TW202217851A - Coated fuel pellets with enhanced water and steam oxidation resistance - Google Patents

Abstract

Disclosed herein is a method comprising coating a fissile, uranium-containing ceramic material with a water-resistant layer, the layer being non-reactive with the fissile, uranium-containing ceramic material. The coating is applied to a surface of the fissile, uranium-containing ceramic material. Also disclosed is a fuel for use in a nuclear reactor.

Description

Coated fuel pellets with enhanced water and steam oxidation resistance

The present invention relates to fuels for nuclear reactors and, more particularly, to methods of improving the water resistance of nuclear fuels.

Uranium dioxide (UO2) is the main uranium compound currently used globally in nuclear fuel. Efforts to improve the safety and efficiency of light water reactors are research into alternative accident tolerant fuels. Several high-density uranium fuels have been considered for existing light water reactors. One promising fuel is uranium silicide (U3Si2) due to its high uranium density (17% higher than UO2), high thermal conductivity, and high melting temperature (1665 °C). See K.E. Metzger et al., Model of U3Si2 Fuel System Using Bison Fuel Code, Proceedings of ICAPP, April 6-9, 2014, Paper No. 14343, pp. 1-5. However, recent testing has shown that U3Si2 may suffer from certain environmental factors and additional features may be required to remedy these potential problems.

This application claims US Patent Application Serial No. 17, filed on October 7, 2020, entitled "COATED FUEL PELLETS WITH ENHANCED WATER AND STEAM OXIDATION RESISTANCE," entitled "COATED FUEL PELLETS WITH ENHANCED WATER AND STEAM OXIDATION RESISTANCE" /065,374, which is a continuation-in-part application claiming priority under 35 U.S.C. § 120 to copending U.S. Patent Application Serial No. 15/898,308 filed on February 16, 2018, claiming 2017 U.S. Provisional Patent Application Serial No. 62/472,659, filed March 17, 2009. The contents of US applications 15/898,308 and 62/472,659 are both incorporated herein by reference in their entirety, the contents of which are hereby incorporated by reference in their entirety.

This invention was made with government support under Contract No. DE-NE0008222 awarded by the Department of Energy. The US Government has certain rights in this invention.

Described herein is a method of protecting fissile material from oxidation by exposure to water or steam. It has been found that while many nuclear fuels have good water resistance at 300 °C, similar to widely used fissile materials such as UO2, the particle boundaries of many nuclear fuels are preferentially attacked by water and steam as the water temperature increases.

Recent tests indicate that these fragile fuel compositions, such as U3Si2, suffer from over-oxidation at temperatures above 360 °C and complete oxidation in a short period of time in steam below 600 °C, as shown in Figure 1. The figure shows the results of thermogravimetric analysis of U3Si2 in a water vapor atmosphere. Thermogravimetric (TG) analysis is commonly used to determine selected characteristics of a material that exhibit mass loss or gain due to, for example, decomposition or oxidation as a function of temperature. Commercially available TG analyzers continuously weigh samples while heating them to a target temperature of up to about 2000°C. As the temperature increases, the various components of the sample decompose or oxidize and the weight percent change in each resulting mass can be measured. Results are plotted as temperature on the X-axis and total mass change on the Y-axis. A significant change in mass during heating indicates that the material is no longer thermally stable. As shown in Figure 1, for a mass change of 16.87%, U3Si2 is completely oxidized to uranium oxide (UO2 and U3O8). Oxidation of fissile material can lead to significant safety concerns in design basis accidents such as coolant loss accidents and hypothetical reactive insertion accidents.

In various aspects, a method of protecting fissile material from oxidation includes coating the fissile material. Coating U3Si2 pellets or protecting U3Si2 particle boundaries, for example, will prevent pellet breakage and coolant after pellets are leaked through the cladding barrier to the fuel during reactor operation and cladding rupture occurs in design basis accident conditions Over-oxidized by high temperature steam. To improve the water and steam oxidation resistance of U3Si2 or other suitable fissile material at temperatures above 360°C, a water resistant coating is applied to the surface of the material using any suitable coating method. Exemplary coating methods include atomic layer deposition, thermal spray techniques such as plasma arc spraying and physical vapor deposition, chemical vapor deposition, electroless plating, and electroplating. The coating material may be one that will coat (ie, adhere to) the surface of the selected fissile material, be non-reactive with the fissile material, have a solubility at least as low as UO2 and preferably less than UO2, and be flexible enough to survive fission. Any material that remains substantially in place and does not peel off from U3Si2 when the material expands in use. For increased commercial viability, the coating material is preferably easy to apply. In various aspects, suitable coating materials may be selected from the group consisting of: ZrSiO4, FeCrAl, Cr, Zr, Al-Cr, CrAl, ZrO2, CeO2, TiO2, SiO2, UO2, ZrB2, Na2O-B2O3- SiO2-Al2O3 glass, Al2O3, Cr2O3, carbon, SiC, Ni, Cr, and combinations thereof.

A nuclear fuel material is also described. The material includes a fissile material such as U3Si2 coated with a water repellent layer. In various aspects, the coating layer may be selected from the group consisting of: ZrSiO4, FeCrAl, Cr, Zr, Al-Cr, CrAl, ZrO2, CeO2, TiO2, SiO2, UO2, ZrB2, Na2O-B2O3-SiO2- Al2O3 glass, Al2O3, Cr2O3, carbon, SiC, Ni, Cr, and combinations thereof.

The water-repellent coating can be located below the integral fuel flammable absorbent (IFBA) layer used to control core reactivity in nuclear reactor operation. The IFBA layer can be a thin layer of zirconium compounds such as zirconium diboride (ZrB2), boron compounds such as B2O3-SiO2 glass, and combinations of zirconium and boron compounds. See, eg, US Patent No. 4,751,041, incorporated herein by reference.

As used herein, the singular forms "a (a)," "an (an)," and "the (the)" include plural references unless the context clearly dictates otherwise. Thus, the articles "a" and "an" as used herein refer to one or more (ie, at least one) of the grammatical object of the article. For example, "an element" means one element or more than one element.

Unless expressly stated otherwise, directional phraseology used herein, such as, but not limited to, top, bottom, left, right, lower, upper, front, back, and variations thereof, shall refer to the The orientation of the elements is not intended to limit the scope of the claims.

In this application, including the claimed scope, unless otherwise indicated, all numbers indicating quantities, values or properties should be understood to be modified in all instances by the word "about". Thus, numbers may be read as if preceded by the word "about" even though the word "about" may not explicitly appear with the number. Accordingly, unless indicated to the contrary, any numerical parameters set forth in the following description may vary depending upon the desired properties sought to be obtained in the compositions and methods according to the present disclosure. At the very least, and without attempting to limit the application of the doctrine of equivalence to the scope of the claimed scope, each numerical parameter described in this specification should be construed at least in light of the number of reported significant digits and by applying ordinary rounding techniques.

Furthermore, any numerical range recited herein is intended to include all subranges subsumed therein. For example, the range "1 to 10" is intended to include any and all subranges between (and including) the recited minimum value of 1 and the recited maximum value of 10, that is, having a minimum value equal to or greater than 1 and A maximum value equal to or less than 10.

One method of forming a water-resistant boundary on fissile material for use in a water-cooled nuclear reactor includes coating the fissile material to a desired thickness with a suitable coating material. The fissile material can be any suitable fissile material. U3Si2 is an exemplary fissile material for this process, and is the preferred material in many aspects for the reasons stated above. Although the coating methods described herein can be used for other fissile materials, such as UO2 and others listed below, for convenience the fissile material may be referred to as U3Si2.

Suitable fissile material may include uranium-containing ceramic fissile material. Uranium-containing ceramic fissile material may include, for example, uranium silicide (eg, U3Si2, U3Si5, U3Si); uranium nitride (eg, UN, U15N); uranium carbide (eg, UC); uranium boride (eg, UBx, UB2) , UB4), where X-series integers (metal borides (eg, uranium boride) may have a wide variety of metal:boron ratios); uranium phosphide (eg, UP); uranium sulfide (eg, US2); uranium oxide (eg, UO2, UCO); or a mixture of any of these.

As a promising candidate for next-generation fuels, U3Si2 provides: 1. higher thermal conductivity than UO2; 2. higher uranium loading than UO2; and 3. allows the fuel to be maintained under normal operating and transient conditions of light water reactors The melting temperature of the solid state. To address the poor water resistance of U3Si2 at higher temperatures (eg, 360 °C and above), in various aspects, a water resistant coating can be applied to one or both of the U3Si2 pellets and the U3Si2 particle boundaries, which will Preventing, or at least substantially slowing, U3Si2 contact with water, and thus improving the water resistance of the fuel pellets in the event of leakage of the fuel coating.

In various aspects, the coating material should form a robust coating over at least exposed portions of the fissile material, such as on pellet and particle boundaries. The term "robust coating" as used herein refers to a coating that has low solubility in coolant, is easy to apply, does not react with the selected fissile material, and has some flexibility as the pellet expands during irradiation. "Low solubility" as used herein is a relative term and for the purposes of this application means that the coating material has a solubility at least as low as that of UO2 (when UO2 is used as the fissile material), and in various aspects less soluble The solubility of UO2 is low.

The coating material may be any material that will coat (ie adhere to) the surface of the selected fissile material and will not react with the fissile material. As stated, the coating material in various aspects has a solubility at least as good as that of UO2, and preferably a solubility lower than that of UO2. Solubility values for UO2 are available in the literature.

In various aspects, the coating material is sufficiently flexible to substantially remain in place when the fissile material expands in use. Those skilled in the art understand that fissile materials expand in use by splitting, the original atoms forming two atoms of the material having a lower density than the original atoms. In addition, gas can be trapped at particle boundaries, which will cause more expansion. Those skilled in the art can roughly calculate the degree of expansion, but the expansion calculation prior to use in the reactor may be inaccurate due to trapped gas. The coating should be sufficiently flexible to avoid delamination as the fissile material expands. However, some deviation may be tolerated to allow for cracked or delaminated portions in the coating as the fissile material expands. In such cases, the coating still functions to reduce exposure of the fissile material to water or steam, thereby slowing oxidation and increasing the effective life of the fissile material. Reducing the rate of oxidation of fissile material in conditions of exposure to water or steam will allow time for corrective action in accident conditions beyond the design basis.

In various aspects, suitable coating materials may be selected from the group consisting of: ZrSiO4, FeCrAl, Cr, Zr, Al-Cr, CrAl, ZrO2, CeO2, TiO2, SiO2, UO2, ZrB2, Na2O-B2O3- SiO2-Al2O3 glass, Al2O3, Cr2O3, carbon, SiC, Cr, Ni, and combinations thereof. Coating of U3Si2 particles can be achieved by adding FeCrAl, CrAl, or Na2O-B2O3-SiO2-Al2O3 glass solids to U3Si2 powder at a temperature lower than that of U3Si2 (1662 °C) but at the sintering temperature of U3Si2 pellets (1200 to 1600 °C). °C) to complete melting. In various aspects, the coating can be formed by depositing particles selected from the group consisting of: ZrSiO4, FeCrAl, Cr, Zr, Al-Cr, CrAl, ZrO2, CeO2, TiO2, SiO2, UO2, ZrB2, Na2O- B2O3-SiO2-Al2O3 glass, Al2O3, Cr2O3, carbon, SiC, Ni, Cr, and combinations thereof. Each of these materials has better water resistance than U3Si2. Coatings can be applied to the perimeter, or sides, surfaces, and top and bottom surfaces of each U3Si2 pellet as appropriate. The fuel pellets can be of any shape and references to perimeter or other surface contours are for convenience and not limitation. In use, the fuel pellets are generally in the form of generally cylindrical pellets that are stacked on the ends to form a generally cylindrical post that is held against the end plug of the fuel rod by a spring positioned between the top pellet and the fuel rod. The top end of the stick between the top end of the pill stack. In this configuration, the top and bottom of the pellet are not exposed to any water that could leak into the fuel rods. Any exposure to oxidizing fluids will be minimal, if any.

For increased commercial viability, the coating material is preferably easy to apply. The coating step used in the method can be any suitable coating process. For example, coating can be performed by a physical vapor deposition process or by atomic layer deposition (ALD). The coating process can, for example, be a thermal spray process, such as a thermal or cold spray process or a plasma arc spray process.

Atomic layer deposition (ALD) is a thin film deposition method in which films are grown on a substrate by exposing the surface of the substrate to alternating gaseous species. ALD is based on the sequential use of gas phase chemical processes. Most ALD reactions use two chemicals, called precursors. These precursors react one by one with the surface of the material in a sequential, self-limiting manner such that the reaction terminates once all reactive sites on the surface are consumed. Therefore, the maximum amount of material deposited on the surface after a single exposure to all precursors (so-called ALD cycle) is determined by the nature of the precursor-surface interaction. Thin films are slowly deposited by repeated exposure to individual precursors. By varying the number of cycles, material can be grown uniformly and with high precision on arbitrarily complex and large substrates. In contrast to chemical vapor deposition, the precursors are never simultaneously present in the deposition chamber, but are instead inserted as a series of sequential, non-overlapping pulses. In ALD, a water resistant coating will be grown on the surface of the U3Si2 pellets by exposing the U3Si2 pellets to a gaseous precursor of the desired coating material.

The precursor selected for deposition also includes a carrier gas. The temperature used in deposition may be in the range of 25°C to 600°C, preferably 200°C to 450°C, and more preferably 265°C to 350°C, or other temperatures having any of the foregoing ranges. Temperatures above 600°C should be avoided.

Alternatively, deposition of the coating may be by sputtering or chemical vapor deposition. In a typical chemical vapor deposition process, the substrate is exposed to one or more reactive precursors, which react and/or decompose on the surface of the substrate to produce the desired deposits. By-products are also often produced, which are removed by gas flow through the reaction chamber.

In various aspects, suitable thermal deposition methods include thermal spray or cold spray methods. In the thermal spraying process, the coating raw material is melted by a heat source or by a plasma generated by a high frequency electric arc between an anode and a tungsten cathode (ie, plasma arc spraying). This softened liquid or molten material is then delivered by the process gas and will be sprayed on the surface of the U3Si2 pellets. This material solidified and formed a solid layer on the surface of the U3Si2 pellets.

Cold spray methods can be performed by delivering the carrier gas to a heater where the carrier gas is heated to a temperature sufficient to maintain the gas at a desired temperature (eg, 100°C to 1200°C) after expansion as the gas passes through the nozzle. In various aspects, the carrier gas can be preheated to a temperature between 200°C and 1200°C at a pressure of, for example, 5.0 MPa. In some aspects, the carrier gas may be preheated to a temperature between 200°C and 1000°C, or in some aspects, between 300°C and 900°C, and in other aspects, between Between 500 °C and 800 °C. The temperature will depend on the Joule-Thomson cooling coefficient of the particular gas used as the carrier. Whether or not a gas cools as it expands or compresses under pressure changes depends on the value of its Joule-Thomson coefficient. For a positive Joule-Thomson coefficient, the carrier gas is cooled and must be preheated to prevent excessive cooling that can affect the performance of the cold spray process. Those skilled in the art can use well-known calculations to determine the degree of heating to prevent excessive cooling. See, for example, for N2 as the carrier gas, the Joule-Thomson coefficient is 0.1°C/bar if the inlet temperature is 130°C. For the gas to affect the tube at 130°C, such as its initial pressure is 10 bar (~146.9 pounds per square inch absolute (psia)) and the final pressure is 1 bar (~14.69 pounds per square inch absolute (psia)) ), the gas needs to be preheated to about 9 bar * 0.1 °C/bar or about 0.9 °C to about 130.9 °C.

For example, the temperature of the helium gas as the carrier is preferably 450°C under the pressure of 3.0 to 4.0 MPa, and the temperature of the nitrogen gas as the carrier may be 1100°C under the pressure of 5.0 MPa, but can also be set at 3.0 to 600 ℃ – 800 ℃ under the pressure of 4.0 MPa. Those skilled in the art will know that temperature and pressure variables can vary depending on the type of equipment used and that equipment can be modified to adjust temperature, pressure and volume parameters.

Suitable carrier gas systems are those that are inert or non-reactive, and in particular those that will not react with the particles or the substrate. Exemplary carrier gases include nitrogen (N2), hydrogen (H2), argon (Ar), carbon dioxide (CO2), and helium (He).

There is significant elasticity with respect to the selected carrier gas. Mixtures of gases can be used. The choice is determined by physics and economics. For example, lower molecular weight gases provide higher velocities, but the highest velocities should be avoided as they can cause particle bounce and thus reduce the number of deposited particles.

The cold spray process relies on controlled expansion of a heated carrier gas to propel particles onto the substrate. The particles impact the substrate or previously deposited layers and undergo plastic deformation by adiabatic shear. Subsequent particle impacts accumulate to form a coating. The particles may also be heated to a temperature of one-third to one-half the melting point of the powder in degrees Kelvin before entering the flowing carrier gas. The nozzle scans (ie, sprays in a pattern where an area is sprayed from side to side in a line from top to bottom) across the area to be coated or where material accumulation is desired.

Referring to Figure 3, a thermal spray assembly 10 is shown. Assembly 10 includes heater 12 , powder or particle hopper 14 , gun 16 , nozzle 18 , and delivery conduits 34 , 26 , 32 and 28 . High pressure gas enters conduit 34 for delivery to heater 12 where heating occurs rapidly, substantially immediately. When heated to the desired temperature, the gas is directed through conduit 26 to gun 16 . Particles held in hopper 14 are released and directed through conduit 28 to gun 16 where they are forced through nozzle 18 towards substrate 22 by means of a jet of pressurized gas 20 . The sprayed particles 36 are deposited on the substrate 22 to form a coating comprising the particles 24 . This process generally describes the cold spray and hot spray assemblies. The thermal spray process occurs at a temperature high enough to soften or melt the deposited particles.

In various aspects, alternative coating methods include plasma arc spray processes, such as that shown in FIG. 4 . The plasma torch 40 produces a jet of hot gas 50 . A typical plasma torch 40 includes a gas port 56 , a cathode 44 , an anode 46 , and a water cooling nozzle 42 , all surrounded by an insulator 48 in a housing 68 . A high frequency arc is ignited between the electrodes, ie between the anode 46 and the tungsten cathode 44 . The carrier gas flowing through the port 56 between the electrodes 44/46 dissociates to form a plasma plume. The carrier gas can be helium (He), hydrogen (H2), nitrogen (N2), or any combination thereof. The jet 50 is produced by an electric arc that heats the gas as the pressurized gas expands through the nozzle 42 . The heated gas forms, for example, an arc plasma core operating at 12,000°C to 16,000°C. The gas expands through the water cooling nozzles 42 as jets 50 . The powder, or particles, are ejected through port 52 as thermal jet 50 where it is softened or melted and pressed against substrate 60 to form coating 54 . The spray rate can be, for example, 2 to 10 kg/hour below a particle velocity of about 450 m/s or less. Coating thicknesses achieved by thermal spraying, such as plasma arc spraying, vary depending on the material being sprayed, but can range, for example, from 0.005 to 5 mm. Typical thicknesses of the coatings described herein may be 5 to 1000 microns, and in various aspects, the thickness of the coatings may be 10 to 100 microns.

The thickness of the water repellent coating varies from 10 microns to 200 microns for plasma arc spray coated coatings, and from 1 to 20 microns for physical vapor deposition coatings and from 0.5 microns for ALD to 2 microns. Coating materials include ZrSiO4, FeCrAl, Cr, Zr, Al-Cr, CrAl, ZrO2, CeO2, TiO2, SiO2, UO2, ZrB2, Na2O-B2O3-SiO2-Al2O3 glass, Al2O3, Cr2O3, carbon, and SiC, and their combination. U3Si2 has less cracking in operation than UO2 due to the much higher thermal conductivity. Even if cracking occurs, the coating can still cover the substantial surface area of the U3Si2 pellets to prevent excessive oxidation.

Water resistant coatings can also be applied via electroless plating techniques. Electroless plating coating techniques may include immersing the object to be coated (eg, substrate, fissile material) in a chemical bath containing metal cations. The metal cations can be chemically reduced to form a metallic coating on the substrate. Reduction can be accomplished by autocatalytic reaction between metal cations and reducing agents such as hypophosphite and/or borohydride. The chemical bath may also contain one or more of the following: complexing agents (to increase phosphate solubility and/or slow down the reaction), stabilizers (to slow reduction through co-deposition with reduced metals), buffers ( To maintain the acidity of the bath), brighteners (to improve surface gloss), surfactants (to keep the deposited layer hydrophilic to reduce pitting and staining), and accelerators (to counteract the effects of The resulting reduction in plating rate). The substrate surface can be activated prior to the electroless plating process to ensure that the autocatalytic reduction process can be performed.

When the electroless plating coating technique is employed, the water resistant coating may comprise metallic nickel (Ni) and/or metallic chromium (Cr). Thus, the metal cations in the chemical bath may comprise one or both of Ni cations or Cr cations. Water resistant coatings can be applied to any of the fissile materials of the present disclosure using electroless plating coating techniques.

The water-resistant coating applied to the fissile material of the present disclosure by electroless plating coating techniques may comprise a thickness of 5 microns to 20 microns, such as, for example, 5 microns to 15 microns, 5 microns to 10 microns, 10 microns to 20 microns microns, 10 microns to 15 microns, or 15 microns to 20 microns. Referring to FIG. 2 described below, the water-resistant coating 74 may also include Ni and/or Cr as previously described.

Water resistant coatings can also be applied by electroplating techniques. Electroplating coating techniques can include the generation of water-repellent metal coatings on objects to be coated (eg, substrates, fissile materials) via reduction of metal cations by direct current. The metal cation can be reduced to form a metallic coating on the substrate. The substrate can act as the cathode of the electrolytic cell, and the anode can include the metal and/or inert conductive material to be applied as a coating. The electrolyte solution can be contacted with the substrate and can include a salt solution containing the metal cations to be reduced and coated on the substrate. The substrate may be conductive.

When electroplating coating techniques are employed, the water resistant coating may include metallic nickel (Ni) and/or metallic chromium (Cr). Thus, the metal cations in the electrolyte solution may comprise one or both of Ni cations or Cr cations. A water-resistant coating can be applied to any of the fissile materials of the present disclosure using electroplating coating techniques. The fissile material may include conductive fissile material.

The water-resistant coating applied to the fissile material of the present disclosure by electroless plating coating techniques may comprise a thickness of 1 to 20 microns, such as, for example, 1 to 5 microns, 2 to 20 microns, 3 to 20 microns microns, 4 microns to 20 microns, 5 microns to 20 microns, 5 microns to 15 microns, 5 microns to 10 microns, 10 microns to 20 microns, 10 microns to 15 microns, or 15 microns to 20 microns. Referring to FIG. 2 described below, the water-resistant coating 74 may also include Ni and/or Cr as previously described.

In addition, the flammable absorbent can also be coated on the peripheral surface of the coated U3Si2 pellets by using an ALD process or a thermal spray process. The bulk fuel combustible absorbent may be a zirconium compound (such as zirconium diboride (ZrB2)), a boron compound (such as B2O3-SiO2 glass), and combinations of zirconium compounds and boron compounds. See, eg, US Patent No. 4,751,041, incorporated herein by reference.

Combustible absorbents are a type of combustible poison used to control the core reactivity in nuclear reactor operation. These combustible absorbents provide temporary reactivity control that is effective primarily during the beginning of the reactor cycle and compensate for the excess reactivity that occurs early in the cycle due to fresh fuel loading. The layer of combustible absorbent material is applied after applying the water-repellent layer so that it covers the water-repellent coating layer.

Oxidation of U3Si2 is a potential safety concern and one of the key issues for implementing U3Si2 fuels in light water reactors. Coating on U3Si2 will slow oxidation especially at higher steam temperatures and is one of the economical ways to address potential safety concerns.

Methods as described herein produce coated fissile material, such as the coated fuel pellets shown in FIG. 2 . A plurality of pellets are typically stacked in the fuel rod 70 . The fissile material 72 in various aspects comprises U3Si2 coated with a water repellent layer 74 selected from the group consisting of: ZrSiO4, FeCrAl, Cr, Zr, Al-Cr, CrAl, ZrO2, CeO2, TiO2, SiO2, UO2 , ZrB2, Na2O-B2O3-SiO2-Al2O3 glass, Al2O3, Cr2O3, carbon, SiC, Ni, Cr, and combinations thereof. The fuel pellet may also include a cover layer 76 of combustible absorbent material such as zirconium diboride (ZrB2), boron compounds (such as B2O3-SiO2 glass), and combinations of zirconium and boron compounds. A gas-filled, such as helium, gas-filled gap 78 may exist between the capping layer 76 and the fuel capping layer 80 . The exterior of the cladding 80 is surrounded by a coolant 82 (usually the water in the water cooling reactor).

Various aspects of the subject matter described in this specification are illustrated in the following examples.

Embodiment 1 - A method comprising: coating a fissile, uranium-containing ceramic material with a water-resistant layer that does not react with the fissile, uranium-containing ceramic material, wherein the coating is applied to the fissile, uranium-containing ceramic material the surface of the material.

Embodiment 2 - The method described in Embodiment 1, wherein the fissile, uranium-containing ceramic material comprises uranium silicide, uranium nitride, uranium carbide, uranium boride, uranium phosphide, uranium sulfide, uranium oxide, or a combination thereof.

Embodiment 3 - The method of Embodiment 1 or 2, wherein the fissionable, uranium-containing ceramic material comprises U3Si2, U3Si5, U3Si, UN, U15N, UC, UB2, UB4, UP, US2, UO2, UCO, or the like combination.

Embodiment 4 - The method of any of Embodiments 1-3, wherein the fissionable, uranium-containing ceramic material is in pellet form.

Embodiment 5 - The method of any one of Embodiments 1 to 4, wherein the water repellent layer is selected from the group consisting of: ZrSiO4, FeCrAl, Cr, Zr, Al-Cr, CrAl, ZrO2, CeO2, TiO2 , SiO2, UO2, ZrB2, Na2O-B2O3-SiO2-Al2O3 glass, Al2O3, Cr2O3, carbon, SiC, Ni, Cr, and combinations thereof.

Embodiment 6 - The method of any of embodiments 1-5, wherein the coating is applied by atomic layer deposition.

Embodiment 7 - The method of any of Embodiments 1-5, wherein the coating is applied by an electroless plating coating technique.

Embodiment 8 - The method of any of embodiments 1-5, wherein the coating is applied by a thermal spray process.

Embodiments 9 - The method described in Embodiment 8, wherein the thermal spray process is physical vapor deposition.

Embodiment 10 - The method of any of Embodiments 1-5, wherein the coating is applied by an electroplating coating technique, and wherein the fissile, uranium-containing ceramic material is conductive.

Embodiment 11 - The method described in Embodiment 8, wherein the thermal spraying process is plasma arc spraying.

Embodiment 12 - The method described in Embodiment 11, wherein the thickness of the coating is 1 micron to 200 microns.

Embodiment 13 - The method described in Embodiment 8, wherein the thermal spray process is a cold spray process.

Embodiment 14 - The method described in Embodiment 8, wherein the thermal spray process is a thermal spray process.

Embodiment 15 - The method of any one of Embodiments 1-14, further comprising applying a layer of a combustible absorbent over the water repellent layer.

Embodiment 16 - The method described in Embodiment 15, wherein the combustible absorbent is selected from the group consisting of ZrB2, B2O3-SiO2 glass, and combinations thereof.

Example 17 - A fuel for use in a nuclear reactor comprising: a fissile, uranium-containing ceramic material coated with a water-resistant layer, wherein the coating is applied to the surface of the fissile, uranium-containing ceramic material.

Embodiment 18 - The fuel described in Embodiment 17, wherein the water resistant layer is selected from the group consisting of ZrSiO4, FeCrAl, Cr, Zr, Al-Cr, CrAl, ZrO2, CeO2, TiO2, SiO2, UO2, ZrB2, Na2O-B2O3-SiO2-Al2O3 glass, Al2O3, Cr2O3, carbon, SiC, Ni, Cr and combinations thereof.

Embodiment 19 - The fuel of any one of Embodiments 17-18, wherein the fissile, uranium-containing ceramic material comprises uranium silicide, uranium nitride, uranium carbide, uranium boride, uranium phosphide, uranium sulfide, uranium oxide , or a combination thereof.

Embodiment 20 - The fuel of any one of embodiments 17-19, wherein the fissionable, uranium-containing ceramic material comprises U3Si2, U3Si5, U3Si, UN, U15N, UC, UB2, UB4, UP, US2, UO2, UCO , or a combination thereof.

Embodiment 21 - The fuel of any one of Embodiments 17-20, further comprising an integral fuel combustible absorbent layer over the water-resistant layer for controlling core reactivity in nuclear reactor operation.

Embodiment 22 - The fuel of Embodiment 21, wherein the absorber layer is selected from the group consisting of ZrB2, B2O3-SiO2 glass, and combinations thereof.

The present invention has been described in terms of several embodiments, which are intended in all aspects to be illustrative and not restrictive. Accordingly, the invention is capable of many variations in detailed implementation, which can be derived by those skilled in the art from the description contained herein.

All patents, patent applications, publications, or other disclosed materials mentioned herein are hereby incorporated by reference in their entirety, as if each individual reference were individually expressly incorporated by reference. All references herein incorporated by reference and any material or portion thereof are said to be incorporated by reference only to the extent that the incorporated material does not contradict existing definitions, statements or other disclosed material set forth in this disclosure in this article. Accordingly, and to the extent necessary, the disclosure as set forth herein supersedes any conflicting material incorporated herein by reference and the disclosure expressly set forth in the comparison of this application.

The present invention has been described with reference to various illustrative and illustrative specific examples. The embodiments described herein are to be understood as providing illustrative features of various details of the various embodiments of the invention; and, therefore, unless otherwise specified, it is to be understood that, where possible, one or more of the disclosed embodiments A feature, element, component, component, composition, structure, module, and/or aspect may be combined with or relative to one or more of the other features, elements, components, components, components, structures, modules, and/or aspects of the disclosed embodiments. Groups and/or aspects may be combined, separated, interchanged and/or reconfigured without departing from the scope of the present invention. Accordingly, those of ordinary skill in the art will recognize that various substitutions, modifications, or combinations of any of the illustrative embodiments can be made without departing from the scope of the invention. Furthermore, those skilled in the art will recognize, or be able to ascertain using no more than routine experimentation, after reviewing this specification, many equivalents to the various embodiments of the invention described herein. Therefore, the present invention is not limited by the description of various specific examples, but is limited by the scope of the patent application.

10: Thermal spray assembly 12: Heater 14: Powder or particle hopper 16: Gun 18: Nozzle 20: Pressurized gas jet 22: Substrate 24: Particles 26: Delivery catheter 28: Delivery catheter 32: Delivery catheter 34: Delivery catheter 36: Sprayed particles 40: Plasma Torch 42: Water cooling nozzle 44: Cathode 46: Anode 48: Insulator 50: Hot Gas Jet 52: port 54: Coating 56: Gas port 60: Substrate 68: Shell 70: Fuel rods 72: Fissile material 74: Water resistant coating 76: Overlay 78: Gap 80: fuel cladding 82: Coolant

The features and advantages of the present disclosure may be better understood by reference to the accompanying drawings.

Figure 1 is a thermogravimetric (TG) analysis of U3Si2 pellets in which the mass increase of U3Si2 pellets in a water vapor atmosphere with a heating rate of 2.5°C/min was measured as a function of temperature.

2 is a schematic diagram of a cross-section of an exemplary fuel pellet in a fuel rod showing the relative positions of the protective coating layer and the fuel burner absorbent layer.

3 is a schematic diagram of an exemplary thermal deposition spray process.

4 is a schematic diagram of an exemplary plasma arc process.

70: Fuel rods

72: Fissile material

74: Water resistant coating

76: Overlay

78: Gap

80: fuel cladding

82: Coolant

Claims (22)

A method that includes: The fission, uranium-containing ceramic material is coated with a water-resistant layer, and the layer does not react with the fission, uranium-containing ceramic material, Wherein the coating is applied to the surface of the fission, uranium-containing ceramic material. The method of claim 1, wherein the fissile, uranium-containing ceramic material comprises uranium silicide, uranium nitride, uranium carbide, uranium boride, uranium phosphide, uranium sulfide, uranium oxide, or combinations thereof. The method of claim 2, wherein the fissionable, uranium-containing ceramic material comprises U3Si2, U3Si5, U3Si, UN, U15N, UC, UB2, UB4, UP, US2, UO2, UCO, or a combination thereof. The method of claim 1, wherein the fissile, uranium-containing ceramic material is in pellet form. The method of claim 1, wherein the water-repellent layer is selected from the group consisting of ZrSiO4, FeCrAl, Cr, Zr, Al-Cr, CrAl, ZrO2, CeO2, TiO2, SiO2, UO2, ZrB2, Na2O-B2O3- SiO2-Al2O3 glass, Al2O3, Cr2O3, carbon, SiC, Ni, Cr, and combinations thereof. The method of claim 1, wherein the coating is applied by atomic layer deposition. The method of claim 1, wherein the coating is applied by an electroless plating coating technique. The method of claim 1, wherein the coating is applied by a thermal spray process. The method of claim 8, wherein the thermal spray process is physical vapor deposition. The method of claim 1, wherein the coating is applied by an electroplating coating technique, and wherein the fissile, uranium-containing ceramic material is conductive. The method of claim 8, wherein the thermal spraying process is plasma arc spraying. The method of claim 11, wherein the thickness of the coating is 1 to 200 microns. The method of claim 8, wherein the thermal spray process is a cold spray process. The method of claim 8, wherein the thermal spray process is a hot spray process. The method of claim 1, further comprising applying a layer of a combustible absorbent over the water repellent layer. The method of claim 15, wherein the combustible absorbents are selected from the group consisting of ZrB2, B2O3-SiO2 glass, and combinations thereof. A fuel for use in a nuclear reactor, comprising: Fission, uranium-containing ceramic materials coated with a water-resistant layer, Wherein the coating is applied to the surface of the fission, uranium-containing ceramic material. The fuel of claim 17, wherein the water-repellent layer is selected from the group consisting of ZrSiO4, FeCrAl, Cr, Zr, Al-Cr, CrAl, ZrO2, CeO2, TiO2, SiO2, UO2, ZrB2, Na2O-B2O3- SiO2-Al2O3 glass, Al2O3, Cr2O3, carbon, and SiC, and combinations thereof. The fuel of claim 17, wherein the fissile, uranium-containing ceramic material comprises U3Si2, U3Si5, U3Si, UN, U15N, UC, UB2, UB4, UP, US2, UO2, UCO, or a combination thereof. The fuel of claim 17, wherein the fissile, uranium-containing ceramic material comprises uranium silicide, uranium nitride, uranium carbide, uranium boride, uranium phosphide, uranium sulfide, uranium oxide, or combinations thereof. The fuel of claim 17, further comprising an integral fuel combustible absorbent layer over the water-resistant layer for controlling core reactivity in nuclear reactor operation. The fuel of claim 21, wherein the absorbent layer is selected from the group consisting of ZrB2, B2O3-SiO2 glass, and combinations thereof.

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