Method of preparing spent carbide nuclear fuel for extraction processing (versions)

FIELD: chemistry.

SUBSTANCE: method includes neutralising complexing ligands contained in nitrate solution of carbide fuel via oxidation thereof with nitric acid in the presence of a catalyst in the form of a polyvalent metal which is located in the nitrate solution or is added before or after dissolving spent carbide nuclear fuel, said metal being selected from: cerium, iron, manganese, technetium, mercury. Further, the method includes heating the nitrate solution of the carbide fuel or performing oxidation directly in the process of dissolving the carbide fuel in nitric acid in the presence of a catalyst with subsequent dissolution in the oxidised solution of the carbide fuel of the oxide or metallic spent nuclear fuel, or performing simultaneous oxidation of complexing ligands and dissolving the oxide or metallic spent nuclear fuel in the solution of the carbide fuel. An alternative solution includes performing similar preparation of the spent carbide nuclear fuel for extraction processing, followed by mixing the oxidised solution of the carbide fuel with solutions of oxide or metallic spent nuclear fuel or direct addition of the required amount of a zirconium nitrate solution or a solution of another polyvalent metal-complexing agent.

EFFECT: avoiding the need to use powerful oxidising agent.

13 cl, 12 ex

 

The invention relates to the field of processing of spent nuclear fuel in nuclear power plants (NPP SNF) and can be used in the preparation of carbide SNF to the extraction processing of extracting a multivalent actinides from solutions containing complexing ligands.

It is known that the fuel on the basis of carbides of uranium and plutonium has several advantages compared to the currently used oxide fuel. High nuclear density carbide when used as fuel in fast reactors increases the efficiency of primary and reproduction rate of the secondary fuel, and a high heat transfer coefficient can increase the heat load in the fuel elements (Cartridges)that enables you to achieve high burnup and, therefore, reduce the cost of the nuclear fuel cycle.

However, the use of carbide fuel is constrained by limited information about its properties and behavior at high burnup, some difficulties of production technology, as well as problems related to its extraction processing. In particular, when dissolved in nitric acid fuel of this type is formed in the solution a significant amount of polybasic carboxylic acids and hydroxy acids,preventing extraction extraction multivalent actinides, that makes it impossible for the handling of these solutions without processing or preparation, which eliminates the complexing action of these substances in relation to plutonium.

There are two approaches to the solution extraction processing solutions carbide SNF, one of which lies in suppressing the action of complexing ligands by linking to them from the elements, complexes which are stronger than the complexes with plutonium. The second way is to complete the destruction of the ligands a strong oxidant with a simultaneous oxidation of the plutonium to Ri(+6).

In the rst approach, there is a method of preparing carbide SNF (Zverev D. V., Kirillov S.N., Dvoeglazov K.N., Shadrin monitoring computerized Logunov, M.V., Mashkin A.N., Schmidt O.V., Arseenkov L.V. Possible Options for Uranium-carbide SNF Processing. ATALANTE 2012 Intern. Conf. on Nuclear Chemistry for Sustainable Fuel Cycl. Elsevier B. V., Procedia Chemistry, 2012, v.7, p.116-122), which consists in a joint dissolution of uranium carbide AMB SNF and SNF from VVER in concentrated nitric acid. The essence of this method is, first of all, the binding of polybasic acids in the solid complex with zirconium, which is manifested in the loss of these compounds in the residue after extraction of the solution with the bulk of uranium and extremely inconvenient when carrying out continuous countercurrent extraction process. However, after the separation of this precipitate PU(+4) freely and fully, and uvlekaetsja TBP diluted.

Under the second approach is known a method of preparation of solution vysokobarievogo carbide mixed uranium-plutonium spent fuel, including the oxidation of contained complexing ligands by ozonation in the presence of a catalyst to ensure extraction extraction multivalent actinides (Natarajan R. Reprocessing of FBTR mixed carbide fuel - some process chemistry aspects. Proc. 16thAnn. Conf. Ind. Nucl. Soc. INSAC-2005. Mumbai, 2005. Paper IT_21). In this process, which is taken as a prototype, plays the role of a catalyst dissolved shrapnel cerium.

The disadvantage of this method is not only a need for a thorough destruction of polybasic carboxylic acids and hydroxy acids, which complexing substances, but also the transition of PU (+4) less extractable state PU (+6), which requires additional redox treatment. Also the disadvantages of this method include the restrictions in the choice of structural materials equipment and distillation of the resulting camerahouse ruthenium, including radioactive isotopes, which destroyed with the formation of deposits on the walls of the ducts.

Also known variation of the catalytic oxidative destruction of one of the types of ligands, namely oxalic acid in the mother solution after precipitation of plutonium by dlitelnogopolzovanija (boiling) nitrate solution in the presence of manganese (+2) as a catalyst (Koltunov B.C. Kinetics and mechanism of oxidation of oxalic acid by nitric acid in the presence of ions of Mn2+. Kinetics and catalysis, 1968, v.9, No. 5, s-1041). However, validation of this method on solutions carbide SNF showed that the completeness of extraction recovery of plutonium is not achieved, i.e. the oxidation of complexing ligands in acceptable time is incomplete.

The invention solves the task of preparing carbide SNF to the extraction processing of extracting a multivalent actinides from solutions containing complexing ligands in a way that eliminates the disadvantages of the prototype, in particular the use of a strong oxidant, by applying a weak oxidizing methods in the presence of catalysts.

To achieve the mentioned technical result in the claimed method of preparing carbide SNF to the extraction processing of extracting a multivalent actinides from its nitric acid solutions containing complexing ligands, it is proposed to carry out the oxidation of complexing ligands by heating nitric acid solution carbide fuel in the presence of a catalyst, or to carry out the oxidation of complexing ligands in the process of dissolution of the carbide fuel in nitric acid, in the presence of a catalyst, followed by dissolving the oxidized solution to Bednogo fuel oxide or metal fuel or conduct simultaneous operations oxidation complexing ligands and dissolution of the oxide or metal SNF in solution carbide fuel.

As a complexing ligand solution carbide fuel contains oxalic acid, Melitopol and other polybasic carboxylic acids and oxyacids, and the oxidation catalyst used polyvalent metal in nitric acid solution selected from the range of: cerium, iron, manganese, technetium, mercury. In the solution of the carbide fuel is dissolved superior amount of oxide spent fuel, which can be used SNF from VVER, RBMK, PWR, BWR, or metal SNF, which can be irradiated standard uranium blocks or spent fuel based on uranium-aluminum alloy. The dissolution of the added songs while destruction of polybasic carboxylic acids and hydroxy acids is carried out in slow mode at temperatures up to 90°C and the duration of treatment up to 10 hours.

In an alternative solution to achieve the mentioned technical result, the proposed method is proposed to conduct training carbide SNF to the extraction processing of extracting a multivalent actinides from its nitric acid solutions containing complexing ligands, by oxidation complexometry is their ligands by heating nitric acid solution carbide fuel in the presence of a catalyst or to carry out the oxidation of complexing ligands in the process of dissolution of the carbide fuel in nitric acid, in the presence catalyst, with subsequent mixing of the oxidized solution carbide fuel solutions oxide or metal SNF or the introduction of a solution of zirconium nitrate or a solution of another polyvalent metal-complexing agents.

The hallmark of the proposed method is the combination of several techniques: the destruction of the above complexing ligands by heating nitric acid solution carbide fuel in the presence of polyvalent metals as catalysts or oxidizing complexing ligands in the process of dissolution of carbide fuel in the presence of polyvalent metals as catalysts, the use of this method for oxidation of polybasic carboxylic acids and hydroxy acids in the containing solution carbide SNF and picking residue by adding solutions of zirconium, including through the carbide dissolution in the solution of additional types of spent fuel (oxide or metal) exceeds the number, or by mixing the oxidized solution carbide fuel solutions oxide or metal SNF.

During this operation the catalytic destruction of complexing ligands and dissolution of additional SNF can be combined by dissolving in C the slow mode with consideration of the kinetics of oxidation of impurities, and catalysts are fission products (cerium, technetium) and impurities corrosion of iron. With this procedure at the stage of extraction of secondary sedimentation is absent.

Thus, significantly simplifies the processing of carbide SNF.

The ability of the proposed technical solutions of the following examples.

Example 1

Carbide SNF AMB was dissolved in 3.0 mol/l nitric acid for 4 h at 90°C to obtain a solution containing 50 g/l U; 0.5 g/l of Pu and other elements 2.2 mol/l HNO3. Next, the resulting solution is sent to PUREX process, but in bacuranao zone sediment is deposited zirconium salts with organic acids, which contains 30-40 mg Pu per gram of sediment. The residual Pu content in the raffinate is ~30 mg/l was also observed color of the organic phase in bacuranao zone extraction, suggesting that this solution cannot be processed without the elimination of complexing action of ligands in solution.

Example 2

Carbide SNF AMB was dissolved in 3.1 mol/l nitric acid for 6 hours at a temperature of 80°C to obtain a solution containing 60 g/l U; 0.6 g/l of Pu and other elements of 2.4 mol/l HNO3. Then to the resulting solution carbide fuel add an aqueous solution of Mn(+2) at a molar against the AI carbide uranium : manganese =40-80:1, then produce heating the resulting solution for 6 hours at 75°C to obtain a solution containing 50-59 g/l U; 0,5-0,59 g/l Pu.

Next, the resulting treated solution is sent to PUREX process, where the residual Pu content in the raffinate is ~5 mg/l During the processing of this solution in bacuranao area extraction cascade no sedimentation and staining of the organic phase. This example indicates the oxidation of polybasic carboxylic acids and hydroxy acids, and the need to link the remaining complexing ligands, due to excessive discharge of plutonium (>1 mg/l).

Example 3

Carbide SNF research reactor BR-10 was dissolved in 3.0 mol/l nitric acid for 6 hours at a temperature of 80°C to obtain a solution containing 60 g/l U; 0.4 g/l of Pu and other elements 2.2 mol/l HNO3. Next, to the obtained solution carbide fuel add an aqueous solution of Mn(+2) at a molar ratio of the carbide of uranium : manganese =40-80:1, and then produce heating the resulting solution for 6 hours at 75°C. After that, the processed solution carbide SNF add a solution of zirconium nitrate to kompleksowe residual quantities of ligands with obtaining a solution containing ~2 g/l Zr.

Next, the resulting treated solution is sent to PUREX-a process that is quite the Pu content in the raffinate is less than 1 mg/l, that meets the discharge standards. This example confirms the possibility of oxidation of polybasic carboxylic acids and hydroxy acids and binding residue using a Zirconia.

Example 4

To a solution of carbide SNF SBA, heated together with Mn(+2), analogously to example 3 add a solution of the VVER spent fuel with a burnup of 40 GW·d/t, containing 3.0 mol/l HNO3300 g/l U; 2.7 g/l Pu and 1 g/l Zr; 0.6 g/l Mo and other elements, balance of processing receive a solution containing 250 g/l U and-2.5 g/l Pu 2.9 mol/l HNO3. Received the combined solution is sent for recycling in PUREX process, where the residual Pu content in the raffinate is less than 1 mg/l, which corresponds to the discharge standards. This example confirms the possibility of oxidation of polybasic carboxylic acids and hydroxy acids and binding residue using a Zirconia.

Example 5

Produce simultaneous dissolution of carbide SNF AMB SNF from VVER 9.3 mol/l nitric acid for 2 h at 90°C to obtain a solution containing 300 g/l U; 2.5 g/l Pu, and 1.2 g/l Zr and other elements, 4.1 mol/l HNO3.

The resulting solution was sent for recycling in PUREX process; however, after removing the main mass of uranium in bacuranao area extraction cascade observed precipitation is and the basis of Zr with capture Pu. The Pu content in the sediment is ~30-40 mg, residual Pu content in the raffinate ~30 mg/l, which suggests that this solution cannot be processed without the elimination of complexing action of ligands in solution.

Example 6

Carbide SNF SBA dissolved in 7.8 mol/l nitric acid for 6 hours at a temperature of 80°C to obtain a solution of 60 g/l U; 0.6 g/l Pu and 6.9 mol/l HNO3. In the resulting solution carbide fuel add an aqueous solution of Mn(+2) at a molar ratio of the carbide of uranium : manganese =40-80:1 and dissolved in a combined solution, the fuel spent fuel from VVER-1000 for 5 h at 85°C. thus obtain a mixed solution containing 305 g/l U; 3 g/l Pu 3.3 mol/l HNO3.

Then the resulting solution is sent to PUREX process, and precipitation is not formed, and the residual Pu content in the raffinate is not more than 1 mg/l, which corresponds to the discharge standards. This example confirms the possibility of oxidation of polybasic carboxylic acids and hydroxy acids and binding residue using zirconium contained in the spent nuclear fuel of VVER.

Example 7

Carbide SNF SBA dissolved in 7.8 mol/l nitric acid for 6 hours at a temperature of 80°C with the addition of concentrated aqueous solution of Mn(+2) at a molar ratio of the carbide of uranium : manganese =40-80:1. You get a solution containing 60 g/l U; 0.6 g/the Pu and other elements of 6.9 mol/l HNO 3. The resulting solution is not heated.

The resulting solution dissolving the spent nuclear fuel of VVER-1000 for 5 h at 85°C. thus obtain a mixed solution containing 305 g/l U; 3 g/l Pu 3.3 mol/l HNO3. Then the resulting solution is sent to PUREX process, and precipitation is not formed, and the residual Pu content in the raffinate is not more than 1 mg/l, which corresponds to the discharge standards. This example confirms the possibility of oxidation of polybasic carboxylic acids and hydroxy acids and binding residue using Zirconia obtained from the spent nuclear fuel of VVER.

Example 8

In the obtained analogously to example 6 solution carbide SNF SBA produce dissolution within 5 h at 85°C SNF from VVER-1000 loaded at a time. A solution of Mn(+2) do not add. You get a mixed solution containing 300 g/l U; 2.5 g/l Pu and 3.1 mol/l HNO3.

Then the resulting solution is sent to PUREX process, and there is no precipitate, but there is some incomplete extraction residual Pu content in the raffinate is ~5 mg/l This example shows a partial oxidation of polybasic carboxylic acids and hydroxy acids at the expense of existing catalysts in the composition of the fission products (DD).

Example 9

In the obtained analogously to example 6 solution carbide SNF SBA produce dissolution for 7 h at 70°C SNF IN THE ER-1000 in slow mode. You get a mixed solution containing 310 g/l U; 3.1 g/l Pu and 3.2 mol/l HNO3.

Next, the resulting mixed solution is sent to PUREX process, where the residual Pu content in the raffinate is not more than 1 mg/l, which corresponds to the discharge standards. This example confirms the possibility of oxidation of polybasic carboxylic acids and hydroxy acids and binding residue using a Zirconia.

Example 10

In the obtained analogously to example 6 solution carbide SNF SBA produce dissolution for 8 h at 70°C RBMK-1000 in slow mode. You get a mixed solution containing 320 g/l U; 1.2 g/l Pu and 3.0 mol/l HNO3.

Next, the resulting mixed solution is sent to PUREX process, where the residual Pu content in the raffinate is not more than 1 mg/l, which corresponds to the discharge standards. This example confirms the possibility of oxidation of polybasic carboxylic acids and hydroxy acids and binding residue using a Zirconia.

Example 11

To a solution of carbide SNF BR-10, obtained analogously to example 6, add a concentrated solution of nitrate of mercury to obtain a solution containing ~3-4 g/l Hg, after which the resulting solution to produce a dilution in slow mode for 9 h at 80°C. the spent fuel of research reactor WWR-m on the basis of the an-aluminum alloy.

Next, the resulting mixed solution is sent to PUREX process, where the residual Pu content in the raffinate is not more than 1 mg/l, which corresponds to the discharge standards. This example confirms the possibility of oxidation of polybasic carboxylic acids and hydroxy acids and binding residue using a Zirconia.

Example 12

Hold back the dissolution of the carbide fuel, for which the solution of SNF from VVER-440, containing 250 g/l U; 2.7 g/l Pu; 1 g/l Zr; 0.6 g/l Mo; 1 g/l Cu and 3.4 mol/l HNO3injected aqueous solution of Mn(+2) at a molar ratio of uranium : manganese =120-250:1, and then heated to a temperature not higher than 90°C. Further, in the resulting heated solution dissolve the carbide of uranium at a molar ratio UC:Mn=20-80:1 and thermostatic at a temperature of 80°C for 7 hours. The obtained mixed solution contained ~300 g/l U, 200 mg/l Mn; 2.7 mol/l HNO3and other elements.

The solution is finely dispersed precipitate, indicating the formation of compounds of zirconium and plutonium with the above ligands or products of their partial decomposition. When transferring this solution to processing in PUREX process after extracting the main mass of uranium in bacuranao area extraction cascade observed interphase formation at the phase boundary.

It should be noted that in the reverse order of dissolution decrees of the data types of spent fuel in the presence of a catalyst, the rate of formation of complexes of zirconium with complexing ligands above, than the rate of their oxidation. If the solution of significant quantities of zirconium precipitation is formed of zirconium with complexing ligands, which are not further oxidized.

1. The method of preparing carbide SNF to extraction processing, including suppression actions contained in the nitric acid solution carbide fuel complexing ligands, the oxidation in the presence of a catalyst, characterized in that the oxidation of complexing ligands is carried out in the presence of a catalyst selected from the group of cerium, iron, manganese, technetium, mercury, heated nitric acid solution carbide fuel, or spend the oxidation of complexing ligands in the process of dissolution of carbide fuel in nitric acid, followed by dissolution of the oxidized solution carbide fuel oxide or metal SNF, or conduct simultaneous operations oxidation complexing ligands and dissolution of the oxide or metal SNF in solution carbide fuel.

2. The method according to claim 1, characterized in that the nitric acid solution carbide fuel is dissolved superior amount of oxide or metal SNF.

3. The method according to claim 1, characterized in that the oxidation catalyst complexes of the ligands used metals that are in anatomicalstructure or enter it before or after dissolution of carbide SNF.

4. The method according to claim 1, characterized in that the solution of the carbide fuel contains as complexing ligands oxalic acid, Melitopol and other polybasic carboxylic acids and oxyacids.

5. The method according to claim 1, characterized in that the oxide SNF use of SNF from VVER, RBMK, or PWR, BWR.

6. The method according to claim 1, characterized in that the metal fuel used waste irradiated standard uranium blocks or spent fuel based on uranium-aluminum alloy.

7. The method according to claim 2, characterized in that the dissolution is carried out at temperatures up to 90°C and the duration of treatment up to 10 hours.

8. The method of preparing carbide SNF to extraction processing, including suppression actions contained in the nitric acid solution carbide fuel complexing ligands, the oxidation in the presence of a catalyst, characterized in that the oxidation of complexing ligands is carried out in the presence of a catalyst selected from the group of cerium, iron, manganese, technetium, mercury, heated nitric acid solution carbide fuel or spend oxidation complexing ligands in the process of dissolution of carbide fuel in nitric acid, followed by mixing with oxidized solution carbide fuel solution of the oxide or metal SNF or the introduction of a solution Nitra is as zirconium or solution other polyvalent metal-complexing agents.

9. The method according to claim 8, characterized in that a solution of the carbide fuel mix a solution with a superior amount of oxide or metal SNF.

10. The method according to claim 8, characterized in that the oxidation catalyst complexing ligands used metals in nitric acid solution or enter it before or after dissolution of carbide SNF.

11. The method according to claim 8, characterized in that the solution of the carbide fuel contains as complexing ligands oxalic acid, Melitopol and other polybasic carboxylic acids and oxyacids.

12. The method according to claim 8, characterized in that as a solution of the oxide SNF use a solution of SNF from VVER, RBMK, or PWR, BWR.

13. The method of claim 8, wherein the solution of metal spent fuel use solution worked irradiated standard uranium blocks or spent fuel based on uranium-aluminum alloy.



 

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1 cl, 2 dwg, 2 tbl, 2 ex

FIELD: modeling plutonium dispersion processes in emergency explosion situations at its using entity.

SUBSTANCE: proposed method that can be used to simulate plutonium properties in case of emergency explosion involving escape of plutonium aerosols into atmosphere and to predict degree of radioactive pollution of terrain in emergency situations includes use of metal cerium as plutonium simulator in modeling processes of plutonium dispersion and escape of its aerosols into atmosphere in case of emergency explosion at using entity.

EFFECT: enhanced environmental friendliness of method.

1 cl

FIELD: immobilization of radioactive wastes.

SUBSTANCE: proposed silicate matrix for conditioning radioactive wastes has SiO2, Na2O, K2O, CaO, Fe2O3, Cr2O3, NiO, Al2O3, ZrO2, oxides of radioactive waste components including nuclear fuel fission products, U, transuranium elements. Proportion of mentioned components used in matrix is as follows, mole percent: SiO2, 60-68; sum of Na2O, K2O, Cs2O, 11-18; sum of CaO, SrO, BaO, 3-6; sum of Fe2O3, Cr2O3, NiO, 2-4; Al2O3, 1-3; ZrO2, 4-7; sum of rare-earth elements, U, and transuranium elements, 1.5; the rest, 3.

EFFECT: enhanced chemical and thermal stability of matrix.

1 cl, 3 dwg, 3 tbl, 8 ex

FIELD: nuclear power engineering; removing radioactive pollutants from surfaces of pieces of equipment or parts by means of circulating solutions.

SUBSTANCE: proposed process for controlling cyclic decontamination involving saturation of decontaminating solution with radionuclides includes chemical treatment of surface pollutants with decontaminating solution, checkup of solution saturation with radionuclides, termination of chemical treatment as soon as saturation of decontaminating solution with radionuclides is brought to limiting value, and removal of saturated decontaminating solution. Ionizing radiation dose rate is remotely measured by means of gamma transducers installed at reference points and chemical treatment is ceased as soon as inequality conditions are satisfied.

EFFECT: enhanced reliability of process due to optimal evaluation of chemical treatment time; enhanced efficiency and quality of decontamination due to reduced secondary sorption of radionuclides.

3 cl, 18 dwg

FIELD: nuclear power engineering.

SUBSTANCE: proposed method designed for controlling cyclic decontamination process by determining optimal time of completing separate decontamination steps involving uninterrupted cleaning of decontaminating solutions in filters and primarily intended for removing radioactive pollutants from surfaces of equipment or separate parts by circulating solution, for instance for decontaminating inner surfaces of nuclear power reactor equipment such as coolant circuits of boiling water reactors (heavy-power pressure-tube reactors RBMK) includes chemical loosening operations and dynamic loosening conducted before and after chemical loosening operation, as well as washing to discharge radioactive pollutants from coolant circuit to filters during each loosening operation. Radioactivity level of pollutants discharged from coolant circuit is periodically checked against reference radionuclides, and each decontaminating operation is completed upon attaining following condition: . In addition, radioactivity level of pollutants discharged from coolant circuit is proposed to be calculated by sum of derived radioactivity of 3-7 reference radionuclides; 58,60Co, 54Mn, 59Fe 95Zr, and 95Nb are used as reference radionuclides.

EFFECT: enhanced reliability of process control due to determining optimal time of completing separate steps, reduced decontamination time, enhanced effectiveness due to reduced secondary sorption of radionuclides.

3 cl, 13 dwg, 3 tbl

FIELD: recovering and degreasing liquid radioactive wastes.

SUBSTANCE: proposed method for decontaminating waste water from radioactive components incorporating in their composition dissolved and/or emulsified mineral oil, dissolved and solid particles of uranium radioactive components, and products of its decay by concentration of radioactive components and mineral oil. Prior to recovery waste water is acidified to pH = 2.5-3.0. Then iron salt based coagulant (III) and modified polyacrylamide based flocculant are introduced. After that waste water is neutralized with alkali to pH > 7 followed by centrifuging purified water and concentrate containing radioactive components and mineral oil. For final procedure concentrate is solidified and buried.

EFFECT: reduced energy requirement, enhanced speed of process.

1 cl, 5 tbl, 5 ex

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