Hydrogen-resistant coating for pressurized water reactor zirconium alloy cladding tube and preparation method of hydrogen-resistant coating

Abstract

The invention relates to a hydrogen-resistant coating for a zirconium alloy cladding tube of a pressurized water reactor and a preparation method of the hydrogen-resistant coating. The preparation method specifically comprises the following steps: polishing the inner wall and the outer wall of the zirconium alloy cladding tube; the polished zirconium alloy cladding tube is placed in a tubular heating furnace, and after air in the furnace is replaced, gas containing oxygen is introduced into the furnace; and the polished zirconium alloy is sequentially subjected to heating, heat preservation and cooling treatment through a tubular heating furnace, and zirconium oxide coatings are prepared on the inner wall and the outer wall of the zirconium alloy cladding tube. Compared with the prior art, the zirconium alloy cladding is subjected to heat treatment and in-situ oxidation to form the ZrO2 coating, so that the zirconium alloy cladding pipe has hydrogen isotope permeation resistance and corrosion resistance, and the problems of hydrogen isotope permeation, coolant corrosion, difficult coating preparation process, high cost and the like in the reactor irradiation process are solved.

Description

Technical Field

[0001] The invention relates to the technical field of reactor zirconium alloy cladding tube surface modification, and in particular to a hydrogen barrier coating for a pressurized water reactor zirconium alloy cladding tube and a preparation method thereof. Background Art

[0002] With the development of the nuclear industry, the production and release of tritium are increasing. As a radioactive isotope of hydrogen, tritium has a much smaller atomic radius than other elements and is a low-toxic radioactive nuclide. Especially under high temperature conditions, if appropriate protective measures are not taken, tritium can easily penetrate through the metal structural materials that contain it, causing problems such as hydrogen embrittlement damage to the material and environmental radioactive pollution.

[0003] Zirconium alloys are currently widely used as fuel cladding and core structural materials for pressurized water reactors due to their excellent mechanical properties, radiation resistance, low thermal neutron absorption cross section, and good corrosion resistance. Considering that zirconium alloys are easy to react with high-temperature water vapor in a loss of coolant accident, producing hydrogen and releasing a large amount of heat, which may lead to nuclear accidents, in addition to improving the corrosion resistance of zirconium alloys by adjusting the chemical composition ratio of commercial zirconium alloys, adding accident-resistant fuel coatings (ATF coatings) to the outer wall of zirconium alloys is also one of the effective ways to improve the accident resistance of zirconium alloy cladding. Currently, common ATF coatings mainly include metal coatings and ceramic coatings. On the other hand, nuclear fuel produces tritium in the reactor mainly through three fission reactions. The produced tritium can penetrate into the reactor coolant through the cladding, causing hydrogen embrittlement damage and radioactive contamination of structural materials. At present, in tritium-related components such as tritium breeder blankets in fusion reactors, it is preferred to coat a ceramic tritium barrier coating (TPB) with low hydrogen permeability on the surface of structural materials such as stainless steel or low-activated steel to reduce tritium penetration.

[0004] At present, the technologies for preparing ATF coating or TPB coating on the surface of metal structural materials mainly include physical vapor deposition (PVD), chemical vapor deposition (CVD), plasma electrolytic oxidation (PEO), embedded aluminum (PC), hot-dip aluminum (HAD), electrochemical deposition (ECD) and other methods. These coating preparation technologies basically have the problems of high cost, complex process flow, unstable process parameters, and difficulty in preparing the inner wall of the tube. Summary of the invention

[0005] The purpose of the present invention is to provide a hydrogen barrier coating for a zirconium alloy cladding tube of a pressurized water reactor and a preparation method thereof, so as to reduce the cost of coating preparation.

[0006] The purpose of the present invention can be achieved by the following technical solutions:

[0007] The present invention provides a method for preparing a hydrogen barrier coating for a zirconium alloy cladding tube of a pressurized water reactor, comprising the following steps:

[0008] S1: polishing the inner and outer walls of the zirconium alloy cladding tube;

[0009] S2: placing the polished zirconium alloy cladding tube in a tubular heating furnace, replacing the air in the furnace and introducing a gas containing oxygen into the furnace;

[0010] S3: The polished zirconium alloy is sequentially heated, kept warm, and cooled down in a tubular heating furnace to form a zirconium oxide coating on the inner and outer walls of the zirconium alloy cladding tube.

[0011] Preferably, the zirconium content in the zirconium alloy cladding tube is ≥95wt%, and the sum of the contents of other elements is ≤5wt%.

[0012] Further preferably, the zirconium alloy cladding tube comprises Sn: 1.2-1.7wt%, Fe: 0.18-0.24wt%, Cr: 0.07-1.13wt%, and the rest is Zr.

[0013] Further preferably, the zirconium alloy cladding tube has an outer diameter of 5 to 50 mm, a wall thickness of 0.3 to 2 mm, and a length of 100 to 5000 mm.

[0014] Preferably, the polishing treatment is selected from at least one of grinding, mechanical polishing, chemical polishing, electrolytic polishing, ultrasonic polishing, fluid polishing, magnetic abrasive polishing, and vibration polishing.

[0015] Further preferably, the roughness of the inner and outer walls of the zirconium alloy cladding tube after polishing is ≤3.2 μm.

[0016] Preferably, replacing the air in the furnace includes evacuating the furnace to a pressure of ≤10 -3 Pa or introduce inert gas into the furnace.

[0017] Preferably, the purity of the inert gas is ≥99.5%, and the gas purity refers to the volume percentage of the gas.

[0018] Further preferably, the inert gas is selected from at least one of helium and argon.

[0019] Further preferably, the inert gas is introduced to wash the furnace more than twice to replace the air in the furnace.

[0020] Preferably, the gas pressure of the oxygen-containing gas is ≥ 0.08 MPa.

[0021] Preferably, the oxygen-containing gas includes high-purity oxygen with a purity of ≥99.5% or a mixed gas of oxygen and an inert gas.

[0022] Preferably, in the mixed gas of oxygen and inert gas, the concentration of oxygen is 0.0005% to 21%, and the inert gas is selected from at least one of helium and argon.

[0023] Preferably, the gas flow rate of the oxygen-containing gas is in the range of 0.1 mL / min to 50 L / min.

[0024] Further preferably, the gas flow direction of the oxygen-containing gas is as follows: it flows into the zirconium alloy tube from one end of the zirconium alloy cladding tube, flows along the axial direction, flows out from the other end of the zirconium alloy cladding tube, and then flows in the axial direction in the opposite direction to the gas outlet of the tubular heating furnace, so as to realize simultaneous oxidation of the inner and outer walls of the zirconium alloy cladding tube and make the prepared inner and outer wall coatings of the zirconium alloy cladding tube more uniform.

[0025] Preferably, the heating is performed from room temperature to 300-700° C. at a heating rate of 50-400° C. / h.

[0026] Preferably, the insulation time is 2 to 100 hours.

[0027] Preferably, the temperature is lowered to room temperature at a rate of 50 to 400° C. / h.

[0028] Preferably, the heating is selected from at least one of resistance heating, induction heating, electron beam heating, laser heating and arc heating.

[0029] On the other hand, the present invention also provides a hydrogen barrier coating for a pressurized water reactor zirconium alloy cladding tube prepared by the above preparation method.

[0030] Preferably, the thickness of the hydrogen barrier coating is in the range of 50 nm to 50 μm.

[0031] During the service of the reactor, the outer wall of the zirconium alloy cladding tube can react with oxygen in the coolant to form zirconium oxide (ZrO 2 ) thin film. ZrO 2 Ceramic materials have low hydrogen isotope permeability and strong corrosion resistance. However, compared with the prefabricated coating, the ZrO formed during service 2 The film inevitably has the problem of discontinuity and unevenness, which makes ZrO 2 The hydrogen permeation resistance and corrosion resistance of ceramic materials cannot be fully utilized. The present invention heat treats the zirconium alloy cladding tube and in-situ oxidizes the inner and outer walls of the zirconium alloy cladding tube to form a zirconium oxide coating. Compared with the process of depositing coatings on the surface of the zirconium alloy cladding by different physical and chemical methods, the in-situ oxidation of the zirconium alloy cladding by heat treatment forms ZrO 2The coating process requires simple facilities and process flow, and the bonding between the coating and the substrate will be stronger. It can also realize the preparation of large-size and inner wall coatings of pipelines, reducing the process difficulty and cost of coating preparation.

[0032] Aiming at the service environment of high temperature, corrosion, hydrogen isotope penetration, etc. faced by zirconium alloy cladding tubes of pressurized water reactors, the present invention designs a hydrogen barrier coating for zirconium alloy cladding tubes of pressurized water reactors and a preparation method thereof, so that the zirconium alloy cladding tubes have both hydrogen isotope penetration barrier properties and corrosion resistance, and solve the problems of hydrogen isotope penetration, coolant corrosion, and difficult coating preparation process and high cost during reactor irradiation.

[0033] Compared with the prior art, the present invention has the following beneficial effects:

[0034] (1) The present invention can form a zirconium oxide hydrogen barrier coating on the inner and outer walls of the zirconium alloy cladding tube by heat treatment.

[0035] (2) The present invention can realize in-situ oxidation on the inner and outer walls of the zirconium tube to form a uniform hydrogen barrier coating by controlling the gas flow to flow along the axial direction of the zirconium alloy cladding tube.

[0036] (3) The inner and outer walls of the zirconium alloy cladding tube are simultaneously oxidized to form a uniform hydrogen barrier coating, which can prevent the radioactive hydrogen isotopes in the cladding tube, i.e., the tritium produced in the target, from penetrating outward into the reactor cooling system, and can also prevent the hydrogen in the water coolant outside the cladding tube from penetrating into the tube and into the target.

[0037] (4) The present invention forms a zirconium oxide coating in situ outside the zirconium alloy cladding tube, thereby effectively avoiding direct contact between the zirconium alloy and the coolant, slowing down the corrosion rate, and having an excellent anti-corrosion effect.

[0038] (5) The process of in-situ heat treatment of zirconium alloy cladding tubes to form functional coatings requires simple facilities and a simple process flow. The coating and the substrate are more firmly bonded, and the preparation of large-size coatings on the inner wall of pipelines can be achieved, thereby reducing the process difficulty and cost of coating preparation. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 It is a front view of a zirconium alloy cladding tube for a pressurized water reactor having a hydrogen barrier coating prepared by the present invention;

[0040] Figure 2 A top view of a zirconium alloy cladding tube for a pressurized water reactor having a hydrogen barrier coating prepared by the present invention (1-zirconium alloy cladding tube; 2-zirconium oxide coating);

[0041] Figure 3This is an optical photograph of a zirconium alloy cladding tube for a pressurized water reactor with a hydrogen barrier coating prepared in Example 1 of the present invention (in the figure, 1 is a zirconium alloy cladding tube with a zirconium oxide coating; 2 is a zirconium alloy cladding tube without a zirconium oxide coating);

[0042] Figure 4 Schematic diagram of the flow direction of oxygen-containing gas in the preparation process of the present invention;

[0043] Figure 5 This is a cross-sectional scanning electron microscope image of a zirconium oxide coating formed by in-situ oxidation on a zirconium alloy cladding tube for a pressurized water reactor according to Example 1 of the present invention (1-zirconium alloy cladding tube; 2-zirconium oxide coating);

[0044] Figure 6 This is a surface morphology of a zirconium oxide coating formed by in-situ oxidation on a zirconium alloy cladding tube for a pressurized water reactor according to Example 1 of the present invention;

[0045] Figure 7 This is a curve showing the change of deuterium partial pressure over time in a deuterium gas permeation test of a zirconium oxide coating formed by in-situ oxidation on a zirconium alloy cladding tube for a pressurized water reactor according to Example 1 of the present invention. DETAILED DESCRIPTION

[0046] The present invention is described in detail below in conjunction with the accompanying drawings and specific embodiments. This embodiment is implemented based on the technical solution of the present invention, and provides a detailed implementation method and specific operation process, but the protection scope of the present invention is not limited to the following embodiments.

[0047] The present invention provides a method for preparing a hydrogen barrier coating for a zirconium alloy cladding tube of a pressurized water reactor, comprising the following steps:

[0048] (1) The inner and outer walls of the Zr-4 alloy cladding tube are polished, and the roughness Ra after polishing is ≤3.2μm;

[0049] (2) Place the zirconium alloy cladding tube polished in step (1) in a tubular resistance furnace and evacuate to a pressure of ≤10 -3 Pa or introduce high-purity inert gas (purity ≥ 99.5%) to wash the furnace more than 2 times to replace the air in the furnace;

[0050] (3) After step (2), high-purity oxygen with a purity of ≥99.5% or containing 0.0005% to 21% O is introduced at ≥0.08Mpa. 2 The high-purity inert gas has a gas flow rate of 0.1 mL / min to 50 L / min, and the gas flow direction is as follows: Figure 4As shown, the gas flows into the zirconium alloy tube from one end of the zirconium alloy cladding tube, flows along the axial direction, flows out from the other end of the zirconium alloy cladding tube, and then flows in the axial direction in the opposite direction to the gas outlet of the tubular heating furnace, so as to realize the simultaneous oxidation of the inner and outer walls of the zirconium alloy cladding tube, and make the inner and outer wall coatings of the prepared zirconium alloy cladding tube more uniform;

[0051] (4) In the above oxygen-containing atmosphere, a tubular resistance furnace heating program is started, and the temperature is heated from room temperature to 300-700°C at a heating rate of 50-400°C / h, and the temperature is kept at this temperature for 2-100 hours; after the temperature is kept at this temperature, a cooling program is started, and the temperature is cooled to room temperature at a cooling rate of 50-400°C / h, thereby completing the preparation of the zirconium oxide coating.

[0052] The thickness of the hydrogen barrier coating for the zirconium alloy cladding tube of a pressurized water reactor prepared by the above method ranges from 50 nm to 50 μm.

[0053] Unless otherwise specified, the reagents, methods, instruments and equipment used in the present invention are conventional reagents, methods, instruments and equipment in the art. Unless otherwise specified, the reagents and materials used in the following examples are commercially available.

[0054] The zirconium alloy cladding tubes used in all embodiments of the present invention are made of nuclear industry grade Zr-4 alloy.

[0055] The composition of the Zr-4 alloy cladding tube is as follows: Sn: 1.2-1.7wt%, Fe: 0.18-0.24wt%, Cr: 0.07-1.13wt%, and the rest is Zr.

[0056] The dimensions of the Zr-4 alloy cladding tube used are: outer diameter Ф5~50mm, wall thickness 0.3~2mm, and length L 100~5000mm.

[0057] Example 1

[0058] A method for preparing a hydrogen barrier coating for a zirconium alloy cladding tube of a pressurized water reactor is as follows:

[0059] (1) The inner and outer walls of the Zr-4 alloy cladding tube were polished by mechanical polishing. The dimensions of the Zr4 alloy cladding tube used were: Ф = 9.5 mm, wall thickness = 0.57 mm, L = 1000 mm;

[0060] Roughness after polishing: Ra = 3.2 μm;

[0061] (2) placing the zirconium alloy cladding tube polished in step (1) in a tubular resistance furnace, and introducing high-purity Ar gas (purity ≥ 99.5%) to wash the furnace twice to replace the air in the furnace;

[0062] (3) Pass 0.1 MPa of 100 ppm O 2The high purity Ar gas is in a gas flow rate of 5 mL / min and the gas flow direction is as follows Figure 4 As shown: it flows into the zirconium alloy tube from one end of the zirconium alloy cladding tube, flows along the axial direction, flows out from the other end of the zirconium alloy cladding tube, and then flows in the axial direction in the opposite direction to the gas outlet of the tubular heating furnace, so that the inner and outer walls of the zirconium alloy cladding tube are oxidized at the same time;

[0063] (4) In an oxygen-containing atmosphere, a tubular resistance furnace heating program is started, and the temperature is heated from room temperature to 400°C at a heating rate of 300°C / h, and the temperature is kept at this temperature for 48 hours. After the temperature is kept at this temperature, a cooling program is started, and the temperature is cooled to room temperature at a cooling rate of 300°C / h, thereby completing the preparation of the zirconium oxide coating.

[0064] Performance Testing

[0065] Figure 3 1 is a Zr-4 alloy cladding tube with a zirconium oxide coating prepared in Example 1 of the present invention. As can be seen from the figure, both the inner and outer walls of the cladding tube are covered with a zirconium oxide coating.

[0066] The zirconia coating prepared above was scanned by a scanning electron microscope. Figure 5 and Figure 6 The cross-sectional scanning electron microscope images and surface morphology images of the zirconium oxide coating formed by in-situ oxidation on the inner and outer walls of the Zr-4 alloy cladding tube in Example 1 are shown respectively. It can be seen from the figure that the ZrO 2 The coating is dense and uniform, and the thickness of the zirconium oxide coating is 600nm.

[0067] The deuterium permeation test was performed on the Zr-4 alloy cladding tube after oxidation treatment in Example 1 using an all-metal ultra-high vacuum gas phase hydrogen isotope permeation measurement device. High-pressure gas phase deuterium gas was diffused and permeated from the high-pressure side to the low-pressure side, and the deuterium partial pressure permeated to the low-pressure side was detected using a quadrupole mass spectrometer. The results are as follows: Figure 7 As shown, it is found that in the ZrO 2 40 kPa of deuterium gas was passed into the inner side of the coated zirconium tube. Within 24 hours at 350°C, the quadrupole mass spectrometer did not detect deuterium gas that penetrated to the outside of the zirconium tube, indicating that the coating can effectively block the penetration of deuterium gas.

[0068] The above description of the embodiments is to facilitate the understanding and use of the invention by those skilled in the art. It is obvious that those skilled in the art can easily make various modifications to these embodiments and apply the general principles described herein to other embodiments without creative work. Therefore, the present invention is not limited to the above embodiments, and improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the present invention should be within the scope of protection of the present invention.

Claims

1. A method for preparing a hydrogen barrier coating for a zirconium alloy cladding tube of a pressurized water reactor, characterized in that: The following steps are involved: S1: polishing the inner and outer walls of the zirconium alloy cladding tube; S2: placing the polished zirconium alloy cladding tube in a tubular heating furnace, replacing the air in the furnace and introducing a gas containing oxygen into the furnace; S3: The polished zirconium alloy is sequentially heated, kept warm, and cooled down in a tubular heating furnace to form a zirconium oxide coating on the inner and outer walls of the zirconium alloy cladding tube.

2. The method for preparing a hydrogen barrier coating for a zirconium alloy cladding tube for a pressurized water reactor according to claim 1, characterized in that: The zirconium content in the zirconium alloy cladding tube is ≥95wt%; the outer diameter of the zirconium alloy cladding tube is 5-50mm, the wall thickness is 0.3-2mm, and the length is 100-5000mm.

3. The method for preparing a hydrogen barrier coating for a zirconium alloy cladding tube for a pressurized water reactor according to claim 1, characterized in that: The polishing treatment is selected from at least one of grinding, mechanical polishing, chemical polishing, electrolytic polishing, ultrasonic polishing, fluid polishing, magnetic grinding polishing, and vibration polishing. After the polishing treatment, the roughness of the inner and outer walls of the zirconium alloy cladding tube is ≤3.2μm.

4. The method for preparing a hydrogen barrier coating for a pressurized water reactor zirconium alloy cladding tube according to claim 1, characterized in that: The replacement of the air in the furnace includes evacuating the furnace to a pressure of ≤10 -3 Pa or an inert gas is introduced into the furnace, wherein the purity of the inert gas is ≥99.5%, and the inert gas is selected from at least one of helium and argon.

5. The method for preparing a hydrogen barrier coating for a zirconium alloy cladding tube for a pressurized water reactor according to claim 1, characterized in that: The gas pressure of the oxygen-containing gas is ≥0.08Mpa; the oxygen-containing gas includes high-purity oxygen with a purity of ≥99.5% or a mixed gas of oxygen and an inert gas; wherein, in the mixed gas of oxygen and the inert gas, the oxygen concentration is 0.0005% to 21%, and the inert gas is selected from at least one of helium and argon.

6. The method for preparing a hydrogen barrier coating for a zirconium alloy cladding tube for a pressurized water reactor according to claim 1, characterized in that: The gas flow rate of the oxygen-containing gas is in the range of 0.1 mL / min to 50 L / min.

7. The method for preparing a hydrogen barrier coating for a zirconium alloy cladding tube for a pressurized water reactor according to claim 1, characterized in that: The gas flow direction of the oxygen-containing gas is as follows: it flows into the zirconium alloy tube from one end of the zirconium alloy cladding tube, flows along the axial direction, flows out from the other end of the zirconium alloy cladding tube, and then flows in the axial direction in the opposite direction to the gas outlet of the tubular heating furnace, thereby achieving simultaneous oxidation of the inner and outer walls of the zirconium alloy cladding tube.

8. The method for preparing a hydrogen barrier coating for a zirconium alloy cladding tube of a pressurized water reactor according to claim 1, characterized in that: The heating is performed from room temperature to 300-700°C at a heating rate of 50-400°C / h, the heat preservation time is 2-100h, and the cooling is performed to room temperature at a cooling rate of 50-400°C / h.

9. The method for preparing a hydrogen barrier coating for a zirconium alloy cladding tube of a pressurized water reactor according to claim 1, characterized in that: The heating is selected from at least one of resistance heating, induction heating, electron beam heating, laser heating and arc heating.

10. The hydrogen barrier coating for a pressurized water reactor zirconium alloy cladding tube prepared by the preparation method according to any one of claims 1 to 9, characterized in that: The thickness of the hydrogen barrier coating ranges from 50 nm to 50 μm.

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