Effective coating configurations for protecting Zr alloy cladding from oxidation and hydriding.

Abstract

A coating for protecting a zirconium alloy-based layer of a nuclear fuel rod cladding is provided. The coating includes a primary layer. The microstructure of the primary layer is comprised of a large number of randomly-spaced grains. The primary layer has a density of about 94.5% or greater. A nuclear fuel rod cladding and a method for manufacturing the nuclear fuel rod cladding are also provided.

Description

[Technical Field]

[0001] REFERENCE TO RELATED APPLICATIONS This application claims priority under 35 U.S.C. § 120 to U.S. patent application Ser. No. 18 / 069,864, entitled "EFFECTIVE COATING MORPHOLOGY TO PROTECT ZR ALLOY CLADDING FROM OXIDATION AND HYDRIDING," filed December 21, 2023, the entire contents of which are incorporated herein by reference in their entirety.

[0002] government support This invention was made with government support under Government Contract No. DE-NE00009033 awarded by the Department of Energy. The government has certain rights in this invention. [Background technology]

[0003] Chromium-based (Cr-base) coatings are currently used on zirconium alloy-based (Zr-base) cladding in accident-tolerant fuel applications. Conventional coatings effectively retard cladding oxidation and / or hydriding at accident temperatures above the design criteria. However, prolonged exposure to coolant or repeated thermal cycling can degrade the initial protective properties of the coating. Therefore, the development of alternative claddings and their manufacturing methods is necessary to optimize the reliability and cost of accident-tolerant fuel without compromising the integrity of the cladding at high temperatures. Summary of the Invention

[0004] The following summary is provided as a reference for understanding some of the innovative features of the embodiments disclosed herein and is not intended to be a complete description. A complete understanding of each embodiment disclosed herein can be obtained by reference to the entire specification, claims, and abstract as a whole.

[0005] In various embodiments, a coating for protecting a zirconium alloy-based layer of a nuclear fuel rod cladding tube is disclosed. In some embodiments, the coating comprises a primary layer. In some embodiments, the microstructure of the primary layer is comprised of a multitude of grains that are randomized. In some embodiments, the primary layer is comprised of a density of about 94.5% or greater.

[0006] In various embodiments, cladding tubes for nuclear fuel rods are disclosed. In some embodiments, the cladding tubes include a zirconium alloy tube and a coating deposited on an exterior surface of the zirconium alloy tube. In some embodiments, the zirconium alloy tube is configured to contain a quantity of nuclear fuel. In some embodiments, the coating includes a chromium-based layer, the chromium-based layer having a randomized grain structure and a density of at least 95%.

[0007] In various embodiments, methods of manufacturing cladding for nuclear fuel rods are disclosed. In some embodiments, the method comprises providing a base layer for the cladding and protecting the base layer. In some embodiments, the base layer is comprised of a zirconium alloy. In some embodiments, protecting the base layer comprises depositing a coating on the base layer. In some embodiments, the coating comprises a chromium-based layer having a randomized microstructure and a density of about 95% or greater.

[0008] These objects, features, and characteristics of the present disclosure, as well as the method of operation and function of structural elements, combination of parts, and economies of manufacture, will become more apparent from a study of the following description and appended claims, taken in conjunction with the accompanying drawings, which form a part hereof, and in which like reference numerals indicate corresponding parts in the various views, which are for purposes of illustration and illustration only and are not intended to define the limits of any aspect disclosed herein. [Brief explanation of the drawings]

[0009] The various aspects described herein, together with their objects and advantages, can be best understood by referring to the following description in conjunction with the accompanying drawings.

[0010] [Figure 1] FIG. 1 is a cross-sectional elevation view of a fuel assembly according to at least one non-limiting embodiment of the present disclosure.

[0011] [Figure 2] 1 is a cross-sectional view of a fuel rod according to at least one non-limiting embodiment of the present disclosure.

[0012] [Figure 3] FIG. 1 is a cross-sectional schematic diagram of a coating microstructure according to at least one non-limiting embodiment of the present disclosure.

[0013] [Figure 4] 1 is a cross-sectional schematic view of a coating on a cladding tube base layer according to at least one non-limiting embodiment of the present disclosure.

[0014] [Figure 5] 1 is a cross-sectional schematic view of a coating on a cladding tube base layer according to at least one non-limiting embodiment of the present disclosure.

[0015] [Figure 6] 1 is a cross-sectional schematic view of a coating on a cladding tube base layer according to at least one non-limiting embodiment of the present disclosure.

[0016] [Figure 7] 1 is a cross-sectional schematic view of a coating on a cladding tube base layer according to at least one non-limiting embodiment of the present disclosure.

[0017] [Figure 8] FIG. 1 is a schematic diagram of a coating microstructure according to at least one non-limiting embodiment of the present disclosure.

[0018] [Figure 9] 1 is a schematic diagram of a fuel rod according to at least one non-limiting embodiment of the present disclosure.

[0019] Corresponding reference characters indicate corresponding parts throughout the several views. The examples shown herein are intended to illustrate various aspects of the present disclosure in one form, and these examples are not to be construed as limiting the scope of any aspect disclosed herein. DETAILED DESCRIPTION OF THE INVENTION

[0020] Certain exemplary embodiments of the present invention are described below, illustrating exemplary embodiments to provide an overall understanding of the principles and methods of composition, function, manufacture, and use of the compositions disclosed herein. Examples of these embodiments are illustrated in the accompanying drawings. Those of ordinary skill in the art will understand that the compositions, articles, and methods specifically described herein and illustrated in the accompanying drawings are non-limiting exemplary embodiments, and that the scope of various examples of the present disclosure is defined only by the claims. Features shown or described in connection with one exemplary embodiment can be combined with features of other embodiments. Such modifications and variations are intended to be within the scope of the present disclosure.

[0021] The use of phrases such as "various examples," "several examples," "one example," or "an example" in this specification means that a particular feature, structure, or characteristic described in connection with that example is included in that example. Thus, the appearances of "various examples," "in some examples," "in one example," "in an example," or similar phrases in this specification do not necessarily refer to the same example. Furthermore, particular features, structures, or characteristics may be combined in any suitable manner in examples. Thus, without limitation, a particular feature, structure, or characteristic illustrated or described in connection with one example may be combined, in whole or in part, with features, structures, or characteristics of other examples or other examples. Such modifications and variations are intended to be included within the scope of this example.

[0022] In the following description, the same reference numerals refer to the same or corresponding parts in each of the figures of the drawings. Also, in the following description, terms such as "front," "rear," "left," "right," "up," "down," "upward," "downward," etc. are used for convenience only and should not be construed as limiting terms.

[0023] As used herein, "density" refers to relative density, which defines the ratio of the volume density of a coating or layer of a material to the reference density of that material. For example, in the specification and claims, if a coating has a density of about 90%, then about 10% of the volume occupied by the coating will be made up of void volume and / or pore volume.

[0024] Those skilled in the art will understand that the term "radial" as used in the specification and claims in connection with a component of a particle's geometry is not necessarily limited to and / or necessarily related to other occurrences of the term "radial" or to a particular orientation of a coating layer that includes the particle. Thus, the radial component of a particle's geometry does not necessarily coincide with the radius of a cylindrical substrate coated with a layer that includes the particle.

[0025] Generally, in a nuclear reactor, such as a pressurized water reactor (hereinafter "PWR"), a heavy water reactor (e.g., CANDU), or a boiling water reactor (hereinafter "BWR"), the reactor core can include multiple fuel assemblies, each including a plurality of elongated fuel elements or fuel rods. For example, FIG. 1 illustrates a cross-sectional elevation view of a fuel assembly 10 according to at least one non-limiting embodiment of the present disclosure. The fuel assembly 10 includes an aligned array of elongated fuel rods 22. The fuel rods 22 can contain a plurality of fuel pellets 26, each containing fissile material capable of supporting a nuclear fission chain reaction, thereby generating heat.

[0026] The fuel rods 22 may be supported by one or more transverse grids 20, which are attached to guide thimbles 18. The guide thimbles 18 extend longitudinally between the top nozzle 16 and the bottom nozzle 12 and are configured to allow the control rods 34 to operatively move therethrough. Opposite ends of the guide thimbles 18 may be attached to the top nozzle 16 and the bottom nozzle 12, respectively. The bottom nozzle 12 may be configured to support the fuel assemblies 10 on a reactor vessel lower core plate 14 in the reactor core. A liquid coolant, such as water or water containing a neutron absorbing material, such as boron, may be pumped upwardly through a plurality of flow openings in the lower core plate 14 and into the fuel assemblies 16. The bottom nozzle 12 of the fuel assembly 10 may direct a flow of coolant to and along the fuel rods 22 within the fuel assembly 10 to extract heat generated by the nuclear fission reactions occurring therein.

[0027] 2 illustrates a schematic cross-sectional view of a fuel rod 22 according to at least one non-limiting embodiment of the present disclosure. Referring to FIGS. 1 and 2, as described above, each fuel rod 22 may include a plurality of nuclear fuel pellets 26. The fuel pellets 26 are contained within an elongated cladding tube 38, closed at both ends by an upper end plug 28 and a lower end plug 30. The pellets 26 may be maintained in a stacked configuration by a plenum spring 32 disposed between the upper end plug 28 and the top of the pellet stack. However, in other embodiments, the pellets 26 may be configured differently using alternative mechanisms.

[0028] Cladding tubes are made from materials that exhibit low neutron loss and excellent corrosion resistance under various reactor environmental conditions. For example, zirconium (Zr) alloys have been adopted as the standard cladding material commonly used in PWR fuel assemblies. Under low-temperature reactor operating conditions, e.g., temperatures below approximately 500°C, Zr alloy cladding tubes can be exposed to coolant without compromising their properties, such as structural integrity and / or overall heat transfer characteristics, due to oxidation and / or hydrogen embrittlement. However, Zr alloy-based cladding tubes may require protective surface treatments depending on the reactor environment and / or operating conditions.

[0029] Accident-tolerant fuels (ATFs) have been developed to enhance the protection of nuclear fuel under unexpected high-temperature operating and / or accident conditions. For example, ATF cladding can incorporate a chromium (hereinafter "Cr") coating, which is compatible with the chemistry and accident environment of PWR and / or CANDU reactors and can be applied relatively inexpensively to Zr alloys. The deposition of the Cr coating reduces the oxidation and / or hydriding rate of the cladding surface at beyond-design-basis-accident (BDBA) temperatures, e.g., temperatures above 1200 °C. However, while Cr is highly compatible with the reactor environment of PWR-type reactors, it is incompatible with conventional BWR chemistry. Furthermore, while ATFs employ relatively thin coatings, less than approximately 100 microns thick, these coatings can increase the net neutron penalty of the resulting cladding, potentially reducing nuclear fuel or burnup efficiency. For example, Cr-based materials have relatively high neutron capture cross sections, so Cr-based coatings should not be excessively thick to enhance protection.

[0030] ATF coatings can be applied to Zr-based substrates by various physical vapor deposition (PVD) techniques, such as cathodic arc (CA), magnetron sputtering (MS), and / or high-power pulsed magnetron sputtering (HiPIMS), which are known to produce Cr-based coatings with high adhesion and a predictable columnar microstructure. For example, FIG. 3 shows a cross-sectional schematic of a portion of a cylindrical Zr alloy tube 80 and a coating layer 82 according to at least one non-limiting embodiment of the present disclosure. The coating layer 82 has a columnar microstructure composed of numerous radially oriented grains 84. The length of each grain 84 can extend through the thickness of the coating. Because each of the grains 84 in the columnar microstructure is similarly oriented, the grain boundaries of each grain are similarly aligned and extend through the thickness of the coating without unpredictable changes in direction and / or orientation.

[0031] The columnar grains of Cr-based coatings deposited by PVD techniques, for example, are typically elongated and have an average diameter ranging from about 100 nanometers to about 10 micrometers, depending on the technique and / or process parameters employed. For example, MS produces larger, micrometer-scale columnar grains, while HiPIMS produces grains with a very fine-grained microstructure and an average grain diameter of less than 1 micrometer. Studies have shown that these relatively small, closely packed columnar grains deposited by HiPIMS have the potential to protect the underlying Zr alloy against short-term exposure to accident conditions, for example, up to about 1 minute, and consistent, normal conditions similar to those encountered in a typical reactor environment, for up to about 60 days.

[0032] However, in contrast to laboratory conditions, coatings relying on a columnar microstructure may not provide sufficient protection under real-world service conditions, where fuel assemblies continue to fission for periods up to approximately six years. During fuel assembly service, the cladding tubes inside the fuel assemblies undergo numerous contraction and expansion cycles due to transients and various inhomogeneities in the reactor environment. Because the grains of a columnar microstructured coating are oriented nearly perpendicular to the underlying substrate, the grain boundaries provide diffusion paths between the Zr-Cr interface of Cr-based coatings for ATFs and the surrounding coolant, potentially promoting Zr hydriding and / or corrosion and / or spalling of the Cr-based coating over time, thereby compromising the protective function of the Cr-based coating. For example, coolants for PWRs typically contain approximately 2–7 ppm hydrogen, which can diffuse along the columnar grain boundaries of Cr-based coatings toward the Zr layer. Furthermore, the inventors of the present disclosure have determined that coatings with a columnar microstructure can develop undesirable microstructural defects when exposed to the stresses associated with repeated expansion and contraction cycles. For example, in a columnar microstructure, each columnar grain is oriented normal to the substrate, which may facilitate crack propagation toward the substrate over time, thereby facilitating coolant intrusion.

[0033] While other grain structures can be produced by adjusting HiPIMS parameters, such as target current, magnetron geometry, target material composition, surface condition, and / or pulse duration, the fine nanometer-scale grains produced by HiPIMS techniques result in the resulting microstructures having very high interfacial areas and therefore remaining vulnerable to the ingress of oxidizing and / or hydriding agents via diffusion. Accordingly, various embodiments of the present disclosure provide various methods and apparatus for protecting, for example, Zr-based cladding tubes from oxidation and / or hydriding and maintaining coating integrity under extended service and / or accident conditions.

[0034] Referring to FIG. 4, a cross-sectional schematic diagram of a coating 100 for protecting a Zr alloy-based layer 90 of a nuclear fuel rod is shown, in accordance with at least one non-limiting embodiment of the present invention. In various embodiments, the coating 100 includes a primary layer 102. In some instances, the thickness of the primary layer 102 is within a range from about 4 micrometers to about 40 micrometers. In other embodiments, the coating 100 can include multiple layers. For example, FIGS. 5-7 illustrate various examples of coatings including a primary layer 102 and one or more additional layers. FIG. 5 illustrates a coating 100′ including an intermediate layer 104 below the primary layer 102. FIG. 6 illustrates a coating 100″ including a primary layer 102 surrounded by an outer layer 106. FIG. 7 illustrates a coating 100′″ including layers 102, 104, and 106.

[0035] 4-7 , the primary layer 102 can be comprised of a metallic material. In some examples, the primary layer 102 can be comprised of a Cr-based metallic material. In particular examples, the primary layer 102 can be comprised of a Cr-based alloy. In examples where the primary layer 102 is comprised of a Cr-based alloy, the Cr-based alloy can include yttrium or molybdenum. Incorporation of this composition into the primary layer 102 can provide corrosion resistance to an underlying Zr alloy substrate intended to be exposed to coolants and / or high-temperature environments. Other compositions of the primary layer 102 are contemplated in this disclosure. For example, in some embodiments, the primary layer 102 is comprised of a ceramic or ceramic-like material including zirconia, or a ceramic or ceramic-like material including chromium, niobium, nitrides thereof, silicides thereof, carbides thereof, or combinations thereof.

[0036] FIG. 8 depicts a schematic microstructure of the primary layer 102 according to at least one non-limiting embodiment of the present disclosure. In various examples, the primary layer 102 includes a microstructure 200 composed of a plurality of grains 210, which are randomized. As used herein, the term "randomized" refers to the configuration, size, shape, and / or position of the grains 210 relative to adjacent grains. Thus, the grains 210 and the grain boundaries formed by them can be arranged without any particular periodicity or orientation in the microstructure 200. Furthermore, the crystal structure, size, and / or shape of each of the plurality of grains 210 can be randomized. For example, the average cross-sectional axial and / or radial component of each grain 210 can be different from that of adjacent grains. In some examples, the shape of each grain 210 can include an axial component ranging from about 1 micrometer to about 50 micrometers and a radial component ranging from about 1 micrometer to about 10 micrometers. In certain examples, at least some of the grains can be equiaxed.

[0037] Continuing to refer to FIG. 8 , the microstructure 200 can be configured to optimize the density of the primary layer 102. For example, the radial and / or axial components of the dimensions of the particles 210 can be set smaller than the thickness of the primary layer 102, thereby enabling the deposition of particles in which at least a portion of the particles 210 are equiaxed. This configuration of particles 210 can be incorporated into the microstructure 200 to minimize excess void volume between adjacent particles. Thus, incorporating this configuration of particles 210 into a random microstructure 200 can enable the primary layer 102 to have a density of at least 94.5% throughout the thickness of the primary layer 102, without relying on submicron particles and / or closely aligned columnar grains. In some examples, the primary layer 102 can be configured to have a density of at least 95%.

[0038] The inventors have discovered that a primary layer 102 having a randomized microstructure 200 and a density of about 95% or greater significantly reduces the probability of linked porosity within the coating 100, increases the tortuosity of the diffusion path through the coating 100, and / or inhibits crack propagation within the coating 100. In some embodiments, a coating 100 incorporating this configuration is deposited on a Zr alloy-based layer of a nuclear fuel rod cladding to inhibit the penetration of coolant and / or other materials dissolved in the coolant from the reactor environment into the underlying Zr alloy, thereby providing long-term corrosion resistance to corrosion and / or hydriding of the Zr alloy. Furthermore, in examples of coatings 100 including multiple layers, one or more of the layers can be configured with a randomized microstructure to impart the benefits described above.

[0039] 5 and 7, the intermediate layer 104 can be configured to inhibit chemical interaction between the primary layer 102 and the underlying Zr alloy surface. For example, the intermediate layer can be composed of a material whose eutectic formation temperature with Zr and / or Cr is greater than 1500°C, greater than 1600°C, greater than 2000°C, or greater than the BDBA temperature. In some examples, the coating 100 can include an intermediate layer 104 composed of an alloy comprising niobium, molybdenum, tantalum, rhenium, osmium, ruthenium, tungsten, or any combination thereof. An intermediate layer 104 incorporating this configuration can inhibit Cr migration from the primary layer 102 to the Zr alloy substrate during transient increases in operating temperature or under high temperature conditions, such as BDBA conditions. Thus, an interlayer 104 incorporating this configuration can be applied to the Zr alloy-based layer 90 to prevent the formation of a low-melting eutectic Cr-Zr layer and / or Zr-Cr intermetallic compounds under high temperature and / or accident conditions, and improve the ballooning and / or burst resistance of the Zr alloy-based layer 90 at relatively high transient and / or accident temperature conditions. In certain examples, the thickness of the interlayer 104 can range from about 0.5 micrometers to about 4 micrometers. In one example, the interlayer 104 is configured with a randomized microstructure.

[0040] 6 and 7 , the top layer 106 can be configured to provide enhanced protection for the ATF under BDBA, high temperature, and / or normal operating conditions. For example, the top layer 106 can be configured from a Cr alloy or a ceramic material. In some examples, the top layer 106 can be configured from a chromium alloy including at least one of yttrium, molybdenum, iron, or aluminum. In particular examples, the top layer 106 is configured as a Cr alloy including yttrium or molybdenum, or a chromium alloy including iron and / or aluminum. In one example, the top layer 106 has a randomized microstructure. In examples where the top layer 106 is configured from a ceramic material, the top layer 106 can include chromium, nitrogen, niobium, or any combination thereof. These alloys and ceramics are known to be resistant to coolants having an O content of, for example, approximately 10 ppm. Thus, the coating 100 including the top layer 106 can be configured to provide protection from excessive corrosion in BWR applications.

[0041] Referring to FIG. 9 , a cross-sectional schematic diagram of a cladding tube 1100 for a nuclear fuel rod 1000 is shown, in accordance with at least one non-limiting embodiment of the present disclosure. In various examples, the cladding tube 1100 includes a Zr alloy tube 1110 and a coating 1120 deposited on an outer surface of the Zr alloy tube 1110. In some examples, the Zr alloy tube 1110 is a cylindrical tube defining a cavity therein. The Zr alloy tube 1110 is configured to contain a quantity of nuclear fuel 1200. For example, when the nuclear fuel 1200 is in the form of a cylindrical pellet, the Zr alloy tube 1110 can be configured to have an inner diameter that is substantially the same as or slightly larger than the outer diameter of the nuclear fuel 1200. In one example, the inner diameter of the Zr alloy tube 1110 is approximately 0.0007 inches larger than the outer diameter of the nuclear fuel 1200.

[0042] In various examples, the coating 1120 includes a Cr-based layer. The Cr-based layer of the coating 1120 can be configured similarly to the primary layer 102 described above. Accordingly, the Cr-based layer of the coating 1120 is configured to have a corrosion-resistant material, a randomized microstructure, and a density of at least 95% to improve the corrosion and / or hydriding resistance of the Zr alloy tube 1110 and / or prevent spalling of the coating 1120.

[0043] The coating 1120 can be configured similarly to the coating 100 described above. Accordingly, the coating 1120 can include an intermediate layer and / or an outer layer configured similarly to the intermediate layer 104 and the outer layer 106 described above. Accordingly, the coating 1120 can be configured to improve the expansion and / or burst resistance of the Zr alloy tube 1110 under relatively high transient and / or accident temperature conditions and / or to protect against excessive corrosion in BWR applications. In some examples, the coating 1120 can include multiple layers having a randomized microstructure.

[0044] The present disclosure provides a method for manufacturing a cladding tube for a nuclear fuel rod. The method includes providing a base layer for the cladding tube, the base layer being composed of a Zr alloy, and protecting the base layer. In various examples of the method, protecting the base layer includes depositing a coating comprising a Cr-based layer on the base layer. In some examples, protecting the base layer includes depositing an intermediate layer before depositing the Cr-based layer and / or depositing an outer layer on the Cr-based layer. The coating of the present method is similar in many respects to other coatings described elsewhere herein, and for the sake of brevity, the description will not be repeated. Thus, the Cr-based layer may include a microstructure composed of a plurality of grains. Furthermore, the intermediate and outer layers of the present method may be similar in composition to the other intermediate and outer layers described above. Thus, the method described herein may be configured to provide long-term, robust protection from corrosion and / or hydriding of the Zr alloy-based layer of the cladding tube under accident conditions and / or in a BWR environment.

[0045] The step of protecting the base layer can be configured to provide a coating layer with a randomized microstructure and a density of about 94.5% or greater. For example, the Cr-based layer of the coating can be deposited by a cold spray process. The inventors have determined that a cold spray process can be used to deposit a Cr-based layer with a randomized grain boundary structure having many subgrains throughout the coating thickness. For example, a cold spray process for depositing a Cr-based layer can include forming a mixture containing a preheated carrier gas and Cr-based particles, and then spraying the mixture at a substrate at a particle velocity ranging from about 240 meters / second to about 1220 meters / second until a desired thickness is achieved. In some examples, a cold spray process for depositing a Cr-based layer includes adding Cr-based particles having an average diameter ranging from about 10 micrometers to about 500 micrometers to a helium and / or nitrogen-based carrier gas stream preheated to a temperature ranging from about 200°C to about 1200°C. Other configurations for the deposition process are also contemplated by the present disclosure. For example, in some examples, the coating layer can be deposited by a thermal spray process or a physical vapor deposition process. Additionally, the protection of the base layer can include a thermomechanical treatment of the deposited layer of the coating. In a particular example, the method can include a cold working step of the deposited layer based on swaging, pilgering, shot peening, and / or laser shock peening, followed by an annealing process.

[0046] The thermomechanical treatment can be configured to modify the grain size and / or structure of the deposited layer as needed to further increase the density of a particular layer of the coating. For example, if the grains of the deposited layer are relatively equiaxed and the layer is already composed of many grains, a cold working step can be configured to impart low to moderate strain to the deposited layer, in the range of about 6% to about 7%, followed by a low-temperature annealing step configured to induce recovery of the grain structure.

[0047] On the other hand, in instances where the grains of the deposited layer are oversized and / or columnar, a thermomechanical treatment can be configured to modify the grain structure to provide a more equiaxed structure. For example, the thermomechanical treatment can include a high degree of cold working to impart strain of 30% or more, followed by a high-temperature annealing step configured to induce recrystallization of the grain structure. Thus, the protective process described in the present method can be configured to modify the microstructure of the deposited coating layer, increasing its density and / or reducing porosity or undesirable high-energy grain boundaries. This allows for a method of manufacturing a coating layer that optimizes the level of protection the coating provides.

[0048] Various aspects of the present disclosure are not limited to those listed in the following numbered clauses.

[0049] Clause 1 - A coating for protecting a zirconium alloy-based layer of a nuclear fuel rod cladding tube. The coating comprises a primary layer. The microstructure of the primary layer is composed of a large number of randomly distributed grains. The primary layer has a density of at least about 94.5%.

[0050] Clause 2—The coating of clause 1, wherein the primary layer has a thickness ranging from about 4 micrometers to about 40 micrometers.

[0051] Clause 3 - The coating of any one of clauses 1 or 2, wherein the primary layer comprises a chromium-based metal layer.

[0052] Clause 4 - A coating according to clause 3, wherein the chromium-based metal layer comprises a chromium-based alloy.

[0053] Clause 5 - The coating of any one of clauses 1 to 4, wherein the coating comprises a ceramic layer.

[0054] Clause 6 - The coating of clause 5, wherein the ceramic layer is comprised of zirconium dioxide or a chromium-based material with at least one of niobium, nitrogen, silicon, or carbon.

[0055] Clause 7 - The coating of any one of clauses 1 to 6, wherein the ceramic layer is a primary layer.

[0056] Clause 8 - A coating according to any one of clauses 1 to 6, wherein a ceramic layer is disposed around the primary layer.

[0057] Clause 9 - The coating of clause 8, wherein the ceramic layer has a thickness ranging from about 1 micrometer to about 10 micrometers.

[0058] Clause 10 - The coating of clause 8, wherein the ceramic layer is composed of a density of about 94.5% or more.

[0059] Clause 11 - The coating of any one of clauses 1 to 10, wherein the coating comprises an intermediate layer disposed between the zirconium alloy-based layer and the primary layer.

[0060] Clause 12 - The coating of clause 11, wherein the intermediate layer has a thickness in the range of about 0.5 to about 4 micrometers.

[0061] Clause 13 - The coating of any one of clauses 11 to 12, wherein the intermediate layer is configured to inhibit chemical interaction between the zirconium alloy and the primary layer.

[0062] Clause 14 - The coating of any one of clauses 11 to 13, wherein the intermediate layer is comprised of an alloy comprising niobium, molybdenum, tantalum, rhenium, osmium, ruthenium, tungsten, or any combination thereof.

[0063] Clause 15 - The coating of any one of clauses 1 to 14, wherein the primary layer is composed of at least 95% density.

[0064] Clause 16 - The coating of any one of clauses 1 to 15, wherein the shape of each of the plurality of particles comprises an axial component in the range of about 1 micrometer to about 50 micrometers and a radial component in the range of about 1 micrometer to about 10 micrometers.

[0065] Article 17 - Cladding tube for nuclear fuel rod. The cladding tube comprises a zirconium alloy tube and a coating deposited on the exterior surface of the zirconium alloy tube. The zirconium alloy tube is configured to contain a quantity of nuclear fuel. The coating comprises a chromium-based layer. The chromium-based layer has a randomized grain structure and a density of at least 95%.

[0066] Clause 18 - A method for manufacturing cladding tubes for nuclear fuel rods. The method comprises providing a base layer for the cladding tube and protecting the base layer. The base layer comprises a zirconium alloy. Protecting the base layer comprises depositing a coating on the base layer. The coating comprises a chromium-based layer. The chromium-based layer of the protected base layer has a randomized microstructure and a density of about 95% or greater.

[0067] Clause 19 - The method of clause 18, wherein the protecting comprises depositing a chromium-based layer by cold spraying, thermal spraying, or physical vapor deposition.

[0068] Clause 20 - The method of any one of clauses 18 to 19, wherein protecting comprises mechanically working at least one deposited layer.

[0069] Various features and characteristics are described herein to provide an understanding of the composition, structure, manufacture, function, and / or operation of the disclosure, including the disclosed methods and systems. It is understood that the various features and characteristics of the disclosure described herein may be combined in any suitable manner, whether or not explicitly combined and described herein. The inventors and applicants expressly intend to include combinations of these features and characteristics within the scope of the disclosure described herein. Accordingly, the claims may be amended to recite any combination of features and characteristics explicitly or implicitly described or supported herein. Furthermore, applicants reserve the right to amend the claims to explicitly disclaim features and characteristics that may exist in the prior art, even if those features or characteristics are not explicitly recited herein. Accordingly, such amendments do not add new matter to the specification or claims, but are subject to the requirements of written description, sufficiency of description, and additional matter.

[0070] With respect to the appended claims, those skilled in the art will understand that the actions described therein may generally be performed in any order. Also, while various operational sequences are shown in a sequence, it should be understood that various actions may be performed in an order other than the order shown, or may be performed simultaneously. Examples of such alternative sequences may include overlapping, alternating, interrupted, reordered, progressive, preparatory, supplemental, concurrent, reversed, or other variations, unless the context dictates otherwise. Furthermore, terms such as past tense adjectives, such as "responsive to" and "related to," are generally not intended to exclude such variations, unless the context dictates otherwise.

[0071] The inventions described herein can comprise, consist of, or consist essentially of various functions and characteristics described herein. The terms "comprise" (and all forms of "comprise," e.g., "comprise" and "comprising"), "have" (and all forms of "have," e.g., "have" and "having"), "include" (and all forms of "include," e.g., "include" and "comprising"), and "contain" (and all forms of "contain," e.g., "contain" and "containing") are open conjunctive verbs. Thus, when a method or system "comprises," "has," "includes," or "contains" a feature and / or characteristic, it is intended to mean that the method or system has that feature and / or characteristic, but is not limited to only having that feature and / or characteristic. Similarly, when an element of a composition, coating, or process "comprises," "has," "includes," or "contains" a feature and / or characteristic, the element has that feature and / or characteristic, but is not limited to having only that feature and / or characteristic, and may have additional features and / or characteristics.

[0072] As used herein (including the claims), the articles "a," "an," and "the" mean "at least one" or "one or more," unless otherwise specified. Accordingly, these articles herein refer to one or more (i.e., "at least one") of the grammatical object of the article. For example, "a component" means one or more components, and therefore, more than one component is contemplated and may be used or employed in practicing the described composition, coating, or process. However, even if the terms "at least one" or "one or more" are used in some instances and not in others, it is understood that the absence of these terms does not limit the grammatical object of the articles "a," "an," and "the" to one. Furthermore, the use of a singular noun shall include the plural, and the use of a plural noun shall include the singular, unless the context of use requires otherwise.

[0073] As used herein, unless otherwise indicated, all numerical parameters are understood to be prefaced and modified in all respects by the term "about." Such numerical parameters have the inherent variability characteristic of the underlying measurement techniques employed to determine the numerical value of such parameters. At the very least, and not as an attempt to limit the application of the doctrine of equivalents to the scope of the claims, each numerical parameter set forth herein should, at the very least, be construed in light of the number of reported significant digits and by applying ordinary rounding techniques.

[0074] Numerical ranges recited herein include all subranges subsumed within the stated range. For example, a range of "1 to 100" includes all subranges between (and including) the recited minimum of 1 and the recited maximum of 100, i.e., having a minimum equal to or greater than 1 and a maximum equal to or less than 100. Also, all ranges recited herein include the endpoints of the recited range. For example, the range "1 to 100" includes the endpoints 1 and 100. Every maximum numerical limitation recited herein is intended to include all subnumerical limitations subsumed therein, and every minimum numerical limitation recited herein is intended to include all upper numerical limitations subsumed therein. Accordingly, applicants reserve the right to amend this specification, including the claims, to expressly describe any subranges encompassed within the explicitly recited ranges. All such ranges are inherently described herein.

[0075] As used herein, particularly in reference to layers, the terms "on," "onto," "over," and variations thereof (e.g., "applied over," "formed over," "deposited over," "provided over," "located over," etc.) mean applied to, formed over, deposited on, provided on, or otherwise disposed on, but not necessarily in contact with, the surface of a substrate. For example, a layer "applied" onto a substrate does not preclude the presence of another layer or layers of the same or different composition between the applied layer and the substrate. Similarly, a second layer "applied over" a first layer does not preclude the presence of another layer or layers of the same or different composition between the applied second layer and the applied first layer.

[0076] While particular examples of the disclosure have been described above for purposes of illustration, it will be apparent to those skilled in the art that many changes can be made in the details of the disclosure without departing from the scope of the disclosure as defined in the appended claims.

Claims

1. A coating for protecting a zirconium alloy-based layer of a nuclear fuel rod cladding tube, comprising: the coating comprises a primary layer; The microstructure of the primary layer is composed of a large number of randomly distributed particles; The coating, wherein the primary layer is comprised of a density of about 94.5% or greater.

2. The coating of claim 1 , wherein the primary layer has a thickness ranging from about 4 micrometers to about 40 micrometers.

3. The coating of claim 1 , wherein the primary layer comprises a chromium-based metal layer.

4. The coating of claim 3 , wherein the chromium-based metal layer comprises a chromium-based alloy.

5. The coating of claim 1 , wherein the coating comprises a ceramic layer.

6. 6. The coating of claim 5, wherein the ceramic layer is comprised of zirconium dioxide or a chromium-based material with at least one of niobium, nitrogen, silicon, or carbon.

7. The coating of claim 5 wherein the ceramic layer is the primary layer.

8. The coating of claim 5 , wherein the ceramic layer is disposed around the primary layer.

9. The coating of claim 8 , wherein the ceramic layer has a thickness in the range of about 1 micrometer to about 10 micrometers.

10. 9. The coating of claim 8, wherein the ceramic layer comprises a density of about 94.5% or greater.

11. The coating of claim 1 , wherein the coating comprises an intermediate layer disposed between the zirconium alloy-based layer and the primary layer.

12. 12. The coating of claim 11, wherein the intermediate layer has a thickness in the range of about 0.5 micrometers to about 4 micrometers.

13. 12. The coating of claim 11, wherein the intermediate layer is configured to inhibit chemical interaction between the zirconium alloy-based layer and the primary layer.

14. 14. The coating of claim 13, wherein the intermediate layer is comprised of an alloy comprising niobium, molybdenum, tantalum, rhenium, osmium, ruthenium, tungsten, or any combination thereof.

15. The coating of claim 1 , wherein the primary layer is comprised of at least 95% density.

16. The shape of each of the plurality of particles is an axial component in the range of about 1 micrometer to about 50 micrometers; 10. The coating of claim 1, wherein the coating has a radial component in the range of about 1 micrometer to about 10 micrometers.

17. A cladding tube for a nuclear fuel rod, a zirconium alloy tube configured to contain a quantity of nuclear fuel; a coating deposited on the exterior surface of the zirconium alloy tube; The cladding tube, wherein the coating comprises a chromium-based layer, the chromium-based layer having a randomized grain structure and a density of at least 95%.

18. 1. A method of manufacturing cladding tubes for nuclear fuel rods, comprising: providing a base layer for the cladding tube, the base layer comprising a zirconium alloy; protecting the base layer, the protecting comprising depositing a coating on the base layer, the coating comprising a chromium-based layer; The method wherein the chromium-based layer of the protected base layer has a randomized microstructure and a density of about 95% or greater.

19. 20. The method of claim 18, wherein the protecting comprises depositing the chromium-based layer by cold spray, thermal spray, or physical vapor deposition.

20. 20. The method of claim 18, wherein the protecting comprises mechanically working at least one deposited layer.

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