Diffusion impervious layer based on accident fault-tolerant fuel cladding Cr coating and preparation method of diffusion impervious layer

Abstract

The invention relates to the technical field of nuclear fuel cladding, in particular to a diffusion impervious layer based on an accident fault-tolerant fuel cladding Cr coating and a preparation method of the diffusion impervious layer, the diffusion impervious layer is composed of any one of thorium Th, niobium Nb, molybdenum Mo and a SiCf / SiC composite coating, and a pure Cr coating is arranged outside the diffusion impervious layer. According to the nuclear power cladding tube, the diffusion barrier layer is arranged between Zr and Cr, so that the Zr matrix and the Cr coating are separated, and diffusion between the Zr matrix and the Cr coating is slowed down, so that the oxidation speed of the Cr coating is reduced, the water loss accident resisting capacity of the cladding is improved, and then the nuclear power cladding tube is safer under the LCOA working condition; due to the fact that the diffusion barrier layer can effectively restrain mutual diffusion between the Cr coating and the zirconium alloy matrix, the high-temperature service performance of the coating is improved, the high-temperature oxidation resistance of the accident fault-tolerant fuel cladding Cr coating is further improved, and the survival time of a fuel cladding pipe under the LOCA accident can be prolonged.

Description

Technical Field

[0001] The invention relates to the technical field of nuclear fuel cladding, in particular to a diffusion barrier layer based on a Cr coating of an accident-tolerant fuel cladding and a preparation method thereof. Background Art

[0002] Zirconium alloy has a low neutron absorption cross-section coefficient, good thermal conductivity, good radiation resistance and corrosion resistance, moderate mechanical properties and good processing performance. Based on the above advantages, zirconium alloy is widely used in the field of nuclear fuel cladding materials for water-cooled reactors. Under the condition of reactor loss of coolant accident, zirconium alloy reacts violently with high-temperature water vapor, releasing a large amount of heat and hydrogen, causing the core to melt and triggering hydrogen explosion, which seriously damages the safety of the reactor.

[0003] At present, the research and development directions of candidate materials for accident-resistant fuel cladding are mainly divided into zirconium alloy surface modification, refractory metal cladding, and SiCf / SiC composite cladding. However, the diffusion coefficient of Zr element to oxygen is relatively high. When using pure Cr coating, due to the mutual diffusion between ZrCr, the coating will diffuse into the Cr coating to form an oxygen transfer channel 30min-120min after the loss-of-coolant accident (LOCA) conditions, allowing oxygen to penetrate the Cr coating and enter the Zr matrix, causing the matrix Zr alloy in the coating to oxidize rapidly and easily diffuse in the Cr coating, thereby reducing the cladding's ability to resist loss-of-coolant accidents.

[0004] In view of this, the present application intends to propose a diffusion barrier layer based on the Cr coating of the accident-tolerant fuel cladding and a preparation method thereof. Summary of the invention

[0005] The object of the present invention is to provide a diffusion barrier layer based on a Cr coating of an accident-tolerant fuel cladding and a preparation method thereof, so as to solve the problem that the diffusion coefficient of Zr element to oxygen is relatively high as mentioned in the above-mentioned background technology. When a pure Cr coating is used, due to the mutual diffusion between Zr and Cr, after 30 minutes to 120 minutes under the loss of coolant accident (LOCA) conditions, the Zr element will diffuse into the Cr coating to form an oxygen transfer channel, so that oxygen penetrates the Cr coating into the Zr matrix, causing the matrix Zr alloy in the coating to be rapidly oxidized and easily diffuse in the Cr coating, thereby reducing the ability of the cladding to resist a loss of coolant accident.

[0006] To achieve the above object, the present invention provides the following technical solutions: A diffusion barrier layer based on a Cr coating of an accident-tolerant fuel cladding, wherein the diffusion barrier layer is composed of any one of thorium Th, niobium Nb, molybdenum Mo, and SiCf / SiC composite coatings, wherein the outer portion of the diffusion barrier layer is a pure Cr coating.

[0007] Furthermore, the Th, Nb, Mo layers and Cr coating are all pure metal coatings.

[0008] Furthermore, the diffusion barrier coating has a thickness of 0.1-3 μm, and the Cr coating has a thickness of 10-20 μm.

[0009] A method for preparing a diffusion barrier layer based on a Cr coating of an accident-tolerant fuel cladding, wherein a diffusion barrier layer and a Cr coating are sequentially plated on a base material by a high-power pulsed magnetron sputtering process, and the high-power pulsed magnetron sputtering process comprises the following steps: S1. Pretreatment of substrate and target: Soak the substrate and target in the cleaning solution for 10-20 minutes, then repeatedly clean their surfaces for 3-5 times to remove stains on the surfaces of the substrate and target. After cleaning, put the substrate and target in a drying oven, set the drying oven temperature to 70-90°C, dry for 10 minutes, take out after drying and naturally cool to room temperature, place the treated substrate on the sputtering machine tray, and place the target in the vacuum chamber; S2. Vacuum chamber treatment: open the vacuum chamber, use a conveying device to send the substrate into the vacuum chamber, evacuate the vacuum chamber, heat and bake for 20 minutes, and then fill the vacuum chamber with argon gas; S3, pre-sputtering by high-speed bombardment of target material: by bombarding the target material surface with high-speed argon ions, part of the target material is sputtered to achieve pre-sputtering; S4, generating a diffusion barrier layer: adjusting the sputtering reaction conditions, replacing the substrate, and again using argon ions to bombard the target surface at high speed, so that the target reaches the substrate surface after sputtering, and forms a diffusion barrier layer on the substrate surface after deposition; S5. Preparation of Cr coating: repeat steps S1-S4 to plate a Cr coating on the diffusion barrier layer. When preparing the Cr coating, the overall deposition time of the coating is 2-24 hours.

[0010] Further, in step S1, the target material is one of Th, Nb, and Mo.

[0011] Further, in step S2, after the vacuum chamber is evacuated, the vacuum degree in the chamber is 1.0-4.2x10 -4 pa.

[0012] Furthermore, in step S4, when pre-sputtering the target material, the pulse frequency is 10 to 500 Hz, the pulse width is 0.1 to 150 μs, the duty cycle is 1 to 100%, the sputtering power is 1000 to 20000 W, the sputtering gas pressure is 0.02 to 1.5 Pa, the bias voltage is -60 to -400 V, the deposition temperature is 100 to 300° C., and the deposition time is 0.5 to 6 h.

[0013] Furthermore, in step S4, when adjusting the sputtering reaction conditions, the following contents are also included: S41. Detecting the pre-sputtering effect: observing the surface morphology and measuring the thickness of the thin film formed by pre-sputtering on the substrate, completing the quality detection and characterization of the deposited film, and recording the detection and characterization results; S42, argon ion flow adjustment: preliminarily detect the argon gas flux entering the vacuum chamber, adjust the equipment valve according to the pre-sputtering results, change the gas flux size, and make the argon gas flux 5-50 standard cubic centimeters per minute; S43, control sputtering power: detect the temperature of the target surface and the quality of the pre-sputtered film, adjust the voltage and current between the target and the coating chamber wall, and reduce the applied voltage and current when the target surface temperature exceeds a predetermined value; S44. Adjusting the deposition rate: adjusting the temperature and rotation speed of the substrate, and then changing the distance between the target and the substrate.

[0014] Further, in step S44, the temperature range of the substrate is 25-200°C, the rotation speed of the substrate is 0.5-5r / min, and the distance between the target and the substrate is 30-200mm.

[0015] Beneficial effects of the present invention: In the present invention, by arranging a diffusion barrier layer between Zr and Cr, the oxidation rate can be reduced by slowing down the diffusion between Zr and Cr, thereby improving the ability of the cladding to resist loss of coolant accidents, thereby making the nuclear power cladding tube safer under LCOA conditions. Since the diffusion layer can effectively inhibit the mutual diffusion between the Cr layer and the zirconium alloy matrix and avoid the formation of a Cr-Zr intermediate layer, the high-temperature service performance of the coating is improved, and the high-temperature oxidation resistance of the Cr coating of the accident-tolerant fuel cladding is further improved, thereby increasing the survival time of the fuel cladding tube under a LOCA accident. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 The present invention is a flow chart of a diffusion barrier layer based on a Cr coating of an accident-tolerant fuel cladding and a preparation method thereof. DETAILED DESCRIPTION

[0017] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention. Example

[0018] See also Figure 1This design proposes an implementation method, a diffusion barrier layer based on the Cr coating of the accident-tolerant fuel cladding, the diffusion barrier layer is composed of any one of thorium Th, niobium Nb, molybdenum Mo, and SiCf / SiC composite coating, wherein the outer part of the diffusion barrier layer is a pure Cr coating, the Th, Nb, Mo layer and Cr coating are all pure metal coatings, the diffusion barrier coating has a thickness of 1.0 μm, and the Cr coating has a thickness of 15 μm.

[0019] In this embodiment, the pure Cr coating and the Th, Nb, and Mo layers outside the diffusion barrier layer are all pure metal coatings, which can reduce the interference of other impurities in the coating on sputtering, thereby ensuring the barrier effect of the diffusion barrier layer and achieving effective isolation of the Cr coating and the substrate, thereby preventing the Zr element from diffusing into the Cr coating to form an oxygen transfer channel, preventing oxygen from penetrating the Cr coating into the substrate, slowing down the oxidation rate of the substrate, and thus ensuring the ability of the cladding to resist loss of coolant during use. Example

[0020] See also Figure 1 This design proposes an implementation method, a method for preparing a diffusion barrier layer based on a Cr coating of an accident-tolerant fuel cladding, wherein a diffusion barrier layer and a Cr coating are sequentially plated on a substrate material by a high-power pulsed magnetron sputtering process, and the high-power pulsed magnetron sputtering process includes the following steps: Step 1, pretreatment of substrate and target: soak the substrate and target in the cleaning solution for 15 minutes, then repeatedly clean their surfaces 5 times to remove stains on the surfaces of the substrate and target. After cleaning, put the substrate and target in a drying oven, set the drying oven temperature to 80°C, dry for 10 minutes, take out after drying and cool naturally to room temperature, place the treated substrate on the sputtering machine tray, and place the target in the vacuum chamber. The target is one of Th, Nb, and Mo. Step 2: Vacuum chamber treatment: Open the vacuum chamber, use the conveying equipment to send the substrate into the vacuum chamber, evacuate the vacuum chamber, heat and bake for 20 minutes, and then fill the vacuum chamber with argon. After the vacuum chamber is evacuated, the vacuum degree in the chamber is 2.5x10 -4 pa; Step 3, glow cleaning: fill the vacuum chamber with argon gas, the argon gas flow rate is 70sccm, the chamber pressure is 0.2pa, and the substrate surface is bombarded with high-speed argon ions using a bias power supply. The bias power supply bias is 500V, the pulse width is 4μs, and the duty cycle is 60%, so that the impurities on the substrate surface are bombarded to the outside of the substrate to achieve glow cleaning: Step 4: Generate a diffusion barrier layer: Select appropriate sputtering reaction conditions and corresponding target materials, use argon ions to bombard the target surface at high speed, and the target reaches the substrate surface after sputtering, and forms a diffusion barrier layer on the substrate surface after deposition. When pre-sputtering the target material, the pulse frequency is 350Hz, the pulse width is 100μs, the duty cycle is 40%, the sputtering power is 2500W, the sputtering gas pressure is 0.2Pa, the bias voltage is -120V, the deposition temperature is 200℃, and the deposition time is 5h; When selecting sputtering reaction conditions, the following should also be included: 41. Detect pre-sputtering effect: observe the surface morphology and measure the thickness of the thin film formed by pre-sputtering on the substrate, complete the quality detection and characterization of the deposited film, and record the detection and characterization results; 42. Argon ion flow adjustment: Preliminarily detect the argon gas flux entering the vacuum chamber, adjust the equipment valve according to the pre-sputtering results, change the gas flux size, and make the argon gas flux 25 standard cubic centimeters / minute; 43. Control sputtering power: detect the temperature of the target surface and the quality of the pre-sputtered film, adjust the voltage and current between the target and the coating chamber wall, and reduce the applied voltage and current when the target surface temperature exceeds the preset value; 44. Adjust the deposition rate: adjust the temperature and rotation speed of the substrate, and then change the distance between the target and the substrate. The temperature range of the substrate is 25°C, the rotation speed of the substrate is 0.5r / min, and the distance between the target and the substrate is 50mm.

[0021] Step 5: Preparation of Cr coating: adjusting the sputtering reaction conditions and the corresponding sputtering target material, and plating a Cr coating on the diffusion barrier layer. Example

[0022] See also Figure 1 This design proposes an implementation method, a method for preparing a diffusion barrier layer based on a Cr coating of an accident-tolerant fuel cladding, wherein a diffusion barrier layer and a Cr coating are sequentially plated on a substrate material by a high-power pulsed magnetron sputtering process, and the high-power pulsed magnetron sputtering process includes the following steps: Step 1, pretreatment of substrate and target: soak the substrate and target in the cleaning solution for 15 minutes, then repeatedly clean their surfaces 5 times to remove stains on the surfaces of the substrate and target. After cleaning, put the substrate and target in a drying oven, set the drying oven temperature to 80°C, dry for 10 minutes, take out after drying and cool naturally to room temperature, place the treated substrate on the sputtering machine tray, and place the target in the vacuum chamber. The target is one of Th, Nb, and Mo. Step 2: Vacuum chamber treatment: Open the vacuum chamber, use the conveying equipment to send the substrate into the vacuum chamber, evacuate the vacuum chamber, heat and bake for 20 minutes, and then fill the vacuum chamber with argon. After the vacuum chamber is evacuated, the vacuum degree in the chamber is 2.5x10 -4 pa; Step 3, glow cleaning: fill the vacuum chamber with argon gas, the argon gas flow rate is 60sccm, the chamber pressure is 0.1pa, and the substrate surface is bombarded with high-speed argon ions by a bias power supply. The bias power supply bias is 400V, the pulse width is 5μs, and the duty cycle is 30%, so that the impurities on the substrate surface are bombarded to the outside of the substrate to achieve glow cleaning: Step 4: Generate a diffusion barrier layer: Select appropriate sputtering reaction conditions and corresponding target materials, use argon ions to bombard the target surface at high speed, and the target reaches the substrate surface after sputtering, and forms a diffusion barrier layer on the substrate surface after deposition. When pre-sputtering the target material, the pulse frequency is 50Hz, the pulse width is 50μs, the duty cycle is 40%, the sputtering power is 5000W, the sputtering gas pressure is 0.2Pa, the bias voltage is 150V, the deposition temperature is 200℃, and the deposition time is 5h; When selecting sputtering reaction conditions, the following should also be included: 41. Detect pre-sputtering effect: observe the surface morphology and measure the thickness of the thin film formed by pre-sputtering on the substrate, complete the quality detection and characterization of the deposited film, and record the detection and characterization results; 42. Argon ion flow adjustment: Preliminarily detect the argon gas flux entering the vacuum chamber, adjust the equipment valve according to the pre-sputtering results, change the gas flux size, and make the argon gas flux 35 standard cubic centimeters / minute; 43. Control sputtering power: detect the temperature of the target surface and the quality of the pre-sputtered film, adjust the voltage and current between the target and the coating chamber wall, and reduce the applied voltage and current when the target surface temperature exceeds the preset value; 44. Adjust the deposition rate: adjust the temperature and rotation speed of the substrate, and then change the distance between the target and the substrate. The temperature range of the substrate is 50°C, the rotation speed of the substrate is 15r / min, and the distance between the target and the substrate is 80mm.

[0023] Step 5: Preparation of Cr coating: adjusting the sputtering reaction conditions and the corresponding sputtering target material, and plating a Cr coating on the diffusion barrier layer.

[0024] In this embodiment, the interference of stains on the surfaces of the substrate and the target material on the subsequent sputtering can be reduced by pre-treating the substrate and the target material. The vacuum chamber treatment can be used to preheat the vacuum chamber, thereby shortening the subsequent heating time of the vacuum chamber. The stains on the surface of the substrate can be further cleaned by glow cleaning to reduce the interference with the subsequent sputtering. When selecting the sputtering reaction conditions, the argon ion flow rate, sputtering power and deposition rate can be changed in turn. When adjusting the argon ion flow rate, the equipment valve can be adjusted according to the pre-sputtering results to change the gas flux entering the vacuum chamber. The argon flow rate can be precisely controlled through the automatic control system to ensure the stability and consistency of the subsequent coating process. Since the sputtering power is the product of the voltage and current applied between the cathode and the anode during the sputtering process, changing the voltage and current values ​​can achieve the adjustment of the sputtering power. The size of the sputtering power can directly affect the sputtering rate and the film quality. A higher sputtering power can increase the sputtering speed, thereby improving the preparation efficiency of the entire diffusion barrier layer. The deposition rate refers to the thickness of the film deposited on the substrate per unit time. Since the deposition rate is affected by the argon flow rate, sputtering power, the distance between the target and the substrate, the stability and rotation speed of the substrate, etc., the deposition rate can be optimized by increasing the argon flow rate and increasing the sputtering power.

[0025] In the present invention, a diffusion barrier layer is provided between Zr and Cr to separate the Zr substrate and the Cr coating, and the diffusion between the Zr substrate and the Cr coating is slowed down, thereby reducing the oxidation rate of the Cr coating, improving the ability of the cladding to resist loss of coolant accidents, and thereby making the nuclear power cladding tube safer under LCOA conditions. Since the diffusion layer can effectively inhibit the mutual diffusion between the Cr coating and the zirconium alloy substrate and avoid the formation of a Cr-Zr intermediate layer, the high-temperature service performance of the coating is improved, and the high-temperature oxidation resistance of the Cr coating of the accident-tolerant fuel cladding is further improved, thereby increasing the survival time of the fuel cladding tube under a LOCA accident.

[0026] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A diffusion barrier layer based on Cr coating of accident-tolerant fuel cladding, characterized by: The diffusion barrier layer is composed of any one of thorium Th, niobium Nb, molybdenum Mo, and SiCf / SiC composite coating, wherein the outer part of the diffusion barrier layer is a pure Cr coating.

2. The diffusion barrier layer based on the Cr coating of the accident-tolerant fuel cladding according to claim 1 is characterized by: The Th, Nb, Mo layers and Cr coating are all pure metal coatings.

3. The diffusion barrier layer based on the Cr coating of the accident-tolerant fuel cladding according to claim 1 is characterized by: The diffusion barrier coating has a thickness of 0.1-3 μm, and the Cr coating has a thickness of 10-20 μm.

4. A method for preparing a diffusion barrier layer based on a Cr coating of an accident-tolerant fuel cladding, characterized in that: A diffusion barrier layer based on a Cr coating of an accident-tolerant fuel cladding according to any one of claims 1 to 3 is used, and a diffusion barrier layer and a Cr coating are sequentially plated on a base material through a high-power pulsed magnetron sputtering process, and the high-power pulsed magnetron sputtering includes the following steps: S1. Pretreatment of substrate and target: Soak the substrate and target in the cleaning solution for 10-20 minutes, then repeatedly clean their surfaces for 3-5 times to remove stains on the surfaces of the substrate and target. After cleaning, put the substrate and target in a drying oven, set the drying oven temperature to 70-90°C, dry for 10 minutes, take out after drying and naturally cool to room temperature, place the treated substrate on the sputtering machine tray, and place the target in the vacuum chamber; S2. Vacuum chamber treatment: open the vacuum chamber, use the conveying equipment to send the substrate into the vacuum chamber, evacuate the vacuum chamber, and heat and bake for 20 minutes during the evacuation process; S3, glow cleaning: filling argon gas into the vacuum chamber, selecting a bias power supply, bombarding the substrate surface with high-speed argon ions, so that impurities on the substrate surface are bombarded out of the substrate, achieving glow cleaning; S4, generating a diffusion barrier layer: selecting appropriate sputtering reaction conditions and corresponding target materials, using argon ions to bombard the target material surface at high speed, the target material reaches the substrate surface after sputtering, and forms a diffusion barrier layer on the substrate surface after deposition; S5. Preparation of Cr coating: adjusting the sputtering reaction conditions and the corresponding sputtering target, plating a Cr coating on the diffusion barrier layer. When preparing the Cr coating, the overall deposition time of the coating is 2-24 hours.

5. A method for preparing a diffusion barrier layer based on a Cr coating of an accident-tolerant fuel cladding, characterized in that: In step S1 , the target material is one of Th, Nb and Mo.

6. A method for preparing a diffusion barrier layer based on a Cr coating of an accident-tolerant fuel cladding, characterized in that: In step S2, after the vacuum chamber is evacuated, the vacuum degree in the chamber is 1.0-4.2x10 -4 pa.

7. A method for preparing a diffusion barrier layer based on a Cr coating of an accident-tolerant fuel cladding, characterized in that: In step S3, during the glow cleaning process, the argon gas flow rate is 20-100 sccm, the bias voltage of the bias power supply is 100-700V, the pulse width is 0.1-150 μs, and the duty cycle is 1-100%.

8. A method for preparing a diffusion barrier layer based on a Cr coating of an accident-tolerant fuel cladding, characterized in that: In step S4, when pre-sputtering the target material, the pulse frequency is 10-500 Hz, the pulse width is 0.1-150 μs, the duty cycle is 1-100%, the sputtering power is 1000-20000 W, the sputtering gas pressure is 0.02-1.5 Pa, the bias voltage is 60-400 V, the deposition temperature is 100-300 ° C, and the deposition time is 0.5-6 h.

9. A method for preparing a diffusion barrier layer based on a Cr coating of an accident-tolerant fuel cladding, characterized in that: In step S4, when selecting the sputtering reaction conditions, the following contents are also included: S41. Detecting the pre-sputtering effect: observing the surface morphology and measuring the thickness of the thin film formed by pre-sputtering on the substrate, completing the quality detection and characterization of the deposited film, and recording the detection and characterization results; S42, argon ion flow adjustment: preliminarily detect the argon gas flux entering the vacuum chamber, adjust the equipment valve according to the pre-sputtering results, change the gas flux size, and make the argon gas flux 5-50 standard cubic centimeters per minute; S43, control sputtering power: detect the temperature of the target surface and the quality of the pre-sputtered film, adjust the voltage and current between the target and the coating chamber wall, and reduce the applied voltage and current when the target surface temperature exceeds a predetermined value; S44. Adjusting the deposition rate: adjusting the temperature and rotation speed of the substrate, and then changing the distance between the target and the substrate.

10. A method for preparing a diffusion barrier layer based on a Cr coating of an accident-tolerant fuel cladding, characterized in that: In step S44, the temperature range of the substrate is 25-200°C, the rotation speed of the substrate is 0.5-5r / min, and the distance between the target and the substrate is 30-100mm.

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