Methods of making trivalent chlorides of lanthanide and actinide metals

Abstract

A method of making a trivalent chloride of an f-block metal can include introducing reactants including a solid f-block metal or hydride thereof and solid NH4CI into a reaction vessel (110). The reactants can be heated in a first phase to a reaction temperature from about 200 °C to about 400 °C to form an ammonium-metal chloride double salt (120). The ammonium-metal chloride double salt can be heated in a second phase to a decomposition temperature greater than about 600 °C to decompose the ammonium-metal chloride double salt, thereby forming a trivalent chloride of the f-block metal (130).

Description

[0001] METHODS OF MAKING TRIVALENT CHLORIDES OF LANTHANIDE AND ACTINIDE METALS

[0002] CROSS REFERENCE TO RELATED APPLICATIONS

[0003] This application claims priority to U.S. Provisional Application No. 63 / 779,601, filed March 28, 2025, which is hereby incorporated herein by reference.

[0004] STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

[0005] Not applicable.

[0006] BACKGROUND

[0007] As electrical power demand for both industry and the public continue to increase, a new generation of nuclear reactors is expected to help support demand for electricity. Uranium trichloride (UCh) is a candidate fissile chemical species for a class of advanced nuclear reactors fueled by molten salts. One example of this class of reactors is the Molten Chloride Fast Reactor (MCFR). One benefit of chloride compounds compared to fluoride compounds in a molten salt reactor is that chloride salts can be used with a fast neutron spectrum that bums minor actinides as well as U-235 and Pu-239. This is useful for efficient breeding and waste reduction processes. If accumulation of long-lived actinides can be minimized, molten salt reactors offer a promising way to produce nuclear energy that is sustainable and safe for the environment.

[0008] SUMMARY

[0009] Methods of making trivalent chlorides of an f-block metal (i.e. lanthanide or actinide metal) are described. In one example, a method can include introducing reactants comprising a solid f-block metal or hydride thereof, and solid NH4CI into a reaction vessel. The reactants can be heated in a first phase to a reaction temperature from about 200 °C to about 400 °C to form an ammonium-metal chloride double salt. The ammonium-metal chloride double salt can be heated in a second phase to a decomposition temperature greater than about 600 °CPCT PATENT APPLICATION Attorney Docket No. 00846-U8828.PCT to decompose the ammonium-metal chloride double salt, thereby forming a trivalent chloride of the f-block metal.

[0010] An example system for making a trivalent chloride of an f-block metal can include a reaction vessel. A solid f-block elemental metal or hydride thereof can be within the reaction vessel. A solid NH4CI can also be in the reaction vessel. A heater can be associated with the reaction vessel and operable to heat the reaction vessel to at least a reaction temperature and a decomposition temperature. The reaction temperature can be a temperature from about 200 °C to about 400 °C at which the solid hydride of the lanthanide or actinide metal reacts with the solid NH4CI to form an ammonium-metal chloride double salt. The decomposition temperature can be a temperature greater than about 600 °C at which the ammonium-metal chloride double salt decomposes, thereby forming a trivalent chloride of the f-block metal.

[0011] There has thus been outlined, rather broadly, features of the invention so that the detailed description thereof that follows may be better understood, and so that the present contribution to the art may be better appreciated. Other features of the present invention will become clearer from the following detailed description of the invention, taken with the accompanying drawings and claims, or may be learned by the practice of the invention.

[0012] BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a flowchart illustrating an example method of making a trivalent chloride of a lanthanide or actinide metal, in accordance with the present disclosure.

[0013] FIG. 2 is a schematic view of an example system for making trivalent chlorides of lanthanide or actinide metals, in accordance with the present disclosure.

[0014] FIG. 3 is a schematic view of another example system for making trivalent chlorides of lanthanide or actinide metals, in accordance with the present disclosure.

[0015] FIG. 4 is a schematic view of an example hydriding system, in accordance with the present disclosure.

[0016] FIG. 5 is a schematic view of an example system for making trivalent chlorides of lanthanide or actinide metals, in accordance with the present disclosure.

[0017] FIG. 6 is a graph of heating profiles corresponding to step 1, in accordance with the present disclosure.PCT PATENT APPLICATION Attorney Docket No. 00846-U8828.PCT FIG. 7 shows XRD spectra of reaction products, in accordance with the present disclosure.

[0018] FIG. 8 shows XRD spectra of reaction products, in accordance with the present disclosure.

[0019] FIG. 9 shows XRD spectra of reaction products, in accordance with the present disclosure.

[0020] FIG. 10 shows XRD spectra of reaction products, in accordance with the present disclosure.

[0021] FIG. 11 is a graph of temperature vs. time of a metal hydride reaction product, in accordance with the present disclosure.

[0022] FIG. 12 shows an XRD spectrum of uranium hydride, in accordance with the present disclosure.

[0023] FIG. 13 shows XRD spectra of reaction products, in accordance with the present disclosure.

[0024] FIG. 14 shows TGA / DSC results of reaction products, in accordance with the present disclosure.

[0025] FIGs. 15 and 16 are SEM images of reaction products, in accordance with the present disclosure.

[0026] FIG. 17 shows XRD spectra of reaction products, in accordance with the present disclosure.

[0027] FIG. 18 shows XRD spectra of reaction products, in accordance with the present disclosure.

[0028] FIG. 19 shows XRD spectra of reaction products, in accordance with the present disclosure.

[0029] FIG. 20 shows XRD spectra of reaction products, in accordance with the present disclosure.

[0030] These drawings are provided to illustrate various aspects of the invention and are not intended to be limiting of the scope in terms of dimensions, materials, configurations, arrangements or proportions unless otherwise limited by the claims.PCT PATENT APPLICATION Attorney Docket No. 00846-U8828.PCT DETAILED DESCRIPTION

[0031] While these exemplary embodiments are described in sufficient detail to enable those skilled in the art to practice the invention, it should be understood that other embodiments may be realized and that various changes to the invention may be made without departing from the spirit and scope of the present invention. Thus, the following more detailed description of the embodiments of the present invention is not intended to limit the scope of the invention, as claimed, but is presented for purposes of illustration only and not limitation to describe the features and characteristics of the present invention, to set forth the best mode of operation of the invention, and to sufficiently enable one skilled in the art to practice the invention. Accordingly, the scope of the present invention is to be defined solely by the appended claims.

[0032] Definitions

[0033] In describing and claiming the present invention, the following terminology will be used.

[0034] The singular forms “a,” “an,” and “the” include plural referents unless the context clearly dictates otherwise. Thus, for example, reference to “a reactant” includes reference to one or more of such materials and reference to “the vessel” refers to one or more of such structures.

[0035] As used herein with respect to an identified property or circumstance, “substantially” refers to a degree of deviation that is sufficiently small so as to not measurably detract from the identified property or circumstance. The exact degree of deviation allowable may in some cases depend on the specific context.

[0036] As used herein, the term “about” is used to provide flexibility and imprecision associated with a given term, metric or value. The degree of flexibility for a particular variable can be readily determined by one skilled in the art. However, unless otherwise enunciated, the term “about” generally connotes flexibility of less than 2%, and most often less than 1%, and in some cases less than 0.01%.

[0037] As used herein, a plurality of items, structural elements, compositional elements, and / or materials may be presented in a common list for convenience. However, these lists should be construed as though each member of the list is individually identified as a separate and unique member. Thus, no individual member of such list should be construed as a dePCT PATENT APPLICATION Attorney Docket No. 00846-U8828.PCT facto equivalent of any other member of the same list solely based on their presentation in a common group without indications to the contrary.

[0038] As used herein, the term “at least one of’ is intended to be synonymous with “one or more of.” For example, “at least one of A, B and C” and “at least one of A, B, or C” explicitly include only A, only B, only C, or combinations of each.

[0039] Numerical data may be presented herein in a range format. It is to be understood that such range format is used merely for convenience and brevity and should be interpreted flexibly to include not only the numerical values explicitly recited as the limits of the range, but also to include all the individual numerical values or sub-ranges encompassed within that range as if each numerical value and sub-range is explicitly recited. For example, a numerical range of about 1 to about 4.5 should be interpreted to include not only the explicitly recited limits of 1 to about 4.5, but also to include individual numerals such as 2, 3, 4, and subranges such as 1 to 3, 2 to 4, etc. The same principle applies to ranges reciting only one numerical value, such as “less than about 4.5,” which should be interpreted to include all of the above-recited values and ranges. Further, such an interpretation should apply regardless of the breadth of the range or the characteristic being described.

[0040] Any steps recited in any method or process claims may be executed in any order and are not limited to the order presented in the claims. Means-plus-function or step-plus- function limitations will only be employed where for a specific claim limitation all of the following conditions are present in that limitation: a) “means for” or “step for” is expressly recited; and b) a corresponding function is expressly recited. The structure, material or acts that support the means-plus function are expressly recited in the description herein. Accordingly, the scope of the invention should be determined solely by the appended claims and their legal equivalents, rather than by the descriptions and examples given herein. Methods of Making Trivalent Chlorides of Lanthanide or Actinide Metals

[0041] The methods described herein can be used to prepare trivalent chlorides of f-block metals (i.e. lanthanide or actinide metals). Trivalent chlorides include compounds that include a metal atom bound to three chlorine atoms. As mentioned above, uranium trichloride (UCI3) is the trivalent chloride of uranium, an actinide metal, which is useful in some molten salt nuclear reactors. The trivalent chlorides of other lanthanide and actinide metals can also be useful, whether to be used in molten salt nuclear reactors or in other applications. UraniumPCT PATENT APPLICATION Attorney Docket No. 00846-U8828.PCT is referred to herein as an example, but it is noted that the methods for making UCI3 can be applied to making trivalent chlorides of other lanthanide and actinide metals as well. Nonlimiting examples of suitable lanthanide and actinide metal chlorides can include UCI3, PuCl3, AmCh, NpCh, CmCh, CeCl3, NdCl3, LaCl3, and PrCl3.

[0042] Current reported methods for synthesis of UCI3 have been demonstrated both with and without the use of a molten salt reaction medium. The use of a molten salt allows easier control of the redox potential of the system to prevent the formation of UCI4, UCI5, or even UC16. Chlorination reactions in a molten salt have been demonstrated starting with U metal using several chlorinating agents such as FeCh, BiCh, and ZnCh. These methods may present difficulty in separating the metal by-products (Fe, Bi, Zn, etc.). Additionally, it is not possible to separate the UCI3 from the molten salt medium used after the chlorination has been completed. Production of pure UCI3 is attractive for maximizing flexibility of the fuel salt composition, as it can be blended with other salts at pre-determined ratios.

[0043] To limit contamination and produce pure, solid uranium chloride, gaseous agents such as Ch and HC1 can be reacted directly with U metal or alloy. For example, chlorination of uranium-aluminium alloy using both HC1 and CI2 gas has been reported. But the resulting chemical form of the uranium chloride was UCI4, which is significantly more corrosive than UCI3.

[0044] Hamilton et. al. reported formation of UCI3 starting with U metal and reacting with HC1 gas. Their process involved two steps, in which the first step was hydriding of the uranium metal in order to increase surface area and improve the kinetics of the chlorination reaction. Auto-brecciating occurs during the uranium hydriding process. The solid uranium pellet becomes a powder because of density differences between metal and hydride solid phases (Reaction 1). The second step was chlorination through Reaction 2 by flowing hydrogen chloride gas through the bed of UH3 powder at temperatures ranging from 250 to 400°C.

[0045] •2

[0046] (1)

[0047] U

[0048]

[0049] H3(S) + 3HCl^ (2)PCT PATENT APPLICATION Attorney Docket No. 00846-U8828.PCT It was reported that 90% uranium hydride was converted to uranium trichloride at 250 °C with an experimental run time of 3 hours. However, at higher temperatures (300 °C and 400 °C) significant UO2 formation was reported.

[0050] While HC1 reaction with U, U alloy, or U hydride can be used to make UCI3 or UCI4, it is problematic due to the use of hazardous, compressed gas. Anhydrous HC1 is delivered from a pressurized gas cylinder as either pure or diluted with an inert gas such as argon. Both handling and storing this hazardous gas require significant, costly safety precautions. Many researchers have reported using ammonium chloride for chlorination of U, as it decomposes into NH3 and HC1 starting at about 300°C (see equation 3).

[0051] N

[0052]

[0053] H.Cl^ NH^ + HCl^ (3)

[0054] Yoon et. al. demonstrated UCI3 synthesis by thermally decomposing ammonium chloride (Reaction 3) followed by reaction of the vapor with U metal. NH4CI and U metal were heated (not in contact as solids) together in a sealed, metal reactor at 420 °C for 5 hours and then heated to 620 °C. They reported UCI3 to be the main product rather than UCI4 and attributed it to reduction by gaseous by-products (H2, NH3). Although the synthesis using ammonium chloride was successful, iron and chromium were found as impurities in the product as well as unreacted uranium. Presence of iron and chromium were attributed to the corrosion of the stainless-steel vessel at higher temperatures and extended time, which poses a problem with this method of synthesis. The use of a heated sealed container also presents a significant risk due to pressurization of the system.

[0055] Hames et. al. reported two-step formation of UCI4 from reaction of NH4CI vapor and U metal in which (NH4)2UCle was formed at 573 K followed by decomposition to UCI4 and NH4CI at 623 K under vacuum. They subsequently reduced UCI4 to UCI3 via reaction with additional U metal. Hypothetically, U may be reduced to the +3 oxidation state in this process if NH3 remains in the gas phase in contact with the ammonium uranium chloride salt.

[0056] Another gaseous reducing agent that could be included in the atmosphere is H2. If uranium has the +3 oxidation state, decomposition of the ammonium uranium chloride could form UCI3 and avoid the need for subsequent reduction by U metal. Starting with UH3 rather than U metal would have the benefit of reducing particle size, which increases surface areaPCT PATENT APPLICATION Attorney Docket No. 00846-U8828.PCT for reaction. This can be useful, as UCI3 (or UCI4) will form around an unreacted core of UH3. Reaction of UH3 with NH4CI theoretically proceeds through reaction (4). Such a gassolid reaction can be rate limited by shrinking core kinetics. One way to overcome this limitation is to minimize the particle size of the solid.

[0057] UH3 (s)+ 3NH4Cl(s)UCl3 (s)+ 3NH3 (5)+ 3H2(4)

[0058] Work by Drozdzyhski reported that the trivalent intermediate (NH4UCI4) could be formed out of an aqueous mixture containing methyl cyanide, propionic acid, and a large excess of ammonium chloride. Methyl cyanide and propionic acid allowed for the dissolved uranium to be kept at trivalent oxidation state during the precipitation of the hydrated NH4UCI4 • 4H2O. The hydrated ammonium uranium chloride was then dried, washed, and decomposed with excess NH4CI under vacuum at 400 °C to produce green UCI3 confirmed by XRD. Due to the extreme dryness requirements of molten salts used in molten salt reactors, aqueous synthesis approaches are undesirable. Complete dehydration is impossible to achieve without producing oxygen-containing impurities in the salt.

[0059] The methods described herein involve an alternative reactor configuration and a two-step reaction for synthesizing trivalent chlorides of an f-block metal from solid f-block metal and / or hydride thereof and NH3 / HCI vapor generated from thermal decomposition of solid NH4CI. As an example, UCI3 can be generated from UH3 powder, although these principles can be applied to other f-block metals and their hydrides. These methods can produce UCI3 that is free of UCI4 or that has a low concentration of UCI4 if any is present. As a general guideline, UCI4 can be present at less than 1 wt%, in some cases less than 0.5 wt%, and in other cases less than 0.05 wt%. This is useful because UCI4 is highly corrosive toward metal components. The methods described herein can also be easier to scale compared to previous methods of making UCI3. In some examples of the methods described herein, solid NH4CI reacts with UH3 to first produce an intermediate double salt followed by thermal decomposition to produce pure UCI3. This process can control the oxidation state of the uranium to the trivalent state. The intermediate formed is an ammonium uranium chloride (AUC) "double salt." As used herein, “double salt” refers to a salt that contains two or more different cations or anions. In some examples, no H2 reduction step is needed in this process.PCT PATENT APPLICATION Attorney Docket No. 00846-U8828.PCT Additionally, the process can be performed without feeding gaseous HC1, which eliminates the use of large quantities of hazardous gas. The formation of the double salt can be done by mixing NH4CI and UH3 powders, or by including both powders together in a vessel without mixing the powders, and heating the powders to a reaction temperature. In certain examples, the reaction temperature can be between 493 K and 593 K. The pressure conditions can be at ambient pressure or slightly above in some examples. This process can be performed in a low-pressure system without gas flow in certain examples. After the double salt has been formed, the double salt can be thermally decomposed at a decomposition temperature (in one example this decomposition temperature can be 923 K) to produce the pure UCI3 product. This process can provide a cheaper and safer alternative to the gaseous HCI / H2 methods. The NH4CI can be vaporized in a flowing stream of argon at a temperature from 300 °C to 350 °C, in some examples, which subsequently flows through a bed of UH3 powder. The intermediate formed from this first step can then be heated to a decomposition temperature, which can be about 650 °C in certain examples, and decomposed to form UCI3. The system used in the methods described herein can be a non-sealed, non-pressurized system. In some examples, the reaction vessel can be entirely constructed of quartz, which can eliminate the metal corrosion. Other example materials that can be used to make the reaction vessel include non-contaminating materials such as alumina or yttria stabilized zirconia.

[0060] With this description in mind, in one example a method of making a trivalent chloride of an f-block metal (e.g. a lanthanide or actinide metal) can include introducing reactants including a solid f-block metal or hydride thereof, and solid NH4CI into a reaction vessel. The reactants can be heated in a first phase to a reaction temperature from about 200 °C to about 400 °C to form an ammonium-metal chloride double salt. The ammonium-metal chloride double salt can be heated in a second phase to a decomposition temperature greater than about 600 °C to decompose the ammonium-metal chloride double salt, thereby forming a trivalent chloride of the f-block metal. The first phase and second phase can refer to periods of time. The first phase refers to the period of time during which the reactants react to form the ammonium-metal chloride double salt. The second phase refers to the period of time during which the ammonium-metal chloride double salt decomposes to form the trivalent chloride.PCT PATENT APPLICATION Attorney Docket No. 00846-U8828.PCT FIG. 1 is a flowchart illustrating one example method 100 of making a trivalent chloride of an f-block metal. This method includes: introducing reactants comprising a solid f-block metal or hydride thereof, and solid NH4CI into a reaction vessel 110; heating the reactants in a first phase to a reaction temperature from about 200 °C to about 400 °C to form an ammonium-metal chloride double salt 120; and heating the ammonium -metal chloride double salt in a second phase to a decomposition temperature greater than about 600 °C to decompose the ammonium-metal chloride double salt, thereby forming a trivalent chloride of the f-block metal 130. In some cases, the reactants can include both solid f-block metal and a hydride thereof.

[0061] The lanthanide or actinide metal can be selected from lanthanum (Ln), cerium (Ce), praseodymium (Pr), neodymium (Nd), promethium (Pm), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), lutetium (Lu), actinium (Ac), thorium (Th), protactinium (Pa), uranium (U), neptunium (Np), plutonium (Pu), americium (Am), curium (Cm), berkelium (Bk), californium (Cf), einsteinium (Es), fermium (Fm), mendelevium (Md), nobelium (No), lawrencium (Lr), and combinations thereof. In certain examples, the metal can be an actinide. In further examples, the metal can be uranium, plutonium, or a combination thereof. Notably, actinide and lanthanide chlorides have free energy of formation which is commensurate with that of uranium. In certain examples, the metal can be uranium. When the metal is uranium, the ammonium-metal chloride double salt can be an ammonium-uranium chloride double salt.

[0062] As mentioned above, the lanthanide or actinide metal can be introduced in the form of at least one of a solid metal or a hydride thereof. In certain examples, the hydride can be a trihydride of the lanthanide or actinide metal. In certain examples, the hydride can be UH3. In these examples, the final product of the method can be UCI3. In other examples, the f-block metal can be provided as a solid metal (i.e. reduced elemental metal).

[0063] The trivalent chloride product can have a high purity in some examples. For example, the purity of the trivalent chloride product (i.e., UCI3 or a trivalent chloride of another lanthanide or actinide metal) can be 99% or greater, or 99.5% or greater, or 99.9% or greater.

[0064] In further examples, the trivalent chloride product can be free or substantially free of certain contaminants, such as tetravalent chlorides of the lanthanide or actinide metal, orPCT PATENT APPLICATION Attorney Docket No. 00846-U8828.PCT oxides of the lanthanide or actinide metal, or a combination thereof. In certain examples, the final product of the method can be UCI3 that is substantially free of UCI4 and UO2. If the final product includes any of the tetraval ent chloride or the oxide of the lanthanide or actinide metal, the amount of the tetravalent chloride or oxide (individually or combined) can be less than about 2%, or less than about 1%, or less than about 0.5%, or less than about 0.1%.

[0065] The method can include two reaction phases at different temperatures. In the first phase, the hydride of the lanthanide or actinide metal and the solid NH4CI can be heated together in a reaction vessel to a reaction temperature from about 200 °C to about 400 °C. The reactants can react together to form an ammonium-metal chloride double salt. In certain examples, the hydride can be UH3 and the ammonium-metal chloride double salt can be an ammonium-uranium chloride double salt. Without being bound to a particular mechanism, it is believed that this first reaction (for the case involving uranium) proceeds according to equation 5:

[0066] UH3+ 4NH4C1 = (NH4)UC14+ 1.5H2(g) + 3NH3(g) (5)

[0067] The ammonium-metal chloride double salt can be an intermediate that is later decomposed in the second phase. In some examples, an atmosphere containing NH3 can be maintained inside the reaction vessel in contact with the intermediate ammonium-metal chloride double salt. The NH3 may not be added from an external source, but can instead be present due to vaporization of NH4CI in the reaction vessel. At least a portion of the NH4CI can vaporize to form NH3 and HC1 vapor during the heating in the reaction vessel. The NH3 in the atmosphere can favor the +3 oxidation state of the metal (such as uranium). In order to maintain the atmosphere containing NH3, vacuum may not be applied to the reaction vessel during the heating phases. However, it can also be useful to prevent pressure buildup inside the reaction vessel during the heating phases, because pressure buildup can lead to risk of rupture of the reaction vessel and accompanying safety concerns. Therefore, the reaction vessel can include a pressure relief outlet that allows some of the gas inside the reaction vessel to escape without removing all the gas from the reaction vessel. In certain examples, the pressure relief outlet can include a bubbler that contains mineral oil in a U-bend. In other examples, a bubbler with a different design can be used. The bubbler can include a liquid inPCT PATENT APPLICATION Attorney Docket No. 00846-U8828.PCT contact with a gas flowing out from the reaction vessel. The liquid can allow a portion of gas from the reaction vessel to escape, thus relieving pressure in the reaction vessel. The liquid can also prevent outside air or other gases from diffusing back into the reaction vessel through the gas outlet. The bubbler can maintain the liquid inside the bubbler so that the liquid does not flow back into the reaction vessel. In some examples, the liquid can be a nonvolatile non-aqueous liquid such as mineral oil. The bubbler can entrap at least a portion of the NH3 and HC1 vapor, which can maintain the NH3 in the atmosphere while also preventing pressure buildup inside the reaction vessel. Other examples of pressure relief outlets can include spring actuated pressure relief valves, power actuated pressure relief valves, and others. In certain examples, the pressure in the reaction vessel can be maintained below about 2 atm, or from about 1.0 atm to about 1.2 atm, or from about 1.0 to about 1.1 atm, during the first phase and the second phase.

[0068] As previously outlined, the reactants can include an f-block metal rather than the hydride. Using uranium metal as an example, reaction can be governed by Equation 6:

[0069] U(s) + 3NH4C1(S) = UCl3(s) + 3NH3(g) + 1.5 H2(g) (6) As with the hydrides, this same mechanism and reaction can be extended to other elemental f-block metals.

[0070] In either case, the solid metal can be provided as a solid piece, powder, particulate or other solid form. However, larger solids will also correspond to relatively slower reaction rates and may include an upper limit due to diffusion limitations into the bulk material. Accordingly, relatively smaller powder or particulate materials can be desirable when time is a significant factor. As a general non-limiting guideline, the hydride or elemental metal can be in particulate form having an average particle size less than about 10 mm, or less than about 5 mm, or less than about 1 mm, or from about 1 pm to about 1 mm. Smaller particle sizes can increase reaction rate by increasing surface area and reducing diffusion limitations associated with shrinking core kinetics. However, in some cases, this process can be effectively performed on larger solid pieces (e.g. having dimensions up to several centimeters), although diffusion limits may dictate comminution into smaller pieces before processing if full conversion is desired.

[0071] The reaction temperature in the first phase can be from about 200 °C to about 400 °C, or from about 200 °C to about 350 °C, or from about 200 °C to about 300 °C, or fromPCT PATENT APPLICATION Attorney Docket No. 00846-U8828.PCT about 250 °C to about 400 °C, or from about 250 °C to about 350 °C, or from about 250 °C to about 300 °C, or from about 300 °C to about 400 °C, or from about 300 °C to about 350 °C in various examples. In some examples, the reactants can be held at the reaction temperature for a period of time. It is noted that “held at the reaction temperature” does not necessarily mean that the reactants are at a single, specific temperature for the entire period of time. Rather, the reactants can have a temperature within one of the ranges described above for the duration of the reaction time. In certain examples, the reactants can be held at the reaction temperature for a reaction time from about 30 minutes to about 10 hours, or from about 30 minutes to about 5 hours, or from about 30 minutes to about 3 hours, or from about 30 minutes to about 2 hours. In further examples, the reactants can be heated to the reaction temperature by ramping the temperature at a ramp rate from about 1 °C / min to about 10 °C / min or from about 1 °C / min to about 5 °C / min.

[0072] After the initial reactants have reacted to form an ammonium-metal chloride double salt intermediate, this intermediate can be heated to a higher decomposition temperature. The decomposition temperature can be 600 °C or greater. In certain examples, the decomposition temperature can be from about 600 °C to about 800 °C, or from about 600 °C to about 700 °C, or from about 600 °C to about 650 °C, or from about 650 °C to about 700 °C. The ammonium-metal chloride double salt intermediate can be held at the decomposition temperature for a decomposition time sufficient to decompose the intermediate to form trivalent metal chloride. In certain examples, the decomposition time can be from about 30 minutes to about 10 hours, or from about 30 minutes to about 5 hours, or from about 30 minutes to about 3 hours, or from about 30 minutes to about 2 hours. In further examples, the ammonium-metal chloride double salt can be heated to the decomposition temperature by ramping the temperature at a ramp rate from about 1 °C / min to about 10 °C / min or from about 1 °C / min to about 5 °C / min.

[0073] An inert gas can be introduced into the reaction vessel. In some examples, the solid reactants can be placed in the reaction vessel and then the interior volume of the reaction vessel can be filled with an inert gas before heating the reaction vessel to the reaction temperature. In certain examples, a continuous flow of inert gas can be introduced into the reaction vessel during the first phase and / or the second phase, while the reaction vessel is heated. In other examples, the flow of inert gas can be stopped before the heating begins. InPCT PATENT APPLICATION Attorney Docket No. 00846-U8828.PCT these examples, there is no inflow of gas into the reaction vessel during heating. However, there can be outflow of gas from the reaction vessel through a pressure relief outlet, as described above. In certain examples, the reaction vessel can be placed inside a larger vessel, such as a glove box, that is filled with inert gas. The inert gas can be argon, radon, krypton, neon, xenon, helium, or a combination thereof.

[0074] It can also be useful to introduce hydrogen gas into the reaction vessel in some cases. Hydrogen can flow into the reaction vessel during the first phase, or during the second phase, or during both phases in various examples. In certain examples, a mixture of argon and hydrogen can be introduced into the reaction vessel. The mixture can include argon with from about 0 vol% hydrogen to about 50 vol% hydrogen. In a particular example, a mixture that includes hydrogen can be introduced into the reaction vessel during the first phase, but then pure argon or other inert gas can be introduced without hydrogen during the second phase. In order to reduce the amount of oxygen and water in the reaction vessel, which may react with the reactants to form undesired byproducts, the inert gas and / or hydrogen that is introduced into the reaction can be treated to remove water and / or oxygen before entering the reaction vessel. In some examples, the inert gas and / or hydrogen can pass through a water trap, an oxygen trap, or a combination thereof before being introduced into the reaction vessel.

[0075] When inert gas and / or hydrogen gas is flowed continuously through the reaction vessel, the flow rate of gas through the reaction vessel can vary depending on the size of the reaction vessel. A space velocity of the flowing gas can be defined as the volumetric flow rate of the gas divided by the volume of the reaction vessel. In some examples, the space velocity can be from about 1 min’1to about 100 min’1, or from about 5 min’1to about 50 min’ This can refer to the volumetric flow rate of gas divided by the entire interior volume of the reaction vessel, or divided by the actual volume occupied by the reactants in the reaction vessel.

[0076] The composition of the product produced by the methods described herein can be affected by the ratio of reactants that are initially placed in the reaction vessel. As an example, when UH3 reacts with NH4CI to form UCI3, it can be useful to introduce these reactants in a molar ratio of about 6:1 or greater (mol NH4Cl / mol UH3). It has been found that using a molar ratio less than about 6:1 can result in more of the tetravalent chloride UCI4 beingPCT PATENT APPLICATION Attorney Docket No. 00846-U8828.PCT formed, whereas using a ratio of about 6:1 or greater results in the trivalent UCI3 being formed. In further examples, much greater molar ratios can be used, such as from about 6: 1 to about 50:1, or from about 6:1 to about 40:1, or from about 6:2 to about 30:1, or from about 20:1 to about 50:1, or from about 20:1 to about 40:1, or from about 20:1 to about 30:1. In some examples, the solid hydride of the lanthanide or actinide metal and the solid NH4CI are the only solid reactants that are used in the reaction. As mentioned above, in some cases hydrogen gas can be added during the reaction as a gaseous reactant.

[0077] The reaction vessel can be made of a material that will not contaminate the trivalent metal chloride product being produced. Some materials, such as some steels or other metals, can cause contamination of the trivalent metal chloride because these materials are susceptible to attack by HC1 gas in the reaction vessel or for other reasons. In some examples, the reaction vessel be made of quartz. A quartz tube with an open top and an open bottom can be used in certain examples. In other examples, a quartz tube with an open top and a closed bottom can be used.

[0078] The present technology also includes systems for making trivalent chlorides of lanthanide or actinide metals. These systems can be used to perform any of the methods described herein. The systems can also include any of the components described herein. In one example, a system can include a reaction vessel, a solid metal or solid hydride of an f-block metal within the reaction vessel, and a solid NH4CI within the reaction vessel. A heater can be associated with the reaction vessel. The heater can be operable to heat the reaction vessel to at least a reaction temperature and a decomposition temperature. The reaction temperature can be a temperature from about 200 °C to about 400 °C at which the solid f-block metal or hydride reacts with the solid NH4CI to form an ammonium-metal chloride double salt. The decomposition temperature can be a temperature greater than about 600 °C at which the ammonium-metal chloride double salt decomposes, thereby forming a trivalent chloride of the f-block metal (i.e. lanthanide or actinide metal). When the heater heats the reaction vessel to the reaction temperature and the decomposition temperature, this can refer to heating the interior of the reaction vessel to these temperatures, so that the reactants inside the reaction vessel are heated to these temperatures.

[0079] FIG. 2 shows a schematic side view of an example system 200 for making a trivalent metal chloride as described herein. This system includes a reaction vessel 210 that is a quartzPCT PATENT APPLICATION Attorney Docket No. 00846-U8828.PCT tube having a bottom inlet connected to an argon gas source 220. The top of the tube is an outlet connected to a bubbler 230 that acts as a pressure relief outlet, allowing some gas to escape but retaining some gas inside the reaction vessel. In this example, a reactant mixture 240 is held in the reaction vessel by a wad of quartz wool 242. In other examples, any other suitable structure can be included in the reaction vessel to hold the reactants. The system also includes a vertical tube furnace 250 surrounding the reaction vessel to heat the reaction vessel and the reactants inside.

[0080] In some examples, the reactants can be in particulate form and the reactants can be mixed together as shown in FIG. 2. In other examples, the reactants can be in particulate form or any other solid form, and the reactants can both be placed inside the reaction vessel but not mixed together. In certain examples, the metal and / or hydride of the lanthanide or actinide metal can be stacked on top of the NH4CI. For example, a quantity of particulate NH4CI can be placed in the reaction vessel first, and then a quantity of particulate f-block metal / hydride or a solid f-block metal / hydride body can be placed on top of the NH4CI. In still further examples, the f-block metal and / or hydride and the NH4CI can be held separately in the reaction vessel so that the reactants are not in direct contact. When the reactants are heated, the NH4CI can at least partially vaporize, and the vapor can react with the metal hydride.

[0081] FIG. 3 shows a schematic side view of another example system for making a trivalent chloride of a lanthanide or actinide metal 300. This system includes a reaction vessel 310 having a gas inlet 312 at the bottom and a gas outlet 314 at the top. An inert gas source 320 and a hydrogen gas source 322 are both connected to the gas inlet. Valves 324 can be used to independently control the flow of inert gas and hydrogen gas to the gas inlet of the reaction vessel. The gas outlet of the reaction vessel is connected to a U-bend 330 filled with mineral oil 332, which acts as a pressure relief outlet. In this example, the reactants inside the reaction vessel include solid NH4CI 344 and solid UH3 346. These reactants are in particulate form, and a layer of the solid UH3 is stacked on top of a layer of the solid NH4CI. These reactants are supported by a wad of quartz wool 342. The reaction vessel is inside a tube furnace 350, and the tube furnace is inside a glove box 360 filled with an inert gas.

[0082] Additionally, in some examples an f-block metal hydride can be formed before starting the reaction with the NH4CI. The formation of the hydride can be performed in thePCT PATENT APPLICATION Attorney Docket No. 00846-U8828.PCT same reaction vessel in some examples, or in a different reaction vessel. Thus, in some cases the systems for making trivalent chlorides of lanthanide or actinide metals can also be used as systems for hydriding the lanthanide or actinide metal to form a hydride before then using the hydride in the reaction with NH4CI to form the trivalent chloride. In one example, a lanthanide or actinide metal, such as uranium, can be placed in the reaction vessel. Then, the reaction vessel can be heated to a hydriding temperature and hydrogen gas can be introduced into the reaction vessel. The hydrogen gas can be introduced as pure hydrogen gas or mixed with an inert gas such as argon. The hydrogen can react with the metal to form the metal hydride.

[0083] FIG. 4 shows a schematic side view of an example hydriding system 400 that can be used to form a hydride of a lanthanide or actinide metal. The system includes a reaction vessel 410 with a gas inlet 412 at the bottom and a gas outlet 414 at the top. An inert gas source 420 and a hydrogen gas source 422 are connected to the gas inlet. Valves 424 can be used to independently control the flow of inert gas and hydrogen gas. In some cases, pure hydrogen gas can be used during hydriding, but in other cases a mixture of hydrogen and inert gas can be used. Theses gases can flow through an oxygen trap 426 and a water trap 428 before entering the gas inlet of the reaction vessel. The gas outlet of the reaction vessel is connected to a pressure relief outlet 430. A basket 440 is placed inside the reaction vessel. The basket can contain a lanthanide or actinide metal, such as uranium. The metal can be in the form of an ingot, a pellet, a particulate, or other forms. The basket is supported by a porous frit 442 inside the reaction vessel. This system also includes a tube furnace 450 to heat the reaction vessel, and a glove box 460 surrounding the tube furnace. Hydrogen gas can flow through the reaction vessel while the metal in the basket is heated to a hydriding temperature to convert the metal into a hydride. In some examples, the hydride can be in the form of a particulate. This example also includes a temperature sensor 462 that measures the temperature in the basket inside the reaction vessel.

[0084] FIG. 5 shows a schematic side view of another example system 500 for making a trivalent metal chloride. This system also includes a reaction vessel 510 with a gas inlet 512 and a gas outlet 514. An inert gas source 520 and a hydrogen gas source 522 are connected to the gas inlet through valves 524 and an oxygen trap 526 and a water trap 528. The reaction vessel can be the same reaction vessel used for the hydriding shown in FIG. 4. OtherPCT PATENT APPLICATION Attorney Docket No. 00846-U8828.PCT components of the system can also be the same, such as the gas sources, the glove box 560, the tube furnace 550, the pressure relief outlet 530, and the temperature sensor 562. In this system, a basket 540 contains a solid f-block metal and / or hydride of a lanthanide or actinide metal. The basket is supported by a porous frit 542 inside the reaction vessel. As an example, solid particulate NH4CI 544 is placed in the reaction vessel below the frit. The NH4CI is supported by a wad of quartz wool 542. Thus, the NH4CI is not in direct contact with the hydride of the lanthanide or actinide metal. When the reaction vessel is heated, the NH4CI can vaporize to form NH3 and HC1 vapor. These vapors can react with the hydride to form the double salt as described above. After forming the double salt, the reaction vessel can be heated to a decomposition temperature to decompose the double salt, thereby forming the trivalent chloride of the lanthanide or actinide metal.

[0085] It is noted that the systems shown in the figures are merely examples, and other systems having a variety of different sizes, shapes, and configurations can be used. The reaction vessels shown in the figures above can be particularly useful for lab testing of the methods described herein. In a larger scale manufacturing system, other types of reaction vessels can be used. In some examples, the reaction vessel can include a tube furnace, a plug flow reactor, a fluidized bed reactor, a rotary furnace, or another type of reactor. Any suitable heat source can be used to heat the reactants in the reaction vessel, such as conductive heating, convective heating, inductive heating, microwave heating, infrared heating, heated hydrogen feed gas, heated inert feed gas, or others.

[0086] Examples

[0087] Example 1

[0088] The following process was performed under an argon atmosphere inside a glove box with H2O < 5 ppm and O2 < 5 ppm. A mixture of UH3 and NH4CI was heated in 20 K increments from 493 K to 593 K to form an ammonium-uranium chloride double salt intermediate. No vacuum was used during the heating. The exact composition of the anhydrous trivalent intermediate has not been fully determined due to the formation of what appear to be several intermediate phases.

[0089] The second phase of the process included thermal decomposition of the ammoniumuranium chloride (AUC) double salt intermediate at or above 923 K under ambient pressurePCT PATENT APPLICATION Attorney Docket No. 00846-U8828.PCT to produce UCI3. The decomposition reaction of the AUC is a multistep process and proceeds through the reaction shown in equation 6. The decomposition reaction produces gaseous NH3and HC1 that are easily removed from the product. Due the reversibility of the reaction below approximately 573 K, the off gasses can be recondensed back to the solid NH4CI.

[0090] (NH4) UC1X= UCh + NH3(g) + HCl(g) (7)

[0091] The intermediate formation setup using the mixed solid reactants used a quartz glass tube loaded with the solid reactants. As the tube was heated, NH4CI thermally decomposed to produce NH3 and HC1 gas. To prevent pressure buildup inside the tube, its outlet was connected to a bubbler containing light mineral oil in the U-bend. The bubbler retained the NH3 / HCI atmosphere but with minimal pressure buildup. The system used in this experiment was similar to the system shown in FIG. 3.

[0092] After the UH3 (black) and dried NH4CI (white) powders are loaded into the quartz tube, the powders are mixed using a stainless-steel rod. The trials reported here were conducted on the gram scale. The molar ratio of NH4CI to UH3 was approximately 6:1. Feed quantities of the reactants for the mixed solid trials are shown in Table 1.

[0093] Table 1

[0094] Trial NH4CI UH3NH4C1:UH3Reaction time (mol / grams) (mol / grams) mol ratio (hr)

[0095] DS-2 0.0249 / 1.33 0.0043 / 1.04 5.8:1 7.7

[0096] DS-7 0.0261 / 1.41 0.0044 / 1.06 5.93:1 8.7

[0097]

[0098] After the reactants were loaded and mixed, the bubbler was plugged to the top of the tube. The tube was then loaded into a furnace and initially heated to 493 K. This was followed by further increases in temperature in 20 K steps up to 593 K over several hours. The heating curves for the two trials are shown in FIG. 6. The time to heat from 493 K to 593 K was approximately 8 hr.

[0099] After undergoing the above-described process, the formation of the intermediate double salt is indicated by distinct color changes in the powder mixture. Several intermediate phases form in layers. The primary bottom phase appears as a light green, this is followed byPCT PATENT APPLICATION Attorney Docket No. 00846-U8828.PCT a small black phase above it, and then a brown phase on top. When decomposed together, these layers produce UCI3.

[0100] The intermediate has been decomposed in two different vessels with both resulting in UCI3 formation. The easiest method of performing the reaction beginning with the mixed reactants is by removing the bubbler from the top of the quartz tube and heating to 923 K and holding for 6 hours. The intermediate may also be ground out of the tube with a stainless steel rod and decomposed in a small glassy carbon crucible at 923 K for 6 hours. When the decomposition was complete, a black crystalline material was produced. The black crystalline decomposition product had a similar appearance whether the decomposition was performed in the quartz tube or in the glassy carbon crucible.

[0101] Analysis of the post-decomposition products was done using X-ray diffraction (XRD), and a Cl ion electrode. The Cl ion electrode was used to determine the ratio of Cl to U in the product. For UCI3, that ratio should be 3. For UCI4, that ratio should be 4. The XRD spectra of the products from the solid-solid intermediate formation are shown in FIGs. 7-10. All major peaks matched the reference pattern for UCI3. No major impurity phases were detected. Samples of this same product were dissolved in 2% nitric acid and analyzed via chloride ion specific electrode. For DS-2, the Cl / U mol ratio was 3.12 within 4% error. For DS-7, the Cl / U mol ratio was 2.96 within 4% error.

[0102] This process was found to be capable of making UCI3 at a very high selectivity without a need for reductive post-processing. The process was performed at atmospheric pressure without pressurization or vacuum. The atmospheric pressure used in the process allows the process to be performed without metallic structural materials that can cause contamination by corrosion products. The process also works without gas flow control. Example 2

[0103] In another example process, uranium was converted to UH3. Depleted uranium metal (supplied by Idaho National Laboratory) was placed into a quartz basket, which was then loaded into a fritted quartz tube. The bottom of the tube was connected to the in-gas line. This was loaded into the vertical tube furnace (VTF) where the top of the tube and a thermocouple were connected to the effluent gas line by NPT fittings. The system used in this example was similar to the system shown in FIG. 4. The tube furnace and the quartz reaction vessel were inside an argon atmosphere glove box (Inert PureLab HE) in which thePCT PATENT APPLICATION Attorney Docket No. 00846-U8828.PCT concentrations of O2 and H2O were < 200 ppm and < 0.5 ppm respectively. The tube furnace was sealed during the experiments, but the uranium metal was handled in the inert atmosphere. UHP H2 was flowed through the tube while heating at 100 standard cubic centimeters per minute (seem). Connected to the H2 feed gas line was a 64-1000 series oxygen getter (Matheson) placed outside of the glove box. The uranium hydriding process is exothermic. To determine when the reaction was completed, a thermocouple inserted into the center the quartz tube was used to measure the temperature of the sample. A temperature spike would indicate when the reaction rate is at its highest.

[0104] For chlorination of UH3, the same vertical tube furnace was used with NH4CI powder (Sigma Aldrich 99.5 % purity) placed below the quartz basket that was loaded with UH3. For each run, approximately 4.20 to 4.80 g of NH4CI was loaded under the fritted quartz disc shown at the midpoint of the quartz tube and held in place with quartz wool stuffed below. The system was set up similar to the system shown in FIG. 5. About 0.75 g of UH3 was loaded into a quartz basket and placed on the other side of the frit. The tube was then sealed with a thermocouple inserted through a normal pipe thread fitting with the end situated directly above the basket to measure the internal temperature of the furnace. The feed gas consisted of argon and in some cases H2. Inside the glovebox was an H2O / O2 trap filled with molecular sieves and copper that was attached to the feed gas line of the vertical tube furnace set up. To utilize the H2O / O2 trap, the copper pellets were activated by heating to 250 °C and flowing 5 % hydrogen gas balanced with N2 at 100 seem through the copper pellets for 60 minutes. The trap was used for all experiments except Trials 1 and 2. UH3 was heated up to 300 °C or 350 °C at a ramp rate of 5 °C / min. All trials had a reaction time of about 3 hours, including the ramp time. The furnace was turned off and allowed to cool to ambient temperature where upon the product was removed and analyzed.

[0105] X-ray diffraction (XRD) was performed using a Bruker D2 Phase on samples loaded into hermetically sealed XRD sample holders to prevent reaction of hydrides / chlorides with air. The XRD scan range varied 20 from 10-80° at a rate of about 2.4° / min. Phases were identified using Match! from the default Match! database along with entries from the Crystallography Open Database and CIF files from The Materials Project website.

[0106] To measure the molar ratio of chlorine to uranium, samples were analyzed using a chloride ion specific electrode (Thermo Scientific Orion). About 30 mg of product wasPCT PATENT APPLICATION Attorney Docket No. 00846-U8828.PCT placed in a centrifuge tube and dissolved in 40 mL of 5% nitric acid by placing on a shaker for 5 to 10 minutes. After the allotted time, the tube was taken off the shaker and the chloride ion probe was placed in the tube to read the concentration of chlorine.

[0107] A TA Instruments SDT-650 was used for TGA / DSC analysis of select samples. About 20 mg of the sample was taken out of the glove box and placed in a platinum container for the measurement. The procedure of analysis goes as followed: a mass flow segment of argon at 30 ml / min, balance flow segment of argon at 30 ml / min, heating to 120 °C with a ramp rate of 5 °C / min, isotherm for 90 minutes, heating to 650 °C with a ramp rate of 5 °C / min, and cooling to 25 °C at a rate of 50 °C / min.

[0108] Two hydriding runs were performed with a total of 30.2 grams of uranium metal in pellet form. FIG. 11 shows a plot of measured temperature near the U metal over the duration of the second run. The solid line is the control temperature based on the furnace thermocouple. The dashed line is the measured temperature via the thermocouple located near the sample. It can be seen that there is an off-set between the sample and furnace temperature during the hold at a furnace temperature of 250 °C. That off-set becomes constant after 15,000 seconds, likely coinciding with completion of the exothermic hydriding reaction. The uranium hydride produced by the hydriding runs was a dark powder. FIG. 12 shows the XRD pattern of the powder, confirming that it is UH3.

[0109] For the uranium chlorination process, conditions for the first three trials are summarized in Table 2. Argon carrier gas was used without the EEO / Chtrap installed in-line in the first two chlorination experiments (Trials 1 and 2). XRD of the product matched a mixture of UO2, UO2CI2, and UCI4 as shown in FIG. 13. Then the EEO / Chtrap was installed for Trial 3, and these peaks vanished. The product from Trial 3 (see FIG. 13) contained only peaks matched to UCI3 and UCI4. Based on these results, the remainder of the chlorination experiments used argon carrier gas that passed through the H2O / O2 trap.

[0110] Table 2

[0111] Summary of conditions for Trials 1-3. Each involved heating NH4CI and UH3 to 340°C at 5°C / min. Argon gas flow at 30 seem.PCT PATENT APPLICATION Attorney Docket No. 00846-U8828.PCT „ , Gas Time at , , , , , , ,

[0112] . Basket Mass Mass Molar ratio

[0113]

[0114] naModificationTPUn'e^ “ UH3 (g) NH4CI (g) NH4C1:UH3

[0115] Installed (hr)

[0116] 1 Quartz

[0117]

[0118] 2.10 0.746 4.254 25.7

[0119] Basket

[0120] Quartz

[0121] 2 Basket with No 2.02 0.735 4.871 29.8

[0122] SS liner

[0123] Quartz

[0124] 3 , Yes 2.75 0.753 4.656 27.9

[0125] Basket

[0126] Table 3 summarizes the conditions for the next six chlorination trials using NH4CI decomposed in a carrier stream of Ar and H2. The argon passed through the FhO / Chtrap for all these trials. The total gas flow in these experiments was 40 seem. For the chlorination step, temperature was ramped to 300 °C or 350 °C at 5 °C / min. All trials had a reaction time of about 3 hours, including the ramp time.

[0127] Table 3

[0128] Summary of conditions UH3 chlorination with NH4CI. Total gas flow for all experiments was 40 seem. Balance gas was argon. UH3 contained in a quartz basked without a liner. Feed gas purified through H2O / O2 trap.

[0129] Temperature . Mass Mass of Molar Ratio (°C)na 0 0 2NH4CI (g) UH3(g) NH4CI to UH3

[0130] 4 0 4.756 0.775 27.6 350 5 25 4.656 0 / 753 27.9

[0131] ------ -------- 7 0 4.756 0.756 27.7 300 8 25 4.756 0.770 27.7

[0132]

[0133] The products formed from reaction at 300 °C were powder, while those formed at 35O°C were solidified into the quartz basket. It was difficult to take samples from the quartz basket after each of the 3 0 °C trials. A small sample was scraped from the Trial 5 product.PCT PATENT APPLICATION Attorney Docket No. 00846-U8828.PCT The amount was insufficient for a high quality XRD analysis, but there was sufficient sample obtained for TGA / DSC analysis. TGA / DSC was run on this sample to determine mass loss that would occur from further heating to 650 °C in an argon atmosphere. The results are shown in FIG. 14, indicating a 34.9% mass loss.

[0134] In the literature, it has been reported that a uranium chloride-ammonium chloride double salt forms during the reaction of NH4CI with U with a formula of (NFL^UCU But that compound contains U in the +4 oxidation state. If the presence of NH3 and H2 maintained a reducing atmosphere which reduced U to the +3 oxidation state, the ammonium uranium chloride compound could have a formula of (NHfhUCU. Upon decomposition to UCI3, the mass loss would be 32%, which is close to that measured by TGA shown in FIG. 14 (34.9%).

[0135] The products from heating to 300 °C or 350 °C were subsequently heated to 650 °C for 45 to 60 minutes while exposed to the argon glove box atmosphere with less than 0.1 ppm of water and oxygen, respectively. This caused the material to convert to a powder. FIGs. 15 and 16 shows SEM micrographs at two different magnification levels of the final product from heating Trial 5 to 650°C. Based on EDS, the crystalline material shown in FIGs.

[0136] 15 and 16, specifically under the plus sign, was 71.8 wt% U and 22.1 wt% Cl. The theoretical weight percent for uranium and chlorine in UCI3 is 69.1 and 30.9 wt%, respectively.

[0137] The powder from each trial after heating to 650 °C was analyzed for phases and chloride concentration using XRD and ISE, respectively. XRD diffraction patterns for the final products from Trials 4, 5, and 6 (initially heated to 350°C) after heating to 650 °C are shown in FIG. 17. Each sample exhibited peaks that match UCI3. Minor UO2 peaks were also identified in Trials 4 and 5. The volume percent H2 in the carrier gas during the heating and hold at 350°C increased from 0% in Trial 4 to 37.5% in Trial 6. Thus, the H2 appears to mitigate UO2 formation at a certain threshold concentration.

[0138] FIGs. 18, 19, and 20 show the XRD diffraction patterns for Trials 7, 8, and 9, respectively. In each figure, the top pattern is from a sample taken after heating to 300 °C, and the bottom pattern is from a sample taken after heating to 650 °C. The intermediates yielded peaks that matched UCI4 and UCI3. The final product yielded peaks for UCI3 and UO2. The sample from Trial 9 was left exposed to air before doing XRD, which is reflected in the XRD pattern (FIG. 23), which has very small peaks.PCT PATENT APPLICATION Attorney Docket No. 00846-U8828.PCT The moles of Cl in samples were directly measured with the ISE, while the number of moles of U was determined from mass and the assumption that the sample consisted of 100%UCh. Equations are given below for these calculations. Tabled summarizes the results of C1:U ratio analysis and XRD phase determination for all the trials.

[0139] , Measured Concentration (PPM') > ,

[0140] moles Cl = - 35.453—^ „— - ■ 1000 ^ - • 0.04 L (8) mol g

[0141] Mass of powder analyzed (mg)

[0142] moles U —

[0143] 344.39— (9 m ^o-7l • 1000 ^ >

[0144]

[0145] g

[0146] Table 3

[0147] Results of analysis of samples (ISE and XRD) obtained from chlorination for chlorination temperature (Ta) of 300 or 350°C followed by decomposition at 650°C. (nm = not measured)

[0148] Cl: U Molar Ratio from ISE XRD phases Trial Ta After After After After Number (°C) chlorination decomposition chlorination decomposition 4 350 nm 2.77 nm UCI3, UO25 350 nm 2.65 nm UCI3, UO26 350 nm 3.22 nm UCI3 7 300 7.08 3.37 UC14, UCI3 UCI3, UO2(min) 8 300 8.44 3.88 UC14, UCI3 UCI3, UO2 (min) 9 300 9.14 4.87 UC14, UCI3 UCI3, UO2 (min)

[0149] The chloride ion concentrations were high after heating to 300 °C. This is evidence of retention of NH4CI on formed uranium chloride compound. This is consistent with formation of an ammonium uranium chloride compound, such as (NELf UCle. After the material was heated to 650 °C, the C1:U ratio decreased greatly to a range of 3.4 to 4.9. ThisPCT PATENT APPLICATION Attorney Docket No. 00846-U8828.PCT indicates that the ammonium uranium chloride undergoes decomposition to UCI3 or UCI4 at this temperature.

[0150] In conclusion, the methods described herein are promising to create UCI3 for commercial and industrial purposes such as producing fuel for molten salt fueled nuclear reactors. Specifically, the chlorination of UH3 to form UCI3 via reaction with NH4CI has been demonstrated via a two-step process. In the first step, the decomposed NH4CI vapor carried in a stream of argon and (optionally) H2 reacts with the hydride at 300 or 350 °C to form an intermediate compound of ammonium chloride and uranium chloride. The C1:U ratio in that intermediate was estimated to be 7 to 9 based on chloride ion selective analysis and estimated to be 6 based on thermogravimetric analysis. Heating the intermediate in an inert atmosphere to 650 °C results in loss of the extra Cl and formation of UCI3 as the major phase based on XRD. The best result was obtained by heating UH3 in the stream of NH4CI vapor, argon, and hydrogen (37.5%) at 350 °C followed by decomposition of the intermediate in argon atmosphere at 650 °C. At this temperature, hydrogen appears to minimize the amount of UO2 formed. For chlorination at 300 °C, increasing the hydrogen concentration in the gas phase appears to reduce the concentration of UCI4 in the intermediate product. Minimizing O2 / H2O concentration in the argon carrier gas helps prevent formation of oxides and oxychlorides. Overall, these results demonstrate a process for making pure, undiluted UCI3 starting with U metal and solid ammonium chloride. This can help eliminate the use of hazardous, high pressure chlorinating gases such as CI2 and HC1.

[0151] Additional Examples

[0152] The present technology can also include any of the following enumerated examples.

[0153] 1. A method of making a trivalent chloride of an f-block metal, comprising:

[0154] introducing reactants comprising a solid f-block metal or hydride thereof and solid NH4CI into a reaction vessel;

[0155] heating the reactants in a first phase to a reaction temperature from about 200 °C to about 400 °C to form an ammonium-metal chloride double salt; andPCT PATENT APPLICATION Attorney Docket No. 00846-U8828.PCT heating the ammonium-metal chloride double salt in a second phase to a decomposition temperature greater than about 600 °C to decompose the ammonium-metal chloride double salt, thereby forming a trivalent chloride of the f-block metal.

[0156] 2. The method of any of examples 1-33 or the system of any of examples 34-43, wherein the f-block metal is an actinide metal.

[0157] 3. The method of any of examples 1-33 or the system of any of examples 34-43, wherein the actinide metal is uranium and wherein the ammonium-metal chloride double salt is an ammonium-uranium chloride double salt.

[0158] 4. The method of any of examples 1-33 or the system of any of examples 34-43, wherein the solid f-block metal is a hydride which is a trihydride of the f-block metal, wherein the solid f-block metal is present as elemental metal, or wherein the reactants include both solid f-block metal hydride and solid f-block elemental metal.

[0159] 5. The method of any of examples 1-33 or the system of any of examples 34-43, wherein the hydride is UH3 and the trivalent chloride is UCI3.

[0160] 6. The method of any of examples 1-33 or the system of any of examples 34-43, wherein the trivalent chloride has a purity of at least 99%.

[0161] 7. The method of any of examples 1-33 or the system of any of examples 34-43, wherein the trivalent chloride is substantially free from a tetravalent chloride of the f-block metal, or an oxide of the f-block metal, or a combination thereof.

[0162] 8. The method of any of examples 1-33 or the system of any of examples 34-43, wherein the trivalent chloride is UCI3 substantially free of UCI4 and UO2.

[0163] 9. The method of any of examples 1-33 or the system of any of examples 34-43, wherein the reaction temperature is from about 300 °C to about 350 °C.PCT PATENT APPLICATION Attorney Docket No. 00846-U8828.PCT

[0164] 10. The method of any of examples 1-33 or the system of any of examples 34-43, wherein the decomposition temperature is from about 600 °C to about 700 °C.

[0165] 11. The method of any of examples 1-33 or the system of any of examples 34-43, further comprising maintaining a pressure below about 2 atm in the reaction vessel during the first phase and the second phase.

[0166] 12. The method of any of examples 1-33 or the system of any of examples 34-43, wherein the pressure is from about 1.0 atm to about 1.2 atm.

[0167] 13. The method of any of examples 1-33 or the system of any of examples 34-43, further comprising introducing an inert gas into the reaction vessel.

[0168] 14. The method of any of examples 1-33 or the system of any of examples 34-43, wherein the inert gas is argon, radon, krypton, neon, xenon, helium, or a combination thereof.

[0169] 15. The method of any of examples 1-33 or the system of any of examples 34-43, further comprising passing the inert gas through a water trap, an oxygen trap, or combination thereof before introducing the inert gas into the reaction vessel.

[0170] 16. The method of any of examples 1-33 or the system of any of examples 34-43, further comprising introducing hydrogen gas into the reaction vessel.

[0171] 17. The method of any of examples 1-33 or the system of any of examples 34-43, wherein an atmosphere in the reaction vessel consists of argon with from 0 vol% to about 50 vol% hydrogen gas.

[0172] 18. The method of any of examples 1-33 or the system of any of examples 34-43, wherein hydrogen gas is introduced into the reaction vessel during the first phase but not during the second phase.PCT PATENT APPLICATION Attorney Docket No. 00846-U8828.PCT

[0173] 19. The method of any of examples 1-33 or the system of any of examples 34-43, wherein at least a portion of the NH4CI vaporizes to form NH3 and HC1 vapor in the reaction vessel during the heating.

[0174] 20. The method of any of examples 1-33 or the system of any of examples 34-43, further comprising entrapping at least a portion of the NH3 and HC1 vapor in the reaction vessel.

[0175] 21. The method of any of examples 1-33 or the system of any of examples 34-43, wherein the at least a portion of the NH3 and HC1 vapor are entrapped using a pressure relief outlet connected to a gas outlet of the reaction vessel.

[0176] 22. The method of any of examples 1-33 or the system of any of examples 34-43, wherein the pressure relief outlet comprises a U-bend filled with mineral oil.

[0177] 23. The method of any of examples 1-33 or the system of any of examples 34-43, wherein the reactants comprise a molar ratio of the NH4CI to the f-block metal of at least 6:1.

[0178] 24. The method of any of examples 1-33 or the system of any of examples 34-43, wherein the reaction vessel does not contain any solid reactants other than the f-block metal or hydride thereof and the NH4CI.

[0179] 25. The method of any of examples 1-33 or the system of any of examples 34-43, wherein the first phase comprises heating the reactants at the reaction temperature for a reaction time from about 30 minutes to about 10 hours.

[0180] 26. The method of any of examples 1-33 or the system of any of examples 34-43, wherein the second phase comprises heating the ammonium-metal chloride double salt at the decomposition temperature for a decomposition time from about 30 minutes to about 10 hours.PCT PATENT APPLICATION Attorney Docket No. 00846-U8828.PCT 27. The method of any of examples 1-33 or the system of any of examples 34-43, wherein at least one of heating the reactants to the reaction temperature or heating the ammonium -metal chloride double salt to the decomposition temperature comprises ramping the temperature at a ramp rate from about 1 °C / min to about 10 °C / min.

[0181] 28. The method of any of examples 1-33 or the system of any of examples 34-43, wherein the reaction vessel comprises quartz, alumina, yttria stabilized zirconia, or a combination thereof.

[0182] 29. The method of any of examples 1-33 or the system of any of examples 34-43, further comprising forming the f-block metal hydride by hydriding a lanthanide or actinide elemental metal.

[0183] 30. The method of any of examples 1-33 or the system of any of examples 34-43, wherein the hydride is formed in the reaction vessel by heating the lanthanide or actinide metal in the reaction vessel in presence of hydrogen gas.

[0184] 31. The method of any of examples 1-33 or the system of any of examples 34-43, wherein the reactants are in particulate form and wherein the reactants are mixed together.

[0185] 32. The method of any of examples 1-33 or the system of any of examples 34-43, wherein the solid f-block metal or hydride thereof is stacked on top of or beneath the NH4CI.

[0186] 33. The method of any of examples 1-33 or the system of any of examples 34-43, wherein the solid f-block metal or hydride thereof and the NH4CI are not in direct contact one with another.

[0187] 34. A system for making a trivalent chloride of an f-block metal, comprising:

[0188] a reaction vessel;

[0189] a solid f-block metal or hydride thereof within the reaction vessel;

[0190] a solid NH4CI within the reaction vessel;PCT PATENT APPLICATION Attorney Docket No. 00846-U8828.PCT a heater associated with the reaction vessel and operable to heat the reaction vessel to at least a reaction temperature and a decomposition temperature;

[0191] wherein the reaction temperature is a temperature from about 200 °C to about 400 °C at which the solid f-block metal or hydride thereof reacts with the solid NH4CI to form an ammonium-metal chloride double salt; and

[0192] wherein the decomposition temperature is a temperature greater than about 600 °C at which the ammonium-metal chloride double salt decomposes, thereby forming a trivalent chloride of the f-block metal.

[0193] 35. The method of any of examples 1-33 or the system of any of examples 34-43, wherein the metal is uranium and wherein the ammonium-metal chloride double salt is an ammonium-uranium chloride double salt.

[0194] 36. The method of any of examples 1-33 or the system of any of examples 34-43, further comprising an inert gas source, a hydrogen gas source, or a combination thereof connected to a gas inlet of the reaction vessel.

[0195] 37. The method of any of examples 1-33 or the system of any of examples 34-43, further comprising a water trap, an oxygen trap, or a combination thereof connected between the inert gas source, hydrogen gas source, or combination thereof and the gas inlet of the reaction vessel.

[0196] 38. The method of any of examples 1-33 or the system of any of examples 34-43, further comprising a pressure relief outlet connected to a gas outlet of the reactor to entrap at least a portion of gas inside the reactor.

[0197] 39. The method of any of examples 1-33 or the system of any of examples 34-43, wherein the pressure relief outlet comprises a U-bend filled with mineral oil.PCT PATENT APPLICATION Attorney Docket No. 00846-U8828.PCT 40. The method of any of examples 1-33 or the system of any of examples 34-43, wherein the reaction vessel comprises quartz, alumina, yttria stabilized zirconia, or a combination thereof.

[0198] 41. The method of any of examples 1-33 or the system of any of examples 34-43, wherein the solid f-block metal or hydride thereof and the solid NH4CI are in particulate form and mixed together.

[0199] 42. The method of any of examples 1-33 or the system of any of examples 34-43, wherein the solid f-block metal or hydride thereof is stacked on top of or beneath the solid NH4CI.

[0200] 43. The method of any of examples 1-33 or the system of any of examples 34-43, wherein the solid f-block metal or hydride thereof and the NH4CI are not in direct contact one with another.

[0201] While the flowcharts presented for this technology may imply a specific order of execution, the order of execution may differ from what is illustrated. For example, the order of two more blocks may be rearranged relative to the order shown. Further, two or more blocks shown in succession may be executed in parallel or with partial parallelization. In some configurations, one or more blocks shown in the flow chart may be omitted or skipped.

[0202] Reference was made to the examples illustrated in the drawings and specific language was used herein to describe the same. It will nevertheless be understood that no limitation of the scope of the technology is thereby intended. Alterations and further modifications of the features illustrated herein and additional applications of the examples as illustrated herein are to be considered within the scope of the description.

[0203] Furthermore, the described features, structures, or characteristics may be combined in any suitable manner in one or more examples. In the preceding description, numerous specific details were provided, such as examples of various configurations to provide a thorough understanding of examples of the described technology. It will be recognized, however, that the technology may be practiced without one or more of the specific details, or with other methods, components, devices, etc. In other instances, well-known structuresPCT PATENT APPLICATION Attorney Docket No. 00846-U8828.PCT or operations are not shown or described in detail to avoid obscuring aspects of the technology.

[0204] Although the subject matter has been described in language specific to structural features and / or operations, it is to be understood that the subject matter defined in the appended claims is not necessarily limited to the specific features and operations described above. Rather, the specific features and acts described above are disclosed as example forms of implementing the claims. Numerous modifications and alternative arrangements may be devised without departing from the spirit and scope of the described technology.

Claims

PCT PATENT APPLICATION Attorney Docket No. 00846-U8828.PCT CLAIMSWhat is claimed is:

1. A method of making a trivalent chloride of an f-block metal, comprising:introducing reactants comprising a solid f-block metal or hydride thereof, and solid NH4CI into a reaction vessel;heating the reactants in a first phase to a reaction temperature from about 200 °C to about 400 °C to form an ammonium-metal chloride double salt; andheating the ammonium-metal chloride double salt in a second phase to a decomposition temperature greater than about 600 °C to decompose the ammonium-metal chloride double salt, thereby forming a trivalent chloride of the f-block metal.

2. The method of claim 1, wherein the f-block metal is an actinide metal.

3. The method of claim 2, wherein the actinide metal is uranium and wherein the ammonium-metal chloride double salt is an ammonium-uranium chloride double salt.

4. The method of claim 1, wherein the hydride is a trihydride of the f-block metal.

5. The method of claim 4, wherein the hydride is UH3 and the trivalent chloride is UCI3.

6. The method of claim 1, wherein the reactants include the solid f-block metal as elemental metal.

6. The method of claim 1, wherein the trivalent chloride has a purity of at least 99%.

7. The method of claim 1, wherein the trivalent chloride is substantially free from a tetravalent chloride of the f-block metal, or an oxide of the f-block metal, or a combination thereof.PCT PATENT APPLICATION Attorney Docket No. 00846-U8828.PCT 8. The method of claim 7, wherein the trivalent chloride is UCI3 substantially free of UCI4 and UO2.

9. The method of claim 1, wherein the reaction temperature is from about 300 °C to about 350 °C.

10. The method of claim 1, wherein the decomposition temperature is from about 600 °C to about 700 °C.

11. The method of claim 1, further comprising maintaining a pressure below about 2 atm in the reaction vessel during the first phase and the second phase.

12. The method of claim 11, wherein the pressure is from about 1.0 atm to about 1.2 atm.

13. The method of claim 1, further comprising introducing an inert gas into the reaction vessel.

14. The method of claim 13, wherein the inert gas is argon, radon, krypton, neon, xenon, helium, or a combination thereof.

15. The method of claim 13, further comprising passing the inert gas through a water trap, an oxygen trap, or combination thereof before introducing the inert gas into the reaction vessel.

16. The method of claim 1, further comprising introducing hydrogen gas into the reaction vessel.

17. The method of claim 16, wherein an atmosphere in the reaction vessel consists of argon with from 0 vol% to about 50 vol% hydrogen gas.PCT PATENT APPLICATION Attorney Docket No. 00846-U8828.PCT 18. The method of claim 16, wherein hydrogen gas is introduced into the reaction vessel during the first phase but not during the second phase.

19. The method of claim 1, wherein at least a portion of the NH4CI vaporizes to form NH3 and HC1 vapor in the reaction vessel during the heating.

20. The method of claim 19, further comprising entrapping at least a portion of the NH3 and HC1 vapor in the reaction vessel.

21. The method of claim 20, wherein the at least a portion of the NH3 and HC1 vapor are entrapped using a pressure relief outlet connected to a gas outlet of the reaction vessel.

22. The method of claim 1, wherein the reactants comprise a molar ratio of the NH4CI to the solid f-block metal or hydride of at least 6:1.

23. The method of claim 22, wherein the reaction vessel does not contain any solid reactants other than the solid f-block metal or hydride and the NH4CI.

24. The method of claim 1, wherein the first phase comprises heating the reactants at the reaction temperature for a reaction time from about 30 minutes to about 10 hours.

25. The method of claim 1, wherein the second phase comprises heating the ammonium-metal chloride double salt at the decomposition temperature for a decomposition time from about 30 minutes to about 10 hours.

26. The method of claim 1, wherein at least one of heating the reactants to the reaction temperature or heating the ammonium-metal chloride double salt to the decomposition temperature comprises ramping the temperature at a ramp rate from about 1 °C / min to about 10 °C / min.PCT PATENT APPLICATION Attorney Docket No. 00846-U8828.PCT 27. The method of claim 1, wherein the reaction vessel comprises quartz, alumina, yttria stabilized zirconia, or a combination thereof.

28. The method of claim 1, further comprising forming the hydride by hydriding a lanthanide or actinide metal.

29. The method of claim 28, wherein the hydride is formed in the reaction vessel by heating the lanthanide or actinide metal in the reaction vessel in presence of hydrogen gas.

30. The method of claim 1, wherein the reactants are in particulate form and wherein the reactants are mixed together.

31. The method of claim 1, wherein the hydride is stacked on top of or beneath the NTUCl.

32. The method of claim 1, wherein the hydride and the NH4CI are not in direct contact one with another.

33. A system for making a trivalent chloride of an f-block metal, comprising:a reaction vessel;a solid f-block metal or hydride thereof within the reaction vessel;a solid NH4CI within the reaction vessel;a heater associated with the reaction vessel and operable to heat the reaction vessel to at least a reaction temperature and a decomposition temperature;wherein the reaction temperature is a temperature from about 200 °C to about 400 °C at which the solid f-block metal or hydride thereof reacts with the solid NH4CI to form an ammonium-metal chloride double salt; andwherein the decomposition temperature is a temperature greater than about 600 °C at which the ammonium-metal chloride double salt decomposes, thereby forming a trivalent chloride of the f-block metal.PCT PATENT APPLICATION Attorney Docket No. 00846-U8828.PCT 35. The system of claim 34, wherein the metal is uranium and wherein the ammonium-metal chloride double salt is an ammonium-uranium chloride double salt.

36. The system of claim 34, further comprising an inert gas source, a hydrogen gas source, or a combination thereof connected to a gas inlet of the reaction vessel.

37. The system of claim 36, further comprising a water trap, an oxygen trap, or a combination thereof connected between the inert gas source, hydrogen gas source, or combination thereof and the gas inlet of the reaction vessel.

38. The system of claim 34, further comprising a pressure relief outlet connected to a gas outlet of the reactor to entrap at least a portion of gas inside the reactor.

39. The system of claim 38, wherein the pressure relief outlet comprises a U-bend filled with mineral oil.

40. The system of claim 34, wherein the reaction vessel comprises quartz, alumina, yttria stabilized zirconia, or a combination thereof.

41. The system of claim 34, wherein the solid f-block metal or hydride thereof and the solid NH4CI are in particulate form and mixed together.

42. The system of claim 34, wherein the solid f-block metal or hydride thereof is stacked on top of or beneath the solid NH4CI.

43. The system of claim 34, wherein the solid f-block metal or hydride thereof and the NH4CI are not in direct contact one with another.

Images