Random grain structured cathodic arc coatings on zirconium alloy nuclear fuel cladding.

Abstract

The present disclosure relates generally to methods, systems and apparatus for forming random grain structure coatings on substrates of components used in nuclear reactors to provide protection against corrosion, and more particularly to improved methods, systems and apparatus for forming random grain structure coatings on zirconium alloy nuclear fuel cladding tubes using a cathodic arc (CA) physical vapor deposition (PVD) process to provide protection against corrosion during both normal reactor operation and transient / accident conditions.

Description

[Technical field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This application claims the benefit of and priority under 35 U.S.C. § 120 of U.S. patent application Ser. No. 17 / 332,104, entitled “CATHODIC ARC APPLIED RANDOMIZED GRAIN STRUCTURED COATINGS ON ZIRCONIUM ALLOY NUCLEAR FUEL CLADDING,” filed May 27, 2021, the contents of which are incorporated herein by reference in their entirety.

[0002] The present disclosure relates generally to methods, systems and apparatus for forming random grain structure coatings on substrates of components used in nuclear reactors to protect against corrosion, and more particularly to improved methods, systems and apparatus for forming random grain structure coatings on zirconium alloy nuclear fuel cladding tubes by cathodic arc (CA) physical vapor deposition (PVD) processing to protect against corrosion during both normal reactor operating conditions and transient and accident conditions.

[0003] The following summary is provided to facilitate understanding of some of the innovative features unique to the aspects disclosed herein and is not intended to be a complete description. A full understanding of the various aspects can be obtained by taking the entire specification, claims, and abstract as a whole.

[0004] In various aspects, disclosed herein are apparatus, systems and methods for coating substrates of components used in nuclear reactors to protect the required substrates from corrosion. In one embodiment, the nuclear reactor is a water-cooled nuclear reactor.

[0005] In various aspects, disclosed herein are methods for providing a random grain structure coating on a substrate of a component for use in a nuclear reactor, such as a water-cooled nuclear reactor.

[0006] In various aspects, the method includes providing a substrate and forming a protective coating layer having first particles selected from the group consisting of pure metallic chromium (Cr), chromium (Cr) alloys, and combinations thereof, on an exterior of the substrate using a cathodic arc (CA) physical vapor deposition (PVD) process. In one embodiment, the protective coating layer may have a random grain structure.

[0007] In various aspects, the component may be a nuclear fuel rod cladding tube for use in a nuclear reactor, preferably a water-cooled nuclear reactor.

[0008] In various embodiments, the substrate may be a zirconium alloy.

[0009] In various embodiments, the first particle may have a diameter of about 100 microns or less, or about 50 microns or less.

[0010] In various embodiments, the first particles may have an average diameter of about 20 microns or less, preferably about 10 microns or less.

[0011] In various embodiments, the first particles forming the protective coating layer may be pure chromium (Cr) particles.

[0012] In various embodiments, the first particles forming the corrosion resistant layer may be chromium (Cr) alloy particles.

[0013] In various embodiments, the chromium (Cr) alloy particles may include one of CrY, FeCrAl, FeCrAlY, CrAlY, or CrMo.

[0014] In various embodiments, the cathodic arc (CA) PVD process includes the steps of providing a Zr alloy tube substrate to be coated, providing a target comprising Cr or Cr alloy to be deposited on the Zr alloy tube substrate, supporting the Zr alloy tube and the Cr or Cr alloy target in a chamber of a CA PVD apparatus, evacuating the chamber, applying a low voltage between the target and the Zr alloy tube, the target comprising Cr or Cr alloy to be deposited on the Zr alloy tube substrate in a thin film form, and using a magnetic field to move the position of the cathodic arc to minimize droplet movement and uniformly erode and deposit the target on the Zr alloy tube substrate.

[0015] In various embodiments, the protective coating layer may have a thickness between about 5 microns and about 150 microns, between about 5 microns and about 100 microns, between about 5 microns and about 50 microns, between about 5 microns and about 20 microns, or between about 5 microns and about 15 microns. In one embodiment, the thickness is between about 5 microns and about 15 microns. In another embodiment, the thickness is about 20 microns.

[0016] In various embodiments, the method may further include polishing or grinding the exterior surface of the protective coating layer on the exterior of the substrate to make the exterior surface smoother.

[0017] In various embodiments, the method may further include, prior to forming the protective coating layer, forming an intermediate coating layer having second particles having a composition selected from the group consisting of Nb, Mo, Ta, Re, Os, Ru and W, and alloys thereof, on the outside of the substrate. The first particles are then applied to the substrate by cathodic arc (CA) PVD processing to form a protective coating layer on the intermediate coating layer. In various embodiments, the intermediate coating layer is applied between the protective coating layer and the outside of the substrate.

[0018] In various embodiments, the second particles may have a diameter of about 100 microns or less, may have an average diameter of about 20 microns or less, or about 10 microns or less.

[0019] In various embodiments, the intermediate coating layer may be formed by a cathodic arc (CA) physical vapor deposition (PVD) process.

[0020] In various embodiments, the intermediate coating layer may have a random grain structure.

[0021] In various embodiments, the intermediate coating layer may have a thickness between about 0.5 microns and about 150 microns, between about 0.5 microns and about 100 microns, between about 0.5 microns and about 50 microns, or preferably between about 0.5 microns and about 15 microns.

[0022] In various aspects, the intermediate coating layer may prevent eutectic formation between the protective coating layer and the substrate, and the thickness of the intermediate coating is minimized to reduce the neutronic penalty while preventing eutectic formation.

[0023] In various embodiments, both the intermediate coating layer and the protective coating layer may have a thickness of between about 0.5 microns and about 150 microns, between about 0.5 microns and about 100 microns, between about 0.5 microns and about 50 microns, or between about 0.5 microns and about 15 microns, respectively, with the total thickness of the intermediate coating layer and the protective coating layer combined being between about 0.5 microns and about 150 microns, between about 1 micron and about 150 microns, between about 1 micron and about 100 microns, between about 1 micron and about 50 microns, or between about 1 micron and about 15 microns. In one embodiment, the total thickness of the two coating layers is about 20 microns.

[0024] These and other objects, features and characteristics of the present invention, as well as the method of operation and function of the associated elements of construction, and the combination of parts and economies of manufacture, will become more apparent from a study of the following description and the appended claims, taken in conjunction with the accompanying drawings, all of which are incorporated herein by reference, and like reference numerals designate corresponding parts throughout the various views, with it being expressly understood, however, that the drawings are for the purpose of illustration and description only and are not intended as a definition of the limits of the invention. [Brief description of the drawings]

[0025] The various features of the aspects described herein are set forth with particularity in the appended claims. However, the various aspects, together with their advantages, both as to organization and method of operation, may be understood by reference to the following description taken in conjunction with the accompanying drawings, in which:

[0026] [Figure 1] FIG. 2 is a schematic diagram of a grain structure by magnetron sputtering, according to at least one non-limiting embodiment of the present disclosure.

[0027] [Diagram 2] FIG. 1 is a schematic diagram of random grain structure and interface variation due to cold spray, in accordance with at least one non-limiting embodiment of the present disclosure.

[0028] [Diagram 3] FIG. 2 is a schematic diagram of a random grain structure without interface variations via cathodic arc (CA) PVD processing, in accordance with at least one non-limiting embodiment of the present disclosure.

[0029] [Figure 4] 1 illustrates generally Nb, Mo, Ta, Re, Os, Ru, or W or alloys of these metals as an intermediate coating layer between a Cr or Cr alloy coating and a Zr alloy tube material, in accordance with at least one non-limiting embodiment of the present disclosure.

[0030] Corresponding reference characters indicate corresponding parts throughout the several views. The exemplifications set forth herein are illustrative of various aspects of the present invention in one embodiment, and such exemplifications are not to be construed as limiting the scope of the present invention in any manner.

[0031] Numerous specific details are described to provide a thorough understanding of the overall structure, function, manufacture, and use of the embodiments as described in this disclosure and illustrated in the accompanying drawings. Well-known operations, components, and elements are not described in detail so as not to obscure the embodiments described herein. The reader will understand that the embodiments described and illustrated herein are non-limiting examples, and therefore, it will be understood that the specific structural and functional details disclosed herein may be representative and exemplary. Variations and modifications thereof may be made without departing from the scope of the claims.

[0032] Before describing the various aspects of the present disclosure in detail, it should be noted that the exemplary embodiments are not limited in application or use to the details disclosed in the accompanying drawings and description. It will be understood that the exemplary embodiments may be implemented or incorporated in other embodiments, variations, and modifications, and may be practiced or carried out in various ways. Moreover, unless otherwise indicated, the terms and expressions used herein have been selected for the purpose of describing the exemplary embodiments for the convenience of the reader, and not for the purpose of limitation thereof.

[0033] In a typical water reactor, such as a pressurized water reactor (PWR), a heavy water reactor (such as CANDU), or a boiling water reactor (BWR), the core contains a number of fuel assemblies, each of which is made up of a number of elongated fuel elements or fuel rods. The fuel assemblies vary in size and design depending on the desired size of the core and the size of the reactor. Each fuel rod contains a fissile nuclear fuel material, such as at least one of uranium dioxide (U02), plutonium dioxide (Pu02), thorium dioxide (Th02), uranium nitride (UN), uranium silicide (U3, Si2), and mixtures thereof. At least a portion of the fuel rods may also contain a neutron absorbing material, such as boron or a boron compound, gadolinium or a gadolinium compound, erbium or an erbium compound, or the like. The neutron absorbing material may be present on or in the pellets in the form of a stack of nuclear fuel pellets. Annular or particulate fuel may also be used.

[0034] Each fuel rod has a cladding that acts as a containment vessel to hold the fissile material. The fuel rods are organized in an array that provides a sufficient neutron flux to the core to maintain a high fission rate, releasing a large amount of energy in the form of heat. A coolant, such as water, is pumped through the core to extract the heat generated in the core and produce useful work, such as electricity.

[0035] The cladding of the fuel rod is composed of zirconium (Zr) and may contain up to about 2% by weight of other metals such as niobium (Nb), tin (Sn), iron (Fe) and chromium (Cr).

[0036] During normal operation, zirconium cladding is exposed to the high temperature (200°C-350°C) and high pressure water environment in the reactor, which causes surface corrosion (oxidation) and associated hydriding of the cladding bulk (due to the release of hydrogen into the metal by oxidation reactions with water), ultimately leading to embrittlement of the metal. This weakening of the metal adversely affects the performance, life and safety margins of the nuclear fuel core. During transients or accidents, zirconium alloys react rapidly with water vapor at temperatures above 1100°C, producing zirconium oxide and hydrogen. In the reactor environment, the hydrogen produced by this reaction can dramatically pressurize the reactor and eventually leak into the containment vessel or reactor building, creating an explosive atmosphere that can cause a hydrogen explosion and allow the spread of fission products outside the containment vessel. Maintaining the fission product boundary is crucial.

[0037] Lahoda et al., in International Application No. 2015 / 175035 (hereinafter "Publication '035"), disclose a chemical vapor infiltration (CVI) or chemical vapor deposition (CVD) process for depositing SiC material onto zirconium alloy nuclear fuel cladding tubes to improve the ability of the zirconium alloy cladding to withstand normal and accident conditions encountered in nuclear water reactors. Publication '035 is incorporated herein by reference in its entirety for all purposes to the extent the incorporated material is not inconsistent herewith.

[0038] Mazzoccoli et al., in U.S. Patent No. 10,290,383 (hereinafter "the '383 patent"), disclose a method for forming a coating of protective ceramic particles integral to a zirconium cladding for a nuclear reactor by rapid heat application using a hybrid thermal-kinetic deposition or cold spray apparatus. The '383 patent is incorporated herein by reference in its entirety for all purposes to the extent that the incorporated material is not inconsistent herewith.

[0039] Lahoda et al., in U.S. Patent Application Publication No. 2020 / 0051702 (hereinafter "the '702 Application"), disclose a method for depositing coatings by cold spray. The '702 Application is incorporated herein by reference in its entirety for all purposes to the extent the incorporated material is not inconsistent herewith.

[0040] Lahoda et al., in U.S. Patent Application Publication No. 2018 / 0096743 (hereinafter "the '743 Application"), disclose a cold spray method for depositing a duplex accident resistant coating for nuclear fuel rods. The '743 Application is incorporated herein by reference in its entirety for all purposes to the extent the incorporated material is not inconsistent herewith.

[0041] Chromium (Cr) coatings have recently been demonstrated to protect zirconium (Zr) alloy nuclear fuel cladding tubes from excessive corrosion not only during normal operation but also during transients and accidents where the cladding temperature can briefly exceed 900°C. The Cr coating should be thin (approximately 5-15 microns) to reduce parasitic neutron absorption.

[0042] Physical vapor deposition (PVD) has been found to provide good coatings with good product control. Magnetron sputtering (MS) has been used and although it initially produces good adherent coatings, the large columnar grain structure (Figure 1) allows a relatively perpendicular and direct path for the cooling water to reach the interface of the Zr alloy and Cr coating, which can lead to corrosion of the zirconium (Zr) under the Cr coating and spalling of the Cr coating. In addition, this grain structure can also facilitate the propagation of cracks from the coating to the underlying zirconium alloy tube, as the grain boundaries are perpendicular to the zirconium tube surface. Another PVD method is high power impulse magnetron sputtering (HiPIMS), which deposits a random grain structure. Unfortunately, HiPIMS is also a costly method of coating deposition because the process is interrupted to reverse the polarity of the electrodes and redeposit material from the gas. Thus, the deposition rate is low, plus the cost is high due to the more complex equipment. 1 shows a schematic of a grain structure formed from an MS comprising Cr or Cr alloy grains 102 deposited on a Zr alloy tube material 104. The Cr or Cr alloy grains 102 have a desired coating thickness TD.

[0043] Another method for depositing coatings on Zirconium (Zr) alloy nuclear fuel cladding tubes is cold spraying. In this process, particles are accelerated in a gas stream towards the tube surface to be coated. These particles impact and deform on the surface, forming a coating with a random grain structure. However, this method results in a large variation in the coating-tube interface due to the large momentum of the particles (Figure 2), increasing the average coating thickness required to achieve the minimum required thickness. This method also results in a very rough surface, which can be easily improved by grinding or polishing, at additional cost. Figure 2 shows a schematic of the random grain structure and interface variation from cold spraying with Cr or Cr alloy particles 102 deposited on Zr alloy tube material 104. The Cr or Cr alloy particles 102 have the desired cladding thickness TD, the additional average coating thickness TA due to interface variation, and a polished surface 106.

[0044] What is needed is a process that creates a random grain structure while at the same time producing a smooth interface between the coating and the underlying zirconium tube surface.

[0045] The present disclosure provides a method for applying a random grain structure coating to substrates of components used in nuclear reactors, such as zirconium (Zr) alloy substrates of nuclear fuel cladding tubes used in water-cooled nuclear reactors, using a cathodic arc (CA) physical vapor deposition (PVD) process.

[0046] The cathodic arc (CA) physical vapor deposition (PVD) process deposits a random grain structure at a very high deposition rate like cold spray. At the same time, it deposits very small molten grains / particles or small atomic aggregates, so the interface between the coating and the zirconium tube is almost unchanged (Figure 3). The cathodic arc (CA) physical vapor deposition (PVD) process creates a slightly rougher surface than MS PVD, but not as rough as cold spray, and this roughness can be improved by light polishing. Thus, the cathodic arc (CA) physical vapor deposition (PVD) process meets the requirements of a random grain structure and a smooth interface between the coating and the tube, while reducing the cost of the deposited coating. Figure 3 is a schematic diagram of a random grain structure without interface variation by cathodic arc (CA) PVD process including Cr or Cr alloy particles 102 deposited on a Zr alloy tube material 104. The Cr or Cr alloy particles 102 have the desired coating thickness TD and a polished surface 106.

[0047] The random grains in the CA PVD coating inhibit easy penetration of cooling water into the interface between the Zr and Cr coatings, reducing the possibility of coating spalling due to undercut corrosion at the interface. These random grains also inhibit cracks from propagating through the coating to the zirconium tubes underneath.

[0048] The present invention can be applied not only to Cr and Cr alloys such as those containing Y or Mo, but also to coatings of other materials that can be used under the Cr or Cr alloy coating in an intermediate layer, such as Nb, Mo, Ta, Re, Os, Ru, or W or alloys of these metals, which can be applied to provide resistance to Cr-Zr eutectic formation (FIG. 4). FIG. 4 shows a schematic of Nb, Mo, Ta, Re, Os, Ru, or W or alloys of these metals as an intermediate coating layer 108 between the Cr or Cr alloy coating 102 and the Zr alloy tube material 104. The Cr or Cr alloy particle 102 has a desired coating thickness TD and a polished surface 106. The intermediate layer 108 has a desired intermediate layer thickness TI.

[0049] Although MS PVD (by other PVD vendors) and HiPIMS PVD (by Framatome) have been used to coat zirconium tubes, we are the first to use cathodic arc (CA) PVD processing to apply a random grain structure coating to zirconium nuclear fuel cladding tubes to improve their corrosion resistance, both under normal operating conditions and during transient and accident events where the temperature of the cladding can exceed 900°C for short periods of time.

[0050] This disclosure provides a method for applying a random grain structure coating onto the zirconium substrate of nuclear fuel cladding tubes using cathodic arc (CA) PVD processing to improve the corrosion resistance of the nuclear fuel cladding tubes under both normal operating conditions and transient / accident conditions.

[0051] In various aspects, the method includes providing a substrate and forming a protective coating layer having first particles selected from the group consisting of pure chromium (Cr), chromium (Cr) alloys, and combinations thereof, on an exterior of the substrate using a cathodic arc (CA) physical vapor deposition (PVD) process. In one embodiment, the protective coating layer has a random grain structure.

[0052] The term "pure Cr" or "pure chromium" as used herein means 100% metallic chromium, which may contain trace amounts of unintentional impurities that perform no metallurgical function. For example, pure Cr may contain a few ppm of oxygen. As used herein, the terms "Cr alloy", "chromium alloy", "Cr-based alloy" or "chromium-based alloy" refer to an alloy in which Cr is the major or majority element and contains small but reasonable amounts of other elements that perform specific functions. The Cr alloy may contain 80 atomic % to 99 atomic % chromium. The other elements in the Cr alloy may include at least one chemical element selected from silicon, yttrium, aluminum, titanium, niobium, molybdenum, zirconium, and other transition metal elements. Such elements may be present, for example, in a content of 0.1 atomic % to 20 atomic %.

[0053] In various embodiments of the method, the particles used in the protective coating layer may be pure metal chromium particles or chromium (Cr) alloy particles, either of which may have an average diameter of about 20 microns or less, or about 10 microns or less. By "average diameter" as used herein, one skilled in the art will recognize that the particles may be both spherical and non-spherical, such that "diameter" is the longest dimension of regularly or irregularly shaped particles, and the average diameter means that the longest dimension of any one grain may vary somewhat above or below about 20 microns, but the average of the longest dimension of all particles used in the coating is generally about 20 microns or less. Additionally, the first particles may have a diameter of about 100 microns or less.

[0054] When the particles of the protective coating layer are chromium-based alloys, they may contain about 80-99.9 atomic % chromium. In various embodiments, the chromium-based alloy may contain at least one element selected from the group consisting of silicon, yttrium, aluminum, titanium, niobium, zirconium, molybdenum, and transition metal elements, in a total content of about 0.1-20 atomic %. In various embodiments, the Cr alloy may be, for example, any of CrY, CrAlY, CrMo, FeCrAlY, or FeCrAl.

[0055] In various aspects of the method, the substrate is preferably a zirconium alloy, and in various aspects, the component may be a cladding tube for a nuclear fuel rod. The substrate may be of any shape relevant to the component to be coated. For example, the substrate may be cylindrical, curved, or flat. For nuclear fuel rods, the substrate is preferably cylindrical. In one embodiment, the substrate may be a zirconium alloy, and the component may be a nuclear fuel rod cladding tube used in water-cooled nuclear reactors.

[0056] In various embodiments of the method, the cathodic arc (CA) PVD process involves a source material and a substrate to be coated placed in a vacuum deposition chamber. The chamber contains a relatively small amount of gas. The negative lead of a direct current (DC) power supply is connected to the source material (the "cathode") and the positive lead to the anode. Often the positive lead is attached to a deposition chamber, which acts as the anode. An electric arc is used to evaporate material from the cathode target. The evaporated material condenses on the substrate to form the desired layer. CA PVD processes are relatively inexpensive to build and use, and require little maintenance due to the robust equipment.

[0057] In various embodiments of the method, the cathodic arc (CA) PVD process includes the steps of providing a Zr alloy tube substrate to be coated, providing a target comprising Cr or Cr alloy to be deposited on the Zr alloy tube substrate, supporting the part, the Zr alloy tube, and the Cr or Cr alloy target in a chamber of a CA PVD apparatus, creating a vacuum in the chamber, applying a low voltage between the target and the Zr alloy tube, the target comprising Cr or Cr alloy to be deposited on the Zr alloy tube substrate in a thin film form, and using a magnetic field to move the position of the cathodic arc to minimize droplet movement and uniformly erode and deposit the target on the Zr alloy tube substrate.

[0058] A protective Cr coating layer is applied to nuclear fuel rod cladding tubes to provide protection during design basis accidents such as loss of coolant accidents (LOCA) as well as to enhance corrosion resistance during normal operation at 280-320°C. Because Zr ignites at around 1100°C, whereas Cr-coated cladding does not ignite until about 1400°C, the Cr protective coating layer helps to buy plant operators more time to respond. The protective coating significantly reduces the amount of hydrogen generated during the course of an accident, thus reducing reactor pressurization and reducing the likelihood of a hydrogen explosion occurring when pressure is released into the containment vessel.

[0059] The protective coating layer may have a desired thickness, for example, between about 5 microns and about 100 microns, but may also be applied to the outside of the substrate at a greater thickness, such as several hundred microns, for example, 100 microns to 150 microns. The protective coating layer should be thick enough to form a protective barrier against corrosion on the substrate, while at the same time being thin enough to reduce parasitic neutron absorption. The protective coating layer reduces, and in various embodiments eliminates, water vapor and air zirconium reactions, and reduces, and in various embodiments eliminates, the formation of zirconium hydrides at temperatures above about 1000° C.

[0060] In various aspects of this method, the protective coating layer may be lightly ground and polished to a smooth outer surface.

[0061] In various embodiments, the method may further include the step of first forming an intermediate coating layer having second particles selected from the group consisting of Nb, Mo, Ta, Re, Os, Ru, and W, and alloys thereof, on the exterior of the substrate prior to forming the protective coating layer.

[0062] The second particles may have a diameter of about 100 microns or less, with an average diameter of about 20 microns or less.

[0063] In various embodiments of the method, the intermediate coating layer may be first applied on the outer side of the substrate by a cathodic arc (CA) physical vapor deposition (PVD) process. The intermediate coating layer may have a random grain structure. The intermediate coating layer is between the protective coating layer and the outer side of the substrate. The intermediate coating layer may be lightly ground and polished before applying the protective coating layer, and the protective coating layer may then be lightly ground and polished.

[0064] In various embodiments of the method, the intermediate coating layer may have a desired thickness of between about 0.5 microns and about 100 microns, between about 0.5 microns and about 50 microns, or preferably between about 0.5 microns and about 15 microns, but may also be applied to the outside of the substrate at a greater thickness, such as several hundred microns, e.g., 100 microns to 150 microns.

[0065] In various aspects of this method, the intermediate coating layer may prevent eutectic formation between the protective coating layer and the substrate.

[0066] As described herein above, the protective coating layer functions as a corrosion protection barrier for the substrate. When the substrate is zirconium alloy clad, the chromium coating provides a protective barrier against corrosion at normal operating conditions, e.g., between 270°C and 350°C in a pressurized water reactor and between 200°C and 300°C in a boiling water reactor. The protective coating layer reduces steam and air zirconium reactions and hydrogen generation at high temperatures, i.e., above 1100°C.

[0067] The intermediate coating layer can optionally be pre-applied to the outside of the substrate prior to the application of the protective coating layer using a cathodic arc (CA) physical vapor deposition (PVD) process. The intermediate coating layer can mitigate the formation of eutectic between the protective coating layer and the substrate, which limits the performance of the protective coating layer at temperatures above 900° C., for example, for Zr or Zr alloy substrates and Cr or Cr alloy coating materials such as CrY, CrAlY, FeCrAl or FeCrAlY, and thus further improve the accident resistance of this embodiment of the protective coating layer at temperatures above 900° C.

[0068] In general, the intermediate coating material can be selected from materials that have a eutectic melting point with zirconium or a zirconium alloy above 1400° C. and have thermal expansion and elastic modulus coefficients that are compatible with the zirconium or zirconium alloy substrate on which it is coated and the protective coating layer that is deposited thereon. The particles used to form the intermediate coating layer can be Nb, Mo, Ta, Re, Os, Ru, and W, or alloys thereof, all of which form eutectics with Zr or Zr alloys above 1400° C., and in various embodiments above 1500° C. In certain embodiments, the particles used to form the intermediate coating layer can be Mo.

[0069] In various aspects of the method, the nuclear fuel rod cladding tube may have two coating layers: a protective coating layer (first particle) of pure Cr or Cr alloy and an intermediate coating layer (second particle) of particles of Nb, Mo, Ta, Re, Os, Ru and W or their alloys. Both coating layers may be applied to the zirconium alloy tube to reduce the reaction of zirconium with steam or air under normal operating and accident conditions. The two coating layers may be applied sequentially using cathodic arc (CA) physical vapor deposition (PVD) processes as described above. In this way, each of the two coating layers has a desired random grain structure and a coating thickness of about 0.5 to about 150 microns, about 0.5 to about 100 microns, about 0.5 to about 50 microns, or about 0.5 to about 15 microns. The total thickness of the two coating layers combined is about 0.5 to about 150 microns, about 0.5 to about 100 microns, about 0.5 to about 50 microns, about 0.5 to about 15 microns, or about 1.0 to about 15 microns. The particles of the first and second layers each preferably have a size of less than about 2.0 microns in average diameter and about 10.0 microns in maximum diameter.

[0070] As explained above, the duplex coating layer of the present method may further improve the accident resistance of the coated zirconium alloy cladding by avoiding eutectic formation between the protective coating layer and the zirconium alloy substrate at the eutectic temperature. The exact temperature will vary depending on the materials used for the substrate and the protective coating layer. Eutectic phase diagrams for determining the eutectic point are readily available in the literature.

[0071] In various embodiments, after the formation of the intermediate and protective coating layers, the method may further include annealing the coating. Annealing provides ductility and creates submicron-sized grains, which are believed to be beneficial for isotropic properties and resistance to radiation damage. Annealing involves heating the coating at a temperature range of 200°C to 800°C, preferably 350°C to 550°C. This relieves stress in the coating and provides it with ductility, which is necessary to maintain the internal pressure within the cladding. As the tube expands, the coating must expand as well.

[0072] The method described herein provides, in various embodiments, a cladding tube formed from a zirconium alloy substrate and having an intermediate coating layer and a protective coating layer formed from a chromium or chromium alloy. In general, the intermediate coating material may be selected from materials having a eutectic melting point with zirconium or a zirconium alloy above 1400°C, preferably above 1500°C in certain embodiments, and may further be selected from materials having a thermal expansion coefficient and elastic modulus coefficient that are compatible with the zirconium or zirconium alloy substrate on which the intermediate coating material is coated and the protective coating layer applied thereon. Examples include transition metals or alloys thereof, such as Nb, Mo, Ta, Re, Os, Ru, W, etc., that have high melting points (above 1700°C) and do not form a eutectic, or metals that form a eutectic but at a higher temperature (above 1400°C) than the eutectic (around 1333°C) that may form between the zirconium alloy tube and the protective coating layer formed from a chromium or chromium alloy.

[0073] The substrate having the two coating layers can also be treated, preferably lightly, by grinding, buffing, polishing, or other known techniques to provide a smoother surface finish.

[0074] The disclosed method of coating nuclear fuel rod cladding tubes using cathodic arc (CA) PVD offers advantages in coating grain structure over using MS PVD and is less expensive than HiPIMS.

[0075] All patents, patent applications, publications, or other disclosure materials described herein and / or described in the Application Data Sheet are incorporated herein by reference in their entirety as if each individual reference were expressly incorporated by reference. All reference materials that are incorporated herein by reference, and any portions thereof, are incorporated herein only to the extent that the incorporated material does not conflict with existing definitions, descriptions, or other disclosure material set forth in this disclosure. Therefore, to the extent necessary, the disclosure set forth herein will supersede any conflicting material incorporated herein by reference, and the disclosure expressly set forth in this application will control.

[0076] The present invention has been described with reference to various exemplary and illustrative embodiments. The embodiments described herein are understood to provide illustrative features of various details of the various embodiments of the disclosed invention, and therefore, unless otherwise specified, it is understood that, to the extent possible, one or more features, elements, components, constituents, ingredients, structures, modules, and / or aspects of the disclosed embodiments may be combined, separated, exchanged, and / or rearranged with one or more other features, elements, components, constituents, ingredients, structures, modules, and / or aspects of the disclosed embodiments without departing from the scope of the disclosed invention. Thus, those skilled in the art will recognize that various substitutions, modifications, or combinations may be made to any of the exemplary embodiments without departing from the scope of the invention. Moreover, those skilled in the art will recognize or be able to ascertain, by reference to this specification, with no more than routine experimentation, many equivalents to the various embodiments of the invention described herein. Thus, the present invention is not limited by the description of the various embodiments, but rather by the scope of the claims.

[0077] Those skilled in the art will generally recognize that the terms used herein, and particularly in the appended claims (e.g., the body of the appended claims), are generally intended as "open" terms (e.g., the term "including" should be interpreted as "including, but not limited to," the term "having" should be interpreted as "having at least," the term "comprising" should be interpreted as "comprising, but not limited to," etc.). Those skilled in the art will further recognize that if a particular number of introduced claim recitations are intended, such intent will be expressly set forth in the claim, and in the absence of such recitation, no such intent exists. For example, as an aid to understanding, the appended claims below may use the introductory phrases "at least one" and "one or more" to introduce the claim recitation. However, the use of such expressions should not be construed as meaning that the introduction of a claim recitation with the indefinite article "a" or "an" limits a particular claim that includes such an introduced claim recitation to claims that include only one of such recitations, even if the same claim also includes an introductory expression such as "one or more" or "at least one" as well as an indefinite article such as "a" or "an" (e.g., "a" and / or "an" typically mean "at least one" or "one or more"), and the same applies to the use of definite articles used to introduce claim recitations.

[0078] Furthermore, even if a particular number of introduced claim recitations is explicitly recited, one of ordinary skill in the art will recognize that such recitation should generally be interpreted to mean at least the recited number (e.g., the mere recitation of "two recitations" without other modifiers generally means at least two recitations, or more than two recitations). Furthermore, when a convention similar to "such as at least one of A, B, and C" is used, such configuration is generally intended in the sense that one of ordinary skill in the art would understand the convention (e.g., "a system having at least one of A, B, and C" includes, but is not limited to, systems having only A, having only B, having only C, having both A and B, having both A and C, having both B and C, and / or having both A, B, and C). When a convention similar to "at least one of A, B, or C, etc." is used, such a configuration is generally intended in the sense that one of ordinary skill in the art would understand the convention (e.g., "a system having at least one of A, B, or C" includes, but is not limited to, systems having only A, having only B, having only C, having both A and B, having both A and C, having both B and C, and / or having both A, B, and C). Those of ordinary skill in the art will further appreciate that disjunctive words and / or expressions, whether in the specification, claims, or drawings, that typically present two or more alternative terms, should be understood to contemplate the possibility of including one of the terms, either of the terms, or both terms, unless the context dictates otherwise. For example, the expression "A or B" is typically understood to include the possibilities of "A" or "B" or "A and B."

[0079] With respect to the appended claims, those skilled in the art will appreciate that the operations recited therein may generally be performed in any order. Also, while the claims are presented in a sequential order, it should be understood that various operations may be performed in orders other than those recited, or may be performed simultaneously. Examples of such alternative orders include overlapping, interleaved, interrupted, reordered, incremented, preparatory, supplemental, concurrent, reversed, or other variant orders, unless the context dictates otherwise. Moreover, terms such as past tense adjectives, such as "in response to" and "in connection with," are generally not intended to exclude such variants, unless the context dictates otherwise.

[0080] It should be noted that references to "one embodiment," "one embodiment," "one example," "one example," etc., mean that a particular feature, structure, or characteristic described in connection with that embodiment is included in at least one embodiment. Thus, the appearance of the phrases "in one embodiment," "in one embodiment," "in one example," and "in one example" in various places throughout this specification do not necessarily all refer to the same embodiment. Furthermore, particular features, structures, or characteristics may be combined as appropriate in one or more embodiments.

[0081] As used herein, the singular forms "a," "an," and "the" include the plural forms as well, unless the context clearly indicates otherwise.

[0082] Directional expressions used herein, such as, but not limited to, up, down, left, right, down, above, front, back, above, below, and variations thereof, refer to the orientation of the elements shown in the accompanying drawings and do not limit the scope of the claims, unless expressly stated otherwise.

[0083] The terms "micron," "microns," "micrometer," or "μm" as used in this disclosure refer to the SI-derived unit of length equal to 1×10^-6 meters.

[0084] The term "about" or "approximately" as used in this disclosure, unless otherwise specified, refers to an acceptable error for a particular value as determined by a person skilled in the art, which depends in part on how the value is measured or determined. In certain embodiments, the term "about" or "approximately" refers to within 1, 2, 3, or 4 standard deviations. In certain embodiments, the term "about" or "approximately" refers to within 50%, 200%, 105%, 100%, 9%, 8%, 7%, 6%, 5%, 4%, 3%, 2%, 1%, 0.5%, or 0.05% of a given value or range.

[0085] As used herein, unless otherwise indicated, all numerical parameters are understood to be prefaced and modified in all instances by the term "about." In this case, numerical parameters have the inherent variability inherent in the underlying measurement technique used to determine the numerical value of that parameter. While not intending to limit the application of the doctrine of equivalents to the scope of the claims, at the very least, each numerical parameter set forth herein should be construed in light of the number of reported significant digits and by applying ordinary rounding approaches.

[0086] Numerical ranges mentioned herein include all subranges subsumed within the mentioned range. For example, the range "1-100" includes all subranges between (and including) the stated minimum of 1 and the stated maximum of 100, i.e., all subranges having a minimum of 1 or more and a maximum of 100 or less. Also, all ranges mentioned herein include the endpoints of the mentioned range. For example, the range "1-100" includes the endpoints 1 and 100. Any maximum numerical limitation mentioned herein is intended to include all lower numerical limitations subsumed therein, and any minimum numerical limitation mentioned herein is intended to include all higher numerical limitations subsumed therein. Accordingly, applicants reserve the right to amend this specification, including the claims, to explicitly state any subranges subsumed within the expressly stated ranges. All such ranges are inherently described herein.

[0087] "Comprise" (and any form of comprise, such as "comprises" or "comprising"), "have" (and any form of have, such as "has" or "having"), "include" (and any form of include, such as "includes" or "including"), and "contain" (and any form of contain, such as "contains" or "containing") are open-ended linking verbs. As a result, a system that "comprises," "has," "includes," or "contains" one or more elements has those one or more elements, but is not limited to having only those one or more elements. Similarly, a system, device, or element of an apparatus that "comprises," "has," "includes," or "contains" one or more features has those one or more features, but is not limited to having only those one or more features.

Claims

1. A method of applying a random particle structure coating onto a substrate of a component used in a nuclear reactor, the method comprising: providing a substrate; forming a protective coating layer having first particles selected from the group consisting of pure metallic chromium (Cr), chromium (Cr) alloys, and combinations thereof on the outside of the substrate using a cathodic arc (CA) physical vapor deposition (PVD) process; wherein the protective coating layer has a random particle structure; A method.

2. The method according to claim 1, wherein the substrate is a nuclear fuel rod cladding tube used in a water-cooled nuclear reactor.

3. The method according to claim 1, wherein the substrate is a zirconium alloy.

4. The method according to claim 1, wherein the first particles have a diameter of about 10.0 microns or less.

5. The method according to claim 1, wherein the first particles have an average diameter of about 2.0 microns or less.

6. The method according to claim 1, wherein the first particles for forming the protective coating layer are pure chromium (Cr) particles.

7. The method according to claim 1, wherein the first particles for forming the protective coating layer are chromium (Cr) alloy particles.

8. The method according to claim 7, wherein the chromium (Cr) alloy particles include one of CrY, CrAlY, FeCrAl, or FeCrAlY particles.

9. The cathodic arc (CA) PVD process comprises: providing the substrate of the component to be coated; providing a target containing the first particles to be deposited on the substrate; supporting the component and the target within a chamber of a CA PVD apparatus; evacuating the chamber; applying a low voltage between the target and the component; using a magnetic field to move the position of the cathodic arc, minimizing the movement of droplets, uniformly eroding the target, and depositing on the substrate of the component; The method according to claim 1.

10. The method according to claim 1, wherein the protective coating layer has a thickness between about 5 microns and about 100 microns.

11. The method according to claim 1, further comprising a step of polishing the outer surface of the protective coating layer on the outside of the substrate.

12. Before forming the protective coating layer, further including the step of first forming an intermediate coating layer having second particles selected from the group consisting of Nb, Mo, Ta, Re, Os, Ru, and W, and alloys thereof on the outside of the substrate. The method according to claim 1, wherein the intermediate coating layer is between the protective coating layer and the outside of the substrate.

13. The method according to claim 12, wherein the second particles have a diameter of 10.0 microns or less and an average diameter of about 2.0 microns or less.

14. The method according to claim 12, wherein the intermediate coating layer is formed by a cathodic arc (CA) physical vapor deposition (PVD) process.

15. The method according to claim 12, wherein the intermediate coating layer has a random particle structure.

16. The method according to claim 12, wherein the intermediate coating layer has a thickness between about 0.5 microns and about 100 microns.

17. The method according to claim 12, wherein the intermediate coating layer has a thickness between about 0.5 microns and about 15 microns.

18. The method according to claim 12, wherein the intermediate coating layer prevents eutectic formation between the protective coating layer and the substrate.

19. The method according to claim 12, wherein the total thickness of the intermediate coating layer and the protective coating layer combined is between about 5 microns and about 50 microns.

20. The method according to claim 12, wherein the second particles are Mo particles.

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