Uranium recovery from uranyl nitrate solutions

Abstract

Useful metals can be recovered from a nitrate solution of metal cations or metal oxygen-containing cations by adding the nitrate solution into a forming column having inlet and outlet nozzles, the nitrate solution being added in a drop-by-drop manner through the inlet. The shaped column comprises a recycle solution comprising a base selected from the group consisting of ammonia, ammonium hydroxide, alkali metal hydroxide, and alkaline earth metal hydroxide. The nitrate is reacted with a base in the recycle solution to produce a precipitate of a metal oxide salt or a metal hydroxide salt. The sediment and the recycle solution exit the forming column through an outlet nozzle, the sediment being collected in a basket below the forming column, while the recycle solution being collected in a collection tank below the basket.

Description

Technical Field

[0001] Various exemplary embodiments disclosed herein are generally directed to the recovery of radioactive metals (eg, uranium) as ceramics from a raw material (eg, uranyl nitrate) used to form uranium oxide gel particles. Background Art

[0002] Metal nitrates are useful precursors to metal oxides prepared by sol-gel methods, where the metal can be a main group metal (such as lead), a transition metal (such as yttrium, iron or zirconium) or a lanthanide metal.

[0003] For example, iron oxide has been prepared by heating the sol-gel reaction product between iron nitrate (III) and ethylene glycol. Depending on the conditions, maghemite and / or hematite can be produced by iron nitrate (III). Lead zirconate titanate (PZT) powder can be prepared by sol-gel method using lead nitrate, zirconium nitrate and tetrabutyl titanate as precursors. Yttrium oxide can be prepared by sol-gel method using yttrium nitrate as a precursor.

[0004] Nitrate precursors can also be used to prepare oxides of radioactive metals. Uranyl nitrate is a water-soluble uranium compound that can be used to make uranium oxide cores for use in nuclear fuel. Plutonium and thorium oxides also have applications in nuclear energy and can be prepared from the corresponding nitrates by the sol-gel process. Radioactive metal oxide gel particles can be prepared using a uranyl nitrate solution containing hexamethyltetramine (HMTA) and urea. The initial formation formula is UO2((NH2)2CO)2 +2 The solution is then heated to a temperature sufficient to initiate the decomposition of the HMTA. When the metal ion-urea complexes are heated, they can dissociate to form UO2 +2 or similar uranium oxide substances. The metal ions hydrolyze and condense as shown in reactions (1) and (2):

[0005] (UO2) +2 ( aq )+2H2O→(UO2(OH)2)( aq ) +2H + (1)

[0006] 2(UO2(OH)2)( aq )→2UO3·2H2O (2)

[0007] At the same time, HMTA decomposes to form ammonium hydroxide. Ammonium hydroxide increases the pH of the solution, promoting hydrolysis and condensation, resulting in the formation of spherical gel particles of metal ion particles 2UO3·2H2O. The uranium oxide gel spheres are collected and sintered to form ceramic particles, which are used as the core of nuclear fuel pellets.

[0008] Uranium nitrate waste is regulated as hazardous radioactive waste. Therefore, discarded or scrapped uranyl nitrate is not easy to dispose of. Radioactive uranium can be recovered from uranyl nitrate solutions using alkali to produce insoluble uranate salts. For example, uranyl nitrate reacts with ammonia or ammonium hydroxide to produce ammonium diuranate.

[0009] Processing ammonium diuranate (ADU) precipitates presents material handling challenges due to the sticky nature of the solid. Transferring unprocessed ADU between vessels can leave large amounts of material behind, leading to difficult cleaning operations and material waste. Summary of the invention

[0010] In view of the current demand for improved methods for recovering uranium from waste uranyl nitrate solutions, a brief overview of various embodiments is given. Some simplifications and omissions may be made in the following overview, which are intended to emphasize and introduce some aspects of the subject matter disclosed herein, but not to limit the scope of the invention. Specific embodiments of certain embodiments sufficient to enable one of ordinary skill in the art to make and use the inventive concept will be provided in the following sections.

[0011] When a sol-gel reaction is performed using metal nitrates to produce metal oxides, typically after the oxide gel is produced, unreacted nitrates remain in the supernatant. Such unreacted metal nitrates are not easy to handle, particularly in cases involving nitrates of heavy and / or radioactive metals. These nitrates are environmental pollutants and can be toxic to humans and animals exposed to them. The present disclosure relates to methods for recovering and reusing metals from discarded metal nitrate solutions.

[0012] Various embodiments disclosed herein relate to the recovery of uranium from uranyl nitrate solutions, however the disclosed methods are not limited to specific uranium or general radioactive metals. The disclosed methods can be extended to the recovery of metals from nitrate solutions of metal cations or metal oxocations.

[0013] A general aspect disclosed herein includes a method for recovering useful metals from a nitrate solution of a metal cation or metal oxygen-containing cation. The method includes the steps of adding a nitrate solution to a forming column having an inlet and an outlet nozzle, the nitrate solution being added in a dropwise manner through the inlet, wherein the forming column contains a recirculating solution containing a base selected from the group consisting of ammonia, ammonium hydroxide, alkali metal hydroxides, and alkaline earth metal hydroxides. The method also includes reacting the nitrate in the solution with the base in the recirculating solution to generate a precipitate of a metal oxide salt or a metal hydroxide salt; allowing the precipitate and the recirculating solution to leave the forming column through the outlet nozzle, collecting the precipitate in a basket below the forming column, while recovering the recirculating solution in a collection tank below the basket, and pumping the recovered recirculating solution from the collection tank to the forming column.

[0014] Embodiments may include one or more of the following features. In various embodiments, the nitrate is a salt of the following cations or oxygen-containing cations:

[0015] transition metals, such as iron, zirconium, or titanium;

[0016] Lanthanide metals, such as cerium; or

[0017] Actinide metals such as uranium, thorium or plutonium.

[0018] In various embodiments disclosed herein, the nitrate is uranyl nitrate, thorium nitrate, or plutonium nitrate. In the case where the nitrate is uranyl nitrate, the base can be ammonia or ammonium hydroxide, and the precipitate is ammonium diuranate.

[0019] In various embodiments, the pellets are held in baskets during the washing and drying steps.

[0020] Methods may include:

[0021] conveying a basket containing the collected precipitate from beneath the forming column into an oxidation furnace; and

[0022] The basket containing the collected precipitate is heated in an oxidation furnace to convert the precipitate into metal oxides.

[0023] A general aspect includes a system for recovering valuable metals from a nitrate solution of a metal cation or metal oxycation. The system also includes:

[0024] a forming column having an inlet and an outlet nozzle, wherein the inlet is configured to allow a nitrate solution to enter the forming column in a dropwise manner;

[0025] a basket, which is located below the outlet nozzle;

[0026] a collection trough located below the basket; and

[0027] A recirculation system, which may include a first pump and a flow path between a collection tank and a forming column, wherein:

[0028] A first pump is configured to pump a recirculating solution comprising a base from the holding tank to the forming column; and

[0029] The holding tank is configured to receive the recirculating solution from the forming column.

[0030] In various embodiments, the forming column is configured to react the base in the recirculating solution with the nitrate solution to produce a precipitate of the metal oxide salt, and the outlet nozzle is configured to allow the recirculating solution and the precipitate to exit the forming column. The basket is configured to collect the precipitate while allowing the recirculating solution to flow into the collection tank.

[0031] Various embodiments relate to a method for recovering uranium from a uranyl nitrate solution by adding the uranyl nitrate solution to a forming column having an inlet and an outlet nozzle, wherein the uranyl nitrate solution is added dropwise through the inlet. The forming column comprises a recirculating solution containing a base, which may be ammonia, ammonium hydroxide, an alkali metal hydroxide, or an alkaline earth metal hydroxide. The uranyl nitrate solution is reacted with the base in the recirculating solution to generate a precipitate of diuranate. The precipitate and the recirculating solution leave the forming column through the outlet nozzle, and the precipitate is collected in a basket below the forming column, while the recirculating solution is recovered in a collecting tank below the basket. The recovered recirculating solution is then pumped from the collecting tank to the forming column.

[0032] In various embodiments, the base is ammonia or ammonium hydroxide and the precipitate is ammonium diuranate. The base may be ammonium hydroxide.

[0033] The base may be an alkali metal hydroxide and the precipitate may be an alkali metal diuranate.

[0034] The method may include the additional steps of: washing the diuranate precipitate with an aqueous washing solution; and drying the washed precipitate. During the washing and drying steps, the precipitate may remain in the basket.

[0035] The method may include the steps of conveying a basket containing the collected precipitate from below the forming column to an oxidation furnace. The basket containing the collected precipitate may then be heated in the oxidation furnace to convert the precipitate into uranium oxide. The uranium oxide may be UO2, U2O5, UO3, U3O8, UO2O2, or a mixture thereof.

[0036] Various embodiments disclosed herein relate to a system for recovering uranium from a uranyl nitrate solution. The system comprises:

[0037] a shaped column having an inlet and an outlet nozzle, wherein the inlet is configured to allow the uranyl nitrate solution to enter the shaped column in a dropwise manner;

[0038] a basket below the outlet nozzle;

[0039] a collection trough beneath the basket; and

[0040] A recirculation system includes a first pump and a flow path between a holding tank and a forming column.

[0041] The first pump is configured to pump a recirculating solution containing an alkali from a collection tank to a forming column, and the collection tank is configured to receive the recirculating solution from the forming column. The forming column is configured to allow the alkali in the recirculating solution to react with the uranyl nitrate solution to produce a precipitate of diuranate. The outlet nozzle is configured to allow the recirculating solution and the precipitate to exit the forming column; and the basket is configured to collect the precipitate while allowing the recirculating solution to flow into the collection tank.

[0042] The system for recovering uranium from a uranyl nitrate solution may also include a washing station, a washing solution outlet, a washing tank below the washing solution outlet, a second pump; and a device for conveying a basket containing collected precipitate from below the outlet nozzle of the forming column to the washing station. In various embodiments, the second pump is configured to pump the washing solution from the washing tank to the washing solution outlet to produce a washing solution flow; and the device for conveying is configured to position the basket below the washing solution outlet so that the collected precipitate is washed by the washing solution flow.

[0043] The system for recovering uranium from a uranyl nitrate solution may also include an oxidation furnace and means for transferring a basket containing washed precipitate from the washing station to the oxidation furnace. The oxidation furnace is configured to convert the precipitate into uranium oxide.

[0044] As described above, the methods and apparatus disclosed herein are not limited to general radioactive metals, or in particular uranium. Various embodiments relate to a method for recovering metals from a metal nitrate solution, the method being by adding a metal nitrate solution to a forming column having an inlet and an outlet nozzle, wherein the metal nitrate solution is added dropwise through the inlet. The forming column comprises a recirculating solution containing an alkali, which may be ammonia, ammonium hydroxide, an alkali metal hydroxide, or an alkaline earth metal hydroxide. The metal nitrate solution is reacted with the alkali in the recirculating solution to produce a precipitate of a metal oxide salt or a metal hydroxide salt. The precipitate and the recirculating solution leave the forming column through the outlet nozzle, and the precipitate is collected in a basket below the forming column, while the recirculating solution is recovered in a collecting tank below the basket. The recirculating solution recovered is then pumped from the collecting tank to the forming column. In various embodiments, the nitrate is a transition metal nitrate, such as iron (III) nitrate or yttrium (III) nitrate. When iron (III) nitrate is used as a precursor, the alkali in the recirculating solution is ammonium hydroxide, and the precipitate is iron (III) hydroxide. Iron (III) hydroxide is converted into iron oxide in a furnace.

[0045] In various embodiments, the nitrate is a lanthanide metal nitrate, such as cerium (III) nitrate. When cerium (III) nitrate is used as a precursor, the base in the recirculating solution is ammonium hydroxide and the precipitate is cerium (III) hydroxide. Cerium (III) hydroxide is converted to yttrium oxide in the furnace. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] For a better understanding of the various exemplary embodiments, reference is made to the accompanying drawings, in which:

[0047] Figure 1 A system for recovering uranium from spent uranyl nitrate solution is shown, including a shaped column for precipitating diuranate;

[0048] Figure 2 A basket for collecting precipitated diuranate is shown; and

[0049] Figure 3 A system for recovering diuranate from spent uranyl nitrate solution and oxidizing the diuranate to uranium oxide is shown. DETAILED DESCRIPTION

[0050] In the present disclosure, a precipitate of a metal oxide salt will be understood to include a precipitate of a metal oxycation salt, a metal hydroxide salt, mixtures thereof, or a metal oxide salt having a hydroxide ligand.

[0051] The systems and methods disclosed herein can be used to recover valuable metals from metal nitrate solutions used as precursors in metal oxide synthesis. When unreacted metal nitrates remain from the synthesis of the desired oxide, it is economically undesirable to discard these nitrates. It is preferred to recover valuable metals from nitrate solutions, either directly converting the metals into the desired products, or recycling the metals for reuse.

[0052] In addition, many oxides are made of toxic heavy metals or radioactive metals. When metal nitrates are used to perform sol-gel reactions to produce metal oxides, unreacted nitrates are usually retained in the supernatant after the oxide gel is produced. Such unreacted metal nitrates are not easy to handle, especially in cases involving nitrates of heavy metals and / or radioactive metals. These nitrates are environmental pollutants and may be toxic to humans and animals exposed to them. Even in cases where the metal itself or the metal nitrate itself is not considered toxic, these metals or metal nitrates may undergo chemical changes once released into the environment to produce toxic compounds. Therefore, waste liquids containing metal nitrates cannot be released into the environment. The present disclosure relates to methods for recovering and reusing metals from discarded metal nitrate solutions.

[0053] A method for recovering useful metals from a nitrate solution of a metal cation or a metal oxygen-containing cation may comprise the following steps:

[0054] The nitrate solution is added to a shaped column having an inlet and an outlet nozzle, and the nitrate solution is added dropwise through the inlet.

[0055] wherein the shaped column comprises a recirculating solution comprising a base selected from the group consisting of ammonia, ammonium hydroxide, an alkali metal hydroxide, and an alkaline earth metal hydroxide;

[0056] reacting the nitrate in the solution with the base in the recirculating solution to produce a precipitate of a metal oxide salt or a metal hydroxide salt;

[0057] allowing the precipitate and the recirculating solution to exit the forming column through an outlet nozzle;

[0058] collecting the precipitate in a basket below the forming column while recovering the recirculating solution in a collection tank below the basket; and

[0059] The recovered recirculating solution is pumped from the holding tank to the forming column.

[0060] Referring now to the drawings, which disclose broad aspects of various exemplary embodiments, wherein like numerals refer to like components or steps.

[0061] Figure 1 A system for recovering useful metals from a nitrate solution of a metal cation or metal oxycation is shown. The system includes a recovery station 100. The recovery station 100 has a forming column 1, which has an inlet 3 and an outlet nozzle 2. The inlet 3 transports the nitrate solution to the forming column 1, where the nitrate solution is added to the forming column 1 in a dropwise manner through the inlet 3. The forming column 1 contains a recirculating solution containing an alkali. The nitrate in the nitrate solution reacts with the alkali in the recirculating solution to generate a precipitate of an oxide salt or a metal hydroxide salt. The precipitate and the recirculating solution leave the forming column through the outlet nozzle 2, and the precipitate is collected in a basket 5 below the forming column 1, while the recirculating solution is recovered in a collection tank 6 below the basket 5. The recovered recirculating solution is then pumped from the collection tank 6 to the forming column 1 by a pump 4.

[0062] In various embodiments, the forming column comprises a recirculating solution comprising ammonia, ammonium hydroxide, lithium hydroxide, sodium hydroxide, potassium hydroxide, calcium hydroxide, or magnesium hydroxide as the base.

[0063] The forming column may contain a recirculating solution containing ammonia or ammonium hydroxide as a base. The base reacts with the oxide salt or metal hydroxide salt to precipitate the metal oxide salt or metal hydroxide salt.

[0064] In various embodiments, the nitrate solution comprises the following nitrates:

[0065] A cation or an oxygen-containing cation of a main group metal, such as a Group 2 metal (e.g., magnesium or calcium), a Group 13 metal (e.g., gallium or indium), a Group 14 metal (e.g., tin or lead), a Group 15 metal (e.g., bismuth), or a Group 16 metal (e.g., tellurium);

[0066] A transition metal cation or an oxygen-containing cation, such as yttrium, zirconium, zinc or iron;

[0067] a cation or an oxocation of a lanthanide metal, such as cerium; or

[0068] A cation or oxocation of an actinide metal, such as thorium, uranium or plutonium.

[0069] In various embodiments, the nitrate salt is iron (III) nitrate. The forming column comprises a recirculating solution containing ammonium hydroxide as a base, and the base reacts with the iron (III) nitrate salt to precipitate iron (III) hydroxide.

[0070] In various embodiments, the nitrate salt is yttrium (III) nitrate. The forming column comprises a recirculating solution containing ammonium hydroxide as a base, and the base reacts with the yttrium (III) nitrate salt to precipitate yttrium (III) hydroxide.

[0071] In various embodiments, the nitrate is a nitrate of a radioactive metal cation or an oxygen-containing cation, such as uranyl nitrate, thorium nitrate, or plutonium nitrate. The forming column may contain a recirculating solution containing an alkali metal hydroxide, an alkaline earth metal hydroxide, an ammonium hydroxide salt, or ammonia as a base. The base reacts with the nitrate to precipitate a salt of the radioactive metal cation or oxide.

[0072] In various embodiments, the nitrate salt is uranyl nitrate, and the formed column may contain a recirculating solution containing an ammonium hydroxide salt or ammonia as a base. The base reacts with the uranyl nitrate to precipitate an ammonium diuranate salt of the formula (NH4)2U2O7.

[0073] In various embodiments, the nitrate is uranyl nitrate, and the shaped column may comprise an alkali metal hydroxide M as the base. 1 The alkali reacts with uranyl nitrate to precipitate a solution of formula M 1 Alkali metal diuranates of 2U2O7.

[0074] In various embodiments, the nitrate is uranyl nitrate, and the shaped column may comprise an alkaline earth metal hydroxide M containing as a base. 2 (OH)2 recirculating solution. The base reacts with uranyl nitrate to precipitate a compound of formula M 2 Alkaline earth metal diuranates of U2O7.

[0075] Further discussion will focus on the recovery of uranium from uranyl nitrate solutions. Figure 1In a system for recovering uranium, uranium is recovered from a nitrate solution of a metal cation or a metal oxocation. The system includes a recovery station 100. The recovery station 100 has a forming column 1, and the forming column 1 has an inlet 3 and an outlet nozzle 2. The inlet 3 transports the uranyl nitrate solution to the forming column 1, in which the uranyl nitrate solution is added to the forming column 1 in a dropwise manner through the inlet 3. The forming column 1 contains a recirculating solution containing an alkali. The uranyl nitrate in the uranyl nitrate solution is reacted with the alkali in the recirculating solution to generate a precipitate of diuranate. For example, if the alkali is ammonium hydroxide or ammonia, an ammonium diuranate precipitate is obtained. The ammonium diuranate precipitate and the recirculating solution leave the forming column through the outlet nozzle 2, and the precipitate is collected in a basket 5 below the forming column 1, while the recirculating solution is recovered in a collecting tank 6 below the basket 5. The recovered recirculating solution is then pumped from the collecting tank 6 to the forming column 1 by a pump 4.

[0076] In embodiments where the nitrate is a nitrate of a radioactive metal cation or an oxygen-containing cation, it is recommended to prepare a shaped column 1 having an outer diameter of 4.5 inches or less, 4 inches or less, 3 inches or less, or 2-4.5 inches to avoid criticality events. In embodiments where the nitrate is a nitrate of a non-radioactive metal cation, the shaped column 1 can have a larger diameter if desired.

[0077] Figure 1 The recovery system may include a washing station 200. A basket 5 containing the recovered precipitate is transported to the washing station 200 and positioned above a washing tank 7. An aqueous washing solution is circulated from the washing tank 7 to an outlet above the basket 5 by a pump 8. The washing solution then flows through the basket 5, washing the precipitate.

[0078] The boundaries of the recovery station 100 are defined by barriers 12 and 13. The boundaries of the washing station 200 are defined by barriers 13 and 14. As described below, the basket 5 may be suspended above the collection tank 6 and / or the washing tank 7 using rails or cables 15.

[0079] In various embodiments, the system for recovering uranium can include a drying station 300. Baskets 5 containing washed precipitate are transported to the drying station 300 and hung from hooks or loops 9 on a drying rack 10. The drying rack suspends the baskets above a drip pan 11.

[0080] Once the precipitate in the basket is dried, the basket 5 containing the dried precipitate is transported to the furnace.

[0081] like Figure 2As shown, the basket 5 includes a porous material 23 formed of a material that is stable at a temperature of 500° C. to 800° C. Suitable materials include metals and alloys, such as stainless steel, titanium, molybdenum, titanium-zirconium-molybdenum alloys, nickel, tantalum, tungsten, nickel, nickel-chromium alloys, and alloys thereof. The porous material 23 may be a wire mesh formed of a metal or a metal alloy. In various embodiments, the porous material 23 may be a perforated metal plate formed of a metal or a metal alloy. The porous material 23 may be a fabric or mesh formed of carbon fibers, ceramic fibers, or wires formed of these fibers.

[0082] The basket 5 includes a non-porous material 22 formed of a metal stable at a temperature of 500° C. to 800° C., such as stainless steel, titanium, molybdenum, titanium-zirconium-molybdenum alloy, nickel, tantalum, tungsten, nickel, nickel-chromium alloy, and alloys thereof. The non-porous material 22 increases the rigidity of the basket 5.

[0083] The basket 5 may include a top 21 with a hook or flange 21a. The hook or flange 21a may be configured to suspend the basket 5 above the collection tank 6 and the washing tank 7 by hooking the rail or cable 15 above the collection tank 6 and the washing tank 7. The hook or flange 21a may also be configured to suspend the basket 5 above the drip tray 11 by hooking the hook or ring 9 on the drying rack 10.

[0084] Figure 3 A second embodiment of a system for recovering uranium from a uranyl nitrate solution is shown. Acid-deficient uranyl nitrate flows from inlet 3 to forming column 1, which may be a glass or metal tube bolted to uranyl nitrate recovery housing 31. Basket 5 is located in or above collection tank 6. Pump 4 pumps an alkaline solution (e.g., ammonium hydroxide solution) from collection tank 6 through conduit 33 to forming column 1 through conduit 32. When pump 4 is running, a constant volume of alkaline solution is maintained in forming column 1. Acid-deficient uranyl nitrate is added dropwise to forming column 1 from inlet 3. Uranyl nitrate reacts with the base to form insoluble diuranate, which, along with the recycled ammonium hydroxide solution, is discharged from a nozzle (e.g., ammonium hydroxide solution) at the bottom of column 1. Figure 1 The insoluble diuranate is collected in the basket 5 and the ammonium hydroxide solution flows into the collection tank 6 and is then pumped back to the forming column 1.

[0085] The baskets 5 are then transferred to a position in or above the wash tank 7. Washing solution is pumped by pump 8 through conduit 34 to an outlet above the baskets 5. The washing solution then flows through the baskets 5 into the wash tank 7. The fluid in the wash tank 7 flows through conduit 35 to the pump 8 and is recirculated back to the wash tank through conduit 34. After washing, the washed baskets 5 and their diuranate contents are transferred to a drying station and stored above the drip tray 11 until the diuranate is dry.

[0086] The baskets 5 and their dried diuranate contents are transferred to a recovery oxidation furnace 37. The recovery oxidation furnace 37 can be heated in a variety of ways. The recovery oxidation furnace 37 can have walls formed of graphite that can be resistively heated. The recovery oxidation furnace 37 can be heated by conductive coils. The recovery oxidation furnace 37 can be heated by a high temperature vertical tube furnace 36. The vertical tube furnace 36 can have ceramic heating elements installed therein, such as molybdenum disilicide (MoSi2) heating elements. The vertical tube furnace 36 can reach a temperature of up to 1800°C.

[0087] The precipitate is oxidized in an oxidation furnace. When the system is used to recover transition metals by converting transition metal nitrates (e.g., iron (III) nitrate), a transition metal oxide salt or a transition metal hydroxide salt (e.g., iron (III) hydroxide) is recovered and heated to produce an oxide, such as iron (III) oxide. Similar procedures are applicable to other actinide nitrates, lanthanide nitrates, and transition metal nitrates. For example, zirconium oxynitrate ZrO(NO3)2, cerium nitrate Ce(NO3)3, and yttrium nitrate Y(NO3)3 can be reacted with ammonia or ammonium hydroxide to produce a precipitate, which can be prepared by using a process according to Figure 1 and / or Figure 2 The system is heated and converted into oxides.

[0088] In the case where basket 5 contains ammonium diuranate, the temperature of recovery oxidizer 37 is controlled according to the desired final uranium oxide product. When ammonium diuranate [(NH4)2U2O7] is heated to about 420°C to 550°C, the compound undergoes denitration and is converted to UO3. When ammonium diuranate is heated to about 550°C to 850°C, the compound is converted to an oxide having an approximate molecular formula of U3O8. However, this conversion occurs under ideal conditions; typically, the final product may be a mixture or alloy of various uranium oxides, such as UO2, U2O5, UO3, U3O8, UO2O2, or mixtures thereof. At temperatures >900°C or >1000°C, ammonium diuranate may be converted to an oxide having an approximate formula of U8O 21 of oxides.

[0089] After the ammonium diuranate is converted to oxide ceramic in the recovery oxidation furnace 37, the basket 5 containing the uranium oxide ceramic is transferred to the glove box 38 for cooling. Once the basket 5 has cooled to an acceptable temperature, the basket 5 is recovered via path 41 and the uranium oxide contents are recovered.

[0090] Although various exemplary embodiments have been described in detail with particular reference to certain exemplary aspects thereof, it will be appreciated that the invention is capable of other embodiments and that its details are capable of modification in various obvious respects. It will be apparent to those skilled in the art that changes and modifications may be made within the spirit and scope of the invention. Therefore, the foregoing disclosure, description and drawings are intended for illustrative purposes only and do not in any way limit the invention, which is limited only by the claims.

Claims

1. A method for recovering useful metals from a nitrate solution of a metal cation or a metal oxygen-containing cation, comprising: adding a nitrate solution into a shaped column having an inlet and an outlet nozzle, the nitrate solution being added in a dropwise manner through the inlet, wherein the shaped column comprises a recirculating solution comprising a base selected from the group consisting of ammonia, ammonium hydroxide, an alkali metal hydroxide, and an alkaline earth metal hydroxide; reacting nitrates in the solution with bases in the recirculating solution to produce a precipitate of a metal oxide salt or a metal hydroxide salt; allowing the precipitate and the recirculating solution to exit the forming column through the outlet nozzle; collecting the precipitate in a basket below the forming column while recovering the recirculating solution in a collection tank below the basket; and The recovered recirculating solution is pumped from the holding tank to the forming column.

2. The method of claim 1, wherein the nitrate is a salt of a cation or an oxygen-containing cation of a main group metal, a transition metal, a lanthanide metal or an actinide metal.

3. The method of claim 1, wherein the nitrate is uranyl nitrate, thorium nitrate or plutonium nitrate.

4. The method according to claim 3, wherein: The nitrate is uranyl nitrate, The base is ammonia or ammonium hydroxide, and The precipitate is ammonium diuranate.

5. The process of claim 4, wherein the base is ammonium hydroxide.

6. The method of claim 3, wherein the nitrate is uranyl nitrate, the base is an alkali metal hydroxide, and the precipitate is an alkali metal diuranate.

7. The method according to claim 1, further comprising: washing the precipitate with an aqueous washing solution; and drying the washed precipitate; wherein the precipitate is retained in the basket during the washing and drying steps.

8. The method according to claim 7, further comprising: conveying a basket containing the collected precipitate from beneath the forming column into an oxidation furnace; The basket containing the collected precipitate is heated in an oxidation furnace to convert the precipitate into metal oxides.

9. The method according to claim 8, wherein: The nitrate is uranyl nitrate, The base is ammonia or ammonium hydroxide, The precipitate is ammonium diuranate, and The metal oxide is UO2, U2O5, UO3, U3O8, UO2O2 or a mixture thereof.

10. The method of claim 1, wherein the nitrate is iron (III) nitrate.

11. The method according to claim 10, wherein: The base is ammonium hydroxide, and The precipitate is iron (III) hydroxide.

12. The method of claim 1, wherein the nitrate is yttrium (III) nitrate or cerium (III) nitrate.

13. The method according to claim 12, wherein: The base is ammonium hydroxide, and The precipitate is yttrium (III) hydroxide or cerium (III) hydroxide.

14. A system for recovering useful metals from a nitrate solution of a metal cation or a metal oxygen-containing cation, comprising: a forming column having an inlet and an outlet nozzle, wherein the inlet is configured to allow a nitrate solution to enter the forming column in a dropwise manner; a basket, said basket being positioned below said outlet nozzle; a collecting trough, the collecting trough being located below the basket; and A recirculation system comprising a first pump and a flow path between a collection tank and a forming column, wherein: The first pump is configured to pump a recirculating solution comprising a base from the holding tank to the forming column; and The collection tank is configured to receive the recirculating solution from the forming column; in: The forming column is configured to react the base in the recirculating solution with the nitrate solution to produce a precipitate of a metal oxide salt; The outlet nozzle is configured to allow the recirculating solution and the precipitate to exit the forming column; and The basket is configured to collect the precipitate while allowing the recirculating solution to flow into the collection tank.

15. The method of claim 14, wherein the nitrate is uranyl nitrate, thorium nitrate or plutonium nitrate.

16. A method according to claim 15, wherein the nitrate is uranyl nitrate, the base is ammonia or ammonium hydroxide, and the precipitate is ammonium diuranate.

17. The system of claim 14, further comprising: washing station; washing solution outlet; a washing tank, the washing tank being located below the washing solution outlet; Second pump; and means for conveying a basket containing collected sediment from beneath the outlet nozzle to a washing station; in: the second pump being configured to pump wash solution from the wash tank to the wash solution outlet to generate a wash solution flow; and The means for conveying is configured to position the basket below the wash solution outlet so that the collected precipitate is washed by the wash solution flow.

18. The system of claim 14, further comprising: Oxidation furnace; and means for conveying a basket containing washed sediment from a washing station to an oxidation furnace; The oxidation furnace is configured to convert the precipitate into a metal oxide.

19. The system of claim 18, wherein: The nitrate is uranyl nitrate, The base is ammonia or ammonium hydroxide, The precipitate is ammonium diuranate, and The oxidation furnace is configured to convert the precipitate into uranium oxide.

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