Use of oxidation-resistant coatings to enhance the tensile strength of thin-walled cladding for increased uranium loading.

Abstract

A cladding tube for containing enriched nuclear fuel in a nuclear fuel assembly is provided. The cladding tube includes a substrate comprised of a zirconium alloy and a coating for the substrate. The substrate has a wall thickness of less than 1 millimeter. The coating includes a primary layer comprised of chromium or a chromium alloy. The primary layer has a thickness of about 5 microns to about 50 microns. Fuel rods for a nuclear reactor core and methods for manufacturing the fuel rods are also provided.

Description

[Technical Field]

[0001] (CROSS-REFERENCE TO RELATED APPLICATIONS) This application claims the benefit of and priority under 35 U.S.C. § 120 to U.S. patent application Ser. No. 18 / 051,925, filed Nov. 2, 2022, entitled "USE OF OXIDATION RESISTANT COATINGS TO INCREASE THIN WALLED CLADDING TENSILE STRENGTH TO INCREASE URANIUM LOADINGS," the 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] Zirconium alloys are widely used as the standard cladding material in nuclear fuel rods. However, fuel assembly and cladding designs currently approved by the Nuclear Regulatory Commission limit the nuclear fuel loading capacity within any one fuel rod of a fuel assembly, thereby limiting the obtainable fuel burnup, generating an excessive number of spent nuclear fuel elements, and / or increasing the downtime required for refueling. Implementing design changes by changing the dimensions of the fuel cladding used in the fuel assembly and / or the nuclear fuel loaded therein would incur significant costs for the fuel assembly manufacturer and / or energy supplier. Therefore, there is a need to develop alternative cladding designs and manufacturing methods to optimize the cost and performance of nuclear fuel rods while maintaining the current dimensions of the fuel rods. Summary of the Invention

[0004] The following summary is provided to facilitate an understanding of some of the innovative features unique to the embodiments disclosed herein, but is not intended to be a complete description. A complete understanding of the various embodiments disclosed herein can be gained by taking the entire specification, claims, and abstract as a whole.

[0005] In various embodiments, a cladding tube for containing enriched nuclear fuel in a nuclear fuel assembly is disclosed. In some embodiments, the cladding tube includes a substrate comprised of a zirconium alloy and a coating for the substrate. In some embodiments, the substrate has a wall thickness of less than 1 millimeter. In some embodiments, the coating includes a primary layer. In some embodiments, the primary layer is comprised of chromium or a chromium alloy and has a thickness of about 5 microns to about 50 microns.

[0006] In various embodiments, a fuel rod for a nuclear reactor core is disclosed. In some embodiments, the fuel rod includes a reinforced cladding tube and a quantity of nuclear fuel comprised of a uranium-containing compound. In some embodiments, the reinforced cladding tube includes a substrate comprised of a zirconium alloy and a coating for the substrate. In some embodiments, the substrate has a wall thickness of about 0.2 millimeters to about 0.6 millimeters and defines a cavity therein. In some embodiments, the coating includes a primary layer comprised of chromium or a chromium alloy and having a thickness of about 5 microns to about 50 microns. In some embodiments, the quantity of nuclear fuel is loaded into the cavity of the substrate of the reinforced cladding tube and is capable of supporting an 18-month fuel cycle with a burnup of about 68 megawatt-days / kilogram-uranium or greater. In some embodiments, the uranium-containing compound is enriched to a level of about 5% or less uranium-235 ("235U").

[0007] In various embodiments, a method for manufacturing a fuel rod for a nuclear reactor is disclosed. In some embodiments, the method includes fabricating a substrate for a cladding tube of the fuel rod, applying a coating to the substrate to fabricate the cladding tube, and loading the cladding tube with a quantity of uranium-based fuel. In some embodiments, the substrate is composed of a zirconium alloy, has a wall thickness of less than 1 millimeter, and defines a cavity therein. In some embodiments, the coating includes a primary layer composed of chromium or a chromium alloy, the primary layer having a thickness of about 5 microns to about 50 microns. In some embodiments, the uranium-based fuel is enriched to a level of about 4.95% U or less, and the quantity of nuclear fuel is capable of supporting an 18-month fuel cycle with a burnup of about 68 megawatt-days / kilogram-uranium or greater.

[0008] These and other objects, features, and characteristics of the present disclosure, as well as the method of operation and function of the associated elements of construction, and combination of parts and economies of manufacture, will become more apparent from a consideration of the following description and appended claims, all of which are incorporated herein by reference in their entirety, when taken in conjunction with the accompanying drawings, in which like reference numerals refer to corresponding parts in the various drawings. It is to be 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 embodiments disclosed herein. [Brief explanation of the drawings]

[0009] The various aspects described herein, together with their objects and advantages, will be best understood by reference to the following description taken in conjunction with the accompanying drawings, in which:

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

[0011] [Figure 2]FIG. 2 illustrates a cross-sectional view of a fuel rod in accordance with at least one non-limiting embodiment of the present disclosure.

[0012] [Figure 3] FIG. 3 is a cross-sectional schematic view of a cladding tube in accordance with at least one non-limiting embodiment of the present disclosure.

[0013] [Figure 4] FIG. 4 is a cross-sectional schematic view of a coating according to at least one non-limiting embodiment of the present disclosure.

[0014] [Figure 5] FIG. 5 is a cross-sectional schematic view of a coating according to at least one non-limiting embodiment of the present disclosure.

[0015] [Figure 6] FIG. 6 is a cross-sectional schematic view of a coating according to at least one non-limiting embodiment of the present disclosure.

[0016] [Figure 7] FIG. 7 is a cross-sectional schematic view of a fuel rod in accordance with at least one non-limiting embodiment of the present disclosure.

[0017] Corresponding reference characters indicate corresponding parts throughout the various views. The exemplifications set forth herein illustrate various aspects of the present disclosure in one form, and such exemplifications are not to be construed as limiting the scope of the aspects disclosed herein. DETAILED DESCRIPTION OF THE INVENTION

[0018] Certain exemplary embodiments of the present disclosure will be described to provide a general understanding of the principles of the compositions, functions, manufacture, and use of the compositions and methods disclosed herein. One or more examples of these embodiments are illustrated in the accompanying drawings. Those skilled 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 with respect to 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.

[0019] References herein to "various examples," "several examples," "one example," "one example," etc., mean that a particular feature, structure, or characteristic described in connection with that example is included in that example. Thus, the appearances of phrases such as "in various examples," "in several examples," "in one example," and "in one example" in various places throughout this specification do not necessarily all refer to the same example. Furthermore, particular features, structures, or characteristics may be combined in any suitable manner in one or more examples. Thus, a particular feature, structure, or characteristic illustrated or described in connection with one example may be combined, in whole or in part, without limitation, with features, structures, or characteristics of one or more other examples. Such modifications and variations are intended to be included within the scope of the present examples.

[0020] In the following description, like reference characters in the drawings indicate like or corresponding parts. It should also be understood that in the following description, terms such as "front," "rear," "left," "right," "upper," "lower," "top," "bottom," etc. are used for convenience only and are not to be construed as limiting terms.

[0021] In a typical nuclear reactor, such as a pressurized water reactor ("PWR"), a heavy water reactor (e.g., CANDU), or a boiling water reactor ("BWR"), the reactor core may 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 may contain a plurality of fuel pellets 26, each comprising fissile material capable of undergoing a nuclear fission reaction to produce the reactor's reaction power.

[0022] The fuel rods 22 may be supported by one or more transverse grids 20 attached to guide thimbles 18. The guide thimbles 18 extend longitudinally between the top nozzle 16 and the bottom nozzle 12, and the control rods 34 are configured to operatively move therethrough. The guide thimbles 18 may have opposite ends, one attached to the top nozzle 16 and the other attached to the bottom nozzle 12. The bottom nozzle 12 may be configured to support the fuel assembly 10 on a reactor vessel lower core plate 14 in the core region of a nuclear reactor (not shown). A coolant liquid, such as water or water containing a neutron absorber such as boron, may be pumped upwardly into the fuel assembly 10 through a plurality of flow openings in the lower core plate 14. The bottom nozzle 12 of the fuel assembly 10 may direct the coolant liquid over and along the fuel rods 22 of the assembly 10 to remove heat generated by the nuclear fission reactions occurring therein.

[0023] FIG. 2 illustrates an enlarged cross-sectional view of a fuel rod 22 according to at least one non-limiting embodiment of the present disclosure. Referring now to FIGS. 1-2, as described above, each of the fuel rods 22 may include a plurality of nuclear fuel pellets 26. The fuel pellets 26 are contained within an elongated cladding tube 38, the ends of which are closed by upper and lower end plugs 28 and 30. The pellets 26 may be maintained in a stack 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 in other configurations using other mechanisms. In addition to containing the nuclear fuel, the cladding tube also provides a medium for heat transfer from the fissile fuel to a coolant surrounding the fuel rod.

[0024] Cladding tubes are typically made of materials that have a low neutron penalty and are corrosion-resistant under various reactor environmental conditions. For example, zirconium ("Zr") alloys have been used as the standard cladding material typically used in nuclear fuel assemblies for PWRs. Under low-temperature reactor operating conditions, e.g., temperatures below about 375°C, Zr alloy cladding tubes do not compromise cladding properties, such as structural integrity and / or overall heat transfer characteristics, even when exposed to coolant. However, depending on the reactor environment and / or operating conditions, Zr alloy-based cladding tubes may require protective surface treatments.

[0025] 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, chromium (hereinafter "Cr") coatings are compatible with the chemistry and accident environment of PWRs and / or CANDUs and are fairly inexpensive to apply to Zr alloys. Therefore, to obtain a relatively inexpensive ATF for PWR reactors, Cr coatings are sometimes deposited on Zr alloy cladding. Depositing Cr coatings can reduce the oxidation rate of the cladding surface at beyond-design-basis-event ("BDBA") temperatures, such as temperatures exceeding 1200°C. However, while Cr is highly compatible with the reactor environment of PWRs, it is not compatible with the chemistry of BWRs under normal operating conditions. Other Cr-based alloys and compounds, such as CrN and CrNbN, are used in BWRs. Furthermore, while ATFs utilize relatively thin coatings having thicknesses of less than about 100 microns, increasing the thickness of the cladding and / or coatings can incur a substantial net neutron penalty, thereby compromising nuclear fuel efficiency and / or burnup.

[0026] In practice, technological developments in the nuclear sector can be difficult to implement. For example, design changes to the overall dimensions of a fuel assembly require manufacturers and / or suppliers to invest significant time and money in fuel rod, nuclear fuel characteristics, and / or licensing regulations before the new design can be licensed for production and / or use. Therefore, when manufacturing nuclear fuel rods, manufacturers typically employ cladding tubes with standard dimensions, such as an outer diameter of approximately 9.5 millimeters, to comply with existing design basis requirements, thereby avoiding unnecessary costs.

[0027] Furthermore, because cladding must meet regulatory strength and / or safety requirements, conventional cladding typically has a standard wall thickness to allow for a predictable safety margin. For example, the design criteria for Zr-alloy-based cladding require a wall thickness of 0.575 mm. Therefore, some cladding is manufactured with a minimum thickness of 0.575 mm to provide sufficient structural integrity for normal reactor operation. As a result, standard cladding limits the volumetric capacity and, therefore, fuel capacity. While the fissile fuel volumetric capacity limit in current cladding can be offset by increasing the uranium-based fuel's 235U enrichment to levels greater than approximately 5%, the uranium-based fuel 235U enrichment limit for LWRs is currently regulated at 4.95%. Furthermore, all facilities handling commercial nuclear fuel, including fuel fabrication, fuel transportation, and nuclear power plant facilities, are constructed, licensed, and operated in accordance with this requirement. Thus, the limited capacity of fissile material in currently available cladding used in LWRs may increase the frequency of refueling required to maintain a given power output and / or the amount of new fuel rods required for refueling.

[0028] Various methods and apparatus provided by the present disclosure optimize the technical and economic aspects of providing fuel rods for fuel assemblies in nuclear reactors, such as LWRs. In some embodiments, this optimization allows for increased nuclear fuel capacity and fuel burnup in a given core using existing fuel technology without increasing the overall footprint of the fuel rods and / or compromising the structural integrity of the cladding therein. Thus, various aspects of the present disclosure provide various methods and apparatus for maximizing the performance of nuclear fuel in existing LWR designs, thereby maintaining nuclear regulatory compliance without requiring costly design change approvals.

[0029] 3, a cross-sectional schematic diagram of a cladding tube 100 for containing enriched nuclear fuel in a nuclear fuel assembly is shown, according to at least one non-limiting embodiment of the present disclosure. In various examples, the cladding tube 100 includes a base layer 110 comprised of a Zr alloy and a coating 120 for the base layer 110. The coating 120 includes a primary layer 120b comprised of Cr or an alloy of Cr.

[0030] In various examples, the base layer 110 has a wall thickness of less than 1 millimeter. In some examples, the base layer 110 may have a wall thickness of about 0.2 millimeters to about 0.575 millimeters, about 0.2 millimeters to about 0.5 millimeters, or about 0.2 millimeters to about 0.475 millimeters. In one example, the base layer 110 has a wall thickness of about 0.456 millimeters.

[0031] In certain examples of the cladding tube 100, the coating 120 may be configured to include one or more layers surrounding and / or underlying the primary layer 120b. For example, FIGS. 4-6 illustrate various multi-layer configurations of the coating 120 deposited on the base layer 110. FIG. 4 illustrates the coating 120 including an intermediate layer 120a positioned between the base layer 110 and the primary layer 120b, while FIG. 5 illustrates the coating 120 including an upper layer 120c surrounding the primary layer 120b. FIG. 6 illustrates the coating 120 including layers 120a, 120b, and 120c. In examples of the cladding tube 100 including the multi-layer coating 120, each of the intermediate layer 120a and / or upper layer 120c may independently be configured to have a thickness of about 10 microns or less.

[0032] 3-6, the primary layer 120b may have a thickness of about 5 to about 50 microns. In some examples, the primary layer 120b may be composed of a Cr alloy containing at least one of yttrium, molybdenum, iron, aluminum, and nitrogen. The primary layer 120b may be configured to impart tensile strength to the underlying layers without significantly increasing the neutron penalty of the coating 120. For example, in a multi-layer coating 120, the primary layer 120b may be configured to have a thickness less than the primary layer 120b of a single-layer coating 120. In certain examples, the primary layer 120b has a thickness of about 5 to about 20 microns.

[0033] 4 and 6, in examples where the coating 120 includes an intermediate layer 120a, the intermediate layer 120a may be composed of a material that has a eutectic formation temperature with Zr and / or Cr above 1500°C, above 1600°C, above 2000°C, or above the BDBA temperature. For example, the intermediate layer 120a may be composed of molybdenum, tantalum, or niobium. Currently available Zr alloy-based cladding tubes with a Cr-Zr interface may begin to form a Cr-Zr eutectic at a relatively low temperature of approximately 1333°C. As described above, an intermediate layer 120a having such a composition can maintain a barrier between the Zr alloy of the base layer 110 and the Cr-based primary layer 120b even at relatively high temperatures, such as above 1500°C. Therefore, by configuring the cladding tube 100 to have the intermediate layer 120a, the formation of a low-melting point Cr-Zr eutectic material can be suppressed, thereby further improving the expansion and / or burst resistance of the cladding tube 100 at relatively high transient and / or accident state temperatures.

[0034] 5-6, the upper layer 120c may be configured to better protect the ATF under BDBA conditions, high-temperature conditions, and / or normal operating conditions. For example, the upper layer 120c may be comprised of a Cr alloy or a ceramic material. In some examples, the upper layer 120c may be comprised of a Cr alloy including at least one of yttrium, molybdenum, iron, and aluminum. In particular examples, the upper layer 120c is configured as a Cr alloy including yttrium or molybdenum, or as a chromium alloy including iron and / or aluminum. In examples where the upper layer 120c is comprised of a ceramic material, the upper layer 120c may include chromium, nitrogen, niobium, or any combination thereof. These alloys and ceramics are known to withstand coolants containing, for example, up to about 10 ppm O. In this manner, the cladding tube 100 including the upper layer 120c may be configured to provide protection against excessive corrosion in BWR applications.

[0035] The cladding tube 100 described above may be configured to provide optimized storage capacity without increasing the cladding tube's overall footprint within a nuclear reactor. For example, the cladding tube 100 may have an outer diameter that is approximately the same as or slightly smaller than the outer diameter of conventional cladding tubes. In some examples, the cladding tube 100 is configured with an outer diameter of approximately 9.5 millimeters or less. In one example, the cladding tube 100 has an outer diameter of approximately 9.5 millimeters and includes a substrate with a wall thickness of less than 0.575 millimeters. In one example, the cladding tube 100 has an outer diameter of approximately 9.5 millimeters and includes a substrate with a wall thickness of approximately 0.46 millimeters. A cladding tube 100 having this configuration may increase internal volumetric loading capacity by approximately 6% and reduce neutron penalty compared to currently available cladding tubes having a wall thickness of 0.575 millimeters, without increasing the cladding tube's exterior surface area and / or overall footprint. Thus, the cladding tube 100 is configured to store a larger volume of fuel without redesigning the reactor enclosure and / or the coolant flow paths within the reactor, thereby avoiding costly design changes.

[0036] Furthermore, the inventors of the present disclosure have discovered that a primary layer 120b having a thickness that is unexpectedly small can enhance the strength and / or burst resistance of the substrate 110. For example, the inventors of the present disclosure have conducted burst tests on Zr alloy cladding tubes, in which cladding tubes including a Cr-based coating having a thickness of about 10-20 microns provided an increase of about 16% compared to uncoated cladding tubes. Thus, a cladding tube 100 including a relatively thin-walled substrate 110 as described above can be configured with a coating 120 to provide a greater fuel storage capacity compared to currently available cladding tubes without sacrificing burst resistance.

[0037] Referring now to FIG. 7 , a cross-sectional schematic diagram of a fuel rod 1000 for a nuclear reactor core including a reinforced cladding 1100 and nuclear fuel 1200 is shown, according to at least one non-limiting embodiment of the present disclosure. In various examples, the fuel rod 1000 includes the reinforced cladding 1100 and a quantity of nuclear fuel 1200. In particular examples, the reinforced cladding 1100 is configured to have an outer diameter of about 9.5 millimeters or less. The quantity of nuclear fuel 1200 is comprised of uranium enriched to a level of less than about 5%, less than about 4%, or less than about 3%. For example, about 4.95% of the uranium content in the quantity of nuclear fuel 1200 may be comprised of 235U. The quantity of nuclear fuel 1200 may be configured as a number of fuel pellets. For example, the quantity of nuclear fuel 1200 may include a number of standard uranium dioxide-based fuel pellets or a number of high-density fuel pellets, such as fuel pellets having an enriched uranium density of about 2% or more than standard fuel pellets.

[0038] Continuing with FIG. 7 , the reinforced cladding tube 1100 includes a base layer 1110 comprised of a Zr alloy and a coating 1120 comprising a primary layer. Because the reinforced cladding tube 1100 is similar in many respects to other cladding tubes disclosed elsewhere in this disclosure, the details of those other cladding tubes will not be repeated here for brevity. In various examples, the base layer 1110 defines a cavity therein and has a wall thickness of about 0.2 millimeters to about 0.575 millimeters. The primary layer of the coating 1120 has a thickness of about 5 microns to about 50 microns and is comprised of chromium or a Cr alloy. A quantity of nuclear fuel 1200 for the fuel rod 1000 is loaded into the cavity of the base layer 1110. In examples where the primary layer of the coating 1120 is comprised of a Cr alloy, the Cr alloy may include at least one of yttrium, molybdenum, iron, aluminum, and nitrogen. In some examples, the coating 1120 comprises multiple layers.

[0039] The substrate 1110 and the coating 1120 may each be independently configured, similar to the substrate 110 and the coating 120 described above. Thus, the thickness of the substrate 1110 and the thickness of the coating 1120 may be configured to provide a greater storage capacity compared to currently available cladding without compromising burst resistance and / or requiring a larger footprint, thereby avoiding costly modifications to existing reactor vessel designs and / or coolant flow conduits therein.

[0040] The enhanced cladding tube 1100 with the above-described high-capacity configuration can optimize the service life of the fuel rod 1000. For example, an enhanced cladding tube 1100 including a substrate 1110 with a wall thickness of approximately 0.456 millimeters can provide approximately 6% increased volumetric capacity compared to currently available cladding tubes with a wall thickness of approximately 0.575 millimeters. When loaded with a quantity of nuclear fuel 1200 configured as high-density fuel pellets composed of uranium enriched to a level of approximately 4.95%, the resulting fuel rod 1000 can perform at a level comparable to a standard-wall cladding tube loaded with fuel enriched to approximately 5.34%, thereby providing a burnup of approximately 68 megawatt-days per kilogram-uranium ("MWd / kg-U") over an 18-month service cycle. Thus, the fuel rod 1000 can be configured to provide a fuel burnup of greater than 5% fuel enrichment without exceeding the upper enrichment limit of 4.95%.

[0041] As discussed herein, the present disclosure provides methods for manufacturing fuel rods. In various examples, the methods include fabricating a substrate for a cladding tube of the fuel rod, applying a coating to the substrate to fabricate the cladding tube, and loading the cladding tube with an amount of uranium-based fuel enriched to a level of about 4.95% or less to fabricate the fuel rod. The substrate has a wall thickness of less than 1 millimeter, defines an internal cavity therein, and is composed of a zirconium alloy. The coating may include a primary layer composed of chromium or a chromium alloy and may have a thickness of about 5 microns to about 50 microns.

[0042] In some examples, the method may include applying a multi-layer coating to a base layer. For example, the method may include applying an intermediate layer to the base layer before applying the primary layer and / or applying a top layer to the primary layer. These intermediate and top layers are similar in many respects to other intermediate and top layers described elsewhere in this disclosure. Accordingly, the intermediate layer may be configured to increase the formation temperature of a eutectic between the base layer and the primary layer. Additionally, the top layer may be configured to protect the bottom layer from corrosion resistance in BWR applications. Accordingly, the method may be configured to further increase the resistance of the fuel rod to expansion, rupture, and / or oxidation at temperatures associated with accident conditions and / or transient events.

[0043] The method may be configured to incorporate various deposition and / or application processes. For example, the primary layer of the coating may be applied using a cold spray process, a thermal spray process, or a physical vapor deposition process such as cathodic arc evaporation, magnetron sputtering, or pulsed laser deposition. In examples where the method includes applying an intermediate layer and / or an overlayer, the intermediate layer and / or the overlayer may be applied using a thermal spray process or a physical vapor deposition process.

[0044] The fuel rods are similar in many respects to other fuel rods described elsewhere in this disclosure. Accordingly, the fuel rods may be constructed with a large-capacity reinforced cladding to provide optimized fuel storage capacity at high temperatures without compromising structural integrity and / or surface properties, thereby providing fuel burnups of greater than 5% enrichment without exceeding the upper enrichment limit of 4.95%. In various examples, the method includes loading the cladding with an amount of nuclear fuel supporting an 18-month fuel cycle at a burnup of approximately 68 megawatt-days / kilogram-uranium or greater. Thus, a method having this configuration can provide a high-burnup fuel rod without increasing enrichment levels and / or requiring redesign of the reactor vessel interior. Thus, the method can optimize the performance of the nuclear fuel in the fuel rod without compromising compatibility with the current reactor vessel and / or requiring costly modifications to the reactor vessel.

[0045] Various aspects of the present disclosure include, but are not limited to, those listed in the following numbered paragraphs:

[0046] Item 1 - A cladding tube for containing enriched nuclear fuel in a nuclear fuel assembly, the cladding tube comprising a substrate and a coating for the substrate. The substrate is comprised of a zirconium alloy and has a wall thickness of less than 1 millimeter. The coating comprises a primary layer. The primary layer is comprised of chromium or a chromium alloy and has a thickness of about 5 microns to about 50 microns.

[0047] Item 2 - The cladding tube of item 1, wherein the substrate has a wall thickness of about 0.2 millimeters to about 0.6 millimeters.

[0048] Item 3 - The cladding tube according to any one of Items 1 to 2, wherein the chromium alloy comprises yttrium, molybdenum, iron, aluminum, nitrogen, or a combination thereof.

[0049] Item 4 - The cladding tube according to any one of Items 1 to 3, wherein the coating further comprises an intermediate layer, the intermediate layer being positioned between the base layer and the primary layer and configured to increase the formation temperature of a eutectic between the base layer and the primary layer.

[0050] Item 5 - The cladding tube according to item 4, wherein the intermediate layer is composed of molybdenum, tantalum, or niobium.

[0051] Item 6 - The cladding tube according to any one of Items 4 to 5, wherein the intermediate layer has a thickness of about 10 microns or less.

[0052] Item 7 - The cladding tube according to any one of items 1 to 6, wherein the coating further comprises an upper layer surrounding the primary layer, the upper layer being composed of a chromium alloy or a ceramic material.

[0053] Item 8—The cladding tube of item 7, wherein the chromium alloy comprises yttrium or molybdenum.

[0054] Item 9 - The cladding tube of item 7, wherein the chromium alloy comprises iron and aluminum.

[0055] Item 10 - The cladding tube of item 7, wherein the ceramic material comprises chromium, nitrogen, niobium, or any combination thereof.

[0056] Item 11 - The cladding tube according to any one of Items 7 to 10, wherein the upper layer has a thickness of about 10 microns or less.

[0057] Item 12 - The cladding tube of any one of items 1 to 11, wherein the substrate has a wall thickness of less than 0.575 millimeters.

[0058] Item 13 - The cladding tube of item 12, wherein the substrate has a wall thickness of about 0.5 millimeters or less.

[0059] Item 14 - A fuel rod for a nuclear reactor core, the fuel rod comprising a reinforced cladding and a quantity of nuclear fuel comprised of uranium. The reinforced cladding comprises a substrate comprised of a zirconium alloy and a coating for the substrate. The substrate has a wall thickness of about 0.2 millimeters to about 1 millimeter and defines a cavity therein. The coating comprises a primary layer. The primary layer is comprised of chromium or a chromium alloy and has a thickness of about 5 microns to about 50 microns. The quantity of nuclear fuel is loaded into the cavity of the substrate of the reinforced cladding and is capable of supporting an 18-month fuel cycle at a burnup of about 68 megawatt-days / kilogram-uranium or greater. The uranium is enriched to about 5% or less.

[0060] Item 15 - The fuel rod of item 14, wherein the chromium alloy of the primary layer comprises yttrium, molybdenum, iron, aluminum, nitrogen, or a combination thereof.

[0061] Item 16 - The fuel rod according to any one of items 14-15, wherein the substrate has a wall thickness of about 0.2 millimeters to about 0.5 millimeters.

[0062] Item 17 - A method of manufacturing a fuel rod for a nuclear reactor, the method comprising: fabricating a substrate for a cladding tube of the fuel rod; applying a coating to the substrate to fabricate the cladding tube; and loading a quantity of uranium-based fuel into the cladding tube. The substrate is composed of a zirconium alloy and has a wall thickness of less than 1 millimeter, defining a cavity therein. The coating comprises a primary layer having a thickness of about 5 microns to about 50 microns, the primary layer being composed of chromium or a chromium alloy. The uranium-based fuel is enriched to a level of about 4.95% or less, and the quantity of uranium-based fuel is capable of supporting an 18-month fuel cycle with a burnup of about 68 megawatt-days per kilogram of uranium or greater.

[0063] Item 18 - The method of item 17, wherein the first layer of the coating is applied using a cold spray process, a thermal spray process, or a physical vapor deposition process.

[0064] Item 19 - The method of any one of items 17-18, wherein the coating further comprises an intermediate layer configured to increase the temperature of formation of a eutectic between the base layer and the primary layer. The intermediate layer is applied using a thermal spray process or a physical vapor deposition process before the primary layer is applied.

[0065] Item 20 - The method of any one of items 17 to 19, wherein the coating further comprises an overlayer, the overlayer being comprised of a chromium alloy or a ceramic material, the overlayer being applied using a thermal spray process or a physical vapor deposition process after the primary layer has been applied.

[0066] Various features and characteristics are described herein to provide an understanding of the composition, structure, manufacture, function, and / or operation of the present disclosure, including the disclosed methods and systems. It will be understood that various of these features and characteristics of the present disclosure described herein may be combined in any suitable manner, whether or not such combinations of features and characteristics are explicitly described herein. The inventors and applicants expressly intend that such combinations of features and characteristics be included within the scope of the disclosure described herein. Accordingly, the claims may be amended to recite any combination of features and characteristics explicitly or inherently described or explicitly or inherently supported herein. Furthermore, applicants reserve the right to amend the claims to affirmatively disclaim any features or characteristics that may exist in the prior art, even if those features or characteristics are not explicitly described herein. Accordingly, any such amendments will not add new matter to the specification or claims, but will comply with the requirements of the specification, specification sufficiency, and additional matter.

[0067] With respect to the appended claims, those skilled in the art will understand that the operations described therein may generally be performed in any order. Additionally, while various operational flows are depicted in a sequential order, it should be understood that various of these operations may be performed in orders other than those depicted, or may be performed simultaneously. Examples of such alternative orders include overlapping, interleaved, interrupted, reordered, incremental, preparatory, supplemental, concurrent, reversed, or other variations, unless the context dictates otherwise. Furthermore, terms such as "in response to," "related to," and other past tense adjectives are generally not intended to exclude such variations, unless the context dictates otherwise.

[0068] The inventions described herein may comprise, consist of, or consist essentially of various features and characteristics described herein. The words "comprise" (and any form of "comprise," such as "comprises" or "comprising"), "have" (and any form of "have," such as "had" or "having"), "include" (and any form of "include," such as "included" or "comprising"), and "contain" (and any form of "contain," such as "contained" or "containing") are open-ended linking verbs. Thus, a method or system that "comprises," "has," "includes," or "contains" one or more features and / or characteristics has the one or more features and / or characteristics, but is not limited to having only the one or more features and / or characteristics. Similarly, an element of a composition, coating, or process that "comprises," "has," "includes," or "contains" one or more features and / or characteristics has those one or more features and / or characteristics, but is not limited to having only those one or more features and / or characteristics, and may have other features and / or characteristics as well.

[0069] As used herein, including the claims, the grammatical articles "a," "an," and "the" are intended to include "at least one" or "one or more," unless expressly stated otherwise. Accordingly, articles are used herein to refer to one or more than one (i.e., "at least one") of the grammatical object of the article. As an example, "a component" means one or more components, and thus, it is conceivable that one or more components may be employed or used in the practice of the described compositions, coatings, and processes. That being said, it should be understood that the absence of the terms "at least one" or "one or more," when used in some cases, should not be construed as limiting the object of the grammatical articles "a," "an," and "the" to one. Furthermore, unless the context dictates otherwise, the use of a singular noun includes the plural, and the use of a plural noun includes the singular.

[0070] As used herein, unless otherwise noted, all numerical parameters should be understood to be prefaced and modified in all instances by the word "about." Such numerical parameters have the inherent variability characteristic of the underlying measurement techniques used 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 least be construed in light of the number of reported significant digits and by applying ordinary rounding techniques.

[0071] Numerical ranges recited herein include all subranges subsumed within the recited range. For example, a range of "1 to 10" includes all subranges between (and including) the recited minimum value of "1" and the recited maximum value of "10," i.e., all subranges with a minimum value of 1 or greater and a maximum value of 10 or less. Also, all ranges recited herein include their endpoints. For example, a range of "1 to 10" includes the endpoints 1 and 10. Each maximum numerical limitation recited herein is intended to include all subranges subsumed therein, and each minimum numerical limitation recited herein is intended to include all subranges subsumed therein. Accordingly, applicants reserve the right to amend this specification, including the claims, to expressly recite any subranges subsumed within any explicitly recited range. All such ranges are inherently set forth herein.

[0072] As used herein, particularly in reference to layers, the terms "on," "upon," "over," and variations thereof (e.g., "applied on," "formed on," "deposited on," "provided on," "located on," etc.) mean applied to, formed on, deposited on, provided on, or positioned on the surface of a substrate, but not necessarily in contact with the surface of the substrate. For example, a layer "applied" on a substrate does not exclude the presence of another layer or other layers, of the same or different composition, between the applied layer and the substrate. Similarly, a second layer "applied" on a first layer does not exclude the presence of another layer or other layers, of the same or different composition, between the applied second layer and the applied first layer.

[0073] While particular examples of the present disclosure have been described above for purposes of illustration, it will be apparent to those skilled in the art that many changes in the details of the present disclosure may be made without departing from the disclosure as defined in the appended claims.

Claims

1. 1. A cladding tube for containing enriched nuclear fuel in a nuclear fuel assembly, comprising: The cladding tube is a substrate composed of a zirconium alloy and having a wall thickness of less than 1 millimeter; a coating for the base layer, the coating comprising a primary layer comprised of chromium or a chromium alloy and having a thickness of about 5 microns to about 50 microns; cladding tube.

2. The cladding tube of claim 1 , wherein the substrate has a wall thickness of about 0.2 millimeters to about 0.6 millimeters.

3. The cladding tube of claim 1 , wherein the chromium alloy comprises yttrium, molybdenum, iron, aluminum, nitrogen, or a combination thereof.

4. the coating comprises an intermediate layer; the intermediate layer is located between the base layer and the primary layer; The cladding tube of claim 1 , wherein the intermediate layer is configured to increase the temperature at which a eutectic forms between the base layer and the primary layer.

5. The cladding tube of claim 4 , wherein the intermediate layer is composed of molybdenum, tantalum, or niobium.

6. The cladding tube of claim 4 , wherein the intermediate layer has a thickness of about 10 microns or less.

7. the coating comprises an upper layer surrounding the primary layer; The cladding tube of claim 1 , wherein the upper layer is comprised of a chromium alloy or a ceramic material.

8. The cladding tube of claim 7 , wherein the chromium alloy comprises yttrium or molybdenum.

9. The cladding tube of claim 7 , wherein the chromium alloy comprises iron and aluminum.

10. The cladding tube of claim 7 , wherein the ceramic material comprises chromium, nitrogen, niobium, or any combination thereof.

11. The cladding tube of claim 7 , wherein the top layer has a thickness of about 10 microns or less.

12. The cladding tube of claim 1 , wherein the substrate has a wall thickness of less than 0.575 millimeters.

13. The cladding tube of claim 12 , wherein the substrate has a wall thickness of about 0.5 millimeters or less.

14. A fuel rod for a nuclear reactor core, The fuel rods are A reinforced cladding tube, a substrate constructed from a zirconium alloy and having a wall thickness of about 0.2 millimeters to about 1 millimeter, the substrate defining a cavity therein; the reinforced cladding tube comprising a coating for the base layer, the coating comprising a primary layer, the primary layer being composed of chromium or a chromium alloy and having a thickness of 5 microns to 50 microns; an amount of nuclear fuel loaded in the cavity of the substrate of the reinforced cladding; Equipped with the nuclear fuel is composed of uranium-containing compounds; the uranium-containing compound is enriched to a level of about 5% or less of 235U; The amount of nuclear fuel is capable of supporting an 18-month fuel cycle at a burnup of about 68 megawatt-days / kilogram-uranium or greater. fuel rod.

15. 15. The fuel rod of claim 14, wherein the chromium alloy of the primary layer comprises yttrium, molybdenum, iron, aluminum, nitrogen, or combinations thereof.

16. The fuel rod of claim 14, wherein the substrate has a wall thickness of about 0.2 millimeters to about 0.5 millimeters.

17. 1. A method of manufacturing a fuel rod for a nuclear reactor, comprising: The method comprises: fabricating a substrate for a cladding tube of the fuel rod, the substrate being comprised of a zirconium alloy, the substrate having a wall thickness of less than 1 millimeter and defining a cavity therein; applying a coating to the substrate to produce the cladding tube, the coating comprising a primary layer, the primary layer being comprised of chromium or a chromium alloy and having a thickness of about 5 microns to about 50 microns; loading the cladding with an amount of uranium-based fuel, the uranium-based fuel being enriched to a level of about 4.95% or less, the amount of uranium-based fuel being capable of supporting an 18-month fuel cycle at a burnup of about 68 megawatt-days / kilogram-uranium or greater; A method comprising:

18. 20. The method of claim 17, wherein the primary layer of the coating is applied using a cold spray process, a thermal spray process, or a physical vapor deposition process.

19. the coating comprises an intermediate layer configured to increase the temperature of formation of a eutectic between the base layer and the primary layer; the intermediate layer is applied using a thermal spray process or a physical vapor deposition process before the primary layer is applied; 18. The method of claim 17.

20. the coating comprises an upper layer comprised of a chromium alloy or a ceramic material; the top layer is applied using a thermal spray process or a physical vapor deposition process after the primary layer is applied; 18. The method of claim 17.

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