 3) as a function of temperature;

[0037] Figure 7 Figure 12 is a graph of the thermal diffusivity of a neutron-irradiated SiC crystal (1000C-A-1 irradiation box sample 1) as a function of temperature;

[0038] Figure 8 Figure 13 is a graph of the thermal diffusivity of a neutron-irradiated SiC crystal (1000C-A-1 irradiation box sample 2) as a function of temperature. DETAILED DESCRIPTION

[0039] The present application will be further described below in conjunction with the embodiments and the accompanying drawings.

[0040] A reactor in-situ temperature measurement method based on the change in the thermal diffusivity of SiC after neutron irradiation, comprising the following steps:

[0041] Step S1, process the SiC crystal material into a thin sheet-shaped sample suitable for the thermal diffusivity measurement device, specifically, process the SiC crystal into a round sheet-shaped sample with a diameter of 5-15 mm and a height of 1-5 mm.

[0042] Step S2, package the SiC crystal sample together with the sample of the material to be irradiated into the irradiation sample box 1, and then place the irradiation sample box 1 into the reactor for neutron irradiation experiment. In this embodiment, the irradiation material sample can be SiC, B4C, nickel-based alloy, etc. The irradiation design temperature of the irradiation sample box 1 can be estimated by adjusting the sample box structure design and calculating.

[0043] Step S3, after the completion of the neutron irradiation experiment, remove the irradiation sample box 1 from the reactor, use a cutting machine to cut and disassemble the irradiation sample box 1 in the hot cell, and take out the required SiC crystal sample.

[0044] Step S4, place the SiC crystal sample into the thermal conductivity instrument device, and measure the thermal diffusivity of the SiC crystal sample at different temperatures.

[0045] Step S4.1, measure and record the thickness of the SiC crystal sample to be measured, which is subsequently input as a parameter into the laser thermal conductivity instrument device.

[0046] Step S4.2, turn on the power switches of the main machine, water bath box, laser, and heating box of the laser thermal conductivity instrument in sequence, place the SiC crystal sample to be measured into the sample chamber, and confirm that the SiC crystal sample to be measured is kept centered and stable in the sample chamber.

[0047] Step S4.3, place the sample chamber on the sample holder of the thermal conductivity instrument, and then lower the sample holder to the bottom of the furnace body.

[0048] Step S4.4, set the measurement parameters on the control computer of the thermal conductivity instrument, and input the thickness of the SiC crystal sample to be measured into the device; the detector parameters are set as follows: amplification, initially set to 200; iris, initially set to 1; duration, initially set to 1s; laser parameters are set as follows: pulse length, set to 2.0ms; charge volt, set to 350V.

[0049] Step S4.5, close the three valves of the gas tank to seal the sample chamber, and use a molecular pump to pump the sample chamber to a pressure of 10 -3 Pa, and then input the temperature steps and their heating rates, holding time, and measurement times on the test software; the heating rate is usually 20K / min; the holding time is usually set to 2min, so as to ensure that the sample holder, sample chamber, and sample are fully heat balanced; the measurement times are usually 3-5 times to ensure good repeatability of the data. For the thermal diffusivity measurement of the SiC crystal sample after neutron irradiation, the temperature steps are set to room temperature to 1450℃, the thermal conductivity is measured every 100℃ (integer point), the heating rate is set to 20K / min, the holding time is set to 2min, and the measurement times are 3 times.

[0050] Step S4.6, record the thermal diffusivity data of the SiC crystal sample at different test temperatures.

[0051] Step S5, draw a curve of the thermal diffusivity of the irradiated SiC crystal sample versus temperature, and the inflection point of the curve is the irradiation temperature of the SiC crystal sample in the reactor.

[0052] As Figures 4-5 shown, the thermal diffusivity of the unirradiated SiC crystal material monotonically decreases with increasing measurement temperature, without obvious turning points. As Figures 7-8As shown, the thermal diffusion coefficient of the SiC crystal material after neutron irradiation presents a trend of first decreasing and then increasing with the measured temperature, and the curve inflection point can be approximately the irradiation temperature of the SiC crystal at the position in the reactor, about 985-989℃. In this experiment, based on the structural parameters of the sample box, the design irradiation temperature of the SiC crystal at the position in the reactor is about 1000℃, and therefore the temperature measurement accuracy of the method is about ±20℃.

[0053] The irradiation temperature of the material to be irradiated in the sample box is closely related to the design parameters of the sample box, such as material, shape, size, gap between components, etc., and therefore the method can also be used to simply and effectively measure the actual irradiation temperature of the material to be irradiated in the sample box, thereby providing an accurate reference for verifying whether the irradiation design parameters of the sample box are qualified. For example, if the measured irradiation temperature of the SiC crystal is within x±20℃, it is proved that the irradiation design parameters of the sample box are effective and qualified, otherwise, it is invalid.

[0054] The structural schematic diagram of the irradiation sample box 1 mentioned in this embodiment is shown in Figures 1 to 3 The design temperature is 1000℃, and the sample box is named as 1000C-A-1 sample box. The outermost layer of the irradiation sample box 1 is a sealed and welded 6061 Al capsule 1a, that is, a capsule-shaped component made of 6061 aluminum alloy, which has a height of 185mm and an outer diameter of 39mm. The next outer layer of the irradiation sample box 1 is a sealed and welded Zr4 capsule 1b, that is, a capsule-shaped structure made of Zr-4 alloy, wherein Zr represents zirconium element, and the Zr4 capsule 1b has a height of 168mm and an outer diameter of 35mm. The innermost layer is an unsealed sleeve and end plug, which plays a heat insulation role, and the sleeve is used to load the SiC crystal sample to be irradiated. In this embodiment, the sleeve is a ceramic sleeve 1c, and the end plug is a ceramic end plug 1d, or the sleeve is an alumina sleeve 1e, and the end plug is a zirconia end plug 1f. The innermost layer of the irradiation sample box 1 loads the SiC crystal sample 2 to be irradiated, and a total of 3 SiC simulation pellets 5, 5 SiC thermal expansion samples, 5 SiC metallographic samples and 5 SiC thermal conductivity samples are loaded. At the same time, 4 pieces of tungsten and 2 pieces of zirconia are also loaded as heating bodies 3. A compression spring a is arranged between the top of the ceramic end plug 1d and the Zr4 capsule 1b, and a gasket 4 is arranged between the heating body 3 and the ceramic end plug 1d. In this embodiment, the gasket 4 is a metal or ceramic gasket.

[0055] The Zr4 capsule 1b is pre-filled with 0.1MPa neon gas, and the 6061 Al capsule 1a is pre-filled with 0.1MPa helium gas. Generally, the irradiation temperature of the material in the reactor can be controlled by adjusting the structural design of the sample box. However, the temperature measurement method of the present application is universal and is not affected by the structural design of the sample box.

[0056] The method for measuring temperature in a reactor based on the change of the thermal diffusion coefficient of SiC after neutron irradiation provided by the embodiment measures the change of the thermal diffusion coefficient of SiC crystal at different temperatures after neutron irradiation to obtain the irradiation temperature of the SiC crystal in the reactor. The method does not need multiple annealing processes, sample transfer and processing, etc. The change curve of the thermal diffusion coefficient of the required SiC crystal material with the test temperature can be obtained at one time in the same device, and then the neutron irradiation temperature of the SiC crystal is determined through the inflection point of the curve, which has the advantages of simple operation and simple steps, greatly reducing the required time and labor cost. The method does not have special requirements for the preparation process and crystal type of the SiC crystal material, but the higher the purity of the SiC crystal, the better the test effect, and high-purity SiC crystal, i.e. SiC crystal with a purity of > 99.9995%, is preferably selected.

[0057] Finally, it should be noted that the above description is only for the preferred embodiments of the present application, and those of ordinary skill in the art can make various similar modifications under the inspiration of the present application without departing from the purpose and scope of the present application. Such changes fall within the scope of the present application.

Claims

1. A reactor temperature measurement method based on the change in the thermal diffusivity of SiC after neutron irradiation, characterized in that, Includes the following steps: Step S1: Process the SiC crystal material into thin sheet samples; Step S2: The SiC crystal sample and the material sample to be irradiated are packaged together into the irradiation sample box (1), and then the irradiation sample box (1) is placed into the reactor for neutron irradiation experiment. Step S3: After the neutron irradiation experiment is completed, the irradiated sample box (1) is removed from the reactor, the irradiated sample box (1) is cut and disassembled, and the irradiated SiC crystal sample is taken out. Step S4: Place the SiC crystal sample into a thermal conductivity meter and measure the thermal diffusivity of the SiC crystal sample at different temperatures; Step S5: Plot the curve of the thermal diffusivity of the SiC crystal sample after irradiation as a function of temperature. The inflection point of the curve is the irradiation temperature at the location of the SiC crystal sample in the reactor.

2. The reactor temperature measurement method based on the change in the thermal diffusivity of SiC after neutron irradiation according to claim 1, characterized in that: In step S4, the thermal diffusivity test of the SiC crystal sample includes the following steps: Step S4.1: Measure and record the thickness of the SiC crystal sample to be tested; Step S4.2: Turn on the power switches of the main unit, water bath, laser and heating chamber of the laser thermal conductivity meter in sequence, put the SiC crystal sample to be tested into the sample chamber, and confirm that the SiC crystal sample to be tested remains centered and stable in the sample chamber. Step S4.3: Place the sample chamber on the sample holder of the thermal conductivity meter, and then lower the sample holder to the bottom of the furnace body; Step S4.4: Set the measurement parameters on the control computer of the thermal conductivity meter and input the thickness of the SiC crystal sample to be measured into the device; Step S4.5: Seal the sample chamber and evacuate it. Then, input the temperature gradient, heating rate, holding time, and number of measurements into the testing software. Step S4.6: Record the thermal diffusivity data of SiC crystal samples at different test temperatures.

3. The reactor temperature measurement method based on the change in the thermal diffusivity of SiC after neutron irradiation according to claim 1, characterized in that: In step S1, the SiC crystal is processed into a circular sample with a diameter of 5-15 mm and a height of 1-5 mm.

4. The reactor temperature measurement method based on the change in the thermal diffusivity of SiC after neutron irradiation according to claim 1, characterized in that: The irradiation sample box (1) includes a sealed 6061Al capsule (1a), inside which is a sealed Zr4 capsule (1b), inside which is a sleeve and an end plug. The sleeve is used to load the SiC crystal sample to be irradiated, and a heating element (3) is loaded inside the sleeve.

5. The reactor temperature measurement method based on the change in the thermal diffusivity of SiC after neutron irradiation according to claim 4, characterized in that: The sleeve is a ceramic sleeve (1c), and the end plug is a ceramic end plug (1d).

6. The reactor temperature measurement method based on the change in the thermal diffusivity of SiC after neutron irradiation according to claim 5, characterized in that: A compression spring (a) is provided between the top of the ceramic end plug (1d) and the Zr4 capsule (1b).

7. The reactor temperature measurement method based on the change in the thermal diffusivity of SiC after neutron irradiation according to claim 5, characterized in that: A gasket (4) is provided between the heating element (3) and the ceramic end plug (1d).

8. The reactor temperature measurement method based on the change in the thermal diffusivity of SiC after neutron irradiation according to claim 4, characterized in that: The sleeve is an alumina sleeve (1e), and the end plug is a zirconia end plug (1f).

9. The reactor temperature measurement method based on the change in the thermal diffusivity of SiC after neutron irradiation according to claim 4, characterized in that: The 6061Al capsule (1a) has a height of 185 mm and an outer diameter of 39 mm, while the Zr4 capsule (1b) has a height of 168 mm and an outer diameter of 35 mm.

10. The reactor temperature measurement method based on the change in the thermal diffusivity of SiC after neutron irradiation according to claim 2, characterized in that: In step S4.5, the heating rate is set to 20K / min, the holding time is set to 2min, and the number of measurements is 3-5.

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