Method for coprecipitation of actinides with different oxidation states and method of obtaining mixed actinide compounds

FIELD: chemistry.

SUBSTANCE: invention can be used to produce heat resistant compounds based on mixed oxides, nitrides or carbides of actinides. A stabilising monovalent cation consisting of oxygen, carbon, nitrogen and hydrogen atoms only or a compound such as a salt which forms the said cation, is added to one or more solutions of actinide(s) containing at least one actinide An¹ and at least one actinide An'¹. A solution or mixture consisting of at least an actinide An¹ with oxidation state (IV), at least one actinide An'¹ with oxidation state (III) and the said stabilising monovalent cation is obtained. A solution of oxalic acid or one of its salts or derivative of that salt is added to the obtained mixture, resulting in simultaneous precipitation of said actinides An¹ (IV) and An'¹ (III), as well as a portion of the stabilising monovalent cation from the said mixture. The obtained precipitate is calcined.

EFFECT: invention enables to obtain homogeneous mixed compounds with controlled composition, whose homogeneity is similar or close to homogeneity of solid solutions of actinides.

29 cl, 6 ex

The present invention relates to a method of co-precipitation of actinides with different degree of oxidation.

In particular, the invention relates to a method of coprecipitation, i.e. the simultaneous deposition of several actinides from used actinoid, at least one has the oxidation state (IV) and at least another oxidation state (III).

Also the invention concerns a method of obtaining a mixed compounds of actinides, in particular mixed oxides, nitrides or carbides of actinides.

The technical field to which the invention relates, may be generally designated as the area receiving mixed compounds of actinides, for example, mixed oxides of the actinides, in particular mixed oxide of uranium and plutonium (U, Pu)O₂and mixed heat-resistant compounds containing part of the group of actinides from thorium to California. The invention aims, in particular, the production of mixed compounds, such as mixed oxides by coprecipitation and subsequent calcination.

Indeed it is known that plutonium, the most frequently primitively to other actinides, in particular uranium, represents the energy type of material that can be used either in light-water nuclear reactors or in nuclear reactors of new generation (such as fast neutron reactors or react in the arts of another type). This strategy has several advantages. In particular, it allows to save fossil raw materials and to reduce unwanted growth of stocks of plutonium, even the inventory of minor actinides in the future.

Thus the reuse of plutonium in reactors with pressurized water has become an industry practice, in which every year a growing fleet of reactors loaded fuel assemblies that use mixed oxide of uranium and plutonium, referred to as MOSS (UO₂-PuO₂).

It is assumed that in the future the new generation reactors will be applied fuel based on uranium, plutonium and minor actinides, such as neptunium, americium, curium and/or California in the form of oxides, carbides or nitrides.

Wide application of nuclear fuel MOSS or advanced fuels, contain, in addition to plutonium and minor actinides, simultaneously makes the required control over the quality and reliability of production and control over the strict application of the materials included in the composition of the fuel, to achieve the required performance fuel conditions of the reactor.

Currently, the powders used in the manufacture of MOSS, prepared by mechanical mixing of oxides UO₂and PuO₂. Obtained from the ect, after pressing, sintering and fine grinding allows to manufacture fuel pellets MOSS, meet modern technical requirements.

The most tried and tested industrial method known as the method MIMAS, includes two basic stages of preparation of the powder: joint grinding powders of uranium oxide and plutonium to obtain a first mixture, called the primary mixture, characterized by a content of plutonium from 25%to 30%, and dry dilution basic mixture with uranium oxide to the desired final plutonium content.

For cooking fuel used powders must exactly match specific properties. In particular, they should have good flowability, high degree of compressibility and ability to be compacted during sintering. An important quality criterion in determining the final properties of the sintered material is a uniform distribution of actinides, such as plutonium, in the material.

High uniformity of such distribution in each sintered tablet is, first, very favorable for the behavior of MOX fuel in the reactor, in particular, with the prospect of increasing the rate of burning, and, secondly, it contributes to the complete dissolution of irradiated fuel during operations regeneration.

This requirement homogeneity of the distribution is of the actinides in the fuel is inevitable for most concepts of fuel for reactors of new generation.

In addition to the methods based on the mixing and joint grinding of powders, there are other ways of sharing conversion by deposition or denitration in the solution of actinides, such as uranium and plutonium, which also allow to obtain, after annealing the mixed compound, usually mixed carbide, nitride or oxide, such as (U, Pu)O₂the distribution of actinides in which is uniform on micron, even submicron level.

The main ways of conversion have in comparison with the mentioned means of mechanical mixing and joint grinding of powders some potential advantages:

a priori easier to ensure a very high distribution of actinides such as U and Pu in the material fuel, for example, in each tablet;

- reduced number of steps and simplifying the technology used in the manufacture of materials based on mixed-resistant phase, usually in the form of a mixed oxide, carbide or nitride, such as fuel MOSS, the possible elimination of points of comminution and mechanical homogenization;

- reduced difficulty of operation, due to the manipulation of powders containing mostly minor actinides;

- reduced waste and industrial waste;

- reducing the possibility of the spine access to plutonium or other fissile actinide and therefore, reducing the risk of proliferation at the stage of preliminary storage of nuclear materials.

In contrast to the industrial process for the production of mixed oxides based almost exclusively on mechanical mixing oxide powders, the main symptom, in most of the ways of conversion, is the mixing of the constituent elements of the synthesized material in solution.

If necessary, the uniform distribution of these elements in the solid that formed after a chemical reaction (chemical reactions), as a rule, is achieved. Another common symptom is the presence of the final stage, which is usually heat treated to produce the target material.

Among the ways the joint conversion of actinides with getting oxides can schematically be divided in three major groups according to the method of obtaining a solid phase on the basis of the initial mixture in solution: methods of deposition methods, Sol-gel and methods of thermal denitration:

the precipitation is the most widely used method, oxalic acid, ammonium, carbonate and peroxide methods to be used primarily for simple conversion of obtaining oxide, in particular, uranium oxide or plutonium, can be adapted and optimized for joint converse is,

in accordance with the same principle ways "Sol-gel" allow you to get a solid state by the application of phase "gelation";

also "simple" heat of solution allows to obtain solid state: such methods of conversion are called thermal generirovanie because the original solution is usually nitric acid medium and evaporation of the solution leads to the formation of intermediate forms salts of nitric acid.

The last two types of conversion methods, namely the method "Sol-gel" and the method of thermal denitration direct relation to the invention do not have.

How "Sol-gel" have the following disadvantages:

- experience in respect of conversion actinoid (actinoid) in industrial scale, is much inferior to the experience gained by the methods of deposition,

the formation of ammonia effluent, which is difficult to process, in particular, when the content of minor actinides,

- the use of a large number of reagents, re-use or removal of the decomposition products is usually necessary.

How denitration which, while simple, allows to obtain products, as a rule, relative to the average quality for which it is often necessary to subsequently apply the DOP is leitlinie additives and/or mechanical or thermal processing.

Ways of conversion, based on precipitation, more precisely, on the coprecipitation require interim arrangements insoluble salt, which is then separated and calcined to obtain the necessary oxide.

These methods can generally be obtained after annealing the mixed compounds such as oxides, of higher quality. Indeed, these methods allow greater flexibility to modify the physico-chemical properties of compounds influence on the process parameters during coprecipitation and/or calcination.

It should be noted that the clearance from other residual contained in the solution elements is, as a rule, at the stage coprecipitation: these residual elements are, for example, impurities present in the solution deposited actinides and which fission products.

This indicator cleaning is more or less high depending on the precipitating reagent and the conditions of its use.

For implementing the method of coprecipitation with achieving greater efficiency requires compliance with the following conditions:

- it is necessary to ensure a relatively high solubility of mixed elements in solution before precipitation;

you need to ensure conditions for a relatively low solubility elements during deposition;

the kinetics of deposition of these elements should be almost identical;

- the resulting insoluble salt should be neither too stable or too unstable to the stage calcination was carried out easily and reliably;

- regulation of intermediate products must not cause insurmountable difficulties.

In the group of coprecipitation methods are usually distinguished in relation to the actinides, in particular uranium and plutonium, the two approaches: one, according to which both elements have the same degree of oxidation, and the other, according to which both elements have different degrees of oxidation.

The first approach is simpler and is the co-deposition of actinides at the same degree of oxidation, which is absolutely necessary for the simultaneous and uniform deposition through co-crystallization of two actinides within the same system, for example, using uranium and plutonium U (IV) and Pu (IV) perform the same role.

The main difficulty in the implementation of these methods is to pre-stabilize the overall degree of oxidation in solution. These methods are described in the document FR-A-2815035, which refers to the actinides in oxidation state (IV).

However, this approach cannot be easily transferred to the production of mixed oxides based on uranium, plutonium, neptunium, protective and/or thorium, and americium, curium, berkelium and/or California.

The most used variant of implementation of these methods when regeneration is the use of U (VI) Pu (IV), which is easy to get in nitric acid solution. Can also be used a mixture of U (IV) - Pu (III) in solution, while maintaining reducing conditions and/or in the presence of compounds that prevent the formation of nitrogen compounds.

These methods coprecipitation according to the second approach, based on the pairs of uranium and plutonium in solution, actinoid ions are used, usually deposited in the form of salts with different molecular structure. The thus obtained precipitation is not consistent joint perfect crystallization of uranium and plutonium. Therefore, the uniformity of the distribution of plutonium is essentially limited. You can specify, for example, on the way to "simultaneous precipitation of U (VI) Pu (IV)in an ammonia environment, in which the formation of the hydroxide of plutonium and diurnal ammonium, which form a heterogeneous powders of oxides, requiring complex types of mechanical processing.

In addition, non-simultaneous deposition and different degrees of solubility observed in these conditions are the causes of the shortcomings inherent in this group the way. You can specify, for example, oxalic precipitation, which States:

a significant difference between the solubility of oxalate of uranium U(VI) solubility of plutonium oxalate (IV);

- the difference between the respective ranges of precipitation of plutonium oxalate (III) and oxalate of uranium (IV).

In addition, the parameters of the method, such as acidity, etc. that do not have the same effect on the solubility of these salts of uranium and plutonium.

In other words, methods of coprecipitation according to the second approach, which uses the actinoids with different oxidation to achieve simultaneous and uniform deposition of the complex relevant actinides must meet one of the following two conditions:

- chemical conditions favorable for the simultaneous and uniform deposition of different structures, each of which can be oxidized to the desired degree, that is, as a rule, difficult to implement, except when using a compromise solution in the conditions of deposition to the detriment of the efficiency of deposition reaches a uniform distribution of actinides in the solid precipitate;

- joint crystallization of actinides within the same crystal structure, suggesting the presence in this structure, at least two locations for actinides, ka is every of which is able to oxidize to a predetermined extent, or having a single location for actinoid able to oxidize to two different degrees. This overall structure, if present, is formed, as a rule, at exactly the specified amount of each of the actinides. This reduces the flexibility of the method of obtaining the mixed compounds in the case when you want to obtain the composition of the actinides, which differs from the composition of compounds obtained joint crystallization.

However, the second approach, which at present is of particular interest for producing compounds of mixed type with a very high uniformity of distribution of actinides in the solid precipitate, and then in the product, such as, for example, fuel tablet, requires overcoming certain difficulties.

From documents describing the coprecipitation of actinides, you must specify the following :

In the document KM. MICHAEL, PS. DHAMI "Recovery of plutonium from oxalate supematante by coprecitation using uranous nitrate" (Extraction of plutonium from oxalic uterine fluid during coprecipitation using nitrate of uranium), BARC/1996/E: 016 (1996)described the extraction of plutonium by coprecipitation contained in oxalic obtained by conversion of the mother solution by adding to the uterine nitrate solution to uranium.

The purpose described in this document, is a sharp decrease in losses PL is tone in the mother solution by secondary deposition of plutonium and opt only one coprecipitation compounds, forming in the calcination mixed oxide, such as (U, Pu)O₂with perfect uniformity.

Also document Rd. BANUSHALI, Ic. PIUS, Sk. MUJERKEE, Vn. VAIDYA "Removal of plutonium and americium oxalate from supernatants by coprecipitation with thorium oxalate" (Extraction of plutonium and americium from oxalic mother solutions when the oxalate coprecipitation of thorium), Journal of radioanalytical and nuclear chemistry 240, (3), str-979 (1999), describes the joint extraction of plutonium and americium from oxalic mother solutions of the additive in the effluent of thorium oxalate, followed by coprecipitation.

The goal pursued in this paper is similar to the purpose of the above-mentioned document. It consists in reducing the losses of plutonium and americium in oxalic mother solution at their deposition ensuring the finding of these radioactive elements in the solid matrix.

In the document .KELLER, D. FANG "Über Karbonatkomplexe des dreiwertigen Americiums compounds des vier - und sechswertigen Urans und Plutoniums" (carbonate complexes of four - and hexavalent uranium and plutonium), Radiochimica Acta 11, 3-4, p.123-127 (1969), reported a method of obtaining a homogeneous sediment (U, Pu)O₂. Uranium and plutonium during the initial oxidation state VI is given jointly by the oxidation state IV by electrolysis in an alkaline medium in the presence of carbonate.

Received carbonate complexes were then precipitated and decompose with obtaining the oxide by heating in terms of vacuu the and. The main disadvantages of this method are the necessity of using an alkaline environment and the complexity of the operation of the ignition.

In the document EP-A-0251399 describes mainly the precipitation of plutonium from the organic phase, such as TBP (tributyl phosphate), which is diluted and containing plutonium and uranium, with the addition of water the mixture of oxalic acid and nitric acid. Besieged plutonium oxalate is dried and heat transfer in the plutonium oxide.

In this method, the uranium contained along with the plutonium in the end connection in very small quantities, is in the organic phase with oxidation state VI, with plutonium has the oxidation state IV. The target compound does not possess the required optimum quality necessary to obtain mixed oxides with excellent distribution.

In the document WO-A-97/25721 described joint precipitation of uranium and plutonium to separate them from the elements contained in the solution of irradiated fuel. This method is used carboxylic or polycarboxylic acid to precipitate uranium in oxidation state VI and plutonium in oxidation state IV. This method does not aim at achieving uniformity in the resulting sludge. The difference between the oxidized States of U and Pu is expressed in this case, as noted in this paper, through a phenomenon rassle the Oia, which leads to preferential deposition of plutonium, uranium same remains largely in solution.

Document Atlas, "J. Nucl. Materials 249 (97), p.46-51, relates to a method of coprecipitation of U and Th. It informs about the special case in which the presence of thorium in one stable oxidation state (IV) in solution eliminates any possibility for the occurrence of redox reactions with uranium (IV), which is not typical for most other complexes consisting of actinides. In this document, which describes a pair of elements of Th (IV) - U (IV), Coosada actinides with the same degree of oxidation. Using thorium, which in solution has only the oxidation state (IV), the specified coprecipitation through co-crystallization of actinoids is relatively simple. This method can be transferred, if necessary, on all other pairs of elements Th - An (IV), where An denotes Pa, Np or Pu. But it does not seem possible application of the method, for example, for Th - U (IV) - Pu (IV), as U (IV) and Pu (IV) cannot simultaneously be present in the solution, in this regard, we can refer to document FR-A-2815035, which will be discussed below.

Developed in this paper, the method is of interest in relation to the production of fuel thorium series (U, Th), but it is completely unusable in them is usamsa as for other homogeneous joint oxides, such as co, oxides of U, Pu, used for MOX fuel, because it does not guarantee to maintain the oxidation state IV during deposition and, therefore, joint crystallization of uranium and plutonium.

In other words, disclosed in the above document, the method has a single goal: obtain joint oxides (U, Th) by coprecipitation. It is not suitable for the preparation of solid perfect solutions (U, Pu)O₂the coprecipitation in the production of fuels such as MOSS, or a large number of mixed oxides containing at least two actinoid of actinides from thorium to California according to the periodic table of elements.

In the already mentioned document FR-A-2815035 says about the way of co-precipitation of actinides in oxidation state (IV) and the way to obtain mixed oxides of actinides by calcination of the resulting sludge. These mixed oxides can be used, for example, in the production of nuclear fuels type of MOSS.

The coprecipitation method described in this paper involves the complexation of actinides with oxidation state (IV) for kinetic or thermodynamic stabilization of the oxidation state (IV) in the mixture in the form of a solution before coprecipitation. The products obtained coprecipitation are mixed connections with perfect uniformity, as would the and obtained joint crystallization. After calcinations get mixed oxides with perfect uniformity.

This method cannot be applied in respect of the following actinides due to the inability to maintain them with oxidation state (IV) in solution under the described conditions: americium, curium, berkelium, or California. To apply this method of coprecipitation is not always easy, in particular, the stabilization of mixtures of actinides (IV) requires several steps and is hardly compatible with the operations of the continuous coprecipitation required in industrial production.

Therefore, there is an unmet need in the way of co-precipitation of actinides in solution and having different oxidation States, namely oxidation States (IV) and (III), in particular in an acidic environment, such as nitric acid.

In particular, there is a need in the way in which to save different oxidation States, respectively, (IV) and (III)of actinides in solution and to achieve efficient co-precipitation of these elements with different oxidation States, respectively, (IV) and (III)must not occur redox reaction between the actinides in solution.

In other words, there is a need in the way in which the solution is stored actinides with different oxidation States, respectively, (IV) and (III)to enable the x afterwards by coprecipitation in mixed homogeneous connections, after allowing the ignition to get mixed compounds such as homogeneous mixed oxides, coming to a perfect solid solution and free from mineral impurities.

Therefore, there is an unmet need in the way that simultaneously could provide:

the coprecipitation stable or present in the solution of actinides with oxidation state (IV) and (III), in particular, in an acidic environment, such as nitric acid,

obtaining a solid, very homogeneous mixed compounds with controlled composition, the uniformity of which is equal or near-homogeneous solid solutions of actinides and containing qualitative and quantitative aspects of the actinides with oxidation state (IV) and (III)initially present in solution.

There is, in particular, the need for the way in which "major" actinides, namely uranium and plutonium that can somadatta with "minor" actinides, namely, neptunium, americium, curium, with the formation of a homogeneous mixed compounds such as oxalate, calcining, which allows to obtain a homogeneous mixed phase, such as oxide.

In addition there is a need in the way, which would be combined:

- media used in the cycle of fuel production, frequent in the spine, with traditional nitric acid environment

with the appropriate equipment (simple, reliable),

- continuous operating mode,

- difficulties in working with chemicals and wastewater in a closed and highly radioactive space.

The aim of the present invention is to provide a method of coprecipitation (or simultaneous deposition), at least one actinoid with oxidation state (IV) and at least one actinide with oxidation state (III), which, among other things, satisfy the aggregate of the above requirements and generally meets the above requirements for the coprecipitation methods.

Another objective of the present invention is a method of co-precipitation of at least one actinide with oxidation state (IV) and at least one actinide with oxidation state (III), which would not contain the drawbacks, limitations, defects and disadvantages inherent in the methods known from the prior art, and which would address the challenges facing technology.

These and other objectives are achieved according to the invention by using a coprecipitation method (or simultaneous deposition) at least one actinoid with oxidation state (IV) and at least one actinide with oxidation state (III)in which:

- according to the first variant done is of the way, which is the most common, which is required to ensure the stability of one or more actinides with oxidation state (IV), or (III) in solution:

a) add a singly charged stabilizing cation consisting only of oxygen atoms, carbon, nitrogen and hydrogen, or connection, such as forming the above-mentioned cation salt of one or more solutions actinoid (actinoid), contains (contain) in General, at least one actinoid An¹and at least one actinoid An'¹so, in order to obtain a solution or mixture comprising at least one actinide An¹with oxidation state (IV)at least one actinide An'¹with oxidation state (III) and the said singly charged stabilizing cation, and oxidation state (IV) and (III) if necessary, receive at the preliminary stage or simultaneously by chemical or electrochemical recovery;

b) in this mixture add a solution of oxalic acid or one of its salts or a derivative of this salt, resulting in the simultaneous precipitation of actinides An¹(IV) and An'¹(III) and part of the singly charged stabilizing cation of the above-mentioned mixture.

Stabilizing a singly charged cation consisting only of oxygen atoms, carbon, nitrogen and hydrogen, or connect the tion, such as forming a cation salt, add, usually in the form of a solution of the specified cation or compounds, such as forming a cation salt, this solution is mixed with the specified one or more solutions of actinides.

Stage a) of the method according to the invention in the first embodiment, its execution may be performed, for example, as follows:

- singly charged stabilizing cation consisting only of oxygen atoms, carbon, nitrogen and hydrogen, or connection, such as forming the cation of the salt, add, at least in the first aqueous solution of at least one actinide An¹so, in order to stabilize the oxidation state (IV) actinoid or An actinoid¹and this oxidation state (IV) was received or will receive, if necessary, at the preliminary stage or simultaneously by chemical or electrochemical recovery;

at least one second aqueous solution of at least one actinide An'¹add the given singly charged stabilizing cation so as to stabilize the oxidation state (III) actinoid or An actinoid'¹moreover , the oxidation state (III) receive, if necessary, at the preliminary stage or simultaneously by chemical or electrochemical recovery;

- mix, prefer the Ino carefully, these first and second solutions, each containing singly charged stabilizing cation; then carry out step b).

The mixture or solution containing at least one actinoid An¹(IV) and at least one actinoid An'¹(III) specified and stable singly charged cation, such as a means of preventing the formation of nitrogen compounds can also be derived directly, and not by mixing the specified at least one first and at least one second solutions each containing singly charged stabilizing cation. In particular, it can be obtained by the addition of singly charged stabilizing cation in a single solution containing at least one actinoid An¹that can be stabilized in oxidation state (IV), and at least one actinoid An'¹that can be stabilized in oxidation state (III), if necessary at the preliminary stage or simultaneously by chemical or electrochemical phase redox regulation of these actinides An¹An'¹with the degree of oxidation, respectively, (IV) and (III). This mixture can also be obtained, mainly only occasionally, during operations for the regeneration fuel, for example, when the joint extraction of the decree is the R actinoid An ¹(IV) and An'¹(III) from the organic phase aqueous solution containing singly charged stabilizing cation.

As a rule, named the mixture can be prepared in different ways, while it contains the actinoids An¹(IV) and An'¹(III)oxidation States are stabilized in the presence of the specified single-charged cation.

In the second embodiment of the method according to the invention, which is a special case in which the respective oxidation States (IV) and (III) at least two contained actinoids are stable in one and the same solution does not require, as in the first embodiment, the stabilizing compounds, such as means, prevent the formation of nitrogen compounds:

- thoroughly mix, at least, the first aqueous solution of at least one actinide An¹with oxidation state (IV) and at least a second aqueous solution of at least one actinide An'¹when oxidation state (III);

type a singly charged cation consisting only of oxygen atoms, carbon, nitrogen and hydrogen and not having redox properties with respect to zoosadism the actinides, or connection, such as forming a specified cation salt to the mixture to obtain the value of the solution with the content of deposited actinides and singly charged cation;

- add a solution of oxalic acid or one of its salts or a derivative of this salt in this mixture, obtained after the introduction of a singly charged cation, resulting in the simultaneous precipitation of actinides An¹(IV) and An'¹(III) and part of the singly charged cation from a mixture.

Typically, the mixture can be obtained in different ways, there are mentioned An actinoid¹(IV) and An'¹(III), and added a singly charged cation.

In the third embodiment of the method according to the invention:

- prepare an aqueous solution with a content of at least one actinide with oxidation state (IV) and at least one actinide with oxidation state (III), for example, by simple mixing at least two solutions, each of which contains one of these actinides with the specified degree of oxidation under the condition that the actinoids with a specified degree of oxidation can simultaneously be present in the same solution;

in this solution actinoid add a solution of oxalic acid or one of its salts or a derivative of this salt, which was introduced singly charged cation consisting only of oxygen atoms, carbon, nitrogen and hydrogen, or connection, such as forming a cation salt, resulting from ukazannoj the solution of actinides is the simultaneous precipitation of actinides with oxidation state (III) and (IV), as well as the parts contained in the solution a singly charged cation.

Thus according to a third variant of the process singly charged cation consisting only of oxygen atoms, carbon, nitrogen, and hydrogen added to the precipitating solution of oxalic acid or one of its salts or a derivative of this salt instead of the additive in the solution is deposited actinides.

According to the third variant of execution, especially in the case when the corresponding oxidation States (IV) and (III) at least two contained actinoids are stable without the use of a stabilizing compound, such as a means of preventing the formation of nitrogen compounds, singly charged cation, for example, is identical to the cation, which could be added to the initial solution of actinides, if I used the second version of the runtime.

According to the third variant of execution in the case when the corresponding oxidation States (IV) and (III) at least two contained actinoids are not stable in solution or in mixtures containing deposited actinides in the mixture or in solutions of actinides used to prepare this mixture, pre-enter additive, namely cationic or nicotianae stabilizing agent. Such additive is chosen, for example, from compounds of the act is one to maintain the reducing properties of a solution, or compounds that prevent the formation of nitrogen compounds.

Preferably, in the third embodiment, the singly charged cation remained unchanged after the addition of oxalic acid or one of its salts or a derivative of this salt, and the actinides are in the oxidation States in which they existed in the solution or mixture of actinides to make the specified supplements.

The present invention is based on a new method of co-precipitation with the use of the method after the addition singly charged cation (consisting only of oxygen atoms, carbon, nitrogen and hydrogen) or simultaneously with the addition of a singly charged cation in solution, which allows quantitative coprecipitation complex actinides (IV) and (III)present in the solution, usually with obtaining a mixed oxalate of one or more actinides (IV) and one or more actinides (III).

A singly charged cation is, as a rule, the so-called "stabilizing" a singly charged cation, which is preferably by means that prevent the formation of nitrogen compounds used for the stabilization of oxidation States (IV) and (III) of the actinides, or according to the second and third options run the cation is added in the pre-mixture of actinides and/or in solution save the eve of acid deposition.

In the General case (the first version of the implementation) of the cation (e.g., ion of hydrazine for U (IV) - Pu (III)) is used to stabilize the oxidation and helps during codeposition of education mixed compounds containing U (IV) and Pu (III).

In the second and third cases, the cation such as ammonium ion, used for Pu (IV), Am (III), promotes during the codeposition of the formation of mixed compounds containing, for example, Pu (IV) and Am (III), without the stabilizing influence on the degree of oxidation.

A singly charged cation is, as a rule, the structure of the precipitated compounds and is generally responsible for the formation of mixed structures oxalate of one or more actinides (IV) and one or more actinides (III) with special properties. The feature of these structures is that:

they usually are much less soluble than the well-known structure of simple oxalate actinide (IV) simple oxalate actinide (III)formed in the coprecipitation conditions in the absence of this cation

typically, the location of the actinides (IV) and (III) the structures are equivalent despite the difference of a charge, this allows for a completely homogeneous coprecipitation (at molecular level), previously contained in the solution group of actinides (IV) and (III) if a wide range is not the relative content of one or more actinides (IV) and one or more actinides (III).

In some cases, when locations are not equivalent, they are similar at the molecular level and can be only partially filled, which allows to obtain properties, very similar to the above,

- minor actinides, such as americium, curium, even berkelium and californium, can somadatta quantitatively, for example, when the degree of deposition of more than 95% for each actinide, initially present in solution at a concentration above 5.10^-3mol/l, together with thorium and/or protactinium and/or uranium and/or neptunium and/or plutonium.

In other words, according to the invention, a solution of at least one actinide (IV) and at least one actinide (III) is prepared with the additive in it singly charged stabilizing cation in the General case, when the cation allows to stabilize or contributes to the stabilization of at least one of actinides with oxidation state (IV), or (III) in this solution. This solution is prepared, for example, by mixing at least one solution actinide (IV) and at least one solution actinide (III) after the addition singly charged cation in each solution.

In case a singly charged cation or salt forming its place, add in a solution of actinides and/or in a solution of oxalic acid or one of the f salt or derivative of this salt, applied during the coprecipitation.

Simultaneous and uniform deposition of actinides can therefore be achieved by addition of a solution of oxalic acid or one of its salts or a derivative of this salt. This achieves quantitative indicators of this deposition exceeding, for example, 95% for each actinide, initially present in solution at concentrations exceeding 5.10^-3mol/l and submicron uniform distribution of all actinides in a solid.

It is obvious that in addition to the described advantages of the method according to the invention has all the advantages mentioned above and inherent in the methods of deposition.

The method according to the invention differs from the method disclosed in FR-A-2815035, the use of actinides with oxidation state (IV) and (III) instead of actinides only with oxidation state (IV).

For comparison it should be noted that the method according to the invention allows to minimize the use of complexing additives for kinetic or thermodynamic stabilization of actinides with oxidation state (IV) prior to coprecipitation.

It also allows you to reach a very high homogeneity soosazhdenie solids, which is at least as high as the uniformity in the method according to FR-A-2815035, in a wide range the Onet chemical conditions and with varying amounts of different actinides.

Mainly the method according to the invention allows the use of any actinoid from thorium to California, to the extent that it is based on the coprecipitation of one or more actinides (IV) and one or more actinides (III). Therefore, it can be used to obtain compounds of mixed type in any combination of possible actinoids, provided that this compound will contain at least one of the following actinides: th, protactinium, uranium, neptunium and plutonium, and at least one of the following actinides: plutonium, americium, curium, berkelium, californium, to ensure that the initial concentration in the solution, at least one actinoid with oxidation state (IV) and at least one actinide with oxidation state (III).

Finally, the method according to the invention can easily be applied when receiving mixed compounds containing actinides in a continuous mode, in particular, it can be applied in chemical technology at industrial facilities for oxalic conversion of plutonium with getting PuO₂.

The method according to the invention is applicable preferably to coprecipitation of the two actinides, but it allows coprecipitation more than two actinides, for example four.

In this case, for example, in the first embodiment, a PR is sotavlyaet solution of n actinides (IV) and m actinides (III), add to it, in particular, singly charged stabilizing cation, namely cation, ensuring stabilization or contributing to it, and at least one actinoid with oxidation state (IV), or (III). This solution is prepared, for example, a thorough mixing of the n solutions of actinoid with oxidation state (IV) and m solutions actinoid with oxidation state (III), m may be equal to or different from n, add the specified singly charged cation in each solution, get a solution from An¹to Anⁿwith oxidation state (IV) and from the solution of An'¹to the solution of An'^mwith oxidation state (III).

This is followed by the simultaneous deposition of these actinides An¹(IV)An²(IV), ...Anⁿ(IV)An'¹(III)An'²(III)An'^m(III) and cation of the above-mentioned mixture.

The second and third embodiments of the method according to the invention are applied similarly for n+m actinides.

Below the invention is described with reference to two actinides, however, it is clear that this description applies to the number of actinoids > 2.

In the first embodiment of the method according to the invention singly charged cation generally perform the role of agents, stabilizing the actinoids with oxidation state (III) and (IV) in solution, while it also serves as a means of preventing the formation of azoty the mentioned compounds. With regard to the first option run singly charged cation is selected, therefore, as a rule, from ion hydrazine, while ions of hydrazine contain one or more alkyl groups.

A stabilizing agent, which is optionally negationem and additionally applied in the third embodiment, may be chosen from compounds that prevent the formation of nitrogen compounds, and/or anti-oxidant compounds. Preferably, it consisted solely of atoms of oxygen, carbon, nitrogen and hydrogen. This stabilizer is selected from the following non exhaustive list:

from sulfonic acids and their derivatives, compounds having properties that prevent the formation of nitrogen compounds, are preferred, in particular, sulfamic acid and its salt,

- hydrazine and its derivatives, compounds with properties that prevent the formation of nitrogen compounds, are preferred, in particular, hydrazine and its salts,

from hydroxylamine and its derivatives, compounds having properties that prevent the formation of nitrogen compounds and/or anti-oxidant properties in relation to some of the actinoids are preferred, in particular, hydroxylamine and its salts,

among the compounds, etc which prevent the formation of nitrogen compounds can be specified on urea and its derivatives, family Asimov, family hydroxyamino acid and its derivatives,

among the compounds that prevent the formation of nitrogen compounds and/or anti-oxidant funds in relation to some of the actinides, in particular, it is possible to specify peroxide,

among anti-oxidant funds in relation to some of the actinides can be specified on ascorbic acid and its salts.

The precipitating agent is oxalic acid, its salts, such as ammonium oxalate or its derivatives, such as alkyl oxalates; indeed its use is associated with a number of additional special advantages, which will be discussed below.

The deposited solution containing An actinoid¹and An'^lwhen the degree of oxidation, respectively, (IV) and (III), as well as the first solution actinoid An¹and the second solution actinide An'¹which are optionally used in its preparation, are generally acidic solutions, predominantly aqueous acidic solutions. It is also preferred that they were aqueous solutions of nitric acid.

The concentration of actinides An¹and An'¹in the deposited solution may vary within wide limits, but generally it is 10^-4- 1 mol/l, preferably 0.1 to 0.2 mol/L.

The ratio between the number of moles of anotherapplication, contained in the solution of actinides and/or precipitating of the solution and used for co-precipitation of actinides, and the number of moles of the precipitated complex actinoid An and An'¹is, as a rule, from 0.5 to 5, preferably from 0.5 to 1.

The concentration of actinides contained in the mixed solution, prepared or available prior to the coprecipitation, are, as a rule, during the initial preparation of the mixtures is equal to the concentration corresponding to the quantity of actinides in mixed connection (e.g., oxide), prepared by annealing the product of co-precipitation.

Preferably, at the time of codeposition of the total molar concentration of actinides with oxidation state (IV) (thorium, protactinium, uranium, neptunium and/or plutonium, depending on the destination) exceeded the total molar concentration of actinides with oxidation state (III) (americium, curium, berkelium, californium and/or plutonium, depending on the destination).

The method is carried out at the stage of preparation of solutions, and on the stages of mixing, coprecipitation or simultaneous deposition, usually in the range from 0° to the boiling point, preferably at a temperature close to the room temperature, for example, from 20 to 60°C.

The pH during the precipitation depends, in particular, from the deposited mixed oxalates, but the n is, as a rule, less than 1, it is preferable that the final acidity, in particular, the environment of deposition after the reaction was about 1 mol/L.

In the second embodiment of the method according to the invention deposited solution with the content of An¹and An'¹according to the oxidation state (IV) and (III)a first and second solutions of actinides An¹and An'¹that was used for its preparation, are, as a rule, acid solutions, predominantly aqueous acid solutions.

Preferably, they were aqueous solutions of nitric acid.

The concentration of actinides An¹and An'¹in the deposited solution may vary within wide limits, but generally it ranges from 10^-4to 1 mol/l, preferably from 0.1 to 0.2 mol/L.

A singly charged cation is (not roll) cation, such as ammonium or Quaternary ammonium.

Then there is the coprecipitation or simultaneous deposition conditions are the same as those of the first variant implementation of the method.

The method according to the second variant execution is carried out, generally at a temperature of from 0°C. to the boiling point, preferably at a temperature close to the room, as at the stage of mixing, and implementation phases precipitating agents and conducting simultaneous wasp is Denia.

The invention relates to a method for producing mixed compounds with the contents of An¹and An'¹where these actinides Coosada method according to the invention described above, whether first, second or third embodiments of the followed by a calcination product of co-precipitation.

Received mixed compounds containing actinides choose, usually of mixed oxides, carbides and nitrides of actinides.

Due to the fact that the compounds obtained by the coprecipitation method according to the invention, are homogeneous mixed oxalates, in particular, compounds in which the actinides (IV) and (III) are equivalent or close to the molecular level locations, mixed, obtained after calcinations compounds such as mixed oxides are compounds with homogeneous distribution of actinides, in particular, in very General terms, the magnitude of not more than microns to molecular scale in the case of obtaining a perfect solid solution.

In addition, mixed compounds such as mixed oxides, can be obtained at any ratio of components.

Mixed compounds may contain in its composition - this is one of the major unexpected advantage of the invention is a mixture of actinides from thorium to California, provided the pressure in this line, at least one of the following actinides: th, protactinium, uranium, neptunium and plutonium, as well as at least one of the following actinides: plutonium, americium, curium, berkelium, californium, to ensure according to the invention the initial presence in solution of at least one actinide with oxidation state (IV), or (III).

Preferably, the total content of actinides (IV), such as thorium, protactinium, uranium, neptunium and plutonium (provided that the degree of oxidation of the latter during coprecipitation is (IV)), exceeding the total content of actinides, such as americium, curium, berkelium, californium, and plutonium (provided that the degree of oxidation of the latter during coprecipitation is (III)). This is the value of the preferred method of coprecipitation according to the invention, in which the total molar content of actinides with oxidation state (IV) exceeds the total molar content of actinides with oxidation state (III) at the time of coprecipitation.

The calcination is conducted, as a rule, under the following conditions:

- temperature is equal to or greater than 650°C,

the atmosphere is oxidizing, inert or reducing, depending on the type of mixed compounds

- the duration of the calcination is generally 1 hour or more.

Oxidative atmosferasolar, typically, oxygen, in particular, oxygen in the air.

The inert atmosphere contains, typically, argon or helium.

Reducing atmosphere contains, as a rule, the inert gas is mixed with hydrogen or methane.

In the synthesis of mixed nitrides atmosphere is a mainly a mixture of nitrogen and hydrogen.

In the synthesis of mixed carbides used primarily inert or reducing atmosphere.

In the synthesis of mixed nitrides or carbides during annealing add additional carbon, usually in oversexualization quantity relative to the quantity of actinides, for example, in the form of activated carbon with a large specific surface (in particular, a few hundred m²/g) to simplify carbothermic reduction at elevated temperatures, typically greater than or equal to 1000°C.

Received mixed connections are used, in particular, for the preparation of nuclear fuel, such as mixed oxide of uranium and plutonium, called MOX or mixed carbide or nitride or oxide of uranium, neptunium, plutonium, americium, or curium, as it is planned for nuclear reactors of new generation.

Obtained from actinides mixed compound according to the invention can be used as source material for p is production mixing powders heat-resistant phases of different composition.

In particular, obtained according to the invention, the oxide of uranium and plutonium can be used either as a primary mixture of powders or in the form of a powder mixture with the final content. Subsequent execution of the method of producing nuclear fuel tablets MOSS is known and contains the traditional stages of pressing, sintering and fine grinding.

The method according to the invention can be successfully used for the fabrication of targets for transmutation (for example, on the basis of Np, Am and/or Cm) or for long-term storage of materials (U, Np, Am, Cm, Th, Pa, Bk, Cf) in the form of oxides, and the oxides produced by the method similar to the methods described below.

More method according to the invention is explained below in the description for clarification and not restrictive.

First described first embodiment of the method according to the invention, which represents the most General case.

In this case, at least in the first aqueous solution, at least the first actinoid An¹with oxidation state (IV) is added singly charged stabilizing cation, which can be called a stabilizing means in the form of cation.

Preferably, a singly charged cation performed the function of a means that prevents the formation of nitrogen compounds.

If necessary, referred to the aq is th solution previously or simultaneously subjected to chemical or electrochemical recovery to make actinoid An ¹oxidation state (IV).

Such chemical or electrochemical reduction can be carried out, for example, in the following conditions:

for uranium: the recovery of uranium (VI) to uranium (IV) in nitric acid medium can be carried out using hydrogen under pressure with a catalyst, in the presence of a means that prevents the formation of nitrogen compounds; for neptunium: recovery of neptunium (VI) or neptunium (V) to neptunium (IV) can be carried out using hydroxylamine nitrate in the environment; for plutonium: the recovery of PU (VI) PU (IV) can be carried out in nitric acid medium with the addition of the hydrogen peroxide; for protective: restoring protective (V) protactinium (IV) can be carried out by electrolysis in acidic complexing environment.

Typically, such a solution actinide (IV) is acidic predominantly aqueous solution of nitric acid.

Singly charged stabilizing cation, which is preferably additional means for preventing the formation of nitrogen compounds, usually choose from ions of hydrazine and acylhydrazone, while the preferred cation is an ion of hydrazine. This single-charged cation is introduced into the solution, usually in the form of compounds, such as forming a singly charged cation salt, depending on the properties of the process is and, such as acid properties or concentration of nitrate solution cation, slow mixing a basic solution of hydrazine with a solution of nitric acid.

The concentration of acid in the solution is generally from 0.1 to 5 mol/l, preferably from 1 to 1.5 mol/L.

The concentration of actinoid An¹with oxidation state (IV) in the solution is generally 10^-4- 1 mol/l, preferably 0.1 to 0.5 mol/L.

In the same way as in the preparation of the first solution actinoid An¹(IV) containing singly charged stabilizing cation, prepared separately, preferably at the same time the second solution actinide An'¹(III), for example, of Pu (III); such preparation is conducted, as a rule, in conditions similar to those described above and used for the first solution, if necessary technological conditions change.

Prior or simultaneous chemical or electrochemical reduction when receiving An'¹(III) may be performed, for example, in the following conditions: for plutonium: the recovery of plutonium (IV), PU (V) or PU (VI) PU (III) can occur in nitric acid medium in the presence of ions of hydrazine by electrolysis with a corresponding potential or by moderate heating of the solution (up to 50-60°C).

It is preferable to add the same singly charged stabilizing cation mainly in the form of funds, prevent the formation of nitrogen compounds, as previously used.

Preferably, the cation that acts as a means of preventing the formation of nitrogen compounds, served ion hydrazine. Typically, a solution of actinide (III) is an acid solution, preferably an aqueous solution of nitric acid.

The concentration of acid in solution actinide (III) is usually 0.1 to 5 mol/l, preferably 1.0 to 1.5 mol/L.

The concentration of actinides'an'¹(III) the second solution is generally 10^-4- 1 mol/l, preferably 0.1 to 0.5 mol/L.

Thus, at least two solutions of actinide (III) and actinide (IV) are primarily aqueous solutions, preferably aqueous solutions of nitric acid.

Thus prepared solutions actinide (IV) and actinide (III) are thoroughly mixed, for example, in the mixer.

Under thorough mixing means to obtain a homogenous environment at the level of Micromuse.

The stability of the oxidation States (IV) and (III) after the addition of stabilizing cation is such that mixing of the two solutions occurs without oxidation-reduction reactions, while before mixing is not produced which moves the lower oxidation state (IV) and (III) An actinoid ¹and An'¹.

Typically, the resulting mixture does not occur, the reaction between An¹(IV) and An'¹(III) and the solution forming the mixture is stable for an extended period of time of 5 hours up to more than 7 days. Therefore, there is a long period for end-stage coprecipitation or simultaneous deposition.

The content of the mixture, at least, in both solutions actinoid (actinoid) (IV) and (III) corresponds to the ratio between An¹and An'¹in the final mixed oxide.

The mixing may be conducted by any content (0<An¹/An'¹<100%). Preferably, the mixing was carried out so that the content of An¹exceeded the content of An'¹.

For example, if you want to get after annealing the mixed oxide of uranium and plutonium formula (U_0,725Pu_0,275)O₂, mix ratio of components in both solutions, one of which is a solution of uranium (IV)and the other solution of plutonium (III), respectively of 72.5% and 27.5%.

Also, for example, in the case when, after annealing is required to obtain a mixed oxide of uranium and curium formula (U_0,90Cm_0,10)O₂mix ratio of components in both solutions, one of which is a solution of uranium (IV), and the other - Rast is the PR of curium (III), respectively 90% and 10%.

It should be noted that in some cases the solution actinoid (actinoid) (IV) and actinide (actinoid) (III), prepared as described above, i.e. by mixing at least two fluids of actinide An'¹(III) and actinide An¹(IV)containing singly charged stabilizing cation can be prepared in a simple way that is sometimes optimal. For example, it can be made more directly by mixing at least two solutions, each of which contains one or more actinides with the addition of a singly charged cation in the mixture or pre-in solutions actinoid (actinoid) before mixing, and this Supplement make, if necessary, at the stage of chemical or electrochemical reduction in order to achieve the appropriate oxidation state (IV) and/or (III). For example, the solution can be prepared in a simple way from a single solution with a content of at least one actinide An¹and at least one actinide An'¹the addition of a singly charged cation in the solution, and this Supplement make, if necessary, at the stage of chemical or electrochemical reduction to achieve the desired oxidation States (IV) and (III).

The next step of the method according to image ateneu is the coprecipitation or simultaneous deposition of one or more actinoid or actinides (IV) and one or more actinoid or actinoids (III), for example, uranium (IV) and plutonium (III).

The specified deposition is carried out mainly by the mixing of a solution of oxalic acid or, if necessary, the solution with the content of oxalate ions, such as ammonium oxalate solution, with the above described mixture of actinides (IV) and (III).

This coprecipitation according to the invention is uniform due to the presence of mixed compounds in the form of oxalates of actinides (IV) and (III), and after annealing the sludge receive the mixed compound, for example, a mixed oxide (An¹An'¹)O₂such as (U, Pu)O₂that is also quite homogeneous, especially in the presence of U (IV) and Pu (III).

In the case of the use of oxalic acid when conducting coprecipitation invention provides a number of additional special advantages, namely:

the reagent is already being used in the way "PUREX processes" during the final conversion of plutonium nitrate formed during the cleaning cycles, the oxide PuO₂. Its use in the method of coprecipitation An¹An'¹such as the method of coprecipitation of U and Pu, is a priori compatible with the equipment in the shops regeneration;

- decomposition of oxalates actinoid flows easily and can lead to the formation of compounds such as oxides with a proven ability to sintering;

- currently fully mastered the control prom the industrial scale contents of this reagent in the effluent.

Preferably, ions, oxalate was used in excess relative to the stoichiometric value when the reactions of actinides contained in the above mixture, consisting of actinides (IV) and (III). This excess ions is preferably such an amount that the concentration of oxalate ions in the supernatant solution above the coprecipitation product, was 0.05-0.25 mol/l, preferably 0.10 to 0.20 mol/l Acidity above-described mixture of actinides (IV) and (III) establish mainly such that the free acidity of the supernatant solution was 0.25 to 2.5 mol/l, mostly 0.5 to 1.5 mol/L.

The coprecipitation is carried out, generally at the same temperature as the temperature at the previous stages, i.e. typically at a temperature of from 0 to 60°C, at which get quite homogeneous connection, for example, a mixed oxalate of actinides (IV) and (III) containing singly charged stabilizing cation.

This connection is separated from the mixture, or more precisely, from the supernatant liquid, any suitable method for separation of liquid and solid substances, for example, filtration, centrifugation, etc.

In the case when you want to get mixed compound, such as a mixed oxide, the extracted product coprecipitation calcined in the atmosphere, corresponding to the type of mixed compounds the Oia in accordance with the programmed corresponding temperature.

For example, if you want to make mixed oxide (An¹An'¹)O₂such as (U, Pu)O₂based on soosazhdenie product consisting of a mixed oxalate of U (IV) and Pu (III), the calcination is carried out mainly in the atmosphere of inert gas at a temperature of at least 650°C. (preferably at about 950°C) for at least one hour (preferably two hours or more).

Preferably, the final temperature of annealing was, for example, 950°C, while the temperature was raised in stages and make the shutter speed, for example, at 150 and 600°C.

The following is a description of the second variant of the process according to the invention, represents a special case in which soosazhdenie actinides may be present in solution with oxidation state (IV) and (III) without any additives cation as a stabilizing oxidation-reduction means and which, as a rule, means preventing the formation of nitrogen compounds.

In the second embodiment, the:

at least the first solution actinoid An¹contains this actinoid with oxidation state (IV) (for example, a nitric acid solution of plutonium (IV)). The concentration of actinoid is usually 10^-4- 1 mol/l, preferably 0.1 to 0.5 mol/liter;

the acidity of the leaves, as a rule, 0.1 to 5 mol/l, preferably 1.0 to 1.5 mol/liter;

at least a second solution actinide An'¹contains this actinoid with oxidation state (III) (for example, a solution of Am (III), such as a nitric acid solution of Am (III)). The concentration of actinide and acidity are in the same range as above.

At least, two solutions are thoroughly mixed together.

In the form of a solution or salt is administered singly charged cation consisting only of oxygen atoms, carbon, nitrogen and hydrogen and not with respect to the present actinoids redox properties, in a solution containing actinides with oxidation state (IV) and (III) to obtain a solution with a content of deposited actinides and singly charged cation.

This single-charged cation should not be confused with the so-called "stabilizing" a singly charged cation used in the first embodiment, since he has no property stabilization of oxidation States.

Referred to singly charged cation chosen from, for example, ammonium and substituted ammonium ions, such as ions of alkylamine, in particular, Quaternary ammonium ions, such as ions of tetralkylammonium, of all ions is preferred ammonium ion.

In the same way as in the first embodiment, the mixing of solutions is b is C the oxidation-reduction reactions and without affecting the oxidation state (IV) and (III) actinoid before mixing.

The total concentration of actinides (IV) in the mixture is typically 10^-4- 1 mol, preferably 0.1 to 0.2 mol/L.

The total concentration of actinides (III) in the mixture is typically 10^-4- 1 mol/l, preferably 0.1 to 0.2 mol/L. Preferably, this concentration did not exceed the total concentration of actinides (IV) in the mixture.

Also the ratio of different solutions of actinides (IV) and (III) in the mixture is usually correspond to the ratios of actinides in the final mixed connection, such as the final mixed oxide.

The description of the sequence of steps of the method in the second embodiment, namely the coprecipitation and calcination, the same as in the first embodiment of the method or in the General case discussed above. More precisely, the deposition preferably carried out by mixing a solution of oxalic acid or, if necessary, the solution with the content of oxalate ions, such as a solution of oxalate of ammonia, with the above described mixture of actinides (IV) and (III).

This coprecipitation according to the invention is uniform due to the presence of mixed compounds in the form of oxalates of actinides (IV) and (III)calcining the precipitate provides getting mixed compounds, for example, a mixed oxide (An¹, An^'1)O₂such as (Pu, Am)O₂that is also quite homogeneous, in particular, in case of application of Pu (IV) and Am (III).

It is preferable to use ions of oxalate in excess relative to the stoichiometric composition when reacted with actinides present in the above-described mixture of actinides (IV) and (III). This excess is preferably such an amount that the resulting concentration of oxalate ions in the supernatant solution above the coprecipitation product was 0.05-0.25 mol/l, preferably 0.10 to 0.20 mol/l Acidity above-described mixture of actinides (IV) and (III) is preferably set such that the free acidity in the supernatant solution was 0.25 to 2.5 mol/l, preferably 0.5 to 1.5 mol/L.

The coprecipitation is carried out, generally at the same temperature as the temperature at previous stages, i.e. typically at a temperature of 0-60°C, you get a completely homogeneous connection, for example, a mixed oxalate of actinides (IV) and (III) and singly charged cation.

The specified connection is separated from the mixture, more precisely, from the supernatant solution, using any suitable means of separation of liquid and solids, such as filtration, centrifugation, etc.

If you want to prepare the mixed compound, such as a mixed oxide obtained by coprecipitation product is subjected to a subsequent annealing in the atmosphere corresponding to the nature of the required smeshanogalogenidnym when the programmed temperature.

For example, if you want to make mixed oxide (An¹, An^'1)O₂such as (Pu, Am)O₂based on the coprecipitation product, consisting of mixed oxalate, Pu (IV) and Am (III), the calcination is carried out mainly in an atmosphere of air at a temperature of not less than 650°C. (preferably 950°C) with a duration of at least one hour (preferably within 2 hours or more).

Preferably, the final temperature of annealing was, for example, 950°C, while the temperature was raised in stages, producing exposure at 150 and 600°C.

The third embodiment of the method, which is less common, is that they add a singly charged cation consisting only of oxygen atoms, carbon, nitrogen and hydrogen, in the precipitating solution instead of the additive in the solution of the deposited actinides.

This cation has no stabilizing action (as it is added is not in the solution of actinides), however it can be identical singly charged stabilizing cation used in the first embodiment, or (not roll) singly charged cation used in the second embodiment.

Precipitating solution is, for example, a solution of ammonium oxalate, and ammonium acts as a singly charged cation.

However, stabilization of the Oia oxidation States (IV) and (III) of actinides in solution with a content of deposited actinides should be provided if necessary by the addition means, prevent the formation of nitrogen compounds and/or cationic or negativnogo antioxidant selected depending on the actinides, for example, of the following compounds: sulfamic acid, urea, hydrogen peroxide, hydroxylamine, ascorbic acid, or recovery under appropriate conditions that do not affect the coprecipitation or a calcination product of co-precipitation, consisting of mixed oxalate.

The description of the sequence of steps of the method according to the third variant of execution, namely deposition is the same as the description of the first variant implementation of the method or the General case discussed above.

Examples 1-6.

The following describes the invention with reference to the examples for clarification and are not restrictive.

Example 1

This example was performed coprecipitation of U (IV) and Pu (III), stable in solution ion hydrazine, a solution of oxalic acid.

Technological conditions were as follows:

A mixture of actinides:

[U(IV)]=[Pu(III)]=0,056 mol/l

[N₂H₅⁺]=0.10 mol/l

[HNO₃]=1.0 mol/L.

The precipitating solution:

[H₂C₂O₄]=0.50 mol/l

[HNO₃]=1.0 mol/l

Simultaneous and uniform deposition is achieved by thorough mixing with the room is the temperature of the mixture of actinides and precipitating solution, taken in equivalent proportions.

During annealing soosazhdenie oxalate in an argon atmosphere for 1 hour at temperatures above 650°C To form mixed completely homogeneous oxide (U, Pu)O₂corresponding solid solution.

The degree of deposition for each actinide amounted to more than 99%.

Example 2

In this example, the coprecipitation of U (IV) and Pu (III), stable in solution ion of hydrazine, conducted with a solution of oxalic acid, the content of uranium and plutonium was different.

Technological conditions were as follows:

A mixture of actinides:

[U(IV)]=0,080 mol/l,

[Pu(III)]=0,0305 mol/l,

[N₂H₅⁺]=0.10 mol/l,

[HNO₃]=1.0 mol/L.

The precipitating solution:

[H₂C₂O₄]=0.51 mol/l,

[HNO₃]=1.0 mol/L.

Simultaneous and uniform deposition was ensured thorough mixing between a room temperature mixture of actinides and precipitating solution, taken in equivalent proportions.

The degree of deposition for each actinide amounted to more than 99%.

During annealing soosazhdenie homogeneous mixed oxalate in an argon atmosphere for 1 hour at temperatures above 650°C was formed mixed, completely homogeneous oxide (U_0,725Pu_0,275)O₂corresponding solid solution.

Example 3

In comprimere coprecipitation of U (IV) and Pu (III), stable in solution ion of hydrazine, conducted with a solution of oxalic acid, and the uranium content was significantly higher than the plutonium content.

Technological conditions were as follows:

A mixture of actinides:

[U(IV)]=0,099 mol/l,

[Pu(III)]=0,0075 mol/l,

[N₂H₅⁺]=0.10 mol/l,

[HNO₃]=1.0 mol/L.

The precipitating solution:

[H₂C₂O₄]=0.51 mol/l,

[HNO₃]=1.0 mol/L.

Simultaneous and uniform deposition was ensured thorough mixing between a room temperature mixture of actinides and precipitating solution, taken in equal proportion.

The degree of deposition for each actinide amounted to more than 99%.

During annealing soosazhdenie homogeneous mixed oxalate in an argon atmosphere for 1 hour at temperatures above 650°C was formed mixed, completely homogeneous oxide (U_0,93Pu_0,07)O₂corresponding solid solution.

Example 4

In this example, spent the coprecipitation of Th (IV) and Pu (III), the latter was stable in solution ion of hydrazine, a solution of oxalic acid, the quantity of precipitated thorium and plutonium was different.

Technological conditions were as follows:

A mixture of actinides:

[Th(IV)]=0.16 mol/l,

[Pu(III)]=0.04 mol/l,

[N₂H₅⁺]=0.20 mol/l,

[HNO_{3 ]=1.0 mol/L.}

_{The precipitating solution:}

_{[H2With2About4]=0.7 mol/l,}

[HNO₃]=1.0 mol/L.

Simultaneous and uniform deposition was ensured thorough mixing between a room temperature mixture of actinides and precipitating solution, taken in equivalent proportions.

The degree of deposition for each actinide amounted to more than 99%.

During annealing soosazhdenie homogeneous mixed oxalate in an argon atmosphere for 1 hour at temperatures above 650°C was formed mixed, completely homogeneous oxide (Th_0,80Pu_0,20)O₂corresponding solid solution.

Example 5

In this example, spent the coprecipitation of Th (IV), U (TV), Np (IV), Pu (III) and Am (III) with a solution of oxalic acid, while U (IV), Np (IV) and Pu (III) were stable in solution in a mixture of ion of hydrazine.

Technological conditions were as follows:

A mixture of actinides:

[Th(IV)]=0.12 mol/l,

[U(IV)]=0.04 mol/l,

[Np(IV)]=0.02 mol/l,

[Pu(III)]=0.02 mol/l,

[Am(III)]=0.0001 mol/l,

[N₂H₅⁺]=0.20 mol/l,

[HNO₃]=1.0 mol/L.

The precipitating solution:

[H₂C₂O₄]=0.7 mol/l,

[HNO₃]=1.0 mol/L.

Simultaneous and uniform deposition was ensured thorough mixing between a room temperature mixture of actinides and precipitating solution, integration of the s equivalent value.

The degree of deposition for each actinide (except americium) was more than 99%, americium, the concentration of which in this example is much less compared to other actinides in the mixture, this level was higher or about 80%.

During annealing soosazhdenie homogeneous mixed oxalate in an argon atmosphere for 1 hour at temperatures above 650°C was formed mixed, completely homogeneous oxide (Th_0,60U_0,20Np_0,10Pu_0,10Am_0,0005)O₂that was close to the state of solid solution or corresponded with him.

Example 6

This example was performed coprecipitation of Pu (IV) and Am (III) with a solution of oxalic acid, the content of plutonium and americium was different. Pu (IV) and Am (III) was found to be stable in the mix despite the lack of funds prevent the formation of nitrogen compounds. Then to the mixture was added ammonium ion using pre-acidified solution of ammonium hydroxide.

Technological conditions were as follows:

A mixture of actinides:

[Pu(IV)]=0.16 mol/l,

[Am(III)]=0.04 mol/l

[NH₄⁺]=0.20 mol/l,

[HNO₃]=0.8 mol/L.

The precipitating solution:

[H₂With₂About₄]=0.7 mol/l,

[HNO₃]=0.8 mol/L.

Simultaneous and uniform deposition was ensured thorough mixing between them at room tempera is ur mixture of actinides and precipitating solution, taken in equivalent proportions.

The degree of deposition for each actinide amounted to more than 99%.

During annealing soosazhdenie homogeneous mixed oxalate in air for 1 hour at temperatures above 650°C formed a homogeneous mixed oxide (Pu_0,80Am_0,20)O₂that was close to the state of solid solution or corresponded with him.

1. The coprecipitation method (simultaneous deposition), at least one actinoid with oxidation state (IV) and at least one actinide with oxidation state (III)in which:
a) stabilizing a singly charged cation consisting only of oxygen atoms, carbon, nitrogen and hydrogen, or connection, such as forming a specified cation salt, add one or more solutions actinoid (actinoid) containing at least one actinide An¹and at least one actinide An'¹obtaining a solution or mixture, consisting at least of actinoid An¹with oxidation state (IV)at least one actinide An'¹with oxidation state (III) and the specified singly charged stabilizing cation, with oxidation States (IV) and (III) receive, if necessary, prior to or simultaneously by chemical or electrochemical reduction;
b) in this mixture add recipients who have the oxalic acid, or one of its salts or a derivative of this salt, resulting in the simultaneous deposition of these actinides An¹(IV) and An'¹(III), and part of the singly charged stabilizing cation of the above-mentioned mixture.

2. The method according to claim 1, in which the singly charged stabilizing cation consisting only of oxygen atoms, carbon, nitrogen and hydrogen, or connection, such as forming such a cation salt, add a solution of the cation or compounds, such as forming the cation of the salt, which is mixed with the specified one or more solutions of actinides.

3. The method according to claim 1 or 2, wherein stage a) is carried out as follows:
stabilizing a singly charged cation consisting only of oxygen atoms, carbon, nitrogen and hydrogen, or connection, such as forming the cation of the salt, add at least one first aqueous solution of at least one actinide An¹to stabilize the oxidation state (IV) actinoid or An actinoid¹and this oxidation state (IV) receive, if necessary, at the preliminary stage or simultaneously by chemical or electrochemical reduction;
specified singly charged stabilizing cation type, at least one second aqueous solution of at least one actinide An'¹for hundred of the waste utilization technologies oxidation state (III) actinoid or An actinoid' ¹moreover , the oxidation state (III) receive, if necessary, at the preliminary stage or simultaneously by chemical or electrochemical reduction;
carefully mix the above at least the first and second solutions, each containing singly charged stabilizing cation.

4. The method according to claim 1 or 2, in which at the stage of (a) singly charged stabilizing cation or compound, such as forming the cation of the salt, add in one solution containing at least one actinoid An¹able to stabilize in oxidation state (IV), and at least one actinoid An'¹able to stabilize in oxidation state (III), to obtain a solution in the form of a mixture of at least one actinide An¹with oxidation state (IV)at least one actinide An'¹with oxidation state (III) and singly charged stabilizing cation, and, if necessary, prior to or simultaneously by chemical or electrochemical phase by oxidation-reduction set for the specified actinoids An¹and An'¹the degree of oxidation, respectively, (IV) and (III).

5. The method according to claim 1 or 2, in which the mixture to which was added a solution of oxalic acid or one of its salts or a derivative of this salt is obtained by coprecipitation named actinoid is in An ¹(IV) and An'¹(III)present in the organic phase aqueous solution containing singly charged stabilizing cation.

6. The coprecipitation method, at least one actinoid with oxidation state (IV) and at least one actinide with oxidation state (III)in which:
thoroughly mix at least a first aqueous solution of at least one actinide An¹with oxidation state (IV) and at least a second aqueous solution of at least one actinide An'¹with oxidation state (III),
a singly charged cation consisting only of oxygen atoms, carbon, nitrogen and hydrogen and not having redox properties with respect to zoosadism the actinides, or connection, such as forming a specified cation salt, add this mixture to obtain a solution with a content of deposited actinides and singly charged cation
a solution of oxalic acid or one of its salts or a derivative of this salt is added to the mixture obtained after the introduction of a singly charged cation, resulting in the simultaneous precipitation of actinides An¹and A'¹with the degree of oxidation, respectively, (IV) and (III) and part of the singly charged cation of the above-mentioned mixture.

7. The coprecipitation method, at least one actinoid with oxidation state (IV) and at least one actinoid with oxidation state (III)in which:
prepare an aqueous solution with a content of at least one actinide An¹with oxidation state (IV) and at least one actinide An'¹with oxidation state (III), for example, by simple mixing at least two solutions, each of which contains one of these actinides with the specified degree of oxidation, and these actinides with the degree of oxidation can jointly be contained in the solution;
in this solution actinoid add a solution of oxalic acid or one of its salts or a derivative of this salt, which was added singly charged cation consisting only of oxygen atoms, carbon, nitrogen or hydrogen, or connection, such as forming the cation of the salt, resulting in the simultaneous precipitation of actinides with oxidation state (III) and (IV) from the specified solution of actinides, as well as the deposition part of the cation contained in the solution.

8. The method according to claim 1, in which the singly charged stabilizing cation selected from cations, can prevent the formation of nitrogen compounds.

9. The method of claim 8, wherein said singly charged stabilizing cation selected from ions of hydrazine, as well as ions of hydrazine with one or more alkyl groups of the mi.

10. The method according to claim 6 or 7, in which a singly charged cation selected from ammonium, and substituted ammonium ions, in particular, Quaternary ammonium ions, such as ions of tetralkylammonium.

11. The method according to claim 1, wherein the step of chemical or electrochemical reduction carried out as follows:
for uranium: the recovery of U (VI) to U (IV) in nitric acid medium hold with hydrogen under pressure in the catalyst in the presence of a means that prevents the formation of nitrogen compounds,
for neptunium: recovery of Np (VI) to Np (IV) or Np (V) to Np (IV) conduct hydroxylamine nitrate in the environment,
for plutonium: the recovery of Pu (VI) Pu (IV) is carried out in nitric acid medium by means of the additive hydrogen peroxide or recovery of Pu (IV, V, VI) to Pu (III) is carried out in nitric acid medium in the presence of ions of hydrazine by electrolysis with a corresponding potential,
for protective: recovery of Pa (V) Pa (IV) is carried out by electrolysis in acidic complexing environment.

12. The method according to claim 7, which further conduct the stabilization of oxidation States (IV) and (III) actinoid stabilizing additive, cationic or cationic not a means selected from compounds that prevent the formation of nitrogen compounds and/or anti-oxidant compounds.

13. The method according to item 12, in which the stabilizing agent is chosen is of sulfamic acids and their derivatives, such as sulfamic acid and its salts, hydrazine and its derivatives such as hydrazine and its salts; hydroxylamine and its derivatives, such as hydroxylamine and its salts; urea and its derivatives; Asimov; hydroxamic acid and its derivatives; hydrogen peroxide; ascorbic acid and its salts.

14. The method according to claim 1 or 6, or 7, in which these solutions actinoid An¹An'¹are acid solutions, preferably aqueous acid solutions.

15. The method according to 14, in which these solutions are aqueous solutions of nitric acid.

16. The method according to claim 1 or 6, or 7, in which the concentration of actinides An¹and An'¹in each of the solutions, of which spend the coprecipitation is 10^-4- 1 mol/l, preferably 0.1 mol/l - 0.5 mol/l in solutions of actinoid An¹or An'¹and preferably 0.1 to 0.2 mol/l in a solution or mixture of actinides An¹(IV) and An'¹(III).

17. The method according to claim 1 or 6, or 7, in which the ratio between the number of moles of stabilizing or not singly charged stabilizing cation in the solution of actinides and/or precipitating of the solution and the number of moles in the precipitated complex actinoid An¹and An'¹is usually 0.5 to 5, preferably 0.5 to 1.

18. The method according to claim 1 or 6, or 7, in which the content of actinides in solution and in the mixture and one or more actinides (IV) and one or more actinides (III) corresponds to the content of actinides in mixed connection, such as the oxide, which can be obtained by annealing the product of co-precipitation.

19. The method according to claim 1 or 6, or 7, in which the sum of the molar concentrations of actinides with oxidation state (IV) in the mixture, on the basis of which is the coprecipitation, exceeds the sum of molar concentrations of actinides with oxidation state (III).

20. The method according to claim 1 or 6, or 7, in which the method is carried out at a temperature of from 0°C. to the boiling point.

21. The method according to claim 1 or 6, or 7, in which the coprecipitation or simultaneous deposition is carried out by thoroughly mixing the solution containing oxalate ions, and mixtures containing at least one actinoid (IV) and at least one actinoid (III).

22. The method according to claim 1 or 6, or 7, in which actinoid or actinoids with oxidation state (IV) is selected from thorium (IV), prolactine (IV), neptunium (IV), uranium (IV) and plutonium (IV).

23. The method according to claim 1 or 6, or 7, in which actinoid or actinoids with oxidation state (III) is selected from the plutonium (III), americium (III)and curium (III), berkelium (III) and California (III).

24. The method according to claim 1 or 6, or 7, in which An¹means uranium, a'an'¹- plutonium.

25. The method of obtaining the mixed compounds of actinides An¹and An'¹in which the actinides with oxidation state (IV) and (III) Coosada the method according to any of the preceding paragraphs, followed by calcination of the resulting sludge.

26. The method according A.25, in which the calcination is conducted in an oxidizing, inert or reducing atmosphere at a temperature of 650°C. or higher for 1 hour or more.

27. The method according to p. 25 or 26, in which received mixed compounds selected from mixed nitrides, carbides and oxides of actinides.

28. The method according to item 27, which when annealed add carbon for the formation of mixed compounds selected from mixed nitrides and carbides of actinides.

29. The method according to p, in which the calcination is carried out at a temperature of 1000°C and above.