Preparation method of thermal noise temperature sensor temperature measurement probe for nuclear engineering

Abstract

The invention discloses a preparation method of a temperature measuring probe of a thermal noise temperature sensor for nuclear engineering, and the temperature measuring probe comprises a measuring resistor, a metal shell, a lead and an insulating layer porcelain column provided with four axial through holes through material preparation, armored body assembly, armored body drawing, measuring end welding and reference end ceramic sealing. The measuring resistor is made of a SiC / C composite ceramic material, the metal shell is made of a tungsten-rhenium alloy pipe, the lead comprises four tungsten-rhenium alloy wires, and the insulating layer knob insulator is made of beryllium oxide (BeO) or boron nitride (BN). The temperature measuring probe can work for a long time at a temperature and is suitable for a high-temperature nuclear environment of 1500-2000 DEG C; the reference end is sealed through ceramic metallization, so that the high-insulation requirement of the temperature measuring probe is met, and the use in an ultrahigh-temperature and strong-irradiation environment is met; temperature calibration is not needed, the problem of temperature drift is solved, and the temperature measurement precision of the temperature measurement probe reaches + / -0.1% t to 0.5% t.

Description

Technical Field

[0001] The present invention relates to the technical field of temperature sensors, and in particular to a method for preparing a temperature measuring probe of a thermal noise temperature sensor for nuclear engineering. Background Art

[0002] Small nuclear reactors are devices that convert nuclear energy into electrical energy. They are compact, have high energy density, and their core temperatures are much higher than those of commercial nuclear reactors. The core temperature and inlet and outlet temperatures of small nuclear reactors are important parameters characterizing the thermal energy conversion process and are crucial for energy efficiency conversion diagnosis and safety monitoring. Compared to the operating environment of temperature sensors in conventional terrestrial nuclear power reactors, small nuclear reactors require temperature sensors to withstand strong radiation and ultra-high temperatures, placing extremely high technical demands on temperature measurement, with a measurement range of 0 to 2200°C. Conventional cheap metal thermocouples cannot meet these high-temperature requirements. Thermocouples made from precious metals and refractory metals are highly susceptible to transmutation under strong neutron irradiation, resulting in significant potential drift.

[0003] The materials used in traditional thermocouples can experience severe temperature inaccuracies due to nuclear transmutation. Nuclear transmutation is the nuclear reaction between a material's chemical components and neutrons under neutron irradiation conditions, known as isotope conversion. This affects the material's physical and chemical properties. While chromium-nickel alloys and nickel-chromium-silicon alloys are generally considered insensitive to nuclear effects, their temperature range is limited to 0 to 1200°C. While platinum-rhodium alloys have a temperature range of 0 to 1800°C, they are also affected by nuclear transmutation. Specifically, nuclear reactions occur when neutrons collide with platinum-rhodium nuclei, affecting the alloy's temperature measurement performance and causing potential drift. Currently, thermal noise temperature sensors are used abroad to address temperature measurement in ultra-high-temperature, intensely irradiated environments. However, their high cost and price limit their application and development in China. Summary of the Invention

[0004] The present invention addresses the shortcomings of existing technologies by providing a method for preparing a thermal noise temperature sensor probe for nuclear engineering applications. The resulting thermal noise temperature sensor, produced using this method, requires no calibration and exhibits no temperature drift in ultra-high temperature and strong radiation environments, maintaining long-term stability in these environments. Compared to imported products, the manufacturing process for the temperature sensor is more stable, more efficient, and less expensive.

[0005] The purpose of the present invention is to adopt the following scheme to achieve:

[0006] A method for preparing a temperature measuring probe of a thermal noise temperature sensor for nuclear engineering comprises the following steps:

[0007] 1) Material preparation:

[0008] The temperature measuring probe comprises a measuring resistor (1), a metal shell (2), a lead wire (3), and an insulating layer porcelain column (4) provided with four axial through holes; the measuring resistor is made of SiC / C composite ceramic material, the metal shell is made of a tungsten-rhenium alloy tube, the lead wire comprises four tungsten-rhenium alloy wires, and the insulating layer porcelain column is made of beryllium oxide (BeO) or boron nitride (BN);

[0009] 2) Armored body assembly:

[0010] Baking of metal shell and insulating layer porcelain column;

[0011] After the four leads are inserted into the four through-holes of the insulating layer porcelain column, they are placed in a metal shell in a clean room with a temperature of 22-26°C and a relative humidity of 12-16% to obtain the armored body. The purpose of assembling in a clean room is to prevent excessive humidity, water vapor and dust from being adsorbed on the insulating layer porcelain column, which would cause oxidation inside the casing and the leads during the subsequent heat treatment process, affecting the insulation performance of the sensor.

[0012] 3) Armor drawing:

[0013] The armored body is drawn, with a single-pass deformation of 10-15%. When the deformation reaches 25-35%, intermediate annealing is performed. After repeated drawing and intermediate annealing treatments, hydrogen protection is required during the intermediate annealing. The hydrogen flow rate is controlled at 4-8L / min to prevent the tungsten-rhenium alloy tube from becoming brittle due to oxidation during the intermediate annealing. The tube is drawn to φ5.0-φ8.0mm. After the drawing is completed, the end of the armored signal cable is sealed with epoxy resin glue, and the armored body is pickled and polished. During polishing, the armored body is polished on a polishing machine to make the surface bright.

[0014] 4) Measuring end welding:

[0015] Strip 10-15mm of the lead wire at one end of the armored body to obtain the short lead end, and strip 50-100mm of the other end to obtain the long lead end. Weld the long lead end to measure the resistance. After welding, fill it with BeO or BN and compact it to 2mm from the pipe mouth. Seal the pipe mouth and check the continuity and polarity.

[0016] 5) Reference end ceramic seal:

[0017] An alumina ceramic coated with a nickel-based brazing filler metal (BNi81CrB) is placed in the reference junction, cured in an oven, and then vacuum sintered. The reference junction is sealed with ceramic, improving its high-temperature resistance. Other sensors currently use high-temperature adhesives such as E7 or epoxy resin for sealing, typically withstanding temperatures of 200-300°C. However, the ceramic seal employed in this application allows the reference junction to withstand temperatures of 600-700°C.

[0018] Oven curing conditions: Place the reference end opening upward in an oven at 100-140°C for 3-5 hours.

[0019] Conventional thermocouple temperature measurement is based on the thermoelectric effect generated by a closed loop of two conductors made of different materials. The thermal noise temperature sensor of the present invention is based on the noise voltage generated by the thermal motion of electrons in the conductor, and its magnitude is determined by the temperature. The working principle of noise temperature measurement is based on the relationship derived from Nyquist thermodynamics:

[0020]

[0021] Where k is the Boltzmann constant, T is the thermodynamic temperature, and R is the resistance value. is the mean square voltage, f u is the upper frequency limit, f l is the lower frequency limit. This relationship shows that all environmental influences (atmospheric or nuclear radiation) and those from mechanical or thermal pretreatment only alter the resistance R. All material properties and their changes are reflected solely in R. The resistance value R can be determined through simple measurement, and all environmental influences can be precisely determined, resulting in a noise temperature sensor that does not experience drift. This characteristic distinguishes noise temperature measurement from other temperature measurement methods, ensuring accurate and long-term stability of temperature measurement without the need for calibration.

[0022] Four sets of leads are drawn from both ends of the measuring resistor. One pair of leads measures the resistance value R, and one pair of leads measures the mean square voltage of the upper and lower frequencies. The temperature T can be calculated through the Nyquist equation to achieve temperature measurement.

[0023] Metal Housing: The metal housing is made of tungsten-rhenium alloy (WRe20, WRe25) tubing, which has a melting point of 3200°C and an annealed elongation of ≥16%. The selected tungsten-rhenium alloy sheath is ultrasonically cleaned by repeatedly scrubbing the inner wall with alcohol gauze until no visible black stain remains. Tungsten-rhenium alloy exhibits high-temperature stability and creep resistance, enabling long-term stable operation under high-temperature and intense radiation conditions. It also exhibits excellent processability. Sheath lengths range from 1.0 to 2.5 meters, with an outer diameter of φ10 to φ16 mm. Ultrasonic cleaning ensures a clean surface, preventing contamination of the insulating porcelain layer and columns by metal oxide scale and residual ions, thereby improving the sensor's high-temperature insulation performance.

[0024] Lead wire: Tungsten-rhenium alloy (WRe20, WRe25) wire is used as the lead wire. The selected lead wire should be repeatedly scrubbed with alcohol gauze until no black stain is noticeable on the gauze. The lead wire diameter should be 1.6-2.0 mm (φ), and the length should be 1.3 times the length of the tubing. Temperature sensor housings typically have a diameter of 10-16 mm (φ). The lead wire diameter should be no less than 11% of the outer diameter of the sheath, as per the national standard GB / T 18404-2022, double-branch armored thermocouple cable; the length should be 1.3 times the outer diameter of the sheath.

[0025] Insulating layer porcelain column: Conventional thermocouples use aluminum oxide and magnesium oxide, which cannot meet the temperature measurement requirements. Therefore, this application uses materials that can meet the temperature range of 0 to 2000°C for insulating porcelain columns, including beryllium oxide (BeO) and boron nitride (BN). The melting point of beryllium oxide is 2570°C, and the melting point of boron nitride is 3000°C, and it has a high insulation resistivity. Porcelain column dimensions: outer diameter φ7.5~φ12.0mm, four axial through holes, aperture φ1.8~φ2.2mm. The insulating layer porcelain column is sintered at a sintering temperature of 800°C~1000°C and kept warm for 1.5h~2.0h. The sintering temperature is controlled according to the performance requirements of beryllium oxide and boron nitride. The first is to increase the density of the porcelain column, and the second is to avoid excessive temperature. The porcelain column is too hard, which is not conducive to drawing and will damage the lead.

[0026] Step 1) The SiC / C composite ceramic material has SiC as the core, and conductive carbon particles are distributed on the surface. The molar ratio of SiC:C is 100:(1~5). SiC is usually used as a matrix material, and has a high thermal conductivity and thermal stability. SiC has a high resistivity and can adjust the resistivity of ceramic resistors. C is added in trace amounts, mainly to enhance conductivity and improve the toughness of ceramics. This application uses a composite ceramic-based resistor with a high melting point and large resistance as a measuring resistor. The SiC / C composite ceramic-based temperature measuring resistor can withstand an ambient temperature of 2800°C, and has radiation resistance and excellent resistivity performance. The resistivity at room temperature is between 10-3 and 10 2 Ω·cm, the resistance is large and the thermal noise signal is large.

[0027] In step 1), the sintering temperature of the insulating layer porcelain column is 800° C. to 1000° C., and the temperature is kept for 1.5 hours to 2.0 hours.

[0028] In step 2), the baking conditions are as follows: the metal shell is baked at a temperature of 200° C. to 300° C. and kept warm for 3 to 6 hours; the insulating layer porcelain column is baked at a temperature of 55 to 85° C. and kept warm for 3 to 6 hours.

[0029] In step 3), a polycrystalline die is used as the drawing die during drawing, and graphite emulsion is used as the lubricant.

[0030] In step 3), the annealing temperature of the intermediate annealing is 1500° C. to 1650° C., and the annealing speed is 0.4 to 1.3 m / min.

[0031] In step 3), during the pickling, the armored body is cleaned and descaled in a 5% to 8% wt HNO3 solution until the surface is smooth, and then rinsed with high-pressure water.

[0032] In step 4), the pipe opening is sealed by argon arc welding, the welding current of the argon arc welding is 30-42A, and the argon gas flow rate is 2-3 L / min.

[0033] In step 5), the vacuum sintering method is as follows: the sintering temperature is 450° C. to 550° C., kept at this temperature for 1 to 2 hours, then raised to 1050° C. to 1120° C., kept at this temperature for 15 to 30 minutes, and then cooled with the furnace.

[0034] The method for preparing a thermal noise temperature sensor temperature measuring probe of the present invention comprises the following steps: material preparation, armor assembly, armor drawing, measuring end welding, and reference end ceramic sealing. The prepared thermal noise temperature sensor temperature measuring probe is subjected to performance testing: an outer diameter measured by a vernier caliper is φ5.0-φ8.0 mm, and a surface roughness measured by a surface roughness measuring instrument is ≤Ra1.6 μm; a room temperature insulation resistance measured by a high resistance meter is ≥1.0×1012 Ω·m, and an insulation resistance at 350°C is ≥2.40×108 Ω·m; an accuracy measured by an automatic temperature calibration system is ±0.1%-0.5%t, and the temperature measurement range can reach 0-2000°C.

[0035] The beneficial effects of the present invention are as follows:

[0036] (1) The temperature measuring probe of the present invention adopts structural materials that are resistant to 2000℃ and radiation, including measuring resistors, metal shells, leads, and insulating layer porcelain columns. It can work at temperatures of 1500℃ to 2000℃ for a long time and is suitable for high-temperature nuclear environments.

[0037] (2) The armored body of the present invention is assembled in a closed clean room, and the temperature and humidity in the clean space are strictly controlled to ensure that the outer casing, lead wires, and insulating layer porcelain columns are in a clean state, avoiding contamination by metal oxide scale and residual ions, and improving the room temperature and high temperature insulation performance of the temperature measuring probe.

[0038] (3) The reference end of the present invention is evenly coated with nickel-based material, and ceramic metallization sealing of the reference end is achieved through sintering, thereby achieving high insulation requirements of the temperature measuring probe and meeting the use in ultra-high temperature and strong radiation environments.

[0039] (4) The temperature measuring probe of the present invention is suitable for long-term temperature measurement in harsh environments with high temperature radiation. 21 n / cm 2It can be used under harsh conditions without temperature calibration, which solves the problem of temperature drift. The temperature measurement accuracy of the temperature probe reaches ±0.1%~0.5%t. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 This is a schematic structural diagram of a temperature measuring probe of a thermal noise temperature sensor for nuclear engineering according to the present invention. DETAILED DESCRIPTION

[0041] like Figure 1 The structure of a thermal noise temperature sensor probe for nuclear engineering applications is shown. It includes a measuring resistor 1, a metal housing 2, lead wires 3, and an insulating ceramic column 4. The measuring resistor 1 is made of SiC / C composite ceramic material, the metal housing 2 is a tungsten-rhenium alloy tube, the lead wires 3 include four tungsten-rhenium alloy wires, and the insulating ceramic column 4 is sintered with beryllium oxide (BeO) or boron nitride (BN). The insulating ceramic column has four axial through-holes. Alumina ceramic 5 is used as a sealant between the reference end sensor connector and the housing, and the surface is metallized.

[0042] Example 1:

[0043] (1) Material preparation

[0044] The measuring resistor is constructed from a SiC / C composite material, with a SiC core and conductive carbon particles distributed on the surface at a molar ratio of 100:2. The metal casing is made of WRe25 alloy tubing, 2.5 meters long and with an outer diameter of φ16 mm. The tubing is ultrasonically cleaned. The lead wires are 3.25 meters long and φ2.0 mm in diameter. They are repeatedly scrubbed with alcohol gauze until no visible black stain remains. The insulating ceramic pillar is made of boron nitride, with an outer diameter of φ12.0 mm and four holes of φ2.2 mm. The insulating ceramic pillar is pre-sintered at 1000°C for 2 hours.

[0045] (2) Armored body assembly

[0046] Assembly is performed in a closed cleanroom, controlled at 26°C and 16% relative humidity. The casing and insulation layer are baked separately before assembly: the outer casing is baked at 300°C, and the insulation layer's ceramic posts are baked at 85°C for 6 hours. The four holes of the boron nitride insulation ceramic posts are installed into the WRe25 alloy leads, which are then installed into the WRe25 alloy casing.

[0047] (3) Armor drawing

[0048] The assembled armor body undergoes a drawing and intermediate annealing process, using a polycrystalline die and graphite emulsion as lubricant. The deformation per pass is 15%. When the cumulative deformation reaches 35%, intermediate annealing is performed in a bright annealing furnace at 1650°C, a speed of 1.2 m / min, and a hydrogen flow rate of 8 L / min. After repeated drawing and intermediate annealing, the armor body is drawn from φ16 mm to φ8.0 mm. After drawing, the ends of the armored signal cable are sealed with epoxy resin. The armor body is then cleaned and polished, and the oxide scale is removed in an 8% wt HNO3 solution to a smooth surface, followed by high-pressure water rinsing. The armor body is then polished on a polishing machine to a bright finish.

[0049] (4) Welding of measuring end

[0050] Polish one end of the armor body smooth and strip the lead wire 15mm; strip the other end 100mm. Laser weld the two ends of the long lead wire and measure the resistance. Then, fill the measuring end with the same material as the insulating ceramic column until it is compacted approximately 2mm from the tube opening. Use a welding fixture that matches the outer diameter of the armor body and argon arc welding at a welding current of 42A and an argon gas flow rate of 3L / min. After welding, use a multimeter to check the lead wire's continuity and electrical polarity.

[0051] (5) Ceramic seal at the reference end

[0052] Alumina ceramic is used as the sealing material between the sensor connector pin and the housing, and the surface is metallized. A nickel-based brazing filler metal (BNi81CrB) is evenly coated on the ceramic surface, and then the reference terminal is installed. With the reference terminal open upward, the device is placed in an oven at 140°C and cured for 5 hours. The entire armored body is sintered in a vacuum furnace at 550°C for 2 hours, then raised to 1120°C for 30 minutes, and then cooled in the furnace.

[0053] The preparation method of the thermal noise temperature sensor temperature measuring probe of the present invention comprises the following steps: material preparation, armor assembly, armor drawing, measuring end welding, and reference end ceramic sealing. The prepared thermal noise temperature sensor temperature measuring probe is tested for performance: the outer diameter is measured to be φ8.0 mm using a vernier caliper, the surface roughness is measured to be Ra1.6 μm using a surface roughness measuring instrument, and the room temperature insulation resistance is measured to be 2.82×10 12 Ω·m, insulation resistance at 350℃ is 3.52×10 8 Ω·m; the accuracy measured by the temperature automatic verification system is 0.5%t, and the temperature measurement range can reach 0~2000℃.

[0054] Example 2:

[0055] (1) Material preparation

[0056] The measuring resistor is constructed from a SiC / C composite material, with a SiC core and conductive carbon particles distributed on the surface at a molar ratio of 100:5. The metal casing is made of WRe20 alloy tubing, 2.0 m long and φ12 mm in outer diameter. The tubing is ultrasonically cleaned. The lead wires are φ1.8 mm in diameter and 2.6 m long, made of WRe20 wire. These wires are repeatedly scrubbed with alcohol gauze until no visible black stain remains. The insulating ceramic pillar is made of beryllium oxide, with an outer diameter of φ9.0 mm and four holes of φ2.0 mm in diameter. The ceramic pillars are pre-sintered at 950°C for 2 h.

[0057] (2) Armored body assembly

[0058] Assembly is performed in a closed cleanroom, controlled at 24°C and 14% relative humidity. The casing and insulation layer are baked separately before assembly: the outer casing is baked at 300°C, and the insulation layer ceramic pillars are baked at 75°C for 5 hours. The four holes of the boron nitride insulation ceramic pillars are installed into the WRe20 alloy leads, which are then installed into the WRe20 alloy casing.

[0059] (3) Armor drawing

[0060] The assembled armor body undergoes a drawing and intermediate annealing process, using a polycrystalline die and graphite emulsion as lubricant. The deformation per pass is 12%. When the cumulative deformation reaches 30%, intermediate annealing is performed in a bright annealing furnace at 1600°C, a speed of 1.0 m / min, and a hydrogen flow rate of 6 L / min. After repeated drawing and intermediate annealing, the armor body is drawn from φ12 mm to φ7.0 mm. After drawing, the ends of the armored signal cable are sealed with epoxy resin. The armor body is then cleaned and polished, and the oxide scale is removed in a 6% wt HNO3 solution until the surface is smooth. High-pressure water rinsing is then used. The armor body is then polished on a polishing machine to a bright finish.

[0061] (4) Welding of measuring end

[0062] Polish one end of the armor body flat and strip the lead wire 13mm; strip the other end 80mm. Laser weld the two ends of the long lead wire and measure the resistance. Then, fill the measuring end with the same material as the insulating ceramic column until it is compacted approximately 2mm from the tube opening. Use a welding fixture that matches the outer diameter of the armor body and argon arc welding at a welding current of 38A and an argon gas flow rate of 2.5L / min. After welding, use a multimeter to check the lead wire's continuity and electrical polarity.

[0063] (5) Ceramic seal at the reference end

[0064] Alumina ceramic is used as the sealing material between the sensor connector pin and the housing, and the surface is metallized. A nickel-based brazing filler metal (BNi81CrB) is evenly coated on the ceramic surface, and then the reference terminal is installed. The reference terminal, open upward, is placed in a 120°C oven and cured for 4 hours. The entire armored body is sintered in a vacuum furnace at 500°C for 1.5 hours, then raised to 1100°C for 25 minutes, and then cooled in the furnace.

[0065] The preparation method of the thermal noise temperature sensor temperature measuring probe of the present invention comprises the following steps: material preparation, armor assembly, armor drawing, measuring end welding, and reference end ceramic sealing. The prepared thermal noise temperature sensor temperature measuring probe is tested for performance: the outer diameter is measured to be φ7.0 mm using a vernier caliper, the surface roughness is measured to be Ra1.4 μm using a surface roughness measuring instrument, and the room temperature insulation resistance is measured to be 3.56×10 12 Ω·m, insulation resistance at 350℃ is 2.98×10 8 Ω·m; the accuracy measured by the temperature automatic verification system is 0.3%t, and the temperature measurement range can reach 0~2000℃.

[0066] Example 3:

[0067] (1) Material preparation

[0068] The measuring resistor is constructed from a SiC / C composite material, with a SiC core and conductive carbon particles distributed on the surface at a molar ratio of 100:3. The metal casing is made of WRe25 alloy tubing, 1.5m long and 10mm in outer diameter. The tubing is ultrasonically cleaned. The lead wires are 1.6mm in diameter and 1.95m long, made of WRe25 wire. The wires are repeatedly scrubbed with alcohol gauze until no visible black stain remains. The insulating ceramic pillar is made of beryllium oxide, with an outer diameter of 7.5mm and four holes of 1.8mm in diameter. The ceramic pillars are pre-sintered at 900°C for 1.5 hours.

[0069] (2) Armored body assembly

[0070] Assembly is performed in a closed cleanroom, controlled at 22°C and 12% relative humidity. The casing and insulation layer are baked separately before assembly: the outer casing at 240°C, and the insulation layer's ceramic pillar at 70°C, each held for 3 hours. The four holes of the boron nitride insulation ceramic pillar are fitted with WRe25 alloy leads, which are then assembled into the WRe25 alloy casing.

[0071] (3) Armor drawing

[0072] The assembled armor undergoes a drawing and intermediate annealing process, using a polycrystalline die and graphite emulsion as lubricant. The deformation per pass is 10%. When the cumulative deformation reaches 25%, intermediate annealing is performed in a bright annealing furnace at 1550°C, a speed of 0.6 m / min, and a hydrogen flow rate of 4 L / min. After repeated drawing and intermediate annealing, the armor is drawn from φ10 mm to φ5.0 mm. After drawing, the ends of the armored signal cable are sealed with epoxy resin. The armor is then cleaned and polished, and the oxide scale is removed in a 5% wt HNO3 solution to a smooth surface, followed by high-pressure water rinsing. The armor is then polished on a polishing machine to a bright finish.

[0073] (4) Welding of measuring end

[0074] Polish one end of the armor body smooth and strip the lead wire 10mm; strip the other end 50mm. Laser weld the two ends of the long lead wire and measure the resistance. Then, fill the measuring end with the same material as the insulating ceramic column until it is compacted approximately 2mm from the tube opening. Use a welding fixture that matches the outer diameter of the armor body and argon arc welding at a welding current of 33A and an argon gas flow rate of 2.0L / min. After welding, use a multimeter to check the lead wire's continuity and electrical polarity.

[0075] (5) Ceramic seal at the reference end

[0076] Alumina ceramic is used as the sealing material between the sensor connector pin and the housing, and the surface is metallized. A nickel-based brazing filler metal (BNi81CrB) is evenly coated on the ceramic surface, and then the reference terminal is installed. With the reference terminal open upward, the device is placed in an oven at 100°C and cured for 3 hours. The entire armored body is sintered in a vacuum furnace at 450°C for 1 hour, then raised to 1050°C for 15 minutes, and then cooled in the furnace.

[0077] The preparation method of the thermal noise temperature sensor temperature measuring probe of the present invention comprises the following steps: material preparation, armor assembly, armor drawing, measuring end welding, and reference end ceramic sealing. The prepared thermal noise temperature sensor temperature measuring probe is tested for performance: the outer diameter is measured to be φ5.0 mm using a vernier caliper, the surface roughness is measured to be Ra1.0 μm using a surface roughness measuring instrument, and the room temperature insulation resistance is measured to be 2.45×10 12 Ω·m, insulation resistance at 350℃ is 3.79×10 8 Ω·m; the accuracy measured by the temperature automatic verification system is 0.2%t, and the temperature measurement range can reach 0~2000℃.

[0078] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications made to the present invention by those skilled in the art without departing from the spirit of the present invention shall fall within the scope of protection of the present invention.

Claims

1. A method for preparing a temperature measuring probe of a thermal noise temperature sensor for nuclear engineering, characterized by: The following steps are involved: 1) Material preparation: The temperature measuring probe comprises a measuring resistor (1), a metal shell (2), a lead (3), and an insulating layer porcelain column (4) provided with four axial through holes; the measuring resistor is made of SiC / C composite ceramic material, the metal shell is made of a tungsten-rhenium alloy tube, the lead comprises four tungsten-rhenium alloy wires, and the sintered insulating layer porcelain column is made of beryllium oxide (BeO) or boron nitride (BN); 2) Armored body assembly: Bake the metal shell and insulating layer porcelain column; After the four lead wires are respectively inserted into the four through holes of the insulating layer porcelain column, they are placed in a metal shell in a clean room with a temperature of 22-26°C and a relative humidity of 12-16% to obtain an armored body; 3) Armor drawing: The armor body is drawn, with a single-pass deformation of 10-15%. When the deformation reaches 25-35%, intermediate annealing is performed and the body is drawn to φ5.0-φ8.0mm. After the drawing is completed, the ends of the armored signal cables are sealed, and the surface of the armor body is pickled and polished. 4) Measuring end welding: Strip 10-15mm of the lead wire at one end of the armored body to obtain a short lead end, and strip 50-100mm of the other end to obtain a long lead end. Weld the long lead end to the measuring resistor. After welding, fill it with BeO or BN and compact it to 2mm from the pipe mouth. Seal the pipe mouth and test the continuity and polarity. 5) Reference end ceramic seal: Alumina ceramics coated with nickel-based brazing filler metal (BNi81CrB) were placed into the reference end, put into an oven for curing, and then vacuum sintered.

2. The preparation method according to claim 1, wherein: Step 1) The SiC / C composite ceramic material has SiC as the core and conductive carbon particles distributed on the surface, and the molar ratio of SiC:C is 100:(1-5).

3. The preparation method according to claim 1, wherein: Step 1) The lead length is 1.3 times the length of the metal shell.

4. The preparation method according to claim 1, wherein: In step 1), the sintering temperature of the insulating layer porcelain column is 800° C. to 1000° C., and the temperature is kept for 1.5 hours to 2.0 hours.

5. The preparation method according to claim 1, wherein: In step 2), the baking conditions are as follows: the metal shell is baked at a temperature of 200° C. to 300° C. and kept warm for 3 to 6 hours; the insulating layer porcelain column is baked at a temperature of 55 to 85° C. and kept warm for 3 to 6 hours.

6. The preparation method according to claim 1, wherein: In step 3), a polycrystalline die is used as the drawing die during drawing, and graphite emulsion is used as the lubricant.

7. The preparation method according to claim 1, wherein: In step 3), the annealing temperature of the intermediate annealing is 1500° C. to 1650° C., and the annealing speed is 0.4 to 1.3 m / min.

8. The preparation method according to claim 1, wherein: In step 3), during the pickling, the armored body is cleaned and descaled in a 5% to 8% wt HNO3 solution until the surface is smooth, and then rinsed with high-pressure water.

9. The preparation method according to claim 1, wherein: In step 4), the pipe opening is sealed by argon arc welding, the welding current of the argon arc welding is 30-42A, and the argon gas flow rate is 2-3 L / min.

10. The preparation method according to claim 1, wherein In step 5), the vacuum sintering method is as follows: the sintering temperature is 450° C. to 550° C., kept at this temperature for 1 to 2 hours, then raised to 1050° C. to 1120° C., kept at this temperature for 15 to 30 minutes, and then cooled with the furnace.

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